用遗传算法研究一维光晶格中玻色凝聚气体基态波函数

以Gross-Pitaevskii（G-P）平均场能量泛函为目标函数,运用遗传算法研究一维光晶格系统中玻色凝聚气体的基态性质,提出了求解系统波函数的一种新方法.通过优化计算,对当前常用的托马斯-费米近似和高斯近似模型进行修正和讨论,并给出最优基态波函数.关键词：玻色凝聚气体遗传算法波函数     

评估学习行为,改革教学模式

本文从调查研究着手,分析了当前大学生学物理存在的问题,提出了具体的教学对策,并对一年来教改实践效果用调查数据作了对比分析,得到了有意义的教学启示,取得了有益经验     

Adiabatic tunneling of Bose–Einstein condensates with modulated atom interaction in a double-well potential

We study the adiabatic tunneling of Bose–Einstein condensates in a symmetric double-well potential when the interaction strength between the atoms is modulated linearly or in a cosine periodic form. It is shown that the system evolves along a nonlinear eigenstate path. In the case of linear modulation under the adiabatic approximation conditions, the tunneling probability of the condensate atoms to the other potential well is half. However, when the system is periodically scanned in the adiabatic process, we find an interesting phenomenon. A small change in the cycle period can lead to the condensate atoms returning to the right well or tunneling to the left well. The system comes from a linear eigenstate back to a nonlinear one, which is completely different from the linear eigenstate evolution. We explain the results by using the energy level and the phase diagram.     

遗传算法在激光器谐振腔优化设计中的应用

讨论了用遗传算法优化设计普通激光器谐振腔参量的方法.以典型的50cm长的氦氖(He-Ne)激光器为例,进行了具体计算.结果表明:对于输出相同的激光功率,模拟优化的谐振腔参量与传统局域化设计(非优化)的结果基本一致.通过适当匹配谐振腔参量,仍可提高激光(单模)的输出功率.     

光栅衍射实验的误差分析及改进途径

平行光未能严格垂直入射光栅将形成误差,常用的对称测量法只能消除误差的一阶修正项,仍存在二阶修正项误差。采用测量最小衍射角的方法能有效地消除一阶、二阶修正项的误差,而且能观测到更高级次的衍射条纹,从而减少读数误差,提高实验精度。     

玻色凝聚原子云的二次干涉及其放大效应

捕限在三维轴对称谐振势阱叠加一维光晶格势的组合势中的玻色凝聚气体,取消磁阱和光晶格势后,将形成沿轴向向两侧运动的干涉边峰.提出一个新的实验方案,使这样的干涉边峰再次相遇叠加,以探讨物质波的二次干涉效应.研究表明,在干涉边峰相干加强的区域,玻色凝聚原子云的密度会得到有效放大.基于现有的实验技术,这个新实验是可以实现的,这种效应也是可以观测得到的.     

轴对称谐振势阱中玻色凝聚气体基态和单涡旋态解

对囚禁在轴对称谐振势阱中的玻色凝聚气体,提出一种新的试探波函数,运用Gross-Pitaevskii(G-P)平均场能量泛函和变分的方法,得到玻色凝聚气体基态和单涡旋态波函数的解析表达式,并计算出凝聚原子的平均能量、原子云轴向和径向尺度比,以及产生单涡旋态的临界角速度等重要物理量与凝聚原子数N之间的关系.其结果与Dalfovo等人直接数值求解G-P方程所得到的结果相一致.关键词：玻色凝聚气体G-P泛函波函数谐振势阱     

Ground State Properties for Bose-Condensed Gas in Anisotropic Traps

Based on the energy functional and variational method, we present a new method to investigate the ground state properties for a weakly interacting Bose-condensed gas in an anisotropic harmonic trap at zero temperature. With this method we are able to find the analytic expression of the ground-state wavefunction and to explore the relevant quantities, such as energy, chemical potential, and the aspect ratio of the velocity distribution. These results agree well with previous ground state numerical solutions of the Gross-Pitaevskii equation given by Dalfovo et al. [Phys. Rev. A 53 （1996） 2477] This new method is simple compared to other methods used to solve numerically the Gross-Pitaevskii equation, and one can obtain analytic and reliable results.     

端羟基聚乳酸的合成与表征

采用共沸除水与醇酸缩合反应相结合的方法合成端羟基聚乳酸。通过L9(3^4)正交实验对合成工艺进行了研究,分析了抗氧剂TPP对反应的影响,并用^1H-NMR和DSC对产物结构进行表征。结果表明,产物主要为聚乳酸-1,4-丁二醇(PIA-1,4-BD)。和分子量相同的聚乳酸-1,4-丁二醇．聚乳酸(PLA-1,4-BD-PLA)比较,PLA-1,4-BD具有较高的Tg。