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28 June 2021, Volume 47 Issue 3 Previous Issue    Next Issue

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Materials Science and Engineering

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Investigated on hot compression behavior and constitutive analysis of pure nickel and GH3625 alloy LIU De-xue, QUAN Zhao-dong, LI Liang, ZHANG Xiao, JIA Zhi 2021, 47 (3):  1-9.  Abstract ( 316 )   PDF (3592KB) ( 333 )   Save Hot compression deformation experiment of pure nickle and GH3625 alloy were conducted on a Gleeble-3500 thermomechanical simulator at a 900 to 1 200 ℃, a deformation rate range of 0.1~10 s－1 and a deformation of 60%. The constitutive equation of pure nickel and GH3625 alloy were constructed. The processing map which under different deformation parameters were drawn and the microstructure characteristics of the stable and unstable regions of the processing map were analyzed. During the hot compression deformation of pure nickel, it was found that the grain appears to hierarchical differentiation. According to the analysis of the process map, the optimum hot deformation temperature of pure nickel is1 050 ℃, the strain rate is 0.1 s－1, the optimum deformation temperature of Inconel alloy is about 1 170 ℃, the strain rate is 0.1 s－1. References | Related Articles | Metrics

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Characterization of Fe-Cr alloy powder prepared by close-coupled vacuum induction melting gas atomization YIN Yan, DONG Kai-ji, LI Zhi-heng, BO Yao, LU Chao, ZHANG Rui-hua 2021, 47 (3):  10-14.  Abstract ( 207 )   PDF (2602KB) ( 322 )   Save Fe-Cr alloy powders were prepared by close-coupled vacuum induction melting gas atomization and shifted through different mesh sizes to obtain powders with four particle size segments of 0-25 μm、25-53 μm、53-105 μm and 105-150 μm. Oxygen and nitrogen analyzer, carbon and sulfur analyzer and inductively coupled plasma emission spectrometer were used to analyze the chemical composition of powder before and after atomization, and the change of oxygen content in all particle size segments and each particle size segment. SEM and laser particle size analyzer were used to observe the surface morphology and microstructure of powder and determine the particle size. The results showed that the chemical composition of Fe-Cr metal powder prepared by close-coupled vacuum induction melting gas atomization can be precisely controlled, and the oxygen content in full-size section was 0.024wt.%. The cooling rate increased exponentially with the decrease of powder particle size. With the increase of powder particle size segment, the surface structure mainly developed from cellular and columnar crystals to dendritic crystals. The oxygen content in each grain size segment decreased with the increase of grain size. The formation of hollow powder was mainly related to bag crushing mechanism and grain solidification shrinkage difference. References | Related Articles | Metrics

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Phase field method study on oriented tilted dendrite growth of alloy by adaptive finite element method ZHU Chang-sheng, GAO Hong-wei, MA Fang-lan, FENG Li, LEI Peng 2021, 47 (3):  15-22.  Abstract ( 213 )   PDF (6123KB) ( 270 )   Save The article established a phase field model that is an oriented tilted dendrite of alloy, and used a non-uniform grid adaptive finite element method to solve the phase field model of thin interface layer thickness. The thesis also researched the evolution process of the tilting dendrite of Al-Cu(w(Cu)=4%) alloy, and quantitatively analyzed the effect of cooling rate and the main crystal spacing on solidification structure. The results demonstrated that the cooling rate and the main crystal spacing and the pulling speed can control the growth angle of the tilting dendrite. With the increase of the cooling rate, the growth of dendrite will deviate from the preferred direction to the direction of temperature gradient. On the contrary, with the increase of main crystal spacing and pulling speed, the growth angle of dendrite will gradually deviate from the temperature gradient direction to the preferred crystal direction. In addition, compared with the uniform grid method, the adaptive finite element method reduces the running time of the CPU by an order of magnitude. And as the computational domain increases, the computational efficiency of the adaptive finite element method is higher. References | Related Articles | Metrics

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Preparation of porous polyaniline withtemplate method and its electrochemical properties WANG Hai-yan, SHANG Tian-rong, MA Shuai-shuai, WANG Chu-han, KUAI Hao 2021, 47 (3):  23-26.  Abstract ( 146 )   PDF (1314KB) ( 242 )   Save The limited oil-water reaction interface was constructed by an adding oxidant water solution approach at a very slow rate, porous polyaniline was prepared without template, and the structure and the electrochemical properties using as the electrode material of supercapacitor were studied. The results showed that the product presented porous structure looking like a tremella. The distribution of pore diameter was mainly in range of less than 10 nm. The charge and discharge time was approximately symmetric and the specific capacitance was 441.6 F/g when the discharge current was 1 A/g. The loss rate of the capacitance was 27.3% after 2 000 of galvanostatic charge discharge (1 A/g). Polyaniline showed good electrochemical properties. References | Related Articles | Metrics

Mechanical Engineering and Power Engineering

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Simulation analysis on the bearing characteristics of textured valve plate surface of floating cup pump YANG Guo-lai, JIN Jing, WANG Wen-yu, BAI Jing-hao, HUANG Fu-tian 2021, 47 (3):  27-32.  Abstract ( 148 )   PDF (2337KB) ( 233 )   Save The floating cup pump as a new research object of the plunger pump, the friction and wear of valve plate limits its high efficiency development. The influence of bionic texture on the bearing characteristics of friction pair was studied by arranging regular bionic texture on the roller plate. Six different shapes of pit were selected to establish a 6-pit lubricating oil film model. Fluent software was used for numerical simulation to analyze the pressure distribution on the upper surface of oil film, the pressure formation mechanism and the influence of working condition parameters and texture parameters on the bearing capacity of the oil film. The research result shows that: The proportion of dynamic pressure is the largest in the bearing capacity of the upper surface of oil film, and spherical pit is most suitable for the design of textured valve plate surface of floating cup pump. The increase of rotational speed, area ratio and depth to diameter ratio are beneficial to the increase of dynamic pressure bearing capacity. References | Related Articles | Metrics

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Rheological properties and gas production law of cattle manure during anaerobic fermentation process at thermophilic temperature LI Jin-ping, JIANG Qin, HUANG Juan-juan, WANG Chun-long 2021, 47 (3):  33-39.  Abstract ( 354 )   PDF (2605KB) ( 383 )   Save In order to study the rheological properties of high concentration fermentation raw materials during anaerobic fermentation process, the HYND-50 vibration online viscometers were used to measure the rheological properties of cattle manure with initial total solid mass fraction of 8% and 15% during the process of anaerobic fermentation biogas production at thermophilic temperature, and the effects of temperature and anaerobic digestion time on its rheological properties and gas production law were studied. The results demonstrated that within the same temperature rising range, the greater the initial total solid mass fraction of cattle manure was, the greater the activation energy was and the worse the fluidity was. During the process of anaerobic fermentation, the apparent viscosities decreased with the anaerobic digestion time, and increased with the increase of initial total solid mass fraction, the densities increased first, then decreased with the anaerobic digestion time and increased with the increase of initial total solid mass fraction. With the increase of initial total solid mass fraction, the maximum daily gas production, cumulative gas production and cumulative methane production increased, when initial total solid mass fraction was 15%, they were 1.29, 1.24 and 1.25 times of which when it was 8% respectively. References | Related Articles | Metrics

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Effect of blade with new structure on aerodynamic performance of wind turbine YANG Rui, YANG Sheng-bing, MA Chao-shan, SUN Xia-yang CHEN Yue-juan, YUE Yi-xuan 2021, 47 (3):  40-44.  Abstract ( 269 )   PDF (2844KB) ( 300 )   Save Aiming at the problem that the blade tip vortex generated during the wind turbine affects the aerodynamic performance of the wind turbine itself and the downstream wind turbine, a strategy for controlling the blade tip vortex is proposed to reduce its impact. The 1/8 model of the Phase Ⅵ blade was used as the original model. new model was made on the basis of that, which holes were opened at the blade tip and the hub at the same time and connected with pipes. The numerical simulation method was used to compare and analyze the wind turbine in original model and the new one under 15 conditions of incoming wind speed from 6 m/s to 20 m/s. The results show that the aerodynamic performance of the original model and the new one are almost the same at low wind speeds, that is, the new model has little effect on the aerodynamic performance of the blades, and the wake diffusion speed is similar. But as the incoming wind speed increases, the impact of the new model on the aerodynamic performance of the wind turbine also increases. The power of the new model wind turbine is significantly higher than that of the original model,and the wake spreads faster in the rotation plane of the wind turbine. The propagation distance in the incoming direction becomes shorter. The new model wake can reduce the impact on downstream wind turbines and improve wind energy utilization efficiency of wind farm. References | Related Articles | Metrics

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Formation and verification of process surface in annotation of product MBD data set WANG Hong-shen, WANG Dao-jun, CAO Yu-fa 2021, 47 (3):  45-49.  Abstract ( 211 )   PDF (1845KB) ( 265 )   Save Because of the principle and method of modeling, the surface in the 3D model often does not have a clear engineering semantics, which may produce ambiguity in tagging the dimension and other information on the 3D model of the project. This problem is not well solved by commercial CAD software. Based on OpenCASCADE 3D modeling kernel, this paper studies the methods to solve the above problems, and puts forward the concepts of modeling surface and process surface. By recognizing the mathematical attributes of the modeling surface and combining the engineering semantics in mechanical engineering, the modeling surface is bound to form a process surface that conforms to the engineering semantics. The information of 3D annotation information of the model is regarded as the attribute of the process surface, which increases the intelligence of the system's 3D dimensioning, and also makes it possible to extract the product semantics information automatically in subsequent product virtual assembly, processing and manufacturing as well as in product service. References | Related Articles | Metrics

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Effect of tip leakage flow on flow structure of semi-open centrifugal pump impeller CHENG Xiao-rui, JIANG Yi-meng, CHANG Zheng-bai, WANG Kun 2021, 47 (3):  50-57.  Abstract ( 260 )   PDF (6980KB) ( 119 )   Save In order to study the effect of the tip leakage flow under different tip clearances on the flow structure of the semi-open impeller centrifugal pump, five different tip clearance size schemes were designed. The SST k-ω turbulence model was used to calculate the whole flow field of the semi-open impeller centrifugal pump. The internal flow structure of the semi-open impeller tip clearance under different working conditions was analyzed and verified by visualization experiment.The results show that with the decrease of the tip clearance, the head and efficiency of the centrifugal pump significantly increase, but when the clearance value is reduced to 0.7 mm, the pump efficiency no longer changes significantly with further decrease of the tip clearance. Choosing the optimum value of the tip clearance has a certain inhibition effect on the development of leakage vortex. It can be found by using the Q criterion to discriminate vortex, as the clearance decreases, the strength of the main tip leakage vortex weakens, the secondary tip leakage vortex in the mainstream channel gradually disappears, and the disturbance to the mainstream decreases. When the clearance is reduced to 0.7mm, the secondary leakage vortex completely disappears, and the strength of the main leakage vortex is the weakest. The degree of interference of the leakage flow at the blade tip on the flow field is affected by the flow rate. At low flow condition, by reducing the tip clearance, the anti-interference ability of flow in the blade region can be improved. References | Related Articles | Metrics

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Analysis of the weak points in the movement of slipper retainer from axial piston pump based on the joint simulation of ADAMS and Pumplinx ZHANG Jing, LIAO Wen-bo, SUI Rui-yang, ZHOU Guo-yang 2021, 47 (3):  58-63.  Abstract ( 291 )   PDF (3453KB) ( 364 )   Save In order to study the accidental fracture of the slipper retainer in the axial piston pump, the forces on the slipper retainer are analyzed in detail. The distribution of forces in all aspects is integrated, which shows that the slipper retainer reflects a bending moment with the boundary of suction and discharge side as the reference line in its structure. After the slipper retainer and the whole pump are simulated by ADAMS rigid flexible coupling finite element and Pumplinx fluid finite element, the calculation results show that while each piston moves around the boundary line of suction and discharge side, the stress concentration of the outer edge of the corresponding slipper retainer hole is the largest, which makes this area become the weak points of the slipper retainer movement, under the action of bending moment, these weak points become the most likely fracture risk area. References | Related Articles | Metrics

Chemical Industry and Light Industry

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Nanofiltration-reverse osmosis process for recovery NaCl in high-salt wastewater ZHANG Dong-qiang, CHEN Yan-an, ZHANG Jing-jing ZHAO Jing, SU Na, DUAN Run-hao 2021, 47 (3):  64-69.  Abstract ( 336 )   PDF (1658KB) ( 358 )   Save In order to realize the recovery of NaCl in high-salt wastewater, a nanofiltration-reverse osmosis double-membrane cascade combined process was used to purify the mixed simulated wastewater contained NaCl and Na2SO4. The concentration ratio, operating pressure, flow rate and temperature were investigated, and the most excellent technical conditions were determined. The experimental results showed that the value of [NaCl]/[Na2SO4] was not less than 41.45 in reverse osmosis concentrate, which indicated that the process can achieve separation of NaCl and Na2SO4 effectively; In addition, the reverse osmosis membrane can separate Cl－ with the rejection rate of Cl－ more than 96%, and the purity of the recovered NaCl can reach over 97.5%. References | Related Articles | Metrics

Automation Technique and Computer Technology

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Learning cooperative control of a class of multi-agent systems with unknown external disturbances YANG Na-na, MENG Xin-you, XUAN Hai-yan 2021, 47 (3):  70-77.  Abstract ( 165 )   PDF (2852KB) ( 268 )   Save For the multi-agent systems with unknown external interferences, in the framework of iterative learning control, combined with adaptive control, firstly, a time-varying gain with differential parameter adaptive law is designed, at the same time, in order to compensate the unknown external interferences, the auxiliary control protocol is proposed. By constructing the composite energy function and based on Barbalat-like lemma, the perfect consensus on the interval [0,T] is proved. Secondly, the formation problem is transformed into the consensus problem by the coordinate transformation.Finally,the effectiveness of the proposed algorithm is verified using a simulation example. References | Related Articles | Metrics

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The analysis of the robustness of cyber-physical power systems based on community-generated structure PU Wu-jun, PAN Huan 2021, 47 (3):  78-85.  Abstract ( 173 )   PDF (2555KB) ( 343 )   Save With the rapid development of sensor technology, the deep integration of information network and power grid, the intelligent level of power system is higher and higher, but it also faces a series of problems such as security, vulnerability and so on. Combining the interdependent network with the load-capacity cascading failure model, a cascading failure model including power network and cyber network island operation is proposed to mainly study the robustness of the cyber-physical system (CPS) with community structure. The traditional community structure generation algorithm is modified to generate a scale-free network with different sizes of communities and adjustable connection probability of communities. The proposed algorithm is adopted to generate the CPS model of the cyber network and the internal coordination of the grid community, the proportion of the remaining nodes of the grid is used as the evaluation index. When the control center is in different communities, the influence of global connection probability, community connection probability, and multiple control centers on the robustness of power CPS is studied by simulating cascading failure reaction. References | Related Articles | Metrics

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Design and analysis of wideband bandpass three-dimensional frequency selective surface YU Zheng-yong, ZHU Jian-ping, TANG Wan-chun 2021, 47 (3):  86-90.  Abstract ( 232 )   PDF (2109KB) ( 478 )   Save A wideband bandpass three-dimensional frequency selective surface (3D FSS) is proposed based on the square waveguide structure. The unit cell of the proposed FSS consists of a cuboid dielectric block with two identically-sized metallic square patches on the top and bottom surfaces and an air-filled square waveguide, in which each surface provides a square slot resonant structure.Theoriginal single resonant mode of the square slot resonance will split into even- or odd- resonant modes by the electromagnetic coupling. Thus, two transmission poles are introduced for obtaining a flat passband with second-order response, and its 3 dB fractional bandwidth of the passband is 25.12%.The operating principle of the proposed FSS is explained by the equivalent circuit model. The simulated results show that the proposed FSS exhibits a stable response to variations of incident angle from 0° to 45° under both TE and TM polarizations. In addition, this 3D FSS has a relatively small unit cell. References | Related Articles | Metrics

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Design and implementation of transmitting and receiving circuits in wireless laser data communication system WANG Hui-qin, MA Yu-kun, CAI Hong-liang, ZHANG Yue, CAO Ming-hua 2021, 47 (3):  91-96.  Abstract ( 281 )   PDF (4255KB) ( 818 )   Save Wireless laser communication has numerous advantages that include high transmission rate, strong anti-jamming ability, low power consumption, etc. In this paper, the red light with the wavelength of 650 nm is used as the signal carrier to design a transceiver circuit for wireless laser communication. And we elaborate the designed principles and methods of laser transmitting circuit and photoelectric receiving circuit. In proposed system, the transmitting circuit has the functions of automatic power control, fault indication and current monitoring, while the receiving circuit has the functions of signal amplification, photocurrent monitoring and automatic noise. Furthermore, the performance of proposed circuit is tested by using the experimental platform, and the correctness and rationality of designed circuit are verified. The exprimental results showed that the designed circuit can achieve reliable transmission when the transmission rate is 16 Mbit/s. References | Related Articles | Metrics

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Nodes importance evolution study on high-speed railway network of China based on graph theory ZHU Yan-bo 2021, 47 (3):  97-104.  Abstract ( 205 )   PDF (1556KB) ( 319 )   Save In order to study the nodes importance and its evolution of the high-speed rail network of China, the network based on graph theory that focused on the actually situation of China high-speed rail network in the year of 2017, 2020 and the national high-speed rail network plan with eight vertical and eight horizontal line (2035) were constructed, respectively. Based on the analysis of the evaluation algorithms for nodes importance of transport network, the evaluation method on the vital nodes of the high-speed railway network of China is proposed, the results obtained by different parameter combinations are analyzed through simulation experiments, and determined Top20 critical nodes of the network with different time intervals, respectively. Then the evolution process of these node centrality is compared, and the reasons for the ranking fluctuation of some important nodes are analyzed. References | Related Articles | Metrics

Architectural Sciences

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Seismic performance of shear wall structure with a new damper used in coupling beam HE Qing-guang, SHANG Jin, DANG Yu 2021, 47 (3):  105-112.  Abstract ( 190 )   PDF (3429KB) ( 338 )   Save An innovative compound damper which can be replaced after earthquake is studied. The compound damper can be installed at the middle of coupling beam to protect the wall and improve the capacity for dissipate energy of coupling beams. Based on ABAQUS procedure, an equivalent simplified model which can effectively reflect characteristics of compound dampers are proposed and compared with the simulation model. The equivalent simplified model is used in the shear wall structure with coupling beams, and dynamic time history analysis is carried out under the rare earthquake. Taking the concrete beam as a reference, seismic performance influenced by alternative stiffness of beams which are installed the compound dampers are studied. The results show that the equivalent simplified model can show the characteristics of the compound dampers well; compound dampers can effectively reduce the inter story drift, base reaction and damage of the structure; when the value of alternative stiffness ratio is 0.4,the better damping effect of the structure can be obtained. References | Related Articles | Metrics

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Simulation analysis of construction process of seismic-isolation retrofit with hoop-type underpinning joints DANG Yu, WEN Jiu-hong 2021, 47 (3):  113-119.  Abstract ( 120 )   PDF (3696KB) ( 277 )   Save Due to seismic-isolation retrofit with hoop-type underpinning joints, the constraints of the structure changes during the construction process. Meanwhile, the construction is carried out in batches and sections, the differences of the construction steps and the jacking machine control mechanisms affect the structure. Thus, finite element method is adopted to simulate the construction process of the seismic-isolation retrofit the existed frame building with the hoop-type underpinning joints. The internal force and the deformation of the structure are discussed for different construction steps and caused by the nonsynchronous jacking machine control mechanisms. Some construction process suggestions and the jacking machine control mechanisms condition are given based on the rule of the internal force and deformation.This study will play a guiding role in the actual construction of seismic-isolation retrofit project, and put forward the reference opinions with numerical basis to ensure the construction safety. References | Related Articles | Metrics

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Stability factors and deformation law of loess high fill slope YE Shuai-hua, ZHANG Yu-qiao, FANG Guang-wen 2021, 47 (3):  120-126.  Abstract ( 273 )   PDF (2468KB) ( 366 )   Save Based on the loess high fill slope project in a certain section of Northwest China, this paper uses PLAXIS 3D software to establish a three-dimensional finite element model of the multistage high fill slope. The effects of changing fill, fill boundary, slope and unloading platform on slope stability were studied. According to the vertical displacement and horizontal displacement of the slope top, slope and foot, the distribution law of the most dangerous points at all levels and the trend of the whole slope deformation are analyzed. The results show that the cohesive force and internal friction angle of filling are the key factors affecting the stability of high fill slopes. Reducing the height of the step at the boundary between the fill and the undisturbed soil, deepening the step width, reducing the slope, and widening the unloading platform can improve the stability of the slope. During the construction of the lower slope, the vertical displacement changes rapidly and horizontal displacement changes slowly. The deformation is good after the construction. During the construction of the higher slope, the vertical and horizontal displacement abrupt change rapidly, and the distribution is not uniform. The consolidation settlement period is long and the deformation amount is large after the construction. It is necessary to strengthen the deformation monitoring of the higher slope after the construction. The research results determine the influence factors of stability, deformation trend and development law of loess high fill slope in Northwest China, and provides a scientific basis for further research on controlling the deformation of loess high fill slope. References | Related Articles | Metrics

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Search model of slope slip surface based on gridding stress field and its application LI Zhong, ZHANG Xi, WANG Hong-xing 2021, 47 (3):  127-131.  Abstract ( 148 )   PDF (1075KB) ( 304 )   Save In order to effectively apply numerical calculation method to slope stability analysis, a mesh slope slip surface search model based on stress field is established. Firstly, the stress field of slope is obtained by establishing finite element analysis model, and the element coordinates and the stress calculation results are extracted. Secondly, a rectangular coordinate system is established according to the geometric size of the slope model, and the slope is discretized into n-grids in the plane according to the grid form, so that each grid can contain one or more original finite element grids. Thirdly, the stress field of the slope is extracted by programming, and the most likely finite element to reach the yield condition is searched and labeled in each grid according to the C-M yield criterion. Then, the potential slip elements are searched in parallel and in series, that is to say, the mesh slope slip surface search model based on stress field is realized. Finally, the international classical slope case is selected, and the slope stability is analyzed and calculated based on the expression of vector and normal safety factor. The method is compared with the traditional method and proved to be feasible and superior. This method is suitable for the evaluation and analysis of slope stability under non-limit shape, and the calculation results are more reasonable. References | Related Articles | Metrics

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Experimental study on bearing characteristics of micro-steel-pipe pile in deep filling area ZHOU Yong, LIU Yong 2021, 47 (3):  132-138.  Abstract ( 207 )   PDF (4080KB) ( 397 )   Save In order to study the bearing characteristics and the reinforcement effect of micro-steel-pipe pile in deep filling area, the stress-strain relationship of the micro-steel-pipe pile, the axial force of pile body and the displacement of pile top under various loads were measured by laboratory test and field test. The elastic modulus of composite section, the load ratio of steel pipe to cement paste, the transfer law of the pile’s axial force and lateral resistance were analyzed. The results show that the steel tube collar effect on the elastic modulus of composite section is small, the measured value is only 1.2 times of the calculated value without considering the collar effect, and the steel-pipe’s internal force in the micro-steel-pipe pile is relatively large, accounting for about 2/3 of the total internal force. The Q-s curve of micro-steel pipe pile is slowly deformed in filling area, and the load shared by end resistance tends to zero, which shows the characteristic of friction pile. The pile has high bearing capacity in the filling area. And the pile is used to reinforce the actual project, and the maximum settlement is up to the limit of the code, which indicates that the reinforcement effect of the micro-steel-pipe pile on the foundation in the deep filling area is fine. References | Related Articles | Metrics

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Seismic performance analysis of reinforced concrete beam bridges considering material deterioration LI Xi-mei, FU A-xiong 2021, 47 (3):  139-145.  Abstract ( 185 )   PDF (3619KB) ( 259 )   Save The deterioration of concrete durability can be reflected in the degeneration of material properties, which will inevitably lead to the reduction of seismic performance of bridge structures. This paper takes 3-span reinforced concrete beam bridge as the research object to formulate ANSYS full bridge model, considering the influence of freeze-thaw and chloride ion environmental factors, then the non-linear time history analysis under uniform excitation of seismic loads is carried out. In the whole service period, the seismic response of bridge structures in different time periods is calculated according to the different degree of material deterioration in different service periods, and the stress and displacement in each period are compared and analyzed. The results show that, the seismic performance of the structure decreases significantly with the deterioration of materials, to which should be paid enough attention in the process of design and management. References | Related Articles | Metrics

Scientific

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Virtually regular modules WANG Yong-duo, LIU Shi-jie 2021, 47 (3):  146-149.  Abstract ( 161 )   PDF (402KB) ( 278 )   Save As a proper generalization of regular modules, the concept of virtually regular modules is presented in this paper. Basic properties of these modules are studied, it is shown that a ring R is a (strongly) virtually regular ring, if and only if every (projective) free R-module is a (semicompletely) virtually regular module. References | Related Articles | Metrics

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Extremality of graph entropy based on Laplacian degrees of k-uniform hypergraphs LU Peng-li, XUE Yu-long 2021, 47 (3):  150-155.  Abstract ( 214 )   PDF (400KB) ( 288 )   Save Motivated by the definition of graph entropy in general graphs, the graph entropy of hypergraphs based on Laplacian degree are defined. Some results on graph entropy of simple graphs are extended to k-uniform hypergraphs. By an operation of edge moving, the maximum and minimum graph entropy based on Laplacian degrees are determined in k-uniform hypertrees, unicyclic k-uniform hypergraphs, bicyclic k-uniform hypergraphs and k-uniform chemical hypertrees, respectively, and the corresponding extremal graphs are determined. References | Related Articles | Metrics

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Ring characterizations on GIac- injective and GIac-flat modules CHEN Dong 2021, 47 (3):  156-161.  Abstract ( 234 )   PDF (400KB) ( 392 )   Save The concept of GIac-injective modules and GIac-flat modules , is introduced respectively, which is a class of modules between GI-injective modules (or GI-flat modules) and copure injective modules (or copure flat modules). Some classes of rings, such as semisimple rings, von Neumann regular rings, hereditary rings and semihereditary rings, are characterized in terms of these modules. References | Related Articles | Metrics

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Upper and lower bounds for the Z-spectral radius of fourth-order weakly symmetric nonnegative tensors and their applications LEI Xue-hong, XU Yun-xia 2021, 47 (3):  162-166.  Abstract ( 140 )   PDF (389KB) ( 210 )   Save For the bounds of fourth-order tensors, by using the definition of Z-eigenvalues of tensors and some techniques of inequalities, new upper and lower bounds for the Z-spectral radius of fourth-order weakly symmetric nonnegative tensors are obtained and proved to be an improvement of some existing result. As applications, new lower bounds for the best rank-one, approximation of tensors and the convergence rate of the greedy rank-one, update algorithm are given, and lower and upper bounds for symmetric pure state with nonnegative amplitudes are obtained by using upper and lower bounds of the Z-spectral radius of tensors. References | Related Articles | Metrics

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Full π-regular subsemigroup lattices of π-regular semigroups TIAN Zhen-ji, MA Cun-de 2021, 47 (3):  167-169.  Abstract ( 200 )   PDF (355KB) ( 279 )   Save The properties and characteristics of full π-regular subsemigroup lattices of π-regular semigroups are mainly studied, and further present the necessary and sufficient conditions for full π-regular subsemigroup lattices of π-regular semigroups to be distributive lattice. References | Related Articles | Metrics

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Neighbor expanded sum distinguishing total coloring of some Mycielski graphs LI Yong-yan, DU Jing 2021, 47 (3):  170-172.  Abstract ( 168 )   PDF (350KB) ( 232 )   Save Discusses the neighbor expanded sum distinguishing total coloring of Mycielski graphs M(Pn)、M(Cn)、M(Sn)、M(Fn) and M(Wn). The neighbor expanded sum distinguishing total chromatic numbers of M(Pn)、M(Cn)、M(Sn)、M(Fn) and M(Wn) are obtained by function construction methods. At the same time, it is proved that NESD conjecture is valid for the above five kinds of Mycielski graphs. References | Related Articles | Metrics