Layer by Layer Reconstruction Methods for the Earth Resistivity from Direct Current Measurements

Several methods for reconstructing the resistivity profile of a layered laterally homogeneous earth from direct current measurements are described. These methods recover the resistivity of the earth layer by layer in a recursive way, and require a very small amount of computational effort. They are obtained by transforming the inverse resistivity problem into an equivalent inverse scattering problem, and by applying efficient signal processing algorithms such as the Schur, fast Cholesky or Levinson recursions to the transformed problem. These algorithms operate on a layer stripping or layer accumulation principle, and are shown to be related to previous reconstruction techniques of Pekeris, Koefoed, Kunetz and Rocroi, and others.     

Performance Bounds for an Inverse Resistivity Problem

A procedure has been proposed for recovering a radially varying electrical resistivity profile from a particular series of dc electrical measurements. Such a procedure has potential applications to the study of the invasion of porous materials by electrically conductive fluids. This paper concerns the sensitivity of such a procedure to inaccuracies in the measurements. It is shown that, for a layered conductivity profile, the sensitivity of the conductivity estimates to measurement inaccuracy grow exponentially with the number of layers. This result indicates that resolution will be severely limited by measurement inaccuracy in the reconstruction of a conductivity profile from this particular series of dc electrical measurements.     

Two-Dimensional DC Resistivity Inversion for Dipole-Dipole Data

A procedure is described for interpreting the results of direct current resistivity measurements in regions where the underlying structure cannot be assumed to be layered but varies little in the ?strike? direction. Automatic inversion of the data is performed with the subsurface model having an arbitrary 2-D conductivity distribution. Results of such inversion are shown for both simple models and for field data where the method is shown to be accurate and to significantly save hand modeling time.     

双层PCB线网均匀化问题及其算法

线网分布均匀性直接影响到PCB上电路的性能。但由于布线问题的计算复杂性很高,在布线过程中很难保证布线的线网均匀性。在本文中,提出了一种双层PCB线网均匀化的方法。     

TSP问题的一种快速求解算法

针对现有遗传算法收敛速度慢和容易"早熟"两大缺陷,提出一种新的遗传算法求解TSP问题.该算法融入不同的启发式算法分别作为交叉和变异算子,并引入外部最优个体集,以改善局部搜索能力弱的情况和增加群体多样性.通过对该算法的测试,论证了其有效性.以此为基础,利用递归分治策略,将上述算法并行化.实验结果表明,该算法可以得到理想的解和收敛速度,具有一定的普适性.     

A High-Performance Upgrade of the Perfectly Matched Layer Multilevel Fast Multipole Algorithm for Large Planar Microwave Structures

An improvement of the perfectly matched layer multilevel fast multipole algorithm (PML-MLFMA) for simulating large planar microwave structures is presented. By exploiting the low-rank property of the PML-MLFMA multimodal aggregation and disaggregation matrices, considerable reductions in memory usage and computation time are obtained. The method has been extensively validated, demonstrating complete error controllability when simulating large planar microwave structures. Reductions in memory requirements and CPU time of more than 60% and 40% have been achieved.      

一个求最大公因数和倒数的新算法及应用

提出了一个求最大公因数和倒数的迭代算法,该算法可求得任意两个正整数a,m的最大公因数,如果(a,m)=1,可求得a关于模m的倒数。具体计算时对模数m是奇数偶数分别考虑。主要特点是避免了长整数除法和幂运算。以RSA中密钥的计算说明算法的应用。     

一种快速DOA估计算法

MUSIC算法需要将天线阵列接收数据的协方差矩阵进行特征分解,并在全空域进行谱峰搜索。该算法具有很高的分辨力、估计精度及稳定性,但是运算量巨大,难以实时实现。通过对等距线阵特点及MUSIC算法的研究,提出了一种无需特征分解和在全空域进行谱峰搜索的快速算法,算法采取降维处理的方法快速估计信号子空间,然后根据基于阵列一次快拍的FFT算法粗略估计的局域信号空间进行谱峰搜索,从而有效降低了算法的计算量,理论分析和计算机仿真结果证明了该算法的有效性。     

一种快速开短路测试算法

文章设计了一种快速开短路测试算法,利用短路群概念。对于N个引脚的连接器,只用N-1个量测步骤即能完成所有引脚两两之间的开短路测试。而通过传统的测试算法,两两引脚之间测试开短路,N个引脚至少需要N(N-1)/2个量测步骤。且随着连接器引脚数的增加,采用新算法节约的测试时间会呈几何级数增加。     

基于自适应逆控制的有源滤波器输出波形校正

传统的控制系统在设计过程中,需要在动态性能和扰动抑制之间进行一些折衷。自适应逆控制为基于前馈的开环控制,采用特别的反馈结构,可以消除对象的扰动而不改变对象的动态特性,使动态特性控制和对象扰动控制成为两个单独的过程,可以进行独立设计,这个特点也是自适应逆控制的最大优势。论文将自适应逆控制理论应用于有源滤波器（APF）中,用来控制电压源型逆变器输出电流波形的校正。仿真、实验结果验证了理论分析的有效性。     

一种Golay码的快速译码算法

本文提出了一种（２４，１２，８）扩展Ｇｏｌａｙ码的新的软判决译码算法，其译一组码字的运算量最多为５０７次二元运算，优于目前已发表的各种算法。我们证明了该算法，并实现了广义最小距离译码。计算机模拟表明在完备译码时其性能与最大似然译码几乎一样。     

一种运动估计的快速搜索方法

本文提出了动态图像压缩中估计运动矢量的一种快速搜索算法。分析与实验表明，该算法的计算量大大低于二维全搜索，而匹配效果优于三步法等快速算法，目硬件实现简单。它适用于动态图像的实时编码。     

一种快速TLS-ESPRIT算法

在众多的高分辨谱估计算法中，TLS－ESPAIT算法以估计精度高、分辨率高和运算量较低而深受欢迎。本文提出一种TLS-ESPRIT算法的快速方法，能够进一步降低运算量。     

一种DOA估计的快速子空间算法

MUSIC算法是一种属于特征结构的子空间超分辨方法，该算法性能优良，但需要估计协方差矩阵并对其进行特征分解，运算量大，很费计算时间。本文对波这方向估计问题进行了研究并提出了一种采取降维处理的快速子空间算法，该算法利用阵列协方差矩阵的一个子矩阵快速得到信号子空问，无需特征分解，且无需估计整个协方差矩阵，只需估计该子矩阵，故快速算法运算复杂度远低于MUSlC算法，而性能损失并不太大。理论分析和计算机仿真结果表明此方法是有效的。     

标准单元模式下的一种快速增量式布局算法

增量式布局是适应高性能设计要求的一种新的布局模式 .它针对电路更改 ,局部地调整单元位置 ,重新获得合理的布局 .本文提出了一种标准单元模式下的快速增量布局算法 .算法采用单元行划分的方法处理布局约束 ,然后将布局调整归结为单元依次插入单元行的问题 ,并构造了一个数学规划求解最佳的插入方案 .同时提出了复杂度为O(n)的双对角线搜索法求解这个特殊的数学规划 .实际电路测试表明算法高效而稳定 ,比简单的启发式算法快十倍 ,并使布局修改减少 2 0 %以上     

一种快速解压的无损压缩算法

随着信息技术的不断发展,大量数据给存储和传输都带来了巨大的挑战。数据压缩能够有效减少数据量,方便数据的处理和传输。无损压缩是一种利用数据的冗余特点进行压缩的压缩方法,解压时可以完全还原数据而不会有任何失真。在研究LZO算法的快速解压原理基础上,设计了一种新的压缩算法。该算法通过减少压缩数据中压缩块的数量,降低了解压程序的执行开销。测试结果表明,新算法可实现比LZO算法更快的解压速度。     

一种适用于米波雷达低角测高环境的快速算法

本文针对米波雷达低角测高环境的特点,充分利用数据协方差矩阵中的信息,基于空间平滑和传播算子的思想,提出了一种适用于米波雷达低角测高环境的快速算法(SSPM算法,Spatial Smoothing and Propagator Method).该方法不需要去相干处理和复杂的特征分解,可直接应用于存在多径干扰的米波雷达低角测高环境.仿真实验及实测数据处理结果均表明了该方法的有效性.     

A Fast Computational Algorithm for the Discrete Cosine Transform

A Fast Discrete Cosine Transform algorithm has been developed which provides a factor of six improvement in computational complexity when compared to conventional Discrete Cosine Transform algorithms using the Fast Fourier Transform. The algorithm is derived in the form of matrices and illustrated by a signal-flow graph, which may be readily translated to hardware or software implementations.     

A Fast Computational Algorithm for the Discrete Sine Transform

A sparse-matrix factorization is developed for the discrete sine transform (DST). This factorization has a recursive structure and leads directly to an efficient algorithm for implementing the DST, a feature most desirable and very similar ot that of the DCT. This algorithm requires fewer arithmetic operations compared to that for the discrete cosine transform (DCT).