Bessel beam through a dielectric slab at oblique incidence: the case of total reflection

The oblique incidence of a Bessel beam on a dielectric slab with refractive index n1 surrounded by a medium of a refractive index n>n1 may be studied simply by expanding the Bessel beam into a set of plane waves forming the same angle with the axis of the beam. In the present paper we examine a Bessel beam that impinges at oblique incidence onto a layer in such a way that each plane-wave component impinges with an angle larger than the critical angle.Comment: 10 pages, 6 figure

Factors Affecting Students' Performance

Determinants of students' performance have been the subject of ongoing debate among educators, academics, and policy makers. There have been many studies that sought to examine this issue and their findings point out to hard work, previous schooling, parents’ education, family income and self motivation as factors that have a significant effect on the students GPA. Most of those studies have focused on students' performance in the U.S. and Europe. However, since cultural differences may play a role in shaping the factors that affect students' performance, it is very important to examine those relevant factors to the UAE society. The aim of this study is to investigate the socio-economic characteristics of students of the College of Business and Economics-UAEU in relation to these students' performance and taking into account variables pertaining to the UAE Society. Using a sample of 864 CBE student and regression analysis, our results show that the most important factor that affects student's performance is the student's competence in English. Besides competence in English, students who participate in class discussion and those on leave outperform other students. The factors that negatively affect student's performance the most are missing too many lectures and living in crowded household. The results also show that non-national students outperform national students and female students outperform their male counterpart.class discussion, competence in English, student performance, socio economic factors

Propagation of time-truncated Airy-type pulses in media with quadratic and cubic dispersion

In this paper, we describe analytically the propagation of Airy-type pulses truncated by a finite-time aperture when second and third order dispersion effects are considered. The mathematical method presented here, based on the superposition of exponentially truncated Airy pulses, is very effective, allowing us to avoid the use of time-consuming numerical simulations. We analyze the behavior of the time truncated Ideal-Airy pulse and also the interesting case of a time truncated Airy pulse with a "defect" in its initial profile, which reveals the self-healing property of this kind of pulse solution.Comment: 9 pages. 5 figure

Aichi Irrigation Project

CER58SSK34.September 1959.Includes bibliographical references.Prepared for Erik Floor and Associates, Inc

Superluminal X-shaped beams propagating without distortion along a coaxial guide

In a previous paper [Phys. Rev. E64 (2001) 066603; e-print physics/0001039], we showed that localized Superluminal solutions to the Maxwell equations exist, which propagate down (non-evanescence) regions of a metallic cylindrical waveguide. In this paper we construct analogous non-dispersive waves propagating along coaxial cables. Such new solutions, in general, consist in trains of (undistorted) Superluminal "X-shaped" pulses. Particular attention is paid to the construction of finite total energy solutions. Any results of this kind may find application in the other fields in which an essential role is played by a wave-equation (like acoustics, geophysics, etc.). [PACS nos.: 03.50.De; 41.20;Jb; 83.50.Vr; 62.30.+d; 43.60.+d; 91.30.Fn; 04.30.Nk; 42.25.Bs; 46.40.Cd; 52.35.Lv. Keywords: Wave equations; Wave propagation; Localized beams; Superluminal waves; Coaxial cables; Bidirectional decomposition; Bessel beams; X-shaped waves; Maxwell equations; Microwaves; Optics; Special relativity; Coaxial metallic waveguides; Acoustics; Seismology; Mechanical waves; Elastic waves; Guided gravitational waves.]Comment: plain LaTeX file (22 pages), plus 15 figures; in press in Phys. Rev.

X-waves Generated at Second Harmonic

The process of optical frequency doubling can lead, in the undepleted regime, to the generation of a X-wave envelope with group velocity locked to the pump beam. Its parameters and its angular spectrum, are directly related to the zero- and first-order dispersive features of the nonlinear process. This constitutes a novel mechanism for spatio-temporal localization of light.Comment: 11 pages, 1 figure, revised version submitted to Optics Letter

Factors Affecting Students' Performance

Determinants of students' performance have been the subject of ongoing debate among educators, academics, and policy makers. There have been many studies that sought to examine this issue and their findings point out to hard work, previous schooling, parents’ education, family income and self motivation as factors that have a significant effect on the students GPA. Most of those studies have focused on students' performance in the U.S. and Europe. However, since cultural differences may play a role in shaping the factors that affect students' performance, it is very important to examine those relevant factors to the UAE society. The aim of this study is to investigate the socio-economic characteristics of students of the College of Business and Economics-UAEU in relation to these students' performance and taking into account variables pertaining to the UAE Society. Using a sample of 864 CBE student and regression analysis, our results show that the most important factor that affects student's performance is the student's competence in English. Besides competence in English, students who participate in class discussion and those on leave outperform other students. The factors that negatively affect student's performance the most are missing too many lectures and living in crowded household. The results also show that non-national students outperform national students and female students outperform their male counterpart

Superluminal effects for quantum tunneling through two successive barriers

We study the phenomenon of one-dimensional non-resonant tunnelling through two successive potential barriers, separated by an intermediate free region R, by analyzing the relevant solutions to the Schroedinger equation. We find that the total traversal time is INDEPENDENT not only of the barrier widths (the so-called "Hartman effect"), but also of the R-width: so that the effective velocity in the region R, between the two barriers, can be regarded as infinite. This agrees with the results known from the corresponding waveguide experiments, which simulated the tunnelling experiment herein considered because of the formal identity between the Schroedinger and the Helmholtz equation [PACS numbers: 73.40.Gk; 03.65.-w; 03.30.+p; 41.20.Jb; 84.40.Az].Comment: plain LaTeX file (8 pages), including 1 figure (in LaTeX). Replaced with improvements in some intermediary equation

Photon localization barrier can be overcome

In contradistinction to a widespread belief that the spatial localization of photons is restricted by a power-law falloff of the photon energy density, I.Bialynicki-Birula [Phys. Rev. Lett. 80, 5247 (1998)] has proved that any stronger -- up to an almost exponential -- falloff is allowed. We are showing that for certain specifically designed cylindrical one-photon states the localization is even better in lateral directions. If the photon state is built from the so-called focus wave mode, the falloff in the waist cross-section plane turns out to be quadratically exponential (Gaussian) and such strong localization persists in the course of propagation.Comment: Short communication -- 4 pages, 2 figure

Effect of eccentricity on conjugate natural convection in vertical eccentric annuli

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically investigated using a finite-difference technique. Numerical results, representing the heat transfer parameters such as annulus walls temperature, heat flux, and heat absorbed in the developing region of the annulus, are presented for a Newtonian fluid of Prandtl number 0.7, fluid-annulus radius ratio 0.5, solid-fluid thermal conductivity ratio 10, inner and outer wall dimensionless thicknesses 0.1 and 0.2, respectively, and dimensionless eccentricities 0.1, 0.3, 0.5, and 0.7. The annulus walls are subjected to thermal boundary conditions, which are obtained by heating one wall isothermally whereas keeping the other wall at inlet fluid temperature. In the present paper, the annulus heights required to achieve thermal full development for prescribed eccentricities are obtained. Furthermore, the variation in the height of thermal full development as function of the geometrical parameter, i.e., eccentricity is also investigated.vk201