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...

background: physical wedges are still widely used as beam modifiers in external beam radiotherapy. however the presence of them in the beam trace may cause beam hardening which may not be considered in many treatment planning systems. the aim of this study is to investigate the beam hardening effect generated by physical wedges via different beam quality indexes as photon spectrum, half value l...

Free vibration characteristics of continuous grading fiber orientation (CGFO) beams resting on variable Winkler and two-parameter elastic foundations have been studied. The beam is under different boundary conditions and assumed to have arbitrary variations of fiber orientation in the thickness direction. The governing differential equations for beam vibration are being solved using Generalized...

in this paper, the stability of a functionally graded magneto-electro-elastic (fg-mee) micro-beam under actuation of electrostatic pressure is studied. for this purpose euler-bernoulli beam theory and constitutive relations for magneto-electro-elastic (mee) materials have been used. we have supposed that material properties vary exponentially along the thickness direction of the micro-beam. gov...

recently, a large amount of studies have been related to nonlinear systems with multi-degrees of freedom as well as continuous systems. the purpose of this paper is to optimize passive vibration absorbers in linear and nonlinear states for an euler-bernoulli beam with a nonlinear vibratory behavior under concentrated moving load. the goal parameter in the optimization is maximum deflection of t...

Coherent beam-beam tune shift of unsymmetrical beam-beam interactions was studied experimentally and numerically in HERA, where the lepton beam has such a large beam-beam parameter (up to xi(y) = 0.272 ) that the single-particle motion is locally unstable at the origin (closed orbit). Unlike the symmetrical case of beam-beam interactions, the ratio of the coherent beam-beam tune shift and the b...

the basic strategy of reduce the ductility demand and related concentrated tensions at moment resistance connections is reduce the section of the beam at connected region to column. by this method plastic hinge done at the reduced cross section and this local reduction decreases the demand of the components of connection. on this basis, in present study a new beam-to-column moment connection wi...

Background: Physical wedges are still widely used as beam modifiers in external beam radiotherapy. However the presence of them in the beam trace may cause beam hardening which may not be considered in many treatment planning systems. The aim of this study is to investigate the beam hardening effect generated by physical wedges via different beam quality indexes as photon spectrum, half value l...

Abstract A simple method is proposed to model the open cracked beam structures. In this method, crack is modeled as a beam element. Hence cracked beam can be assumed to be a beam with stepped cross sections, and problem of determining natural frequency and mode shape of cracked beam, can be solved as determining these characteristics for a beam with different length and cross section. With this...

introduction bnct is an effective method to destroy brain tumoral cells while sparing the healthy tissues. the recommended flux for epithermal neutrons is 109 n/cm2s, which has the most effectiveness on deep-seated tumors. in this paper, it is indicated that using d-t neutron source and optimizing of beam shaping assembly (bsa) leads to treating brain tumors in a reasonable time where all iaea ...