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    Compensation method for multistage opamps with high capacitive load using negative capacitance

    , Article IEEE Transactions on Circuits and Systems II: Express Briefs ; Volume 63, Issue 10 , 2016 , Pages 919-923 ; 15497747 (ISSN) Rasekh, A ; Sharif Bakhtiar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    It is shown that negative capacitance (NC) circuits can be systematically used to improve the gain-bandwidth product of the operational amplifiers (opamps). The NC circuit moves the nondominant pole of the opamp to higher frequency by decreasing the parasitic capacitance of the critical node. The impedance at the input of the NC circuits is neither purely capacitive nor negative at all frequencies. A design guide is presented by deriving the circuit model for a conventional NC circuit and investigating the extent of the improvement that can be achieved in a circuit by the use of the NC circuit. The model is then used to present the design guide for widebanding the multistage opamps with... 

    Design and performance of a cylindrical capacitive sensor to monitor the electrical properties

    , Article Journal of Applied Sciences ; Volume 8, Issue 9 , 2008 , Pages 1699-1705 ; 18125654 (ISSN) Golnabi, H ; Azimi, P ; Sharif University of Technology
    In this study, design and operation of a cylindrical capacitive sensor based on the dielectric and reactance capacitance changes of the gap medium is reported. The proposed system was used to determine the electrical properties of different water liquids as a result of the capacitance variations. For capacitance measurement, the cylindrical gap can be filled up by water liquids under study, the electrical characteristics of different water liquids, mixture of ethanol and water, mixture of methanol and water, mixture of petroleum and water and other liquid mixtures were studied. In this research a big difference about 16200 nF was noticed in the measured capacitance of the corresponding... 

    Investigation of conductivity effects on capacitance measurements of water liquids using a cylindrical capacitive sensor

    , Article Journal of Applied Sciences ; Volume 10, Issue 4 , 2010 , Pages 261-268 ; 18125654 (ISSN) Behzadi, G ; Golnabi, H ; Sharif University of Technology
    In this study by using a Cylindrical Capacitive Sensor (CCS), the Electrical Conductivity (EC), effects on the capacitance measurements of the water liquids was investigated. Theoretical values of the capacitance measurements of water liquids with the cylindrical length in the range 0.5-5 cm are calculated. Our obtained results indicate that measured capacitance value by CCS depends on the liquid capacitance and reactance capacitance. Liquid capacitance value of the distilled water for permittivity of 80 is about 33.5 pF and reactance capacitance value is about 0.290 μF, when the cylindrical length value is about 1.6 cm. The reactance capacitance for the mineral, tap and dilute salt water... 

    Effect of the reactance term on the charge/discharge electrical measurements using cylindrical capacitive probes

    , Article Journal of Applied Sciences ; Volume 11, Issue 18 , 2011 , Pages 3293-3300 ; 18125654 (ISSN) Behzadi, G ; Fekri, L ; Golnabi, H ; Sharif University of Technology
    In this study, operation of the contact Cylindrical Capacitive Sensor (CCS) for the reactance capacitance measurement of the water liquids by using the charge/discharge measurement module is investigated. The effect of geometric factor on the capacitance measurement of different liquid samples is also studied. The measured capacitances for the distilled, mineral, tap and salt water samples are reported by using two contact CCSs with the active length of 16 and 74 mm. The measured capacitances by small contact CCS for the saltwater is 1.76 uF and by big contact CCS is 47.8 uF, which shows a big difference for different probes. In another study, the effects of the liquid conductance on the... 

    Optimizing the materials response in humidity capacitive sensors

    , Article Journal of Nano- and Electronic Physics ; Volume 7, Issue 3 , October , 2015 ; 20776772 (ISSN) Noroozi Afshar, E ; Golnabi, H ; Gorji, N. E ; Sharif University of Technology
    Sumy State University  2015
    The number of humidity outputs on the cap of a cylindrical capacitance sensor is optimized by designing three different probes with direct and indirect windows. The time interval is measured within which 30- 70 % humidity can influence the dielectric constant and conductivity of the capacitance when exposed to a range of relative humidity. It is then compared with a simple set-up including a simplified equivalent circuit. The direct probes had four and double outputs on the window of the cylindrical capacitive sensor while the indirect probe had a thin plastic layer only. We observed that the dielectric constant and its conductivity depend closely to the humidity outgoing pathway and also to... 

    Length effects on capacitance measurements of a cylindrical cell probe

    , Article Australian Journal of Basic and Applied Sciences ; Volume 4, Issue 11 , 2010 , Pages 5599-5613 ; 19918178 (ISSN) Sharifian, M ; Golnabi, H ; Sharif University of Technology
    Using two different capacitive cell probes; and monitoring capacitance and resistance values of the air and water liquids, the cell length and conductance effects of the water liquids are studied. Variations of the dielectric air capacitance and reactance capacitance parameter of liquids with cylinder length are investigated. In another study the probe length affects on the capacitance and resistance measurements for the liquid filling process are investigated. Different theories are also developed to calculate the capacitance values for the constructed probes. Capacitance per unit length from the Coulomb theory is different from the Gauss law that is a constant value. Measured air... 

    Precise formulation of electrical capacitance for a cylindrical capacitive sensor

    , Article Journal of Applied Sciences ; Volume 9, Issue 8 , 2009 , Pages 1556-1561 ; 18125654 (ISSN) Azimi, P ; Golnabi, H ; Sharif University of Technology
    In this study a more precise formulation of electrical capacitance for a cylindrical capacitive sensor is reported. By using different theoretical models such as Coulomb law, Gauss law and Laplace equation the electrical capacitance is calculated. Based on the given models the relation between the capacitance and the geometrical parameters (e.g., cylindrical length) is formulated and by using suitable software capacitance variation is computed and compared for different methods. In Coulomb method, the electrical potential is first solved numerically by using Mathematica and then the electrical capacitance is computed. It is found that the active capacitor length is crucial parameter in the... 

    Single source capacitated multi facility weber problem-an interactive two phase heuristic

    , Article Computers and Operations Research, Elsevier ; Volume 39, Issue 7 , July , 2012 , Pages 1465–1476 Eshghi, K ; Manzour-al-Ajdada, S. M. H ; Torabia, S. A ; Sharif University of Technology
    Multi-Facility Weber Problem (MFWP), also known as continuous location–allocation problem, entails determining the locations of a predefined number of facilities in a planar space and their related customer allocations. In this paper, we focus on a new variant of the problem known as Single-Source Capacitated MFWP (SSCMFWP). To tackle the problem efficiently and effectively, an iterative two-phase heuristic algorithm is put forward. At the phase I, we aim to determine proper locations for facilities, and during the phase II, assignment of customers to these facilities is pursued. As an alternative solution method, a simulated annealing (SA) algorithm is also proposed for carrying out the... 

    High-Performance, flexible, all-solid-state wire-shaped asymmetric micro-supercapacitors based on three dimensional CoNi2S4 nanosheets decorated-nanoporous Ni-Zn-P Film/Cu wire

    , Article Journal of Physical Chemistry C ; Volume 123, Issue 35 , 2019 , Pages 21353-21366 ; 19327447 (ISSN) Shahrokhian, S ; Naderi, L ; Sharif University of Technology
    American Chemical Society  2019
    Demand increasing for next generation portable and miniaturized electronics has aroused much interest to explore microscale and lightweight energy storage devices. Herein, we demonstrate successful development of flexible wire-shaped micro-supercapacitors (micro-SCs) based on novel CoNi2S4/E-NZP film@Cu wire electrode. The etched Ni-Zn-P (E-NZP) film was synthesized by directly deposition of NZP film on Cu wire, followed by a chemical etching process. Alkaline etching treatment provides a micro- and mesoporous structure with high surface area and facilitates the penetration of electrolyte ions into the electrode matrix. Then, CoNi2S4 nanosheets as electroactive material are electrochemically... 

    Simultaneous measurements of the resistance and capacitance using a cylindrical sensor system

    , Article Modern Physics Letters B ; Volume 22, Issue 8 , 2008 , Pages 595-610 ; 02179849 (ISSN) Golnabi, H ; Azimi, P ; Sharif University of Technology
    In this article, the design and operation of a cylindrical capacitive sensor based on the dielectric reactance capacitance and conductance changes of the gap medium is reported. The proposed system was used to determine characteristics of different water liquids as a result of the capacitance and resistance variations. The air gap capacitance (dry signal) is measured and then by filling the gap with a liquid, the capacitance (wet signal) is monitored for different liquids. A reported sensor is used for the distilled, tap, boiled, and salt water measurements and the capacitance and resistance results are compared. A big difference of about 38.5 μF in the measured capacitance values for the... 

    Investigation of water electrical parameters as a function of measurement frequency using cylindrical capacitive sensors

    , Article Measurement: Journal of the International Measurement Confederation ; Volume 46, Issue 1 , 2013 , Pages 305-314 ; 02632241 (ISSN) Golnabi, H ; Sharifian, M ; Sharif University of Technology
    In this study electrical properties of different water liquids at frequency range of 100-2000 Hz are investigated by using the short invasive and non-invasive cylindrical capacitive sensors (CCSs). Operation of the capacitance measurement module for such probes is based on the auto balancing bridge method. Comparison of the measured capacitances and measured resistances for different water liquids shows decrease by increasing the frequency. In another study the dielectric constant of distilled water, mineral water, tap water and salt water are measured. The effects of the frequency on the resistivity, permittivity and conductance of the different water liquids are also investigated  

    On the effect of disorder on stray capacitance of transformer winding in high-voltage power supplies

    , Article IEEE Transactions on Industrial Electronics ; Volume 64, Issue 5 , 2017 , Pages 3608-3618 ; 02780046 (ISSN) Aghaei, M ; Kaboli, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Stray capacitance of transformer winding is an important parasitic element influencing the behavior of the switching power converters, especially for high-voltage transformers. There are various methods for calculating the stray capacitance in transformers and inductors with ordered windings. However, an ordered winding is less likely with an increased number of turns and layers. In this paper, it is shown that a slight disorderliness in winding leads to a considerable difference between the value of winding stray capacitance of the former ordered winding and its slightly disordered scheme. Therefore, regular methods for calculating the stray capacitance have significant errors in a... 

    Monitoring temperature variation of reactance capacitance of water using a cylindrical cell probe

    , Article Journal of Applied Sciences ; Volume 9, Issue 4 , 2009 , Pages 752-758 ; 18125654 (ISSN) Behzadi, G ; Golnabi, H ; Sharif University of Technology
    In this study by using a capacitive cell probe the temperature variation of the electrical properties of the water liquids is investigated. Variation of the reactance capacitance parameter of liquids with temperature in the range of 17-60°C is measured for the plain water and water mixtures. The temperature variations of the capacitance for the cool distilled and tap water samples are studied for the range of 17-29°C obtained. Present results indicate an averaged variation of 4.69 μF/°C for the distilled water and 3.24 μF/°C for tap water in warm up process to a near room temperature. The cooling behaviors for the warm mineral, tap and salt water liquids are also investigated in this study.... 

    A stable and high-energy hybrid supercapacitor using porous Cu2O-Cu1.8S nanowire arrays

    , Article Journal of Materials Chemistry A ; Volume 8, Issue 4 , 2020 , Pages 1920-1928 Esfandiar, A ; Qorbani, M ; Shown, I ; Ojaghi Dogahe, B ; Sharif University of Technology
    Royal Society of Chemistry  2020
    A three-dimensional electrode based on porous Cu2O-Cu1.8S nanowires is prepared by means of a facile fabrication process. In this electrode, nanowires are decorated with Cu1.8S polyhedral nanostructures on the top, which are directly grown on a copper foam, thereby eliminating the need for a polymer binder. As an electrochemical electrode, it exhibits an extrinsic pseudocapacitive charge storage mechanism, which is different from that of battery-like Cu2O-CuO and Cu(OH)2 electrodes. The areal and volumetric capacitances of the Cu2O-Cu1.8S electrode can reach 2.6 F cm-2 and ∼200 F cm-3, respectively, at 2 mA cm-2, which are much higher than those obtained using copper(i, ii) oxide and... 

    Accelerating 3-D capacitance extraction in deep sub-micron VLSI design using vector/parallel computing

    , Article 13th International Conference on Parallel and Distributed Systems, ICPADS, Hsinchu, 5 December 2007 through 7 December 2007 ; Volume 2 , December , 2007 ; 15219097 (ISSN); 9781424418909 (ISBN) Shahbazi, N ; Sarbazi Azad, H ; Sharif University of Technology
    The widespread application of deep sub-micron and multilayer routing techniques makes the interconnection parasitic influence become the main factor to limit the performance of VLSI circuits. Therefore, fast and accurate 3D capacitance extraction is essential for ultra deep sub-micron design (UDSM) of integrated circuits. Parallel processing provides an approach to reducing the simulation turn-around time. In this paper, we present parallel formulations for 3D capacitance extraction based on P-FFT algorithm, on a personal computer (PC) or on a network of PCs. We implement both vector and parallel versions of 3D capacitance extraction algorithm simultaneously and evaluate our implementation... 

    Adsorption Processes in Capacitive Deionization

    , M.Sc. Thesis Sharif University of Technology Vaezi, Mehran (Author) ; Taghavinia, Nima (Supervisor)
    Today the water crisis affects billions around the world.According to existance of large amount of salty water on the earth, it seems one of the best soloution is desalination of salty water.There are methods for removing ions from water such as thermal methods, membrane methods , chemical methods and capacitive deionization.Capacitive deionization is based on the deviation of ions in the electric field.CDI system contains of two conductive porous electrodes that an elecric field is applied between them.While the brine pass through the space between the elecrodes the ions are absorbed by elecrodes. After a while the electrodes get saturated so a reverse potential is needed to regenerate the... 

    New approach to VLSI buffer modeling, considering overshooting effect

    , Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 21, Issue 8 , August , 2013 , Pages 1568-1572 ; 10638210 (ISSN) Mehri, M ; Kouhani, M. H. M ; Masoumi, N ; Sarvari, R ; Sharif University of Technology
    In this brief, we use the alpha power law model for MOS devices to reach a more accurate modeling of CMOS buffers in very deep submicrometer technologies. We derive alpha model parameters of a CMOS buffer for 90-, 65-, and 45-nm technologies using HSPICE simulations. By analytical efforts we find the output resistance of a minimum-size buffer and compare it with those extracted from HSPICE simulations. We propose a new model for the output resistance of a given-size buffer in any technology, which demonstrates 3% error on average as opposed to the conventional model. Also a new buffer resistance is proposed analytically and numerically to calculate the crosstalk for interconnect analysis... 

    On the pseudocapacitive behavior of nanostructured molybdenum oxide

    , Article Journal of Solid State Electrochemistry ; Volume 14, Issue 4 , 2010 , Pages 643-650 ; 14328488 (ISSN) Farsi, H ; Gobal, F ; Raissi, H ; Moghiminia, S ; Sharif University of Technology
    Nanostructured molybdenum oxide was potentiodynamically deposited onto a stainless steel surface from an aqueous bath by cycling the potential between 0 and -0.75 V vs. Ag/AgCl. The deposit consisted of particulates in the range of 30 to 80 nm. Electrochemical studies under galvanostatic charge/discharge and also impedance spectroscopy revealed capacitive behavior in the potential range of -0.3 to -0.55 V vs. Ag/AgCl with the value of 477 F g-1 at 0.1 mA/cm2. An equivalent circuit comprising of three parallel branches consisting of double-layer capacitance, Warburg impedance, and a constant phase element signifying pseudo-capacitance each coupled with their corresponding resistances was... 

    Facile synthesis of nanoporous CuS nanospheres for high-performance supercapacitor electrodes

    , Article Journal of Energy Chemistry ; Volume 26, Issue 4 , 2017 , Pages 762-767 ; 20954956 (ISSN) Heydari, H ; Moosavifard, S. E ; Shahraki, M ; Elyasi, S ; Sharif University of Technology
    In recent years, development of high-performance supercapacitor electrode materials has stimulated a great deal of scientific research. The electrochemical performance of a supercapacitor strongly depends on its material structures. Herein, we report a simple strategy for high-performance supercapacitors by building pseudocapacitive CuS nanospheres with nanoporous structures, nanosized walls (<10 nm) and relatively large specific surface area of 65 m2/g. This electrode demonstrates excellent electrochemical performance including a maximum specific capacitance of 814 F/g at 1 A/g, significant rate capability of 42% capacitance retention at an ultrafast rate of 50 A/g, and outstanding... 

    Low-noise differential transimpedance amplifier structure based on capacitor cross-coupled gm-boosting scheme

    , Article Microelectronics Journal ; Volume 39, Issue 12 , 2008 , Pages 1843-1851 ; 00262692 (ISSN) Jalali, M ; Nabavi, A ; Moravvej Farshi, M. K ; Fotowat Ahmady, A ; Sharif University of Technology
    This paper presents a capacitor cross-coupled gm-boosting scheme for differential implementation of common-gate transimpedance amplifier (CG-TIA). A differential transimpedance amplifiers (DTIA) is designed by this scheme using two modified floating-biased CG stage with improved low corner frequency. Despite conventional methods for single-ended to differential conversion that increase the power and the noise for the same gain, the new DTIA gives a higher gain and hence reduces the input-referred noise power. Design of the DTIA circuit using 0.13 μm CMOS technology illustrates near 1.7 dB improvement in the circuit sensitivity and 5.2 dB enhancement in transimpedance gain compared to its...