The radiation impedance of a rectangular piston

The radiation impedance of a rectangular piston is expressed as the Fourier transform of its impulse response, which is obtained from the recent work of Lindermann [1]. The analytical evaluation of the transform is performed and new integral expressions are presented for both the radiation resistance and reactance. The integrals are readily evaluated in terms of elementary functions at both the low and high frequency limits. The integrals are also expressed as series of Bessel functions which are valid for all frequencies and aspect ratios. Numerical results are presented to illustrate the behavior of the radiation resistance and reactance as a function of the aspect ratio of the piston and a normalized frequency parameter. Additional numerical results are then presented to illustrate the accuracy of the analytical expressions for the radiation resistance and reactance at low and high frequencies. Finally, numerical results are presented to illustrate the application and accuracy of using standard FFT algorithms to evaluate the radiation resistance and reactance directly from the impulse responses.     

Hysteresis characteristics of an analytical vector hysteron

The analytical way to describe uniaxial single-domain particles, using new symmetry considerations on the magnetic anisotropy, as a vector hysteresis unit (vector hysteron), is presented. The main characteristics of the vector hysteron such as the longitudinal hysteresis loops, transversal hysteresis loops and rotational hysteresis loops are presented. An extension of the vector hysteron and a vector hysteron that can be applied to the ferroelectric hysteresis are also presented.     

Electroproduction of low energy charged pions on9Be,12C and16O

Measurements of electroproduced pions with an energy of 10MeV are presented. The results of a calculation based on the PWIA are compared with the presented data as well as with data at higher pion energies.     

Fourier transformable properties of paraboloidal mirror segments

Theoretical and experimental results are presented to demonstrate advantages of paraboloidal mirror segments over lenses as Fourier transforming and image reconstructing elements in an optical data processing system. Experimental results of spatial filtering are also presented.     

Analytic perturbation functions for static interactions in perturbed angular correlations of ®rays

Analytic expressions are presented for powder and single crystal perturbation functions in ®–®-angular correlations for static interactions. Magnetic dipole interactions for arbitrary spin as well as non-axially symmetric electric quadrupole interactions up to spin 5/2 are treated. Symmetry properties of all matrices involved are discussed, as well as their consequences for the perturbation functions. A new complementarity rule for powder perturbation functions is presented.     

窄线宽光纤激光器进展

详细介绍采用光纤光栅获得窄线宽光纤激光器的各种技术,并讨论获得单模激光输出以及提高功率输出的方法。介绍了目前的最新进展,尤其是镱铒共掺磷酸盐玻璃DBR光纤激光所获得的最新数据,激光功率200mW,线宽1．75kHz。对光纤掺杂、光敏性以及光栅刻写等关键技术也进行了探讨。还重点介绍了作为应用之一的高功率激光系统前端种子源。     

Spectroscopic Studies of High Pressure Argon Plasms

Results of spectroscopic investigations on high pressure argon arcs are presented. The experimental investigations were performed on cascade arcs at pressure levels up to 250 atm. Measurements of the radial temperature distribution as well as of the width and shift of selected spectral lines were performed. Results concerning the AI 4300 line are presented. A comparison with theoretical values shows fair agreement.     

Quantum cooperative mechanism of enzymatic activity

Electron spectrum of enzyme-substrate complex instability, induced by electron and phonon mediated, electron-electron interactions are proposed as possible origin of specificity and efficiency of enzyme action. Some implications of the presented hypothesis of gene activity regulation and quantum theory of liquid crystals are presented.     

Numerical calculation of the correlation moments of the sound field scattered by a rough surface

Numerically calculated two-dimensional correlation moments of the surface-scattered sound field are presented in the form of correlation surfaces and analyzed. The models of three-dimensional anisotropic and two-dimensional quasi-harmonic surface waves are considered. Data are presented on the angular dependence of the space-time correlation domains of the scattered sound field for receivers spaced across the propagation path in both horizontal and vertical directions, as well as on the shapes of the time-frequency and space-frequency correlation domains.     

Multiphoton ionization studies of amines with UV-VIS lasers

Three and four photon ionization studies at 355 and 532 nm are presented for the isomeric propylamines and n-pentylamine. Ionic fragmentation patterns and ion yields are presented as a function of laser wavelength and fluence. These time-of-flight (TOF) mass spectra are compared with both electron impact data and the TOF mass spectra of the previously reported butylamines. A brief discussion of the dynamics of the decomposition process is presented in light of the butylamine results and competitive ionic fragmentation pathways.     

塑料透镜在光学系统中的应用

本文对塑料透镜在光学系统中的应用进行了介绍,并对塑料透镜与玻璃透镜进行了比较。着重介绍了非球面塑料透镜在各种光学系统中的应用以及它所显示出的优越性。同时对塑料透镜的原材料、塑料透镜的设计、金属模具的设计和加工、塑料透镜的成型工艺和表面处理进行了介绍。最后还介绍了克服塑料透镜各种缺点应采取的措施。     

Optimum design of laminates with natural frequency constraints

A method of optimally designing symmetric fibre reinforced composite laminates subject to constraints on natural frequencies is presented. The problem is cast as a non-linear mathematical programming problem in which the thickenesses of material placed at preassigned orientation angles are treated as the design variables. The resulting optimization problem is solved by using an interior penalty function algorithm. Several non-linear programming problems are solved by taking minimization of weight or maximization of fundamental frequency/buckling load/maximum transverse deflection under the stated loading condition as the behaviour constraints. The numerical results are presented in the form of design studies which reveal the influence of different design constraints on the optimum design. These design studies illustrate that the method presented offers an efficient and practical optimum design procedure for composite laminates.     

Multi-domain spectral method for modal analysis of optical waveguide

A multi-domain spectral method for scalar optical modal analysis is developed and presented. The method is mesh-free and is applicable to three-dimensional optical waveguide structures that are invariant in one direction. The mode profile is represented as a superposition of one-dimensional preselected basis functions with variable coefficients. As common to spectral methods, the presented method is inherently fast and efficient. Different optical waveguides are analyzed for comparison purpose to exhibit the validity and accuracy of the presented method.     

Interaction of a long pulsed high-density electron beam with a jet of solid-target destruction products

Results are presented from experimental studies of the destruction of a solid target by a high-density nonrelativistic electron beam at a deposited power density of 20 MW/cm² in millisecond pulses. Results of studying beam transportation under these conditions are presented as well.     

An electron-retardation device to improve the resolution of a turner-type UV photoelectron spectrometer

A simple pre-retardation device without intermediate images that may be used to increase the resolution of Turner-type UV photoelectron spectrometers has been analyzed by means of electron trajectory calculations. A set of qualitative rules based on the calculations as well as performance tests of the actual device are presented. High-resolution spectra of naphthalene and anthracene are presented as an illustration and compared in detail with recent model calculations of Franck—Condon profiles by Ohno [9].     

新分数阶超混沌系统的研究与控制及其电路实现

为了提高混沌信号的复杂性,提出了一个新的分数阶四维超混沌系统,并对该系统的混沌动力学特性进行详细的理论分析和数值仿真,Maltab仿真证实了该分数阶超混沌系统存在混沌的最小阶数为3.2阶.同时运用Multisim软件对该系统进行电路实验仿真验证.最后设计了简单有效的线性反馈控制器,并进行电路实现,仿真结果证明了控制器是有效的. 关键词： 分数阶超混沌系统 动力学特性 电路仿真 反馈控制     

Phase transitions and relaxation characteristics of Quantum Magnets and Quantum Glasses

An overview is presented of the phase changes as well as certain relaxation characteristics of model quantum magnets, magnetic glasses and proton glasses. Although the systems considered are quite varied, they are connected by the common themes of tunneling, transverse Ising model, long-ranged interactions and above all, the occurrence of quantum phase transitions. Because the interactions are long-ranged, mean-field theory is eminently suitable for analyzing both the equilibrium and nonequilibrium properties. Wherever pertinent, detailed comparisons with experimental data have been presented.     

Evaluation of mutual radiation impedances between circular pistons by impulse response and asymptotic methods

A general approach is presented to evaluate the mutual radiation impedance between circular pistons of arbitrary size and spacing in an infinite rigid planar baffle. The impedance is expressed as a Fourier transform of a generalized impulse response which is defined by an integral relationship. Although the integral must, in general, be numerically evaluated, several special cases of interest can readily be evaluated by using asymptotic techniques. Several asymptotic expressions for the mutual radiation impedance are developed and their limitations are noted. Numerical results are then presented for the generalized impulse response and mutual radiation impedance corresponding to pistons of equal size and arbitrary spacing. The time domain characteristics of the generalized impulse responses as a function of spacing are noted and related to the frequency characteristics of the mutual radiation impedances as a function of spacing. In addition, the accuracy of a simple closed form expression for the mutual radiation impedance is presented as a function of normalized frequency and spacing.     

Underwater sounds of the Pacific Ocean in the shelf zone of Shikotan Island

Results of underwater sounds measurement in the Shikotan’s shelf zone of the Pacific Ocean at the depth of 130 m in the range of frequencies 1.9–11000 Hz at the wind velocity from 0 to 40 m/s are presented. The statistic non-linear relation between the variations of the underwater sound levels and wind velocities has been revealed. Data on biological, seismic, as well as the sounds of rain and ice of this region are presented.     

Analytical methods for modeling of ultrasonic nondestructive testing of anisotropic media

Many modern structural materials exhibit anisotropic elastic behavior leading to complicated wave propagation phenomena. To ensure the reliability of ultrasonic nondestructive testing techniques, these material properties as well as the influence of microstructural inhomogeneities and the effects of interfaces on ultrasonic wave propagation have to be taken into account. In this respect, mathematical modeling provides an efficient method of assisting analysis. Two computationally efficient analytical approaches--a Gaussian beam and a point source superposition technique--are presented, which are well-suited for performing ultrasonic wave propagation and scattering simulations for anisotropic media. Results for homogeneous as well as inhomogeneous anisotropic media like composites and weld material are presented.