密度泛函理论研究镥二聚体低电子能态的相对稳定性、结构以及成键性质

用密度泛函理论方法研究了镥二聚体（Lu2）低能量电子态的性质,计算了电子态相对能量、平衡键长、振动频率以及基态解离能,考察了密度泛函性质、相对论有效势种类以及Hartree—Fock交换作用大小对计算结果的影响．结果表明,无论采用何种密度泛函和相对论有效势,体系的基态都为三重态,与其他一些基于分子轨道理论的从头计算方法得到的结论是一致的．另外,与分子轨道从头计算结果以及实验结果比较发现,采用杂化密度泛函理论和Stuttgart小核有效势计算得到的结果总体吻合最好．最后,特别分析研究了B3LYP计算中Hartree—Fock交换作用大小对基态键长和基态解离能的影响,发现随着交换作用的增大,键长增长,解离能减小,这是由于5d轨道杂化导致的共价成键作用减弱造成的．     

定形相变墙板改善轻质墙体夏季隔热性能研究

本文提出了将定形相变蓄能墙板安装在轻质保温墙体内侧,取代传统重质材料,改善围护结构夏季隔热性能的方法.以北京地区为例,比较了定形相变蓄能墙板与重质混凝土在改善轻质围护结构隔热性能方面的差异,并从相变温度和相变墙板厚度两个方面对定形相变蓄能墙板的使用效果进行了优化.研究表明定形相变蓄能墙板能有效改善轻质保温墙体的隔热性能,而对建筑自身承重增加很小.     

灰色最优聚类理论模型及其应用

本文根据灰色关联度的定义，运用广义加权距离构造目标函数，建立了一种灰色最优聚类理论模型，并结合实例说明了该模型的应用     

求解约束优化问题的一种新的遗传算法

提出一种新的求解约束优化问题的遗传算法,算法通过重新定义可行解与不可行解的适应度函数分别对它们进行选择,有效避免了惩罚函数法引入参数所带来的困难,重新设计的交叉算子使得算法对解空间的寻优范围扩大了.数值实验结果表明算法具有较好的鲁棒性,且对最优解位于约束边界上的一类问题具有很大优势.     

一个非线性时滞偏微分方程种群模型的稳定性与周期性

讨论了一个具有年龄结构非线性非自治时滞偏微分方程种群模型解的渐近性态,得到了零解稳定以及周期解存在的充分条件.     

Density Functional Study on Structures and Relative Stability of Gd(H2O)n3+(n=8,9)

用密度泛函理论方法研究了气相和水溶液中Gd(H₂O)_n³⁺(n=8,9)化合物的结构和相对稳定性,其中水溶剂效应利用极化连续介质方法结合多种溶质空腔模型进行模拟．气相计算得到的化合物结构与实验观察结果一致．计算结果表明,在气相中9配位Gd(H₂O)₉³⁺比8配位Gd(H²O)₈³⁺稳定,而在水溶液中稳定顺序刚好相反,这一结果不依赖于计算中采用的空腔模型种类,而且也与实验结果吻合．最后,通过采用各种空腔模型计算Gd³⁺的水合自由能,并与实验值比较,发现当化合物只包含第一层配位水分子时,UA0、UAHF及UAKS空腔模型最适合研究Gd³⁺在水溶液中的性质．     

两个含有2,6-二氟苯甲酸配体稀土配合物的合成及晶体结构

利用2,6-二氟苯甲酸和1,10-菲咯啉作为配体分别与Tm^3+、Yb^3+离子在常温下反应,制得2个稀土配合物[Tm(dfba)2(phen)(μ2-dfba)]2 (1)和[Yb(dfba)2(phen)(μ2-dfba)]2 (2)(dfba-=2,6-二氟苯甲酸根,phen=1,10-菲咯啉)。用元素分析、红外光谱对2个稀土配合物进行了表征,并用单晶X射线衍射确定了配合物的晶体结构;测定了配合物1和2的热稳定性。结构分析表明配合物1和2具有相似的晶体结构。每个Ln^3+与2个dfba-配体和1个phen分子配位,形成[Ln(dfba)2(phen)]+结构单元,[Ln(dfba)2(phen)]+单元再通过2个不同的dfba-配体桥联形成双核分子[Ln(dfba)2(phen)(μ2-dfba)]2(Ln=Tm,Yb)。     

Detection of a Physical Difference between the CDM Halos in Simulation and in Nature

Numerical simulation is an important tool that is helpful for us to understand the process of structure formation in the universe. However, many simulation results of cold dark matter （CDM） halos on a small scale are inconsistent with observations： the central density profile is too cuspy and there are too many substructures, Here we point out that both the problems may be connected with a hitherto unrecognized bias in the simulated halos. Although CDM halos in nature and in simulation are both virialized systems of collisionless CDM particles, gravitational encounter cannot be neglected in the simulated halos because they contain many fewer particles. We demonstrate this by two numerical experiments, showing that there is a difference on the microcosmic scale between the natural and simulated halos. The simulated halo is more akin to globular clusters where gravitational encounter is known to lead to such drastic phenomena as core collapse. Such an artificial core collapse process appears to link the two problems together in the bottom-up scenario of structure formation in the ACDM universe. The discovery of this bias also has implications on the applicability of the Jeans theorem in galactic dynamics.     

高速相干光通信平衡探测器研究

通过对相干光通信平衡探测器原理及关键技术进行分析,设计了一套高速平衡探测系统,并在室内构建了相干光通信测试平台.测试实验发现:该平衡探测器可以实现不同速率的相干探测,可为相干光通信提供有利的条件.在2.5Gbps通信速率下直接探测时,单管灵敏度可以达到-26dBm,动态范围为-26~3dBm;在本振光为3dBm时,相干探测的灵敏度可以达到-46.5dBm,动态范围为-46.5~3dBm.     

Effects of the Be_(22)W phase formation on hydrogen retention and blistering in mixed Be/W systems

We have performed first-principles density functional theory calculations to investigate the retention and migration of hydrogen in Be_(22) W, a stable low-W intermetallic compound. The solution energy of interstitial H in Be_(22) W is found to be 0.49 eV lower, while the diffusion barrier, on the other hand, is higher by 0.13 eV compared to those in pure hcp-Be. The higher solubility and lower diffusivity for H atoms make Be_(22) W a potential beneficial secondary phase in hcp-Be to impede the accumulation of H atoms, and hence better resist H blistering. We also find that in Be_(22) W, the attraction between an interstitial H and a beryllium vacancy ranges from 0.34 eV to 1.08 eV, which indicates a weaker trapping for hydrogen than in pure Be. Our calculated results suggest that small size Be_(22) W particles in hcp-Be might serve as the hydrogen trapping centers, hinder hydrogen bubble growth, and improve the resistance to irradiation void swelling, just as dispersed oxide particles in steel do.