对流扩散方程的稳定化流线扩散法最小二乘非协调有限元分析

将最小二乘法和稳定化的流线扩散法相结合,研究了对流扩散方程的非协调有限元格式,用矩形EQ_1~(rot)元和零阶R-T元分别来逼近位移和应力,利用单元本身的特殊性质,证明了离散格式解的存在惟一性,得到了位移H~1-模和应力H(div)-模的最优误差估计.     

Ga掺杂对ZnO纳米结构可见光发射的抑制效应

采用碳热还原反应和原位掺杂的方法制备了不同Ga掺杂浓度的ZnO纳米结构. X射线衍射 显示掺杂纳米结构中为单一的氧化锌纤锌矿结构. 扫描电子显微镜 观测发现随掺杂浓度的增大, 纳米结构的形貌逐渐从纳米六棱柱变为纳米锥.光致发光 和X射线光电子能谱 测量分别发现随着掺杂浓度升高, 纳米结构的可见发光强度和其中空位 氧峰相对强度逐渐减小直至消失, 两者存在很强的相关性. 上述结果为ZnO可见光发射的氧空位机理提供了新的实验证据. 对Ga掺杂抑制纳米结构中氧空位的原因进行了分析.     

Evaluation and prediction of the degradation of space Si solar cells induced by a low-earth-orbit radiation environment

Space-graded silicon solar cells are evaluated by 1 MeV and 2 MeV electron-irradiation. The mean degradation of the maximum power (P_max) is presented and analyzed. The degradation at both electron energies has been correlated with the displacement damage dose (D_d). A good linearity between the electron D_d and the mean P_max degradation is obtained. The concept of D_d has also been used to predict the Si solar cell response in a low-earth-orbit (Altitude 799 km, Inclination 99^o) radiation environment, considering the shielded effect of a 120 μ m-thick silica coverglass on reducing the radiation. Compared with the on-orbit data from a Si solar array of a Chinese satellite (duration from April 2007 to July 2010), a good match can be found between the on-orbit data and the predicted results using D_d methodology, indicating the method is appropriate for evaluating the radiation damage of the solar cells, and also to provide a new technique for studying radiation effects on the optoelectronic detectors used in many high energy physics applications, where harsh radiation environments produce damage in optoelectronic device materials.     

Exact solution of phantom dark energy model

We investigate the phantom dark energy model derived from the scalar field with a negative kinetic term.By assuming a particular relation between the time derivative of the phantom field and the Hubble function,an exact solution of the model is constructed.Absence of the ’big rip’ singularity is shown explicitly.We then derive special features of phantom dark energy model and show that its predictions are consistent with all astrophysical observations.     

摩擦阻力与软笔书法入门

1 书法教学之玄处书法入门往往从点画开始,有了笔画之基础奢望字型的间架结构和布局规律.但不管是名师如何把关指点还是学生怎样勤奋,各动作到位,例如,逆推,翻转,顺按,转峰等.全按要求做,挑不出毛病,总有部分入门者,做出来的笔画是软软的.老师称之为不实,无力.学生发问,何以为实,何以有力,则告之应稳键涩行,又问何以涩行,则告之,只可意会不能言传、由学生凭悟性自悟,何以悟法则无法,遂成教之悟处,学之玄处.     

ANALYSIS OF LASING PERFORMANCES OF Yb3+-DOPED YAG, FAP, KYW CRYSTALS

The Yb³⁺ laser emitting at a 1.03μm wavelength has been evoking strong interest recently due to its advantages of long fluorescence lifetime, broad absorption band and the fact that it never shows concentration quenching. On the other hand, as a laser of three-level system it has, in general, a relatively high threshold power, which makes it important to seek some suitable host crystals to reduce this. Here, we present a comparison of the lasing performances of Yb³⁺-doped YAG [Y₃Al₅O₁₂], FAP [Ca₅(PO₄)₃F] and KYW [KY(WO₄)₂] crystals, including threshold power and slope efficiency, with those of the Nd:YAG laser based on the threshold formula of three-and four-level systems deduced by the authors. The results show that the Yb³⁺ laser can output a power larger than the Nd:YAG laser does in the case of comparably higher pumping power, if the length of the lasing rod and the concentration of the active ions satisfy some conditions. The theoretical results are also close to the experimental results reported.     

关于正则轨道问题的一个例子

本文给出了关于正则轨道问题的一个反例.     

碳纳米管的离子束焊接研究

用C+离子束轰击多壁碳纳米管后, 发现了大量的由无定形碳纳米线组成的连接结构. 这种用高分辨透射电子显微镜和电子衍射分析确认的离子束焊接方法, 不但可以作为准备纳米电子（光子）学器件和线路的手段, 结合微操纵技术, 也有可能对其它系统器件排布的制作有所贡献.     

泰克频谱仪IQT文件的后台处理及在电子冷却实验中的应用

泰克实时频谱仪存储的IQT格式数据文件的特殊结构给后期实验数据处理带来不便。分析了IQT文件的存储结构,说明了泰克实时频谱仪的IQT格式数据文件的后台处理过程,通过数学方法提高了文件中频变弱信号的强度;通过对频谱仪实验数据进行数学处理,得到了兰州重离子加速器冷却储存环36Ar18+离子束的纵向电子冷却力大小随离子-电子相对速度的变化曲线。该处理方法弥补了频谱仪离线分析软件的局限性。     

土木工程结构健康监测系统的研究状况与进展

土木工程结构健康监测的研究是近年来国际学术研究的热点问题之一,涉及许多不同的研究领域,如数据采集系统、信号处理、结构分析等.阐述了实施土木工程结构健康监测的必要性和迫切性,介绍了结构健康监测系统的概念、组成及其应用,分析研究了结构健康监测系统的各个子系统的功能、特点和实现方法,重点讨论了实现各子系统的理论、方法和存在的若干力学问题,论述了结构健康监测在国内外土木工程领域的应用状况,最后对结构健康监测领域的几个重要问题做了展望.