On the Locus of Speed-Accuracy Trade-Off in Reaction Time: Inferences From the Lateralized Readiness Potential.

Lateralized readiness potentials (LRPs) were used to determine the stage(s) of reaction time (RT) responsible for speed-accuracy trade-offs (SATs). Speeded decisions based on several types of information were examined in 3 experiments, involving, respectively, a line discrimination task, lexical decisions, and an Erikson flanker task. Three levels of SAT were obtained in each experiment by adjusting response deadlines with an adaptive tracking algorithm. Speed stress affected the duration of RT stages both before and after the start of the LRP in all experiments. The latter effect cannot be explained by guessing strategies, by variations in response force, or as an indirect consequence of the pre-LRP effect. Contrary to most models, it suggests that SAT can occur at a late postdecisional stage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance evaluation of an importance sampling technique in a Jackson network

Importance sampling is a technique that is commonly used to speed up Monte Carlo simulation of rare events. However, little is known regarding the design of efficient importance sampling algorithms in the context of queueing networks. The standard approach, which simulates the system using an a priori fixed change of measure suggested by large deviation analysis, has been shown to fail in even the simplest network settings. Estimating probabilities associated with rare events has been a topic of great importance in queueing theory, and in applied probability at large. In this article, we analyse the performance of an importance sampling estimator for a rare event probability in a Jackson network. This article carries out strict deadlines to a two-node Jackson network with feedback whose arrival and service rates are modulated by an exogenous finite state Markov process. We have estimated the probability of network blocking for various sets of parameters, and also the probability of missing the deadline of customers for different loads and deadlines. We have finally shown that the probability of total population overflow may be affected by various deadline values, service rates and arrival rates.     

Improving responsiveness of soft aperiodic tasks using proportional slack time

In a real-time system with both hard real-time periodic jobs and soft real-time aperiodic jobs, it is important to guarantee that the deadline of each periodic job is met, as well as to provide a fast response time for each aperiodic job. We propose an algorithm, called Proportional Slack Reserve (PSR), that produces an efficient schedule for such an environment. For every execution unit of a periodic job, the PSR algorithm reserves time which can be used for execution of aperiodic jobs. If reserved time is not available, the algorithm assigns a deadline to an aperiodic job for achieving better responsiveness of aperiodic jobs. The proposed algorithm can fully utilize processing power while meeting all deadlines of periodic jobs. It can also easily reclaim the time unused by the periodic job. We analytically show that for each aperiodic job, the response time in a PSR schedule is no longer than that in a TBS schedule, which is known to be efficient for servicing aperiodic jobs. We also present simulation results in which the response time of PSR is significantly improved over that of TBS, and moreover the performance of PSR compares favorably with TB(N) considering scheduling overhead.     

基于价值密度和截止期的网格作业调度算法

对商业网格中的作业调度问题进行研究,采用作业的到达时间、计算量、预算和截止期4个参数定义作业的优先级。在此基础上提出基于价值密度和相对截止期的网格作业调度算法,并对其进行仿真。仿真结果表明,该算法在实现价值率、按时完成作业数和加权作业按时完成率3个性能指标上优于现有算法,兼顾了消费者和服务者的利益。     

基于PTIDES执行策略的调度算法

分析现有PTIDES执行策略调度算法,综合考虑事件的截止期和执行时间,改进传统最小空闲时间优先算法,将空闲时间作为事件调度优先权,提出零空闲时间优先PTIDES调度算法——ZSFPTIDES。实例分析表明,ZSFPTIDES调度算法能避免事件在处理过程中因得不到及时处理而夭折的现象,减小事件的抢占切换率,优化分布实时嵌入式系统的调度性能。     

最早截止期优先调度算法的改进

在基于IEEE802.16d协议的服务流调度过程中,为了保证优先级较高的任务优先得到服务,并尽量将调度过程对系统资源的消耗控制在可承受的范围内,在分析已有的非抢占式及抢占式两种方案的最早截止期优先(EDF)算法优缺点的基础上,重点考虑时间特性、重要性特性、顺序参考三方面作为调节参数,同时兼顾传输距离,对已有的EDF算法进行改进。提出了基于重要性因素抢占的半抢占式EDF算法。通过仿真实验,把改进后的EDF算法应用到IEEE802.16d协议的实时轮询业务(RTPS)服务流调度中。结果表明,改进后的EDF算法较好地平衡了抢占及非抢占式EDF算法的优缺点,具备较前两者更小且更稳定的延时。     

总线式顾客－服务器网络失效性分析

本文讨论了总线式顾客－服务器网络系统的失效性．用马尔可夫过程导出平衡状态和非平衡状态的各状态概率，并分析系统的失效率，同时为死限有要求的用户提出增加系统可靠性的方法．     

有预算和截止期约束的网格作业调度算法

在商业网格计算环境中,作业有预算和截止期限制。如何向消费者提供有质量保障的服务,同时考虑服务提供者的利益,是一个关键问题。现有的作业调度算法只从消费者的角度出发对作业完成的时间和成本进行优化。同时从消费者和服务者的角度,利用作业的属性定义了作业的价值密度,在此基础上提出了高价值密度优先的网格作业调度算法HVDF。仿真结果表明,HVDF算法在实现价值率和按时完成作业数两个性能指标上优于现有算法。     

CPU时间片组合拍卖遗传算法

提出一种综合考虑Agent时间片和执行截止期限要求的CPU时间片组合拍卖遗传算法。该算法定义了问题模型,采用可以去除不具备竞争力标的预选择策略,减少遗传算法的计算复杂度。在遗传算法求解过程中,设计适合该问题的变长染色体编码方式、交叉算子、换序算子和换标算子。仿真实验结果表明,该算法取得了符合要求的最优解。     

基于Petri网的工作流时间动态预测及验证

目前,工作流管理系统不能有效的处理时间管理问题,为了动态预测活动发生的时间间隔,验证时间的一致性,预知潜在的时间冲突,首先建立基于时间Petri网的扩展工作流网(XTWF-net),然后根据工作流管理联盟规定的几种基本结构推导出时间预测规则,并采用面向对象技术实现了预测算法,最后给出了动态验证的方法和决策策略.