Journal of Applied Sciences

Simplification of Bit Metric Calculation for 32QAM

WANG Lei, XU Da-zhuan

2010, 28(4): 331-336. doi:10.3969/j.issn.0255-8297.2010.04.001

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We present a simplified 32QAM bit metric calculation method. By dividing the complex plane and merging similar regions, the bit metric is obtained by calculating the distance between the received symbol and a line assigned to each region. Simulation shows that computational complexity in calculating bit metrics is greatly reduced without degrading the performance as compared to the log-MAP and max-log-MAP methods.

Performance of Asymmetrical Retro-reflected Free Space Optical Link

DING De-qiang1;2, KE Xi-zheng1

2010, 28(4): 337-341. doi:10.3969/j.issn.0255-8297.2010.04.002

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Performance of asymmetrical free space optics (FSO) depends on retro-reflector. In this paper,a mathematic model of laser beam reflected by corner cube retro-reflector (CCR) is set up and applied to analyze the effect of atmosphere turbulence on the modulating retro-reflector(MRR) link. Further, channel compensation of CCR reflection characteristics for the received power fluctuation induced by atmospheric turbulence is discussed. Simulation results show that wavelength, angle of incidence, and refractive index of CCR are the key factors influencing performances of the asymmetrical link, and SNR fluctuation is decreased by reflection of CCR.

Alternant Routing of Wireless Sensor Networks Based on Parity of Transport Radius Multiples

TIAN Wei, YANG Zhen

2010, 28(4): 342-346. doi:10.3969/j.issn.0255-8297.2010.04.003

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We develop an alternant routing scheme aimed at energy efficiency of wireless sensor networks (WSN). The proposed method is based on the parity of transport radius multiples. The distance from the node to the sink is to calculate, then to make certain the lower integer multiple of the transport radius, the node forwards data alternately based on the parity of the multiples, and suppresses distant sinks and restricts data forwarding from nearby sending nodes. Network simulator (NS) simulation results show that, compared to the BPS algorithm, Alternant routing algorithm based on transport semi-diameter multiple (TSMAR) can lessen forwarding nodes, improve energy efficiency, and prolong the network lifetime.

Steganalysis of LSB Matching Based on Local Gaussian Mixture Model in Spatial Domain

ZHENG Er-gong, PING Xi-jian, ZHANG Tao

2010, 28(4): 347-353. doi:10.3969/j.issn.0255-8297.2010.04.004

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Based on a local stationary model of images, we propose a locally adaptive method to combat the least significant bit(LSB) matching steganography. We model the LSB matching embedding as additive Gaussian noise, use the Gaussian mixture model to describe local detail components, and estimate the model parameters with the expectation maximization algorithm. The smallest variance is selected as an estimation of
local stego-noise variance. The weighted sum features of the local variance histogram are extracted to characterize changes in regions with different complexity between the cover and stego images. Features extracted from an image and its down-sampled version are combined and sent into a classifier. The experimental results on two sets of uncompressed images show that the proposed steganalyzer outperforms the prior art and provides
reliable results for embedding rates as low as 0.25 bits per pixel.

Automatic Detection of Bridge over Water in High-Resolution Remote-Sensing Image

PENG Bi-fa1;2, TAN Yi-hua1;2, TAO Chao1;2, TIAN Jin-wen1;2

2010, 28(4): 354-360. doi:10.3969/j.issn.0255-8297.2010.04.005

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An automatic detection method to identify bridges over water in high-resolution remote-sensing images is proposed. The input image is first segmented into two water and non-water areas according to homogeneity of the water area. The image is scanned, and the bridge is extracted from the non-water area. The orientation of the bridge is determined using region growing and multiple-direction scanning. The bridge is then accurately outlined from the coarse extraction by extension along its orientation. Experimental results show that the proposed method can automatically detect bridge over water in high-resolution remote-sensing images. Performance evaluation indicates that the proposed method is robust and accurate.

Improving High Frequency Modulation Image Fusion with Modulation Transfer Function Filters

JIA Yong-hong1;2, ZHANG Xiao-ping1, JIA Shi-feng3, ZHANG Qian1

2010, 28(4): 361-366. doi:10.3969/j.issn.0255-8297.2010.04.006

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A new high frequency modulation fusion method is proposed to improve spectral quality of GeoEye-1 fusion image with high resolution. The modulation transfer function (MTF)used as a filter for degrading image is first measured from GeoEye-1 images. High frequency modulating parameters are then obtained based on the minimum mean square error criterion. Fused images obtained by using the proposed method have spatial resolution close to non-degraded pan images. Compared with fusion methods of weighted high-pass filtering used in ERDAS IMAGINE and MTF-GIF, the proposed method is the best in terms of preservation of spectral information and spatial resolution.

Nonlinear Diffusion for Image Denoising Using Lattice Boltzmann Method

WANG Zhi-qiang1, YAN Zhuang-zhi1, QIAN Yue-hong2

2010, 28(4): 367-373. doi:10.3969/j.issn.0255-8297.2010.04.007

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To overcome poor efficiency and difficulty in parallelization of traditional numerical method for image denoising with a nonlinear diffusion model, we propose a new lattice Boltzmann method to embed the image edge features into the relaxation parameters of the lattice Boltzmann equation for image nonlinear diffusion. While keeping stability in calculation, the algorithm allows large steps in the iteration so that the computation efficiency is improved. Additionally, the algorithm is easy to be parallelized. Experiment results show that the lattice Boltzmann method has better quality, accuracy and algorithmic efficiency in image denoising as compared to the additive operator splitting (AOS) algorithm.

Seabed Classification Based on Principal Component Analysis of Multiple Features Combined with Sonar Image

2010, 28(4): 374-380. doi:10.3969/j.issn.0255-8297.2010.04.008

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Aimed at seabed classification, statistical characteristics are extracted from the echo, and a full feature vector is constructed. The principal component analysis (PCA) is carried out to obtain the set of characteristics that most contribute to the classification. Based on the study, seabed classification is carried out and tested with two sets of experiments. Using two types of classification methods to analyze, the data from Jiaozhou Bay and comparison is made. It is concluded that the result based on PCA of many features combined with a sonar map is better than that obtained solely from sonar image classification.

Non-linear Filtering for SAR/INS Integrated Navigation Considering SAR Image Navigation Measurement Characteristics

WANG Dan, XIONG Zhi, CHEN Fang, LIU Jian-ye

2010, 28(4): 381-386. doi:10.3969/j.issn.0255-8297.2010.04.009

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The SAR image navigation system is highly nonlinear when it takes long time to output measurement in the SAR integrated navigation system (SAR/INS), and when the inertial navigation error cannot be modified in time. Using conventional Kalman filtering to deal with the nonlinear system, the filter accuracy is affected and even becomes divergent. In order to improve the integrated navigation precision, based on SAR/INS coupled navigation system and the unscented Kalman filtering (UKF), we propose a UKF algorithm for unequal interval problems, and solve problems of information fusion in SAR/INS. Performances of conventional Kalman filtering and the UKF algorithm are studied in simulation analyses of covariance. The result
demonstrates that the method proposed in this paper produces better filtering precision.

Estimation of Nitrogen Content in Rice Leaves with Hyperspectral Reflectance Measurements Using Wavelet Analysis

FANG Mei-hong, LIU Xiang-nan

2010, 28(4): 387-393. doi:10.3969/j.issn.0255-8297.2010.04.010

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To solve the problem in diagnosing nitrogen nutrient in rice leaves based on hyperspectral reflectance, we extract weak information from the spectral signal to estimate nitrogen content by applying wavelet analysis to decompose the reflectance spectra. Hyperspectral data were collected in China’s northeast city Changchun. The data were used to develop predictive models of nitrogen contents and test the accuracy of the models. We decompose the reflectance and derivative spectra of rice canopy into eight levels using the Db5 function of Daubechies wavelets, and establish 192 models among the obtained wavelet coefficients at different levels and different decomposition positions. By comparison, wavelet coefficients with high precision are selected to establish the best model. The results indicate that wavelet coefficients can be used to obtain accurate prediction of nitrogen content with a high correlation coefficient up to 0.99. The wavelet-based approach outperforms predictive models based on a range of existing spectral indices, showing good prospects in applications for estimating biochemical components of crops that need to extract weak information from hyperspectral data.

Fusion of Multi-scale Wavelet Decomposition and Application to MEMS Gyroscope Data Processing

REN Ya-fei, KE Xi-zheng

2010, 28(4): 394-398. doi:10.3969/j.issn.0255-8297.2010.04.011

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A wavelet-domain data fusion model is proposed. Data from a set of sensors are decomposed into multiple scales. The details of all scales and the approximation of the most coarse scale are fused with local weights, and the signal is reconstructed from the fused result. This model is confirmed with the mathematical theory based on practical application. Multi-scale wavelet transform of a random sequence is analyzed, and the statistical relations between the smooth signal and detail signal at various scales are studied. Superiority of the wavelet multi-scale data fusion algorithm is shown mathematically. Experimental results show that bias stability of MEMS gyroscope can be improved after data fusion.

Circuit Design as Implementation of Four Dimensional Hyper-chaos and Its Projective Synchronization

LIU Ming-hua1;2, FENG Jiu-chao1;3

2010, 28(4): 406-413. doi:10.3969/j.issn.0255-8297.2010.04.013

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We obtain a four-dimensional system by adding a nonlinear state feedback controller to a threedimensional chaotic system. The dynamical behaviors of this 4D system are investigated, including the Lyapunov exponent spectrum and bifurcation diagram. The results show that it is a 4D hyperchaotic system with two positive Lyapunov exponents. Projective synchronization for the 4D hyperchaotic system is realized based
on the stability criterion of linear systems. An electronic circuit is designed and implemented with projective synchronization of the 4D hyperchaotic system. The circuit consists of four parts: anti-adders, integrators, inverters and multipliers. Experimental observations are in agreement with numerical simulations.

Metamaterial Antenna Based on Anisotropic Permittivity

SUN Yong-zhi, RAN Li-xin, WANG Wei-guang, CHEN Qiu-lin, ZHU Wei-qiang

2010, 28(4): 413-416. doi:10.3969/j.issn.0255-8297.2010.04.014

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We present an equation of dispersion characteristics for anisotropic metamaterial in this paper. In a particular direction, the dielectric constant of the material is zero at certain frequency. This property is used to produce the high-directional antenna. We develop a new metamaterial with a metallic cross-sectional structure, and simulate the radiated field of an omni-directional dipole antenna placed in the metamaterial. The radiated field is concentrated around the normal to the interface between the metamaterial and the air so that to give highly directional radiation. The gain of the antenna is 17.68 dB at 11.5 GHz, and the half power beam width is 5 degrees. The experimental results are consistent with the simulation.

Eigenvalues of Incidence Matrices Applied to the Analysis of Petri Net Structures

LIAO Jing-jing, WANG Ming-zhe

2010, 28(4): 417-423. doi:10.3969/j.issn.0255-8297.2010.04.015

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By computing eigenvalues of special square matrices derived from the incidence matrices of Petri net models, some important structural properties of Petri nets are analyzed. According to the differences between two types of nets, i.e., choice-free and link-free nets, and non-choice-free and non-link-free nets, two methods are used to transform them into the same class of square matrices. We then obtain sufficient conditions for structure boundedness, conservativeness, repetitiveness and consistency based on the theory of M-matrices. An example of radar model is given to show application in analyzing Petri net structures.

Application of Ellipsoid Optimization in Subspace Predictive Control

WANG Jian-hong, WANG Dao-bo

2010, 28(4): 424-429. doi:10.3969/j.issn.0255-8297.2010.04.016

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Subspace predictive control based on subspace identification is discussed for joint system identification and control design. This combination enables automatic tuning of the parameters in model predictive control and avoids many steps in the LQG-controller design. It is independent of any priori information of the controller. Considering the constrain conditions, an ellipsoid optimization algorithm is proposed to generate a sequence of ellipsoids with decreasing volume. An upper bound of the maximum number of possible iteration steps is derived. As an example of helicopter, efficiency of the proposed subspace predictive control strategy is realized.

Reconstruction of System State with Distributed Parameters Using Measurements from Finite Points

LI Qian-??20Li-Chu-??20Li-Shao-Yuan

2010, 28(4): 430-435. doi:10.3969/j.issn.0255-8297.2010.04.017

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The state space of distributed parameter system (DPS) is infinite dimensional and cannot be measured directly by a finite number of sensors. To solve this problem, we propose a state reconstruction method using a finite number of point measurements. Feasibility of the method is shown theoretically. Numerical simulation indicates that it can achieve good state reconstruction. In contrast to distributed parameter observers,
the proposed method only requires measurements taken at discrete time, and it can give better reconstruction of system’s early states.

Flight Control of Receiver Aircraft for Probe-Drouge Aerial Refueling Docking

YUAN Suo-Zhong, Liu-Zhao

2010, 28(4): 436-440. doi:10.3969/j.issn.0255-8297.2010.04.018

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Abstract: A reference observer-based tracking controller is designed to achieve successful docking between the drogue of a tanker aircraft and the probe of a receiver aircraft. A reference trajectory generation module is used to turn the relative position between the drogue and the probe into a smooth reference trajectory. An output tracking observer is designed to estimate the feed-forward control signal and the reference states
to be tracked, and a full state feedback controller provides accurate tracking. Simulation results show that integration of observer and controller is effective for achieving accurate aerial refueling docking.

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