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30 April 2012, Volume 18 Issue 2
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Communication and Information
Generalized Multiplicative Watermarking Based on Human Visual System
2012, 18(2): 111-116. doi:
10.3969/j.issn.10072861.2012.02.001
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Generalized multiplicative watermarking can suit local contents in the host signal, and has a good performance in hostinterference rejection. We propose an improved scheme of generalized multiplicative watermarking that incorporates the human visual system (HVS). We explore the maximum watermark carrying capability of each DCT coefficient in JPEG compression in terms of the just noticeable distortion (JND). This way, the watermarked image maintains a good visual quality without perceptible distortion in texture and edge areas to assure transparency. Experiments show satisfactory performance of watermark detection after the marked image is JPEG compressed.
SINR Performance Analysis of Single Carrier FDMA MIMO System in Uplink of LTE-Advanced
2012, 18(2): 117-121. doi:
10.3969/j.issn.1007-2861.2012.02.002
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In the uplink of long term evolution (LTE), discrete Fourier transform spread orthogonal frequency division multiplex (DFT-S-OFDM) is used as implementation of single carrier frequency division multiple access (SC-FDMA). In the LTE-Advanced standard, DFT-S-OFDMA will still be used in the uplink to obtain high peak rate and good performance. Single user multiinput multioutput (SU-MIMO) and pre-coding are also used in SC-FDMA uplink. This paper proposes a method to analyze signal-to-interferenceplusnoise ratio (SINR) performance of DFT-S-OFDMA system. A closedform SINR expression based on transmitter-receiver implementation structure and minimum mean square error (MMSE) equalization for receiver is derived by channel frequency response and noise variance. The SINR thus obtained can be applied in adaptive modulation and coding (AMC). Simulation results show that, with the proposed equivalent SINR, the block error rate (BLER) performance of SC-FDMA over slow fading channel is well matched with that over additive white Gaussian noise (AWGN) channel.
Investigation on Square Loop Scatterers by Maxwellian Circuits
2012, 18(2): 122-126.
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Different from traditional numerical methods, the theory of Maxwellian circuits (MC) combines the field theory and the circuit theory, providing a perfect connection of the two. In this paper, square loop scatterers are analyzed with MC. The methods of solving square loop scatterer and broadband characteristics of MC are investigated, and current distributions obtained. Numerical results show that the solutions are the same as those obtained with the method of moments (MoM). It has been found that MC can provide solutions over a quite wide range of frequencies, which is more efficient and practicable than other numerical methods.
Multiple Classification of Audio Based on Improved BP Neural Network
2012, 18(2): 127-131.
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Audio is an important medium that carries substantial information to meet human needs. To improve accuracy of audio classification, we propose a new algorithm with Mel frequency cepstrum coefficient (MFCC) parameters as the feature vectors, and use a back propagation (BP) neural network model based on improved transfer function to classify six types of audio signals. Experiments show that the proposed algorithm has good performance and the improved transfer function converges faster that the traditional BP algorithm. It can reduce training time, and improve classification accuracy up to more than 90%.
Wavelet Analysis of Ultra-narrow Band VMCK Signals
2012, 18(2): 132-138.
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The very minimum chirp keying (VMCK) is a novel ultra-narrow band communication scheme in which the up-chirp or down-chirp waveform corresponds to one or zero. This paper proves that VMCK is a kind of wavelet signal. The Mexican hat wavelet is used in time-frequency analysis of VMCK communications. Multi-cycle VMCK signal is also discussed. The results show that the spectrums of VMCK signals are arranged in different ways. The spectrum of up-chirp signals shifts to high frequency in the bit symbol, while the downchirp is in the opposite way. With the multi-cycle VMCK signals, the greater the modulation factor, the more the frequency shifts. The results show reliability of the wavelet analysis.
Mechatronics Engineering and Automation
Modeling Passive Ventilation System and Predicting Inner Temperature
WANG Xian-ming,ZHAO Zhe-shen
2012, 18(2): 139-144. doi:
10.3969/j.issn.1007-2861.2012.02.006
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This paper focuses on the passive ventilation system modeling for Hangzhou Science and Technology Pavilion of Green Architecture. The input and output variables of the model are determined according to the passive ventilation principles and the correlation analysis among the input and output data under various climatic conditions. The passive ventilation model with multiple inputs is built. Its consistency is validated theoretically and experimentally. Office temperature of the next day is predicted depending on the weather forecast parameters obtained from the Internet. Thus, precise time to start airconditioning systems can be determined for energy efficiency.
Vibration Analysis of Composite Resin Plate Embedded with Shape Memory Alloy
2012, 18(2): 145-150. doi:
10.3969/j.issn.1007-2861.2012.02.007
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Shape memory alloy (SMA) has advantages of great recovery stress and elastic modulus varied with the temperature, and therefore can be embedded in composite structure to actively control structure deformation and vibration. We derive recovery stress and elastic modulus at different temperatures by modifying the phasechange coefficient Ω of Liang’s constitutive model. Based on the stressstrain relation, the recovery stress is translated into recovery strain. Using ANSYS, we simulate the influence of recovery stress on the natural frequency and vibration response of composite plate under both ends of fixed conditions. In the experiments on composite plate with both ends under the same condition, we find characteristics of the natural frequency varying with temperature. The analysis results obtained with ANSYS are closed to experimental results, verifying correctness of the related method.
DSP-Based Gait Pattern Control of Exoskeleton Robot for WalkAid
2012, 18(2): 151-155. doi:
10.3969/j.issn.1007-2861.2012.02.008
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The exoskeleton robot is a health-aid device for the elderly and handicapped to walk. This paper presents a method of gait pattern control for exoskeleton robots based on digital signal processing (DSP). It converts the continuous gait pattern into discrete, and sends it to the input of a DSP system in order to realize robot gait patterns through actuators. At the end of each gait cycle, the encoder collects the angle information of the gait. The control system then processes feedback data and compensates for the gait error periodically. The described method is verified with a prototype with satisfactory results.
Computer Engineering and Science
Property Extraction Based on LSC Model Checking
2012, 18(2): 156-162.
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This paper uses live sequence chart (LSC) to describe scenariobased requirement specifications. According to the principle that design model must be consistent with the specification of requirement model, and aiming at extraction of safety, reachability and liveness, the paper proposes three criteria for generating and extracting properties from LSC specification automatically. The extracted result can be used for automatic verification, providing protection for consistency of requirement model with the design model.
Approach to Test Generation and Reduction for Web Applications
2012, 18(2): 163-169. doi:
10.3969/j.issn.1007-2861.2012.02.010
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Software testing is important for ensuring software quality. To test complicated Web applications, some new problems need to be considered. In this paper, we present an approach to the generation and reduction of tests for Web applications. The navigational behavior of a Web application is described in a formal model. The model is partitioned according to the counterexamples generated by model checking against the given safety properties for navigation. The test sequences are generated according to the partitioned model, and reduced based on the characteristics of Web applications. The presented example shows that the described approach is effective.
Mathematics.Physics and Chemistry
Dual 0-Sum of Star Body and L
0
Dual Mixed Volume
HU Yan,JIANG Jun-hua
2012, 18(2): 170-173. doi:
10.3969/j.issn.1007-2861.2012.02.011
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The radial combination of the dual 0-sum is defined, and from which a new star body is obtained, then some related properties are established. Moreover, L
0
-ual mixed volume is obtained, and the related results are presented.
Least-Squares Matrix-Valued Padé-Type Approximation Based on Inner Matrix Euv
2012, 18(2): 174-177. doi:
10.3969/j.issn.1007-2861.2012.02.012
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To obtain better results of matrix Padétype approximation, an improved algorithm is given for the matrix Padétype approximation, which is called an orthogonal polynomial algorithm of matrix Padétype approximation based on the matrix 〖WTHX〗E〖WTBX〗uv〖WTBZ〗 in the inner space. Matrix Padétype approximation can be quite sensitive to perturbation to the coefficients of the power series. In order to fill this gap, a leastsquares algorithm of matrix Padétype approximation is constructed. The numerator and denominator of the two algorithms determinant expressions are given.
Prediction of α-synuclein with A-β Peptide and β-synuclein Interaction Sites
2012, 18(2): 178-182.
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The abnormal aggregation of α-synuclein plays an essential role in the Parkinson’s disease. A recent study demonstrates the α-synuclein may interact with many different proteins such as A-β peptide and β-synuclein. A-β peptide promotes abnormal aggregation of α-synuclein. However, β-synuclein is resistant to α-synuclein accumulation. The mechanism of promotion or inhibition of the aggregation is not yet clear. We simulate the interaction of α-synuclein with A-β peptide and β-synuclein, and predict the interaction binding sites. The paper provides theoretical evidence for further research of abnormal aggregation.
Stopping Redundancy of a Maximum Distance Separable Code
YANG Jian-sheng,YE Lin-lin
2012, 18(2): 183-185. doi:
10.3969/j.issn.1007-2861.2012.02.014
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The bound on the stopping redundancy of an ［n,2,n-1］ MDS code is considered. With a new construction, we obtain a much stronger bound.
Logarithmic Model of Strain for Constitutive Equations of Hyperelastic Collagen Materials
2012, 18(2): 186-190. doi:
10.3969/j.issn.1007-2861.2012.02.015
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We have obtained natural characterization of incompressibility constraint, leading to stressstrain relations for isotropic, incompressible hyperelastic collagen materials using the logarithmic strain tensor measure. We have also obtained two sets of suitablydefined invariants of the logarithmic strain tensor. Constitutive equations for logarithmic strain and Cauchy stress are derived directly from the elastic energy density. Comparisons between the model and experimental data in uniaxial tension indicate efficiency of the constitutive model and dependence of material parameters.
Numerical Simulation of Flows over Micro-coaxial Rotor Based on Moving Overlapped Grids
2012, 18(2): 191-196. doi:
10.3969/j.issn.1007-2861.2012.02.016
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Unsteady viscous flows of a microcoaxial rotor are simulated and studied using moving overlapped grids and the dualtime stepping method. We discuss the small space between the up- and down-rotor and large flow viscosity, and introduce a sliding mesh based on moving overlapped grids, which ensure accurate exchange of flow information. Micro-single rotor flows with a low Reynolds number are calculated. The results are consistent with experimental results, showing effectiveness of the algorithm. Microcoaxial rotor flows are then simulated with this method. The results indicate that the blade tip vortex, which moves down in a spiral way, plays a leading role in microcoaxial rotor flows. It makes the total thrust of the rotor periodic due to its interaction with the rotary rotor.
Two-Lane Traffic Cellular Automata Model Taking into Account Twice Changing of Driving Manners
2012, 18(2): 197-202. doi:
10.3969/j.issn.1007-2861.2012.02.017
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Drivers tend to change their driving manners frequently. In this paper, a traffic cellular automata model for a two-lane highway, which takes into account such changes twice, referred to as TTChange-CA model, is proposed. Numerical results show that the original mixture proportion and lane changing probabilities of two kinds of vehicles have almost no influence on traffic flow. Compared with TChange-CA model of two-lane road, meaning that there is only one change of driving manners, the TTChange-CA model can increase the traffic flux, speed and the critical density. Therefore it can increase the road utilization rate. The traffic density, flux and compactness of the spatialtemporal diagram for TTChange-CA model are between the two-lane SDNaSch and WWH models, and can better describe the traffic flow.
Approximate Algorithms for Inner Elastic Field of Polygonal Inhomogeneity in Anisotropic Full-Planes
GAO Feng,XU Kai-yu,PAN Er-nian
2012, 18(2): 203-208.
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This paper presents an exact closedform solution and a simple iteration method for polygonal inhomogeneity in anisotropic full planes. Based on the equivalent bodyforce concept of eigenstrain, the induced elastic fields are first expressed in terms of the line integral on the boundary of the inclusion with the integrand being the Green’s functions. The exact closedform solutions are then applied to a polygonal wire within an anisotropic fullplane. Using the iteration method we have developed, we compute the inner elastic fields of a squareshaped and a triangleshaped wire within an anisotropic fullplane, and compare them with the results obtained with boundary element method (BEM). The results show that they are close to each other.
Civil Engineering
Experimental Research on Cracked Timber Columns Strengthened with CFRP under Eccentric Load
OUYANG Yu,GONG Yong
2012, 18(2): 209-213. doi:
10.3969/j.issn.1007-2861.2012.02.019
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Based on the test results of nine timber columns under eccentric loading, the loadbearing capacity, ductility and failure modes of the columns with and without carbon fiber reinforced polymer (CFRP) strengthening were compared and analyzed. The test results indicate that when the columns are wrapped only with transverse CFRP, the loadbearing capacity of the cracked columns is improved significantly while that of the intact columns decreases slightly. When the columns are strengthened using both longitudinal and transverse straps of CFRP, significant improvement in the strength and slight increase of the ductility of the columns can be observed. It was also found that for both the intact and cracked columns the ductility can be improved significantly even when only transverse CFRP is applied.
Analysis of Thermal Stresses around Spherical Cavity in Saturated Porous Medium under Convective Heating/Cooling Boundary Conditions
PANG Feng,ZHANG Ya,HE Lu-wu
2012, 18(2): 214-220. doi:
10.3969/j.issn.1007-2861.2012.02.020
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Based on the local thermal non-equilibrium (LTNE) saturated thermoporoelasticity theory, temperature, pore pressure and thermal stresses around a spherical cavity in an infinite fluid saturated porous medium are investigated, subject to convective heating/cooling on its impermeable and fixed boundary. Solutions of LTNE saturated thermo-poroelasticity are obtained by Laplace transform. Numerical analysis is performed to examine the effects of LTNE under convective heating/cooling boundary conditions on temperature, pore pressure and thermal stresses around the cavity. The results show that the LTNE effects become more pronounced when convective heat transfer boundary conditions are used. Thermally induced pore pressure and the magnitude of thermal stresses are significantly higher than the corresponding ones in classical saturated thermo-poroelasticity. This is particularly true under convective heating/cooling boundary conditions with moderate Biot numbers.
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