110 research outputs found
Gold seal of Viṣṇuvarman
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To engrave his virtues on the disc of the moon… Inscriptions of the Aulikaras and Their Associates
Dániel Balogh, 2019
Gold seal of Viṣṇuvarman. Left: four faces of the object. Right: mirror image of inscribed face and hand tracing of inscription. Photograph courtesy of Devendra Handa, tracing by the author
Role of Risk Stratification and Genetics in Sudden Cardiac Death
No full textSudden cardiac death (SCD) is a major public health issue due to its increasing incidence in the general population and the difficulty in identifying high-risk individuals. Nearly 300,000-350,000 patients in the United States and 4- to 5 million patients in the world die from SCD. Coronary artery disease and advanced heart failure are the main etiology for SCD. Ischemia of any cause precipitates lethal arrhythmias, and ventricular tachycardia and ventricular fibrillation are the most common lethal arrhythmias precipitating SCD. Pulse-less electrical activity, brady-arrhythmia and electromechanical dissociation also result in SCD. Most sudden cardiac deaths occur out-of-the-hospital setting, so it is difficult to estimate the public burden, which results in overestimating the incidence of SCD. The insufficiency and limited predictive value of various indicators and criteria for SCD result in the increasing incidences. As a result, there is a need to develop better risk stratification criteria and find modifiable variables to decrease the incidence. Primary and secondary prevention and treatment of SCD need further research. This critical review is focused on the etiology, risk factors, prognostic factors and importance of risk stratification of SCD.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Approximability of modularity clustering and related results
No full textFor the problem of Modularity Clustering, first introduced by Newman and Girvan in 2004, we are given a graph and the goal is to partition the vertex set into an unknown number of clusters such that we maximize a certain objective function which evaluates the fitness of the clusters. This fitness function measures the statistically surprising distribution of edges between different clusters and in the clusters themselves. Despite having found widespread popularity in the fields of biology and social sciences, this problem is known to be NP-hard and up till the work in this thesis, only heuristics were known. In this thesis, we initiate a study of the approximability of modularity clustering. We give the first approximation algorithms and the first hardness of approximation results for the problem. In doing so, we employ various techniques like semidefinite programming and the regularity lemma. Our main results in- clude a factor 1.0009 inapproximability for dense graphs and a logarithmic (in the degree) approximation for sparse graphs. We also extend some of these results to directed and weighted graphs and the more general problem of Max-cut where negative edge weights are allowed.Ph. D.Includes bibliographical referencesIncludes vitaby Devendra J. Desa
Developing Protection schemes for Offshore Wind Parks
No full textThe increasing demand for electricity and the need to decelerate the use of fossil fuels to prevent a dramatic climate change have urged the need for new sources of energy. Thus, electrical sustainable energy is an ever growing field. Investigations into performance improvements and extraction of maximum benefits from Renewable Energy Sources (RES) is the need of the hour. In particular, wind power contributes to a significant share of renewable electricity generation and has seen great leaps in terms of implemented technologies. The advancements in wind turbine technology have introduced converter based generation, thereby affecting the electrical grid's inertia and short circuit current contributions. These short circuit contributions have been of particular interest for protection engineers in the development of protection systems worldwide. TenneT, which is the TSO of the Netherlands, faces the challenge regarding the protection scheme implementation for their upcoming offshore wind farm connections involving Type 4 Wind Turbines (WT). The lower magnitudes of current flow, post fault and the presence of balanced currents irrespective of the type of fault are some of the major challenges. The system starting from the busbar (where WTs are connected) is owned by the system operator and the WT along with the cable connecting to the busbar, or the Point of Common Coupling (PCC) is an asset of the Wind Park Operator (WPO). Non-technical issues such as the ownership of components at the point of common coupling between the wind park operators and the system operators together along with the technical challenges described earlier necessitates the development of a standard protection scheme that provides satisfactory performance. Implementation of end-to-end connection protection system for the individual component protection is also challenging considering the challenges associated with the ownership of the assets. Therefore , it is necessary to analyse the performance of conventional protection systems (single unit operation). The performance of definite time overcurrent, directional overcurrent, under voltage and distance protection have been studied for faults on PCC and the infeed WPO strings. The study aims at finding the right choice of primary and back up protections that are independent of the type of short circuit currents available by the generation technologies. In addition, the research aims to develop a new busbar protection scheme that can detect and identify the fault location with the challenges explained before. Following the undesirable behaviour observed with overcurrent and directional overcurrent protection system the author then proposes two new schemes using conventional protection systems. The considerations regarding successful operation of under voltage protection and distance protection are further addressed. Finally, a new scheme involving fault generated travelling waves to detect fault on the network is extensively tested. All the protection systems are then compared to describe their merits and demerits to make a decision about the primary and backup protection implemented.Electrical Engineering | Electrical Power Engineerin
Vapor-Phase Incorporation of Ge in CZTSe Absorbers for Improved Stability of High-Efficiency Kesterite Solar Cells
No full textWe report an approach to incorporate Ge into Cu2ZnSnSe4 using GeSe vapor during the selenization step of alloyed metallic precursors. The vapor incorporation slowly begins at T ≈ 480 °C and peaks at 530 °C, resulting in a Ge-based composition shift inside the previously formed kesterite layer. We initially observe the formation of a Ge-rich surface layer that merges into a homogeneous distribution of the incorporated element during the further dwelling stage of the annealing. This approach is very versatile and could be used in many similar fabrication processes for incorporating Ge into CZTSe-absorber layers. Because the vapor-based composition shift in the layer happens after the formation of the absorber film towards the end of the fabrication process, most process parameters and the precursor structure may not need any significant re-optimization. The careful integration of this step could help to reduce Sn-related deep defects and accompanying VOC losses. The best CZTGSe-power-conversion efficiency obtained in this series is 10.4 % (with EG = 1.22 eV, FF = 54%, JSC = 36 mA/cm2, VOC = 540 mV, VOCdef,SQ = 417 mV). These results demonstrate the potential of this approach for Ge incorporation into kesterite absorbers
Electrokinetically-driven deterministic lateral displacement for particle separation in microfluidic device
No full textAn electrokinetically driven deterministic lateral displacement device is proposed for the continuous, two-dimensional fractionation of suspensions in microfluidic platforms. The suspended species are driven through an array of regularly spaced cylindrical posts by applying an electric field across the device. We explore the entire range of orientations of the driving field with respect to the array of obstacles and show that, at specific forcing angles, particles of different size migrate in different directions, thus enabling continuous, two-dimensional separation. We discuss a number of features observed in the motion of the particles, including directional locking and sharp transitions between migration angles upon variations in the direction of the force, that are advantageous for high-resolution two-dimensional separation. A simple model based on individual particle–obstacle interactions accurately describes the migration angle of the particles depending on the orientation of the driving field and can be used to reconfigure the electric field depending on the composition of the samples.Peer reviewe
Fractional Calculus and its Applications in Physics
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
Synthesis and characterization of bulk Cu2ZnSnX4 (X: S, Se) via thermodynamically supported mechano-chemical process
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Current Status of Bacillus thuringiensis: Insecticidal Crystal Proteins and Transgenic Crops
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