Loading...
Search for:
current-voltage
0.005 seconds
Total 31 records
Current-voltage characteristics of graphane p-n junctions
, Article IEEE Transactions on Electron Devices ; Volume 57, Issue 1 , 2010 , Pages 209-214 ; 00189383 (ISSN) ; Khorasani, S ; Sharif University of Technology
2010
Abstract
In contrast to graphene, which is a gapless semiconductor, graphane, the hydrogenated graphene, is a semiconductor with an energy gap. Together with the 2-D geometry, unique transport features of graphene, and the possibility of doping graphane, p and n regions can be defined so that 2-D p-n junctions become feasible with small reverse currents. This paper introduces a basic analysis to obtain the current-voltage characteristics of such a 2-D p-n junction based on graphane. As we show, within the approximation of Shockley's law of junctions, an ideal I-V characteristic for this p-n junction is to be expected
Melatonin as a powerful bio-antioxidant for reduction of graphene oxide
, Article Journal of Materials Chemistry ; Volume 21, Issue 29 , 2011 , Pages 10907-10914 ; 09599428 (ISSN) ; Akhavan, O ; Irajizad, A ; Sharif University of Technology
2011
Abstract
Graphene is usually synthesized through deoxygenation of graphene oxide (GO) by hydrazine as the most common and one of the strongest reducing agents. But, due to the high toxicity of hydrazine, it is not a promising reductant in large-scale production of graphene. Here, for the first time, we used melatonin (MLT), as a powerful antioxidant and a biocompatible competitor of hydrazine in reduction of GO suspension. X-ray photoelectron spectroscopy (XPS), current-voltage and optical characteristics of the sheets indicated that the deoxygenation efficiency of the GO suspensions by MLT and under heating in an alkaline condition for 3 h was comparable with the efficiency obtained by hydrazine in...
Detection and Classification of Partial Discharges in High Voltage DC
, M.Sc. Thesis Sharif University of Technology ; Vakilian, Mehdi (Supervisor)
Abstract
In past decades, the measurement of partial discharges (PDs) in high voltage equipments, was appreciated as one of the most efficient methods for evaluation of the equipment insulation condition. Generators, transformers, cables and transmission lines are especially checked to detect the presence of any partial discharge.
In AC high voltage systems, the measurement method is well established and known. The Phase resolved method is used to determine the partial discharge signals. These methods have been used for many years and their success in differentiating the various sources of partial discharge have proven. Although phase resolved method works on AC; due to lack of frequency...
In AC high voltage systems, the measurement method is well established and known. The Phase resolved method is used to determine the partial discharge signals. These methods have been used for many years and their success in differentiating the various sources of partial discharge have proven. Although phase resolved method works on AC; due to lack of frequency...
The effects of oxidation conditions on structural and electrical properties of silicon nanoparticles obtained by ultra-low-energy ion implantation
, Article Nanotechnology ; Volume 16, Issue 12 , 2005 , Pages 2987-2992 ; 09574484 (ISSN) ; Shalchian, M ; Ben Assayag, G ; Coffin, H ; Bonafos, C ; Schamm, S ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
2005
Abstract
In this paper, we have studied the effect of annealing under slightly oxidizing ambient (N2+O2) on the structural and electrical characteristics of a limited number of silicon nanoparticles embedded in an ultra-thin SiO2 layer. These nanoparticles were synthesized by ultra-low-energy (1 keV) ion implantation and annealing. Specific experimental methods have been used to characterize the ncs populations. They include transmission electron microscopy (TEM) Fresnel imaging for evaluating the distances and widths of interest and spatially resolved electron energy loss spectroscopy (EELS) using the spectrum-imaging mode of a scanning transmission electron microscope (STEM) to measure the size...
Spin filtering and spin diode devices in quantum wire systems
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 27, Issue 3 , 2005 , Pages 325-331 ; 13869477 (ISSN) ; Mardaani, M ; Esfarjani, K ; Sharif University of Technology
2005
Abstract
Theoretical studies on the spin-dependent transmission and current-voltage characteristic in a mesoscopic system, which consists of two semi-infinite ferromagnetic (FM) leads (as source and drain) separated by a typical periodic quantum dot (QD) are presented. The calculations are based on the tight-binding model and transfer matrix method, and investigate the magnetoresistance (MR) and the spin polarization within the Landauer-Büttiker formalism. The spin-dependent transport behavior can be controlled via a gate voltage and an applied bias in the ballistic regime. The numerical results are shown for a periodic polymer chain with nonmagnetic (NM) and FM leads, and also, with two FM leads....
Numerical and Experimental Investigation of Core-shell Microstructures Printing by an Electrohydrodynamic 3D Printer
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
Abstract
Electrohydrodynamic (EHD) printing is a novel approach for manufacturing high-resolution structures in micro and nanoscale. This technology is the promoted version of inkjet printing which has reduced nozzle clogging risk and improved the accessible resolution. In this method, ink droplets or jets are formed under the action of an electric field and are used as building blocks of the intended part or pattern. Most research in this field has focused on the formation of monolayer droplets and jets by this technology; however, the EHD printer has a great potential to produce core-shell microstructures in a controlled manner too. These microparticles have unique properties and applications due...
Increasing the antioxidant activity of green tea polyphenols in the presence of iron for the reduction of graphene oxide
, Article Carbon ; Volume 50, Issue 8 , 2012 , Pages 3015-3025 ; 00086223 (ISSN) ; Kalaee, M ; Alavi, Z. S ; Ghiasi, S. M. A ; Esfandiar, A ; Sharif University of Technology
2012
Abstract
An easy method for green and low-temperature (40 °C) reduction of graphene oxide (GO) by increasing the antioxidant activity of green tea polyphenols (GTPs) in the presence of iron was developed. The reduction level (obtained by X-ray photoelectron spectroscopy) and electrical conductivity (obtained by current-voltage measurement) of the GO sheets reduced by GTPs in the presence of iron were comparable to those of hydrazine-reduced GO and much better than those of the GO reduced by only GTPs (in the absence of iron) at reduction temperatures of 40-80 °C. Raman spectroscopy indicated that application of GTPs in the presence of iron, in contrast to hydrazine, resulted in better recovering of...
Escherichia coli bacteria reduce graphene oxide to bactericidal graphene in a self-limiting manner
, Article Carbon ; Volume 50, Issue 5 , 2012 , Pages 1853-1860 ; 00086223 (ISSN) ; Ghaderi, E ; Sharif University of Technology
2012
Abstract
Interactions of chemically exfoliated graphene oxide (GO) nanosheets and Escherichia coli bacteria living in mixed-acid fermentation with an anaerobic condition were investigated for different exposure times. X-ray photoelectron spectroscopy showed that as the exposure time increased (from 0 to 48 h), the oxygen-containing functional groups of the GO decreased by ∼60%, indicating a relative chemical reduction of the sheets by interaction with the bacteria. Raman spectroscopy and current-voltage measurement confirmed the reduction of the GO exposed to the bacteria. The reduction was believed to be due to the metabolic activity of the surviving bacteria through their glycolysis process. It was...
Bacteriorhodopsin as a superior substitute for hydrazine in chemical reduction of single-layer graphene oxide sheets
, Article Carbon ; Volume 81, Issue 1 , 2015 , Pages 158-166 ; 00086223 (ISSN) ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Bacteriorhodopsin (bR) molecules were utilized as light-driven proton pumps for green as well as effective reduction of single-layer graphene oxide (GO) sheets. The bR molecules and graphene sheets were separated from each other in an aqueous environment by using a polytetrafluoroethylene membrane filter, in order to prevent their direct interactions (including attachment of the bR molecules onto the GO). Although reduction of GO using hydrazine or bR showed similar deoxygenation levels (based on X-ray photoelectron spectroscopy), the former resulted in formation of CAN bonds which can substantially decrease the electrical conductivity of the reduced sheets. The electrical characteristics of...
An analytical-numerical approach for parameter determination of a five-parameter single-diode model of photovoltaic cells and modules
, Article International Journal of Sustainable Energy ; Volume 35, Issue 4 , 2016 , Pages 396-410 ; 14786451 (ISSN) ; Mokhtari, H ; Azizian, M. R ; Söder, L ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
Parameter extraction of the five-parameter single-diode model of solar cells and modules from experimental data is a challenging problem. These parameters are evaluated from a set of nonlinear equations that cannot be solved analytically. On the other hand, a numerical solution of such equations needs a suitable initial guess to converge to a solution. This paper presents a new set of approximate analytical solutions for the parameters of a five-parameter single-diode model of photovoltaic (PV) cells and modules. The proposed solutions provide a good initial point which guarantees numerical analysis convergence. The proposed technique needs only a few data from the PV current-voltage...
Voltage and frequency consensusability of autonomous microgrids over fading channels
, Article IEEE Transactions on Energy Conversion ; Volume 36, Issue 1 , 2021 , Pages 149-158 ; 08858969 (ISSN) ; Khorsandi, A ; Baghaee, H. R ; Sadati, N ; Shirvani Moghaddam, S ; Guerrero, J. M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this article, a novel cooperative secondary voltage/frequency control considering time-varying delays and noises in fading channels is presented for an autonomous alternating current (AC) voltage sourced-based converter (VSC)-based microgrid (MG), including inverter-interfaced distributed generations (DGs). Fading phenomenon makes complex random fluctuations on the voltage and frequency of every DG received from its neighbor DGs. In multi-agent cooperative systems, in addition to the total additive noise and time-variant delay, a multiplicative complex random variable is considered to model the main received signal and its replicas due to multipath propagation. The proposed...
From continuous to quantized charging response of silicon nanocrystals obtained by ultra-low energy ion implantation
, Article Solid-State Electronics ; Volume 49, Issue 7 , 2005 , Pages 1198-1205 ; 00381101 (ISSN) ; Grisolia, J ; Ben Assayag, G ; Coffin, H ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
2005
Abstract
In this paper, we present a study on the contribution of silicon nanocrystals to the electrical transport characteristics of large (100 μm × 100 μm) and small (100 nm × 100 nm) metal-oxide-semiconductor (MOS) capacitors at room temperature. A layer of silicon nanocrystals is synthesized within the oxide of these capacitors by ultra-low energy ion implantation and annealing. Several features including negative differential resistance (NDR), sharp current peaks and random telegraph signal (RTS) are demonstrated in the current-voltage and current-time characteristics of these capacitors. These features have been associated to charge storage in silicon nanocrystals and to the resulting Coulomb...
Power Flow Control and Power Quality Enhancement in Grid-Connected Microgrid with Back-to-Back Converter
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
A microgrid system consists of some distributed generators (DGs) and local loads which can operate in both grid-connected and islanded modes of operation. An islanded mode of operation is required when the grid voltage deteriorates and its power quality drops. This islanding operation can be attained by opening grid-side switches or by using back-to-back (b-to-b) converters. Due to the increase of highly sensitive loads and to have better power control and higher power quality, the use of back-to-back converters has recently attracted interests among researchers. However, the major drawback of this solution is the cost of a b-to-b converter. Therefore the aim of this project is to gain some...
Optoelectronic properties of cauliflower like ZnO-ZnO nanorod/p-Si heterostructure
, Article Solid-State Electronics ; Volume 80 , 2013 , Pages 33-37 ; 00381101 (ISSN) ; Dariani, R. S ; Iraji Zad, A ; Zahedi, F ; Sharif University of Technology
2013
Abstract
The cauliflower like ZnO nanostructures are grown on ZnO nanorods using spray pyrolysis method. First, ZnO nanorod arrays are grown on p-type silicon substrate without catalyst by chemical vapor transport and condensation method in a horizontal tube furnace. Afterwards, the cauliflower like ZnO nanostructures is deposited on top of the ZnO nanorod array. The PL spectra of cauliflower like ZnO nanostructures consist of UV emission bands around 387 nm and a visible emission at ∼440 nm. The current-voltage (I-V) measurement under dark and UV illumination condition are performed to study photodetection of the cauliflower like ZnO-ZnO nanorod/p-Si heterostructure. The experimental data of dark...
UV photodetection of laterally connected ZnO rods grown on porous silicon substrate
, Article Sensors and Actuators, A: Physical ; Volume 180 , 2012 , Pages 11-14 ; 09244247 (ISSN) ; Dariani, R. S ; Iraji Zad, A ; Sharif University of Technology
2012
Abstract
Here, the UV photodetection of ZnO rods grown on porous silicon substrates are reported. Laterally interconnected ZnO rods have been synthesized by chemical vapor transport and condensation method on porous silicon substrates. As characterized by current-voltage measurements the I-V characteristics have linear behavior, indicating space charge effect. The device exhibits photocurrent response of 0.027 A/W for 325 nm UV light under -5 V bias. The rise and decay time constants under these conditions are 19 and 62 s, respectively
Detemining the thickness of barriers and well of Resonance Tunneling Diodes by specified I-V characteristic
, Article Applied Mechanics and Materials ; Volume 110-116 , 2012 , Pages 5464-5470 ; 16609336 (ISSN) ; 9783037852620 (ISBN) ; Ghorbanalipour, S ; Faez, R ; Sharif University of Technology
Abstract
In this paper, a method of determining physical dimension of Double Barrier Quantum Well (DBQW) of Resonance Tunneling Diodes (RTDs) is presented by using I-V characteristic governing on them. In this procedure, first we have used performance metrics related to RTDs I-V characteristic such as Peak to Valley Current Ratio (PVCR), peak current density (JP), valley current density (JV) and Voltage Swing (VS), and by some other arbitrary points, we have fitted a curve to the RTD current-voltage equation by MATLAB software. Then we have obtained the physical parameter of I-V equation and adjusted some of them with modification coefficients. Next, by choosing the material of barriers and the well...
Copper oxide nanoflakes as highly sensitive and fast response self-sterilizing biosensors
, Article Journal of Materials Chemistry ; Volume 21, Issue 34 , Jul , 2011 , Pages 12935-12940 ; 09599428 (ISSN) ; Ghaderi, E ; Sharif University of Technology
2011
Abstract
Vertical copper oxide nanoflakes were synthesized on a Cu foil through oxidation in alkaline conditions. X-ray photoelectron spectroscopy showed that after exposing the nanoflakes to an Escherichia coli bacterial suspension, the outermost surface of the nanoflakes was chemically reduced through the glycolysis process of the bacteria. Current-voltage (I-V) characteristics of the nanoflakes (measured perpendicular to surface of the Cu foil by using conductive atomic force microscopy) indicated that electrical resistivity of the nanoflakes increased about one order of magnitude after exposure to the bacterial suspension. The nanoflakes reduced by the bacterial suspension could also be...
Design and simulation of a high power single mode 1550nm InGaAsP VCSELs
, Article IEICE Electronics Express ; Volume 8, Issue 13 , 2011 , Pages 1096-1101 ; 13492543 (ISSN) ; Marjani, A ; Marjani, S ; Sharif University of Technology
Abstract
In the present work, a new structure of vertical cavity surface emitting laser (VCSEL) is designed and simulated. In this structure, InGaAsP is used as the active region which is sandwiched between GaAs/AlGaAs distributed bragg mirror at the top of structure and GaAs/AlAs distributed bragg mirror at the bottom. In this work, the hole etching depth was continued down to the top of lower spacer layer while in the previous work the hole etching depth was only down to top of the upper spacer. In this way, the threshold current decrement of 76.52% and increment the power by 28% from 5mW to 6.4mW at bias current of 9mA was achieved. In this paper, device characteristics such as light power versus...
Photocatalytic reduction of graphene oxides hybridized by ZnO nanoparticles in ethanol
, Article Carbon ; Volume 49, Issue 1 , January , 2011 , Pages 11-18 ; 00086223 (ISSN) ; Sharif University of Technology
2011
Abstract
Graphene oxide platelets synthesized by using a chemical exfoliation method were dispersed in a suspension of ZnO nanoparticles to fabricate ZnO/graphene oxide composite. Formation of graphene oxide platelets (with average thickness of ∼0.8 nm) hybridized by ZnO nanoparticles (with average diameter of ∼20 nm) was investigated. The 2D band in Raman spectrum confirmed formation of single-layer graphene oxides. The gradual photocatalytic reduction of the graphene oxide sheets in the ZnO/graphene oxide suspension of ethanol was studied by using X-ray photoelectron spectroscopy for different ultra violet (UV)-visible irradiation times. After 2 h irradiation, the relative concentration of the...
Fault analysis on AC railway supply system
, Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; February , 2015 , Pages 567-572 ; 9781479976539 (ISBN) ; Mokhtari, H ; Zolghadri, M. R ; Khodabandeh, M ; Abazai, A ; Seyyedi Khakshani, R ; Mazaheri, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
A short circuit fault in an AC railway supply system could have undesired consequences; including high-amplitude current flow in the power path, the rail potential rise in the fault vicinity. This paper studies the problem of the rail voltage rise in Tehran-Karaj railway system by the use of a steady state circuit model for the AC autotransformer during a phase-to-ground fault. By using this model, all the currents and voltages of the system can be easily calculated for all possible short circuit fault locations. With the help of the derived analytical model, one can also predict the possible fault locations which may cause the protection system to operate. The estimation of the system...