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npj Computational Materials 2023年第1期9卷 479-488页

作者： Lars L.Schaaf Edvin Fako sandip de Ansgar Schäfer Gábor Csányi Engineering Laboratory University of CambridgeCB21PZ CambridgeUK BASF SE Carl-Bosch-Straße 3867056 LudwigshafenGermany

We introduce a training protocol for developing machine learning force fields(MLFFs),capable of accurately determining energy barriers in catalytic reaction *** protocol is validated on the extensively explored hydrogenation of carbon dioxide to methanol over indium *** the help of active learning,the final force field obtains energy barriers within 0.05 eV of density Functional *** to the computational speedup,not only do we reduce the cost of routine in-silico catalytic tasks,but also find an alternative path for the previously established rate-limiting step,with a 40%reduction in activation ***,we illustrate the importance of finite temperature effects and compute free energy *** transferability of the protocol is demonstrated on the experimentally relevant,yet unexplored,top-layer reduced indium oxide *** ability of MLFFs to enhance our understanding of extensively studied catalysts underscores the need for fast and accurate alternatives to direct ab-initio simulations.

关键词： surface catalytic fields

Study of Secondary Cosmic Rays and Astronomical X-Ray Sources using Small Stratospheric Balloons

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Research in Astronomy and Astrophysics 2024年第6期24卷 94-109页

作者： Rupnath Sikdar sandip K.Chakrabarti debashis Bhowmick Indian Centre for Space Physics 466BarakholaSingabari RoadNetai NagarKolkata700099West BengalIndia

The X-ray sources of the universe are extraterrestrial in nature which emit X-ray *** closest strong X-ray source is the Sun,which is followed by various compact sources such as neutron stars,black holes,the Crab pulsar,*** this paper,we analyze the data received from several low-cost lightweight meteorological balloon-borne missions launched by the Indian Centre for Space *** main interest is to study the variation of the vertical intensity of secondary cosmic rays,the detection of strong X-ray sources,and their spectra in the energy band of^(1)0–80 keV during the complete *** to the lack of an onboard pointing system,low exposure time,achieving a maximum altitude of only~42 km,and freely rotating the payload about its axis,we modeled the background radiation flux for the X-ray detector using physical *** also present the source detection method,observation of the pulsation of the Crab(^(3)3 Hz),and spectra of some sources such as the quiet Sun and the Crab pulsar.

关键词： X-rays:stars balloons instrumentation:detectors

Effect of metal fractions on rice grain metal uptake and biological parameters in mica mines waste contaminated soils

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Journal of Environmental Sciences 2024年第2期136卷 313-324页

作者： Saibal Ghosh sandip Mondal Jajati Mandal Abhishek Mukherjee Pradip Bhattacharyya Agricultural and Ecological Research Unit Indian Statistical InstituteGiridihJharkhand 815301India School of Science Engineering&EnvironmentUniversity of SalfordManchester M54WTUK

Heavy metals from mica waste not only deteriorate the soil quality but also results in the uptake of metals in the *** present investigation was conducted to evaluate the effects of different fractions of metals on the uptake in rice,soil microbial and biochemical properties in mica waste-contaminated soils of Jharkhand,*** each active mine,soil samples were randomly collected at distances of100 m(zone 3).Sequential metal extraction was used to determine the fractions of different metals(nickel(Ni),cadmium(Cd),chromium(Cr)and lead(Pb))including water-soluble(Ws)and exchangeable metals(Ex),carbonate-bound metals(CBD),Fe/Mn oxide(OXD)bound metals,organically bound metals(ORG),and residues(RS).The Ni,Cr,Cd and Pb in rice grain were 0.83±0.41,0.41±0.19,0.21±0.14 and 0.17±0.08 mg/kg *** the variable importance plot of the random forest(RF)algorithm,the Ws fraction of Ni,Cr and Cd and Ex fraction of Pb was the most important predictor for rice grain metal ***,the partial dependence plots(PDP)give us an insight into the role of the two most important metal fractions on rice grain metal *** microbial and enzyme activity was significantly and negatively correlated with Ws and Ex metal fractions,indicating that water-soluble and exchangeable fractions exert a strong inhibitory effect on the soil microbiological parameters and enzyme activities.

关键词： Metal fractions Microbial parameters Mica waste soil Soil enzymes Rice Random forest

Dark Energy Accretion onto Van der Waal's Black Hole

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Communications in Theoretical Physics 2019年第2期71卷 209-219页

作者： sandip Dutta Ritabrata Biswas department of Mathematics The University of BurdwanGolapbag Academic ComplexBurdwan-713104Purba Bard-dhamanWest BengalIndia

We consider the most general static spherically symmetric black hole metric. The accretion of the fluid flow around the Van der Waal's black hole is investigated and we calculate the fluid's four-velocity, the critical point and the speed of sound during the accretion process. We also analyze the nature of the universe's density and the mass of the black hole during accretion of the fluid flow. The density of the fluid flow is also taken into account. We observe that the mass is related to redshift. We compare the accreting power of the Van der Waal's black hole with Schwarzschild black hole for different accreting fluid.

关键词： black hole physics thermodynamics accretion disc extended Chaplygin gas

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

Effect of Graphene Nanoplate and Silicon Carbide Nanoparticle Reinforcement on Mechanical and Tribological Properties of Spark Plasma Sintered Magnesium Matrix Composites

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Journal of Materials Science & Technology 2014年第11期30卷 1059-1070页

作者： Aniruddha Das sandip P.Harimkar School of Mechanical and Aerospace Engineering Oklahoma State UniversityStillwaterOK 74078USA

Processing of magnesium （Mg） matrix composites reinforced with low reinforcement content （up to 4-5 vol.%） of graphene nanoplates （GNPs） and silicon carbide （SIC） nanoparticles using bait milling and spark plasma sintering （SPS） is reported. Near full densification was observed for all the composite compositions at the sintering temperature of 450 ~C （soaking time of 5 min and applied pressure of 50 MPa）. detailed analysis of the microstructure and mechanical and tribological （under dry sliding contact with alumina counter-face） properties with reinforcement content in Mg-GNP and Mg-SiC is presented. Mg-GNP and Mg-SiC composites reinforced with about 2 vol.% of reinforcement content exhibited significant improvement in microhardness and wear resistance as compared with Mg compacts.

关键词： Microstructure and properties Wear Tribology Magnesium matrix composites

Phase Diagram of Na2S2O3＋t-Butanol ＋Water at Ambient Pressure and Temperature

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Chinese Journal of Chemistry 2011年第11期29卷 2562-2564页

作者： Sabale, sandip R. School of LiJe Sciences Shanghai University Shanghai 200444 China department of Chemistry Jaysingpur College Jaysingpur 416101 （MS） lndia

In the present work, we report the studies concerning liquid-liquid-solid equilibria for the ternary system sodium thiosulphate （Na2S203）＋t-butanol＋water at ambient pressure and at room temperature （303±2 K）. The solubility data of Na2S203 are reported for solutions in water, t-butanol and solutions of varying concentrations of t-butanol in water. The phase diagram for the said system is developed, described and compared with similar systems studied such as Na2S2O3＋ethanol＋water, K2CO3＋methanol＋water, etc. These results have been explained in terms of structural properties of aqueous t-butanol solutions and further discussed in terms of the effect of ions to cause phase separation.

关键词： sodium thiosulphate t-butanol water phase equillibria

design of a Robust Optimal decentralized PI Controller Based on Nonlinear Constraint Optimization For Level Regulation: An Experimental Study

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IEEE/CAA Journal of Automatica Sinica 2020年第1期7卷 187-199页

作者： Soumya Ranjan Mahapatro Bidyadhar Subudhi sandip Ghosh department of Electrical Engineering National Institute of Technology RourkelaRourkela 769008India School of Electrical Sciences Indian Institute of TechnologyFarmagudiGoa 403401India department of Electrical Engineering Indian Institute of TechnologyVaranasi 221005India

This paper presents the development of a new robust optimal decentralized PI controller based on nonlinear optimization for liquid level control in a coupled tank system. The proposed controller maximizes the closed-loop bandwidth for specified gain and phase margins, with constraints on the overshoot ratio to achieve both closed-loop performance and robustness. In the proposed work, a frequency response fitting model reduction technique is initially employed to obtain a first order plus dead time(FOPDT) model of each higher order subsystem. Furthermore, based on the reduced order model, a proposed controller is designed. The stability and performance of the proposed controller are verified by considering multiplicative input and output uncertainties. The performance of the proposed optimal robust decentralized control scheme has been compared with that of a decentralized PI controller. The proposed controller is implemented in real-time on a coupled tank system. From the obtained results,it is shown that the proposed optimal decentralized PI controller exhibits superior control performance to maintain the desired level, for both the nominal as well as the perturbed case as compared to a decentralized PI controller.

关键词： decentralized control multivariable system process control parameter uncertainty robustness

Investigation on surface structuring generated by electrochemical micromachining

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Advances in Manufacturing 2017年第3期5卷 217-230页

作者： sandip Kunar B. Bhattacharyya department of Production Engineering Jadavpur UniversityKolkata 700032 India

Surface geometrical features and their function- ality depend on the manufacturing process which is employed for fabrication of surface structures. Maskless electrochemical micromachining （EMM） is used to generate various surface structures for diminishing and controlling friction and wear to increase the lifetime, reliability, and efficiency of mechanical systems. This paper presents a method for the generation of structured surfaces on stainless steel （SS-304） surfaces by using maskless EMM. The micropatterned tool is composed of 800 μm diameter circular holes in a 5 × 5 matrix form. The indigenously developed EMM set up consists of an EMM cell, electrical power supply system, and a controlled vertical cross-flow electrolyte circulation arrangement to control the influence of process parameters during the generation of the micro features of structured surfaces. The single structured cathode tool is used for the mass production of structured surfaces with a short fabrication time in the industrial context by avoiding the use of an individual masking process for each workpiece. The process has been characterized in terms of the effects of predominant process parameters such as machining voltage, electrolyte concentration, duty ratio, pulsed frequency, and machining time on the machined surface characteristics such as current efficiency, machining accuracy, and depth of the circular pattern on the stainless steel surfaces. A mathematical model is also developed to determine the theoretical depth of the dimple pattern and correlate the theoretical depths with actual depths as obtained by experimentation. Moreover, an effort has been made to study the structuringcharacteristics on the basis of micrographs obtained duringthe EMM.

关键词： Electrochemical micromachining (EMM)Surface structuring Circular pattern Machiningparameters - Current efficiency Machining accuracy ·Machining depth

Adaptive sampling for generalized probabilistic roadmaps

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控制理论与应用（英文版） 2012年第1期10卷 1-10页

作者： sandip KUMAR Suman CHAKRAVORTY department of Aerospace Engineering Texas A&M University College Station

In this paper, an adaptive sampling strategy is presented for the generalized sampling-based motion plan- ner, generalized probabilistic roadmap （GPRM）. These planners are designed to account for stochastic map and model uncertainty and provide a feedback solution to the motion planning problem. Intelligently sampling in this framework can result in large speedups when compared to naive uniform sampling. By using the information of transition probabilities, encoded in these generalized planners, the proposed strategy biases sampling to improve the efficiency of sampling, and increase the overall success probability of GPRM. The strategy is used to solve the motion planning problem of a fully actuated point robot and a 3-DOF fixed-base manipulator on several maps of varying difficulty levels, and results show that the strategy helps solve the problem efficiently, while simultaneously increasing the success probability of the solution. Results also indicate that these rewards increase with an increase in map complexity.

关键词： Adaptive sampling GPRM Probabilistic roadmaps (PRM) Stochastic maps Model uncertainty Linkmanipulator