Table of Content

25 August 2014, Volume 20 Issue 4

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A New Biological Implant Meterial Wear Test Machine

FAN Yong-wei, HUA Zi-kai, WU Yi-tian, HUA Wei-ping

2014, 20(4):  397-403.  doi:10.3969/j.issn.1007-2861.2014.02.002

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Wear is a major problem affecting long-term performance of orthopaedic implants. It is important to study strength and wear of the implants by evaluating orthopaedic biomaterials in vitro to achieve successful clinical applications in human bodies. This paper introduces a new type of biological implant material pin on disc (POD) wear testing device (Biotribo-POD) that can test biotribology of biological materials. A testing machine is used to simulate and predict clinical biological materials such as artificial joints wear characteristics including hip, knee and shoulder. The study focuses on implant materials. A
6-station Biotribo-POD, which can experiment with 6 pins simultaneously. It includes a pin guiding module, a motion module, a framework module and a loading module, providing multidirectional slide track shapes and variable load with a computer program. Thus influences with different motion paths can be studied.

Finite-Time Stabilization for a Class of Uncertain Nonholonomic Mobile Robots Based on Dynamic Feedback

CHEN Hua1, CHEN Yi2, WANG Chao-li3, DU Qing-hui3, CHEN Jun-feng2

2014, 20(4):  404-410.  doi:10.3969/j.issn.1007-2861.2014.01.041

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This paper considers a finite-time stabilization problem for a class of uncertain nonholonomic mobile robots with dynamic inputs. Using input-state transformation, a three-input chained systems can be obtained. A discontinuous three-step switching controller is presented by applying the theory of finite-time stability and a new switching design algorithm, which can stabilize the closed-loop system to the original equilibrium point in a finite time interval. Simulation results show effectiveness of the proposed approach.

Kinematics and Trajectory-Planning of a Welding Robot

FAN Yu, CAI Gan-wei

2014, 20(4):  411-419.  doi:10.3969/j.issn.1007-2861.2014.02.001

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The structure of a welding robot is designed to overcome the problem of low strength in traditional tandem welding robots caused by placing the motors on revolute joints. The forward and inverse kinematic problems are solved using the D-H method and the inverse transform method, respectively. The inverse solution of the points on the locus is obtained by polynomial-fitting with Matlab. Thus the input functions are described with a polynomial, providing a simple method to design the control system. The method in a mechanism simulation is verified by Pro/E.

Equilibrium Simulation of Electricity Markets under Different Renewable Energy Support Policies

ZHAO Chen, ZHANG Shao-hua

2014, 20(4):  420-428.  doi:10.3969/j.issn.1007-2861.2014.02.003

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Development of clean and renewable energy is encouraged around the world to reduce greenhouse gas emission. With the implementation of support policies such as feedin tariff (FIT) and tradable green certificate (TGC), the mandatory quota of renewable energy must be fulfilled. This study examines how the two policies affect the oligopolistic electricity markets. Using the equilibrium theory of Cournot competition, equilibrium models for electricity market considering FIT and TGC policies are established respectively. The market regulator can regulate the price of subsidy or TGC using a bi-level optimization
model to maximize social welfare. Impacts of the two policies on the electricity markets are analyzed and compared in numerical simulation. Practically meaningful results are obtained.

Characteristics of Dynamic Friction Torque for Inertial Gyro High-Speed Micro Ball Bearing

LI Song-sheng1,2, LING Jie1,2, CHEN Jian1,2

2014, 20(4):  429-441.  doi:10.3969/j.issn.1007-2861.2014.02.004

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Internal dynamic friction torque of the high-speed precision ball bearing affects performance of inertial gyros. A mathematic model of friction torque is established by taking into account the characteristics of lubrication oil and friction mechanism, and based on the quasi-dynamics of high-speed micro ball bearing and the principle of energy conservation. The friction torque is calculated and analyzed under different bearing working conditions including structure parameters and lubrication oil parameters in high-speed operations. Experimental results show the validity and feasibility of the mathematical model.
Guidance can be provide for the design, optimization, and applications of high-speed micro ball bearing.

Design of Electromyography Prosthesis Controller Based on ARM

BU Feng, LI Chuan-jiang, CHEN Jia-jia, LI Huan, GUO Wei-hai

2014, 20(4):  442-449.  doi:10.3969/j.issn.1007-2861.2014.01.042

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As most electromyography prosthesis controller systems are based on a threshold to control hand’s opening and closing, with poor operational flexibility, it is proposed to use ARM in the system. A STM32 ARM core processor is used as the main chip. It collects the flxor carpi ulnaris and flexor carpi radialis electomyography signals with 2 A/D signal converters, and extractes 4 kinds of characteristic values both in the time and frequency domains. By using a BP neural network classification algorithm, the system realizes real-time online identification of 5 kinds of palm action modes. Experimental results show that the system’s online recognition rate for the 5 actions is up to 97%, meeting the real-time requirements of prosthetic hand control.

Edge Based Depth Coding for Virtual View Synthesis

LIU Chao, AN Ping, ZHAO Bing, YAN Ji-chen, ZHANG Zhao-yang

2014, 20(4):  450-457.  doi:10.3969/j.issn.1007-2861.2103.07.043

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Depth maps typically consist of homogeneous areas partitioned by sharp edges representing depth discontinuities, and sharp discontinuities are important in the view rendering. As different depth distortions have different impacts on the virtual view synthesis, an edge based depth coding method is proposed for virtual view synthesis. The depth map is first divided into edge regions and smooth regions. Full search is used for edge regions in which SKIP and 16×16 modes are used in smooth regions. Besides, a median trilateral filter is designed according to the structure similarity between depth and corresponding
video. Experimental results indicate that, compared with JM, the proposed algorithm improves coding efficiency and can achieve high-quality 3D rendering.

Structure Parameter Estimation of Radio Wave Refractive Index in Rail Transit Tunnel Based on FLUENT

ZHANG Yong-jing, ZHAO Dong-dong

2014, 20(4):  458-465.  doi:10.3969/j.issn.1007-2861.2013.07.031

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To evaluate the characteristics of turbulent flow in a rail transit tunnel environment, this paper simulates the turbulent flow field due to the fast moving trains in a subway tunnel. Using parameters obtained from Shanghai Metro Line 1, the distribution diagrams of pressure and temperature fields are obtained. In the simulation, a commercial software package for computational fluid dynamics (CFD), FLUENT, is used. A set of data from the distribution diagrams is selected to solve the refractive index structure parameters of radio wave under such environmental condition. The calculated results are compared  with published experimental data, showing a good agreement. Therefore, the proposed method provides a useful solution to refractive index structure parameters of radio wave.

Wide Stopband SIW Filter with Right-Angle Coupling Structure

REN Long1,2, MENG Ling-qin1,2, ZHU Jun-hao1, ZHOU Jing-chao1, LIU Jie1

2014, 20(4):  466-471.  doi:10.3969/j.issn.1007-2861.2013.07.033

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A wide stopband filter based on substrate integrated waveguide (SIW) is proposed. Using a right-angle coupling structure, the filter has two transmission zeros (TZs) in the upper stopband. These TZs are located near the resonant frequencies of the two different second-order modes (TE102/TE201), respectively. To further improve the stopband performance, two rectangular slots are etched on the top metal layer of the SIW. The insertion loss is approximately 1.9 dB at the center frequency of 10 GHz. The return loss in the passband is more than 20 dB. The stopband attenuation within 10.518.8 GHz is better than 20 dB, and the second harmonic response is effectively inhibited. Compared with the traditional bandpass filter based on SIW, the stopband bandwidth of this filter is widened by 48%. Measured results well agree with numerical simulations.

Influence of Magnetism of α-Al on Unidirectional Solidification Structure of Al-Cu Hypoeutectic Alloys in a Strong Magnetic Field

LIU Qian, REN Zhong-ming, ZHONG Hua, LI Chuan-jun, YU Jian-bo

2014, 20(4):  472-479.  doi:10.3969/j.issn.1007-2861.2013.07.022

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This paper studies the effect of magnetic anisotropy of  α-Al single crystal on the dendritic morphology in Al-Cu hypoeutectic alloy under a static high magnetic field during directional solidification. Magnetic susceptibility of  α-Al single crystal slices with different crystal orientations are measured with the Faraday method. The results shows that the anisotropic and asymmetric magnetic property of the crystal cell of  α-Al containing Cu. The <111>-crystal direction is a hard magnetization direction while <311> or <310>-crystal direction is an easy magnetization direction. Magnetic susceptibility decreases with increase of Cu content in  α-Al. In addition, magnetic susceptibilities of the four crystal orientations among [111] are different. Besides, applying a 6 T longitudinal high magnetic field, the  α-Al dendrite deviates from the heat flow direction, which is parallel to the solidification direction without a magnetic field at a growth speed of 50 μm/s.This phenomenon may be attributed to the crystal magnetic anisotropy energy of  α-Al.

Thermal Structural Integrity Analysis of Nozzle Throat with Needled Integral Felt C/C Composites

XU Yu-rong1, YANG Min2

2014, 20(4):  480-488.  doi:10.3969/j.issn.1007-2861.2013.07.035

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The temperature and stress fields of solid rocket motor (SRM) throat made of needled integral felt C/C composites during and after firing process are calculated using finite element method (FEM) in this paper. The calculated maximum stress in nozzle throat is compared with the final strength obtained in the material test. It has been found that the nozzle throat with needled integral felt C/C composites is safe during SRM firing, but the final axial tensile stress of nozzle throat after SRM firing exceeds the material tensile strength, leading to structure failure. The results are verified by SRM firing test and scanning electron microscope (SEM) analysis.

Algorithm for Processing Optically Captured Motion Data

SHI Juan1, WANG De-yu1,2, TANG Gang1

2014, 20(4):  489-497.  doi:10.3969/j.issn.1007-2861.2014.01.023

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Coordinate values of the markers arranged on the lower extremity of the experimental subject were recorded using an optical motion capture system. Reaction force from the outside was measured with a load board. A program was developed using Matlab to import the above data to quickly calculate the coordinates, displacement, velocity and acceleration of the barycenter in segments of the lower extremity. The joint angle, angular velocity, angular acceleration, joint force, torque and other motion parameters were also calculated. With existing analysis software, the processing methods were complicated and time consuming. This study aims to solve the problem. Using polynomial fitting, curves of various parameters are smoothed, and correctness of the algorithm is verified by comparing the processing results with those generated by Visual 3D software.

An Integrated Indoor Location Technology Based on RFID and DR

LI Ping1, YANG Ning1, ZHONG Shao-shan2

2014, 20(4):  498-504.  doi:10.3969/j.issn.1007-2861.2014.02.014

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Radio frequency identification (RFID) is influenced by the environment, when the RFID is used as an indoor location way. The signal intensity of e-tag becomes weak and can’t be read, which will decrease the location precision, and even cause the location system fail. An integrated location system based on RFID and dead reckoning (DR) is proposed to apply on indoor location of dynamic object. The RFID can eliminate the accumulative error with time. The DR system can assist the RFID system, when the e-tag signal lost. Based on the experiment, the integrated location system can improve the effect and precision of indoor location.

Yellow Traffic Light and Traffic Safety

SHEN Li-ming1, SHEN Jia-qi2, ZHANG Xiao1

2014, 20(4):  505-512.  doi:10.3969/j.issn.1007-2861.2014.01.001

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Current traffic regulations do not have a definite conclusion on whether motor vehicles are allowed to pass through an intersection when the traffic lights turn yellow. When facing a beaming yellow traffic light, drivers’ reaction varied, resulting in negative impacts on road safety. This paper analyzes systematic  characteristics of moving motorists and motor vehicles, and reveals the importance of the yellow traffic light. The right of passing through a yellow traffic light is  examined from two different perspectives. A conclusion is drawn that a vehicle should be allowed to pass through the intersection while the traffic light is yellow. A case study is presented for a reasonable length of time of the yellow traffic light and other relevant parameters.

Stabilization of a Class of Discrete-Time Singular Markov Jump Systems

ZHONG Jin-biao1, DU Xin2, ZHU Xun-lin3

2014, 20(4):  513-520.  doi:10.3969/j.issn.1007-2861.2014.01.007

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This paper discusses stability and stabilization for a class of discrete-time singular Markov jump systems with partly unknown transition probabilities. By introducing slack matrix variables, a sufficient condition is obtained to guarantee stochastic stability of open-loop systems. A method for designing state feedback controller is then proposed. These conditions are given in terms of linear matrix inequalities (LMIs). A numerical example is given to show effectiveness and less conservatism of the obtained results.

Polycyclic Aromatic Hydrocarbons (PAHs) in Atmospheric Particulate Matter (PM_2.5 and PM₁₀) from a Suburban Area in Shanghai: Levels, Sources and
Risk Assessment

WU Ming-hong, CHEN Liu-lu, CHEN Zu-yi, FENG Jia-liang, MA Jing

2014, 20(4):  521-530.  doi:10.3969/j.issn.1007-2861.2014.01.004

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A study of airborne particle-bound polycyclic aromatic hydrocarbons (PAHs) was conducted in a suburban area of Shanghai during six months to assess the levels and sources of PAHs in air, and its potential health risk to local residents. The total concentration of PAHs in PM10 and PM2.5 ranged from 5.25～136 and 3.56～149 ng/m³  with a mean of 36.9 and 28.5 ng/m³. As the result of isomeric ratios, it is suggested that the combustion and traffic are the main source of airborne PAHs. The median value of BaP ranges from 0.6 to 16 ng/m³. The toxic equivalent quantities (TEQs) are 5.4 ng/m³ of PM10 and 4.1 ng/m³ of PM_2.5. The incremental lifetime cancer risk (ILCR) model taking into account inhalation and dermal contact routes is used to quantitatively estimate the exposure risks for three age groups of female and male adults, adolescents, and children. According to the age groups, the values of ILCR in a decreasing order are as following: adults > children > adolescents; and that of females is higher than males. These values of all age groups are higher than the lowest level provided by United States Environmental Protection Agency (ILCR=10⁻⁶), indicating unacceptable probability distributions. That implies air quality in China is still facing a serious problem and challenge.