一个统一的程序验证框架

本文提出了一个简单的方法，其中程序和其性质都由一个逻辑：时序逻辑中的公式表示．文中给出了一个程序的转换模块的定义，提出了时序执行语义的概念．它是一个时序公式，精确地说明了一个程序．将时序逻辑作为规范语言，程序正确性就意味着说明程序的公式蕴含说明性质的公式，其中蕴含即为一般的逻辑蕴含．因此，本文的方法为并发程序的规范及验证提供了一个统一的框架．它允许充分利用现有的用于证明并发系统时序性质的各种完全证明系统．一个缓冲系统的简单例子用来说明本文的方法．此例子表明本文的方法是可行的.     

C语言与AutoCAD接口研究

Ｃ语言与ＡｕｔｏＣＡＤ的结合，为ＣＡＤ工作提供了极其强大而有效的手段。本文介绍了Ｃ语言与ＡｕｔｏＣＡＤ的连接方式，应用程序中函数的定义、调用、参数传递以及数据的存储结构等。阐述了应用程序的编译、连接、安装和内存分配问题，还展示了一个绘制机械零件图形的应用程序实例。     

Phosphate exchange characteristics of wet and dried sediment samples from a hypertrophic reservoir: Implications for the measurements of sediment phosphorus status

This paper examines changes in the phosphate exchange characteristics induced in sediment samples by drying during preparation for analysis. Comparison of selected sediment parameters measured in wet and dried subsamples of a range of sediments from hypertrophic Hartbeespoort Dam showed that air drying resulted in major changes in their physical and chemical composition. Particle size distribution in the dried sediments showed a shift towards larger particles, particularly in samples in which smaller particles were abundant, indicative of irreversible aggregation of finer particles. Drying decreased the bioavailable phosphorus (NTA-extractable) content of sediments but reduced the phosphate buffering capacity and increased the phosphate equilibrium concentrations by a factor of 3, thereby increasing the phosphate release potential of dried sediments. Since sediment phosphorus status is often studied with a view to assessing the role of sediments in phosphorus cycling and eutrophication control, it is concluded that inappropriate decisions could result from the use of dried samples for analysis. The implications of these results in the marginal zones of lakes, which experience natural dehydration during periods of draw-down, are discussed.     

The CBP Parameter: A Module Characterization Approach for DSP Software Optimization

Memory consumption is an important metric for DSP software implementation. In this paper, we develop a module characterization technique that promotes more economical use of memory resources at the system level. Our work is developed in the context of software synthesis from signal/video/image processing applications expressed as synchronous dataflow (SDF) graphs. SDF is a restricted form of dataflow where each computational module (actor) consumes and produces a fixed number of data values (tokens) on each execution. Usually, no assumption is made about when during the execution of an actor, the tokens are actually consumed and produced; the firing of an actor is treated as an atomic event for most purposes. However, we show in this paper that it is possible to concisely and precisely capture key properties pertaining to the relative times at which tokens are produced and consumed by an actor. We show this by introducing the consumed-before-produced (CBP) parameter, which provides a general method for characterizing the token transfer of an SDF actor. Good bounds on the CBP parameter can aid an SDF compiler in performing more aggressive optimizations for reducing buffer sizes on the edges between actors. We formally define the CBP parameter; derive some useful properties of this parameter; illustrate how the value of the parameter is derived by examining in detail the multirate FIR filter, which is a fundamental actor in multirate signal processing applications; and examine CBP parameterizations for several other practical SDF actors.     

铜酞菁缓冲层改善有机电致发光器件性能的机理研究

利用铜酞菁薄膜充当缓冲层，研究了缓冲层对有机电致发光器件性能的影响，研究结果表明含有铜钛菁缓冲层的器件性能时显优于不含有缓冲层的器件，加入铜酞菁冲层后器件发光稳定性也得到了改善。本文对相关机理进行了探讨，分析认为，铜酞菁本身的热稳定性和它能够降低空 穴注入势垒的性质是提高器件性能的主要原因。     

可编程多轴控制器的开放式数控系统

采用开放式运动控制器作为下位机、PC平台和Win9x/NT操作系统作为上位机的结构，组建双CPU开放式数控系统。在开放式软件设计中，采用了类的封装和继承技术，不同功能模块间以及功能模块和系统内核间采用基于客户机和服务器模型的通信技术。利用旋转缓冲区技术，实现了上位机和下位机之间任意大小的数据文件下载。将该数控系统应用于工程实际中，验证了系统的开放性和实用性。     

VBR MPEG-2业务统计复用特性的研究

VBR MPEG－2业务是ATM网络中的重要视频业务类型。本文建立了两个流体流视频复用模型，对其信元丢失率和传输延时特性进行了定性分析，得到了一些重要结论。通过对VBR MPEG－2业务进行复用仿真，验证了这些结论，并对业务源参数、复用缓冲器容量、业务强度与信元丢失率、传输延时特性之间的关系进行了分析。对ATM交换机和复用器的设计与性能分析具有一定指导意义。     

Internet中分组丢弃缓存管理技术的研究

Internet中，基于分组丢弃的缓存管理技术是分组转发设备的重要功能模块，其算法对网络性能会产生重大影响。本文对现有主要的分组丢弃技术及其派生算法作了总结，并就存在的问题和不足提出了研究建议。     

计算机高速网络的拥塞控制:一种基于速率的PI方法

本文运用现代控制理论和方法,针对计算机高速互联网中最大服务交通流即能控交通流的调节问题,提出了一种基于速率的具有比例加积分(PI)控制器结构的拥塞控制理论和方法.在单个节点的交通流的模型基础上,运用控制理论中系统稳定性分析方法,讨论如何利用信终端节点缓冲占有量的比例加积分的反馈形式来调节信源节点的能控交通流的输入速率,从而使被控网络节点的缓冲占有量趋于稳定;同时使被控网络节点的稳定队列长度逼近指定的门限值.仿真结果显示,在所设计的PI控制方案下,网络的有关性能较好.     

Potentiodynamic behaviour of tin in different buffer solutions

The anodic oxidation of tin in carbonate-bicarbonate solutions covering a wide range of pH and electrolyte composition has been studied by voltammetric techniques and scanning electron microscopy (SEM). The influence of switching potentials, potential scan rate, rotation speed and surface condition are reported. SEM micrographs of the electrode surface show considerable differences in the characteristics of the surface products, whether they were formed in the potential region of the electroformation of stannous oxide and hydroxide or Sn(IV)-containing species which dehydrates into the most stable species. From the dependence of the charges on the potential scan rate it may be inferred that a direct oxidation of Sn(0) to Sn(IV) exists besides the sequence Sn(0) to Sn(II), and Sn(II) to Sn(IV). The effect of the initial surface state on the anodic reactions is better recognized for a rotated electrode. Analysis of the first and second voltammetric cycles through the changes of the anodic current densities with rotation speed, suggests that the initial electrooxidation process at a freshly prepared electrode surface does not follow a dissolution-precipitation mechanism. The formation of soluble corrosion products is enhanced in the potential range of the secondary passivity as the ionic strength of the buffer increases.