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Equivariant Cobordism of Torus Orbifolds

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Chinese Annals of Mathematics,Series B 2021年第6期42卷 861-890页

作者： soumen sarkar DongYoup SUH Department of Mathematics Indian Institute of Technology MadrasChennai 600036India Department of Mathematical Sciences KAISTDaejeon 305701Republic of Korea

Torus orbifolds are topological generalizations of symplectic toric *** authours give a construction of smooth orbifolds with torus actions whose boundary is a disjoint union of torus orbifolds using a toric topological *** a result,they show that any orientable locally standard torus orbifold is equivariantly cobordant to some copies of orbifold complex projective *** also discuss some further equivariant cobordism results including the cases when torus orbifolds are actually torus manifolds.

关键词： Manifold with corners Torus action Torus orbifolds Equivariant cobordism

Ancient rip current records and their implications: an example from the Cretaceous Ukra Member, Kutch, India

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Journal of Palaeogeography 2020年第2期9卷 181-197页

作者： Subir sarkar Amlan Koner Department of Geological Sciences Jadavpur UniversityKolkata 700032India

Poorly-sorted conglomerate patches rich in granules or sturdy fossils or both, and reddish mud matrix within the interstices stand out amidst fine-grained siliciclastic shelf sediments of the trangressive systems tract(TST) of the Lower Cretaceous Ukra Member, Kutch Basin, India. The siliciclastic shelf sediments contrast the conglomerates with their remarkable lateral extension. The fossils belong to a low-diversity group of sedentary bivalves that can be traced into the shoreface facies assemblage. The shelf sandstones are almost always sculpted by wave structures,especially hummocky cross-stratification while textures in the conglomerates suggest that the sediment settling was generally from suspensions. Textural variations in conglomerates reflect an immediate variation in flow viscosity prior to the downloading. The current structures obtained from the conglomerates record offshoreward palaeocurrent, in contrast to the shore-parallel palaeocurrent in the TST. The hummocky cross-stratified(HCS) beds are interpreted as seasonal storm deposits, while the conglomerate patches are taken as rip current deposits induced by waves of much longer periods. The glauconite-rich shale that alternates with conglomerates is probable fair-weather products. The conglomerates could not be recognized either in the coarse-grained shoreface deposits occupying the lower part of the overall fining-upward TST or in the coarsening-upward and glauconite-depleted highstand systems tract(HST). In contrast to the TST, the HST is dominantly tide-imprinted, having shore-normal palaeocurrent direction. It appears that intensification of waves and weakening of tides during transgression favored strong rip currents generation, which had presumably caused severe damage to the sea coast and to the shell banks growing preferably at the necks of the rip current channels. Rapid lateral facies transitions in the shoreface deposits at the basal part of the TST suggest enhanced irregularity in the coast

关键词： Rip current fan Ukra Member TST shelf Longshore current Shore-normal flux Mass flow deposits Global warming Ukra Sea

Unified Smith Predictor Based H_∞ Wide-Area Damping Controller to Improve the Control Resiliency to Communication Failure

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IEEE/CAA Journal of Automatica Sinica 2020年第2期7卷 584-596页

作者： Mithu sarkar Bidyadhar Subudhi Sandip Ghosh G H Raisoni College of Engineering Nagpur 440016India Indian Institute of Technology Goa-403401India Indian Institute of Technology Banaras Hindu University(BHU)Varanasi 221005India

Inter-area low frequency oscillation in power system is one of the major problems for bulk power transmission through weak tie *** of wide-area signal is more effective than the local area signal in damping out the inter-area *** area measurement system(WAMS)is convenient to transmit the wide area signal through the communication channel to the remote *** failure is one of the disastrous phenomena in a communication *** this paper,a dual input single output(DIso)Hm controller is designed to build the control resiliency by employing two highest observability ranking wide area signals with respect to the critical damping inter-area *** proposed controller can provide sufficient damping to the system and also the system remains stabilized if one of the wide-area signals is *** time delay is an unwanted phenomenon that degrades the performance of the *** unified Smith predictor approach is used to design a Hm controller to handle the time ***'s two-area and IEEE-39 bus test systems are considered to verify the effectiveness of the proposed *** the simulation results,it is verified that,the proposed controller provides excellent damping performance at normal communication and improves the controller resiliency to counteract the communication failure.

关键词： Communication failure dual input single output(DIso)controller H_∞control inter-area oscillation unified Smith predictor

Seismic behavior of batter pile groups embedded in liquefiable soil

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Earthquake Engineering and Engineering Vibration 2021年第3期20卷 583-604页

作者： J.S.Rajeswari Rajib sarkar Department of Civil Engineering Indian Institute of Technology(ISM)DhanbadDhanbad 826004India

A comparative study of the seismic performance of 2×1 pile groups considering different degrees of batter(0°for vertical,10°and 20°)embedded in single homogeneous liquefiable sand through fully coupled three-dimensional dynamic analyses is *** effects of inertial interaction are considered with structures having two different *** performance of pile groups is investigated for the fixed and pinned pile to cap connections for both floating and end bearing types of pile *** ratios of piles were also varied to enable a comprehensive *** have been carried out for three earthquake motions having varied dominant *** is observed that batter pile groups in liquefiable soils provide beneficial effects on piles and superstructure responses for both fixed and pinned head pile to cap connections for long period ***,for short period structures,a beneficial effect is most evident for fixed head connection.

关键词： batter pile liquefaction period of structure pile to cap connection slenderness ratio

Syn-sedimentary tectonics and facies analysis in a rift setting: Cretaceous Dalmiapuram Formation, Cauvery Basin, SE India

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Journal of Palaeogeography 2018年第2期7卷 146-167页

作者： Nivedita Chakraborty Subir sarkar Department of Geology Kabi Jagadram Roy Govt. General Degree College Department of Geological Sciences Jadavpur University

The Cretaceous(Albian-Cenomanian) Dalmiapuram Formation is one of the economically significant constituents in the hydrocarbon-producing Cauvery rift basin, SE India that opened up during the Late Jurassic e Early Cretaceous Gondwanaland fragmentation. The fossil-rich Dalmiapuram Formation,exposed at Ariyalur within the Pondicherry sub-basin of Cauvery Basin, rests in most places directly on the Archean basement and locally on the Lower Cretaceous(Barremian-Aptian) Basal Siliciclastic Formation. In the Dalmiapuram Formation, a facies association of tectonically-disturbed phase is sandwiched between two drastically quieter phases. The early syn-rift facies association(FA 1), records the first carbonate marine transgression within the basin, comprising a bar-lagoon system with occasionally storms affecting along the shore and a sheet-like non-recurrent biomicritic limestone bed on the shallow shelf that laterally grades into pyrite e glauconite-bearing dark-colored shale in the deeper shelf. Spectacular breccias together with varied kinds of mass-flow products comprise the syn-rift facies association(FA 2). While the breccias occur at the basin margin area, the latter extend in the deeper inland sea. Clast composition of the coarse clastics includes large, even block-sized limestone fragments and small fragments of granite and sandstone from the *** beds of quieter intervals between tectonic pulses occur in alternation with them. Faulted basal contact of the formation, and small grabens filled by multiple mass-flow packages bear the clear signature of the syntectonic activity localized contortions, slump folds, and pillow beds associated with mega slump/slide planes and joints, which corroborates this contention further. This phase of tectonic intervention is followed by another relatively quieter phase and accommodates the late syn-rift facies association(FA 3). A tidal bar-interbar shelf depositional system allowed a transgressive systems tract motif to gr

关键词： Syn-sedimentary tectonics Facies analysis Carbonate shelf Cretaceous Dalmiapuram Formation Cauvery Basin

Analysis of flow over backward facing step with transition

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Frontiers of Structural and Civil Engineering 2015年第1期9卷 71-81页

作者： Dwarikanath RATHA Arindam sarkar Civil Engineering Department Thapar University Patiala Punjab 147001 India School of Infrastructure Indian Institute of Technology Bhubaneswar 751013 India

The present study deals with the study of the velocity distribution and the separation phenomenon of flow of air over a two dimensional backward facing step. The flow of air over a backward facing step has been investigated numerically using FLUENT. Flow simulation has been carried out in a backward facing step having an expansion ratio （ratio of the height before and after the step） of 1：1.94 and the results obtained are compared with the published experimental results. Comparison of flow characteristics between steps with three different transitions is made. The variation ofreattachment length for all the three cases are analyzed for wide range of Reynolds number ranging from 100 to 7000 which covers the laminar, transition and turbulent flow of air. Simulation of the flow over steps with expansion ratios of 1：1.24, 1：1.38, 1：1.47, 1：1.53, 1：1.94, 1：2.20 are also carried out to examine the effect of different expansion ratios on the reattachment length. It is found that the primary reattachment length increases with increase in the expansion ratio. The primary reattachment length at the bottom wall downstream of the step is minimum for the step with round edged transition and maximum for the step with a vertical drop transition.

关键词： Reattachment length backward facing step transition flow separation k-ε model

Overprint of neotectonism along the course of River Chel,North Bengal,India

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Journal of Palaeogeography 2016年第3期5卷 221-240页

作者： Sunipa Mandal Subir sarkar Department of Geological Sciences Jadavpur University

This paper aims to unveit neotectonic imprints in topography, drainage and sediments in the 46.25 km tong course of the River Chet from its source down to its attuvial fan at the base of the Himatayan Mountain Front in the Darjeeting-Jatpaiguri districts of India. A semi-circutar ridge detimits its primary catchment. Within confinement of this watershed basin the drainage pattern is composite being convergent atong the periphery and divergent on a butte inside. AtE these geomorphic neotectonic imprints are accom- panied by ramp and fiat structures and spectacutar mytonitization of rocks. High hypsometric index and convex shape of the hypsometric curve derived from the centrat near-straight course of the river between the primary catchment and the Main Frontat Thrust （MFT） atso reftects tectonic youthfutness of the river course. It is wett manifested atso in widety variabte stream index and stream gradient index ratios （SL/K） often exceeding 2. In response to neotectonism, this river course as a whore shifted westward between 1962 and 2007. Maximum reduction of the stream gradient on top of the MFT is etoquent enough about recent uptift of the thrust ridge. The high average stope gradient of canyon watt about 45.68° is wett consistent with this uptift. Very tow channet-width/vaUey-height ratio along the river further corroborates the uptift. The attuviat fan system of the River Chet is comprised of five morphogenetic fans stacked one above another with a tendency to shrink and shift progressively upstope. They differ from each other in terms of titt, axiat orientation, primary depositionat surface gradient and convexity in transverse section and thus present a writ of ongoing tectonism. Progressive upward increase in the share of distat crystattine rocks in ctast composition within attuviat fan package is a dear proxy for southerty advancement of the MFT. Concomitant increase in maximum ctast size is in good agreement with sediment source uptift. Art the five fans

关键词： Uptift of Main Frontat Thrust Neotectonism Hypsometric index Stream-sradient index,Atluviat fan system evotution Fan attributes Ctast size and composition

Dual-Core Photonic Crystal Fiber Plasmonic Refractive Index Sensor: A Numerical Analysis

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Photonic Sensors 2019年第2期9卷 151-161页

作者： Alok Kumar PAUL Ajay Krishno sarkar Department of Electrical & Electronic Engineering Rajshahi University of Engineering & Technology Rajshahi-6204 Bangladesh

A numerical analysis on dual core photonic crystal fiber (DC-PCF) based surface plasmon reso.ance (SPR) refractive index sensor is presented. The guiding parameters and required sensing performances are examined with finite element method (FEM) based software under MATLAB environment. According to simulation, it is warranted that the proposed refractive index sensor offers the maximum amplitude sensitivity of 554.9 refractive index unit (RIU-1) and 636.5 RIU 1 with the maximum wavelength sensitivity of 5800nm/RIU and 11 500nm/RIU, and the sensor resolutions of 1.72 ×10^-5RIU and 8.7× 10^-6 RIU, at analyte refractive index (RI) of 1.40 for x- and y-polarized modes, respectively. As the sensing performance in different wavelength ranges is quite high, the proposed sensor can be used in simultaneous detection for different wavelength ranges. Therefore, the proposed device is of a suitable platform for detecting biological, chemical, biochemical, and organic chemical analytes.

关键词： Photonic crystal fiber biosensor refractive index sensor finite element method plasmonic material

Enhanced strength in novel nanocomposites prepared by reinforcing graphene in red soil and fly ash bricks

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International Journal of Minerals,Metallurgy and Materials 2019年第10期26卷 1322-1328页

作者： Jit sarkar D.K.Das Department of Metallurgical and Materials Engineering Indian Institute of TechnologyKharagpur 721302West BengalIndia Department of Mechanical Engineering Indian Institute of Technology(Indian School of Mines)Dhanbad 826004JharkhandIndia

Low-dimensional nanomaterials such as graphene can be used as a reinforcing agent in building materials to enhance the strength and durability. Common building materials burnt red soil bricks and fly ash bricks were reinforced with various amounts of graphene, and the effect of graphene on the strength of these newly developed nanocomposites was studied. The fly ash brick nanocomposite samples were cured as per their standard curing time, and the burnt red soil brick nanocomposite samples were merely dried in the sun instead of being subjected to the traditional heat treatment for days to achieve sufficient strength. The water absorption ability of the fly ash bricks was also discussed. The compressive strength of all of the graphene-reinforced nanocomposite samples was tested, along with that of some standard (without graphene) composite samples with the same dimensions, to evaluate the effects of the addition of various amounts of graphene on the compressive strength of the bricks.

关键词： graphene burnt red soil brick fly ash brick nanocomposites compressive strength