增加复合抛物面聚光器(CPC)最大聚光角的几种方法及结果比较

本文简单阐述了复合抛物面聚光器(CPC)的结构与设计原理,介绍了三类增加CPC最大聚光角θmax的方法:平移、截底和旋转,给出了各方法中最大聚光角θmax随几何尺寸变化的计算公式.对不同聚光比的实际CPC,给出了.在三类方法变化情况下,最大聚光角增量δθmax随几何变量的变化曲线,并对影响CPC最大聚光角变化的关键因素进行了讨论与分析.     

一水甲酸锂最佳相位匹配角的计算

本文计算了mm2型—水甲酸锂晶体的相位匹配角和有效非线性系数随基波波长变化的规律。发现对每个基波都存在着一个或两个最佳相位匹配角(θ,φ),并作出了θ,φ随基波波长变化的拟合公式。按计算所得的角度切割的—水甲酸锂倍频元件分别得到了0.53μ、0.35μ和0.266μ的倍频光.     

电流变液中的旋光现象

根据光波在介质中的传播理论，由麦克斯韦方程出发，对非均相结构电流变流导出在外电场与光场交互作用下旋光角ψ与入射线偏振光振动方向与外加电场方向间夹角θ及ζ（取决于电流变液材料本身及外加电场强度）的函数关系式。对不同浓度、不同场强下的SiO2电为液的旋光进行了测量，实验发现，同一场强作用下，旋光角ψ随浓度c的增大而增大；对于同一浓度，旋光角ψ随场强E增大而增大；在浓度c与场强E一定的情况下，旋光角ψ还随θ角而变化。实验结果与理论预测吻合较好。     

球面沟槽多轴联动铣削的加工

本项研究是针对球面沟槽的铣削加工进行研究。球面沟槽共有α，β，γ，θ四种构型，均为球面向心等深槽，呈网络分布。该项研究基于五轴联动加工中心进行了球面沟槽铣削加工的研究。通过仔细分析图纸，攻克了难点，根据空间几何关系进行计算，推导出了α槽、β槽以及γ槽等与向心角θ和水平角w之间的几何关系式，以及在加工运动过程中，随着θ角的变化，机床坐标轴y、z与θ角的几何关系式。     

影响单摆振动周期的参数研究

应用振动分析的方法,研究了单摆的周期受摆角、摆球的线度、地球纬度、摆球离地面的高度、介质黏度和介质密度参数的影响;作出了周期比随参数变化的曲线.结果表明:单摆的周期随摆角、摆球的线度、摆球离地面的高度、介质黏度和介质密度的增大而增大,随地球纬度的增大而减小.     

极紫外与X射线波段正入射两镜反射系统的研究

基于三级象差理论,分析了几何象差对正入射望远镜性能的影响,总结了弥散斑角宽度θ随着系统f数和半视场角uP的变化趋势.弥散斑的角宽度θ随着半视场角uP的增大而增大,随着系统f数的增大而减小.当f数小于10或者半视场角uP大于0.005弧度时,弥散斑角宽度θ变化比较剧烈.详细讨论了四种典型的反射系统,Dall-Kirkham系统和反Dall-Kirkham系统的弥散斑角宽尺寸在一个数量级上,大约为卡塞格林系统的十倍.R-C系统的弥散斑角宽最小,几乎是卡塞格林系统的十分之一.通过本文的结论公式可以估算一个光学系统的象差尺寸并避免进行光线追迹.     

一个新的精确可解的三维解析势

提出了一种新的精确可解的三维解析势函数,即环形非球谐振子。势函数为V（γ,θ）=1/2mω^2γ^2 h^2/2mA/γ^2 h^2/2mb/γ^2sin^2θ。将环形非球谐振子势的Schroedinger方程在球坐标系中进行变量分离,得到了角向方程和径向方程,给出了精确的能谱方程,获得了用普遍的associated-Legendre多项式表示的归一化的角向波函数和用合流超几何函数表示的归一化的径向波函数。球谐振子、非球谐振子和环形振子的有关结果均作为特例包含在本文的一般结论之中。     

彩虹及在非均匀球中的应用

利用广义洛伦兹-米氏理论，研究了多层球折射率按指数规律变化时，其一阶彩虹角分布随折射率变化的情况。研究结果表明，无论折射率为指数增大还是指数衰减，多层球彩虹角位置均与折射率分布密切相关，为探测非均匀球的折射率及梯度分布以及燃烧室的温度分布提供了有效的信息。     

磁场中手性碳纳米环的类超导效应

利用导出的任意手性碳纳米环（TCNTs）的电子状态－能量关系式,对磁场中任意手性TCNTs所具有的类似超导环的性质及持续电流的手性效应进行理论探讨。在T＝0K时,金属型和半导体型TCNTs象介观一维正常金属环一样具有类似超导环的性质、即持续电流以磁通量子φ0为周期随φ线性变化,且对手性角θ、环半径R极为敏感。手性TCNTs类似超导环的性质比高对称TCNTs明显得多,但随R增大而减弱,且减弱的快慢也与手性角θ有关。     

双层膜极向Kerr效应的增强与其本征值之间的关系

应用相干光迭加的普遍原理，从理论上导出了双层膜情况下，介质增强后的极向Ｋｅｒｒ角（θ_k）与磁光介质本征的极向Ｋｅｒｒ角（θ⁰_k）之间关系的解析表达式，指出了光经玻璃衬底面入射到磁光介质时测量的Ｋｅｒｒ角θ_k与磁光介质本征Ｋｅｒｒ角θ⁰_k的不同，提出了一种简便的测量θ⁰_k的方法，并讨论了Ｋｅｒｒ角θ_k介质增强的物理原因，从理论上导出了等离子体吸收边情况下，双层膜的Ｋｅｒｒ角θ_k增强的关系式。 关键词：     

Double-beam fourier spectroscopy with two inputs and two outputs

A theoretical treatment of double-beam Fourier spectroscopy, with two inputs and two outputs measured by a single detector, is presented. One of the novel features is the use of the radiation that returns to the source in a conventional Fourier spectrometer, i.e., the anti-interferogram beam. The double beam feature allows simultaneous measurement of the difference in the spectra of the sample and a reference standard with optical cancellation of common features. Several versions of spectrometers suited for specific applications are discussed as special cases. Applications include the ability to measure small absorptivity or reflectivity against strong and varying background, to compare the emission spectra of two nearly equal sources, or the sensitivity of two different detectors. Moreover, by suitably chopping the input or output beams, the noise due to fluctuations in source intensity may be strongly reduced.     

Simulation of two dimensional systems with two dimensional electrostatics

Some of the problems associated with Monte Carlo and molecular dynamics simulations of three dimensional ionic and dipolar systems are discussed, with emphasis on the use of periodic boundary conditions (PBC). It is shown that analogous problems may arise in two dimensional systems provided that the interactions are two dimensional electrostatic interactions, that is, interactions derived from the two dimensional Laplace equation. The PBC hamiltonian is evaluated by considering the appropriate two dimensional lattice sums, and a computable form for the effective pair interactions in PBC developed. The idea of an external dielectric constant is introduced and its effects included in the PBC hamiltonian. Formulae for evaluating the dielectric constant from a simulation with any external dielectric constant are given. Perturbation formulae showing the effects on the structure and mean square dipole moment of a dipolar system which are caused by a change in external dielectric constant are derived. A formula for the shift in mean square dipole moment of an ionic system is also developed. The problem of interpreting results from such simulations is discussed briefly.     

Entanglement dynamics of two distant atoms in two detuning cavities

We investigate the entanglement dynamics via the concurrence of two distant atoms interacting off-resonantly with two cavity fields in Fock states,respectively.We find that the evolution of entanglement has sudden death and sudden birth phenomena,that with the increase of photon numbers in the two cavities,the alternate frequency of sudden death and sudden birth turns fast,and that the amplitude of concurrence oscillates regularly with oscillation frequency becoming slow when the cavity fields have the same photon numbers.While,the maximum of concurrence declines and the amplitude of concurrence oscillates irregularly when the two cavity fields have different photon numbers.In addition,we find the length of death time is dependent on the initial entanglement.     

Tunnelling through two barriers

Recent theoretical studies of the tunnelling through two opaque barriers claim that the transit time is independent of the barrier widths and of the separation distance between the barriers. Such a result is based on the use of the stationary phase method and the hypothesis of a single transmitted wave packet. In this Letter, we propose an alternative treatment based on a multiple peaks decomposition of the transmitted wave. We observe, that if multiple reflections are allowed for correctly (infinite peaks) the transit time between the barriers appears exactly as expected.     

Generalized two phonon theory

Recent laser experiments and theoretical discussions of coherent two photon transient phenomena have prompted us to develop a generalized theory for the case of anN+2 level quantum system interacting with two optical fields. New perturbation solutions, derived from an effective two level Hamiltonian, are presented in the form of a continued fraction expansion where the leading term agrees with earlier treatments. The theory applies to homogeneously broadened systems where the intermediate transitions are far off resonance. When inhomogeneous broadening plays a role, the expansion parameter is no longer unique and the theory breaks down. Nonperturbative solutions are then required which are also capable of explaining other features not appearing in the perturbative approach. An important example is intensity-dependent dephasing. Exact and approximate solutions of this kind are derived.     

Quantum logic operations on two distant atoms trapped in two optical-fibre-connected cavities

Based on the coupling of two distant three-level atoms in two separate optical cavities connected with two optical fibres, schemes on the generation of several two-qubit logic gates are discussed under the conditions of Δ = δ - 2ν cos πk/2 >> g/2 and ν ~ g. Discussion and analysis of the fidelity, gate time and experimental setups show that our schemes are feasible with current optical cavity, atomic trap and optical fibre techniques. Moreover, the atom-cavity- fibre coupling can be used to generate an N-qubit nonlocal entanglement and transfer quantum information among N distant atoms by arranging N atom-cavity assemblages in a line and connecting each two adjacent cavities with two optical fibres.     

Invasion percolation between two sites in two, three, and four dimensions

The mass distribution of invaded clusters in non-trapping invasion percolation between an injection site and an extraction site has been studied, in two, three, and four dimensions. This study is an extension of the recent study focused on two dimensions by Araújo et al. [A.D. Araújo, T.F. Vasconcelos, A.A. Moreira, L.S. Lucena, J.S. Andrade Jr., Phys. Rev. E 72 (2005) 041404] with respect to higher dimensions. The mass distribution exhibits a power-law behavior, P(m)∝m^−α. It has been found that the index α for p_e<p_c, p_c being the percolation threshold of a regular percolation, appears to be independent of the value of p_e and is also independent of the lattice dimensionality. When p_e=p_c, α appears to depend marginally on the lattice dimensionality, and the relation α=τ−1, τ being the exponent associated with cluster size distribution of a regular percolation via n_s∝s^−τ, appears to be valid.