1,721,147 research outputs found
A simple method for calculating coupling efficiency in optical interconnection system involving various misalignment parameters
No full textA simple method is presented to approximate the coupling efficiency in optical interconnection systems, which are affected by alignment parameters of various optical elements. The method considers geometric effects of alignment parameters, not considering the material-dependent losses which are insensitive to the misalignment parameters. To indicate the independent contribution of a given alignment parameter, we define a partial coupling efficiency (PCE) that reflects the effect of only one parameter on a local coupling efficiency at an optical element. The total coupling efficiency (TCE) in the whole system is approximated by multiplications of the PCEs calculated for each parameter and normalization factors. For an interconnection scheme using a 45degrees-ended waveguide, we demonstrate by considering many misalignment parameters simultaneously that our approximation is well matched to the results of the simulated TCE. (C) 2004 Elsevier Ltd. All rights reserved
A heuristic for an assembly line balancing problem with incompatibility, range, and partial precedence constraints
No full textThis paper considers a new type of an assembly line balancing problem which occurs in a company manufacturing electronic home appliances. The problem has some special characteristics. The main difficulty in this problem is that the precedence diagram is not enough to describe the precedence relationships between the tasks. It is shown that the usual line balancing model is a special case of the problem considered in this paper. After considering two subproblems, a heuristic algorithm for the problem is proposed. The algorithm is based on some network theories. Computational results based on some real world problems show the proposed algorithm works well in practice. A full system which incorporates graphic user interface is developed and currently in use. (C) 1997 Elsevier Science Ltd
Dynamic analysis of structures using modified Lanczos co-ordinates
No full textAn efficient dynamic analysis method using the modified Lanczos co-ordinates is presented. The proposed method is obtained by applying the modified Lanczos algorithm using Lanczos vectors that satisfy the stiffness-orthonormality condition to the conventional Lanczos co-ordinates method. The modified Lanczos co-ordinates method is more efficient than the conventional method in the case of structures under multi-input loads. The effectiveness of the modified Lanczos co-ordinates method is verified by analysing a numerical example. Copyright (C) 2003 John Wiley Sons, Ltd
Heat and fluid flow in pulsed current GTA weld pool
No full textIn this study the heat transfer, fluid flow and phase change of the weld pool in pulsed current gas tungsten are (GTA) welding were investigated. Transporting phenomena from the welding are to the base material surface, such as current density, heat flux, are pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding are. Various driving forces for the weld pool convection were considered, namely self-induced electromagnetic, surface tension, buoyancy, and impinging plasma are force. Furthermore, the effect of deformed free surface due to the are pressure acting on the weld pool surface was considered. Heat and mass transfer equations, including the generalized Navier-Stokes equation and electric transport equation, were solved by a finite difference method. Because the fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model for pulsed: current welding was applied to AISI 304 stainless steel and compared with the results of the constant current. (C) 1998 Elsevier Science Ltd. All rights reserved
Simple approximation of coupling efficiency in the optical interconnection system involving various optical elements and alignment variables
No full textDouble EIM and scalar BPM analyses of birefringence and wavelength shift for TE and TM polarized fields in bent planar lightwave circuits
No full textWe have applied the effective index method to reduce the two-dimensional refractive index profile into the one-dimensional refractive index structure and modified the wave equations to obtain the paraxial wave equations. Then, TE and TM polarized fields in the curved single-mode planar waveguides are analyzed by using the scalar beam-propagation method employing the finite-difference method with a slab structure. The birefringence for TE and TM polarized fields in bent waveguides is calculated from the phase difference of the optical fields. The wavelength shift due to the birefringence of TE and TM polarized fields in bent waveguides is also calculated
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