Generalized differential quadrature analysis of electro-magneto-hydrodynamic dissipative flows over a heated Riga plate in the presence of a space-dependent heat source: The case for strong suction effect

The importance of including an electromagnetic actuator as a moving boundary on the dissipative flows of weakly conducting fluids had led to many published facts. But, nothing is known on the generalized differential quadrature analysis of magnetohydrodynamics over a Riga plate with emphasis on the case of viscous dissipation and space-dependent heat source. After deriving the simplified boundary layer equation that models the transport phenomenon, appropriate variables were used to non-dimensionalize and parameterize the partial differential equations. Thereafter, the resulting set of ordinary differential equations was solved numerically by applying a powerful differential quadrature algorithm. Based on the outcome of the simulation, it can be concluded that the viscous frictional effect can be minimized at the Riga plate either by weakening the suction process or by heightening the magnetic parameter. Moreover, the Lorentz forces have a hastening effect on the fluid motion, in the case when those magnetic causes are directed in the same sense of the developed flow.     

A VARIATIONAL FINITE LAYER TECHNIQUE FOR THE INVESTIGATION OF THERMALLY INDUCED STRESS CONCENTRATIONS IN COMPOSITE STRUCTURES

The technical relevance of stress fields near free laminate edges under mechanical and/or hygrothermal loads (“free-edge effect”) has long been recognized. However, the state of stress near free laminate corners (i.e., at corners that are generated by two merging straight free laminate edges) has gone nearly unnoticed in the open literature. To gain further insight into the mechanics of free-corner stress fields (“free-corner effect”), the present contribution is devoted to the closed-form analysis of displacements, strains and stresses in the vicinity of free rectangular corners of symmetric crossply laminates under uniform thermal load by means of a layerwise C⁰-continuous displacement approach. The laminate is discretized into an arbitrary number of mathematical layers through the thickness. However, concerning the two in-plane directions, no discretization is employed, but on the contrary, unknown in-plane functions are assumed that are then determined by application of the principle of minimum potential energy of the laminate. Due to some simplifying prerequisite assumptions concerning the utilized displacement approach and performing a separation of the in-plane variables, the resultant governing Euler–Lagrange equations are ordinary second-order differential equations that can be solved in a closed–form way. Hence, all state variables of the given thermoelastic free-corner problem can be written in a closed-form manner, which makes the present method easily applicable and allows a good insight into the underlying mechanics. Given boundary conditions of traction-free laminate edges are satisfied in an average sense. The present method is easily applicable, requires little computational effort, and is in excellent conformity with accompanying finite element computations. Because the presented approach enables a closed-form analytic formulation with respect to the in-plane coordinates, it is appropriate to designate the methodology as a finite layer technique.     

基于单开链有序求解的机构正向运动学建模原理及其两种求解方法

提出了一种基于单开链有序求解的机构正向运动学建模原理。将机构分解为一系列具有不同约束度值的单开链单元，再根据约束度总和为零的原则，将一系列单开链单元划分为若干个自由度为零、耦合度为κ_i的基本运动链（BKC_i），逐一按BKC_i建立含最少虚拟变量数目的机构位置方程；给出了具体的数值法和封闭法两种方法。由于数值法较简单，故用κ维搜索法直接求解机构位置方程；封闭法求解时先用Mathematica进行符号处理，从含变量数为κ的机构位置方程中导出一个一元高次的非线性位置正解封闭方程，再求解该一元高次方程。分别给出4个实例予以详细说明与验证。所提原理及求解方法思路清晰，可使机构正向位置方程中的变量和计算量大大减少，适用于求解任意复杂平面机构、空间并联机构的位置正解。     

平面分层媒质空域Green 函数快速计算

格林函数法是电磁场数值分析中的一种基本方法,平面分层媒质的空域格林函数通常表达成Sommer-feld积分形式。文中针对该问题快速求解的几种基本方法进行了系统分析,对各种分析方法进行了分类,根据研究进展情况,概述了传统离散复镜像法(DCIM)、二阶DCIM、增强型DCIM(EDCIM)、柱面波逼近和支割线积分以及其他方法,阐明了各种方法的优缺点;对计算得到的闭式Green函数在具体电磁散射与辐射计算中产生的误差控制、定阶、维数、媒质有耗问题进行了分析,给出了一种简便的有耗媒质DCIM方法,数值计算结果显示文中方法的正确性。     

基于门形三条直线的P3L问题的闭式解

研究了应用线特征进行摄像机位姿测量的三线透视问题（P3L）在三条直线共面并成门形摆放时的闭式解问题，研究了该种情况下解的特性，得出当摄像机光心位于过三条直线的两个交点且垂直于三条直线的平面时，该问题存在无穷多解，当光心不在此平面时则存在唯一解，应用几何方法给出了该结论的证明，给出闭式解求解方法，对该方法进行的计算机仿真证明了方法的正确性，该方法对实际应用有一定的指导意义。     

Closed-Form Estimators for Blind Separation of Sources – Part II: Complex Mixtures

The problem of multiuser detection in wireless communications systems adopts,in flat-fading channels, a blind source separation (BSS) formulation ofinstantaneous linear mixtures. This contribution addresses the closed-formsolutions to BSS in the complex-mixture scenario. The algebraic devices whichspan a unifying framework for the complex BSS closed-form estimators aredeveloped. With the aid of these tools, results originally encountered in thereal-mixture case are extended to the complex case, thus highlighting theremarkable parallelism existing between the real and complex problems in thecontext of their analytic solutions. Computer simulations illustrate thetheoretical results and compare the proposed methods to other BSS procedures.     

Closed-Form Estimators for Blind Separation of Sources – Part I: Real Mixtures

The problem of multiuser interference cancellation in wireless cellularcommunication systems accepts a blind source separation (BSS) model. Thepresent contribution studies the closed-form solutions to BSS in thereal-mixture case. Connections among a number of seemingly disparate methodsare unveiled, new procedures are put forward, and their asymptotic(large-sample) performance is analyzed. Simulation experiments illustrate andvalidate the theoretical results. Altogether, a unifying generic framework forclosed-form BSS methods is developed.     

SINGLE-STAGE AND MULTISTAGE MASS TRANSFER: SIMPLE RATE-BASED ANALYTICAL SOLUTION

An analytical solution to steady-state mass transfer in a binary system, of general application in mass transfer processes, was found by straightforward mathematical analysis. The analysis resulted in simple closed-form equations that define single-stage and multistage mass transfer, for cross-flow and co-current flow, entirely as expressions of the transfer unit concept. The traditional equilibrium stage and efficiency model is not validated by the analysis.     

2D analytical calculation of the electric field in lightly doped Schottky barrier double-gate MOSFETs and estimation of the tunneling/thermionic current

In this paper we present a new approach to calculate the channel electric field within a Schottky barrier Double-Gate MOSFET (SB-DG-MOSFET) in subthreshold region by solving Poissons equation. The Poisson equation is solved two dimensionally in an analytical closed-form with the conformal mapping technique. A comparison with data simulated by TCAD Sentaurus simulator for channel lengths down to 22 nm was made and shows an accurate agreement. Futhermore, a new way for the estimation of the tunneling current in SB-DG-MOSFET by applying the above 2D solution for the electric field and a 2D solution of the electrostatic potential is presented. Calculating the tunneling current, we use Wentzel-Kramers-Brillouin (WKB) approximation for the estimation of the tunneling probability. For the calculation of the tunneling and thermionic current a comparison with TCAD Sentaurus for channel lengths down to 65 nm was made.     

双基地MIMO雷达多目标定位及幅相误差估计

本文提出了一种存在幅相误差下的双基地MIMO雷达角度估计方法.利用三次迭代最小二乘算法估计存在幅相误差下的收、发阵列流形,根据信号子空间和噪声子空间的正交性,无需幅相误差的任何信息,采用MUSIC-like算法得到目标的DOD和DOA,且角度自动配对.针对MIMO雷达孔径扩展的特点,分别通过第一个发射阵元和第一个接收阵...