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    Web graph compression by edge elimination

    , Article Data Compression Conference, DCC 2006, Snowbird, UT, 28 March 2006 through 30 March 2006 ; 2006 , Pages 459- ; 10680314 (ISSN) Mahdian, A ; Khalili, H ; Nourbakhsh, E ; Ghodsi, M ; Brandeis University ; Sharif University of Technology
    2006

    Storage-aware value prediction

    , Article Proceedings - 13th Euromicro Conference on Digital System Design: Architectures, Methods and Tools, DSD 2010, 1 September 2010 through 3 September 2010, Lille ; 2010 , Pages 722-728 ; 9780769541716 (ISBN) Salehi, M ; Baniasadi, A ; Sharif University of Technology
    2010
    Abstract
    Despite the huge potential, value predictors have not been used in modern processors. This is partially due to the complex structures associated with such predictors. In this paper we study value predictors and investigate solutions to reduce storage requirements while imposing negligible coverage cost. Our solutions build on the observation that conventional value predictors do not utilize storage efficiently as they allocate too much space for small and frequently appearing values. We measure data width requirement and entropy in a subset of predictor resources and show that values stored in predictors show limited sizes and very small entropy. We exploit this behavior and suggest... 

    Simulation and estimation of normal dispersion phenomenon in an acentric organic crystal (NPP) by the quantum photonic approach

    , Article Modelling and Simulation in Materials Science and Engineering ; Volume 15, Issue 8 , 2007 , Pages 869-878 ; 09650393 (ISSN) Kaatuzian, H ; Zarch, A. W ; Oskouei, A. A ; Amjadi, A ; Sharif University of Technology
    2007
    Abstract
    In this paper, we present a nano-quantum photonic approach for the calculation of normal dispersion phenomena in organic crystals such as N-(4-nitrophenyl)-L-prolinol(NPP). We assume that a laser beam consists of a flow of energetic particles that interact with the distorted π-electron system. We approximate the distorted π-electron cloud by an ellipse to simplify calculations. By the precise analysis of photon interaction with the π-electron system of benzene ring in the NPP crystal, we obtain the refractive index in any wavelength by Monte Carlo simulation. The maximum error between our simulation results and the measurement data is 0.058, which is agreeable. © 2007 IOP Publishing Ltd  

    Data mining on partial discharge signals of power transformer's defect models

    , Article 2010 45th International Universities' Power Engineering Conference, UPEC 2010, Cardiff, 31 August 2010 through 3 September 2010 ; 2010 ; 9780956557025 (ISBN) Darabad, V. P ; Vakilian, M ; Sharif University of Technology
    2010
    Abstract
    Partial discharge (PD) is a common phenomenon which occurs in insulation of high voltage equipments, such as; transformers and has a damaging effect on the insulation. If data mining techniques be used to find specifications and features of different types of partial discharges in power transformers, one can monitor the insulation condition of such equipment online and continuously. Those results can be employed to develop preventive measures more exactly and consequently the maintenance would require less time and cost for electric utility and improve the life time expectancy of the transformers. In this paper experiments are set up to create models for some types of PD that occurs in Power... 

    Privacy Against Brute-Force Inference Attacks

    , Article 2019 IEEE International Symposium on Information Theory, ISIT 2019, 7 July 2019 through 12 July 2019 ; Volume 2019-July , 2019 , Pages 637-641 ; 21578095 (ISSN) ; 9781538692912 (ISBN) Osia, S. A ; Rassouli, B ; Haddadi, H ; Rabiee, H. R ; Gunduz, D ; The Institute of Electrical and Electronics Engineers, Information Theory Society ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    Privacy-preserving data release is about disclosing information about useful data while retaining the privacy of sensitive data. Assuming that the sensitive data is threatened by a brute-force adversary, we define Guessing Leakage as a measure of privacy, based on the concept of guessing. After investigating the properties of this measure, we derive the optimal utility-privacy trade-off via a linear program with any f-information adopted as the utility measure, and show that the optimal utility is a concave and piece-wise linear function of the privacy-leakage budget  

    Seismic microzonation of shiraz city, southwest of iran

    , Article Geotechnical Earthquake Engineering and Soil Dynamics IV Congress 2008 - Geotechnical Earthquake Engineering and Soil Dynamics, Sacramento, CA, 18 May 2008 through 22 May 2008 ; Issue 181 , 2008 ; 08950563 (ISSN); 9780784409756 (ISBN) Ghalandarzadeh, A ; Sahraeian, S ; Kavand, A ; Kamrani Moghaddam, B ; Sharif University of Technology
    2008
    Abstract
    This paper aims to study the soil dynamics characteristics of central part of Shiraz city near the monument of Persepolis, southwest of Iran. The parameter investigated is natural period of soil sediment. The technique used to obtain this parameter is microtremor measurements. Microtremor measurements were obtained at 120 stations in the city. The data was recorded for two periods of fifteen minutes. Segmental Cross Spectra were applied to calculate spectra. Nakamura's method (H/V) was used for analyzing the measured data. At each site, natural period values were obtained. Because of low accuracy of amplification factors that achieved by microtremor measurements, this factor is neglected in... 

    A new empirical correlation for predicting effective molecular diffusivity of gas-heavy oil-porous media systems

    , Article Special Topics and Reviews in Porous Media ; Volume 3, Issue 1 , 2012 , Pages 23-33 ; 21514798 (ISSN) Zamanian, E ; Mirjordavi, N ; Kazemeini, M ; Ghazanfari, M. H ; Sharif University of Technology
    2012
    Abstract
    Molecular diffusivity is an essential parameter for modeling of mass transfer in enhanced oil recovery processes. However, experimentally determined diffusivities for light gas-heavy oil systems in the presence of porous media are relatively rare. A few correlations are available in the literature that predict diffusivity of gases into heavy oil in presence of porous media. In this work the pressure-decay method was applied to obtain effective molecular diffusion of CO 2, CH 4 and N 2-heavy oil systems in both bulk and porous media systems at different temperatures. The diffusivity of gases in heavy oil was determined by matching the numerically calculated pressures to the measured data. A... 

    Optimization assisted asphaltene deposition modeling in porous media during a natural depletion scheme

    , Article Petroleum Science and Technology ; Volume 30, Issue 9 , Mar , 2012 , Pages 958-965 ; 10916466 (ISSN) Hematfar, V ; Bagheri, M ; Kharrat, R ; Ghazanfari, M ; Ghotbi, C ; Sharif University of Technology
    2012
    Abstract
    Changes in thermodynamic properties such as pressure, temperature, and composition may result in asphaltene precipitation and deposition in porous media. In addition, asphaltene deposition can cause wettability alteration, permeability reduction, and ultimately a decrease in the productivity of a reservoir. Natural depletion is one of the most common processes of asphaltene deposition in which pressure changes destabilize the dissolved asphaltene in the oil and settle them onto the rock surface. In this work, natural depletion experiments in consolidated core samples were performed under simulated reservoir conditions to obtain reliable data and analyze the asphaltene deposition mechanisms.... 

    Phase-noise measurement of microwave oscillators using phase-shifterless delay-line discriminator

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 58, Issue 2 , January , 2010 , Pages 468-477 ; 00189480 (ISSN) Gheidi, H ; Banai, A ; Sharif University of Technology
    2010
    Abstract
    In this paper, a modified method based on the frequency discriminator technique for measuring phase noise of microwave oscillators is presented. In the proposed method, the phase shifter is omitted. In contrast, a 90° hybrid with one more channel containing a phase detector, and a low-noise amplifier is added to the measurement setup. It can be said that an in-phase/quadrature phase-noise detection has been developed. With the proposed method, tuning of the variable phase shifter is not needed anymore. Therefore, the measurement is done automatically, and as a result, the measurement time is decreased. Another considerable advantage of this method is that the method is theoretically... 

    In-flight estimation of time-varying aircraft center of gravity position based on kinematics approach

    , Article Journal of Aircraft ; Volume 55, Issue 5 , 2018 , Pages 2037-2049 ; 00218669 (ISSN) Dehghan Manshadi, A ; Saghafi, F ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2018
    Abstract
    In-flight aircraft center of gravity (COG) position estimation is investigated in this study based on the kinematics approach. The Quad-M basics of system identification requirements are carefully investigated for time-invariant and time-varying COG estimation during airdrop maneuver as a case study that contains both conditions. Modeling and simulation of airdrop maneuver are employed to prepare the required maneuver and measurement data for this investigation. The relative-acceleration equation, as a model structure, and parameter modeling of time-varying COG location and acceleration are introduced into the system identification and parameter estimation framework. The Kalman filter method... 

    Measurement and prediction of the rate of deposition of flocculated asphaltene particles from oil

    , Article International Journal of Heat and Mass Transfer ; Volume 52, Issue 19-20 , 2009 , Pages 4624-4634 ; 00179310 (ISSN) Jamialahmadi, M ; Soltani, B ; Müller Steinhagen, H ; Rashtchian, D ; Sharif University of Technology
    2009
    Abstract
    Asphaltene deposition is one of the unresolved problems in oil industries. Little information is available on the critical question of "how fast" the flocculated asphaltene particles deposit across the production wells from the flowing oil. In this study, the mechanisms of deposition of flocculated asphaltene particles from oil have been studied experimentally and theoretically under forced convective conditions using an accurate thermal approach. The effects of oil velocity, flocculated asphaltene concentration and temperature on the rate of asphaltene deposition are investigated. It is observed that during the first few weeks the deposition mechanism is dominant and the erosion of the... 

    Aircraft mass properties estimation during airdrop maneuver: A nonlinear filtering approach

    , Article Journal of Aircraft ; Volume 58, Issue 5 , 2021 , Pages 982-996 ; 00218669 (ISSN) Dehghan Manshadi, A ; Saghafi, F ; Sharif University of Technology
    AIAA International  2021
    Abstract
    Unlike a single-body approach, modeling based on a two-body approach has been employed to prepare the required system dynamic model as a time update equation in the applied filtering technology and measurement data for the estimation process. This more precise mathematical model enabled better understanding about the dynamics of the change in the aircraft mass properties during the airdropping operation. The problem is defined as estimation of the optimal mass properties parameters for the best possible fit of the model output to the real data. The parameter estimation problem is investigated by a nonlinear filtering methodology in two sequential steps. In the first step, the single extended... 

    Evaluating reliability of SSD-Based I/O caches in enterprise storage systems

    , Article IEEE Transactions on Emerging Topics in Computing ; Volume 9, Issue 4 , 2021 , Pages 1914-1929 ; 21686750 (ISSN) Ahmadian, S ; Taheri, F ; Asadi, H ; Sharif University of Technology
    IEEE Computer Society  2021
    Abstract
    I/O caching techniques are widely employed in enterprise storage systems in order to enhance performance of I/O intensive applications in large-scale data centers. Due to higher performance compared to Hard Disk Drives (HDDs) and lower price and non-volatility compared to Dynamic Random-Access Memories (DRAM), Flash-based Solid-State Drives (SSDs) are used as a main media in the caching layer of storage systems. Although SSDs are known as non-volatile devices but recent studies have reported large number of data failures due to power outage in SSDs. To overcome the reliability implications of SSD-based I/O caching schemes, RAID-1 (mirrored) configuration is commonly used to avoid data loss... 

    Applying flow zone index approach and artificial neural networks modeling technique for characterizing a heterogeneous carbonate reservoir using dynamic data: Case Study of an Iranian reservoir

    , Article Society of Petroleum Engineers - Trinidad and Tobago Energy Resources Conference 2010, SPE TT 2010, 27 June 2010 through 30 June 2010 ; Volume 2 , June , 2010 , Pages 677-690 ; 9781617388859 (ISBN) Shahvar, M. B ; Kharrat, R ; Matin, M ; Sharif University of Technology
    2010
    Abstract
    Although static characterization of reservoirs is an inevitable part of any reservoir studies, the most robust models of the reservoirs can be obtained through integrating static and dynamic data. The following study which is done in a heterogeneous carbonate reservoir utilizes the capillary pressure and relative permeability data to verify the task of static rock typing and investigate the role of hydraulic units in capillary pressure and relative permeability modeling. For this purpose, at first, various rock typing techniques are applied to the field data to seek the best method which has the most consistency with capillary pressure curves. Using Desouky method which is based on hydraulic... 

    2D analysis of the effects of geometry on the response of high-T c superconductive bolometric detectors

    , Article IEEE Transactions on Applied Superconductivity ; Volume 19, Issue 3 , 2009 , Pages 484-488 ; 10518223 (ISSN) Fardmanesh, M ; Kokabi, A. R ; Pourhashemi, A ; Moftakharzadeh, A ; Khorasani, S ; Banzet, M ; Schubert, J ; Sharif University of Technology
    2009
    Abstract
    We present a new approach for analytical modeling and calculating the response of high-Tc superconductive transition edge sensors in a wide range of modulation frequencies for different configurations of the film patterns. The method used here is based on solving the heat transfer differential equation for two different time varying heat sources, which are related to the absorbed radiated power. The used method employs two-dimensional boundary conditions for describing meander-line patterned devices. The results from the applied method are in better agreement with those obtained from the frequency response measurements of the characterized samples, than the previously developed models. In...