稳恒扩展裂纹尖端的弹粘塑性场

采用弹粘塑性力学模型代替通常的弹塑性模型，对于I型和Ⅱ型问题，分别求得了不可压缩材料中平面应变动态扩展裂纹尖端的指数奇异性场和对数奇异性场，消除了弹塑性解中存在的塑性激波。通过数值计算，分别求得了两种奇异属性的分界线，建立起统一的裂纹尖端奇异性场。     

斜冲击界面动力学研究

讨论了界面受到斜冲击时的动力学问题。有效冲击摩擦系数被处理成冲击过程及初始冲击角的函数 ;界面的法向响应描述计及弹性接触、弹性变形极限以及依赖于应变、应变率及温度的完全塑性接触 ;界面在冲击过程中的构形变化也予考虑 ,并采用平均应变、应变率及最大温升的概念与估算。这种新的斜冲击界面动力学模型用于数值模拟刚性球对于延性靶的斜冲击实验 ,计算与实验比较 ,结果是令人满意的。     

Percolation theory approach to transport phenomena in porous media

The percolation theory approach to static and dynamic properties of the single- and two-phase fluid flow in porous media is described. Using percolation cluster scaling laws, one can obtain functional relations between the saturation fraction of a given phase and the capillary pressure, the relative permeability, and the dispersion coefficient, in drainage and imbibition processes. In addition, the scale dependency of the transport coefficient is shown to be an outcome of the fractal nature of pore space and of the random flow pattern of the fluids or contaminant.     

A survey of experimental heat transfer data for nucleate pool boiling of liquid metals and a new correlation

The experimental data for heat transfer during nucleate pool boiling of saturated liquid metals on plain surfaces are surveyed and a new correlation is presented. The correlation is h = Cq^0.7p_r^m, where C and m are, respectively, 13.7 and 0.22 p_r < 0.001 and 6.9 and 0.12 for p_r > 0.001 (h is in W/m² K and q in W/m²). This correlation has been verified with data for K, Na, Cs, Li, and Hg from 17 sources over the reduced pressure (p_r) range of 4.3 × 10⁻⁶ to 1.8 × 10⁻². The correlation of Subbotin et al. was found unsatisfactory, but a modified correlation was developed that also gives good agreement with most of the data.     

Molecular Dynamics Simulation of HIV-1 Integrase Dimer Complexed with Viral DNA

The biological function of HIV‐1 integrase (IN) is to integrate viral DNA into the host cell chromosome, and the specific binding of IN with viral DNA is a precondition for IN to function correctly. Beforehand, the binding mode of IN dimer (IN₂) with the 27 bp segment of viral DNA before 3′ processing (3′‐P) was obtained via a molecular docking method. Based on the binding mode, the aim of this article was to explore the changes of motive mode and correlative motion for the IN₂ and DNA systems after their binding through dynamical cross‐correlation map (DCCM) and principal component analysis (PCA). Finally, solvent effect during the association was analyzed briefly. The results show that there is a significantly increased positive correlation in the interface region between IN₂ and viral DNA, and some obvious motive mode changes of the two systems (IN₂ and DNA) were also observed after their binding. It was found that water molecules played an important role in the recognition between IN₂ and viral DNA through analyzing the water‐mediated hydrogen bonds.     

An efficient correlation for calculating compressibility factor of natural gases

Compressibility factor (z-factor) values of natural gases are necessary in most petroleum engineering calculations. Necessity arises when there are few available experimental data for the required composition, pressure and temperature conditions. One of the most common methods of calculating z-factor values is empirical correlation. Firstly, a new correlation based on the famous Standing-Katz (S-K) Chart is presented to predict z-factor values. The advantage of this correlation is that it is explicit inzand thus does not require an iterative solution as is required by other methods. Secondly, the comparison between new one and other correlations is carried out and the results indicate the superiority of the new correlation over the other correlations used to calculate z-factor.     

Excess Gibbs energies and volumes of the ternary system chloroform + tetrahydrofuran + cyclohexane at 298.15 K

Vapour–liquid equilibria and densities for the ternary system chloroform + tetrahydrofuran + cyclohexane and for the binary mixtures containing chloroform have been determined at 298.15 K. Vapour–liquid equilibrium data have been collected by head-space gas-chromatographic analysis of the vapour phase directly withdrawn from an equilibration apparatus. Density measurements have been carried out by means of a vibrating tube densimeter. Molar excess Gibbs energies G^E and volumes V^E, as well as activity coefficients and apparent molar volumes of the components, have been obtained from the measured quantities and discussed. The binary chloroform + tetrahydrofuran displays negative deviations from ideality, while chloroform + cyclohexane positive deviations, for both volume and Gibbs energy. The G^E's and V^E's for the ternary system are positive in the region rich in cyclohexane while negative in the region rich in chloroform + tetrahydrofuran. This indicates that hydrogen bonding between chloroform and tetrahydrofuran molecules produces negative values of G^E and V^E and strongly influences the behaviour of the ternary system.     

A thermodynamic consistency test for the binary constant-temperature VLE data using numerically optimized binary parameters

A thermodynamic consistency (TC) test for the constant-temperature VLE data was investigated by numerically optimizing the binary parameters of the activity coefficient equations to satisfy the Gibbs–Duhem (GD) equation. It was shown that the one parameter Margules equation can best satisfy the GD equation, even if significant experimental errors are involved. A thermodynamic consistency (TC) criterion was defined using the one parameter Margules equation. The TC criterion showed that, of the 37 alkane–alkane, 18 methanol–water and 44 ethanol–water binaries, 36, 16 and 1 binaries are reliable, respectively. Simple liquid mixtures meet the TC criterion.     

Molecular dynamics simulation of the equilibrium liquid–vapor interphase with solidification

The equilibrium structure of the finite, interphase interfacial region that exists between a liquid film and a bulk vapor is resolved by molecular dynamics simulation. Argon systems are considered for a temperature range that extends below the melting point. Physically consistent procedures are developed to define the boundaries between the interphase and the liquid and vapor phases. The procedures involve counting of neighboring molecules and comparing the results with boundary criteria that permit the boundaries to be precisely established. Two-dimensional radial distribution functions at the liquid and vapor boundaries and within the interphase region demonstrate the physical consistency of the boundary criteria and the state of transition within the region. The method developed for interphase boundary definitions can be extended to nonequilibrium systems. Spatial profiles of macroscopic properties across the interphase region are presented. A number of interfacial thermodynamic properties and profile curve-fit parameters are tabulated, including evaporation/condensation coefficients determined from molecular flux statistics. The evaporation/condensation coefficients away from the melting point compare more favorably with transition state theory than those of previous simulations. Near the melting point, transition theory approximations are less valid and the present results differ from the theory. The effects of film substrate wetting on evaporation/condensation coefficients are also presented.     

Infinite dilution activity coefficient and vapour liquid equilibrium measurements for dimethylsulphide and tetrahydrothiophene with hydrocarbons

The activity coefficients at infinite dilution (γ^∞) of dimethylsulphide (DMS) in four hydrocarbon solvents were measured using the dilutor technique at temperatures between 288 K and 303 K. The four hydrocarbons were hexane, 1-hexene, 2,2,4-trimethylpentane and 2,4,4-trimethyl-1-pentene. The dilutor technique is based on the stripping of the highly diluted solute, i.e. DMS, by a constant flow of inert gas. The gas composition was analysed by gas chromatography and the rate of solute removal was calculated from the area of the peaks.