地源热泵的运行特性模拟研究

依据圆柱源理论,建立起了耦合地面热泵机组和地下埋管换热器特性的模拟模型,该模型可用于长期运行的地源热泵系统的短时间步长运行特性模拟。探讨了模拟过程中有关参数的确定方法,并运用所建模型对地源热泵的冬季和夏季运行特性进行了模拟。运行特性模拟与实验数据的验证结果表明,所建模型可以对地源热泵的运行特性做出符合实际的预测。     

短脉冲强激光在稀薄等离子体中传播时的电磁类孤立子

 采用二维粒子模拟方法，研究了短脉冲强激光在稀薄等离子体中传播时电磁类孤立子的产生和时空演化过程。通过分析电磁场与等离子体波的非线性能量交换和激光场的频率谱结构等，给出了电磁类孤立子形成的基本物理图像，讨论了等离子体参数对电磁类孤立子形成的影响。模拟结果表明：类孤立子的形成是由于局部电磁波振荡频率减小至等离子体频率引起的，初始等离子体密度越高越容易形成空间局域结构。     

风冷热泵冷热水机组动态过程仿真

本文给出了风冷热泵冷热水机组动态过程模型。系统的高、低压段被分成制冷剂侧、管壁、以及水或空气侧三个控制容积。针对每个控制容积建立了质量和能量平衡的微分方程。由于压缩机、热力膨胀阀阀体、以及四通换向阀具有较小的热惯性,因而采用稳态模型描述压缩过程、膨胀过程、以及内泄露过程。膨胀阀感温包中的制冷剂温度对于蒸发器出口温度的延迟用一阶惯性环节来描述。通过“预测-校正”和“自适应步长”方法实现系统仿真。仿真结果与测试数据吻合良好。     

Constructing Solutions of an Ill-Posed Nonlinear Singularly Perturbed Problem for an Equation of Elliptic Type

Mathematical Notes -     

儿童的铅中毒问题──Ⅱ．彩色油墨中铅的测定

用能量色散Ｘ射线荧光分析法测定了某厂生产的４４种彩色油墨纸中的铅含量．结果发现，除５种油墨外，其它３９种彩色油墨纸中的铅含量均比对照纸中高９倍以上，其中桔黄色、桔红色树脂胶版油墨高５００倍以上，棕色树脂胶版油墨高３７９倍，深黄色和柠檬黄色树脂铅印油墨分别高１７０和１１３倍．这表明，彩色油墨印刷品可能是儿童慢性铅中毒的重要污染源．     

BEPCⅡ束流相关本底的蒙特卡罗模拟研究(Ⅱ)—束流-气体相互作用

介绍了用蒙特卡罗方法研究正常对撞模式下束流本底中的束流-气体相互作用的原理与效果.使用通用的模拟工具,研究了BEPCⅡ的束流-气体本底对设计中的BESⅢ的影响.结果显示,在储存环上设置挡板后,探测器的本底在允许的范围之内.模拟结果对BEPCⅡ-BESⅢ的设计建造具有指导意义.     

Speed of adaptation in structured populations

Adaptation of populations takes place with the occurrence and subsequent fixation of mutations that confer some selective advantage to the individuals which acquire it. For this reason, the study of the process of fixation of advantageous mutations has a long history in the population genetics literature. Particularly, the previous investigations aimed to find out the main evolutionary forces affecting the strength of natural selection in the populations. In the current work, we investigate the dynamics of fixation of beneficial mutations in a subdivided population. The subpopulations (demes) can exchange migrants among their neighbors, in a migration network which is assumed to have either a random graph or a scale-free topology. We have observed that the migration rate drastically affects the dynamics of mutation fixation, despite of the fact that the probability of fixation is invariant on the migration rate, accordingly to Maruyama's conjecture. In addition, we have noticed a topological dependence of the adaptive evolution of the population when clonal interference becomes effective.     

热动力学问题的数值计算

 对含热传导的流体动力学方程组，用有限元方法进行数值求解。采用傅里叶热传导计算热流、用热流连续条件计算单元间接触面的温度、用三角形传热法计算体单元表面的热流，考虑各向同性弹塑性流体材料模型、三项式物态方程和导热系数与状态的相关性，给出了傅里叶热传导、接触传热、热应力应变效应、以及混合物冲击压缩特性等算例。对混合物冲击温度的数值模拟表明，小颗粒混合物在冲击压缩过程中，颗粒间的温度有差别、稍有波动，并随时间趋向于一致，以至热平衡。     

自由电子激光振荡器的二维数值模拟

在柱二维坐标系中,用数值计算方法求解了摇摆器内电子模拟方程组、光场方程组和无源区(不含摇摆器区)经非自适应方法变换后的无源旁轴波动方程并设计了相应的程序R_2D。用该程序计算的数值结果表明,在有源条件下二维数值模拟结果与高斯光束近似下的数值模拟结果符合较好;取完全相同的计算条件R-2D程序与洛斯阿拉莫斯实验室(LANL)的FELEX程序的计算结果符合较好;初步认为LANL实验数据的物理图象合理,数值结果基本可信;最后给出北京自由电子激光器(BFEL)的一些物理数据。     

Thermal helium clusters at 3.2 Kelvin in classical and semiclassical simulations

The thermodynamic stability of⁴He_4–13 at 3.2 K is investigated with the classical Monte Carlo method, with the semiclassical path-integral Monte Carlo (PIMC) method, and with the semiclassical all-order many-body method. In the all-order many-body simulation the dipole-dipole approximation including short-range correction is used. The resulting stability plots are discussed and related to recent TOF experiments by Stephens and King. It is found that with classical Monte Carlo of course the characteristics of the measured mass spectrum cannot be resolved. With PIMC, switching on more and more quantum mechanics. by raising the number of virtual time steps results in more structure in the stability plot, but this did not lead to sufficient agreement with the TOF experiment. Only the all-order many-body method resolved the characteristic structures of the measured mass spectrum, including magic numbers. The result shows the influence of quantum statistics and quantum mechanics on the stability of small neutral helium clusters.