Vertical-cavity surface-emitting lasers (VCSELs) with emission in a single-mode, singlepolarization beam at a wavelength of 894.6 nm have been fabricated for use in Cs-based atomic clocks. For polarization control, monolithically integrated surface gratings are employed. Simulated and experimental results show that the longitudinal position of the surface grating has a significant influence on ...

Fatigue crack propagation tests were conducted on the powder metallurgy nickel-base superalloy KM4 at room temperature. Two different heat treatments were investigated, one which produced a relatively coarse grain size around 55 μm, and another which produced a very fine grain size around 6 μm. Tests were conducted at 50 Hz and 1000 Hz in an advanced servohydraulic testing machine at R-ratios b...

Abstract: In this study, the effects of variation of thickness and the number of quantumwells as well as the contact length were investigated. In this paper, a vertical cavity surfaceemitting laser was simulated using of software based on finite element method. Thenumber of quantum wells was changed from 3 to 9 and the results which are related tooutput power, resonance ...

Research has shown that oscillatory or modulated flows can achieve a significant increase in heat transfer relative to the corresponding steady flow, providing that critical or threshold amplitude is achieved. The threshold condition is associated with the production of near-surface turbulence by the oscillatory motion. A similar process is hypothesized as a mechanism of highamplitude acoustic ...

In most computer vision applications, it is required to segment objects from a background. In case of a muti-modal image the segmentation is an involved problem in comparison to a bi-modal image. This paper deals with an adaptive technique for choosing local threshold values for faithful image segmentation. The image segmentation is done by generating a threshold surface which is determined by ...

in order to identify the pressure patterns causing the cold weather over the northwestern iran, daily lowest temperatures of six stations of the study area during january- march months of the 1986-2003 period were obtained from meteorological organization of islamic republic of iran (irimo) in the quality controlled format. according to the defined threshold, the very cold days were extracted a...

Equations governing the elastic scattering of electrons are applied to the knock-on displacement of atoms along a substrate, yielding analytical expressions for the surface-translation energy, threshold incident energy, and displacement rate. For a surface perpendicular to the incident beam, scattering angles around 90° contribute most to the kinetic energy of surface atoms. Tilting the specime...