一种用于APLA→JAVA系统可靠性评估模型

软件可靠性问题是软件测试中的重要难题之一,由于程序语言的复杂性以及被测程序的多样性,一直没有一个好的可靠性模型来评价它.鉴于此,依据软件可靠性工程理论,参考APLA→JAVA系统的特点,提出了一种基于测试的软件可靠性评估模型,讨论了模型的参数评估和置信区间,并给出了模型的评价方案.数据分析表明该模型具有合理性和可行性.

Production of heavy and superheavy nuclei in massive fusion reactions

Within the framework of a dinuclear system (DNS) model, the evaporation-residue excitation functions and the quasi-fission mass yields in the 48Ca induced fusion reactions are investigated systematically and compared with available experimental data. Maximal production cross sections of superheavy nuclei based on stable actinide targets are obtained. Isotopic trends in the production of the superheavy elements Z = 110, 112–118 based on the actinide isotopic targets are analyzed systematically. Optimal evaporation channels and combinations as well as the corresponding excitation energies are proposed. The possible factors that influencing the isotopic dependence of the production cross sections are analyzed. The formation of the superheavy nuclei based on the isotopes U with different projectiles are also investigated and calculated.

Production of new superheavy Z=108-114 nuclei with U-238, Pu-244, and Cm-248,Cm-250 targets

Within the framework of the dinuclear system (DNS) model, production cross sections of new superheavy nuclei with charged numbers Z=108-114 are analyzed systematically. Possible combinations based on the actinide nuclides U-238, Pu-244, and Cm-248,Cm-250 with the optimal excitation energies and evaporation channels are pointed out to synthesize new isotopes that lie between the nuclides produced in the cold fusion reactions and the Ca-48-induced fusion reactions experimentally, which are feasible to be constructed experimentally. It is found that the production cross sections of superheavy nuclei decrease drastically with the charged numbers of compound nuclei. Larger mass asymmetries of the entrance channels enhance the cross sections in 2n-5n channels.

Average property of fragmentation reaction and momentum dissipation induced by halo-nuclei in heavy ion collisions

We study systematically the average property of fragmentation reaction and momentum dissipation induced by halo-nuclei in intermediate energy heavy ion collisions for different colliding systems and different beam energies within the isospin dependent quantum molecular dynamics model (IQMD). This study is based on the extended halo-nucleus density distributions, which indicates the average property of loosely inner halo nucleus structure, because the interaction potential and in-medium nucleon-nucleon cross section in IQMD model depend on the density distribution. In order to study the average properties of fragmentation reaction and momentum dissipation induced by halo-nuclei we also compare the results for the halo-nuclear colliding systems with those for corresponding stable colliding systems with same mass under the same incident channel condition. We find that the effect of extended halo density distribution on the fragment multiplicity and nuclear stopping (momentum dissipation) are important for the different beam energies and different colliding systems. For example the extended halo density distributions increase the fragment multiplicity but decrease the nuclear stopping for all of incident channel conditions in this paper.

Dependence of isoscaling parameters on nucleon-nucleon cross section and momentum-dependent interaction

Influences of the isospin dependence of the in-medium nucleon-nucleon cross section and the momentum-dependant interaction (MDI) on the isotope scaling are investigated by using the isospin-dependent quantum molecular dynamics model (IQMD). The results show that both the isospin dependence of the in-medium nucleon-nucleon cross section and the momentum-dependent interaction affect the isoscaling parameters appreciably and independently. The influence caused by the isospin dependence of two-body collision is relatively larger than that from the MDI in the mean field. Aiming at exploring the implication of isoscaling behaviour, which the statistical equilibrium in the reaction is reached, the statistical properties in the mass distribution and the kinetic energy distribution of the fragments simulated by IQMD are presented.

Influence of isospin dependence of nucleon-nucleon cross section and momentum dependent interaction on the isoscaling in intermediate energy collisions

The influences of the isospin dependent in-medium nucleon-nucleon cross section and the MomentumDependent Interaction(MDI) on the isotope scaling have been investigated within the Isospin dependent Quantum Molecular Dynamics Model(IQMD). The results show that both the isospin dependent in-medium nucleon-nucleon cross section and the momentum interaction reduce the isoscaling parameter a appreciably, which means they decrease the dependence of yield ratios of two systems on the isospin difference between two systems.

Topological constraints on scroll and spiral waves in excitable media

A conservation equation for topological charges of phase singularities (scroll and spiral waves) in excitable media is given. It provides some topological properties of scroll (spiral) waves: for example, the topological charge of the generated or annihilated spiral pair must be opposite. Additionally, we obtain another equation on scroll waves, which shows that singular filaments of scroll waves occur on a set of one-dimensional curves which may be either closed loops or infinite lines.

Study on dynamic fusion barrier in heavy-ion fusion reactions

By means of the improved quantum molecular dynamics model, the incident energy dependent dynamical fusion potential barriers for heavy nucleus reaction systems are investigated. It is found that with decrease of incident energy the lowest dynamic barrier is obtained which approaches to the adiabatic static barrier and with increase of the incident energy the dynamic barrier goes up to the diabatic static barrier. Based on the dynamical study a microscopic understanding of the extra-push in fusion reactions of heavy systems and a new explanation of tunneling process for the fusion at the incident energy below the static and above the lowest dynamic barrier are presented. In order to understand the energy dependence of the dynamical barrier we also pay a great attention to study the neck formation and shape deformation during the dynamic lowering of the barrier.

Entrance channel effects on the role of isospin-dependent momentum interaction in isospin fractionation in heavy ion collisions

An isospin degree of freedom is inserted into the momentum dependent interaction in the quantum molecular dynamics model to obtain an isospin dependent momentum interaction given in a form practically usable in isospin dependent quantum molecular dynamics model. We investigate the entrance channel effects for the role of isospin momentum dependent interaction on the isospin fractionation ratio and its dynamical mechanism in the intermediate energy heavy ion collisions. It is found that the isospin dependent momentum interaction induces a significant reduction of isospin fractionation ratio under all entrance channel conditions. However the strong dependence of isospin fractionation ratio on the symmetry potential is preserved after considering the isospin degree of freedom in the momentum dependent interaction.

Probing high-density behavior of symmetry energy from pion emission in heavy-ion collisions

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the emission of pion in heavy-ion collisions in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation densities is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances Delta(1232) and N*(1440). The total pion multiplicities and the pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6. Ska and SIB, and also for the cases of different stiffness of symmetry energy with the parameter SLy6. Preliminary results compared with the measured data by the FOPI Collaboration favor a hard symmetry energy of the potential term proportional to (rho/rho(0))(gamma s) with gamma(s) = 2. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

Influence of entrance channels on the formation of superheavy nuclei in massive fusion reactions

Within the framework of the dinuclear system (DNS) model, the production cross sections of superheavy nuclei Hs (Z=108) and Z=112 combined with different reaction systems are analyzed systematically. It is found that the mass asymmetries and the reaction Q values of the projectile target combinations play a very important role on the formation cross sections of the evaporation residues. Both methods to obtain the fusion probability by nucleon transfer by solving a set of microscopically derived master equations along the mass asymmetry degree of freedom (ID) and distinguishing protons and neutrons of fragments (2D) are compared with each other and also with the available experimental data. (C) 2010 Elsevier B.V. All rights reserved.

PROBING THE SYMMETRY ENERGY AT SUPRA-SATURATION DENSITIES FROM PION EMISSION IN HEAVY-ION COLLISIONS

Within the framework of the improved isospin dependent quantum molecular dynamics (ImIQMD) model, the emission of pion in heavy-ion collisions in the region 1 A GeV as a probe of nuclear symmetry energy at supra-saturation densities is investigated systematically, in which the pion is considered to be mainly produced by the decay of resonances Delta(1232) and N*(1440). The pi(-)/pi(+) yields are calculated for selected Skyrme parameters SkP, SLy6, Ska and SIII, and also for the cases of different stiffness of symmetry energy with the parameter SLy6. Preliminary results compared with the measured data by the FOPI collaboration favor a hard symmetry energy of the potential term proportional to (rho/rho(0))(gamma s) with gamma(s) = 2.

基于紧束缚分子动力学模型的Na4,Na8和Na20团簇结构及热力学性质研究

利用距离相关的紧束缚的分子动力学模型（DDTB－MD），通过提取不同温度下的势能、构型、无单位键长涨落平均位移、扩散系数、围绕质心的径向分布等参量，系统的研究了菱形结构和T形结构的Na4、Td结构和D2d结构的Na8，以及Na20的热力学的性质。对于Na4，比较了金属团簇Na4的菱形结构和T形结构两种异构体之间热力学性质的异同。发现在团簇温度升高的过程中，两种异构体都会发生从类固到类液的相变。T形结构的Na4熔点要比菱形结构的低。在相变的过程中都会发生赝转动和异构化。还发现了赝转动的判据不仅仅只是温度，还包括无单位键长涨落的δ值。菱形结构的Na4在200K左右不一定会发生赝转动，只有观察到温度处于200K左右，δ值≥0.08的时候，赝转动则必然会观察到。菱形结构Na4的赝转动过程中会发现T形结构的异构化，但其维持时间很短，不稳定，很快又转变为菱形结构。而T形结构在170K就能观察到异构化和赝转动的发生，在这个温度下会不断的在菱形与T型之间发生异构，而处于菱形结构的时间要比T型长的多。表现为菱形结构的稳定性要大于T型。对于Na8的两种不同的异构体（分别为Td结构和D2d结构），发现尽管两个异构体的基态能量很接近，但他们的稳定性、熔化过程的热力学性质等有着很大的差别，这也反映了它们在几何结构上的差别。对称性强的Td结构更紧密，在熔化过程中表现出更高的稳定性，具有较高的熔点，具有类晶体的性质.对称性弱的D2d结构则具有较低的熔点，很宽的熔化温度范围，具有类似非晶体的性质. 再比较了基态结构下的Na8和Na20。通过提取对不同的子系统在不同温度下的无单位键长涨落等参数，发现金属原子团簇Na20在熔化过程中表现出了并不像通常金属团簇那样的表面先熔化，而是从内部开始先熔化的奇异特性

云南碧塔海自然保护区生态旅游开发模式研究

Bita lake provincial natural reserve is located in Shangri La region of North western Yunnan,and was set as a demonstrating area for ecotourism exploitation in 1998.After a year's exploitation construction and half a year's operation as a branch of the 99' Kunming International Horticulture Exposition to accept tourists,it was proved that the ecotourism demonstrating area attained four integrated functions of ecotourism,i.e,tourism,protection,poverty clearing and environment education.Five exploitation and management models including function zoned exploitation model, featured tourism communication model signs system designing model,local Tibetan family reception model and environmental monitoring model,were also successful,which were demonstrated and spreaded to the whole province.Bita lake provincial natural reserve could be a good sample for the ecotourism exploitation natural reserves of the whole country.