南水北调中线北汝河渠道倒虹吸深基坑降水减压数值模拟

降水减压是北汝河渠道倒虹吸工程的难点,通过工程区水文地质的分析和概化,基于Modflow软件,建立了倒虹吸深基坑降水减压条件下的地下水三维渗流数值模拟模型,通过模型识别,确定了研究区水文地质参数,利用识别后的数值模型对5个不同深基坑降水减压方案的地下水流场进行了预测,确定了降水减压最优方案.     

WJ—1型智能微粒检测仪的设计

库尔特计数技术是液体中不溶性微粒大小和数目测定的有效方法，本文介绍了它的基本原理和以该原理为基础研制的ＷＪ－１型智能微粒检测仪，该仪器采用负压传感器－双电磁阀组成的主动虹吸控制系统，代替了水银虹吸法，没有污染，目前已用于药品输液制剂的微粒检测。     

An extraction algorithm for a set of elementary siphons based on mixed-integer programming

Elementary siphons are useful in the development of a deadlock prevention policy for a discrete event system modeled with Petri nets.This paper proposes an algorithm to iteratively extract a set of elementary siphons in a class of Petri nets,called system of simple sequential processes with resources (S~3PR).At each iteration,by a mixed-integer programming(MIP) method,the proposed algorithm finds a maximal unmarked siphon,classifies the places in it,extracts an elementary siphon from the classified places,and adds a new constraint in order to extract the next elementary siphon.This algorithm iteratively executes until no new unmarked siphons can be found.It finally obtains a unique set of elementary siphons and avoids a complete siphon enumeration.A theoretical analysis and examples are given to demonstrate its efficiency and practical potentials.     

柔性制造系统Petri网模型的化简

在一类S3PR网柔性制造系统Petri网模型N中,位置特殊资源不可能出现在网的严格极小信标和基本信标之中.因此,对于包含此类资源的网系统,为了缩小网规模,需要对其化简.化简算法对网模型进行处理,将位置特殊资源及相关操作库所、变迁和弧删去.同原网系统相比,最终得到的网系统具有较少的库所、变迁和较简单的网结构.