2019 volumne 40卷 Issue 01
Zhang Yikun,Tang Yan,Chen Qiang
Abstract: The selection of features,  the representation of features, and the mode of fusion were key processes of 3D model retrieval technology . In the paper, we propose a new 3D model retrieval method which was based on multiple feature fusion was proposed. It combined the fast ORB features and the precise shape context features. ORB features described the local information. After extracting the Canny edge information, the shape context features were extracted to describe the global information, then the final similarity was calculated based on shape context features and ORB features. Experimental results demonstrated that our method could effectively improve retrieval performance.
Lee Yuan 1,Zhang Jianming 2,Zhong Yudong 2,Qian Hongtao 3
Abstract: The singular integral was one of the difficult problems for the Boundary Element Method to solve the physical problems. Its precision had great influence on the accuracy of the calculation result. Element subdivision was the key to solve the singular integral. Aiming at the problem of dynamic analysis. An element subdivision method related to time-step length was proposed. Compared with the traditional method, this method not only considerd the position of the source point in the cell, but also the position of the wave front, which could reflect the segmentation characteristic of the kernel function. Therefore it could more accurately simulate the impact of longitudinal wave and shear wave on the integral of the element. In this paper, the accuracy of the method and its effect on the calculation accuracy were verified by two examples. The results showed that the error was 15.5% less than that of the traditional method for the first analysis step with singularity.
Zhao Shuangyan,Jia Jinyuan,Zhou Wen
Abstract: With the development of Web3D technology,  Web service demand for 3D household models on line application surged. Taking advantage of lightweight technology and so on , the processing, transmission, rebuilding, and real-time rendering problems were solved for large scale WebVR household models. Based on WebVR, this paper put forward the online visual service of W eb3D lightweight household models repository was introduced. The detailed process of the lightweight household models , and some related key technologies, including lightweight progressive meshes processing, fine-grained preprocessing, viewpoint based transforming and so on were also introduced. The results showed that lightweight technology could process the household models rapidly.
Wang Zhe1,2,Zhao Shifeng1,2,Tian Yun 1,2,Wang Xuesong1,2,Zhou Mingquan1,2
Abstract: Cerebral blood vessel segmentation was a key step in three-dimensional (3D) reconstruction, computer aided diagnosis and quantitative analysis. Due to complex geometric structure, small area percentage, low contrast vessel segmentation was still a challenging problem. Based on traditional statistical method with intensity, an improved K-means algorithm based on self-adapting clustering centers with gradient of remaining voxels preserved from previous step was used for further extraction of thin vessels. Firstly, one Rayleigh distribution and two Gaussian distributions were adapted to model background, tissues and vessel areas, respectively. And EM algorithm was used to estimate parameters for Gaussian distributions. Then posterior probability is used to extract the main body of blood vessels. Secondly, the remaining part containing the low contrast vessel areas and vessel edges was computed for gradient. An improved K-means method with self-adapting clustering centers was proposed to detect those areas. Experiment result demonstrated that our method was better than traditional statistical methods, especially at low contrast branches and vessel edges.
Zhang Hongbin 1,Wang Kewen 2
Abstract: By optimizing the operation mode of the active distribution network, the operation plan of distributed generation, reactive equipment and energy storage equipment could be arranged rationally , and the operation efficiency of distribution network would be improved . The operation cost and the voltage qualification rate in a distribution network were used as the minimize objective, and the operation requirement of power grid and equipment were used as constraints, day-ahead and real-time optimization models with active and reactive power coordination were established . Characteristics of all kinds of variables in the optimization model , and effect degrees of time series in variables were analyzed. Solution modules corresponding to continuous variables, two types of discrete variables, and the coordination between time intervals were established, and the overall optimum was achieved through the iteration among modules. Combined with the characteristics of distribution network, the modular processing method was a simplification of the traditional nonlinear mixed integer dynamic programming algorithm, which has obvious advantages in computing resource demand. The calculation and analysis in the 118- bus example showed that the proposed algorithm was feasible and practical.
Zhang Jian 1,Bear strong 1,Wang Mingdong 1,Zhu Yongsheng 2
Abstract: In order to increase the utilization rate of distributed energy and the to reduce network loss and voltage deviation,the multi-objective model of dynamic reactive power optimization with active and reactive power coordination for the distribution network was proposed in this paper.It consisted of Energy Storage System,Capacitors Banks,Static VAR Compensation,On-load Tap Changer, and distribution generation. The analytic hierarchy process was used to transform the multi-objective into a single target. The Big-M method was used to linearize the model, and the relaxation theory is used to relax the convexity into the form of the second-order cone programming. Case study of the improved IEEE 33 network verified the effectiveness of the proposed model.Cplex was used to get the switching capacity and time each active management device. It was proved that the proposed method in this paper was reasonable.
Teng Zhijun 1,Guo Liwen 1,Lu Jinling 1,Hou Yanquan 2
Abstract: In order to effectively reduce the influence of channel occupancy on the reputation evaluation of nodes,and to improve the accuracy of the reputation model,to track the data interrupt attacks and selective forwarding attacks,  a TS-BRS reputation model was presented based on time series information analysis to evaluate the behavior of nodes. Considering the influence of channel state on network node behavior time series and channel state time series.And ithe adaptive maintenance function μ was also introduced to update reputation value, add the influence of node behavior on reputation value in reappearing stage, and improve the adaptability of evaluation model. The simulation results showed that the new reputation evaluation model could effectively improve the detection rate and detection speed for malicious nodes.The reputation value of a mailcious node could converge more quickly. 
Mu Xiaomin 1,Liu Yali 1,Zhang Jiankang1,Zhao Lingxiao 1
Abstract: For the channel estimation problem of the uplink in a large-scale MU-MIMO systems, a sparse channel estimation algorithm based on parallel factor (PARAFAC) decomposition was proposed. In this paper, a sparse mathematical model was used to construct a sparse channel model, and sparse theory was combined with tensor decomposition to perform PARAFAC modeling of the received signal at the base station. Under the condition of uniqueness decomposition, a bilinear alternating least squares (BALS) fitting algorithm was used to jointly estimate the signal matrix and the channel matrix of multiple users.The simulation results showed that the proposed algorithm had better estimation performance than the classical orthogonal matching tracking algorithm and other sparse channel estimation algorithms. Compared with the pilot sequence based estimation method, the accuracy of the channel estimation was greatly improved.Only a small amount of pilot was needed.The pilot overhead was reduced, and high spectral efficiency communication transmission was realized. 
Wang Bo 1,Zhang Chunli 1,2,Zhu Yanzhi 3
Abstract: The mechanics model of the infinite elastic plate on orthotropic foundation were established under the rectangular coordinate system. And the dynamic equations of plate and foundation were derived under moving loads based on the thin plate theory. By means of the coordinate transformation and Fourier integral transform, the integral forms of dynamic responses of plate and foundation were obtained. Numerical example was given on condition that harmonic vibrating rectangular load was applied on the pavement plate surface. The calculation procedure was performed by MATLAB software. Studies were conducted to investigate the effect of parameters on the plate displacements. The results showed that the dynamic response of the subgrade and pavement interaction could be accurately described by considering the orthogonality of the soil
Huang Xiaodi,Gu Ying,He Jun
Abstract: The accelerated simulation method based on generalized extreme value distribution and shift generalized lognormal distribution was proposed to effectively estimate the extreme value distribution of structural response under random loading.In order to investigate the efficiency of the two accelerated simulation methods in the estimation of the tail of the distribution of structural extreme response, the parameter estimation process of generalized extreme value distribution and shift generalized lognormal distribution based on simulated samples was discussed in detail in this paper.A comparative analysis of these two kinds of accelerated simulation method about computation cost and accuracy in the estimate of the tail of the extreme value distribution of the random variable, the tail of the extreme value distribution of the random response of the linear srtucture, and the tail of the extreme distribution of the stochastic response of the nonliner structure was made.The characteristics and applicable scope of the two accelerated simulation methods were given. In the end, the suggestion on how to choose two accelerated simulation methods was given. 
Li Bin 1,2,3,Fang Hongyuan 1,2,3,Wang Fuming1,2,3
Abstract: Polymer grouting technology was a kind of economical and efficient method for leakage of pipeline. However, the application of this technology for the restore statue of the mechancial properties of the pipe afer repairing was not yet clear.In this paper, the three-dimensional numerical model of the road structure,subgrade and pipe-soil interaction were established by the ABAQUS software.The longitudinal and circumferential mechanical properties of normal pipes, disengaging pipe and polymer-repaired pipe under traffic load were compared and analyzed. The results showed traffic load had obvious influence on the pipe stresses and deformations in the range of 6m and 4m on both sides of its position, and the influence was positively correlated with the amplitude of traffic load.The stresses at the bell and spigot joints were highly discontinous.When traffic load was 1.0MPa, the stresses and deformations of the pipe are obviously greater than that of traffic load is 0.5MPa;The stresses and deformations of the pipe recovered to the normal pipe level after the disengaging was repaired by the polymer, and a reliable and effective repairing effect was achieved.The research results provided a theoretical basis for the implementation of targeted pipe repair.
Wu Xiaoguang 1,He Shulei 1,Zheng Peng 1,Yin Yue 1,Guo Zhiqiang 2
Abstract: In a on-site examination on the plate type elastomeric pad bearings on three expressways in Shanxi Province,the main problems of this type of pad bearings were local cavitation and bearing shear deformation. Then the uniaxial tensile test, biaxial tensile test and plane shear test were carried out to obtain the actual characteristic parameters of bridge bearing. By establishing a finite element model of the plate rubber bearing, the ultimate void ratio and ultimate shear angle of the rubber bearing were obtained. Finally, through the software trial calculation, the simulation the force of the pad bearings was conducted with both the local cavitation and the shear deformation ,the failure identification formula and the failure curve of the rubber bearing in the plate under the simultaneous action of the two diseases were fitted, If the combination of partial void and shear deformation satisfied the failure criteria or was outside the failure curve range, the bearing failure was indicated.The failure criterion obtained in this paper could cast extra light on the basis for the replacement of the plate rubber bearing, and were of great engineering value.
Wang Jianming,Li Xiaoxiao
Abstract: Welded structures were commonly used for railway vehicles and equipment. Fatigue failure of welded structures with fluctuating loads usually occursed at weld seams. So Random Vibration Bench Test and Numerical Simulation for Fatigue Life of Welded EMU Tank were studied. Through the bench test, the acceleration power spectrum of the structure was input, simulating the random vibration of water tank fatigue conditions to get the tank vibration time domain signal. It was regarded as a fatigue simulation of the input load. The finite element model of tank and weld was established by shell element, and the internal liquid was equivalent by the additional mass method. According to BS7608 standard, different weld grade S-N curves were selected, prediction of fatigue life of water tank is based on nominal stress approach under test conditions. The simulation results show that fatigue failure site and fatigue life of weld in tank was similar to those that in the experimental tests of random vibration. This research proved the correctness of the fatigue life prediction method of weld, and could provide a theoretical reference for the fatigue design of the welded structures for EMU tank.
Wu Jinxing,Liu Shaolin,Peng Xu
Abstract: The two layers tube model of spiral tube heat exchanger with different tube diameter (6mm<d0<14mm), different thickness of space bar(2mm<S2<4.5mm), and different tube pitch(2mm<Z<14mm)was study for the structure parameters of the spiral tube heat exchanger. Water was used as the heat transfer fluid, and the numerical simulation research about the characteristics of heat transfer and flow of the shell side fluid of the spiral tube heat exchanger was carried out by using Realizabl κ-ε model of Fluent software.The influence of tube diameter, thickness of space bar and tube pitch on Nusselt number,synergetic number,entransy loss rate, entransy thermal resistance,and comprehensive heat transfer performance evaluation factor was analyzed. The experimental model was made by combining the numerical model;and the performance test was carried out.The research results showed that the comprehensive heat transfer performance evaluation factor of the spiral tube heat exchange could reach the maximum when the pipe diameter was 6mm, the thickness bar was 3.5mm,and the tube pitch was 14mm.The difference between the simulation results and the experimental data of temperature and pressure drop was1~4℃,0.8~1.2kPa.

He Shengxin,Liu Kunkun,Wang Rui,Zhang Erliang,Li Yanmin
Abstract: Analyze and characterize the complex profile features of the shot peening surface, select the three-dimensional roughness parameter that best characterizes the surface topography, and explore the relationship between it and the hardness of the material. Using the same shot peening process parameters for 316, 420, 2205 Three kinds of stainless steel were subjected to shot peening treatment, and 27 commonly used roughness parameters were used for characterization. Through variance analysis, the optimal shape parameter Sq was selected, and combined with Sa for multi-scale analysis, the optimal evaluation scale was 800 μm. Measurement 3 The original surface hardness of each material was analyzed in combination with their respective Sq values. The results showed that Sq is the optimal surface topography parameter, which can best characterize the complex contour features of the shot peened surface. There is an inverse relationship between Sq and original hardness, and the decrease with increasing material hardness.
Sun Bin,Guo Wei,Gu Jianbing,Mi Liwei
Abstract: Using molecular dynamics simulation and ReaxFF reactive force-field, the mechanical properties of graphene oxide(GO)/styrene butadiene rubber (SBR) composites, including young’s modulus, hardness and friction properties, were investigated in this paper. The simulation results showed that compared with pure SBR, the young’s modulus of composites increased by 77%, hardness increased by 20.3%, friction coefficient decreased by 18% and wear rate decreased by 38%. By calculating the variation of hydrogen bond energy and interaction energy between GO and SBR during the friction process, the mechanisms enhancing friction performance was proposed. In the process of friction, the interaction potential energy between SBR matrix and GO increases gradually. One of the reasons for the increase of interaction potential energy was the enhancement of hydrogen bonds energy. The increase of the interaction potential energy made the stress transfer well from the SBR matrix to the graphene oxide with higher intensity, thus improving the friction properties of the composites.
Li Zhangxiao 1,Song Wei 1,Tian Ye 2
Abstract: The techniques in deep learning and evolutionary computation were adopted to forecast the exchange rate and to optimize the portfolio respectively. Firstly, recurrent neural network is used to build an exchange rate forecasting model, to forecasting the price of instrument and to calculate its expected yield. Then, a bi-objective portfolio model, i.e., maximizing the expected yield and minimizing the risk. For approximating the real market, the proposed model could allow long and short selling, and could also consider the influence of spread. Based on the expected yields of multiple instruments and the proposed portfolio model,a multi-objective evolutionary algorithm was adopted to search for the optimal portfolio. According to the back test on the historical data of multiple instruments, it was verified that the proposed approach could make profit in the exchange market
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