浅析通信中虚拟用户交换机的设置

虚拟用户交换机是目前比较热门和实用的技术之一,也是（Centrex）是一个商务通信概念,他是将用户交换机的功能集中到局用交换机中,由局用交换机代其维护和管理,一般将局用交换机的部分用户分成组,不仅为这些组提供用户交换机的功能（PABX）,还能够使其充分利用局用交换机已有的新功能和新业务。总之,Centrex是利用局用程控交换机的资源组成专用网来实现为公用网用户提供用户交换机功能的新业务介绍了其数据配置的详细过程。     

“吃”污泥的微型电站——在产生清洁电能方面，燃料电池效率极高

燃料电池将氢气（H2）的化学能量转化成电能和热能，电池是H2输入发生器。磷酸型燃料电池（PAFC）一直用于为医院、宾馆和办公楼提供电能和热水。最近，PAFC得到了进一步的发展，已经可以从下水道污泥和垃圾这样的废料中提取H2、以及生产诸如H2副产品这样的产品了。这些应用将使PAFC更加环境友好和更加经济，有助于创造一个可持续发展的社会。     

华为推出新一代交换机 意图抢思科企业市场地盘

在企业业务市场一直充当挑战者的华为，正在越来越明确地指向。“虽然我们的市场份额还与他们（思科）相差得很远，但我们的交换机产品可以完全超越他们。“昨天，在华为下一代网络暨交换机产品的发布会上，华为企业业务CEO徐文伟在接受媒体采访时表示。     

华为推出新一代交换机 意图抢思科企业市场地盘

在企业业务市场一直充当挑战者的华为，正在越来越明确地指向。”虽然我们的市场份额还与他们（思科）相差得很远，但我们的交换机产品可以完全超越他们。“昨天，在华为下一代网络暨交换机产品的发布会上，华为企业业务CEO徐文伟在接受媒体采访时表示。     

一种容错ATM交换机仿真分析

讨论了一种容错ATM交换机结构。在该交换机中通过提供子交换单元和扩展链路来增加冗余路径的数目，该结构可以容错多个故障，并且冗余路径的数目随着交换机级数的增加而指数增长。通过仿真的方法得到了该交换机的生存概率、容错水平和费效比3个参数，可以看出该交换机容错性能和费效比高于目前文献上可查到的容错ATM交换机。     

计量保证方案中的测量过程控制

本文对计量保证方案（MAP）的核心──测量过程的统计控制进行研究．探讨测量过程的主要控制技术：t检验和F检验，把t分布和F分布的分位数的计算问题统一地归结为了1/2整数倍贝塔分布的分位数计算．并设计编制计算程序，快速、系统地算得任意自由度t分布和F分布的分位数，为测量过程的控制和计量保证方案的实施提供了一个有效的数据处理方法．     

YB3（Y3）高效节能电动机电磁特点浅析

YB3（Y3）是电动机行业关注的热点，具有节能、环保、低噪，安全等优点。本文通过对YB3（Y3）高效节能电动机特点的研究，总结YB3（Y3）在YB2（Y3）萼础上结构变化特点，为推广YB3（Y3）高效节能电动机，促进国民经济生产节能和和谐发展提供借鉴。     

探讨扩声系统电平调节方法（2）

如果将上面举例的多级电压放大器比作一台调音台，调音台示意电路图见图2，则也可以将组成调音台中各部分对应成上述多级电压放大器中的五级电压放大单元，A1对应成单声道输入通道的输入放大级（包括Tr1,Tr2，IC，及其外围元器件组成的复合差分电压放大单元），也就是增益调节级（GAIN），这一级可以通过调节电位器W1来改变负反馈电阻值达到改变电压放大倍数，通常增益调节范围可以达40dB以上；     

公用电话计费系统检定方法的新思路

现在许多城市开始推广网络IP电话及集中管理计费电话。集中管理计费是由电信部门在程控交换机端对全市（地区）的公用电话统一计费，用户端不再对通话过程计时，只对由交换机返回的信息进行显示的电话计费方式。而网络IP电话是一种基于Intemet，由电脑担当交换机角色进行计费的方式。通过网络传输信息，用户不需要电话进线．也应是一种集中管理计费。     

雅马哈O3D数字调音台的主要功能及其特点

雅马哈03D调音台是一种既有传统模拟调音台操作界面,又能提供多项处理功能的全新数码调音台。它具有26路输入（包括8路数字输入）、一组立体声输出（模拟或数字）、4总线输出、4辅助发送、2内置效果发送、8编组数字输出（经YGDAI卡）,每个输入通道拥有四     

Heuristic control of multiple batch processors with incompatible job families and future job arrivals

We analyse the problem of minimising the mean cycle time of a batch processing stage containing K?>?1 batch processors in parallel with incompatible job families and future job arrivals. We provide an integer linear programming formulation and a dynamic program formulation for small problem instances. For larger problem instances, we propose an online heuristic policy MPC_REPEAT. At each instance a decision has to be made, MPC_REPEAT decomposes the problem of simultaneously assigning multiple batches to multiple processors into sequentially assigning multiple batches to multiple processors. When job families are uncorrelated, we show via simulation experiments that MPC_REPEAT has significantly lower mean cycle time than a previously proposed look-ahead method except when: (MPC_REPEAT ignores some job families AND the traffic intensity is high.) Our experiments also reveal that increasing the job family correlation of consecutive job arrivals results, with a few exceptions, in a mean cycle-time reduction, for both policies evaluated. This reduction in cycle time generally increases with: increasing number of job families, decreasing number of processors, and increasing time between job arrivals. Our findings imply that controlling the upstream processors, such that job families of consecutive job arrivals are correlated, can reduce the cycle time at the batch processing stage. Furthermore, the expected mean cycle time reduction due to this strategy can be substantially larger than that expected from switching to a more complex batch processing stage policy, under less stringent conditions.     

Service‐level assurance in high‐availability multi‐unit systems using the M‐for‐N backup scheme

In this paper, we investigate service‐level assurance in high‐availability multi‐unit systems using the M‐for‐N backup scheme. M‐for‐N shared protection (backup) systems with priority control (i.e. prioritized protection switching and prioritized re‐housing of repaired units) can be applied to actual telecommunication devices that are subject to service‐level agreement (SLA) involving reliability measures. A priority level is assigned to each end user in such a system and the switching and unit re‐housing process is subject to the priority. The main contribution of this paper is to give a practical computation method of the user‐perceived availability under the priority control. Our case studies for real telecommunication systems reveal the effect of priority control on the user‐perceived availability. Copyright © 2011 John Wiley & Sons, Ltd.     

CONTROL OF MULTIPRODUCT BULK SERVICE DIFFUSION/OXIDATION PROCESSES

This paper demonstrates how knowledge of future arrivals can be used to control bulk service diffusion and oxidation processes. The objective of the research reported herein is to reduce the average time that lots spend waiting to be processed. A review of the current literature reveals that several researchers have dealt with the control of bulk service queueing systems; however, only one has addressed the use of knowledge of future arrivals and it only considered the case of a single product and a single server. This research reexamines the single product-single server case, and men explores the multiple products-single server case. For both cases, a control strategy is devised and evaluated through the use of systems simulation. The steady-state performance of each control strategy is then compared to the steady-state performance of the theoretical optimal control strategy not considering the timing of any future arrivals (i.e. a Minimum Batch Size strategy). The experimental results indicate that the control strategies developed in this paper perform well under most circumstances.     

Reliability and performance analysis of time – space – time switching networks with multiple separated space switches

Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches.     

Control of multiproduct bulk server diffusion/oxidation processes. Part 2: multiple servers

We investigate how knowledge of future arrivals can be used to control bulk server diffusion and oxidation processes in semiconductor manufacturing to reduce the average waiting time of lots. While past research has dealt with the control of bulk server queueing systems, only a few studies have addressed the use of knowledge of future arrivals, and those studies were limited to a single server system. We extend prior strategies for the single product-single server case to a multiple product-multiple server case, and devise a control strategy that is tested through the use of simulation. The performance of the new policy is compared to that of the optimal control strategy ignoring future arrivals (i.e., a Minimum Batch Size strategy). Results indicate that the new strategy performs well under a wide variety of circumstances. To demonstrate the control strategy performance in a realistic setting, a detailed simulation model of the diffusion area of an existing wafer fab was developed. The model was run with several start rates and the results compared to those from a Minimum Batch Size strategy. Results indicate that the new strategy performs well over a wide range of start rates.     

Electrical switching and memory phenomena observed in redox dendrimer thin films

This article reports on the fabrication of dendrimer molecular thin film sandwich devices with electrical switching and memory properties. The storage media consists of a redox-gradient N,N?-(1,4-phenylene)bis(N,N′N′N″,N″-pentakis(4-methoxyphenyl)-1,3,5-benzenetriamine) (4AAPD) dendrimer layer sandwiched between two N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) thin films. The TPD thin films are used as potential barriers. The 4AAPD layer acts as a potential well where redox-state changes and consequent electrical transitions of the embedded 4AAPD molecules can be effectively triggered. Experimental results indicate that electrical switching could be reproducibly obtained in the dendrimer sandwiches upon crossing a threshold bias voltage. After switching, the device conductivity can be increased more than three orders of magnitude, which is stable for several days in ambient conditions. This work demonstrates the possibility of using solid-state redox-gradient dendrimer layer as information storage media.     

Digital switching in the quantum domain

Presents a switching architecture such that digital data can be switched in the quantum domain. The proposed mechanism supports unicasting as well as multicasting, and is strict-sense nonblocking. In addition, with appropriate interface conversion, this architecture can also be used to switch classical information. This results in a quantum switch that can be used to build classical and quantum information networks. To present this idea, we define the connection digraph which can be used to describe the behavior of a switch at a given time, then we show how a connection digraph can be implemented using elementary quantum gates. Compared with a traditional space or time domain switch, the proposed switching mechanism is much more scalable. Assuming an n/spl times/n quantum switch, the space consumption grows linearly, i.e., O(n), while the time complexity is O(1) for unicasting, and O(log/sub 2/n) for multicasting. Based on these advantages, a high-throughput switching device can be built simply by increasing the number of I/O ports.     

Modeling of charge switching in ferroelectric capacitors

To simulate charge switching in ferroelectric capacitors, a pair of exponential growth and decay currents is mapped to the process of polarization reversal. This is based on the fact that these exponential currents [i.e., i = I(m) e(t/tau) (t < or = 0) and i = I(m) e(-t/tau) (t > or = 0)], are completely specified by two constants I(m) and tau and each accommodates an integral charge Q = I(m) x tau. Equating this charge to the remanent spontaneous polarization allows for the modeling of switching current. For practical circuit simulations for charge switching, this modeling of switching current is simplified to an exponential decay current whose integral charge is set equal to the total reversed spontaneous polarization. This is because an exponential decay current can be conveniently implemented by charging a series resistor and capacitor (RC) circuit with a pulse-voltage source. The voltage transitions of the pulse source are associated with the polarization reversal and can be controlled with a noninverting Schmitt trigger that toggles at the positive and negative coercive voltages of a ferroelectric capacitor. The final circuit model incorporates such electrical and geometrical parameters as capacitance, remanent spontaneous polarization, coercive field, electrode area, and film thickness of a ferroelectric, thin-film capacitor.     

Modeling for multilevel switching in oxide-based bipolar resistive memory

We report a physical model for multilevel switching in oxide-based bipolar resistive memory (ReRAM). To confirm the validity of the model, we conduct experiments with tantalum-oxide-based ReRAM of which multi-resistance levels are obtained by reset voltage modifications. It is also noticeable that, in addition to multilevel switching capability, the ReRAM exhibits extremely different switching timescales, i.e. of the order of 10(-7)?s to 10(0)?s, with regard to reset voltages of only a few volts difference which can be well explained by our model. It is demonstrated that with this simple model, multilevel switching behavior in oxide bipolar ReRAM can be described not only qualitatively but also quantitatively.     

Combined ZVS?ZCS topology for high-current direct current hybrid switches: design aspects and first measurements

Power electronic switches have been considered for load switching ever since their invention. This is because semiconductor switches enable fast, arc-less, reliable and maintenance-free switching. The main disadvantages in relation to conventional switches (i.e. circuit breakers), however, are their sensitivity to transients, high on-state losses and the presence of leakage current. The advantages of both types of switches can be exploited by combining the semiconductor and the mechanical switch and thereby their disadvantages, arc formation and regular maintenance, can also be eliminated. For hybrid switches (HSs), both zero voltage switching (ZVS) and zero current switching (ZCS) are frequently used. A new hybrid switching topology has been developed where both ZVS and ZCS techniques are applied to the mechanical switch. The `symbiosis' between these solid-state switching techniques and a mechanical switch eliminates several of the disadvantages, resulting in a more reliable direct current (DC) HS that requires less maintenance. The first turn-off measurement (up to 5 kA) from a prototype that has been developed for a 3-kV DC grid is presented