Design and analysis of bidirectional deployable parabolic cylindrical antenna

A bidirectional deployable parabolic cylindrical reflector for an L-band synthetic aperture radar is presented in this study, in which a self-deployed antenna with low weight was designed. The antenna consists of four curved surfaces formed from thin sheets of composite materials connected by hinges along the edges, and the reflective surface is provided by the front surface. The edge profiles of connecting lines were obtained through geometric analysis. A scaled model, including design and manufac- ture, was demonstrated to validate the process from the folded state to the fully deployed state. The non-contact synchronous vision measuring method was used to test the basic frequency of the scaled model, and the test results gave the verification of the analyses. Compared with the existing unidirectional deployable antenna, this new type of bidirectional deployable antenna can be applied to larger-size antennas and has better performance because the glass-woven tape connections were substituted with more reliable hinges. Static, modal, harmonic response, and transient response analyses of the full-sized reflector structure were mod- eled with the commercial finite element （FE） package ABAQUS. The modeling techniques were developed to predict the struc- tural dynamic behavior of the reflector and the results showed that the first natural frequency was 0.865 Hz, and the reflector structure had good stiffness in three directions. This proposed structure has very high stiffness-to-mass ratio because of its hollow solid construction. A preliminary simulation of radiation properties of the parabolic cylindrical antenna, fed by an off-set linear feed horn array, was conducted to obtain the radiation pattern of the feed and the reflector.

Electron states and electron Raman scattering in semiconductor double cylindrical quantum well wire

The differential cross section for an electron Raman scattering process in a semiconductor GaAs/AlGaAs double quantum well wire is calculated,and expressions for the electronic states are presented.The system is modeled by considering T = 0 K and also with a single parabolic conduction band,which is split into a subband system due to the confinement.The gain and differential cross-section for an electron Raman scattering process are obtained.In addition,the emission spectra for several scattering configurations are discussed,and interpretations of the singularities found in the spectra are given.The electron Raman scattering studied here can be used to provide direct information about the efficiency of the lasers.

Receiver tube heat transfer analysis of a CCP collector designed based on branched fractals geometry

For the development of systems related to renewable energy and specifically for thermo-solar energy,it is essential to study and analyze the different thermal phenomena of heat transfer,in search of the best conditions that allow strengthening the designs.Phenomena such as radiation,convection,and conduction are highly studied,from the field of materials to the field of infrastructure,finding day to day optimal solutions that guarantee a great use of the solar resource available on the earth's surface.This study presented the results of heat transfer analysis on a receiver pipe in a CCP;designed using the theory of branched fractal geometry to improve the heat transfer associated with concentrating solar capture systems.A fractal structure as a branch or arboreal fractal type network,influenced thermal and electrical parameters,as electrical resistance,thermal resistance,and convective heat transfer,so increasing the level branch heat transfer can be enhancement along of the pipe.The use of renewable energies in agriculture benefits the industrial processes that require a continuous power system,due to climatic conditions and geographical location is not a guarantee in food production fields,which reason solar capture systems contribute to food dehydration processes,water heating,refrigeration,and energy production.