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28 December 2021, Volume 47 Issue 6 Previous Issue    Next Issue

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Materials Science and Engineering

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Research on mechanical properties of multi-component iron-based amorphous composite ZHAO Yan-chun, LI Ze-feng, WANG Bo, KOU Sheng-zhong, LI Wen-sheng 2021, 47 (6):  1-5.  Abstract ( 197 )   PDF (1405KB) ( 234 )   Save Fe-15Mn-5Si-10Cr-xC(x=0.6~1.0) amorphous alloy composites were prepared by vacuum magnetic levitation melting water-cooled copper crucible negative pressure copper mold suction casting method. The thermodynamic parameters of Fe-15Mn-5Si-10Cr-xC(x=0.6~1.0) alloy was adjusted by changing the content of C element. And the microstructure and mechanical properties of the alloys were studied. The results show that adding the C elements, the atom size difference δ increases, the mixing entropy ΔSmix improves while the mixing enthalpy ΔHmix reduces. The as cast microstructure of the alloy is composed of amorphous phase and undercooled γ-Fe austenite phase. Martensitic transformation occurs and work hardening is obvious during compressive stress loading. The ΔSmix and ΔHmix of the Fe-15Mn-5Si-10Cr-0.9C alloy are 1.13RJ·mol－1·K－1and －19.6 kJ·mol－1, respectively. And the compressive yield strength, fracture strength and the plastic strain are up to 1 300, 2 378 MPa and 17.2%. References | Related Articles | Metrics

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Study on electrochemical corrosion of 347H stainless steel ZHAO Ji-peng, WANG Jun, LIU Tian-zeng, LI Jun-chen, FENG Li 2021, 47 (6):  6-14.  Abstract ( 241 )   PDF (6484KB) ( 252 )   Save Electrochemical workstations were used to detect the electrochemical corrosivity of hot-rolled 347H stainless steel, solution pickled 347H stainless steel and solution treated 347H stainless steel in corrosive media 3.5wt.%NaCl, 5%wt.%H2SO4 and 5wt.%NaOH.The effect of solution treatment on the electrochemical corrosion behavior of 347H stainless steel was studied by drawing polarization curves and electrochemical impedance spectroscopy. The results showed that in the 3.5wt.%NaCl corrosion medium, solid solution pickling 347H stainless steel shows the best corrosion resistance, while solid solution treatment reduces the corrosion resistance of 347H stainless steel. In 5wt.%H2SO4 corrosion medium, corrosion resistance through 1 160 ℃ solid solution treatment with 2 h,347H stainless steel has been improved. The self-corrosion current density of hot-rolled 347H stainless steel in 5wt.%NaOH corrosion medium is an order of magnitude smaller than that of other 347H stainless steel. Therefore, hot-rolled 347H stainless steel is more resistant to corrosion of 5wt.%NaOH corrosion medium. References | Related Articles | Metrics

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Non-doped fluorescent white organic electroluminescent device based on perylene WU You-zhi, LIANG Nan, ZHAO Yu-kang, ZHANG Cai-rong 2021, 47 (6):  15-20.  Abstract ( 145 )   PDF (1536KB) ( 285 )   Save By using two typical traditional fluorescent materials as the light-emitting layer, an non-doped all fluorescent white organic light-emitting diode (WOLED) is fabricated. In the device, two thin layers of perylene are located at both sides of ambipolar host material CBP (4,4’-N,N′-dicarbazole-biphyenyl) as blue emitters, an ultra-thin rubrene layer inserted into CBP as orange emitter. A simple and efficient OLED is obtained by varying the insertion position of rubrene in CBP, the highest current efficiency is 6.6 cd/A (external quantum efficiency is 2.6%), the maximum brightness is18 480 cd/m2,and Commission Internationale de l’Eclairage (CIE) co-ordinates can reach the ideal white light equilibrium point (0.33, 0.33) at a current density of 200 mA/cm2. References | Related Articles | Metrics

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Effect of fume extraction torch in CO2 gas shielded arc welding with flux-cored wire HUANG Yong, LIU Hong-yu, MAO Yu, ZHANG Jia-jie, WANG Lu-wei 2021, 47 (6):  21-25.  Abstract ( 153 )   PDF (2842KB) ( 187 )   Save Fume extraction torch was adopted to complete CO2 gas shielded arc welding with flux-cored wire. Through recording fume diffusion pattern and change of welding current and welding voltage, analyzing droplet transition form by high-speed camera, comparing appearance of welds and revealing the weld defects by X-ray non-destructive testing technology, and comparing them with the situation without fume extraction, the performance of fume extraction torch under different fume extraction powers and torch inclination angles and its influence on welding process and welding quality are studied. The results show that welding fumes are effectively absorbed into fume extraction torch, the overall shape of the fumes is conical, and as the increase of fume extraction power, its stiffness increases and the effect of fume extraction is enhanced. The droplet transition form still appears as repelled globular transfer, and fume extraction only slightly increases the droplet transition frequency. Under different powers and given torch inclination angles, the welds are well formed and there are no defects in welds. References | Related Articles | Metrics

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Hydrothermal synthesis of Ce-ZnSnO3 material and its gas sensitivity to n-butanol gas XUE Kang, JIANG Li-li, HOU Xin-gang, CHEN Yi-xing 2021, 47 (6):  26-30.  Abstract ( 146 )   PDF (3409KB) ( 276 )   Save A novel Ce-ZnSnO3material was synthesized by hydrothermal method based on the actual detection demand of n-butanol gas in chemical plants. The crystal structure, microstructure and oxygen defect content of the material were characterized by XRD, SEM, TEM and XPS. The feasibility of Ce-ZnSnO3 as coating material for gas sensor was studied. The results showed that the response of the material to n-butanol gas with concentration of 0.01% at 350 ℃ is 2 606.473, the response/recovery time is only 6 s/26 s, and the material has excellent selectivity,which is promised sensing material for the detection of n-butanol gas. References | Related Articles | Metrics

Mechanical Engineering and Power Engineering

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Study on design method of centrifugal pump blades axially cutting and translating shroud of the impeller ZHAO Wan-yong, LIANG Yun-sheng, PENG Hu-ting, MA De-dong 2021, 47 (6):  31-37.  Abstract ( 256 )   PDF (5140KB) ( 407 )   Save It is common in the engineering practice that the working flow of the centrifugal pump is higher than that required by the water delivery system. The translation of the shroud to reduce the width of the impeller outlet can reduce the working flow to achieve the purpose of energy saving in the pumping station. Numerical simulation method is used to study the effect of axially shifting impeller shroud on the performance of centrifugal pump. Combined with the theory, the conversion formula of the front cover plate changing the head of the centrifugal pump is deduced. The results show that cutting the outer diameter of the impeller and translating the shroud of the impeller will reduce the working head of the centrifugal pump. The difference is that the former moves the head curve downward and the decline is greater, while the latter's head curve becomes steeper, but maintain a higher head in small flow conditions. Compared with cutting the outer diameter of the impeller, the hydraulic performance of the centrifugal pump is deteriorated. The translation of the shroud of the impeller suppress the development of the continuous vortex in the impeller under low flow conditions, and the efficiency of the centrifugal pump is increased, which is more suitable for the occasions where multiple pumps work in parallel. According to the basic equation of the pump, the conversion formula of shifting shroud to change centrifugal pump head is derived, and the error of the conversion formula is corrected by using multiple regression analysis. After the test of different centrifugal pump models, the results show that the conversion formula can relatively accurately predict the change of H-Q curve in the range of 0.8~1.0 times working conditions of the centrifugal pump when the moving amount of the shroud of the impeller is small. References | Related Articles | Metrics

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Study on effect of blade tip slot on blade tipflow field of the wind turbine YANG Rui, WEN Wei-yue, ZHOU Nan-nan, YANG Wei, GU En-xin 2021, 47 (6):  38-44.  Abstract ( 229 )   PDF (3736KB) ( 347 )   Save Taking the 1/8 scaled model of the NREL Phase VI blade as the research object, three annular slots from the leading edge to the tip surface of the blade are designed in the blade tip region to change the distribution of the blade tip flow field. Using the CFD method, the pressure distribution on the blade tip surface and the development process of the tip vortex are analyzed through the speed change, and the influence of the blade tip slot on the tip vortex of the wind turbine is studied. The research results show that when the speed is lower than 900 r/min, the blade tip slot has little effect on the aerodynamic performance of the blade. When the speed is higher than 900 r/min, the blade tip slot can reduce the strength of the vortex core, accelerate the tip vortex dissipation, and increase the aerodynamic efficiency of the blade. The air flow jetted from the annular slots has a significant blocking effect on the incoming flow, and can reduce the axial velocity in the wake region. In terms of accelerating the dissipation of the tip vortex and reducing the strength of the tip vortex, the slot at the blade tip of the wind turbine is considered to be an effective design when the speed is higher than 900 r/min. References | Related Articles | Metrics

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Study on high-speed milling characteristics of 2A12 aluminum alloy based on J-C constitutive model ZHAO Jia-li, SHAO Kun-peng, ZHANG Pan-pan, DAI Yian-xia 2021, 47 (6):  45-49.  Abstract ( 236 )   PDF (3360KB) ( 270 )   Save Aiming at the optimization problem of cutting parameters in the high-speed cutting process, a finite element model for high-speed cutting of 2A12 aluminum alloy with cemented carbide tools was established based on ABAQUS , and the influence of cutting parameters and tool parameters on cutting force was analyzed through simulation method, and milling experiments were carried out to compare the simulation results, the error is within 17%, which verifies the availability of the simulation model. It provides a theoretical basis for selecting reasonable tool geometry and cutting parameters in the process of high-speed milling of aluminum alloy workpieces. References | Related Articles | Metrics

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A novel cleaning method for wind turbine data based on QM-DBSCAN ZHENG Yu-qiao, LIU Yu-han, HE Zheng-wen, Dong Bo, Wei Jian-feng 2021, 47 (6):  50-55.  Abstract ( 287 )   PDF (1531KB) ( 270 )   Save For the issue of wind Speed-Power data hard cleaning in wind farms, a novel method based on QM-DBSCAN is proposed. Firstly, the wind condition which can best represent the operating state of the wind turbine is selected as the research object, and the anomalous data are classified according to the distribution characteristics. Then, the quartile method, standard DBSCAN algorithm and QM-DBSCAN method were used to identify and eliminate the abnormal data. The Spearman correlation coefficient was adopted to verify the effectiveness of the proposed method. The results indicated that the QM-DBSCAN method had the best elimination effect, which was 0.003 5 and 0.004 7 higher than the quartile method and the DBSCAN method, respectively. References | Related Articles | Metrics

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A fatigue life prediction model of multi-axial notched specimens with notch effect LIU Jian-hui, PAN Xue-mei, LU Xin, ZI Rong, CHEN Xiao-chuang 2021, 47 (6):  56-60.  Abstract ( 195 )   PDF (1412KB) ( 409 )   Save In order to study the multi-axial fatigue of notched specimens, based on the theory of damage mechanics and the idea of von Mises equivalent rule, a multi-axial damage constitutive equation considering notch effect was established, which comprehensively considers the effect of normal stress and shear stress in the multi-axial damage process; and further, a multi-axial fatigue life prediction model that can be applied to metal notched parts was proposed in this paper. The model was evaluated by the multi-axial notched fatigue test data of GH4169 nickel-based superalloy, SAE1045 steel and LY12CZ aluminium alloy. The results show that the multi-axial fatigue life predicted by the proposed model was in good agreement with the test results, and the prediction accuracy was significantly improved compared with the traditional local stress strain approach. At the same time, the model is easy to calculate and is convenient for engineering application. References | Related Articles | Metrics

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Simulation and rigid-flexible coupling analysis of orbiting scroll overturning of scroll compressor based on ADAMS ZHAO Man, LI Xin-qing 2021, 47 (6):  61-65.  Abstract ( 282 )   PDF (3162KB) ( 359 )   Save Aiming at the problems of orbiting scrolloverturning and clearance of moving pair of scroll compressor, based on the analysis of its structural characteristics and force conditions, a three-dimensional model of the scroll compressor rotor system was established by Solidworks, and the motion simulation and rigid-flexible coupling simulation of the model were carried out by ADAMS. The simulation results show that the maximum inclinationangle occurs at the rotation angle of 313.2°~330.6° withinthe spindle cycle under the constant clearance value.The clearance has no effect on the centroid displacement of theorbiting scroll under the overturning, but will increase the vibration of theorbiting scroll. The flexibilization of the orbitingscroll has no effect on its centroid displacement, but the maxiumum value of its centroid point displacement in the radial direction is 3.17 times of that under the rigid condition, which intensifies the overturning of the orbiting scroll and reduces its service life. References | Related Articles | Metrics

Chemical Industry and Light Industry

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Synthesis of phosphorus-containing benzimidazole-based copper complex and properties of flame-retardant epoxy resin YANG Bao-ping, CHEN Xiao-dong, WANG Nian-nian, CUI Jin-feng, GUO Jun-hong 2021, 47 (6):  66-73.  Abstract ( 175 )   PDF (4541KB) ( 329 )   Save In order to modify the flame retardant property of epoxy resin, a new type of phosphorous/nitrogen dihydric compound, phosphoric acid 4-(1H-benzoimidazol-2-yl)-phenyl ester diphenyl ester (PBIm), was prepared by substitution reaction and condensation reaction, and used as an organic functional group to react with copper acetate-hydrate to synthesize phosphorus-containing benzimidazole-based copper complex flame retardant PBIm-Cu. It was added to epoxy resin (EP) to prepare flame retardant epoxy resin composite (PBIm-Cu /EP). The structure of the flame retardants PBIm and PBIm-Cu was characterized by infrared spectroscopy, X-ray photoelectron spectroscopy, hydrogen nuclear magnetic spectrum and phosphorus nuclear magnetic spectrum. Thermogravimetric analyzer (TGA), limiting oxygen index (LOI) and cone calorimeter (CCA) were used to test the thermal stability and flame retardancy of composite materials. The PBIm-Cu/EP system with a PBIm-Cu mass fraction of 7% passed the V-1 level in the vertical combustion test, and the LOI was increased to 31.6%. Moreover, compared with pure EP, the peak heat release rate (PHRR), total heat release rate (THR) and total smoke exhaust rate (TSP) were decreased by 64%, 41% and 43%, respectively, and the residual weight rate reached 26.7%. SEM results show that the surface of the carbon layer after the combustion of PBIm-Cu/EP material is smooth, continuous and dense. References | Related Articles | Metrics

Automation Technique and Computer Technology

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Study on life extension strategy based on real-time life prediction of feedback control system LI Wei, LI Zong-ren, MAO Hai-jie 2021, 47 (6):  74-83.  Abstract ( 276 )   PDF (3371KB) ( 398 )   Save Aiming at the problem that the performance of the feedback control system cannot meet the time limit of the control task due to the implicit degradation of the actuator, a dynamic matrix control (DMC) life extension method based on the real-time life prediction of the feedback system is proposed. Firstly, based on the Wiener and Poisson process, a composite model more suitable for the actual degradation process of actuator is established. Secondly, by analyzing the impact of the implicit degradation of the actuator on the performance of the control system, the analytical solution of the remaining life (RUL) of the system is given, and the real-time and rapid prediction of system RUL is realized. Then, based on the RUL prediction information and combined with the DMC method, the RUL of the system is extended by the online targeted adjustment of the element values of the constraint matrix Q and R, so as to ensure the achievement of the time limit requirements of control tasks. Finally, the effectiveness of the proposed method is verified by a double tank liquid level system, and the life extension effect and robustness are better than the existing LQR method. References | Related Articles | Metrics

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Dynamic output feedback control of networked systems with access constraints and random delay ZHU Chao-qun, ZHANG Pan 2021, 47 (6):  84-93.  Abstract ( 184 )   PDF (950KB) ( 169 )   Save The dynamic output feedback control problem is investigated for a class of random-delay networked control systems with medium access constraints. Considering the effects of medium access constraints and random delay, the systems are modelled as a class of Markov jump systems with parameter uncertainty. Based on Lyapunov stability theory and LMI technology, the sufficient conditions for stochastic stability are derived, and the corresponding dynamic output feedback controller is designed to make the closed-loop system robust stability with a given H-infinity performance. Finally, an illustrative example is provided to demonstrate the effectiveness of the proposed method. References | Related Articles | Metrics

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Performance analysis of SWIPT NOMA based satellite-terrestrial system ZHAO Jin-long, HUO Ming-ming, TAN Deng-tai 2021, 47 (6):  94-99.  Abstract ( 198 )   PDF (2276KB) ( 193 )   Save In order to improve the resource utilization and user fairness of satellite-terrestrial system, a simultaneous wireless information and power transfer (SWIPT) non-orthogonal multiple access (NOMA) technology assisted satellite-terrestrial system transmission scheme is proposed. Firstly, the outage performance of the system is investigated in the presence of imperfect channel state information (CSI), and the outage probability expression is derived. Secondly, by analyzing the asymptotic outage probability, it is observed that there is an error floor in the high SNR region due to the existence of imperfect CSI. In addition, the effects of channel estimation errors and shadow fading on system throughput and energy efficiency are studied. Finally, the numerical simulation results are provided to validate theoretical derivation and the performance gains obtained by introducing SWIPT NOMA technology into the satellite-terrestrial system. References | Related Articles | Metrics

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Financial distress prediction based on Adaboost algorithm combined with DEGWO-SVM ZHU Chang-sheng, TIAN Hui-xing, FENG Wen-fang 2021, 47 (6):  100-107.  Abstract ( 161 )   PDF (1822KB) ( 216 )   Save A new Adaboost-DEGWO-SVM combination model is proposed in this paper to solve the problems of difficult parameter selection and low classification accuracy of support vector machine (SVM) in financial distress prediction. Firstly, the financial data of all A-share listed companies were preprocessed in 2017, and 1∶1 modeling dataset of distressed companies (ST) and normal companies was extracted. Then, the difference evolutionary algorithm (DE) was used to improve the global search capability of GWO, and to solve the problem that the gray wolf algorithm is prone to fall into the local optimal, so as to realize the optimization of the parameters of SVM. Finally, Adaboost algorithm is used to improve the classification ability of DEGWO-SVM model. Experimental results show that the proposed Adaboost-DEGWO-SVM combined forecasting model has obvious advantage in dilemmaprediction, compared with DEGWO-SVM, the classification accuracy rate isincreased 4.34%, Ⅰ errors and Ⅱ errors aredecreased by 0.043 5, and compared with the single SVM, theclassification accuracy rate is increased 13.04%, Ⅰ errors and Ⅱ errors decreased 0.130 4 and 0.130 5, it is a kind of potential corporate financial distress prediction model. References | Related Articles | Metrics

Architectural Sciences

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Analysis of floor response spectrum influencing factors of isolated structure-equipment coupled system DANG Yu, XIE Peng-fei 2021, 47 (6):  108-114.  Abstract ( 179 )   PDF (3120KB) ( 193 )   Save The dynamic analysis model of isolated structure-equipment coupled system was established in SIMULINK environment. The dynamic responses of two actual isolated structure-equipment coupled systems were calculated by time history analysis with multiple ground motions, and the mean spectrum of the floor acceleration amplification factor was obtained as the floor response spectrum, and compared with the floor response spectrum of the isolated structure without considering the coupled effect. The effects of equipment dynamic characteristics, isolated structure dynamic characteristics, building site and location of equipment on floor response spectrum of isolated structure-equipment coupled system were discussed. The results show that with the increase of equipment mass and damping, the coupled effect between isolation structure and equipment becomes more obvious. Especially when the mass ratio of equipment to floor is more than 1%, the coupled effect between equipment and structure should be considered. The dynamic characteristics of isolated structure, equipment dynamic characteristics and site conditions all affect the spectrum value and spectrum shape of floor response spectrum, but the effect of different locations of the equipment on the floor spectrum is tiny and can be neglected. References | Related Articles | Metrics

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Seismic response analysis of embedded double-layer oil storage tank considering soil-structure interaction LI Tian-ping 2021, 47 (6):  115-121.  Abstract ( 160 )   PDF (5555KB) ( 325 )   Save The traditional buried single-layer steel oil tank is exposed to the internal and external corrosive environment for a long time, which is easy to leak and pollute the soil and groundwater. The double-layer FF (Fiber Reinforced Plastics- Fiber Reinforced Plastics) and SF (Steel-Fiber Reinforced Plastics) storage tanks have good corrosion resistance and low cost. The material strength can meet the requirements of use, and hasbetter safety performance than single-layer steel storage tanks. The numerical calculation model for buried FF and SF double-layer oil storage tanks was established,considering the viscoelastic boundary and fluid-solid coupling. The seismic response of buried FF and SF double-layer oil storage tanks was studied, and the influence of parameters was analyzed. The results show that the dynamic response of the tank under liquid filling condition is obviously larger than that without liquid filling condition. The dynamic response of the system under near-field earthquake is larger than that under far-field earthquake. The dynamic action of oil storage tank increases with the increase size of body shape. In this paper, it is found that the dynamic response of FF and SF storage tanks is similar in model analysis and practical application, and both of them have a good application prospect, good economy and practicability in future engineering practice. References | Related Articles | Metrics

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Effect of long-term loading on mechanical behavior of square CFST columns with inner profiled I-shaped steel subjected to axial loading ZHAO Meng-meng, SHI Yan-li 2021, 47 (6):  122-130.  Abstract ( 142 )   PDF (5112KB) ( 122 )   Save A numerical analysis model of the CFST columns with inner profiled I-shaped steel subjected to long-term axial loadingwas established by ABAQUS. The model was verified by experimental results. Based on the model, the mechanical property of composite columns was analyzed and compared with those of the composite column without long-term loading. Finally, the effect of parameters on the creep deformation and bearing capacity of members was analyzed in terms of long-term load ratio, concrete strength, steel-bearing steel rate and steel-containing steel ratio. The results show that long-term loading causes the steel tube and inter profiled steel to enter plastic yield in advance, increases the contact stress between them and concrete when the composite column reaches the ultimate bearing capacity, and improves its restraint on concrete. The ultimate bearing capacity of composite columns increases under long-term loading and the corresponding strain increases. The parametric analysis shows that the increase of concrete strength increases the influence of long-term load on composite columns, while the increase of steel content of steel pipe and section steel reduces the influence of long-term loading. References | Related Articles | Metrics

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Analysis of deformation law of Lanzhou metro station deep foundation pit with red sandstone stratum ZHU Yan-peng, LI Geng, MA Xiao-rui, WEI Peng-yun, LIU Xin, YIN Li-jie 2021, 47 (6):  131-137.  Abstract ( 163 )   PDF (4351KB) ( 174 )   Save In order to study the deformation law caused by dewatering and excavation of foundation pit in red sandstone stratum with high water level, taking the deep foundation pit project of Lanzhou Dongfanghong square subway station as the background, the horizontal displacement of piles and ground settlement around foundation pit during dewatering and excavation were monitored on site. The finite difference software Flac3D was used tosimulate the displacement of foundation pit during dewatering and excavation. The monitoring results show that the position of the maximum horizontal displacement of the pile gradually moves down with the increase of foundation pit excavation, and finally it is near the bottom of the foundation pit, about 1 to 2 m abovethe bottom of foundation pit. The maximum settlement value of the surface appears at a distance of 5 to 7 m from the side of the foundation pit, about 0.29 to 0.41 times of the depth of foundation pit. Soil and water loss between piles is the main cause of excessive ground subsidence. Comparing the simulated results with the measured ones, it is concluded that the variation trend of simulated and monitored surface subsidence is basically the same. The simulated value of the horizontal displacement of the pile is very close to the measured value when it is less than 12 m away from the ground. When it is more than 12 m away from the ground, the measured value is obviously larger than the simulated value. References | Related Articles | Metrics

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Study on the evolution of urban space form and the relationship between city and water in zhangye city ZHANG Xiao-juan, WAN Qing, PU Fa-liang 2021, 47 (6):  138-144.  Abstract ( 153 )   PDF (3302KB) ( 206 )   Save Based on the aerial imagery and ancient literature data, the spatial data analysis method was used to study the dynamic evolution of urban spatial morphology in Zhangye City from 1949 to 2012. The results show that: The city has changed from slow development to rapid development, and the land intensive utilization rate has increased. The relationship between city and water is from far to near, from passive to interactive, the urban ecological function of the water system is increasingly prominent, and the water environment has been given more rich connotations. Based on the goals of sustainabledevelopment and water ecological construction, in the future, Zhangyeshould renovatethe river system, construct the water ecological security pattern, repair and protect the urban wetland and strengthen the ecological green space construction to create the water culture characteristic, and to promote sustainable development. References | Related Articles | Metrics

Scientific

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An iterative method for inhomogeneous heat equation of sideways problem XIONG Xiang-tuan, QIAO Yu 2021, 47 (6):  145-150.  Abstract ( 159 )   PDF (588KB) ( 252 )   Save The sideways problem of nonhomogeneous heat equation is discussed, which is seriously ill-posed. By using the iterative regularization method, a regular approximate solution of the problem is obtained, and the Hlder type error estimate of this solution relative to the exact solution is given under a prior and a posterior regularization parameter selection rules, which shows that the iterative regularization method is effective to solve such problems. References | Related Articles | Metrics

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Generalized Jacobsthal number and its combinatorial meaning YANG Sheng-liang, REN Feng-yun 2021, 47 (6):  151-155.  Abstract ( 172 )   PDF (588KB) ( 159 )   Save The concept of generalized Jacobsthal sequence of order k is introduced. The generating function of Jacobsthal sequence of order k and the related combinatorial identities are obtained. The enumerations of two classes of lattice paths are studied and the two combinatorial interpretations of Jacobsthal numbers of order k are given. References | Related Articles | Metrics

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Generalized C3 modules WANG Yong-duo, QIN Li-fang 2021, 47 (6):  156-159.  Abstract ( 131 )   PDF (519KB) ( 166 )   Save As a proper generalization of C3 modules, the concept of generalized C3 modules (briefly G-C3 modules) is introduced in this paper. Basic properties of these modules are studied and it is shown that a hereditary ring R is a right V-ring if and only if every finitely cogenerated R-module is a G-C3 module if and only if every finitely copresented R-module is a G-C3 module. References | Related Articles | Metrics

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The prime hyperfilter theorem on strong join-hyperlattices XIE Xiang-yun, ZHAO Xue-xin 2021, 47 (6):  160-164.  Abstract ( 170 )   PDF (529KB) ( 277 )   Save The notion of strong join-hyperlattices and the notions of hyperideals and hyperfilters in strong join-hyperlattices are introduced. The hyperideal generated by a∈L is studied and the distributivity of I(a∧b) is proved. Moreover, hyperlattices with condition “*” is discussed and the prime hyperfilter theorem of strong join-hyperlattices is also given. References | Related Articles | Metrics

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Analysis of temperature field and thermal stresses of thermoelectric material beams under transient thermal shock TENG Zhao-chun, YANG Wen-xiu 2021, 47 (6):  165-171.  Abstract ( 222 )   PDF (1960KB) ( 320 )   Save Based on the characteristics of thermoelectric materials, the governing equations of the transient model of thermoelectric materials are obtained by the thermoelectric equilibrium equation and constitutive equation. The nonlinear transient temperature field of the thermoelectric material beam is obtained by using the separated variable method combined with the initial and boundary conditions of the model, and the transient thermal stress field is obtained according to the thermal stress theory analysis. Then the characteristic curves of the transient temperature field and transient thermal stress field of the thermoelectric material beam with parabolic distribution are given by using the mathematical software MATLAB. The thermal stress analysis of thermoelectric material beam under thermal shock load in thermoelectric coupling environment is studied. The changes of temperature field and stress field with thickness at different times are discussed, and the thermal stress characteristic curves of p-type and n-type Bi2Te3 thermoelectric material beams are compared. The results show that the transient temperature field increases and decreases with the increase of thickness under the influence of transient term, and the transient temperature field and transient thermal stress field finally tend to steady state and no longer change with time; the thermal stress of Bi2Te3 thermoelectric material beam after steady state is greater than that of transient state; the thermal stress of p-type Bi2Te3 thermoelectric material beam is always greater than that of n-type Bi2Te3 thermoelectric material beam. References | Related Articles | Metrics