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Influence of quenching medium on the dendrite morphology,hardness,and tribological behaviour of cast Cu-Ni-Sn spinodal alloy for defence application

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Defence Technology（防务技术） 2023年第12期30卷 83-100页

作者： bipin sankar Karthik V Shankar Vamu Sunil Hemanth Kashyap S Nikhil Nair Adarsh A.Nair Abhinav P M Department of Mechanical Engineering Amrita Vishwa VidyapeethamAmritapuriIndia

Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and *** paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)*** analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values *** analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze *** hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal ***,the grain size was approximately 30%finer for spinodal bronze when compared with regular *** the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal *** was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze *** results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.

关键词： Quenching Water Brine SAE 40 oil Grain size Hardness Wear rate Spinodal decomposition CuSn Spinodal alloy CuNiSn

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Classical interpretations of relativistic precessions

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Chinese Physics B 2014年第4期23卷 147-156页

作者： sankar Hajra Indian Physical Society 2A & 2B Raja S. C. Mallick Road

Relativists have exposed various precessions and developed ingenious experiments to verify those phenomena with extreme precisions. The Gravity Probe B mission was designed to study the precessions of the gyroscopes rotating round the Earth in a nearly circular near-Earth polar orbit to demonstrate the geodetic effect and the Lense-Thirring effect as predicted by the general relativity theory. In this paper, we show in a very simple and novel analysis that the precession of the perihelion of Mercury, the Thomas precession, and the precession data （on the de Sitter and Lense-Thirring precessions） collected from the Gravity Probe B mission could easily be explained from classical physics, too.

关键词： Thomas precession precession of planetary orbits de Sitter precession Lense-Thirring precession

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Three-mode optomechanical system for angular velocity detection

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Chinese Physics B 2018年第8期27卷 254-260页

作者： Kai Li sankar Davuluri Yong Li Beijing Computational Science Research Center Beijing 100193China

We propose a scheme for measuring the angular velocity of absolute rotation using a three-mode optomechanical system in which one mode of the two-dimensional （2D） mechanical resonator is coupled to an optical cavity. When the total system rotates, the Coriolis force acting on the 2D mechanical resonator due to the absolute rotation will affect the mechanical motion and thus change the phase of the output field from the cavity. The angular velocity of the absolute rotation can be estimated by monitoring the spectrum of the output field from the cavity via homodyne measurement. The minimum measurable angular velocity, which is determined by the noise spectrum, is calculated. The working range of the gyroscope for measuring angular velocity is discussed.

关键词： optomechanics gyroscope

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Gasification kinetic modelling of Victorian brown coal chars and validity for entrained flow gasification in CO_(2)

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International Journal of Mining Science and Technology 2021年第3期31卷 473-481页

作者： Tao Xu Yongping Wu sankar Bhattacharya College of Energy Engineering Xi’an University of Science and TechnologyXi’an 710054China Department of Chemical Engineering Monash UniversityVictoria 3800Australia

The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this *** study was conducted in a thermogravimetric analyzer(TGA)at 750–1100℃,30%–90%CO_(2)concentration using different char particle sizes within 20–106 *** was found that random pore model and modified volumetric model are applicable for TGA results,but volumetric model and grain model are *** effect of particle size under106 mm on gasification rate is very *** energies of Maddingley char and Yallourn char in CO_(2)gasification are 219–220 and 197–208 k J/mol,*** pre-exponential factors are in the same order of magnitude,and they increased as particle size decreased.A mathematical model was developed to predict carbon conversion over time for entrained flow gasification of Victorian brown coal chars at 1000–1400℃.

关键词： Victorian brown coal Gasification kinetics Modelling Entrained flow gasification

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Detection and Localization of Load Redistribution Attacks on Large-scale Systems

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Journal of Modern Power Systems and Clean Energy 2022年第2期10卷 361-370页

作者： Andrea Pinceti Lalitha sankar Oliver Kosut the School of Electrical Computer and Energy EngineeringArizona State UniversityTempeUSA

A nearest-neighbor-based detector against load redistribution attacks is *** detector is designed to scale from small-scale to very large-scale systems while guaranteeing consistent detection *** testing is performed on a realistic large-scale system to evaluate the perfor-mance of the proposed detector against a wide range of attacks,from simple random noise attacks to sophisticated load redistribution *** detection capability is analyzed against different attack parameters to evaluate its sensitivity.A statistical test that leverages the proposed detector is introduced to identify which loads are likely to have been maliciously modified,thus,localizing the attack *** test is based on ascribing to each load a risk measure(probability of being attacked)and then computing the best posterior likelihood that minimizes log-loss.

关键词： Attack detection cyber-security false data injection(FDI)attack load redistribution attack machine learning nearest neighbor

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Suitable triggering algorithms for detecting strong ground motions using MEMS accelerometers

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Earthquake Engineering and Engineering Vibration 2015年第1期14卷 27-35页

作者： Ravi sankar Jakka Siddharth Garg Department of Earthquake Engineering Indian Institute of Technology

With the recent development of digital Micro Electro Mechanical System （MEMS） sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor＇s sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network （network of MEMS accelerometer stations）. We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used （i.e., window width of STA, LTA and threshold level）.

关键词： strong ground motion triggering algorithms seismic event detection MEMS accelerometers STA/LTA based algorithms

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Numerical Study of Double Diffusive Convection in Partially Heated Vertical Open Ended Cylindrical Annulus

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Advances in Applied Mathematics and Mechanics 2010年第6期2卷 763-783页

作者： Mani sankar Department of Mathematics East Point College of Engineering and TechnologyBangalore-560049India

A numerical investigation of laminar natural double diffusive convection in an open ended vertical cylindrical annulus with unheated entry and unheated exit is *** boundary conditions of uniform wall temperature/uniform wall concentration(UWT/UWC)and uniform heat flux/uniform mass flux(UHF/UMF)are *** of dimensionless induced volume rate Q,average Nusselt number Nu and Sherwood number Sh are obtained for air flow under various buoyancy ratio N,Grashof numbers due to heat and mass transfer GrT and GrM,Schmidt number Sc and combinations of unheated entry,heated section and unheated exit *** the flow under consideration is a boundary layer type,the governing partial differential equations was discretized to a linear system of equations by the use of an implicit finite difference *** nonlinear convective terms are approximated by second upwind difference method for the numerical *** numerical results reveal that the presence of unheated entry and unheated exit severely affects the heat and mass transfer *** numerical solutions are found to approach asymptotically the closed form solutions for fully developed ***,the present numerical results are validated with the existing solutions for pure thermal convection and are found to be in good agreement.

关键词： Discrete heating cylindrical annulus upwind difference doubles diffusive convection buoyancy ratio

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Time variant multi-objective linear fractional interval-valued transportation problem

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Applied Mathematics(A Journal of Chinese Universities) 2022年第1期37卷 111-130页

作者： Dharmadas Mardanya sankar Kumar Roy Department of Applied Mathematics with Oceanology and Computer Programming Vidyasagar UniversityMidnapore 721102West BengalIndia

This paper studies a time-variant multi-objective linear fractional transportation problem. In reality, transported goods should reach in destinations within a specific time. Considering the importance of time, a time-variant multi-objective linear fractional transportation problem is formulated here. We take into account the parameters as cost, supply and demand are interval valued that involved in the proposed model, so we treat the model as a multi-objective linear fractional interval transportation problem. To solve the formulated model, we first convert it into a deterministic form using a new transformation technique and then apply fuzzy programming to solve it. The applicability of our proposed method is shown by considering two numerical examples. At last, conclusions and future research directions regarding our study is included.

关键词： fractional transportation problem multi-objective optimization interval number time variant parameter fuzzy programming Pareto optimal solution

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Transportation Problem with Multi-choice Cost and Demand and Stochastic Supply

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Journal of the Operations Research Society of China 2016年第2期4卷 193-204页

作者： sankar Kumar Roy Department of Applied Mathematics with Oceanology and Computer Programming Vidyasagar UniversityMidnaporeWest Bengal 721102India

This paper analyzes the multi-choice stochastic transportation problem where the cost coefficients of the objective function and the demand parameters of the constraints follow multi-choice *** that the supply parameters of the constraints in a transportation problem(TP)follow logistic *** main objective of this paper is to select an appropriate choice from the multi-choices for the cost coefficients of the objective function and the demand of the constraints in the TP by introducing Lagrange’s interpolating polynomial in such a way that the total cost is minimized and satisfies the required *** stochastic programming,the stochastic supply constraints of the TP are transformed into deterministic ***,a non-linear deterministic model is *** Lingo software,the optimal solution of the proposed problem is *** illustrate the methodology,a real-life problem on the TP is considered.

关键词： Transportation problem Multi-choice programming Lagrange’s interpolating polynomial Stochastic programming

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Improving optomechanical gyroscopes by coherent quantum noise cancellation processing

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Science China(Physics,Mechanics & Astronomy) 2018年第9期61卷 19-25页

作者： Kai Li sankar Davuluri Yong Li Beijing Computational Science Research Center Beijing 100193 China Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha 410081 China

Coherent quantum noise cancellation(CQNC) method is used to beat standard quantum limit(SQL) for improving the performance of quantum optomechanical gyroscopes. The protocol for realizing CQNC is achieved by constructing an effective negative mass mechanical oscillator, which is simulated by an ancillary cavity. This oscillator shows an antiresponse relative to that of a real mechanical oscillator. Thus, the optomechanical back-action noise is counteracted or restrained, and we could increase our signal by increasing the coupling strength without increasing the noise.

关键词： CQNC optomechanics gyroscope

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