两类服务对象轮询模型的平均运行周期

系统地研究了两类服务对象轮询服务模型的平均运行周期．首先扩展了现有的每队列只具有单类服务对象的单类服务对象轮询服务模型，提出了每队列内具有两类服务对象的两类服务对象轮询服务模型(这两类对象分别采用门限服务和限定服务)．然后，在该模型稳定条件下，通过构造出队列队长的嵌入式马尔可夫链、概率母函数和Laplace-Stieltje变换，求解出平衡状态下该模型的平均运行周期．并且，通过指出队列稳定性与模型稳定性之间的差异，给出了在部分或者全部的限定式服务队列不稳定时．模型的平均运行周期．最后仿真验证了理论结果的正确性．     

基于混合服务策略轮询系统的性能分析

周期轮询系统已被广泛运用于各个领域,如计算机网络、工业制造系统等。在周期轮询系统中,最基本的队列调度策略有门限服务、限定服务以及完全服务。这些调度策略各有其优缺点,文章提出了一种基于混合服务的调度策略,对一些队列采用门限服务,对另一些队列采用限定服务,这样既可以避免在单一的完全服务中低优先级队列有可能出现的队列饥饿现象,又可以对不同的队列提供不同的服务质量。该文通过嵌入马尔可夫链和概率母函数的方法对基于混合服务的轮询系统进行分析,推导出队列的平均队长,并与采用门限服务的轮询系统进行比较,从而说明混合服务系统的优点。     

非对称门限服务与完全服务的性能解析

为了能在无线传感器网络选择一种合适的非对称轮询服务,对非对称门限服务与完全服务的性能进行了分析和比较判定了两种服务在不同情况下其各自特性的优越性.通常在分析非对称轮询服务的时候,一般采用由浅入深的分析方法.所以两队列的服务模型将会作为基础,借此进行拓展,对多队列的非对称服务进行解析.分析过程中使用了马尔科夫链和概率母函数的方法构建了服务系统的数学模型.通过对数学模型的解析给出了非对称服务系统平均排队队长和平均查询周期的表达式.根据理论值的精确计算与实验仿真值的对比结果,可以验证出二者是保持一致的.并且,对未来在无线传感器网络中实现非对称的门限服务和完全服务进行了初步设计,可以实现将多跳的路由协议,转变成单跳的轮询协议,减少数据传输的冲突性.     

完全服务和非对称门限服务两级轮询系统特性分析

区分优先级的轮询服务一直是研究人员讨论并探索的热点,本文则是采用了对称性与非对称性相结合的区分优先级的两级轮询服务模型.系统依托并行方式的处理模式,既提高了轮询系统的利用率,也降低服务器在查询转换期间所耗费的时间.并且运用马尔科夫链和概率母函数的方法建立了轮询系统的数学模型,通过对数学模型的解析精确地给出了两级非对称服务系统平均排队队长及查询周期的表达式.同时,根据系统终端循环周期的二阶特性量近似相等的方法,针对两级非对称模型给出了一种平均等待时间的近似解析式.     

支票挂失查询语音服务系统的设计与实现

自动声讯服务日益成为信息查询或传递的一条重要途径,文中介绍了支票挂失查询语音服务系统的功能,结构以及系统设计中 音卡编程的状态轮询方法和数据库的操作方法。     

"冻结系数法"应用范围的新结果

本文给出了一类时变线性系统稳定性的判定准则,从而指出了一类具体的时变线性系统 应用"冻结系数法"的可靠性,文中的方法适用于线性高阶微分方程描述的系统,且判据简洁, 易于应用.     

基于Globus的流媒体网格信息服务系统

流媒体网格系统信息服务需要整合网格系统中各种静态、动态的资源信息,提供统一的信息访问接口.Globus MDS提供了一种网格信息服务系统,适用于计算网格的信息服务,但不能完全适用于流媒体网格.介绍了Globus的信息服务模型,讨论如何基于Globus MDS构建适合流媒体网格的信息服务系统.针对Globus MDS的层次式查询机制,使用信息缓存和哈希查询技术对其进行改进.实验表明,改进的查询机制可以提高信息的查询效率,满足实时流媒体服务要求.     

中心站点和普通站点完全服务排队系统分析

通过对具有最高优先级的排队轮询系统的分析,用物理方法及其机理原理,提出最高优先级及普通队列都采用完全服务的统一服务机制,得出系统平均排队长和平均查询周期的解析式。     

基于服务网格的微服务架构服务治理研究

由于微服务细粒度的服务拆分方式和去中心化的架构设计相比于传统SOA架构更适合当前互联网敏捷开发、快速迭代的需求,但是传统微服务的服务治理技术难以实现不同技术框架和通讯协议建设的服务之间互联互通,并且存在服务治理与服务高耦合的问题.本文基于服务网格思想实现一个具有服务注册发现、负载均衡、协议转换的网络代理作为微服务架构的服务治理独立组件,并通过Netty框架、protobuf序列化方式、Etcd注册中心和加权轮询的负载均衡算法最大化网络代理性能,实验结果表明本文的设计克服了传统微服务存在的问题,并且网络代理具备高可用、高并发、高吞吐量的性能.     

工业网络中的循环服务

在PROFIBUS中，主站使用循环服务-CSRD(带应答的循环发送请求)轮询所有的从站。因为轮询的时间间隔决定了采样时间，所以了解循环服务的最大轮询间隔时间对PROFIBUS用户来说是十分重要的。在这篇论中，我们得出了一种判断循环服务最大轮询间隔时间的公式。并且，如果周期服务的轮询间隔时间不能够确定时，我们可以在一个轮询表中重复响应的周期服务以减少轮询间隔时间。之后，为了解决如何在轮询表中放置重复的周期服务的问题，我们使用了等距离法。     

Stability conditions for multisequence systems with cyclic service

The conditions under which several multiqueue systems with cyclic service (also referred to as polling systems) will be stable are investigated. The stability conditions established are more general than those established by other authors. In particular, both station stability and system stability are considered for polling systems for which an exact analysis has been obtained and for those for which an exact analysis has not yet been obtained     

Mathematical methods to study the polling systems

Reviewed were the mathematical methods that are used to investigate the polling systems which found wide application in modeling and design of various transport and industrial processes. Emphasis was made on the models of polling systems used to investigate the wireless broadband networks. The polling systems were classified; presented were stochastic models and methods of investigating discrete-time and continuous-time systems, systems with cyclic, periodic, and random queue polling, as well as the methods of their optimization.     

Closed-form waiting time approximations for polling systems

A typical polling system consists of a number of queues, attended by a single server in a fixed order. The vast majority of papers on polling systems focus on Poisson arrivals, whereas very few results are available for general arrivals. The current study is the first one presenting simple closed-form approximations for the mean waiting times in polling systems with renewal arrival processes, performing well for all workloads. The approximations are constructed using heavy traffic limits and newly developed light traffic limits. The closed-form approximations may prove to be extremely useful for system design and optimisation in application areas as diverse as telecommunications, maintenance, manufacturing and transportation.     

Absolute stability of parametrically perturbed third-order systems

Consideration was given to the behavior of the third-order systems in phase space. Regularities of motion of the phase trajectories were established, and a criterion for absolute nonoscillation was obtained. For the absolutely nonoscillatory systems, the Hurwitz conditions serve as the absolute stability criterion. For the oscillatory systems, an additional Bulgakov condition was introduced to eliminate the possibility of parametric resonance. This condition which is verified on the invariant set defined using the Poincaré transform was shown to be a criterion for absolute stability of the oscillatory systems. The results obtained were used to solve the problem of absolute stability of a third-order control system with nonstationary sectorial nonlinearity.     

Multicycle Polling Scheduling Algorithms for FieldBus Networks

The paper deals with the scheduling of periodic information flow in a FieldBus environment. The scheduling problem is defined from an analytical point of view, giving a brief survey of the most well-known solutions. One of these is called multicycle polling scheduling, which is based on the hypothesis that all the production periods of the periodic processes to be scheduled are harmonic. Although in some process control or manufacturing scenarios, this hypothesis may be acceptable, there are many real industrial processes to which it cannot be applied. The aim of the paper is to make a contribution towards solving the scheduling problem. It essentially concerns extension of the theory on which multicycle polling scheduling is based to a much more realistic and general scenario, where the periods of all the processes to be scheduled have arbitrary values. The authors present a new formulation of multicycle polling scheduling, called extended multicycle polling scheduling, and demonstrate that it comprises the scenario currently considered in the literature. Two algorithmic solutions for extended multicycle polling scheduling are then proposed, giving a computational complexity analysis which will highlight the capability of the algorithmic scheduling solutions to be performed on-line. The paper concludes by comparing the multicycle polling scheduling approach known in literature and the one presented in the paper. Comparison is performed by evaluating the use of available bandwidth to serve both periodic and asynchronous traffic in the two approaches.     

Global stability of congestion controllers for the Internet

We consider a single link accessed by a single source which responds to congestion signals from the network. The design of controllers for such sources in the presence of feedback delay has received much attention recently. Here, we present conditions for the global, asymptotic stability and semiglobal exponential stability of congestion controllers. These conditions are natural extensions of conditions obtained through linearized analysis of such systems. Our result on exponential stability provides the missing link in the proof of how one obtains a single deterministic congestion control equation from a system with many congestion-controlled sources and random disturbances. Using numerical examples, we compare the conditions on the congestion-control parameters obtained using local and global stability analysis.     

线性多时变时滞系统的指数稳定性

本文基于一个新型滞后动态系统指数稳定性定理和两个准备引理, 采用 Lyapunov 函数稳定性分析新方法, 建立了线性多时变时滞系统保守性少的稳定性条件. 与文献中已有的一些结果不同, 所建立的稳定性条件不依赖于时变时滞的变化率. 因此, 所建立的结果适用于具有非常快变时滞的系统. 文中给出了一个例子展示所得结果好于直接采用标准的 Razumikhin 型条件所得的结果.     

Stability of nonlinear 2D systems described by the continuous-time Roesser model

This paper considers systems with two-dimensional dynamics (2D systems) described by the continuous-time nonlinear state-space Roesser model. The sufficient conditions of exponential stability in terms of vector Lyapunov functions are established. These conditions are then applied to analysis of the absolute stability of a certain class of systems comprising a linear continuous-time plant in the form of the Roesser model with a nonlinear characteristic in the feedback loop, which satisfies quadratic constraints. The absolute stability conditions are reduced to computable expressions in the form of linear matrix inequalities. The obtained results are extended to the class of continuous-time systems governed by the Roesser model with Markovian switching. The problems of absolute stability and stabilization via state- and output-feedback are solved for linear systems of the above class. The solution procedures for these problems are in the form of algorithms based on linear matrix inequalities.     

Improved Stability Criteria for Discrete-time Delay Systems via Novel Summation Inequalities

This paper is concerned with the stability analysis of linear discrete time-delay systems. New discrete inequalities for single summation and double summation are presented to estimate summation terms in the forward difference of Lyapunov-Krasovskii functional (LKF), which are more general than some commonly used summation inequalities. Through the construction of an augmented LKF, improved delay-dependent stability criteria for discrete time-delay systems are established. Based on this, a time-delayed controller is derived for linear discrete time-delay systems. Finally, the advantages of the proposed criteria are revealed from the solutions of the numerical examples.