Search for: propagation-mechanism
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    On free vibration of functionally graded euler-bernoulli beam models based on the non-local theory

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 12 , 2012 , Pages 169-173 ; 9780791845288 (ISBN) Moheimani, R ; Ahmadian, M. T ; Sharif University of Technology
    In this paper, the governing equations and boundary conditions of a functionally graded Euler-Bernoulli beam are developed based on the non-local theory of elasticity. Afterward, the free vibration is investigated and the effects of the axial load, the non-local parameter and the power index on the natural frequency of a hinged-hinged beam is assessed. The results indicate that the non-local parameter has a decreasing effect on the frequency while the power index has an increasing effect. It is also noted that the effect of the axial load is increasing too  

    Using cubic B-spline interpolation for efficient ray-tracing-based ultrawideband propagation modeling

    , Article Proceedings - IEEE International Conference on Ultra-Wideband, 14 September 2011 through 16 September 2011, Bologna ; 2011 , Pages 12-15 ; 21626588 (ISSN) ; 9781457717642 (ISBN) Mohtashami, V ; Shishegar, A. A ; Sharif University of Technology
    Site-specific ultrawideband propagation modeling involves dealing with frequency variations of the propagation mechanisms and antenna patterns in the ray tracing program. Typically, electromagnetic field calculations have to be performed in a lot of frequencies to accurately construct the frequency response of the channel at a receiving point. This imposes a heavy computational burden on ray tracing specially in calculating the coverage map or finding the statistics of channel parameters where the number of receiving locations is large. In this paper, the computational complexity of ray tracing in ultrawideband propagation modeling is reduced by using cubic B-spline interpolation. The... 

    Efficient ultrawideband propagation modelling by using the cubic B-spline function in ray tracing calculations

    , Article IET Microwaves, Antennas and Propagation ; Volume 6, Issue 12 , 2012 , Pages 1347-1358 ; 17518725 (ISSN) Mohtashami, V ; Shishegar, A. A ; Sharif University of Technology
    IEEE  2012
    In site-specific ultrawideband propagation modelling, electromagnetic field calculations need to be performed by ray tracing at numerous frequencies of the band in order to properly include the frequency variations of the propagation mechanisms and antenna patterns. This is computationally intensive especially in calculating the coverage map or finding the statistics of the channel parameters where field calculations need to be carried out at a lot of receiver locations. In this study, the cubic B-spline function is incorporated in ray tracing to increase the computational efficiency of site-specific ultrawideband propagation modelling. This function can accurately reconstruct a signal from... 

    Experimental and numerical investigation of pulse-shaped split Hopkinson pressure bar test

    , Article Materials Science and Engineering A ; Volume 539 , 2012 , Pages 285-293 ; 09215093 (ISSN) Naghdabadi, R ; Ashrafi, M. J ; Arghavani, J ; Sharif University of Technology
    Employing a proper pulse shaper in the conventional split Hopkinson pressure bar (SHPB) test helps to achieve dynamic equilibrium condition and to fulfill a constant strain rate condition in the test specimen. To this end, the parameters affecting the incident pulse shape, i.e., pulse shaper thickness, pulse shaper diameter, striker bar length and striker bar velocity are experimentally studied. Moreover, simulation results, validated by experimental data together with wave propagation analysis, are exploited to provide general guidelines to properly design a pulse shaper. It is recommended to use a relatively large diameter pulse shaper for testing work-hardening materials. Also, for... 

    Neuroplasticity in dynamic neural networks comprised of neurons attached to adaptive base plate

    , Article Neural Networks ; Volume 75 , 2016 , Pages 77-83 ; 08936080 (ISSN) Joghataie, A ; Shafiei Dizaji, M ; Sharif University of Technology
    Elsevier Ltd  2016
    In this paper, a learning algorithm is developed for Dynamic Plastic Continuous Neural Networks (DPCNNs) to improve their learning of highly nonlinear time dependent problems. A DPCNN is comprised of a base medium, which is nonlinear and plastic, and a number of neurons that are attached to the base by wire-like connections similar to perceptrons. The information is distributed within DPCNNs gradually and through wave propagation mechanism. While a DPCNN is adaptive due to its connection weights, the material properties of its base medium can also be adjusted to improve its learning. The material of the medium is plastic and can contribute to memorizing the history of input-response similar... 

    A study of the effect of diffraction and rough surface scatter modeling on ray tracing results in an urban environment at 60 GHz

    , Article 1st Conference on Millimeter-Wave and Terahertz Technologies, 29 December 2009 through 31 December 2009 ; 2009 , Pages 27-31 ; 9781424468089 (ISBN) Eslami Rasekh, M ; Shishegar, A. A ; Farzaneh, F ; Sharif University of Technology
    Channel characterization is an important step in the design of wireless communication systems. While channel sounding procedures are a useful method in determining channel behavior, they also require expensive and time consuming procedures and equipment. Ray tracing has been an important substitute for measurement in deterministic channel modeling and characterization of the wireless channel. Much has been done to improve the precision and efficiency of this method for lower frequency bands (generally below 5 GHz) over the years. Recently, with the worldwide announcement of a broad unlicensed band in the millimeter wave spectrum around 60 GHz, a great amount of attention has been paid to...