摘要:

This paper is concerned about power series expansions for hypergeometric functions in two variables. The usual power series representations for such functions have limited range of validity. Of particular interest is the case when the magnitude of one of the variables becomes large. Using a Barnes-type integral representation the region of convergence is transferred to the desired domain. The poles that occur in the Barnes-type integral are assumed to be simple. Thus explicit expansions are obtained for each of the fourteen hypergeometric functions that belong to this class.

ISSN:0920-5071    

DOI:10.1163/156939300X01111

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A novel kind of microstrip patch antenna is proposed in this paper. The antenna layout consists of a probe-fed circular patch integrated on a grounded slab of inhomogeneous artificial dielectric. A rigorous full wave analysis of this radiation component is here developed starting from the determination of new expressions for the spectral dyadic Green's function that take into account the inhomogeneity presence. The spectral Green's dyad is also obtained in the Hankel domain and a complete and accurate Method of Moments (MoM) is presented. Finally, several numerical results, obtained by means of a self produced code based on the theory here developed are presented in order to show the main capabilities of the novel antenna. Particularly, the comparison between the radiation pattern and the input impedance of such an antenna and those obtained for a similar one with a homogeneous substrate shows an improvement of both the directivity and bandwidth.

ISSN:0920-5071    

DOI:10.1163/156939300X01120

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The binomial transformer is a well known concept in impedance matching. By the use of multiple quarter wavelength sections broadband matching is achieved. Many textbooks handle the problem starting from the approximated theory of small reflections. In this paper, a new and exact derivation for the impedances of the different sections is given. It is shown that not the section coefficients must satisfy a binomial distribution (as commonly used), but a transformation of these coefficients. Furthermore, an alternative formulation starting form the theory of small reflections is given. The results of the different methods are compared. It is shown that the alternative formulation gives the best agreement with the exact method.

ISSN:0920-5071    

DOI:10.1163/156939300X01139

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Recently Zangari and Censor discussed the non-uniqueness of the spatiotemporal world-view, and proposed a representative alternative based on the Fourier transform as a mathematical model. It was argued that this so called spectral representation, by virtue of the invertibility of the Fourier transform, is fully equivalent to our conventional spatiotemporal world-view, although in the two systems the information is ordered in a radically different manner. Criticism of the new conception can be traced back to the fundamental principles of simultaneity and causality, whose role in the spectral domain has not been sufficiently demonstrated. These questions are carefully investigated in the present study. Simple but concise examples are used to verbally and graphically clarify the mathematics involved in integral transforms, like the Fourier transform under consideration. The transition from the spatiotemporal domain to the spectral domain entails not only a different patterning of data points. What is involved here is that every point in one domain is affecting all points in the other domain, and to follow what happens to simultaneity and causality under such circumstances is not a trivial feat. Even for the general reader, the discussion based on the simple examples should suf fice to critically follow the arguments as they unfold. For completeness, the general mathematical formulations are given too. In order to follow the footprints of the spatiotemporal simultaneity and causality concepts into the spectral domain, a special strategy is implemented here: Certain spatiotemporal situations are stated, and then their outcome in the spectral domain is examined. For example, it is shown that if a causal sequence of events is flipped over in time,

ISSN:0920-5071    

DOI:10.1163/156939300X01148

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The scattered fields of a number of targets in free space are measured. Their complex natural resonances are extracted from the late time responses, using the generalized pencil-of-function method. The complex natural resonances, as the targets are immersed in a lossy medium, are investigated using Baum's transform. The results of the complex natural resonances for various targets are expected to be utilized for target identification.

ISSN:0920-5071    

DOI:10.1163/156939300X01157

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Circular conducting waveguides filled with gyroelectric media are studied in this paper and the dyadic Green's functions in these waveguides are obtained for the first time. The electric and magnetic fields in the waveguide are expressed in terms of cylindrical vector wave function expansion. It is shown that each of the eigenmodes in the waveguide consists of two eigenwaves whose wave numbers can be determined by the characteristic equation. Dispersion relation is obtained by applying boundary conditions to the eigenmodes. Mode orthogonality is discussed before the orthogonal relations are formulated and then used to determine the expansion coefficients of electric and magnetic fields. The complete expansions of both the electric and the magnetic dyadic Green's functions are finally obtained. The calculated dispersion curves are depicted and discussed while effects of gyrotropy are shown.

ISSN:0920-5071    

DOI:10.1163/156939300X01166

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Thesingularity of the static Green's function incurs mathematical difficulty. It is pointed out that this singularity is unnecessarily complicated and can be removed by a physically meaningful assumption which regularizes the static Green's function without substantially affecting the electromagnetic theory. Further, this regularization smooths the electric field in the close proximity of the source and leads to that the electrostatic force due to a charged particle exerted on itself is zero. Thereby, the Poisson equation of the regularized static Green's function can be obtained in a simple manner. Then, the wave equations of the electric scalar potential and the magnetic vector potential are derived in a new approach. Furthermore, we derive the Lorentz gauge, rather than assume it.

ISSN:0920-5071    

DOI:10.1163/156939300X01175

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this paper, scattering and coupling problems of the directional coupler for the dielectric rectangular waveguides are analyzed by the mode-matching method in the sense of least squares for the fundamental mode incidence. This directional coupler is composed of three parallel dielectric rectangular waveguides cores which are placed at equal space in the dielectric medium. Namely, respective cores are core regions of three respective rectangular waveguides. The central rectangular core among them has periodic groove structures of finite extent on its two surfaces which face each other and other two waveguide cores are perfect. In the central waveguide, the fundamental mode is incident from perfect part toward the periodic structure of this waveguide. The power of the incident mode to the central waveguide is coupled to other two waveguides through periodic groove structure. The coupled mode propagates in the other waveguides to the same or opposite direction for the direction of the incident mode when the Bragg condition is selected appropriately. The method of this paper results in the integral equations of Fredholm type of the second kind for the unknown spectra of scattered fields. The results of the first order approximate solutions of the integral equations are presented in this paper.

ISSN:0920-5071    

DOI:10.1163/156939300X01184

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The principal result of this work is the existence of coupled magnon-plasmon surface polaritons, i.e., nonradiative spin-electromagnetic surface waves on the lateral surface of a superlattice that consists of the alternating layers of GaAs-AlGaAs quantum well system and ferromagnetic insulator. Dispersion relations for the waves are considered at quantum Hall-effect conditions when a static quantizing magnetic field is perpendicular to the quantum well plane.

ISSN:0920-5071    

DOI:10.1163/156939300X01193

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The present report discusses a structure dependent model of emissivity of snow cover. A snow cover was represented by a medium comprised of discrete scatterers. In the case of dry snow, ice grains stood for scatterers. For wet snow, two geometrical configurations of the water component were considered: I is a mixture of ice grains and water drops; II is a mixture of ice grains covered with water film and water drops. Scatters were assumed to have a spherical from and the lognormal distribution of sizes. Calculations of radiobrightness temperature of snow cover were made using data of glaciological measurements of its physical parameters and microstructure. Results of calculations were compared with measurements of radiobrightness temperature at various states of the snow cover.

ISSN:0920-5071    

DOI:10.1163/156939300X01201

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor