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potential-energy-surfaces
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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...
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...
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...
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
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
Optimal placement of unified power flow controllers (UPFCs) using mixed-integer non-linear programming (MINLP) method
, Article 2009 IEEE Power and Energy Society General Meeting, PES '09, 26 July 2009 through 30 July 2009, Calgary, AB ; 2009 ; 9781424442416 (ISBN) ; Fotuhi Firuzabad, M ; Khodaei, A ; Faried, S. O ; Sharif University of Technology
Abstract
Utilization of Unified Power Flow Controllers (UPFCs) can be more beneficial in the restructured power systems due to their capabilities in increasing the transmission line capacities as well as shunt reactive compensation. So, these devices should be installed such that the most benefit can be gained. In this paper, the problem of optimal placement of UPFCs is solved using Mixed-Integer Non-Linear Programming (MINLP) method. Hence, the problem is completely formulated based on this method and is solved using available commercial solvers. The salient feature of this method is having potential to simultaneously determine the optimal location of multi UPFCs. Also, since a full AC Optimal Power...
Conformation of gemcitabine: an experimental NMR and theoretical DFT study
, Article Scientia Iranica ; Volume 25, Issue 3C , 2018 , Pages 1354-1363 ; 10263098 (ISSN) ; Tafazzoli, M ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
The structural and conformational behavior of gemcitabine (20; 20-diuoro cytidine) was investigated by advanced NMR experiments and a computational quantum mechanical method (DFT) using Potential Energy Scanning (PES) in gas and solution phases in the Polarizable Continuum Model (PCM). Three stable conformers (G1, G2, and G3) were predicted from minimum points in a potential energy diagram. In order to measure coupling constant values, a set of 2D spectra (H-H COSY, H-C HMQC, and H-C HMBC) was analyzed. Optimized structures and spin-spin coupling constant calculations in gas and solution phases were performed by B3LYP/6-311++G(d,p) method. Both energy and NMR parameters showed that G1-form...
A performance-based markov modeling for reliability evaluation of competitive electricity markets
, Article Proceedings of the 10th IASTED International Conference on Power and Energy Systems, PES 2008, 16 April 2008 through 18 April 2008, Baltimore, MD ; 2008 , Pages 215-220 ; 9780889867383 (ISBN) ; Ranjbar, A. M ; Fotuhi Firuzabad, M ; Sharif University of Technology
2008
Abstract
In the new deregulated environment of electric power utility industry, new system reliability criteria and analytical tools are required. This paper proposes an analytical probabilistic model for reliability evaluation of competitive electricity markets. The market reliability is evaluated by using Markov state space diagram. Since the market is a continuously operated system, the concept of absorbing states is applied to it in order to evaluate the reliability. The market states are identified by using market performance indices and the transition rates are calculated by using historical data. To illustrate interesting feature of the proposed methodology, a case study is carried out over a...
Observability and estimation of transformer tap setting with minimal PMU placement
, 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) ; Hosseini, S. H ; Sharif University of Technology
2008
Abstract
One of the most important applications of phasor measurement units (PMUs) is power system state estimation. Some models have been proposed for including phasor measurements in the state estimation. But, all of these models have treated transformer tap settings (voltage transformer turns ratio and phase-shift transformer angle) as fixed parameters of the network. The accuracy of state estimation may decrease when a tap changes or the true value is unknown. In this paper, each transformer tap setting is added as a new state variable to the states vector, converting the linear PMU based state estimation to a nonlinear one. Also, the network observability is analyzed including the observability...
Concept of best energy transfer scenario and a true expression for power factor
, 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
The best energy transfer scenario (BETS) is a situation under which the optimum transfer of power (or energy) from the electric utility to an electric power consumer is achieved. Such a scenario is important because it is used as a reference point to evaluate how efficient the load operates. The index of power factor (PF) is used to quantify such an efficiency. The closer the PF to unity corresponds to more efficient performance of the load. This paper is to show that the conventional definition of the BETS is inadequate and results in an unfair value for the PF unless the transmission line is perfect and lossless (which is an unrealistic condition). The paper also investigates an...
Optimum simultaneous clearing of energy and spinning reserve markets using cost/benefit analysis
, 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) ; Fotuhi Firuzabad, M ; Zareipour, H ; Sharif University of Technology
2008
Abstract
Considering the high level of interactions between energy and reserve markets, simultaneous clearing of these markets has been shown to provide more efficient solutions, than a sequential market clearing process. In addition, determining reserve requirements based on probabilistic approaches results in more economical efficiency, while maintaining an acceptable level of reliability, compared to deterministic approaches. This paper proposes a new method for clearing energy and spinning reserve markets simultaneously, while at the same time, spinning reserve requirements are determined based on a cost/benefit analysis as a probabilistic-based approach. This cost/benefit analysis considers both...
A new algorithm for fault location on transmission lines
, Article 2009 IEEE Power and Energy Society General Meeting, PES '09, Calgary, AB, 26 July 2009 through 30 July 2009 ; 2009 ; 9781424442416 (ISBN) ; Daniar, S ; Akhbari, M ; Sharif University of Technology
IEEE
2009
Abstract
In this paper, a new algorithm for fault detection/location on transmission line based on linear state estimation is presented. The proposed technique uses phasor measurements from PMU's. Fault location and voltage of fault point are added as the new state variables in a linear state estimator based on PMU data. In addition, by using the ability of bad data identification in the state estimation, a new scheme for fault location and identification of faulted transmission line is proposed. For test and validation of the proposed algorithm, simulation results on a six bus test case are presented. ©2009 IEEE
Optimal reactive power dispatch using the concept of dynamic VAR source value
, Article 2009 IEEE Power and Energy Society General Meeting, PES '09, 26 July 2009 through 30 July 2009, Calgary, AB ; 2009 ; 9781424442416 (ISBN) ; Parniani, M ; Sharif University of Technology
Abstract
Voltage stability is the ability of a power system to maintain acceptable voltages at all buses in the system under normal conditions and after being subjected to a disturbance. This paper employs the management of reactive power generation to improve the voltage stability margin (VSM), in the framework of optimal reactive power dispatch (ORD) problem. Scheduling of VAR sources is performed using the concept of relative value of VAR sources. The proposed methodology has been tested on the IEEE 14-bus test system. Simulation results show that after the optimal reactive power scheduling, VSM of the systems is increased considerably. In addition, it is observed that reactive power reserve is...
Risk based maintenance optimization of overhead distribution networks utilizing priority based dynamic programming
, Article 2009 IEEE Power and Energy Society General Meeting, PES '09, 26 July 2009 through 30 July 2009, Calgary, AB ; 2009 ; 9781424442416 (ISBN) ; Fotuhi Firuzabad, M ; Abiri Jahromi, A ; Sharif University of Technology
Abstract
This paper presents a priority based dynamic programming approach for long term maintenance scheduling of overhead distribution networks. The proposed approach is based on risk management approach and utilizes the model of decoupled risk factors. Two heuristic factors are defined and utilized in order to establish a maintenance priority list and to curtail the dynamic programming search space. The proposed methodology yields a significant computational saving compare to the previously reported dynamic programming. Risk management approach enables the asset managers to consider the actual condition of electrical equipments and expected consequence of their failures. Furthermore, the decoupled...
Limiting fault currents in wind power plants using superconductive shielded core reactors
, 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) ; Salehfar, H ; Varahram, H ; Sharif University of Technology
2008
Abstract
In this paper we investigate the effects of superconducting shielded core reactor (SSCR) on the operation of induction generators. Large number of induction generators used in wind power plants generally increase the short circuit current level of the system. The reason is that they provide parallel reduced-impedance paths for the fault currents. Taking advantage of SSCR in wind power plants allows for using these generating units in large numbers with no concerns about the system fault current increments. The study is performed on a test system using the conventional model of an induction generator and a new effective model for SSCR based on its shielding behavior. Mathematical equations...
New Karplus equations for 2JHH, 3JHH, 2JCH, 3JCH, 3JCOCH, 3JCSCH, and 3JCCCH in some aldohexopyranoside derivatives as determined using NMR spectroscopy and density functional theory calculations
, Article Carbohydrate Research ; 2007 , Pages 2086-2096 ; 00086215 (ISSN) ; Volume 342, Issue 14 ; Ghiasi, M ; Sharif University of Technology
2007
Abstract
The 1H-13C coupling constants of methyl α- and β-pyranosides of d-glucose and d-galactose have been measured by one-dimensional and two-dimensional 1H-13C heteronuclear zero and double quantum, phase sensitive J-HMBC spectra to determine a complete set of coupling constants (1JCH, 2JCH, 3JCH, 2JHH, and 3JHH) within the exocyclic hydroxymethyl group (CH2OH) for each compound. In parallel with these experimental studies, structure, energy, and potential energy surfaces of the hydroxymethyl group for these compounds were determined employing quantum mechanical calculations at the B3LYP level using the 6-311++G** basis set. Values of the vicinal coupling constants involving 1H and 13C in the...