Search for: electronic-equipment
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    Iterative interference cancellation for a coded multicarrier frequency-hopping CDMA (MC-FH-CDMA) system

    , Article Scientia Iranica ; Volume 11, Issue 3 , 2004 , Pages 248-254 ; 10263098 (ISSN) M. Ebrahimi, T. M ; Nasiri Kenari, M ; Sharif University of Technology
    Sharif University of Technology  2004
    In this paper a low complexity iterative multi-user receiver for the coded MC-FH-CDMA system, is considered, which has been introduced in [1]. The structure of the proposed receiver consists of a Multi-User Likelihood Calculator (MULC) and a bank of SISO channel decoders, one for each active user. Based on the received signal and a priori information about code bits, provided by SISO decoders in the previous iteration, MULC computes the extrinsic information of the coded symbols of active users in the form of a Log-Likelihood Ratio (LLR). This information is used by channel decoders as a priori information to compute an update of LLRs. The processing proceeds in an iterative manner, similar... 

    The externality from communal metering of residential water: the case of Tehran

    , Article Water Resources and Economics ; Volume 23 , July , 2018 , Pages 53-58 ; 22124284 (ISSN) Vesal, M ; Rahmati, M. H ; Taheri Hosseinabadi, N ; Sharif University of Technology
    Elsevier B.V  2018
    Many countries use a single water meter for multiple units within a building. This creates a cost externality where the cost of water consumed is spread over all units. Using administrative data from Tehran Water and Wastewater Co. for 2013 and 2014, we find an increase in the number of units on a communal meter on average increases per unit use by 0.4%. Estimation at different levels of units reveals that almost all communal meters have higher per unit water use. The results suggest that removing this externality could save 2.7% water consumption in our sample. © 2018 Elsevier B.V  

    Application of the transmission line matrix method to the calculation of the shielding effectiveness for metallic enclosures

    , Article IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) ; Volume 3 , 2002 , Pages 302-305 ; 15223965 (ISSN) Attari, A. R ; Barkeshli, K ; Ndagijimana, F ; Dansou, J ; Sharif University of Technology
    An efficient method for the analysis fo the shielding effectiveness in high frequency communication circuits based on the Transmission Line Matrix (TLM) method is presented. Since the formulation is in the time domain, wide band effects are easily and accurately modeled. Through comparisons, results obtained from that proposed numerical method with those obtained from measurement show that the TLM method gives more accurate results than other methods reported  

    Pattern of Learning of Technological Capabilities in Knowledge Based Firms: Cases in Electronics Equipment Industry

    , M.Sc. Thesis Sharif University of Technology Zeinaloo, Mahdi (Author) ; Souzanchi Kashani, Ebrahim (Supervisor)
    Knowledge based companies have a very important role in progress toward an economy based on knowledge and technology. One of the most important issues about these companies is pattern of Learning Technological capabilities. This issue and the question about the focus of companies about acquire and development of technological capabilities are subjects that have instructive points for both minor and major scales, for companies themselves, and public directing and investing. In this paper pattern of learning of technological capabilities are reviewed for four Knowledge based companies in electronics equipment industry, also the time needed for acquiring levels of technological capabilities for... 

    Secure untraceable off-line electronic cash system

    , Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 637-646 ; 10263098 (ISSN) Baseri, Y ; Takhtaei, B ; Mohajeri, J ; Sharif University of Technology
    Eslami and Talebi (2011) [25] proposed an untraceable electronic cash scheme and claimed that their scheme protects the anonymity of customers, detects the identity of double spenders and provides the date attachability of coins to manage the bank database. In this paper, illustrating Eslami and Talebi's scheme, as one of the latest untraceable electronic cash schemes, and showing its weaknesses (in fulfilling the properties of perceptibility of double spender, unforgeability and date attainability of coins) and its faults (related to exchange protocol), we propose a new untraceable electronic cash scheme which is immune to the weaknesses of the former. Our scheme contains anonymity,... 

    Two-dimensional warranty cost analysis for second-hand products

    , Article Communications in Statistics - Theory and Methods ; Volume 40, Issue 4 , 2011 , Pages 684-701 ; 03610926 (ISSN) Shafiee, M ; Chukova, S ; Saidi-Mehrabad, M ; Niaki, S. T. A ; Sharif University of Technology
    In spite of the recent steady increase of the volume of the second-hand markets, often customers remain in doubt regarding the quality and durability of the secondhand products. Aiming to reduce and share this uncertainty, dealers offer warranty on their products. Offering warranty for second-hand products is a relatively new marketing strategy employed by dealers of used electronic equipment, furniture, automobiles, etc. Usually, for used products, the dealer's expected warranty cost is a function of product reliability, past age and usage, servicing strategy and conditions and terms of the warranty policy/contract. Sometimes the offered policy is limited by two parameters, typically the... 

    Privacy consideration for trustworthy vehicular ad hoc networks

    , Article ICEIE 2010 - 2010 International Conference on Electronics and Information Engineering, Proceedings, 1 August 2010 through 3 August 2010 ; Volume 1 , 2010 , Pages V1437-V1442 ; 9781424476800 (ISBN) Khomejani, S ; Movaghar, A ; (IACSIT) ; Sharif University of Technology
    For increasing safety of driving, intelligent vehicles in vehicular ad hoc networks (VANETs) communicate with each other by sending announcements. The existence of a system that guarantees the trustworthiness of these announcements seems necessary. The proposed approach generating announcements should be preserved from internal and external attackers that attempt to send fake messages. In this paper, we use a group-based endorsement mechanism based on threshold signatures against internal attackers. We choose NTRUSign as a public key cryptosystem for decreasing signature generation and verification times. This approach optimizes the network overhead and consequently its performance. In this... 

    A fractional order model for steer-by-wire systems

    , Article IECON Proceedings (Industrial Electronics Conference) ; 2009 , Pages 4161-4166 Tahami, F ; Afshang, H ; Sharif University of Technology
    The steer by wire system for vehicles has attracted much attention in recent years. Steer by wire systems provide many benefits in terms of functionality and at the same time present significant challenges too. It is essential to investigate the stability of steer by wire systems using a more sophisticated model rather than common approximated models. Fractional order modeling offers a good modeling framework for complex dynamical systems involving flexible structures such as multi-mass drives. In this paper a nonlinear fractional order model for steer by wire systems is presented  

    Applicability of the FSEM for analyzing wire flat rolling process

    , Article Engineering Computations (Swansea, Wales) ; Volume 23, Issue 5 , 2006 , Pages 515-524 ; 02644401 (ISSN) Kazeminezhad, M ; Taheri, A. K ; Sharif University of Technology
    Purpose - The purpose of this paper is to present an assessment of the ability of combined finite and slab element method (FSEM) for analyzing the wire flat rolling process. Design/methodology/approach - Using the FSEM, the effective strain field of flat rolled wire is predicted for different reductions in height and frictional conditions. The validity of the method is assessed by performing the Vickers microhardness measurements on the flattened wire cross section. Also, the creation of macroscopic shear bands in cross section of the flat rolled wire is investigated and confirmed by microhardness and metallographic examinations. Moreover, the lateral spread and width of contact area are... 

    Pumping effect of bubble growth and collapse in microchannels: Thermo-hydraulic modeling

    , Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 431-436 ; 10263098 (ISSN) Sajadi, B ; Saidi, M. H ; Sharif University of Technology
    In the past two decades, microfluidic systems have become more appealing due to their wide applications in many areas, such as electronics, biotechnology, medicine, etc. Recently, the advantages of using the bubble growth phenomenon as a robust actuator in microfluidic devices have directed research interests towards the investigation of various applications. In this research, a new transient thermo-hydraulic model has been developed for bubble growth in confined volumes. The present model has been used to describe the pumping effect produced by the bubble growth and collapse phenomenon in microchannels. The results show relatively good agreement with experimental data. This study is useful... 

    An improved sales forecasting approach by the integration of genetic fuzzy systems and data clustering: Case study of printed circuit board

    , Article Expert Systems with Applications ; Volume 38, Issue 8 , August , 2011 , Pages 9392-9399 ; 09574174 (ISSN) Hadavandi, E ; Shavandi, H ; Ghanbari, A ; Sharif University of Technology
    Success in forecasting and analyzing sales for given goods or services can mean the difference between profit and loss for an accounting period and, ultimately, the success or failure of the business itself. Therefore, reliable prediction of sales becomes a very important task. This article presents a novel sales forecasting approach by the integration of genetic fuzzy systems (GFS) and data clustering to construct a sales forecasting expert system. At first, all records of data are categorized into k clusters by using the K-means model. Then, all clusters will be fed into independent GFS models with the ability of rule base extraction and data base tuning. In order to evaluate our K-means... 

    Fuzzy trajectory tracking control of an autonomous air vehicle

    , Article ICMEE 2010 - 2010 2nd International Conference on Mechanical and Electronics Engineering, Proceedings, 1 August 2010 through 3 August 2010 ; Volume 2 , August , 2010 , Pages V2347-V2352 ; 9781424474806 (ISBN) Soleymani, T ; Saghafi, F ; Sharif University of Technology
    The development and the implementation of a new guidance law are addressed for a six dimensional trajectory tracking problem, three dimensions for position tracking and three dimensions for velocity tracking, of a micro air vehicle. To generate the desired trajectory a virtual leader is defined which is moved in space. In the guidance law, position and velocity feedbacks are used by fuzzy controllers to generate two acceleration commands. Then, a fuzzy coordinator is applied to coordinate the acceleration commands. Nonlinear six-degree-of-freedom equations of motion are used to model the vehicle dynamics. Also, a bank-to-turn acceleration autopilot for vehicle is considered to follow the... 

    Neural networks control of autonomous underwater vehicle

    , Article ICMEE 2010 - 2010 2nd International Conference on Mechanical and Electronics Engineering, Proceedings, 1 August 2010 through 3 August 2010 ; Volume 2 , August , 2010 , Pages V2117-V2121 ; 9781424474806 (ISBN) Amin, R ; Khayyat, A. A ; Ghaemi Osgouie, K ; Sharif University of Technology
    This paper describes a neural network controller for autonomous underwater vehicles (AUVs). The designed online multilayer perceptron neural network (OMLPNN) calculates forces and moments in earth fixed frame to eliminate the tracking errors of AUVs whose dynamics are highly nonlinear and time varying. Another OMLPNN has been designed to generate an inverse model of AUV, which determine the appropriate propeller's speed and control surfaces' angles receiving the forces and moments in the body fixed frame. The designed approximation based neural network controller with the use of the backpropagation learning algorithm has advantages and robustness to control the highly nonlinear dynamics of... 

    Characteristic ratio assignment in fractional order systems

    , Article ISA Transactions ; Volume 49, Issue 4 , October , 2010 , Pages 470-478 ; 00190578 (ISSN) Tabatabaei, M ; Haeri, M ; Sharif University of Technology
    In this paper the characteristic ratios and generalized time constant are defined for all-pole commensurate fractional order systems. The sufficient condition for stability of these systems in terms of their characteristic ratios is obtained. Also an analytical approach for characteristic ratio assignment (CRA) to have a non-overshooting fast closed loop step response is introduced. The proposed CRA method is then employed to design a fractional order controller. Computer simulation results are presented to illustrate the performance of the CRA based designed fractional order controllers  

    Stable semi-analytical method for analysis of plasmonic propagation on periodically patterned metal plates

    , Article Proceedings of SPIE - The International Society for Optical Engineering, 26 January 2010 through 28 January 2010 ; January , 2010 ; 0277786X (ISSN) ; 9780819480057 (ISBN) Yasrebi, N ; Khorasani, S ; Karami Taheri, H ; Rashidian, B ; Hosseini, A ; Sharif University of Technology
    The need for antennas with improved characteristics for communication and radar applications has resulted in an ever-increasing demand for research in the field of high impedance surfaces, which can work as an artificial magnetic conductor. One method in fabrication of these surfaces is formation of a metamaterial by patterning a metallic surface in the shape of space filling curves (e.g. Hilbert or Peanu Curves). In this paper, we present a novel semi-analytical solution to the problem of plasmonic propagation on these surfaces. The method is based on a previously presented Green's function formalism, which has been reported in an earlier paper of ours. We have modified and improved the... 

    Throughput modeling of distributed reservation protocol

    , Article IEEE Transactions on Mobile Computing ; Volume 15, Issue 2 , 2016 , Pages 503-515 ; 15361233 (ISSN) Ajorloo, H ; Manzuri Shalmani, M. T ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    To evaluate the performance of distributed mediumaccess control (MAC) layer of emerging ultra wideband (UWB) and 60-GHz millimeter wave (mmWave) wireless personal area networks (WPANs) based on distributed reservation protocol (DRP) of ECMA-368 and ECMA-387 standards, we provide an analytical model for the probability distribution of steady state throughput as a function of the network dimensions size, number of devices, antenna beamwidth, transmission range, bit error rate (BER), antenna disturbance rate (ADR), aggregation length, payload size, and incoming frame rate. Using this model, the optimal payload size is computed as an example of optimization problem.We also propose a formula for... 

    The size-dependent electromechanical instability of double-sided and paddle-type actuators in centrifugal and Casimir force fields

    , Article Scientia Iranica ; Volume 24, Issue 3 , 2017 , Pages 1077-1090 ; 10263098 (ISSN) Mokhtari, J ; Farahani, M ; Kanani, A ; Rach, R ; Keivani, M ; Abadyan, M ; Sharif University of Technology
    Sharif University of Technology  2017
    The present research is devoted to theoretical study of the pull-in performance of double-sided and paddle-type NEMS actuators fabricated from cylindrical nanowire operating in the Casimir regime and in the presence of the centrifugal force. D'Alembert's principle was used to transform the angular velocity into an equivalent static, centrifugal force. Using the couple stress theory, the constitutive equations of the actuators were derived. The equivalent boundary condition technique was applied to obtain the governing equation of the paddle-type actuator. Three distinct approaches, the Duan-Adomian Method (DAM), Finite Difference Method (FDM), and Lumped Parameter Model (LPM), were applied... 

    Content evaluation of different waste PCBs to enhance basic metals recycling

    , Article Resources, Conservation and Recycling ; Volume 139 , 2018 , Pages 298-306 ; 09213449 (ISSN) Arshadi, M ; Yaghmaei, S ; Mousavi, S. M ; Sharif University of Technology
    Elsevier B.V  2018
    This research aims to expand the body of information that researchers require before starting electronic waste (E-waste) recovery experiments. With this purpose, the basic metal contents, alkalinity, polymer components, iron magnetic separation, metal recovery priority and economic values of different types of waste printed circuit boards (PCBs) were investigated. The selected wastes were computer PCBs (CPCBs), CPCBs with wires, mobile phone PCBs (MPPCBs), television PCBs (TVPCBs), fax machine PCBs (FPCBs), copy machine PCBs (COPCBs) and central processing units (CPUs). These E-wastes were prepared in the three fraction sizes of F1<1 mm, 1 < F2<3 mm, and 3 < F3<8 mm to evaluate the metal... 

    Fast detection of open-switch fault in cascaded H-bridge multilevel converter

    , Article Scientia Iranica ; Volume 25, Issue 3D , 2018 , Pages 1561-1570 ; 10263098 (ISSN) Shahbazi, M ; Zolghadri, M. R ; Khodabandeh, M ; Ouni, S ; Sharif University of Technology
    Sharif University of Technology  2018
    Cascaded H-bridge converter has been utilized recently in different high-power applications due to its modular and simple structure. In order to have a balanced operation after a fault occurrence in this converter, it is necessary to detect the switch fault and its location. In this paper, a fast power-switch fault detection method is presented to identify a fault and its location. Only one voltage measurement per phase is required by this method, and the fault detection is faster compared to the existing methods. Moreover, it is suitable for implementation on an FPGA device due to the use of simple math, relational, and state machine blocks. The proposed method is verified by computer... 

    A linear programming optimization model for optimal operation strategy design and sizing of the CCHP systems

    , Article Energy Efficiency ; Volume 11, Issue 1 , 2018 , Pages 225-238 ; 1570646X (ISSN) Kialashaki, Y ; Sharif University of Technology
    Springer Netherlands  2018
    Combined cooling, heat, and power (CCHP) system offers numerous potential advantages for the supply of energy to residential buildings in the sense of improved energy efficiency and reduced environmental burdens. To realize the potential for being more beneficial, however, such systems must reduce total costs relative to conventional systems. In this study, a linear programming optimization model was presented for optimum planning and sizing of CCHP systems. The purpose of the model is to give the design of the CCHP system by considering electrical chiller and absorption chiller simultaneously in economic viewpoint. A numerical study was conducted in Tehran to evaluate the CCHP system model....