arXiv subjects

Anil Kumar Singh

Publications and source records attributed to Anil Kumar Singh.

23 records · Page 2Linked to original sources

arXiv2017

Reversible control of interface-water induced carrier density in graphene-on-SiO$_2$ by thermal cycling under gate-voltage

A reversible handle on graphene carrier density, other than the gate electric field, is desirable for memory applications of graphene. Our experiments show that the commonly observed carrier density hysteresis in graphene on SiO$_2$ due to interface water/oxygen vanishes at temperatures below 250 K. The state of these species, which affects the graphene carrier density, at low temperatures can be reversibly controlled by thermal cycling to room temperature at different gate voltages. Further, devices prepared with relatively dry interface, and thus showing negligible hysteresis at room temperature, show a marked increase in hysteresis on heating above room temperature. Thus thermal-cycling, to high temperatures and under gate-voltage, provides a reversible handle on carrier density. These results are discussed in terms of temperature and interface-water density dependence of redox-reaction kinetics.

cond-mat.mes-hall↗

arXiv2016

Inhomogeneous screening of gate electric field by interface states in graphene FETs

The electronic states at graphene-SiO$_2$ interface and their inhomogeneity was investigated using the back-gate-voltage dependence of local tunnel spectra acquired with a scanning tunneling microscope. The conductance spectra show two, or occasionally three, minima that evolve along the bias-voltage axis with the back gate voltage. This evolution is modeled using tip-gating and interface states. The energy dependent interface states' density, $D_{it}(E)$, required to model the back-gate evolution of the minima, is found to have significant inhomogeneity in its energy-width. A broad $D_{it}(E)$ leads to an effect similar to a reduction in the Fermi velocity while the narrow $D_{it}(E)$ leads to the pinning of the Fermi energy close to the Dirac point, as observed in some places, due to enhanced screening of the gate electric field by the narrow $D_{it}(E)$

cond-mat.mes-hall↗

arXiv2016

Surface Treatment of 45S5 Bio-glass using Femtosecond Laser to Achieve Superior Growth of Hydroxyapatite

45S5 Hench bio-glass (BG) has gained interest in research because of its potential clinical applications. Several studies in-vivo and in-vitro have been in progress to improve bio-integration efficiency of this glass. In present contribution, surface modification of Hench BG has been done employing a femtosecond (fs) laser beam, resulting in increased effective surface area of the sample. These surface modified samples were subsequently immersed in simulated body fluid for varying number of days and characterized using Scanning electron microscope, energy dispersive X-ray analysis, X-ray diffraction, and micro-Raman spectroscopy. In-vitro studies indicated superior growth of hydroxyapatite (HAP) layer on the laser treated samples in comparison to the untreated samples. Presence of strong XRD peaks confirmed faster growth of HAP on laser treated samples. Raman peaks, five times more intense and relatively narrower represented higher crystallinity of hydroxyapatite layer on laser treated BG.

physics.bio-ph↗

arXiv2015

Responding to Retrieval: A Proposal to Use Retrieval Information for Better Presentation of Website Content

Retrieval and content management are assumed to be mutually exclusive. In this paper we suggest that they need not be so. In the usual information retrieval scenario, some information about queries leading to a website (due to `hits' or `visits') is available to the server administrator of the concerned website. This information can used to better present the content on the website. Further, we suggest that some more information can be shared by the retrieval system with the content provider. This will enable the content provider (any website) to have a more dynamic presentation of the content that is in tune with the query trends, without violating the privacy of the querying user. The result will be a better synchronization between retrieval systems and content providers, with the purpose of improving the user's web search experience. This will also give the content provider a say in this process, given that the content provider is the one who knows much more about the content than the retrieval system. It also means that the content presentation may change in response to a query. In the end, the user will be able to find the relevant content more easily and quickly.

cs.IR↗

arXiv2011

A Concise Query Language with Search and Transform Operations for Corpora with Multiple Levels of Annotation

The usefulness of annotated corpora is greatly increased if there is an associated tool that can allow various kinds of operations to be performed in a simple way. Different kinds of annotation frameworks and many query languages for them have been proposed, including some to deal with multiple layers of annotation. We present here an easy to learn query language for a particular kind of annotation framework based on 'threaded trees', which are somewhere between the complete order of a tree and the anarchy of a graph. Through 'typed' threads, they can allow multiple levels of annotation in the same document. Our language has a simple, intuitive and concise syntax and high expressive power. It allows not only to search for complicated patterns with short queries but also allows data manipulation and specification of arbitrary return values. Many of the commonly used tasks that otherwise require writing programs, can be performed with one or more queries. We compare the language with some others and try to evaluate it.

cs.CL↗