夸克平均场模型的有限核及超核研究

夸克平均场模型采用组分夸克模型描述重子,已被用于研究有限核及超核的性质.介子平均场直接与核子内的组分夸克相互作用,从而改变了核介质内重子的性质.夸克平均场模型能够给出令人满意的球型核及超核的性质,该模型也预言了核介质中核子体积的膨胀及核子有效质量的降低.     

The opacity coefficient method—nongray determination of inhomogeneous atmospheric extinction

The computation of radiation transmittance in nongray, inhomogeneous atmospheric models is frequently complicated by complex bands of line spectra which range in value over many orders of magnitudes and depend strongly on either or both of pressure and temperature. We present here a new opacity sampling technique which is shown to determine correctly the wavelength-averaged extinction due to path-dependent realizations of banded line spectra. The technique is easy to implement computationally and is applicable to a wide variety of atmospheric problems in which frequent iteration of the radiative transfer model is required. We consider two such instances: modeling of solar flux attenuation for use in a time-dependent planetary ionosphere model and retrieval from nadir measurements of backscattered solar irradiance. The power of the new method lies in its straightforward analytical treatment of both atmospheric inhomogeneity and spectral complexity. It is thus relevant for both retrieval and radiative transfer modeling purposes.     

肋片对后台阶湍流流动影响的数值模拟

采用二阶全展开ETG有限元方法作为大涡模拟空间离散格式,计算了Reynolds数为47625条件下的后台阶湍流流动,结果与相关实验资料符合良好,在此基础上分析了附加肋片高度和肋距对后台阶湍流流动的影响.计算结果表明,不同肋高和肋距对台阶下游流动具有较大的影响,相应条件下台阶下游的涡系及其时变过程都发生了很大的变化,计算给出了台阶回流段长度随肋高和随肋距变化的曲线,并指出,在台阶下游附加肋片可以作为后台阶湍流流动一种简单有效的被动控制方式.     

Bose-Einstein Condensation in Linear Sigma Model at Hartree Approximation

The BEG of charged pions is investigated in the framework of O（4） linear sigma model. By using Cornwall- Jackiw-Tomboufis formalism, we have derived the gap equations for the effective masses of the mesons at finite temperature and finite isospin density. The critical temperature and phase diagram of BEG are discussed in the non-chiral limit at Hartree approximation.     

微振动激励作用下编组站镜架对光束指向的影响

 编组站是靶场光路传输系统的重要组成部分,编组站镜架的稳定性对光路的传输有着直接的影响。为了分析微振动对光束指向性的影响,采用有限元分析软件建立镜架的有限元模型,将数字式地震仪测得的镜架安装平台的速度功率谱密度函数作为载荷施加到分析模型上,计算得到了编组站光学元件（A,B,C,D）在基座微振动激励作用下的转角漂移分别为0.338,0.327,0.289,0.241 mrad,均小于稳定性指标0.460 mrad的要求;采用加速度传感器对光学元件A的转角漂移测试结果为0.340 mrad,与分析结果的误差为0.6%,说明所采用的计算分析方法是有效的,为精密镜架的设计分析提供了有效的方法。     

On the accuracy of classical, semiclassical and quantum methods in collision line broadening calculations: Comparative analysis for C2H2-Ar, He systems

Accuracies of classical, semiclassical and quantum methods are comprehensively examined in calculations of impact line widths of C₂H₂ molecules perturbed by Ar and He. The field of comparative study covers both infrared absorption and Raman scattering lines of acetylene having rotational quantum number J=0-30 at temperatures 173 and 296 K. Calculations have been made by fully classical method and by three basic least approximate semiclassical methods, namely, Neilsen-Gordon (NG) method, peaking approximation (PA) and Smith-Giraud-Cooper (SGC) method. Most accurate ab initio potential energy surfaces (PES) of Yang et al. (1996) [21] and Mozsynski et al. (1995) [22] have been applied to model C₂H₂-Ar and C₂H₂-He interactions. The comparison has been made also with available experimental data and with the results of rigorous fully quantum-mechanical calculations within close coupling and coupled states approaches in identical conditions. Semiclassical methods are proved to be not so much accurate as it is generally believed since all they gave in the cases considered seriously underestimated results. The fundamental issue of the adequacy of simplified trajectories in collision broadening calculations is finally reasonably solved. In cases of C₂H₂-Ar and C₂H₂-He systems the use of the “exact” isotropic trajectories (i.e. driven only by the isotropic part of PES) is the main reason of failing of NG, PA and SGC methods. Thus the neglecting of back-influence of the RT exchange on the classical path is a principal defect of semiclassical methods. Finally, the application of simplified trajectories is recognized as inadequate and risky in broadening calculations for molecules having relatively small rotational constants when accurate ab initio PES are applied.     

Selectivity of seismic electric signal (SES) of the 2000 Izu earthquake swarm: a 3D FEM numerical simulation model

Although seismic electric signal (SES) has been used for short-term prediction of earthquakes, selectivity of SES still remains as one of the mysterious features. As a case study, we made a numerical simulation based on a 3D finite element method (FEM) on the selectivity of SES observed in the case of the 2000 Izu earthquake swarm. Our numerical results indicated that the existence of conductive channel under Niijima island could explain the reported SES selectivity.     

Phase diagram of a 2D Ising model within a nonextensive approach

In this work we report Monte Carlo simulations of a 2D Ising model, in which the statistics of the Metropolis algorithm is replaced by the nonextensive one. We compute the magnetization and show that phase transitions are present for q ≠ 1. A q - phase diagram (critical temperature vs. the entropic parameter q) is built and exhibits some interesting features, such as phases which are governed by the value of the entropic index q. It is shown that such phases favors some energy levels of magnetization states. It is also shown that the contribution of the Tsallis cutoff is capital to the existence of phase transitions.     

Enhanced nonlinearity in photonic crystal fiber by germanium doping in the core region

Germanium doping in silica can be used as a method for nonlinearity enhancement.Properties of the enhanced nonlinearity in photonic crystal fiber(PCF)with a GeO2-doped core are investigated theoretically by using all-vector finite element method.Numerical result shows that the nonlinear coefficient of PCF is greatly enhanced with increasing doping concentration,furthermore,optimal radius of the doped region should be considered for the desired operating wavelength.     

磁环中非晶丝的阻抗效应分析

依据Landau-Lifshitz阻尼项和Gilbert阻尼项的磁矩转动方程,提出统一形式的磁化率张量表达式.基于等效磁导率将非晶丝中各向异性的电磁场求解问题转化为等效的各向同性问题,进而分析了套在绝缘磁环或导电磁环中非晶丝的阻抗.采用基于有限元的数值方法仿真磁环中非晶丝的阻抗,仿真结果验证了理论分析结论.理论分析和仿真实验均表明,外磁体的附加阻抗将严重降低阻抗变化率,破坏巨磁阻抗特性.为此,提出采用回路形式降低附加阻抗的方法,并基于仿真实验验证了该方法的有效性. 关键词： 巨磁阻抗效应 非晶材料 Maxwell方程 有限元