基于相似矩阵的折半属性约简算法

针对大多数属性约简算法时间复杂度比较高的问题,利用粗糙集理论提出了一种新的解决办法,该方法基于相似矩阵概念,利用属性在相似矩阵中出现的频率给出了属性重要性的计算公式,以此作为启发式知识来约间决策表中的冗余属性,并将折半查询的思想运用到算法中以加快约简的速度。实验表明该算法是简单有效的.     

基于粗糙集约简的生产成本决策

成本决策是成本管理的重要环节,为了将先进的人工智能方法融入生产成本决策过程中,并使得决策因素最小化,在深入研究粗糙集理论的基础上,提出了一种新的基于区分矩阵的最小属性约简方法,并详细阐述了该方法的含义和性质,以及算法的搜索策略与执行过程,有效解决了任意相容决策表的最小属性约简问题,并结合现有改进的值约简算法,达到了决策...     

一种基于FPGA的改进粗糙集属性约简方法

粗糙集理论是一种新型的数学工具,主要用于分析处理模糊和不确定知识。属性约简是其中的一个重要环节。本文结合遗传算法,提出了一种基于FPGA改进的粗糙集属性约简方法,在原研究的基础上,先利用属性重要度求解决策表的核属性,再运用于属性约简,从而减少遗传操作的迭代次数,加快属性约简速度。     

基于平均多粒度决策粗糙集和NNBC的滚动轴承故障诊断

采用求同排异思想的悲观多粒度粗糙集是一种规避风险的决策策略,其限制条件过于苛刻,导致约简后的征兆属性集维数过低,难于对滚动轴承的状态做出准确判断。为此,提出一种基于平均多粒度决策粗糙集和非朴素贝叶斯分类器(Non-Naive Bayesian Classifier, NNBC)的滚动轴承故障诊断方法。该方法提取训练样本中滚动轴承的故障特征,用于构建平均多粒度决策粗糙集;采用基于平均多粒度决策粗糙集的属性约简算法,降低训练样本中征兆属性集的维数;根据约简后的训练样本构建NNBC,用于判断待诊样本中滚动轴承状态。实验结果表明该方法能够准确地判断滚动轴承的故障类型及故障程度。     

基于粗糙集与信息熵的不完备测试信息条件下故障诊断

针对测试信息不完备条件下故障诊断决策问题,引入粗糙集和信息熵方法。利用决策属性支持度求相对核,以此作为启发信息;通过建立属性知识与信息熵的联系,提出基于信息熵的属性约简方法。结合决策属性支持度和信息熵设计了约简算法流程,减少属性集搜索空间,求得到最优属性约简集。实例表明,该算法适用于协调的不完备决策信息系统和不协调的不完备决策信息系统,能够解决不完备测试信息条件下故障诊断决策问题。     

集值信息系统的属性约简

属性约简是粗糙集理论研究中的重要内容之一。本文主要研究集值信息系统的属性约简问题。在集值信息系统中基于拟序关系引入了信息量的概念,给出了属性特征的判定方法,以及信息量与属性约简之间的关系。根据信息量定义了属性重要性,研究了属性重要性与属性约简之间的关系。进而得到了基于信息量和属性重要性的属性约简算法,给出了该算法的时间复杂度。通过实例说明,该算法是有效的。     

基于粗糙集与最小二乘支持向量回归的汽轮机主蒸汽流量预测

针对传统主蒸汽流量计算方法的不足,提出了一种新的主蒸汽流量预测方法,该方法综合了粗糙集理论与最小二乘支持向量回归算法的优点,利用ROSETTA V1.4.41研究实验平台中的遗传约简算法对输入变量的属性进行约简,再利用最小二乘支持向量回归算法建立主蒸汽流量的预测模型。实验表明,与未经粗糙集理论处理过的BP神经网络、支持向量回归算法和最小二乘支持向量回归算法所建模型相比,该方法具有更好的预测精度和泛化能力,且建模速度显著提高。     

基于属性分辨力的决策表属性约简

决策表的属性约简,又称知识约简,是粗糙集理论最核心内容之一,最优属性约简是NP难问题。根据粗糙集理论,本文定义了特征集以及属性分辨力概念,提出了基于特征集和属性分辨的启发式搜索算法,在一定程度上提高了搜索效率。     

模糊决策属性约简及其在工位评估中的应用

受粗糙集理论中知识约简的启发,在模糊多属性决策理论中提出属性约简的概念,构建属性约简方法,寻求属性集合中所有最简单的保序属性约简子集以及属性约简核.用属性约简子集代替原有的属性集合,通常可以显著简化模糊多属性决策问题.还将此属性约简方法应用到生产线工位绩效评估中,表明此属性约简算法的实用性.     

模糊粗糙集在轴承故障模式识别中的应用

提出一种基于模糊粗糙集理论的模式识别方法,将动态聚类法和方差分析法引入连续属性模糊化,获取模糊隶属函数,避开了粗糙集理论属性离散化过程带来的信息丢失;利用F检验判断分类的合理性,克服了人为确定分类数目的缺点;应用模糊化得到的模糊决策表进行条件属性约简,通过属性值约简,提取了清晰、简明的故障模式规则。轴承故障模式识别结果表明,该方法对比一般粗糙集理论,有效地提高了模式识别精度,在实际模式识别中具有很好的应用价值。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。