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1,080 results on '"Chattopadhyay, P. K."'

151. First order transition from antiferromagnetism to ferromagnetism in Ce(Fe$_{0.96}$Al$_{0.04})_2$

Author

Manekar, M. A., Chaudhary, S., Chattopadhyay, M. K., Singh, K. J., Roy, S. B., and Chaddah, P.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
Abstract

Results of dc magnetization study are presented showing interesting thermomagnetic history effects across the antiferromagnetic to ferromagnetic transition in Ce(Fe$_{0.96}$Al$_{0.04})_2$. Specifically, we observe (i)ZFC/FC irreversibility rising with increasing field; (ii) virgin curve lying outside the envelope M-H curve. We argue that these effects are quite different from the characteristics seen in spin-glasses or in hard ferromagnets; they can be understood as metastabilities associated with a first order magnetic phase transition., Comment: 10 pages and 5 figures

Published
2000
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152. First order metamagnetic transition in CeFe$_2$ based pseudobinary alloys

Author

Manekar, Meghmalhar, Chaudhary, Sujeet, Chattopadhyay, M. K., Singh, Kanwal Jeet, Roy, S. B., and Chaddah, P.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

We present results of dc magnetisation study showing that the low temperature antiferromagnetic state in various CeFe$_2$-based pseudobinary alloys can be transformed into ferromagnetic state through a magnetic field induced phase transition. We highlight the presence of hysteresis and phase coexistence across this metamagnetic transition and argue that the observed phase transition is of first order in nature., Comment: 11 pages of text and 9 figures ; to appear in Journal of Physics: Condens. Matter

Published
2000
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157. Three-Phase NPC-LDN Hybrid Transformerless Multilevel Inverter

Author

Tak, Neha and Chattopadhyay, Sumit K.

Abstract

The proposed inverter topology is evolved from multiple level-doubling-network (LDN) based state-of-the-art topology, where power frequency isolation-transformer is used at the ac output. The proposed work removes the transformer by replacing the main bridges by three-phase TNPC (T-type neutral point clamped) converter. The major issue of this hybrid topology is capacitor balancing of NPC with LDN operation. To solve this issue two different methods are proposed in this article. In these methods, an additional circuitry is added for capacitor balancing. The worst-case power handled by this additional converter is negligible compared to power handling capability of the entire converter. Hence, a full-capacity transformer is replaced by a nonisolated dc–dc converter of fractional rating. Both manufacturing cost and operating cost (losses) are substantially reduced. The proposed topology does not require any isolated auxiliary power supply as well as only one dc source is used for entire topology. Operation of the proposed topology is verified with PV fed grid-connected single stage operation and restricted the leakage current within limit. To validate the concept simulation is carried out in MATLAB/Simulink. A laboratory prototype is developed for experimental verification of the concept. Hardware results matched well with the simulation.

Published
2024
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158. Two-Stage Three-Phase Transformerless Hybrid Multilevel Inverter for Solar PV Application

Author

Tak, Neha and Chattopadhyay, Sumit K.

Abstract

The proposed inverter topology is emerged from the multiple level-doubling-network (LDN) based topology for grid-connected solar photovoltaic (PV) system, where dc buses of three phases could not be merged without electrical isolation. Three-phase T-neutral point clamped (TNPC) is used to merge all the three phases without transformer. Due to LDN operation, balancing the capacitors of TNPC (main bridge) is a major challenge. A dc–dc converter is customized in this work, which is normally required for two-stage operation of solar PV inverter. This converter topology reduces the size and losses of filter inductors due to high-resolution inverter output voltage in addition to restricting the leakage current well below the relevant standards. To validate the concept, experiments are carried out using hardware prototype and those matched well with simulation result.

Published
2024
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161. Behavior of ion acoustic solitons in a two-electron temperature plasma of a multi-pole line cusp plasma device (MPD).

Author

Shaikh, Zubin, Patel, A. D., Chattopadhyay, P. K., Ghosh, Joydeep, Joshi, H. H., and Ramasubramanian, N.

Subjects
PLASMA devices, SOLITONS, PLASMA temperature, MACH number, ELECTRON temperature, MAGNETIC fields
Abstract

This article presents the experimental observations and characterization of ion acoustic solitons (IASs) in a unique multi-pole line cusp plasma device (MPD), in which the magnitude of the pole-cusp magnetic field can be varied. In addition, by varying the magnitude of the pole-cusp magnetic field, the proportion of the two-electron-temperature components in the filament-produced plasmas of the MPD can be varied. The solitons are experimentally characterized by measuring their amplitude-width relation and Mach numbers. The nature of the solitons is further established by making two counter-propagating solitons interact with each other. Later, the effect of the two-temperature electron population on soliton amplitude and width is studied by varying the magnitude of the pole cusp-magnetic field. It has been observed that different proportions of two-electron-temperature significantly influence the propagation of IASs. The amplitude of the solitons has been found to be inversely proportional to the effective electron temperature (Teff). [ABSTRACT FROM AUTHOR]

Published
2023
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181. Controlling the rotation of drift tearing modes by biased electrode in ADITYA-U tokamak

Author

Macwan, Tanmay, primary, Singh, Kaushlender, additional, Dolui, Suman, additional, Kumar, Ankit, additional, Raj, Harshita, additional, Gautam, Pramila, additional, Edappala, Praveenlal, additional, Ghosh, J., additional, Tanna, R. L., additional, Kumar, Rohit, additional, Jadeja, K. A., additional, Patel, K. M., additional, Aich, Suman, additional, Kumar, Sameer, additional, Raju, D., additional, Chattopadhyay, P. K., additional, Sen, A., additional, Saxena, Y. C., additional, and Pal, R., additional

Published
2021
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183. Plasma column position measurements using magnetic diagnostics in ADITYA-U tokamak

Author

Aich, S, primary, Kumar, R, additional, Macwan, T M, additional, Kumavat, D, additional, Jha, S, additional, Tanna, R L, additional, Sathyanarayana, K, additional, Ghosh, J, additional, Jadeja, K A, additional, Patel, K, additional, Patel, Sharvil, additional, Ranjan, Vaibhav, additional, Kalal, Madanlal, additional, Varia, Dinesh, additional, Sadharkiya, D, additional, Raju, D, additional, Chattopadhyay, P K, additional, Gupta, C N, additional, and Saxena, Y C, additional

Published
2021
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184. Interferon alfa-2b in patients with low-grade lymphomatoid granulomatosis and chemotherapy with DA-EPOCH-R in patients with high-grade lymphomatoid granulomatosis: an open-label, single-centre, phase 2 trial

Author

Melani, Christopher, Dowdell, Kennichi, Pittaluga, Stefania, Dunleavy, Kieron, Roschewski, Mark, Song, Joo Y, Calattini, Sara, Kawada, Jun-ichi, Price, David A, Chattopadhyay, Pratip K, Roederer, Mario, Lucas, Andrea N, Steinberg, Seth M, Jaffe, Elaine S, Cohen, Jeffrey I, and Wilson, Wyndham H

Abstract

Lymphomatoid granulomatosis is a rare Epstein-Barr virus-associated B-cell lymphoproliferative disorder with a median overall survival of less than 2 years. In this study, we hypothesised that low-grade lymphomatoid granulomatosis is immune-dependent and high-grade lymphomatoid granulomatosis is immune-independent. On the basis of this hypothesis, we investigated the activity and safety of new treatment with immunotherapy in patients with low-grade disease and standard chemotherapy in patients with high-grade disease.

Published
2023
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