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Search Results: 1 - 10 of 7729 matches for " Siddhartha Das "
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Combustion and Ball Milled Synthesis of Rare Earth Nano-Sized Ceria Powder  [PDF]
Ranjan Sen, Siddhartha Das, Karabi Das
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.25054
Abstract: This paper reports a study on nanocrystalline ceria powder prepared by high energy ball-milling and combustion synthesis methods. The combustion synthesis was carried out using ceric ammonium nitrate as oxidizer and citric acid, glycine or citric acid plus glycine as fuel. The minimum crystallite size of ceria powder is obtained by combustion synthesis of ceric ammonium nitrate and citric acid. The ceria powder produced by combustion synthesis of ceric ammonium nitrate and citric acid and glycine has less agglomeration of particles than other techniques.
Preparation and Antibacterial Activity of Silver Nanoparticles  [PDF]
Ratan Das, Sneha Gang, Siddhartha Sankar Nath
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2011, DOI: 10.4236/jbnb.2011.24057
Abstract: Uniform silver nanoparticles have been prepared through the chemical reduction of silver ions by ethanol in presence of sodium linoleate. TEM micrograph shows a uniform distribution of the particles with an average size of 12 nm. Further, the antimicrobial activity of silver nanoparticles shows that these nanoparticles can be used as effective growth inhibitors against Staphylococcus Basillus, Staphylloccoccus Aureus, and Pseudimonas Aureginosa.
Punch grafting as a treatment for residual lesions of vitiligo
Das Siddhartha,Pasricha J
Indian Journal of Dermatology, Venereology and Leprology , 1992,
Abstract: Sixty patients having 70 residual lesions of vitiligo not responding to medical treatment for a period of at least 4 months were subjected to punch grafting. The donor skin was taken from the buttock, thigh or leg of the same patients with a 4 mm skin biopsy punch and placed on the recipient area prepared by excising the vitiliginous skin with a 3 mm skin biopsy punch. The recipient areas were placed at a distance of 1 cm from the margin of the lesion and 1-2 cm from each other. Out of total of 280 grafts applied in these lesions, 256 (91.1%) gfafts were successful, while 21 grafts were rejected, 2 grafts became depigmented and 1 graft developed into a keloid. The pigment spread centrifugally around each of the successful grafts and 76% of grafts showed a pigment-spread of more than 6 mm within 6 months. Pigment continued to spread even in the grafts applied 2 years ago and the maximum spread so far has been 22 mm. The pigment-spread was faster in the lesions situated on the trunk, neck, face and proximal parts of the extremities. Lesions on the dorsal aspects of hands, fingers, feet and maleoli were slow to repigment. Treatment of the lesion with topical psoralen followed by sun exposure led to a faster spread of pigmentation.
Formation and post-formation dynamics of bacterial biofilm streamers as highly viscous liquid jets
Siddhartha Das,Aloke Kumar
Physics , 2013, DOI: 10.1038/srep07126
Abstract: It has been recently reported that in presence of low Reynolds number (Re<<1) transport, preformed bacterial biofilms, several hours after their formation, may degenerate in form of filamentous structures, known as streamers. In this letter, we explain that such streamers form as the highly viscous liquid states of the intrinsically viscoelastic biofilms. Such "viscous liquid" state can be hypothesized by noting that the time of appearance of the streamers is substantially larger than the viscoelastic relaxation time scale of the biofilms, and this appearance is explained by the inability of a viscous liquid to withstand an external shear. Further, by identifying the post formation dynamics of the streamers as that of a viscous liquid jet in a surrounding flow field, we can interpret several unexplained issues associated with the post-formation dynamics of streamers, such as the clogging of the flow passage or the exponential time growth of streamer dimensions.
Implications of Interactions between Steric Effects and Electrical Double Layer Overlapping Phenomena on Electro-Chemical Transport in Narrow Fluidic Confinements
Siddhartha Das,Suman Chakraborty
Physics , 2010,
Abstract: In this paper, we study the non-trivial interactions between the ionic Steric effects and Electric Double Layer (EDL) overlap phenomenon on the resultant electro-chemical transport in narrow fluidic confinements. Through a comprehensive mathematical model, we demonstrate that more prominent Steric effects may result in greater magnitudes of the channel centerline potential. However, since the magnitude of the zeta potential also gets perpetually enhanced with Steric interactions, this phenomenon cannot by be considered by itself as a trivial interpreter of an augmentation in the extent of the effective EDL overlap. Further investigations in this regard, however, do reveal an intricate coupling between EDL overlap phenomenon and finite ionic size effects, so as to result in an effective enhancement in the extent of EDL overlap, far beyond what is predicted by classical electrochemical considerations. Insights are also provided on the possible implications of the intricate interactions of the underlying physico-chemical mechanisms on the design of future- generation nanofluidic devices.
Relationship between the microstructure and properties of thermomechanically processed Fe?17Mn and Fe?17Mn?3Al steels
Renuprava Dalai,Siddhartha Das,Karabi Das
- , 2019, DOI: https://doi.org/10.1007/s12613-019-1710-3
Abstract: Two austenitic Mn steels (Fe?17Mn and Fe?17Mn?3Al (wt%, so as the follows)) were subjected to thermomechanical processing (TMP) consisting of forging followed by solutionization and hot rolling. The rolled samples were annealed at 650 and 800°C to relieve the internal stress and to induce recrystallization. The application of TMP and heat treatment to the Fe?17Mn/Fe?17Mn?3Al steels refined the austenite grain size from 169 μm in the as-solutionized state to 9–13 μm, resulting in a substantial increase in hardness from HV 213 to HV 410 for the Fe?17Mn steel and from HV 210 to HV 387 for the Fe?17Mn?3Al steel. The elastic modulus values, as evaluated by the nanoindentation technique, increased from (175 ± 11) to (220 ± 12) GPa and from (163 ± 15) to (205 ± 13) GPa for the Fe?17Mn and Fe?17Mn?3Al steels, respectively. The impact energy of the thermomechanically processed austenitic Mn steels was lower than that of the steels in their as-solutionized state. The addition of Al to the Fe?17Mn steel decreased the hardness and elastic modulus but increased the impact energy.
A decision support framework for performance evaluation of Indian technical institutions
Manik Chandra Das,Bijan Sarkar,Siddhartha Ray
Decision Science Letters , 2013, DOI: 10.5267/j.dsl.2013.06.005
Abstract: There are many opportunities and challenges in the area of Indian technical education due to liberalization and globalization of economy. One of these challenges is how to assess the performance of technical institutions based on multiple criteria. The purpose of this paper is to describe and illustrate an application of a structured approach to determine relative performance and ranking of seven Indian Institutes of Technology (IITs) under multi-criteria environment. To evaluate the alternatives in respect to stakeholders’ preference we suggest a new methodology consisting of fuzzy AHP, DEA and TOPSIS. Fuzzy AHP technique is used to determine the weights of criteria and some linguistic terms are applied to assess performance under each criterion, then in order to determine the value of linguistic terms we use the data envelopment analysis (DEA) method. Finally TOPSIS method is used to aggregate performance scores under different criteria into an overall performance score for each institution and ranking the institution according to their overall performance score. The proposed fuzzy AHP–DEA–TOPSIS methodology is applicable to any multiple criteria decision making (MCDM) problem due to its generic nature.
Effect of Impurities in Description of Surface Nanobubbles
Siddhartha Das,Jacco H. Snoeijer,Detlef Lohse
Physics , 2010, DOI: 10.1103/PhysRevE.82.056310
Abstract: Surface nanobubbles emerging at solid-liquid interfaces of submerged hydrophobic surfaces show extreme stability and very small (gas-side) contact angles. In a recent study Ducker (W. A. Ducker, Langmuir 25, 8907 (2009).) conjectured that these effects may arise from the presence of impurities at the air-water interface of the nanobubbles. In this paper we present a quantitative analysis of this hypothesis by estimating the dependence of the contact angle and the Laplace pressure on the fraction of impurity coverage at the liquid-gas interface. We first develop a general analytical framework to estimate the effect of impurities (ionic or non-ionic) in lowering the surface tension of a given air-water interface. We then employ this model to show that the (gas-side) contact angle and the Laplace pressure across the nanobubbles indeed decrease considerably with an increase in the fractional coverage of the impurities, though still not sufficiently small to account for the observed surface nanobubble stability. The proposed model also suggests the dependencies of the Laplace pressure and the contact angle on the type of impurity.
Improved Bounds on RIP for Generalized Orthogonal Matching Pursuit
Siddhartha Satpathi,Rajib Lochan Das,Mrityunjoy Chakraborty
Mathematics , 2013, DOI: 10.1109/LSP.2013.2279977
Abstract: Generalized Orthogonal Matching Pursuit (gOMP) is a natural extension of OMP algorithm where unlike OMP, it may select $N (\geq1)$ atoms in each iteration. In this paper, we demonstrate that gOMP can successfully reconstruct a $K$-sparse signal from a compressed measurement $ {\bf y}={\bf \Phi x}$ by $K^{th}$ iteration if the sensing matrix ${\bf \Phi}$ satisfies restricted isometry property (RIP) of order $NK$ where $\delta_{NK} < \frac {\sqrt{N}}{\sqrt{K}+2\sqrt{N}}$. Our bound offers an improvement over the very recent result shown in \cite{wang_2012b}. Moreover, we present another bound for gOMP of order $NK+1$ with $\delta_{NK+1} < \frac {\sqrt{N}}{\sqrt{K}+\sqrt{N}}$ which exactly relates to the near optimal bound of $\delta_{K+1} < \frac {1}{\sqrt{K}+1}$ for OMP (N=1) as shown in \cite{wang_2012a}.
Linear Network Coding for Multiple Groupcast Sessions: An Interference Alignment Approach
Abhik Kumar Das,Siddhartha Banerjee,Sriram Vishwanath
Computer Science , 2014,
Abstract: We consider the problem of linear network coding over communication networks, representable by directed acyclic graphs, with multiple groupcast sessions: the network comprises of multiple destination nodes, each desiring messages from multiple sources. We adopt an interference alignment perspective, providing new insights into designing practical network coding schemes as well as the impact of network topology on the complexity of the alignment scheme. In particular, we show that under certain (polynomial-time checkable) constraints on networks with $K$ sources, it is possible to achieve a rate of $1/(L+d+1)$ per source using linear network coding coupled with interference alignment, where each destination receives messages from $L$ sources ($L < K$), and $d$ is a parameter, solely dependent on the network topology, that satisfies $0 \leq d < K-L$.
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