Abstract:

In view of the widespread challenge of structural instability that limits the engineering application of aerobic granular sludge (AGS), this study proposes a synergistic strategy combining extended hydraulic retention time (HRT) and nitrate addition to enhance the structural stability of AGS. The aim is to elucidate the synergistic effects of these two factors on enhancing the structural stability of AGS. Four sequencing batch reactors (SBRs) were operated under distinct conditions: R0 (control), R1 (external nitrate addition only), R2 (extended HRT-induced starvation), and R3 (combined extended HRT and external nitrate addition). Synthetic wastewater was utilized as the substrate to systematically investigate the impact of different operational conditions on AGS performance. Experimental results indicated that extending HRT effectively induced starvation conditions, leading to effective consumption of polysaccharides (PS) within the extracellular polymeric substances (EPS). Consequently, the protein (PN) to PS ratio in EPS was significantly increased, promoting a denser and more structurally stable granule formation. Specifically, the granule integrity coefficients in reactors R0, R1, R2, and R3 were 84.26%, 85.69%, 95.13%, and 97.12%, respectively. Corresponding EPS concentrations were 78.06, 96.3,0.00, and 91.42 mg/g (based on VSS), with PN/PS ratios of 4.7,5.5,1.12, and 9.30, respectively. These findings highlight that the combined strategy of extended HRT and nitrate supplementation effectively accelerated granulation and significantly enhanced structural strength. Regarding pollutant removal performance, the average chemical oxygen demand (COD) removal efficiencies for reactors R0, R1, R2, and R3 were 89.01%, 88.25%, 83.94%, and 88.56%, respectively. Similarly, average total nitrogen (TN) removal efficiencies were 74.49%, 82.50%, 81.02%, and 81.41%, respectively. Among the reactors, R3 exhibited the best nitrogen removal efficiency and sludge stability. Microbial community analyses revealed that Proteobacteria (56.49% relative abundance) dominated the microbial consortium in R3. Notably, under nitrate-induced starvation stress, the enrichment of the functional genus Zoogloea (16.13% relative abundance) significantly increased EPS secretion (97.40 mg/g), thus effectively driving the granulation process. These results further confirm that targeted microbial community optimization through nitrate regulation represents an effective approach to improve the structural stability of AGS.

Abstract:

Constructing a predictive model for urban water supply pipeline failure events is crucial for assessing the likelihood of pipeline failures and serves as an important basis for the renovation and upgrading of water supply networks. The modeling methods for water supply pipeline failure models include classification and regression. Current research on failure models often employs only one of these methods for case analysis, lacking a comparison of the applicability and accuracy of both modeling methods. To address this gap, based on data from a specific instance of a water supply network, this paper establishes water supply pipeline failure classification and regression models using three machine learning algorithms: Random Forest (RF), Backpropagation Neural Network (BPNN), and Support Vector Machine (SVM). The concordance index (C-index) is used to compare the accuracy of the classification and regression models. Additionally, classification and regression indicators are employed to analyze the impact of modeling dataset division, as well as composition ratios of the dataset on the water supply pipeline failure models. The results show that the failure models constructed by RF exhibit the best performance, with the C-index of the classification models being 5.4% to 32.8% higher than that of the corresponding regression models. Compared to dividing the modeling dataset by year, randomly dividing the modeling dataset can enhance the predictive accuracy of both types of models. Furthermore, the impact of the modeling dataset composition ratio on the predictive accuracy of both types of models varies; as the proportion of non-failure pipeline data increases, the accuracy of the classification model in predicting pipeline failure events decreases, while the regression model shows reduced error in predicting pipeline failure times. Therefore, when constructing water supply pipeline failure models in practice, it is necessary to choose the modeling method appropriately based on the characteristics of the target dataset and pay attention to the impact of dataset division methods and composition ratios on the model results.

Abstract:

Ultra-high performance concrete (UHPC) has been widely used in bridge engineering in recent years due to its superior mechanical properties and durability. To reduce costs while maintaining the high performance of UHPC, this paper investigates the mechanical properties and failure characteristics of ribbed UHPC bridge decks reinforced with 1.2% volume fraction of straight copper-plated micro steel fibers, under different reinforcement conditions (ordinary steel bars and high-strength steel bars), through bending and punching shear performance tests. The results indicate that UHPC ribbed bridge decks exhibited good ductility and flexural failure modes under different reinforcement conditions. The use of high-strength rebar significantly improved the ultimate bearing capacity, fully utilizing the material properties of the high-strength reinforcement. In terms of punching shear performance, the UHPC ribbed bridge decks showed a punching-flexural failure mode with substantial ductility. High-strength rebar increased the punching shear capacity by approximately 25% at the same reinforcement ratio, but further increases in reinforcement ratio had limited impact on bearing capacity. The findings demonstrate that using lower volume fractions of steel fibers and high-strength rebar can reduce costs while maximizing the superior properties of UHPC and high-strength steel bars, enhancing both the durability and economic efficiency of structures.

Abstract:

In order to explore the influence mechanism of arch formation process on the seismic response of large-span concrete filled steel tube (CFST) arch bridges, the typical arch formation process and the stress accumulation history of the arch rib section are first explained. A nonlinear dynamic sequential analysis method is proposed for large-span CFST arch bridges considering the construction process, and the accuracy of the proposed method in obtaining the initial state of bridge is validated against Midas/Civil professional construction analysis module. The influence laws of the arch formation process are investigated from the perspectives of seismic responses of steel pipe and infilling concrete strains, as well as seismic response of the main arch displacement. Based on the "mediating effect analysis", the influencing mechanism of the arch formation process on the seismic response of large-span CFST arch bridges is addressed. Finally, a mapping relationship between the seismic strain responses of steel pipe and infilling concrete obtained with and without considering the arch formation process is established. A simplified corrective analysis method is proposed for seismic response of large-span CFST arch bridges. The research results indicate that the proposed analysis method can achieve accuracy very close to that of Midas/Civil professional construction analysis, with a peak stress error of only 6.8% for steel pipes and almost overlapping stress curves for infilling concrete. When considering the arch formation process of the main arch, the strain distribution of the steel pipe and infilling concrete no longer conforms to the plane section assumption. Under earthquakes, whether the arch formation process is considered leads to different elastic-plastic states in the CFST main arch, with the discrepancies increasing as the peak ground acceleration (PGA, a_PG) rises. When the plastic development degree of the main arch section is low, the differences in the initial state of the completed bridge are critically influential. Conversely, when the plastic development degree is high, the degree of material plasticity becomes the key influencing factor. The proposed simplified corrective analysis method has high accuracy, with average peak strain errors of only 2.9% for the steel pipes and 5.5% for the infilling concrete.

Abstract:

To investigate the tensile bearing capacity of aluminum alloy flange joint of steel-aluminum alloy hybrid gantry, seven full-size flange specimens were designed considering the thickness of flange plate, the number of bolt and the bolt edge distance. Firstly, the failure modes and the variation laws of bearing capacities of flange joints were studied by axial tensile test. Then, based on the test results, a finite element analysis model was established to analyze the effects of stiffened plate thickness, screw diameter and tube wall thickness on the bearing performance of flange joints. Finally, based on the test results and finite element analysis results, the calculation theory of aluminum alloy flange node bearing capacity was proposed. The results of the study show that the damage patterns of the specimens can be roughly classified into three categories: fracture of the weld between the aluminium alloy stiffener plate and the flange plate, fracture at the weld and the heat-affected zone of the joint between the aluminium flange plate and the aluminium tube, slight deformation of the flange plate, dislocation of the aluminium tube, and large deformation of the aluminium alloy flange plate and entry into plasticity. The load-displacement curve can be roughly divided into elastic stage, elastic-plastic stage and damage stage. When the thickness of the flange plate was increased from 10 mm to 14 mm and 18 mm, the ultimate load increase by 66.7% and 76%, respectively, and the ultimate displacement decrease was 14% and 15%, respectively. When the number of bolts was increased from 4 to 6 and 8, the increase in ultimate load was 89.4% and 124.5% and the decrease in ultimate displacement was 38.2% and 44.2% respectively. Increasing the bolt margin parameter from 0.75 to 0.875 and 1.0 resulted in an increase in ultimate load of 10.3% and 20.1%, respectively, with little change in ultimate displacement. The finite element parameter analysis showed that the stiffener plate thickness, bolt diameter and round tube wall thickness had no significant effect on the nodal load capacity. The proposed design method of the aluminium alloy flange node, which takes into account the strength attenuation in the heat-affected zone of the welding of aluminium alloy material, can provide a reference for the design of steel-aluminium alloy hybrid gantry.

Abstract:

To address the issues of low strength and high material costs associated with ultra-lightweight engineered cementitious composites (ULECC), a sustainable ULECC that balances strength and cost has been developed based on micro-mechanical design theory. Two types of lightweight fillers were used: fly ash cenospheres (FAC) and hollow glass microspheres (HGM), along with cellulose filaments (CF) for nano-enhancement. The influence of the water-binder ratio was also examined. A total of five different mix ratios were designed, three of which can be classified as ULECC. The results indicate that the proposed ULECC, with only 1% PE fiber addition, achieves a density as low as 1 296 kg/m³, a strength of 41.9 MPa, and a tensile strain of 10.28%. The water-binder ratio is a key factor affecting ULECC′s mechanical properties. As this ratio decreases, the compressive strength, initial cracking strength, and tensile strength of ULECC gradually increase, while ductility first decreases and then increases. Scanning electron microscopy (SEM) analysis shows that incorporating lightweight fillers increases porosity and reduces the matrix′s fracture toughness, leading to a significant rise in ductility. Compared to traditional engineered cementitious composites (ECC), ULECC provides competitive deformation capability without excessive damage strength, which greatly improves sustainability and reduces material costs.

Abstract:

Recycled micro-powder has excellent carbon sequestration potential, and the wet carbonation method enhances its carbon sequestration performance. In this study, micron bubbles and ultrasonic-assisted methods were used to improve the carbon sequestration efficiency of wet carbonation. Then the recycled micro-powder slurry after carbonation was compressed into artificial aggregate, and a secondary carbonation was further conducted to improve the mechanical strength of artificial aggregate. The CO₂ volumetric method of aluminum film bag was proposed to evaluate the carbon sequestration amount and carbonation degree of recycled micro-powder. Finally, the carbon footprints of this carbonated recycled micro-powder and artificial aggregate are calculated. The results indicate that the wet carbonation method proposed in this study can effectively improve the carbonation efficiency of recycled micro-powder. The use of aluminum film bag for CO₂ volumetric method of the carbon fixation in recycled micro-powder is straghtforward and practical. The carbon sequestration amount of recycled micro-powder in aluminum film bag with 100% CO₂ concentration for 0.5 h is comparable to that of the wet carbonation method proposed in this study for 5 minutes. The compressive strength of the artificial aggregate made of non-carbonated recycled micro-powder is 42.7 MPa after carbonation curing. However, when recycled micro-powder treated with wet carbonation is remolded into artificial aggregates, the post-carbonation strength is relatively lower compared to the control group, mainly due to the reduction of carbonation reactants. Carbon footprint calculation shows that carbonized recycled micro-powder artificial aggregates can achieve a significant reduction in carbon emissions.

Abstract:

To improve the stability bearing capacity of cold-formed steel composite columns and further expand the application scenarios of cold-formed steel components, an innovative cold-formed steel-solid waste foam concrete (CFS-SWFC) special-shaped composite edge column was proposed. Unlike traditional welded steel tube concrete components, cold-formed steel composite columns are susceptible to buckling due to their varying wall thickness and are assembled using self-tapping screws, making the interaction between the cold-formed steel and the core concrete unclear. Four special-shaped hollow columns and six CFS-SWFC special-shaped composite section columns were tested under axial compression to compare and analyze their buckling mechanisms and failure modes. A numerical analysis model of CFS-SWFC was established. Based on experimental validation, a multi-parameter extended analysis was carried out to study the effects of strength, wall thickness, and cross-sectional dimensions on the bearing capacity of the specimens. A calculation method for the bearing capacity of CFS-SWFC was proposed based on the current code GB 50936—2014. The results indicate that the use of solid waste foam concrete enhances the stability and bearing capacity of the specimens by 271%. Although the increase in concrete strength leads to a maximum decrease in deformation capacity of 18%, the final failure mode remains largely unchanged. The strength of SWFC, the thickness of CFS, and the cross-sectional dimensions have a significant impact on the ultimate bearing capacity. Notably, for larger cross-sectional components, an increase in SWFC strength results in a relatively higher enhancement of the ultimate load-carrying capacity. There is a discernible interaction effect between the composite edge columns and the solid waste foam concrete. The current calculation method, which takes the yield of the steel tube as a prerequisite, is not applicable to this type of cross-section. After modifications, the proposed formula demonstrates a good correlation with the experimental results, with a maximum error of 13%.

Abstract:

To calculate the multi-axis fatigue life of structural steel and its welded connections under complex stress conditions, the stress fields on the unstable propagation area of multi-axial fatigue cracks in the inclined butt-welded joint were calculated theoretically based on an ellipsoidal fracture model. The initiation and stable propagation lengths of multi-axial fatigue cracks, as well as the maximum fracture index (under the maximum fatigue load) and the fracture index amplitude (under the fatigue load amplitude) defined by the ellipsoidal fracture model on the fatigue failure area, were calculated. A unified multiaxial fatigue model was established that satisfies the stress boundary conditions and expresses the model parameters, the maximum fracture factor, and the fracture-factor amplitude as functions governing fatigue-crack initiation and steady-state propagation life. The formulation comprehensively accounts for the contributions of individual stress components to multiaxial fatigue of full-penetration oblique cruciform welds and oblique butt weld connections under combined tension-shear cyclic loading. Closed-form unified multiaxial fatigue-life calculation expressions for full-penetration oblique cruciform welds and oblique butt weld connections subjected to tension-shear cyclic stresses are derived. The calculation results show that the calculation errors of the unified multi-axial fatigue life calculation formulas for the multi-axial fatigue life of inclined full-penetration welded cruciform joint of Q345qC steel and butt-welded joint of SAE1050 steel are from -26.8% to -0.2% and -87.1% to 10.2%, respectively. By comparison, the calculation error of the fatigue life formula recommended in the current code are from -63.5% to -13.3% and -79.2% to 237.33%, respectively. The proposed multi-axis fatigue model can be applied to the multi-axis fatigue life assessment of structural steel.

Abstract:

In addition to horizontal seismic actions, vertical ground motion also significantly affects the damage state of non-structural components such as suspended ceilings. However, there is currently insufficient research on the vertical acceleration response of structures under vertical ground motion. To address this gap, a case study is conducted using a real frame structure with different-sized floor slabs. This study performs vertical mode analysis of the structure and conducts time history analyses under four categories of seismic motions, totaling 80 records. The vertical acceleration response of the structure and its influencing factors are studied, and a standardized vertical design response spectrum for seismic analysis of non-structural components is fitted. The results show that the vertical peak floor acceleration amplification factor for the floors range from 1.21 to 8.16, which is much higher than the horizontal amplification factors specified in various national standards. The vertical acceleration response of the structure is influenced by the self-vibration frequency of slabs, the dominant frequency of vertical ground motions, the height of the floors and the position of slabs within the floors. The vertical response of the structure may be amplified significantly due to the vertical flexibility of the structure, which have obvious adverse effects on non-structural components. Additionally, a standardized design spectrum and mathematical expression for vertical acceleration of the structure are obtained, which can be better used for the seismic analysis of non-structural components.

Abstract:

To study the seismic performance of assembled steel truss cap, a full-scale specimen was designed and manufactured. Subsequently, low cyclic loading tests were conducted to analyze its failure mechanisms, hysteretic and skeleton curves, stiffness degradation, ductility, energy dissipation capacity and strain, etc. Based on the experimental results, a finite element model of the specimen was established using ANSYS for parametric analysis. The variation trends on skeleton curves of the model under different parameters were obtained, and an empirical formula of skeleton curve before destruction was proposed. The test results indicate that the specimen is mainly damaged by local buckling deformation at the mid-section of main material. When localized damage occurs at this central region, the specimen reaches its ultimate bearing capacity. The specimen can bear significant horizontal forces, with the horizontal ultimate load approximately 12 times the design value. The ductility coefficient is about 15, indicating that the specimen has considerable ductility and deformation ability. The seismic performance of the specimen improves mainly with the decrease of the height of the cap, the ratio of diameter to thickness of the main material and the downforce. Furthermore, the empirical formula of the skeleton curve before destruction aligns well with the finite element data.

Abstract:

The interface of dry-type vertical seam without grouting for prestressed concrete hybrid tower uses epoxy resin structural adhesive and bending bolts with pre-tension applied to resist shear. Compared with the traditional grouted wet connection with connecting steel bars, this approach can greatly improve on-site installation efficiency. Aiming at the shear performance of the vertical seam interface of dry-type connection, one direct shear static test and two direct shear fatigue tests were carried out on full-scale specimens. The failure mode, bond-slip curves, and bearing capacity calculation of the vertical seam interface under static shear loading were systematically investigated. Furthermore, the fatigue failure mode, degradation of shear stiffness, and methods for fatigue life prediction of the seam interface were further analyzed. The results of experimental research and theoretical analysis show that both static and fatigue tests of the dry-type vertical seams have brittle failure modes. The interface failures can be divided into two regions: interface debonding and delamination of the concrete protective layer—each occupying roughly 50% of the damaged area. The pre-tension applied by the bending bolts can effectively improve the shear capacity of the structural adhesive interface. The upper limit of load is the key factor affecting the shear fatigue performance of vertical seams, and the fatigue life is negatively correlated with the upper limit of load. The shear capacity of the vertical seam interface is provided jointly by the friction force generated by the direct shear of concrete and the pre-tension of the bending bolts. The calculation formula of the shear capacity of the vertical seam interface deduced by the superposition method shows high accuracy. The Fib Model Code specification formula is capable of predicting the shear fatigue life of vertical seams with commendable accuracy and a built-in safety margin, rendering it highly valuable for engineering applications.

Abstract:

To address the limitations of traditional timber structure damage identification algorithms in parameter space completeness, utilization efficiency of high-dimensional data, and integrated local-global damage diagnosis capabilities, this paper proposes a multi-modal data fusion damage identification method based on a graph neural network (GNN). First, with the acceleration response of structural nodes and material parameters as inputs, the graph structure data is constructed by fusion of sensor topological relations to realize the interactive transmission and collaborative identification of damage features between nodes. Second, this paper proposes a joint recognition algorithm, which is composed of a local damage identification network (LCGCN-LDI) and a global material deterioration network (GCN-MPI), to identify the damage of nodes and correct the material property parameters respectively. Finally, experimental validation shows that the joint identification algorithm achieves an overall structural damage recognition accuracy of 94.7%, and a local damage detection accuracy of 97.6%; the prediction error of natural vibration frequency is reduced from 28.9% to 9.4%. The results show that the joint recognition algorithm outperforms traditional algorithms in identifying complex damage in traditional timber structures, exhibiting high accuracy and robustness.

Abstract:

Variations in ambient temperature can cause significant fluctuations in ultrasonic signals, complicating the distinction of target parameters such as damage and stress. To address this issue, this study investigates the characteristics and mathematical representation of temperature effects on ultrasonic signals. The influence of temperature on ultrasonic signals ultimately manifests as spatial changes in signal vectors. Therefore, we construct characteristic vectors in the time-domain vector space using a specific set of functions, allowing the temperature effect to be directly projected into several acoustic measurement features within the ultrasonic time domain, represented by basis functions. The magnitude of these features is determined by the temperature increment and the choice of basis function, with their signs consistent with the projection direction. Experimental ultrasonic test signals were collected from laboratory concrete beams, while theoretical solutions based on wave equations provided time-domain signals under varying temperatures. We constructed a characteristic vector space using power function bases and employed power-law features to describe the nonlinear effects of temperature. Results show that both experimental and theoretical signals exhibit identical distribution patterns in their temperature-effect power-law features, reflecting the energy magnitude of temperature effects. These features decrease exponentially with increasing order of the basis function. Based on power-law characteristics, distinct characteristic values at the same temperature can be derived, each representing temperature effect information across different dimensions. The relationship between a given characteristic and temperature increments follows a power-law mapping, while different characteristic values at identical temperatures exhibit an exponential relationship with increasing power exponents. This establishes a mathematical description of temperature effects during ultrasonic testing, providing an effective tool for characterizing temperature effects across various scenarios.

Abstract:

To adjust existing deterministic typhoon intensity models and account for stochastic influences, a correction term containing both mean and random noise is introduced into the ordinary differential equations governing deterministic typhoon intensity. Various skewed distribution models serve as candidate probability distributions for the random noise. Using historical typhoon data from the Northwest Pacific, the geographically weighted method estimates geographic variation in mean, standard deviation, skewness, and excess kurtosis of the correction term. Furthermore, the method of moments estimates parameters for candidate probability distribution models of the random noise within the correction term, with the optimal probability distribution model determined by KS distance. By comparing simulated results of historical typhoon intensity evolution, the impact of both mean and stochastic components of the error term on model performance is examined. The results indicate that introducing the correction term significantly improves the model′s ability to simulate historical typhoon intensities and enhances its capacity to capture the stochastic nature of typhoon intensity. Additionally, this paper validates model effectiveness in extreme wind speed analysis of typhoons.

Abstract:

Against the backdrop of sustained growth in China′s air conditioning industry and climate change, heat pump air conditioners have emerged as a key solution for achieving the "dual carbon" goals due to their high energy efficiency. However, fins are prone to condensation and frost formation under humid operating conditions, leading to reduced heat transfer efficiency and increased system energy consumption. To achieve multi-objective optimization of low-temperature air-source heat pump outdoor heat exchanger fins, this study reviews performance evaluation metrics and optimization methodologies for fins under both dry and wet conditions. Results indicate that air-source heat pump outdoor heat exchanger fin performance can be comprehensively assessed across three dimensions: material properties, heat transfer flow characteristics, and drainage performance. Optimization under dry conditions primarily focuses on enhancing heat transfer through structural improvements. Existing strategies for enhancing single-fin performance under wet conditions primarily concentrate on micrometer-scale surface topography design and wettability control. Techniques such as laser etching or chemical deposition create micrometer-scale groove networks to reduce pressure drop while maintaining heat transfer efficiency. Fin surface protrusions and pits developed based on vortex induction principles, with heights ranging from 0.6 to 1.61 mm, increase the Nusselt number by up to 19.03%. Future trends involve integrating surface structures for induced nucleation in wet conditions while leveraging biomimetic principles for rapid drainage. Additionally, designing hybrid surfaces combining hydrophilic and hydrophobic properties can delay frost formation and enhance fin drainage. This paper further identifies key research directions to improve heat exchanger efficiency, flow dynamics, and drainage performance, meeting modern industrial and civil demands for high-efficiency, energy-saving heat transfer equipment.

Abstract:

To investigate the flow field and aerodynamic characteristics of a projectile during flight under adverse weather conditions, this study applies the two-way momentum-coupled Eulerian-Lagrangian method to analyze the aerodynamic performance of a 155 mm howitzer shell in a heavy rain environment based on the Marshall-Palmer raindrop spectrum. The unsteady tracking of raindrop particle trajectories is conducted using the discrete phase model (DPM), while the random walk diffusion model is incorporated to simulate the effects of turbulent diffusion in the continuous phase on raindrop motion. A novel methodology is proposed that combines the Lagrangian multiphase flow (LMF) model with the Lagrangian wall film (LWF) model to simulate the formation and evolution of wall films resulting from raindrop impacts on the projectile surface. The results show that raindrop impacts lead to the formation of wall films that exhibit flow trajectories, with the films predominantly distributed on the windward surface (particularly around the projectile nose and band regions). The maximum wall film thickness reaches approximately 0.02 mm, and the maximum film mass is about 0.16 mg; The formation of wall films increases the surface roughness, significantly raising the shear stress, the maximum shear stress escalates from 666 Pa in rain-free conditions to 2 350 Pa under heavy rain,and the maximum value increasing from 0.008 to 0.025; Rainfall also adversely affects the projectile′s aerodynamic coefficients, with the maximum drag coefficient increasing by 6.75% , while the lift coefficient experiences a slight reduction, with a maximum decrease of 1.9%. This approach effectively captures the dynamic evolution of wall films on the projectile surface under heavy rain conditions and their impact on aerodynamic performance, providing theoretical support for the projectile design and performance optimization in complex environmental conditions.

Abstract:

Aiming at the defects that the weight coefficients of linear quadratic regulator (LQR) of two-wheeled balance robot needs to be manually selected, an improved carnivorous plant algorithm (ICPA) is used to optimize the LQR weight coefficients, which realizes the self-stability and high-precision trajectory tracking of two-wheeled balance robot. Firstly, the dynamic equations of the balance robot system is constructed by Lagrange equation method, and the LQR optimization PID control strategy is used to ensure the optimal control force. Secondly, an adaptive capture coefficient is proposed in the growth process of carnivorous plant algorithm, which balances the growth of carnivorous plants and preys, and improves the ability of global exploration in the early stage and local optimization in the later stage. Then, the interference factor is designed in the reproduction process of carnivorous plant algorithm to expand the search space and further improve the global optimization ability. Finally, based on EA cost function, the weight coefficients of LQR controller is optimized by ICPA, and the control strategy model of two-wheeled balanced robot is established in MATLAB/Simulink environment. The experimental results show that the PID controller optimized by the proposed ICPA-LQR optimized PID controller has faster dynamic response speed, stronger anti-interference ability and better overall performance than the control effect optimized by the carnivorous plant algorithm, sparrow search algorithm, moth fire extinguishing algorithm and improved particle swarm optimization algorithm. Under disturbance, the dynamic deviation of the control two-wheeled balance robot tracking complex trajectory dip angle is less than 0.05 rad, the deviations of the horizontal and vertical coordinates is less than 0.2 m, the deviation of the steering angle is less than 0.2 rad, and the deviation of the wheel position angle is less than 3 rad, which can accurately track the given reference trajectory under the premise of maintaining dynamic balance, behaving strong generalization ability.

Abstract:

A fault tolerant control scheme based on integral sliding mode surface is developed for spacecraft attitude stabilization in the presence of actuator faults, misalignments, magnitude saturation and external disturbances simultaneously. This approach is based on a novel integral-type sliding mode control strategy to compensate for these un-desired issues without controller reconfiguration. Especially, it guarantees the reachability of the system states by involving adaptive control technique to relax the boundary information in advance. A sufficient condition for the controller to accommodate magnitude saturation is also presented and then the fault tolerant attitude control system can be guaranteed theoretically to be asymptotically stable by using Lyapunov method. Numerical simulation results shows that the proposed control law can quarantee the stability of the spacecraft attitude control system in the presence of actuators' failures, and it has good robust performance.

Abstract:

To investigate the ground motion intensity measures suitable for evaluating high-rise structures under near-fault ground motions with pulse-like effect, this paper proposes a new ground motion intensity measure considering period elongation effect and higher mode effect based on acceleration spectrum. Taking two high-rise reinforced chimney structures (120 m and 240 m) as research objects, the correlation between damage indices (ParkAng damage index, maximum inter-story drift ratio, maximum structural curvature, maximum floor acceleration, and maximum roof displacement) of high-rise structures and 37 ground motion intensity measures was studied under near-fault ground motions using OpenSEES. Results show that the proposed intensity measure was the optimal index in predicting the ParkAng damage of high-rise concrete structures under near-fault ground motions. High correlation between velocity-related intensity measures and structural damage index was observed. As the structural period increased, the correlation between damage indices and displacement-related intensity measures was improved. Besides, peak ground acceleration had limitations in characterizing the deformation and failure of high-rise structures, but it could be used to analyze the seismic performance of non-structural components. The research results can provide reference for selecting proper measures and structural damage indices to evaluate the seismic performance of high-rise structures under near-fault ground motions.

Abstract:

It is well known that unmanned aerial vehicle (UAV) is more and more widely applied in military and civil areas. In order to play the better role of UAV, it is needed to utilize multi UAVs cooperative formation to accomplish cooperative reconnaissance, combat, defense and spraying pesticides and other tasks. The multi UAVs cooperative formation control technology mainly contains the following key techniques: data fusion technology, sensing technology, task allocation technology, path planning technology, formation control technology, communication network technology and virtual/physical verification platform technology. Firstly, summarize the research and development of key technologies worldwide. Then, the classification for multi UAVs formation control methods is mainly investigated, and the problems about formation design and adjustment, formation reconfiguration are summarized. Finally, the challenges and future development for multi UAV cooperative formation are prospected. Research shows: at present, the theory of multi UAV formation flight has acquired fruitful results, while the real cooperative formation flight test can only be implemented in the simple communication environment. The real time performance for task allocation and path planning is not high. The robustness of control methods to cope with the unexpected situation is low. The cooperative sensing ability for multi UAV with multi sensor is insufficient. The simulation of the entity is lacked. Breaking through the above key technologies, carrying out the cooperative formation flight of multi UAV in complex sensing constraints and complex communication environment, putting forward more effective control method and carrying out the UAV physical formation flying test so that the UAV can finish the task better may be the future research directions.

Abstract:

The advent of Industry 4.0 has spawned the widespread application of digital twin technology, providing digital solutions for intelligent manufacturing and product life-cycle management. In the field of civil engineering, the enhancement of digital disaster prevention and civil structure management is a critical component in the development of future smart cities. On one hand, the establishment of precise and reliable digital twins of real-life civil structures can facilitate disaster prevention from extreme hazards, as well as identify and warn against potential risks. On the other hand, digital twins lay the foundation for technological advancements in the digital construction and management of future cities. This study first categorizes the fundamental concepts and developmental stages of digital twin technology. Then, the acquisition of twining data and construction of digital twins for civil structures are systematically summarized. Building on this foundation, a comprehensive review and outlook is presented on the application of digital twin technology in civil engineering, encompassing the operation and maintenance of structures, disaster simulation and digital twin cities.

Abstract:

The development of advanced nano-integrated circuit processes has led to a decreasing threshold charge in microelectronic devices, resulting in an increased rate of soft errors caused by single-event effects in digital circuits. To enhance the radiation resistance of standard cells in integrated circuits, this paper proposes a NAND gate structure that is resistant to single-event transients (SETs). In the triple well process, by shorting the substrate and source of each NMOS transistor in the pull-down network, the radiation resistance of the NAND gate was effectively improved, and the hardening of the proposed NAND gate became more effective as the number of inputs increased. Particle incidence simulation experiments were performed by Sentaurus TCAD software in hybrid simulation mode. For the NMOS transistor connected to the output node, the three-dimensional physical model that has been calibrated by the process was used, and the Spice model provided by the manufacturer was adopted for other MOS transistors. Simulation results show that the proposed two-input NAND in 40 nm process could reduce the output voltage fluctuation amplitude in three-input cases at the linear energy transfer (LET) value of incidence particle of 10 MeV·cm²/mg. Besides, the effect of immunity to single particle incidence was achieved in the input mode with N₂ transistor closed. For the hardened three-input NAND gate, the output voltage disturbance could be reduced by up to 85.4% even in the “worst case”. Therefore, the proposed hardening method for NAND gate has a significant effect against SET.

Abstract:

Due to the complex background of ship targets and much irrelevant interference in visual images, it is difficult to conduct ship detection. In addition, there are few datasets for multi-category ship detection and the samples are often unbalanced, which makes the ship target detection performance degraded. Considering the ship detection background interference, an improved YOLOv3 model was proposed by introducing SimAM attention mechanism, which was used to enhance the weight of the ship target in the extracted features and suppress the weight of background interference, thus improving the model detection performance. Meanwhile, strong real-time data augmentation was applied to improve the unbalanced distribution of sample scales, and transfer learning was combined to improve the ship detection accuracy in the condition of a restricted number of samples. The visualization results of extracted features show that the improved model could suppress irrelevant background features, and the abilities of feature extraction and target localization were enhanced. Without introducing additional learnable parameters, the proposed model achieved 96.93% and 71.49% for mAP.5 and mAP.75 on the SeaShips dataset, and detection speed reached 66 frames per second, indicating a good balance between detection accuracy and efficiency. The improved model optimized the target features more effectively compared with the Saliency-aware CNN and eYOLOv3 models, resulting in an improvement of mAP.5 by 9.53% and 9.19%. The mAP.5 for ship type target detection on Singapore Maritime Dataset reached 81.81%, indicating that the proposed model has good generalization performance.

Abstract:

In the ultra-dense network environment, each access point is deployed in the hotspot area, which forms a complex heterogeneous network. Users need to choose the appropriate network to access, so as to achieve the best performance. Network selection problem is to choose the optimal network for the user, so that the user or network performance reaches the best. In order to solve the access selection problem of users in ultra-dense networks, we proposed an ultra-dense network access selection algorithm based on the improved deep Q network (DQN), considering network states, user preferences, and service types, and combining with load balancing strategies. First, by analyzing the influence of network attributes and user preferences on network selection, the appropriate network parameters were selected as the parameters of the access selection algorithm. Then, the problem of network access selection was modeled by Markov decision-making process, and the states, actions, and reward functions of the model were designed. Finally, the optimal network strategy was obtained by using DQN to solve the network selection model. In addition, the target function of traditional DQN was optimized to avoid overestimation of Q value by DQN, and a priority experience replay mechanism was introduced to improve learning efficiency. Simulation results show that the method could well solve the problem of overestimation of traditional DQN, accelerate the convergence of neural network, effectively reduce user congestion, and improve network throughput performance.

Abstract:

With the increasing scale of network, the accurate and real-time prediction of network flow is essential for traffic scheduling and routing design. However, due to the nonlinearity and uncertainty of network flow data, some traditional methods fail to achieve good prediction accuracy. Considering the complex spatialtemporal features of network flow, a novel network flow prediction method based on spatialtemporal features fusion (ST-Fusion) was proposed, combined with encoderdecoder architecture. First, the encoder was designed with two parallel feature channels: temporal and spatial channels. The temporal features were extracted by integrating gated recurrent unit (GRU) and self-attention mechanism, and the graph convolutional network (GCN) was used to extract the spatial features. Then, the temporal and spatial features extracted by the encoder were fused by using the bilateral gated mechanism. Finally, the fused features were input into the GRU-based decoder to generate prediction results. Experiments were conducted on three public datasets (GEANT, ABILENE, and CERNET) using evaluation metrics including MAE, RMSE, ACCURACY, and VAR. Experimental results showed that the ST-Fusion method achieved better performance in network flow prediction.

Abstract:

In view of the weaknesses of poor computing and storage capabilities of edge devices, lightweight processing was carried out on the backbone network CSPDarkNet53 for feature extraction in the traditional YOLOv5 model, and a lightweight gesture recognition algorithm MPE-YOLOv5 was proposed to realize the deployment of the model in low-power edge devices. Considering the problem that it is difficult to identify large-scale transformation targets and tiny targets due to less feature extraction in lightweight model, efficient channel attention (ECA) mechanism was added to alleviate the loss of information after high-level feature mapping due to the reduction of feature channel. A detection layer for tiny targets was added to improve the sensitivity to tiny target gestures. EIoU was selected as the loss function of the detection frame to improve the positioning accuracy. The effectiveness of the MPE-YOLOv5 algorithm was verified on the self-made dataset and NUS-Ⅱ public dataset, and the MPE-YOLOv5 algorithm was compared with lightweight M-YOLOv5 algorithm and original YOLOv5 algorithm on the self-made dataset. Experimental results show that the model parameters, model size, and computational complexity of the improved algorithm were 21.16%, 25.33%, and 27.33% of the original algorithm, and the average accuracy was 97.2%. Compared with the lightweight model M-YOLOv5, MPE-YOLOv5 improved the average accuracy by 8.72% while maintaining the original efficiency. The proposed MPE-YOLOv5 algorithm can better balance between the detection accuracy and real-time reasoning speed of the model, and can be deployed on edge terminals with limited hardware.

Abstract:

To improve the ductility of steelultra-high performance concrete (UHPC) composite structures, we proposed a type of demountable steelUHPC composite slab based on demountable shear connectors. The flexural tests for demountable steelUHPC composite slabs with different shear connection degrees were designed and completed. The failure mode, ultimate capacity, stiffness, cracking behavior, and relative slip of demountable steelUHPC composite slabs were analyzed and compared with those of steelUHPC composite slabs with welded shear connectors. The demountability of demountable steelUHPC composite slabs was discussed. The ultimate flexural capacity and flexural stiffness of demountable steelUHPC composite slabs were theoretically analyzed, and related calculation formulas were deduced. Results showed that the failure mode of demountable steelUHPC composite slabs was longitudinal horizontal shear bonding failure. Reducing the stud spacing could enhance the cooperative deformation capacity of demountable steelUHPC composite slabs, resulting in the improvement of their ultimate flexural capacity, stiffness at the elastic-plastic stage, and crack control ability. Different from the steelUHPC composite slabs with welded shear connectors, the steel slab and UHPC slab of the demountable steelUHPC composite slabs could be easily disassembled even in the condition of large deformation. The formulas for the ultimate flexural capacity and flexural stiffness of demountable steelUHPC composite slabs were derived. It was proposed that the height of UHPC slab should be reduced when calculating the flexural stiffness, and the reduction coefficient (β_U) was suggested to be 0.85 in serviceability state. The theoretical calculation results were in good agreement with the test results. The research results can provide theoretical basis for the design and application of steelUHPC composite slabs with demountable shear connectors.

Abstract:

To study the mechanical performance of concrete-filled double-skin steel tubular long columns under compressive and torsional loads, two ordinary circular steel tube reinforced concrete columns and two double-layered steel tube reinforced concrete columns were subjected to low-cycle reciprocating tests under pure torsion and torsion-compression loading using a developed Stewart six-degree-of-freedom loading platform. Based on the tests, the bearing capacity, torsional deformation, energy dissipation, and hysteresis performance of each specimen were compared and analyzed, and finite element parameter analysis was conducted. The study shows that both ordinary circular steel tube reinforced concrete columns and double-layered circular steel tube reinforced concrete columns have good torsional resistance. Compared with ordinary circular steel tube reinforced concrete columns, the initial stiffness and bearing capacity of double-layered steel tube reinforced concrete columns are slightly improved, the hysteresis curve is more full, and the energy dissipation capacity and ductility are greatly improved. Parameter analysis shows that when the steel content is constant, the larger the thickness ratio of the inner steel tube, the more beneficial it is for torsional resistance; and within a certain range of axial loads, the torsional resistance of steel tube reinforced concrete columns can be improved.

Abstract:

In order to give full play to the advantages of the high degree of industrialization of assembly and the excellent mechanical properties of steel-concrete composite structures, a kind of assembled double-slotted channel steel-concrete composite floor slab was proposed. Three groups of simply supported composite floor slab specimens were tested under four-point loading, and the mechanical properties of the composite floor slab under vertical static load were studied. The development law of floor cracks, deflection and strain (steel bar, steel beam, concrete slab) with load was analyzed. Based on the limit equilibrium method, the bearing capacity calculation formula considering the tensile membrane effect and stiffness strengthening coefficient was proposed. The results showed that the deformation of the composite slab is characterized by two-way slab. When the specimens are destroyed, the corner cracks and arc cracks appear on the top of the slab, the central area of the concrete slab bottom shows mesh cracks and oblique cracks extending to the corner, and the plastic bending of the double main girder occurs. When the center deflection of the floor reaches l₀/40, the load of the specimens is 327.63 kN, 436.92 kN and 406.12 kN respectively, and the bearing capacity of the composite floor is higher. The strain development of the steel bar is larger in the direction perpendicular to the steel beam and yields along the plastic hinge line. The calculation formula considering the tensile membrane effect and the stiffness strengthening coefficient is in good agreement with the test results, and the load-deflection curve of the floor is accurately predicted.

Abstract:

Considering the failure mechanism and weaknesses of traditional fabricated shear wall structures under strong earthquakes, a new type of fabricated shear wall with functions of energy dissipation and shock absorption was proposed. On the basis of model test and numerical simulation, seismic performance tests were carried out on four specimens with scale ratio of 1∶1.54 and shear span ratio of 1.52. Further analysis was conducted to investigate the effects of bolt number, axial compression ratio, and reinforcement ratio of edge members on the seismic performance of the new fabricated shear wall, including failure modes, hysteretic performance, bearing capacity, displacement ductility, stiffness degradation, and energy dissipation capacity. Test results show that the four specimens experienced shear compression failure, which was the same as the cast-in-place shear wall with the same shear span ratio. However, the proposed shear wall had better hysteretic performance and energy dissipation capacity, and the energy dissipation capacity was higher than that of the cast-in-place shear wall at the failure point. When the number of bolts decreased, the hysteretic performance of the new fabricated shear wall decreased, the wall deformation increased, while the bearing capacity remained almost unchanged. When the axial compression ratio or reinforcement ratio of edge members decreased, the bearing capacity decreased, and the ultimate displacement increased. Finally, the finite element model of the specimens was established by ABAQUS program. Comparisons of numerical results and test results showed a good agreement, verifying the correctness of the model, which can be applied to the analysis of the new fabricated shear wall.

Abstract:

To improve the construction efficiency of building envelope and solve the long-term problems of falling off and ignition of traditional external insulation systems, a kind of rock wool composite insulation external formwork (RWCIEF) system integrating insulation and building formwork was proposed. The RWCIEF structure from inside to outside was designed as follows: inner reinforcing layer, rock wool insulation core material, adhesive layer, insulation transition layer, and outer reinforcing layer. Taking Harbin as an example, the optimal thickness of rock wool insulation core material was determined based on the life cycle cost (C_lc). The feasibility of RWCIEF in engineering was explored by combining finite element analysis with theoretical calculation. The bending properties, construction bearing capacity, and stress and deformation under temperature effect of RWCIEF were calculated and analyzed. The influences of groove form, groove width, groove depth, and groove spacing on the bending properties of RWCIEF were discussed. Results showed that the theoretical calculation results of bending properties of RWCIEF were in good agreement with the finite element analysis results. The grooving treatment effectively improved the bending properties of RWCIEF. Considering the bending properties, thermal characteristics, and processing angle, groove forms of symmetrical cross grooves or symmetrical longitudinal grooves were suggested, with the groove depth and width of 10 mm and the groove spacing of 150 mm. The designed RWCIEF met the construction bearing capacity and could fully guarantee the construction quality of the thermal insulation works of the outer enclosure structure. The maximum tensile stress and compressive stress caused by temperature effect did not exceed the bearing capacity of the outer reinforcing layer of RWCIEF, which indicates that RWCIEF is unlikely to hollow in summer or crack in winter. The proposed RWCIEF system can provide a new idea and method for the future research directions of exterior envelope insulation and building formwork engineering.

Abstract:

Image segmentation is to divide the region with special meanings into several disjoint sub-regions according to certain rules, which is the key link between image processing and image analysis. The traditional watershed image segmentation method is widely used, which has the advantages of fast and simple. However, it is easily interfered by noise, and the segmentation results are prone to lose important edge information, resulting in over-segmentation. In view of the problem of the traditional watershed image segmentation method, an improved watershed image segmentation method based on adaptive structural elements was proposed. First, the adaptive structural elements with variable shapes were constructed by using local density, symmetry, and boundary features of adjacent pixels of image targets, so as to ensure a good consistency between the proposed structural elements and the shape of image targets. Then, the adaptive structural elements were used to obtain the morphological gradient of the image, which could improve the positioning accuracy of the target edge. The L₀ norm gradient minimization and morphological open-close hybrid reconstruction were used to modify the gradient image, so as to reduce the local invalid minimum points in the gradient image and suppress the occurrence of over-segmentation. Finally, watershed segmentation was performed on the modified gradient image to realize accurate segmentation of the target region of the image. Experimental results show that the method could effectively restrain over-segmentation of traditional watershed algorithm and improve the accuracy of the target edge positioning, with high precision of image segmentation.

Abstract:

Autonomous navigation based on sequential images (ANBSI) is the key technology of pinpoint landing missions for future deep space exploration and also is one of the major development directions for deep space exploration technology. The necessity of developing ANBSI for planetary pinpoint landing is elaborated in this paper. Firstly, state-of-art developments of ANBSI are reviewed in terms of active sensing and passive sensing. Then, the key techniques applied in ANBSI for planetary landing are summarized and analyzed. Finally, according to the analysis of the key techniques, the main issues of ANBSI are raised and their future developments are overviewed.

Abstract:

In view of the problems of low brightness and obvious color distortion of the sky in restored images in most existing algorithms for image dehazing, a haze removal method for UAV aerial images based on atmospheric light value and graph estimation was proposed. First, the depth-of-field image was obtained according to the color attenuation prior theory, and the mean value of the region with the minimum deviation in the depth-of-field image was taken as the atmospheric light value. Then, a random walk clustering method was designed to estimate the atmospheric light map. The random walk algorithm was used to cluster the image into N sub-regions, and the mean value of the first 0.1% pixels of the sub-regions was taken as the regional atmospheric light value, which was then combined and refined by guided filtering to obtain the atmospheric light map. Next, the two atmospheric light estimators were fused into a new atmospheric light map with atmospheric light valuegraph estimation, which is a more accurate atmospheric light estimator. The transmittance was obtained by haze-lines prior method, and a dark compensation method was proposed to improve the transmission accuracy. Finally, according to the atmospheric scattering model, a clear restored image was obtained based on the fused atmospheric light map and optimized transmittance. Experimental results show that compared with other algorithms, the proposed algorithm improved the information entropy, mean gradient, blur coefficient, and contrast by 1.1%, 6.3%, 8.5%, and 6.4%, respectively, with better subjective visual effect and more abundant information.

Abstract:

In order to investigate the flexural behavior of ultra-high performance concrete (UHPC) lightweight composite decks under local wheel load, four demountable steelUHPC composite slabs connected by high-strength bolts were designed and four-point bending test was conducted. The influence of steel plate type and spacing of shear connector on the flexural characteristics of demountable steelUHPC composite slabs was analyzed, including failure mode, load-deflection curve, interface relative slip, crack width, and sectional strain distribution. Results showed that under positive bending moment, the failure mode of composite slabs adopting Q355 steel plate was that the high-strength bolt was cut off. While the failure mode of composite slabs using steel plate with negative Poisson’s ratio (NPR) was as follows: part of high-strength bolts was cut off, part of pre-embedded elongated nuts with cushion was pulled out, and UHPC collapsed due to instantaneous instability. Besides, under the same spacing of high-strength bolts, the relative slip of plate end of composite slabs employing NPR steel plate was relatively small, indicating that NPR steel plate can effectively delay and restrain the relative slip between steel plate and UHPC plate, thus improving the synergistic deformation capacity, flexural stiffness, and flexural bearing capacity for composite slabs. According to the sectional strain distribution analysis, due to the negative Poisson’s ratio effect, high stiffness, and high yield strength of NPR steel plate, the tensile strain between NPR steel plate and the bottom UHPC layer maintained strain compatibility during the whole loading process, and the upward displacement for sectional plastic neutral axis could be ignored with increasing load. Therefore, under the premise that NPR steel plate is employed to improve the flexural performance of steelUHPC composite slab system, the thickness of UHPC should be reasonably matched with the performance of NPR steel plate, so as to give full play to their material properties, and avoid the buckling failure prior to the material strength failure of UHPC.

Abstract:

This paper proposes a low-latency intelligent network data transmission scheduling algorithm for real-time network transmission demand scenarios of low latency, stable transmission, and high quality of experience (QoE). The algorithm consists of two parts: data block queuing control strategy and congestion control strategy. The data block queuing control strategy presents a cost-effective model that integrates the creation time and effective time of data blocks, effectively solving the problem of uneven information transmission under transmission time constraint. The congestion control strategy proposes a deep deterministic policy gradient (DDPG) method based on the Gumbel distribution sampling reparameterization with mixed experience prioritization model, which solves the problem that DDPG is not applicable to the congestion control of discrete network action space and significantly improves the quality of network congestion control by adaptively adjusting the sending parameters through learning. Results show that the proposed queuing algorithm could effectively improve QoE in real-time transmission scenarios, and the improved DDPG for congestion control could significantly reduce transmission delay. In the same scenario, compared with traditional network data transmission scheduling algorithms, by integrating the proposed queuing and congestion control strategies, the improved intelligent network data transmission scheduling algorithm could maintain a good balance between low latency and stable transmission and provide higher data transmission quality.

Abstract:

In view of the problem that general pre-trained models are not suitable for named entity recognition tasks in the medical domain, a neural network architecture that integrates knowledge graph in the medical domain was proposed. The elastic position and masking matrix were used to avoid semantic confusion and semantic interference in self-attention calculation of pre-trained model. The idea of multi-task learning in fine-tuning was adopted, and the optimization algorithm of recall learning was employed for pre-trained model to balance between general semantic expression and learning of the target task. Finally, a more efficient vector representation was obtained and label prediction was conducted. Experimental results showed that the proposed architecture achieved better results than the mainstream pre-trained models in the medical domain, and had relatively good results in the general domain. The architecture avoided retraining pre-trained models in particular domain and additional coding structures, which greatly reduced computational cost and model size. In addition, according to the ablation experiments, the medical domain was more dependent on the knowledge graph than the general domain, indicating the effectiveness of integrating the knowledge graph method in the medical domain. Parameter analysis proved that the optimization algorithm which used recall learning could effectively control the update of model parameters, so that the model retained more general semantic information and obtained more semantic vector representation. Besides, the experimental analysis showed that the proposed method had better performance in the category with a small number of entities.

Abstract:

To investigate widely applicable shear capacity calculation methods of reinforced concrete column-steel beam (RCS) hybrid connection, this study analyzed the shear failure experimental data of RCS connections in recent years. The experimental results were compared with the calculation results of Chinese specification, Nishiyama method, Parra method, and ASCE guideline, and the parametric applicability of each method was discussed. The comparison results showed that all the four methods had engineering value. The minimum discreteness of the results of Parra method was obtained, and the calculation process of Chinese specification was the simplest. The results of parametric study showed that all the four methods were suitable for connections with different stirrup ratios and positions. However, conservative estimates were obtained for specimens with small axial load ratios (from 0 to 0.2) and column-through connections. For the Chinese specification, the predicted strength of connections with concrete strength higher than 60 MPa was unsafe, while the predicted strength of connections with transverse beams was conservative. Therefore, it is suggested to introduce concrete strength coefficient and confined coefficient of transverse beam into the equation considering the influence of these two factors.

Abstract:

To reasonably select a suitable set of ground motion parameters and effectively reduce the uncertainty of structural damage prediction, various ground motion parameters were preferentially selected based on the elastic network regression technique. First, the elastic network regression model was established based on various ground motion parameters and the seismic capacity of a generic set of single-degree of freedom (SDOF) systems obtained from the results of incremental dynamical analysis. Second, the values of regression coefficients in the elastic network regression model and the number of times that the regression coefficients have non-zero values were used to define the sensitivity and frequency of ground motion parameters, respectively. Third, the ranking of ground motion parameters used for seismic capacity prediction was established in terms of sensitivity and frequency of ground motion parameters obtained from the results of elastic network regression on a generic set of SDOF systems. Results were statistically organized to evaluate the influence of various ground motions, structural types and structural limit-states. The analysis result obtained from an 8-story steel frame verified that the use of ground motion parameters selected based on elastic network regression can effectively reduce the uncertainty of structural damage prediction. In addition, results showed that the standard deviation of the residuals in the regression analysis for different structural limit-states was significantly reduced when the representative ground motion parameters were employed in the least squares regression model. Moreover, representative ground motion parameters that are less affected by various ground motions, structural types and structural limit-states were selected based on the ranking results obtained from a generic set of SDOF systems. Findings of this study can provide a theoretical basis for the comparison of ground motion parameters used for the prediction of structural seismic capacity.

Abstract:

To study the bending performance of prestressed steelbamboo composite I-shaped beams, 12 prestressed composite I-shaped beams were designed and manufactured for bending tests, considering prestress loads, prestressing schemes, and loading schemes as basic parameters. The experimental phenomenon was observed, and failure characteristics were analyzed during the test. The influences of different parameters on the load-bearing capacity, strain distribution, and deformation performance were explored, and an approximate formula for the bearing capacity of the prestress composite beam was proposed. The results indicated that the prestressed composite beams have relatively good performances from the perspectives of combination effect, deformation characteristic, and bearing capacity. Failure modes of tested specimens were mainly owing to the bamboo flanges damage and the local buckling of steel plates. With the technique of prestress and the increase of prestress level, the deformation performances can be improved effectively, as well as the load-bearing capacity considering the same deflection situation. Moreover, the improvements can be more significant with the two-point prestressing scheme. The mid-span strain distribution of prestressed composite beams conforms to the plane section assumption, and the neutral axis moves down with the increase of the prestressing level. Finally, the bearing capacities based on the theoretical calculation matched well with the experimental results, which showed the applicability of the proposed methods.

Abstract:

With the gradual deepening of the study of seepage erosion in soil, the research methods of soil particle loss and deformation and failure mechanism show the characteristics of multi-scale. The computational fluid dynamics-discrete element coupling method (CFD-DEM) provides an effective method to study the macroscopic mechanical characteristics of soil on the microscale, considering the influence of fluid-solid interaction. Regarding the current application status of CFD-DEM coupling method in geotechnical engineering, this paper systematically summarizes the advantages and disadvantages of existing fluid-solid coupling calculation methods, focusing on the modeling strategies of CFD-DEM coupling method. These strategies include solid particle shape modeling and inter-particle contact models, control equations and parameter calculation methods for the fluid phase, as well as CFD-DEM coupling calculation. Furthermore, the paper conducts an in-depth exploration of related issues and concludes by proposing future development directions for the CFD-DEM coupling method.

Abstract:

To study the influence of the alkaline activator on the performance of steel slag cement, the effects of alkaline activators (water glass、Na₂CO₃/NaOH、NaOH) on the macroscopic mechanical properties of steel slag cement are studied in this article. Further, the microscopic characteristic is investigated by hydration heat release, X-ray diffraction (XRD), thermogravimetric analysis (DSC-TG), scanning electron microscope (SEM) and mercury intrusion porosimetry test (MIP). The results show that the alkaline activators increased the basicity in the early hydration liquid phase of steel slag cement, accelerating depolymerization of steel slag vitreous to produce H₃SiO-₄ and H₃AlO^2-₄, improving the reaction rate, facilitating the formation of C-S-H gel and zeolite products, which is manifested by the shortening of setting time and induction period, the increase of reaction heat, cumulative heat release and early mechanical strength; the influence of alkaline activators on the properties of steel slag cement is related to its molecular structure of activators, and the order of influence was water glass, Na₂CO₃/NaOH, NaOH in descending order; Water glass could increase the alkalinity of liquid phase in steel slag cement, and the SiO^2-₃ could react with Ca(OH)₂ to produce C-S-H gel. The addition of alkaline activators can promote the hydration reaction of steel slag cement, which is helpful to the improvement of the mechanical properties and the compactness of the microstructure of steel slag cement.

Abstract:

To investigate the seismic behavior of reinforced concrete (RC) columns with stay-in-place ultra-high performance concrete (UHPC) formworks, named URC columns for short, we selected different assembly methods and surface treatment methods of UHPC formworks as design parameters and carried out pseudo-static tests on nine URC columns and one RC column. The assembly methods of UHPC formworks were boltangle steel connection, bolt connection, and epoxy resin mortar. The surface treatment methods of UHPC formworks were natural surface, bubble film printing, and adding ribs. The pseudo-static tests were conducted to study the influence of different assembly methods and surface treatment methods on the seismic behaviors of the URC columns. Additionally, on the basis of the assumption of plane section, a formula was proposed to predict the eccentric compressive bearing capacity of the URC columns. Results show that the bonding surface between UHPC formwork and concrete core had no apparent damage before the peak load, indicating that the URC columns have good integrity. In particular, the URC columns connected by boltangle steel had no interface bonding failure even under the failure load. Compared with the traditional RC column, the ultimate bearing capacity, ductility, and energy consumption of the URC columns were increased by 6.4%43.3%, 11.4%48.7%, and 27.7%85.3%, respectively. Among the three assembly methods, the URC columns connected by bolt and angle steel had the highest bearing capacity and the most reliable connection. Finally, the results calculated by the proposed formula were in good agreement with the test results, which can provide reference for practical application.

Abstract:

In order to compare the mechanical performance differences between grouted sleeve lapping connectors and butt connectors, uniaxial tensile and high stress repeated tension-compression tests were conducted on 41 lap connectors and 20 butt connectors. Results showed that under uniaxial tension and high stress repeated tension-compression loading, the total elongation ratio with maximum force of two kinds of connectors was greater than 6% and the ductility coefficient was greater than 4. The strength basically met the requirements of the codes. Under uniaxial tension after high stress repeated tension-compression, the bearing capacity of both connectors increased, while the initial stiffness and ductility of the specimens decreased. Moreover, the residual deformation of the lap connector was reduced by the anti-deflection measures, but the measured value of the residual deformation of the lap connector was slightly larger than that of the butt connector due to the limited constraint stiffness of the anti-deflection measures. However, the residual deformation of the lap connector and the butt connector of anti-deflection generally met the requirements of the specification. After high stress repeated tension-compression, during uniaxial tension testing, the middle section of the sleeve of the lap connector was longitudinally compressed and circumferentially stretched in the early stage of loading. In the later stage of loading, it experienced longitudinal stretch and circumferential compression, while the sleeve of the butt connector was longitudinally stretched and circumferentially stretched throughout the loading process. In the case of uniaxial tension after high stress repeated tension-compression, the maximum longitudinal tensile strain of the middle section of the sleeve near the bar side of the anti-deflection and non-deflection lap connector was 0.10 to 0.39 times and 0.13 to 0.18 times of the butt connector, respectively. Furthermore, the maximum circumferential compressive strain was 0.09 to 0.49 times and 0.02 to 0.32 times of the butt connector, respectively, which indicated that the lap connector had relatively low requirements on the material of the sleeve. When the diameter of rebar was the same, the material cost of the lap connector was about 35% lower than that of the butt connector.

Abstract:

To study the impact of corrosion of both longitudinal bar and stirrup on the bonding performance of steel bar and concrete, we fabricated 25 corroded reinforced concrete (RC) specimens by the accelerated corrosion method of electroosmosis-constant current-dry wet cycles. Pullout tests were carried out on the specimens, and the influences of parameters such as longitudinal bar corrosion, stirrup corrosion, cover thickness, and stirrup spacing on bonding properties were studied. The effect of corrosion on the bonding force between concrete and steel bar was analyzed, and the degradation of the bonding performance was attributed to the reduction of the material behavior and the degradation of the constraint effect. On the basis of the test results, a modified bondslip constitutive model was established and verified considering design parameters and both corrosion of longitudinal bar and stirrup. A stressslip model of corroded longitudinal bar was obtained by combining the proposed constitutive model and infinitesimal algorithm. In the OpenSees platform, the stressslip model was applied to the zero-length section element, and the numerical model of corroded RC components considering bondslip behavior was established by adopting fiber-based beam-column element and zero-length section element. The accuracy of the model was verified according to the quasi-static test data of the corroded RC column, and the fiber model considering only corrosion damage was used for auxiliary verification. Results show that the bonding force between concrete and steel bar increased first and then decreased with the increase in the corrosion degree. Increasing the cover thickness could slightly improve the bonding force, while the increase in stirrup density could significantly improve the bonding force. Compared with the fiber model, the bearing capacity, cumulative energy dissipation, and ultimate displacement errors were reduced by 12.8%, 23.5%, and 14.2% in the constructed fiber model, indicating that the constructed model can reasonably calculate the contribution of steel bar slip and accurately predict the overall seismic response of the corroded RC columns.

Abstract:

To investigate the dynamic performance and unloading failure characteristics of coal under non-hydrostatic conditions, based on 3D dynamic and static loading experiment, the effect of unloading method on the macroscopic failure characteristics of unloading coal samples after dynamic disturbance was studied. Firstly, Ф50 mm split Hopkinson pressure bar system was used to carry out the dynamic experiment of coal sample under 3D dynamic and static loading for the purpose of studying the influence of axial compression and strain rate on the dynamic response of coal samples. Secondly, based on the response surface theory, a regression model considering the interaction of factors was constructed by using the central composite test method and the significance of single factor and factor interaction were analyzed. Afterwards, combined with factor interaction, Weibull distribution and Drucker-Prager criterion, the strength statistical damage constitutive model of coal was modified. The reliability of the model was verified by comparing the theoretical and experimental results. Finally, with the help of loading and unloading electro-hydraulic servo device, the influence and mechanism of axial pressure, impact pressure and unloading mode on the failure characteristics of coal samples were explored. The results showed that the constructed strength statistical damage model has a correlation coefficient R²≥0.88, which can characterize the dynamic response behavior of coal samples. The coal samples with synchronous unloading after impact are mostly spalled, and the tensile interface moves backward and eventually disappears with the increase of axial pressure, unable to form spall failure. The failure modes of coal samples under non-synchronous unloading mainly include overall integrity, spalling and compression-shear failure. However, when the impact pressure is in the range of 0.4 to 0.6 MPa and the axial pressure is 14.5 MPa, a mixed failure mode of ‘spalling + compression-shear’ is observed.

Abstract:

In order to improve the separability of powdered activated carbon, a new type of magnetic activated carbon was prepared using chemical co-precipitation.Using methylene blue as target pollutants, performance of the powdered magnetic activated carbon was studied under varied conditions of pH, contact time and initial methylene blue concentrations, via the comparison with powdered activated carbon. The results showed that the adsorption capacity of synthetic magnetic powdered activated carbon was higher than that of the powdered activated carbon, and an alkaline pH value and adequate contact time were favorable for the pollutants removal. Under the condition of 100 mg/L methylene blue concentration, 0.4 g/L magnetic activated carbon dosage of, pH 9 and a reaction time of 300 minutes, the removal rate of methylene blue reached 98.9%. The adsorption behavior of methylene blue on magnetic activated carbon fitted the Langmuir isotherm and Elovich dynamics model. Thermodynamic analysis indicated that the adsorption was spontaneous endothermic reaction of single molecule layer, and the chemical adsorption played an important role during the adsorption process. The magnetic activated carbon had a good recyclable performance, it could complete precipitation in 10 minutes under natural condition, and could be quickly separated in 30 seconds under the action of outside magnetic field.

Abstract:

To meet the requirements of large deployment ratio and high precision for deployable membrane mechanism in space missions, a deployable membrane mechanism based on Miura elastic creases was proposed and subjected to model, analyze and develop prototype. According to the crease distribution law and geometric relations, Miura-ori geometric model was established to investigate the influence law of the crease parameters on the deployment ratio and creases total length, and to calculate and optimize the crease parameters. In ABAQUS/Explicit, the numerical simulation models of the four-creases basic unit with θ= 90° and θ<90° were established respectively to analyze the mechanical behavior of the key membrane creases, and the feasibility of two-dimensional elastic crease was preliminarily proved. The elastoplasticity of the triangular membrane of Miura-ori was further studied, and the change curve of stress with folding process at the intersection of creases was plotted and the peak stress of which was within the range of material elasticity. And the space deployable membrane mechanism prototype was developed to conduct validation and analysis. The results show that the mechanism configuration design scheme is reasonable and a membrane folding scheme based on Miura-ori with large deployment ratio and small creases total length could be obtained by optimizing the crease parameters, and the high surface flatness of the deployed membrane proves the feasibility and superiority of Miura elastic creases.

Abstract:

To accurately evaluate the safety and comfortability of structures after a long period of service under dynamic loads such as earthquakes and wind, it is critical to establish a structural dynamic model that can accurately reflect the dynamic responses of actual buildings under seismic, wind and other dynamic loads utilizing the monitoring/inspection data. In this paper, for popular frame building structures, an equivalent simplified dynamic modeling method is proposed by using a few numbers of wireless mobile sensors. First, the principle of equivalent interstory shear force for a simplified model of buildings is proposed, which proves that the simplified model constructed based on this principle has the ability to accurately simulate the dynamic response of actual buildings. Second, the form of simplified model of frame structure was derived, and the characteristics of the simplified model parameters were studied. Then, an iterative identification method for the parameters of the simplified model was proposed, which can identify all parameters of the simplified model by solely using a small number of wireless mobile sensors. Finally, a numerical simulation example of a 12-story 3-span steel frame structure was conducted, which investigates the predictive capability of the equivalent simplified model constructed by the method proposed herein to predict the dynamic responses of the actual frame structure subjected to different types of horizontal excitations, under the condition of without knowing the specific format of structural stiffness degradation and using only a small number of moving acceleration sensors. Simulation results show that the equivalent simplified model can very accurately predict the dynamic responses of the actual frame structure subjected to different types of horizontal excitations. Therefore, the model updating method for the equivalent simplified model of frame structures proposed herein will have important application potential in evaluating the structural safety and comfort of existing frame building structures under dynamic loads, such as wind and earthquake.

Abstract:

Carbon dioxide (CO₂) capture, utilization and storage, as an emerging technology that can help reduce coal chemical plant greenhouse gas emission by large scale, have drawn significant attention. Pipeline transportation is an essential part of the technology, but high cost has greatly limited its application. Therefore the main objective is to develop an optimization model for supporting CO₂ pipeline transportation system planning to reduce the overall carbon capture utilization and storage (CCUS) system cost by optimizing key technology process of a CO₂ transportation system. The developed model was further applied to Shaanxi Yanchang's CCUS project for planning its CO₂ transportation system. The results indicated that in case of low demand of CO₂ storage, a gas-phase CO₂ pipeline transportation system coupled with in-situ compression and injection was recommended. In the case of high demand of CO₂ storage, this study would recommend a super-critical / density phase transportation system which could have lower system cost than gas phase pipeline system as the cost for compression at the site of storage can be saved

Abstract:

To explore the improvement mechanism of welding round steel at soffit on the flexural performance of eccentric concrete-filled steel tube (CFST) members, we established a numerical model of CFST beams reinforced with round steel by using ABAQUS software and verified the model by test results. By analyzing the bending momentdeflection curve, bending momentaxial strain curve, hoop strain curve, restraint index, and neutral axis offset of eccentric CFST members reinforced with round steel, the improvement mechanism of the flexural performance of the eccentric CFST members was revealed. Besides, the influence of the diameter of the round steel and the slenderness ratio of the beams on the flexural performance of eccentric CFST members reinforced with round steel was analyzed. Results show that welding round steel could lower the position of the neutral axis of the section and increase the hoop strain of the steel tube on the compression side. Therefore, the concrete area in compression was increased, and the restraint effect of the steel tube on the compression side on the concrete was enhanced. Furthermore, the flexural bearing capacity and flexural stiffness of the eccentric CFST members were improved, and the larger the diameter of the round steel, the greater the improvement. The ultimate bending moment of the eccentric CFST members decreased with the increase in the axial compression ratio, and the larger the diameter of round steel and the slenderness ratio of beams, the greater the reduction. Welding round steel had a better effect on improving the bending performance of the eccentric member with a large slenderness ratio, and the larger the axial compression ratio, the better the improvement effect.

Abstract:

The existing graph-construction methods for graph optimization-based SLAM are summarized. The SLAM methods can be divided into three main classes, Kalman filter-based, partical filter-based and graph optimization-based, and the advantages and disadvantages of each class are overviewed. Moreover, there are mainly three graph modeling methods for the graph optimization-based SLAM problem, namely dynamic Bayesian network (DBN)-based model, factor graph-based model and Markov random field-based model. The key techniques of the front-end stage in graph optimization-based SLAM method, which mainly include data association between consecutive frame and loop closure detection, are discussed. Some newest research achievements on feature extraction, matching method, motion estimation, loop closure detection are introduced.

Abstract:

There are a large number of new and old concrete interfaces in prefabricated concrete structures. The template effect causes the enlargement of cement mortar porosity in the interfacial zones, which weakens their mechanical properties and durability. In order to quantitatively describe the porosity distribution characteristics of cement mortar in interfacial zones, new and old concrete specimens with smooth vertical interfaces and different water cement ratios were prefabricated. Scanning electron microscopy (SEM) was used to obtain the gray images of each specimen at different positions from the interface. Digital image processing (DIP) tools were used for image information enhancement and binarization. Thus, the ratio of pore pixels to total pixels was obtained, namely nominal porosity. With test results, the distribution characteristics of nominal porosity in the interfacial zones of new and old concrete with smooth vertical interfaces were analyzed. On the basis of the stable relationship between nominal porosity and real porosity, a porosity distribution model was established for the interfacial zones of new and old concrete with smooth vertical interfaces. Furthermore, considering the continuous variation of new and old concrete contents in the chiseled section, the porosity distribution model of chiseled interfacial zone was established. Results show that the nominal porosity reached the maximum at the interface, then decreased gradually towards the interior of concrete, and finally tended to be stable. The overall variation trend could be characterized by Gaussian function. With the increase in water cement ratio, the nominal porosity of each position from interface to interior concrete presented a relatively increasing trend, but the relative nominal porosity from the interfacial zone to the interior stable zone was nearly the same for the concrete with different water cement ratios.

Abstract:

Starting from the tactile sensing performance of human skin, the progress and key technologies of tactile sensors for e-skin (electronic skin) akin to human skin by multidisciplinary fields are comprehensively reviewed. The sensing principle, new materials and structures, advanced design and making methods, sensing characteristics and performance of tactile sensors are analyzed. The recent domestic and foreign research advances of electronic skin tactile sensor array in flexibility, elasticity, spatial resolution, sensitivity, fast response, transparency, lightweight, multifunction and other aspects are summarized. It is difficult to achieve the tactile sensors for e-skin with high stretchable and flexible, less complex production process for high sensitivity e-skin, strong extensibility and low cost. The tactile sensors for e-skin can be widely used in robotics, medical health, aeronautics and space military, intelligent manufacturing, automotive security and other fields. The development of tactile sensors for e-skin toward the direction of high stretchable and flexible, high sensitivity in wide range, multifunction, self-healing and self-cleaning, self-powered and transparent, has been pointed out.

Abstract:

To update the structural finite element model through stochastic static displacement measurement data and maintain the computational efficiency, we proposed a stochastic model updating method based on homotopy meta-model and Bayesian sampling method. First, the objective function was constructed by using the static displacement of the structure, and the delayed rejection adaptive sampling algorithm was used to estimate the posterior probability density of the updated parameters. In the process of sampling, the homotopy meta-model was adopted instead of the finite element model to calculate the static displacement of the structure. Numerical examples and test results show that when updating the finite element model of variable cross-section beam, as opposed to the quadratic response surface model, by incorporating the homotopy meta-model into the static Bayesian model method, the posterior probability density of the updated parameters could reproduce the stochastic response of the structure more accurately, making the probability density function of the stochastic response of the updated structure more consistent with that of the measured results. Even when the coefficient of variation of the stochastic measurement error was large and the difference between the prior information and the real updated parameters was large, the proposed method could quickly obtain the posterior probability density of the updated parameters, so that the probability density function of the structural stochastic displacement response calculated by the updated parameters was consistent with that of the measured results. The homotopy meta-model combined with Bayesian sampling algorithm can update the stochastic model of the structure quickly and accurately within the probability framework.

Abstract:

The rapid development and extensive application of ships highlight the vital role of the analysis and control of ship deck flow field. To improve the flow field of ship deck, a novel active flow control method based on jet is proposed, and by taking the position of helicopter rotor disk as an example, the effect of different jet device parameters on the optimization of helicopter rotor disk flow field is analyzed. First, the numerical simulation model of the flow field of the ship deck was established to examine the influence of active flow control on the ship deck flow field based on the Navier-Stokes equation. Then, the k-ε turbulence model was chosen and the effectiveness of the method was validated. Finally, the streamline and velocity distribution of ship deck flow field with jet device were simulated. Combined with the influence of flow field information on rotor force, the flow control effect of jet device on ship deck flow field was compared and analyzed. The results show that the addition of upper jet can reduce the influence range of reflux zone in the deck flow field and the velocity gradient of rotor disk flow field accordingly. The reduction of the velocity gradient of the rotor disk flow field tends to effectively reduce the aerodynamic variation and the response of the rotor. Adding jet devices under different inflow angles may reduce the response and improve the safety of the helicopter by controlling the deck flow field. As the jet velocity exerts a significant influence on the flow field control effect, the optimal jet velocity should be selected with reference to the installation position of the jet device to achieve better control effect.

Abstract:

To study the influences of roughness, gravel content, and normal stress on the shear mechanical properties of the interface between limestone spoil mixture and concrete, a series of interface shear tests were carried out on limestone spoil mixtures with four types of gravel content and concrete surfaces with five types of roughness under different normal stress conditions by using a new large-scale direct shear apparatus. The influences of roughness, gravel content, and normal stress on the shear strength of the interface were investigated, and the internal relationships between roughness, gravel content, normal stress, and the shear mechanical properties of the interface, as well as the mechanism of shear strength were revealed. Test results show that under the same normal stress condition, as the roughness increased, the shear strength of the interface increased and then decreased, and the rough interface significantly increased the degree of dilation of the interface, but with the increase in normal stress, the influence of roughness on the shear strength and normal deformation of the interface was weakened. Under the condition of same normal stress, with the increase in gravel content, the variation of the shear strength of the interface was closely related to the magnitude of the normal stress. Besides, the shear strength of the interface was highly consistent with the Mohr-Coulomb strength criterion, and the influence of roughness and gravel content on the apparent cohesion of the interface was more significant than that on the internal friction angle of the interface. To a great extent, rational roughness and gravel content can improve the shear strength of the interface between spoil mixture and concrete.

Abstract:

To explore the mechanical properties of integral abutment-RC pile-soil structure, we designed and prefabricated four integral abutment-RC pile models with different pile foundation reinforcement ratios and cross-section shapes taking an integral abutment bridge in China as background. The quasi-static test of integral abutment-RC pile-soil interaction under low cyclic loading was carried out. The effects of reinforcement ratio and cross-section shape of RC pile on the mechanical properties of abutment-RC pile-soil system were mainly studied, and the soil resistance behind abutment, the soil resistance beside pile, and the distribution of pile strain and bending moment were analyzed. Results show that under the action of cyclic displacement of abutment, the distribution of soil resistance near the abutment back along the height direction changed from “triangular” distribution to “parabolic” distribution, and that away from the back of the abutment was basically in “triangular” distribution. The resistance of soil behind abutment was affected by the reinforcement ratio and section shape of RC pile, so it is necessary to increase the reinforcement ratio of RC pile or use rectangular section to improve the integrity of integral abutment-RC pile-soil system. The cumulative deformation of pile affected the distribution of soil resistance on the sides of pile, which reduced the soil resistance behind pile and increased the soil resistance in front of pile. The specimens with larger reinforcement ratio or rectangular cross-sectional RC piles were less affected by the cumulative deformation, and the integrity of abutment-pile foundation-soil structure was better. When the integral abutment-RC pile structure moved to the river span side, the distribution of pile strain and bending moment was consistent with that of traditional pile foundation. When moving to the riverbank, the maximum strain and bending moment of pile appeared at the joint between the bottom of abutment and the top of pile. Increasing the reinforcement ratio of RC pile or adopting rectangular cross-sectional RC pile can effectively reduce the strain and bending moment of pile body and improve the mechanical performance of RC pile foundation.

Abstract:

In order to explore the erosion damage mechanism of polymer cement protective layer on concrete surface of water transfer project under the action of high-speed water flow, the erosion characteristics of protective layer were studied by using improved high-pressure water gun erosion test equipment. Four characteristic parameters including maximum length, maximum width, maximum depth, and volume of erosion area were extracted by 3D scanning. The erosion damage pattern, damage parameter evolution law, and damage mechanism of protective layer under different spray pressure, spray length, spray angle, and spray time were analyzed. Taking the maximum erosion depth of protective layer as the target value, a prediction model of protective layer erosion depth based on Logistic regression function was established. Results show that under the same working conditions, the four erosion damage characteristic parameters of protective layer all increased with the increase in spray pressure and erosion time. With the increase in spray length (from 0.5 cm to 6.6 cm), the erosion pattern of protective layer changed from "hourglass" to "strip". In this process, the damage effect of hydraulic fracturing on the interface between protective layer and concrete decreased. The proposed prediction model of erosion depth of protective layer achieved good accuracy, and the erosion damage degree of protective layer could be significantly reduced by increasing the spray length and spray angle, which provides a reference for the surface protection design of concrete engineering.

Abstract:

To describe the nonlinear magneto-mechanical coupling effect of materials more accurately, a coupled magneto-elastic model and a variable stiffness model were proposed based on nonlinear magneto-strictive strain equation, effective field theory, and energy balance equation. The magneto-mechanical effects and variable stiffness effects of ferromagnetic materials were studied, and the theoretical results of the nonlinear magnetization model were coupled with the simulation process using numerical analysis software. The results showed that the defect leakage field distribution obtained by the simulation was consistent with the existing research results, which verified the feasibility and accuracy of the proposed model and simulation method. The effects of stress, defect size, and defect location on the surface magnetic field were also analyzed. The results showed that under the action of tensile load, the normal magnetic field signal on the surface of the sample was like an S-shaped curve, and the tangential signal was like a conical curve, and its extreme values first decreased and then increased with the increase in the load. When there was a defect in the sample, the signals obtained on different acquisition paths were very different, and the peak value of the leakage magnetic field on the defect edge path was negatively correlated with the defect length, but the peak distance and span were opposite. On the collection route far from the defect, the peak value and span of the leakage magnetic field signal were positively correlated with the defect length.

Abstract:

To study the effect and mechanism of cohesive sediment gradation on cavitation and cavitation erosion in high velocity flow, we selected two cohesive sediment gradation curves and conducted research in a self-developed small looped water tunnel. Sediment-laden flows with different mass percentages of cohesive sediment smaller than a certain grain size were prepared, and the real-time pressure within cavitation and cavitation erosion zones in working section of water tunnel was measured by a dynamic pressure data acquisition system. Concrete specimens with different mix proportions were prepared. Tests of cavitation erosion on the concrete specimens under different mass percentages of cohesive sediment smaller than a certain grain size were carried out for 4 h. The mass loss of concrete specimen per hour was adopted to characterize the cavitation erosion amount . Results show that the time-averaged pressure and cavitation number at each measurement point in the cavitation erosion zone of the working section of water tunnel gradually increased with the decrease in the mass percentage of cohesive sediment smaller than a certain grain size. With the decrease in the mass percentage of cohesive sediment smaller than a certain grain size, the cavitation erosion amount of concrete specimens gradually increased. The anti-cavitation erosion capacity of concrete specimens with higher strength was significantly greater than that with lower strength at the same flow velocity. Cavitation zone was mainly located in the front of the specimen at lower velocity, while it was located in the rear at higher velocity. Under the same sediment concentration, the higher the percentage of cohesive fine grain used in the test, the greater the cavitation erosion amount was.

Abstract:

The wear of cutter is an important factor affecting the efficiency of shield tunneling, which is also a basis for determining the time and frequency of cutter replacement. As it is difficult to evaluate the overall wear state of the cutters in the process of shield tunneling, three wear degrees (light, moderate, and severe) were proposed based on the relationship between the wear amount of each cutter and the limited wear at the cutters change site. The theoretical relationship between three main tunneling parameters (thrust, torque, and tunneling speed) and the cutting force component of a single cutter was derived, and a method for recognizing the overall wear state of cutters was proposed by using the wavelet packet algorithm to decompose the tunneling parameter signals. In this method, the eigenvectors composed by the standard deviation of the wavelet packet coefficient of decomposed signal nodes were used as the wear recognition index. Sensitivity analysis was performed to find out the most sensitive node eigenvector of the cutter wear. Then the functional relationship between the wear state and the wear recognition index was determined by fitting. The analysis of the section from Dayun station to Baohe station of Shenzhen Metro Line 14 showed that the method could accurately recognize the overall wear state of the shield cutters. Among the three tunneling parameters, the recognition accuracy was the highest when using the tunneling speed signal, followed by the thrust signal, and the torque signal was the lowest. The proposed method is easy to use and cost-effective, since it only needs to analyze the automatically collected tunneling signals without installing any sensors, which provides reference for cutter replacement.

Abstract:

To satisfy the needs of plant cultivation in space, the scenario of a space plant cultivation facility(SPCF) was conducted, based on the limited resources and microgravity in space environments. The study contents included water and nutrient control around roots, atmospheric environment control in cultivation room, and light environment control, etc. The facility was designed with six functional modules, consisting of water and nutrient supply module, atmospheric environmental control module, light module, measurement and control module, cultivation room module, and root tray module. The integration and testing of the facility were carried out and the rationality of the design of each functional module was verified. Finally, the combination testing platform was used to verify the integrated performances of various functional modules of the facility, evaluate plant functions (biological characteristics, material and energy exchange, nutritional quality, and biosafety), and verify plants cultivation processes (process rationality, resource requirements and supply, and mutual impact with the environment). The verification results indicated that the performance of water supply, nutrient supply, atmospheric environmental control, illumination control, as well as the measurement and control is well, meeting the demands of plant growth in space. Lettuce grow vigorously with a production efficiency of 101.31 g (fresh weight)·(kWh)^-1·d^-1·m^-2 and a light energy utilization rate of 0.31 g (dry weight)·mol^-1 photons. More importantly, the lettuce is nutrient rich and safe for consumption. The scenario of facility design and cultivation procedures are reasonable and feasible with good performance and high production capacity. This study establishes technical foundations for the future development of plant cultivation facility targeting space environments.

Abstract:

Imitating the human visual characteristics has become a research hot and challenging research topic for machines to move towards intelligent perception and intelligent cognition. Human eyes are more sensitive to edge of objects in the scene because edge contains abundant information. To realize this visual characteristic in machines, a feature point extraction and matching method of humanoid-eye binocular images is proposed. Firstly, smallest univalue segment assimilating nucleus (SUSAN) operator with outstanding edge feature extraction capability is selected as feature detector. Then, the sampling neighborhood of scale invariant feature transform (SIFT) descriptor is improved to reduce the matching error of gradient information far away from feature points due to viewpoint and view direction differences, and the main gradient information close to feature points is retained. Whereafter, a multi-scale structure is established for the input image, and the main gradient information of the same feature is computed at different scales. Finally, the square root kernel is used to compare the similarity of the gradient information, and the multi-scale descriptor is generated to enhance the uniqueness of the description vector. In the experiment, a variety of evaluation indexes are used to evaluate the proposed multi-scale descriptor and overall algorithm respectively, and compared with the classical SIFT, speeded up robust features (SURF), Root-SIFT and the advanced boosted efficient binary local image descriptor (BEBLID), SuperGlue, DFM algorithms. The results show that the proposed multi-scale descriptor improves the matching accuracy of edge feature points and has stronger adaptability to illumination changes, thereby demonstrating better matching stability. Compared with other algorithms, the proposed algorithm has higher matching accuracy.

Abstract:

Due to its self-lubricity and self-sealing, ferrofluid micropump is more in line with the needs of microfluidic technology applied in biomedicine, life science, chemical analysis, aerospace and other fields. However, current structural designs face challenges in simultaneously achieving simple processing, high reliability, stable flow characteristics, so the application and development are limited. In order to improve the reliability and stability of ferrofluid micropump and promote its development and application, a new type of centrifugal ferrofluid micropump is designed based on the external field control principle of ferrofluid, the magnetorheological effect and the hydrodynamic behavior between medium fluid. Numerical calculations are employed to analyze the flow characteristics of medium fluid. The results show that the micropump can effectively realize the pumping process.At a rotating speed of 10 r/min, the pumping flow can reach 0.07 kg/T in one cycle, and the medium fluid mass exchange between the inlet and outlet of the pump chamber can be blocked under the alternating action of two ferrofluid. Due to the dynamic and static interaction between ferrofluid and the pump chamber structure, the outlet flow rate has a slight pulsation (On the order of 10^-5), but it still remains in laminar flow state (Re＜1). Moreover, due to mechanical factors such as inertia force being related to characteristic size while viscous force and characteristic size are unrelated, the pumping power of the structure is highly sensitive to outlet size and length. As a result, effective pumping cannot be achieved at a speed of 4 r/min and the length of the outlet section is 9 mm. The pressure fluctuation and the self-sealing performance of the phase interface between the ferrofluid and the pumping medium fluid are analyzed simultaneously. The peak value of the pressure fluctuation on the phase interface is much smaller than the self-sealing performance of the ferrofluid, differing by three orders of magnitude. The feasibility of the centrifugal ferrofluid driver is verified from the perspective of the sealing stability and the interface stability of the ferrofluid.

Abstract:

Rivet lap joint is a typical structure susceptible to multi-site damage, which is prone to initiate rivet holes-edge crack. It significantly threatens the safety of aircraft structures. Due to the randomness of the crack number, position, size, there exists a complex contact relationship between rivets and plates. In order to efficiently and accurately calculate the stress intensity factor of multi rivet lap joint structures for crack propagation life analysis, a weight function analysis method for rivet lap joint structure is proposed to address the complex crack issues in lap joint structures. Firstly, the crack configurations of rivet lap joint structures are reasonably simplified and classified, the corresponding weight functions are used to calculate the stress intensity factors of different crack configurations. Then, finite element analysis is conducted to compute the stress intensity factor to validate the accuracy of the weight function method. Finally, combined with the Paris crack growth formula, fatigue crack growth of the rivet lap joint structures are predicted, and the effectiveness of the present method is verified by experiments. The results show that the relative difference between the stress intensity factor calculated by the weight function method and the finite element method is less than 5%. The predicted crack growth life is in good agreement with the test results, and the computational efficiency is three orders of magnitude faster than that of the finite element method. This paper provides an effective method for the stress intensity factor and fatigue crack growth analyses of rivet lap joint structures.

Abstract:

To further improve the cooling performance of the combustor flame tube, a binaural hole film cooling structure with higher cooling performance is proposed. The flow, heat transfer and cooling characteristics of traditional cylindrical hole, diffuser hole, convergent hole and binaural hole with blowing ratio from 0.67 to 2.01 were analyzed by numerical simulation. The results show that, compared with the other three film hole shapes, the aspect ratio of the cooling wall is in the range from 0 to 40, the kidney-shaped vortices formed by the cooling air flow at outlet of the binaural hole under the action of high temperature main flow are smaller in size, weaker in strength, larger in distance between the centers of the vortices, wider in transverse distribution of the cooling air flow, and lower in heat transfer coefficient on the wall, the film cooling performance is improved. When the blowing ratio is 2.01, compared with cylindrical hole, the flow coefficient of diffuser hole is increased by 13.7% , the wall heat transfer coefficient ratio is decreased by 1.5% , the flow coefficient of the convergent hole is unchanged, the heat transfer coefficient ratio is decreased by 2.7%. However, the flow coefficient of the binaural aperture decreased by 3.1% and that in the aspect of heat transfer coefficient ratio decreased by 11.25%. When the blowing ratio is 1.33, compared with diffusion hole and convergent hole, the flow coefficient of binaural hole is lower. When the slenderness ratio less than 40, the heat transfer coefficient ratio of binaural hole is the lowest and the cooling effect is the best.

Abstract:

It is well known that unmanned aerial vehicle (UAV) is more and more widely applied in military and civil areas. In order to play the better role of UAV, it is needed to utilize multi UAVs cooperative formation to accomplish cooperative reconnaissance, combat, defense and spraying pesticides and other tasks. The multi UAVs cooperative formation control technology mainly contains the following key techniques: data fusion technology, sensing technology, task allocation technology, path planning technology, formation control technology, communication network technology and virtual/physical verification platform technology. Firstly, summarize the research and development of key technologies worldwide. Then, the classification for multi UAVs formation control methods is mainly investigated, and the problems about formation design and adjustment, formation reconfiguration are summarized. Finally, the challenges and future development for multi UAV cooperative formation are prospected. Research shows: at present, the theory of multi UAV formation flight has acquired fruitful results, while the real cooperative formation flight test can only be implemented in the simple communication environment. The real time performance for task allocation and path planning is not high. The robustness of control methods to cope with the unexpected situation is low. The cooperative sensing ability for multi UAV with multi sensor is insufficient. The simulation of the entity is lacked. Breaking through the above key technologies, carrying out the cooperative formation flight of multi UAV in complex sensing constraints and complex communication environment, putting forward more effective control method and carrying out the UAV physical formation flying test so that the UAV can finish the task better may be the future research directions.

Abstract:

To study the development status of wearable soft upper limb exoskeleton and its key technical challenges, the current literature in this field was analyzed and summarized. Exoskeletons can effectively provide functions such as protection and support to address limb fatigue and physical function decline resulting from high-intensity and repetitive work, as well as limb movement disorders caused by stroke or occupational diseases. Additionally, they have the capability to restore or enhance human movement ability through additional power and functionality. Wearable soft exoskeletons, as a new development direction of exoskeletons, have obvious advantages over traditional rigid exoskeletons, such as structural flexibility, human-machine interaction, and wearable comfort. Firstly, this paper provides a detailed analysis of three main driving methods of soft upper limb exoskeleton (rope drive, pneumatic, shape memory alloy). The relevant research results and corresponding structural characteristics of different driving methods are throughly examined. Then, the key technical challenges of soft upper limb exoskeleton are analyzed and expounded from four aspects: structure, material, control and auxiliary technology. Finally, considering the needs of exoskeleton applications in different fields, future trends in soft upper limb exoskeleton technology are speculated to focus on flexibility, comfort, compliance and intelligence. This study shows that the technology for wearable soft upper limb exoskeletons is still in its early stages, with many technical challenges to be solved. Futhurmore, breakthroughs in key technological challenges can be facilitated by novel soft actuators, soft sensors and other related advancements.

Abstract:

A fault tolerant control scheme based on integral sliding mode surface is developed for spacecraft attitude stabilization in the presence of actuator faults, misalignments, magnitude saturation and external disturbances simultaneously. This approach is based on a novel integral-type sliding mode control strategy to compensate for these un-desired issues without controller reconfiguration. Especially, it guarantees the reachability of the system states by involving adaptive control technique to relax the boundary information in advance. A sufficient condition for the controller to accommodate magnitude saturation is also presented and then the fault tolerant attitude control system can be guaranteed theoretically to be asymptotically stable by using Lyapunov method. Numerical simulation results shows that the proposed control law can quarantee the stability of the spacecraft attitude control system in the presence of actuators' failures, and it has good robust performance.

Abstract:

In view of the weaknesses of poor computing and storage capabilities of edge devices, lightweight processing was carried out on the backbone network CSPDarkNet53 for feature extraction in the traditional YOLOv5 model, and a lightweight gesture recognition algorithm MPE-YOLOv5 was proposed to realize the deployment of the model in low-power edge devices. Considering the problem that it is difficult to identify large-scale transformation targets and tiny targets due to less feature extraction in lightweight model, efficient channel attention (ECA) mechanism was added to alleviate the loss of information after high-level feature mapping due to the reduction of feature channel. A detection layer for tiny targets was added to improve the sensitivity to tiny target gestures. EIoU was selected as the loss function of the detection frame to improve the positioning accuracy. The effectiveness of the MPE-YOLOv5 algorithm was verified on the self-made dataset and NUS-Ⅱ public dataset, and the MPE-YOLOv5 algorithm was compared with lightweight M-YOLOv5 algorithm and original YOLOv5 algorithm on the self-made dataset. Experimental results show that the model parameters, model size, and computational complexity of the improved algorithm were 21.16%, 25.33%, and 27.33% of the original algorithm, and the average accuracy was 97.2%. Compared with the lightweight model M-YOLOv5, MPE-YOLOv5 improved the average accuracy by 8.72% while maintaining the original efficiency. The proposed MPE-YOLOv5 algorithm can better balance between the detection accuracy and real-time reasoning speed of the model, and can be deployed on edge terminals with limited hardware.

Abstract:

In the ultra-dense network environment, each access point is deployed in the hotspot area, which forms a complex heterogeneous network. Users need to choose the appropriate network to access, so as to achieve the best performance. Network selection problem is to choose the optimal network for the user, so that the user or network performance reaches the best. In order to solve the access selection problem of users in ultra-dense networks, we proposed an ultra-dense network access selection algorithm based on the improved deep Q network (DQN), considering network states, user preferences, and service types, and combining with load balancing strategies. First, by analyzing the influence of network attributes and user preferences on network selection, the appropriate network parameters were selected as the parameters of the access selection algorithm. Then, the problem of network access selection was modeled by Markov decision-making process, and the states, actions, and reward functions of the model were designed. Finally, the optimal network strategy was obtained by using DQN to solve the network selection model. In addition, the target function of traditional DQN was optimized to avoid overestimation of Q value by DQN, and a priority experience replay mechanism was introduced to improve learning efficiency. Simulation results show that the method could well solve the problem of overestimation of traditional DQN, accelerate the convergence of neural network, effectively reduce user congestion, and improve network throughput performance.

Abstract:

The existing graph-construction methods for graph optimization-based SLAM are summarized. The SLAM methods can be divided into three main classes, Kalman filter-based, partical filter-based and graph optimization-based, and the advantages and disadvantages of each class are overviewed. Moreover, there are mainly three graph modeling methods for the graph optimization-based SLAM problem, namely dynamic Bayesian network (DBN)-based model, factor graph-based model and Markov random field-based model. The key techniques of the front-end stage in graph optimization-based SLAM method, which mainly include data association between consecutive frame and loop closure detection, are discussed. Some newest research achievements on feature extraction, matching method, motion estimation, loop closure detection are introduced.

Abstract:

The advent of Industry 4.0 has spawned the widespread application of digital twin technology, providing digital solutions for intelligent manufacturing and product life-cycle management. In the field of civil engineering, the enhancement of digital disaster prevention and civil structure management is a critical component in the development of future smart cities. On one hand, the establishment of precise and reliable digital twins of real-life civil structures can facilitate disaster prevention from extreme hazards, as well as identify and warn against potential risks. On the other hand, digital twins lay the foundation for technological advancements in the digital construction and management of future cities. This study first categorizes the fundamental concepts and developmental stages of digital twin technology. Then, the acquisition of twining data and construction of digital twins for civil structures are systematically summarized. Building on this foundation, a comprehensive review and outlook is presented on the application of digital twin technology in civil engineering, encompassing the operation and maintenance of structures, disaster simulation and digital twin cities.

Abstract:

Autonomous navigation based on sequential images (ANBSI) is the key technology of pinpoint landing missions for future deep space exploration and also is one of the major development directions for deep space exploration technology. The necessity of developing ANBSI for planetary pinpoint landing is elaborated in this paper. Firstly, state-of-art developments of ANBSI are reviewed in terms of active sensing and passive sensing. Then, the key techniques applied in ANBSI for planetary landing are summarized and analyzed. Finally, according to the analysis of the key techniques, the main issues of ANBSI are raised and their future developments are overviewed.

Abstract:

Starting from the tactile sensing performance of human skin, the progress and key technologies of tactile sensors for e-skin (electronic skin) akin to human skin by multidisciplinary fields are comprehensively reviewed. The sensing principle, new materials and structures, advanced design and making methods, sensing characteristics and performance of tactile sensors are analyzed. The recent domestic and foreign research advances of electronic skin tactile sensor array in flexibility, elasticity, spatial resolution, sensitivity, fast response, transparency, lightweight, multifunction and other aspects are summarized. It is difficult to achieve the tactile sensors for e-skin with high stretchable and flexible, less complex production process for high sensitivity e-skin, strong extensibility and low cost. The tactile sensors for e-skin can be widely used in robotics, medical health, aeronautics and space military, intelligent manufacturing, automotive security and other fields. The development of tactile sensors for e-skin toward the direction of high stretchable and flexible, high sensitivity in wide range, multifunction, self-healing and self-cleaning, self-powered and transparent, has been pointed out.

Abstract:

In order to improve the separability of powdered activated carbon, a new type of magnetic activated carbon was prepared using chemical co-precipitation.Using methylene blue as target pollutants, performance of the powdered magnetic activated carbon was studied under varied conditions of pH, contact time and initial methylene blue concentrations, via the comparison with powdered activated carbon. The results showed that the adsorption capacity of synthetic magnetic powdered activated carbon was higher than that of the powdered activated carbon, and an alkaline pH value and adequate contact time were favorable for the pollutants removal. Under the condition of 100 mg/L methylene blue concentration, 0.4 g/L magnetic activated carbon dosage of, pH 9 and a reaction time of 300 minutes, the removal rate of methylene blue reached 98.9%. The adsorption behavior of methylene blue on magnetic activated carbon fitted the Langmuir isotherm and Elovich dynamics model. Thermodynamic analysis indicated that the adsorption was spontaneous endothermic reaction of single molecule layer, and the chemical adsorption played an important role during the adsorption process. The magnetic activated carbon had a good recyclable performance, it could complete precipitation in 10 minutes under natural condition, and could be quickly separated in 30 seconds under the action of outside magnetic field.

Abstract:

Considering the failure mechanism and weaknesses of traditional fabricated shear wall structures under strong earthquakes, a new type of fabricated shear wall with functions of energy dissipation and shock absorption was proposed. On the basis of model test and numerical simulation, seismic performance tests were carried out on four specimens with scale ratio of 1∶1.54 and shear span ratio of 1.52. Further analysis was conducted to investigate the effects of bolt number, axial compression ratio, and reinforcement ratio of edge members on the seismic performance of the new fabricated shear wall, including failure modes, hysteretic performance, bearing capacity, displacement ductility, stiffness degradation, and energy dissipation capacity. Test results show that the four specimens experienced shear compression failure, which was the same as the cast-in-place shear wall with the same shear span ratio. However, the proposed shear wall had better hysteretic performance and energy dissipation capacity, and the energy dissipation capacity was higher than that of the cast-in-place shear wall at the failure point. When the number of bolts decreased, the hysteretic performance of the new fabricated shear wall decreased, the wall deformation increased, while the bearing capacity remained almost unchanged. When the axial compression ratio or reinforcement ratio of edge members decreased, the bearing capacity decreased, and the ultimate displacement increased. Finally, the finite element model of the specimens was established by ABAQUS program. Comparisons of numerical results and test results showed a good agreement, verifying the correctness of the model, which can be applied to the analysis of the new fabricated shear wall.

Abstract:

To investigate the ground motion intensity measures suitable for evaluating high-rise structures under near-fault ground motions with pulse-like effect, this paper proposes a new ground motion intensity measure considering period elongation effect and higher mode effect based on acceleration spectrum. Taking two high-rise reinforced chimney structures (120 m and 240 m) as research objects, the correlation between damage indices (ParkAng damage index, maximum inter-story drift ratio, maximum structural curvature, maximum floor acceleration, and maximum roof displacement) of high-rise structures and 37 ground motion intensity measures was studied under near-fault ground motions using OpenSEES. Results show that the proposed intensity measure was the optimal index in predicting the ParkAng damage of high-rise concrete structures under near-fault ground motions. High correlation between velocity-related intensity measures and structural damage index was observed. As the structural period increased, the correlation between damage indices and displacement-related intensity measures was improved. Besides, peak ground acceleration had limitations in characterizing the deformation and failure of high-rise structures, but it could be used to analyze the seismic performance of non-structural components. The research results can provide reference for selecting proper measures and structural damage indices to evaluate the seismic performance of high-rise structures under near-fault ground motions.

Abstract:

In view of the problems of low brightness and obvious color distortion of the sky in restored images in most existing algorithms for image dehazing, a haze removal method for UAV aerial images based on atmospheric light value and graph estimation was proposed. First, the depth-of-field image was obtained according to the color attenuation prior theory, and the mean value of the region with the minimum deviation in the depth-of-field image was taken as the atmospheric light value. Then, a random walk clustering method was designed to estimate the atmospheric light map. The random walk algorithm was used to cluster the image into N sub-regions, and the mean value of the first 0.1% pixels of the sub-regions was taken as the regional atmospheric light value, which was then combined and refined by guided filtering to obtain the atmospheric light map. Next, the two atmospheric light estimators were fused into a new atmospheric light map with atmospheric light valuegraph estimation, which is a more accurate atmospheric light estimator. The transmittance was obtained by haze-lines prior method, and a dark compensation method was proposed to improve the transmission accuracy. Finally, according to the atmospheric scattering model, a clear restored image was obtained based on the fused atmospheric light map and optimized transmittance. Experimental results show that compared with other algorithms, the proposed algorithm improved the information entropy, mean gradient, blur coefficient, and contrast by 1.1%, 6.3%, 8.5%, and 6.4%, respectively, with better subjective visual effect and more abundant information.

Abstract:

This paper proposes a low-latency intelligent network data transmission scheduling algorithm for real-time network transmission demand scenarios of low latency, stable transmission, and high quality of experience (QoE). The algorithm consists of two parts: data block queuing control strategy and congestion control strategy. The data block queuing control strategy presents a cost-effective model that integrates the creation time and effective time of data blocks, effectively solving the problem of uneven information transmission under transmission time constraint. The congestion control strategy proposes a deep deterministic policy gradient (DDPG) method based on the Gumbel distribution sampling reparameterization with mixed experience prioritization model, which solves the problem that DDPG is not applicable to the congestion control of discrete network action space and significantly improves the quality of network congestion control by adaptively adjusting the sending parameters through learning. Results show that the proposed queuing algorithm could effectively improve QoE in real-time transmission scenarios, and the improved DDPG for congestion control could significantly reduce transmission delay. In the same scenario, compared with traditional network data transmission scheduling algorithms, by integrating the proposed queuing and congestion control strategies, the improved intelligent network data transmission scheduling algorithm could maintain a good balance between low latency and stable transmission and provide higher data transmission quality.

Abstract:

In view of the problem that general pre-trained models are not suitable for named entity recognition tasks in the medical domain, a neural network architecture that integrates knowledge graph in the medical domain was proposed. The elastic position and masking matrix were used to avoid semantic confusion and semantic interference in self-attention calculation of pre-trained model. The idea of multi-task learning in fine-tuning was adopted, and the optimization algorithm of recall learning was employed for pre-trained model to balance between general semantic expression and learning of the target task. Finally, a more efficient vector representation was obtained and label prediction was conducted. Experimental results showed that the proposed architecture achieved better results than the mainstream pre-trained models in the medical domain, and had relatively good results in the general domain. The architecture avoided retraining pre-trained models in particular domain and additional coding structures, which greatly reduced computational cost and model size. In addition, according to the ablation experiments, the medical domain was more dependent on the knowledge graph than the general domain, indicating the effectiveness of integrating the knowledge graph method in the medical domain. Parameter analysis proved that the optimization algorithm which used recall learning could effectively control the update of model parameters, so that the model retained more general semantic information and obtained more semantic vector representation. Besides, the experimental analysis showed that the proposed method had better performance in the category with a small number of entities.

Abstract:

Image segmentation is to divide the region with special meanings into several disjoint sub-regions according to certain rules, which is the key link between image processing and image analysis. The traditional watershed image segmentation method is widely used, which has the advantages of fast and simple. However, it is easily interfered by noise, and the segmentation results are prone to lose important edge information, resulting in over-segmentation. In view of the problem of the traditional watershed image segmentation method, an improved watershed image segmentation method based on adaptive structural elements was proposed. First, the adaptive structural elements with variable shapes were constructed by using local density, symmetry, and boundary features of adjacent pixels of image targets, so as to ensure a good consistency between the proposed structural elements and the shape of image targets. Then, the adaptive structural elements were used to obtain the morphological gradient of the image, which could improve the positioning accuracy of the target edge. The L₀ norm gradient minimization and morphological open-close hybrid reconstruction were used to modify the gradient image, so as to reduce the local invalid minimum points in the gradient image and suppress the occurrence of over-segmentation. Finally, watershed segmentation was performed on the modified gradient image to realize accurate segmentation of the target region of the image. Experimental results show that the method could effectively restrain over-segmentation of traditional watershed algorithm and improve the accuracy of the target edge positioning, with high precision of image segmentation.

Abstract:

The development of advanced nano-integrated circuit processes has led to a decreasing threshold charge in microelectronic devices, resulting in an increased rate of soft errors caused by single-event effects in digital circuits. To enhance the radiation resistance of standard cells in integrated circuits, this paper proposes a NAND gate structure that is resistant to single-event transients (SETs). In the triple well process, by shorting the substrate and source of each NMOS transistor in the pull-down network, the radiation resistance of the NAND gate was effectively improved, and the hardening of the proposed NAND gate became more effective as the number of inputs increased. Particle incidence simulation experiments were performed by Sentaurus TCAD software in hybrid simulation mode. For the NMOS transistor connected to the output node, the three-dimensional physical model that has been calibrated by the process was used, and the Spice model provided by the manufacturer was adopted for other MOS transistors. Simulation results show that the proposed two-input NAND in 40 nm process could reduce the output voltage fluctuation amplitude in three-input cases at the linear energy transfer (LET) value of incidence particle of 10 MeV·cm²/mg. Besides, the effect of immunity to single particle incidence was achieved in the input mode with N₂ transistor closed. For the hardened three-input NAND gate, the output voltage disturbance could be reduced by up to 85.4% even in the “worst case”. Therefore, the proposed hardening method for NAND gate has a significant effect against SET.

Abstract:

To study the connection method between reinforced bars of the precast concrete(PC) structure,81 plug-in filling hole for lap-joint of steel bar sample tests were made,and the main factors,such as reinforced bar diameter,concrete strength and anchorage length etc.were considered during the tests.The test results indicated that the ultimate failure state of all the anchoring specimens were the external reinforced bar yielding or broken up by pulling,and the abnormal anchorage was not destroyed.When the basic anchoring length was reduced by 10% or even 20%,specimens still showed enough safety.Based on this,the basic anchoring length of plug-in filling hole for lap-joint of steel bar can be given as 0.8 la.

Abstract:

Due to the complex background of ship targets and much irrelevant interference in visual images, it is difficult to conduct ship detection. In addition, there are few datasets for multi-category ship detection and the samples are often unbalanced, which makes the ship target detection performance degraded. Considering the ship detection background interference, an improved YOLOv3 model was proposed by introducing SimAM attention mechanism, which was used to enhance the weight of the ship target in the extracted features and suppress the weight of background interference, thus improving the model detection performance. Meanwhile, strong real-time data augmentation was applied to improve the unbalanced distribution of sample scales, and transfer learning was combined to improve the ship detection accuracy in the condition of a restricted number of samples. The visualization results of extracted features show that the improved model could suppress irrelevant background features, and the abilities of feature extraction and target localization were enhanced. Without introducing additional learnable parameters, the proposed model achieved 96.93% and 71.49% for mAP.5 and mAP.75 on the SeaShips dataset, and detection speed reached 66 frames per second, indicating a good balance between detection accuracy and efficiency. The improved model optimized the target features more effectively compared with the Saliency-aware CNN and eYOLOv3 models, resulting in an improvement of mAP.5 by 9.53% and 9.19%. The mAP.5 for ship type target detection on Singapore Maritime Dataset reached 81.81%, indicating that the proposed model has good generalization performance.

Abstract:

Carbon dioxide (CO₂) capture, utilization and storage, as an emerging technology that can help reduce coal chemical plant greenhouse gas emission by large scale, have drawn significant attention. Pipeline transportation is an essential part of the technology, but high cost has greatly limited its application. Therefore the main objective is to develop an optimization model for supporting CO₂ pipeline transportation system planning to reduce the overall carbon capture utilization and storage (CCUS) system cost by optimizing key technology process of a CO₂ transportation system. The developed model was further applied to Shaanxi Yanchang's CCUS project for planning its CO₂ transportation system. The results indicated that in case of low demand of CO₂ storage, a gas-phase CO₂ pipeline transportation system coupled with in-situ compression and injection was recommended. In the case of high demand of CO₂ storage, this study would recommend a super-critical / density phase transportation system which could have lower system cost than gas phase pipeline system as the cost for compression at the site of storage can be saved