A self‐scalable load injection service

Load testing of applications is an important and costly activity for software provider companies. Classical solutions are very difficult to set up statically, and their cost is prohibitive in terms of both human and hardware resources. Virtualized cloud computing platforms provide new opportunities for stressing an application's scalability, by providing a large range of flexible and less expensive (pay‐per‐use model) computation units. On the basis of these advantages, load testing solutions could be provided on demand in the cloud. This paper describes a Benchmark‐as‐a‐Service solution that automatically scales the load injection platform and facilitates its setup according to load profiles. Our approach is based on: (i) virtualization of the benchmarking platform to create self‐scaling injectors; (ii) online calibration to characterize the injector's capacity and impact on the benched application; and (iii) a provisioning solution to appropriately scale the load injection platform ahead of time. We also report experiments on a benchmark illustrating the benefits of this system in terms of cost and resource reductions. Copyright © 2013 John Wiley & Sons, Ltd.     

Scheduling Algorithms for Packet-Oriented MAC Protocols in Wireless Multimedia Systems

Future generation wireless multimediacommunications will require efficient Medium AccessControl (MAC) protocols able to guarantee suitable Qualityof Service (QoS) levels for different traffic classes whileachieving a high utilization of radio resources. This paperproposes a new scheduling technique to be adopted at the MAClevel in wireless access systems, named Dynamic Scheduling-Time DivisionDuplexing (DS-TDD), that efficiently managesvideo, voice, Web and background traffics. A theoretical approachis proposed in this paper to evaluate the DS-TDD performance withvoice and Web traffics. Simulation results have permitted tohighlight the following promising characteristics of the DS-TDDscheme: (i) a high capacity of real-time traffics isattained with a QoS insensitive to Web and background trafficloads; (ii) a high throughput can be guaranteed whilepreserving the QoS levels of the different traffic classes;(iii) heavier downlink traffic loads do not modify the QoSof uplink traffics. Finally, extensive comparisons with differentscheduling schemes proposed in the literature have permitted tohighlight the better performanceof DS-TDD.     

Profiling Voids Embedded in a Slab by a Non-Linear Model

In this paper, by applying a non linear model for the electromagnetic inverse scattering, a technique for the dielectric profiling of a planarly layered medium is investigated and applied to void localization and diagnostics inside a homogeneous lossless slab (one-dimensional geometry). Data are collected under plane wave multifrequency normal incidence. Suitable finite dimensional representations for the unknown functions are introduced and their influence on the model is discussed. The resulting functional equation is solved by the method of weighted residuals and the solution algorithm amounts to minimizing a non quadratic function, where particular attention is devoted to reduce the occurrence of local minima. Finally, the inversion algorithm is validated by applications to both simulated and experimental data.     

Consistency-based and abductive diagnoses as generalised stable models

If realistic systems are to be successfully modelled and efficiently diagnosed using model-based techniques, a more expressive language than classical logic is required. In this paper, we present a definition of diagnosis which allows the use of a nonmonotonic construct, negation as failure, in the modelling language. This definition is based on thegeneralised stable model semantics of abduction. Furthermore, we argue that, if negation as failure is permitted in the modelling language, the distinction between abductive and consistency-based diagnosis is no longer clear. Our definition allows both forms of diagnosis to be expressed in a single framework. It also allows a single interference procedure to perform abductive or consistency-based diagnosis, as appropriate.This paper is an extended and revised version of ref. [29].     

Testable heuristics for the 0–1 knapsack problem

Two kinds of heuristics, fixed time and cut time, are proposed in order to use the running time available in solving 0–1 knapsack problems profitably.Translated from Kibernetika, No. 2, pp. 44–52, March–April, 1991.     

Comparison of finite element reliability methods

The spectral stochastic finite element method (SSFEM) aims at constructing a probabilistic representation of the response of a mechanical system, whose material properties are random fields. The response quantities, e.g. the nodal displacements, are represented by a polynomial series expansion in terms of standard normal random variables. This expansion is usually post-processed to obtain the second-order statistical moments of the response quantities. However, in the literature, the SSFEM has also been suggested as a method for reliability analysis. No careful examination of this potential has been made yet. In this paper, the SSFEM is considered in conjunction with the first-order reliability method (FORM) and with importance sampling for finite element reliability analysis. This approach is compared with the direct coupling of a FORM reliability code and a finite element code. The two procedures are applied to the reliability analysis of the settlement of a foundation lying on a randomly heterogeneous soil layer. The results are used to make a comprehensive comparison of the two methods in terms of their relative accuracies and efficiencies.     

Affordances in the design of enactive systems

Enactive interfaces must incorporate intuitive activity that characterizes naturalistic perception. However, the manner in which information is presented is not more important than the contents: what information is presented. In this contribution, we address the contents of perception. We argue that people perceive affordances, that is, the possible actions that are available in any given situation. We further argue that enactive interfaces should be designed to optimize presentation of information about the possible actions that are available to a person using the enactive interface. The design of enactive interfaces might be guided by an extension of the theory of ecological interface design (Vicente in Hum Factors 44:62–78, 2002) to include multimodal information that is accessed through fast, intuitive exploratory movement. We review two empirical studies that illustrate our arguments. Careful analysis of affordances, together with our increasing understanding of the enactive perception of affordances, should influence the design of enactive interfaces.     

包含热模型的大功率MOSFET新型电路模型

功率转换器的功率密度越来越高，发热问题越来越严重，这种功率转换器的设计对现代大功率半导体技术提出了新的挑战；因而，热问题的优化设计和核实变得比大功率器件的电模型更加重要，本文提出一种新的PSPICE模型，可以利用它计算MOSFET芯片在瞬变过程中的温度。其中的热阻可以从制造商提供的产品使用说明书得到。本文介绍的模型提供发热和电气参数之间的动态关系。它建立了与许可的热环境的关系，例如，栅极驱动电路、负载、以及散热器的分析与优化设计。利用这个模型可以改善散热器的设计。由于决定功率损耗的参数是分布在一定范围内，受生产制造的影响很大，因而散热器的设计往往由于无法预先知道功率损耗而无法进行。     

Golden interfaces: The Surface of Self-Assembled Monolayers

Self-assembled monolayers (SAMs) of alkanethiols and disulfides on gold form organic interfaces with properties largely controlled by the end groups of the molecules composing the film. SAMs provide a unique link between the science of organic surfaces and technologies that seek to exploit their adaptable character. Many techniques are useful for probing the structure of SAMs although only scanning tunneling microscopy (STM) at picoamperes reveals the details of the packing of their end groups at the sub-angstrom level. This review demonstrates that STM effectively tests new types of control over the microscopic structure–property relationships characteristic of SAMs on gold that should prove useful to their application.