Net Operations

Two kinds of net operations.addition and Cartesian production of P/T nets,are introduced.They are defined on the set of underlying net of P/T systems.The conditions for preserving structural properties of Petri net after these operations are discussed.It is shown that the set of P/T nets forms and Abelian group for net addition operation and the inverse net of a P/T net in usual meaning of net theory is exactly the inverse of this P/T net as an element of the P/T net group;and that the set of P/T nets forms an Abelian ring for net addition and Caresian product operations.     

改性膨润土对天然橡胶的力学性能影响研究

本文讨论了改性膨润土对天然橡胶的力学性能的影响，并同未改性膨润土及白炭黑作了比较。用Ｘ光衍射仪和红外光谱分析了膨润土改性前后的结构变化。     

SBS APP复合改性沥青的研究

采用SBS、APP复合改性渣油,可以得到性能优良的改性沥青材料。其最佳配料和共混工艺条件为:SBS/(SBS+APP)之比0.4、外掺量20%、转速1930rPm、共混时间1.0 hr,共混温度20℃。     

导电环接触电阻的改进测量方案

介绍了导电环接触电阻测量方法的现状,提出了在测量过程中防止导线缠绕的两种改进方案,通过分析验证,说明改进后的测量方案能够很好的完成导电环接触电阻的测量.     

福建煤炭集团结构调整问题初探

本文在简要介绍福建煤炭集团的战略定位和发展趋势的基础上 ,分析了福建煤炭集团产业结构存在的主要问题 ,提出了当前福建煤炭集团结构调整的对策思考。     

四方连续式面料图案的自动生成算法

提出了自动合成四方连续面料图案的数学模型;介绍了人机交互色彩调配算法;从数学模型、色彩处理、应用前景库三方面对有关设计思想和实现方法作了详细说明.     

N-溴丁二酰亚胺／吡啶氧化合成己二酰基双偶氮化合物

以己二酰二氯和不同取代基的苯肼合成了N,N'-二芳基己二酰二肼类中间体,然后在N-溴丁二酰亚胺(NBS)／吡啶氧化体系下室温合成了8种己二酰基双偶氮化合物。第一步反应条件为:n(己二酰二氯):n(取代苯肼)=1:2,反应温度0-5℃,反应时间4 h,收率80%-93％;第二步反应条件为:n(N,N’-二芳基己二酰二肼):n(NBs／吡啶)=1:2,氧化反应时间0．5-1．0 h,收率80%-94%。并用元素分析、IR、1H NMR对合成的中间产物及目标化合物进行了表征。     

Cloud analysis by modeling the integration of heterogeneous satellite data and imaging

This paper presents a computer-aided cloud-analysis approach by effectively modeling the integration of heterogeneous satellite-observed data and remote sensing images. First, automatic cloud detection and tracking methods are proposed to identify the georeferenced cloud objects in satellite remote sensing images. Then, a data integration modeling mechanism is designed to collect meaningful properties of those detected clouds by integrating the heterogeneous satellite-observed data and imaging into a unified cloud database. Finally, based on the integrated global data schema, a two-phase data mining method employing the decision tree algorithm is implemented to analyze and forecast the meteorological activities of all the cloud objects. Experimental results have shown that the proposed data integration model can effectively extract and synthesize all the useful information from heterogeneous data sources to generate a unified view of knowledge, on the basis of which the evolvement trends of clouds can be analyzed properly.