火箭燃气射流对斜板冲击流场的数值模拟

采用高精度，高分辨率的二阶ＴＶＤ有限体积方法，对二维无粘射流冲击斜板的复杂流动场进行了数值模拟，得到了和实验规律相一致的计算结果。     

基于VTK三维地震数据体绘制系统框架

针对地震数据信息量大的特点,文中提出了一种针对三维地震数据体绘制系统的框架。解决的方法是将数据处理、用户交互、渲染绘制分离成三个模块,并且设计了层次结构来保持模块之间的独立性,便于各个模块的修改、更换和扩展,提高了可视化绘制系统快速开发的灵活性。基于三维可视化开发工具包VTK,设计并编程实现了一个地震数据体绘制系统界面。通过实验结果证明,此体绘制方案是可行的、有效的。     

Maximal contractions in Boolean algebras

In the present paper,the concepts of deductive element and maximal contraction are introduced in Boolean algebras,and corresponding theories of consistency and maximal contractions are studied.An algorithm principle is proposed to compute all maximal contractions for a consistent set with respect to its refutation in Boolean algebras.It is pointed out that the quotient algebra of the first-order language with respect to its provable equivalence relation constitutes a Boolean algebra,and hence the computation of R-contractions for closed formulas in first-order languages can be converted into the one in Boolean algebras proposed in this paper.Furthermore,the concept of basic element is introduced in Boolean algebras,which contributes to the definitions of clause and Horn clause transplanted from logic to a special type of Boolean algebras generated by basic elements.It is also pointed out that the computation of R-contractions for clauses in the classical propositional logic can be converted into the one in Boolean algebras generated by basic elements proposed in this paper.     

基于Copula函数的洪水峰量联合设计方法研究

为明晰洪水峰量联合设计的特点,以岗南水库洪水为例,基于Gumbel Copula函数,分析了AND、OR、Kendall、生存Kendall 4种重现期的优缺点,采用极大似然法、同频率法、条件最可能组合法3种方法计算了联合设计值。结果表明: ①AND和OR重现期在危险域和安全域的识别上存在局限性;相对而言,Kendall重现期更合理,但其安全域是无界的,这与实际不符;生存Kendall重现期则界定了有界的安全域,使得重现期的概念在逻辑上更科学合理。② 3种设计值计算方法的差别不大,但从简单实用角度出发,推荐采用同频率法计算设计值。③不同重现期标准的设计值差别比较明显,基于OR重现期计算的设计值总是最大的,生存Kendall、Kendall重现期设计值次之,AND重现期设计值最小。④推荐采用生存Kendall重现期进行两变量洪水设计,因其有比较严谨的理论基础,且设计结果兼顾了安全性与经济性。⑤两变量联合设计值与单变量设计值的差异受变量间相关性的影响较大,且变量相关性越弱,差异越大。研究显示,基于生存Kendall重现期、采用同频率法计算设计值是目前较为科学合理的洪水峰量联合设计途径。     

The volume integral method of eddy-current modeling: Verification

The volume integral method of eddy-current modeling represents a flaw in metal as a set of electric dipoles located within volume elements or cells defining the flaw volume. Given this dipole distribution, impedance changes may be computed. The electric field of the dipole distribution is determined by an integral equation relating, by means of the electric field Green's tensor, the electric field due to the source to the total electric field in the flaw. The integral equation is solved by assuming that the total electric field is constant in each volume element, resulting in a matrix equation. The method has been programmed for use on a microcomputer. The method and computer program are verified using the analytical solution for a small spherical flaw and three sets of measured impedance data, measured by air-core coils along profiles overlying both surface-breaking and buried simulated flaws of known dimensions. Operating frequencies ranged between 900 and 4000 Hz. Generally agreement is good at lower frequencies ( 1000 Hz). At higher frequencies ( 4000 Hz), the agreement is not as good. This is thought to be due to the inability of the constant electric field approximation to model the steep electric field gradients present in the host metal at high frequency. The results are also sensitive to the method of computation of the electric field due to the source. Some improvements can and should be made to the method.     

Electrical conductivity,self-diffusion,and volume expansion of alkali halides at the melting point

In an earlier paper, Heisenberg's uncertainty principle was invoked at the melting point T _m of crystalline solids to provide fundamental justification for Lindemann's melting law and to compute diffusion coefficients of several alkali halides. The uncertainty principle defines breakdown of Debye zone boundary (ZB) phonons as valid collective excitations when phonon energies and line widths due to anharmonicity become comparable at T _m. Upon breakdown, random, high-frequency single-particle motion or partial decoupling of crystal ions sets in. Lifetimes of these single-particle ZB motions are determined from the minimum-uncertainty product inequality by assuming that it becomes an equality at T _m for ZB phonons. The present paper addresses improved formulation of that work and extended application to ionic electrical conductivities of 18 molten alkali halides at T _m. It is shown that use of the Debye model produces an approximate lower bound to the mean free time, not the unconstrained direct estimate previouslu implied. This feature is generally reflected in results for ionic conductivities and alkali halide diffusion coefficients for which comparison experimental data were found. However, in spite of this lower-bound formulation and the simple nature of the computation, the results compare favorably with experiment. A model of random single-particle harmonic motion superimposed on the lower-frequency collective motion is proposed to account for volume expansion accompanying the partial decoupling for hard-sphere ions. Experimental comparisons for 15 alkali halides show the decoupling volume change to account largely for the total volume change of melting (in the hard-sphere approximation), yielding a closer agreement with experiment than recent calculations aimed explicitly at the total volume change.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

A λ-unifiability test for set theory

We present a semi-decision algorithm for the unifiability of two set-theoretic formulas modulo -reduction. The algorithm is based on the approach developed by G. Huet for type theory, but requires additional measures because formulas in set theory are not all normalizable. We present the algorithm in an Ada-like pseudocode, and then prove two theorems that show the completeness and correctness of the procedure. We conclude by showing that -unification is not a complete quantifier substitution method for set theory-unlile first-order unification and first-order logic. In this respect set theory is similar to type theory (higher-order logic).This material is based upon work supported by the National Science Foundation under award number ISI-8560438. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author and do not necessarily reflect the views of the National Science Foundation.     

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本文把与井简直接连通的大裂缝及井筒定义为“裂缝—井筒系统”,通过气体状态方程的变换和续流总量的计算,探索出井底大裂缝的容积及其储量的计算方法。     

Study of viscosity of mono-, di-, and trialkylamines

Viscosities of several mono-, di-, and trialkylamines have been measured in the temperature range 298 to 333 K. It is observed that viscosities are highly dependent on shape, size, and association through H-bond or through dipole. Following the transition state theory, energy, Gibbs free energy, and entropy of activation of viscous flow have been calculated. The values of expansion energy for these liquids have also been calculated using free volume theory, and subsequently amines have been classified as volume-restrained or energy-restrained liquids. The group contribution method of Van Velzen, Cardozo, and Langenkamp for estimating viscosity has been examined with the present and literature data, and the new group contribution increments N _i and B _i for amines have been evaluated.     

二元稀土系AB5型贮氢电极合金的放电容量与晶胞体积和4f电子浓度的关系

制备了6个系列通式为AαA‘1-αB5的RE(NiCoMnTi)5贮氢电极合金(其中，AαA‘1-α为La，Ce，Pr，Nd4个元素中任意2个的组合)，测定了它们在100次循环中的最大放电容量Cmax及部分合金的晶胞体积Vcell．结果表明：Cmax主要由Vcell决定，Cmax先随Vcell的增大而增加，在Vcell≈85．66x10^-^3。nm^3时达到一极大值，然后又随Vcell的增大而减小；同时，Cmax还与4f电子浓度ne4f／naRE有关，A侧具有相同4f电子浓度的合金其Cmax随4f电子浓度的变化趋势相似．