基于虚拟仪器的水轮机组监测与诊断分析系统

随着水电机组在国家电力工业中的比重和水轮发电机组单机功率的增加,对水电机组的状态监测和故障诊断技术提出了更高的要求。本文采用虚拟仪器系统作为开发平台设计并组建水轮发电机组监测和故障诊断系统。该系统实现了水轮发电机组振动信号的数据采集、数据处理和分析,并进行故障诊断。。     

基于模糊相似度的实值属性信息系统规则约简

为了克服传统的规则约简方法容易导致信息丢失和约简错误的不足，提出了一种对实值属性信息系统进行规则约简的算法.该算法在粗糙集理论的基础上，把模糊集合相似度引入到信息系统的规则约简中，通过把每一个实值属性的取值归一化，使得每一条规则所对应的条件属性值都落在0到1范围内；并且把每一条规则看作一个模糊集合，通过模糊集合的相似性来考察规则的相似性；在规则约简过程中，用改进的模糊集合相似度参数进行规则约简，并针对国际水稻信息系统（IRIS）数据库进行了实验.结果表明，该算法能够正确地对实值属性信息系统进行规则约简.     

新疆重瓣榆叶梅花食用色素粗成分等测定

本文以自制新疆重辩榆叶梅花食用色素为实验材料,分别对色素中的灰分、总糖、粗蛋白、粗脂肪、氨基酸总量和有害微量元素As、Ph、Hg和Cu的含量进行了检测。     

下与上几乎半预连续模糊多值映射

在模糊半预开集的基础上,引入了模糊下与上几乎半预连续多值映射的概念,借助于映射F*与F*研究了它们的性质及其等价刻画.结果表明,所引入的几乎半预连续模糊多值映射具有一系列好的性质,从而丰富了已有的结果.     

基于粗糙集理论-主成分分析的Elman神经网络短期风速预测

为了解决传统静态前馈神经网络(FNN)在短期风速预测中易陷入局部最优值及动态性能的不足,引入Elman动态神经网络建立风速预测模型,采用主成分分析法(PCA)对原始风速数据进行特征提取以优化神经网络的输入,改进激励函数和网络结构以寻求函数收敛速度和预测精度的最优解。针对Elman神经网络预测模型在风速波动的峰值处预测误差较大及预测精度存在波动性,提出采用粗糙值理论对模型预测值进行修正与补偿,进一步提高预测精度。实验证明:所提出的方法能有效提高预测精度,增强神经网络模型的泛化能力,具有较好的实用性。     

粗糙度对接触界面动态特性的影响研究

接触界面的刚度和阻尼对机械结构的动态特性有重要影响,为了描述接触界面粗糙度对机械结构动态特性的影响,建立了振动应力波在粗糙接触界面传播的数学模型,并进行了数值仿真和模型试验。试验结果表明：较小的表面粗糙度有利于振动应力波通过接触界面传播;随着粗糙度值的增加,通过接触界面的振动应力波减少,说明较大的粗糙度界面消耗振动能量,但是产生了高次谐波,使振动状态变得复杂。     

基于粗糙集与模糊–多级可拓模型的变电站项目后评价

为提高投资决策水平、完善投资决策机制,针对变电站投资建设项目后评价,提出了一种基于粗糙集与模糊?多级可拓法的评价方法.首先,在国家电网公司现有项目后评价体系的基础上,结合变电站的建设特点,确定了具体的评价指标体系,并基于粗糙集理论确定项目后评价指标权重;然后,将模糊综合评价理论与多级可拓评价方法结合,提出了一种改进的模...     

Lennard–Jones Chain Model for Self-Diffusion of n-Alkanes

The Lennard–Jones chain model, which was developed from the equation for the self-diffusion coefficient in a Lennard–Jones fluid and the molecular dynamics simulation data of a tangent hard-sphere chain fluid, is used to calculate the self-diffusion coefficient of n-alkanes. n-Alkanes are characterized by a Lennard–Jones segment diameter, a segment–segment interaction energy, and a chain length expressed as the number of segments. The equation represents the experimental self-diffusion coefficients with an average absolute deviation of 3.93% for 16 n-alkanes covering wide ranges of temperature and pressure. The correlated results are compared with those of the rough Lennard–Jones model. A generalized version of the Lennard–Jones chain model is presented which requires only the carbon number in order to predict n-alkane self-diffusivity.     

The complexity of counting colourings and independent sets in sparse graphs and hypergraphs

We consider certain counting problems involving colourings of graphs and independent sets in hypergraphs. Using polynomial interpolation techniques, we show that these problems are #P-complete. Therefore, efficient approximate counting is the most one can realistically expect to achieve. Rapidly mixing Markov chains which can be used for approximately solving some of these counting problems have been recently developed by the author and others. Received: June 19, 1998.     

On the absence of strict boundaries—Vagueness, haziness, and fuzziness in philosophy, science, and medicine

This contribution deals with developments in the history of philosophy, logic, and mathematics during the time before and up to the beginning of fuzzy logic. Even though the term “fuzzy” was introduced by Lotfi A. Zadeh in 1964/1965, it should be noted that older concepts of “vagueness” and “haziness” had previously been discussed in philosophy, logic, mathematics, applied sciences, and medicine. This paper delineates some specific paths through the history of the use of these “loose concepts”. Vagueness was avidly discussed in the fields of logic and philosophy during the first decades of the 20th century—particularly in Vienna, at Cambridge and in Warsaw and Lvov. An interesting sequel to these developments can be seen in the work of the Polish physician and medical philosopher Ludwik Fleck.Haziness and fuzziness were concepts of interest in mathematics and engineering during the second half of the 1900s. The logico-philosophical history presented here covers the work of Bertrand Russell, Max Black, and others. The mathematical–technical history deals with the theories founded by Karl Menger and Lotfi Zadeh. Menger's concepts of probabilistic metrics, hazy sets (ensembles flous) and micro-geometry as well as Zadeh's theory of fuzzy sets paved the way for the establishment of soft computing methods using vague concepts that connote the nonexistence of sharp boundaries.