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    Study of Microstructure and Hot Deformation Behavior of Aluminum Nanocomposites Reinforced with SiC Nanoparticles

    , M.Sc. Thesis Sharif University of Technology Mobarhan Bonab, Mohammad Ali (Author) ; Simchi, Abdolreza (Supervisor)
    Hot deformation behavior of Al-SiC nanocomposites was investigated in this study. Aluminum powders with mean size of 60 micron and SiC nanopowders (mean size of 45nm) in amounts of 1 and 2 volume percents, as reinforced part, were mixed and milled for 40 hours by planetary ball mill. After degassing at 450 oC for 1 hour, milled powders were pressed into Aluminum cans (in Argon atmosphere) and then hot extruded. Extrusion ratio was 1:14. High density billets (with 98% of theoretical density) were produced because of that high extrusion ratio. TEM microstructure studies showed that fine distribution of reinforcements and Aluminum Oxides obtained via this procedure. Hardness and Uniaxial... 

    Synthesis of Super Hydrophobic and Anti-Wear Coating with SiO2 and SiC Nano Particles on Glass Surface )

    , M.Sc. Thesis Sharif University of Technology Zahmatkesh Saredorahi, Amir Hossein (Author) ; Dolati, Abolghasem (Supervisor)
    In this research we developed a superhydrophobic and anti-wear coating on a glass substrate using SiO2 nanoparticles to form a transparent superhydrophobic thin film and SiC nanoparticles to improve the wear resistance of coating.
    Silica nanoparticles were produced via a simple sol gel method from Tetraethylorthosilicate (TEOS) as precursor. Hexamethyldisilazane (HMDS) and Tetramethylclourosilane (TMCS) were used as hydrophobic inducing agents and at last SiC nanoparticles were dispersed in the solution in order to provide wear resistance. The final results indicate the contact angle (CA) of water droplet on the surface was about 158° and sliding angle (SA) lower than 9°. Studying the... 

    Surface and Interface Effects on the Elastic Fields of an Edge Dislocation Inside a Silicon Nanotube with Thin Siox Coating

    , M.Sc. Thesis Sharif University of Technology Azizi, Pegah (Author) ; Mohammadi Shodja, Hossein (Supervisor)
    The exact analytical elastic fields within a double-walled silicon nano-tube with a thin layer of SiOx coating associated with surface/ interface effects as well as the classical theory of elasticity due to the presence of an edge dislocation with an arbitrary Burger’s vector and position inside of the silicon is determined via complex potential function method. Stress contours within surface elasticity and classical theory are given, and both theory results are compared. Then, the effects of surface Lamé Constants, magnitude and direction of Burger’s vector, shear modulus, nano-tube size, and position of the edge dislocation on the distribution of stress components are illustrated, and the... 

    Fine-grained architecture in dark silicon era for SRAM-based reconfigurable devices

    , Article IEEE Transactions on Circuits and Systems II: Express Briefs ; Vol. 61, Issue. 10 , 2014 , Pages 798-802 ; ISSN: 15497747 Yazdanshenas, S ; Asadi, H ; Sharif University of Technology
    In this brief, we present a fine-grained dark silicon architecture to facilitate further integration of transistors in static random access memory-based reconfigurable devices. In the proposed architecture, we present a technique to power off inactive configuration cells in nonutilized or underutilized logic blocks. We also propose a routing circuitry capable of turning off the configuration cells of connection blocks (CBs) and switch boxes (SBs) in the routing fabric. Experimental results carried out on the Microelectronics Center of North Carolina benchmark show that power consumption in configuration cells of lookup tables, CBs, and SBs can, on average, be reduced by 27%, 75%, and 4%,... 

    Flow behavior and mechanical properties of a high silicon steel associated with dynamic strain aging

    , Article Journal of Materials Engineering and Performance ; Volume 21, Issue 9 , September , 2012 , Pages 1919-1923 ; 10599495 (ISSN) Akhgar, J. M ; Serajzadeh, S ; Sharif University of Technology
    Springer  2012
    Flow behavior of two grades of steel including a high silicon (HS) steel and a plain low carbon steel as the reference were considered in this work. Tensile testing at temperatures varying between 25 and 550 °C and different strain rates in the range of 4×10-5 to 0.1 s-1 were conducted and the mechanical properties, such as elongation at fracture point and strain rate sensitivity were then determined. It is observed that for both steels, dynamic strain aging occurs in the employed deformation conditions, however, the region of serrated flow and the type of the serration were somehow different. For the case of the HS steel, the serrated flow region is shifted to the higher temperatures and... 

    A reconfigurable network-on-chip architecture for heterogeneous CMPs in the dark-silicon era

    , Article Proceedings of the International Conference on Application-Specific Systems, Architectures and Processors ; 18-20 June , 2014 , pp. 76-77 ; ISSN: 10636862 ; ISBN: 9781479936090 Modarressi, M ; Sarbazi Azad, H ; Sharif University of Technology
    Core specialization is a promising solution to the dark silicon challenge. This approach trades off the cheaper silicon area with energy-efficiency by integrating a selection of many diverse application-specific cores into a single billion-transistor multicore chip. Each application then activates the subset of cores that best matches its processing requirements. These cores act as a customized application-specific CMP for the application. Such an arrangement of cores requires some special on-chip inter-core communication treatment to efficiently connect active cores. In this paper, we propose a reconfigurable network-on-chip that leverages the routers of the dark portion of the chip to... 

    Design and fabrication of a new expandable transtibial liner with manual volume control: A prototype

    , Article Journal of Biomedical Physics and Engineering ; Volume 10, Issue 4 , 2020 , Pages 543-548 Nouri, M. J ; Aminian, G ; Farahmand, F ; Rahgozar, M ; Sharif University of Technology
    Shiraz University of Medical Sciences  2020
    Diurnal volume changes is one of the main factors influencing socket fit in trans-tibial prosthesis and causing pressure problem issues. Embedded bladder liners have been recently a potential approach to deal with this problem. The aim of this technical note was to introduce a new transtibial silicone liner designed based on hybrid socket theory. To make expandability in the liner, an integrated wax structure was constructed over the selected areas of the positive model and then removed after lamination process. In addition, a mechanical system with manual control was designed to fit the liner with the residual limb volume by pumping the water in or out of the liner through connec-tive... 

    Fourier transform infrared spectroscopy and scanning tunneling spectroscopy of porous silicon in the presence of methanol

    , Article Sensors and Actuators, B: Chemical ; Volume 132, Issue 1 , 2008 , Pages 40-44 ; 09254005 (ISSN) Razi, F ; Rahimi, F ; Iraji zad, A ; Sharif University of Technology
    Porous silicon samples were obtained from p+- and n-type silicon wafers. Gas sensing measurements showed that the electrical conductivity of porous Si on p+- and n-type wafers increases strongly and decreases weakly in the presence of methanol gas, respectively. Scanning tunneling spectroscopy (STS) indicates that the adsorption of methanol on the surface of n-porous silicon decreases the average density of states especially in the band gap. Fourier transform infrared (FTIR) spectroscopy reveals that after methanol exposure partial surface oxidation occurs which produces electron traps as well as methanol adsorption on the porous surfaces. These observations imply that the number of... 

    Electrical properties of nanocontacts on silicon nanoparticles embedded in thin SiO2 synthesized by ultralow energy ion implantation

    , Article Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures ; Volume 23, Issue 6 , 2005 , Pages 2821-2824 ; 10711023 (ISSN) Ben Assayag, G ; Shalchian, M ; Coffin, H ; Claverie, A ; Grisolia, J ; Dumas, C ; Atarodi, S. M ; Sharif University of Technology
    In this paper, we present the room temperature current-voltage characteristics of large (100×100 μ m2) and a nanoscale (100×100 nm2) metal-oxide-semiconductor (MOS) capacitor containing few silicon nanocrystals. The layer of silicon crystals is synthesized within the oxide of this capacitor by ultralow energy ion implantation and annealing. Current fluctuations in the form of discrete current steps and sharp peaks are apparent in the static and dynamic I (V) characteristics of the capacitor. These features have been associated to quantized charging and discharging of the nanoparticles and the resulting Coulomb interaction to the tunneling current. © 2005 American Vacuum Society  

    Fluoride Removal from Sludge's of Evaporation Lagoons of Isfahan’s UCF Plant

    , M.Sc. Thesis Sharif University of Technology Khayambashi, Afshin (Author) ; Samadfam, Mohammad (Supervisor) ; Firouz Zare, Mahmoud (Co-Advisor) ; Ghasemi, Mohamad Reza (Co-Advisor)
    Nuclear energy is one of the most important sources of energy from the economical point of view and also in terms of cleanliness and safety. Hence, strategically, uranium is one of the most basic elements of the earth and nowadays, the importance of this element is more marked due to the nuclear industry developement. Therefore, uranium recovery from the wastes generated during nuclear fuel production in Isfahan’s uranium conversion plant- in which yellow cake is converted to uranium hexafluoride- is quite pivotal. In this experimental research, we have to remove Fluoride from waste after dissolution by several methods like precipitation. After that uranium is extracted from the sludge of... 

    Fabrication of Silicon Nanowires with various Silicon Substrates and Investigation of the structural Properties and their Behavior

    , M.Sc. Thesis Sharif University of Technology Teymouri, Arastoo (Author) ; Askari, Masoud (Supervisor)
    In this thesis, Silicon nanowires were synthesized using carbothermal method via Vapor-Liquid-Solid mechanism catalyzed by gold nanoparticles deposited on various substrates. Silicon nanowires just grew on (100) and (111)-oriented silicon substrates. For a particular set of process parameters, we observed a critical thickness of the nucleating gold film, that had depened on a kind of various substrates. We studied the dependence of the Au-Si alloy droplet size and size distribution on the starting gold film thickness and the annealing conditions. We used a modified heating sequence that deconvoluted the effect of various substrates consumption and gas-phase silicon supply on the Au-Si alloy... 

    Design and Construction of Tunneling Spectroscope to Study Reaction of Gas with Porous Silicon Surface

    , M.Sc. Thesis Sharif University of Technology Seify, Omid (Author) ; Iraji zad, Azam (Supervisor)
    Studying the interactions between gas molecules and surface is one of the important issues in the field of sensing. In nanometer scales, it can play a key role in fabricating novel nanosensors. Tunneling spectroscopy, on the other hand, is a powerful method for studying the local electrical properties of surface. Our purpose in this project is to design and construct a local tunneling spectroscope, which is able to probe the effects of adsorption of gas molecules on local density of state (LDOS) in sub-nanometer scales. The designed and constructed local tunneling spectroscope system includes a small chamber, which is isolated from any vibrations by means of a set of dampers. In the main... 

    Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/porous Si

    , Article Journal of Sensors and Actuators B: Chemical ; Volume 146, Issue 1 , 8 April , 2010 , PP. 53–60 Razi, F. (Fatemeh) ; Iraji Zad, A. (Azam) ; Rahimi, F. (Fereshteh) ; Sharif University of Technology
    We prepared porous silicon samples coated by continuous palladium layer in electroless process. Scanning electron microscopy (SEM) showed cauliflower-shape Pd clusters on the surface. I–V curves of Schottky like Pd/porous Si samples were measured in air and in hydrogen. These measurements showed a metal–interface–semiconductor configuration rather than an ideal Schottky diode. Variations of the electrical current in the presence of diluted hydrogen at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (100–40,000 ppm) without any saturation behavior. Hydrogen sensing properties of these samples were investigated at room temperature for a duration... 

    Multi-scale modeling of edge effect on band gap offset in polygonal cross-section silicon nanowires

    , Article Computational Materials Science ; Volume 79 , November , 2013 , PP. 262–275 Khoei, A. R. (Amir Reza) ; DorMohammadi, H ; Aramoon, A ; Sharif University of Technology
    The band gap offset is an effect of coordination numbers (CNs) of atom reduction at the edge of transversal cross-section of Silicon nanowires (SiNWs). In this paper, a hierarchical multi-scale technique is developed to model the edge effect on the band gap shift of SiNWs since the geometric effect is dominant in the energy gap due to the appearance of strain in the self-equilibrium state. The multi-scale model is performed based on the molecular dynamics approach and finite element method for the micro- (atomistic) and macro-scale levels, respectively. The Cauchy–Born (CB) hypothesis is used to relate the atomic positions to the continuum field through the deformation gradient. Finally, the... 

    Analysis of lattice temperature effects on a GaInP/6H-SiC strained quantum-well lasers

    , Article Asian Journal of Chemistry ; Volume 25, Issue 9 , Oct , 2013 , Pages 4715-4717 ; 09707077 (ISSN) Marjani, S ; Faez, R ; Hosseini, S. E ; Sharif University of Technology
    In this paper, simulative study on the effects of lattice temperature on a GaInP/6H-SiC strained quantum-well (QW) laser's device is presented. Loss mechanisms are severe in the edge-emitting lasers. As a consequence, the wall-plug efficiency is sensitive to changes in temperature. The lasers used in this work were separate-confinement quantum-well lasers with a single strained GaInP, located in a latticematched waveguide core and cladding region of 6H-SiC. This paper provides the key results of the wall-plug efficiency upon the lattice temperature  

    Influence of Mold Preheating and Silicon Content on Microstructure and Casting Properties of Ductile Iron in Permanent Mold

    , Article Journal of Iron and Steel Research International ; Volume 18, Issue 3 , 2011 , Pages 34-39 ; 1006706X (ISSN) Jafar, K. A ; Behnam, A. A ; Sharif University of Technology
    The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides, graphite nodule counts and shrinkage volume were investigated. The results showed that the percentage of carbides and the shrinkage volume decreased when the mold preheating increased. The ductile iron with the carbon equivalent of 4.45% and the silicon content of 2.5% without any porosity defects was achieved when the mold preheating was 450 °C. Increasing the silicon content in the range of 2.1%-3.3% led to the increase in graphite nodule count and graphite size and the decrease in percentage of carbides. It is due to the increase in induced expansion pressure during the graphite... 

    Decorated CNT based on porous silicon for hydrogen gas sensing at room temperature

    , Article RSC Advances ; Volume 6, Issue 50 , 2016 , Pages 44410-44414 ; 20462069 (ISSN) Ghorbani Shiraz, H ; Razi Astaraei, F ; Fardindoost, S ; Hosseini, Z. S ; Sharif University of Technology
    Royal Society of Chemistry  2016
    A new triple-component sensor for detection of H2 was developed based on porous silicon and CNTs. An increase in deposition of CVD catalysis was shown to promote a high and fast response. Also, it was shown that the composite system exhibited good selectivity  

    Introduction to emerging SRAM-Based FPGA architectures in dark silicon Era

    , Article Advances in Computers ; Volume 110 , 2018 , Pages 259-294 ; 00652458 (ISSN); 9780128153581 (ISBN) Seifoori, Z ; Ebrahimi, Z ; Khaleghi, B ; Asadi, H ; Sharif University of Technology
    Academic Press Inc  2018
    The increased leakage power of deep-nano technologies in the one hand, and exponential growth in the number of transistors in a given die particularly in Field-Programmable Gate Arrays (FPGAs) have resulted in an intensified rate of static power dissipation as well as power density. This ever-increasing static power consumption acts as a power wall to further integration of transistors and has caused the breakdown of Dennard scaling. To meet the available power budget and preclude reliability challenges associated with high power density, designers are obligated to restrict the active percentage of the chip by powering off a selective fraction of silicon die, referred to as Dark Silicon.... 

    Dark silicon and the history of computing

    , Article Advances in Computers ; Volume 110 , 2018 , Pages 1-33 ; 00652458 (ISSN); 9780128153581 (ISBN) Lotfi Kamran, P ; Sarbazi Azad, H ; Sharif University of Technology
    Academic Press Inc  2018
    For many years, computer designers benefitted from Moore's law and Dennard scaling to significantly improve the speed of single-core processors. The failure of Dennard scaling pushed the computer industry toward homogenous multicore processors for the performance improvement to continue without significant increase in power consumption. Unfortunately, even homogeneous multicore processors cannot offer the level of energy efficiency required to operate all the cores at the same time in today's and especially tomorrow's technologies. As a result of lack of energy efficiency, not all the cores in a multicore processor can be functional at the same time. This phenomenon is referred to as dark... 

    Key parameters in hydrothermal synthesis and characterization of low silicon content SAPO-34 molecular sieve

    , Article Microporous and Mesoporous Materials ; Volume 126, Issue 1-2 , 2009 , Pages 1-7 ; 13871811 (ISSN) Izadbakhsh, A ; Farhadi, F ; Khorasheh, F ; Sahebdelfar, S ; Asadi, M ; Yan, Z. F ; Sharif University of Technology
    Low silicon content SAPO-34 was successfully synthesized using the conventional hydrothermal crystallization in the static condition. Effects of different synthesis conditions including crystallization temperature and the silicon source were investigated through X-ray diffraction patterns. It was concluded that the silicon source had a significant effect on silicon incorporation into the alumino-phosphate building blocks in the course of crystallization. Using precipitated silica instead of silica sol resulted in the formation of impurities of alumino-phosphates phases whose crystalline structures collapse at the high temperature of calcination. For the low silicon SAPO-34 synthesis, the...