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Conformational behavior and potential energy profile of gaseous histidine
, Article Journal of Molecular Structure: THEOCHEM ; Volume 960, Issue 1-3 , November , 2010 , Pages 73-85 ; 01661280 (ISSN) ; Tavasoli, E ; Fattahi, A ; Sharif University of Technology
2010
Abstract
Histidine as a natural amino acid is found to be biologically important and is known to function as a nucleophile or enzyme co-factor, or in proton transfer process. The properties of gaseous aromatic amino acid histidine depend on the structural forms it may take in gas-phase. Ab initio method has been used to characterize the gas-phase conformer/tautomers of histidine. Wide range of possible structures for histidine was surveyed at the MM level, and then the geometries of the unique conformers were refined at the B3LYP/6-311++G (d,p) levels. At this theoretical level, 25 conformers were located for both tautomers of histidine i.e., His [NπH] and His [NτH]. The MM level provides a poor...
A modified square well model in obtaining the surface tension of pure and binary mixtures of hydrocarbons
, Article Journal of Chemical Thermodynamics ; Volume 40, Issue 7 , 2008 , Pages 1131-1135 ; 00219614 (ISSN) ; Taghikhani, V ; Ghotbi, C ; Ayatollahi, S ; Sharif University of Technology
2008
Abstract
A model based on the perturbation theory of fluids was proposed to correlate the experimental data for surface tension of pure hydrocarbons in a wide range of temperature. The results obtained for the pure hydrocarbons were directly used to predict the surface tension for binary hydrocarbon mixtures at various temperatures. In the proposed model, a modified form of the square well potential energy between the molecules of the reference fluid was taken into account while the Lennard-Jones dispersion energy was considered to be dominant amongst the molecules as the perturbed term to the reference part of the model. In general, the proposed model has three adjustable parameters which are chain...
A combined first principles and analytical treatment for determination of the surface elastic constants: Application to Si(001) ideal and reconstructed surfaces
, Article Philosophical Magazine Letters ; Volume 92, Issue 1 , Sep , 2012 , Pages 7-19 ; 09500839 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2012
Abstract
Behavior of nanostructures, which are characterized by a large surface-to-volume ratio, is greatly influenced by their surface parameters, such as surface elastic moduli tensor. Accurate determination of the surface elastic constants by first principles is of particular interest. To this end, through consideration of the fundamental thermodynamic arguments for free solid surfaces, an analytical formulation for the change in specific Helmholtz surface free energy is developed. Relating this formulation to the corresponding energy calculated via first principles leads to the determination of the surface elastic moduli tensor. The surface mechanical properties, namely surface energy, surface...
Survying the Process of Photodissociation of Methane with Using the Femto Second Lasers
, M.Sc. Thesis Sharif University of Technology ; Sadighi Bonabi, Rasoul (Supervisor)
Abstract
In this project , the dissociation of methane in the presence of Ti:Sapphire laser with parameters of 1014wcm-2, 800nm wave lengths and 100fs pulse width have been investigated theoretically, by using the Gaussian03 package –computational chemistry program that is capable of predicting many properties of atomic and molecular systems. It is based upon the fundamental laws of quantum mechanism. By considering some limitations in approximate techniques and incapability of advancing them, numerical calculation of solving the time dependent Schrödinger equation in order to improve the results and find more quantum dynamic information is applied. Therefore at first, by Gaussian03 package some of...
Separation of Hydrogen Molecule from Methane Molecule by Intense Femtosecond Laser Pulses
, M.Sc. Thesis Sharif University of Technology ; Sadighi Bonabi, Rasoul (Supervisor)
Abstract
Conversion of Methane molecule to valuable heavier hydrocarbon and hydrogen by using of short pulse lasers is investigated. The dynamical information of molecule such as orientation, dipole moment variations with binding length, and potential energy levels are initially produced by using Gaussian software. Based on this information the Schrödinger wave equation for this polyatomic molecule is numerically solved. Then by selecting the various laser parameters and installing of them in the Hamiltonian of the mentioned system, the dependence of hydrogen transition and separation probability on these parameters are investigated. In this work by radiating of the laser beam along the C2 symmetry...
Ant colony optimization-based approach to optimal reactive power dispatch: A comparison of various Ant systems
, Article 2007 IEEE Power Engineering Society Conference and Exposition in Africa, PowerAfrica, Johannesburg, 16 July 2007 through 20 July 2007 ; 2007 ; 1424414784 (ISBN); 9781424414789 (ISBN) ; Hosseini, S. H ; Sharif University of Technology
2007
Abstract
The optimal reactive power dispatch (ORPD) problem is formulated as a combinatorial optimization problem involving nonlinear objective Junction with multiple local minima. In this paper, as a new approach, different ant colony optimization (ACO) algorithms are applied to the reactive power dispatch problem. Ant system (AS), the firstly introduced ant colony optimization algorithm, and its direct successors, elitist ant system (EAS), rank-based ant system (ASrank) and max-min ant system (MMAS), are employed to solve the reactive power dispatch problem. To analyze the efficiency and effectiveness of these modern search algorithms, the proposed methods are applied to the IEEE 30-bus system and...
Theoretical investigation of the hydrogen abstraction reaction of the OH radical with CH2FCH2F (HFC-152): A dual-level direct dynamics study
, Article Journal of Physical Chemistry A ; Volume 111, Issue 33 , 2007 , Pages 8095-8103 ; 10895639 (ISSN) ; Parsafar, G. A ; Sharif University of Technology
2007
Abstract
The hydrogen abstraction reaction of the OH radical with CH 2FCH22F (HFC-152) is studied theoretically over the 150-3000 K temperature range. In this study, the two most recently developed hybrid density functional theories, namely, BBlK and MPWBlK, are applied, and their efficiency in reaction dynamics calculation is discussed. The BBlK/6-31+G(d,p) method gives the best result for the potential energy surface (PES) calculations, including barrier heights, reaction path information (the first and second derivatives of PES), geometry of transition state structures, and even weak hydrogen bond orientations. The rate constants were obtained by the dual-level direct dynamics with the...
Van der Waals energy surface of a carbon nanotube sheet
, Article Solid State Communications ; Volume 152, Issue 3 , February , 2012 , Pages 225-230 ; 00381098 (ISSN) ; Shayeganfar, F ; Neek Amal, M ; Sharif University of Technology
Abstract
The van der Walls interaction between a carbon nanotube sheet (CNTS) and a rare gas atom, is studied using both atomistic and continuum approaches. We present analytical expressions for the van der Waals energy of continuous nanotubes interacting with a rare gas atom. It is found that the continuum approach does not properly treat the effect of atomistic configurations on the energy surfaces. The energy barriers are small as compared to the thermal energy, which implies the free motion above the CNTS in heights about one nanometer. In contrast to the energy surface of a graphene sheet, the honeycomb lattice structure in the energy surface of a CNTS is imperceivable. Defects alter the energy...
Topologic Properties Of The Energy Landscape Network In Frustrated Systems
, M.Sc. Thesis Sharif University of Technology ; Ejtehadi, Mohammad Reza (Supervisor)
Abstract
The study of Energy Landscape of physical systems has a key role in complex problems. In this project we have enumerated the energy landscape of a finite squared lattice spin glass with nearest neighbored interactions to study its behavior. We choose the coupling constants of this spin glass system with Heb rule. According to this rule the coupling constants are chosen in a way to make specific patterns of spin configuration as a local minimum. We have studied these spin glasses with different number of patterns. In our computation we saw a significant difference between spin glasses with odd and even number of patterns. We addressed this behavior to properties of coupling constant...
Surface energy effects on the yield strength of nanoporous materials containing nanoscale cylindrical voids
, Article Mechanics of Materials ; Volume 42, Issue 9 , September , 2010 , Pages 852-862 ; 01676636 (ISSN) ; Avazmohammadi, R ; Naghdabadi, R ; Sharif University of Technology
2010
Abstract
Surfaces and interfaces behave differently from their bulk counterparts especially when the dimensions approach small scales. The recent studies have shown that the surface/interface free energy (surface stress) plays an important role in the effective mechanical properties of solids with nanosized inhomogeneities. In this work, within a micromechanical framework, the effect of surface stress is taken into account to obtain a macroscopic yield function for nanoporous materials containing cylindrical nanovoids. Gurtin-Murdoch model of surface elasticity is incorporated in the generalized self-consistent method to obtain a closed-form expression for the transverse shear modulus of transversely...
Surface elasticity revisited in the context of second strain gradient theory
, Article Mechanics of Materials ; Volume 93 , 2016 , Pages 220-237 ; 01676636 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Elsevier
Abstract
Surface/interface stresses, when notable, are closely associated with a surface/interface layer in which the interatomic bond lengths and charge density distribution differ remarkably from those of the bulk. The presence of such topographical defects as edges and corners amplifies the noted phenomena by large amounts. If the principal features of interest are such studies as the physics and mechanics of evolving microscopic-/nanoscopic-interfaces and the behavior of nano-sized structures which have a very large surface-to-volume ratio, traditional continuum theories cease to hold. It is for the treatment of such problems that augmented continuum approaches like second strain gradient and...
Forecasting market participant behavior in power market
, Article 10th IASTED International Conference on Power and Energy Systems, PES 2008, Baltimore, MD, 16 April 2008 through 18 April 2008 ; January , 2008 , Pages 192-198 ; 9780889867383 (ISBN) ; Ehsan, M ; Firuzabad, M. F ; Sharif University of Technology
2008
Abstract
Genco's offering strategies could change SCUC convergence; as a result, generation plants profit is adjusted. The minimum profit alteration with production changeless, defined as discrete strategies. Here, different discrete strategy base on marginal cost was tested and compare with other strategies. Revenue was calculated with game theory method to find Nash equilibrium as mix game; then, market power indices was estimated. These models help ISO to simulate power market and analyze it before markets occurred. Because of uncertainty in producer's strategy, model was implemented in probabilistic pivotal strategy and finally checked simulation on IEEE 30 buses test case system and market power...
On thermoelastic fields of a multi-phase inhomogeneity system with perfectly/imperfectly bonded interfaces
, Article International Journal of Solids and Structures ; Volume 45, Issue 22-23 , 2008 , Pages 5831-5843 ; 00207683 (ISSN) ; Mohammadi Shodja, H ; Sharif University of Technology
2008
Abstract
The stress fields of cylindrical and spherical multi-phase inhomogeneity systems with perfect or imperfect interfaces under uniform thermal and far-field mechanical loading conditions are investigated by use of the Boussinesq displacement potentials. The radius of the core inhomogeneity and the thickness of its surrounding coatings are arbitrary. The discontinuities in the tangential and normal components of the displacement at the imperfect interfaces are assumed to be proportional to the associated tractions. In this work, for the problems where the phases of the inhomogeneity system are homogeneous, the exact closed-form thermo-elastic solutions are presented. These solutions along with a...
Is the unity power factor realizable at the load terminals?
, Article IEEE Power and Energy Society 2008 General Meeting: Conversion and Delivery of Electrical Energy in the 21st Century, PES, Pittsburgh, PA, 20 July 2008 through 24 July 2008 ; 2008 ; 9781424419067 (ISBN) ; Khajehoddin, S. A ; Bakhshai, A ; Sharif University of Technology
2008
Abstract
Contrary to the widespread understanding, this paper shows by means of mathematics and numerics that a perfect power factor correction cannot be made at the load terminals only. To achieve a perfect power factor correction, the supply commitment is required as well. In the absence of such commitment, the power factor cannot reach unity unless we refine the very definition of power factor. But the refined power factor is then slightly higher than the conventional one. The refined expression for power factor is a function of the load parameters as well as the line characteristics. For an ideal power system (with no line losses), this coincides with the conventional formula. © 2008 IEEE
Design of Doped TiO2 Dye-sensitized Solar Cells with Different Arrangement Modes of Photoanode Electrodes
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
In this thesis, pure –known as T- and chromium doped titanium dioxide nanoparticles –known as -CTx- with different dopant atomic ratio (0.1 to 5 %at.) were synthesized using a facile, fast and efficient method. FESEM and XRD studies showed no morphologic and structural change via Cr doping of nanoparticles (size in the range of 20-30 nm). However, according to DRS analysis, Cr intrusion in TiO2 crystal structure, drastically reduced band gap energy of pure TiO2 from 3.14 eV to 1.81 eV for CT3 powder and improved absorption range of UV-Vis spectrum. Mott-Schottky plots indicated that, Cr doping, caused reduction in donor density of TiO2 and an upward shift in the conduction band edge....
Experimental investigation of extra-long pulsating heat pipe application in solar water heaters
, Article Experimental Thermal and Fluid Science ; Volume 42 , 2012 , Pages 6-15 ; 08941777 (ISSN) ; Soltanieh, M ; Shafii, M. B ; Sharif University of Technology
Elsevier
2012
Abstract
In this study, the aim is to investigate the application of pulsating heat pipes (PHPs) as a heat transfer tool in a solar water heater (SWH). For this purpose, an extra-long pulsating heat pipe (ELPHP) is designed, constructed and installed in a thermosyphon solar water heater. In this work the ELPHPs are made of copper tubes of internal diameter 2.0. mm. The number of meandering turns is 6 and the working fluid employed is distilled water. The lengths of condenser and evaporator sections are 0.8 and 0.96. m, respectively. The length of adiabatic section varies between 0.7 and 1.8. m. Inclination of the ELPHPs varies between 15° and 90° but is 45° for evaporator section. Four different...
Investigation of magnetic field effect on surface and finite-site free energy in one-dimensional Ising model of nanosystems
, Article Phase Transitions ; Volume 84, Issue 7 , Dec , 2011 , Pages 613-623 ; 01411594 (ISSN) ; Abroshan, H ; Akbarzadeh, H ; Parsafar, G ; Fortunelli, A ; Sharif University of Technology
2011
Abstract
We investigate a one-dimensional (1-D) Ising model for finite-site systems. The finite-site free energy and the surface free energy are calculated via the transfer matrix method. We show that, at high magnetic fields, the surface free energy has an asymptotic limit. The absolute surface energy increases when the value of f (the ratio of magnetic field to nearest-neighbor interactions) increases, and for f ≥10 approaches a constant value. For the values of f ≥0.2, the finite-site free energy also increases, but slowly. The thermodynamic limit in which physical properties approach the bulk value is also explored
Investigation of size effects on the physical properties of one-dimensional ising models in nanosystems
, Article Molecular Physics ; Volume 109, Issue 3 , Feb , 2011 , Pages 385-395 ; 00268976 (ISSN) ; Daryaei, E ; Parsafar, G ; Fortunelli, A ; Sharif University of Technology
2011
Abstract
Ising models in nanosystems are studied in the presence of a magnetic field. For a one-dimensional (1-D) array of spins interacting via nearest-neighbour and next-nearest-neighbour interactions we calculate the heat capacity, the surface energy, the finite-size free energy and the bulk free energy per site. The heat capacity versus temperature exhibits a common wide peak for systems of any size. A small peak also appears at lower temperatures for small arrays when the ratio of magnetic field spin interaction energy over the nearest-neighbour spin-spin interaction energy, f, is within 0 < F ≤ 0.10 . The peak becomes smaller for longer array and eventually vanishes for long arrays,...
Surface free energy of platinum nanoparticles at zero pressure: A molecular dynamic study
, Article Solid State Communications ; Volume 150, Issue 5-6 , February , 2010 , Pages 254-257 ; 00381098 (ISSN) ; Abroshan, H ; Parsafar, G. A ; Sharif University of Technology
2010
Abstract
Metallic nanoparticles are interesting because of their use in catalysis and sensors. The surface energy of the FCC platinum nanoparticles are investigated via molecular dynamics simulation using Quantum Sutton-Chen (QSC) potential. We have calculated the Gibbs free energy for the FCC platinum bulk and also for its nanoparticle. All calculations have been carried out at zero pressure. We have used the thermodynamic integration method to obtain the Gibbs free energy. The total Gibbs free energy is taken as the sum of its central bulk and its surface free energy. We have calculated the free energy of a platinum nanoparticle as a function of temperature
Locating series FACTS devices using line outage sensitivity factors and particle swarm optimization for congestion management
, Article 2009 IEEE Power and Energy Society General Meeting, PES '09, 26 July 2009 through 30 July 2009, Calgary, AB ; 2009 ; 9781424442416 (ISBN) ; Hosseini, S. H ; Sharif University of Technology
Abstract
This paper proposes a particle swarm optimization based algorithm for locating series FACTS devices in deregulated electricity markets in order to reduce and manage congestion. Line outage sensitivity factors are used to reduce the solution space and to pinpoint the lines which are more suitable for FACTS device placement. Total congestion cost and total generation cost are the two objective functions that are employed in the optimization process. In order to verify and validate the effectiveness of the proposed method, it was applied to IEEE 14-bus and IEEE 57-bus test systems. The results obtained by the proposed method were compared with those of congestion rent contribution method