Quantified Computation Tree Logic

Computation Tree Logic (CTL) is one of the most syntactically elegant and computationally attractive temporal logics for branching time model checking. In this paper, we observe that while CTL can be verified in time polynomial in the size of the state space times the length of the formula, there is a large set of reachability properties which cannot be expressed in CTL, but can still be verified in polynomial time. We present a powerful extension of CTL with first-order quantification over sets of reachable states. The extended logic, QCTL, preserves the syntactic elegance of CTL while enhancing its expressive power significantly. We show that QCTL model checking is PSPACE-complete in general, but has a rich fragment (containing CTL) which can be checked in polynomial time. We show that this fragment is significantly more expressive than CTL while preserving the syntactic beauty of CTL.     

Computing Inlet Pressure Head of Multioutlet Pipeline

Expressions for the factor K to relate the total frictional head loss, average outlet operating pressure head, and the inlet pressure head of a multioutlet pipeline are developed. In the developed expressions, the factor K is a function of the number of outlets on different pipe diameters, combination of diameters, and position of the first outlet from the inlet. Values of the factor K obtained from the developed expressions are compared with constant values being taken as per existing practice. The comparison suggests using the developed expressions for accurate computation of the factor K for multioutlet pipelines especially comprising of two or more diameters. An example is presented to compute the inlet pressure head of a multioutlet pipeline using the factor K.     

Molecular structure and electrochemical properties of alkyldithiocarbamates

Cyclic voltammetry, chronoamperometry, chronocoulometry and rotating disc electrode techniques have been used to study redox properties of dithiocarbamate lithium salts solutes in 0.1 M LiClO₄/DMSO solution. The investigated compounds have been synthesized from N,N′-dimethylethylenediamine to which one or two dithiocarbonyl groups were attached by a reaction with CS₂ in an alkaline solution. Voltammetric studies of the oxidation of these moieties showed the irreversible, though reproducible, broad peak at scan rates ranging from 0.01 to 0.5 V s⁻¹. The chronoamperometric and rotating disc electrode experiments confirmed the consumption of 1e/active group. Upon changing the electrode from Pt to glassy carbon only slight shift of the anodic peak potential, and negligible current change has been observed. These findings are interpreted as an indication that the electrode materials do not participate directly in the dithiocarbamate radicals formation (for example, via chemisorption) and in further dimerization of the radicals to thiuram disulfide. The latter process is assumed to proceed at the rate close to the diffusion limit. The calculated symmetry coefficient are distinctly lower than 0.5, the value predicted by the Butler-Volmer theory. Such an outcome implies that the potential range where the reaction proceeds is much more positive than the standard potential of the reaction. The oxidation of the compound containing two electroactive groups has led to the formation of a wide spectrum of diverse disulfide compounds differing one from another by the molecular weight (diffusion coefficient) owing to the various degree of the coupling.The semi-empirical quantum-chemical calculations showed the structure reorganization of the dithiocarbamate anions upon electron detachment enforced by localization of the unpaired electron on the sulfur atoms. It may favour kinetically the formation of thiuram disulfide through the fast homogeneous dimerization of the dithiocarbamate radicals.     

Computation of Mixed-Mode Stress Intensity Factors for Cracks in Three-Dimensional Functionally Graded Solids

This work applies a two-state interaction integral to obtain stress intensity factors along cracks in three-dimensional functionally graded materials. The procedures are applicable to planar cracks with curved fronts under mechanical loading, including crack-face tractions. Interaction-integral terms necessary to capture the effects of material nonhomogeneity are identical in form to terms that arise due to crack-front curvature. A discussion reviews the origin and effects of these terms, and an approximate interaction-integral expression that omits terms arising due to curvature is used in this work to compute stress intensity factors. The selection of terms is driven by requirements imposed by material nonhomogeneity in conjunction with appropriate mesh discretization along the crack front. Aspects of the numerical implementation with (isoparametric) graded finite elements are addressed, and examples demonstrate the accuracy of the proposed method.     

圆仓混凝土顶盖模架内力近似分析

本文对圆仓锥形砼顶盖空间支模系统 ,施工阶段困难的内力分析进行简化 ,建立简单的计算简图和计算公式。根据砼施工 (浇注 )局部性的特点 ,该近似杆件内力计算的结果 ,可确保支模体系安全可靠 ,内力分析简单快捷。     

自由基聚合动力学模型及其计算

本文建立了自由基聚合的动力学模型，并利用Ｒｕｎｇｅ－Ｋｕｔｔａ数值解法对组成模型的非线性常数微分方程进行了求解。利用该模型对苯乙烯的本体聚合，溶液聚合进行了模拟计算，与文献报导的实验数据比较表明：此模型能较好的模拟自由基聚合动力学。     

地质体三维实体建模的数据预处理方法

研究了三维地质体实体建模对地质勘探数据的要求,结合三维地质体实体建模相关过程和操作,阐述了数据预处理的重要性。提出了数据预处理的数据检查、数据修正和建模辅助3个过程,并对这3个过程中的轮廓线自相交、轮廓线之间相交、任意简单多边形的重心计算算法、三维空间中的辅助标记添加等主要问题和相应解决算法进行了详细论述。实验结果表明,该些方法能够简化建模算法,具有很高的可操作性。     

Distributed Source Localization under Anchor Position Uncertainty

In this work, a distributed source position- ing approach is developed based on Alternating direction method of multipliers （ADMM）. First, a centralized posi- tioning method is developed under case of the anchor un- certainty. And then, the method is realized in a distributed way using ADMM. Simulation results show that the cen- tralized one is robust to the anchor errors and distributed one has similar performance as the centralized one.     

基于回溯与引导的关键代码区域覆盖的二进制程序测试技术研究

基于路径覆盖的测试方法是软件测试中比较重要的一种测试方法,但程序的路径数量往往呈指数增长,对程序的每一条路径都进行测试覆盖基本上是不可能的。从软件安全测试的观点看,更关心程序中的关键代码区域(调用危险函数的语句、圈复杂度高的函数、循环写内存的代码片断)的执行情况。该文提出了覆盖关键代码区域的测试数据自动生成方法,该方法基于二进制程序,不依赖于源码。通过回溯路径获取所有可达关键代码区域的程序路径,并通过路径引导自动为获得的路径生成相应的测试数据。路径引导策略基于程序的符号执行与实际执行,逐步调整输入,使用约束求解器生成相应的测试用例。理论分析与实验结果显示该文给出的方法可以降低生成测试数据所需要的运行次数,与传统的覆盖路径测试数据生成方法相比,所需要的运行次数显著降低,提高了生成测试数据的效率。     

基于移动路径预测的车载边缘计算卸载切换策略研究

车载云计算环境中的计算卸载存在回程网络延迟高、远程云端负载大等问题,车载边缘计算利用边缘服务器靠近车载终端,就近提供云计算服务的特点,在一定程度上解决了上述问题。但由于汽车运动造成的通信环境动态变化进而导致任务完成时间增加,为此该文提出一种基于移动路径可预测的计算卸载切换策略MPOHS,即在车辆移动路径可预测情况下,引入基于最小完成时间的计算切换策略,以降低车辆移动性对计算卸载的影响。实验结果表明,相对于现有研究,该文所提算法能够在减少平均任务完成时间的同时,减少切换次数和切换时间开销,有效降低汽车运动对计算卸载的影响。