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Thermoelastic creep analysis of a functionally graded various thickness rotating disk with temperature-dependent material properties
, Article International Journal of Pressure Vessels and Piping ; Volume 111-112 , 2013 , Pages 63-74 ; 03080161 (ISSN) ; Livani, M ; Sharif University of Technology
2013
Abstract
A semi-analytical solution for rotating axisymmetric disks made of functionally graded materials was previously proposed by Hosseini Kordkheili and Naghdabadi [1]. In the present work the solution is employed to study thermoelastic creep behavior of the functionally graded rotating disks with variable thickness in to the time domain. The rate type governing differential equations for the considered structure are derived and analytically solved in terms of rate of strain as a reduced to a set of linear algebraic equations. The advantage of this method is to avoid simplifications and restrictions which are normally associated with other creep solution techniques in the literature. The thermal...
Modeling of hot isostatic pressing of metal powder with temperature–dependent cap plasticity model
, Article International Journal of Material Forming ; Volume 6, Issue 3 , September , 2013 , PP. 363-376 ; Molaeinia, Z ; Keshavarz, Sh ; Sharif University of Technology
Abstract
In this paper, the coupled thermo–mechanical simulation of hot isostatic pressing (HIPing) is presented for metal powders during densification process. The densification of powder is assumed to occur due to plastic hardening of metal particles. The constitutive model developed is used to describe the nonlinear behavior of metal powder. The numerical modeling of hot powder compaction simulation is performed based on the large deformation formulation, powder plasticity behavior, and frictional contact algorithm. A Lagrangian finite element formulation is employed for the large powder deformations. A modified cap plasticity model considering temperature effects is used in numerical simulation...
A new low voltage precision CMOS current reference with no external components
, Article IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing ; Volume 50, Issue 12 , 2003 , Pages 928-932 ; 10577130 (ISSN) ; Atarodi, S. M ; Sharif University of Technology
2003
Abstract
A novel current reference with low temperature and supply sensitivity and without any external component has been developed in a 0.25 μm mixed-mode process. The circuit is based on a bandgap reference (BGR) voltage and a CMOS circuit similar to a beta multiplier. An NMOS transistor in triode region has been used in place of a resistor in conventional beta multiplier to achieve a current which has a negative temperature coefficient and only oxide thickness dependent. The BGR voltage has a positive temperature coefficient to cancel the negative temperature coefficient of the beta multiplier. The simulation results using Bsim3v3 model show max-to-min fluctuation of less than 1 % over a...
Kinetic modelling of enzymatic biodiesel production from castor oil: Temperature dependence of the Ping Pong parameters
, Article Canadian Journal of Chemical Engineering ; Volume 94, Issue 3 , 2016 , Pages 512-517 ; 00084034 (ISSN) ; Kariminia, H. R ; Khorasheh, F ; Sharif University of Technology
Wiley-Liss Inc
2016
Abstract
Biodiesel is considered an alternative replacement for petroleum diesel, and enzymatic reaction is one method for biodiesel production. Understanding the kinetics of this reaction is important to achieve higher production rates. The kinetics of transesterification of castor oil using Novozym 435 was investigated in this study. The genetic algorithm was employed for estimation of kinetic parameters including Vmax, KmTG, and KmA in the Ping Pong kinetic model at different temperatures. In most enzymatic reactions that follow the Ping Pong mechanism, inhibition by alcohol has been taken into consideration. Here, we examined a competitive inhibition mechanism and found no inhibition effect at...
Transient thermal behavior of radial fins of rectangular, triangular and hyperbolic profiles with temperature-dependent properties using DTM-FDM
, Article Journal of Central South University ; Volume 24, Issue 3 , 2017 , Pages 675-682 ; 20952899 (ISSN) ; Rahimi Gorji, M ; Ganji, D. D ; Moayebidorcheh, T ; Pourmehran, O ; Biglarian, M ; Sharif University of Technology
Central South University of Technology
2017
Abstract
This work focuses on transient thermal behavior of radial fins of rectangular, triangular and hyperbolic profiles with temperature-dependent properties. A hybrid numerical algorithm which combines differential transformation (DTM) and finite difference (FDM) methods is utilized to theoretically study the present problem. DTM and FDM are applied to the time and space domains of the problem, respectively. The accuracy of this method solution is checked against the numerical solution. Then, the effects of some applicable parameters were studied comparatively. Since a broad range of governing parameters are investigated, the results could be useful in a number of industrial and engineering...
The Pr and oxygen correlation in the GdPr123 system
, Article Modern Physics Letters B ; Volume 16, Issue 25 , 2002 , Pages 943-953 ; 02179849 (ISSN) ; Daadmehr, V ; Akhavan, M ; Sharif University of Technology
2002
Abstract
We prepared single-phase polycrystalline Gd1-xPrx Ba2Cu3O7-δ samples with x = 0, 0.10, 0.15, and 0.20. The deoxygenation process of these samples was performed by an annealing method. Electrical resistivity measurements revealed depression of the transition temperature with the increase of x and δ. We calculated the hole concentration in the CuO2 plane for different values of x and δ. A linear dependence of transition temperature and hole concentration in the CuO2 plane was found as a function of 2δ + x. It is proposed that a combination of the localization and filling of holes should be considered as the effective mechanisms for the appearance of the Pr anomaly in HTSCs
Electroosmotic flow of power-law fluids with temperature dependent properties
, Article Journal of Non-Newtonian Fluid Mechanics ; Volume 185-186 , 2012 , Pages 49-57 ; 03770257 (ISSN) ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
Elsevier
2012
Abstract
The influence of variable fluid properties on mixed electroosmotic and pressure driven flow of non-Newtonian fluids is investigated in this paper. The non-linear coupled energy and momentum equations are solved by means of an iterative numerical approach. The results reveal that the temperature dependent effects only become significant at very high values of the Debye-Hückel parameter in case of combined electroosmotic and pressure driven flow and could safely be neglected in other cases. It is observed that the physical properties variation lead to a higher mean velocity in case of pressure assisted flow and a lower mean velocity in case of pressure opposed flow. Furthermore, the...
Measurement of Thermophysical Properties of Aqueous Solutions of Alkanolamine
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Siroos (Supervisor) ; Taghikhani, Vahid (Supervisor) ; Jalili, Amir Hossin (Supervisor)
Abstract
In this study, density, viscosity and surface tension of aqueous solution of Sulfolane, ( TEA+TMS+H2O) and (DIPA+TMS+H2O) systems were measured . Density, viscosity and surface tension were measured using pycnometer, Cannon – Fenske viscometer and Capillary rise method, respectively. Surface tension measurements of (DIPA+TMS+water) were carried out by the ring method using a LAUDR TD3 tensiometer,. The experiments were carried out in low concentrations and atmospheric pressure in the temperature range (70 - 30) . The obtained Data was modeled using empirical and thermodynamic models. Density calculation was done using the Setchenov and Redlich – Kister models.and the results indicated that...
CFD Modeling of Vortex Tube in Order to Investigate the Energy Separation in Pure and Mixed Gases
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fatollah (Supervisor)
Abstract
Vortex Tube is a mechanical device without any moving parts. It separates a compressed gas stream into a low and a high temperature region (temperature or energy separation effect). Advantages of VT are existence of no moving parts, no external power (electricity or flames) required to operate, tiny and lightweight, inexpensive tube & parts material, convenience and pollution free. Heating, cooling, cleaning and drying gases, separating gas mixtures, gas liquefaction, natural gas pressure reduction and dehydration are the applications of vortex tube. The main Objectives in this research are investigation of various types of gas streams including pure gas or mixture of gases in vortex tube...
Complexity of density dependencies of thermal and internal pressure compared to that of total pressure
, Article Industrial and Engineering Chemistry Research ; Volume 52, Issue 23 , May , 2013 , Pages 8034-8045 ; 08885885 (ISSN) ; Parsafar, G ; Sharif University of Technology
2013
Abstract
A simple equation of state (EoS) has recently been introduced (J. Phys. Chem. B2009, 113, 11977-11987) as (Z - 1)v2 = e + f/ρ + gρ2, where Z ≡ pv/RT is the compressibility factor, v = 1/ρ is molar volume, and e, f, and g are temperature dependent parameters. This EoS has been found to be accurate for all types of nano and bulk solids and bulk fluids, in the entire temperature and pressure ranges for which experimental data are reported, except for the isotherms within 1 ≤ T r = T/Tc ≤ 1.1 for the spherical and near spherical species and for a wider temperature range for the cylindrical molecules. The aim of this work is to investigate the validity of a three-term expression similar to the...
On Temperature Dependency of Delay for Local,Intermediate, and Repeater Inserted Global Copper Interconnects
, Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 23, Issue 12 , 2015 , Pages 3143-3147 ; 10638210 (ISSN) ; Sarvari, R ; Sharif University of Technology
Abstract
Cryogenic technologies not only improve the performance of interconnects but also the performance of transistors and consequently drivers and repeaters. Although in cryogenically cooled integrated circuits the local temperature of interconnects and transistors may be as low as 50 K, it may easily reach to 600 K in high-temperature chips. In this brief, we investigated the impact of temperature on the delay of local, intermediate, unit-repeater-inserted (URI), and cascaded repeater-inserted (CRI) global copper interconnects for minimum technology node with available transistor model (32-nm technology). Our results show that temperature variation of driver resistance could change the delay of...
Induced superconductivity in Fermi arcs
, Article Physical Review B ; Volume 100, Issue 3 , 2019 ; 24699950 (ISSN) ; Jafari, S. A ; Sharif University of Technology
American Physical Society
2019
Abstract
When the interface of a superconductor (SC) with a Weyl semimetal (WSM) supports Fermi arcs, the chirality blockade eliminates the induction of superconductivity into the bulk of time-reversal symmetry (TRS) breaking WSM. This leaves the Fermi arc states as the only low-energy degrees of freedom in the proximity problem. Therefore the SC|WSM system will be a platform to probe transport properties which involve only the Fermi arcs. With a boundary condition that flips the spin at the boundary, we find a Z2 protected Bogoliubov Fermi contour (BFC) around which the Bogoliubov quasiparticles disperse linearly. The resulting BFC and excitations around it leave a distinct T2 temperature dependence...
A deep look into the dynamics of saltwater imbibition in a calcite nanochannel: temperature impacts capillarity regimes
, Article Langmuir ; Volume 36, Issue 31 , 2020 , Pages 9035-9046 ; Koleini, M. M ; Greenwell, H. C ; Ayatollahi, S ; Ghazanfari, M. H ; Sharif University of Technology
American Chemical Society
2020
Abstract
This research concerns fundamentals of spontaneous transport of saltwater (1 mol·dm-3 NaCl solution) in nanopores of calcium carbonates. A fully atomistic model was adopted to scrutinize the temperature dependence of flow regimes during solution transport under CaCO3 nanoconfinement. The early time of capillary filling is inertia-dominated, and the solution penetrates with a near-planar meniscus at constant velocity. Following a transition period, the meniscus angle falls to a stabilized value, characterizing the capillary-viscous advancement in the calcite channel. At this stage, brine displacement follows a parabolic relationship consistent with the classical Lucas-Washburn (LW) theory....
N-benzyl-DABCO-tribromide as an efficient and mild reagent for deprotection of dithioacetals
, Article Synthetic Communications ; Volume 36, Issue 8 , 2006 , Pages 1093-1096 ; 00397911 (ISSN) ; Boeini, H. Z ; Zargarani, D ; Bardajee, G. R ; Sharif University of Technology
2006
Abstract
N-Benzyl-DABCO-ammonium tribromide was found to be an efficient and recyclable reagent for the deprotection of dithioacetals in dichloromethane/ methanol at room temperature. The reaction can be performed cleanly, in short time, and in high yield. Copyright © Taylor & Francis Group, LLC
Lattice relaxation in many-electron states of the diamond vacancy
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 71, Issue 3 , 2005 ; 10980121 (ISSN) ; Vesaghi, M. A ; Esfarjani, K ; Ghods Elahi, T ; Sayari, M ; Hashemi, H ; Gorjizadeh, N ; Sharif University of Technology
2005
Abstract
Symmetric lattice relaxation around a vacancy in diamond and its effect on many electron states of the defect have been investigated. A molecular approach is used to evaluate accurately electron-electron (e-e) interaction via a semiempirical formalism which is based on a generalized Hubbard Hamiltonian. Coupling of the defect molecule to surrounding bulk is also considered using an improved Stillinger-Weber potential for diamond. Strong dependence of the electronic energy levels to the relaxation size of the nearest neighbor (NN) atoms indicates that in order to obtain quantitative results the effect of lattice relaxation should be considered. Except for the high spin state of the defect 5A...
Modeling of hot isostatic pressing of metal powder with temperature-dependent cap plasticity model
, Article International Journal of Material Forming ; Volume 6, Issue 3 , September , 2013 , Pages 363-376 ; 19606206 (ISSN) ; Molaeinia, Z ; Keshavarz, S ; Sharif University of Technology
2013
Abstract
In this paper, the coupled thermo-mechanical simulation of hot isostatic pressing (HIPing) is presented for metal powders during densification process. The densification of powder is assumed to occur due to plastic hardening of metal particles. The constitutive model developed is used to describe the nonlinear behavior of metal powder. The numerical modeling of hot powder compaction simulation is performed based on the large deformation formulation, powder plasticity behavior, and frictional contact algorithm. A Lagrangian finite element formulation is employed for the large powder deformations. A modified cap plasticity model considering temperature effects is used in numerical simulation...
An analytical study on laser forming process of sheet metals, using new elasto-plastic temperature dependent material model
, Article Advanced Materials Research ; Volume 622 , 2013 , Pages 569-574 ; 10226680 (ISSN) ; 9783037855638 (ISBN) ; Banazadeh, A ; Sharif University of Technology
2013
Abstract
The laser forming process is one of the last technologies on forming of sheet metals with laser beam heat distribution. In this process laser beam moves across the top surface of the sheet metal and the heated zone expands and causes a great moment that deforms the sheet metal. Subsequently, the heated zone gets cooled and provides a reverse strain and moment. The final bending angle is a combination of two phases. Due to the complexity of the process, it is studied with different approaches; FEM analysis and analytical as well as empirical methods. The laser forming is a sensible process regarding the material properties. Also, because of the temperature change during the process, it is...
Modeling the detection efficiency in photodetectors with temperature-dependent mobility and carrier lifetime
, Article Superlattices and Microstructures ; Volume 122 , 2018 , Pages 557-562 ; 07496036 (ISSN) ; Ahmadpour, M ; Mosavi, A ; Alharbi, N ; Gorji, N. E ; Sharif University of Technology
Abstract
We proposed a modeling procedure to calculate the impact of temperature on the detection efficiency in photodetectors based on CdTe materials. Temperature increase impacts on the electrical properties of the materials such as carrier mobility and carrier recombination lifetime. This impact which can be effective in some cases has been normally ignored in the modeling approaches presented in the literature. Here we show that increasing the temperature from 190 K to 300 K not reduces the mobility of both electrons and holes but also significantly reduces the carrier lifetime. The result will impact on electric-field within the depletion width of the device, drift and diffusion lengths which...
Continuum Analysis of Defects Based on Atomistic Simulat
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor) ; Jahanshahi, Mohsen (Co-Advisor)
Abstract
In this study, a new multi-scale hierarchical technique has been employed to investigate the role of temperature on nano-plates with hex atomic structure. Different number of primary edge dislocations is considered and the temperature varies from 0 up to 800 K. Primary edge dislocations are created by proper adjustment of atomic positions to resemble discrete dislocations (DD’s) and then the application of equations of motion to the relaxed configuration of this adjustment. The interatomic potential used for atomistic simulation is Finnis-Sinclair Embedded-Atom-Method (FS-EAM) as many-body interatomic potential and the Nose-Hoover thermostat has been implemented to adjust the modulation of...
A Temperature-Dependent Coarse-Graining Method for Nano Crystalline Materials
, M.Sc. Thesis Sharif University of Technology ; Khoie, Amir Reza (Supervisor) ; Jahanshahi, Mohsen (Co-Advisor)
Abstract
The molecular dynamic (MD) method was first reported by Alder and Wainwright in the late 1950s to study the interaction of hard spheres. Molecular dynamic (MD) simulation is a technique for computing equilibrium and forwarding properties for classical many-body systems. This is a reasonable and often excellent approximation for a wide range of systems and properties. Although molecular dynamics method provide the kind of detail necessary to resolve molecular structure and localized interaction, this fidelity comes with a price. Namely, both the size and time scales of the model are limited by numerical and computational boundaries.The multi scale approach taken by the computational materials...