Workflow performance analysis and simulation based on multidimensional workflow net

Workflow model performance analysis plays an important role in the research of workflow techniques and efficient implementation of workflow management. Instances dwelling times (IDT) which consist of waiting times and handle times in a workflow model is a key performance analysis goal. In a workflow model the instances which act as customers and the resources which act as servers form a queuing network. Multidimensional workflow net (MWF-net) includes multiple timing workflow nets (TWF-nets) and the organization and resource information. This paper uses queuing theory and MWF-net to discuss mean value and probability distribution density function (PDDF) of IDT. It is assumed that the instances arrive with exponentially distributed inter-arrival times and the resources handle instances within exponentially distributed times or within constant times. First of all, the mean value and PDDF of IDT in each activity is calculated. Then the mean value and PDDF of IDT in each control structure of a workflow model is computed. According to the above results a method is proposed for computing the mean value and PDDF of IDT in a workflow model. Finally an example is used to show that the proposed method can be effectively utilized in practice.     

Fairness based channel borrowing strategy in multimedia LEO satellite communications

A novel bandwidth allocation strategy along with a connection admission control technique was proposed to improve the utilization of network resources. It provides the network with better quality-of-service (QoS) guarantees, such as new call blocking probability (CBP) and handoff call dropping probability (CDP) in multimedia low earth orbit (LEO) satellite networks. Simulation results show that, compared with other bandwidth allocation schemes, the proposed scheme offers very low call dropping probability for real-time connections while, at the same time, keeping resource utilization high. Finally we discussed the fairness for the borrowed nonreal-time connections under three different channel borrowing methods. Translated from Journal on Communications, 2006, 27(8): 10–17 [译自: 通信学报]     

外压容器的可靠性计算

本文以可靠性理论为基础，讨论了外压容器可靠性计算的方法和步骤．并针对一台减压塔进行了各零部件及整体的可靠性计算，给出其可靠度及失效概率．计算结果表明，共照常规设计外压容器，尽管考虑到一定的安全裕度，但仍存在着失效可能，不能保证容器可靠运行．     

归纳概率解释的研究述评

随着概率论的日趋完善，概率演算已经为人们所熟知，尽管科尔莫哥洛夫（Kolmogorov）公理的经济性可以使我们对概率做出多种解释，但对它的解释却漏洞百出。正因如此，人们主要围绕着概率解释的标准、如何对概率进行合理解释以及概率解释未来的发展的方向3个方面，对这个问题进行了广泛的研究。于是主要从这3个方面分别对这些研究成果进行了述评，借此厘清概率解释理论研究发展的总脉络。     

管线断裂失效概率模型及计算

以相关管道档案、检验报告作为原始资料, 配合现场调查及观测, 采用“ 在役压力管道失效风险分析系统(SAPP)” , 对管线断裂失效风险进行分析。将管线中各缺陷安全状况与失效风险有机地结合起来, 在当前检测缺陷数据基础上, 通过适当选取概率模型, 计算管线的失效风险概率。对于准确了解管线的安全状态, 制定具有针对性的检修计划, 加强管线维护, 保障装置的安全稳定运行有重要的现实意义。     

阳离子可染涤纶的耐久性拒水拒油整理

通过采用防水剂FS-506对阳离子可染涤纶进行拒水拒油整理的实验，重点探讨整理荆浓度、交联剂浓度以及焙烘温度和时间对拒水拒油整理效果的影响，并得出优化的工艺条件．试验结果表明，经FS-506整理后的阳离子可染涤纶具有令人满意的耐久拒水拒油性能．     

间接使用扩展规则求解#SAT问题

针对求解#SAT问题时算法时间会随着子句集的规模迅速增加的问题,提出一种间接应用扩展规则的MCEHST算法。该算法首先求出子句集的所有极小碰集,然后应用扩展规则计算这些极小碰集所能扩展出的极大项的数量,即模型数。实验结果表明:MCEHST算法运行时间随子句集规模增加的速度要比CDP和CER算法慢;当子句的长度较短、子句数较多时,MCEHST算法的时间效率较高。     

PTA工艺合成阳离子染料可染聚酯

阳离子染料可染聚酯是由聚酯齐聚物与第三单体ＳＩＰＥ经共聚而成。采用连续式ＰＴＡ工艺路线生产阳离子染料可染聚酯时,聚酯齐聚物的聚合度、第三单体ＳＩＰＥ的添加方式和添加时机对最终产品阳离子梁料可染纤维的性能有重大影响,但通过在共聚前添加适量的ＥＧ,并控制一定的ＰＨ值,可以获得满意的结果。     

K-OUT-OF-N（F）C输油管道系统的可靠性计算

用K -OUT -OF -N(F)C系统来描述输油管道系统 ,利用概率理论和Markov链的有关性质推导出K -OUT -OF -N(F)C输油管道系统可靠度的精确计算公式和近似计算公式 ,并通过算例对精确计算公式和近似计算公式进行了比较 ,得出了近似计算公式的误差比较小 ,可以应用于工程中 ,并且通过数值计算得出n在大于 10时 ,利用近似公式计算K -OUT -OF -N(F)C输油管道系统的可靠度的结论 ,有益于对输油管道系统的可靠性进行合理的、整体性的评价 ,为输油管道的安全运行提供有效理论依据。     

Evaluation of the effect of geometrical parameters on stope probability of failure in the open stoping method using numerical modeling

Stress-induced failure is among the most common causes of instability in Canadian deep underground mines. Open stoping is the most widely practiced underground excavation method in these mines, and creates large stopes which are subjected to stress-induced failure. The probability of failure(POF)depends on many factors, of which the geometry of an open stope is especially important. In this study,a methodology is proposed to assess the effect of stope geometrical parameters on the POF, using numerical modelling. Different ranges for each input parameter are defined according to previous surveys on open stope geometry in a number of Canadian underground mines. A Monte-Carlo simulation technique is combined with the finite difference code FLAC3D, to generate model realizations containing stopes with different geometrical features. The probability of failure(POF) for different categories of stope geometry, is calculated by considering two modes of failure; relaxation-related gravity driven(tensile)failure and rock mass brittle failure. The individual and interactive effects of stope geometrical parameters on the POF, are analyzed using a general multi-level factorial design. Finally, mathematical optimization techniques are employed to estimate the most stable stope conditions, by determining the optimal ranges for each stope's geometrical parameter.