高能p+p(p)碰撞中J/ψ和γ的硬衍射产生

讨论从ISR到SSC能区p+p(p)→p+J/ψ(Υ)+X过程.假定Pomeron(p)的结构以胶子为主且在小x处有的行为后,在QCD最低阶计算了两个主要子过程的硬衍射截面和作为背景项的Drell-Yan模式的相应截面.与背景项在高能时随Ins增加不同,硬衍射项基本上随(InS)²增加,因而在TeV能区以上时后者将大大超过前者.这种性质对其它硬衍射过程具有普适性.因此如果关于P的上述假定正确,在准确地测定P的结构后,选择适当的硬衍射过程,可能在超高能时提供探测物理粒子的新实验方法.     

Derivation of macroscopic equations for individual cell‐based models: a formal approach

In this paper we review the theory of cells (particles) that evolve according to a dynamics determined by friction and that interact between themselves by means of suitable potentials. We derive by means of elementary arguments several macroscopic equations that describe the evolution of cell density. Some new results are also obtained—a formal derivation of a limit equation in the case of attractive potential as well as in the case of repulsive potential with a hard‐core part are presented. Finally we discuss the possible relevance of those results within the framework of individual cell‐based models. Several classes of potentials, including hard‐core, repulsive and potentials with attractive parts are discussed. The effect of noise terms in the equation is also considered. Copyright © 2005 John Wiley & Sons, Ltd.     

Transfer of charge in liquid alloys

Hard sphere diameters of liquid alkali metal alloys (Na-Cs and K-Rb) are calculated at 373 K ensuring the minimum Helmholtz free energy of the system. These diameters are then used to fix the packing density of the alloy. On alloying, the hard sphere diameters of Na in Na-Cs and K in K-Rb alloys expand whereas those of Cs and Rb contract.     

Molecular dynamics calculations of the hard-sphere equation of state

The equation of state of the hard-sphere fluid is studied by a Monte Carlomolecular dynamics method for volumes ranging from 25V ₀ to 1.6V ₀ , whereV ₀ is the close-packed volume, and for system sizes from 108 to 4000 particles. TheN dependence of the equation of state is compared to the theoretical dependence given by Salsburg for theNPT ensemble, after correction for the ensemble difference, in order to obtain estimates for the thermodynamic limit. The observed values of the pressure are compared with both the [3/2] and the [2/3] Padé approximants to the virial series, using Kratky's value for the fifth virial coefficientB ₅ and choosingB ₆ andB ₇, to obtain a least-squares fit. The resulting values ofB ₆ andB ₇ lie within the uncertainties of the Ree-Hoover-Kratky Monte Carlo estimates for these virial coefficients. The values ofB ₈,B ₉, andB ₁₀ predicted by our optimal [3/2] approximant are also reported. Finally, the Monte Carlo-molecular dynamics equation of state is compared with a number of analytic expressions for the hard-sphere equation of state.Work supported by the Office of Basic Energy Sciences, U.S. Department of Energy.     

A new graph expansion of virial coefficients

It is well known that the virial coefficients of the pressure of thermodynamic systems can be represented in terms of graphs. The existing graph expansions are compared with a new one, the overlap graph expansion. The merits of overlap graphs in general and especially for hard disks and spheres are discussed.     

Generalized enskog theory for homogeneous systems

We propose a generalization of the Enskog equation for homogeneous dense systems including the complete three-particle dynamics. To this end the time derivative of the one-particle distribution is represented in the thermodynamic limit as the sum of three terms describing the effect of the initials-particle correlations, collisions withins-particle clusters, and coupling ofs-particle clusters to the surrounding gaseous medium, respectively. The analysis of casess=2 ands=3 is performed both for hard spheres and for a smooth, repulsive interaction. On assuming the equilibrium structure and spatial dependence of terms reflecting the effect of the medium, we obtain fors=2 the Enskog equation, and fors=3 a new equation, going beyond the Enskog theory. Apart from the Enskog collision term it contains additional contributions, and can be shown to reduce to the Choh-Uhlenbeck equation in the long-time, low-density limit.     

RESEARCH OF STEPPING PRESSURE AND CONTROL OF NEAR FIELD ROOF OF TASHAN COAL MINE BASED ON NUMERICAL SIMULATION1)

煤层坚硬顶板采用水力压裂技术进行定向弱化可有效控制来压步距,降低事故风险。基于黏聚力模型,利用有限元二次开发建立了压裂前后煤层开采数值计算模型,模拟分析了顶板垮落规律及影响因素,优化裂缝间距设计。结果表明：来压跨距与顶板厚度、强度呈正相关性,与埋深呈负相关性。预制裂缝在拉应力集中区可促进起裂扩展,应全面勘测各岩层位地质参数,利用计算出的应力集中区位置设计裂缝间距,实现经济有效地控制来压步距。     

Structure of interfaces from uniformity of the chemical potential

It is shown that a generalized chemical potential suggested by the potential-distribution theory is uniform even in a nonuniform fluid. Leng, Rowlinson, and Thompson had already observed its uniformity through the liquid-vapor interface in the penetrable-sphere model, in mean-field approximation. Following those authors, we exploit the uniformity of that generalized chemical potential to obtain unified and transparent derivations of the results of Ono and Kondo and of van der Waals on the liquid-vapor interfaces in the lattice-gas model and in the model of attracting hard spheres, respectively, both in mean-field approximation.Work supported by the National Science Foundation and the Cornell University Materials Science Center.     

Liquid mixture excess properties by the hard sphere model

The excess properties of mixing were calculated for seven systems Ar-CH₄; Ar-N₂; Ar-O₂; Ar-CO; CO-CH₄; O₂-N₂; N₂-CO, using the Caranhan and Starling equation of state of rigid spheres and the Longuet-Higgins and Widom model. Two sets of calculations were done one using the experimentalG ^E to calculateS ^E ,H ^E andV ^E , and the other making use of Miller’s cross parameter values. The calculated values are compared with those of Snider and Herrington and Miller’s values and also with the experimental values. The agreement was found to be good.     

Runaway Electron Measurements in the EAST Tokamak

An experimental study of runaway electrons in the EAST tokamak has been performed by a recently developed multi‐channel hard x‐ray diagnostics based on NaI(TL) scintillator detectors. It is found that in the current quench phase, the inductive loop voltage plays an important role in the generation of runaway electrons. And the avalanche mechanism was the main mechanism for runaway electrons after the disruptions. The distribution and transportation of runaway electrons were also investigated by multi‐channel hard x‐ray diagnostics. It is also found that the intensity of runaway electrons emission in the core plasma was much higher than those in the downside of the cross‐section, while the emission intensity of runaway electrons in the core plasma was almost the same. Calculated shrinking coefficient of runaway electrons emission after the plasma disruption was about 26 m/s according to the experimental data (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)