Python条件变量实现多线程编程机制分析

在多线程编程中，线程间正确的同步和通讯是应用程序设计的关键和核心。Python线程（threading）模块为用户提供更易用的高级多线程API和更强大的多线程管理方案。其中Condition条件对象为复杂线程同步问题提供有力的支持。文章从Condition类的属性和方法出发，详细剖析条件变量的同步机制，并结合教师上课和学生做作业的应用，给出同时应用两个条件变量实现多线程同步算法。     

多线程同步技术在电感自动测试系统中的应用

以多线程同步技术在电感自动测试系统程序开发中的应用为例,该文着重论述了Windows系统提供的线程同步机制和LabWindows／CVI中的多线程数据保护机制,并给出了如何通过事件和线程安全变量来实现多线程间的同步控制和数据保护的方法。该技术的使用大大提高了整个系统的性能,提高了单台测试仪的产能,在实际生产中取得了良好的效益。     

多线程同步数据处理方法研究

线程处理使C#程序能够执行并发处理,以便可以同时执行多个操作。描述了线程状态,阐述了利用C#进行程序设计时线程同步数据处理的几种方式：使用监视器来同步变量的访问、使用事件来同步线程和使用Mutex同步多个对象并避免锁死,多线程同步数据处理方法能避免多线程数据处理时出现的线程同步错误．     

微内核架构多线程机制的形式化设计研究

微内核架构因其有效的模块隔离性而成为操作系统方面研究的热点,多线程机制是微内核架构需要解决的关键性能问题。有不少的工作对微内核架构多线程机制进行了研究,但存在频繁的系统地址空间切换和实现复杂度高的问题。采用形式化的方式对微内核架构多线程和安全机制进行描述和设计,提出一个微内核线程分层对象语义模型,用以 设计多线程机制的线程间通信、调度和互斥同步方案。在已实现和验证的微内核操作系统VTOS中对多线程功能和性能进行了测试,结果表明 VTOS有效地实现了多线程机制,并具有很好的系统性能。     

基于三维视景的火箭飞行安控系统的任务管理

在PC机上进行基于三维视景的功能应用开发需要考虑充分并合理利用CPU资源的问题。该文分析基于三维视景的火箭飞行安全控制系统的多任务组成，并从多线程技术角度讨论系统的任务管理方法，即系统各个组成结构模块的任务调度策略和运行方式，解决系统多线程实现中的一些关键问题，包括任务的驱动类型、时钟管理、线程同步与互斥方法，并使用任务模式简化了视景渲染线程与其他线程的交互，保证了系统多任务处理时正确的逻辑关系和数据传递的正确性。     

基于信号量的Linux多线程同步研究

信号量是进程或线程之间相互通讯的手段之一。有效地使用可以在多线程之间实现同步和互斥，以保证程序的正确的运行。在对线程的数据结构和相关的10个函数分析的基础上，以一个具体的例子给出如何使用信号量机制实现多线程之间的同步。     

数据保护技术在多线程应用程序开发中的应用研究

正确使用多线程技术能够更好地开发并发性任务和提高测控系统性能,在避免系统阻塞和减少系统运行时间方面有着明显优点.详细介绍了LabWindows/CVI环境中多线程机制以及线程池中关键的数据保护技术,设计了一个实例程序,同时实现了线程池、数据保护、异步定时器等多线程技术,实例同时说明了通过不同方法访问线程安全变量的差异.     

Prophet推测多线程系统设计与实现

推测多线程技术通过推测执行的方式开发应用程序的线程级并行性,以提高程序执行性能。该技术一般通过执行模型来检测运行时可能的线程推测错误情况,并采取合适的机制恢复程序正确运行。描述的Prophet是一种基于硬件实现的推测多线程执行模型。重点描述了Prophet执行模型针对执行模型设计的关键问题的解决方案,包括Prophet的线程状态控制和多版本的Cach。系统,Prophet的多版本Cache系统提供了推测数据缓存功能,并使用基于总线监听的Cache协议实现了数据依赖违规检测。还给出了使用Olden基准程序对Prophet执行模型进行功能和性能测试的结果,并分析说明了Prophet系统可以有效地开发应用程序的线程级并行性。     

嵌入式图形系统Nano-X多线程改造

分析嵌入式图形系Nano-X客户端和服务器的通讯机制；针对通讯机制中同步和异步的请求应答过程，分别采用有效的方式保证不同线程对临界资源进行正确的互斥访问，使Nano-X支持多线程的应用程序，同时又不影响程序的运行效率。     

DotNet环境下分布式并发离散事件仿真建模与实现

DotNet环境对多线程技术提供了良好的支持，对于分布式离散事件，多线程技术能够以最少代价、最便捷的方式实现其并发活动的仿真。异步多线程仿真编程中的主要问题是线程的引入与控制、对各结点间的仿真时钟同步问题、线程间活动的同步与消息传递、临界变量的访问与保护机制等。从系统实现角度对这些问题进行分析是建模的必要条件件。本文进一步讨论了各结点间通过消息交互的加工过程，最后以控制台方式将分布式离散事件仿真中的主要关键活动编程实现。通过对仿真实现全过程的讨论可以看出，多线程技术能够有效地实现分布式并发离散事件的仿真。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。