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    Measurement of Critical Current Density in Bulk Superconductors Based on Small Point Contact Characterization

    , Article Journal of Superconductivity and Novel Magnetism ; 2013 , Pages 1-4 ; 15571939 (ISSN) Hosseini, N ; Zabetian, A ; Kananian, S ; Fardmanesh, M ; Sharif University of Technology
    A new approach to measure the critical current density of bulk superconductors is presented in this paper. In the proposed technique, the characterization uses a pulsed current which passes through a small point contact at the middle of the bulk and distributes uniformly, while the other contact is a copper ring around the bulk. By increasing the pulsed current above a threshold current, a normal zone appears and develops into a semi-oblate spheroid forming around the contact point. By analyzing its size and shape, and electromagnetic fundamentals, the voltage-current relationship in the normal zone is obtainable. In addition, experimental works have been performed and the results are in... 

    Artificial neural network simulator for supercapacitor performance prediction

    , Article Computational Materials Science ; Volume 39, Issue 3 , 2007 , Pages 678-683 ; 09270256 (ISSN) Farsi, H ; Gobal, F ; Sharif University of Technology
    Artificial neural network was used to calculate the performance of a model supercapacitor as signified by the power density, energy density and utilization to the synthetic, intrinsic and operating characteristics. A four-layer neural net having two hidden layers having 6 and 15 nodes was found to be well capable of simulating the capacitor performance with the convergence achieved often a relatively small number of epochs. As for the input parameters, crystal size, surface lattice length, exchange current density of the capacitor active material and the cell current employed while utilization, energy density and power density were the outputs. © 2006 Elsevier B.V. All rights reserved  

    Measurements of the plasma current density and q-profiles in IR-T1 tokamak

    , Article Journal of Fusion Energy ; Volume 29, Issue 3 , June , 2010 , Pages 232-236 ; 01640313 (ISSN) Ghoranneviss, M ; Salar Elahi, A ; Abbaspour Tehrani Fard, A ; Tajdidzadeh, M ; Sharif University of Technology
    The purposes of this paper are determination of the current density and safety factor profiles, J(r) and q(r), in IR-T1 tokamak. For these purposes, a diamagnetic loop with its compensation coil, and also an array of magnetic probes were designed, constructed, and installed on outer surface of the IR-T1 tokamak chamber, and then the poloidal beta and poloidal and radial magnetic fields measured. Moreover, a few approximate values of the internal inductance for the different possible profiles of the plasma current density are also calculated. From the results, current density and q-profiles obtained  

    Electrodeposition of nanocrystalline Zn/Ni multilayer coatings from single bath: influences of deposition current densities and number of layers on characteristics of deposits

    , Article Applied Surface Science ; Volume 404 , 2017 , Pages 101-109 ; 01694332 (ISSN) Bahadormanesh, B ; Ghorbani, M ; Lotfi Kordkolaei, N ; Sharif University of Technology
    Zn/Ni nanocrystalline multilayer coatings were electrodeposited using single bath method and switching current densities. Effect of deposition current densities (i1 and i2) and number of layers (n) on composition, surface morphology and roughness, microhardness, phase structure and corrosion resistance of Zn/Ni multilayers were studied and compared with that of single layer. Analyzing and optimizing the influences of mentioned parameters on corrosion resistance of multilayers carried out through Response Surface Methodology. The model based on RSM results demonstrated that improvement in corrosion resistance due to increase in “difference of deposition current densities” was more effective... 

    The effect of additives on anode passivation in electrorefining of copper

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 46, Issue 8 , 2007 , Pages 757-763 ; 02552701 (ISSN) Ojaghi Ilkhchi, M ; Yoozbashizadeh, H ; Sadegh Safarzadeh, M ; Sharif University of Technology
    In copper electrorefining process, some additives are added to the electrolyte to improve the morphology of cathode deposits as well as the quality of products. In the present investigation, the effects of thiourea, glue and chloride ions (as additives) on the passivation of industrial copper anodes under high current densities have been reported. Experiments were conducted at 65 °C; using a synthetic electrolyte containing 40 g/l Cu2+ and 160 g/l H2SO4. Results obtained from chronopotentiometry experiments showed that increasing the concentration of chloride ion leads to increase in passivation time. The results also indicated that from a certain level on, namely 2 ppm, the increase in... 

    Current density in the intermediate state of superconductors

    , Article Superconductor Science and Technology ; Volume 17, Issue 10 , 2004 , Pages 1189-1191 ; 09532048 (ISSN) Zakeri, Kh ; Alizad, R ; Sharif University of Technology
    In this investigation we have taken the viewpoint of the Landau theory for the normal state and have suggested a covariant equation for current density. This suggestion is based on the exact analysis of electrodynamic relations in the intermediate state of superconductors. Our analysis is restricted to the simplest electrodynamic relations. At first we have employed Maxwell's equations with the general Ohm-London equation and have found the general covariant current which takes a covariant form after Lorentz transformation. Finally we have checked it by considering two inertial frames in a simple state  

    Role of Pr doping in Gd1113

    , Article Physica Status Solidi C: Conferences ; Volume 1, Issue 7 , 2004 , Pages 1855-1858 ; 16101634 (ISSN) Kariminezhad, M ; Khosroabadi, H ; Akhavan, M ; Sharif University of Technology
    Tetragonal Gd1-xPrxBaSrCu3O 7-δ polycrystalline samples (0 ≤ x ≤ 0.9) have been prepared by the standard solid-state reaction and characterized by XRD. A hump on the ρ(T) curve have been observed at about 80 K for large values of x. The normal state resistivity have been investigated with two and three dimensional variable range hopping (2&3D-VRH) and Coulomb gap (CG). For low concentration of Pr, 2D-VRH is the dominant mechanism, but with the increase of x, 3D-VRH is dominant. The magnetoresistance measurements of the samples have been analysed by the Ambegakor and Halperin (AH) phase slip model. The field dependences of the pinning energy and critical current density have been studied for... 

    The effects of porosity distribution variation in GDL on PEM fuel cell performance

    , Article Second International Conference on Fuel Cell Science, Engineering and Technology, Rochester, NY, 14 June 2004 through 16 June 2004 ; 2004 , Pages 587-594 ; 0791841650 (ISBN); 9780791841655 (ISBN) Roshandel, R ; Farhanieh, B ; Saievar Iranizad, E ; Sharif University of Technology
    American Society of Mechanical Engineers  2004
    Gas diffusion layers are one of the important parts of the PEM fuel cell as they serve to transport the reactant gases to the catalyst layer. Porosity of this layer has a large effect on the PEM fuel cell performance. The spatial variation in porosity arises due to two effects: 1. Compression of the electrode on the solid landing areas and 2. Water produced at the cathode side of gas diffusion layers. Both of these factors change the porosity of gas diffusion layers and affects fuel cell performance. To implement this performance analysis, a mathematical model which considers oxygen and hydrogen mass fraction in gas diffusion layer and the electrical current density in the catalyst layer,... 

    Optimization of waveform shape and frequency in periodic reverse electroplating

    , Article 12th International Conference on Microelectronics, ICM 2000, 31 October 2000 through 2 November 2000 ; Volume 2000-October , 2000 , Pages 335-339 ; 9643600572 (ISBN) Motieifar, A ; Khorasani, S ; Rashidian, B ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2000
    In this report, the time-dependent carrier concentration in electrolytic cells, due to some basic periodic shapes, has been studied. Exact analytical solutions for step, sinusoidal and periodic pulse reverse inputs are derived. The effect of frequency, forward and reverse amplitudes, and pulse modulation width are investigated. Analytical solution of the model is obtained as a Fourier series, using Laplace transformations applied to a one-dimensional model with linearized Butler-Volmer electrode kinetics. The results are applied to an acid-copper bath and discussed. It is shown that there exist optimal operation points or optimal current waveforms to obtain efficient and enhanced deposition... 

    Copper corrosion in sodium dodecyl sulphate solutions and carbon nanotube nanofluids: A modified Koutecky-Levich equation to model the agitation effect

    , Article Corrosion Science ; Volume 53, Issue 12 , December , 2011 , Pages 4241-4247 ; 0010938X (ISSN) Baghalha, M ; Kamal Ahmadi, M ; Sharif University of Technology
    Copper corrosion in sodium dodecyl sulphate (SDS) solutions and carbon nanotube (CNT) nanofluids were studied by potentiodynamic polarization. For the corrosion current densities calculations, Koutecky-Levich equation was modified to model the combined charge and mass transport. 0.005. M SDS reduced the copper corrosion current density by 81%. Higher SDS concentrations enhanced corrosion. Stirring SDS solutions increased the corrosion current density by ∼75%. By adding CNT to SDS solution, the corrosion current density first decreased and then remained constant. Stirring CNT nanofluids didn't change the corrosion current density. An adsorbed CNT layer on copper controlled the corrosion... 

    Numerical simulation of electro-deposition process influenced by force convection and migration of ions

    , Article Journal of Electroanalytical Chemistry ; Volume 782 , 2016 , Pages 117-124 ; 15726657 (ISSN) Zahraei, M ; Saidi, M. S ; Sani, M ; Sharif University of Technology
    Elsevier B.V  2016
    Electro-deposition process is one of the main steps in the LIGA procedure to fabricate microstructures. In this paper, one-dimensional modeling of Nickel electro-deposition process is implemented on Rayan and developed for simulation of time-dependence diffusion and migration of charge species with reduction reactions on the cathode surface. This model is proposed by considering governing equations on electro-kinetic phenomena consist of Nernst-Plank equation and Poisson's equation of electric potential. Transport of ions toward the cathode is considered based on the effect of convection, reaction rate, diffusion and migration. The numerical results cover two series of data consisting of... 

    Characterization of the ion beam current density of the rf ion source with flat and convex extraction systems

    , Article Silicon ; Volume 10, Issue 6 , 2018 , Pages 2743-2749 ; 1876990X (ISSN) Salehi, M ; Zavarian, A. A ; Arman, A ; Hafezi, F ; Rad, G. A ; Mardani, M ; Hamze, K ; Luna, C ; Naderi, S ; Ahmadpourian, A ; Sharif University of Technology
    Springer Netherlands  2018
    The characterization of ion beam current density distribution and beam uniformity is crucial for improving broad-beam ion source technologies. The design of the broad ion beam extraction system directly affects these two parameters, therefore, depending on the application, the design and geometry of the source is changed. In this study, the effect of the presence or the absence of a neutralization process on the ion beam density was investigated. Also, the effect of the probe bias on the ion beam current measurement was evaluated. Eventually, using a flat probe, the ion beam profiles obtained from the extraction system of the ion source (Model RFIS 60, ACECR, Iran) were measured at energies... 

    Critical Current Density Optimization of High-T_c Superconductor

    , M.Sc. Thesis Sharif University of Technology Baharlooie, Elahe (Author) ; Fardmanesh, Mehdi (Supervisor)
    Fabrication of bulk superconductors with high critical current density widely has been studied because they have many applications, for example, Fault Current Limiter (SFCL), Superconducting Magnetic Energy Storage (SMES), and magnetic levitation. Providing pinning center by addings impurity into superconductor is usual and simple solution for increasing the superconductor critical current density. In this project we have fabricated superconductor YBCO bulk and optimized its critical current density. There are two major stream in this thesis, first design of Vibrating System Magnetization (VSM) for critical current measurements and then fabrication of YBCO bulk and optimization of its... 

    3-D simulation of turbulent density

    , Article 2006 ASME Joint U.S.- European Fluids Engineering Division Summer Meeting, FEDSM2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2 FORUMS , 2006 , Pages 361-367 ; 0791847500 (ISBN); 9780791847503 (ISBN) Hormozi, S ; Firoozabadi, B ; Ghasvari Jahromi, H ; Afshin, H ; Sharif University of Technology
    American Society of Mechanical Engineers  2006
    Density current is a dense fluid, which is continuously released from a source and spreads down a sloping surface inside a lighter, motionless fluid. A low-Reynolds number k-ε model (Launder and Sharma, 1974) has been used to simulate the behavior of 3-D density currents. Density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been verified with the experimental data sets. Although the k-ε Launder and Sharma model is applied here to a conservative density current, it seems the analysis is valid in general for turbidity current laden with fine particles. Copyright © 2006 by ASME  

    Formation of clusters in the 2D t-J model: The mechanism for phase separation

    , Article Journal of Physics Condensed Matter ; Volume 18, Issue 20 , 2006 , Pages 4935-4944 ; 09538984 (ISSN) Fledderjohann, A ; Langari, A ; Mutter, K. H ; Sharif University of Technology
    The emergence of phase separation is investigated in the framework of a 2D t-J model by means of a variational product ansatz, which covers the infinite lattice by two types of L × L clusters. Clusters of the first type are completely occupied with electrons, i.e. they carry maximal charge Qe = L2 and total spin 0, and thereby form the antiferromagnetic background. Holes occur in the second type of clusters - called 'hole clusters'. They carry a charge Qh0.5) it turns out that hole clusters are occupied with an even... 

    Thermally activated phase slip and variable range hopping in Tm(Ba 2-xPrx)Cu3O7+δ

    , Article Physica Status Solidi C: Conferences ; Volume 1, Issue 7 , 2004 , Pages 1891-1894 ; 16101634 (ISSN) Mokhtari, Z ; Khosroabadi, H ; Akhavan, M ; Sharif University of Technology
    The magnetoresistance measurement of single phase polycrystalline Tm(Ba2-xPrx)Cu3O7+δ samples have been analyzed by the Ambegaokar and Halperine (AH) phase slip model. The magnetic field dependence of pinning energy power factors increase with the increase of Pr doping. The derived critical current density from the AH theory decreases with increasing magnetic field and Pr-doping for all superconducting samples. It shows that the Pr-doping plays the role of weak link. We have also investigated the normal state resistivity with the hopping model. We have found a CG-VRH cross-over with the increase of Pr content near metal insulator transition. The deacrease of the localization length of the... 

    Characterization of pulse reverse Ni-Mo coatings on Cu substrate

    , Article Surface and Coatings Technology ; Vol. 238 , 2014 , pp. 158-164 ; ISSN: 02578972 Surani Yancheshmeh, H ; Ghorbani, M ; Sharif University of Technology
    The effect of pulse reverse current (PRC) method on Ni-Mo coatings electroplated from chloride solution was investigated by various plating parameters such as plating duration, the anodic duty cycle, the anodic current density and the cathodic current density. By increasing the anodic duty cycle and anodic current density, the Mo content of coatings reached 68wt.% and 78wt.%, respectively at cathodic current densities of 500 and 300mAcm-2. The Mo content of coatings increases by the preferential dissolution of Ni on the anodic pulse and also by the replenishment of Mo complexes in the diffusion layer near the substrate surface during the anodic pulse. In comparison with the direct current... 

    Engineered cost-effective growth of Co-based nanoflakes as a sustainable water oxidation electrocatalyst

    , Article Journal of Physics D: Applied Physics ; Volume 50, Issue 47 , 2017 ; 00223727 (ISSN) Pourreza, M ; Naseri, N ; Sharif University of Technology
    Developing low-cost, scalable and reproducible synthesis methods for water oxidation reaction (WOR) catalysts is highly desirable and also challenging in energy, environmental and industrial applications. In this context, electrochemical deposition is known as an easy and cost-effective technique in nanomaterial growth. Herein, cobalt-based nanoflakes were grown on a flexible and commercially available steel mesh substrate by electrodeposition approach with a crystalline structure as a mixture of oxide, hydroxide and oxyhydroxide phases. For the first time, the correlation between electrodeposition parameters, time and current density, and morphological characteristics of the grown... 

    Ni-P/Zn-Ni compositionally modulated multilayer coatings – part 2: corrosion and protection mechanisms

    , Article Applied Surface Science ; Volume 442 , 2018 , Pages 313-321 ; 01694332 (ISSN) Bahadormanesh, B ; Ghorbani, M ; Sharif University of Technology
    Elsevier B.V  2018
    The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the deposition current density. The corrosion resistance of the deposits was studied and compared with that of monolayers of Ni-P and Zn-Ni alloys via Tafel polarization, EIS and salt spray tests. Characterization of corrosion products by means of EDS and XRD revealed more details from the corrosion mechanism of the monolayers and multilayers. The corrosion current density of Ni-P/Zn-Ni CMMCs were around one tenth of Zn-Ni monolayer. The CMMC with incomplete layers performed lower polarization resistance and higher corrosion current density compared to the CMMC with... 

    Electroplating Nano Crystalline Acidic Zinc for Reduction of Corrosion Rate

    , M.Sc. Thesis Sharif University of Technology Bahrampour, Saba (Author) ; Baghalha, Morteza (Supervisor)
    In this project, nonocrystalline zinc coatings with grain sizes within the range of 22-63 nanometers were produced on yellow-brass plates by electroplating in an acidic chloride bath in the presence and absence of additive has been investigated.current densities and bath stirring speeds change from 2 to 6 A/dm2 and 0 to 400 rpm respectively.To determine crystallite size, X-ray diffraction technique (XRD) was utilized;it was found that the use of additive has effectively refined the grain size and optimum current density is 3 A/dm2 to reach this objective.. it was observed that grain size increased continuously with increase in bath stirring speed. The results coming from XRD tests were...