Abstract:In order to study the evolution of mechanical properties of layered composite rocks with differentconfining pressures, various interfacial dip angles and interfacial spacings, the ZTR -2000 microcomputercontrolled rock triaxial test system was used to carry out experimental research on rock samples under differentconfining pressures. The results show that the axial compressive strength decreases with the increase of theinclination angle of the interface layer, and increases with the increase of the confining pressure. When theconfining pressure is low, the distance between the interface layers can increase the compressive strength. Athigh confining pressure, the distance between the interface layers has little effect on the compressive strength.The elastic modulus of layered composite rock changes regularly with the interval between layers. The failuretype of rock sample is affected by dip angle and interfacial layer spacing.

Abstract:In order to study the mechanical properties of reinforced concrete columns with lithium slag, a numerical simulation of 14 reinforced concrete columns with lithium slag was carried out based on ANSYS finite element software, and the simulation results were compared with the test results.The failure modes, material stressstrain nephogram, ultimate bearing capacity and load-deflection curves were studied.The effects of the content oflithium slag and eccentricity on the mechanical properties of uncorroded components and the effects of acid raincorrosion time and the content of lithium slag on the mechanical properties of corroded components were discussed.The results show that for the non-corroded members, the influence of different lithium slag content on thesmall eccentric members is more obvious, and the influence of different eccentricity on the bearing capacity andstiffness of members is very significant; and in a certain range, the ultimate bearing capacity of the column canbe improved by adding lithium slag. For corroded members, the addition of lithium slag can improve the bearingcapacity and lateral stiffness of the corroded column to a certain extent, and the ultimate bearing capacity of thecolumn decreases with the increase of corrosion time. The addition of lithium slag can delay the influence ofcorrosion time on the bearing capacity to a certain extent.

Abstract:In order to solve the problems of low design efficiency and lack of visual construction caused by manual electrical circuit generation of electrical components in existing three-dimensional building electrical design,a three-dimensional building electrical automatic wiring design scheme based on hybrid particle swarm is proposed. A mathematical model of three-dimensional wiring conforming to standard and national standard is established. Based on objective functions such as the room type, the circuit partitioning strategy is proposed for initializing floor plans. Integrated circuit path length, and the number of elbow and energy constraint are optimizedfor the objective function to calculate the optimum electrical floor room 3D automatic wiring design. Finally, thefeasibility of the design is verified by the simulation results.

Abstract:The horizontal connections of the existing precast hollow slab bridges are prone to hinge joint damagedue to the design, construction, and operation environment. To study the influence of hinge damage on the structural performance, the statistical analysis on three damage types, including damage position, length, and extent,was studied based on the field inspection results of hinge damage of precast hollow slab bridges. Using the grillage method, a series of finite element models of precast hollow slab bridges were established to study and analyze the influence on the structural performance with various damage conditions. The research results show that:① The closer the damage position is to the middle span, the greater the influence on structural forces. ② Withthe increment of damage length, the bending moments of the middle slab increase linearly with the unilateralhinge damage condition under live load. The side slab with unilateral hinge damage and middle slab with bilateralhinge damage will result in the single slab bearing, and the critical damage length is 0.6L and 0.7L respectively.③ The change of slab’s moment and deflection is small when the damage length or depth is small under liveload. And the bending moment and deflection increase greatly under live load when the damage length and depthare both large. ④ Under the single slab bearing condition, the bending bearing capacity of the middle slab ofstandard 20 m length does not meet the code requirements, and neither the bending bearing capacity nor thecrack check meets the code requirements. The research results can give useful suggestions for the safety assessment and maintenance of precast hollow slab bridges with hinge joints damage.

Abstract:Statistical analysis is firstly carried out for the ground conditions and retaining structures for deep excavations of the metro stations of Nanchang Metro Lines 1~4, which splits the River Terraces into two typicalcategories of ground conditions (type Ⅰ and type Ⅱ) with corresponding retaining structures for deep excavations for metro stations. Then taking Nanchang Metro Line 2 Dinggong Road South Station, Line 1 Zhujiang RoadStation and Line 3 Zhenxing Avenue Station as examples, numerical analyses with the small strain stiffnesshardening(HSS) soil model are conducted and the predicted deflection of retaining walls and ground settlementare in agreement with field data. This shows that using HSS soil model and E₅₀^ref=1.5N for sand deformation modulus(N is the corrected count of blow) can well predict the deflection of retaining walls and ground settlement.On this basis, this paper numerically and statistically analyzes the deflection of retaining walls and ground settlement in Nanchang area, and draws conclusions that for the deep excavations of the subway stations in Nan chang typical river terraces, the ratios of the maximum lateral deflection of retaining wall structures and themaximum ground settlement to the excavation depth are δ_h,max/H=0.05%~0.12% and δ_v,max/H=0.03%~0.10%,respectively, and the ratio between the maximum ground settlement and maximum lateral deflection is about δ_v,max/δ_h,max=0.45~1.4.

Abstract:With the growth of machine learning algorithm models and data sets, a single node cannot effectively bear the computing and storage requirements required for large -scale training. A common solution is to run large-scale machine learning algorithms on distributed clusters. However, the performance of distributed clusters is significantly affected by stragglers. In recent studies, researchers have used coding calculations to solve the straggler problem, but the performance of coding calculation schemes for large-scale matrix multiplication has not been fully studied and analyzed. This paper examines the task completion time of the coding calculation scheme for large-scale matrix multiplication, and considers the total calculation overhead of all nodes participating in distributed computing. The expression of the task completion time for each working node to complete the calculation task according with the total time under the uniform distribution scenario and the total computing time of the cluster machines is given. The performance of the three coding schemes is compared and analyzed. The effects of different situations on the task completion time and the total computing cost of the computing node are compared through experiments, and a heuristic algorithm is proposed to provide the basis for the selection of different coding calculation schemes.

Abstract:With the explosive growth of the second generation blockchain platforms and applications, smart contracts as executable code deployed in the blockchain are facing more and more security problems. At present, most of the researches on the security of smart contracts focus on the mining of security vulnerabilities, while insufficient attention has been paid to the impact of the fairness of smart contracts on security. To address this problem, a fairness verification method based on model checking is proposed, which is used to verify the fairness of Puzzle contract, and a known transaction order dependency vulnerability is found. The results show that the proposed method can provide a new idea for verifying the fairness of smart contracts.

Abstract:Traditional prediction model only focuses on time factors. Aiming at that deficiency, a prediction model which introduces weather factor and considers date attribute was proposed. Firstly, the degree of correlation between weather factors and passenger flow was determined by significance test. Then, to gradually screen the low-relevant weather factors, grey relation analysis (GRA) was adopted to calculate the non-linear correlation between various weather factors and passenger flow. After each screening, the bi-directional LSTM neural network was used to forecast and the GRA-BiLSTM prediction model was proposed. The results show that taking weather factors with GRA value less than 0.6 as input will reduce the prediction accuracy. Compared with the traditional LSTM, the prediction error of GRA-BiLSTM，which is obtained by gradually eliminating the weather factors with low correlation, is significantly reduced on both work days， and non_work days and the convergence speed and robustness are better than the traditional machine learning as well.

Abstract:To ensure the safety and efficiency in high-speed trains’ operation, this paper develops a new multiple-model based fault diagnosis and adjustment scheme for high-speed trains. Such a scheme has capacity of diagnosis for failure modes and values and can track a given speed curve asymptotically. Common faults of traction motors are firstly analyzed; a failure mode set is established; and the parameterized model of each failure mode is obtained. An adaptive estimator is then designed based on the parameterized model of each failure mode to obtain an estimator set, and performance functions based on the estimation error are designed to achieve fault diagnosis for high-speed trains with unknown traction motor failures. An adaptive fault adjustment controller is finally designed according to the information of the diagnosed fault to ensure the stability of the system and the asymptotic tracking of the given speed curve. Simulation results show that the proposed high-speed train adaptive fault diagnosis and adjustment strategy can effectively diagnose and compensate unknown traction faults.

Abstract:The working path of the palletizing robot was expounded, and the forward and inverse kinematics solutions were carried out according to the D-H parameters and the coordinate transformation diagram of each joint of the robot. Trajectory planning in joint space and Cartesian space for robot palletizing task was conducted by MATLAB. Considering the requirements of pulsation continuity and reducing computation, POS optimization algorithm was applied to solve the optimal time of polynomial trajectory of 3-5-3 times for a stacking cycle of a stacking robot under the condition of maximum speed constraint, which solved the problems of high order of polynomial trajectory planning, large computation and lack of convex hull.

Abstract:Cermet has the characteristics of metal and ceramics, and the advantages of high strength and good toughness. It is one of the research hotspots in the field of materials. In this paper, FeCoCrNiAl high-entropy alloy powder and Al2O3 ceramic powder are used as raw materials, and non-toxic water-soluble epoxy resin is used as a binder. An orthogonal test scheme is designed using gel injection molding process to prepare FeCoCrNiAl/ Al2O3 cermet. The effects of epoxy resin addition, powder solid content, dispersant addition and powder composition on the shrinkage, density and flexural strength of FeCoCrNiAl/Al2O3 cermet body are discussed. The results show that the order of the effects of various factors on the overall performance of the body are powder solid content＞ dispersant＞ powder component＞ epoxy resin addition. Among them, the powder solid content has the greatest effect on the performance of the body, and with its increase, the shrinkage rate of the green body gradually decreases, the bending strength gradually increases, and the density first increases and then decreases. The FeCoCrNiAl/Al2O3 cermet prepared by the gel injection molding method has a uniform composition, and the fracture exhibits typical brittle fracture characteristics.

Abstract:Rail milling is an effective way to repair rail profile and eliminate rail surface damage. The repairment of rail profile through milling is realized by arranging the cutter grains on the facing cutter according to target rail profile, and then driving the rail milling train to mill longitudinally along rail surface. The profile of rail milling depends on the arrangement and layout of the cutter grains. The characteristics of facing cutter and its combination of cutter grains are restored using 3D scanning technology based on reverse engineering; The layout of cutter grains is adjusted according to the designed 60D rail profile and its fitting degree is verified. Finally, the field test of the designed 60D profile facing cutter shows that the single milling amount is about 1 mm in the range of -10°~+10° at the top of the rail head, and the milling error is less than 0.3 mm.

Abstract:In view of the shortcomings of traditional LSD line detection algorithm, such as the tendency to lose details and discontinuity of line extraction, this paper presents an LSD line detection algorithm based on bilateral filter proposed to improve Canny edge image extraction. The Canny algorithm was used to extract the edge image, based on which LSD line detection algorithm is used to extract the line. For the Canny edge detection using gaussian filtering, the image edge will be blurred while reducing the noise. The bilateral filtering has a better protection effect on the edge of the image. Therefore, the algorithm adopts bilateral filtering instead of Gaussian filtering in the Canny edge detection to extract the edge image. At the same time, the LSD line detection algorithm based on bilateral filter to improve Canny edge image extraction was applied to the rail surface boundary extraction. The results show that LSD linear extraction algorithm based on Canny edge detection and edge image extraction based on bilateral filtering was better for the linear extraction of rail surface boundary. The relevant evaluation indexes have been greatly improved and the peak signal-to-noise ratio of the experimental images increased by 6.49% and 13.58% respectively. It lays a foundation for the subsequent identification of rail surface defects and has certain practical value.

Abstract:Numerical simulation technology was used to study the filling stage of gas -water -assisted injection molding (GWAIM) process which is an innovative technology. The numerical simulation model of the filling process was established. The Cross-WLF viscosity model was used and the volume of fluid was adopted to track the free interfaces. The penetration process, temperature evolution, the effects of process parameters on the residual wall thickness of the GWAIM process and process optimization were systematically studied. The results showed that the residual wall thickness was uniform and the fluctuation range was small, and the temperature difference between the parts before gas injection and after water injection was large. The residual wall thickness tended to increase with the increase of gas injection delay time. The residual wall thickness of the product increased slightly and tended to be stable with the increase of water injection delay time. With the increase of gas injection speed and mold temperature, the residual wall thickness became smaller. With the increase of water injection velocity and melt injection temperature, the residual wall thickness of the parts decreased in a small range.Through orthogonal experimental range analysis, it is concluded that the gas injection delay time is the most important factor affecting the residual wall thickness of the parts, and the optimal combination of process parameters is gas injection delay time of 3 s, water injection delay time of 3 s, gas injection speed of 3 m/s, water injection speed of 2 m/s, mold temperature of 320 K and melt injection temperature of 503 K.

Abstract:Shore-to-ship transformer is an important power equipment in the port shore-to-ship power supply system, compared with the influence of the traditional transformer magnetizing inrush current, the magnetizing inrush current of ship transformer will not only cause the transformer's own relay protection device to malfunction, but also cause overcurrent trip of the frequency conversion power and misoperation of shore power system's own protection. In order to study the influencing factors of inrush current and its suppression methods in shore power system, the mathematical analytical expressions of the magnetizing inrush current when the secondary side of the ship transformer is Y and △ are deduced in detail. Based on this, a ship transformer simulation platform is built in PSCAD/EMTDC，the influence of variable factors such as core remanence and resistance on the dynamic characteristics of magnetizing inrush current is deeply studied, and the corresponding suggestions are given to suppress the magnetizing inrush current. Simulation model is combined with actual parameters of ship transformer, and the correctness of the theoretical analysis is verified, which provides a theoretical basis for solving problems in practical engineering.

Abstract:In this paper, MoS₂ nanosheets were successfully prepared using liquid phase ice-bath ultra-sonication method. The morphologies, microstructures and thickness of MoS₂ nanosheets were characterized by using SEM, TEM and AFM. The SEM and TEM analysis exhibited that MoS₂ powders were successfully exfoliated into MoS₂ nanosheets. AFM analysis showed that the thickness of MoS₂ nanosheets was the monolayer nanosheets. The tribological results showed that MoS₂ nanosheets were conducive to reducing the friction coefficient under high load and rotational speed, and the friction coefficient was about 0.09. The morphology and composition of the worn surface was examined and analyzed using SEM, and MoS₂ nanosheets could effectively reduce the wear for tribosystem. The investigation could provide the guidance for preparing the MoS₂ nanosheets with superior tribological performance.

Abstract:Based on the theory of conditional value-at-risk, the study proposes a quantitative method to measure the risk of power deviation of wind integrated power system, introduces the concept of source network coordinated optimal operation in the scheduling process, and constructs an optimal scheduling model based on the theory of Conditional Value-at-Risk and source network coordinated operation. Multi-objective compound backtracking search (MOCBS) algorithm is used to solve the optimal scheduling model efficiently and accurately. Final ly, IEEE30 nodes is taken as an example to verify the model. The results show that the proposed model can effectively measure the potential risks of system operation and verify the superior performance of MOCBS algorithm.

Abstract:In this study, through the soil-water characteristic curve model, evaporation rate-matric suction model and moisture content-evaporation rate model, the evaporation model of tailings cemented paste was established to determine the moisture content of tailings cemented paste at different ages. According to research findings, while the concentration of tailings cemented paste is 65%, different types of tailings have little difference in change of moisture content for 1 d and 3 d, because the initial water content is higher. Tailings cemented paste with more clay content have higher moisture content for 7 d. While the concentration of tailings cemented paste is 72%, the moisture content is obviously affected by the clay content. High clay content means high clay particles, and moisture content in the tailings cemented paste is higher, which is because clay minerals reduce evaporation in the tailings cemented paste.

Abstract:The goal of association rule mining is to discover the association or correlation between data item sets, which is an important topic in data mining. For very large data sets, traditional algorithms are inefficient. This paper improves them and gives an association rule mining algorithm based on graph theory and maximum path. The algorithm first constructs the transaction sets into a Boolean matrix. After the matrix is cleaned, the transaction set is converted into the form of a graph, and then an adjacency matrix is generated according to the association rule graph. When the step size is k and k＞2, traverse from the first non-zero element by line to find the path with the largest weight, and the row and column index of the connected elements is the frequent k+2 item set. Experimental results show that the algorithm firstly reduces the number of scans of the data set. Secondly, for large data sets, compared with the traditional Apriori algorithm, it can significantly shorten the time and greatly improve the efficiency.