An optical alternative to the hall test

Effective mass ratios, m*, of electrons in n-type InSb, GaAs, and near intrinsic and n-type Hg_1−xCd_xTe for 0.20 < × < 0.30 over the temperature range 77K < T < 296K were measured using Faraday rotation spectroscopy. m* ranged from 0.0186 to 0.0357 for InSb with carrier concentrations, N, in the range 1.76 < N < 110 × 10¹⁶ cm⁻³ at 296K, in good agreement with available values in the literature. Effective masses of HgCdTe were found to be about twice as large at room temperature as band edge effective mass, m*_be calculations. These calculations can be corrected for thermal excitation by adding a factor, m**, to the band edge calculation: m* = m** m*_be, where m** was found empirically to be m** = 4.52 × 10₋₃T + 0.78. The electron’s mobility is proportional to the ratio of the electron’s Faraday rotation to its absorption; that is, the absorption due to the intraband transitions of the electron itself, not the sample’s total absorption, which may include holes, interband transitions, and the like. The constant of proportionality, or the “mobility constant”, was measured in n-type GaAs and InSb doped above 18 × 10¹⁶ cm⁻³ using absorption directly. Both HgCdTe and InSb have large intrinsic carrier concentrations, on the order of 10¹⁶ cm⁻³. Hole absorption is the majority component of the sample’s absorption at lower n-type dopant concentrations. In these cases, the mobility constant was determined using an absorption cross section.     

An efficient method to compute spurious end point contributions in PO solutions

A method is given to compute the spurious end point contributions in the physical optics (PO) solution for electromagnetic scattering from conducting bodies. The method is applicable to general three-dimensional structures. The only information required to use the method is the radius of curvature of the body at the shadow boundary. Thus, the method is very efficient for numerical computations. As an illustration, the method is applied to several bodies of revolution to compute the end point contributions for backscattering in the case of axial incidence. It is shown that in high frequency situations, the end point contributions obtained using the method are equal to the true end point contributions.     

A fast method to compute the potential in the multisphere model[EEG application]

A series expansion is derived for the potential distribution, caused by a dipole source in a multilayered sphere with piecewise constant conductivity. When the radial coordinate of the source approaches the radial coordinate of the field point the spherical harmonics expansion converges only very slowly. It is shown how the convergence can be improved by first calculating an asymptotic approximation of the potential and using the so-called addition-subtraction method. Since the asymptotic solution is an approximation of the true solution, it gives some insight on the dependence of the potential on the conductivities. The formulas are given in Cartesian coordinates, so that difficulties with coordinate transformations are avoided. Attention is paid to the (fast) computation of the partial derivatives of the potential, which is useful for inverse algorithms     

An iterative method for computing carrier distribution in 2-D carrier controlled optical guides

A convenient, iterative method for determining injection current generated two-dimensional carrier distributions, and consequent control of refractive index profiles, in optical guided-wave devices is presented. This method is "user-friendly" and readily adaptable to a large variety of materials and geometries. It is particularly useful for a quick and quite accurate assessment of the feasibility of operation of novel device structures. Results obtained by this quasianalytic method are shown to agree very favorably with those obtained from more general but far more complicated commercially available software.     

An optical multi-mesh hypercube: a scalable optical interconnectionnetwork for massively parallel computing

A new interconnection network for massively parallel computing is introduced. This network is called an optical multi-mesh hypercube (OMMH) network. The OMMH integrates positive features of both hypercube (small diameter, high connectivity, symmetry, simple control and routing, fault tolerance, etc.) and mesh (constant node degree and scalability) topologies and at the same time circumvents their limitations (e.g., the lack of scalability of hypercubes, and the large diameter of meshes). The OMMH can maintain a constant node degree regardless of the increase in the network size. In addition, the flexibility of the OMMH network makes it well suited for optical implementations. This paper presents the OMMH topology, analyzes its architectural properties and potentials for massively parallel computing, and compares it to the hypercube. Moreover, it also presents a three-dimensional optical design methodology based on free-space optics. The proposed optical implementation has totally space-invariant connection patterns at every node, which enables the OMMH to be highly amenable to optical implementation using simple and efficient large space-bandwidth product space-invariant optical elements     

一种新的计算稀疏数据立方体的方法

在飞速发展的信息社会中，数据的使用量逐渐增多，在大量的数据中存在很多稀疏数据。现介绍一个高度运行雏层次聚集立方体（DHAC，dimension hierarchy aggregate cube）和对应的增量更新算法，使用该算法进行稀疏数据立方体的计算。     

An efficient method for computing optical waveguides with discontinuous refractive index profiles using spectral collocation method with domain decomposition

An accurate and efficient solution method using spectral collocation method with domain decomposition is proposed for computing optical waveguides with discontinuous refractive index profiles. The use of domain decomposition divides the usual single domain into a few subdomains at the interfaces of discontinuous refractive index profiles. Each subdomain can be expanded by a suitable set of orthogonal basis functions and patched at these interfaces by matching the physical boundary conditions. In addition, a new technique incorporating the effective index method and the Wentzel-Kramers-Brillouin method for the a-priori determination of the scaling factor in Hermite-Gauss or Laguerre-Gauss basis functions is introduced to considerably save computational time without experimenting with it. This method shares the same desirable property of the spectral collocation method of providing a fast and accurate solution but avoids the oscillatory solutions and improves the poor convergence problem of the simple spectral collocation method with single domain where regions of discontinuous refractive index profiles exist. Applications to several two- and three-dimensional waveguide structures having exact or accurate approximate solutions are given to test the accuracy and efficiency; all the results are found to be in excellent agreement.     

OLED:显示器换代技术

在继等离子(PDP)和液晶显示(LCD)之后，显示领域又杀出一匹黑马：OLED电视。有机电致发光已经在一些产品中展示出先导作用，其优异的性能甚至令等离子和液晶显示望尘莫及。     

A direct method to compute the coupling between nonidentical microwave cavities

A new technique to compute the coupling, as a function of frequency, between nonidentical resonators is presented in this paper. The structure is separated by introducing electric and magnetic wall boundary conditions on the plane of separation, and coupling coefficient is computed directly from the eigenvalues of the four individual structures. The proposed technique has been used to compute the coupling between coaxial combline resonators. It is found to be computationally much faster than the iterative technique. The computed results are in good agreement with the measured results.     

Raytran: a Monte Carlo ray-tracing model to compute lightscattering in three-dimensional heterogeneous media

A model of radiation transfer in three-dimensional (3D) heterogeneous media is designed and evaluated. This model implements state-of-the-art Monte Carlo ray-tracing techniques and is dedicated to the study of light propagation in terrestrial environments. It is designed as a virtual laboratory, where scenes of arbitrary complexity can be described explicitly and where the relevant radiative processes can be represented in great detail, at spatial scales relevant to simulate actual measurements. The approach capitalizes on the existing understanding of the elementary radiative processes and recognizes that the major difficulty in accurately describing the radiation field after its interaction with a typical terrestrial scene results from the complexity of the structure and the diversity of the properties of the elements of the scene. The output of the model can be customized to address various scientific investigations, including the determination of absorption profiles or of light-scattering distributions. The performance of the model is evaluated through detailed comparisons with laboratory measurements of an artificial target as well as with other established reflectance models for plant canopies     

An improved Boolean algebra method for computing the network reliability

This paper presents a new method, the HHL 91 algorithm, for calculating the network system reliability by sum of disjoint products (sdp). The main feature of the HHL 91 is its ability to properly arrange the order of minimal paths as well as to apply inversion to products of several variables. While the Abraham algorithm and its successors yield relatively short sdp forms of the structure functions of coherent network systems, this new method generates shorter disjoint products than any other known sdp method. Because the system reliability formula is considerably reduced in size, there will be a sharp decrease both in computation time and in rounding errors.     

An analytic method to compute the stress dependence on the dimensions and its influence in the characteristics of triple gate devices

Triple-gate devices are considered a promising solution for sub-20 nm era. Strain engineering has also been recognized as an alternative due to the increase in the carriers mobility it propitiates. The simulation of strained devices has the major drawback of the stress non-uniformity, which cannot be easily considered in a device TCAD simulation without the coupled process simulation that is time consuming and cumbersome task. However, it is mandatory to have accurate device simulation, with good correlation with experimental results of strained devices, allowing for in-depth physical insight as well as prediction on the stress impact on the device electrical characteristics. This work proposes the use of an analytic function, based on the literature, to describe accurately the strain dependence on both channel length and fin width in order to simulate adequately strained triple-gate devices. The maximum transconductance and the threshold voltage are used as the key parameters to compare simulated and experimental data. The results show the agreement of the proposed analytic function with the experimental results. Also, an analysis on the threshold voltage variation is carried out, showing that the stress affects the dependence of the threshold voltage on the temperature.     

基于视觉词袋模型的图像分类改进方法

文中主要基于视觉词袋（BOVW, Bag-Of-Visual-Words）模型对图像进行分类处理,并对传统视觉词袋模型存在的不足进行了改进,提出了一种基于视觉词典的权重直方图来表达图像,采用优化的k-means聚类算法（k-means+）用于视觉词典的构建,代入KNN（K-Nearest-Neighbors）分类器进行分类。通过对Caltech 101和Caltech 256这两个经典数据库进行实验,实验结果表明该改进方案较传统方法提高了分类的正确率。     

An efficient algorithm to compute the complete set of discreteGabor coefficients

The discrete Gabor (1946) transform algorithm is introduced that provides an efficient method of calculating the complete set of discrete Gabor coefficients of a finite-duration discrete signal from finite summations and to reconstruct the original signal exactly from the computed expansion coefficients. The similarity of the formulas between the discrete Gabor transform and the discrete Fourier transform enables one to employ the FFT algorithms in the computation. The discrete 1-D Gabor transform algorithm can be extended to 2-D as well.     

An alternative method to share the initial fixed cost of a localarea network

The managers of local area networks must often determine how to share the initial fixed cost of the network among its users. The methods commonly used for this task are unsatisfactory. An alternative technique to solve this problem is presented and applied to the network of an actual corporation. The technique is based on four simplifications derived from the Shapley Value. The simplifications generate the same cost division as the Shapley Value and are easier to calculate. The results of the method are demonstrated and the network managers reaction is noted     

A modified beam propagation method to model second harmonicgeneration in optical fibers

A finite-difference implementation of the beam propagation method (BPM) is used to solve the paraxial, scalar wave equation with a nonlinear source term. A transparent boundary condition capable of handling asymmetric modes is incorporated in the finite-difference algorithm. This nonlinear BPM is used to model the generation and propagation of second harmonic light in an optical fiber which has been prepared for second harmonic generation (SHG) by the formation of a _χ⁽²⁾ grating. This method can be used to predict the guided mode in which the generated second harmonic light propagates based on the modes of the writing (fundamental and second harmonic) and reading (fundamental only) light. The effects of self-phase modulation (SPM) and cross-phase modulation (XPM) are included in the model     

An improved method to compute lists of binary vectors that optimizea given weight function with application to soft-decision decoding

Many algorithms, tree-searching and decoding algorithms in particular, need to generate some lists of binary vectors by increasing value of a given weight function and without omission. To this end, there are not many alternatives to the Dijkstra and the Viterbi algorithm. In this letter a technique suggested by Battail in 1986 to perform this task is reviewed. Then a new technique is deduced from it, that proves to be more efficient than all the others. As an illustration of its good performance we compare a maximum-likelihood-decoding (MLD) algorithm that can be derived from it, with current state-of-the-art complete MLD algorithms for general binary linear codes     

保密存取光学图象的一种重要方法

本文叙述了一种对图象保密存取的光信息处理系统，该系统采用付氏滤波对图象加密，采用相干法反馈系统对图象解密。其实验结果证明了系统的可行性。