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Numerical storm surge model with higher order finite difference method of lines for the coast of Bangladesh

Acta Oceanologica Sinica 2019年第6期38卷 100-116页

作者： Gour chandra Paul Md. Emran Ali Department of Mathematics University of RajshahiRajshahi 6205Bangladesh Department of Textile Engineering Northern University BangladeshDhaka 1230Bangladesh

In this study, the method of lines (MOLs) with higher order central difference approximation method coupled with the classical fourth order Runge-Kutta (RK(4,4)) method is used in solving shallow water equations (SWEs) in Cartesian coordinates to foresee water levels associated with a storm accurately along the coast of Bangladesh. In doing so, the partial derivatives of the SWEs with respect to the space variables were discretized with 5-point central difference, as a test case, to obtain a system of ordinary differential equations with time as an independent variable for every spatial grid point, which with initial conditions were solved by the RK(4,4) method. The complex land-sea interface and bottom topographic details were incorporated closely using nested schemes. The coastal and island boundaries were rectangularized through proper stair step representation, and the storing positions of the scalar and momentum variables were specified according to the rules of structured C-grid. A stable tidal regime was made over the model domain considering the effect of the major tidal constituent, M2 along the southern open boundary of the outermost parent scheme. The Meghna River fresh water discharge was taken into account for the inner most child scheme. To take into account the dynamic interaction of tide and surge, the generated tidal regime was introduced as the initial state of the sea, and the surge was then made to come over it through computer simulation. Numerical experiments were performed with the cyclone April 1991 to simulate water levels due to tide, surge, and their interaction at different stations along the coast of Bangladesh. Our computed results were found to compare reasonable well with the limited observed data obtained from Bangladesh Inland Water Transport Authority (BIWTA) and were found to be better in comparison with the results obtained through the regular finite difference method and the 3-point central difference MOLs coupled with the RK(4,

关键词： shallow water equations method of lines higher order finite difference approximation method surge nested scheme

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Effects of resistivity on standing shocks in low angular momentum flows around black holes

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Research in Astronomy and Astrophysics 2021年第6期21卷 222-232页

作者： chandra B.Singh Toru Okuda Ramiz Aktar South-Western Institute for Astronomy Research Yunnan UniversityKunming 650500China Hakodate Campus Hokkaido University of EducationHachiman-Cho 1-2HakodateHokkaido 040-8567Japan Department of Astronomy Xiamen UniversityXiamen 361005China

We study two-dimensional low angular momentum flow around a black hole using the resistive magnetohydrodynamic module of PLUTO *** have been performed for the flows with parameters of specific angular momentum,specific energy and magnetic field which may be expected for the flow around Sgr A*.For flows with lower resistivityη=10^(-6)and 0.01,the luminosity and shock location on the equator vary *** power density spectra of luminosity variation show peak frequencies which correspond to the periods of 5×10^(5),1.4×10^(5)and 5×10^(4)*** quasi-periodic oscillations(QPOs)occur due to interaction between the outer oscillating standing shock and the inner weak shocks occurring at the innermost hot *** for cases with higher resistivityη=0.1 and 1.0,the high resistivity considerably suppresses the magnetic activity such as MHD turbulence and the flows tend to be steady and symmetric with respect to the *** steady standing shock is formed more outward compared with the hydrodynamical *** low angular momentum flow model with the above flow parameters and with low resistivity has a possibility to explain long-term flares of Sgr A*with frequencies~one per day and~5-10 days in the latest observations by chandra,Swift and XMM-Newton monitoring of Sgr A*.

关键词： accretion accretion disks magnetohydrodynamics(MHD) methods:numerical shock waves Galaxy:center

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Incidence and management of white grub, Schizonycha ruficollis on seedlings of teak （Tectona grandis Linn, f,）

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Insect Science 2007年第5期14卷 411-418页

作者： NITIN KULKARNI KAILASH chandra PRAFULLA NARAHAR WAGH KAILASH chandra JOSHI RAM BHAJAN SINGH Forest Entomology Division Tropical Forest Research Institute Jabalpur (M. P.) Central Regional Station Zoological Survey of India Vijay Nagar Jabalpur (M. P.) Forest Development Corporation of Maharashtra Nagpur India

In investigation was conducted annually from 2002 to 2005 between the second week of May and the end of September on the incidence of scarab beetle, Schizonycha ruficollis （Fabricius） in a teak （Tectona grandis L.f.） nursery at Ramdongari, Nagpur, India. The immature stages, that is white grubs of the scarab beetle damaged 14%-52% of teak seedlings in the nursery beds, whereas the adult of the species, that is scarab beetles, were recorded on three new host trees （ Ziziphus xylopyra, Acacia catechu and A. leucophloea） in addition to the reported hosts such as ziziphus （Z. jujuba and Z. mauritiana）. Beetles of the S. ruficollis started emerging from the nursery beds just after the pre-monsoon showers and continued for 10-18 days. While beetle of S. ruficollis defoliated tree hosts available in the surroundings, the immature stages of the beetle caused major damage by feeding on root systerfls of teak seedlings with symptoms of wilting and mortality in forest nursery beds. The result of chemical and biological treatments for the management of grubs of S. ruficollis in nursery beds indicated phorate 10% granular at the rate of 20 g/m^2 and chlorpyriphos 20% emulsifiable concentrate at the rate of 5.0 mL/m^2 to be effective. Grubs of S. ruficollis have not been recorded previously as a major pest of teak （T. grandis）. This is also the first report on occurrence of S. ruficollis adults on tree hosts such as Z. xylopyra, A. catechu and A. leucophloea. White grubs being pests of economic importance and the toughest insects to manage, information given in this paper on incidence, pest status and management of Schizonycha ruficollis is of importance to researchers and forest nursery managers.

关键词： bioecology Coleoptera field incidence forest nursery insect pest management,insecticides Melolonthinae Scarabaeidae

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Machine learned interatomic potentials using random features

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npj Computational Materials 2022年第1期8卷 48-57页

作者： Gurjot Dhaliwal Prasanth B.Nair chandra Veer Singh Department of Mechanical and Industrial Engineering University of Toronto5 King’s College RdTorontoM5S 3G8ONCanada Institute for Aerospace Studies University of Toronto4925 Dufferin StTorontoM3H 5T6ONCanada Department of Materials Science and Engineering University of Toronto184 College StTorontoM5S 3E4ONCanada

We present a method to model interatomic interactions such as energy and forces in a computationally efficient *** proposed model approximates the energy/forces using a linear combination of random features,thereby enabling fast parameter estimation by solving a linear least-squares *** discuss how random features based on stationary and non-stationary kernels can be used for energy approximation and provide results for three classes of materials,namely two-dimensional materials,metals and *** and energy predictions made using the proposed method are in close agreement with density functional theory calculations,with training time that is 96%lower than standard kernel *** Dynamics calculations using random features based interatomic potentials are shown to agree well with experimental and density functional theory *** frequencies as computed by random features based interatomic potentials are within 0.1%of the density functional theory ***,the proposed random features-based potential addresses scalability issues encountered in this class of machine learning problems.

关键词： random stationary interatomic

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An efficient algorithm to clip a 2D-polygon against a rectangular clip window

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Applied Mathematics(A Journal of Chinese Universities) 2022年第1期37卷 147-158页

作者： Sushil chandra Dimri Umesh Kumar Tiwari Mangey Ram Department of Computer Science and Engineering Graphic Era(Deemed to be University)DehradunUttarakhandIndia

Polygon clipping is of great importance in computer *** of the popular algorithms to clip a polygon is Cohan–Sutherland Hodgeman algorithm which is based on line ***–Sutherland Hodgeman algorithm clips the polygon against the given rectangular clip window with the help of line clipping ***–Sutherland algorithm requires traversing the polygon in anti clockwise direction(positive orientation).In this work we propose an efficient polygon clipping algorithm against a rectangular clip *** algorithm uses parametric representation of polygon *** the concept of point clipping,we can find required intersection points of edges of polygon with clip window *** suited numerical illustrations are used to explain the proposed polygon clipping *** proposed algorithm is computationally less expensive and comprehensive.

关键词： point clipping polygon clipping clip window line segment computational complexity

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Impact of Land-Use Change on Soil Microbial Community Composition and Organic Carbon Content in the Dry Tropics

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Pedosphere 2017年第5期27卷 974-977页

作者： chandra Mohan KUMAR Nandita GHOSHAL Centre of Advanced Study in Botany Department of Botany Institute of Science Banaras Hindu University

Restoration of forests poses a major challenge globally, particularly in the tropics, as the forests in these regions are more vulnerable to land-use change. We studied land-use change from natural forest(NF) to degraded forest(DF), and subsequently to either Jatropha curcas plantation(JP) or agroecosystem(AG), in the dry tropics of Uttar Pradesh, India, with respect to its impacts on soil microbial community composition as indicated by phospholipid fatty acid(PLFA) biomarkers and soil organic carbon(SOC) content. The trend of bacterial PLFAs across all land-use types was in the order: NF > JP > DF> AG. In NF, there was dominance of gram-negative bacterial(G^-) PLFAs over the corresponding gram-positive bacterial(G^+) PLFAs. The levels of G^- PLFAs in AG and JP differed significantly from those in DF, whereas those of G^+ PLFAs were relatively similar in these three land-use types. Fungal PLFAs,however, followed a different trend: NF > JP > DF = AG. Total PLFAs, fungal/bacterial(F/B) PLFA ratio, and SOC content followed trends similar to that of bacterial PLFAs. Across all land-use types, there were strong positive relationships between SOC content and G-, bacterial, fungal, and total microbial PLFAs and F/B PLFA ratio. Compared with bacterial PLFAs, fungal PLFAs appeared to be more responsive to land-use change. The F/B PLFA ratio, fungal PLFAs, and bacterial PLFAs explained 91%, 94%,and 73% of the variability in SOC content, respectively. The higher F/B PLFA ratio in JP favored more soil C storage, leading to faster ecosystem recovery compared to either AG or DF. The F/B PLFA ratio could be used as an early indicator of ecosystem recovery in response to disturbance, particularly in relation to land-use change.

关键词： ecosystem recovery fungal/bacterial ratio natural forest phospholipid fatty acid (PLFA) plantation

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Pressure-Induced Instability Characteristics of a Transient Flow and Energy Distribution through a Loosely Bent Square Duct

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Energy Engineering 2022年第1期119卷 429-451页

作者： Sreedham chandra Adhikari Ratan Kumar Chanda Sidhartha Bhowmick Rabindra Nath Mondal Suvash chandra Saha Department of Mathematics Jagannath UniversityDhaka1100Bangladesh School of Mechanical and Mechatronic Engineering University of Technology SydneyNew South WalesAustralia

Due to widespread applications of the bent ducts in engineering fields such as in chemical,mechanical,bio-mechanical and bio-medical engineering,scientists have paid considerable attention to invent new characteristics of fluid flow in a bent duct(BD).In the ongoing study,a spectral-based numerical technique is applied to explore flow characteristics and energy distribution through a loosely bent square duct(BSD)of small *** is accelerated due to combined action of the non-dimensional parameters;the Grashof number Gr(=1000),the curvatureδ(=0.001),and the Prandtl number Pr(=7.0)over a wide domain of the Dean number 0

关键词： Square-shaped duct curvature secondary flow energy distribution chaos

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Graphene derivatives as efficient hole transport materials for lead-free double perovskite（Cs2SnI6） solar cells: a numerical study

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Optoelectronics Letters 2025年第3期 155-159页

作者： Sarita YADAV Saral K.GUPTa.chandra Mohan Singh NEGI Department of Physical Science Banasthali Vidyapith

The double perovskite Cs2SnI6has notable optical and electrical characteristics, rendering it a highly prospective candidate for deployment as the absorber layer in perovskite solar cells （PSCs）. We simulated the performance of PSCs using lead-free Cs2SnI6double perovskite absorber layer and graphene derivatives, namely graphene oxide （GO） and reduced graphene oxide （rGO）, as hole transport layers （HTLs）. Our findings show that r GO offers an excellent hole extraction property with minimal interfacial recombination compared to GO.

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Observation of free oscillations after the 2010 Chile and 2011 Japan earthquakes by superconducting gravimeter in Kutch,Gujarat,India

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Geodesy and Geodynamics 2023年第1期14卷 52-64页

作者： chandra Sekhar Pedapudi Madhusudhana Rao Katlamudi Severine Rosat Institute of Seismological Research GandhinagarGujaratIndia Department of Earth Sciences Gujarat UniversityAhmedabadGujaratIndia Institut Terre et Environnement de Strasbourg CNRS UMR 7063StrasbourgFrance

In this paper,we present observations of free oscillations of the Earth after major earthquakes in Chile(February 27,2010,Mw8.8)and Japan(March 11,2011,Mw9.1)using data from the dual-sphere superconducting gravimeter(SG-055),installed at Badargadh(23°0.47 N,70°0.62 E),Kutch,Gujarat,India in March *** see the noise characteristics,we calculated the power spectral density of the gravity time series of 5 quiet days in the frequency band 0.05-20 mHz using the new low noise model(NLNM)as a *** compared the noise level of the Badargadh site to other SG sites around the *** shows that the Badargadh SG is in a low noise *** find that the noise increases at frequencies below 1 *** a characteristic is also observed in Djougou(Afrique,Benin)and Strasbourg(France).Using theoretical tides for Gujarat,we estimated a scale factor of about-814 nm/s~2/V for Gravl(lowersphere)and about-775 nm/s~2/V for Grav2(upper-sphere).We corrected the influence of atmospheric pressure from the one-second gravity data before switching to the frequency *** extracted a total of 53 Earth’s Free Oscillations(EFO)modes during the earthquake in Japan and about 47 EFO modes during the earthquake in *** are able to extract the lowest0S2spheroidal mode(0.30945 mHz or54 min)and0S0radial mode(0.81439 mHz or 20 min).The longer time series shows individual0S2singlets and0S3(0.46855 mHz)singlets due to the Coriolis splitting *** cross-referenced the frequencies of these modes using the PREM model and previous global *** correlation coefficient between the observed and the PREM model for these two events are 0.999 for Japan earthquake and 0.993 for Chile *** validates the quality of the data useful for low-frequency studies in *** also calculated the relative deviations of our observed fundamental modes with previously determined observed and theoretical *** found that the relative deviations of our observed free oscillations

关键词： Superconducting gravity data Free oscillations PREM model

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Game theory-based attack and defense analysis in virtual wireless networks with jammers and eavesdroppers

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Digital Communications and Networks 2021年第3期7卷 327-334页

作者： Bassma S.Alsulami chandra Bajracharya Danda B.Rawat Department of Electrical Engineering and Computer Science Howard UniversityWashingtonDC20059USA Department of Electrical Engineering Capitol Technology UniversityLaurelMD20708USA

Dynamic spectrum sharing and cognitive radio networks were proposed to enhance the Radio Frequency(RF)spectrum ***,there are several challenges to realize them in real systems,such as sensing uncertainty causing issues to licensed users,business models for licensed service *** virtualization is regarded as a technology that leverages service level agreements to sublease unused or underutilized RF spectrum that addresses aforementioned issues and helps to significantly enhance the utilization of the RF spectrum,offer improved coverage and capacity of networks,enhance network security and reduce energy *** wireless virtualization,wireless networks'physical substrate is shared and reconfigured dynamically between virtual wireless networks through Mobile Virtual Network Operations(MVNOs).Wireless virtualization with dynamic configurable features of Wireless Infrastructure Providers(WIPs),virtualized wireless networks are vulnerable to a multitude of attacks,including jamming attacks and eavesdropping *** paper investigates a means of defense through the employment of coalition game theory when jammers try to degrade the signal quality of legitimate users,and eavesdroppers aim to reduce secrecy ***,we consider a virtual wireless network where MVNO users'job is to improve their Signal to Interference plus Noise Ratio(SINR)while the jammers target to collectively enhance their Jammer Received Signal Strength(JRSS),and an eavesdropper's goal is to reduce the overall secrecy *** results have demonstrated that the proposed game strategies are effective(in terms of data rate,secrecy rate and latency)against such attackers compared to the traditional approaches.

关键词： Game theory based security Virtual wireless networks Jamming and eavesdropping

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