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    Analysis & Design of Bragg Mirror-Based Optical Fibers

    , M.Sc. Thesis Sharif University of Technology Jazayeri, Amir Mohammad (Author) ; Mehrany, Khashayar (Supervisor)
    The Bragg reflection mechanism is in this thesis employed to design optical fibers with specific characteristics. First, optical Bragg fibers (BF) with radial periodicity are considered and optimized to have the minimum leakage loss by introduction of a new parameter referred to as the point-wise wave-number. In this fashion, the optical effects of geometrical factors of the to-be-designed fiber are brought together in the point-wise wave-number and the sought-after parameters of the fiber are thus analytically found. Despite a few approximations made in extraction of optimum parameters, rigorous numerical analysis of the here-proposed optical BF clearly demonstrates that it outperforms... 

    Deployment of an array of water-cherenkov detectors for extensive air shower experiments

    , Article 30th International Cosmic Ray Conference, ICRC 2007, Merida, Yucatan, 3 July 2007 through 11 July 2007 ; Volume 5, Issue HE PART 2 , 2007 , Pages 909-912 Sheidaei, F ; Bahmanabadi, M ; Khakian Ghomi, M ; Habibi, F ; Samimi, J ; Pezeshkian, Y ; Anvari, A ; Sharif University of Technology
    Universidad Nacional Autonoma de Mexico  2007
    A new small array of cherenkov detectors has been deployed in Tehran, 1200 m above sea level. This array contains of four tanks full of distilled water with diameter of 64 cm and height of 130 cm. The effective area of each tank is about 6.5 × 103cm2 . They are used to detect the air showers and to record the arrival time of the secondary particles. We have collected about 486643 EAS in 5270 h of observation time from Nov-2006 to May-2007. We find zenith and azimuth distribution of EAS with this array. A cosn θ distribution with n = 7.3±0.1 was obtained for zenith angle. Since this tank of distilled water is cheaper and more available than Scintillators it is preferable to use them instead... 

    Prosthetic knee using of hybrid concept of magnetorheological brake with a T-shaped drum

    , Article 2015 IEEE International Conference on Mechatronics and Automation, ICMA 2015, 2 August 2015 through 5 August 2015 ; Aug , 2015 , Pages 721-726 ; 9781479970964 (ISBN) Sayyaadi, H ; Zareh, S. H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    This paper focuses on developing a new configuration on magnetorheological (MR) brake damper as prosthetic knee. Knee uses magnetic fields to vary the viscosity of the MR fluid, and thereby its flexion resistance. Exerted transmissibility torque of the knee greatly depends on the magnetic field intensity in the MR fluid. In this study a rotary damper using MR fluid is addressed in which a single rotary disc will act as a brake while MR fluid is activated by magnetic field in different walking gait. The main objective of this study is to investigate a prosthetic knee with one activating rotary disc to accomplish necessary braking torque in walking gait via implementing of Newton's equation of... 

    PEM Power Density Optimization Based on Non-Uniform Catalyst Distribution

    , M.Sc. Thesis Sharif University of Technology Ebrahimi, Sasan (Author) ; Roshandel, Ramin (Supervisor)
    In many previous Polymer Electrolyte Membrane Fuel Cell (PEMFC) models,the catalyst distribution in Catalyst Layer (CL) was assumed to be uniform and there are just a few models which consider variation of catalyst loading across the CL. In this research, a half-cell PEMFC cathode model is applied to investigate the effect of catalyst loading in CL plane under the land and channels of bipolar plates. In addition, the agglomerate model which has been shown to be more complete representation of the fuel cell CL is used. It is necessary to mention, in many previous PEMFC models, the catalyst layer was treated as a pseudohomogenous layer. In both models, the micro structure of CL and its effect...