Simulation of scatterers in nonlinear radio location using the volterra series

The application of the Volterra-Picard series made it possible to develop an appropriate mathematical model for the radioelectronic object of investigation typical in the field of nonlinear radio location. This model allows us to estimate the impact of the nonlinear radar action on the generation and scattering of unmasking signal. In addition this model makes it possible to take into account the physics of processes occurring in a semiconductor under its exposure to high-power microwave radiation.     

RCS SCALE-MODEL-TESTING METHOD BY VARIANCE IN THE SIZE FOR SIMPLY SHAPED SCATTERERS

t According to a general representation of physical scale factor of RCS for variance in the size of simply shaped scatterers, a novel RCS model-testing method is described. The computed results of the prototype scatterers by this method from the model-testing agree well with their measured values both for two kinds of simply shaped scatterers, cylinders and ladder-shaped plates.     

水下管道泄漏检测技术及定位方法研究

为了实时进行水下管道泄漏监测和定位,采用干涉的方法,研制了一种基于Sagnac干涉仪的直线型分布式光纤管道泄漏监测系统。分析了该干涉仪应用于泄漏检测的原理及其泄漏源定位方法,并通过实验研究了管道压力对检测系统的影响。当管道压力大于0.35MPa时,系统的检测效果较佳,且定位误差小于1.17%;压力小于0.35MPa时,无法实现泄漏点定位。结果表明,当管道压力大于0.35MPa时,研制的水下管道泄漏检测系统能有效检测管道泄漏发生,且较准确地确定泄漏源位置。     

Exterior moment method analysis of conducting scatterers by using the interior Green's function

A new method using a Green's function in the interior region of a conducting scatterer is proposed to obtain a mutual admittance matrix in an exterior moment method analysis. A numerical example of a two-dimensional magnetic strip source located on an exterior surface of a perfectly conducting rectangular cylinder shows the validity of the method.<>     

Exterior moment method analysis of conducting scatterers by usingthe interior Green's function and the method of least square

A method previously proposed by the authors in 1988 for obtaining the mutual admittance matrix in the moment method analysis by using the interior Green's function is improved by introducing the method of least square (MLS). A numerical example of a two-dimensional problem shows that accurate results can be obtained by introducing the MLS even when arbitrary sources are assumed for numerical experiments in the interior region     

Constrained iterative reconstruction by the conjugate gradient method

The conjugate gradient method incorporating the object-extent constraint is applied to image reconstruction of a three-dimensional object using an incomplete projection-data set. The missing information is recovered by constraining the solution with the knowledge of the outer boundary of the object-extent which may be a priori measured or known. The algorithm is derived from the least-squares criterion as an advanced version of conventional iterative reconstruction algorithms such as SIRT (Simultaneous Iterative Reconstruction Technique) and ILST (Iterative Least Squares Technique). In the case of reconstruction from noisy projection data, a method based on the minimum mean-square error criterion is also proposed. Computer simulated reconstruction images of a phantom using limited angle and number of views are presented. The result shows that the conjugate gradient method incorporating the object-extent constraining provides the fastest convergence and the least error.     

On the applicability of OSRC method to homogeneous scatterers

The author investigates the application of radiation boundary conditions to two-dimensional scattering by a homogeneous penetrable cylinder. The second-order radiation boundary operator proposed by G.A. Kriegsmann et al. (1987) is applied on a conformal outer boundary enclosing the object. By taking the specific case of a lossless circular cylinder for which the exact solution exists it is shown that the on-surface radiation condition (OSRC) method does not necessarily yield accurate results for all values of material constants. Highly erroneous results are produced for certain values of permittivity and permeability, while acceptable results can be obtained for others. The author suggests that the cause of these erroneous results is related directly to the error in the reactive portion of the complex scattered power. However, as the outer boundary of the radiation condition recedes away from the object contour, the error is shown to diminish. Numerical results are presented for the bistatic echo width for both transverse electric (TE) and transverse magnetic (TM) polarizations     

复光波的图像处理

本文介绍了复光波图像处理的新方法,该方法简单易行.在图像增强和噪声抑制方面有一定的效果.已成功地用于海岸变迁的研究中.     

Stationary, nonstationary, and hybrid iterative method of momentssolution schemes

The purpose of this paper is to report on the convergence rates of two iterative matrix solution methods individually and then to combine the two methods into a hybrid scheme to achieve additional convergence rate benefits. One iterative matrix solver investigated is the sparse iterative method (SIM) which is a stationary, Jacobi-like solver but uses a sparse and not a banded matrix, with matrix elements corresponding to strong interactions, rather than position in the matrix. In this paper, the SIM is modified to include an adaptive relaxation scheme to improve its convergence speed and numerical stability. Another iterative scheme investigated is the nonstationary biconjugate gradient stabilized (BiCGSTAB) method. It is shown that the BiCGSTAB is considerably improved when the method is preconditioned by the sparse matrix used in the SIM method. Finally, a hybrid scheme is proposed which combines both SIM-AR and BiCGSTAB-precon and it is shown that the hybrid gives best results on the problems considered. Examples giving convergence time versus accuracy are presented for two problems: a wire-grid plate, and a wire-grid partial helicopter     

Analysis of coplanar components by using an iterative method

An iterative method based on the concept of a wave using a fast Fourier transformation on the waveguide environment (modal fast Fourier transformation: MFFT) for the investigation of a coplanar spiral inductor is presented. This method is used to calculate S-parameters of shielded microwave components including air bridges. The general formulation and the implementation procedure of the method are described. The application of the theory is verified by a comparison of experimental data.     

Detection of chirp-radar signals by means of proton-spin echoes

Chirp-radar pulse compression by means of proton-spin echoes has been experimentally investigated. These experiments are easier than those with electrons, because they are feasible at room temperature, and it is possible to change the relaxation time and resonance width continuously. In radar applications, the main difficulties are likely to be found in leakage and attenuation. These difficulties can be reduced by working at frequencies as high as possible and improving the experimental setup.     

成像型激光探测系统中光斑精确定位方法研究

为了在探测图像中实现对激光光斑的精确定位,进而达到系统对激光光源精确定向的目的,引入了亚像素检测的算法.并针对小同大小的光斑分别采用了重心法和基于空问矩的综介检测方法.进行了理论分析和实验验证.取得了小同光强下光斑坐标均值和均方差数据。结果表明.这种方法在扩展检测动态范围的基础上可以使激光光斑定位精度达到在0.2个像素以内。这一结果对保证系统对激光源的精确定向是有帮助的。     

阵列测量方式下的电阻率井壁成象

电阻率成象测井是石油测井中最新一代的测井方法 ,对测井仪器响应的精确模拟 ,可以为此类仪器的优化设计和资料解释提供依据。针对电阻率成象仪激励条件比较复杂的特点 ,同时考虑井下地层固有的非均质性 ,选用有限元方法对仪器产生的位场进行分析 ,并对一些典型的地层模型进行模拟 ,给出其电阻率井壁成象结果 ,直观反映井壁地层特征     

A new iterative algorithm for extrapolation of data available in multiple restricted regions with application to radar imaging

A new iterative method for extrapolation of incomplete segmented data available in multiple separated bands is proposed and tested. The method uses the Burg algorithm to find the linear prediction parameters and an iterative procedure to improve the estimation of the linear prediction parameters and the extrapolation of the data. This method is especially effective when the spectra (Fourier transform of the observed data) are in discrete forms, in the context of radar imaging represented here, this means the objects consist of distinctly spaced scattering centers. The advantages of this algorithm are demonstrated using both numerically generated and realistic experimental data pertaining to high resolution radar imaging.     

Solution of diffraction problems by means of the modified Galerkin method

Using the problem of matching of planar waveguides as an example, an approach to solution of diffraction problems with the help of the modified Galerkin method is considered.     

Detection and visualization method of dynamic state transition for biological spatio-temporal imaging data

In the statistical analysis of functional brain imaging data, regression analysis and cross correlation analysis between time series data on each grid point have been widely used. The results can be graphically represented as an activation map on an anatomical image, but only activation signal, whose temporal pattern resembles the predefined reference function, can be detected. In the present study, we propose a fusion method comprising innovation approach in time series analysis and statistical test. Autoregressive (AR) models were fitted to time series data of each pixel for the range sufficiently before or after the state transition. Then, the remaining time series data were filtered using these AR parameters to obtain its innovation (filter output). The proposed method could extract brain neural activation as a phase transition of dynamics in the system without employing external information such as the reference function. The activation could be detected as temporal transitions of statistical test values. We evaluated this method by applying to optical imaging data obtained from the mammalian brain and the cardiac sino-atrial node (SAN), and demonstrated that our method can precisely detect spatio-temporal activation profiles in the brain or SAN.     

Time-domain analysis of multiple parallel transmission lines by means of equivalent circuits

Thévénin's equivalent circuit for a single transmission line is well known. The letter presents an application of Thévénin's equivalent circuit for multiple parallel transmission lines to the time-domain analysis of wave propagation over such lines. For purposes of illustration, a system of two coupled transmission lines is treated.     

City-view image location identification by multiple geo-social media and graph-based image cluster refinement

“What is this” and “where am I” are two common questions that arise when people travel abroad. Recently, landmark image identification has shown great promise for the addressed problems, where most previous approaches are either visual-based or location-based. However, regarding city-view image location identification, there could be a number of buildings in a close proximity. Moreover, it is common that photos were taken indoors. The conditions may degrade the performance of previous approaches. To remedy the deficiencies, this paper unifies visual features, geo-tags, and check-in data, based on cross-domain social media, for city-view image location identification. Besides, this paper shows an effective and memory-efficient implementation based on sparse coding, where a new dictionary selection approach is presented. Further, this paper proposes a location-aware graph-based regrouping approach, leveraging spanning graph construction, on clusters of photos to refine clustering results. Experimental results show the improvement over the baselines (location-based, visual-based, etc.).     

Fast method for face location and tracking by distributed behaviour-based agents

The authors present a novel approach for fast human face location and tracking in colour image sequences. First, a number of colour-sensitive behaviour-based agents are uniformly distributed in the 2-D image environment to search the skin-like pixels and mark the face-like regions by activating their evolutionary behaviour. Then the shape information of each face candidate region is examined and the face regions are finally determined by fuzzy shape feature analysis. Experimental results show that the tracking speed is about 30 frames per second for a 160 /spl times/ 120 video size and 12 fps for a 320 /spl times/ 240 video size.     

基于双感应测井仪低数据量的反演方法研究

将一种迭代方法和双共轭梯度法用于实际工程中常用的双感应测井仪（DIT）的反演和剖面成象。基于目标区内、外电场积分方程,建立DIT的反演积分方程,利用MoM将积分方程高散为矩阵方程。在每次反演迭代过程中,用数值模式匹配法（NMM）求解DIT的感应电动势和格林函数。文中利用沿井轴的DIT不完备的低信息量对地层剖面进行反演,数值模拟结果表明该迭代方法的实际工程应用的潜力。