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91.
Abstract—This article proposes a novel zero-current switching series resonant inverter-fed voltage multiplier based high-voltage DC-DC converter. The series resonant inverter in the proposed topology has two power switches (insulated-gate bipolar transistors), two resonant capacitors, and only one high-voltage transformer with center-tapped primary windings. The power switches are connected in the form of a half-bridge network. The leakage inductances of the transformer's primary windings together with resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating power switches with an interleaved half-switching cycle. The secondary winding of the high-voltage transformer is connected to a voltage multiplier circuit to rectify and boost the voltage. The converter operates in discontinuous conduction mode, and its output voltage is regulated by pulse-frequency modulation. Therefore, all the power switches turn ON and OFF at the zero-current switching condition. The main features of the proposed converter are lower power loss, less cost, and smaller size compared to previously proposed series resonant high-voltage DC-DC converters. The experimental results of a 130-W prototype of the proposed converter are presented both for dynamic and steady-state operation. The results confirm the excellent operation and performance of the converter. 相似文献
92.
Ayaz Arif Khan Muhammad Umer Fayaz Muhammad Nasir Khan Mazhar Iqbal Asif Majeed Rehana Bilkees Surayya Mukhtar Muhammad Javed 《Journal of Materials Science: Materials in Electronics》2018,29(16):13577-13587
Here in, we report the charge transport mechanism in semiconducting La0.5Ca0.5Mn0.5Fe0.5O3 (LCMFO) polycrystalline material synthesized via sol–gel auto combustion route. X-ray diffraction (XRD) analysis confirmed the orthorhombic phase of the prepared material. Temperature dependent resistivity and impedance spectroscopy measurements have been carried out to probe the dielectric and electrical conduction mechanism which revealed a change of Mott variable range to the small polaronic hopping conduction mechanism around 303 K. The complex impedance and modulus spectra undoubtedly showed the contribution of both grain and grain boundary effect on the conduction properties of LCMFO. An equivalent circuit [(RgbQgb) (RgQg)] model has been used to address the electrical parameters associated with the different phases (grains and grain boundaries) having different relaxation times. The values of resistances of two phases obtained after fitting the equivalent circuit in the nyquist plot have been analyzed which confirmed the change of conduction mechanism around 303 K. The resultant change in conduction mechanism is also supported by the conductivity plots. 相似文献
93.
Khan Abdul Manan Yun Deok-won Zuhaib Khalil Muhammad Iqbal Junaid Yan Rui-Jun Khan Fatima Han Changsoo 《International Journal of Control, Automation and Systems》2017,15(2):802-814
International Journal of Control, Automation and Systems - In this paper, we have addressed two issues for upper limb assist exoskeleton. 1) Estimation of Desired Motion Intention (DMI); 2) Robust... 相似文献
94.
Ahmad Awais Ahmad Mudassar Habib Muhammad Asif Sarwar Shahzad Chaudhry Junaid Latif Muhammad Ahsan Dar Saadat Hanif Shahid Muhammad 《The Journal of supercomputing》2019,75(4):2269-2288
The Journal of Supercomputing - The main challenge in database-as-a-service is the security and privacy of data because service providers are not usually considered as trustworthy. So, the data... 相似文献
95.
T. Hayat Z. Iqbal M. Qasim S. Obaidat 《International Journal of Heat and Mass Transfer》2012,55(7-8):1817-1822
In this article, the flow and heat transfer of Eyring Powell fluid over a continuously moving surface in the presence of a free stream velocity are investigated. Convective boundary conditions have been used in the problem formulation. The solution for velocity and temperature are computed by applying the homotopy analysis method (HAM). The effects of emerging fluid parameters (?), (δ) and Prandtl number (Pr) on the velocity and temperature are illustrated through graphs and tables for different values of λ. It is found that the boundary layer thickness is an increasing function of (?) and decreasing function of (δ). However the temperature and thermal boundary layer thickness decrease when the values of (?) and (δ) are increased. 相似文献
96.
X. Shi N. Iqbal S.S. Kunwar G. Wahab H.A. Kasat A.M. Kannan 《International Journal of Hydrogen Energy》2018,43(6):3520-3526
Zeolitic Imidazolate Frameworks (ZIF) is one of the potential candidates as highly conducting networks with large surface area with a possibility to be used as catalyst support for low temperature fuel cells. In the present study, highly active state-of-the-art PtCo@NCNTs (Nitrogen Doped Carbon Nanotube) catalyst was synthesized by pyrolyzing ZIF-67 along with Pt precursor under flowing ArH2 atmosphere. The multi-walled NCNTs were densely grown on the surface of ZIF particles after pyrolysis. The high resolution TEM examination was employed to examine the nature of the PtCo particles as well as multi-walled NCNTs. Rotating disk electrode study was used for measuring oxygen reduction reaction performance for PtCo@NCNTs in 0.1 M HClO4 and compared with commercial Pt/C catalyst. Fuel cell performance with PtCo@NCNT and commercial Pt/C catalysts was evaluated at 70 °C using Nafion-212 electrolyte using H2 and O2 gases (100% RH) and the observed peak power density of 630 and 560 mW cm?2, respectively. 相似文献
97.
Shahid Husain M. Altamush Siddiqui 《Numerical Heat Transfer, Part A: Applications》2018,73(9):624-653
Numerical and experimental analysis of natural convection subcooled boiling flow in a high aspect ratio narrow vertical annulus operating at atmospheric pressure is carried out. The computational model is developed using RPI wall boiling model. The annular gap is 3.5?mm and aspect ratio is 352. A new empirical relation for nucleation site density is developed for the present geometrical configuration and implemented in the Fluent code with the help of user-defined function (UDF). The results from the numerical analysis are then compared with the experimental results which show excellent agreement. The wall superheat is found to be maximum at the point of boiling incipience which increases with heat input. The wall temperature shows a gradual decrease in the boiling region. The average heat transfer coefficient increases almost linearly for both subcooled and saturated boiling region. 相似文献
98.
M. Iqbal 《Solar Energy》1979,23(2):169-173
Empirical equations have been developed which correlate the monthly average daily horizontal diffuse and beam radiation with the fraction of maximum possible number of bright sunshine hours. These correlations are based on measured data from three widely spread Canadian stations.Depending upon whether or not the total horizontal radiation is known, the two correlations for the diffuse radiation are: .The correlation for beam radiation is: . 相似文献
99.
Raz Muhammad Yaseen Iqbal Carlos R. Rambo 《Journal of Materials Science: Materials in Electronics》2014,25(4):1652-1656
Ba4.5Re9Ti18O54 (Re = La, Nd) ceramics were prepared via a solid state mixed oxide route. X-ray diffraction (XRD) analysis revealed the formation of the major Ba4.5Re9Ti18O54 phase along with rutile (TiO2) as a secondary phase. Rietveld structure refinement of the recorded XRD data confirmed that the crystal structure of Ba4.5Nd9Ti18O54 (BNT) was orthorhombic (Pnma) with unit cell parameters a = 22.3412 Å, b = 7.6824 Å and c = 12.1952 Å. Ba4.5La9Ti18O54 (BLT) exhibited high relative permittivity (95.6), low quality factor (2,102 GHz) and a high temperature coefficient of resonance frequency (+352 ppm/°C). The substitution of Nd for La caused a decrease in both the relatively permittivity and temperature coefficient of resonance frequency to 84.2 and 167 ppm/°C respectively and an increase in quality factor to 8,007 GHz. Raman spectroscopic analysis revealed that lattice defects may be responsible for the observed decrease in quality factor of BLT ceramics in comparison to BNT. The Raman shifts at 533.5 and 613.6 cm?1, related to Ti–O bond stretching, decreased for BNT ceramics, which may be a possible reason for the observed decrease in relative permittivity. 相似文献
100.
Ahmed Iqbal I. Ani Rizwan Rajput 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(2):177-188
BACKGROUND: Generally the fabrication of polymeric membranes is a complicated and expensive process since it involves several steps. The preliminary preparation steps involve polymer drying and dissolution and is very time consuming and expensive. Currently, conventional electrothermal heating (CEH) is used to dissolve polyethersulfone in an aprotic solvent for membrane fabrication. Usually CEH requires 6 to 8 h at temperatures of 80 to 95 °C. This paper reports the fabrication and characterization of polyethersulfone (PES) asymmetric ultrafiltration membrane made from microwave (MW) synthesis casting solution consisting of various compositions of double solvents and lithium bromide (LiBr) additive. RESULTS: Homogeneous dual solvent dope solutions prepared via microware irradiation took only 1 h instead of the 7 h when prepared using CEH. The results also revealed that the membrane permeation and rejection rates, pore size and porosity were dependent on the ratio of LiBr to acetone. Membranes with LiBr kept at 2 and 3 wt% exhibited both high rejection and permeation rates with minimum pore sizes of 1.067 and 1.214 nm respectively. The presence of LiBr and the occurrence of chain scission were elucidated using Fourier transform infrared (FTIR) spectroscopy while its hydrophilic property was confirmed by water absorption and contact angle measurements. CONCLUSIONS: It was concluded that the microwave technique is capable of producing 1 L membrane solutions in less than 1 h. The membranes prepared from the microwave solutions show good rejection and permeation rates. Copyright © 2011 Society of Chemical Industry 相似文献