Solvability of problems of excitation of plane-layered metamaterial media

It is shown that the problem of excitation of a magnetodielectric layer with parameters ? and μ equal to minus unity by a point source is not always solvable. Conditions under which the problem has a solution are established. It is found that, in the vicinity of the singular point ? = μ = ?1, determination of the field is an illposed problem: Small variations in these parameters result in large changes of the field.     

Infrared Texture Simulation Using Gaussian-Markov Random Fields

Infrared battlefield simulation is a most important subject today to test infrared weapons. The reality and details of simulated scenes are always relied on the infrared textures. A texture is considered to be a stochastic, possibly periodic, two-dimensional image field. A texture model can be described as a mathematical procedure. Markov random field(MRF) model is a famous model to synthesize the visible textures of various kinds. In this paper, the Gaussian-Markov random fields(GMRF) are firstly used to sample the distribution of temperature field on the surface of terrain. And the Planck's radiation law is applied to calculate the emittance in the bands of 3～5 μ m or 8～14 μ m. The emittance distribution of the terrain can be normalized and colored by the range of 0 to the gray levels decreased by 1. Then an infrared texture is generated by GMRF by given a set of certain parameters.     

Scattering of modes by the end of a diaphragm-loaded planar dielectric waveguide

A planar dielectric waveguide loaded with an infinitely thin perfectly conducting diaphragm is considered. The problem of the guided mode reflection from the end of such a waveguide is analyzed with the help of the integral equation method and the variational method. Dependences of the fundamental mode reflection coefficient on the waveguide parameters and on the dimension of the aperture are calculated.     

The resonance field of a radiator surrounded by an inhomogeneous spherical plasma shell

The field of a radiator located in free space and surrounded by an inhomogeneous spherical plasma shell whose permittivity passes through the point ? = 0 is found and investigated. It is shown that the behavior of the permittivity in the vicinity of the value ? = 0 substantially affects the formation of the source field. The resonance properties of the obtained solution to the problem are studied for a sphere of a small electrical dimension.     

The resonance properties of the near field in finite thin Veselago and Pendry lenses

The problem of excitation of a finite thin plate made from a metamaterial with the electrodynamic parameters ? _r ?? ?1, ?? _r ?? ?1 and ? _r ?? ?1, ?? _r = 1 by a point source is considered. Resonance phenomena in the near field of plates are found that are caused by the interaction of the formed surface waves. It is shown that the near field of the plate has the form of standing surface waves localized near wide faces of the plate, and the high Q factor of the observed resonances leads to the extremely strong dependence of the excited near-field amplitude on the electric and geometric parameters of the plates.     

Adaptive Exponential Smoothing Models for Reliability Estimation

Four methods are discussed for determining the smoothing parameters in an adaptive exponential smoothing model which is used to assess reliability of a complex system tested in stages. The adaptive model is defined as Ri = ?iri + (1 - ?i)Ri-1, i = 2,...k, where Ri-1 is the assessed reliability at stage (i -1), ri is the ratio of the number of successes to the number of trials at stage i. Among the four procedures given here for determining the smoothing parameters xi two empirical methods and an empirical Bayes procedure are considered in some detail including a numerical example in which these techniques are compared.     

Tables to Facilitate Calculation of an Asymptotically Optimal t Test for Equality of Location Parameters of a Certain Extreme-Value Distribution

A t test, proposed by Ogawa and based on the use of a few sample quantiles selected from large samples, is considered for testing the hypothesis H0: ?1 = ?2 against the hypothesis H1: ?1 ? ?2 concerning the location parameters ?1 and ?2 of two extreme-value distributions with common unknown scale parameter ?. Tables that simplify the calculation of the test statistic and an example illustrating their use are provided.     

The effect of chirality on the existence of backward waves in metamaterials made from resonance planar chiral elements

Artificial media made from lattices of resonance planar chiral elements (RPCEs), such as planar double open rings and plane spirals, are considered. The effect of chirality on the electromagnetic properties of such media is investigated theoretically. It is shown that, when RPCEs are identically oriented, backward waves do not propagate in the medium, although there is a region where permittivity ? and permeability μ are negative simultaneously. However, such a metamaterial exhibits chirality and, hence, the refractive index turns out to be imaginary even when energy dissipation is disregarded. It is found that a medium with the opposite orientation of neighboring RPCEs is nonchiral; in such a medium, the resonance property of ? and μ is retained; the refractive index is real; and backward waves are present at frequencies at which both ? and μ are negative. For these media, it is found that there are regions where the directions of propagation of the wave energy and phase coincide (right-handed passbands), a region where these directions are opposite (left-handed passbands), and regions of evanescent waves.     

Effects on VLSI Yield of Doubly-Stochastic Impurity Distributions

An expression is derived for the doubly-stochastic distribution of the number of impurities in the base region of a bipolar transistor; the distribution results from uncertainty in ion implantation parameters. Expressions are derived for device yield, and VLSI (very large scale integration) chip yield with an N-bit parity check. These derivations can be extended to other devices in a straightforward manner. As an example, calculations have been performed using specific parameters, which have led to the following observations: 1. The doubly stochastic effect is most sensitive to uncertainty in the straggle (standard deviation) of the emitter impurity distribution. 2. Uncertainty of the order of 5% in an implantation parameter causes substantial broadening of the distribution of impurities, for the case considered. 3. Device yield decreases rapidly for dimensions less than a well-defined threshold (? 0.75 ?m for the case considered). 4. Chip yield, without a parity check, exhibits a threshold effect at device yield = 1-1/Nchip.(Nchip ? number of devices per chip.) The device yield must exceed this threshold to produce large chip yields. 5. The use of a parity check reduces the device yield threshold to 1-10/NChip. Use of fewer bits per parity check reduces the threshold further. 6. For the example considered, the minimum device dimensions for large chip yields is of the order of 1 to 1.5 ?m, using a 16-bit parity check. The minimum device size for reliable system performance for other cases will depend upon specific device parameters.     

A new magnetic semiconductor Cd1−x MnxGeP2

A new semiconductor material, which comprises a solid solution of a ternary diamond-like semiconductor and transition element Mn, was grown and investigated. According to X-ray diffraction data, the crystal structure of the material is similar to that of the CdGeP₂ host substance with a chalcopyrite-type crystal structure. The interplanar distances and the unit cell parameter decrease with an increase in Mn content: a=5.741 ? → 5.710 ? → 5.695 ? in the series of CdGeP₂ → Cd_1−x Mn_xGeP₂ → Cd_1−y Mn_yGeP₂ compounds (x<y). The surface composition and in-depth concentration profiles for elements of a Cd-Mn-Ge-P quaternary system were investigated using electron microscopy and energy dispersive X-ray spectroscopy. The molecular concentration ratio for Mn and Cd at a depth of 0.4 μm is Mn/Cd=0.2. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 3, 2001, pp. 305–309. Original Russian Text Copyright ? 2001 by Medvedkin, Ishibashi, Nishi, Sato.     

Magnetooptical properties of quantum wells with D (−) centers

The D ^(?) states in a quantum well under the magnetic field longitudinal with respect to the axis of growth of the structure are considered. In the context of the model of the zero-radius potential, an equation that defines the dependence of the binding energy of the D ^(?) state on the parameters of the potential of the structure, the coordinates of the D ^(?) center, and the strength of the magnetic field is derived. The results are compared with the experimental data on the dependence of the binding energy of the D ^(?) state on the magnetic field. There is satisfactory agreement between the theoretical calculations and experimental data in the range of magnetic fields B < 10 T. The role of dimensionality in the modification of the coordinate dependence of the binding energy on the 2D → 1D → 0D transition is clarified. The impurity magnetooptical absorption coefficient in a multiple quantum well structure is calculated, and the spectral dependence of the coefficient is studied. It is shown that a substantial contribution to the broadening of the absorption lines is made by the dispersion of quantum well widths in the structure.     

High intensity magnetic fields for the identification and study of donors in epitaxial gallium arsenide

High intensity magnetic fields are needed for the far infrared photoconductivity method to be used reliably in the identification of unitentional contaminants in ultra high purity epitaxial GaAs. We show experimental evidence that the inhomogeneous Stark broadening of the 1s→2p (m=?1) transition of the hydrogen-like donor almost disappears as the magnetic field is increased to 20 Tesla. Since the spectral lines also become narrower and the central cell correction (chemical shift) becomes larger, the “signature curve” method of identification permits positive identification of donor species. In particular, the donors Ge and Se have been identified in specimens that were reported to contain carbon and Sn respectively.     

基于铷原子D1线塞曼能级间跃迁的光脉冲减速

基于铷原子D1线塞曼子能级间跃迁,可以观察到光脉冲减速现象。在实验中,当一束弱的右旋圆偏振探测光和一束强的左旋圆偏振耦合光同时耦合87Rb原子D1线F=2→F’=1塞曼子能级间跃迁时,就能在原子介质中获得高色散低吸收的电磁诱导透明现象,观察到光脉冲减速效应。耦合光越弱,光脉冲减速越大;光脉冲宽度越小,光脉冲延迟时间与脉冲宽度的比值越大。     

一种X波段梳状线可调带通滤波器

设计了一款X波段压控可调梳状线带通滤波器,通过调整加载变容二极管的偏置电压改变电容值大小,从而达到调整滤波器中心频率的目的。根据恒定带宽条件对滤波器耦合系数以及外部Q值的要求,确定梳状线滤波器的尺寸参数,并对其进行电磁仿真优化,最终制作的X波段可调滤波器尺寸为16 mm?20 mm?21 mm,控制电压7.6~15.4 V,实现滤波器中心频率8~10 GHz连续可调。在调谐频率范围内,滤波器通带宽度15%,回波损耗小于–10 dB,矩形系数小于2.8。     

Monoisotopic silicon 28Si in spin resonance spectroscopy of electrons localized at donors

The fine structure of the spectra of a shallow-level Li donor center and a Fe⁰ deep donor (S = 1), which occupy tetrahedral interstices in a silicon lattice, is studied in monoisotopic silicon ²⁸Si due to considerable narrowing of the lines of ESR spectra. In the case of the Li donor center, experimental data are found to confirm the role of internal strains in the crystal when observing the ESR spectra of the ground state 1s T ₂ and state E at T = 3.8–10 K with g < 2.000. The anisotropy in the distribution of strains, which turned out to have a tetragonal type, is investigated using the angular dependences of the line width of the spin resonance corresponding to the triplet state T _2z of Li. Similar anisotropy is found in the case of the introduction of Fe⁰ ions into the initial crystals based on the theory of angular dependences of the width of ESR lines caused by the transitions ?1 → 0 and 0 → +1 (ΔM _s = 1) in comparison with the transition ?1 → +1 (ΔM _s = 2).     

IR photodetectors in the range of λ = 1.5–8 μm, based on silicon with multicharged nanoclusters of manganese atoms

It is demonstrated that infrared photodetectors based on silicon with multicharged nanoclusters of manganese atoms can be designed that operate in the wavelength range of ?? = 1.55?C8 ??m. Photodetectors fabricated on such materials have the following parameters: a spectral sensitivity range of ?? = 1.55?C8 ??m, an operating temperature range of T = 77?C250 K, an optimal electric field of E = 5 V/cm, an optimal size of V = 3 × 2 × 1 mm³, a sensitivity threshold of S = 10^?9 W/cm², and a response time of ?? < 10^?6 s.     

Electromagnetic scattering from an infinite circular metalliccylinder coated by an elliptic dielectric one

The scattering from an infinite, circular, perfectly conducting cylinder coated by an elliptic dielectric cylinder is considered. The electromagnetic field is expressed in terms of both circular and elliptical cylindrical wave functions, which are connected with one another by well-known expansion formulas. In the special case of small h=ka/2 (a is the interfocal distance of the elliptic dielectric and k its wavenumber), exact, closed-form expressions of the form S(h)=S(0)[1+gh ²+O(h⁴)] are obtained for the scattered field and the various scattering cross sections. Both polarizations are considered for normal incidence. Graphical results for various values of the parameters are given     

Scattering by an infinite circular dielectric cylinder coatingeccentrically an elliptic metallic one

The scattering of a plane electromagnetic wave by an infinite-circular dielectric cylinder, containing eccentrically an elliptic metallic one is considered. The electromagnetic field is expressed in terms of both circular and elliptical-cylindrical wave functions, connected with one another by well-known expansion formulas. Translational addition theorems for circular cylindrical wave functions are also used for the satisfaction of the boundary conditions in the dielectric cylinder. When the solution is specialized to small values of h=k₁c/2, with k₁ the wavenumber of the dielectric cylinder and c the interfocal distance of the elliptic conductor, semianalytical expressions of the form S(h)=S(0)[1+gh²+O(h ⁴)] are obtained for the scattered field and the various scattering cross sections of this configuration. Both polarizations are considered for normal incidence. Numerical results are given for various values of the parameters     

镜像法分析静电感应晶体管特性

针对埋栅型静电感应晶体管(SIT)提出一种柱栅模型.用镜像法计算了器件内电势分布,并在此基础上计算了沟道势垒、栅效率、电压放大因子等.结果表明:沟道势垒直接取决于沟道过夹断因子;栅效率随栅尺寸和位移栅压的减小而减小,并随位移栅压一起趋向于0;在小电流情况下电压放大因子随电流的增大而增大,到一定数值后,电压放大因子趋于常数.最后给出了SIT I-V特性解析表达式,它既适用于类三极管特性(加大栅压下)也适用于混合特性(较小栅压下),且由此得到的I-V特性曲线和实验符合较好.     

Improved Estimation of Eigenvalues and Eigenvectors of Covariance Matrices Using Their Sample Estimates

The problem of estimating the eigenvalues and eigenvectors of the covariance matrix associated with a multivariate stochastic process is considered. The focus is on finite sample size situations, whereby the number of observations is limited and comparable in magnitude to the observation dimension. Using tools from random matrix theory, and assuming a certain eigenvalue splitting condition, new estimators of the eigenvalues and eigenvectors of the covariance matrix are derived, that are shown to be consistent in a more general asymptotic setting than the traditional one. Indeed, these estimators are proven to be consistent, not only when the sample size increases without bound for a fixed observation dimension, but also when the observation dimension increases to infinity at the same rate as the sample size. Numerical evaluations indicate that the estimators have an excellent performance in small sample size scenarios, where the observation dimension and the sample size are comparable in magnitude.