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- 저자 : R. D. Jha (검색결과 3 건)
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Electron-Electron Interactions based Metal-Insulator Transition in Ga Doped ZnO Thin Films
R V Muniswami Naidu,A Subrahmanyam,A Verger,M K Jain,S V N Bhaskara Rao,S N Jha,D M Phase 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.4
We report on the charge carrier transport mechanisms of undoped and Ga doped (2 wt. % and 4 wt. %)ZnO thin films grown by pulsed dc magnetron sputtering technique. Temperature dependent resistivity measurements showed typical semiconducting behaviour for undoped ZnO thin films where as Ga doped ZnO thin films showed metallic nature at higher temperatures and insulating nature with a metal to insulator transition at lower temperatures. The observed transition temperatures are 91 K and 140 K for 2 wt. % and 4 wt. %Ga doped ZnO films respectively. The observed metal insulator transition is attributed to the electron-electron interactions at low temperatures. The variations in the transition temperatures are explained based on the disorderness induced in the system due to the doping effect. ZnO doped with 4 wt. % Ga showed the lowest resistivity of 5.7 × 10−4Ω cm with a carrier concentration of 1.2 × 1021/cm3. Undoped and doped ZnO thin films are about 90% transparent in the visible region. Blue shift is observed in the absorption edge with the effect of doping and it is explained based on B-M shift. The Fermi level measured from valance band spectroscopy showed a shift of +0.6 eV for 2 wt. % Ga doped ZnO thin film and +0.7 eV for 4 wt. %Ga doped ZnO thin film compared to the Fermi edge of undoped ZnO thin films. This ascertains the movement of Fermi level in to the conduction band with the effect of doping.
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Divakar R. Jaiswar,Purnima D. Amin,Durgesh Jha 한국약제학회 2016 Journal of Pharmaceutical Investigation Vol.46 No.7
In the present study aim was to prepare stable solid solution azithromycin dihydrate (AZI) by hot melt extrusion technology (HME). Soluplus and Kollidon VA 64 were selected among polymers based on Hansen solubility parameter calculation in order to prepare amorphous of AZI. Further physicochemical properties of extrudates were characterized by DSC, FTIR, XRD, SEM and contact angle measurement. DSC revealed single broad endothermic peak in extrudates indicated miscibility of AZI into polymeric carriers, which formed monophasic solid system termed as solid solution. XRD confirmed amorphous nature of AZI in extrudates. DSC and XRD suggested molecular dispersion of AZI in polymeric carriers. Amorphous AZI exhibited statistically significant high solubility (P\0.0001) in water in comparison with pure AZI. Solid solution batch AZI 03 showed significant enhancement in solubility (P = 0.0004) in pH 6. The dissolution in dissolution medium pH 6 and water resulted in statistically significant differences (P\0.05) in the percentage amorphous AZI dissolved compared to the percentage AZI dissolved over the period of 60 min. Solid solution formulation showed better wettability than that of pure AZI. Amorphization and increased wettability attributed to solubility and dissolution rate enhancement. Assay and amorphous solid solution characteristics of AZI were found to be stable under accelerated storage condition as per ICH guideline for a period of six months. Therefore, hot melt extrusion technology was suitable method to prepare stable solid solution and dissolution rate enhancement for poorly soluble active like AZI.
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Synchronization and Operation of Parallel Inverters using Droop Control
L. K. Sahoo,N. D. Thakur,K. Rai,P Sensarma,R. D. Jha,P. Mohanty,A Sharma 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
To obtain a continuous power supply Distributed Generation (DG) with a Decentralized Power System (DPS), i.e. replacing a single UPS unit with multiple, smaller units in parallel, is emerging as new paradigm. The technically challenging aspect of DPS is the synchronization of inverters and load sharing among the parallel connected inverters. In this paper, a control method is proposed and implemented for synchronization and parallel operation of inverters. Droop control method has been used for equal power sharing, and design of power control loop. The design issues for voltage control loop are analyzed with the discussion of relative stability of the system. A current control loop is designed and analyzed to provide synchronization between the inverters.
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