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    Thermal-aware Accelerator Placement and Task Assignment for Energy Improvement in Data Center

    , M.Sc. Thesis Sharif University of Technology Kazemi Abharian, Sanaz (Author) ; Goudarzi, Maziar (Supervisor)
    Abstract
    With the proliferation of data centers, their ever-growing energy consumption has gained lots of attention from both academy and industry . Two primary parts that use majority of energy in data centers are IT equipment and cooling system or Computing Room Air Conditioning (CRAC) unit. Energy consumption of cooling system strongly relies on thermal performance of data center. Therefore, applying thermal management techniques for decreasing energy consumption of CRAC is a common practice. Moreover, the energy consumption of IT equipment affects the energy consumption of CRAC directly. Demand for more computing resources in data centers and their physical limits has, motivated the use of FPGAs ... 

    Optimal Design of Tolerances in the Non-rigid Assemblies under the Thermal Impact

    , M.Sc. Thesis Sharif University of Technology Hemati Nik, Javad (Author) ; Khodaygan, Saeed (Supervisor)
    Abstract
    Tolerance allocation in the recent mechanical assembly is significant because it straightly affects product performance and cost. Loose tolerances may cause the quality defect while tight tolerances can increase the cost. Thermal effects and the temperature gradients are one of the factors that caused changes in the size and geometry of the components during the performance of mechanical assemblies. This thesis proposes a new approach for tolerance design considering the thermal effects, to achieve lower manufacturing cost and good product quality. Finite element analysis is used to determine the deformation of components in an assembly. The neural network is trained using experimental... 

    Development of consistent Thermomechanical ALE Formulation with Application to Simulation of Machining

    , Ph.D. Dissertation Sharif University of Technology Tadi Beni, Yaghob (Author) ; Movahhedy, Mohammd Reza (Supervisor) ; Farrahi, Hossein (Supervisor)
    Abstract
    Accurate description of kinematics of continuum mechanics is essential in simulation of large deformation problems in solid mechanics. From the numerical viewpoint, two main approaches have been used for such description; the Lagrangian approach and the Eulerian approach. However, each of these approaches suffer from shortcomings which hinders their application in large deformation problems. A more general approach called the Arbitrary Lagrangian-Eulerian method (ALE) provides an opportunity to exploit the advantages of both Lagrangian and Eulerian approach, while avoiding their shortcoming. In an ALE analysis, the FE mesh is neither attached to the material nor fixed in space, necessarily.... 

    Thermal Relaxation Time Of Healthy and Cancerous Tissue In Pulsed Laser Using Monte Carlo Simulation

    , M.Sc. Thesis Sharif University of Technology Khaze, Mehran (Author) ; Amjadi, Ahmad (Supervisor)
    Abstract
    Thermal relaxation time is the time when maximum temperature of a particle get to 1/e of it’s initial value. The destruction of a tissue depends to this important parameter. This parameter has studied by Monte Carlo simulation of pulsed laser in to environment as healthy and cancerous tissue. The main goal of this method is providing proper temperature in a special area so that minimize thermal destruction around that area. In this thesis, temperature distribution of tissue that is caused by pulsed laser, has solved by new method;in this new method the pulse duration uses for Monte Carlo simulation. Also using the solution of radiation transfer equation by Discretes Ordinate Method, new... 

    Thermal interaction of laser beam with particulate flow in mini-channels

    , Article ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2011, 19 June 2011 through 22 June 2011 ; Volume 2 , June , 2011 , Pages 355-366 ; 9780791844649 (ISBN) Zabetian, M ; Saidi, M. S ; Saidi, M. H ; Shafii, M. B ; Sharif University of Technology
    2011
    Abstract
    Optical propulsion via laser source is a relatively new and non-contact tool for manipulation of microscopic objects. The method is based on the radiation pressure of light photons on the micron sized particles. Applications of the technique mainly cover microscopic separation, purification and cellular studies. Due to high power intensity of laser beams, absorption of light may result in heating and damage of objects to be manipulated. In addition, the difference between heated and cold zones can lead to a naturally driven flow around the objects. So precisely controlled conditions should be set up to avoid thermal effects. In this work, a theoretical study is conducted to investigate the... 

    A fast method for numerical simulation of casting solidification

    , Article Communications in Numerical Methods in Engineering ; Volume 24, Issue 12 , October , 2008 , Pages 1723-1740 ; 10698299 (ISSN) Tavakoli, R ; Davami, P ; Sharif University of Technology
    2008
    Abstract
    An efficient numerical method for simulation of casting solidification is presented. The presented method is based on a stable explicit finite difference solution of the heat equation in conjunction with the temperature recovery method to incorporate latent heat effect. The computational cost of the presented method is approximately the same as an explicit method (per time step), while it is free from the time step limitation due to the stability criterion. A simple domain decomposition method is included to improve the computational performance of the presented method. The efficiency, stability and accuracy of the presented method are supported with illustrative examples. Copyright © 2007... 

    Phase behavior modeling of asphaltene precipitation for heavy crudes: A promising tool along with experimental data

    , Article International Journal of Thermophysics ; Vol. 33, issue. 12 , December , 2012 , p. 2251-2266 ; ISSN: 0195928X Tavakkoli, M ; Kharrat, R ; Masihi, M ; Ghazanfari, M. H ; Fadaei, S ; Sharif University of Technology
    Abstract
    Thermodynamic modeling is known as a promising tool for phase behavior modeling of asphaltene precipitation under different conditions such as pressure depletion and CO2 injection. In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, while the oil and gas phases are modeled with an equation of state. The PR-EOS was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on an improved solid model has been developed and used for predicting asphaltene precipitation data for one of... 

    Phase behavior modeling of asphaltene precipitation for heavy crudes: A promising tool along with experimental data

    , Article International Journal of Thermophysics ; Volume 33, Issue 12 , December , 2012 , Pages 2251-2266 ; 0195928X (ISSN) Tavakkoli, M ; Kharrat, R ; Masihi, M ; Ghazanfari, M. H ; Fadaei, S ; Sharif University of Technology
    2012
    Abstract
    Thermodynamic modeling is known as a promising tool for phase behavior modeling of asphaltene precipitation under different conditions such as pressure depletion and CO2 injection. In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, while the oil and gas phases are modeled with an equation of state. The PR-EOS was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on an improved solid model has been developed and used for predicting asphaltene precipitation data for one of... 

    Modeling of high temperature rheological behavior of AZ61 Mg-alloy using inverse method and ANN

    , Article Materials and Design ; Volume 29, Issue 9 , 2008 , Pages 1701-1706 ; 02641275 (ISSN) Talebi Anaraki, M ; Sanjari, M ; Akbarzadeh, A ; Sharif University of Technology
    2008
    Abstract
    Inverse method and artificial neural network were employed in modeling the rheological behavior of the AZ61 Mg alloy. The hot deformation behavior of these alloys was investigated by compression tests in the temperature range 250-350 °C and strain rate range 0.0005-0.1 s-1. Investigation of stress-strain curves and microstructure of the compression specimen illustrate occurrence of dynamic recrystallization. To determining parameters of two suggested constitutive equations global optimization technique, genetic algorithm, was used. The predicted results by inverse method and ANN depicted a good agreement with the experimental data even if the ANN results has shown the best predicted... 

    Studies on recycling of zinc-containing waste

    , Article REWAS'04 - Global Symposium on Recycling, Waste Treatment and Clean Technology, Madrid, 26 September 2004 through 29 September 2004 ; 2005 , Pages 2797-2799 ; 8495520060 (ISBN) Taghavi, S. M ; Halali, M ; Sharif University of Technology
    2005
    Abstract
    In this report, the possibility of recovering zinc oxide from zinc containing wastes, also the effect of temperature, time and depth of bed on recycling has been studied. Zinc oxide with a purity of 93.5% was obtained  

    Comparative evaluation of advanced gas turbine cycles with modified blade cooling models

    , Article 2006 ASME 51st Turbo Expo, Barcelona, 6 May 2006 through 11 May 2006 ; Volume 4 , 2006 , Pages 537-546 ; 0791842398 (ISBN); 9780791842393 (ISBN) Tabari, A ; Khaledi, H ; Hajilouy Benisi, A ; Sharif University of Technology
    2006
    Abstract
    Advanced gas turbine cycles use advanced blade cooling technologies to reach high turbine inlet temperature. Accurate modeling and optimization of these cycles depend on blade cooling model. In this study, different models have been used to simulate gas turbine performance. The first model is the continuous model and the second is stage-by-stage model with alternative methods for calculating coolant, stagnation pressure loss and SPR. Variation of specific heat and enthalpy with temperature are included in both models. The composition of gas stream in turbine is changed step by step due to air cooling. These models are validated by two case study gas turbine results, which show good agreement... 

    Analytical prediction of panel flutter using unsteady potential flow

    , Article Journal of Aircraft ; Volume 40, Issue 4 , 2003 , Pages 805-807 ; 00218669 (ISSN) Soltani, N ; Esfahanian, V ; Haddadpour, H ; Sharif University of Technology
    American Inst. Aeronautics and Astronautics Inc  2003
    Abstract
    An analytical procedure for supersonic flutter analysis of two-dimensional panels was developed using unsteady potential flow aerodynamic theory. The local spatial influence was considered as an integral over the plate area. The U-g method was used for flutter prediction. Results indicate a stabilizing effect of the unsteady potential flow aerodynamics theory compared to the quasi-steady first-order piston theory  

    Behaviour of metal powders during cold and warm compaction

    , Article Powder Metallurgy ; Volume 49, Issue 3 , 2006 , Pages 281-287 ; 00325899 (ISSN) Simchi, A ; Veltl, G ; Sharif University of Technology
    2006
    Abstract
    An instrumented die was used to investigate the behaviour of metal powders during cold (ambient temperature) and warm (up to 140°C) compaction. This instrument enables simultaneous measurement of density, die wall friction coefficient, the triaxial stresses acting on the powder during the course of compaction and ejection pressure. Commercial iron, titanium, aluminium, 316L stainless steel (SS) and aluminium-silicon powders were employed for investigation. The results demonstrated the advantages of powder preheating on the compaction behaviour of metal powders concerning green density, dimensional changes, frictional behaviour, ejection characteristics and compactibiiity. However, the... 

    Densification and microstructural evolution during co-sintering of Ni-base superalloy powders

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 37, Issue 8 , 2006 , Pages 2549-2557 ; 10735623 (ISSN) Simchi, A ; Sharif University of Technology
    2006
    Abstract
    This work presents the effect of co-sintering on the densification and microstructural evolution in the two-layer stepwise graded composite of INCONEL 718 and INCONEL 625 superalloys. A pressureless co-sintering method in conjunction with a powder layering technique was used. The sintering was carried out in solid state and liquid phase in temperature ranging from 1260 °C through 1300 °C for 60 minutes in a low pressure of an argon atmosphere. Nonisothermal sintering behavior was also examined by dilatometric analysis. Similarly, the sintering response of the individual layers was characterized. The results reveal an enhanced densification rate during co-sintering of the composite layers.... 

    An investigation on the sintering behavior of 316L and 17-4PH stainless steel powders for graded composites

    , Article Materials Science and Engineering A ; Volume 424, Issue 1-2 , 2006 , Pages 282-289 ; 09215093 (ISSN) Simchi, A ; Rota, A ; Imgrund, P ; Sharif University of Technology
    2006
    Abstract
    This paper presents the densification and microstructure of bilayer structures made from 316L and 17-4PH stainless steels powders during sintering. The requirements for such objects could be magnetic properties at one area of the part and non-magnetic properties at another area of the object. A pressureless solid state sintering method in conjunction with a powder layering technique was used. The sintering was carried out at temperatures ranging from 1100 to 1340 °C for 120 min in hydrogen and vacuum atmospheres. Non-isothermal sintering behavior was also examined by dilatometric analysis. It was found that the strain rate of 17-4PH stainless steel powder is higher than that of 316L during... 

    Temperature and voltage dependence of magnetic barrier junctions with a nonmagnetic spacer

    , Article European Physical Journal B ; Volume 42, Issue 2 , 2004 , Pages 187-191 ; 14346028 (ISSN) Shokri, A. A ; Saffarzadeh, A ; Sharif University of Technology
    2004
    Abstract
    The temperature and voltage dependence of spin transport is theoretically investigated in a new type of magnetic tunnel junction, which consists of two ferromagnetic outer electrodes separated by a ferromagnetic barrier and a nonmagnetic (NM) metallic spacer. The effect of spin fluctuation in magnetic barrier, which plays an important role at finite temperature, is included by taking the mean-field approximation. It is found that, the tunnel magnetoresistance (TMR) and the electron-spin polarization depend strongly on the temperature and the applied voltage. The TMR and spin polarization at different temperatures show an oscillatory behavior as a function of the NM spacer thickness. Also,... 

    Effective compton cross section in non-degenerate high-temperature media

    , Article Journal of Quantitative Spectroscopy and Radiative Transfer ; Volume 95, Issue 1 , 2005 , Pages 61-69 ; 00224073 (ISSN) Shekh Momeni, F ; Samimi, J ; Sharif University of Technology
    2005
    Abstract
    The effective compton cross section in a non-degenerate plasma (n≪{((kT/c)2 + 2mkT)/h2}3/2) is investigated in a wide range of temperatures. The results show a decreasing behavior with temperatures especially for kT ≫ mec2. The results may be important in phenomena like accretion discs or ultra-relativistic blast waves in GRB models, where the emitted radiation has to pass through a medium containing high-energy electrons. © 2004 Elsevier Ltd. All rights reserved  

    The influence of heat treatment and hot deformation conditions on γ′ precipitate dissolution of Nimonic 115 superalloy

    , Article International Journal of Advanced Manufacturing Technology ; Volume 45, Issue 9-10 , 2009 , Pages 841-850 ; 02683768 (ISSN) Shahriari, D ; Sadeghi, M. H ; Akbarzadeh, A ; Cheraghzadeh, M ; Sharif University of Technology
    Abstract
    In precipitation hardenable materials, it is desirable to determine the precipitate dissolution temperature for homogenizing the microstructure by controlling the size and distribution of the precipitates. In this research, the influence of various heat treatment and hot deformation conditions on the kinetics of γ ′ dissolution and its morphological evolution in Nimonic 115 was studied. In addition, hot deformation behavior of the material was investigated using hot compression experiments at varying temperature (between 1,050°C and 1,175°C) and strain rates (between 0.01 and 1 s-1) up to a true strain of 0.8. The values obtained for the solvus temperature of γ ′ precipitates by two methods... 

    γ' Precipitate dissolution during heat treatment of nimonic 115 superalloy

    , Article Materials and Manufacturing Processes ; Volume 24, Issue 5 , 2009 , Pages 559-563 ; 10426914 (ISSN) Shahriari, D ; Sadeghi, M. H ; Akbarzadeh, A ; Sharif University of Technology
    2009
    Abstract
    In precipitation hardenable materials, it is desirable to determine the precipitate dissolution temperature for homogenizing the microstructure by controlling the size and distribution of the precipitates. In this research, differential thermal analysis, dilatometry technique, heat treatments followed by microstructure evaluation were used to determine the -γ' dissolution temperature of Nimonic 115. It is assumed that the variation of enthalpy is governed by the changes in y volume fraction and γ concentration with time and temperature, and any contribution of the coarsening of γ' is neglected. The values obtained for the solvus temperature of γ precipitates by the three methods are all in... 

    An investigation on the sintering behavior of high strength Al-Zn-Mg-Cu alloy prepared from elemental powders

    , Article 2006 Powder Metallurgy World Congress and Exhibition, PM 2006, Busan, 24 September 2006 through 28 September 2006 ; Volume 534-536, Issue PART 1 , 2007 , Pages 489-492 ; 02555476 (ISSN); 0878494197 (ISBN); 9780878494194 (ISBN) Shahmohammadi, M ; Sirnchi, A ; Danninger, H ; Arvand, A ; Sharif University of Technology
    Trans Tech Publications Ltd  2007
    Abstract
    In the present work, the sintering behavior of high strength Al-5.6Zn-2.5Mg-1.6Cu (in wt.%) alloy compacts was investigated. Green parts made by pressing of mixed elemental powders were sintered at different temperatures between 400 and 600°C The effect of the sintering temperature on density, dimensional change and microstructure of the Al alloy was studied. Microstructural evaluation was accompanied by XRD and DSC methods in order to determine the temperature and chemical composition of the liquid phases formed during sintering. It was found that three transient liquid phases are formed at 420, 439 and 450°C Microstructural study revealed the progressive formation of sintered contacts due...