Resource allocation optimization for quantitative service differentiation on server clusters

The goal of service differentiation is to provide different service quality levels to meet changing system configuration and resource availability and to satisfy different requirements and expectations of applications and users. In this paper, we investigate the problem of quantitative service differentiation on cluster-based delay-sensitive servers. The goal is to support a system-wide service quality optimization with respect to resource allocation on a computer system while provisioning proportionality fairness to clients. We first propose and promote a square-root proportional differentiation model. Interestingly, both popular delay factors, queueing delay and slowdown, are reciprocally proportional to the allocated resource usage. We formulate the problem of quantitative service differentiation as a generalized resource allocation optimization towards the minimization of system delay, defined as the sum of weighted delay of client requests. We prove that the optimization-based resource allocation scheme essentially provides square-root proportional service differentiation to clients. We then study the problem of service differentiation provisioning from an important relative performance metric, slowdown. We give a closed-form expression of the expected slowdown of a popular heavy-tailed workload model with respect to resource allocation on a server cluster. We design a two-tier resource management framework, which integrates a dispatcher-based node partitioning scheme and a server-based adaptive process allocation scheme. We evaluate the resource allocation framework with different models via extensive simulations. Results show that the square-root proportional model provides service differentiation at a minimum cost of system delay. The two-tier resource allocation framework can provide fine-grained and predictable service differentiation on cluster-based servers.     

Parallel and distributed simulation of sediment dynamics in shallow water using particle decomposition approach

This paper describes the parallel simulation of sediment dynamics in shallow water. By using a Lagrangian model, the problem is transformed to one in which a large number of independent particles must be tracked. This results in a technique that can be parallelised with high efficiency. We have developed a sediment transport model using three different sediment suspension methods. The first method uses a modified mean for the Poisson distribution function to determine the expected number of the suspended particles in each particular grid cell of the domain over all available processors. The second method determines the number of particles to suspend with the aid of the Poisson distribution function only in those grid cells which are assigned to that processor. The third method is based on the technique of using a synchronised pseudo-random-number generator to generate identical numbers of suspended particles in all valid grid cells for each processor. Parallel simulation experiments are performed in order to investigate the efficiency of these three methods. Also the parallel performance of the implementations is analysed. We conclude that the second method is the best method on distributed computing systems (e.g., a Beowulf cluster), whereas the third maintains the best load distribution.     

基于C8051 F340的多直流电机控制系统的设计

多电机的协调工作是机器人控制领域的关键技术之一.提出了以C8051F340为控制器、LMD18200为电机驱动器的解决方案.详细介绍了其硬件设计和软件实现方法.在机械手的运动控制应用中,该控制方法结构简单、可靠.     

基于快速DAD的动态HMIPv6模型研究

针对现有层次化移动IPv6协议模型所呈现的不足,如移动锚节点负载过重、转交地址配置时延过大等问题,通过快速DAD机制,提出了一种新型的动态HMIPv6协议模型.     

Ontological approach for products-centric information system interoperability in networked manufacturing enterprises

Standardisation initiatives (ISO and IEC) try to answer the problem of managing heterogeneous information, scattered within organizations, by formalising the knowledge related to products technical data. While the product is the centred object from which, along its lifecycle, all enterprise systems, either inside a single enterprise or between cooperating networked enterprises, have a specific view, we may consider it as active as far as it participates to the decisions making by providing knowledge about itself. This paper proposes a novel approach, postulating that the product, represented by its technical data, may be considered as interoperable per se with the many applications involved in manufacturing enterprises as far as it embeds knowledge about itself, as it stores all its technical data, provided that these are embedded on a common model. The matter of this approach is to formalise of all technical data and concepts contributing to the definition of a Product Ontology, embedded into the product itself and making it interoperable with applications, minimising loss of semantics.     

主动网络技术分析及其在网上交易的应用研究

随着网络技术的发展,网上交易已成为交易的一个重要方式,但在业务性能上仍有很大的缺陷.主动网络技术的发展为解决这一问题提供了方案.文中首先对主动网络技术进行了分析;其次,研究了将主动网络技术应用到网上交易的优势.通过对网上交易的案例:网上股票报价业务模型进行分析,从定量的分析结果得出,主动网络技术在网上交易方面比传统的基于TCP/IP协议的网络有巨大优势,能有效地改善传统网络环境下网上交易的业务性能.     

基于移动代理的分布式入侵检测系统的研究

目前的分布式入侵检测系统存在单点失效、网络带宽占用高、扩展性不强等缺点.文中针对这些缺点提出了一种基于移动代理的分布式入侵检测系统模型.该系统运用移动代理作为各种入侵的独立检测实体到主机监控代理上收集数据并聚集、关联这些数据,这使得系统减小了数据传输量、分散了计算,同时也提高了系统的可扩展性.着重讨论了系统部件失效的检测和自动恢复机制,使系统更加稳定可靠.对实验结果分析表明这种结构很好地减少了带宽的占用,容易对新的攻击进行扩展,失效的代理也能自动准确地恢复.     

Usability Research in the Writing Lab: Sustaining Discourse and Pedagogy

Redesigning Purdue's Online Writing Lab (OWL) presented the opportunity for collaboration among Writing Center and Professional Writing Program members. While the article briefly describes the OWL redesign process, the argument focuses on collaboration and presents a model for sustainable intraprogram collaboration. Following Hawhee, usability research is defined as “invention-in-the-middle,” which offers a model for understanding research process as part of the infrastructure of new media instruction as described by DeVoss, Cushman, and Grabill. This article offers four stakeholder perspectives on the process of participatory technology design: of writing center administrators, graduate students, technical writing practitioners, and writing program graduate faculty members. The model asserted by this article presents a dynamic understanding of expertise and of fluidity in the roles of participants. Collaborative usability research, seen as invention-in-the-middle, contributes both to long-term sustainability of technological artifacts as well as the discursive interactions among stakeholders whose work supports these artifacts.     

Developing Sustainable Research Networks in Graduate Education

The traditional modes of knowledge production and circulation in academia are (slowly but surely) shifting from the hierarchical, top-down systems of print to the distributed, bottom-up systems of the Web. It is in the context of these shifts and the rapid development of Web 2.0 tools and methods that we argue for a concomitant shift in the predominant practices of graduate education in rhetoric—particularly for students of digital rhetoric. In this article, we describe the development of a research network that combines the power of digital networking with the collaborative facilitation offered by communities of practice and consider how research networks can be grown and sustained as part of the graduate education of technorhetoricians.     

Study of the LTI relations between the outputs of two coupled Wiener systems and its application to the generation of initial estimates for Wiener-Hammerstein systems

This paper consists of two parts. In the first, more theoretic part, two Wiener systems driven by the same Gaussian noise excitation are considered. For each of these systems, the best linear approximation (BLA) of the output (in mean square sense) is calculated, and the residuals, defined as the difference between the actual output and the linearly simulated output is considered for both outputs. The paper is focused on the study of the linear relations that exist between these residuals. Explicit expressions are given as a function of the dynamic blocks of both systems, generalizing earlier results obtained by Brillinger [Brillinger, D. R. (1977). The identification of a particular nonlinear time series system. Biometrika, 64(3), 509-515] and Billings and Fakhouri [Billings, S. A., & Fakhouri, S. Y. (1982). Identification of systems containing linear dynamic and static nonlinear elements. Automatica, 18(1), 15-26]. Compared to these earlier results, a much wider class of static nonlinear blocks is allowed, and the efficiency of the estimate of the linear approximation between the residuals is considerably improved. In the second, more practical, part of the paper, this new theoretical result is used to generate initial estimates for the transfer function of the dynamic blocks of a Wiener-Hammerstein system. This method is illustrated on experimental data.