VISA事件机制的分析、设计与实现

VISA是虚拟仪器体系结构的简称,为虚拟仪器提供了标准化的I/O接口软件规范.事件是指VISA系统内部或外部需要应用程序响应的消息,是VISA资源和VISA应用程序之间的通信手段.事件机制是VISA机制体系的一个重要组成部分,其目的是提醒应用程序注意到某些特殊情况的发生.VISA提供了6个标准函数接口用于事件机制,但并未给出函数的具体实现方法.本文在分析了VISA的事件机制模型和两种事件处理机制的基础上,详细全面地给出了VISA事件函数的设计思想和实现方法.     

任务调度问题机制设计

讨论分布环境中的算法问题,即网络上的计算机不执行给定的算法,而是执行最利于其主人工作的情况。作为这样的参与者即操纵算法的代理,算法设计者应事先确保代理的利益通过真实报告是最大的。引用了机制设计的概念,主要讨论了一个具有代表性的问题一任务调度问题。该问题不能通过标准的机制设计的方法去实现,因此,文中提出了几种特别方法,包括近似机制、随机机制以及验证机制。     

SNMPvl、SNMPv2c和SNMPv3协议结构的分析与比较

本文从数据定义语言、管理信息库、协议操作规范及安全与访问控制这四个方面,对SNMP协议的三个版本进行了横向比较,有助于对SNMP协议的了解和使用.     

建立应急机制的制度基础

最近若干年里，建立应急机制，应付突发事件，成了热门话题。比如，反恐应急机制、恶性犯罪应急机制、石油危机应急机制、农业问题应急机制、外交应急机制、生态灾难应急机制等。在过去几个月的非典期间，建立公共卫生事件应急机制又成了热门话题。     

一种基于诚实机制的最优负载分配方法*

为了激励代理参与机制合作和提高系统性能,提出一种新的最优负载分配算法;对输出函数的单调性给出一种新的、简单的证明方法;给出机制设计及实现方法。理论分析及仿真实验结果表明,应用该机制设计,可以激励计算机代理诚实地向系统报告它们的类型值(计算机真实的处理能力),以最小化系统总体响应时间;该任务分配算法优于现有的同类算法。     

并行与分布式仿真时间推进同步机制综述

并行分布仿真对复杂大规模动态系统的研究以及探索,对长远的应用提供了便利,目前已成为研究的热点。然而时间同步管理是关注并确保并行分布仿真正确执行的一种机制,它不但要确保正确的执行因果逻辑关系,而且要保证仿真系统的可重复性。时间管理是影响并行分布仿真系统高效运行的重要因素之一。在分别论述四类基本的时间推进同步机制,即保守机制、乐观机制、混合机制和自适应机制的同时,还分析了各自的优缺点,指出了今后的研究发展方向。     

关于物理符号机制与联接机制的集成

近几年来正在兴起物理符号机制(专家系统、基于知识系统等)与联接机制(神经网络)集成的研究,国外也已取得了一定的研究成果,引起关注。长期来两种机制一直处于完全独立地、甚至可以说对立地发展着,何以又能朝结合的方向发展,采用何种方法和途径来实现两者的结合呢?本文仅就这二个问题发表一些看法。     

基于IPFS生物数据的存储传输

随着生物数据的价值被不断地挖掘出来,对其进行有效存储和高效地传输变得尤为重要。论文通过结合星际文件系统(Interplanetary File System,IPFS),提出了基于IPFS的生物数据存储传输系统,用来提高生物数据的存储传输效率;在生物数据传输方面,引入了数据交换机制和秒传机制来提高生物数据传输速度;在生物数据存储方面,通过采用一种高效的数据存储结构和引入版本控制机制来提高生物数据存储效率。与此同时,通过对生物数据的存储传输进行了深入调研,并进行对比实验验证系统的效果,实验结果表明,相比于HTTP、FTP的存储传输效率,论文提出的系统具有较高的存储效率与传输速度。     

一种简单高效的移动agent控制机制

移动agent的控制机制包括移动agent的定位、终止和孤儿检测机制,该机制在移动agent系统中起着非常重要的作用。目前对agent的各种定位机制研究较多,对后两种机制研究较少,因此当前的移动agent系统大多不具备孤儿检测的能力。本文在分析研究各种控制机制的基础上,指出现有的能量机制和影子机制实现孤儿检测能力所面临的问题,而后提出了一种利用权值和路径代理机制相结合的移动agent控制机制,该机制不仅能定位移动agent的位置,而且还能有效地检测和处理在网络某结点的孤儿agent,也能根据需要终止移动agent的执行,从而能及时有效地回收被无用agent占用的软硬件资源,同时还避免了能量和影子机制的缺点,是一种较理想的控制机制。另外,该机制还具有实现简单、灵活性强等优势。     

计算机病毒基础知识

随着计算机的发展和互联网的普及，计算机中的信息也显得越来越重要。但与此同时，计算机病毒的种类也迅速增加，并很快蔓延至全世界，对计算机的安全构成了巨大的威胁。计算机病毒是一种附着在其他程序上的可以实现自我“繁殖”的程序代码。计算机“病毒”一词最早是由美国计算机病毒研究专家Fcohen博士提出的。“病毒”一词是借用生物学中病毒的概念。我们可以发现它在很多方面都与生物病毒有相似之处。计算机病毒的破坏行为体现在病毒的杀伤力。病毒破坏的激烈程度取决于病毒作者的主观愿望和他所具有的技术力量。数以万计不断发展扩张…     

The influence of IT: perspectives from five Australian schools

Abstract Information and Communication Technologies (ICT) are now widespread in Australian schools but with variation in how, where, when and how much they are used. Computers may be located in a computer laboratory, distributed throughout the school, or students may use their own laptop computers. IT may be a subject in its own right or ICT may be used across all areas of the curriculum. It is how ICT is used in the school setting that is important in providing students with the skills to be participate in a 'knowledge society'. This paper examines the ways in which information and communication technologies influence teaching and learning in five Australian schools. Data were gathered through observation, interviews and document analysis in schools operating at the elementary and secondary grades in relatively technology rich environments. Each of the schools participated in the Australian component of the Second Information Technology in Education Study – Module 2 (SITES-M2) of innovative pedagogical practices. Several of the studies were of specific projects where ICT was the key enabler of the learning programme. Others focused on an entire school's approach to ICT as an agent for changed approaches to learning.     

利用MODIS EVI时间序列数据分析福建省植被变化(2000~2017年)

以全国森林覆盖率最高的福建省为研究对象,利用2000~2017年夏季的MODIS EVI植被指数数据和气象与非气象因子进行协同分析,以揭示近17年福建植被的时空变化及其影响因子。结果表明:研究期内福建的EVI均值整体上升,从2000年的0.454上升至2017年的0.505,17 a间上升了11.2%,表明福建省的植被整体处于变好的状态,且在中部和西南部的变化最明显。相关分析表明,在研究期内,气象因子(气温和降水)对EVI变化的影响不显著,植被的变好主要为非气象因子的作用。EVI的提高主要得益于2003年福建省建设生态省后森林覆盖率的提高,并和2012年开始的水土流失治理有明显关系,这说明人类活动的积极作用对福建植被的变好起到了关键的作用。     

Back to the Future: An Historical Perspective on the Pendulum-Like Changes in Literacy

This article focuses on the pendulum-like change in the way people read and use text, which was triggered by the introduction of new reading and writing technologies in human history. The paper argues that textual features, which characterized the ancient pre-print writing culture, disappeared with the establishment of the modern-day print culture and has been “revived” in the digital post-modern era. This claim is based on the analysis of four cases which demonstrate this textual-pendulum swing: (1) The swing from concrete iconic-graphic representation of letters and words in the ancient alphabet to abstract phonetic representation of text in modern eras, and from written abstract computer commands “back” to the concrete iconic representation in graphic user interfaces of the digital era; (2) The swing from scroll reading in the pre-print era to page or book reading in the print era and “back” to scroll reading in the digital era; (3) The swing from a low level of authorship in the pre-print era to a strong authorship perception in the print era, and “back” to a low degree of authorship in the digital era; (4) The swing from synchronic representation of text in both visual and audio formats during the pre-print era to a visual representation only in print, and “back” to a synchronic representation in many environments of the digital era. We suggest that the print culture, which is usually considered the natural and preferred textual environment, should be regarded as the exception.     

A Review of:“Safety in Manual Materials Handling.” By COLIN G. DRURY. (Cincinnati: US Dept. of Health,Education & Welfare, 1978.) [Pp. viii+ 209.]

The extension force against resistance was recorded in 23 postures for 12 subjects to find explanations for the decrease in back strength in asymmetric postures. A reduction in muscle force in asymmetric postures was found up to 40%, but was strongly dependent on the plane in which asymmetry occurred, and on the posture to which it referred. A quantitative relationship between the forces exerted in different asymmetric postures is discussed, as a basis for formulating universal ergonomic guidelines for optimal working postures. The reduction in force in different asymmetric postures can be explained by length of the muscle, the activation of the muscle, and the moment angle of the muscle.     

北半球及典型区雪深时空分布与变化特征

基于欧空局的GlobSnow雪水当量数据集和国家青藏高原科学数据中心的北半球长时间序列雪深数据集NHSD研究了北半球及9个典型区的雪深时空分布与变化特征。结果表明：北半球1988~2018年平均雪深总体呈显著下降趋势（p<0.01）,年际变化幅度为-0.55 cm·（10 a）^-1。在高纬度地区,加拿大北部和阿拉斯加年平均雪深下降明显（p<0.01）,下降速率分别为3.48 cm·（10 a）^-1和3 cm·（10 a）^-1,两地区月平均雪深在冬季显著下降。西西伯利亚平原和东欧平原年平均雪深呈下降趋势,其中东欧平原雪深下降较为明显（p<0.01）,变化速率为-2.3 cm·（10 a）^-1,两地区的月平均雪深在春季显著下降,其中5月份最为明显。东西伯利亚山地的雪深年际变化呈增加趋势,除堪察加半岛外,其月平均雪深在冬季呈显著增加趋势。对于高山区,阿尔卑斯山脉和落基山脉的年平均雪深呈缓慢增长趋势,而青藏高原地区雪深呈缓慢下降趋势。阿尔卑斯山脉的月平均雪深在冬季呈显著增加趋势,5月份显著减小。落基山脉和青藏高原雪深变化呈现出空间异质性：在整个研究时段,落基山脉北部月平均雪深呈下降趋势,中部和南部呈上升趋势;青藏高原的北部边缘山脉雪深呈显著上升趋势,中部大多数地区呈下降趋势。喜马拉雅山脉的北坡雪深增加,南坡雪深减小,但其变化率绝对值小于0.5 cm·a^-1。东南部雪深较大的念青唐古拉山脉冬季雪深呈显著下降趋势。对9个典型区雪深的年内分析（2001~2010年平均值）结果显示：高山区雪深峰值远低于高纬度地区雪深峰值。除青藏高原外,高山区的积雪融化起始日期明显早于高纬度地区。     

A new mining approach for uncertain databases using CUFP trees

In the past, many algorithms have been proposed to mine frequent itemsets from transactional databases, in which the presence or absence of items in transactions was certainly known. In some applications, items may also be uncertain in transactions with their existential probabilities ranging from 0 to 1 in the uncertain dataset. Apparently, the processing in uncertain datasets is quite different from those in certain datasets. The UF-tree algorithm was proposed to construct the UF-tree structure from an uncertain dataset and mine frequent itemsets from the tree. In the UF-tree construction process, however, only the same items with the same existential probabilities in transactions were merged together in the tree, thus causing many redundant nodes in the tree. In this paper, a new tree structure called the compressed uncertain frequent-pattern tree (CUFP tree) is designed to efficiently keep the related information in the mining process. In the CUFP tree, the same items will be merged in a branch of the tree even when the existential probabilities in transactions are not the same. A mining algorithm called the CUFP-mine algorithm is then proposed based on the tree structure to find uncertain frequent patterns. Experimental results show that the proposed approach has a better performance than UF-tree algorithm both in the execution time and in the number of tree nodes.     

The Possibilities of Community OR in a Third World Country

This paper shows a few possibilities for the application of Community OR in a Third World country based on experience in Venezuela. These possibilities are discussed in a framework of the relationship between the state and community organizations. Emphasis lies in showing that Community OR in Venezuela requires a deep critical commitment to emancipation in order to help community organizations develop in a rather hostile environment. Lastly, results in dealing with community organizations in Venezuela using the Interpretive Systemology approach are presented.     

Tools for the job: a report of two surveys of information and communications technology training and use for literacy in primary schools in the West of England

Substantial investment has been made in improving computer hardware and raising the profile of information and communications technology (ICT) in English primary schools in recent years, in line with the belief that skills in ICT are essential for our future workforce ( DfEE/QCA 2000 ). This study compares practising teachers' responses in 1998 and 2001 to a questionnaire about the aims and uses of ICT in primary schools for literacy activities. It discusses the changes in what teachers want and their understanding of the task the government has given them to do. A commonly cited problem is finding time to absorb the new technology to maximise its pedagogic potential.     

Production control: Current developments and future trends

Manufacturing industry is going through a period of unprecedented change as a result of the developments in micro-electronic technology. This is bringing about a transformation not only in hardware, in the form of computer-aided manufacturing, but in the manner in which production is organised and controlled.It is in the latter connection that the present paper sets out to review current developments and future trends. In particular the machine readable bar-code is seen as a key element in extending computerised control to cover not only the machines, but tools, materials and parts and their movement in the development of fully integrated manufacturing systems.As the move towards automation gathers pace it is forecast that manufacturing industry will become more process industry like in form, with consequences for the way in which production is organised and controlled.Finally consideration is given to the manner in which these current developments in the field of production are giving rise to a structural alteration in industrial labour requirements in which, in the future, fewer people will be required but on highly enriched work tasks.