in this paper, the effects of reflected waves of the facets on the internal optical intensity of semiconductor dfb lasers are investigated. the uniformity of optical intensity along the cavity length is evaluated with flatness parameter. the dependence of this parameter on coupling coefficient, reflectivity and grating phase at the facets is also studied. this investigation shows that in some s...

by extending wireless networks and because of their different nature, some attacks appear in these networks which did not exist in wired networks. security is a serious challenge for actual implementation in wireless networks. due to lack of the fixed infrastructure and also because of security holes in routing protocols in mobile ad hoc networks, these networks are not protected against attack...

In the framework of the planar t-J model for cuprates we analyze the development of a pseudo gap in the density of states, which at low doping starts to emerge for temperaturesT < J and persists up to the optimum doping. The analysis is based on numerical results for spectral functions obtained with the finite-temperature Lanczos method for finite two-dimensional clusters. Numerical results are...

The general problem of calculating the propagation electromagnetic radiation from particles or stars moving in vicinity a supermassive black hole is considered geometrical optics approximation within framework theory relativity. Different approaches that can be used to calculate certain characteristics radiation, including redshift, intensity and rotation plane polarization, which have been pre...

in this study, the role of interaction of pi electrons on the strength of simultaneous σ-hole interactions (pnicogen, chalcogen and halogen bonds) is investigated using the quantum chemical calculations. x-ben||taz∙∙∙y1,y2,y3 complexes (x = cn, f, cl, br, ch3 , oh and nh2, taz= s-triazine and y1,y2 and y3 denotes ph2f, hsf, and clf molecules) is introduced as a model. the results show that inte...

introduction: the mechanisms of hepatic encephalopathy are not fully understood. moreover, there is no comprehensive data concerning the effects of nitric oxide (no) system on anxiolytic-like behaviors induced by bile duct ligation (bdl). methods: male mice weighing 25-30 g were used and anxiety-like behaviors were tested using hole-board task. results: the data indicated that cholestasis incre...

the effects of substituents on the symmetry and the nature of halogen bonds in [n∙∙∙x∙∙∙n]+-type systems are presented for the yc5h4n∙∙∙x∙∙∙nc5h5 (y = no2, cn, h, ch3, och3, oh, nh2, x = cl, br, i) complexes. some structural parameters, energy data and electronic properties were explored with the density functional theory (dft) calculations. in addition, electrostatic potentials were used in es...

Introduction: We have investigated cardiac SPECT with slant hole collimator in which the holes are slanted towards the target organ, to provide greater sensitivity over the parallel hole collimator. In addition, parallel hole collimator was used to obtain a comparison in FWHM, sensitivity, Compton and photoelectric area values in the simulations. Materials and Methods...

in the linear system ax = b the points x are sometimes constrained to lie in a given subspace s of column space of a. drazin inverse for any singular or nonsingular matrix, exist and is unique. in this paper, the singular consistent or inconsistent constrained linear systems are introduced and the effect of drazin inverse in solving such systems is investigated. constrained linear system arise ...