An Investigation of the Effect of the Canonical Transformation on the Lagrangian

The transformation of the Euler-Lagrange derivative under the point transformation is explicitly stated, and from this view point, the canonical transformation is reinvestigated. In our arguments, the canonical transformations are discussed strictly separately from the canonical equations. A proof is given that the Lagrangian can be restored after any infinitesimal canonical transformation. Some identities are obtained giving relations between canonically transformed and untransformed Lagrangians. Using the identities, the relation between the Noether charge and the generator of the canonical transformation is investigated. The chiral gauge, Galilei and scale transformations are considered as applications to field theory.     

光纤光栅传输矩阵研究

利用模耦合理论给出并分析了一般坐标系下相移布喇格光纤光栅中的传输矩阵及其特性,所给出的传输矩阵具有分段不变性,而且不能被分解为一个矩阵和一个相移矩阵的乘积.利用该传输矩阵可以研究均匀、相移、啁啾、超结构等光纤光栅及光栅的级联等.计算了相移光栅的反射谱和相移量的关系,以及两个光栅级联时的反射谱.结果表明,同样相移量时的反射谱和已有文献不同,两个光栅级联时,也不同于已有文献,各自的谐振波长与光栅的级联没有关系.     

Study of the Mechanism of the Autowave Structure Formation at the Reaction Front

A qualitative mechanism of the formation of wave structures at the reaction front is proposed. It is assumed that the structures are formed as a result of the interaction of two subsystems, one of which is responsible for the front formation, and the other is responsible for the formation of structures themselves. Three models are considered; two-dimensional analogues of concentric and spiral waves are numerically demonstrated in each. Fitzhugh–Nagumo, Fisher–Kolmogorov–Petrovskii–Piscounov (Fisher–KPP), and Oregonator models were used as subsystems.     

The main periodicities of the motion of the center of the sun relative to the center of mass of the solar system and solar activity

The dynamic parameters of the motion of the Sun relative to the center of mass of the Solar System, viz., the distance of the center of the Sun relative to the center of mass and the angular momentum of the Sun, as well as its changes, are investigated. The frequency spectra of these parameters and of the Wolf numbers are calculated and the main spectral components are revealed. It is shown that a periodicity of 178.8 years is not predominant in the dynamic parameters of the motion of the Sun; in this frequency range a periodicity of 169 years connected with the influence of Neptune predominates. The coincidence of the periodicities in the Wolf numbers and dynamic parameters of the motion of the Sun is shown. The causes of all components of the frequency spectrum are indicated.     

Analysis of the temperature dependence of the spectral characteristics for the hollow-core photonic-crystal fibers

The temperature dependence of the spectral characteristics of monocapillaries made of S87-2 glass and filled with air and ethanol is experimentally and theoretically studied in temperature intervals 23–90°C and 23–40°C, respectively. The same measurements are performed using the photonic-crystal fibers made of AR-Glass (Schott). The transmission spectra of the air-filled fibers are slightly transformed when the temperature is varied in the above interval. It is demonstrated that the transmission peak is red-shifted and the shift is proportional to the temperature when the cavities are filled with ethanol. It is also demonstrated that the temperature dependence of the shape of the transmission spectra is predominantly determined by the parameters of the medium that fills the hollow channel rather than the fiber material. The temperature sensitivities of the photonic-crystal fiber filled with ethanol and a monocapillary are 1.25 and 0.40 nm/°C, respectively.     

On the loss of smoothness of the solutions of the Euler equations and the inherent instability of flows of an ideal fluid

Certain classes of flows of an ideal incompressible liquid which with time gradually lose their smoothness are studied. The loss of smoothness is expressed as infinite growth of the vorticity as t--> infinity for three-dimensional flows and an increase of the gradient of the vorticity for planar and axisymmetric flows. Examples of such flows in the planar and axisymmetric cases are flows with a rectilinear streamline; this can be established using a special local Lyapunov function. Incompressible flows of a dusty medium are another example (it turns out that collapse is impossible for such flows, but the vorticity and the rate of deformation, as a rule, grow with no limit). Other examples can be constructed by composition of shear flows. It is shown that in the vorticity metric almost all stationary planar flows are unstable with respect to three-dimensional disturbances and in the vorticity gradient metric planar and axisymmetric flows with a rectilinear streamline are unstable. (c) 2000 American Institute of Physics.     

Particle physics at the turn of the century

Aspects of particle physics are reviewed from an experimental viewpoint. The elementary constituents of the Universe are described, as are the fundamental forces through which they interact. Recent results are emphasized and there is some speculation about the future. No attempt has been made to give a complete bibliography, but a few references to recent reviews and original articles are given. A glossary of acronyms is included.     

Measurements of the QED structure of the photon

The structure of both quasi-real and highly virtual photons is investigated using the reaction , proceeding via the exchange of two photons. The results are based on the complete OPAL dataset taken at centre-of-mass energies close to the mass of the Z boson. The QED structure function and the differential cross-section for quasi-real photons are obtained as functions of the fractional momentum x from the muon momentum which is carried by the struck muon in the quasi-real photon for values of ranging from 1.5 to 400 GeV. The differential cross-section for highly virtual photons is measured for GeV and GeV, where and are the negative values of the four-momentum squared of the two photons such that . Based on azimuthal correlations the QED structure functions and for quasi-real photons are determined for an average of 5.4 GeV. Received: 8 February 1999 / Published online: 28 September 1999     

Theoretical Description of the Radial Distributions of the Ions and of the Electrons in the Subnormal Positive Column

A relatively simple set of differential equations describing the radial profiles of the number densities and of the radial drift velocities of the ions and the electrons and of the radial electric field intensity in the subnormal positive column is derived. The inertia of the ions is taken into consideration, but the ion temperature is supposed to be zero. Corresponding boundary conditions are used. For discharges in argon under diffusion and under free-fall conditions numerical solutions are given.     

Numerical Investigation of the Effects of the Injection Current on the SHB-Effects of VCSEL''s

A spatially independent model of vertical-cavity surface-emitting lasers (VCSEL's) is built up in this paper by integrating the spatially dependent rate equations over the cross section of the active reigon of VCSEL's. The LP cosine modes in a weakly guiding cylindrical waveguide are used to represent the transverse modes in the VCSEL's cavity. This model is performed numerically with the 4^th order Runge-Kutta method in a self-consistent way. The dynamic and steady state characteristics of the multi-transverse mode competitions are investigated in detail. Different kinds of injection currents such as a disk-contact and ring-contact injection current are employed in these numerically implementations. Some interesting results are obtained and analyzed detailedly.     

On the determination of the statistical characteristics of the magnesium acceptor in GaN

The temperature dependence of the free hole concentration is studied in Ga:Mg samples grown by the MOCVD technique. Relevant parameters are determined, like the ionization energy, the degree of compensation and the concentrations of donors and acceptors. Methods for the determination of these parameters are discussed. It is shown that reliable data on the ionization energy and the compensation can be obtained while determination of the concentrations of donors and acceptors is much less reliable. The value of the degeneracy factor of the acceptor level is explored since it influences the degree of compensation and the free carrier concentration. The occurrence of the maximum in the free carrier concentration with the increase of Mg dopand concentration in MOCVD samples is examined. It is shown that multicharged donors are needed for the explanation, among which the complex formed by magnesium atom and the nitrogen vacancy is the plausible candidate.     

Modeling of the vibrational structure of the vibronic spectra of diphenylpolyenes by the parametric method

The structures of the electronic-vibrational spectra and of the excited states of a number of diphenylpolyene molecules are determined within the framework of the second approximation of the parametric method. The system of parameters of the structural fragments of molecules is improved and good agreement with spectral experiment is obtained. It is shown that there is a high degree of transferability of the polyene and acene parameters of the method and that the models obtained are adequate to the real structure of molecules. It is also shown that the method proposed makes it possible to perform predictive qualitative and quantitative calculations of the spectra of these molecules, as well as of the spectral characteristics necessary for modeling photochemical molecular transformations. In the series of diphenylpolyene molecules, an interpretation of the vibrational structure of the spectra is proposed and the specific features of variation of the geometry upon excitation of molecules are considered.     

ON the question of the uniqueness of the energy-momentum complex in the special and general theory of relativity

Modification of the Fock method is used to look systematically for the complexes of energy and momentum which are conserved as a consequence of the vacuum field equations of the second order (real and complex scalar field, real vector field, symmetric tensor field of the linearized and non-linear Einstein theory). In contrast to Fock's results for fields described by equations of the first order, the complexes are not defined uniquely. The non-uniquenesses are eliminated by supplementary conditions.This paper is based on a diploma thesis worked out at the Department of Theoretical Physics, Faculty of Mathematics and Physics, Charles University.     

Analysis of the low—lying spectrum of the He—tetramer

There is a type of nodal surface imposed by symmetry on wavefunctions.These surfaces are crucial to the ordering of low-lying states.Based on an analysis of this type of surface and based on existing theoretical results,the feature of the low-lying spectrum of the He-tetramer is studied,and the candidates of bound states and narrow resonances are suggested.     

On the predictability of the positions of the convergence zones in the ocean

The disagreement between the experimental and calculated positions of the first convergence zone are known from many publications. The most probable cause for such a disagreement, namely, the incorrect specification of the input data for the calculations, is considered. The lack of simultaneity between the hydrological surveys of the region and the acoustic experiments is emphasized. The experimental data obtained by the author in five ocean regions are presented. These data characterize the diurnal variability of the distance from the source to the nearest boundary of the convergence zone. The relations proposed by different researchers for calculating the sound speed from the temperature, salinity, and hydrostatic pressure are analyzed. It is shown that these relations lead to a substantial difference in the estimated depth dependence of the hydrostatic gradient of the sound speed. The position of the first convergence zone is calculated for the propagation conditions determined by vertical temperature and salinity profiles with the subsequent recalculation of these profiles into sound speed profiles by using eight different formulas known from the literature. It is shown that different formulas lead to different values of the distance to the first zone; this difference is substantially greater than that between the calculations and experiment. The necessity of improving the recalculation relations in view of the experimental data on sound propagation in natural oceanic waveguides, including the data on the actual positions of the convergence zones, is emphasized.     

离心机动态失准角测量方法的研究

针对精密离心机动态失准角测量中存在的问题,提出以双轴光电自准直仪为核心测量仪器的失准角测量方法,在测量系统中采用真空光路屏蔽技术,减少了由于测量环境空气扰动带来的误差。对组成测量系统的各环节进行了误差分析与设计,理论分析与实验表明系统测量不确定度可达到0 2″。     

单边干涉图的数据处理方法研究

干涉成像光谱仪干涉图的采样方式一般有两种,即单边采样和双边采样,单边采样干涉图往往保留零光程差附近的部分“短双边”采样数据以利于数据处理.本文对空间调制干涉成像光谱仪不同干涉图采样方式下的光谱复原方法进行了研究,讨论了空间调制干涉成像光谱仪单边干涉图的切趾与相位修正,提出了更为合理和准确的方法.研究发现,合理设置短双边数据在减小仪器的原始数据量的同时,能够保证复原光谱的准确度.     

On the linearity of the self-diffusion process

Formal arguments are given that the self-diffusion process, understood as the mutual diffusion process in a system which consists of two mechanically similar species of particles, and which is at total equilibrium if the species labels are ignored, is an inherently linear, but nonlocal, transport process. There are no nonlinear Burnett effects, and the nonlocal diffusion coefficient is independent of the composition of the mixture. The present state of knowledge, from theory and from computer experiments, concerning the various quantities which appear in the formal analysis is summarized for both fluid and Lorentz systems.Work performed under contract with the U.S. Department of Energy.