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28 October 2020, Volume 46 Issue 5 Previous Issue    Next Issue

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Materials Science and Engineering

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Microstructure and properties of annealed MoCrFeMnNi high entropy alloys LA Pei-qing, WANG Jiao, XIAO Hai-bo, ZHENG Yue-hong, YANG Li-jie, SHENG Jie 2020, 46 (5):  1-6.  Abstract ( 458 )   PDF (5320KB) ( 514 )   Save High entropy alloys have attracted extensive attention due to their high strength, corrosion resistance and high temperature oxidation resistance. In our research, a high-entropy alloy MoCrFeMnNi was prepared by aluminothermic reaction method. Microstructures and properties of 700 ℃/12 h, 800 ℃/6 h, 1 000 ℃/3 h annealed alloys were investigated respectively by XRD, SEM, EDS, microhardness test and compression experiment. The results show that the high entropy alloy MoCrFeMnNi prepared by the aluminothermic method has typical dendritic morphology, and the crystal structure is mainly composed of BCC phase, FCC phase and a small amount of dispersion phase. The dendritic region is BCC structure, rich in Mo and Cr elements. The interdendritic region is FCC structure, rich in Ni element. With the increase of annealing temperature, the nanoscale σ phase is gradually precipitated between dendrites, leading to the increase of alloy hardness, which may reach up to 667 HV and 1 050 MPa after annealing at 800 ℃/6 h. After annealing at 1 000 ℃/3 h, the σ phase agglomerates into a spherical and acicular shape and is partially dissolved at high temperature. With decrease of σ phase, the hardness of the alloy decreases, the compressive strength is equal to that of as-cast state, and the plasticity of the alloy is significantly improved. References | Related Articles | Metrics

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Effect of sample area on load characteristics of AZ31B magnesium alloy treated by micro-arc oxidation WANG Sheng, HAUANG Zhi-jie, LAN Ye-feng, LIU Kang-kang WANG Xiao-long, MA Ying 2020, 46 (5):  7-12.  Abstract ( 204 )   PDF (2599KB) ( 761 )   Save In order to clarify the effect of sample area on the load characteristics and film properties of micro-arc oxidation, four AZ31B magnesium alloy samples with different areas were treated by micro-arc oxidation in unipolar pulse power supply mode. In the treatment, the equivalent resistance and equivalent capacitance of the load are collected by a LCR tester, the voltage and current waveforms of the load are recorded by oscilloscope, and the load voltage waveform is fitted by using software MATLAB, so as to investigate the effect of sample area on the load characteristics in the process of micro-arc oxidation. Our results indicate that with the increase of treatment voltage, the equivalent capacitance of all loads decreases continuously, the equivalent resistance increases continuously, and the discharge time constant of the loads increases continuously as well. The increase of the equivalent resistance indicates that the thickness of the film increases with increase of the treatment voltage. In addition, with the increase of the treated area, the equivalent resistance of the loads decreases, the load capacitance increases, and the discharge time constant of the loads decreases either. This indicates that the growth of the film becomes slower with increase of the treated area, and the larger the treated area is, the closer the load waveform is to the square wave. Therefore, it is more practical for the unipolar pulses. The equivalent resistance of the loads can reflect the thickness of the film. References | Related Articles | Metrics

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Simulation of phase field method for solidification microstructure of Fe-C alloy by lateral constraint FENG Li, WANG Jun, ZHU Chang-sheng, ZHONG Jun-he, AN Guo-sheng 2020, 46 (5):  13-20.  Abstract ( 173 )   PDF (6974KB) ( 89 )   Save Taking Fe-C binary alloy as an example, the evolution process of dendrite and eutectoid microstructure under transverse restraint was simulated in this study by adopting the multiphase field method. The influence of length and thickness of transverse restraint on growth morphology of dendrite and that of eutectoid microstructure was discussed in terms of simulated microstructures. All results coming from our simulation indicate:The normal growth of dendrite and eutectoid is limited by the existence of transverse constraint, and the morphology of microstructure above the transverse constraint changes obviously; With the increase of the length of transverse constraint, the dendrite spacing above the transverse constraint decreases obviously, and the layer spacing of the eutectoid structure becomes larger as a result;With the increase of transverse constraint thickness, the growth rate of new dendrites above transverse constraints decreases, and the deflection of Fe3C phase in eutectoid structure increases, resulting in larger interlayer spacing. References | Related Articles | Metrics

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In-situ observation of fracture behavior of Cu mesh reinforced Al/Cu composite ZHANG Xiao-bo, ZHANG Quan-xin 2020, 46 (5):  21-26.  Abstract ( 231 )   PDF (3835KB) ( 294 )   Save A kind of copper mesh woven by orthogonal method was introduced into aluminum matrix as reinforcement phase to prepare Al/Cu composite. The microstructure evolution, the relationship between fracture mechanism and mechanical properties of the Al/Cu composite were both observed and investigated on line by means of in-situ tensile scanning electron microscope (SEM). It is found in this study that under the same rolling deformation, both 25 ℃ cold rolling and 400 ℃ hot rolling may break the reinforced copper mesh and make it uniformly distributed in the matrix aluminum plate. Recorded load-displacement curves of the composite plate under in-situ tension exhibit obvious elastic stage, plastic stage and failure stage. Microcracks initiate around the Cu particles or stress concentrations. The main crack and its propagation are mainly formed by joint action of delamination cracking of the interface around the Cu particles and propagation of the microcracks along the slip line. Finally, the fracture path along the slip line takes 45 °with the uniaxial tensile direction. The plastic fracture of Al layer and the delamination-induced fracture on the Al/Cu bonding interface are the two main failure modes of the Al/Cu composite plate. References | Related Articles | Metrics

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Functionalization of Fe3O4 magnetic nanoparticles using RAFT reagent CHEN Zhen-bin, ZHOU Yong-shan, ZHANG Xia-yun 2020, 46 (5):  27-33.  Abstract ( 222 )   PDF (2429KB) ( 327 )   Save Ferric oxide nanoparticles (Fe3O4 NPs) were prepared in this study by reverse microemulsion method, and modified by silane coupling agent KH570 so as to introduce cellulc double bond on the surface of Fe3O4 NPs, and then react with 2-cyanopropan-2-propanyl dodecyl trithiocarbonate to obtain RAFT reacted Fe3O4 NPs (Fe3O4-g-KH570-RAFT NPs)). The structure and morphology of Fe3O4 NPs products at different stages were also characterized. Effects of reaction time and other process conditions on GrRAFT were investigated quantitatively in the study by taking the grafting rate of RAFT reagent (GrRAFT) as an index. The results show that the average particle size of the prepared Fe3O4-g-KH570-RAFT NPs is about 10.4 nm. When the reaction time takes 14 h, the reaction temperature is 65 ℃, and nKH570/nRAFT becomes 1/2, the highest grafting rate GrRAFT may reach up to 79.34%. References | Related Articles | Metrics

Mechanical Engineering and Power Engineering

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Vertical earth pressure calculation model for buried pipelines with straight grooves AN Zong-wen, WANG Ying-ying, ZHANG Yong-ming 2020, 46 (5):  34-40.  Abstract ( 252 )   PDF (2335KB) ( 326 )   Save In order to solve the problem that the steel-plastic conversion structure parts in the trench pipeline, which are subject to the soil loading, are easy to deform and fracture, leading further to the failure of the structure parts and the leakage of the pipeline, a soil-caused vertical pressure calculation model, which is based on the theory of double shear unified strength, for rigid/flexible buried pipeline has been derived and established in this paper. The validity of the model is analyzed and verified by our examples calculated. The proposed model takes effects of main stress as well as back-filling soil into account. It is therefore shown that compared with Marston's theory the pressure value calculated by our model is reduced by 40%, which provides a new method for soil-caused vertical pressure calculation for straight groove buried pipeline. References | Related Articles | Metrics

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Knowledge modeling of fault diagnosis for turbine generator sets based on ontology YAN Chang-feng, LI Yu, WANG Hui-bin, ZHANG Qiang AI Ke-yong, WU Li-xiao 2020, 46 (5):  41-48.  Abstract ( 236 )   PDF (4269KB) ( 331 )   Save Since the knowledge representation method of fault diagnosis in turbine generator sets is lack of complete in the field of terms, complex terminology, system heterogeneity and difficulty in sharing and reuse etc, a new method for ontology-based knowledge representation is well adopted in terms of fault diagnosis requirements. Methods for ontology construction and a knowledge representation model for the fault diagnosis of turbine generator sets are proposed respectively. The model defines its ontology concepts, attributes, relationships, examples and axioms, and provides a clear formal specification for knowledge representation. Furthermore, Protégé_4.3 is used to construct the ontology of turbine generator sets fault diagnosis domain with fault type, fault characteristic, fault reason and maintenance strategy, and the knowledge is proved to be consistent in the ontology by designing algorithms. Turbine generator sets fault is simulated by SQI mechanical fault comprehensive simulation test bench, and the reasoning test of ontology knowledge is verified by the inference engine named FaCT++. The result indicates that the knowledge model of ontology-based fault diagnosis is feasible. References | Related Articles | Metrics

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Research onevane-type flow fluctuation generator based on butterfly bamper YANG Ling-shan, MENG Tao, LI Xiao-peng, LI Dong-sheng 2020, 46 (5):  49-52.  Abstract ( 207 )   PDF (1635KB) ( 218 )   Save The measurement of a flowmeter needs to be in a relatively stable environment, and flow fluctuation produced by a pipeline in actual measurement has an impact on measurement results of the flowmeter. In order to investigate the influence of different flow fluctuations on the measurement results of the pipeline, a blade-type flow fluctuation generator is designed in this paper, which drives a butterfly valve to swing back and forth through a motor to form the flow fluctuation in the pipeline. The generator can change the oscillation frequency and swing angle of the motor to produce different flow fluctuations and imitate the flow fluctuations that may occur in a water flow system. Our experiments have demonstrated that the flow fluctuation generated by the blade-type flow fluctuation generator can propagate along upstream and downstream of the pipeline, and the flow fluctuation will also varies as the oscillation frequency and swing angle of the generator are changed simultaneously or individually. References | Related Articles | Metrics

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Effect of blade inlet position on cavitation performance of the secondary circuit coolant pump of sodium-cooled fast reactor YANG Cong-xin, YU Chang-hong, YU Hong-chang, NIU Hong-jun 2020, 46 (5):  53-60.  Abstract ( 177 )   PDF (4354KB) ( 293 )   Save In order to improve cavitation performance of SCCP-SFP (the secondary circuit coolant pump of sodium-cooled fast reactor), model pumps A, B and C are constructed respectively by extending the blade inlet edge of the prototype three times on the premise of ensuring that other geometric parameters remain unchanged. Based on the RNG k-ε turbulence model, the Zwart-Gerber-Belamri and Schnerr&Sauer cavitation model, three-dimensional steady numerical simulation for each model pump under single-phase and two-phase cavitation conditions is carried out in this research, and then hydraulic performance curves, cavitation performance curves and internal flow field parameters of each model pump under different working conditions are predicted as well. By comparing the hydraulic performance and internal flow field parameters of the prototype with each model pump, conclusions may be drawn:The blade inlet edge extension has little effect on the hydraulic performance of the sodium pump, and the decline of hydraulic performance of the model pump B is the smallest.The critical cavitation margin for each model pump is reduced in varying degrees, and the cavitation performance of model pump B is the best.By properly extending the inlet edge of the blade, the cavitation performance of the sodium pump is obviously improved. References | Related Articles | Metrics

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Hydraulic optimization of spatial guide vane on submersible well pump based on the orthogonal design CHENG Xiao-rui, ZHANG Xue-lian 2020, 46 (5):  61-67.  Abstract ( 228 )   PDF (1454KB) ( 406 )   Save The orthogonal design method is used to optimize design of a submersible well pump spatial guide vane. Three main geometric parameters of the submersible well pump spatial guide vane are selected, which are the inlet width, the axial length of the guide vane blade and the axial distance between the outlet edge of the guide vane blade and the field exit of the guide vane respectively. Nine groups of schemes are designed on the basis of the orthogonal method. All results from our numerical calculations and range analyses show that the axial length of the guide vane blade has a significant effect on the head and shaft power of the submersible well pump, and the inlet width of the guide vane is more sensitive to variation of the submersible well pump efficiency. The performance of the submersible well pump can be improved by fixing a certain outlet distance between the outlet edge of the guide vane blade and the field exit of the guide vane. Based on multi-objective optimization design methodology, the optimal scheme of this investigation is determined as follows: the inlet width is 25 mm, the axial length of the guide vane blade is 101 mm and the axial distance between the outlet edge of the guide vane blade and the field exit of the guide vane may take 20 mm.By further analyzing efficiency of the first three stages of the impeller and the static pressure and streamline distribution at the exit of the guide vane, it is found that current excellent design of the spatial guide vane makes the internal fluid state of the guide vane better and ensures the impeller efficiency to maintain a higher level. At the same time, the flow stability in the submersible well pump becomes better. References | Related Articles | Metrics

Chemical Industry and Light Industry

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Experiment investigation on characteristic of electromagnetic shielding materials in electrical instrument control device MA Hong-qiang, ZHANG Chun-e, LIANG Nuo, LIU Ye-min CHEN Wei-guo, HAN Xi-lian 2020, 46 (5):  68-72.  Abstract ( 449 )   PDF (2825KB) ( 400 )   Save In order to reduce electromagnetic interference between strong and weak electric systems of electrical instrument control device and ensure safety as well as reliable operation of the device in natural gas store station, this study adopts a kind of experimental method to test and analyze shielding effectiveness of wire mesh, aluminum foiled anti-radiation tape and radiation protection cloth. Tested results show that the shielding effectiveness of electromagnetic shielding materials is less affected by radiation distance of interference electromagnetic waves, but greatly affected by frequency of the interference electromagnetic waves. The electromagnetic shielding effectiveness of wire mesh, aluminum foiled anti-radiation tape and radiation protection cloth may increases at first and then decreases with increase of frequency of the interference electromagnetic wave. In the frequency band of 0~500 MHz, shielding performance of wire mesh and radiation protection cloth is better than that of aluminum foiled anti-radiation tape. In the frequency band of 500~1 000 MHz, the shielding performance of aluminum foiled anti-radiation tape and radiation protection cloth is better than that of wire mesh. In the frequency band of 1 000~2 500 MHz, the electromagnetic shielding performance of wire mesh and aluminum foiled anti-radiation tape is better than that of radiation protection cloth. References | Related Articles | Metrics

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Modal analysis and harmonic response analysis of impeller rotor-bearing-dry gas seal system ZHANG Wei-zheng, LIN Zhi, DING Xue-xing, WU Chuan-yang 2020, 46 (5):  73-77.  Abstract ( 206 )   PDF (2295KB) ( 406 )   Save Taking dynamic characteristics of alarge system “impeller rotor-bearing-dry gas seal” system as a research object, a finite element model has been established by adopting ANSYS software. The model is used to analyze the gas sealing system under full load condition, and natural frequencies and vibration modes in various stages are obtained. The modal analysis of the system under non-loading condition is then carried out, and the natural frequencies under above two conditions are compared and analyzed with each other. Compared with the above two natural frequencies, it is found that the force acting on the dry gas sealing system and the impeller rotor reduces natural frequency of the system. Finally, taking the unbalance of the system as body load, the steady-state unbalanced response curve of the system can be obtained by a harmonic response analysis method. References | Related Articles | Metrics

Automation Technique and Computer Technology

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An online fusion estimation method forstate of charge of lithium ion batteries MA Xiang-ping, JIN Hao-qing, ZHU Qi-xian, WANG Xiao-lan 2020, 46 (5):  78-84.  Abstract ( 249 )   PDF (1871KB) ( 378 )   Save The SOC is one of the important parameters in battery management system. In order to improve the accuracy of the ampere-hour integral method for estimation of SOC and solve the problem that estimation error increases with time, an error prediction model of ampere-hour integration method is established in this paper by using Extreme Learning Machine Algorithm. The model takes working current of battery as input and the corresponding ampere-hour integration method SOC estimation error as output. The error prediction model is integrated with the ampere-hour integration method to correct estimated value of the SOC of the ampere-hour integration method. An on-line estimation method of SOC of lithium-ion battery based on Ampere-hour integration method and Extreme Learning Machine Algorithm is therefore developed. Results from our simulation show that, compared with the ampere-time integration method, the integrated method can effectively reduce estimation errors of the SOC and overcome the problem that the estimation errors resulting from the ampere-time integration method increases with time. References | Related Articles | Metrics

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New modulation of H-bridge multi-level inverter HU Wen-hua, TAN Guang-hui, ZHANG Chao-fan 2020, 46 (5):  85-91.  Abstract ( 274 )   PDF (3124KB) ( 407 )   Save In order to solve the problem of output power imbalance when traditional PD modulation method is applied to cascaded H-bridge multilevel inverter, this paper proposes an optimal modulation strategy on the basis of 1/4 output period carrier cycle, which makes the output power of all levels of inverter balanced. The maximum switching frequency of a switch tube is reduced to 1/2 compared to original, thus reducing the switching loss as a result. The optimal modulation strategy proposed in this paper requires only less triangular carriers as well as simpler modulation than traditional PD modulation. The author takes a four-unit cascaded H-bridge multilevel inverter as an example for theoretical analysis, and the correctness of the proposed method has been verified by simulation experiments. References | Related Articles | Metrics

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Fault diagnosis method of rolling bearing based on VMD-MPE -KPCA feature extraction mixed with MRVM CHEN Peng, ZHAO Xiao-qiang, ZHU Qi-xian 2020, 46 (5):  92-99.  Abstract ( 210 )   PDF (4188KB) ( 333 )   Save In view of the nonlinear, non-stationary and strong interference characteristics of rolling bearing vibration signals in strong noise environment, which leads to difficulty of fault feature extraction and low accuracy of fault diagnosis, this paper proposes a rolling bearing fault diagnosis method on the basis of combination of variational mode decomposition (VMD)-multi-scale permutation entropy (MPE)- kernel principal component analysis (KPCA) and multi-class relevant vector machine (MRVM). In this method, high-dimensional fault features of rolling bearing vibration signals are extracted first by VMD-MPE, and then the extracted fault features are visually reduced dimensionally by KPCA. Finally, the dimensionally-reduced fault features are input into MRVM which can realize different sample probability output for rolling bearing fault diagnosis. The effectiveness of the proposed method is verified by a set of rolling bearing fault data published by Western Reserve University in the United States. The results show that the proposed rolling bearing fault diagnosis method based on “VMD-MPE-KPCA” feature extraction and MRVM may extract and identify rolling bearing fault features effectively. If compared with those fault diagnosis methods reported in related literature, the fault identification accuracy of the proposed hybrid intelligent fault diagnosis method reaches up to 99.18%. References | Related Articles | Metrics

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A method for sorting nodes in complex networks based on degree and H index expansion LU Peng-li, YU Zhou 2020, 46 (5):  100-106.  Abstract ( 448 )   PDF (1793KB) ( 468 )   Save The importance of identifying influential nodes in complex networks has attracted more and more attentions. Commonly used centrality indexes to identify the influence of nodes include betweenness centrality, degree centrality, closeness centrality, H-index centrality, K-shell centrality and so on. These indexes have some limitations in identifying influential nodes. On the basis of H-index centrality and degree centrality, a local DH index centrality index is proposed in this paper to identify influential nodes in the networks. This index takes into account the degree and H-index of the node itself and the H-index of neighboring nodes as well. The proposed index can evaluate the effectiveness of each centrality method to identify the influence of nodes in the networks by using SIR propagation model and monotone function (M). Our experimental results show that this proposed index can identify the influential nodes in some networks more effectively than commonly used centrality index. References | Related Articles | Metrics

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DOA estimation of millimeter wave signal based on focusing matrix MIAO Feng-man, CHE Kai-qi, LI You-yu 2020, 46 (5):  107-112.  Abstract ( 256 )   PDF (631KB) ( 374 )   Save The angle of arrival (DOA) estimation of millimeter-wave signal source varies with frequency, which leads to large estimation error. A DOA estimation algorithm for millimeter-wave signal conversion to narrowband signal is proposed in this study. By establishing a millimeter wave signal reception model in the frequency domain, the proposed algorithm treats receiving signals as multiple unrelated narrowband signals and “focuses” them on a reference frequency in order to reduce the impact of the beam due to frequency changes, and then uses the ESPRIT algorithm to make millimeter wave DOA estimation. The simulation results show that the proposed algorithm may effectively reduce the DOA estimation error under moderate signal-to-noise ratio. When the number of array elements reaches 70, a relatively stable DOA estimation can be achieved, which can improve the link quality for directional transmission of millimeter-wave systems. References | Related Articles | Metrics

Architectural Sciences

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Horizontal dynamic equivalent rigidity of foundation beam on elastic half space WANG Xue, ZHOU Feng-xi 2020, 46 (5):  113-117.  Abstract ( 257 )   PDF (1032KB) ( 360 )   Save Based on the basic equation of elastodynamics and taking into account the dynamic interaction between elastic beam and elastic half-space, a mechanical analysis model is established. An analytical expression of horizontal dynamic equivalent stiffness of an elastic half-space foundation beam is obtained by using Fourier integral transformation. The variation of horizontal dynamic equivalent stiffness and damping of the elastic foundation beam is analyzed respectively by numerical examples. The results show that the horizontal dynamic stiffness and damping coefficient of the elastic foundation beam are not constant, but are related to phase velocity of the elastic foundation beam. When the phase velocity is equal to velocity of Rayleigh wave, the horizontal dynamic equivalent stiffness reaches the peak, and the longitudinal vibration of the elastic foundation beam transfers the maximum energy to the elastic half-space. The horizontal dynamic equivalent stiffness of the elastic foundation beam is closely related to the frequency and number of waves in the beam. With increase of wave number, the real and imaginary parts of the horizontal dynamic equivalent stiffness increase accordingly. References | Related Articles | Metrics

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Influence of basal treatment patterns on deformation of deep excavation in soft ground YANG Bo, TAN Yong, XU Chang-jie 2020, 46 (5):  118-123.  Abstract ( 269 )   PDF (1830KB) ( 410 )   Save The reinforcement of soil in the passive area of soft soil foundation pit plays an important role in controlling excavation deformation and protecting the surrounding environment. There are few systematic studies, from the point of view of three-dimensional space at present, on the influence of pit bottom reinforcement mode on foundation pit deformation. By means of finite element analysis software ABAQUS and measured engineering data, the deformation of a deep foundation pit of a soft soil subway station in Shanghai was investigated in this paper. The investigations were carried out respectively with respect to conditions of reinforcement of entire basal soil, or reinforcement along pit perimeter, or reinforcement by evenly distributed blocks, and reinforcement by grout struts. Our investigations show clearly thatif the reinforcement by grout struts with the same reinforcement ratio (the ratio of longitudinal length of the reinforcement along the foundation pit to longitudinal length of the foundation pit) is arranged in the foundation pit of same length, the restraining effect of the reinforcement in the center of excavation section on the deformation of the foundation pit is higher than that of the reinforcement on the side of the excavation section.Increasing the reinforcement ratio of the reinforcement by grout struts can effectively reduce deformation of the foundation pit.Among the four different strengthening methods, the reinforcement of entire basal soil has the greatest restraining effect on the deformation of the foundation pit. For a long and narrow soft soil deep foundation pit, the restraining effect of reinforcement by evenly distributed blocks and reinforcement along pit perimeter on excavation deformation are not apparent, and there is little difference with each other. References | Related Articles | Metrics

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Load transfer mechanism of tension-type anchor cable in the loess layer WANG Yong-hua, WANG Xiao-yong, ZHANG Ji-wen 2020, 46 (5):  124-129.  Abstract ( 186 )   PDF (742KB) ( 267 )   Save On the basis of previous research achievements and reasonable assumptions, load transfer mechanism of tension-type anchor cable in loess area is analyzed,and a theoretical calculation formula of the critical anchorage length of tension-type anchor cable in loess stratum is obtained. The influence of various parameters on the critical anchorage length is analyzed either. According to requirements of the current code, the rationality of the theoretical formula of the critical anchorage length of pile-anchor support system for deep foundation pit in loess area has been verified by our experiments. According to requirements of the current code, our tests have verified rationality of the theoretical formula of the critical anchoring section length of the pile-anchor support system of the deep foundation pit in the loess area. Analyses to measured data show that under condition of loess stratum, through the reasonable setting of the anchoring section of the anchor cable, the ultimate bond strength of the anchoring section can be higher than that recommended by the current code. The load-displacement curve of the tested anchor cable verifies different load service conditions and load transfer changes of the tension-type anchor cable in the loess stratum, which reflects the working state of the anchor cable under all levels of tension load. Our achievements of this study can provide guidance for the design and field test of tension-type anchor cable in loess layer. References | Related Articles | Metrics

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Deflection calculation of concrete composite box girder with steel truss webs YANG Xia-lin, ZHANG Yan, JI Wei 2020, 46 (5):  130-136.  Abstract ( 231 )   PDF (2361KB) ( 272 )   Save In order to study the calculation method of deflection for concrete composite box girder with steel truss webs and factors influencing the composite box girder′s deflection, steel truss webs are converted into steel webs with equivalent thickness, the longitudinal displacement function of cantilever plate is modified, and a formula considering steel truss webs′ shearing deformation and shear lag effect is deduced for predicting deflection by variational method. Then, a finite element model of the composite box girder is established by using the finite element software ANSYS. The numerically predicted values and theoretically calculated values are compared and analyzed respectively. On this basis, the influence of height-span ratio and the horizontal inclination angle of abdominal rod on the additional deflection produced by steel truss webs' shearing deformation and shear lag effect are both studied in details. The results show that: the accuracy of deflection calculation can be improved by modifying the longitudinal displacement function of cantilever plate of composite box girder; for composite box girder with reasonable height span ratio, the additional deflection produced by steel truss webs′ shearing deformation and shear lag effect may not be ignored; the horizontal inclination angle of abdominal rod only affects the additional deflection caused by steel truss webs′ shearing deformation. References | Related Articles | Metrics

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Performance of concrete composite columns with lining hollow octagon steel tube-reinforced on impact resistance ZHANG Kai-hang, WANG Rui, ZHAO Hui, ZHU Xiang 2020, 46 (5):  137-143.  Abstract ( 208 )   PDF (5602KB) ( 240 )   Save In order to study impact behaviors of the lining hollow octagon steel tube-reinforced concrete column, an experimental study on the impact resistance of the lining hollow octagon steel tube-reinforced concrete column without guideway was carried out by using a guideway falling weight impact testing machine. In the test process, the time history curve of impact force and displacement of specimens in the whole process of impact were recorded by using force sensor and high-speed camera. At the same time, the effects of boundary conditions, impact energy and axial pressure ratio on the failure pattern and energy dissipation of the steel tube-reinforced concrete column were also observed and investigated. Our tested results show that the outsourced reinforced concrete can work in coordination with hollow octagon steel pipe and steel pipe concrete. When bearing impact loading, the impact height has the most significant influence on the energy dissipation capacity of the specimen, followed by the boundary condition. The influence of axial compression ratio is weak, and the influence of the wall thickness of circular steel tube becomes the weakest. References | Related Articles | Metrics

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Improved calculation formula of fundamental frequency for the fabricated concrete simple supported skew girder bridges YU Zhen-gang, LI Yan, YANG Ting-ting, LU Kai-yuan 2020, 46 (5):  144-148.  Abstract ( 511 )   PDF (1526KB) ( 479 )   Save Taking a prestressed concrete prefabricated simply supported girder bridge asengineering background, the influence of oblique angle, span, bridge width and transverse torsional stiffness on the fundamental frequency of the bridge is analyzed by numerical method. The results show that as the skew angle becomes larger, the first three orders of the vertical natural vibration frequencies increase. With the increase of the span, the whole vertical stiffness becomes lower, the fundamental frequency reduce obviously, but the rate to deduction decreased gradually. The fundamental frequency affected by the mechanical characteristic of coupling of bending and torsion increases with the increase of torsional stiffness. Based on the influence of key factors above on the base frequency of the skew beam bridge, an improved formula, taking the torsional stiffness and the skew angle into account, for estimating the base frequency of the concrete simply supported skew beam bridge is therefore proposed. The precision and the applicability of the formula are verified by all measured data of several real bridges. References | Related Articles | Metrics

Scientific

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The Poisson algebra structure of the deformed Lie algebra of differential operators GAO Shou-lan, WU Qi-wei, ZHENG Shu-min 2020, 46 (5):  149-154.  Abstract ( 199 )   PDF (514KB) ( 266 )   Save Poisson algebras are thealgebras having both an algebra structure and a Lie algebra structuretogether with the Leibniz law. By using the Z-gradingthe Poisson algebra structure on the deformed Lie algebra of differential operators L~ is determined, through the Leibniz law, which shows the associative Poisson algebra structure on L~ is trivial. References | Related Articles | Metrics

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Normal subsemigroup lattices of Clifford semigroups TIAN Zhen-ji, ZHAO Mei 2020, 46 (5):  155-157.  Abstract ( 163 )   PDF (384KB) ( 211 )   Save The decomposition of the normal semigroup lattices of Clifford semigroups is studied, and then confirms the necessary and sufficient conditions for normal subsemigroup lattices of Clifford semigroups to be distributive lattices (upper semidistributive lattices, lower semidistributive lattices). References | Related Articles | Metrics

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Fixed-time control synchronization of stochastic memristive neural networks with time-varying delays PU Hao, HUANG Jiang-wen, QIN Jin, WANG Zheng-wei, WANG Xing 2020, 46 (5):  158-165.  Abstract ( 164 )   PDF (486KB) ( 266 )   Save The fixed-time control synchronization of stochastic memristive neural networks with time-varying delays is studied. Based on the set-valued mapping, stochastic differential inclusion theory, fixed-time stability theory, Lyapunov function, I$\hat{t}$o's formula and some inequality methods, under the appropriate feedback control ui(t) which related to delay τ, statistics perturbation term and transition jump Ti, some new sufficient condition is obtained for fixed time control synchronization. References | Related Articles | Metrics

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An efficient and accurate operating splitting method for solving 3D heat conduction equations WU Li-li 2020, 46 (5):  166-172.  Abstract ( 234 )   PDF (455KB) ( 459 )   Save The operator splitting local one-dimensional method is employed to resolve three-dimensional (3D) heat conduction equations. Two kinds of Padé approximations are used to calculate the temporal derivative, and two kinds of high-order difference formulas are used to calculate the spatial derivatives. Then, two kinds of efficient splitting local one-dimensional schemes are derived. The accuracy of them are the fourth-and sixth-order, respectively. The unconditional stability of both methods is proved by the rigorous matrix analysis theory. Numerical examples are resolved to validate the performances of the present method. References | Related Articles | Metrics