粒度对硝胺类含能化合物撞击感度影响的理论研究

为了研究粒度对硝胺类含能化合物撞击感度的影响规律,选取了HMX、RDX、CL-20三种典型硝胺类含能化合物作为研究对象,建立了不同纳米颗粒大小的化合物模型,采用B3LYP/6-31G方法对各个模型的性能进行了计算与分析。结果表明,单位分子的能量E及最高占据轨道与最低空轨道能量差△ε总体上随RDX、HMX、CL-20颗粒大小的增大而减小,即硝胺类含能化合物的撞击感度随化合物颗粒大小的增大而增大。可见,将硝胺类炸药纳米化可有效降低其撞击感度。     

外电场对不同组分比例的HMX/NQ共晶炸药感度影响的理论研究

借助分子动力学方法对不同电场不同组分比例的HMX/NQ共晶炸药晶体表面成键能和力学性质进行了研究。利用B3LYP和MP2(full)的方法在6-311++G(d,p)和6-311++G(2df,2p)水平上计算了HMX/NQ(1:1)复合物中不同电场HMX中N–NO_2键离解能和撞击感度h50。结果表明:1:1比例的共晶炸药最稳定、力学性质较好。共晶主要发生在HMX(0 2 0)和(1 0 0)晶面上。共晶复合物的形成使HMX引发键N–NO_2增强,感度降低。正方向外电场增大了晶面成键能和N–NO_2键离解能,升高了h50值,降低了HMX的撞击感度;而负方向外电场对其影响正好相反。正方向外电场使剪切模量G和拉伸模量E值增大,炸药延展性下降。     

利用演化神经网络研究有机污染物色谱保留值

利用分子连接性指数作为分子的描述性参数,定量刻画两类主要环境污染物的分子结构,通过演化神经网络分别建立了多环芳烃（PAH）和酚两类有机污染物的结构与色谱保留值之间的定量关系。计算过程中,采用留十法（Ieave-10-out）对所有化合物进行了计算,并将计算值与实验值进行了比较。     

分子局部图形绘制及电势分析软件设计与实现

随着计算机技术的迅速发展,分子图形学在研究分子结构、计算机辅助分子设计中发挥着日益显著的作用.本文作者利用Visual C#呈序设计语言,结合已有的Raswin和WaferPainter两个开源软件,通过对.PDB(蛋白质数据库)文件、原子电量数据文件的读取、分析和计算,改进了原有软件仅限于观看分子的整体结构、绘制整体三维静电势、无法根据用户需要显示局部细节及二维静电势图的缺陷,实现了在用户定制的坐标范围内完成局部分子图、分子的平面静电势图的绘制等功能,这在蛋白质分子结构研究、分析原子间的作用力以及辅助分子设计方面有着重要意义.     

高能推进剂TNT当量的计算研究

由于硝胺炸药本身具有较高的机械感度和冲击波感度,因此现代高能推进剂的安全性受到关注,为了对其安全性进行评估,有必要研究计算NEPE高能推进剂的TNT当量.该文选取由实际爆炸输出来确定爆炸物TNT当量的方法来进行NEPE高能推进剂TNT当量的计算研究.通过10kgTNT炸药和NEPE高能推进剂空中爆炸实验,运用最小二乘原理,利用曲线拟合法,得到了与实验结果吻合较好的TNT炸药、NEPE高能推进剂空中爆炸的仿真压力表达式.求出了压力在0.006MPa～0.500 MPa时,NEPE高能推进剂的TNT当量与对比距离的关系.根据仿真结果,在0.006MPa～0.500 MPa压力范围内,NEPE高能推进剂的TNT当量为1.26.     

分子筛催化甲苯歧化SE1反应机理的分子模拟研究

应用分子模拟半经验量子力学Mopac 6．0-AM1近似计算方法分析了分子筛催化甲苯歧化反应的S_E~1反应历程,确定了反应历程中的反应态、过渡态和产物态,得到了反应活化能和反应热等相关信息,对内禀反应坐标的计算进一步验证了反应过程中的能量变化。计算结果表明,分子筛催化的甲苯歧化反应沿S_E~1反应历程可通过两步基元反应完成;质子由分子筛向甲苯分子转移的过程为反应的快速步骤,其活化能达到428．54 kJ·mol~(-1),需要在高温下进行;甲苯歧化总反应的热效应很小,与实验数据相吻合。     

以偶然正确性概率为基础的测试充分度准则

提出了一种基于偶然正确性概率的测试充分度准则。考虑偶然正确性问题对测试的充分度衡量带来的影响,设计了一种算法来计算程序中的一个错误因为偶然正确性的发生而使输出结果正确的概率。根据动静态数据流信息分析,追溯了动态语句实例之间的定义-使用依赖关系,并据此建立了定义-使用依赖关系图。对不同语句结构和跳转条件定义各种影响因子,量化这些影响因子对错误的掩盖程度。给出了一种算法来计算程序的一次执行过程的测试充分度。选取五个C语言程序作为实验对象,计算基于偶然正确性的测试充分度准则与错误发现效率之间的关系,并与语句覆盖度的错误发现率进行了比较。实验结果显示基于偶然正确性的测试充分度准则能较好地发现错误。     

PCA-ANN对炸药爆速的预测研究

以炸药分子的结构描述符和爆轰性能等参数,利用主成分分析(PCA)结合BP神经网络的方法,建立了炸药分子结构与爆速之间的定量关系预测模型,并对20种炸药的爆速进行了预测,其相对误差均低于9%.结果表明,所建立的模型较好地反映了炸药分子结构与爆速之间的关系,具有较高的预测精度.该方法为设计新型炸药分子时正确估算其爆速提供了一条新的途径.     

新型二芳基取代-1,2,4-三唑类化合物的抗炎构效关系和分子对接研究

目的:建立新型二芳基取代-1,2,4-三唑类化合物的定量构效关系,设计新型COX-2抑制剂.方法:采用PM3半经验量子化学法全优化18种二芳基取代-1,2,4-三唑类选择性环氧合酶(COX-2)抑制剂的结构,从数据中搜寻或计算它们的226种参数,利用逐步回归法,建立经典结构-活性关系(2D-QSAR);用Autodock对接软件研究二芳基取代-1,2,4-三唑类化合物与环氧合酶(COX-2)的对接,分析该类化合物与环氧合酶在复合物的立体结构以及分子对接自由能与抑制活性的关系.结果:建立合理二芳基取代-1,2,4-三唑类化合物COX-2抑制剂定量构效关系,表明活性二芳基取代-1,2,4-三唑类选择性环氧合酶(COX-2)抑制剂具有类似塞来昔布等三环类环氧合酶-2抑制剂的立体结构,并且对接自由能与抑制剂活性有较好的相关性.结论:所得的模型可以解释已有的构效关系,而且预测同类化合物能力较好,可指导设计新抑制剂.     

D-σ-A型分子整流器的理论研究

采用DFT的方法分别对一系列有望成为分子整流器的共轭分子的几何及电子结构进行了理论计算。通过B3LYP／6—31G＊＊算法确定了电子供体（Donor）和受体（Acceptor）分子。为使单分子整流器可在较大偏压下使用,尝试了不同的键桥结构。计算结果表明,分别作为供体和受体分子的硝基苯、苯胺之间具有最大的LUMO能级差。D-σ-A型分子中,电子最低未占据轨道（LUMO）局限在分子的受体片段上,而电子最高占据轨道（HOMO）局限在供体片段上。受体和供体片段之间的键桥结构为-CH2CH2CH2CH2-时,分子的势能差最大,为2．47eV。     

Computing the Treewidth and the Minimum Fill-In with the Modular Decomposition

Abstract. Using the notion of modular decomposition we extend the class of graphs on which both the treewidth and the minimum fill-in can be solved in polynomial time. We show that if C is a class of graphs that are modularly decomposable into graphs that have a polynomial number of minimal separators, or graphs formed by adding a matching between two cliques, then both the treewidth and the minimum fill-in on C can be solved in polynomial time. For the graphs that are modular decomposable into cycles we give algorithms that use respectively O(n) and O(n ³ ) time for treewidth and minimum fill-in.     

On the computation of the gap metric

This paper deals with the computation of the gap metric introduced by Zames and El-Sakkary [17]. It is shown that the gap between two systems (P₁, P₂) is precisely the maximum of the two expressions for (i, j) equal to (1, 2) and (2, 1), and (N_i, D_i) being normalized right coprine factorizations of P_i, I = 1, 2, in the sense of Vidyasagar [12]. This expression is computable using well-known techniques from interpolation theory.     

On the stability of the information state system

The purpose of this paper is to present some preliminary results on the stability of the information state system. The information state system underlies the (infinite dimensional) dynamics of an H_∞ controller for a nonlinear system. Thus it is important to understand its stability and the structure of its equilibrium points. We analyse the important case corresponding to the mixed sensitivity problem. We prove the existence of an equilibrium information state, convergence under very general conditions to such an equilibrium state p_e and uniqueness of this state (up to an irrelevant constant). In this case the equilibrium p_e is usually singular in the sense that it takes on the value − ∞ except on a low dimensional subset of its domain.This meshes with the article [9] which analysed the effect of using p_e to initialize the information state controller and gave explicit formulas which in many cases produce a dramatic reduction in the amount of computation required to implement the controller. What this article suggests is that indeed p_e is the only equilibrium initialization possible.     

Changing the diameter of the locally twisted cube

The hypercube network Q _n has been proved to be one of the most popular interconnection networks. The n-dimensional locally twisted cube LTQ _n is an important variant of Q _n . One of the critical performance factors of an interconnection network is the diameter which determines the maximum communication time between any pair of processors. In this paper, we investigate the diameter variability problems arising from the addition and deletion of edges in LTQ _n . We obtain three results in this paper: (1) for any integer n≥2, we find the least number of edges (denoted by ch ^?(LTQ _n )), whose deletion from LTQ _n causes the diameter to increase, (2) for any integer n≥2, when ch ^?(LTQ _n ) edges are deleted, the diameter will increase by 1 and (3) for any integer n≥4, the least number of edges whose addition to LTQ _n will decrease the diameter is at most 2 ^n?1.     

On the representation of McCarthy's in the -calculus

We study the encoding of , the call-by-name λ-calculus enriched with McCarthy's amb operator, into the π-calculus. Semantically, amb is a challenging operator, for the fairness constraints that it expresses. We prove that, under a certain interpretation of divergence in the λ-calculus (weak divergence), a faithful encoding is impossible. However, with a different interpretation of divergence (strong divergence), the encoding is possible, and for this case we derive results and coinductive proof methods to reason about that are similar to those for the encoding of pure λ-calculi. We then use these methods to derive the most important laws concerning amb. We take bisimilarity as behavioural equivalence on the π-calculus, which sheds some light on the relationship between fairness and bisimilarity.     

On the profile of the corona of two graphs

The concept of profile, together with bandwidth, originates from handling sparse matrices in solving linear systems of equations. Given a graph G, the profile minimization problem is to find a one-to-one mapping f:V(G)→{1,2,…,|V(G)|} such that ∑_v∈V(G)max_x∈N[v](f(v)−f(x)) is as small as possible, where N[v]={v}∪{x:x is adjacent to v}. This paper studies the profile of the corona G∧H of two graphs G and H. In particular, bounds for the profile of the corona of two graphs are established. Also, exact values of the profiles of coronas G∧H are obtained when G has certain properties, including when G is a caterpillar, a complete graph or a cycle.     

Subsampling techniques and the Jackknife methodology in the estimation of the extremal index

For a sequence of independent, identically distributed random variables any limiting point process for the time normalized exceedances of high levels is a Poisson process. However, for stationary dependent sequences, under general local and asymptotic dependence restrictions, any limiting point process for the time normalized exceedances of high levels is a compound Poisson process, i.e., there is a clustering of high exceedances, where the underlying Poisson points represent cluster positions, and the multiplicities correspond to the cluster sizes. For such classes of stationary sequences there exists the extremal indexθ, 0?θ?1, directly related to the clustering of exceedances of high values. The extremal index θ is equal to one for independent, identically distributed sequences, i.e., high exceedances appear individually, and θ>0 for “almost all” cases of interest. The estimation of the extremal index through the use of the Generalized Jackknife methodology, possibly together with the use of subsampling techniques, is performed. Case studies in the fields of environment and finance will illustrate the performance of the new extremal index estimator comparatively to the classical one.