排序方式: 共有21条查询结果,搜索用时 31 毫秒
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Brajesh Tiwari Babu Baijnath Prasad Rajveer Jha Dharmendra Kumar Singh V. P. S. Awana 《Journal of Superconductivity and Novel Magnetism》2014,27(10):2181-2183
In the present short letter, we report on the low dimensional 4d and 5d transition metals-chalcogenide based compounds i.e., Ta2PdxS6, showing semiconducting to superconducting transition at around 4K with their upper critical fields outside the Pauli paramagnetic limit. It seems couple of different superconducting phases do exist in these new set of compounds. Our short letter in this regards is thought provoking, asking to explore various unearthed possible new superconducting phases in (Nb/Ta)2Pdx(S/Se/Te)y systems. 相似文献
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In this paper, a STATCOM (static synchronous compensator) is used to encounter the potential SSR (subsynchronous resonance) observed by IG (Induction Generator) based series compensated wind farms. The basic controller used for STATCOM control is identical to that of the literature. An idea of a unique meta‐heuristic swarm‐based optimization technique called BFOA (bacterial foraging optimization algorithm) based optimal‐controller is introduced for optimal parameter selection of the basic controller used in the control scheme of the STATCOM. The investigation is carried out with 500 MW IG‐based wind farm exposed to three‐phase LLL‐G fault close to the PCC (point of common coupling) and implemented with MATLAB in both steady and transient states for the three different cases, namely, without STATCOM, with the basic STATCOM controller, and in the presence of the proposed BFOA‐optimal controller‐based STATCOM. In both the states, the observed eigenvalues of the test system, together with the time domain results of the generator rotor dynamics for three distinct cases, reveals the effectiveness of the suggested BFOA‐optimal controller tuned STATCOM in mitigating the potential SSR. 相似文献
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Rajveer Jha Jeevan Jyoti V. P. S. Awana 《Journal of Superconductivity and Novel Magnetism》2013,26(10):3069-3074
We report the effect of Gd inclusion in the NbN superconductor thin films. The films are deposited on single crystalline Silicon (100) by DC reactive sputtering technique, i.e., deposition of Nb and Gd in presence of reactive N2 gas. The fabricated relatively thick films (400 nm) are crystallized in cubic structure. These films are characterized for their morphology, elemental analysis, and roughness by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDAX), and Atomic Force Microscopy (AFM) respectively. The optimized film (maximum T c ) is achieved with gas ratio of Ar:N2 (80:20) for both pristine and Gd-doped films. The optimized NbN film possesses T c (R=0) in zero and 140 kOe fields are at 14.8 K and 8.8 K, respectively. The Gd-doped NbN film showed T c (R=0) in zero and 130 kOe fields at 11.2 K and 6.8 K, respectively. The upper critical field H c2(0) of the studied superconducting films is calculated from the magneto-transport [R(T)H] measurements using GL equations. It is found that Gd doping deteriorated the superconducting performance of NbN. 相似文献
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Bakshi Garima Vaish Arti Yaduvanshi Rajveer Singh 《Wireless Personal Communications》2019,108(2):895-905
Wireless Personal Communications - This paper presents a novel design of antenna using sapphire. An aperture coupled two- layer stacked rectangular dielectric resonator antenna structure design... 相似文献
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Rajveer Singh Rathore Dhananjay Kumar Srivastava Avinash Kumar Agarwal Nishith Verma 《Journal of hazardous materials》2010,173(1-3):211-222
This study investigates the development and potential application of activated carbon fibers (ACF) functionalized with ammonia for control of NO and particulate matter (PM) in diesel engine exhaust. A tubular reactor packed with ACF was used to experimentally study the oxidation of NO at room temperature. Tests were conducted at ACF functionalized with three aqueous ammonia concentrations (3, 5, 10 M), three basic reagents (ammonia, pyridine, amine) and three NO concentrations (100, 300, 500 ppm). After offline investigation, the ACF-packed tubular reactor was installed downstream of the engine's exhaust to ascertain the PM capturing efficiency of ACF. The experimental conditions for PM removal included three weights of ACF (2, 3.5, 4.5 g), three engine loads (0, 25, 50 Nm) and three temperatures (150, 300, 450 °C). The maximum 70% conversion for NO was obtained at NO concentration of 300 ppm for ACF functionalized with 5 M ammonia, whereas maximum 90% reduction in PM was observed at engine load of 25 Nm and 450 °C. The study shows significant potential for the ACF based filters in capturing both homogeneous and heterogeneous pollutants emitted from automobiles. Our previously developed transport model incorporating the mechanism for the oxidation of NO was also used to explain the experimental data. 相似文献
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Rajveer?Jha V.?P.?S.?AwanaEmail author 《Journal of Superconductivity and Novel Magnetism》2015,28(8):2229-2233
We report bulk superconductivity at 2.5 K in LaO0.5F0.5BiSe2 compound through the DC magnetic susceptibility and electrical resistivity measurements. The synthesized LaO0.5F0.5BiSe2 compound is crystallized in tetragonal structure with space group P4/nmm and Reitveld refined lattice parameters are a = 4.15(1) Å and c = 14.02(2) Å. The lower critical field of H c1 = 40 Oe, at temperature 2 K is estimated through the low field magnetization measurements. The LaO0.5F0.5BiSe2 compound showed metallic normal state electrical resistivity with residual resistivity value of 1.35 m Ω cm. The compound is a type-II superconductor, and the estimated H c2(0) value obtained by WHH formula is above 20 kOe for 90 % ρ n criteria. The superconducting transition temperature decreases with applied pressure till around 1.68 GPa and with further higher pressures a high- T c phase emerges with possible onset T c of above 5 K for 2.5 GPa. 相似文献
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Rajveer Jha Poonam Rani V. P. S. Awana 《Journal of Superconductivity and Novel Magnetism》2014,27(2):287-291
In this letter, we present the superconducting property characterization of a phase pure, reasonably good quality YBa2Cu3O7?δ sample. Studied compound is crystallized in orthorhombic Pmmm space group with lattice parameters a, b, and c being 3.829(2), 3.887(1) and 11.666(3) Å, respectively. Bulk superconductivity is observed below 90 K as evidenced by resistivity and dc/ac magnetization measurements. The resistivity under magnetic field (ρTH) measurements showed clearly both the intra-grain and inter-grain transitions, which are supplemented by detailed (of varying frequency and amplitude) ac susceptibility studies as well. The upper critical field at 0 K, i.e. H c2(0) being determined from ρTH measurements with 50 % criteria of resistivity drop, is ~70 T. Studied polycrystalline YBa2Cu3O7?δ is subjected to detailed heat capacity (C P ) studies. C P exhibited well-defined anomaly at below 90 K, which decreases with applied field. Although the C P anomaly/peak at T c reduces with applied field, the same is not completely suppressed in high applied fields of up to 12 T. The Sommerfeld constant (γ) and Debye temperature (Θ D), as determined from low temperature fitting of C P (T) data to Sommerfeld–Debye model, are 10.65 mJ/mole-K2 and 312.3 K, respectively. The results are compared with existing literature on bulk polycrystalline superconducting YBa2Cu3O7?δ sample. 相似文献
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Poonam Rani Rajveer Jha V. P. S. Awana 《Journal of Superconductivity and Novel Magnetism》2013,26(7):2347-2352
We report the effect of silver addition on superconducting performance of bulk YBCO (YBa2Cu3O7) superconductor. All the studied samples are prepared by conventional solid-state reaction method. Rietveld fitted X-ray diffraction data confirmed the single phase formation for all the studied samples. Detailed AC susceptibility measurements as a function of driven AC amplitude (1 Oe–17 Oe) of these samples revealed the enhancement of grains coupling with increasing Ag content in YBCO + Ag x composite system. 10 wt% Ag added YBCO superconductors exhibited the optimal intergranular coupling. The Scanning Electron Microscopy (SEM) observations indicate an increase in the grains connectivity in terms of narrow grain boundaries for doped samples. The average grain size is found to increase with Ag doping. It is concluded that limited addition of Ag in bulk YBCO superconductor significantly improves the grains coupling and, as a result, the optimal superconducting performance. YBCO + Ag composites could prove to be potential candidates for bulk superconducting applications of the studied high-T c system. 相似文献