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    Errorless codes for CDMA systems with near-far effect

    , Article IEEE International Conference on Communications, 23 May 2010 through 27 May 2010, Cape Town ; 2010 ; 05361486 (ISSN) ; 9781424464043 (ISBN) Shafinia, M. H ; Kabir, P ; Pad, P ; Mansouri, S. M ; Marvasti, F ; Sharif University of Technology
    In this paper we propose a new model for the near-far effect in a CDMA system. We derive upper and lower bounds for the maximum near-far effect for errorless transmission. Using these bounds, we propose some near-far resistant codes. Also a very low complexity ML decoder for a subclass of the proposed codes is suggested  

    Implementation of Outdoor Sound Source Localization System Using Sound Sensor Arrays

    , M.Sc. Thesis Sharif University of Technology Fathi, Ehsan (Author) ; Gholampour, Eman (Supervisor) ; Sharif Khani, Mohammad (Supervisor)
    Sound source localization has been one of the fundamental problems in many areas, including radar, teleconferencing or videoconferencing, localization of earthquake epicenters and underground explosions, microphone arrays, robots, etc. All of sound source localization ideas are like human auditory system. The human auditory system is a complex and organic information processing system. It can feel the intensity and spatial orientation and other information of sound. The distance of the two ears on our head is about 20cm. When the sound reaches each ear, there are small time difference, intensity difference and phase difference. After analyzing these differences by the brain, the human can... 

    Near-Far Effects in CDMA Systems

    , M.Sc. Thesis Sharif University of Technology Shafinia, Mohammad Hossein (Author) ; Marvasti, Farokh (Supervisor)
    On one hand Code Devision Multiple Access (CDMA) as an efficient spread spectrum multiple access solution was under consideration in recent years. On the other hand one of the main challenges in cellular networks was near-far effect and fading effect which cause different received powers from different users.
    In this thesis we are going to investigate near-far effects in overloaded CDMA systems from different aspects. Firstly we will investigate on the robust systems over near-far effect, propose near-far resistance codes and a very low complexity ML decoder for a subclass of these codes. Secondly we deal evaluation of the sum capacity of finite dimensional CDMA systems. These systems... 

    Capacity bounds of finite dimensional CDMA systems with power allocation, fading, and near-far effects

    , Article IEEE Communications Letters ; Volume 17, Issue 1 , 2013 , Pages 15-18 ; 10897798 (ISSN) Kabir, P ; Shafinia, M. H ; Marvasti, F ; Sharif University of Technology
    This paper deals with fading and/or near-far effects with or without power control on the evaluation of the sum capacity of finite dimensional Code Division Multiple Access (CDMA) systems. CDMA systems under consideration have binary or finite non-binary inputs and signature matrices. Important results of this paper are that the knowledge of the received power variations due to input power differences, fading and/or near-far effects can significantly improve the sum capacity  

    Thermo acoustic study of carbon nanotubes in near and far field: Theory, simulation, and experiment

    , Article Journal of Applied Physics ; Volume 117, Issue 9 , 2015 ; 00218979 (ISSN) Asadzadeh, S. S ; Moosavi, A ; Huynh, C ; Saleki, O ; Sharif University of Technology
    American Institute of Physics Inc  2015
    Carbon nanotube webs exhibit interesting properties when used as thermo-acoustic projectors. This work studies thermo-acoustic effect of these sound sources both in near and far field regions. Based on two alternative forms of the energy equation, we have developed a straightforward formula for calculation of pressure field, which is consistent with experimental data in far field. Also we have solved full 3-D governing equations using numerical methods. Our three-dimensional simulation and experimental data show pressure waves are highly affected by dimensions of sound sources in near field due to interference effects. However, generation of sound waves in far field is independent of... 

    Beam focusing using two-dimensional graphene-based meta-reflect-array

    , Article 24th Iranian Conference on Electrical Engineering, ICEE 2016, 10 May 2016 through 12 May 2016 ; 2016 , Pages 613-616 ; 9781467387897 (ISBN) Zangeneh Nejad, F ; Abdollahramezani, S ; Arik, K ; Khavasi, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    A highly efficient two-dimensional meta-reflect-array manipulating the phase and amplitude of far-infrared electromagnetic wave is proposed. The reflect array consists of patterned graphene nano-disks resides on a subwavelenght thick optical cavity to enhance the interaction of electromagnetic wave. It is shown that the reflected wave from each unit cell can almost cover the 2π range phase shift by changing the radius of the graphene nano-disks while at the same time maximizes its amplitude. Proposing a transmission line model for the proposed structure, we realize a meta lens as a flat optics functionality. © 2016 IEEE  

    Ranking locations for hydrogen production using hybrid wind-solar: a case study

    , Article Sustainability (Switzerland) ; Volume 13, Issue 8 , 2021 ; 20711050 (ISSN) Almutairi, K ; Mostafaeipour, A ; Jahanshahi, E ; Jooyandeh, E ; Himri, Y ; Jahangiri, M ; Issakhov, A ; Chowdhury, S ; Hosseini Dehshiri, J ; Hosseini Dehshiri, S ; Techato, K ; Sharif University of Technology
    MDPI  2021
    Observing the growing energy demand of modern societies, many countries have rec-ognized energy security as a looming problem and renewable energies as a solution to this issue. Renewable hydrogen production is an excellent method for the storage and transfer of energy generated by intermittent renewable sources such as wind and solar so that they can be used at a place and time of our choosing. In this study, the suitability of 15 cities in Fars province, Iran, for renewable hydrogen production was investigated and compared by the use of multiple multi-criteria decision-making methods including ARAS, SAW, CODAS, and TOPSIS. The obtained rankings were aggregated by rank averaging, Borda... 

    An improved actuator disc model for the numerical prediction of the far-wake region of a horizontal axis wind turbine and its performance

    , Article Energy Conversion and Management ; Volume 185 , 2019 , Pages 482-495 ; 01968904 (ISSN) Behrouzifar, A ; Darbandi, M ; Sharif University of Technology
    Elsevier Ltd  2019
    Actuator disc models are frequently used to provide a semi-analytical approach to estimating aerodynamic loads on rotary blades. The basic idea is to distribute the aerodynamic loads on a virtual rotating disc instead of simulating the actual rotating blade. These loads are then imposed to represent the source terms of the Navier-Stokes equations, which can be solved numerically using the computational fluid dynamic methods. The thickness of the actuator disk grid is one important factor considerably affecting calculations of the wind turbine rotor. Past researches generally considered the idea of fixed grid thickness exerting along the blade in their actuator disk modeling. However, this... 

    Fabrication of Plasmonic Structures and Investigation of the Effect of Surface Plasmon Resonance on Dye Sensitized Solar Cell

    , Ph.D. Dissertation Sharif University of Technology Sharifi, Nafiseh (Author) ; Irajizad, Azam (Supervisor)
    Dye-sensitized solar cells (DSCs) are third generation of solar cells, which composed of a porous layer of wide band gap semiconductor such as TiO2, covered with a molecular dye that absorbs sunlight, and a counter electrode contacted by a liquid redox electrolyte. Photovoltaic performance is the collective measure of light harvesting, charge separation and charge collection efficiencies. Light harvesting has a significant role in improvement of photovoltaic performance. Molecular engineering of dyes to improve absorption spectrum or to have a broad absorption spectrum,andlight scattering layes are approaches for this porpuse. This research is focused on photon management in DSCs using... 

    Studying higher mode effects on the performance of nonlinear static analysis methods considering near-fault effects

    , Article KSCE Journal of Civil Engineering ; Volume 17, Issue 2 , March , 2013 , Pages 426-437 ; 12267988 (ISSN) Ghahari, S. F ; Moradnejad, H. R ; Rouhanimanesh, M. S ; Sarvghad Moghadam, A ; Sharif University of Technology
    Daily development in civil engineering arena and the importance of economical aspects in the design of structures have motivated the engineers to shift their approaches from designing upon strength to designing upon performance. This is of more importance regarding the forces induced by earthquakes which have unpredicted and random nature. However, it is not possible to design or assess exactly the structural performance against strong ground motion using analytical methods which are applied for static loads and therefore precise dynamic analysis methods are needed. Despite significant progress in the analytical methods and engineering software, using nonlinear time history analysis is very... 

    A unimodal person authentication system based on signing sound

    , Article Proceedings - IEEE-EMBS International Conference on Biomedical and Health Informatics: Global Grand Challenge of Health Informatics, BHI 2012 ; 2012 , Pages 152-154 ; 9781457721779 (ISBN) Khazaei, D ; Maghooli, K ; Afdideh, F ; Azimi, H ; Sharif University of Technology
    IEEE  2012
    Person authentication based on only the name, password or person identification number is not secured enough. In recent years researchers have focused on human physiological and behavioral parameters, because these parameters are more unique and human-specific than traditional ones. This approach of person authentication is usually called biometric authentication. Signature is the most commonly used behavioral biometric which is investigated in two ways of online and offline by researchers. In online procedure, the temporal indices of signature such as signing velocity, and acceleration are involved to increase the accuracy relative to offline methods and to recognize counterfeit signatures.... 

    Comprehensive three-dimensional split-field finitedifference time-domain method for analysis of periodic plasmonic nanostructures: Near- and far-field formulation

    , Article Journal of the Optical Society of America B: Optical Physics ; Volume 28, Issue 11 , 2011 , Pages 2690-2700 ; 07403224 (ISSN) Shahmansouri, A ; Rashidian, B ; Sharif University of Technology
    Optical Society of American (OSA)  2011
    The three-dimensional split-field finite-difference time-domain (SF-FDTD) method is combined with the totalfield- scattered-field method for injecting a plane wave. A formulation is derived for calculating the incidence transformed fields of SF-FDTD on a one-dimensional auxiliary grid. The resulting fields obtained in the scattered zone are used to calculate the far fields, based on a proposed fully time-domain near-to-far-field transformation. The far-field information is used to calculate the extinction cross section of the periodic structure under oblique incidence. To analyze metallic periodic structures, a formulation with a reduced number of variables is proposed based on the auxiliary... 

    Axisymmetric problem of energetically consistent interacting annular and penny-shaped cracks in piezoelectric materials

    , Article Journal of Applied Mechanics, Transactions ASME ; Volume 78, Issue 2 , 2011 ; 00218936 (ISSN) Shodja, H. M ; Moeini Ardakani, S. S ; Eskandari, M ; Sharif University of Technology
    The axisymmetric problem of a concentric set of energetically consistent annular and penny-shaped cracks in an infinite piezoelectric body subjected to uniform far-field electromechanical loading is addressed. With the aid of a robust innovated technique, the pertinent four-part mixed boundary value problem (MBVP) is reduced to a decoupled Fredholm integral equation of the second kind. The results of two limiting cases of a single penny-shaped crack and a single annular crack are recovered. The contour plots of dimensionless intensity factors (IFs) at each crack front provide the stress and electric displacement intensity factors (SIFs and EDIFs, respectively) for all combination of crack... 

    Electroelastic fields in interacting piezoelectric inhomogeneities by the electromechanical equivalent inclusion method

    , Article Smart Materials and Structures ; Volume 19, Issue 3 , 2010 ; 09641726 (ISSN) Shodja, H. M ; Kargarnovin, M. H ; Hashemi, R ; Sharif University of Technology
    Consider two piezoelectric ellipsoidal inhomogeneities of arbitrary size, orientation and material constants, which in turn are surrounded by an infinite isotropic medium. The system under consideration is subjected to far-field non-uniform electromechanical loadings. Based on the extension of the electromechanical equivalent inclusion method (EMEIM), the present paper develops a unified solution for determination of the associated electroelastic fields in the vicinity of interacting inhomogeneities. Accordingly, each of the piezoelectric inhomogeneities is broken down into two equivalent inclusions with proper polynomial eigenstrains and eigenelectric fields. The robustness and efficacy of... 

    Effective medium theory for graphene-covered metallic gratings

    , Article Journal of Optics (United Kingdom) ; Volume 18, Issue 10 , 2016 ; 20408978 (ISSN) Rahmani, B ; Bagheri, A ; Khavasi, A ; Mehrany, K ; Sharif University of Technology
    Institute of Physics Publishing 
    We propose an effective medium theory for a one-dimensional periodic array of rectangular grooves covered by a graphene sheet. Parameters of the effective medium model are given by explicit analytical expressions for both major polarizations TM and TE, and for all incident angles. In extraction of this model, we assumed single mode approximation inside the grooves. The effect of non-specular diffraction orders outside the grating, as well as the plasmonic response of the graphene sheet in the far-infrared spectrum, is addressed by introducing an effective surface conductivity at the interface of the metallic grating and the ambient environment. It is shown that surface plasmons in graphene... 

    Mode choice and number of non-work stops during the commute: application of a copula-based joint model

    , Article Scientia Iranica ; Volume 25, Issue 3A , 2018 , Pages 1039-1047 ; 10263098 (ISSN) Rasaizadi, A ; Kermanshah, M ; Sharif University of Technology
    Sharif University of Technology  2018
    Commute mode choice and number of non-work stops during the commute are joint decisions interacting with each other. If an individual chooses a vehicle for the commute, regarding vehicle's restrictions, there could be some stops. On the other hand, if an individual needs to have some stops, a vehicle can be selected for the commute regarding the number of stops. In this study, to consider the interaction between these decisions, we employed a copula-based joint modeling framework. The data used in this study are drawn from origin-destination travels data of Shiraz-Iran conducted in 1997. The commuting mode choice modeling is undertaken using a multinomial logit model, and the number of... 

    A lamellar inhomogeneity near a multiphase reinforcement

    , Article Acta Mechanica ; Volume 206, Issue 1-2 , 2009 , Pages 39-52 ; 00015970 (ISSN) Ojaghnezhad, F ; Shodja, H. M ; Sharif University of Technology
    In composites, the stress intensity factors (SIFs) of a lamellar inhomogeneity near a multiphase reinforcement are of interest. Based on extension of Eshelby's equivalent inclusion method, a unified approach is presented to study the effect of a multiphase inhomogeneity on the SIF at the tip points of two- and threedimensional lamellar inhomogeneities under nonuniform far-field loadings. Alteration of the SIF due to the presence of a coating layer around the inhomogeneity is addressed. Furthermore, the effect of geometry and stiffness of each phase of a multiphase reinforcement on the mixed mode SIFs of a lamellar inhomogeneity is investigated. In contrast to cracks whose SIFs are the same... 

    Analysis of power control for indoor wireless infrared CDMA communication

    , Article 25th IEEE International Performance, Computing, and Communications Conference, 2006, IPCCC 2006, Phoenix, AZ, 10 April 2006 through 12 April 2006 ; Volume 2006 , 2006 , Pages 297-302 ; 1424401976 (ISBN); 9781424401970 (ISBN) Aminzadeh Gohari, A ; Pakravan, M. R ; Sharif University of Technology
    we study the uplink performance of wireless infrared code-division multiple access (CDMA) networks using OOK with optical orthogonal codes (OOC's). The analysis is performed in two cases assuming a cellular network architecture, in which all users are uniformly distributed in the cell's area. The first case is when all users transmit with the same power and no power control mechanism is used. Then, the system that deploys power control mechanism is analyzed and the performance improvements are demonstrated. The impact of imperfect power control which is caused by errors in channel estimation is also analyzed and the analytical and numerical results for all cases are included. The results... 

    A joint model of destination and mode choice for urban trips: A disaggregate approach

    , Article Transportation Planning and Technology ; Volume 36, Issue 8 , Jul , 2013 , Pages 703-721 ; 03081060 (ISSN) Seyedabrishami, S ; Shafahi, Y ; Sharif University of Technology
    Trip destination and mode choice are highly influenced by travelers' perceptions and behaviors; selecting a destination and a vehicle for a trip are two interdependent problems. This paper presents and applies a disaggregate joint model for traveler destination and mode choice. The choice model uses fuzzy set and probability theory to deal with the uncertainty embedded in travelers' perceptions and behaviors. The model is structured as a decision tree in which the fuzzy and non-fuzzy classification of influential variables regarding destination selection and mode choice expand the tree. The most influential explanatory variables among all the variables categorized for travelers' household,... 

    Interaction of two nearby CNTs/nanovoids embedded in a metal matrix using modified nonlocal elasticity

    , Article Composites Part B: Engineering ; Volume 43, Issue 8 , December , 2012 , Pages 3167-3181 ; 13598368 (ISSN) Niaki, S. A ; Naghdabadi, R ; Sharif University of Technology
    Interaction of Carbon Nanotubes (CNTs) and nanovoids embedded in a metal matrix is studied comparatively. For this purpose, two nearby CNTs/nanovoids are modeled as two similar cylindrical inclusions/holes in an infinite matrix. The nonlocal stresses around the CNTs/nanovoids are obtained by applying the integral constitutive equation of the nonlocal elasticity to the stresses from the complex stress potential method. Also, in order to bring different nonlocality effects of dissimilar media into account, the influence function of the nonlocal elasticity is modified. Effects of the CNTs/nanovoids size and distance as well as far-field loading ratio on the stress state in the matrix are...