太阳风粒子数据映射模型的设计与实现

为了能够快速获得第三级太阳风粒子可分析处理的结构化数据,本文采用将数据映射到内存和采用语言集成查询技术解决数据的完整映射和快速访问。通过设计数据映射模型,将用PDS数据的数据标签和数据产品分别映射到模型的值域和属性域,解决本地或网络数据内存映射的问题。为测试这个实例,采用双倍缓冲和贝塞尔插值技术对数据能谱进行了实时绘制。结果表明该模型具有高效性、完备性和高吻合度。这个基于内存映射的模型能够较好地解决异构数据快速结构化数据访问的数据源动力不足问题,为进一步处理和分析太阳高能粒子的频谱、成份和通量及随时间、空间变化的分布特征等提供了基础。     

Classification of cardiac sound signals using constrained tunable-Q wavelet transform

The features extracted from the cardiac sound signals are commonly used for detection and identification of heart valve disorders. In this paper, we present a new method for classification of cardiac sound signals using constrained tunable-Q wavelet transform (TQWT). The proposed method begins with a constrained TQWT based segmentation of cardiac sound signals into heart beat cycles. The features obtained from heart beat cycles of separately reconstructed heart sounds and murmur can better represent the various types of cardiac sound signals than that from containing both. Therefore, heart sounds and murmur have been separated using constrained TQWT. Then the proposed novel raw feature set has been created by the parameters that have been optimized while constraining the output of TQWT together with that of extracted by using time-domain representation and Fourier–Bessel (FB) expansion of separated heart sounds and murmur. However, the adaptively selected features have been used to obtain the final feature set for subsequent classification of cardiac sound signals using least squares support vector machine (LS-SVM) with various kernel functions. The performance of the proposed method has been validated with publicly available datasets and the results have been compared with the existing short-time Fourier transform (STFT) based method. The proposed method shows higher percentage classification accuracy of 94.01 as compared to 93.53 of STFT based method. In comparison with STFT based method, it is noteworthy that the proposed method uses well defined and lower dimensionality of feature vector that can reduce the computational complexity.     

Topological derivative-based technique for imaging thin inhomogeneities with few incident directions

Many non-iterative imaging algorithms require a large number of incident directions. Topological derivative-based imaging techniques can alleviate this problem, but lacks a theoretical background and a definite means of selecting the optimal incident directions. In this paper, we rigorously analyse the mathematical structure of a topological derivative imaging function, confirm why a small number of incident directions is sufficient, and explore the optimal configuration of these directions. To this end, we represent the topological derivative-based imaging function as an infinite series of Bessel functions of integer order of the first kind. Our analysis is supported by the results of numerical simulations.     

A collocation approach to solve the Riccati-type differential equation systems

In this paper, a collocation method is presented for the solutions of the system of the Riccati-type differential equations with variable coefficients. The proposed approach consists of reducing the problem to a nonlinear algebraic equation system by expanding the approximate solutions in terms of the Bessel polynomials with unknown coefficients. The unknown coefficients of the Bessel polynomials are found by using the matrix operations of derivatives together with the collocation method. The proposed method gives the analytic solutions when the exact solutions are polynomials. Also, an error analysis technique based on the residual function is introduced for the suggested method. The reliability and efficiency of the proposed scheme are demonstrated by some numerical examples. Comparing the methodology with some known techniques shows that the presented approach is relatively easy and highly accurate. All of the numerical calculations have been done by using a program written in Maple.     

高频振动方向和振幅测量的模糊图像处理方法

根据振动模糊图像和静止图像在频谱上存在的对应关系,即振动模糊图像频谱存在着对应于零阶贝塞尔函数零点的暗纹(贝塞尔条纹);提出对一幅振动模糊图像,经过二维傅里叶变换、灰度均衡以及Radon变换等步骤检测振动模糊图像频谱图上贝塞尔条纹的方向和位置,来实现振动方向和振幅测量的方法;试验证明可以实现平面内任意方向振动的测量,振幅测量精度亚像素级。     

On Advances in Statistical Modeling of Natural Images

Statistical analysis of images reveals two interesting properties: (i) invariance of image statistics to scaling of images, and (ii) non-Gaussian behavior of image statistics, i.e. high kurtosis, heavy tails, and sharp central cusps. In this paper we review some recent results in statistical modeling of natural images that attempt to explain these patterns. Two categories of results are considered: (i) studies of probability models of images or image decompositions (such as Fourier or wavelet decompositions), and (ii) discoveries of underlying image manifolds while restricting to natural images. Applications of these models in areas such as texture analysis, image classification, compression, and denoising are also considered.     

Stokes flow past a swarm of porous circular cylinders with Happel and Kuwabara boundary conditions

The problem of creeping flow past a swarm of porous circular cylinders with Happel and Kuwabara boundary conditions is investigated. The Brinkman equation for the flow inside the porous cylinder and the Stokes equation outside the porous cylinder in their stream function formulations are used. The force experienced by each porous circular cylinder in a cell is evaluated. Explicit expressions of stream functions are obtained for both the inside and outside flow fields. The earlier results reported by Happel and Kuwabara for flow past a solid cylinder in Happel’s and Kuwabara’s cell model, have been deduced. Analytical expressions for the velocity components, pressure, vorticity and stresstensor are also obtained     

低碳石灰煅烧合金罐内物料传热的近似计算

假定长柱状颗粒堆积体系为连续介质所建立的传热微分方程结合第一类齐次边界条件,得到了基于第一类Bessel函数的温度分布无穷级数表达式T（t,t）,近似计算了合金罐内颗粒石灰石的传热时间及物料预热对传热时间的影响,计算结果与工业化实验结果较为接近.     

Efficient computational method for transient EM response of large-loop source over layered earth

Calculations of the ElectroMagnetic （EM） response produced by a large horizontal loop placed over layered medium are rather complex because its integral expression contains the product of two Bessel functions and has a divergent term. In this paper, an improved fast Hankel and Gaver-Stehfest transforms are introduced to solve the strong-oscillation and slow-decay properties of the integrand, where one Bessel function in the product is substituted by a carefully chosen polynomial of high accuracy and the other used as the digital filter coefficients in the convolution integral. Comparisons prove the validity and the efficiency of the proposed method.     

Stability analysis of the Fourier–Bessel method for the Cauchy problem of the Helmholtz equation

This paper is concerned with the Cauchy problem connected with the Helmholtz equation in a smooth-bounded domain. The Fourier–Bessel method with Tikhonov regularization is applied to achieve a regularized solution to the problem with noisy data. The convergence and stability are obtained with a suitable choice of the regularization parameter. Numerical experiments are also presented to show the effectiveness of the proposed method.