A New Approach to Problems of MIMO Detection and Multiuser Demodulation

In this study, we present the results of theoretical analysis and computer simulation of the application of non-Gaussian approximation in demodulation problems in MIMO systems. The results of this study can also be applied in multiuser demodulation problems in systems with non-orthogonal signals. As a result of theoretical analysis, an approximation of a priori distribution of the estimated parameters, as well as a theoretical justification for the application of methods for solving systems of linear and nonlinear equations in solving the problem of demodulation in multi-user systems, were proposed. The results of modeling by the Monte Carlo method, as well as comparison with known demodulation algorithms for MIMO systems, which confirm the effectiveness of the proposed theoretical approach of non-Gaussian approximation for additional consideration of a priori information during demodulation, are presented.

     

纳米级集成电路与超纯水

阐述美国《国家半导体技术发展路线》中存储器的发展目标对其关键材料超纯水在水质和耗量降低上的要求,以我国8英寸/0.18μm和12英寸生产线的相关数据与其对照,表明在总有机碳、溶解氧等项水质参数已可满足该发展要求,而在SiO2、微粒限定、检测技术以及超纯水耗量降低等方面尚有差距和问题,并提出相应的解决方案,讨论了降低超纯水等项水资源消耗的途径。重申了水回收的意义,关注“功能水”和高效、省能的GDI(聚合型电去离子)装置将是有益的。     

Krylov subspace iterative techniques: on the detection of brain activity with electrical impedance tomography

In this paper, we review some numerical techniques based on the linear Krylov subspace iteration that can be used for the efficient calculation of the forward and the inverse electrical impedance tomography problems. Exploring their computational advantages in solving large-scale systems of equations, we specifically address their implementation in reconstructing localized impedance changes occurring within the human brain. If the conductivity of the head tissues is assumed to be real, the pre-conditioned conjugate gradients (PCGs) algorithm can be used to calculate efficiently the approximate forward solution to a given error tolerance. The performance and the regularizing properties of the PCG iteration for solving ill-conditioned systems of equations (PCGNs) is then explored, and a suitable preconditioning matrix is suggested in order to enhance its convergence rate. For image reconstruction, the nonlinear inverse problem is considered. Based on the Gauss-Newton method for solving nonlinear problems we have developed two algorithms that implement the PCGN iteration to calculate the linear step solution. Using an anatomically detailed model of the human head and a specific scalp electrode arrangement, images of a simulated impedance change inside brain's white matter have been reconstructed.     

A generalized multi-standby multi-failure mode system with various repair facilities

We consider a system of (m + 1) non-identical units—one functioning and m standby. Each unit of the system has the following states: normal, N types of partial failures and corresponding to them N types of total failures. There are k distinct major repair facilities and one on the spot repairman. One unit can pass from one state to another with known probability and then the time of staying in this state has a general distribution. The system starts to work at t = 0 and fails when the (m + 1)th unit after a total failure is finally rejected. Using semi-Markov techniques we obtain Laplace transforms of transition probabilities. Considering particular cases we derive known results for systems which have been defined in the past.     

Reliability and availability analysis of two-unit warm standby microcomputer systems with self-reset function and repair facility

Reliability and availability analysis of systems having one active unit and one warm standby unit with self-reset function and one maintenance facility is presented. Two failure models are discussed. The failure unit is repaired through self-reset or maintenance according to different failure models. The state transition diagram and equation are described. The formulae for reliability and steady-state availability are given.     

一种新的SAT问题预处理算法

提出了一项新的正向推理技术:对称扩展的一元子句推导(Symmetric Extended Unit Propagation)。与传统的一元子句推导技术相比,文中的方法通过在一元子句推导过程中添加对称的蕴涵关系从而能够推导出更多的一元子句。基于这项新技术实现了一个可满足性问题(SAT)预处理器Snowball。实验结果验证了该项技术的有效性,表明该预处理器Snowball能够有效地化简SAT问题的规模并减少解决SAT问题的时间。     

三维寄生电感提取中一种多右端方程求解方法

本文介绍应用PEEC模型提取VLSI电路中3-D互连寄生电感电阻中出现的多右端线性方程组求解问题.在种子投影多右端方程求解方法EGCR^[5]的基础上,本文提出一种改进的EGCR方法MEGCR,达到有控制地扩大搜索空间以减少所需正交化时间的目的.它显著加快了多右端方程组的求解速度,在可比精度下,右端数约为30时,综合运用多右端技术及多极加速的本文方法比先进的FastHenry^[1]快数十倍.     

TCP performance issues over wireless links

This article discusses the problems arising when the TCP/IP protocol suite is used to provide Internet connectivity over existing and emerging wireless links. Due to the strong drive toward wireless Internet access through mobile terminals, these problems must be carefully studied in order to build improved systems. We review wireless link characteristics using wireless LANs and cellular communications systems as examples. We then outline the performance problems of the TCP/IP protocol suite when employed over those links, such as degraded TCP performance due to mistaking wireless errors for congestion. We present various proposals for solving these problems and examine their benefits and limitations. Finally, we consider the future evolution of wireless systems and the challenges that emerging systems will impose on the Internet protocol suite     

A Fiber Routing Problem in Designing Optical Transport Networks with Wavelength Division Multiplexed Systems

In this paper, we consider a fiber routing problem arising from the design of optical transport networks. The problem is to find an optimal routing of multiple rings and an optimal location of wavelength division multiplexed (WDM) systems for carrying demand traffic. This problem can be conceptualized as a Steiner (multiple) ring problem with link capacity constraints. We formulate the problem as a mixed-integer programming model and develop a new branch-and-cut procedure along with preprocessing routines and valid inequalities for optimally solving the problem. Exploiting the inherent special structures of the formulation, we focus on developing strong valid inequalities and devising an effective Tabu search heuristic for solving large-scale problems. Computational results indicate that preprocessing rules and valid inequalities provide a tight lower bound, and in turn reduce the effort required to solve the problem within the framework of the branch-and-cut procedure. Moreover, the proposed Tabu search heuristic works quite well for solving large-scale problems. Motivated by promising computational results, we provide insights into implementing the proposed branch-and-cut procedure for deploying fiber optic networks in practice.     

Formation of an Individual Modeling Environment in a Hybrid High-Performance Computing System

Russian Microelectronics - In this paper, we consider the problem of solving scientific problems in the field of materials science in the environment of high-performance computing systems....     

也谈单位阶跃函数在一阶动态电路分析中的用法

对单位阶跃函数在一阶动态电路分析中的用法进行了分析，指出单位阶跃函数在三种情况下的用法，供教师和同学们参考。     

A column generation and partitioning approach for multi-commodity flow problems

Multi-commodity network flow problems, prevalent in transportation, production and communication systems, can be characterized by a set of commodities and an underlying network. The objective is to flow the commodities through the network at minimum cost without exceeding arc capacities. In this paper, we present a partitioning solution procedure for large-scale multi-commodity flow problems with many commodities, such as those encountered in the telecommunications industry. Using a cycle-based multi-commodity formulation and column generation techniques, we solve a series of reduced-size linear programs in which a large number of constraints are relaxed. Each solution to a reduced-size problem is an improved basic dual feasible solution to the original problem and, after a finite number of steps, an optimal multi-commodity flow solution is determined. Computational experience is gained in solving randomly generated test problems and message routing problems in the communications industry. The tests show that the procedure solves large-scale multi-commodity flow problems significantly faster than existing linear programming or column generation solution procedures.     

Simultaneous solution of system dynamic equations and control-function optimisation using the conjugate-gradient algorithm

An algorithm is presented for simultaneously iteratively solving the system equations and optimising the control function for linear systems with quadratic performance indexes, using the conjugate-gradient algorithm. A potential advantage is that the integrations of differential equations often associated with methods for solving such problems are replaced by quadratures.     

基于SQL Server应用的大数据量实时处理

对大数据量的实时处理问题是大型数据库应用系统中的共性问题,人们往往采用更换处理能力更强、存储容量更大的服务器来解决问题。这虽然也是解决问题的方法之一,但却不是一种好的方法。针对这一问题,结合SQL Server的功能特点,给出了3种应用技术和策略,即统计分析与实时处理数据分开存储策略、临时表技术和数据库的发布与订阅技术。通过对使用结果的分析,说明了这些技术和策略对完成大数据量业务的实时处理有一定的作用。不足之处是对系统的硬件等提出新的要求,因此在具体应用上要加以权衡。     

商用中央空调应用现状问题及解决措施

对各种商用中央空调的吊顶机组的渗水问题、设备选型的保守问题、系统设计与施工的不合理问题、招投标中的不公正问题等作简单探讨,所提出的解决措施希望能够供同行人士参考。     

Design of embedded systems: formal models, validation, andsynthesis

This paper addresses the design of reactive real-time embedded systems. Such systems are often heterogeneous in implementation technologies and design styles, for example by combining hardware application-specific integrated circuits (ASICs) with embedded software. The concurrent design process for such embedded systems involves solving the specification, validation, and synthesis problems. We review the variety of approaches to these problems that have been taken     

Finite array antenna, scattering, and transmission-line analysisusing the FFT

An efficient unified approach to the solution of a wide class of electromagnetic problems involving finite structures-including analysis of finite-array antennas (both transmission and reflection), scattering problems, and calculation of transmission-line eigenwaves-is presented. This approach is based on the fact that these problems can be described by the same mathematical tool, namely, convolution-type systems of linear algebraic equations (systems with matrices having a Toeplitz type of structure). Efficient methods are proposed for solving them     

Principles and methods of testing finite state machines-a survey

With advanced computer technology, systems are getting larger to fulfill more complicated tasks: however, they are also becoming less reliable. Consequently, testing is an indispensable part of system design and implementation; yet it has proved to be a formidable task for complex systems. This motivates the study of testing finite stare machines to ensure the correct functioning of systems and to discover aspects of their behavior. A finite state machine contains a finite number of states and produces outputs on state transitions after receiving inputs. Finite state machines are widely used to model systems in diverse areas, including sequential circuits, certain types of programs, and, more recently, communication protocols. In a testing problem we have a machine about which we lack some information; we would like to deduce this information by providing a sequence of inputs to the machine and observing the outputs produced. Because of its practical importance and theoretical interest, the problem of testing finite state machines has been studied in different areas and at various times. The earliest published literature on this topic dates back to the 1950's. Activities in the 1960's mid early 1970's were motivated mainly by automata theory and sequential circuit testing. The area seemed to have mostly died down until a few years ago when the testing problem was resurrected and is now being studied anew due to its applications to conformance testing of communication protocols. While some old problems which had been open for decades were resolved recently, new concepts and more intriguing problems from new applications emerge. We review the fundamental problems in testing finite state machines and techniques for solving these problems, tracing progress in the area from its inception to the present and the stare of the art. In addition, we discuss extensions of finite state machines and some other topics related to testing     

Interaction and navigation of robots based on ultrawideband direct chaotic communication

The possibility of using both standard narrowband and ultrawideband wireless communication technologies for groups of robots is considered. It is shown that the use of direct chaotic communication systems for both robot-to-robot communications and robot navigation is promising. Experimental results are presented that confirm that these systems can be used in solving robot navigation problems.