一种基于正弦映射的混沌交织器设计及应用*

移动信道编码中交织器的设计直接影响Turbo码的距离谱和性能,其主要作用是提高低重序列的输出码重和减小译码输出之间的相关性。随机交织器在数据帧较长时性能比较好,通过码序列位置重置实现交织,利用正弦函数的混沌映射有很好的随机性和瞬时正交性的特点,实现了一种新型混沌随机交织器,提高了交织器的误码率性能,并且在伽利略卫星系统中应用达到接近理论值的编码效率和误码率的特性。     

ADL: An Activity Description Language for Real-Time Networks

This paper introduces and motivates ADL, a new formal notation for the specification of the temporal and functional behaviour of concurrent processes. ADL is tailored to be directly compatible with the DORIS design method. It combines a graphical Activity State-Machine (ASM) notation and a model-based Activity Functional Behaviour (AFB) notation. The abstract syntax, and static and dynamic semantics for the ASM notation are given, the dynamic semantics being given proof-theoretically in many-sorted logic extended with the RTL ‘occurrence’ relation, Θ, and the ERTL ‘holding’ relation, Φ. ADL is used to specify a small network, and proofs are given of its timeliness and safety properties. Received November 1998 / Accepted in revised form May 2000     

Triggered Updates for Temporal Consistency in Real-Time Databases

A real-time database systemhas temporal consistency constraints in addition to timing constraints.The timing constraints require a transaction to be completedby a specified deadline, and the temporal consistency constraintsrequire that temporal data read by a transaction be up-to-date.If a transaction reads out-of-date data, it will become temporallyinconsistent. A real-time database system consists of differenttypes of temporal data objects, including derived objects. Thevalue of a derived object is computed from a set of other objects,known as the read-set of the derived object. The derived objectmay not always reflect the current state of its read-set; a derivedobject can become out-of-date even if its read-set is up-to-date.Any subsequent transaction reading the derived object will thenbecome temporally inconsistent. In this case, in order to readup-to-date objects, a transaction will have to wait until someother transaction updates the out-of-date object. However, indoing so, the waiting transaction may miss its deadline, particularlyif the update is not periodic but instead arrives randomly. Wepropose to update the outdated objects so that not only is thetemporal consistency improved, but also the number of misseddeadlines does not increase significantly, and as a result thereis an overall improvement in the performance of the system. Wepropose, implement and study a novel approach, to be known astriggered updates, to improve temporal consistency in firm real-timedatabase systems when updates are not periodic. We identify propertiesof triggered updates and explain how they work by giving bothan intuitive and a probabilistic analysis. We present strategiesfor generating triggered updates, discuss their suitability invarious contexts and perform a detailed simulation study to evaluatetheir performance. Results show that it is possible to improvetemporal consistency without degrading the timeliness of real-time database systems to a great deal.     

一种无线传感器网络双要素用户认证会话机制

针对无线传感器网络中外部用户直接访问内部传感器节点的安全威胁,提出了一种基于双要素用户认证方案的简单会话机制.该机制通过智能卡和密码两种因素来验证用户的有效性,并根据可供管理员配置的时间间隔来确定用户在会话中的状态,进而根据用户状态来限制其可用操作.该机制有效地缓解了用户认证单次有效的通信压力,且避免了用户认证长期有效的安全风险,同时它也为外部用户查询无线传感器内部节点的应用层增加了可实现性.     

酸化油生物柴油磁场降黏与超声波降黏试验研究

分别采用磁场及超声波对酸化油生物柴油进行了降黏试验研究.结果表明:在磁场降黏试验中,磁感应强度为580 mT,磁化时间为15 h时,降黏率最大为6％,但降黏效果具有时效性;在超声波降黏试验中,当超声波作用时间30 min,超声波作用强度70 W/cm2,超声波作用频率1.25 MHz,试样温度40℃时,最大降黏率为6.92％,静置150 min后降黏率为3.42％.     

基于时间序列提取信号特征的通用自动标检软件开发

为推行精益生产,提出一种基于时间序列提取信号特征值的通用自动标检软件开发的方法。从自动标定/ 检验工装通用架构及基于时间序列提取信号特征值2 方面,阐述基于多核多线程时间片轮转调度及依据既定信号类 型,基于分段时间序列借助约简算法快速提取信号特征值。结果表明：该方法在既定时段能可靠完成约定产品的标 定、检验与功能测试,优化生产排程,缩减约定产品生产周期。     

浅谈SNG在电视新闻直播中的应用

SNG实现了电视新闻事件的现场实况报道,让观众同步目睹新闻事件的发生,开启了非计划性的、非常态化的、动态性的电视新闻直播技术新篇章。文章首先介绍了SNG的概念及技术原理,接着分析了SNG对电视新闻直播的影响,最后对SNG在电视新闻节目中的应用形式和弱点进行了总结。     

The incremental benefits of changes in the timeliness of information

The managers of all purposeful organizations rely on historical information as an aid to decision making. Information enables managers to formulate expectations about the future. Less timely information is generally inferior because the manager's expectations will contain greater error; and the operating results obtained may therefore be less satisfactory. The timeliness of information often can be improved by incurring incremental systems costs. However, the degree to which such improvements will produce benefits is uncertain. This research uses modeling to explore the relationship between information timeliness and the benefits derived by implementing optimal decisions based upon the information. The most significant finding is that the shape of this relationship is dependent upon the scope of the action set available to the decision maker. If a continuous range of options is available (such as a pricing decision), then the relationship is linear. If only a few discrete options are present (as in linear programming) the relationship is more complex but describable. The decision maker is therefore found to be in a position to offer guidance to the systems designer which will facilitate enhancement of the benefit/cost characteristics of the organization's information resource.     

一种实用的面向Web的公平防抵赖协议

针对大多数电子政务和商务系统是基于Web架构开发,用户端表现为浏览器瘦客户端环境,所实现的防抵赖机制大都不满足公平性,现有的公平防抵赖协议由于交互的复杂性难以应用于实际环境的问题,提出一种新的在线可信第三方公平防抵赖协议.引入可信第三方减少通信双方之间的交互次数,将公平防抵赖功能嵌入到一次HTTP请求与应答交互中,并采用证据链接思想将证据签名验证与撤销检查集中由可信第三方完成,简化证据验证与管理,降低了用户端进行撤销检查与签名时间戳生成的操作开销.该协议具备公平性与及时性特点.     

元甲煤矿复合顶板工作面深孔注浆加固技术研究

针对元甲煤矿20103工作面复合顶板较为软弱,回采时频繁发生冒顶的问题,通过现场观测结合数值模拟对引起工作面冒顶的原因进行了分析,结果表明,煤壁片帮低是引起冒顶的关键因素。为提高煤体强度,提出在两巷打超前深孔,采用高渗透性易凝结浆体材料进行煤壁的注浆预加固,并对合理的注浆层位及最佳注浆时机进行了分析确定。现场应用效果表明,采用该注浆加固技术后,有效控制了工作面煤壁片帮及冒顶,保证了工作面的安全高效生产。