分布式系统死锁的预防、避免和检测

分布式系统涉及到资源和数据的高度共享,从而可能引发死锁。分布式系统的死锁是由于资源和通讯产生的。从分布式系统死锁产生的条件,解决策略,以及分布式系统中死锁预防、避免和检测的各种算法进行了具体阐述。     

并发操作系统中基于有色Petri网的死锁检测与避免

1.引言系统的并发性与资源的共享性是并发操作系统的主要特征,其目的是最大限度地提高计算机资源的利用率。死锁是并发操作系统必须解决的一个重要问题。人们试图用不同的方法来解决死锁问题。如Dijkstra提出的有名的死锁避免的“银行家算法”,Coffman等人给出的死锁检测算法。 Petri网模型作为模拟与分析并发、异步、分布式系统的一种有效工具,已被用于解决操作系统中的许多问题。如进程通讯中的生产者/消费者问题、哲学家用餐问题,资源竞     

基于Petri网的数据库系统并发控制活性分析

从数据库系统在时刻t的状态N出发,构造出相应的Petri网模型,进而构造出其可达标识图。通过分析可达标识图,可判断系统是否为死锁状态。若不是死锁状态,系统是否可能出现死锁,什么情况下系统肯定不会出现死锁。最后,给出了数据库系统中事务并发操作的死锁检测方法与避免措施。     

MPI同步通信顺序模型死锁静态检测算法

静态检测MPI程序同步通信死锁比较困难,通常需要建立程序模型。顺序模型是其他所有复杂模型的基础。通过一种映射方法将顺序模型转化为字符串集合,将死锁检测问题转化为等价的多队列字符串匹配问题,从而设计并实现了一种MPI同步通信顺序模型的静态死锁检测算法。该算法的性能优于通常的环检测方法,并能适应动态消息流。     

分布式系统死锁的Petri网分析

阐述了分布式系统中的死锁问题,采用Petri网对分布式系统中的死锁进行分析,给出了几种解决死锁的模型,并分析了这些模型的优缺点,指出了分析和解决死锁的一般方法.     

基于SUIF2的静态死锁检测方法研究

死锁是并发程序中常见的错误之一,且由于并发程序运行的不确定性使得死锁难以检测。针对该问题,通过对C多线程程序死锁的分析,提出了一种基于SUIF2的静态死锁检测方法,设计了基于SUIF2的C多线程程序静态死锁检测的框架结构和锁集分析算法。最后通过一个实例说明了该检测方法的有效性。     

死锁检测工具的能力分析与综合应用

并发软件运行的不确定性使得死锁检测十分困难。现有的工作集中在使用分析、验证或测试的单一途径来检测死锁。通过分析现有工具的死锁检测能力,提出了综合使用工具的死锁检测方法。同时根据分析、验证和测试途径的不同特点,给出了评估工具检测结果的度量方法。实验结果显示了该方法的有效性。     

分布式系统死锁的Petri网分析

阐述了分布式系统中的死锁问题，采用Petri网对分布式系统中的死锁进行分析，给出了几种解决死锁的模型，并分析了这些模型的优缺点，指出了分析和解决死锁的一般方法。     

强干扰下数据采集系统稳定通讯解决方案

本文介绍了RS-232串行总线及USB通用串行总线技术，讨论了其抗干扰性，分析了串口出现误码及USB接口出现死锁现象的原因．提出了一种强干扰下数据采集系统稳定通讯的解决方案。使用RS-232传送指令，USB传送采集数据，当监测到通讯死锁时，通过指令控制USB接口重新初始化，保证了强干扰下通讯的稳定可靠性。     

基于Petri网的并发系统活性分析

本文从数据库系统在时刻t的状态N出发，构造出相应的Petri网模型，进而构造出其可达标识图．通过分析可达标识图，可判断系统是否为死锁状态．若不是死锁状态，系统是否可能出现死锁，什么情况下系统肯定不会出现死锁．最后，给出了数据库系统中事务并发操作的死锁检测方法与避免措施．     

“铁路通号工程”国家级工程实践教育中心建设思路

为了适应高速铁路发展对通号专业技术人才和工程应用型人才的需求,按照"面向工业界、面向未来、面向世界"的工程教育理念,提出以传统优势专业铁路通信、信号控制为依托,建设"铁路通号工程"国家级工程实践教育中心的建设思路,在系统分析本科生、研究生培养模式和"铁路通号工程"人才必备的能力体系的基础上,构建适应通信信号一体化的"铁路通号卓越工程师"企业实训平台。     

基于远距离工业通信的空间数据库建模方法研究*

为适应远距离工业通信数据显著的空间特征和复杂的结构特征,在现有空间数据库技术的基础上,充分考虑专业工程技术人员的实际需要,提出了基于远距离工业通信领域数据资源共享的空间数据库建模方法。该模型定义了一组基于关系型的适应远距离工业通信网络运行规则的层次结构,并引入了QR-树的空间索引机制。其结果表明,该模型不仅能较好地解决分类误差,而且其索引机制与传统索引机制相比有较高的检索、插入与删除等操作性能。     

USB通信协议分析和系统设计

主要介绍了当前在智能仪器设计中广泛应用的USB通信技术，重点介绍和分析了USB通信系统软件结构和枚举过程，能有效的帮助技术人员在没有USB总线分析仪等昂贵的硬件设备的情况快速调试USB通信。并将该技术用于智能化心血管功能检测仪的设计中，已可靠地实现了与计算机之间的USB通信功能，显著提升了智能仪器的通信性能，具有良好的推广应用价值。     

A rule-based system for automatic assignment of technicians to service faults

We present a model and a prototype system for the assignment of technicians to handle computer system faults (including hardware, software and communications) that are reported by users connected to the organization's computer network. The model attempts to simulate the assignment process of technicians, as carried out by the manager of a help desk. The model has been developed on the basis of a detailed study of the process of handling faults and the assignment of technicians in a number of organizations.In order to validate the model, simulation tests have been carried out, designed to compare the results of the model's assignment process, in hundreds of cases, against assignments carried out by experts who participated in the experiments. The results show that in 48% of the cases, the system's assignment of technicians was better than that of the experts, and that in 92% of the cases, the system achieved results as good or better than did the experts.     

Competency-based on-the-job training for aviation maintenance and inspection--a human factors approach.

More than 90% of the critical skills that an aviation maintenance technician uses are acquired through on-the-job training (OJT). Yet many aviation maintenance technicians rely on a 'degenerating buddy system', 'follow Joe around', or unstructured approach to OJT. Many aspects of the aviation maintenance environment point to the need for a structured OJT program, but perhaps the most significant is the practice of job bidding which can create rapid turnover of technicians. The task analytic training system (TATS), a model for developing team-driven structured OJT was developed by the author, and first introduced in Boeing Commercial Airplane Group to provide competency-based OJT for aviation maintenance and inspection personnel. The goal of the model was not only to provide a comprehensive, highly structured training system that could be applied to any maintenance and inspection task, but also to improve team coordination, attitude and morale. The first goal was accomplished by following the systems eight-step process, the latter through incorporating human factors principles such as decision making, communication, team building and conflict resolution into the process itself. In general, the process helps to instill mutual respect and trust, enhance goal-directed behavior, strengthen technicians' self-esteem and responsiveness to new ideas and encourage technicians to make worthwhile contributions. The theoretical background of the model is addressed by illustrating how the proven training methodologies of job task analysis and job instruction training are blended with human factors principles resulting in a unique team-driven approach to training. The paper discusses major elements of the model including needs identification, outlining targeted jobs, writing and verifying training procedures, an approval system, sequencing of training, certifying trainers, implementing, employing tracking mechanisms, evaluating, and establishing a maintenance/audit plan. Relevance to industry. TATS has been successfully installed in several maintenance and inspection areas of The Boeing Company. Four major U.S. airlines--United Airlines, TransWorld Airlines, Northwest Airlines, and USAirways have participated in two years of development and field testing in their maintenance operations (assisted by the author and Dr. Barbara Kanki of NASA Ames Research Center).     

An improved MIP-based approach for a multi-skill workforce scheduling problem

This paper deals with scheduling complex tasks with an inhomogeneous set of resources. The problem is to assign technicians to tasks with multi-level skill requirements. Here, the requirements are merely the presence of a set of technicians that possess the necessary capabilities. An additional complication is that a set of combined technicians stays together for the duration of a work day. This typically applies to scheduling of maintenance and installation operations. We build schedules by repeated application of a flexible matching model that selects tasks to be processed and forms groups of technicians assigned to combinations of tasks. The underlying mixed integer programming (MIP) model is capable of revising technician-task allocations and performs very well, especially in the case of rare skills.     

Symphony和I/A series系统功能的对比分析

为使从事集散控制系统设计与应用的热控专业技术人员尽快掌握不同厂家生产的集散控制系统,从集散控制系统的网络通信、硬件配置和软件结构三个方面,对Symphony和I/A series系统的功能进行了对比分析,阐述了两者之间的对应关系及主要区别,给出了分析结果。这对从事集散控制系统设计与应用的热控专业技术人员具有一定的参考价值。     

Effects of CSCW on organizations

We consider the potential impact of Computer Supported Cooperative Work, with special reference to large technically advanced projects involving several organizations. It is vital that such projects are managed efficiently, without delays, since a product that reaches the market a few months earlier than its competitors enjoys a great advantage. Traditional methods of coordinating large projects, based on hierarchical communication, tend to produce delays, since technicians at remote sites are obliged to solve coordination problems by passing them up the hierachy. It would be better if such problems were solved by improvising conferences among the technicians; Computer Supported Cooperative Work will provide the technical means of implementing this heterarchical style of management without losing control of the project. The use of computers as a social medium raises methodological and ethical issues which are discussed in the final section.     

Visual Analytics in Dental Aesthetics

Dental healthcare increasingly employs computer-aided design software, to provide patients with high-quality dental prosthetic devices. In modern dental reconstruction, dental technicians address the unique anatomy of each patient individually, by capturing the dental impression and measuring the mandibular movements. Subsequently, dental technicians design a custom denture that fits the patient from a functional point of view. The current Workflow does not include a systematic analysis of aesthetics, and dental technicians rely only on an aesthetically pleasing mock-up that they discuss with the patient, and on their experience. Therefore, the final denture aesthetics remain unknown until the dental technicians incorporate the denture into the patient. In this Work, we present a solution that integrates aesthetics analysis into the functional Workflow of dental technicians. Our solution uses a video recording of the patient, to preview the denture design at any stage of the denture design process. We present a teeth pose estimation technique that enables denture preview and a set of linked visualizations that support dental technicians in the aesthetic design of dentures. These visualizations assist dental technicians in choosing the most aesthetically fitting preset from a library of dentures, in identifying the suitable denture size, and in adjusting the denture position. We demonstrate the utility of our system with four use cases, explored by a dental technician. Also, we performed a quantitative evaluation for teeth pose estimation, and an informal usability evaluation, with positive outcomes concerning the integration of aesthetics analysis into the functional Workflow.     

Computer simulation and discrete-event models in the analysis of a mammography clinic patient flow

OBJECTIVE: This work develops a discrete-event computer simulation model for the analysis of a mammography clinic performance. MATERIAL AND METHODS: Two mammography clinic computer simulation models were developed, based on an existing public sector clinic of the Brazilian Cancer Institute, located in Rio de Janeiro city, Brazil. Two clinics in a total of seven configurations (number of equipment units and working personnel) were studied. Models tried to simulate changes in patient arrival rates, number of equipment units, available personnel (technicians and physicians), equipment maintenance scheduling schemes and exam repeat rates. Model parameters were obtained by direct measurements and literature reviews. A commercially-available simulation software was used for model building. RESULTS: The best patient scheduling (patient arrival rate) for the studied configurations had an average of 29 min for Clinic 1 (consisting of one mammography equipment, one to three technicians and one physician) and 21 min for Clinic 2 (two mammography equipment units, one to four technicians and one physician). The exam repeat rates and equipment maintenance scheduling simulations indicated that a large impact over patient waiting time would appear in the smaller capacity configurations. CONCLUSIONS: Discrete-event simulation was a useful tool for defining optimal operating conditions for the studied clinics, indicating the most adequate capacity configurations and equipment maintenance schedules.