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Multi-Secondary Transformer: A Modeling Technique for Simulation - II
Patel, A.,Singh, N.P.,Gupta, L.N.,Raval, B.,Oza, K.,Thakar, A.,Parmar, D.,Dhola, H.,Dave, R.,Gupta, V.,Gajjar, S.,Patel, P.J.,Baruah, U.K. Journal of International Conference on Electrical 2014 Journal of international Conference on Electrical Vol.3 No.1
Power Transformers with more than one secondary winding are not uncommon in industrial applications. But new classes of applications where very large number of independent secondaries are used are becoming popular in controlled converters for medium and high voltage applications. Cascade H-bridge medium voltage drives and Pulse Step Modulation (PSM) based high voltage power supplies are such applications. Regulated high voltage power supplies (Fig. 1) with 35-100 kV, 5-10 MW output range with very fast dynamics (${\mu}S$ order) uses such transformers. Such power supplies are widely used in fusion research. Here series connection of isolated voltage sources with conventional switching semiconductor devices is achieved by large number of separate transformers or by single unit of multi-secondary transformer. Naturally, a transformer having numbers of secondary windings (~40) on single core is the preferred solution due to space and cost considerations. For design and simulation analysis of such a power supply, the model of a multi-secondary transformer poses special problem to any circuit analysis software as many simulation softwares provide transformer models with limited number (3-6) of secondary windings. Multi-Secondary transformer models with 3 different schemes are available. A comparison of test results from a practical Multi-secondary transformer with a simulation model using magnetic component is found to describe the behavior closer to observed test results. Earlier models assumed magnetising inductance in a linear loss less core model although in actual it is saturable core made-up of CRGO steel laminations. This article discusses a more detailed representation of flux coupled magnetic model with saturable core properties to simulate actual transformers very close to its observed parameters in test and actual usage.
Dubey, Pawan K.,Tripathi, Vrajesh,Singh, Ram Pratap,Sastry, K.V.H.,Sharma, G.Taru Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.9
Objective of this study was to examine the effect of sodium nitroprusside (SNP), a nitric oxide (NO) donor on steroid synthesis, growth and apoptosis of buffalo granulosa cells (GCs) in vitro. Follicular fluid of antral follicles (3-5 mm diameter) was aspirated and GCs were cultured in 0 (control), $10^{-3}$, $10^{-5}$, $10^{-7}$, $10^{-9}\;M$ of SNP for 48 h. To evaluate whether this effect was reversible, GCs were cultured in presence of $10^{-5}\;M$ SNP+1.0 mM $N^{\omega}$-nitro-L-arginine methyl ester (L-NAME) a NO synthase (NOS) inhibitor or hemoglobin (Hb, $1.0{\mu}g$) as NO scavenger. Nitrate/nitrite concentration was evaluated by Griess method, progesterone and estradiol concentrations by RIA and apoptosis by TUNEL assay. SNP ($10^{-3}$, $10^{-5}$, $10^{-7}\;M$) significantly (p<0.05) inhibited estradiol and progesterone synthesis, growth, disorganized GCs aggregates and induced apoptosis in a dose dependent manner. However, $10^{-9}\;M$ SNP induced the progesterone synthesis and stimulated GCs to develop into a uniform monolayer. Combination of SNP $10^{-5}$ M+L-NAME strengthened the inhibitory effect while, SNP+Hb together reversed these inhibitory effects. In conclusion, SNP at greater concentrations ($10^{-3}$, $10^{-5}$ and $10^{-7}\;M$) has a cytotoxic effect and it may lead to cell death whereas, at a lower concentration ($10^{-9}\;M$) induced progesterone synthesis and growth of GCs. These findings have important implications that NOS derived NO are involved at physiological level during growth and development of buffalo GCs which regulates the steroidogenesis, growth and apoptosis.
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Srivastava, A. K.,Singh, P. K.,Pawar, S. U.,Gao, H.,Mardina, P. Springer Science + Business Media 2016 Journal of materials science Materials in electron Vol.27 No.5
<P>Fe doped CeO2 powder was prepared using solution combustion method. Powder X-ray diffraction and scanning electron microscopy methods are used to characterize the combustion derived powder. The optical absorption spectrum exhibits three bands due to Fe3+ and Fe2+ ions. Electron paramagnetic resonance (EPR) spectrum of this sample exhibits number of resonance signals due to Fe3+ ions. The number of spins (N) participating in resonance and its paramagnetic susceptibility (chi) has been evaluated. From EPR and optical studies it is observed that iron ions are present in trivalent state.</P>
Eu2+ and Mn2+ Co-doped BaMgAl10O17 Blue- and Green-Emitting Phosphor: A Luminescence and EPR Study
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Srivastava, A. K.,Jirimali, H. D.,Li, J.,Gao, H.,Kumaran, R. S.,Singh, P. K. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.6
<P>Eu2+ and Mn2+ co-doped BaMgAl10O17 phosphor has been prepared by a solution combustion method. The structural, morphological and compositional analysis of the BaMgAl10O17:Eu2+ and Mn2+ powders have been studied by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The electron paramagnetic resonance (EPR) spectrum exhibited resonance signals with the effective g values of g a parts per thousand 4.88 and g a parts per thousand 1.98. The resonance signal with the effective g value of g a parts per thousand 4.88 is characteristic of Eu2+ ions whereas g a parts per thousand 1.98 is due to Mn2+ ions. The number of spins participating in resonance, Gibbs free energy, magnetic susceptibility, Curie constant, effective magnetic moment, zero-field splitting parameter and hyperfine splitting constant have been evaluated. From optical and EPR correlation, it is inferred that Eu2+ and Mn2+ are present in the BaMgAl10O17 matrix.</P>
Cr3+-Doped Yb3Ga5O12 Nanophosphor: Synthesis, Optical, EPR, Studies
Singh, V.,Sivaramaiah, G.,Rao, J. L.,Singh, N.,Pathak, M. S.,Jirimali, H. D.,Singh, P. K.,Srivastava, A. K.,Dhoble, S. J.,Mohapatra, M. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.8
<P>Gallium garnets of lanthanides are multifunctional materials especially known for their complicated structure and magnetic properties. In addition, with a suitable transition metal dopant ion, these matrices have been proved to be excellent materials for lasers. In particular, gallium garnet of ytterbium (Yb3Ga5O12) is known to possess excellent properties with regards to these applications. In this connection, Yb3Ga5O12 doped with Cr3+ nanophosphors were synthesized by a solution combustion route. The synthesized material was characterized by powder x-ray diffraction and scanning electron microscopy for phase purity and homogenous morphology. In order to ascertain the oxidation state of the doped ion, diffuse reflectance (DRF), photoluminescence (PL) and electron paramagnetic resonance (EPR) experiments were performed on the sample. The DRF and PL data suggested the stabilisation of the trivalent Cr ion in the matrix. The EPR spectra exhibited two resonance signals with effective g values at g approximate to 7.6 and 4. The EPR data corroborated the DRF and PL results, suggesting the stabilisation of Cr3+ in the matrix at octahedral-type geometries.</P>
Singh, R.P.,Sastry, K.V.H.,Pandey, N.K.,Shit, N.G.,Agarwal, R.,Singh, R.,Sharma, S.K.,Saxena, V.K.,Jagmohan, Jagmohan Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.8
The LDH isozymes are key catalysts in the glycolytic pathway of energy metabolism. It is well known that the distribution of the LDH isozymes vary in accordance with the metabolic requirements of different tissues. The substrates required for energy production change noticeably at successive stages of testes development suggesting a significant flexibility in the expression of glycolytic enzymes. Therefore, expression of LHDA and LDHB mRNAs was examined in adult and prepubertal quail testis. The mRNA of both LDHA and LDHB were expressed and no significant difference was observed in prepubertal testes. The mRNA levels of LDHB significantly increased during testicular development. In the adult testis, LDHA mRNA was not expressed. Expression studies revealed the presence of different LDH isozymes during testicular development. In contrast, electrophoresis of both testicular samples revealed only single band at a position indicative of an extreme type of LDH isozyme in quail testes. Furthermore, nucleotide and amino acid sequence analysis revealed significant similarity to chicken, duck and rock pigeon. These sequence results confirmed the similarity of LDHA and LDHB subunit protein in different avian species.