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Performance improvement in multi-ship imaging for ScanSAR based on sparse representation

Science China(Information Sciences) 2012年第8期55卷 1860-1875页

作者： XU Gang1,SHENG JiaLian1,ZHANG Lei1&XING MengDao1,2 1N ational Key Laboratory of Radar Signal Processing,Xidian University,Xi’an 710071,China 2National Key Laboratory of Microwave Imaging,Institute of Electronics,Chinese Academy of Sciences,Beijing 100080,China National Key Laboratory of Radar Signal Processing Xidian University Xi’an China National Key Laboratory of Microwave Imaging Institute of Electronics Chinese Academy of Sciences Beijing China

There is always a compromise between unambiguous wide-swath imaging and high cross-range resolution owing to the constraint of minimum antenna area for conventional single-channel spaceborne synthetic aperture radar(SAR)imaging.To overcome the inherent systemic limitation,multi-channel SAR imaging has been developed.Nevertheless,this still suffers from various problems such as high system complexity.To simplify the system structure,a novel algorithm for high resolution multi-ship ScanSAR imaging based on sparse representation is proposed in this paper,where the SAR imaging model is established via maximum a posterior estimation by utilizing the sparsity prior of multi-ship targets.In the scheme,a wide swath is generated in the ScanSAR mode by continuously switching the radar footprint between subswaths.Meanwhile,high crossrange resolution is realized from sparse subapertures by exploiting the sparsity feature of multi-ship imaging.In particular,the SAR observation operator is constructed approximately as the inverse of conventional SAR imaging and then high resolution SAR imaging including range cell migration compensation is achieved by solving the optimization.Compared with multi-channel SAR imaging,the system complexity is effectively reduced in the ScanSAR mode.In addition,enhancement of the cross-range resolution is realized by incorporating the sparsity prior with sparse subapertures.As a result,the amount of data is effectively reduced.Experiments based on measured data have been carried out to confirm the effectiveness and validity of the proposed algorithm.

关键词： synthetic aperture radar(SAR) ScanSAR wide-swath sparse representation high resolution

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Two-dimensional finite volume method for dam-break flow simulation

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International Journal of Sediment Research 2009年第1期24卷 99-107页

作者： M. ALIPARAST Ab Pardazesh Binalood (APB) Consulting Engineers

A numerical model based upon a second-order upwind cell-center finite volume method on unstructured triangular grids is developed for solving shallow water equations. The assumption of a small depth downstream instead of a dry bed situation changes the wave structure and the propagation speed of the front which leads to incorrect results. The use of Harten-Lax-vau Leer(HLL) allows handling of wet/dry treatment. By usage of the HLL approximate Riemann solver,also it make possible to handle discontinuous solutions. As the assumption of a very small depth downstream of the dam can change the nature of the dam break flow problem which leads to incorrect results,the HLL approximate Riemann solver is used for the computation of inviscid flux functions,which makes it possible to handle discontinuous solutions. A multidimensional slope-limiting technique is applied to achieve second-order spatial accuracy and to prevent spurious oscillations. To alleviate the problems associated with numerical instabilities due to small water depths near a wet/dry boundary,the friction source terms are treated in a fully implicit way. A third-order Runge-Kutta method is used for the time integration of semi-discrete equations. The developed numerical model has been applied to several test cases as well as to real flows. The tests are tested in two cases:oblique hydraulic jump and experimental dam break in converging-diverging flume. Numerical tests proved the robustness and accuracy of the model. The model has been applied for simulation of dam break analysis of Torogh in Iran. And finally the results have been used in preparing EAP(Emergency Action Plan).

关键词： Finite volume Harten-Lax-van Leer Scheme Dam break Emergency action plan high resolution

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high ORDER ACCURACY SCHEME FOR 2-D TRANSONIC FLOWS

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Chinese Journal of Aeronautics 1996年第2期9卷 86-91页

作者： Li Haidong Liu Qiusheng Shen Mengyu (Department of Engineering Mechanics, Tsinghua University, Beijing, China, 100084) Department of Engineering Mechanics Tsinghua University Beijing 100084 China

According to Taylor's expansion formula, a kind of derivatives computation method is presented, which can achieve arbitrary order of accuracy. Then it is combined with a flux difference splitting technique and a flux limiter to construct the desiredscheme that is suitable for non-oscillatory shock-capturing calculation. TVD typeRunge-Kutta method is used for temporal discretization. Several steady and unsteadynumerical experiments demonstrate that the scheme is a robust solver for transonicflows with high accuracy and high resolution of shock wave structures.

关键词： accuracy transonic flow cascade flow shock waves high resolution

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Defining a Standard Methodology to Obtain Optimum WRF Configuration for Operational Forecast: Application over the Port of Huelva (Southern Spain)

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Atmospheric and Climate Sciences 2016年第2期6卷 329-350页

作者： Raúl Arasa Ignasi Porras Anna Domingo-Dalmau Miquel Picanyol Bernat Codina Mª Ángeles González Jésica Piñón Technical Department Meteosim S.L. Barcelona Spain Department of Astronomy and Meteorology University of Barcelona Barcelona Spain

In this contribution, we calibrate the meteorological model weather and research forecasting (WRF) for operational forecasting in the Port of Huelva managed by the Authority Port of Huelva. Meteorological forecasting will allow reducing the impact of the meteorological phenomena over weather sensitive activities in the region. Concretely, the meteorological modeling developed will be used to analyze meteorological hazard impacts and to improve the management of the local air quality. To achieve these goals, numerous sensitive analyses corresponding to different model options have been developed. These analyses consider different physical and dynamical options, the coupling of very high resolution physiographic database (topography and land uses), and data assimilation. Comparing experiments, results with observational measures provide us by the Spanish National Meteorology Agency (AEMET). During a representative period, the optimum WRF configuration for the region is obtained. Calibration has been focused on wind due to this is the main risk factor in the region. When the model is satisfactorily calibrated, WRF is evaluated using whole modeling years 2012 and 2013, working with very high horizontal resolution, up to 0.333 km of horizontal grid resolution. Results obtained from the evaluation indicate that the numerical weather prediction system developed has a confidence level of 70% for the temperature, 81% and 66% for the wind speed and wind direction respectively, and 90% for the relative humidity. Methodology designed defines the quality control assurance of high-accuracy forecasting services of Meteosim S.L.

关键词： WRF Sensitive Analysis Meteorological Modelling Physical Options LES high resolution

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Speech emotion recognition based on statistical pitch model

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Chinese Journal of Acoustics 2006年第1期25卷 87-96页

作者： WANG Zhiping ZHAO Li ZOU Cairong Department of Radio Engineering Southeast University Nanjing 210096

A modified Parzen-window method, which keep high resolution in low frequencies and keep smoothness in high frequencies, is proposed to obtain statistical model. Then, a gender classification method utilizing the statistical model is proposed, which have a 98% accuracy of gender classification while long sentence is dealt with. By separation the male voice and female voice, the mean and standard deviation of speech training samples with different emotion are used to create the corresponding emotion models. Then the Bhattacharyya distance between the test sample and statistical models of pitch, are utilized for emotion recognition in speech. The normalization of pitch for the male voice and female voice are also considered, in order to illustrate them into a uniform space. Finally, the speech emotion recognition experiment based on K Nearest Neighbor shows that, the correct rate of 81% is achieved, where it is only 73.85% if the traditional parameters are utilized.

关键词： emotion recognition statistical models classification method standard deviation high frequencies low frequencies high resolution uniform space test sample

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Experimental research for direction of arrival estimation based on signal phase matching principle

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Chinese Journal of Acoustics 2007年第1期26卷 28-38页

作者： HOU Hong XIAO Hui SUN Jincai College of Marine Engineering Northwestern Polytechnical University Xi'an 710072

In order to test the validity of signal phase matching principle （SPMP） applied to direction of arrival （DOA） estimation, experiments are carried out at a reservoir using 16 sensors array. Two kinds of method, Least Square Method for Signal Matching principle （LSMSPM） and singular value decomposition method for signal matching principle （SVDSPM）, are used for DOA estimation. Their performances were analyzed and compared with MUSIC and conventional beam-forming （CBF） method. The results show that the 3 dB beam width obtained by SPMP is 1/4 to 1/7 as much as that obtained by CBF and 1/2 to 1/3 by MUSIC method. In addition, LSMSPM and SVDSPM are available for multi-sources DOA estimation and high resolution DOA estimation, which demonstrates that DOA estimation by SPMP method is better than that by MUSIC and CBF method.

关键词： DOA estimation Signal Matching decomposition method high resolution singular value phase matching

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Estimating the directions of arrival based on multi-subarray subspace fitting

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Chinese Journal of Acoustics 2006年第1期25卷 16-25页

作者： ZHU Weiqing LIU Xiaodong ZHANG Dongsheng LIAO Zheng ZHANG Fangsheng Ocean Technique Lab. Institute of Acoustics The Chinese Academy of Sciences Beijing 100080

A multi-subarray subspace fitting method which take mutual coupling among array elements into account to estimate the directions of arrival was presented. The mutual coupling matrix of uniform linear arrays is modeled with a banded symmetric Toeplitz matrix. According to the DOF （Degree of Freedom） of mutual coupling matrix, part of the array eleiaents at the two sides are neglected. The theoretical characteristics of ESPRIT algorithm, one of the subspace fitting algorithms, are studied. For large N and uniform linear array, the MCLS- ESPRIT estimation error is asymptotically jointly Gaussian distributed with zero means, and its covariance expression is obtained. It is known from the simulation that there exists a subarray with lowest estimation error for certain number of the array elements and the signal sources, and its performance of estimating the directions of arrival is close to the ideal situation when mutual coupling does not exist while its variance has some increase. The method has been applied to bathymetric sidescan sonar with high resolution, and good results have been obtained. At the cost of increasing the number of the array elements, the method can reduce the affection of the mutual coupling among array elements.

关键词： mutual coupling estimation error uniform linear array Toeplitz matrix high resolution sidescan sonar fitting method linear arrays

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Surface Humidity Changes in Different Temporal Scales

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American Journal of Climate Change 2015年第3期4卷 226-238页

作者： Igor Zurbenko Ming Luo Department of Epidemiology and Biostatistics State University of New York at AlbanyRensselaerUSA

As the key driven factor of hydrological cycles and global energy transfer processes, water vapour in the atmosphere is important for observing and understanding climatic system changes. In this study, we utilized the multi-dimensional Kolmogorov-Zurbenko filter (KZ filter) to assimilate a near-global high-resolution (monthly 1°?× 1°?grid) humidity climate observation database that provided consistent humidity estimates from 1973 onwards;then we examined the global humidity movements based on different temporal scales that separated out according to the average spectral features of specific humidity data. Humidity climate components were restored with KZ filters to represent the long-term trends and El Nino-like interannual movements. Movies of thermal maps based on these two climate components were used to visualize the water vapour fluctuation patterns over the Earth. Current results suggest that increases in water vapour are found over a large part of the oceans and the land of Eurasia, and the most confirmed increasing pattern is over the south part of North Atlantic and around the India subcontinent;meanwhile, the surface moisture levels over lands of south hemisphere are becoming less.

关键词： Specific Humidity Climate El Nino-Like Movement Long-Term Trend KZ Filters Spatial Pattern Temporal Scales high resolution Visualization

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求解对流扩散方程的高阶紧致Padé有限体积格式

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高等学校计算数学学报 2017年第1期39卷 43-54页

作者：牛云霞李春光景何仿董建强凤超北方民族大学数学与信息科学学院新疆大学科学技术学院(阿克苏校区)数学教研组北方民族大学土木工程学院新疆大学科学技术学院(阿克苏校区)工程技术系

自然界许多物理现象都可用对流扩散方程来描述,如质量、能量以及动量守恒问题等.实际应用问题中的对流扩散方程往往比较复杂,难以求出精确解,因此研究其数值求解方法具有十分重要的意义.对流扩散方程的经典解法对于解光滑问题可以得到... 详细信息

自然界许多物理现象都可用对流扩散方程来描述,如质量、能量以及动量守恒问题等.实际应用问题中的对流扩散方程往往比较复杂,难以求出精确解,因此研究其数值求解方法具有十分重要的意义.对流扩散方程的经典解法对于解光滑问题可以得到较好的计算结果,但对于大梯度问题以及边界层等问题,会产生较大误差.紧致格式使用较少的模板可以获得较高的精度,因此高精度紧致方法成了近年来的研究热点[1-4].针对已有高阶紧致格式在分辨率和守恒性方面的问题,本文借鉴文献[4][5]中的思想构造了非定常对

关键词： exponential transformation Padé compact finite volume scheme convection-diffusion equation high resolution

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理想磁流体的散度自由移动网格方法

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高等学校计算数学学报 2005年第S1期 119-122页

作者：汤华中韩建强北京大学数学科学学院北京大学数学科学学院北京 100871

1 引言考虑高维MHD方程其中ρ,ptot,u=(u1,u2,u3)T,和B=(B1,B2,B3)T表示流体密度,总压(ptot=p+pmag), 流体速度,和磁场．磁压pmag定义为pmag=1/2B．B．总能量E包含内能,动能和磁能: E=ρe+ρ/2u·u+1/2B．B,这里e表示单位质量内能．对... 详细信息

1 引言考虑高维MHD方程其中ρ,ptot,u=(u1,u2,u3)T,和B=(B1,B2,B3)T表示流体密度,总压(ptot=p+pmag), 流体速度,和磁场．磁压pmag定义为pmag=1/2B．B．总能量E包含内能,动能和磁能: E=ρe+ρ/2u·u+1/2B．B,这里e表示单位质量内能．对于完全气体,内能和气体压力之间满足状态方程:p=(γ-1)ρe,其中γ为绝热指数．

关键词： Moving mesh method high resolution monitor function mass-conservation divergence-free.

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