In this paper a new method to determine the fracture properties and strain energy release rate for Carbon- Polyester composite has been introduced.  Fracture characteristics such as critical stress intensity factor and critical strain energy release rate for mode I, mode II and mixed mode loading were determined using Arcan type specimen. 130 layers of carbon fiber polyester woven composite wit...

NASA Lewis Research Center is engaged in a program to develop a series of backward wave osci l la tors (BWO's) for the frequency range 500 to 2000 GHz. Generically BWO's are electron beam travel ing wave tubes operating in a dispersive regime in which the group velocity and the phase veloci ty of the induced electromagnetic wave are in opposite direct ions. The osc i l la t ion frequency of a B...

background and aims. at present, cone beam computed tomography (cbct) has become a substitute for computed tomography (ct) in dental procedures. the metallic materials used in dentistry can produce artifacts due to the beam hardening phenomenon. these artifacts decrease the quality of images. in the present study, the number of artifacts as a result of beam hardening in the images of dental imp...

This paper presents a new theory for the lateral buckling of web-tapered I-beams. Linear analysis is first conducted by taking account into the tapering effects of web-tapered I-beams, where the deformation compatibilities of the two flanges and web are considered in terms of the basic assumptions of thin-walled members. Subsequently, the total potential for the lateral buckling analysis of web...

The present research deals with the flexural-torsional buckling analysis of sandwich web and/or flanges tapered doubly-symmetric I-beam. All section walls are composed of two metal face layers and a functionally graded (FG) porous core. It is assumed that the material properties of the porous core vary gradually in the longitudinal direction according to the simple power-law function considerin...

I studied experimentally the beam self-collimation and splitting in two-dimensional microwave photonic crystals. Using a microwave photonic crystal fabricated from alumina rods, I present an experimental proof of principle for an earlier theoretical proposal [A. Matthews et al., Opt. Commun. 279, 313 (2007)] of a photonic crystal beam splitter based on the self-collimation effect.

In this paper, we study two different Graded Index (GRIN) photonic crystal (PC) structures which are named as structure type I and type II. The PC structures are made of the square rod in an air background. To design a GRIN PC structure the lattice constant has been altered in the direction transverse to propagation. We investigated focusing effect             and waveguiding behavior of electr...

X-ray transmission depends on a composition element and its thickness of the specimen. When a highly collimated beam of monoenergetic photons passes through a medium of the thickness , it suffers a decrease in intensity according to the relation t ) exp( 0 t I I M ρ μ − = , where M μ is the mass absorption coefficient, and ρ is the density, is the incident beam intensity. In case of compound, A...

I consider the thermal bremsstrahlung emission from hot accretion flows (Bondi/ADAFs), taking into account the finite size of the observing telescope's beam (R beam) relative to the Bondi accretion radius (R A). For R beam ≫ R A soft X-ray emission from the hot interstellar medium surrounding the black hole dominates the observed emission while for R beam ≪ R A hard X-ray emission from the accr...