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Table of Content

    28 April 2022, Volume 48 Issue 2 Previous Issue    Next Issue
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    Materials Science and Engineering
    First principles on the effect of Cr content on the electronic structure and mechanical properties of Fe3Al alloy
    LI Ya-min, ZHANG Jun-xia
    2022, 48 (2):  1-8. 
    Abstract ( 480 )   PDF (4161KB) ( 677 )   Save
    Effect of Cr content on the electronic structure and mechanical properties of DO3-Fe3al alloy was investigated by using the first principle method based on density functional theory. The occupation of Cr in the supercell model was determined by calculating the formation heat and binding energy of the system before and after doping, and the micro mechanism of the effect of Cr on the mechanical properties of Fe3Al alloy was revealed by calculating the elastic modulus, population, density of states and differential charge density. The results showed that Fe Ι bit is preferentially occupied when the Cr content is 3.125 at.%, while the content is 6.25 at.%), it tends to occupy Fe Ι and Al bit. The doping of Cr improves the stability of the system and the brittleness of the alloy, and the toughening effect increases with the increase of Cr content. Cr doping changes the distribution of electrons between atoms, with the increase of Cr content, the number of p-d hybrid electrons between Fe and Al decreases and the covalent bond decreases, at the same time, the charge transferring between atoms increases, the increase of Fe-Fe bond and the existence of Fe-Cr and Al-Cr anti bonds enhance the metallicity of the system, in addition, decrease of the covalent bond on the (100) plane but the increases of bonding strength between atoms on the (010) plane are all the essential reasons that the addition of Cr can improve the toughness of Fe3Al alloy.
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    Effective thermal conductivity and microstructure design of fully ceramic microencapsulated fuel pellet based on finite element calculations
    ZHANG Xu-dong,DENG Jun-kai, MA Da-yan, CAO Hui-ying, ZHANG Rui-qian, TANG Rui
    2022, 48 (2):  9-15. 
    Abstract ( 398 )   PDF (3469KB) ( 491 )   Save
    To study the thermal conductivity of a fully ceramic microencapsulated (FCM) pellet, the sphere method was used to predict the effective thermal conductivity of the multilayered tri-isotropic (TRISO) particle by finite element method. Meanwhile, the effective thermal conductivity of the FCM pellet was calculated by a multi-scale equivalent representative volume element method and optimized by adjusting the content and distribution of TRISO particles. The simulation results showed that the effective thermal conductivity of the TRISO particle and FCM pellet can be predicted quickly and accurately by using the sphere method and the multi-scale equivalent method, and the effective thermal conductivity of the TRISO particle can be improved byadjusting the thickness of the SiC layer.An FCC-stacked microstructure using TRISO presented to makethe FCM pellet possesse higher content fuel particles and exhibits improved heat conduction performance.
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    Preparation of amorphous Ni-Mo alloy by pulse electrodeposition and its hydrogen evolution properties
    YANG Ya-hui, LI Qing-lin
    2022, 48 (2):  16-20. 
    Abstract ( 286 )   PDF (2358KB) ( 467 )   Save
    Electrolytic aquatic hydrogen is one of the widely technologies to product hydrogen because of the advantages of abundant raw materials, clean production process and high efficiency. The different amorphous Ni-Mo alloy coatings were prepared by pulse electrodeposition under different current density and duty cycle, and the effects of current density and duty cycle on the properties of the coating were studied. The results showed that the Mo content is decreased and the surface become the rougher with the increase of the duty cycle and the current density, and the amorphous Ni-Mo alloy coating with very rough surface can be obtained under the current density of 2.5A·dm-2 and the duty cycle of 0.8. In addition, the alloy coating possessed smaller grain size is prepared under the duty cycle of 0.6 and the current density of 2.0 A·dm-2. The Ni-Mo alloy with the rough surface show better catalytic performance for hydrogen evolution under the large overpotential, and the alloy coating with the high Mo content and the fine grain size has good catalytic activity for hydrogen evolution.
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    Study on deformation characteristics and mechanical behavior of rock under low temperature freezing state
    XI Xin-lin
    2022, 48 (2):  21-27. 
    Abstract ( 411 )   PDF (3601KB) ( 471 )   Save
    In order to study mechanical behaviorof frozen rock under different water content in frozen soil area, the uniaxial compression test and Brazilian splitting test of tuff and basalt frozen soil specimens at room temperature 20 ℃ and low temperature -20 ℃ were carried out. By observing its deformation behavior and acoustic emission activity, the fracture failure process and the effect of water content on the strength and deformation properties of the material were studied. The results showed,the fracture process of frozen rock can be divided into the following stages:Ⅰ stage is crack pore closure;Ⅱ stage is elastic deformation;Ⅲ stage is crack initiation and stable crack propagation;Ⅳ stage is unstable crack propagation. At the same time, the stress level at the beginning of stage Ⅲ increases with the increase of water saturation. The peak stress intensity and strain increase with the increase of water content, and the relationship between them can be approximated by a straight line. Rock brittleness decreases with the increase of water content, and the influence of indirect tensile strength on water content is more sensitive than uniaxial compressive strength.
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    Effect of water temperature on the performance of foam concrete based on orthogonal experiment
    WANG Jun, WANG Xin-qi, GUO Hong-jie, DU Hang-wei
    2022, 48 (2):  28-33. 
    Abstract ( 306 )   PDF (3015KB) ( 329 )   Save
    In order to eliminate the error caused by multiple factors on the test results, the effect of different preparation water temperatures on the performance and internal pores of the foamed concrete was studied. The orthogonal test (three factors and three levels) was set, and the optimal water binder ratio is 0.6, the optimal content of fly ash is 15%, and the optimal content of rubber powder is 2%. Seven different water temperatures(15、20、25、30、35、40、45 ℃) were set on above basis, and theeffect of water temperature on the main physical and mechanical properties and internal pore size of foam concrete was studied by collecting the experimental data of compressive strength, dry density, water absorption of foam concrete specimens and micro data of internal morphology. The test results showed that there is a numerical relationship between the compressive strength, dry density, water absorption and water temperature of the foam concrete, and there is a correlation between the physical and mechanical properties. When the foaming water temperature is 30℃ and 35℃, the foamed concrete has the best foaming effect. The number of interconnected pores in the foamed concrete is small, the pore size is uniform, the porosity is high, the average pore size is about 1.9mm, and the physical and mechanical properties meet the requirements of the specification.
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    Mechancial Engineering and Power Engineering
    Study on dynamic characteristics of wind power speed-increasing box considering temperature effect
    ZHAO Rong-zhen, HUA Zhi-feng
    2022, 48 (2):  34-42. 
    Abstract ( 223 )   PDF (3233KB) ( 495 )   Save
    Aiming at the abnormal temperature phenomenon of wind power speed-increasing gearbox, based on Block flash temperature theory and Hertz contact theory, a calculation method considering the contact temperature of tooth surface under random wind load is proposed. Based on this method, and according to the coupling modeling theory of planetary gear trains, a calculation model for the dynamic performance of the wind power speed-increasing gearbox is established. The model not only reveals the functional relationship between random wind load, tooth surface contact temperature and tooth profile thermal deformation, but also shows the effect of non-linear factors such as random wind load and tooth surface contact temperature on the dynamic response of wind power gearboxes. The results show that the random dynamic change characteristics of the input load of the wind power speed-increasing box will cause the contact temperature of the tooth surface to fluctuate within a certain range. The dynamic tooth surface contact temperature will cause thermal deformation of the gear tooth profile, thereby affecting the time-varying meshing stiffness of the gear, and ultimately affecting the dynamic characteristics of the gearbox. This study may provide a theoretical reference for solving the abnormal temperature phenomenon of wind power speed-increasing gearboxes.
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    Influence of thermal-pressure deformation on clearance leakage of piston pair in ultra-high pressure water pump
    ZHAO Jing, JI Hong, LIU Yin-shui, ZHANG Jian-jun
    2022, 48 (2):  43-48. 
    Abstract ( 266 )   PDF (3464KB) ( 426 )   Save
    The leakage of the clearance of the piston pair is the main factor affecting the volumetric efficiency of the piston pump, and the thermal-pressure coupling deformation of the micron clearance of the piston pair can not be ignored under ultra-high pressure.Based on the thermal-fluid-structure coupling method, the dominant pressure deformation model and the thermo-compression coupling deformation model were established to simulate the differential pressure flow in the two-dimensional axisymmetric model of the piston pair with 5 μm unilateral clearance height. The results show that when the inlet pressure of the piston pair is 110 MPa, the compressive deformation is dominant at the inlet of the clearance, and the unilateral clearance increases by more than 4 μm, while the thermal deformation is dominant at the outlet of the clearance, and the unilateral clearance decreases by 1.1 μm.The clearance leakage of the piston pair is 4 times as much as that of the piston pair without deformation under the model dominated by compression deformation. The clearance leakage of the piston pair calculated by thermal-pressure coupling deformation model is 1.3 times that of the piston pair without deformation.The research results provide a method for accurately predicting the clearance leakage flow of the piston pair of the ultra-high pressure water pump.
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    Friction behavior of UHMWPE composites under different water lubrication conditions
    YANG Dong-ya, TIAN Song, REN Jun-fang, WANG Hong-gang, GAO Gui, CHEN Sheng-sheng
    2022, 48 (2):  49-54. 
    Abstract ( 230 )   PDF (2813KB) ( 345 )   Save
    In order to study the effect of different water lubrication conditions on the friction process of UHMWPE/rubber composites, different UHMWPE composites with different rubber fillings were prepared by high temperature mixing and hot pressing. Using MRH-3 ring-block friction testing machine, through the control variable method, the friction and wear properties of different components of composites were quantitatively studied, so as to optimize the final UHMWPE composites. On this basis, the effect of three water lubrication conditions on the friction process of the optimal material was studied, and the wear surface was analyzed by SEM to explore the friction mechanism from the microscopic level. The results show that water lubrication conditions have a significant effect on the tribological properties of UHMWPE composites, and the corresponding wear mechanisms are different. The improvement of lubrication conditions can shorten the running-in period and lengthen the stable wear period. The wear conditions of water-lubricated bearing materials of naval vessels under different water-lubricated conditions are comprehensively evaluated from both microscopic and quantitative aspects, which can provide theoretical guidance for working condition planning and practical application.
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    Effect of turbine guide vane position on sealing efficiency prediction model
    DU Lin-mao, ZHAO Guo-chang
    2022, 48 (2):  55-60. 
    Abstract ( 165 )   PDF (3638KB) ( 435 )   Save
    In order to study the effect of turbine guide vane position on gas ingestion, the reduced-order model for predicting the sealing efficiency of the turbine disk cavity is optimized.Numerical simulation method and regression analysis are used to analyze the variation law of the pressure field in the annulus at different positions of the guide vanes. Based on the calculated data and literature experimental data, the parameters related to the flow state of the annulus in the prediction model are optimized. The results show that there is a positive linear relationship between the control parameters of the annulus Reynolds number and the relative position of the guide vane and the rim seal in the model.
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    Cooperative optimization of ride comfort and handling stability of semi-trailer tractor based on improved genetic algorithm
    ZHAO Xiang-yang, WU Qi-bin
    2022, 48 (2):  61-66. 
    Abstract ( 243 )   PDF (2258KB) ( 426 )   Save
    In order to realize the cooperative optimization of ride comfort and handling stability, the suspension system of a tractor semitrailer is taken as the research object. The maximum acceleration in z direction above the seat cushion under pulse input and the amplitude of yaw rate under angle step input are taken as the objectives. The leaf spring stiffness of front or rear suspension, the saddle stiffness of front or rear suspension and the damping coefficient are selected as the design variables. what’s more,based on objective function, the improved NSGA -Ⅱ genetic algorithm is used to optimize and match the design variables. Finally, the optimal parameters are imported into the pre established vehicle simulation model of ADAMS/CAR software for simulation test analysis, which deepens the application of genetic algorithm in the multi-objective optimization of semi suspension tractor. The results show that the ride comfort and handling stability after optimization are improved effectively. The research also provides an effective matching method for studying the ride comfort and handling stability of vehicles.
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    Chemical Industry and light Industry
    Vibration analysis of static ring based on rotor-bearing-dry gas seal system
    ZHANG Wei-zheng, ZHAO Zhi-hong, JIANG E, HONG Hai-min
    2022, 48 (2):  67-72. 
    Abstract ( 216 )   PDF (1952KB) ( 409 )   Save
    Taking the rotor-bearing-dry gas seal system as the research object, considering the effect of bearing oil film force and outside instantaneous excitation force on the stability of dry gas seal system, the rotor-bearing-axial vibration model of dry gas seal system is established, a nonlinear Reynolds equation under the microscale is solved by using approximate analytical method, at the same time, the equation of axial stiffness and axial damping of gas film are derived by using the coupled vibration equation, and the calculation is programmed. By analyzing the response time history diagram and phase track diagram under different spiral slot number, the optimal range of spiral slot number for the axial vibration characteristics of the system is investigated. Compare and analyze the stability range of dry gas seal groove parameters of dry gas seal ring-gas film systems and rotor-bearing-dry gas seal system under the actual working conditions, so as to provide theoretical guidance for the research and design of nonlinear stability of dry gas seal.
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    Automation Technique and Computer Technology
    Sensor control strategy of Gaussian mixture labeled multi-Bernoulli filter
    CHEN Hui, LIU Ya-ting, WANG Li
    2022, 48 (2):  73-80. 
    Abstract ( 225 )   PDF (2006KB) ( 290 )   Save
    Aiming at the sensor control problem in the optimization of multi-target tracking, a fast sensor control strategy based on Gaussian mixture labeled multi-Bernoulli filter is proposed, and is used in the risk assessment based on the target threat assessment. First, the paper presents the realization form of the Gaussian mixture labeled multi-Bernoulli filter, and studies the calculation of the Cauchy Schwarz divergence between two Gaussian mixtures. Secondly, multi-Bernoulli is used to partially replace the labeled multi-Bernoulli filter pseudo update step in sensor control, that is, removing tagging is adopted in the process of multi-Bernoulli update, which significantly reduces the complexity of sensor control algorithm. In addition, based on the general sensor control method, the ultimate control scheme is solved by maximizing the target information gain of the maximum threat degree as the criterion. Simulation results show the effectiveness and rapidity of the proposed algorithm.
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    Chest X-ray emphysema detection algorithm based on channel attention and dilated convolution
    LI Ce, XU Da-you, JIN Shan-gang, GAO Wei-zhe, CHEN Xiao-lei
    2022, 48 (2):  81-89. 
    Abstract ( 240 )   PDF (6278KB) ( 306 )   Save
    Emphysema detection algorithm in chest X-ray plays an important role in clinical aided diagnosis. In order to solve the problems in existing algorithms, such as lacking feature channel screening ability, small receptive field of feature map, easy to be disturbed by local tissue noise, sample imbalance, EDACD (a chest X-ray emphysema detection algorithm based on channel attention and dilated convolution) is proposed in this paper. Firstly, the feature extraction network SE-ResNet and the feature pyramid network SE-FPN with channel selection ability are constructed by using channel attention module. At the same time, the dilated convolution is used to replace some common convolutions in SE-ResNet, and the robustness of the features is improved by increasing its receptive field. Finally, the focus loss is used as the classification loss function to make the network focus on training difficult samples. In addition, in the training process, the limited contrast adaptive histogram equalization algorithm is used to preprocess the image, which further highlights the characteristics of emphysema. Through data expansion and clustering labels to optimize the anchor parameters, so as to overcome the scarcity of labeled emphysema data and the inappropriate traditional anchors setting of emphysema. The subjective and objective experiment results in Chestx-Det10 and Chestx-Det14 datasets show that the proposed algorithm has better detection ability than the contrast algorithms.
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    Fault detection of batch process based on dynamic MDONPE algorithm
    ZHAO Xiao-qiang, LIU Kai
    2022, 48 (2):  90-96. 
    Abstract ( 182 )   PDF (1953KB) ( 291 )   Save
    To solve the problem of poor fault detection effect due to the nonlinear and dynamic characteristics of the data in the batch process, a multiway differential orthogonal neighborhood preserving embedding (MDONPE) algorithm based on the sliding window (SW) is proposed. Firstly, the data of the batch process is preprocessed to find the nearest neighbors of the samples, and the difference operations between the samples and the nearest neighbors is carried out. Then the orthogonal neighborhood preserving embedding algorithm with orthogonal constraints is obtained by orthogonalizing NPE algorithm, and the orthogonal neighborhood preserving embedding algorithm is used to reduce dimensions and extract features. The sliding window strategy is used to combine and achieve the error accumulation by selecting the sampling data within the window width, which can make the features of the fault samples more obvious. Finally, the fault is judged by detection, and the T2 and SPE statistics are used to judge if faults have occurred. The data of the Penicillin fermentation simulation process are used and compared with MPCA and KNPE algorithms. The results show that the proposed algorithm has better detection effect than other algorithms in fault detection.
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    Identification of essential proteins based on protein complex and topology properties
    LU Peng-li, YU Jing-juan
    2022, 48 (2):  97-106. 
    Abstract ( 293 )   PDF (5371KB) ( 368 )   Save
    The identification of essential proteins is helpful to understand the process of life at the molecular level, thus the identification of essential proteins has gradually become an important research work. However, the identification of essential proteins that only focused on the topological characteristics is not accurate enough. To improve the recognition accuracy, a new method EIC was proposed, which integrated the local central information and global topological features of protein complex for identifying essential proteins. Different Protein-Protein Interaction (PPI) networks of DIP and MIPS were used as materials.Some experiments of different assessment method were used including precise-recall curves and jackknife methodology.By comparing the proposed method with the existing methods such as DC, BC, EC, SC, LAC, NC and the recent method UC, the ability of recognizing essential proteins by the proposed method EIC is more effective, in that it may enhance the accuracy for identifying essential proteins.
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    Architectural Sciences
    Dynamic response analysis of wind turbine structure under wind and sand load excitation
    LI Wan-run, HUANG Jie, DING Ming-xuan, LI De-qiang, WANG Xue-ping, DU Yong-feng
    2022, 48 (2):  107-114. 
    Abstract ( 309 )   PDF (2758KB) ( 572 )   Save
    To study the damage of wind-sand load to wind turbine, the dynamic response analysis of wind turbine under the load was analyzed. Based on 2 MW wind turbine, three finite element models are established, which do not consider blades, consider blade rotation, and consider soil-structure interaction. The Davenport wind speed spectrum and harmonic superposition method are used to simulate the pulsating wind speed time history, and the dynamic calculation model of wind and sand load is established by the law of conservation of momentum and wind and sand flow density. The dynamic responses of the model under the action of wind load and wind sand load are simulated by ANSYS. The results show that: the response of wind power generation structure under wind sand load is large, and its effect can not be ignored. The results obtained by numerical simulation with simplified lumped mass model are unsafe, and soil-structure interaction has obvious amplification effect on the displacement response under wind load and wind sand load.
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    Experimental study on modal parameters of pedestrian bridge with static crowd-structure interaction
    MA Fa-rong, ZHU Qian-kun, ZHANG Qiong, DU Yong-feng
    2022, 48 (2):  115-122. 
    Abstract ( 229 )   PDF (6083KB) ( 530 )   Save
    In this paper, the effect of modal parameters of pedestrian bridge under static crowd-structure interaction is studied, and the steel structure pedestrian glass bridge is used as the research platform. The research contents are as follows: the dynamic parameter of the pedestrian bridge under the excitation of the test environment and the dynamic parameters of the structure under different positions are changed under the action of the static crowd in different positions of the pedestrian bridge. The results show that under the static population-structure interaction, with the increase of the number of people acting, the natural frequency of the structure decreases and the damping ratio increases gradually. The sitting posture has the greatest influence on the structural frequency, the natural vibration frequency of the structure decreases from 4.381Hz to 3.643Hz, which is decreased by 16.8% under the action of four people, and the semi-squatting position has the greatest effect on the damping ratio. The damping ratio of the structure increases from 0.660% to 4.888%, which is increased by 640.6% under the action of four people. When the static population is located at the peak point of a certain order mode, the frequency of the corresponding modal structure is the smallest and the damping ratio is the largest.
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    Research on operation characteristics of phase change energy storage solar vacuum collector
    HAN Xi-lian, ZHU Yao-yu
    2022, 48 (2):  123-130. 
    Abstract ( 201 )   PDF (3207KB) ( 456 )   Save
    In order to understand the operation conditions of the phase-change energy storage solar vacuum heat collector, the operation of single vacuum tube and three vacuum tubes in series under different working conditions were experimentally studied. The experiments were mainly divided into two phases: endothermic and exothermic. The research results of the single vacuum tube operation show that the daily heat collection efficiency can reach30%~45% in the endothermic stage in sunny and cloudy conditions. The heat collection efficiency in cloudy conditions is very low, only about 6%. During the endothermic phase, due to the natural convection of the water in the U-shaped copper tube and the paraffin after liquefaction, the paraffin in the vacuum tube will have the temperature stratification phenomenon of high paraffin temperature at the top and low paraffin temperature at the bottom. During the exothermic phase, the amount of hot water provided in sunny conditions is the biggest, and the hot water temperature is also high. After calculation, it can provide 2.89 L of hot water at 50 ℃, 4.44L of hot water at 40 ℃ and 9.56 L of hot water at 30 ℃. The experimental results of the series operation show that the average paraffin temperature of each vacuum tube will be different during the heat absorption process. The closer to the water outlet of the series system, the higher the average temperature of the paraffin in the vacuum tube; the hot water temperature and hot water volume that can be provided by the series system are significantly increased.In a single-day experiment, 7.64 L hot water of 60 ℃ and 13.07 L hot water of 40 ℃ can be provided.
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    Application of ARIMA-NAR neural network model based on Kalman filter in deformation monitoring of deep foundation
    NIU Quan-fu, LI Yue-feng, ZHANG Man, FU Jian-kai, MA Ya-na
    2022, 48 (2):  131-135. 
    Abstract ( 295 )   PDF (1340KB) ( 338 )   Save
    Deformation monitoring of deep foundation pits is becoming more and more important in the security control of urban construction. Because of the unavoidable noise in the monitoring data and the prediction residual problem from the single prediction model, it is necessary to improve the prediction accuracy of deep foundation excavation. Taking ZJ52 of a deep foundation pit in Lanzhou as an example, and based on Kalman filtering, the paper used a combined model of ARIMA-NAR neural network to predict and analyze the change trend of the observation point. The results show that the average absolute error, average relative error and residual variance from the established model are 0.43 mm, 0.04 mm and 2.23 mm, respectively. The prediction results are better than those of single ARIMA and NAR neural network models. The prediction results from ARIMA-NAR neural network with Kalman filtering can provide reliable guidance for the security construction of this project.
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    Effective fatigue stress parameter model of reinforced concrete beams based on real-time strain monitoring information
    LIU Fang-ping, DENG Yong-jun, YI Wen-tao, YAN Lei
    2022, 48 (2):  136-143. 
    Abstract ( 256 )   PDF (3194KB) ( 450 )   Save
    In order to obtain the fatigue stress value reflecting the real response state of reinforced concrete beams, an effective fatigue stress parameter value model based on real-time strain monitoring information was proposed. In view of the cyclic characteristics of real-time strain monitoring data, it was simplified into standard cyclic blocks. Low-frequency and high-frequency operations were carried out to realize the extraction of real structural data. Based on “Fourier transform”, the transformation analysis and authenticity verification were carried out, and the realstrain data was obtained. Based on the characteristic of dynamic strain standard cyclic block, the main peak value was only considered in the statistic of random wave stress peak value, the material ratio limit was used as the starting point of reading instead of the mean line. The true fatigue stress characteristic value ofbeams could be obtained by transformation. Without affecting the fatigue damage of beams, based on the principle of strain energy and damage equivalence, the variable-amplitude stress spectrum was converted into the equivalent fatigue stress spectrum. Finally, the “real-time state analysis model” for evaluating the current damage status of beams and the “predictive trend analysis model” for predicting the later damage status of beams were established.
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    Scientific
    Gorenstein FP-injective modules and dimensions over formal triangular matrix rings
    WU De-jun, ZHOU Hui
    2022, 48 (2):  144-150. 
    Abstract ( 270 )   PDF (778KB) ( 261 )   Save
    Let T be a formal triangular matrix ring, where A and B are rings and U is a(B, A)-bimodule. A characterization of Gorenstein FP-injective left T-modules over the formal triangular matrix ring T is given. Moreover, the Gorenstein FP-injective dimension of a left T-module is discussed.
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    An optimal control problem governed by fractional order dynamic equation on time scales
    REN Qiu-yan, YANG Qiao-ling
    2022, 48 (2):  151-155. 
    Abstract ( 142 )   PDF (698KB) ( 182 )   Save
    By imposing some suitable conditions on the related functions, for any given control policy, the existence of a unique solution for the nonlinear fractional order controlled system can be obtain. Moreover, the existence of an optimal solution for the optimal control problem governed by fractional order dynamic equation on time scales is studied.
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    A necessary condition for boundary controllability of coupled parabolic equations with variable coefficients
    XIE Wei-song, ZHANG Qing-qing
    2022, 48 (2):  156-162. 
    Abstract ( 233 )   PDF (756KB) ( 383 )   Save
    The boundary controllability of non-scalar variable coefficient linear parabolic equations is studied. A necessary condition for boundary null controllability is established, which has only one boundary control for a system with two equations depending on the same coefficient that is time-dependent. The necessary condition is proved based on the observability inequality of the equations.
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    Effect of gravity on wave propagation in piezoelectric medium based on fractional thermoelastic theory
    MA Yong-bin, ZHANG Jian-min
    2022, 48 (2):  163-172. 
    Abstract ( 224 )   PDF (4048KB) ( 311 )   Save
    Based on the fractional thermoelastic theory, the effect of gravity on wave propagation in half space under periodic loading is studied. The governing equations under the fractional generalized thermoelastic theory are given, and the normal mode analysis is used to solve the governing equations. The distribution laws of dimensionless physical quantities such as temperature, displacement, stress and electric displacement in the half space infinite piezoelectric medium are obtained. The effects of fractional order parameters and gravity on the physical quantities are mainly studied. The results show that the thermoelastic coupling effect appears in the half space infinite piezoelectric medium due to the periodic load, and the fractional order parameters and gravity significantly affect the distribution of physical quantities.
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