自适应光学中的大气色散效应

用Zernike多项式展开的方法讨论了双波长自适应光学系统中的大气色散效应。根据位相展开系数的双频相关求得了大气色散产生的剩余位相误差。结果表明:虽然大气色散会使位相补偿不完全,但用比发射激光波长更短的光源为信标,并将信标位相畸变量与比值λ_2/λ_1(信标波长/发射波长)的乘积作为位相预畸变,能较好地校正发射光束的位相畸变。     

用压痕法研究玻璃的动疲劳强度

本文借助扫描电镜在对带压痕的钠钙硅玻璃试件的断面分析中，提出了理想的径向裂纹模型，分析了由压痕引起的表面接触残余应力裂纹长短对裂纹在开裂纹在开裂和亚监界扩展区的疲劳强度的影响，并设计了相应的强度实验进行了比较。     

Synthesis and characterization of poly(epoxy‐imide) crosslinked networks

Poly(epoxy imide)s were prepared by a reaction between a hydroxyl‐group‐containing soluble copolyimide and commercial epoxy resins at 220 °C for 2 h. Poly(epoxy imide) thin films exhibited higher thermal stability and lower dielectric constants than a commercial flip‐chip package material (U300). The thermal stabilities of the poly(epoxy imide)s were 1.4–2.0 times higher than that of U300. The thermal stability increased with increasing crosslink density and with decreasing bulky CF₃ groups (which were easily decomposable). The dielectric constants of the poly(epoxy imide)s were 1.1–1.3 times lower than that of U300, and this is highly desirable for the microelectronic packaging industry. The dielectric constant dramatically decreased when bulky CF₃ groups were added and when the functionalities of epoxy resins decreased. The residual stresses, slopes in the cooling curves, and glass‐transition temperatures of the poly(epoxy imide)s were measured with a thin‐film stress analyzer. Low residual stresses and slopes in the cooling curves were achieved with a higher crosslink density. However, in the presence of bulky CF₃ groups, the copolyimide backbone structure did not affect the residual stress values. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4293–4302, 2004     

毫米波LFMCW雷达调频非线性剩余频差的估计

针对LFMCW雷达中调频非线性剩余频率误差的估计问题，提出了一种基于过零检测和周期图的参数估计方法，详细分析了相位调制正弦信号的过零检测误差，仿真试验表明，该方法能够精确地估计调频非线性剩余频差，具有较高的运算效率，并给出了一个实际试验结果。     

Comparison of three solvers for viscoelastic fluid flow problems

The computational efficiency of three numerical schemes has been examined for the solution of a linearized system of equations resulting from the finite element discretization of a viscoelastic fluid flow problem. The first scheme is a modified frontal solver, which solves the linear system of equations directly. The other two, one based on a biconjugate gradient stabilized (BiCGStab) method and another based on a generalized minimal residual (GMRES) method, are iterative schemes. The stick-slip problem and the four-to-one contraction problem were analyzed and the viscoelastic fluid was assumed to obey the Oldroyd-B model. The two iterative schemes are superior to the direct scheme in terms of CPU time consumed and the BiCGStab scheme is even faster than the GMRES scheme. The range of convergence for both iterative schemes is compatible with that of the direct scheme.     

General Relativity as a (Constrained) Yang-Mills Theory and a Novel Gravity with Torsion

We show that General Relativity (GR) with cosmological constant may be formulated as a rather simple constrained SO(D – 1, 2) (or SO(D, 1))-Yang-Mills (YM) theory. Furthermore, the spin connections of the Cartan-Einstein formulation for GR appear as solutions of a genuine SO(D – 1,1)-YM. We also present a theory of gravity with torsion as the most natural extension of this result. The theory comes out to be strictly an YM-theory upon relaxation of a suitable constraint. This work sets out to enforce the close connection between YM theories and GR by means of an alternative construction.     

内射模的t－平坦性

设Ｒ为环，ｔ是左Ｒ－模范畴的一个遗传挠理论．文中证明了下述各点等价：（１）每个内射左Ｒ－模是ｔ－平坦的；（２）每个ｔ－有限表现左Ｒ－模的内射包络是ｔ－平坦的；（３）每个ｔ－有限表现左Ｒ－模是自由Ｒ－模的子模；（４）每个ｔ－有限表现左Ｒ－模是自反的且其对偶模是Ｈ－有限生成的．     

On a Universality of the Heat Equation

We prove that there are solutions u(t,x) of the heat equation u_t = u_xx such that every continuous function f : [a, b] → ? can be uniformly approximated by a subsequence of u (n, ·), n? ?.     

Activation energy of hydrogen in Lu

The impurity induced charge density is calculated in jellium by solving the Schr?dinger equation self-consistently following the procedure of Manninen and Nieminen and using Kohn-Sham density functional formalism. The host-ion contribution is included through the spherical solid model potential (SSMP). The calculated activation energy 0.27 eV is found in good agreement with experimental value 0.28±0.02 eV. The estimated residual resistivity 1.02 μΩ cm/at% for Lu-H system using the resulting phase shifts agrees reasonably well with the observed value 1.75±0.10 μΩ cm/at%. The calculated configurational energy shows that hydrogen prefers tetrahedral(T)-sites over octahedral(O)-sites in Lu matrix. This has been confirmed by Bonnet experimentally. A very shallow value ofs-type bound state of energy −0.00316 Ryd predicts that there is no formation of lutetium hydride solution and H⁺ exists as a free ion in Lu matrix.     

GPS姿态测量中相位模糊的解算方法

文中从GPS姿态测量原理出发，讨论了解决相位模糊这一关键问题，首先讨论了采用有限基线长度或相位平滑伪距值来确定相位模糊搜索空间，然后利用存在的冗余相位观测量采用相位残差及基线长度统计检验对相位整周模糊向量进行搜索，最后得到唯一正确的整周模糊向量，进而可解算出对应的基线矢量，从而得到载体姿态。利用上述方法对GPS实测数据进行处理，可在较短时间内解决相位模糊问题。