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28 August 2023, Volume 49 Issue 4 Previous Issue    Next Issue

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Materials Science and Engineering

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Hot salt corrosion behavior of TiAlN/Cr、TiAlN/CrN and TiAlN/CrAlN multilayer coatings HE Ze-nian, WANG Shun-hua, PU Ji-bin 2023, 49 (4):  1-10.  Abstract ( 219 )   PDF (10106KB) ( 216 )   Save The hot salt corrosion of titanium alloys has attracted extensive attention. Metal nitride protective coating is an effective way to extend the service life of titanium alloys. In this study, the TiAlN/Cr coating, TiAlN/CrN coating, TiAlN/CrAlN-5 coating and TiAlN/CrAlN-10 coating were deposited on titanium alloy surface by Multi-arc Ion Plating technology. The differences in hot salt corrosion behavior of four kinds of multilayer coatings were compared by Scanning Electron Microscope (SEM), Energy Dispersion analyzer (EDS), X-ray diffractometer (XRD), Scratch tester and 3D Laser Microscope. Meanwhile, the microstructure and phase composition of the coatings were analyzed before and after hot salt corrosion. The results indicated that the addition of Al element and the optimization of modulation period can improve the surface quality of the coating. Among them, TiAlN/CrAlN-10 multilayer coating shows excellent heat resistance to salt corrosion due to its high interface density. References | Related Articles | Metrics

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The influences of trace Fe,Ni and Ti complex addition on the microstructure and mechanical properties of Al-20Si alloy ZHANG Jie, ZHANG Yu, WANG Ping-bo, WANG Kai-long LAN Ye-feng, LI Qing-lin 2023, 49 (4):  11-16.  Abstract ( 132 )   PDF (4754KB) ( 132 )   Save The elementsFe, Ni and Ti were added in the form of AlFeNiTi master alloy (atomic ratio 1∶1∶1∶1), which were fused by vacuum arc melting furnace, andthe influence of the addition amounts of the master alloy (0.5%,1.0%,1.5%,2.0%,2.5%, mass fraction) on Si phase, α-Al and mechanical properties of Al-20Si alloy were studied. The results showed that when the addition concentration of AlFeNiTi master alloy is 2.0%, the morphology of primary Si is transferred from coarse irregular block and five folds to fine and regular block and its average size is reduced from 91 μmto 40 μm by 56.1%. The eutectic Si is modified from coarse needle/flake-like morphology to the edge passivation and fine granular shape. Moreover, the primary α-Al is refined from coarse dendrites to fine rosette-like structure and the secondary arm dendrites spacing is significantly decreased, and the ultimate tensile strength(UTS)is increased by 41.1% from 129 MPa to 182 MPa, and the elongation(EL) isenhanced by 78.7% from 0.8% to 1.43%. References | Related Articles | Metrics

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Effect of WC content on microstructure and fribological properties of directional Ni60 coating YIN Xiang, MA Cheng-yan, ZHOU Kai, WANG Xin-min, WANG Yi, WEI Heng-li 2023, 49 (4):  17-23.  Abstract ( 120 )   PDF (6079KB) ( 140 )   Save Ni60/WC directional coatings were prepared on 45 steel substrate by flame spraying and induction remelting + forced cooling. The effects of WC mass-fraction(5%, 20%, 35%, 50%) were investigated on microstructure, hardness and tribological properties of directional coatings. The results showed that the dendrites near the interface of the directional coating show a trend of combined preferential growth with the increase of WC mass-fraction. All kinds of hard phases in the directional coating are evenly distributed in the grain boundaries, which plays a role in strengthening the grain boundaries. The hardness of coating showed a positive correlation with the WC mass-fraction,and friction coefficient and wear rate of directional structure coating first decrease and then increase with the increase of WC mass-fraction. References | Related Articles | Metrics

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Modeling and experimental of hammering force of electromagnetic drive based on aluminum alloy CUI Shuai-hua, LIN Xiao-hui, ZHU Si-jie, CAI Wei-huang, SUN Yu-qi 2023, 49 (4):  24-29.  Abstract ( 84 )   PDF (2895KB) ( 65 )   Save A mathematical model for predicting the mechanical hammering force on the surface deformation of a workpiece was developed using 6061 aluminum alloy as the research object. LS-Dyna finite element analysis was performed on the model, and a mechanical hammering device consisting of an industrial robot and a voice coil motor was built to investigate the effect of hammering force on the surface deformation and hardness of the workpiece, and then the theoretical model was verified and modified. The results showed that the surface deformation of the workpiece increases with the increase of hammering force, and the FEM simulation results are similar to the prediction results of the mathematical model with an average error of 9.05%; further analysis of the experimental results of single-point hammering shows that the correction coefficient of the hammering model is 0.7. Meanwhile, the surface hardness is the higher when the hammering force is the larger, and the surface hardness of the workpiece increases by 90.45% when the hammering force is 69 N. References | Related Articles | Metrics

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Effect of rolling on microstructure of 7050 aluminum alloy FSW joint JIN Yu-hua, ZHOU Zi-zheng, XING Yi-chu, WU Bo 2023, 49 (4):  30-34.  Abstract ( 72 )   PDF (4098KB) ( 67 )   Save The 5 mm-thick joint of 7050 aluminum alloy friction stir welding was rolled by self-made rolling tool on the surface, and the surface roughness, deformation degree and microstructure evolution of the joints before and after rolling were analyzed. The results showed that the surface roughness of the joint is improved after rolling, and Ra decreases from 7.45 μm as-welded to 6.82 μm. The depth direction of the joint is divided into three layers from the surface down, which are the deformation layer, transition layer and microplastic deformation layer. The deformation layer is the microregion with the most significant strain, the strain of which shows the gradient distribution. The surface deformation is the largest and decreases with increasing depth from the joint surface. The deformed layer undergoes maximum deformation as a result of which the original isoaxial grain in the nugget zone is deformed and refined, forming nanostructures of varying thickness within a certain depth from the joint surface. References | Related Articles | Metrics

Mechanical Engineering and Power Engineering

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Research on rotor fault feature extraction method based on GSRDPGE algorithm ZHOU Hong-fei, ZHAO Rong-zhen 2023, 49 (4):  35-41.  Abstract ( 78 )   PDF (3160KB) ( 125 )   Save Aiming at the difficulty of fault classification caused by high dimension and information redundancy of rotating machinery fault data set, the Group Sparsity Discriminant Preserving Graph Embedding (GSRDPGE) algorithm is proposed to reduce data dimension effectively. First, the algorithm improved the inter-class sparse coding and obtained a more discriminant inter-class sparse weight matrix. Then, the influence of outliers in feature sets on sparse coding was removed by the weighting method. Finally, the optimal discriminant projection matrix was calculated with the objective of minimizing the intra-class reconstruction divergence and maximizing the inter-class reconstruction divergence. The proposed method was validated with an Iris simulation data set and double span rotor system fault data set, and compared with several other typical dimension reduction methods. The results show that this method can simultaneously take into account the global and local aspects of the data distribution status, make the differences between fault categories more prominent, and improve the accuracy of fault pattern recognition. The results show that this method can provide a reference for intelligent rotor fault diagnosis. References | Related Articles | Metrics

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Thermodynamic characteristics of heat pump scroll compressor PENG Bin, ZHOU Tian-hao, LIU Hui-xin, LIU Shuai, YANG Bao-kun, HE Ji-xiang 2023, 49 (4):  42-48.  Abstract ( 99 )   PDF (3458KB) ( 184 )   Save Based on the geometric parameters of heat pump scroll compressor, first law of thermodynamics, the laws of conservation of mass and energy and so on, the geometric model and thermodynamic model of the heat pump scroll compressor were established in this paper, and the method of Euler was used to solve this model, then the changing trend of temperature, pressure and mass of working fluid in the working chamber of compressor were obtained. The leakage changing law of the heat pump scroll compressor under different working conditions was analyzed. Finally, the established thermodynamic model was verified by building a test platform. The results show that the suction pressure and temperature have the greatest influence on the compression chamber. When the suction pressure decreases by 0.1 MPa, the leakage of the third compression chamber decreases by 9.45%. When the suction temperature decreases by 5 ℃, the leakage of the third compression chamber decreases by 6.841%. While the influence of speed change on the leakage of each working chamber of scroll compressor is average, and the experiment values are close to the simulation values, which verifies the correctness of the model. The research in this paper provides a some theoretical reference for the performance optimization of the scroll compressor of heat pumps. References | Related Articles | Metrics

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Research on output power modeling method of large wind turbine ZHANG Yan, MA Zhuang, DONG Bo, ZHENG Yu-qiao 2023, 49 (4):  49-53.  Abstract ( 93 )   PDF (2650KB) ( 258 )   Save The variation characteristics of input wind speed directly affect the output power modeling of wind turbine. In this paper, nonlinear least square method and differential evolution algorithm are used to calculate parameters, and Logistic function is used to model the output power of wind turbine, combined with the high accuracy of heuristic algorithms in finding the optimal construction. Then, the modeling accuracy of the three methods for output power model is compared. The results show that the nonlinear least squares method is more suitable for the calculation of the proposed model parameters. The high accuracy of the traditional output power model is derived from the artificially defined rated power value in the model, while the Logistic function output power model does not need to artificially define the rated power value, the modeling accuracy of which is better under the same conditions. References | Related Articles | Metrics

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3D design system of axial flow pump impeller based on OpenCASCADE GU Ming-lei, LIU Hou-lin 2023, 49 (4):  54-60.  Abstract ( 92 )   PDF (4851KB) ( 141 )   Save At present, pump design systems generally rely on the secondary development of commercial CAD software, which is easily restricted. Therefore, a three-dimensional design system of axial flow pump impeller with independent intellectual property rights is developed based on related modeling functions of OpenCASCADE and the human-computer interaction interface constructed by Qt. Designers only need to input the design parameters of the axial flow pump to get the appropriate geometric shape of the axial flow pump impeller. An axial flow pump impeller with the specific speed of 869 was designed and verified by flow field simulation. Compared with the design result of CFturbo software, the results show that there is no software environment restriction in the system and the design steps are more suitable with the domestic design habits, which can meet the design requirements of head and efficiency, and provide a reference for parametric design of other types pump. References | Related Articles | Metrics

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Analysis of flow characteristics and structure optimization of marine flange cast steel globe valve JIN Wei-zeng, ZHANG Li, ZHANG Xi-heng 2023, 49 (4):  61-67.  Abstract ( 84 )   PDF (3634KB) ( 143 )   Save Taking DN65 marine flange cast steel bellows globe valve as an example, the finite element analysis of the flow resistance coefficient in the fully open state was carried out using Flow-Simulation software, and the flow resistance coefficient and flow coefficient were then calculated, followed by the experimental verification according to the GB/T30832 standard. The results show that the two results are consistent, demonstrating the accuracy of the numerical simulation and the method. According to the flow chart, it is found that the body of the valve is the key factor affecting the flow resistance coefficient and flow coefficient. Then, the effect of the body flow structure on the medium flow was analyzed. Meanwhile, remaining the length of the valve body structure was unchanged, the structure of the valve port was optimized, and the pressure loss on both ends was reduced, which in turn greatly reduce the cut-off valve flow resistance coefficient of the marine flange cast steel corrugated pipe, and improve its flow capacity. Finally, further verification was performed by the experimental method, which is of great significance to the optimization design of the valve, especially for straight-through globe valves. References | Related Articles | Metrics

Chemical Industry and Light Industry

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Performance analysis of stepped convergent groove mechanical seal based on cavitation model ZHANG Wei-zheng, HONG Hai-min 2023, 49 (4):  68-73.  Abstract ( 72 )   PDF (2750KB) ( 67 )   Save In order to solve the problem of precision machining of the mechanical seal of the wave face, a step-convergent mechanical seal structure derived from the change of the wave degree seal is proposed, and its sealing performance is parametrically analyzed by CFD numerical simulation with consideration of liquid film cavitation effect. The results show that with the increase of trough depth, number of slots, slot opening, and sealing pressure, the bearing capacity and leakage of liquid film increase. With the increase of the speed, the bearing capacity increases and the leakage amount decreases; as the thickness of the film increases, the bearing capacity decreases, and the amount of leakage increases. Under the working conditions of small film thickness, high speed, and low sealing pressure, it is easier to produce liquid film cavitation and reduce fluid leakage. Smaller trough depth will enhance the shear of the fluid, the cavitation effect will be enhanced, and the leakage amount will be reduced, so as to achieve the purpose of reducing leakage. References | Related Articles | Metrics

Automation Technique and Computer Technology

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Observer-based output feedback control of cyber-physical systems under cyber attacks ZHU Chao-qun, JIA Xuan 2023, 49 (4):  74-81.  Abstract ( 90 )   PDF (1337KB) ( 87 )   Save An observer-based output feedback control strategy is investigated for security control problem of cyber-physical systems (CPS) subject to false data injection (FDI) attacks and packet dropouts. Firstly, the closed-loop Markov jump system model with FDI attacks, packet dropouts and external disturbance is established by considering the effects of FDI attacks and the case of packet dropouts. Then, the sufficient conditions for the closed-loop system to be stochastic stability are conducted by utilizing the Lyapunov theory, the stochastic analysis technology and linear matrix inequality approach, and the observer-based output feedback controller is derived with the prescribedH∞ performance. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed method. References | Related Articles | Metrics

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Control research on T-type grid-connected converter based on sliding mode predictive JIANG Ya-fei, ZHAO Gang 2023, 49 (4):  82-87.  Abstract ( 50 )   PDF (3703KB) ( 49 )   Save Model predictive control (MPC) has been widely used in grid-connected converter control systems with the advantages, such as easy implantation and multi-target tracking. However, the unfixed switching state of the traditional model predictive control algorithm will reduce the accuracy of current tracking and even produce large current ripple. Therefore, a double closed loop control method based on model predictive direct power fixed frequency control (DPCMPC) and sliding mode control (SMC) is proposed. The SMC outer ring is used to obtain a given value of the active power of the system, and the steady-state performance of the system is improved by introducing a zero voltage vector and the power ripple is reduced. In order to verify the theoretical analysis, a complete simulation and experimental test model was constructed, and the results show that the proposed control method has good steady-state and dynamic performance. References | Related Articles | Metrics

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Research on the blockchain-based secure management system for socialized examination results YUAN Xiao-peng, MIAO Si-rui, MA Rong, FENG Tao, FANG Jun-li 2023, 49 (4):  88-94.  Abstract ( 104 )   PDF (589KB) ( 163 )   Save Most of the current results information of secure results management system is managed through centralized servers, and the data storage is highly bound to the management database at all levels, which easily leads to problems such as data leakage and tampering, and is also impossible to effectively monitor the operation of the relevant personnel. With the development of blockchain technology, its decentralization and other features are gradually attracting attention. In this paper, a blockchain-based security management system for socialized examination results is proposed. The system uses homomorphic encryption to encrypt the result data and then store it in IPFS through a P2P network and blockchain technology. The keywords are sent to the blockchain after homomorphic encryption when the data is queried, and the ciphertext data is retrieved, followed by the query results returned to the user. The authenticity and validity of the data information in the result management system can be guaranteed by P2P network and blockchain technology, thus a safe and reliable system is achieved to ensure the fairness and impartiality of socialized examinations. References | Related Articles | Metrics

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Decentralized blockchain transaction scheme based on digital commitment LI Yang, WAN Hong-yu, ZHU Jian-ming, WANG Xiu-li, WANG You-wei 2023, 49 (4):  95-101.  Abstract ( 54 )   PDF (589KB) ( 141 )   Save As a security transaction framework based on information transaction between blocks, blockchain has a high degree of transparency and decentralization. Zhang Xiaoyan et al. proposed a transaction framework which combines digital commitment and cryptographic algorithm, which can hide the transaction amount during transaction process. However, there are two problems should be considered. First, the recording of the transaction process is operated by trusted full-functional accounting nodes, making the process not decentralized for the blockchain. Secondly, there is also a risk of data leakage during transaction process as the transaction amounts and correlation parameters are required to be transmitted multiple times. In order to solve the above problems, this paper proposes a multi-key homomorphic encryption transaction scheme based on digital commitment with every node records transaction data. The transaction amount hidden in the commitment can be directly updated in the encrypted state, and correlation parameters do not need to be transmitted multiple times. The transaction scheme proposed in this paper has higher efficiency and provable security, which provides a novel idea for the security transaction framework in the blockchain. References | Related Articles | Metrics

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IPv6 address alive prediction based on generative adversarial network CHEN Yong-qun, CHEN Yu-cheng, HU Hua-miao, DAI Jia-hao KANG Ying-yun, WANG Wei 2023, 49 (4):  102-107.  Abstract ( 75 )   PDF (1968KB) ( 86 )   Save It is difficult to detect the whole IPv6 deployment because of the massive address space. Based on the IPv6 unicast address structure, hitlist mechanism is adopted to solve this problem. First, the IPv6 addresses from public ipv6 address data sources are collected, cleaned and stored in the database according to structure of the original IPv6 address set. After that, the dependency between the stable and unstable segments of the address set is studied. An IPv6 address survivability prediction model based on the generation adversarial network are proposed. By considering the discrete nature of IPv6 addresses structure, deterministic binomial neurons and random binomial neurons are designed, and Sigmoid is used to adjust the pass-through estimator to solve the problem of high computational complexity of the back propagation of binomial neurons. The IPv6 address set is trained in each specific AS domain, and the obtained generator is used as an IPv6 address survivability prediction model to generate an IPv6 address hitlist. Experimental analysis results and internet probe results show that the proposed model can effectively generate new IPv6 addresses, and the probability of getting an ICMPv6 response in actual detection is higher than that of sequential or random scans. The survival rates have great difference from 0 to 61%. References | Related Articles | Metrics

Architectural Sciences

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Study on the calculation method of impact resistance of double-skin steel-concrete composite wall SUN Ji-hong, AN Guo-qing, WANG Rui 2023, 49 (4):  108-116.  Abstract ( 86 )   PDF (6805KB) ( 154 )   Save In order to study the impact resistance of double-skin steel-concrete composite (SC) wall, the numerical model under coupled axial and impact loads was established using ABAQUS software. The accuracy of the finite element modeling was validated against the test results of SC members under drop-hammer impact. Firstly, the impact-resistance mechanism of SC wall was analyzed. Then, the influences of the steel plate ratio, axial-load ratio and other parameters on dynamic responses were investigated. Finally, a simplified equation was developed to predict the maximum mid-span deflection of axial-loaded SC wall under impact load. The results show that: the whole impact process can be divided into four phases, the sandwiched concrete is the main energy-dissipation component during impact; ratio of axial compression stress to strength would weaken the impact resistance of test specimen, and the effect is more obvious when the ratio of axial compression stress to strength exceeds 0.2; steel content of steel plate, impact velocity, impact mass and spacing of tension bars have significant influences on the impact resistance; the empirical formula suggested can well predict the maximum mid-span deformation of axial-loaded SC wall under an impact load. References | Related Articles | Metrics

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Seismic response analysis of subway tunnel in liquefiable soil layer considering soil spatial variability YAO Fang-zheng, LIU Bo-cheng, CI Wei, YANG Shang-chuan, LI Rui 2023, 49 (4):  117-121.  Abstract ( 59 )   PDF (2953KB) ( 108 )   Save The seismic response of subway tunnels is studied by introducing random field theory and considering the spatial variability of soil mechanics parameters. Based on FLAC3D finite difference software, the numerical model of a subway tunnel with liquefiable soil layer below was established. It is found that under the assumption of homogeneous soil the deformation of the tunnel is quite different from that of the arch and the arch waist, and the overall displacement of the tunnel occurs in the horizontal direction. While the seismic response of tunnel considering the spatial variability is much larger than that of the above deterministic calculation which shows that the traditional assumption of homogeneous soil overestimates the safety of the tunnel under earthquake. References | Related Articles | Metrics

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Stress calculation of spherical hinge contact surface in swivel system of long-span bridge LI Tian-ping, LI Wen-zhou 2023, 49 (4):  122-128.  Abstract ( 108 )   PDF (4473KB) ( 222 )   Save In order to study the contact problem of the spherical hinge contact surface under normal load during the rotation construction of large span bridges, the rotation contact surface was simplified based on Hertz theory. First, the mechanical characteristics of the spherical hinge were systematically analyzed, and the contact characteristics of the micro convex bodies between the rotation contact surfaces were studied. The calculation formula for the internal stress of the rotating contact surface was then derived, followed by the analysis of the stress distribution in the rotating contact surface, and the description of the stress distribution characteristics of the rotating contact surface. Afterward, the contact stress was calculated by extending a single pair of micro convex bodies to the contact surface of the rotating body. The results show that at the contact interface, the radial stress increases with the increase of the distance from the center of the spherical joint, and the compressive stress of the upper and lower spherical joints presents the characteristics of small middle edges and large edges. Finally, the theoretical model was compared with the numerical simulation results, and the theoretical results are in good agreement with the numerical simulation results (error<5%), which provides theoretical guidance for the designation and manufacturation of spherical joints, improving the safety of swivel construction, and promoting the further development of swivel construction technology towards large span diameter and large tonnage. References | Related Articles | Metrics

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Experimental study of MMC model parameters in numerical analysis of foundation pit excavation HU Jian-lin, SUN Li-cheng, CUI Hong-huan, GAO Peng-fei, YANG Jian 2023, 49 (4):  129-136.  Abstract ( 107 )   PDF (4042KB) ( 157 )   Save In order to get accurate numerical simulation parameters of the modified Mohr coulomb model, based on a deep foundation pit engineering example, each soil layer of soil samples of a deep foundation pit was taken to carry out the triaxial shear test, unloaded-load test again and consolidation test, respectively, under different confining pressure. The secant modulus and unloading elastic modulus were obtained from the stress-strain relation curve, following the comparison between the model parameters and compression modulus. It can be concluded that:under different confining pressures, the silty soil in the test is softened. Under the confining pressure of 200 kPa, there was no peak point in the effective deviation-strain curve of fine sand, showing hardening failure. Before the soil is damaged, the stress-strain curve form of the soil is hardly affected by the process of unloading and reloading, with nearly the same unloading and reloading modulus before and after the obtained deviant stress peak point. The tangent modulus, secant modulus, and compression modulus of the test silty soil are approximately equal. With the increase of the reference stress, the ratio of the unloading modulus to the compression modulus increases in a quadratic function. The accuracy of the parameters is verified by numerical simulation, so experimental research is an important way of parametric precision. References | Related Articles | Metrics

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Study on the wallboard diaphragm wall for foundation pit support ZHENG Xiao-jing, ZHU Sheng-xiang 2023, 49 (4):  137-145.  Abstract ( 111 )   PDF (6939KB) ( 178 )   Save With the rapid development of urbanization, the shortcomings of traditional diaphragm wall for deep foundation pit support are gradually emerging. A new supporting structure of wallboard diaphragm wall was proposed, and its structure and working mechanism were expounded. The finite element software MIDAS/GTS was used to study the mechanical characteristics, deformation behavior and the influence of surrounding soil displacement of the new structure during the excavation of foundation pit. The results show that the wallboard diaphragm wall redistributes the internal force by adjusting the thickness and reducing the depth of some walls entering the soil. The main wall and milling plate work in coordination, and the structure is more reasonable. The thickness and spacing of the main wall of this new type of support structure are important factors that affect its stress and displacement, and should be taken seriously in design. References | Related Articles | Metrics

Scientific

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GV-Noetherian rings and their weak GV-injective modules ZHANG Xiao-lei, QI Wei 2023, 49 (4):  146-150.  Abstract ( 418 )   PDF (548KB) ( 284 )   Save The Cartan-Eilenberg-Bass Theorem for GV-Noetherian rings is given. The class of weak GV-injective modules is introduced to characterize DW-rings and von Neumann regular rings. In particular, it is proved that the ring is von Neumann regular if and only if any weak GV-injective module is an absolutely pure module, and if and only if any weak GV-injective module is coflat. Finally, the Megibben Theorem for GV-Noetherian rings is obtained. Meanwhile, some examples are provided to distinguish Noetherian rings, GV-Noetherian rings, and w-Noetherian rings. References | Related Articles | Metrics

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A new regularization method for the Cauchy problem of the Helmholtz equation with Neumann boundary conditions YU Ya-hui, LI Zhen-ping 2023, 49 (4):  151-156.  Abstract ( 92 )   PDF (483KB) ( 144 )   Save A Cauchy problem for the Helmholtz equation with Neumann boundary conditions in a rectangle domain is discussed in this paper. This problem is a serious ill-posed inverse problem of partial differential equations, that is, the solution does not depend continuously on the input data. Based on the classical Tikhonov regularization method using the idea of modifying the kernel function by self-designed filters subsets, a new regularization method is presented for approximating the solution to this problem based on themethod of separating variables. After performing error analysis on the exact and approximate solutions under both a priori and a posteriori selection rules of the regularization parameters, the Hlder-type error estimates satisfying convergence and stability are obtained. References | Related Articles | Metrics

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Criteria for generalized strictly diagonally dominant matrices ZHANG Jin-song 2023, 49 (4):  157-161.  Abstract ( 129 )   PDF (471KB) ( 124 )   Save By using the elements of each matrix itself only, some improved criteria for generalized strictly diagonally dominant matrices are obtained, which enlarge the identification range. Numerical examples are presented. References | Related Articles | Metrics

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Boundedness of fractional maximal commutators with variable kernels on variable exponent morrey spaces YANG Xu-sheng, WANG Su-ping 2023, 49 (4):  162-165.  Abstract ( 74 )   PDF (480KB) ( 132 )   Save By using the properties of kernel function Ω(x,z), it is proved that the commutators ΜΩ,α,b generated by the fractional Maximal operator with variable kernel ΜΩ,α and Lipschitz function b is a bounded operator on variable exponent Morrey spaceMp(·),u(Rn), which generalizes the previous results related to non-variable kernels. References | Related Articles | Metrics

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Free vibration analysis of functionally graded grapheme-reinforced composite thick plates with simply supported on four sides LEI Fang-ming 2023, 49 (4):  166-172.  Abstract ( 101 )   PDF (1879KB) ( 183 )   Save The vibration characteristic of four-edge simply supported functionally graded graphene reinforced thick plates is investigated by using the quasi-3D plate theory. The main properties of FG-GRC thick plates are calculated for different distributions within the improved Halpin-Tsai model. The governing equations are proposed according to the Hamilton’s principle, and the solutions were obtained by using the Navier’s method. Some parameters are adjusted to clarify the effects of the weight fraction of graphene nanosheets (GPLs), the total number of layers of FG-GRC plate, the distribution pattern of GPLs, and the aspect ratio on the natural frequency of free vibration. The quasi-3D plate theory takes into account the effect of thickness stretching, therefore, it is more accurate than the classical plate theory, first-order plate theory, and Reddy third-order plate theory in the calculation of thick plate. References | Related Articles | Metrics