Discrete event systems with stochastic processing times

Discrete event dynamic systems are studied in which the underlying algebra is the max-algebra and the coefficients in the system, referring to processing times in practice, are stochastic. The processing times and/or the transportation times within a network show stochastic fluctuations. The restrictions are that the stochastic processing times of the nodes in the network are independent and identically distributed. The asymptotic behavior of the system is investigated, and the average duration of one cycle of the process is calculated. A specific example of the theory is considered. The state space is two-dimensional, and the probability distributions are exponential. It is shown that the process approaches a stationary limit as time proceeds. The case when the probability distributions are discrete is also treated. Several examples are given. Two-dimensional systems and, more generally, finite-dimensional systems are considered     

基于覆盖的构造性学习算法SLA及在股票预测中的应用

覆盖算法是神经网络学习算法中的一个十分有效的方法，它克服了基于搜索机制的学习方法和规划学习方法计算复杂性高，难以用于处理海量数据的不足，为神经网络提供一个构造性的学习方法，但该方法是建立在所有训练样本都是精确的假设上的，未考虑到所讨论的数据具有不精确的情况，若直接将该方法应用于数据不精确情况，所得到效果不理想．主要讨论数据具有不精确情况下的时间序列的预测问题，为此将原有的覆盖算法进行改进，引入“覆盖强度”和“拒识样本”的概念，并结合这些新概念给出相应的覆盖学习算法(简称SLA)，最后将SLA算法，应用于金融股市的预测，具体应用到以上(海)证(券)综合指数构成的时间序列的预测，取得了较好的结果，这表明了SLA方法的可行性和应用前景。     

Hierarchical data structures and algorithms for computer graphics.I. Fundamentals

The fundamentals of hierarchical data structures are reviewed and it is shown how they are used in the implementation of some basic operations in computer graphics. The properties of hierarchical structures are discussed, focusing on quadtrees and octrees. The latter are defined, some of the more common ways in which they are implemented are examined, and an explanation of the quadtree/octree complexity theorem is provided. Vector quadtrees and vector octrees are discussed. The performance of basic operations using quadtrees is considered     

大型水电站厂房结构流固耦联振动特性数值模拟

水电厂房内的多场耦合振动分析是工程界十分关心的问题.为了实现发电厂安全生产的目标,过去在对其进行共振校核时,往往只对结构进行模态分析,而忽略了流体的存在;但是厂房流道内存在着大量的流体,流体的存在改变了厂房结构的动力特性,是属于典型的流固耦合振动问题.因此,在对其进行共振校核时应该考虑流体的影响.由于机理的复杂性、建模、数值模拟的困难性,迄今为止关于这方面的分析研究成果很少.本文借助于2个实际工程,对厂房结构与流体复杂的耦合振动问题进行分析,并对其进行比较,详细的阐述了厂房结构-流体的耦合振动特点.本文的研究成果对于解决流体-结构相互作用问题具有重要的工程意义,同时对于解决其他类型的流固耦合振动问题也具有很高的参考价值.     

Global methods for stroke segmentation

Two methods for stroke segmentation from a global point of view are presented and compared. One is based on thinning methods and the other is based on contour curve fitting. For both cases an input image is binarized. For the former, Hilditch's method is used, then crossing points are sought, around which a domain is constructed. Outside the domain, a set of line segments are identified. These lines are connected and approximated by cubic B-spline curves. Smoothly connected lines are selected as segmented curves. This method works well for a limited class of crossing lines, which are shown experimentally. In the latter, a contour line is approximated by cubic B-spline curve, along which curvature is measured. According to the extreme points of the curvature graph, the contour line is segmented, based on which the line segment is obtained. Experimental results are shown for some difficult cases. Received October 31, 1998 / Revised January 12, 1999     

融合连续区域特性和背景学习模型的显著计算

为了提高显著性模型的计算效率,提出基于连续区域特性和背景学习的模型,分别提取图像的显著区域,并进行融合.首先计算区域显著目标像素与周围像素位置的距离,提出基于贝叶斯的区域显著性对比的度量方法.然后采用连续性区域合并,合并空洞区域与其最相似的邻居区域.之后采用3种典型的显著性算法处理同一幅图像,得到不同的显著特征图,采用反差法得到各特征图的背景,建立混合高斯背景模型,加权学习合成背景图,再与原图作差得到前景显著区域.最后结合细胞调节规律融合得到的显著区域.在SED1、ASD图像库中测试文中算法,所得的F-measure、平均误差都较优.     

Views on visualization

The field of visualization is maturing. Many problems have been solved and new directions are sought. In order to make good choices, an understanding of the purpose and meaning of visualization is needed. In this paper, visualization is considered from multiple points of view. First, a technological viewpoint is adopted, where the value of visualization is measured based on effectiveness and efficiency. An economic model of visualization is presented and benefits and costs are established. Next, consequences and limitations of visualization are discussed (including the use of alternative methods, high initial costs, subjectiveness, and the role of interaction). Example uses of the model for the judgment of existing classes of methods are given to understand why they are or are not used in practice. However, such an economic view is too restrictive. Alternative views on visualization are presented and discussed: visualization as an art, visualization as design and, finally, visualization as a scientific discipline.     

一种认知行为模式的概率化确定方法

研究认知行为模式的确定,提出一种认知行为模式的概率化确定方法,首先,简要介绍认知行为模式的SRK框架,分析三种认知行为模式的特点以及该框架在人因可靠性分析中的应用,然后,概述认知行为模式的确定方法-Hanaman决策树,分析该方法的特点以及存在的不足,强调在认知行为模式的确定过程中考虑不确定性的必要性.随后,将不确定性...     

某型无人机导航/飞控系统设计与仿真

某型无人机以DSP为核心部件,介绍了其导航/飞控系统硬件设计、结构,其中主要包括数据采集、数据通信,介绍了导航/飞控软件,给出流程框图,设计了用于验证该系统的仿真系统;仿真系统引入大气模拟系统和GPS模拟系统,介绍大气模拟系统结构原理和GPS工作原理,仿真各子系统之间采用CAN总线进行连接,并且挂载真实舵机,检测舵机偏转检测,形成负反馈;最后,给出系统仿真步骤和仿真内容,得出仿真结果,验证该系统可行、正确.     

关于神经网络的能量函数

能量函数在神经网络的研究中有着非常重要的作用,人们普遍认为：只要能量函数沿着网络的解是下降的,能量函数的导数为零的点是网络的平衡态,能量函数有下界,则网络是稳定的且网络的平衡态是能量函数的极小点,文中取反例说明上述条件下不能保证网络的稳定性,并取例说明即使网络稳定也不能保证网络的平衡态与能量函数的极小点,证明了在网络具有上述条件的能量函数的情况下网络稳定的充分必要条件是网络的解有界,讨论了网络的平     

A goodness-of-fit test for normality based on polynomial regression

Statistical models are often based on normal distributions and procedures for testing such distributional assumption are needed. Many goodness-of-fit tests are available. However, most of them are quite insensitive in detecting non-normality when the alternative distribution is symmetric. On the other hand all the procedures are quite powerful against skewed alternatives. A new test for normality based on a polynomial regression is presented. It is very effective in detecting non-normality when the alternative distribution is symmetric. A comparison between well known tests and this new procedure is performed by simulation study. Other properties are also investigated.     

二维剪切排样的束搜索启发式算法

针对约束二维矩形剪切排样问题,提出了一种基于束搜索的三阶段剪切排样算法。其切割过程包括三个阶段：板材剪切成段,段剪切成条带,条带切割成准确尺寸毛坯。采用动态规划确定段的价值,复杂度低的拼接递推不同长度子板的初始价值和板材的初始可行解,束搜索优化板材的排样方式。束搜索的节点用矩形对表示,分别是段组合而成的局部方式和未填充的剩余子板。以局部方式价值与剩余子板的初始价值之和作为节点的估计值。按估计值选择精英节点继续分支,其他节点直接删除不再回溯。实验结果表明该算法可缩短三阶段同质排样的计算时间,且所获得的余料大,利于余料的回收管理和再利用。     

软件理解研究与进展

软件理解是进行软件维护的一个重要步骤,是一个逐层推进的递增模式匹配过程。软件理解由任务,策略,概念,模型,方法和工具等环节组成。文中分析了软件理解的任务和策略。对软件理解的各种模型进行了比较,详细论述了目前活跃在学术界的各种软件理解方法,并对目前存在的各种软件理解工具或环境进行了归类和比较。     

多属性决策的Vague集方法

对多属性决策问题和信息集结问题进行了研究,分析了已有Vague集方法,并通过例子说明其不足之处.提出了一种多属性决策的Vague集方法.定义了方案对目标的支持(反对、中立)度等概念,利用目标优属度矩阵对属性值及属性权重进行集结,从而得到方案的Vague估计值.定义正(负)理想Vague值,并用TOPSIS法对方案进行排序和选优.算例验证了该方法的有效性和可行性.     

A new way to stabilize discrete-time plants under compact uncertainty

A method is proposed for stabilization of uncertain discrete-time plants of which only compact sets are known to which plant parameters and exogenous perturbations belong. The parametric family of feedbacks is quantified and subsequently a stabilizing feedback is localized on the resultant finite discrete set by using on-line measurements of the state path. This method is termed locatization. Its salient features are quantification and the localization algorithm. Three localization procedures are described which are used under various assumptions on the form of the uncertainty. Solvability conditions are provided for the stabilization problem and estimates of transient processes are reported.     

基于Horn逻辑扩展模型的安全协议反例的自动构造

根据安全协议的Horn逻辑扩展模型和相应的安全协议验证方法,提出了自动构造不满足安全性质的安全协议反例的求解策略,并给出了重要定理的证明,设计了一系列自动构造协议攻击的构造算法,并在基于函数式编程语言Objective Caml开发的安全协议验证工具SPVT中实现了这些算法,给出了主要算法的优化方法,详细分析了主要算法的时间复杂度,从理论上证明了算法是线性时间算法.最后,用SPVT对一些典型的安全协议进行了验证,得到了不安全协议的反例,并对反例进行了分析.得到的反例非常方便于阅读,与Alice-Bob标记非常接近,从而使任何领域的专家都可以用这种形式化的方法检查安全协议是否存在真实的反例.     

一种语料缺乏条件下的藏语音素自动切分方法

藏语语音合成及语音学研究中,经常需要切分音素。人工切分费时费力,但是由于藏语语料缺乏,训练的藏语声学模型不够精确和鲁棒,自动切分的音素边界不够准确。以藏语拉萨方言为研究对象,在确定拉萨方言音素集、建立拉萨方言发音词典的基础上,通过计算音素模型间的距离,确定了拉萨方言和英语的共同音素,融合拉萨方言和英语GMM HMM模型,并自动判断语音中的静音和短时停顿,构造语音对应的词网络,查询发音词典,将词网络扩展为模型（音素）网络,使用Viterbi算法将每一帧特征参数对应到模型的每一个状态上,进而对音素进行切分。实验表明,切分效果要优于单纯的藏语模型方法。     

锅炉汽包水位三冲量控制的水位补偿计算及应用

锅炉汽包水位主要采用三冲量控制,但是汽包中汽液的密度变化造成水位测量不准,从而导致控制效果变差。本文采用多测孔技术各增设了三块现场仪表来分别测量汽包的实时温度和压力,进而对汽包水位进行补偿计算,并在DCS系统进行了组态和现场应用。实际应用效果表明提高了水位测量精度,满足了汽包控制及联锁的要求。     

Inference of finite-state transducers from regular languages

Finite-state transducers are models that are being used in different areas of pattern recognition and computational linguistics. One of these areas is machine translation, where the approaches that are based on building models automatically from training examples are becoming more and more attractive. Finite-state transducers are very adequate to be used in constrained tasks where training samples of pairs of sentences are available. A technique to infer finite-state transducers is proposed in this work. This technique is based on formal relations between finite-state transducers and finite-state grammars. Given a training corpus of input-output pairs of sentences, the proposed approach uses statistical alignment methods to produce a set of conventional strings from which a stochastic finite-state grammar is inferred. This grammar is finally transformed into a resulting finite-state transducer. The proposed methods are assessed through series of machine translation experiments within the framework of the EUTRANS project.     

粒及粒计算在逻辑推理中的应用

讨论了信息粒的结构及其实例。基于Rough集方法定义了决策规则粒,构造了决策规则粒库,它被用作逻辑推理。定义了粒语言,描述了这种语言的语法、语义、粒语句的运算法则和粒之相关的几个性质。定义了粒之间的相互包含(inclusion)和相似(closeness)。基于这些概念,构造了一种逻辑推理的新模型。这种推理模式的特点在于它既是逻辑的又是集合论的。所谓逻辑的就是说推理是遵循一种逻辑运算;所谓集合论的是指这种推理可利用对应于这种逻辑公式的意义集的运算进行推理,还用实例说明了这种推理模式是可行和有效的。