On profit evaluation in a modular system with two types of failures

A single unit maintained system consisting of two types of modules has been discussed. Failure of the type I module brings the system to the failed state, whereas failure of the type II module brings the system to the less productive state. The system is identified by up and down states and the expected profit is obtained. Two cases are discussed. In the first case, earnings (cost) in the failed state are assumed to be a continuous function of the repair rate, and the optimum repair rate which maximizes expected profit is obtained. In the second case, earnings (cost) in the failed state are taken as a discrete function of the repair rate. A procedure is suggested which enables one to make an optimum choice of repair policy. Numerical examples are included to illustrate the results.     

A Small-Scale Distributed Microprocessor System Using Shared Memory Technique

A simple technique for arranging interprocessor communication through a shared random access memory (RAM) in a small-scale distributed microprocessor system is presented. An arbiter which employs a simple hardware and requires no external clock is proposed. The arbiter consists of a controller and a scanner. The controller receives a shared memory request from a microprocessor and sends a GRANT or WAIT signal back to the microprocessor according to a command from the scanner. The scanner schedules the shared memory accessing for each microprocessor. The technique can be used for interprocessor communication at a rate of less than 87 kbytes/s with 4 Z-80 microprocessors working at a 2-MHz clock signal. The microprocessors in the system need not be identical, but are required to have a WAIT state and a FETCH state indicator. The system can be increased up to 6 microprocessors and is good for a small-to-medium scale real-time control application. A front-end communication system using the proposed system is also presented as an application.     

Phasor-Domain Modeling of Resonant Inverters for High-Frequency AC Power Distribution Systems

The circuit modeling and analysis of resonant inverters is complex because the state variables such as inductor currents and capacitor voltages are AC dominant. The phasor dynamic modeling method maps the periodical time-varying state variables into stationary frame for each harmonic of interest. Correspondingly, the circuit is decomposed into two DC subcircuits, the state variables of which are the time-varying Fourier coefficients of the original AC variables. A small-signal model can be derived by applying small perturbation and linearization to the Fourier coefficients. A phasor-domain modeling method is used to investigate the resonant inverters in high-frequency AC power distribution systems. A resonant inverter system with five energy storage elements is modeled and simulated, and compared with switch simulation for both steady state and transients. The phasor model simulation matches the switch model simulation in both steady state and transients, but takes much less computing time. In addition, this model closely relates to the power converter topology in time domain, and therefore, keeps the physical meaning of the state variables. It can be used for high accuracy of modeling, simulation, and circuit analysis and control design. It can be extended to a higher order of resonant topologies including parasitic components. A high-frequency AC system with two pulse-phase-modulation-controlled resonant inverters is modeled and simulated, and the current distribution control is investigated with the phasor model. The model simulation is compared with switch-level simulation and experimental results.     

声表面波器件输入及输出负载阻抗匹配研究

针对声表面波器件测量中网络分析仪的负载阻抗与射频传输线特性阻抗不匹配,导致传输线上反射波幅值较大的问题,提出一种减少传输线上反射波的负载阻抗匹配系统与方案。负载阻抗匹配方案针对声表面波器件测量中输入与输出端分别设计不同的无源负载阻抗匹配网络,使输入输出端同时达到匹配状态。负载阻抗匹配系统集成了未匹配通道与匹配通道,根据负载阻抗不同调整匹配参数。对一个中心频率为101.764MHz,带宽为30MHz的声表面波器件使用该匹配方案前后中心频率处的衰减进行测量对比,实验结果表明采用该匹配方案后在中心频率点处输入及输出反射损耗分别为-49.36dB和-38.13dB,比未采用匹配方案时分别减少了44.99dB和29.44dB。     

Suboptimal control of plants with uncertain parameters

A two-level technique for optimal system design is proposed, in which trajectory sensitivity cost is included with state and control variable terms. The resulting optimal system would be less sensitive to plant-parameter variations than one designed without such a trajectory-sensitivity cost term.     

放大转发下分布式协作传输链路选择算法

针对放大转发下的多中继无线协作系统中的传输链路选择问题进行了研究。提出了一种分布式链路选择算法,对提出算法系统中断性能进行了理论分析,给出中断性能在高信噪比下的渐进结果。理论及仿真结果表明:①建议算法在获得N+1阶分集增益的同时能得到与中心式选择算法相近的系统性能;②建议算法的反馈信令开销小于2 bit;③直传链路信道状态对系统性能的影响大于中继链路信道状态对系统的影响。     

基于人工噪声的多用户MIMO系统加密算法

当多用户MIMO系统中的用户数多于或等于发射端天线数时,现有的基于人工噪声的物理层加密算法会导致合法用户无法正常接收。为提高此时的多用户MIMO系统的安全性,该文提出一种新的基于人工噪声的多用户MIMO系统加密算法。首先,发送端对多个合法用户进行联合处理,建立多用户联合信道状态矩阵;然后,将联合信道状态矩阵进行奇异值分解,并根据最小的奇异值进行预编码,以消除人工噪声对合法用户的影响;最后,提出一种优化功率分配的方案。仿真结果表明,该算法将多用户MIMO系统的保密容量平均增加了0.1 bit/(s?Hz),从而提高多用户MIMO系统的安全性。     

Evaluation of a dynamic reliability problem based on order ofcomponent failure

A dynamic reliability problem is considered where system components are operating in time. A general framework for analyzing the relationship of prior information and variance of a Monte Carlo estimator is developed. The variance of an estimator based on less prior information is less than that of an estimator based on more prior information. The first application derives a sequential destruction method as a special case in this general framework. The method uses the order of component failure as prior information instead of the time to failure of components. The second application shows that the use of less prior information than the order of component failure can circumvent difficulties faced by a state transition method. A numerical example is presented     

A Newtonian metaphor for organizational change

A Newtonian metaphor for describing the effect of a radical change stimulus on the productive ability of work groups is presented in this paper. The impact of a downsizing process on a Fortune 500 company was modeled in terms of its effect on employee perceptions of their work context and their capacity for doing productive work. Also investigated was the extent to which downsizing led to entropy (disorder) or negentropy (order) as employees revised their work schemas. The results indicate that a mechanistic shift in information processing perceptions and a decline in capacity to maintain effective work behaviors occurred as a result of the downsizing. An interesting finding was that the magnitude of this productivity decline depended only on the initial and terminal information processing perceptions of the managers and not their intermediate perceptions, suggesting that the managers' perceptual state demonstrated the open systems property of equifinality     

A unified approach to fault-tolerance in communication protocolsbased on recovery procedures

Discusses fault tolerance in computer communication protocols, modeled by communicating finite state machines, by providing an efficient algorithmic procedure for recovery in such systems. Even when the communication network is reliable and maintains the order of messages, any kind of transient error that may not be detected immediately could contaminate the system, resulting in protocol failure. To achieve fault-tolerance, the protocol must be able to detect the error, and then it must recover from that error and eventually reach a legal (or consistent) state, and resume its normal execution. A protocol that possesses the latter feature of recovering and continuing its execution starting from a legal state is also called a self-stabilizing protocol. Our recovery procedure does not require the application of an intrusive checkpointing procedure. The stable storage requirement for each process is less than that required for other proposed recovery procedures. The recovery procedure provides us with a legal protocol state, which is the global state before reaching any illegal state and before the effects of the error make other states illegal. Only a minimal number of processes affected by error propagation are required to rollback. Our recovery procedure can be used to recover from any number of transient errors in the system. Our recovery procedure has also been modeled in PROMELA, a language to describe validation models, which shows the syntactic correctness of our recovery protocol design. Finally, our procedure is compared with the existing approaches of handing the errors, and an illustrative example is provided     

基于PSG和Jones矩阵法的快速高精度PMD测量

对基于Jones矩阵法的偏振模色散(PMD)测量方法进行了充分的研究,提出了计算测量Jones矩阵的通用公式,提高了测量Jones矩阵的精度;建立了基于高速数字化偏振态产生器(PSG)和Jones矩阵法的快速高精度PMD测量系统,将测量PMD时间缩短为＜15 s,重复测量精度可达0.028 ps.实验表明,这种快速高精度PMD测量系统具有很好的实用价值.     

A Communication Theory Bibliography Speaks Out—Softly

A bibliography of communication theory books and articles was constructed by the Center for Communication Research at the University of Texas at Austin. As the compilation consisted of comprehensive suggestions from many sources, a study was prompted which sought to examine the bibliographic entries in order to determine the existence of overall patterns. The entries exhibited an interesting time-line pattern, but other observations were less productive. Further study with re-grouped terms, utilizing synonymy tables is suggested.     

固体模块在真空粗抽控制电路中的应用

叙述了固体电子模块在真空粗抽泵、阀控制电路中的应用及其原理；同时还介绍一种在断电瞬间利用不同电器瞬态过程时差来改变继电器锁定状态的保护电路。     

一类Markov跳变系统鲁棒方差控制

 针对一类结构参数不完全已知的离散时间不确定Markov跳变系统,研究其闭环系统状态稳态方差小于某一给定上界约束时的鲁棒控制器设计问题。运用线性矩阵不等式方法(LMI),对系统进行了方差分析,给出并证明了控制器存在的条件,进而用一组线性矩阵不等式的可行解给出了控制器的一个参数化表示。最后仿真结果表明了该方法的有效性。     

生产线中生产节拍与速度的若干问题的探讨

生产节拍是生产加工物料系统中用于衡量生产率的指标，也是我们进行系统整体配置的依据，生产线中各设备速度的变化与配合实现了生产加工物流系统的生产节拍。本文主要就生产节拍在生产线设计中的应用，以及生产线中各设备速度的合理设计做了详尽的阐述，具有实用价值。     

Carbon Nanotube Wires Sheathed by Aramid Nanofibers

Coaxial fibers are the key elements in many optical, electrical, and biomedical applications. Recent success in materials synthesis has provided versatile choices for the core part, but the search of high‐performance sheath materials remains much less productive. These surface coatings are however as important as the core for their role as protection layers and interaction medium with the externals, thereby critically affecting the real performance of coaxial fibers. Here it is shown that aramid nanofibers (ANFs) with exceptional environmental stability and mechanical properties can be advanced coating materials for both wet‐ and dry‐spun carbon nanotube (CNT) wires. Co‐wet‐spinning ANFs with CNT aqueous dispersion can produce coaxial fibers with a compact sheath comprised of aligned ANFs, showing much enhanced mechanical properties by transferring stress to the sheath without sacrificing the conductivity. On the other hand, an immersion‐precipitation process is used to prepare a porous sheath made from randomly distributed nanofibers on dry‐spun CNT wires, which can be combined with ionic conductive gel electrolyte as a strong packaging layer for flexible solid‐state supercapacitors. The excellent intrinsic characteristics as well as variable ways of structural organizations make ANF‐based coatings an attractive tool for the design of multifunctional high‐performance hybrid materials.     

多模终端待机低功耗设计

如今的移动通信网络是由多种制式及多个频段融合而成的多模网络,对于商用终端而言,多种难题交织在一起,其中待机时长是必须要解决的一个关键问题.为此,不同于传统增大电池容量的方法,采用降低待机功耗的策略:时域的时隙控制、频域的电流控制、睡眠和唤醒的电源门控制、低频时钟高频化,其中高频时钟校准低频时钟是降低睡眠态功耗的关键措施.这一系列方案的实施,使得终端在多模实际网络环境下的待机电流小于5 mA,终端的待机低功耗达到了有竞争力的商用水平.     

Excess Time, a Measure of System Repairability

The performance of systems subject to failure and repair cycles can be described by a variety of stochastic processes. Downtime is a measure of system worth which is commonly found in the reliability literature. Another measure, excess time, has been proposed in a recent paper. Both downtime and excess time are measures of the accumulated time during which the system has been inoperative. The parameter t of excess time counts only productive units of time. Thus B(t) is the excess of unproductive time over productive time. The properties and applications of excess time are reviewed and summarized.     

钣金加工计算机辅助工艺系统

钣金加工在机械制造领域的作用越来越关键,钣金计算机辅助工艺设计制造是一个极为重要的理念,它可降低成本,提高生产质量,提高生产效率.阐述了钣金计算机工艺研究的目的、解决的问题、研究的内容、总体设计以及原型系统的开发流程等内容.     

Traffic Analysis of Delayed Delivery Services Considering the Correlation Between Circuit Switching and Message Switching

To improve the ratio of successful calls, a new switching system permitting callers to store messages when the called party is busy or does not answer can be constructed by adding a message storing function to the conventional circuit switching system. The mutual traffic influences exerted by this combination of circuit and message switching systems have not yet been clarified. This paper considers a two-stage loss system traffic model consisting of a circuit switching system that has a message switching system connected to it. The traffic characteristics of this model are analyzed using the nonindependent state transition probability, which depends upon the interacting states of the circuit and message switching system. A method of solving the state equations by determining the state transition probabilities of the message switching system from the state probabilities of the circuit switching system is proposed. Using this method, the mutual traffic influence of the circuit and message switching systems is evaluated.