Table of Content

30 October 2014, Volume 20 Issue 5

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Speical Paper

Metamaterials and Metamaterial-Based Antenna Technology

CHEN Zhi-ning1,2

2014, 20(5):  531-540.  doi:10.3969/j.issn.1007-2861.2014.03.011

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The study of metamaterials is among the most important and attractive topics of the electromagnetic field theory and applications in the past 15 years. Much effort has been devoted to scientific research into the new physical phenomena with great progress. This paper presents the thoughts about the applications of metamaterials in innovative antenna designs from an engineering perspective. The new understanding of metamaterials offers us great possibility to translate the physical concepts of metamaterials in laboratories to innovative antenna designs in practical engineering applications. The technologies have been successfully developed, significantly improving key performances of antennas at microwave and millimeter-wave bands. The recently invented metamaterial-based antennas demonstrate not only wide operating bandwidth, high antenna efficiency, high gain, but also significantly reduced volume with simple mechanical structures.

Research Progress in Microwave Wireless Power Transmission Technologies and System Efficiency Evaluation

YANG Xue-xia, ZHOU Hua-wei, ZHOU Yong-jin, MEI Huan

2014, 20(5):  541-549.  doi:10.3969/j.issn.1007-2861.2014.04.003

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Microwave wireless power transmission (MPT) are the key technology of solar power satellite and aircraft in near space, it could also be applied in charging the wireless sensors and harvesting the ambient electromagnetic power. After comparing the microstrip and coplanar waveguide rectenna element and arrays, the demands on receiving antennas and rectifying circuits are summarized. The topological models and truncated Gauss aperture level distribution of the transmitting antenna are analyzed to obtain the maximum microwave beam capture efficiency. Based on above key technique, a C-band MPT system is designed and 35% dc-dc (direct current-direct current) efficiency is evaluated. The remaining problems and the development of MPT technology are discussed at the end.

Civil Engineering

Elastic Bodies with Different Modules in Tension and Compression

ZHAO Hui-ling1, YE Zhi-ming1,2

2014, 20(5):  550-558.  doi:10.3969/j.issn.1007-2861.2013.07.034

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Elastic bodies having different modules in tension and compression exhibit nonlinear behaviors. The constitutive equations of an elastic body with different modules depend on the material itself, and also on the stress and strain state of each point in the body. Recent achievements of research on the constitutive equations are presented. Also discussed are the improvements in the finite element method (FEM) employed to solve different module problems. Analytical methods of the elastic body with different modules are introduced. Problems to be solved next are outlined.

Axisymmetrical Vertical Vibration of Hollow Cylindrical Pile in Saturated Poro-Viscoelastic Soil Layer

HAN Jing, YANG Xiao

2014, 20(5):  559-572.  doi:10.3969/j.issn.1007-2861.2013.07.038

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Considering radial deformation of pile and radial stress of saturated soil layers on the pile profile, and regarding the pile and soil layer as a single phase elastic medium and a saturated poro-viscoelastic medium, respectively, the dynamical behavior of vertical vibration of an end-bearing elastic hollow cylindrical pile in a saturated poro-viscoelastic soil layer is studied. With the Helmholtz decomposition and variable separation, the axisymmetrical analytical solutions for vertical stationary vibrations of hollow cylindrical piles and the analytical expression of complex dynamic stiffness of the pile top are presented in the frequency domain. The responses of dynamic stiffness factor and equivalent damping of pile top with frequency are shown using a numerical method. Effects of material and geometry parameters of the saturated poro-viscoelastic soil and pile on the dynamic stiffness factor and equivalent damping are examined. Although static stiffness of the pile top of a hollow cylindrical pile for the axisymmetrical analytical solution and classical Euler-rod model solution are almost the same, there exist distinct differences for dynamic stiffness factor and equivalent damping between the axisymmetrical analytical solution and classical Euler-rod model solution. Further, the ratio between the inner and outer radii of the hollow cylindrical pile has great influence on dynamic stiffness and equivalent damping of pile top. Therefore, there are limitations for the applicability of the pile with the classical Euler-rod model. A more accurate analysis should be based on the axisymmetrical model.

Analysis of Disturbance Influence of Different Shield Crossing Forms of Soft Soil on Existing Tunnel

WANG You-cheng1, ZHANG Meng-xi1, LI Lei1, WU Hui-ming2, ZHANG Xiao-qing1

2014, 20(5):  573-585.  doi:10.3969/j.issn.1007-2861.2014.01.019

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Based on an actual soil layer of tunnel overlapping section of Shanghai Metro, a 3-D finite element method is used to simulate the excavation process of three crossing forms of new tunnels, including crossing from upper and under of an existing tunnel, under crossing from an existing tunnel, and upper crossing from an existing tunnel. Settlement of the existing tunnel of each crossing form is analyzed. A reasonable measure is given to control settlement of the existing tunnel in each crossing form. The results show that there is not only deformation but also torsion of circular section of the existing tunnel. The key of a new tunnel crossing an existing tunnel from upper and under is to control the maximum settlement during the excavation process instead of final status settlement value of the existing tunnel. The key of a new tunnel under crossing an existing tunnel is to control the final status settlement curve of the existing tunnel. The key of a new tunnel upper crossing an existing tunnel is to control the floating upwards of the existing tunnel. Reliability of the numerical simulation is verified by comparison between the measured and simulated data. The results of this research provide a basis for choosing the form for a
new tunnel crossing an existing tunnel, constructing new tunnels, and protecting existing tunnels.

Relationship between Shear Strength and Moisture Content for Guilin Laterite

ZHANG Tian-feng, SUN De-an, LIU Wen-jie

2014, 20(5):  586-595.  doi:10.3969/j.issn.1007-2861.2014.01.012

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Laterite is a typical problematic soil. Its strength characteristics are more complex than ordinary clay. A series of consolidated quick direct shear tests on compacted Guilin laterite with the same initial dry density and different moisture contents were performed to investigate the factors affecting the strength of the laterite. Changes in cohesion and internal friction angle with moisture content were obtained. Test results show that the cohesions decrease as the initial moisture content increases. The friction angles at peak and residual increase firstly and then decrease as the initial moisture content increases. Besides, the dilatancy of Guilin laterite during shearing is discussed. Comparison of the test data and the calculated values by using Bishop’s and Fredlund’s equations for unsaturated soils show that the two equations cannot properly predict strength of unsaturated Guilin laterite.

Influences of Bridge Construction on Stability of Cutting Slope Using Numerical Simulation

LI Zhong-geng, XU Jin-ming, WU Hong-bin

2014, 20(5):  596-604.  doi:10.3969/j.issn.1007-2861.2014.01.026

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Stability of a cutting slope at various stages, including those before and after the pile group construction, during the bridge construction, and under the train operation, were simulated using a strength reduction method, the Mohr-Coulomb failure criterion, and the finite element analysis technique. The existing specifications were used to simulate the live load and braking force of the pier top under the train operation. A three-dimensional finite element model was then established according to the practical locations of the geomaterials in the cutting slope. The influences of the loads on stability of the slope in bridge construction and operations were investigated. The study shows that the stability factors of the slope were 1.35 and 1.63 before and after the pile group constructions, respectively. The stability factors were 1.61, 1.60, 1.58, and 1.57 as the height of pier were 6.0, 12.0, 18.0, 22.5 m, respectively. In completion of the bridge construction and under the train operation, the safety factors decreased to 1.55 and 1.53, respectively. During the entire construction, the safety factors were decreased obviously. Nevertheless, the Mises stresses in the plastic zone increased as these safety factors decreased. The results presented herein may be used as references in the design and construction of bridges in a rock slope under various surrounding conditions.

Communication and Information Engineering

Adaptive Robust Reversible Data Hiding Based on Modification of DCT Coefficient

YANG Qian-xing, LI Feng-yong, ZHANG Xin-peng, SHEN Wen-feng

2014, 20(5):  605-611.  doi:10.3969/j.issn.1007-2861.2013.07.047

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This paper proposes a robust reversible information hiding scheme based on DCT coefficients modification in JPEG images. The mean of six consecutive DCT coefficients close to zero is found. Since the mean of these six coefficients changes very little after compression, robustness can be achieved. The coefficients are modified to embed information using two different levels to resist attack. If the stego-image is not recompressed, the secret information can be correctly extracted, and the original image can be recovered. If the stego-image is recompressed, the secret information is still extractable without error, but the original image cannot be recovered. Experimental results show that the proposed scheme is effective after recompression attack with Q = 85 or above, and the stego-images have good visual quality.

Micro-Electro-Mechanical System-Inertial Measurement Unit Indoor Pedestrian Dead Reckoning Based on Motion Classification and Step Frequency Adjustment

LI Ruo-han1, ZHANG Jin-yi1,2,3, XU De-zheng2, CHEN Xing-xiu1, XU Qin-le2

2014, 20(5):  612-623.  doi:10.3969/j.issn.1007-2861.2014.01.018

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As a new navigation method, pedestrian dead reckoning (PDR) has attracted much attention because it is less susceptible to environmental factors. To solve the indoor PDR problem, data of a micro-electro-mechanical system-inertial measurement unit (MEMS-IMU) are collected and analyzed. A step detection algorithm is developed for motion classification and interval symmetry, and step length estimation model is established for step frequency adjustment. Thus a MEMS-IMU indoor PDR based on the motion classification and step frequency adjustment is constructed to realize accurate positioning. For different individuals, personalized step estimation model parameters are used to improve the positioning performance. Experimental results show that, the indoor PDR based on motion classification and step frequency adjustment reduces positioning error by 32.6% as compared to a traditional method using peak detection and a nonlinear model, achieving high positioning accuracy without resorting to any other positioning techniques.

RFID Limited System Link Analysis of Stacked Tags

XIAO Fang-xin, ZHANG Xue-fan, LI Shuai, PENG Zhang-you, ZHAI Xu-ping, REN Xiu-fang, MENG Chun-yang

2014, 20(5):  624-632.  doi:10.3969/j.issn.1007-2861.2013.07.048

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Radio frequency identification (RFID) tags produce electromagnetic (EM) coupling when stacked together, causing performance degradation of RFID systems. This problem is different from the well-known RFID collision problem. This paper first obtains the connection between the tag’s reading power and antenna gain of both forward link and reverse link by theoretical derivation. The tag antenna gain is simulated when two tags are close to each other. By comparing with the reading power of two tags measured in the experiment, the following conclusions are made. Performance of RFID systems is limited by the forward link when tags are stacked. Antenna gain and power transmission coefficient of stacked tags are key factors that influence tags reading rate. Conclusions can provide a reference for developing high performance tags in dense tag environment.

CEUS Image Segmentation of Carotid Arteries Using Multi-scale Fuzzy Clustering and DGVF Model

ZHANG Qi1, HUANG Chun-chun1, HAN Hong2, LI Chao-lun2, WANG Wen-ping2

2014, 20(5):  633-644.  doi:10.3969/j.issn.1007-2861.2014.01.016

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Contrast-enhanced ultrasound (CEUS) is of great value for the diagnosis and treatment of vascular diseases. Extraction of carotid arterial contours is important for the measurement of morphological and elastic properties of arteries. Since manually tracing of arterial contours is time-consuming, subjective, and unrepeatable, computer-aided methods are required. However, speckle noise in the CEUS images causes poor robustness and difficult initialization in traditional computer-aided image segmentation methods. This paper integrates multi-scale fuzzy C-means clustering with particle swarm optimization to extract coarse boundaries of carotid arteries. Then boundaries are used as initial contours of the directional gradient vector flow (DGVF) model, and deform them until convergence to get final refined contours. Experimental results on 48 CEUS images from 14 patients show that the proposed method is superior to the traditional method, and can automatically and accurately extract boundaries of carotid arteries in CEUS images.

Computer Engineering and Science

A 40-Bit Multiplication Routine of Ternary Optical Computer

HU Xiao-jun, JIN Yi, OUYANG Shan

2014, 20(5):  645-657.  doi:10.3969/j.issn.1007-2861.2014.01.003

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According to the advantages of ternary optical computer such as reconfigurable arithmetic unit, large number of data bits and no-carry-delay MSD adder, a 40-bit multiplication routine is designed and developed. In the routine, the numerical value is expressed with the MSD number system as in a ternary optical computer. Partial products are generated via a three-valued logic transform (M). The product is obtained by summing all partial products through an MSD adder using an iterative method. A fast-calculation method is applied in the M transform, and a pipeline technology used in the MSD adder to accumulate the partial products. The operation steps and simulation experiments of the routine are given in detail, and the performance comparing with electronic computer
analyzed.

Construction and Application of Ontology in Traffic Surveillance Video Systems

XU Zheng1, JIANG Ya-yun1,2, LI Zhen-yu1

2014, 20(5):  658-668.  doi:10.3969/j.issn.1007-2861.2014.01.017

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Although application of surveillance video in traffic monitoring grows tremendously, traffic violations still cause a large number of accidents and personal injuries every year. In mass surveillance video retrieval systems, events are difficult to find and understand. Introduction of ontology into surveillance video retrieval systems can improve effectiveness and efficiency. This paper presents a model of ontology construction. Formal descriptions of objects, concepts, temporal relation, spatial relation and events are given and included in the model. A method of constructing concept ontology is explored for traffic violations by identifying the concepts and concept hierarchy. This paper uses protégé 4.2 to conduct traffic violations ontology, and exports the ontology using JCreator that displays the Rdf/OWL code generated by the ontology.