Locally minimal uniformly oriented shortest networks

The Steiner problem in a λ-plane is the problem of constructing a minimum length network interconnecting a given set of nodes (called terminals), with the constraint that all line segments in the network have slopes chosen from λ uniform orientations in the plane. This network is referred to as a minimum λ-tree. The problem is a generalization of the classical Euclidean and rectilinear Steiner tree problems, with important applications to VLSI wiring design.A λ-tree is said to be locally minimal if its length cannot be reduced by small perturbations of its Steiner points. In this paper we prove that a λ-tree is locally minimal if and only if the length of each path in the tree cannot be reduced under a special parallel perturbation on paths known as a shift. This proves a conjecture on necessary and sufficient conditions for locally minimal λ-trees raised in [M. Brazil, D.A. Thomas, J.F. Weng, Forbidden subpaths for Steiner minimum networks in uniform orientation metrics, Networks 39 (2002) 186-222]. For any path P in a λ-tree T, we then find a simple condition, based on the sum of all angles on one side of P, to determine whether a shift on P reduces, preserves, or increases the length of T. This result improves on our previous forbidden paths results in [M. Brazil, D.A. Thomas, J.F. Weng, Forbidden subpaths for Steiner minimum networks in uniform orientation metrics, Networks 39 (2002) 186-222].     

Electro-optical performance of polymer stabilized cholesteric texture cell: The influence of chiral dopant and monomer concentration

Reverse-mode polymer stabilized cholesteric texture (PSCT) cells with various chiral dopant and monomer concentrations were fabricated. Experimental results indicate that the chiral dopant concentration and the monomer concentration significantly influence the threshold voltage and hysteresis of the cells. The chiral dopant and monomer deform the hysteresis loop. Increasing the monomer concentration reduces the width of the hysteresis loop of the reverse-mode PSCT cell.     

通信网交换系统的发展趋向

本文对宽带综合通信网交换系统几个主要方面技术的发展趋向作了概括介绍，内容包括：电子交换的分布结构、ＡＴＭ交换的开始应用，个人通信的无线进网，宽带交换引用光子技术和多媒体交换结构分析。     

一种接入信息高速公路的新技术ADSL

新近出现的非对称数字用户线（ＡＤＳＬ）技术利用用户网中现有的铜双绞线提供１．５～６Ｍｂ／ｓ的下行数字信道，为接入信息高速公路提供了一条新途径，本文首次论述ＡＤＳＬ的基本概念，技术，发展现状和应用，最后论述我们对发展我国ＡＤＳＬ接入设备的几点建议。     

ATM交换结构综述

本文从国内外ATM交换领域有关最新研究成果出发，全面综述了宽带综合业务数字网中ATM交换结构的实现方法，并对它们的重要特点和性能进行了讨论。提出了ATM交换结构研究中存在的主要问题和今后的发展方向。     

光子交换技术的前景简述

本文首先指出光纤通信向全光网推进的趋向，认真研究光子交换技术的必要性。其后简单说明光子交换有关的波分多路／波分多址系统，空分交换器，交叉连接结点，波长路由器和波长转换器，光电子集成／光子集成技术。最后给出作者个人见解的结论．     

综合网络管理技术

阐明综合网络管理概念，综述国际标准化组织作的努力及国外发展情况，一个示例说明ＩＮＭＳ技术，最后介绍几项关键技术。     

公安110报警指挥系统组网设计

１１０是电话网中的匪警特服号，现代信息化社会的发展要求１１０接警响应迅速而准确，本文介绍了公安１１０报警指挥系统的组成原理，给出了该系统与公共市话网和公安专网的组网实现方法，并对工程设计中的系统可靠性问题进行了详细的讨论，该系统也可用于１１９报警等其待服业务。     

Circuit-switching networks with FIFO plus justifying blockout service on infinite graphs

A class of circuit-switching open queueing networks is discussed. The main result of the paper is that if extra message flows are not too intensive and the path distribution is mainly concentrated on the paths of (graph) distance 1 (nearest neighbour connections), then the network has a unique stationary working regime, no matter how large the configuration graph of the network is. Standard properties of this regime are established such as decay of correlation and continuity.     

Markovian network processes: Congestion-dependent routing and processing

A Markovian network process describes the movement of discrete units among a set of nodes that process the units. There is considerable knowledge of such networks, often called queueing networks, in which the nodes operate independently and the routes of the units are independent. The focus of this study, in contrast, is on networks with dependent nodes and routings. Examples of dependencies are parallel processing across several nodes, blocking of transitions because of capacity constraints on nodes, alternate routing of units to avoid congestion, and accelerating or decelerating the processing rate at a node depending on downstream congestion. We introduce a general network process representing the numbers of units at the nodes and derive its equilibrium distribution. This distribution takes the form of a product of functions of vectors in which the arguments of the functions satisfy an interchangeability property. This new type of distribution may apply to other multi-variate processes as well. A basic idea in our approach is a linking of certain micro-level balance properties of the network routing to the processing rates at the nodes. The link is via routing-balance partitions of nodes that are inherent in any network. A byproduct of this approach is a general characterization of blocking of transitions without the restriction that the process is reversible, which had been a standard assumption. We also give necessary and sufficient conditions under which a unit moving in the network sees a time average for the unmoved units (called the MUSTA property). Finally, we discuss when certain flows between nodes in an open network are Poisson processes.This research was sponsored in part by Air Force Office of Scientific Research contract 84-0367.