Calculation Of Radiation Losses Research Articles

Diffuse ultrasonic transmission between two half spaces coupled through a single glass bead

We consider ultrasonics in glass blocks in contact through a single 3 mm glass bead held in place by contact forces of up to five Newtons. Hertzian contact theory predicts resonant transmission at a few isolated frequencies between 65 and 120 kHz. Resonances, based on calculations of radiative losses to the blocks, are predicted to be narrow, with widths of order 50Hz. Wide-band diffuse ultrasound from 50 to 800 kHz launched by an impulse in the upper block leads to a diffuse signal in the upper block that slowly diminishes due to absorption. It leads to a diffuse signal in the lower block that slowly increases in amplitude due to transmission—through the air and through the bead—before dissipating due to absorption. The spectrum in the lower block includes a broadband part demonstratable as due to transmission through the airgap. It also includes a part due to transmission through the bead and confined to a few isolated frequency bands. These transmission bands have widths of several kHz. We also investigate slow dynamics at the contact points by studying the change and recovery of the diffuse transmission after large amplitude conditionings.

On-line Application for the Calculation of Shadows on Collecting Surfaces

The calculation of radiation losses on collecting surfaces due to shadows effect of surrounding objects is a key aspect in the design process of both photovoltaics and solar thermal collecting fields. This aspect is of special relevance in small size installations located in residential areas. Even the calculations procedures involved are well known, they are complicated and need skilled planners that usually cannot be afforded within the constrained budgets of this kind of projects.The authors present a new cloud application available for free at www.omnilus.com designed with the goal of maximum user simplicity while based in detailed calculation procedures. Not only yearly shadow losses are calculated but also monthly averaged values, so that it is possible to use this value to reduce monthly averaged daily solar radiation values used for systems calculation. This work, presents an overlook of the application, details on the calculation procedure used, and one case example.

Calculation of Radiative Loss in Index Contrast of AlxGa1-xAs Waveguides

Abstracts In this paper we used a theoretical and numerical investigation model to calculate the radiation losses, penetration depth and effective indices for Al x Ga 1-x As planar optical waveguides at a wavelength of 1550 nm. Newton-Raphson method was used to find the radiation modes and its wavenumber. It was found that the change in the refractive index of Al x Ga 1-x As optical waveguide is responsible of scattering effects and radiation towards the substrate. Keywords: Radiation, Loss, Optical planar waveguides, refractive index. Introduction Due to the limited control in waveguide fabrication the radiation losses naturally occur in most materials, and the energy does not remain in the core [1]. Lots of energy can flow either through the substrate or cladding region. One of reasons is due to physical discontinuities of the dielectric waveguide cause guided energy loss by radiation [2, 3] . Losses usually arise due to radiative scattering into the surrounding material and into backward-propagating modes due to the change in the refractive index of the core [4, 5]. There are several methods to calculate radiation modes such as the Fourier decomposition method (FDM), Perturbation calculus (PC) and the spectral decomposition method (SDM) [6, 7]. In this paper, we present a numerical model that gives insight into the physical processes involved in waveguide losses and which permits us to derive design guidelines for low-loss optical waveguides Al

Tight-binding calculation of radiation loss in photonic crystal CROW

The tight binding approximation (TBA) is used to relate the intrinsic, radiation loss of a coupled resonator optical waveguide (CROW) to that of a single constituent resonator within a light cone picture. We verify the validity of the TBA via direct, full-field simulation of CROWs based on the L2 photonic crystal cavity. The TBA predicts that the quality factor of the CROW increases with that of the isolated cavity. Moreover, our results provide a method to design CROWs with low intrinsic loss across the entire waveguide band.

Waveguiding losses of micro-structured fibres—plane wave method revisited

We present a numerical method for the analysis of translationally invariant systems with anisotropic and dispersive electric and magnetic properties. This material model enables us to calculate the mode structure of photonic devices such as photonic crystal fibres (PCF) containing inclusions with anisotropic, conducting, magnetic, or negative index materials. The method is based on the popular plane wave (PWM) discretisation scheme applied to the generalised vectorial transmission line equations. The analysis is focused on the calculation of radiation losses. For this purpose we consider a uniaxial perfectly matched layer (UPML) termination of the otherwise periodic system. We asses the accuracy of the method and the properties of spurious modes created inside the UPML.

Vectorial Eigenmode Solver for Bent Waveguides Based on Mode Matching

Vectorial eigenmode solver for circularly bent dielectric waveguides is described. The approach is strictly analogous to the well-known film mode-matching method for straight waveguides. Accurate calculation of radiation loss is enabled by leaving the calculation window open in the radial direction. In order to increase numerical stability and accuracy, a new computer code was written for cylindrical functions of complex order and argument. A high-contrast bent rib guide is used for comparison of results with a commercial mode solver.

Explicit formulas of normalized radiation modes in multilayer waveguides

A new formulation for the normalization of radiation modes in one-dimensional lossless multilayer waveguide structures is derived using the transmission matrix method. In this formulation, an individual radiation mode is excited by two sources located at opposite ends of the two outermost regions of the waveguide. Proper choice of the absolute phase of one of the sources results in simple expressions for the normalized radiation modes. Calculation of radiation loss of grating-assisted directional couplers is used as an example to show the simplicity and usefulness of this method.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pulse propagation in superconducting coplanar striplines

The phenomenological loss equivalence method (PEM), the enhanced two-fluid model for thin-film superconducting materials, and the dynamical calculation of radiation losses in planar structures are used-in the context of a linear filter approach-to model attenuation and dispersion of ultrafast pulses in coplanar striplines. The numerical simulation of this modeling shows excellent agreement with experimental results available in the literature. Simple relationships between the peak attenuation and delay time of the propagation pulse, and penetration depth at absolute zero and conductivity at critical temperature may open the possibility of using pulse distortion to characterize thin-film, high-temperature superconducting materials.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Incipient soot formation in dichloromethanemethaneair premixed flames

Measurements are presented of critical sooting equivalence ratio and peak flame temperature for mixtures of dichloromethane and methane in air. Flame temperature variation was achieved by controlling total mass flux through an atmospheric-pressure, uncooled flat flame burner. A comparison of coated and uncoated thermocouple measurements is given, showing the effect of catalytic surface reactions to be negligible compared to errors in the calculation of radiation loss. The data are correlated using a global model developed for soot inception studies in premixed hydrocarbon flames. The importance of evaluating the correlation in primitive as opposed to parametric variables is shown. The model features two parameters, an activation energy difference and a variable β that has previously been correlated with fuel type in hydrocarbon studies. In chlorinated mixtures, the activation energy difference for incipient soot temperature dependence agrees well with that reported for aliphatic hydrocarbons. The fuel-dependent correlation parameters used for hydrocarbons, C H ratio and number of CC bonds, are not sufficient to explain the behavior of chlorinated mixtures. The parameter β is shown to depend on the Cl H ratio in addition to possible dependence on C H ratio and/or number of CC bonds. Analysis showns this is consistent with the known chemical effects of chlorine on hydroxyl radicals and fuel molecules. At constant temperature, the effects of chlorine on hydroxyl concentration and fuel pyrolysis are shown to be of comparable magnitude.

Opacity effects on the radiative losses of coronal loops

view Abstract Citations (29) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Opacity Effects on the Radiative Losses of Coronal Loops Kuin, N. P. M. ; Poland, A. I. Abstract This paper presents calculations of radiative losses, which include the effects of geometry and optical depth, that can be used to improve the energy losses in many flux-tube calculations for loops with constant and variable cross sections. The results include the non-LTE ionization state of hydrogen and helium, thus allowing the determination of the ionization energy in the gas and the relative importance of collisional and radiative processes. These calculations show that optical depth effects are important under solar conditions in the temperature range of 8000-40,000 K. Publication: The Astrophysical Journal Pub Date: April 1991 DOI: 10.1086/169859 Bibcode: 1991ApJ...370..763K Keywords: Coronal Loops; Opacity; Radiative Transfer; Solar Flares; Solar Prominences; Computerized Simulation; Magnetohydrodynamics; Optical Thickness; Stellar Models; Solar Physics; RADIATIVE TRANSFER; SUN: CORONA; SUN: FLARES; SUN: PROMINENCES full text sources ADS |

Mode-dependent radiation loss in Y junctions and directional couplers

Calculation of radiation loss in symmetric dielectric optical waveguide Y-junction power dividers and evanescent-field directional couplers is presented. The loss is calculated as a function of the separating angle for the odd and even exciting normal modes in several test structures. It is shown that for most practical cases, the even normal mode is more lossy than the odd normal mode. The difference increases with the separating angle and with the guidance strength. This radiation-loss difference is, in general, smaller for directional couplers than for Y-junction power dividers. Introducing a proper curvature to the output waveguides of a structure can serve to minimize this difference.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Calculation of radiation loss in integrated-optic tapers and Y-junctions

Mode conversion and radiation loss in integrated-optic tapers and Y-junctions are calculated by means of the beam propagation method combined with the effective refractive-index method. Simple design rules for the tapers and Y-junctions are derived from the obtained results.

Coupled Mode Theory of Round Optical Fibers

This paper presents a comprehensive theory of mode coupling in optical fibers with imperfections. The paper begins with the derivation of a general coupled wave theory based on the modes of the ideal fiber. The general theory is applied to a simplified description of guided and radiation modes of the fiber that is valid for small core-cladding index differences. The simplified theory results in expressions for the coupling coefficients that are nearly as simple as those of the slab waveguide. As an example, the theory is applied to the calculation of radiation losses caused by pure core diameter changes and by elliptical deformations of the fiber core.

Radiation Losses of the Dominant Mode in Round Dielectric Waveguides

The radiation loss theory that has been developed in a series of earlier papers is extended to the dominant mode of the round dielectric waveguide. The theory is applied to the calculation of radiation losses of abrupt steps, gradual tapers, and random wall perturbations of the round dielectric waveguide. The radiation losses caused by an abrupt step, and consequently the losses of tapers, are far higher for the dominant mode of the round dielectric waveguide than they are for corresponding steps and tapers of the dielectric slab waveguide. However, the losses caused by infinitesimal random wall perturbations of the round waveguide are nearly equal to the random wall losses predicted on the basis of the slab waveguide theory. In fact the losses of the dominate mode as well as the circular electric TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</inf> mode of the round rod due to random wall perturbations are very nearly the same. The theory is limited to circular symmetric distortions of the round dielectric rod (diameter changes). The radiation losses caused by steps of the round dielectric waveguide that carries the dominate guided mode have been verified by experiments at millimeter wave frequencies.