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2018, 38(5): .

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2018, 38(5): .

Abstract(588) PDF(378)

Abstract:

Research on Three-Block Local Grid Refinement Method in MRT-LBM

QU Yan-peng, ZHANG Kun, CHEN Song-ying

2018, 38(5): 441-448. doi:10.15918/j.tbit1001-0645.2018.05.001

Abstract(1108) PDF(531)

Abstract:
To improve the computational accuracy of hydrodynamic force and torque for a moving particle in viscous flow, a three-block local grid refinement method was proposed based on the multi-relaxation-time (MRT) lattice Boltzmann method (LBM). Firstly, the flow field was divided into three blocks comprising coarse, buffer and cage domain. The dynamic physical parameters, such as density, velocity and stress of the superposition nodes, were considered to be continuous at the interface between every two blocks, the distribution functions of different blocks were developed to be transferred at every block buffer layer. Then pre-collision sub-step implementation was employed to initialize the physical value for the new domain grid points, and to construct the three domain structures. Finally, calculations were implemented based on the standard Boltzmann, full-domain refinement, two-block and three-block local grid refinement four methods respectively for the Couette flow with an asymmetrical placed particle. Simulation results show that, the level of dynamic fluctuation with the three-block grid refinement method is significantly suppressed. And for a lid-driven cavity flow, two singular corners under the lid refined with three-block meshes, Reynolds number 1000 flow, the calculation result shows the velocity distribution along mid-plane of the cavity is agree well with benchmark's results, and the noise on the pressure contour is significant reduced and stress oscillations evidently get down. All results prove that the present method is effective to high resolution computation with LBM.

Game Algorithm of Multi-Objective Reliability Design Optimization Based on Simulating Animal Behavior

FENG Jia-zhen, ZHANG Jian-guo, QIU Ji-wei

2018, 38(5): 449-453. doi:10.15918/j.tbit1001-0645.2018.05.002

Abstract(861) PDF(446)

Abstract:
By reforming players' behaviors based on animal behavior, a simulating animal behavior-based game algorithm was proposed to solve the problem of multi-objective reliability design optimization. Every objective was regarded as a player, and the design vector was decomposed into players' strategy sets through random vector mapping technology. Selfish and mutually beneficial behaviors of animals were conferred to corresponding players based on the behavior matching rule. Then, the mapping relation between the payoff function and the objective function of every player was constructed through the simulated animal behaviors. The players that simulated mutually beneficial behaviors leagued together, and competed with other players that simulated selfish behaviors. The equilibrium solution was obtained after multi-round games. The design results of the vehicle brake show that the proposed algorithm is more efficient than competitive and cooperative games.

Pressure Drop Analysis of an Improved Radial Type Magnetorheological Valve

HU Guo-liang, ZHONG Fang, HU An-qi, ZHENG Kai-yang, DING Ru-qi

2018, 38(5): 454-461,475. doi:10.15918/j.tbit1001-0645.2018.05.003

Abstract(862) PDF(497)

Abstract:
An improved radial type magnetorheological valve was developed by guiding the magnetic flux into the annular gap, changing the material properties of the typical single radial type MR valve, and making the valve have both annular flow and radial flow path simultaneously. A finite element analysis was carried out with ANSYS/Emag software to simulate the effects of material properties on the magnetic flux distribution and pressure drop change in the valve, and combined with the derived magnetorheological valve model to predict the valve performance. The experimental test rig was set up to validate the simulation results. The experimental results show that, the pressure drop of the improved radial type MR valve is superior to that of typical radial type MR valve under the same geometry conditions and the same electromagnetic parameters. At the applied current of 1.8 A, the maximum pressure drop of typical radial type MR valve is approximately 3 MPa, while the maximum pressure drop of improved radial type MR valve is approximately 4 MPa, increasing the pressure drop by 33% and enlarging its application range.

Research on Variable Diameter Design and Target Interaction Optimization of Turret Disassembling Platform

YAN Peng-cheng, SHAO Shuai, SUN Jiang-sheng, ZHANG Lian-wu

2018, 38(5): 462-468. doi:10.15918/j.tbit1001-0645.2018.05.004

Abstract(1020) PDF(586)

Abstract:
In order to solve the problems of poor universal and miscellaneous types of existing various self-propelled gun turret assembling platforms, a variable diameter turret assembling platform was designed based on the analysis of their size requirements. To realize a lightweight design and improve the stiffness and strength of the platform, a method of target interaction optimization design based on topology optimization and size optimization was proposed. Firstly, setting the minimum quality of the tray, causing the platform damaged easily, as the optimal target, the maximum allowable displacement and the allowable stress as constraint conditions, the cell density as design variables, the topology optimization of the tray was carried out. Then the topology optimization results were regularized, and setting the improvement of stiffness and strength as the optimization target, no increasing quality as constraint conditions, the important size parameters as design variables, the size optimization of the tray was implemented. The results show that, the quality can be reduced from 1 421 kg to 1 032 kg after optimization, the structural stiffness and strength are greatly improved. The effectiveness of the optimized results is verified by tooling test.

Dynamic Experiment Error Analysis Method Based on Conditional Sampling Under Epistemic Uncertainty

LIAO Xiang, ZHANG He, LI Hao-jie, GUO Hua, LI Chang-sheng

2018, 38(5): 469-475. doi:10.15918/j.tbit1001-0645.2018.05.005

Abstract(862) PDF(437)

Abstract:
A dynamic experiment error (DEE) analysis method was proposed for analyzing the probability distribution of dynamic experiment error based on conditional sampling under epistemic uncertainty(EU)to improve the error analysis accuracy tampered with lack of experiment equipment and model information.Firstly,the EU of experiment system was divided into measure device EU and model EU,and the relationship between two kinds of their probability distribution was formulated.Then a conditional sampling method was designed to establish the relationship between DEE distribution and EU.The best DEE and EU parameters were gotten by comparing the sampled distribution with the experiment result.Finally,the method was validate in a fuze air burst distance experiment.Compared with experiment result and the error distribution simulation result without taking the epistemic uncertainty into account,the error distribution resulted in this method is more match with the experiment result.

Simulation Study on Fluid Non-Uniformity of Multi-Cylinder Diesel Engine Cooling System

DU Wei, BAO Wen-hua, LIU Fu-shui

2018, 38(5): 476-480. doi:10.15918/j.tbit1001-0645.2018.05.006

Abstract(832) PDF(508)

Abstract:
The cooling water system of multi-cylinder diesel engine was discussed with software Fluent to simulate the flow field of in-line 3、4、5、6-cylinder diesel engine. The results show that, for the cooling water jacket inlet and outlet in the same end of the crankshaft inline diesel engine, from the first cylinder near the inlet to the last cylinder remote from the inlet, the pressure of the inter-water channel of each cylinder is gradually reduced, the pressure of the inlet and the outlet of each cylinder head is gradually increased, and the flow rate of each cylinder head gradually decreases. At same inlet flow, the pressure difference between the inlet and outlet of each cylinder is gradually decreased with the increase of the cylinder numbers, the flow resistance of the entire cooling jacket is reduced, the mean value of the inlet and outlet pressure difference of each cylinder head gradually decreases, the difference between the maximum and minimum flow rate in each cylinder head of the engine increases, and flow non-uniformity of each cylinder head increases significantly.

Mass Center Adjustment Method of Quadruped Robot Moving on Slopes

MA Zong-li, ZHANG Pei-qiang, LÜ Rong-ji, WANG Jian-ming

2018, 38(5): 481-486. doi:10.15918/j.tbit1001-0645.2018.05.007

Abstract(827) PDF(438)

Abstract:
In order to implement stable movement on slopes, the shins of quadruped robot were designed to use the hydraulic cylinder in this paper. A mass center adjustment method of quadruped robot was proposed based on trot gait, implemented by decreasing the length of the front shins and keeping the length of the rear shins no change. Firstly,the robot stability was judged according to the superposition degree between the projection point of the mass center and the cross point of the supporting diagonals, and the definite relationship of attitude adjustment was got. Then, a planning method of foot trajectory of no-impact complex cycloid was improved to reduce the contact impact of robot moving on slopes. Finally, the robot moving on slopes in trot gait was simulated by using Adams and Matlab. The simulation results show that, the robot can move steadily on 20° slope with trot gait by using the proposed method of mass center adjustment and the planning method of foot trajectory.

Fuzzy Evaluation of Urban Traffic Congestion Based on Neural Network

ZHU Yun, WANG Jian-yu, YANG Ying, LIU Bo-hang

2018, 38(5): 487-492. doi:10.15918/j.tbit1001-0645.2018.05.008

Abstract(914) PDF(420)

Abstract:
To solve the problem of the congestion of urban traffic network, a fuzzy evaluation model of urban road traffic congestion was developed based on the fuzzy analytic hierarchy process and neural network theory. Firstly, taking AHP as the criterion, a road traffic congestion evaluation index system was established with three levels, including microcosmic, meso and macro layer. Then a fuzzy consistent judgment matrix was used to define the evaluation factor weights of road traffic congestion, a fuzzy neural network evaluation model was built based on BP neural network to judge the road traffic congestion situation, the threshold intervals of the road traffic congestion evaluation were determined as five grades, including moderate congestion, severe congestion, mild congestion, relatively smooth and smooth. The traffic congestion data of 20 traffic districts in Shanghai in 2016 were taken as example to implement the method. The results show the feasibility and effectiveness of the method.

Vehicle Optimal Speed Profile When Running on Curved Roads

JIN Hui, DING Feng, ZHOU Min

2018, 38(5): 493-498. doi:10.15918/j.tbit1001-0645.2018.05.009

Abstract(1190) PDF(675)

Abstract:
To explore the influence of the factor of the horizontal curvature on fuel economy, a vehicle eco-speed optimization algorithm based on the information of road curvature was developed. Firstly, with the aid of the establishment of the BIT-TFCM instantaneous fuel consumption model and vehicle dynamics model, the steady-state optimal speeds corresponding to various circular curves with different radii were obtained. When entering or departing a curve, the optimal speed profile can be calculated with the dynamic programming algorithm. The fuel consumption can be reduced by 5.69%~15.91% with this algorithm compared with typical driving model using the co-simulation of Matlab/Simulink and CarSim. This technique can obviously improve the vehicle fuel economy when running on curved roads, and can provide decision-making for speed control of unmanned vehicles.

Study on Characteristics of the Dual-Chamber Hydro-Pneumatic Suspension

SANG Zhi-guo, DONG Ming-ming, ZHAO Kai, GU Liang

2018, 38(5): 499-504. doi:10.15918/j.tbit1001-0645.2018.05.010

Abstract(837) PDF(426)

Abstract:
With excellent isolation performances,hydro-pneumatic suspensions are widely employed as vibration isolation system in many engineering field.The dual-chamber hydro-pneumatic suspension is a modified version of the traditional hydro-pneumatic suspension.The expressions for the equivalent stiffness and damping coefficient were derived from the modeling of dual-chamber hydro-pneumatic suspension expressed by a set of differential equations.Both the equivalent stiffness and damping coefficient show their strong dependency on the excitation frequency and amplitude.Based on the harmonic balance method,the effects of three key parameters,the stiffness of two accumulators and the damping coefficient of throttle,on the equivalent stiffness and damping coefficient were analyzed.The validity of the expression was confirmed through experiment result.

A Topology Optimization Method of Waveform Digital Filter Based on Dendrogram

XUE Cheng-bo, MA Yue, REN Shi-wei

2018, 38(5): 505-510. doi:10.15918/j.tbit1001-0645.2018.05.011

Abstract(1033) PDF(483)

Abstract:
In this paper, an optimizing methodology for wave digital filter (WDF) equivalent circuit was proposed. This binary tree based method can simplify simulation system and improve system performance on speed. The WDF with binary tree representation was provided with a clear and intuitive structure to solve the low expressing efficiency issue in traditional WDF topology. The shape of this tree can directly indicate essential information of WDF equivalent circuit, such as module parallelism and the longest path. Moreover, considering the port symmetry of the WDF adapter, an optimizing methodology was presented for WDF binary tree to reduce processing steps in each simulating cycle and improve the overall performance of simulation. The optimization results show that,the reflection step length can be reduced by 42.86%, while the incidence step length can be reduced by 38.9%, the total operation time can be reduced to 0.366 ms.

High Resolution ISAR Imaging of Space Target Based on Two-Dimensional Sparse Characteristics

MA Jun-tao, GAO Mei-guo, GUO Bao-feng, HU Wen-hua, XIA Ming-fei

2018, 38(5): 511-518,550. doi:10.15918/j.tbit1001-0645.2018.05.012

Abstract(792) PDF(547)

Abstract:
Aiming at the ISAR imaging problem of three-axis stabilized space target, a two dimensional high resolution ISAR imaging method was proposed based on sparse characteristics and orbit model. Firstly, a phase-stable wave shape dictionary was developed with target orbital data to realize high range resolution and motion compensation. Then, considering the translational motion and attitude stabilization of target running on orbit, the effective accumulation angle of three-axis stabilized space target was calculated with target rotation vector analysis. According to the sparse characteristics of high range resolution profile (HRRP), the cross-range matching dictionary size was decided effectively, and a dictionary structure was proposed to adapt to the migration through resolution cell (MTRC). The simulation results show that the sparse matching dictionary can correctly reflect the attitude change of space target, solve the MTRC problem of scatters, and significantly improve the two-dimensional resolution of the space target ISAR image.

Polynomial Fitting Acceleration Method Based on Time-Series Segmentation

JI Wei-xing, ZHANG Lu-lu, CHEN Juan, ZOU Tian-gang, LUO Hui, GUO Jing, GAO Zhi-wei

2018, 38(5): 519-524. doi:10.15918/j.tbit1001-0645.2018.05.013

Abstract(893) PDF(488)

Abstract:
Polynomial fitting is one of the most important approaches of time-series data compression, and the calculation process involves multiple matrix multiplication and inversion, which lead to high computational complexity. Due to the large number of time series instances, the incoming data need to be high performance and real-time processing. Considering the characteristics of time-series data, especially for the periodic sampled time series data, a polynomial fitting acceleration method was proposed. Reusing the intermediate calculation results, both of polynomial fitting methods with fixed and variable segment length were taken to speed up the polynomial fitting of time-series data. Experimental results show that the proposed method can achieve a speedup of 28x and 17x for fixed length segmentation and variable segmentation respectively.

Predicting Software Security Vulnerabilities with Component Dependency Graphs

WEI Sheng-jun, HE Tao, HU Chang-zhen, SHAN Chun

2018, 38(5): 525-530. doi:10.15918/j.tbit1001-0645.2018.05.014

Abstract(958) PDF(457)

Abstract:
Aiming at the prediction of vulnerability, a vulnerability prediction method based on the component dependency graph was proposed. Firstly, the complexity, coupling and cohesion metrics of a software component were defined based on the component dependency graph. Then these metrics were used to establish a machine learning model to predict vulnerabilities in a component. Finally, a crawler tool was designed and implemented to collect all public security vulnerabilities in Mozilla Firefox from version 1.0 to version 43. Based on these data, the prediction model was trained and tested. The results show that the proposed metrics are also effective in vulnerability prediction.

Objective Evaluation of Timbre Thickness for Speech Based on Feature Fusion Matrix

TU Zhong-wen, ZHANG Qin, JIN Cong, ZHAO Wei

2018, 38(5): 531-536. doi:10.15918/j.tbit1001-0645.2018.05.015

Abstract(1095) PDF(740)

Abstract:
A new method was proposed based on a feature fusion matrix for objective evaluation of speech timbre thickness in this paper. The feature matrix was consisted of two parts, the speech feature parameter of MFCC and LPC, and the non-speech feature of resonance factor, body mass index, and vital capacity weight index. These features were fused in different combinations to establish a feature matrix. Finally, a softmax classifier was employed to classify the timbre thickness for speech into six levels. Experimental results show that the proposed method can achieve high performance for objective assessment.

A Real-Time Mobile Traffic Classification Approach Based on Timing Sequence Flow

LIU Yi, SONG Tian, LIAO Le-jian

2018, 38(5): 537-544. doi:10.15918/j.tbit1001-0645.2018.05.016

Abstract(795) PDF(414)

Abstract:
The rapid development of mobile Internet brings many special problems in the fields of network security, network measurement and quality of service. In order to further study the characteristics of mobile Internet, researchers need to quickly and accurately classify the mobile traffic flow from the traditional network traffic. In this paper, combining lightweight flow table and deep packet inspection(DPI)technology, a real-time mobile network traffic classification approach was proposed. To reduce the scale of flow table, DPI overhead and improves the accuracy of mobile traffic classification, the network flow was expanded into the sequence flow segments according to the interval-time relationship, and the mobile traffic was classified accurately according to DPI of firstNpackets in the sequence flow segments. The real-time network traffic experiments show that, the identification accuracy rate can reach 91.55%, the average overhead of one DPI only takes 20 packets,and the scale of flow table can be reduced to 0.21%. Compared with the P0F, the accuracy of the propose approach can be improved significantly.

A Image Compression Algorithm Based on Multi-Node Cooperation in Wireless Multimedia Sensor Networks

WU Chun-ming, ZHENG Hong-kuo, WANG Yan-jiao, FU Rao, YU Ming, SUN Yong

2018, 38(5): 545-550. doi:10.15918/j.tbit1001-0645.2018.05.017

Abstract(797) PDF(679)

Abstract:
To solve the problem of limited energy and computing ability in wireless multimedia sensor networks and to eliminate the computation for the relationship between compression energy consumption and image quality in the process of image compression, combining the compression process of JPEG-XR and the structural characteristics of network, a method of image compression was proposed based on multi-node cooperation. Firstly, the camera nodes were connected to ordinary neighbor nodes and then to cluster-heads to construct a network structure, making the process of image compression and transmission distributed in cooperative clusters. Then a cooperative method was used to implement the multi-node cooperation in compression process. The simulation results show that, in low bit rate condition, the PSNR of this method can increase about 3dB compared with JPEG method. And in terms of network life, the network load can be balanced better and the network lifetime can be extended greatly with the new method.

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