一种工作流访问控制安全模型的研究与设计

工作流技术广泛应用于电子政务系统中,但工作流系统中的访问控制问题却没有引起足够重视和得到有效解决。本文根据工作流系统中的访问控制安全需求,提出和设计了一种新的安全模型,为工作流系统提供安全管理和授权设置,提供保密性和完整性强制访问控制。     

新型三维Ni(Ⅱ)聚合物[Ni(H2O)6·(Hdyma)2]n的合成及晶体结构

合成了新型聚合物[Ni(H2O)6·(Hdyma)2]n[Hdyma=2-(1,3-二噻烷-2-亚基)丙二酸],并通过元素分析和X射线单晶衍射手段对其结构进行了表征.[Ni(H2O)6·(Hdyma)2]n属于单斜晶系:空间群为P21/n;晶胞参数a=0.904 8(2) nm,b=0.514 03(13) nm,c=2.332 6(6) nm,β=99.755(4)°,V=1.069 2(5) nm3,Z=2,Dc=1.793 mg/ m3,μ(Mo Kα)=13.66 cm-1,F(000)=596,R1=0.030 5,wR2=0.076 4.中心Ni原子配位数为6,并分别与6个水分子配位.配位水之间、配位水与两个配体Hdyma之间形成多种氢键,构筑成三维网状超分子配位聚合物.     

关于半素环交换性的一些刻画

我们主要证明了如下一些结果:半素环R是交换环当且仅当R满足下列条件之一:(1)对任意x,y∈R,有(xmyl)n-ysxt∈Z(R),其中l,m,n,s,t为正整数.(2)对任意x,y∈R,有(xkys)n-xly∈Z(R),其中k,s,n,l是正整数,k≥l,且n,s至少有一个大于1.     

信用风险度量的结构化方法

在对单一资产信用风险的度量方法--结构化模型进行详细介绍的基础上,分析对比了企业价值方法和首越时间(first passage time,FPT)方法两种代表性模型的优势与缺陷,探讨了该方法的参数计算过程中应注意的问题;从组合管理的角度出发,对结构化方法框架下违约相关性的计算进行了分析,并给出了该类模型在国内的应用前景与展望.     

分布式无源检测系统中自适应检测融合

针对在分布式多基地雷达无源检测系统中,检测概率通常未知或时变的信息不完全的检测融合问题,研究了一种在线自适应检测融合算法,该算法基于Neyman-Pearson准则,通过局部判决估计未知的每个接收站的检测概率,从而实现最优判决融合.计算机仿真结果说明了其有效性.     

Rational design of geranylgeranyl diphosphate synthase enhances carotenoid production and improves photosynthetic efficiency in Nicotiana tabacum

Restricted genetic diversity can supply only a limited number of elite genes for modern plant cultivation and transgenesis.In this study,we demonstrate that rat...     

基于单周期产品的广告投入供应链博弈分析

在供应链管理环境下,供应商和经销商关于广告成本的分担是一件具有挑战的工作.对单周期产品而言,广告的促销作用表现为需求期望和方差的变化上,而期望和方差之间不同的变化模式对策略的选择又会带来一定的影响.以一个供应商和一个经销商就单周期产品广告策略为背景,以费用分担为供应商主要契约形式,研究供应商的最优分担比率及其对经销商的广告投入的激励.考察了需求方差和期望关于广告投入不同反应模式对供应链双方决策的影响.最后探讨了如何结合供应商回购策略,进行供应链契约设计以达到渠道最优.     

基于离散变量遗传算法的注塑模浇口位置优化设计

建立了一个注塑模浇口位置设计的多目标优化模型,以浇口位置作为设计变量,优化充填过程中入口压力、温度分布等主要工艺参数以减小制品的翘曲程度.将拟精确罚函数和基于信息熵的多种群离散变量遗传算法相结合,发展了一种求解注塑模浇口位置多目标优化问题的迭代格式.在遗传进化中采用了多种群遗传策略和基于信息熵的空间减缩搜索技术,从而大大提高了遗传进化的效率.将该算法与注塑模流动数值模拟程序结合进行浇口位置优化设计.算例表明所提出的方法适用于注塑模浇口位置优化,并且有较好的计算效率和精度.     

女子手球比赛的临场技术指标与比赛成绩的相关分析

本文旨在通过对雅典奥运会女子手球比赛各支球队的技术指标与比赛成绩的相关分析,梳理中国女子手球队技术指标与比赛成绩的关联性,为中国女子手球队提供科学训练的理论依据,为求获得优异成绩,实现突破,提供科学的方法及必要的理论支持.     

Pulmonary toxicity induced by three forms of titanium dioxide nanoparticles via intra-tracheal instillation in rats

Titanium dioxide (TiO2) nanoparticles are in wide commercial use worldwide. To evaluate if acute pulmonary toxicity can be induced by nano-TiO2 particles, rats were intra-tracheally instilled with 0.5, 5, or 50 mg/kg of 5, 21, and 50 nm TiO2 primary particles. Toxic effects were determined with the coefficients of lung tissues to body weight, histopathology, biochemical parameters of blood, activity of lactate dehydrogenase (LDH), alkaline phosphatase (ALP) and acid phosphatase (ACP) in tissues, and the phagocytotic ability of alveolar macrophages (AMs). All the indicators were observed in sacrificed rats one week post-exposure. There was a significant difference of coefficients of pulmonary tissues between the high-dose group and the low- or moderate-dose groups with an exposure of 5 nm TiO2. At the same time, 5 nm TiO2 primary particles increased the activity of LDH and ALP when exposure dose was >5 mg/kg. A significant difference in LDH and ALP activity was observed between the 50 mg/kg group and 0.5 or 5 mg/kg group with exposure of 5 nm TiO2. Lung tissues showed increased ALP activity only if treated with 5 and 50 mg/kg of 21 nm TiO2 particles. There was no significant difference in LDH and ALP activity in the 50 nm TiO2 group and control group. Histopathologic examination of lung tissues indicated that the pulmonary response to exposure to TiO2 particles in rats manifested as dosedependent inflammatory lesions, which mainly consisted of infiltration of inflammatory cells and interstitial thickening. Analysis of uptake of neutral red dye showed that 50 nm TiO2 particles significantly increased phagocytotic ability of AMs compared with controls (P < 0.05), whereas exposure with 5 nm TiO2 reduced the phagocytotic ability of AMs when the exposure dose was 50 mg/kg. These results suggest that particle size and exposure dose may have important roles in pulmonary toxicity. The toxic effect of TiO2 nanoparticles in lung tissue exhibited a dose–response relationship. After exposure with TiO2 particles of >5.0 mg/kg, 5 and 21 nm TiO2 particles induced standing pulmonary lesions; and 5 nm TiO2 particles may suppress the phagocytotic ability of AMs if exposure dose was ≥50 mg/kg. Pulmonary toxicity caused by 5 nm TiO2 particles was more severe than that caused by 21 and 50 nm TiO2 particles.