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The question of Pr in HTSC
, Article Proceedings of the Second Regional Conference on Magnetic and (MSS-01), Irbid, 9 September 2001 through 13 September 2001 ; Volume 321, Issue 1-4 , 2002 , Pages 265-282 ; 09214526 (ISSN) ; Sharif University of Technology
2002
Abstract
Among all the rare earth elements, Pr is known to behave as a singularity in the high-Tc families. When high-temperature cuprates are doped with Pr the superconductivity is quenched, and a metal insulator transition occurs. The origin of this behavior, being of fundamental interest, may also shed light on the mechanism of high-temperature superconductivity, since any reasonable theory for this mechanism should explain the behavior of the Pr-based system. The physical properties and the several theories which have been proposed to describe the anomalous behavior of Pr-doped systems in the normal and superconducting states are reviewed. © 2002 Elsevier Science B.V. All rights reserved
Mis-substitution effect in Gd1-xPrxBa2Cu3O7-δ system
, Article Proceedings of the Second Regional Conference on Magnetic and (MSS-01), Irbid, 9 September 2001 through 13 September 2001 ; Volume 321, Issue 1-4 , 2002 , Pages 301-304 ; 09214526 (ISSN) ; Khosroabadi, H ; Akhavan, M ; Sharif University of Technology
2002
Abstract
On polycrystalline Gd1-xPrxBa2Cu3O7-δ, samples with x = 0.00, 0.05, 0.10, and 0.15, SEM, XRD, and electrical transport experiments have been carried out. Although the samples are homogenous, granular, and show a superconducting transition, the Tc decreases and the transition temperature width increases with increasing doping concentration x. Using Rietveld analysis of the XRD patterns, we have examined the real substitution positions of Gd, Pr, and Ba atoms in these samples. Our results show that the mentioned atoms occupy their own sites, and there is no Gd or Pr at the Ba site and vice versa (i.e., no mis-substitution). Thus, in our samples, Pr atom at rare earth sites suppress the...
Possible superconductivity in bu-rich prl23
, Article Journal of Superconductivity and Novel Magnetism ; Volume 17, Issue 6 , 2004 , Pages 749-753 ; 15571939 (ISSN) ; Modarreszadeh, M ; Taheri, P ; Akhavan, M ; Sharif University of Technology
2004
Abstract
Polycrystalline (Pr1-xBax)Ba2Cu3O 7-δ samples with 0.0 < x < 0.6 are prepared by the standard solid state reaction technique. X-ray diffraction and resistivity measurements are performed. For x < 0.3, the 123 phase is formed, but for x > 0.3, due to the solubility limit, the 123 phase is not the dominant phase. The normalized resistivity increases with the increase of Ba doping to about x = 0.08, and then decreases in the 123 phase up to x = 0.3. The existence of an extremum in the resistivity is explained as the competition between scattering by impurities and increase of the number of carriers by Ba doping. For x > 0.3, due to a large increase in the non-123 phase formation, the...
Pseudogap in Gd-based 123 HTSC
, Article Physica B: Condensed Matter ; Volume 336, Issue 3-4 , 2003 , Pages 410-419 ; 09214526 (ISSN) ; Akhavan, M ; Sharif University of Technology
2003
Abstract
The Gd(Ba2-xPrx)Cu3O7+δ single phase polycrystalline samples with 0.00 ≤ x < 1.00 were investigated for pseudogap phenomenon in comparison with the (Gd1-xPrx)Ba2Cu3O7-δ compound. The measured XRD and its Rietveld refinement show that Pr is substituted at Ba site, with its stoichiometric order, and an orthorhombic-tetragonal transition occurs at x = 0.20. For x ≥ 0.60, the solubility limit of the system exceeds. Based on the resistivity measurements, the effect of Pr substitution in 123 structure of HTSC at Gd or Ba site is to increase the pseudogap temperature Ts, although, Pr at Ba site has a stronger effect on the suppression of Ts and superconductivity. Pr-doping not only reduces the...
Simulation of Transport Phenomena in Gas Injection in the Eye
, M.Sc. Thesis Sharif University of Technology ; Abdekhodaie, Mohammad Jafar (Supervisor) ; Goodarznia, Iraj (Supervisor)
Abstract
Retinal detachment is a disorder of the eye in which a part or entire retina detaches from underlying layers. It is a medical emergency and if it is not treated, all vision may be lost. Surgery is the only way to treat retinal detachment. Pneumatic retinopexy (PR) is an office-based procedure for repairing some retinal detachment. PR has three cardinal steps: applying laser or cryopexy around all breaks to seal them, injection of gas into the vitreous cavity and appropriate head position so that the bubble closes the retinal breaks.
In this thesis, we are trying to model PR procedure and predict the behavior of intraocular gas. In general, once the gas is injected into the eye, because...
In this thesis, we are trying to model PR procedure and predict the behavior of intraocular gas. In general, once the gas is injected into the eye, because...
Flux dynamics in-Ln(Ba2-xPrx)Cu3O 7+δ (Ln = Tm, Lu)
, Article Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers ; Volume 45, Issue 2 A , 2006 , Pages 742-751 ; 00214922 (ISSN) ; Akhavan, M ; Sharif University of Technology
2006
Abstract
Single-phase Tm(Ba2-xPrx)Cu3O 7+δ and Lu(Ba2-xPrx)Cu3O 7+δ compounds with Pr content 0.0 ≤ x ≤ 1.0 have been prepared by solid-state reaction technique. The oxygen content of our samples is more than 7. X-ray diffraction (XRD) patterns demonstrate an orthorhombic to tetragonal transition with an increase in Pr content in both systems. For each system, a solubility limit exists for substitution of Pr at the Ba site. The intergrain region investigated by the thermally activated flux creep (TAFC) and Ambegaokar-Halperin (AH) models, show that the pinning energy decreases with increasing Pr content; it also decreases in each sample with increasing magnetic field as a power-law relation. The...
Magnetoresistance in Gd(Ba2-xPrx)Cu3O7+δ system
, Article Physica C: Superconductivity and its Applications ; Volume 390, Issue 2 , 2003 , Pages 134-142 ; 09214534 (ISSN) ; Akhavan, M ; Sharif University of Technology
2003
Abstract
The magnetoresistance measurements of single phase polycrystalline Gd(Ba2-xPrx)Cu3O7+δ and (Gd1-xPrx)Ba2Cu3O7-δ samples have been compared and analyzed by the Ambegaokar and Halperin phase slip model. The derived power law dependences of pinning energy to applied magnetic field and temperature have been studied for different amounts of Pr doping. The power factors depend on the Pr doping. Moreover, in both systems, the magnetic field dependence of the pinning energy power factor increases for small amounts of Pr doping, while for larger amount of Pr doping, it decreases. The derived critical magnetic field at zero temperature limit is in good agreement with other model-based and...
Effect of Pr doping on transport properties of Nd(Ba2-xPr x)Cu3O7+8
, Article Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers ; Volume 44, Issue 11 , 2005 , Pages 7934-7942 ; 00214922 (ISSN) ; Akhavan, M ; Sharif University of Technology
2005
Abstract
Solid-state-reacted polycrystalline Nd(Ba2-xPr x)Cu3O7+8 materials have been prepared and investigated using X-ray diffraction and resistivity measurements. Our results show that Nd(Ba2-xPrx)Cu3O7+8 is a superconductor when x < 0.3. The Tc depression in superconductivity of Pr at Ba sites is due to both hole filling/localization and depairing effects. The normal state conductivity undergoes a dimensional crossover from two-dimensional to three-dimensional in the frame of the variable range hopping regime. The localization length of carriers shows that Pr doping localizes carriers in the normal state and causes the Tc depression. The magnetoresistance of the samples has been investigated...
Phase behavior assessment of deposition compound (asphaltene) in heavy oil
, Article 11th ADIPEC: Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 10 October 2004 through 13 October 2004 ; 2004 , Pages 783-799 ; Nikookar, M ; Ganbarnezhad, R ; Pazuki, G. R ; Hosienbeigi, H. R ; Sharif University of Technology
Society of Petroleum Engineers (SPE)
2004
Abstract
In this paper, the soave-Redlich-Kwong (SRK) Eos is modified based on perturbation theory. The parameter of the new cubic equation of state considered reduced temperature and a centric factor dependent. The average of absolute deviations of predicted vapor pressure, vapor volume and saturated liquid density of 30 pure compounds are 0.814.2.G14 and 5.814%, respectively. Also comparison with the new equation of vaporization of pure compounds are given. The florry-Hugines (FH) model is similarly modified by an adjustable parameter. This parameter is defined based on molecular weight of asphaltene to molecular weight of heavy oil ratio in form of polynomial function. The phase behavior of...
Control of an Islanded Multi-DG Microgrid under Unbalanced and Nonlinear Loads Conditions
, Ph.D. Dissertation Sharif University of Technology ; Mokhtari, Hossein (Supervisor) ; Karimi, Houshang (Co-Advisor)
Abstract
Nowadays, the use of distributed generation (DG) units and microgrid systems is mainly limited to their operation in the grid-connected mode. In the grid-connected mode, a microgrid including its loads and DG units is connected to the main grid at the point of common coupling (PCC). In this case, the main grid provides fixed voltage and frequency for the microgird and each DG unit regulates its power components based on the conventional dq-current control strategy. Autonomous (islanded) operation of a microgrid, however, is not as straightforward as its operation in the grid-connected mode, i.e., control and power management of an islanded microgrid is very difficult due to the stochastic...
Robust Control of an Islanded Microgrid Based on Droop Strategy
, M.Sc. Thesis Sharif University of Technology ; Karimi, Hoshang (Supervisor)
Abstract
Nowadays, the use of distributed generation (DG) units and microgrid systems is mainly limited to their operation in the grid-connected mode. In the grid-connected mode, a microgrid including its loads and DG units is connected to the main grid at the point of common coupling (PCC). In this case, the main grid provides fixed voltage and frequency for the microgird and each DG unit regulates its power components based on the conventional dqcurrent control strategy. Autonomous (islanded) operation of a microgrid, however, is not as straightforward as its operation in the grid-connected mode, i.e., control and power management of an islanded microgrid is very difficult due to the stochastic...
Design and Implementation of Grid Connected Inverter For Renewable Energy Sources
, M.Sc. Thesis Sharif University of Technology ; Rajabi, Abbas (Supervisor) ; Imaneini, Hossein (Co-Advisor)
Abstract
Renewable energy sources have significantly used in recent years and the associated technologies have been widely developed. Grid connection of most renewable technologies, such as photovoltaic and wind turbine, is accomplished using power electronic converters. Control of injected active and reactive power as well as current and frequency control of is, so, implemented through the power converter. Inverter is among the equipments widely used for grid connection The purpose of this project was to design and develop an inverter for grid connection of renewable generation technologies for laboratory use. The inverter is aimed to control both injected active and reactive power. A full-bridge...
Design and Construction of 8 Kilowatt-hour Battery Bank Connected to the Grid in order to Reduce the Peak Load
, M.Sc. Thesis Sharif University of Technology ; Rajabi Ghahnavieh, Abbas (Supervisor) ; Moeini Aghtaie, Moein (Co-Supervisor)
Abstract
With the increase of electric energy demand, one of the human concerns is to create the infrastructure for the production and transmission of energy in order to meet this need. Since the network must have the ability to supply the load during the peak load times, practically during the non-peak load times, many production capacities remain unused and their productivity decreases. One of the ways to reduce this problem due to the increase in penetration of batteries in the network can be the participation of battery banks to inject power into the network during peak load times. The goal of this project is to develop an 8 kilowatt-hour battery bank system that can inject 2 kilowatts of power...
Integrating hybrid power source into an Islanded MV microgrid using CHB multilevel inverter under unbalanced and nonlinear load conditions
, Article IEEE Transactions on Energy Conversion ; Volume 28, Issue 3 , 2013 , Pages 643-651 ; 08858969 (ISSN) ; Ghazanfari, A ; Mokhtari, H ; Karimi, H ; Sharif University of Technology
2013
Abstract
This paper presents a control strategy for an islanded medium voltage microgrid to coordinate hybrid power source (HPS) units and to control interfaced multilevel inverters under unbalanced and nonlinear load conditions. The proposed HPS systems are connected to the loads through a cascaded H-bridge (CHB) multilevel inverter. The CHB multilevel inverters increase the output voltage level and enhance power quality. The HPS employs fuel cell (FC) and photovoltaic sources as the main and supercapacitors as the complementary power sources. Fast transient response, high performance, high power density, and low FC fuel consumption are the main advantages of the proposed HPS system. The proposed...
A novel LQR based optimal tuning method for IMP-based linear controllers of power electronics/power systems
, Article Proceedings of the IEEE Conference on Decision and Control, 12 December 2011 through 15 December 2011 ; 2011 , Pages 7711-7716 ; 01912216 (ISSN) ; 9781612848006 (ISBN) ; Edrington, C. S ; Mokhtari, H ; Sharif University of Technology
2011
Abstract
This paper presents a new method for tuning linear controllers such as Proportional-Integrating (PI) and Proportional-Resonant (PR) structures which are frequently used in different power electronic and power system applications. Those controllers are placed within a general structure offered by the Internal Model Principle (IMP) of control theory. In this paper, the first perspective uses the well-known concept of Linear Quadratic Regulator (LQR) to address the problem as a regulation problem. Matrix Q of the LQR design is then finely adjusted in order to assure desired transient response for the system. The second perspective is based on redefining the LQR problem in order to make it...
Measurement and correlation of CO2 solubility in the systems of CO2 + toluene, CO2 + benzene, and CO2 + n-hexane at near-critical and supercritical conditions
, Article Journal of Chemical and Engineering Data ; Volume 51, Issue 6 , 2006 , Pages 2197-2200 ; 00219568 (ISSN) ; Taghikhani, V ; Ghotbi, C ; Sharif University of Technology
2006
Abstract
The solubility of CO2 in the systems of CO2 + benzene, CO2 + n-hexane, and CO2 + toluene was meticulously measured at (293.15, 298.15, and 308.15) K and different pressures using a pressure-volume-temperature (PVT) apparatus. Also the effect of pressure on the solubility of CO2 in the organic solvents used in this work was investigated. The Peng-Robinson equation of state (PR EOS) with only one temperature-independent binary interaction parameter was used in correlating the experimental data. The results showed that the PR EOS can accurately correlate the experimental data for the solubility of CO2 in the organic solvents at high pressure. In case of the systems CO2 + benzene and CO2 +...
A control method for integrating hybrid power source into an islanded microgrid through CHB multilevel inverter
, Article PEDSTC 2013 - 4th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2013 , Pages 495-500 ; 9781467344845 (ISBN) ; Hamzeh, M ; Mokhtari, H ; Sharif University of Technology
2013
Abstract
This paper proposes a control strategy for an islanded microgrid to effectively coordinate hybrid power source (HPS) units and to robustly control individual interfaced inverters under unbalanced and nonlinear load conditions. Cascaded H-bridge (CHB) multilevel inverters are flexibly deployed in order to enhance the power quality and redundancy. The HPS employs fuel cell (FC) as the main and supercapacitors (SC) as complementary power sources. Fast transient response; high performance; and high power density are the main characteristics of the proposed HPS system. The presented control strategy consists of a power management strategy for the HPS units and a voltage control strategy for the...
A proportional-resonant controller-based wireless control strategy with a reduced number of sensors for parallel-operated UPSs
, Article IEEE Transactions on Power Delivery ; Volume 25, Issue 1 , 2010 , Pages 468-478 ; 08858977 (ISSN) ; Caglar Onar, O ; Mokhtari, H ; Khaligh, A ; Sharif University of Technology
Abstract
In this paper, a novel droop method to control the power sharing of parallel uninterruptible-power-supply (UPS) systems is presented. In a clear-cut contrast to the previously reported works, the controller is a proportional-resonant controller which ensures good transient response and steady-state objectives. Furthermore, the need for sensing the output current for the power-sharing control is removed by implementing it in a software routine. This brings a less complicated and less expensive structure in which the number of feedback sensors is reduced from three to two. The droop paralleling strategy is based on the drop in the inverter output frequency and amplitude. The application of...
Error performance analysis for generalized orthogonal frequency division multiplexing
, Article Computers and Electrical Engineering ; Volume 61 , 2017 , Pages 139-150 ; 00457906 (ISSN) ; Khalaj, B. H ; Haghbin, A ; Sharif University of Technology
Abstract
Generalized Frequency Division Multiplexing (GFDM) is a cyclic filtered multicarrier modulation that may be employed for many new wireless applications. However, due to its non-orthogonal structure, a trade-off between the complexity and error performance should be considered in the design of GFDM receivers. This study proposes an orthogonal cyclic filtered multicarrier modulation called Generalized Orthogonal Frequency Division Multiplexing (GOFDM), which is based on the cyclic Perfect Reconstruction-Quadrature Mirror Filter (PR-QMF) bank. We first derive the frequency domain matrix descriptions for GOFDM linear receivers based on which, the impact of PR-QMF bank on the GOFDM error...
Evaluation of PR steel frame connection with torsional plate and its optimal placement
, Article Scientia Iranica ; Volume 25, Issue 3A , 2018 , Pages 1025-1038 ; 10263098 (ISSN) ; Estekanchi, H.E ; Yekrangnia, M ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
Characteristics of connections in steel moment-resisting frames are of utmost importance in determining the seismic performance of these structural systems. The results of several previous experimental studies have indicated that Partially Restrained (PR) connections possess excellent properties, which make them a reliable substitution for Fully Restrained (FR) connections. These properties include needing less base shear, being more economic, and, in many cases, being able to absorb more energy. In this study, the behavior of two proposed PR connections with torsional plate is studied through finite element simulations. The results of the numerical studies regarding initial stiffness and...