Table of Content

28 February 2014, Volume 20 Issue 1

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Composite Materials

Advances and Prospects of Nanocomposites

DU Shan-yi

2014, 20(1):  1-14.  doi:10.3969/j.issn.1007-2861.2013.07.054

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This work provides an overview of recent advances in the polymer nanocomposites research. The key research opportunities and challenges in the development of carbon nanotube graphene, interfacial bonding strength in structural and functional nanocomposites are addressed in the context of fiber reinforced polymer composites. The state of knowledge in mechanical and physical properties of polymer nanocomposite is presented with a particular emphasis on buckypaper enabled polymer nanocomposites, electrically and optically functional nanocomposites, smart and intelligent nanocomposites, and functional and multifunctional nanocomposites. Critical issues in the nanocomposites research and applications are discussed.

Manufacturing of CMCs by Chemical Vapor Infiltration Process

CHENG Lai-fei, ZHANG Li-tong, MEI Hui, LIU Yong-sheng, ZENG Qing-feng

2014, 20(1):  15-32.  doi:10.3969/j.issn.1007-2861.2013.07.049

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This paper reviews the development trends, and flexible, robust and toughness control and design in the simulation and visualization of ceramic matrix composites (CMCs) manufacturing by chemical vapor infiltration (CVI) process. The gaseous route involves gas transfer, reaction thermodynamics and kinetics, and pore structure modeling, which is a typical multi-scale and multi-physics problem. Quantum chemistry, chemical thermodynamics, microscopic kinetics, finite element, the level-set and artificial intelligence methods are applied to achieve densification process simulation and composition analysis of composite materials, accurately reflect anisotropy of gas transfer in the porous preform and the deposition process, and provide more accurate control parameters for process optimization. CVI is a flexible and robust process for manufacturing CMCs. It has extensive applications and abilities in process control, adjustment, design, assemble, error-correction andcompatibility. It is suitable for microstructure control of CMCs, and is the most advanced
fundamental method for manufacturing CMCs. Strength and toughness are the core issues for CMCs, including coordination of the moduli among reinforcement fibers, matrix and inter-phases, residual thermal stresses control, and the volume fraction design for both the matrix and the fibers. Tough CMCs can be manufactured with reasonable control and design of these parameters so as to meet the requirements under different environmental
conditions.

Survey of Aerospace Structural Health Monitoring Research Based on Optic Fiber Sensor Networks

ZHANG Bo-ming, GUO Yan-li

2014, 20(1):  33-42.  doi:10.3969/j.issn.1007-2861.2013.07.041

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An overview of classification and characteristics of optical fiber sensors is presented. Applications of fiber optic sensor in aerospace composite materials structural health monitoring and their development are discussed. The applications include Boeing, Airbus, NASA (National Aeronautics and Space Administration) and others. Problems related to fiber optic sensor network applications that need be considered and addressed are pointed out. Prospects of the sensor-based health monitoring technology in the aerospace industry are predicted.

Propagation Characteristics of Guided Waves in 2D Lattice Sandwich Plate and Computation of Dispersion Curves

TAO Yong1, YIN Xi-yue2, FAN Xi-gang2, ZHANG Xiang-lin2,CHEN Ming-ji3, FANG Dai-ning1

2014, 20(1):  43-50.  doi:10.3969/j.issn.1007-2861.2013.07.040

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Based on an equivalent analysis model, the dispersion equations of guided waves in 2D lattice sandwich plate are derived, and the dispersion curves calculated. A finite element model is also built according to the real structure of 2D lattice. Propagation of guided waves in hexagonal lattice sandwich plate is simulated using ABAQUS software. It is demonstrated that the equivalent analysis model can well describe the guided waves propagating along the whole sandwich plate at low frequencies.

Preparation of High Thermal Conductivity C/C Composite

FENG Zhi-hai, FAN Zhen, KONG Qing, YU Li-qiong, XU Lin

2014, 20(1):  51-58.  doi:10.3969/j.issn.1007-2861.2013.07.045

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2D high thermal conductivity C/C composite and 3D high thermal conductivity C/C composite were produced through hot pressing and liquid impregnating method, with mesophase pitch-based carbon fiber and mesophase pitch as raw materials. Thermal conductivity as high as 443 W/(m·K) and 340 W/(m·K) was achieved for 2D high thermal conductivity C/C composite and 3D high thermal conductivity C/C composite, respectively. The effects of structure parameters on the thermal conductivity were analyzed according to the analytical thermal model of C/C composites. The results show that thermal conductivity of carbon matrix, porosity and interface have different effects on the thermal conductivity of composites.

Preparation of Alumina Short Fiber Preform Using Mold Pressing Technique in Vacuum and Its Quality

ZHANG Bing-feng, YANG Fang, ZHOU Ji-ming, QI Le-hua

2014, 20(1):  59-67.  doi:10.3969/j.issn.1007-2861.2013.07.044

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To solve the problem related with short fiber preform preparation such as long preparing time, binder segregation and dimensional instability when removed from the mold, a new preform preparation technique was proposed. The method was characterized in short preparation time by using vacuum and pressure. MgCl₂·MgF₂ was selected as an effective binder. A series of alumina preforms with different fiber volume fraction of 10%, 15%, 20% and 25% were successfully fabricated. Processing conditions for the preform preparation were as follows: the preform was dried for 2 hours at 45 °C, and then gradually heated to 1 100 °C within 1.5 hours. The prepared preform had excellent surface quality, good core strength, and uniform pore and fiber distribution without  fiber loss. Compression tests showed that the alumina preforms met the requirements of infiltration experiments for fabricating composites.

Molecular Dynamics Simulation of Diffusion Properties of Li_xC₆ in Li-Ion Battery

JI Xiang1, SONG Yi-cheng2,3, ZHANG Jun-qian2,3

2014, 20(1):  68-74.  doi:10.3969/j.issn.1007-2861.2013.07.013

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Simulation of the Li-ion diffusion behavior in graphite during the charging process is performed by using molecular dynamics. The Li-ion diffusion properties of the graphite anode material are studied at 300 K. Diffusion coefficients of LiC₆, LiC₁₂ and LiC₁₈ are calculated by Einstein relationship. The relationship between diffusion coefficients of Li_xC₆ and Li concentration is obtained. The results show that diffusion coefficient changes with Li concentrations in the charging process. Stage Ⅰ and stage Ⅱ diffusion coefficient decreases with the increasing Li concentration. The diffusion coefficient near LiC₁₂ changes greatly because of the structural phase transition. The simulation results show visual images of the atomic configuration Li_xC₆. The results of the study provide data for Li modelling of Li electrode deformation.

Investigation on Compressive Failure Mechanism of 2D Cross-ply C_f/Al Composites by Extrusion Directly Following Vacuum Pressure Infiltration Process

ZHOU Ji-ming, ZHENG Wu-qiang, QI Le-hua, MA Yu-qin

2014, 20(1):  75-82.  doi:10.3969/j.issn.1007-2861.2013.07.042

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2D cross-ply carbon fiber reinforced aluminum matrix composites were fabricated by extrusion directly following vacuum pressure infiltration. The compressive property and failure mechanism of 2D-C_f/Al composites were investigated at room temperature by applying loadings along different directions with respect to the fiber layer. The results show that the composite with ideal infiltration quality and dense microstructure could be fabricated successfully by extrusion directly following vacuum pressure infiltration the aluminum alloy and fibers are evenly distributed, and seldom defects can be found in composite. The compression yield strength perpendicular to the fiber layer is almost 2.5 times as that parallel to the fiber layer. Further analysis shows that the different properties are caused by different failure mechanisms. When the loading direction is perpendicular to the fiber layer, composites failure is mainly caused by shear fracture. When the loading direction is parallel to the direction of fiber, interface debonding and fiber bending failure are the main failure mechanism.

Communication and Information Engineering

A Planar Printed Yagi Antenna with Adjustable Beam

GONG Bo, YANG Xue-xia

2014, 20(1):  83-91.  doi:10.3969/j.issn.1007-2861.2013.07.002

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Based on the high directivity of Yagi antenna, a planar Yagi printed antenna with six adjustable beams is designed. In order to increase the bandwidth, a tie type structure is used as the driven dipole, of which the two arms are located on the opposite side of the substrate. Only one PIN (positive-intrinsic-negative) diode switch is loaded between the ground and the driven dipole arm on the ground to control the antenna element with its radiation direction having no extra bias circuits required. The measured results well match the simulation, and show that the bandwidth of the return coefficient below −10 dB is 400 MHz, gain of the reconfigurable antenna is 7.5 dB on the main radiation directions of 30°, 90°, 150°, 210°, 270° and 330°, and the half power beam width of each direction is below 60°. This reconfigurable antenna with the scanning function of six directions and good directivity can be applied to small base stations or other wireless communication systems.

Real-Time Rectification and Stereoscopic Display for Multi-view Imaging

YAN Ji-chen1, AN Ping1, LI Chun-hua1,2, ZHAO Bing1,LIU Chao1, ZHANG Zhao-yang1

2014, 20(1):  92-98.  doi:10.3969/j.issn.1007-2861.2014.07.015

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Multi-view images captured by a parallel multi-camera array manually placed tend to produce vertical parallax. To eliminate vertical parallax, the multi-view images must be rectified. This paper presents a simple and effective algorithm for multi-view rectification, and builds a stereoscopic display system based on this algorithm. A multithread technique is used to achieve soft synchronization of the cameras, and to perform real-time optimization. When image resolution is 1 280×960, the upload rate is 25 frame/s, and the target 3D display resolution is 1 920×1 080, the display rate of the system can reach 20 frame/s by using the bilinear interpolation. If interpolation methods with low complexity are used, the display rate can reach more than 20 frame/s. A 3DTV system with real-time rectification of eight cameras and stereoscopic display is built by using the proposed algorithm.

Adaptive Nonlocal Means Image Denoising for Better Preservation of Textures

CHEN Gang, QIAN Zhen-xing, WANG Shuo-zhong

2014, 20(1):  99-106.  doi:10.3969/j.issn.1007-2861.2013.07.023

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The principal neighborhood dictionaries (PND) nonlocal means (NLM) is an effective method for image denoising, which is based on principal component analysis(PCA). However, it does not make full use of the image contents and is less effective in texture regions. This paper proposes modification to the PND method by adjusting a filter parameter h to achieve better accuracy. Experimental results show that the proposed outperforms PND method and can preserve more edge and texture details while achieving satisfactory denoising results.

Mathematics.Physics and Chemistry

A Method of Triple Newton-Thiele Type Rational Interpolation

CUI Rong-rong1,2, GU Chuan-qing1

2014, 20(1):  107-113.  doi:10.3969/j.issn.1007-2861.2013.07.021

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The bivariate Thiele-type interpolating branched continued fractions and Newton interpolation polynomials are combined. By introducing the so-called blending partial differences, a triple rational interpolation scheme is obtained. The characteristic theorem and error estimation are presented. Finally, an example is given.

Determination of Vitamin B₁₂ in Fortified Foods by UltraHighPerformance Liquid Chromatography-Tandem Mass Spectrometry

MA Ying-qing1, WANG Xia1, ZHANG Xiao-gang1, LUO Li-qiang2

2014, 20(1):  114-119.  doi:10.3969/j.issn.1007-2861.2013.07.016

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A simple, fast and accurate method for determination of vitamin B₁₂ in fortified foods is developed using ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample is concentrated by solid phase extraction (SPE) column. The linear range of the method is from 0.5 to 100.0 μg/L with a correlation coefficient of 0.999 9. The detection limit is 1.0 μg/kg. The proposed method exhibits high sensitivity and good reproducibility for determining vitamin B₁₂.

Mechatronics Engineering and Automation

Impacts of Short-Term Generation Rights Transaction on Network Loss for Power System

XUE Mei-juan, YAO Li-xiao, QU Xiao-yong, LIU Jia-jun

2014, 20(1):  120-126.  doi:10.3969/j.issn.1007-2861.2013.07.020

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Network loss caused by the power generation right trade and impact on the system based on DC power flow equation are calculated. The method takes into account each power flow state, and better conforms to the practical situation of generation right trade. By analyzing the mechanism and process of generation right trade, a trading power allocation curve is fitted using cubic spline interpolation. This avoids the drawback of average allocation of trading power within the trading hours under the daily generation right trade mode. The curve can be adjusted by trading power, and can replace the average allocation method. The proposed method is verified by an IEEE13 node example.