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Gaurav Sharma

Other affiliations: Northeastern University, D. E. Shaw & Co., Hewlett-Packard  ...read more
Bio: Gaurav Sharma is an academic researcher from Shenzhen University. The author has contributed to research in topics: Medicine & Photocatalysis. The author has an hindex of 82, co-authored 1244 publications receiving 31482 citations. Previous affiliations of Gaurav Sharma include Northeastern University & D. E. Shaw & Co..


Papers
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Journal ArticleDOI
TL;DR: In this article, a Pareto optimization framework is proposed for determining the complete range of available primary choices that optimally negotiate the tradeoffs between the metrics for the different attributes.
Abstract: The choice of primaries for a color display involves tradeoffs between different desirable attributes such as a large color gamut, high spectral reproduction accuracy, minimal observer metamerism, and low power consumption. Optimization of individual attributes often drives primary choices in different directions. For example, expansion of color gamut favors narrow spectral bandwidth saturated primaries and minimization of observer metamerism favors broadband primaries. To characterize the tradeoffs between the different attributes in primary design for three primary and multiprimary displays, we propose a Pareto optimization framework for determining the complete range of available primary choices that optimally negotiate the tradeoffs between the metrics for the different attributes. Using results obtained in our proposed framework, we explore the impact of number of primaries, the relation between alternative design objectives, and the underlying primary spectral characteristics. The proposed strategy is more informative and comprehensive for primary design and primary selection, and can also be extended to co-optimize primary design and selection of control values to fully leverage the advantages of multiprimary displays. Introduction The design of the spectral power distribution (SPD) of the primaries plays a critical role in color display systems. The choice of primaries determines the display gamut, i.e., the range of colors that the display can reproduce. For example, to maximize the (chromaticity) gamut, the chromaticities of the RGB primaries in the recent Rec. 2020 standard [1] are defined such that correspond approximately to spectrally-monochromatic primaries with wavelengths of 630nm, 532nm, and 467nm, respectively. An alternative strategy for realizing a wider gamut is to utilize more than three primaries, which is done in multiprimary displays. For both three primary and multiprimary color displays, other display metrics like luminance or power consumption also depend on the primaries’ characteristics, which means deliberate design is essential to construct practical display systems. Prior work has considered several different metrics for evaluating a set of display primaries. Going beyond the simplistic consideration of only the 2D gamut chromaticity area, several metrics have also been defined in terms of the SPDs of the primaries, and designs that optimize these metrics have also been obtained. Specifically, primary designs have been optimized for maximizing coverage of a pre-specified target gamut volume [2] or absolute gamut volume in a perceptually uniform color space [3]. For wide gamut designs based on narrow spectral bandwidth primaries, observer metamerism is often a concern, and designs have been proposed to optimize spectral reproduction [4] and minimize observer metamerism [5, 6, 7]. These prior works, however, focus on single objective to be optimized, and the question of how to adequately trade off these metrics against each other has received little attention. Primary designs have been proposed to mitigate the tradeoff between color gamut volume and optical power [8, 9], and between color gamut area and observer metamerism [7]. Alternatively an importance-weighted optimization has also been proposed [10], where the overall objective function for display primary design is formulated as a weighted sum of several metrics. However, the assignment of importance weights is empirical, and may be hard to set a priori without knowing the nature of the inter-relations between the different metrics. In this paper, we propose a multi-objective/Pareto optimization framework to investigate the optimal tradeoff relations among different display metrics. Instead of a single design optimizing a numerical metric quantifying a single display trait (or a weighted combination), the Pareto optimization framework characterizes the complete set of solutions for which none of the metrics quantifying the different traits can be improved upon without compromising performance of at least one of the other metrics. As a result, instead of optimizing a single trait while disregarding all others, the Pareto optimal solution space fully characterizes the range of available primary choices that optimally negotiate the tradeoffs between the different traits for color displays. Using results obtained in our proposed framework, we explore and quantify the impact of number of primaries and the relation between alternative design objectives. The proposed strategy is more informative and comprehensive for primary design and selection, and can also be extended to co-optimization of primary design and selection of control values to fully leverage the advantages of multiprimary displays. This paper is organized as follows. The next section lays the mathematical foundation for our problem setting by introducing spectral models for the display system and for object colors and their inter-relations via colorimetric/spectral reproduction objectives. Metrics quantifying the display attributes of color gamut coverage, power consumption, and observer metamerism, are then defined and the multi-objective optimization problem is formulated in terms of these metrics. The following section describes our implementation of the Pareto optimization framework using a parameterized representation of the primaries for computational efficiency. Results obtained using the framework are presented next where the nature of the optimal tradeoff relations and the underlying spectral properties of the primaries are discussed. As summary of the conclusions and a discussion of the results forms the final section. Preliminaries In this section, we introduce a spectral model for the display, the spectral representation for the surface colors that the display will attempt to reproduce, and corresponding color representations taking into account observer variability. Finally, we discuss the control process for the display by which the control values for the primaries are determined. 84 IS&T International Symposium on Electronic Imaging 2017 Color Imaging XXII: Displaying, Processing, Hardcopy, and Applications https://doi.org/10.2352/ISSN.2470-1173.2017.18.COLOR-040 © 2017, Society for Imaging Science and Technology

3 citations

Proceedings ArticleDOI
01 Apr 2016
TL;DR: Current scheme used by researchers that aim to strengthen security from attacks in Ad-hoc networks are surveyed.
Abstract: In the last decades security become a major issue due to increase technology. Among all the existing scheme certificateless aggregate schemes are very efficient techniques in recent scenario which is very helpful to provide security. Certificateless aggregate schemes are most attractive topic for researchers to give a lot of potential to secure our network with malicious adversaries. This paper surveys current scheme used by researchers that aim to strengthen security from attacks in Ad-hoc networks.

3 citations

Journal ArticleDOI
TL;DR: Tobacco based dentifrices are worryingly more frequently used by females in contrast to males and are also popular in children, thus posing a unique conundrum to tobacco control advocates.
Abstract: Dear Editor, Thirty‐five percent adults (274.9 million) consume tobacco in India in some form or other with 21% (163.7 million) adults using only smokeless tobacco, 9% (68.3 million) only smoking and 5% (42.3 million) users of both smoking and smokeless tobacco.[1] The history and cultural rooting of smokeless tobacco when compared to smoking represents a distinctive challenge in India’s tobacco control measures. The usage of tobacco based dentifrice may sound improbable and odd but it is very frequently practiced in rural areas of South Asia. The overall national prevalence of usage of tobacco based dentifrices was found to 5% in patients aged above 15 years in India.[1] However, tobacco based dentifrices are worryingly more frequently used by females (6.3%) in contrast to males (3.3%) and are also popular in children, thus posing a unique conundrum to tobacco control advocates.[1,2] Tobacco toothpaste (creamy snuff) and tooth powder are perhaps the most commonly marketed tobacco based dentifrices.[2] The various other tobacco based dentifrices used commonly are Gul (a pyrolyzed tobacco product), mishri (roasted and powdered tobacco), gudakhu (paste of tobacco and molasses), tapkeer (dry powdered snuff) and tobacco water (manufactured by passing tobacco smoke through water used only for gargling) that are commonly used in various parts of rural Asia.[1]

3 citations

Journal ArticleDOI
TL;DR: In silico characterization of a putative energy taxis cluster, Cc-5, which is present in only one amongst 34 known and sequenced myxobacterial genomes, Corallococcus coralloides, is reported, suggesting that C. coralloide can sense and then respond to changing concentrations of molecular oxygen.
Abstract: An efficient signal transduction system allows a bacterium to sense environmental cues and then to respond positively or negatively to those signals; this process is referred to as taxis. In addition to external cues, the internal metabolic state of any bacterium plays a major role in determining its ability to reside and thrive in its current environment. Similar to external signaling molecules, cytoplasmic signals are also sensed by methyl-accepting chemotaxis proteins (MCPs) via diverse ligand binding domains. Myxobacteria are complex soil-dwelling social microbes that can perform a variety of physiologic and metabolic activities ranging from gliding motility, sporulation, biofilm formation, carotenoid and secondary metabolite biosynthesis, predation, and slime secretion. To live such complex lifestyles, they have evolved efficient signal transduction systems with numerous one- and two-component regulatory system along with a large array of chemosensory systems to perceive and integrate both external and internal cues. Here we report the in silico characterization of a putative energy taxis cluster, Cc-5, which is present in only one amongst 34 known and sequenced myxobacterial genomes, Corallococcus coralloides. In addition, we propose that this energy taxis cluster is involved in oxygen sensing, suggesting that C. coralloides can sense (either directly or indirectly) and then respond to changing concentrations of molecular oxygen. This hypothesis is based on the presence of a unique MCP encoded in this gene cluster that contains two different oxygen-binding sensor domains, PAS and globin. In addition, the two monooxygenases encoded in this cluster may contribute to aerobic respiration via ubiquinone biosynthesis, which is part of the cytochrome bc1 complex. Finally, we suggest that this cluster was acquired from Actinobacteria, Gammaproteobacteria or Cyanobacteria. Overall, this in silico study has identified a potentially innovative and evolved mechanism of energy taxis in only one of the myxobacteria, C. coralloides.

3 citations


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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

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01 Jun 2012
TL;DR: SPAdes as mentioned in this paper is a new assembler for both single-cell and standard (multicell) assembly, and demonstrate that it improves on the recently released E+V-SC assembler and on popular assemblers Velvet and SoapDeNovo (for multicell data).
Abstract: The lion's share of bacteria in various environments cannot be cloned in the laboratory and thus cannot be sequenced using existing technologies. A major goal of single-cell genomics is to complement gene-centric metagenomic data with whole-genome assemblies of uncultivated organisms. Assembly of single-cell data is challenging because of highly non-uniform read coverage as well as elevated levels of sequencing errors and chimeric reads. We describe SPAdes, a new assembler for both single-cell and standard (multicell) assembly, and demonstrate that it improves on the recently released E+V-SC assembler (specialized for single-cell data) and on popular assemblers Velvet and SoapDeNovo (for multicell data). SPAdes generates single-cell assemblies, providing information about genomes of uncultivatable bacteria that vastly exceeds what may be obtained via traditional metagenomics studies. SPAdes is available online ( http://bioinf.spbau.ru/spades ). It is distributed as open source software.

10,124 citations

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