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Chakrabarti, K.,Nambissan, P.M.G.,Mukherjee, C.D.,Bardhan, K.K.,Kim, C.,Yang, K.S. Elsevier 2006 Carbon Vol.44 No.5
<P><B>Abstract</B></P><P>Polyacrylonitrile (PAN)-based carbon fibers, embedded with multi-wall carbon nanotubes (MWCNT) in different concentrations, have been prepared by an electrospinning technique and investigated using scanning electron microscopy, Raman, and positron annihilation spectroscopy. An analysis of the positron lifetime and Doppler broadened spectral line shape has been made. Positron lifetime spectra for all the samples give best fit for three distinct lifetime components. Raman data has been used to estimate the sp<SUP>2</SUP> mole fraction in the fiber. It is found that the gradual changes incorporated in the fiber due to the addition of MWCNTs are reflected as well defined changes in the positron lifetime and the <I>S</I> parameter of the Doppler broadened spectral line. Annihilation parameters are discussed from the point of view of formation of distinct positron trapping sites in the form of vacancy type defects at the interfaces of MWCNTs and the PAN matrix, and their variations in concentration due to different amount of MWCNTs added.</P>
Metal Surface Treatment Effects on Screen Printed Silicon Solar Cells
Chakrabarty K.,Mangalaraj D.,Kim K. H.,Dhungel S. K.,Park J. H.,Singh S. N. The Korean Institute of Electrical and Electronic 2003 Transactions on Electrical and Electronic Material Vol.4 No.4
High series resistance due to the presence of glass frit is one of the major problems for screen printed silicon solar cells. Cells having electrical parameters below the prescribed values are usually rejected during solar module fabrication. Therefore, it is highly desirable to improve the electrical parameters of the silicon solar cells and thereby to increase the overall production yield. It was observed that, the performance of low quality mono-crystalline silicon solar cells made by standard screen printing technology could be improved remarkably by novel surface treatment. We have chemically treated the surface using sodium hydroxide (NaOH) and silver nitrate ($AgNO_3$) solutions. NaOH treatment helps to reduce the series resistance by decreasing the presence of excess glass frit on the top silver grid contact. The $AgNO_3$ treatment is used to reduce the series resistance comes from the deposition of silver on the grids by filling the holes present (if any) within the grid pattern.
SPECTRAL PROPERTIES OF GALACTIC AND EXTRAGALACTIC BLACK HOLE CANDIDATES
CHAKRABARTI SANDIP K. The Korean Astronomical Society 1996 Journal of The Korean Astronomical Society Vol.29 No.suppl1
We review current theoretical understanding of the spectral properties (low and high states, transition of states, quasi-periodic oscillations etc.) of the low mass as well as supermassive black hole candidates.
K. Chakrabarty,D. Mangalaraj,Kim, Kyung-Hae,Park, J.H.,J. Yi The Korean Institute of Electrical and Electronic 2003 Transactions on Electrical and Electronic Material Vol.4 No.6
This paper describes the effect of halogenic gettering during oxide passivation of commercial solar cell with the $N^{+}$-P-$N^{+}$ structure. In order to study the effect of halogenic gettering on $N^{+}$-P-$N^{+}$ structure mono-crystalline silicon solar cell, we performed conventional POCl$_3$ diffusion for emitter formation and oxide passivation in the presence of HCl vapors. The $N^{+}$-P-$N^{+}$ structure based silicon solar cells were found to have higher short circuit current and minority carrier lifetime. Their performance was also found to be superior than the conventional $N^{+}$-P-$N^{+}$ structure based mono-crystalline silicon solar cell. The cell parameters of the $n^{+}$-p-$p^{+}$ and $n^{+}$-p-$n^{+}$ structure based cells, passivated by HCl assisted oxidation were measured. The improvement in $I_{sc}$ was attributed to the effect of the increased diffusion length of minority carriers, which came from the halogenic gettering effect during the growth of passivating oxide. The presence of chlorine caused gettering of the cells by removing the heavy metals, if any. The other advantage of the presence of chlorine was the removal of the diffusion induced (in oxygen environment) stacking faults and line defects from the surfaces of the silicon wafers. All these effects caused the improvement of the minority carrier lifetime, which in-turn helped to improve the quality of the solar cells.
Chakrabarty, D.,Datta, S.K. The Korean Society of Plant Biotechnology 2010 Plant biotechnology reports Vol.4 No.3
Six parent and their 12 gamma ray-induced somatic flower colour mutants of garden rose were characterized to discriminate the mutants from their respective parents and understanding the genetic diversity using Random amplification of polymorphic DNA (RAPD) markers. Out of 20 primers screened, 14 primers yielded completely identical fragments patterns. The other 7 primers gave highly polymorphic banding patterns among the radiomutants. All the cultivars were identified by using only 7 primers. Moreover, individual mutants were also distinguished by unique RAPD marker bands. Based on the presence or absence of the 48 polymorphic bands, the genetic variations within and among the 18 cultivars were measured. Genetic distance between all 18 cultivars varied from 0.40 to 0.91, as revealed by Jaccard's coefficient matrix. A dendrogram was constructed based on the similarity matrix using the Neighbor Joining Tree method showed three main clusters. The present RAPD analysis can be used not only for estimating genetic diversity present in gamma ray-induced mutants but also for correct identification of mutant/new varieties for their legal protection under plant variety rights.
Metal Surface Treatment Effects on Screen Printed Silicon Solar Cells
K.Chakrabarty,D.Mangalaraj,김경해,S.K.Dhungel,J.H.Park,이준신,S.N.Singh 한국전기전자재료학회 2003 Transactions on Electrical and Electronic Material Vol.4 No.4
High series resistance due to the presence of glass frit is one of the major problems for screen printed silicon solar cells. Cells having electrical parameters below the prescribed values are usually rejected during solar module fabrication. Therefore, it is highly desirable to improve the electrical parameters of the silicon solar cells and thereby to increase the overall production yield. It was observed that, the performance of low quality mono-crystalline silicon solar cells made by standard screen printing technology could be improved remarkably by novel surface treatment. We have chemically treated the surface using sodium hydroxide (NaOH) and silver nitrate (AgNO3) solutions. NaOH treatment helps to reduce the series resistance by decreasing the presence of excess glass frit on the top silver grid contact. The AgNO3 treatment is used to reduce the series resistance comes from the deposition of silver on the grids by filling the holes present (if any) within the grid pattern.