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    Ultrawide band negative refraction based on moving media concept

    , Article Applied Computational Electromagnetics Society Journal ; Volume 27, Issue 11 , November , 2012 , Pages 931-937 ; 10544887 (ISSN) Jafargholi, A ; Jafargholi, A ; Sharif University of Technology
    2012
    Abstract
    The anomalous wave propagation in a homogeneous, isotropic and lossless medium that moves with a constant velocity along the axis of a rectangular waveguide; and its interesting properties lead us to the fact that the moving media may be regarded as double negative metamaterial (DNG). In this paper, the correct sign of the permittivity and permeability of an equivalent stationary media, for each TE and TM modes and for both low and high dielectric velocities are investigated and it is shown that this medium acts as a DNG material over specific frequency ranges  

    Broadband miniaturized efficient array antennas

    , Article Applied Computational Electromagnetics Society Journal ; Volume 28, Issue 3 , 2013 , Pages 188-194 ; 10544887 (ISSN) Jafargholi, A ; Jafargholi, A ; Sharif University of Technology
    2013
    Abstract
    This paper introduces a new array architecture, in which antenna elements are arranged in a spiral curve. The spiral array enhances ultra-wideband (UWB) pattern characteristics compared to alternative array geometries of similar elements, without requiring a complex feed network for frequency change compensation. A number of examples are illustrated to demonstrate the array capability in broadband array designs. It is revealed that for the same number of elements and curvature lengths, a spiral array has a wider radiation bandwidth than the corresponding circular and linear array antennas. In addition, it is also demonstrated that the spiral architecture discussed here can be best suited for... 

    Compact broadband printed monopole antenna

    , Article Applied Computational Electromagnetics Society Journal ; Volume 28, Issue 4 , 2013 , Pages 321-326 ; 10544887 (ISSN) Jafargholi, A ; Jafargholi, A ; Sharif University of Technology
    2013
    Abstract
    A compact printed monopole antenna for broadband application is presented. The proposed antenna, having a total physical size of 21 × 6.5 mm consists of a patch fed by a coaxial line and an SMA connector as partial finite ground plane. The modified patch plane with a slot in its feed point helps to increase the impedance bandwidth of the proposed antenna. The optimal design may offer an ultra-wide impedance bandwidth from 2.56 GHz to 20 GHz. A prototype is fabricated and tested. The agreement between the simulated and measured results is quite good  

    Terahertz spectrum splitting by a graphene-covered array of rectangular grooves

    , Article Optics Letters ; Volume 42, Issue 23 , 2017 , Pages 4808-4811 ; 01469592 (ISSN) Tavakol, M. R ; Saba, A ; Jafargholi, A ; Khavasi, A ; Sharif University of Technology
    2017
    Abstract
    We propose a bidirectional terahertz (THz) spectrum splitter using a practically simple metamaterial structure consisting of rectangular grooves covered by graphene. Thanks to the graphene optoelectronic tunability and by adjusting the grooves width, this structure provides nearly 2π phase shift. At the same time, the reflection efficiency is acceptable throughout the phase shifts. We design each of the meta-atoms using a circuit model, and then we synthesize the final supercell based on the generalized Snell’s law so that the structure reflects different frequency waves to totally different directions. The full-wave simulations demonstrate the beam splitting with a remarkable efficiency of... 

    Wideband printed slot bowtie antenna using symmetric vias

    , Article Microwave and Optical Technology Letters ; Volume 58, Issue 6 , 2016 , Pages 1301-1304 ; 08952477 (ISSN) Mazaheri, M. H ; Amani, N ; Jafargholi, A ; Sharif University of Technology
    John Wiley and Sons Inc  2016
    Abstract
    This letter presents a symmetrical slot-type bowtie antenna with widened impedance bandwidth and high efficiency. Two symmetric vias are exploited underneath each slot in order to increase the antenna bandwidth up to 84% with simultaneous preservation of high efficiency (>90%), and low cross-polarization (<-10 dB). The proposed antenna is fed with 50Ω ungrounded coplanar waveguide (CPW) with no need to balun insertion and tuning stub. The proposed antenna has low profile and simple structure in comparison with previous complex wideband bowtie antennas. The commercial CST Microwave Studio software is adopted for the simulations. The antenna is fabricated and measured, while good agreement is... 

    Co channel interference cancellation by the use of iterative digital beam forming method

    , Article Progress in Electromagnetics Research ; Volume 87 , 2008 , Pages 89-103 ; 10704698 (ISSN) Emadi, M ; Sadeghi, K. H ; Jafargholi, A ; Marvasti, F ; Sharif University of Technology
    Electromagnetics Academy  2008
    Abstract
    This paper deals with the possibilities of cancellation of unwanted signals by steering nulls of the pattern in the direction of arrival of signal while keeping the main beam to the desired direction. New iterative adaptive digital beam forming technique is presented here to enhance the conventional effectiveness of beam forming in common commercial application. Simulation and measurement results confirm that this algorithm can achieve effective Co-Channel Interference (CCI) suppression, while increasing the strength of the desired signal  

    Using level restoring method for dual supply voltage

    , Article 2006 7th International Symposium on Antennas, Propagation and EM Theory, ISAPE 2006, Guilin, 26 October 2006 through 29 October 2006 ; 2006 , Pages 1170-1173 ; 1424401623 (ISBN); 9781424401628 (ISBN) Emadi, M ; Farbiz, F ; Sadeghi, K. H ; Jafargholi, A ; Sharif University of Technology
    2006
    Abstract
    A new level converter for use in dual voltage SOI digital circuits is presented. The technique which uses the idea of keeper transistors, consumes less power compared to the traditional methods. The effects of load capacitance on the circuit are studied by extensive simulations  

    Fast and accurate time delay estimation in noisy environments

    , Article 2nd Microwave and Radar Week in Poland - International Radar Symposium, IRS 2006, Krakow, 24 May 2006 through 26 May 2006 ; 2006 ; 8372076219 (ISBN); 9788372076212 (ISBN) Bayat, S ; Emadi, M ; Mousavi, M. R ; Jafargholi, A ; Sharif University of Technology
    2006
    Abstract
    The problem of time delay estimation (TDE) in the presence of zero mean white Gaussian noise is addressed. A novel and efficient algorithm for obtaining Conditional Maximum Likelihood (CML) estimates of delays, attenuation factors and the number of paths from a transmitter to a receiver is introduced. This approach is quite suitable for the cases in which time delay difference is less than the duration of signal autocorrelation  

    Design and Analysis of Graphene-based Terahertz Nanocircuits

    , M.Sc. Thesis Sharif University of Technology Jafargholi, Ali (Author) ; Borji, Amir (Supervisor)
    Abstract
    In the year 2004 when the first instance of graphen was built in laboratory, entice the attraction of many research groups. Because in spite of absence of graphen to that time, physicists given the unique properties for it. So it was the time to use that marvel properties which only theoretically available, to design and built one atom thick circuits. In this dissertation for the first time, we want by using method of moment and multilayer green functions in spectral domain, analyze graphene-based ribbon and stepped electrical conductivity distribution waveguides and calculate their characteristics such as propagation constant, surface currents and characteristics impedance with external... 

    Fast and high resolution statistical based algorithm for PCL radar detection in noisy environment

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 1259-1262 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Emadi, M ; Mousavi, M ; Granpayeh, A ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    This paper presents a new statistical based clean algorithm for multiple target detection in noisy environments. For this purpose the variance and average of the ambiguity function as the output of matched filter will be computed. This information used for separating the real targets from the false ones, in noisy environment and heavy clutter up to - 13 dB. © 2006 IEEE  

    Fast and high-resolution PCL radar detection in noisy environment

    , Article 2nd Microwave and Radar Week in Poland - International Radar Symposium, IRS 2006, Krakow, 24 May 2006 through 26 May 2006 ; 2006 ; 8372076219 (ISBN); 9788372076212 (ISBN) Bayat, S ; Emadi, M ; Mousavi, M. R ; Jafargholi, A ; Nayebi, M. M ; Sharif University of Technology
    2006
    Abstract
    Multiple target detection in conventional PCL (Passive Coherent Location) radar systems by means of Ambiguity Function Processing and without any powerful algorithm is impossible. Presented Gradual Clean Algorithm (GCA) is a new and simple method, which could provide the perfect detection in noisy environment and heavy clutter condition up to SNR=-15 dB and SCR=-100 dB (clutter is assumed as a distributed target with large RCS). Determining the number of real targets and keeping the false alarm probability approximately constant are the presented algorithm capabilities  

    Sensitivity analysis of configuration in bistatic radars

    , Article 2nd Microwave and Radar Week in Poland - International Radar Symposium, IRS 2006, Krakow, 24 May 2006 through 26 May 2006 ; 2006 ; 8372076219 (ISBN); 9788372076212 (ISBN) Bayat, S ; Emadi, M ; Mousavi, M. R ; Jafargholi, A ; Nayebi, M. M ; Sharif University of Technology
    2006
    Abstract
    There are inherent errors in target location and velocity measurement caused by bistatic geometry in addition to the errors that are caused in monostotic radars. In this paper, the accuracy of measurement with respect to some parameters like baseline variance and DOA estimation is considered and bistatic parameters sensitivity with respect together is formulated  

    Optimized FM PCL radar waveform

    , Article 2nd Microwave and Radar Week in Poland - International Radar Symposium, IRS 2006, Krakow, 24 May 2006 through 26 May 2006 ; 2006 ; 8372076219 (ISBN); 9788372076212 (ISBN) Bayat, S ; Emadi, M ; Mousavi, M. R ; Jafargholi, A ; Nayebi, M. M ; Sharif University of Technology
    2006
    Abstract
    To make a balance between time of detection and resolution of detection in radar, it must select an optimized time interval for integrations and signal bandwidth. In this paper, a new algorithm for finding best width of window and bandwidth of the FM signals for FM PCL radar is designed  

    High accurate multiple target detection in PCL radar systems

    , Article 2006 CIE International Conference on Radar, ICR 2006, Shanghai, 16 October 2006 through 19 October 2006 ; 2006 ; 0780395824 (ISBN); 9780780395824 (ISBN) Jafargholi, A ; Mousavi, M. R ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    A new approach in multiple target detection in PCL (Passive Coherent Location) radars based on TV and Radio ambiguity function processing is presented. Fast computation and high Accuracy are the presented algorithm capabilities. Presented algorithm is a new and simple method which could provide perfect detection in noisy environment up to SNR= -30 dB  

    Wide-band VHF nulling by five elements spiral array antenna

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 446-448 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Mousavi, M ; Emadi, M ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    Genetic algorithm for optimization of beam forming in spiral array antenna is used. The goal is to achieve a -20 dB in null over the wide frequency band. Our simulation shows -20 dB over 75 MHz Null Band width, in VHF band. © 2006 IEEE  

    VHF-LB SDR phased array jamming resistant antenna

    , Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 442-445 ; 0780395867 (ISBN); 9780780395862 (ISBN) Jafargholi, A ; Emadi, M ; Esmi, N ; Mousavi, M ; Nayebi, M. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2006
    Abstract
    Genetic algorithm for optimization of beam forming in linear array antenna is used. The goal is to achieve a -30 dB null depth in pattern, with null steering capability over the frequency band. The simulation result is -85 dB that the SuperNEC results accepted this result by -56 dB Null Depth. Software Define Radio (SDR) Technology and digital I/Q modulator are used to implement the system. © 2006 IEEE  

    Intelligent semi-active vibration control of eleven degrees of freedom suspension system using magnetorheological dampers

    , Article Journal of Mechanical Science and Technology ; Volume 26, Issue 2 , 2012 , Pages 323-334 ; 1738494X (ISSN) Zareh, S. H ; Sarrafan, A ; Khayyat, A. A. A ; Zabihollah, A ; Sharif University of Technology
    2012
    Abstract
    A novel intelligent semi-active control system for an eleven degrees of freedom passenger car's suspension system using magnetorheological (MR) damper with neuro-fuzzy (NF) control strategy to enhance desired suspension performance is proposed. In comparison with earlier studies, an improvement in problem modeling is made. The proposed method consists of two parts: a fuzzy control strategy to establish an efficient controller to improve ride comfort and road handling (RCH) and an inverse mapping model to estimate the force needed for a semi-active damper. The fuzzy logic rules are extracted based on Sugeno inference engine. The inverse mapping model is based on an artificial neural network... 

    Performance and exhaust emission characteristics of a spark ignition engine operated with gasoline and CNG blend

    , Article Proceedings of the Spring Technical Conference of the ASME Internal Combustion Engine Division ; 2012 , Pages 179-187 ; 15296598 (ISSN) ; 9780791844663 (ISBN) Dashti, M ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology
    2012
    Abstract
    Using CNG as an additive for gasoline is a proper choice due to higher octane number of CNG enriched gasoline with respect to that of gasoline. As a result, it is possible to use gasoline with lower octane number in the engine. This would also mean the increase of compression ratio in SI engines resulting in higher performance and lower gasoline consumption. Over the years, the use of simulation codes to model the thermodynamic cycle of an internal combustion engine have developed tools for more efficient engine designs and fuel combustion. In this study, a thermodynamic cycle simulation of a conventional four-stroke spark-ignition engine has been developed. The model is used to study the... 

    A comparative study of the performance of a SI engine fuelled by natural gas as alternative fuel by thermodynamic simulation

    , Article 2009 ASME Internal Combustion Engine Division Fall Technical Conference, ICEF 2009, Lucerne, 27 September 2009 through 30 September 2009 ; 2009 , Pages 49-57 ; 9780791843635 (ISBN) Dashti, M ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2009
    Abstract
    With the declining energy resources and increase of pollutant emissions, a great deal of efforts has been focused on the development of alternatives for fossil fuels. One of the promising alternative fuels to gasoline in the internal combustion engine is natural gas [1-5]. The application of natural gas in current internal combustion engines is realistic due to its many benefits. The higher thermal efficiency due to the higher octane value and lower exhaust emissions including CO2 as a result of the lower carbon to hydrogen ratio of the fuel are the two important feature of using CNG as an alternative fuel. It is well known that computer simulation codes are valuable economically as a cost... 

    Analytical and experimental analyses of nonlinear vibrations in a rotary inverted pendulum

    , Article Nonlinear Dynamics ; Volume 107, Issue 3 , 2022 , Pages 1887-1902 ; 0924090X (ISSN) Dolatabad, M.R ; Pasharavesh, A ; Khayyat, A. A. A ; Sharif University of Technology
    Springer Science and Business Media B.V  2022
    Abstract
    Gaining insight into possible vibratory responses of dynamical systems around their stable equilibria is an essential step, which must be taken before their design and application. The results of such a study can significantly help prevent instability in closed-loop stabilized systems by avoiding the excitation of the system in the neighborhood of its resonance. This paper investigates nonlinear oscillations of a rotary inverted pendulum (RIP) with a full-state feedback controller. Lagrange’s equations are employed to derive an accurate 2-DoF mathematical model, whose parameter values are extracted by both the measurement and 3D modeling of the real system components. Although the governing...