Table of Content

    28 December 2018, Volume 52 Issue 12 Previous Issue    Next Issue
    Modelling and Simulation of Temperature and Humidity Distribution in Curing Rooms of Concrete
    TANG Jiedong,ZHAI Xiaoqiang
    2018, 52 (12):  1543-1551.  doi: 10.16183/j.cnki.jsjtu.2018.12.001
    Abstract ( 903 )   Save
    Temperature and humidity distribution of curing rooms which are mainly used in the production line of concrete component factory are studied by simulation. Considering high temperature and high humidity in the curing room, wall condensation and mist condensation are used to simulate the condensation in the room. The simulation results show that the relative humidity of most areas reaches 100% very fast, but the temperature distribution is extremely uneven and temperature difference is up to 26℃. In addition, by changing the nozzle orientation, position and quantity, it is found that the temperature is more uniform when the nozzle is downward; when the nozzle is located in 46% to 65% of the total height of the room, the temperature distribution achieves the best uniformity; the increase in the number of nozzles can improve the temperature distribution between the nozzles.
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    Vertical Deformation Mechanism of Diaphragm Wall Due to Unloading in Deep Excavation
    XIAO Xiao,LI Mingguang,CHEN Jinjian,XIA Xiaohe
    2018, 52 (12):  1552-1558.  doi: 10.16183/j.cnki.jsjtu.2018.12.002
    Abstract ( 36 )   Save
    The numerical analysis method is adopted to study the vertical deformation mechanism of the retaining wall caused by unloading. A hypothetical model which considers the interaction between wall and soil, is established in the finite difference software. The ideal elastoplastic model is adopted to simulation the characteristics of contact property between soil and diaphragm wall. The vertical displacement of soil, the relative displacement of soil and wall and the distribution of friction under the 3 kinds of soil parameters are compared and analyzed. The results show that the vertical displacement of the wall can be divided into two parts the soil rebounded one and relatively sliding between subsoil and wall tips. The displacement of soil is mainly affected by unloading effect which is determined by soil parameter. The settlement of the wall decreases with the increase of soil cohesion. The uplift of the wall increases with the increase of friction angle. The relative sliding of wall tips and soil is governed by the frictional forces on two sides of the wall. With the increase of contact property, the frictional force increases and will lead to larger vertical displacements.
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    Synchronization of the Composite Network Constructed by the R?ssler Chaotic System
    YU Hongjie,DONG Yixuan
    2018, 52 (12):  1559-1564.  doi: 10.16183/j.cnki.jsjtu.2018.12.003
    Abstract ( 22 )   Save
    The Rossler chaotic system is considered as neurons,a sub network of star-shaped is firstly established. Then a composite large network is constructed by connecting the center neuron of the sub network with all-to-all-coupling connection. Using and extending the stability criterion (SC)synchronization method of two chaotic systems, theoretical research and numerical simulation are carried out for the constructed network. The system coupled equations of the network and the synchronization error development equations between the neurons in the network are provided. By controlling the dependent coupling intensity factor, the influence of parameters on network synchronization form and process are discussed in detail, and the possible chaos synchronization types and the ranges of the controlled parameter are obtained. Also, it is proved that the SC synchronization method is effectively useful to solve the chaotic synchronization problem of the composite network composed of the star-shaped and all-to-all-coupling.
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    Analytical Solutions on Steady Seepage Field of Deep Buried Circular Tunnel After Considering Anisotropic Flow
    XU Changjie,LIANG Luju,DING Wenxiang
    2018, 52 (12):  1565-1570.  doi: 10.16183/j.cnki.jsjtu.2018.12.004
    Abstract ( 23 )   Save
    Based on traditional analytical solutions of deep buried circular tunnel’s seepage field under isotropic seepage condition, a seepage coefficient ratio was introduced and analytical solutions of deep buried circular tunnel’s seepage field under anisotropic seepage condition was derived through coordinate transformation and conformal mapping. Results of parameter analysis indicate that the solutions could degenerate to the classical solutions under isotropic seepage condition when the seepage coefficient ratio is equal to 1. On the other hand, when the seepage coefficient ratio was not equal to 1, equal headlines of the circular tunnel’s seepage field were ellipses and hydraulic gradient on the direction of smaller seepage coefficient was larger than the other direction, which means the distribution of seepage field was inhomogeneous. However, this inhomogeneity weakened gradually with longer distance to the center of the circular tunnel. The calculation results of these analytical solutions are all in agreement with numerical analysis results, which confirmed the effectiveness of the proposed analytical solutions. The research results can provide a reference for relevant projects.
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    Calculation of Initial Stiffness of T-Stubs Under Consideration of Bending Stiffness of Bolts
    WU Nianduo,QIANG Xuhong,LIU Xiao,LUO Yongfeng
    2018, 52 (12):  1571-1579.  doi: 10.16183/j.cnki.jsjtu.2018.12.005
    Abstract ( 25 )   Save
    In order to reveal more information on initial stiffness of T-stubs, a brief introduction on calculative methods for predicting mechanical behaviors of T-stubs was firstly presented . Though comparing these methods, the continuous beam model which bending stiffness of bolts are considered was determined to calculate initial stiffness of T-stubs. Comparisons between theoretical and numerical results on initial bending stiffness of a series of T-stubs are presented and good agreements exist. Further, parametric analysis was conducted mainly on flange thicknesses and locations of bolts of T-stubs. The parametric analysis results show that with increase of flange thicknesses the distance between axis of bolts and edges of flange decreases, the influence of bending stiffness on initial stiffness of T-stubs increases. For mild steel T-stubs, when bending stiffness of bolts is considered, initial stiffness improve less than 5%. But for high strength steel (HSS) T-stubs, initial stiffness improves even more than 30%. Thus for HSS T-stubs, bending stiffness of bolts cannot be neglected when calculated initial stiffness of T-stubs.
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    Influence of Driving Pile on Diaphragm Wall Deformation of Adjacent Foundation Pit
    LI Jingpei,CUI Jifei,LI Lin,ZHAO Gaowen
    2018, 52 (12):  1580-1586.  doi: 10.16183/j.cnki.jsjtu.2018.12.006
    Abstract ( 25 )   Save
    Based on the solution to a spherical cavity expansion in semi-infinite soil, an elastic solution or assessing the deflection of the diaphragm wall caused by pile driving is derived by using the elastic foundation beam theory. To determine the supporting condition of the diaphragm wall, simplifications are made to the internal support conditions of the excavation and the constraint conditions at the end of the diaphragm wall. A detailed discussion is conducted to analyze the effects of pile depth and distance between diaphragm wall and pile. The results indicate that pile driving has pronounced effects on the adjacent underground diaphragm wall, especially for the diaphragm wall under the excavation surface. With the increase of pile depth the lateral displacement of diaphragm would be gradually larger after the end of pile below the excavation surface. And when the depth of the pile is more than the depth of the diaphragm wall, the influence on the diaphragm wall will be gradually weakened. The displacement of the diaphragm wall becomes larger with the increase of the pile diameter. The closer the pile is to the diaphragm wall, the greater the displacement of the diaphragm wall is, and when the distance between the pile and the diaphragm wall reaches 15 times of the pile diameter, the effect can be ignored.
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    Distribution Characteristics of Stress and Pore Pressure Induced by Pile Jacking
    ZHANG Yaguo,LI Jingpei
    2018, 52 (12):  1587-1593.  doi: 10.16183/j.cnki.jsjtu.2018.12.007
    Abstract ( 31 )   Save
    A series of centrifuge model tests were conducted on the spatial distribution characteristics of stress and pore pressure due to pile installation. According to test data, the existing cavity expansion theory was modified, and a pile installation model, which took ground surface heave into account, was proposed. The reliability of this model was validated by the centrifuge test data. The results showed that variation characteristics of total radial stress and the pore-water pressure were controlled by the distance from the pile axis and depth of the soil element. For a certain depth, the stress and pore-water pressure of soil increased as the pile tip reached and decreased as the tip passed. For the same distance from pile, the increases of stress and pore-water pressure caused by deep penetration were larger than those induced by shallow penetration. The reason was that the free ground surface influenced the stress conditions. If the pile penetration depth in the silty clay reaches 7~7.5 times pile diameter, the influences can be ignored. The studies of this paper will provide the basis for time-dependent prediction of pile foundation capacity.
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    Discrete Element Analysis for Instability of Undercrossing Shield Tunnel Face
    ZHANG Mengxi,ZHANG Zisheng,WANG Wei,Lü Yan,HAN Jiayao,JIN Qi
    2018, 52 (12):  1594-1602.  doi: 10.16183/j.cnki.jsjtu.2018.12.008
    Abstract ( 35 )   Save
    Based on the tunneling case for Shanghai railway transportation line, undercrossing tunneling simulation was performed by using the DEM (discrete element method) software PFC2D. The instability mode, surface subsidence and support pressure ratio were investigated to analyze the coverage from existing tunnel to the instabilities of the shield tunnel face, and were compared with the monitoring of the surface subsidence, to discuss the universal law of the face collapse along the longitudinal excavation. The consequences of DEM simulation showed the instability mode was varied when the tunnel face was close to the existing tunnel before crossing, performing the expansion of the chimney, the discontinuity of the surface subsidence tank and the decrease of the limiting support pressure ratio. When the tunnel face passed through the existing tunnel, it had very little influence on the instability mode. The limiting support pressure ratio lied between 0.4 and 0.6 in both situations of single shield tunnel and undercrossing shield tunnel. And the ratios in the undercrossing were lower than the one in the single so that it was more difficult to collapse in the undercrossing. According to the comprehensive analysis of simulation results, the existing tunnel had a significant impact on the instability mode when the tunnel face was in the range of twice the tunnel diameter in front of the existing tunnel.
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    Numerical Analysis of the UV Curing and Demolding Process for High Aspect Ratio Micro Structure
    WU Hao,YI Peiyun,PENG Linfa,LAI Xinmin
    2018, 52 (12):  1603-1608.  doi: 10.16183/j.cnki.jsjtu.2018.12.009
    Abstract ( 21 )   Save
    Focusing on the demolding issues of high aspect ratio structures, this paper attempts to explain the reasons behind this problem. Firstly, the material properties of the cured resist was measured, and Ogden model was used to describe its behavior. Then, a roll to roll UV curing and demolding numerical model was constructed and analyzed. It was found that the adhesive forces between mold and structures is the major cause of maximum stress in cured resist when aspect ratio is set to 4∶1. Moreover, a longer curing time, a thinner residual layer thickness, a smaller structure aspect ratio and a bigger structure gap can lead to smaller maximum stress during the curing and demolding process.
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    Angle Estimation Algorithm with Spare Array for Different Carrier Frequencies Radiation Sources
    CHEN Lu,BI Daping,CUI Rui,HAN Jiahui
    2018, 52 (12):  1609-1617.  doi: 10.16183/j.cnki.jsjtu.2018.12.010
    Abstract ( 27 )   Save
    Aiming at the angle estimation problem of uniform linear array in multiple carrier frequencies radiation sources passive reconnaissance, the angle estimation algorithm based on maximum likelihood estimation for multiple radiation sources with different carrier frequencies was proposed. The algorithm was divided into two steps. First, by deriving the maximum likelihood function and the gradient of the multiple radiation source signals intercepted by the uniform linear array, the angles of the multiple radiation sources of different carrier frequencies were estimated simultaneously by using the steepest descent method. Second, in order to solve the problem of phase ambiguity in different carrier frequencies, the lattice algorithm was proposed to compute the nearest integer points to the fuzzy phase. The cuckoo optimization algorithm was proposed to estimate the fuzzy number corresponding to integer points. Unambiguous angles of multiple radiation sources were obtained. The simulation results show that the proposed algorithm has better performance in angle estimation and unwrapping phase ambiguity than the traditional algorithms in terms of low signal to noise ratio (SNR), low sampling number and multiple radiation sources.
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    Separation of Single Channel Radio Mixed Signal Based on Variational Mode Decomposition
    JIANG Chundong,WANG Jingyu,DU Taihang,HAO Jing,LONG Chao
    2018, 52 (12):  1618-1626.  doi: 10.16183/j.cnki.jsjtu.2018.12.011
    Abstract ( 18 )   Save
    Aiming at the separating difficulty of single channel radio mixed signal and low accuracy of its separation under complex electromagnetic environment, a separating method of single channel radio mixed signal by using twice variational mode decomposition (VMD) algorithm is proposed. Firstly, the VMD algorithm is used to roughly separate single channel radio mixed signal for the first time. And the VMD algorithm is compared with the ensemble empirical mode decomposition (EEMD) algorithm. The results show that the separated signals by the former are better in the time domain, frequency domain, signal to noise ratio and similarity coefficient than those obtained by the latter. Then, the parameters of variational mode decomposition algorithm are optimized by using the improved quantum particle swarm optimization algorithm, thus the number of components and the value of penalty factor are determined. And then, the optimized parameters of VMD algorithm are used to fine separated signals from VMD algorithm. The numerical simulation results and the experimental signal analysis results show that the signal accuracy of the second separation is higher than the first one. And it is proved that the proposed algorithm is valid for separating the single channel radio mixed signal.
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    Components and Propagation Characteristics of Seabed Seismic Waves
    MENG Luwen, LUO Xiayun, CHENG Guangli, ZHANG Mingmin
    2018, 52 (12):  1627-1633.  doi: 10.16183/j.cnki.jsjtu.2018.12.012
    Abstract ( 27 )   Save
    To obtain components and propagation characteristics of seabed seismic waves, the wave field in the two-layer semi-infinite liquid-solid ocean model is expressed in the form of complex integral. The far-field approximation solution of the wave field complex integral is obtained by using the saddle point method. The wave components corresponding to the integral solution and its characteristics are then presented. Results show that the wave components at the seabed interface are direct acoustic wave, reflected acoustic wave, lateral wave, transmitted longitudinal wave, transmitted transverse wave, leaky Rayleigh wave and Scholte wave. The wavefronts of the direct acoustic wave, reflected acoustic wave and transmitted waves are spherical, and those of the lateral wave and Scholte wave are conical and cylindrical respectively. In addition, the high-order staggered-grid finite difference method is applied to simulate the wave propagation process, and wave field snapshots are shown. The wave components and their propagation characteristics are visually displayed. The numerical simulation results are in good agreement with the theoretical analysis.
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    Synthesis and Catalyse Mechanism of Hydrophobic Nanoporous Silica Anti-Reflection Film
    YU Wenying,SHEN Yulong,XU Juan,MA Xinxiu,ZHANG Zhanxian, CHEN Shijie,ZHOU Tao,LIU Yongsheng
    2018, 52 (12):  1634-1641.  doi: 10.16183/j.cnki.jsjtu.2018.12.013
    Abstract ( 31 )   Save
    In this paper, we have developed base-catalyzed and acid-catalyzed approach of pure SiO2 sols by one-pot sol-gel method, respectively. Through the test and comparison of the transmittance and the wear resistance of the two groups of samples, the effect of alkali and acid catalysis on the performance of the film was put forward, and the catalytic mechanism was analyzed. Base catalyst monolayer film transmission can be as high as 98.781%, while the acid catalyst is 95.285%. This shows that the base catalyst can get films with higher transmittance. The mechanical property of the alkali film is poor, while the mechanical properties of the acid film are good, and the mechanism of hydrophobic wear-resistant film is given. By measuring surface water contact angles of the films before and after surface treatment we found that alkali film and acid film water contact angle can reach 126.5° and 94.5°, respectively. The result shows that the hydrophobic performance of films can be improved obviously after surface treatment.
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    Current Control Strategy for Photovoltaic Grid-Connected Inverter Based on PIR Regulator
    ZHI Qin,WU Yingyang,JIN Zhijian,SHEN Haijun
    2018, 52 (12):  1642-1648.  doi: 10.16183/j.cnki.jsjtu.2018.12.014
    Abstract ( 29 )   Save
    To solve the problem of grid voltage distortion affecting the current control performance of photovoltaic inverter, a current control strategy based on proportional-integral-resonant (PIR) regulator is proposed. Firstly, the control structure of photovoltaic inverter with inner current-loop and outer DC voltage-loop is determined. PIR regulator is used to suppress the grid voltage distortion or disturbance in inner current-loop and track the fundamental current. Due to the high orders of the LCL filter and PIR regulator in the photovoltaic inverter, there are many problems in the design of control parameters. Then, a parametric design method of PIR regulator based on the discrete-time root locus is proposed, which avoids the performance deviation or unstability of the regulator when the regulator parameters based on continuous domain are directly applied to the digital controller. Analysis results show that the design parameters can still make the system have a good adaptability during the changes of the grid frequency and LCL filter parameters. Finally, a simulation model based on Simulink verifies the feasibility of the current control strategy based on PIR regulator and the correctness of designed controller parameters.
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    Performance of Resistance Spot Welding Joints for AISI 430 Ferritic Stainless Steel
    FENG Qiaobo,LI Yongbing,LOU Ming1,LAI Xinmin
    2018, 52 (12):  1649-1654.  doi: 10.16183/j.cnki.jsjtu.2018.12.015
    Abstract ( 26 )   Save
    The experiments of resistance spot welding for AISI 430 Ferritic stainless steel sheet with 1.2mm thickness was carried out by using the robot DC servo spot welding system. The effect of the welding current on the mechanical properties, the nugget diameter, the microstructure, the micro-hardness and the failure mode were researched. The results show that with the increase of welding current, the strength of the joint increases. When the current reaches 10kA, the splashing phenomenon occurs in spot welding, and it leads to the decrease of joint strength. The joint nugget region consists of coarse ferrite with a small amount of martensite and carbide precipitates. The hardness of the nugget area is higher than that of the base metal zone and heat affected zone. Joints mainly occur button fracture when the nugget diameter is more than 4.8mm. When the nugget diameter is less than 4.8mm, it is interfacial fracture, and usually is brittle fracture.
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    The Model and Solution for Collaborative Production Planning with Order Splitting in Cloud Manufacturing Platform
    WANG Jing,PAN Kailing,LIU Ao,WANG Xinxin
    2018, 52 (12):  1655-1662.  doi: 10.16183/j.cnki.jsjtu.2018.12.016
    Abstract ( 21 )   Save
    In cloud manufacturing platform, a multi-plants and multi-periods collaborative production problem was discussed by introducing two adjustive variables, which are the maximal number of enterprises that process an order and the minimal order splitting ratio, respectively. We established a collaborative production planning model with constrains of production time window and production capacity. Then, a self-adaptive simulated annealing genetic algorithm using bi-level code was designed. Our proposed approach was compared with a commercial optimization software CPLEX under different data sizes in numerical simulation. Lastly, the sensitivity analysis of the major parameters in the model was carried on. The experimental results provide a decision-making basis for operation decision makers of cloud manufacturing platform.
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