材料复介电常数测量方法研究进展

介绍了材料复介电常数测量方法的研究进展,包括理论基础,发展过程,以及最新的应用.其中主要以谐振法,传输反射法,自由空间法为研究对象,就各类方法的优缺点与适用情况进行分析,也简要介绍了时域测量法.     

H_2/N_2/O_2射流扩散火焰的直接数值模拟

直接数值模拟(DNS),大涡模拟(LES)与雷诺时均模拟(RANS)是数值模拟燃烧流动的三大主要方法,而射流扩散火焰在燃烧理论,实验研究与数值模拟中都扮演着十分重要的角色,本文采用完全可压缩的Naive-Stokes方程,对喷口直径为D=1 mm,Re=2000的射流扩散火焰进行了直接数值模拟.本文首先分析了冷态时H_2,O_2的混合,发现燃料与氧气在流向长度大于6D后的区域混合得十分充分.随后本文分析了燃烧后的统计特性,主要包括速度场,密度,温度以及主要组分与混合分数的分布,并将DNS结果与实验结果进行对比分析.     

一维多孔硅光子晶体反射特性及制作的理论研究

在一维光子晶体光学传输特性理论的基础上,运用传输矩阵法推导了一维多孔硅光子晶体的反射特性,并对其反射特性与结构参数的关系进行了分析。给出了采用脉冲电化学阳极腐蚀法制备一维多孔硅光子晶体的制作模型。利用计算机数值模拟的方法给出了各种一维多孔硅光子晶体的典型反射谱。为多孔硅光子晶体的实际应用奠定了理论基础。     

A New Low-Impedance High Power Microwave Source

We propose a new low-impedance high power microwave source based on the axial transit time effect, i.e. alow-impedance axial transit-time oscillator. The analysis and simulation are carried out to investigate the char-acteristics of this new configuration. In the numerical simulation, the microwave output peak power of 6 GWis obtained with an electron beam in the electron energy 580keV and in the beam current 20kA. The diodeimpedance is 29Ω The power of the input electron beam is 11.6 GW. The beam-to-microwave power conversionefficiency is 51.7%. The frequency is 3.9 GHz by numerical simulation.     

无反射势阱中相对论粒子的束缚态

给出了具有无反射势型标量势与矢量势的Klein-Gordon方程和Dirac方程的s波束缚态解. 关键词： 无反射势 Klein-Gordon方程 Dirac方程 束缚态     

激光大气传输中热晕的数值模拟

采用快速傅里叶变换,研究了激光在大气传输中的热晕现象。得出了一定条件下,热晕随激光输入功率和传播距离的稳态变化规律,并计算了激光在大气中传输10km时发生热晕的功率阈值。在瞬态情况下,研究了有风和无风热晕现象。     

利用受激布里渊散射效应补偿激光大气传输过程中的畸变

提出了利用受激布里渊散射的阈值效应主动在非配合,扩展目标上实现小面积信标的方法,在不同的大气扰动条件（Cn^2=10^-16--10^-12)下,对激光的远距离（10km)补偿传输过程进行了模拟计算,获得了到达目标上的相位共轭光的光强分布。分别在不同的实验环境进行了激光补偿传输实验,其中激光补偿传输距离最远达到250m。实验结果证实了利用受激布里渊散射实现激光大气传输补偿的有效性,证明利用阈值效应在目标上主动获得小面积信标的方法是可行的。     

扩展物体漫反射光传输及成像的数值模拟研究

对扩展漫反射体的成像进行了数值模拟研究，利用近轴近似标量波动方程及其分步相屏算法，对漫反射体反射的相对于接收孔径光轴的近轴光传输及其成像进行数值模拟计算分析，结果表明该模拟算法是可行的，也对图像传输的湍流效应进行了初步计算和讨论。     

耦合边处理的特征无反射边界条件研究

详细分析特征无反射边界条件(Characteristic Non-reflecting Boundary Conditions)中边耦合处理方法,提出耦合处理的数学方法,数值模拟表明,该方法处理声波扰动时有明显的优势.对可压缩圆孔射流进行直接数值模拟,结果与试验吻合较好,表明提出的耦合边处理的特征边界数学分析方法是可行的.     

湍流大气中无衍射涡旋光束的展宽及相位奇点的演化

以经过圆形孔径截断的Bessel涡旋光束和Bessel-Gauss涡旋光束为例,数值模拟了近似无衍射涡旋光束在湍流大气中传输时引起的光束扩展和畸变光场中相位奇点的变化。仿真结果表明,与Bessel涡旋光束相比,Bessel-Gauss涡旋光束由大气湍流引起的束宽扩展较小,且在一定条件下其相位奇点代数和与入射涡旋光束的拓扑荷数保持一致;在远距离传输时,Bessel-Gauss涡旋光束相位奇点代数和的起伏偏差远小于Bessel涡旋光束。Bessel-Gauss涡旋光束在自由空间光通信中作为信息载体具有较大的优势。     

Transmission time of a particle in the reflectionless Sech-squared potential: Quantum clock approach

We investigate the time for a particle to pass through the reflectionless Sech-squared potential. Using the Salecker-Wigner and Peres quantum clock an average transmission time of a Gaussian wave packet representing the particle is explicitly evaluated in terms of average momentum and travel distance. The average transmission time is shown to be shorter than the time of free-particle motion and very close to the classical time for wave packets with well-localized momentum states. Since the clock measures the duration of scattering process the average transmission time can be interpreted as the average dwell time.     

Tunneling time based on the quantum diffusion process approach in multichannel and optical potential cases

We analyze the effects of inelastic scattering on the tunneling time theoretically, using generalized Nelson’s quantum mechanics. This generalization enables us to describe quantum system with channel couplings and optical potential in a real time stochastic approach, which seems to give us a new insight into quantum mechanics beyond Copenhagen interpretation     

Supersymmetric quantum mechanics and the index theorem

We consider the classical mechanics of the spinning particle and investigate which Abelian interactions can be added without breaking supersymmetry. A quantum theory is presented. The well known index theorem for the Dirac operator is extended to take into account the effect of anti-symmetric Abelian tensor fields. Furthermore interactions with non-Abelian anti-symmetric tensor fields are investigated. It turns out in both cases that these fields do not give any non-trivial contributions to the index.     

Jack Superpolynomials: Physical and Combinatorial Definitions

Jack superpolynomials are eigenfunctions of the supersymmetric extension of the quantum trigonometric Calogero-Moser-Sutherland Hamiltonian. They are orthogonal with respect to the scalar product, dubbed physical, that is naturally induced by this quantum-mechanical problem. But Jack superpolynomials can also be defined more combinatorially, starting from the multiplicative bases of symmetric superpolynomials, enforcing orthogonality with respect to a one-parameter deformation of the combinatorial scalar product. Both constructions turn out to be equivalent.     

Invisible defects in complex crystals

We show that invisible localized defects, i.e. defects that cannot be detected by an outside observer, can be realized in a crystal with an engineered imaginary potential at the defect site. The invisible defects are synthesized by means of supersymmetric (Darboux) transformations of an ordinary crystal using band-edge wavefunctions to construct the superpotential. The complex crystal has an entire real-valued energy spectrum and Bragg scattering is not influenced by the defects. An example of complex crystal synthesis is presented for the Mathieu potential.     

Dirac Equation and Some Quasi-Exact Solvable Potentials in the Turbiner's Classification

In this paper quasi-exact solvability(QES)of Dirac equation with some scalar potentials based on sl(2)Lie algebra is studied.According to the quasi-exact solvability theory,we construct the configuration of the classes II,IV,V,and X potentials in the Turbiner’s classification such that the Dirac equation with scalar potential is quasi-exactly solved and the Bethe ansatz equations are derived in order to obtain the energy eigenvalues and eigenfunctions.     

Transmission time and bandwidth in pulse code modulation (application of the statistical thermodynamic formalism)

Employing the statistical thermodynamic formalism developed in an earlier paper, it is possible to determine compact sets of transmission times for the words of PCM (pulse code modulation) messages. In particular, we deal with pulses of zero or unit heights. These compact signals, which lead to shorter message times and eliminate redundancy even when successive words are correlated (Markov source), may, however, require additional bandwidth. We examine two simple cases where autocorrelation functions, and therefore power spectra, can be evaluated. In one case, that of the Markov source, it proves possible to accomplishboth shorter transmission time and narrower bandwidth (half-width of the power spectrum), showing that optimization of transmission times can be very worthwhile. Techniques for deriving autocorrelation functions are discussed at length.     

Generation and classification of the translational shape-invariant potentials based on the analytical transfer matrix method

For the conventional translational shape-invariant potentials (TSIPs), it has demonstrated that the phase contribution devoted by the scattered subwaves in the analytical transfer matrix quantization condition is integrable and independent of n. Based on this fact we propose a novel strategy to generate the whole set of conventional TSIPs and classify them into three types. The generating functions are given explicitly and the Morse potential is taken as an example to illustrate this strategy.     

Generation and classification of the translational shape-invariant potentials based on the analytical transfer matrix method

For the conventional translational shape-invariant potentials (TSIPs), it has demonstrated that the phase contribution devoted by the scattered subwaves in the analytical transfer matrix quantization condition is integrable and independent of n. Based on this fact we propose a novel strategy to generate the whole set of conventional TSIPs and classify them into three types. The generating functions are given explicitly and the Morse potential is taken as an example to illustrate this strategy.