6009铝合金激光电弧复合焊接头腐蚀性能研究

通过金相观察、电化学腐蚀试验、晶间腐蚀试验和静态腐蚀失重试验,发现当热源间距为2mm时,接头在3.5%NaCl溶液中的电化学腐蚀特性优于3mm和4mm时的接头。同时,该条件下焊接接头晶间腐蚀敏感性低于其它热源间距的接头。但热源间距对接头的均匀腐蚀速率影响很小。经过固溶淬火加时效处理的焊接接头耐电化学腐蚀性优于焊态接头,晶间腐蚀敏感性低于后者。另外,此热处理方法有助于减缓接头区均匀腐蚀速率。进一步分析表明,热源间距为2mm时的接头中,柱状晶在生长过程中,树枝晶得不到充分的发展,分枝较少,结晶后显微疏松等晶间杂质少,组织比较致密。固溶淬火加人工时效消除了焊缝的氢气孔,减少了侵蚀性阴离子对基体的吸附作用;同时,大量Mg、Si原子重新溶入铝合金基体,晶界杂质原子较焊态减少。     

QSAR/QSPR模型验证方式与预测能力的关系研究

QSAR研究中,判断模型预测能力至关重要。长期以来,模型的预测能力是使用留一法或留k法等内部验证来确定,但在2004年形成的OECD规则中,已明确规定必须使用外部验证集去评价模型的预测能力。为了研究内部验证和外部验证与模型预测能力之间的关系,本文以45种睾酮和二氢睾酮衍生物以及37种萘锟酯衍生物为研究对象,以E-Dragon计算的分子描述符作为自变量,在增n减l算法选择变量的基础上,采用SVM算法对同种物质的不同活性以及不同物质的不同活性建立QSAR模型,研究QSAR/QSPR建模时的不同验证方式与模型预测能力的关系。研究结果表明,模型的预测能力与内部验证结果的好坏无必然联系,而结合外部验证的检验结果则是判断模型预测能力的可靠依据。     

金刚石与石墨局域态密度和能带结构的第一原理分析

计算与分析电子结构对类金刚石薄膜材料的研究尤为重要.本文用第一原理分子动力学模拟,以研究金刚石和石墨的局域态密度和能带结构.第一原理计算赝势平面波法和密度泛函理论(DFT)去计算,电子交换相关能采用广义梯度近似(GGA)去描述,这种方法可以正确无误的预测半导体带隙与尺寸的关系.金刚石的禁带很宽,为绝缘体,Sp3杂化轨道在费米能级附近提供部分能态密度.石墨是零带隙半金属的内部结构根源就在于离域π键,费米能级处的能态密度几乎全部来自p能级的贡献.研究结果预测,结构变化和Sp杂化轨道产生的函数关系,是很多物理性质不同的最根本原因,而物理性质的研究则可以最直观的体现这种函数关系,可以更深入地研究金刚石和石墨这两种物质.     

Construction of vertex-disjoint paths in alternating group networks

The existence of parallel node-disjoint paths between any pair of nodes is a desirable property of interconnection networks, because such paths allow tolerance to node and/or link failures along some of the paths, without causing disconnection. Additionally, node-disjoint paths support high-throughput communication via the concurrent transmission of parts of a message. We characterize maximum-sized families of parallel paths between any two nodes of alternating group networks. More specifically, we establish that in a given alternating group network AN _n , there exist n−1 parallel paths (the maximum possible, given the node degree of n−1) between any pair of nodes. Furthermore, we demonstrate that these parallel paths are optimal or near-optimal, in the sense of their lengths exceeding the internode distance by no more than four. We also show that the wide diameter of AN _n is at most one unit greater than the known lower bound D+1, where D is the network diameter.     

安全仪表系统的功能安全设计

针对安全仪表系统（SIS）的产品开发,分析了应用于石化领域的安全仪表系统的基本特性、冗余结构和常见产品类型。在介绍IEC 61508标准的基础上,提出了安全仪表系统产品开发过程中整体安全生命周期、产品硬件及安全相关软件的功能安全设计方法;最后以SIL2级压力变送器为例,着重阐述了SIS系统结构设计和故障诊断覆盖要求。     

以图频繁集为基础的核心节点发现

结合基于图的关联规则挖掘和双向搜索的策略,产生最大频繁项集,从而提出基于图的最大频繁项集(graph based maximum frequen tset,GBMFS)生成算法。运用此算法,结合社会网络的动态特征,发现社会网络中所存在的团伙的核心成员。最后,在实际系统中对相关的算法进行了验证。     

Some new error inequalities for a generalized quadrature rule of open type

Some new error inequalities for a generalized quadrature rule of open type are established. Especially, two sharp inequalities are derived when n is an odd and an even integer, respectively.     

LabVIEW应用环境下数据库存储性能测试

针对Access、SQL Server 2000以及LabVIEW自带的TDMS数据库进行了相关存储性能的测试.对前两种数据库分别采用LabSQL和数据库连接工具包所提供的算法进行了比较分析.     

The Distributed Workflow Management System — FlowAgent

While mainframe or 2-tier client/server system have serious problems in flexibility and scalability for the large-scale business processes,3-tier client/server architecture and object-oriented system modeling which construct business process on service components seem to bring software system some scalability.As enabling infrastructure for object-oriented methodology,distributed WFMS(Workflow Management System)can flexibly describe business rules among autonomous service tasks,and support scalability of large-scale business process.But current distributed WFMS still have difficulty to manage a large number of distributed tasks,the Multi-Task DOmain‘architecture of FlowAgent will try to solve this problem,and bring a dynamic and distributed environment for task-scheduling.