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Nano Research 2008年第4期1卷 333-340页

作者： Madathumpady Abubaker Habeeb Muhammed Subramani Ramesh Sudarson sekhar Sinha Samir kumar Pal Thalappil Pradeep DST Unit on Nanoscience(DST UNS) Department of Chemistry and Sophisticated Analytical Instrument FacilityIndian Institute of Technology MadrasChennai 600036India Unit for Nanoscience and Technology Department of ChemicalBiological and Macromolecular SciencesSatyendra Nath Bose National Centre for Basic SciencesBlock JDSector IIISalt LakeKolkata 700098India

Two fl uorescent quantum clusters of gold,namely Au25 and Au8,have been synthesized from mercaptosuccinic acid-protected gold nanoparticles of 45 nm core diameter by etching with excess *** etching at pH~3 yielded Au_(25),that at pH 7-8 yielded Au_(8).This is the fi rst report of the synthesis of two quantum clusters starting from a single *** simple method makes it possible to synthesize well-defined clusters in gram *** these clusters are highly fl uorescent and are highly biocompatible due to their low metallic content,they can be used for diagnostic applications.

关键词： Gold cluster glutathione pH ligand etching fl uorescence

Systematic Review on Social Engineering: Hacking by Manipulating Humans

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Journal of Information Security 2021年第1期12卷 104-114页

作者： Chandra sekhar Bhusal School of Science Engineering and Information Technology Federation University Ballarat Australia

Despite the availability of advanced security software and hardware mechanisms available, still, there has been a breach in the defence system of an organization or individual. Social engineering mostly targets the weakest link in the security system i.e. “Humans” for gaining access to sensitive information by manipulating human psychology. Social engineering attacks are arduous to defend as such attacks are not easily detected by available security software or hardware. This article surveys recent studies on social engineering attacks with discussion on the social engineering phases and categorizing the various attacks into two groups. The main aim of this survey is to examine the various social engineering attacks on individuals and countermeasures against social engineering attacks are also discussed.

关键词： Direct Human Interaction Phishing Social Engineering Phases Preventive Measures

Overview of mental health issues of COVID-19:need of the hour

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General Psychiatry 2020年第3期33卷 189-190页

作者： Barikar Chandrappa Malathesh Seshadri sekhar Chatterjee Soumitra Das Department of Psychiatry National Institute of Mental Health and Neuro SciencesBangaloreIndia Department of Psychiatry West Bengal University of Health SciencesKolkataIndia NorthWestern Mental Health ParkvilleVictoriaAustralia

To the Editor,First detected in Wuhan,China,severe acute respiratory syndrome coronavirus 2(SARS CoV 2)virus is creating havoc worldwide and having an unprecedented impact on public health and society,so much so that it was declared a'Public Health Emergency of International Concern’in January 2020 and further as a‘pandemic’in March *** far,it has affected more than 1.7 million people all over the world,causing 110 thousand deaths across 195 countries.

关键词： acute respiratory Wuhan

English Language Corpora as a Secondary ELT Resource for Indian Learners

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Sino-US English Teaching 2013年第1期10卷 10-22页

作者： Niladri sekhar Dash Indian Statistical Institute Kolkata India

The author proposes here for utilizing ELC （English Language Corpora） as a secondary resource for developing ELT （English Language Teaching） materials for teaching English to Indian learners. We argue for using ELC as one of the most authentic representative collections of modem English language from where we extract necessary linguistic data, information, and examples to develop basic as well as additional resources of ELT, such as, text books, reference materials, syllabuses, grammar books, dictionaries, and terminology databases, etc., for Indian learners. keeping the requirements of individual learners in mind we propose to customize materials to make these maximally useful within the broader scheme of CALT （Computer Assisted Language Teaching）. In our view, ELT resources developed from ELC are more useful for Indian learners, because ELC represents diversified varieties of usage of modem English in real situations, which Indian learners need to assimilate to be at par with others across the globe. Also ELC-based ELT resources are more interesting and beneficial to Indian learners, if instructors carefully utilize these resources keeping in mind the requirements of learners. If Indian ELT learners want to compete in global frame, then utilization of ELC-based ELT resources is the most useful solution, which we can ignore at the cost of our own peril.

关键词： corpus primary resource secondary resource dictionary grammmar Indian learners idioms

Higher-Order Compact Scheme for the Incompressible Navier-Stokes Equations in Spherical Geometry

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Communications in Computational Physics 2012年第1期11卷 99-113页

作者： T.V.S.sekhar B.Hema Sundar Raju Y.V.S.S.Sanyasiraju Department of Mathematics Pondicherry Engineering CollegePuducherry-605014India Department of Mathematics Indian Institute of TechnologyMadrasChennai-600036India

A higher-order compact scheme on the nine point 2-D stencil is developed for the steady stream-function vorticity form of the incompressible Navier-Stokes(NS)equations in spherical polar coordinates,which was used earlier only for the cartesian and cylindrical *** steady,incompressible,viscous and axially symmetric flow past a sphere is used as a model *** non-linearity in the N-S equations is handled in a comprehensive manner avoiding complications in *** scheme is combined with the multigrid method to enhance the convergence *** solutions are obtained over a non-uniform grid generated using the transformation r=ex while maintaining a uniform grid in the computational *** superiority of the higher order compact scheme is clearly illustrated in comparison with upwind scheme and defect correction technique at high Reynolds numbers by taking a large *** is a pioneering effort,because for the first time,the fourth order accurate solutions for the problem of viscous flow past a sphere are presented *** drag coefficient and surface pressures are calculated and compared with available experimental and theoretical *** is observed that these values simulated over coarser grids using the present scheme aremore accuratewhen compared to other conventional *** has also been observed that the flow separation initially occurred at Re=21.

关键词： Fourth order compact scheme Navier-stokes equations spherical polar coordinates drag coefficient.

Lexical Generativity of Bengali Prefixes： A Corpus-Based Investigation

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Sino-US English Teaching 2012年第5期9卷 1171-1180页

作者： Niladri sekhar Dash Indian Statistical Institute Kolkata India

Prefixation is a dynamic method of word formation in Bengali. Sometimes prefixes become derivational to create new words, which differ in part-of-speech and meaning from the words with which these are attached. Thus, prefixation acquires an identity of a morphodynamic process in the language through which new words take birth, while old words change their forms, functions, and meanings to increase lexical stock of Bengali. With reference to a large lexical database of prefixed words obtained from the Bengali corpus （Dash, 2009）, this paper tries to explore the nature and type of morphosemantic processes that occur at the time of prefixation to highlight the patterns of change in forms and meaning of prefixed words. Also, it aims at laying a theoretical foundation about the nature of lexical generativity of prefixes used in formation of words. The application relevance of this study may be attested in descriptive linguistics, applied linguistics, and language technology, since analysis of forms and functions of prefixes supplies necessary information for developing text materials for Bengali language teaching, compiling dictionaries, designing systems for machine learning, and developing databases for machine translation. Indirectly, it ventilates into the nature of complexities embedded in linguistic generativity of the Bengali speakers

关键词： Bengali prefix prefixation lexical generativity morphosemantics meaning

Prediction of influence of process parameters on tensile strength of AA6061/TiC aluminum matrix composites produced using stir casting

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Transactions of Nonferrous Metals Society of China 2016年第6期26卷 1498-1511页

作者： J.JEBEEN MOSES I.DINAHARAN S.JOSEPH sekhar Department of Mechanical Engineering St.Xavier's Catholic College of Engineering Department of Mechanical Engineering Science University of JohannesburgAuckland Park Kingsway Campus

Stir casting was used to produce AA6061/15%TiC （mass fraction） aluminum matrix composites （AMCs）. An empirical relationship was developed to predict the effect of stir casting parameters on the ultimate tensile strength （UTS） of AA6061/TiC AMCs. A central composite rotatable design consisting of four factors and five levels was used to minimize the number of experiments, i.e., castings. The factors considered were stirring speed, stirring time, blade angle and casting temperature. The effect of those factors on the UTS of AA6061/TiC AMCs was derived using the developed empirical relationship and elucidated using microstructural characterization. Each factor significantly influenced the UTS. The variation in the UTS was attributed to porosity content, cluster formation, segregation of TiC particles at the grain boundaries and homogenous distribution in the aluminum matrix.

关键词： aluminum matrix composite stir casting TiC tensile strength

Effect of metal fluorides on chromium ions doped bismuth borate glasses for optical applications

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Chinese Physics B 2019年第3期28卷 366-372页

作者： L Haritha k Chandra sekhar R Nagaraju G Ramadevudu Vasanth G Sathe Md.Shareefuddin Department of Physics Telangana University Department of Physics Osmania University Department of Physics Vasavi College of Engineering UGC-DAE Consortium of Scientific Research

Fluoride based glasses with composition CaF_2-ZnF_2-Bi_2 O_3-B_2 O_3 doped with chromium ions have been investigated using physical, optical, electron paramagnetic resonance(EPR), Fourier-transform infrared spectroscopy(FTIR), and Raman studies. The amorphous nature of samples was confirmed from x-ray diffraction spectra. The density is evaluated from the Archimedes principle and the values of optical band gap and Urbach energy values were evaluated from the optical absorption spectra. Thus, molar volume, refractive index, etc., were also evaluated. The observed decrease in density and the optical band gap with CaF2 is explained using the crystalline density of metal fluorides and the ionicity of fluorine ions,respectively. The three peaks near 450 nm, 606 nm, and 720 nm, which are shown in the absorption spectra, are accredited to ~4 A)(2 g) → ~4 T_(1 g), ~4 A_(2 g)→ ~4 T_(2 g), ~4 A_(2 g)→~2 E transitions, respectively. Resonance signals at g≈ 4.82 and g≈ 1.99 were observed in EPR spectra which are assigned. FTIR and Raman analysis were carried out to examine the impact of metal fluorides on the structure of bismuth borate glasses.

关键词： glasses x-ray diffraction electron paramagnetic resonance Fourier-transform infrared spectroscopy(FTIR) Raman spectra

Evaluation of Radarsat-2 quad-pol SAR time-series images for monitoring groundwater irrigation

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International Journal of Digital Earth 2019年第10期12卷 1177-1197页

作者： Amit kumar Sharma Laurence Hubert-Moy Buvaneshwari Sriramulu M.sekhar Laurent Ruiz S.Bandyopadhyay Shiv Mohan Samuel Corgne Univ Rennes UMR LETG CNRSRennesFrance Indo-French Cell for Water Science Indian Institute of ScienceBangaloreIndia Department of Civil Engineering Indian Institute of ScienceBangaloreIndia UMR 1069 SAS INRAAgro-campus OuestRennesFrance Géosciences Environnement Toulouse Universitéde ToulouseCNRSIRDToulouseFrance EOS Indian Space Research OrganizationBangaloreIndia PLANEX Physical Research LaboratoryAhmedabadIndia

Groundwater assists farmers to irrigate crops for fulfilling the crop-water *** agriculture system is characterized by three cropping seasons known as kharif(monsoon),Rabi(post-monsoon)and summer(pre-monsoon).In tropical countries like India,monitoring cropping practices using optical remote sensing during kharif and Rabi seasons is constraint due to the cloud cover,which can be well addressed by microwave remote *** the proposed research,the strength of C-band polarimetric Synthetic Aperture Radar(SAR)time series images were evaluated to classify groundwater irrigated croplands for the kharif and Rabi cropping seasons of the year *** present study was performed in the Berambadi experimental watershed of kabini river basin,southern peninsular India.A total of fifteen polarimetric variables were estimated includes four backscattering coefficients(HH,HV,VH,VV)and eleven polarimetric indices for all Radarsat-2 SAR *** cumulative temporal sum(seasonal and dual-season)of these parameters was supervised classified using Support Vector Machine(SVM)classifier with intensive ground observation *** results using the best equation(highest accuracy and kappa)shows that the kharif,Rabi and irrigated double croplands are respectively 9.58 km2(20.6%),16.14 km2(34.7%)and 6.22 km2(13.4%)with a kappa coefficient respectively 0.84,0.74 and 0.94.

关键词： Radarsat-2 Synthetic Aperture Radar Polarimetric Indices Irrigated Cropland Support Vector Machine Classifier kabini Critical Zone Observatory

Effect of Frey's procedure on islet cell function in patients with chronic calcific pancreatitis

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Hepatobiliary & Pancreatic Diseases International 2018年第4期17卷 358-362页

作者： Ritesh kumar Jaya Prakash Sahoo Biju Pottakat Sadishkumar kamalanathan Pazhanivel Mohan Vikram kate Sitanshu sekhar kar Jayakumar Selviambigapathya Department of Endocrinology Metabolism Jawaharlal Institute of Postgraduate Medical Education and Research(JIPMER)Pondicherry 605006India Department of Surgical Gastroenterology Jawaharlal Institute of Postgraduate Medical Education and Research(JIPMER)Pondicherry 605006India Department of Medical Gastroenterology Jawaharlal Institute of Postgraduate Medical Education and Research(JIPMER)Pondicherry 605006India Department of Surgery Jawaharlal Institute of Postgraduate Medical Education and Research(JIPMER)Pondicherry 605006India Department of Preventive and Social Medicine Jawaharlal Institute of Postgraduate Medical Education and Research(JIPMER)Pondicherry 605006India

Background: Frey’s procedure involves both drainage and resection of the pancreas in subjects with chronic calcific pancreatitis(CCP). The procedure may affect the pancreatic endocrine function after surgery. The present study was to evaluate the effect of Frey’s procedure on both beta and alpha cell function in CCP ***: Thirty CCP patients who underwent Frey’s procedure were included. According to the glycemic status, patients were divided into the diabetes mellitus(DM), prediabetes, and normal glucose tolerance(NGT) groups. Islet cell function was assessed before and 3 months after ***: At baseline, there was a significant difference in beta cell function among the three groups [NGT group 1.71(1.64–2.07) vs prediabetes group1.50(0.83–1.61) vs DM group 0.33(0.12–0.55), P < 0.0001], but the insulin resistance was not different among them. Post glucose hyperglucagonemia representing alphacell dysfunction during oral glucose tolerance test was present in all of them, but showed no significant difference [NGT group 0.15(0.06–0.31) vs prediabetes group 0.32(0.05–0.70) vs DM group 0.07(0.02–0.18), P = 0.20]. Frey’s procedure did not change beta cell function and insulin resistance. However, alphacell dysfunction deteriorated after surgery [0.10(0.03–0.27) vs 0.33(0.09–0.68), P = 0.004].Conclusions: Although Frey’s procedure does not affect the beta cell function and insulin resistance in CCP patients, the alpha-cell dysfunction deteriorates after surgery.

关键词： Beta-cell Diabetes mellitus Glucagon Insulin secretion sensitivity index Matsuda index