Eina per al desenvolupament de reflectors de conjunts òptics

Avui en dia, una bona il·luminació vial és molt important, tant per als conductors com per als vianants. Els fanals o conjunts òptics estan compostos per una font de llum que és la làmpada, el reflector i la carcassa que els protegeix. Trobar la forma exacta d’un reflector amb unes propietats òptiques en particular és de gran importància en el sector luminotècnic. En aquest projecte es vol dissenyar i desenvolupar una sistema capaç d’ajudar a obtenir el reflector adequat, un programari que permeti dissenyar un reflector a partir d’una boca qualsevol, i mitjançant una làmpada, capturar la intensitat de llum que el reflector projecta sobre al terra o una superfície del carrer. L’aplicació desenvolupada vol facilitar el procés de selecció d’un bon reflector als enginyers luminotècnics

Effect of Wildlife Highway Warning Reflectors on Deer-Vehicle Accident, December 1984

he number of deer-vehicle accidents in Iowa and around the country has steadily increased during the past 30 years. This i s basically due to: ( 1 ) increased volume of traffic; 12) an expanding network of hard surface roads, especially 4 lane interstates; and (3) a general increase in deer populations. Initidtion of a 55 MPH speed limit in 1974 and gasoline shortages in 1975 reduced deer-vehicle accident rates briefly, but since 1975, rates have continued to climb. Various methods of reducinq these accidents have been attempted in other states. These include: instal lation of rc?flective devlres, deer crossing signs, fencing, underpasses, clearing right--of--waysa,n d controlled hunting to reduce deer population s i z e . These methods have met with varying degrees of success, depending on animal behavior, deet- population fluctuations, method used, topoyr-aphy, road-side vegetation, traffic patterns, and highway configuration. This project was designed to evaluate a new ntethod of reducing deer-vehicle accidents. There are qenerally 4 important aspects of deer-vehicle accidents: danger to human l i f e , vehicle damage, loss of a valuable wildlife resource, and cost of processing accident reports. In !owe, during 1983, there were over 15,OOC) reported deer--vehicle accidents and probably many more that were not reported (Gladfelter 1984). The extent of human injury or death in Iowa i s not known, but studies in southern Michigan show that human injur ies occurred in about 4% of the deer-vehicle accidents (A1 lcn and MrCullough 1976). T h i s would indicate that in Iowa there could have been 200 human injury cases from deer-vehicle accidents i n 1983. These injuries usual 1 occur from secondary collisions when motorists try to avoid a deer on the highway, and hit some other object Vehicle darnaye from these accidents can into thousands of dollars because of the high speed involved and the size of the animal. The total amount of vehicle damage occurring in Iowa is unknown, but if the average vehicle damage was between $500-$800 per accident, estimated property damage would be between $2 1/2--$4 million annually. The value of deer lost in these accidents cannot be estimated, but recreational potential of this natural resource is surely diminished for hunters and wildlife enthusiasts. Also, there ir a great deal of money spent by governmental agencies for manpower to process accident reports and remove dead animals from highways.

Spectral analysis of the angular distribution function of back reflectors for thin film silicon solar cells

Nowadays, one of the most important challenges to enhance the efficiency of thin film silicon solar cells is to increase the short circuit intensity by means of optical confinement methods, such as textured back-reflector structures. In this work, two possible textured structures to be used as back reflectors for n-i-p solar cells have been optically analyzed and compared to a smooth one by using a system which is able to measure the angular distribution function (ADF) of the scattered light in a wide spectral range (350-1000 nm). The accurate analysis of the ADF data corresponding to the reflector structures and to the μc-Si:H films deposited onto them allows the optical losses due to the reflector absorption and its effectiveness in increasing light absorption in the μc-Si:H layer, mainly at long wavelengths, to be quantified.

Backscattering Reduction of Corner Reflectors using SCS Technique

Reduction of radar cross -section of dihedral corner reflectors using simulated corrugated surface (.SCS) is reported. This technique is found lo be more effective in the reduction of RCS or corner reflectors for normal incidence . A typical reduction of 40-50 dB is achieved using this method

Corrugated Flanged Horn Feed for Offset Paraboloidal Reflectors

A technique for improving the coupling between a feed horn and reflector by using corrugated metallic flanges is presented. Experimental data for flanges of varying parameters are given and theoretical explanation is supplemented

Backscattering Reduction of Corner Reflectors using SCS Technique

Reduction of radar cross -section of dihedral corner reflectors using simulated corrugated surface (SCS) is reported. The technique is found to be more effective in the reduction of RCS or corner reflectors for normal incidence . A typical reduction of 40-50 dB is achieved using this method.

Eina per al desenvolupament de reflectors de conjunts òptics

Avui en dia, una bona il·luminació vial és molt important, tant per als conductors com per als vianants. Els fanals o conjunts òptics estan compostos per una font de llum que és la làmpada, el reflector i la carcassa que els protegeix. Trobar la forma exacta d’un reflector amb unes propietats òptiques en particular és de gran importància en el sector luminotècnic. En aquest projecte es vol dissenyar i desenvolupar una sistema capaç d’ajudar a obtenir el reflector adequat, un programari que permeti dissenyar un reflector a partir d’una boca qualsevol, i mitjançant una làmpada, capturar la intensitat de llum que el reflector projecta sobre al terra o una superfície del carrer. L’aplicació desenvolupada vol facilitar el procés de selecció d’un bon reflector als enginyers luminotècnics

Accelerated aging of thick glass second surface silvered reflectors under sandstorm conditions

Concentrated solar power systems are expected to be sited in desert locations where the direct normal irradiation is above 1800 kWh/m2.year. These systems include large solar collector assemblies, which account for a significant share of the investment cost. Solarreflectors are the main components of these solar collector assemblies and dust/sand storms may affect their reflectance properties, either by soiling or by surface abrasion. While soiling can be reverted by cleaning, surface abrasion is a non reversible degradation.The aim of this project was to study the accelerated aging of second surface silvered thickglass solar reflectors under simulated sandstorm conditions and develop a multi-parametric model which relates the specular reflectance loss to dust/sand storm parameters: wind velocity, dust concentration and time of exposure. This project focused on the degradation caused by surface abrasion.Sandstorm conditions were simulated in a prototype environmental test chamber. Material samples (6cm x 6cm) were exposed to Arizona coarse test dust. The dust stream impactedthese material samples at a perpendicular angle. Both wind velocity and dust concentrationwere maintained at a stable level for each accelerated aging test. The total exposure time in the test chamber was limited to 1 hour. Each accelerated aging test was interrupted every 4 minutes to measure the specular reflectance of the material sample after cleaning.The accelerated aging test campaign had to be aborted prematurely due to a contamination of the dust concentration sensor. A robust multi-parametric degradation model could thus not be derived. The experimental data showed that the specular reflectance loss decreasedeither linearly or exponentially with exposure time, so that a degradation rate could be defined as a single modeling parameter. A correlation should be derived to relate this degradation rate to control parameters such as wind velocity and dust/sand concentration.The sandstorm chamber design would have to be updated before performing further accelerated aging test campaigns. The design upgrade should improve both the reliability of the test equipment and the repeatability of accelerated aging tests. An outdoor exposure test campaign should be launched in deserts to learn more about the intensity, frequencyand duration of dust/sand storms. This campaign would also serve to correlate the results of outdoor exposure tests with accelerated exposure tests in order to develop a robust service lifetime prediction model for different types of solar reflector materials.

Parabolic dish reflectors for solar applications approximated by simple surfaces

Two different concentrating mirrors have been constructed that resemble parabolic dish reflectors. Both mirrors are made of slightly curved strips of flat, bendable material. The strips of the most simplified mirror have only large-radius circles and straight lines as boundaries. The necessary equations for making the mirrors have been derived. Also a simple way to make a stiff, lightweight frame and support for the mirror strips has been developed. Models of the mirrors have been built and successfully used for cooking and baking.This report is an extended version of a paper to be published in Solar Energy that contains complete derivations of all mirror design equations.

Antenna Simulations and Measurements of Focal Plane Array Facet Reflectors

We present a conceptual prototype model of a focal plane array unit for the STEAMR instrument, highlighting the challenges presented by the required high relative beam proximity of the instrument and focus on how edge-diffraction effects contribute to the array's performance. The analysis was carried out as a comparative process using both PO & PTD and MoM techniques. We first highlight general differences between these computational techniques, with the discussion focusing on diffractive edge effects for near-field imaging reflectors with high truncation. We then present the results of in-depth modeling analyses of the STEAMR focal plane array followed by near-field antenna measurements of a breadboard model of the array. The results of these near-field measurements agree well with both simulation techniques although MoM shows slightly higher complex beam coupling to the measurements than PO & PTD.

An Efficient Hybrid GO-PWS Algorithm to Analyze Conformal Serrated-Edge Reflectors for Millimeter-Wave Compact Range

A method to analyze parabolic reflectors with arbitrary piecewise rim is presented in this communication. This kind of reflectors, when operating as collimators in compact range facilities, needs to be large in terms of wavelength. Their analysis is very inefficient, when it is carried out with fullwave/MoM techniques, and it is not very appropriate for designing with PO techniques. Also, fast GO formulations do not offer enough accuracy to reach performance results. The proposed algorithm is based on a GO-PWS hybrid scheme, using analytical as well as non-analytical formulations. On one side, an analytical treatment of the polygonal rim reflectors is carried out. On the other side, non-analytical calculi are based on efficient operations, such as M2 order 2-dimensional FFT. A combination of these two techniques in the algorithm ensures real ad-hoc design capabilities, reached through analysis speedup. The purpose of the algorithm is to obtain an optimal conformal serrated-edge reflector design through the analysis of the field quality within the quiet zone that it is able to generate in its forward half space.

Performance Comparison Between Serrated Edge and Rolled Edge Reflectors Inside CATR Facilities

CATR facilities are attractive antenna measurement facilities. Main reasons which contribute to this fact lie on its inherent reduced volume, on-the-fly measurements and the extension of both to a wide range of frequencies. However, these features rely on the assumption that the field collimation scheme is able to generate a plane wave distribution (quiet zone) where the AUT is to be placed and operated in RX mode. Unfortunately, electromagnetic theory states that this field distribution is not possible to be generated by a finite size scatterer operated as the collimator of a nonzero wavelength time-harmonic propagating field. This is the background of this paper, where two well-known electromagnetic field collimators will be discussed: the serrated edge reflector and the blended rolled edge reflector. To reach this purpose, electromagnetic hybrid analysis techniques developed at Technical University of Madrid will be applied.

Optical and structural properties of InAlN/GaN Bragg reflectors examined by transmission electron microscopy and electron energy loss spectroscopy

Molecular beam epitaxy growth of ten-period lattice-matched InAlN/GaN distributed Bragg reflectors (DBRs) with peak reflectivity centered around 400nm is reported including optical and transmission electron microscopy (TEM) measurements [1]. Good periodicity heterostructures with crack-free surfaces were confirmed, but, also a significant residual optical absorption below the bandgap was measured. The TEM characterization ascribes the origin of this problem to polymorfism and planar defects in the GaN layers and to the existence of an In-rich layer at the InAlN/GaN interfaces. In this work, several TEM based techniques have been combined.

High-Acoustic-Impedance Tantalum Oxide Layers for Insulating Acoustic Reflectors

This work describes the assessment of the acoustic properties of sputtered tantalum oxide films intended for use as high-impedance films of acoustic reflectors for solidly mounted resonators operating in the gigahertz frequency range. The films are grown by sputtering a metallic tantalum target under different oxygen and argon gas mixtures, total pressures, pulsed dc powers, and substrate biases. The structural properties of the films are assessed through infrared absorption spectroscopy and X-ray diffraction measurements. Their acoustic impedance is assessed by deriving the mass density from X-ray reflectometry measurements and the acoustic velocity from picosecond acoustic spectroscopy and the analysis of the frequency response of the test resonators.