Current Issue : April - June Volume : 2015 Issue Number : 2 Articles : 5 Articles
A new method of designing circularly symmetric shaped dual reflector antennas using distorted conics is presented. The surface of\nthe shaped subreflector is expressed using a new set of equations employing differential geometry.The proposed equations require\nonly a small number of parameters to accurately describe practical shaped subreflector surfaces. A geometrical optics (GO) based\nmethod is used to synthesize the shaped main reflector surface corresponding to the shaped subreflector. Using the proposed\nmethod, a shaped Cassegrain dual reflector system is designed.The field scattered fromthe subreflector is calculated using uniform\ngeometrical theory of diffraction (UTD). Finally, a numerical example is provided showing how a shaped subreflector produces\nmore uniform illumination over the main reflector aperture compared to an unshaped subreflector....
This letter presents a novel wide band miniaturized-element frequency selective surface (MEFSS).The simulation and measurement\nresults show that the bandwidth of the proposed MEFSS is remarkably enhanced compared to that of an original second-order\nMEFSS while its size and total thickness are still small.Aparametric study is also conducted to understand the operating mechanism\nof the proposed structure.The phenomenon observed in the parametric study is explained with an equivalent circuit model....
The development of a novel switched-mode 2.45GHz microwave (MW)multi applicator system intended for laparoscopic and open\nsurgical the rmoablative treatments is presented. The system differs from the other synchronous and asynchronous commercially\navailable equipments because it employs a fast sequential switching (FSS) technique for feeding an array of up to four high efficiency\nM Wapplicators. FSS technology, if properly engineered, allows improving system compactness, modularity, overall efficiency, and\noperational flexibility. Full-wave electromagnetic (EM) and thermal (TH) simulations have been made to confirm the expected\nperformances of the FSS technology. Here we provide an overview of technical details and early ex-vivo experiments carried out\nwith a full functional ????-prototype of the system....
This paper presents a comparative study on\nheat transfer in a packed column. Two methods of heating\nare considered: microwave and convective. Transient onedimensional\nmathematical models were proposed to\ndescribe the both alternatives. To account for significant\ndifferences in the temperatures between the gas and solid\nphase a heterogeneous model was applied in the modelling.\nThe numerical simulations were carried out for different\noperating conditions. The effects of the gas inlet temperature\nand the microwave power, the bed porosity, the\npenetration depth of microwaves and the gas velocity were\nexamined. The simulation results were compared on the\nbasis of the time profiles of the average bed temperature\nand the outlet gas temperature. The same electric power\nutilized in the microwave heated packed column and the\nconvective heated packed column was established as the\nkey criterion for the comparisons. The compared profiles\nintersect indicating the time ranges in which the one or the\nother solution provides higher temperature of the bed. It\nwas displayed that the microwave heated packed column\nshould be preferred when longer heating times are required.\nIn turn, the convective heated packed column is the better\nchoice when shorter heating times are needed....
Ultrawideband (UWB) waveforms achieve excellent spatial resolution for better characterization of targets in tomographic imaging\napplications compared to narrowband waveforms. In this paper, two-dimensional tomographic images of multiple scattering\nobjects are successfully obtained using the diffraction tomography approach by transmitting multiple independent and identically\ndistributed (iid)UWBrandomnoise waveforms.Thefeasibility of using a randomnoise waveformfor tomography is investigated by\nformulating a white Gaussian noise (WGN) model using spectral estimation. The analytical formulation of object image formation\nusing random noise waveforms is established based on the backward scattering, and several numerical diffraction tomography\nsimulations are performed in the spatial frequency domain to validate the analytical results by reconstructing the tomographic\nimages of scattering objects. The final image of the object based on multiple transmitted noise waveforms is reconstructed by\naveraging individually formed images which compares very well with the image created using the traditional Gaussian pulse. Pixel\ndifference-based measure is used to analyze and estimate the image quality of the final reconstructed tomographic image under\nvarious signal-to-noise ratio (SNR) conditions. Also, preliminary experiment setup andmeasurement results are presented to assess\nthe validation of simulation results....
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