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Journal of Natural Gas Chemistry 2008年第3期17卷 256-263页

作者： B.ravi Kumar Rajeev Kumar Department of Chemical Engineering Indian Institute of Technology

The oxidative dehydrogenation （ODH） of propane was conducted on gallium, aluminum, and chromium doped Si30VMgO catalysts. On doping, the concentrations of the phases responsible for the activity and selectivity increased in their concentrations. The reaction studies were conducted in a tubular steel reactor at temperatures of 753, 783, 813, and 843 K and atmospheric pressure. The total flow rates of the feed were chosen as 30, 40, 50, and 60 ml/min. The propane to oxygen ratios were chosen at 1 ： 1, 2 ： 1, and 3 ： 1, respectively. The effect of various dopants on the activity and selectivity of the catalysts was studied. Deactivation studies were conducted over all the catalysts. The kinetic data were analyzed in terms of power law models and Langmuir-Hinshelwood （LH） models. The kinetic data results were analyzed by comparing the effect of dopants. Statistical model discrimination was done for the proposed models. AIC and BIC criteria were used for discrimination of the models.

关键词： oxidative dehydrogenation propane gallium aluminum chromium kinetic

High-resolution fabrication of nanopatterns by multistep iterative miniaturization of hot-embossed prestressed polymer films and constrained shrinking

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Microsystems & Nanoengineering 2022年第1期8卷 281-289页

作者： Shady Sayed P.ravi Selvaganapathy Department of Mechanical Engineering McMaster UniversityHamiltonON L8S 4L8Canada

The fabrication of nanostructures and nanopatterns is of crucial importance in microelectronics,nanofluidics,and the manufacture of biomedical devices and ***,the creation of nanopatterns by means of conventional nanofabrication techniques such as electron beam lithography is expensive and ***,we develop a multistep miniaturization approach using prestressed polymer films to generate nanopatterns from microscale patterns without the need of complex nanolithography *** polymer films have been used as a miniaturization technique to fabricate features with a smaller size than the initial imprinted ***,the height of the imprinted features is significantly reduced after the thermal shrinking of the prestressed films due to the shape memory effect of the polymer,and as a result,the topographical features tend to disappear after *** have developed a miniaturization approach that controls the material flow and maintains the shrunken patterns by applying mechanical constraints during the shrinking *** combination of hot embossing and constrained shrinking makes it possible to reduce the size of the initial imprinted features even to the *** developed multistep miniaturization approach allows using the shrunken pattern as a master for a subsequent miniaturization ***-defined patterns as small as 100 nm are fabricated,showing a 10-fold reduction in size from the original *** developed approach also allows the transfer of the shrunken polymeric patterns to a silicon substrate,which can be used as a functional substrate for many applications or directly as a master for nanoimprint lithography.

关键词： constrained polymer size

State of the art in finite element approaches for milling process:a review

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Advances in Manufacturing 2023年第4期11卷 708-751页

作者： Shailendra Chauhan Rajeev Trehan ravi Pratap Singh Department of Industrial and Production Engineering Dr.B R Ambedkar National Institute of TechnologyJalandharPunjabIndia

Over a century,metal cutting has been observed as a vital process in the domain of *** the numerous available metal-cutting processes,milling has been considered as one of the most employable processes to machine a variety of engineering materials *** the milling process,material removal occurs when the workpiece is fed against a rotating tool with multiple cutting *** order to maximize the profitability of metal cutting operations,it is essential that the various input and output variable relationships are analyzed and *** experimental method of studying milling processes is costly and time demanding,particularly when a large variety of elements such as cutting tool shape,materials,cutting conditions,and so on,are *** to these issues,other alternatives emerged in the form of mathematical simulations that employ numerical *** finite element approaches have well-proven to be the most practical and commonly utilized numerical *** finite element model(FEM)can be used to determine the various physical interactions occurring during the machining process along with the prediction of various milling characteristics,such as cutting forces,cutting temperature,stresses,etc.,with the help of milling *** the present article,various research studies in the broad milling process domain practiced with numerous finite element approaches have been critically reviewed and *** further highlights the several experimental and finite element approaches-based research studies that attempted to analyze and optimize the overall performance of the different milling *** recent years,various investigators have explored numerous ways to enhance milling performance by probing the different factors that influence the quality *** of the studies have also been found to be focused on the economic impacts of milling and various process inputs that affect milling ***,various milli

关键词： Milling Finite element modeling(FEM) Micro milling Turn-milling

Federated Approach for Privacy-Preserving Traffic Prediction Using Graph Convolutional Network

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Journal of Shanghai Jiaotong university(Science) 2024年第3期29卷 509-517页

作者： LONARE Savita BHRAMARAMBA ravi Pimpri Chinchwad College of Engineering Pune 411044India Department of Computer Science and Engineering GITAMViskhapatnam 530045India

Existing traffic flow prediction frameworks have already achieved enormous success due to large traffic datasets and capability of deep learning ***,data privacy and security are always a challenge in every field where data need to be uploaded to the *** learning(FL)is an emerging trend for distributed training of *** primary goal of FL is to train an efficient communication model without compromising data *** traffic data have a robust spatio-temporal correlation,but various approaches proposed earlier have not considered spatial correlation of the traffic *** paper presents FL-based traffic flow prediction with spatio-temporal *** work uses a differential privacy(DP)scheme for privacy preservation of participant's *** the best of our knowledge,this is the first time that FL is used for vehicular traffic prediction while considering the spatio-temporal correlation of traffic data with DP *** proposed framework trains the data locally at the client-side with *** then uses the model aggregation mechanism federated graph convolutional network(FedGCN)at the server-side to find the average of locally trained *** results of the proposed work show that the FedGCN model accurately predicts the *** scheme at client-side helps clients to set a budget for privacy loss.

关键词： federated learning(FL) traffic flow prediction data privacy graph convolutional network(GCN) differential privacy(DP)

Studies on long lasting optical properties of Eu^(2+) and Dy^(3+) doped di-barium magnesium silicate phosphors

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Chinese Chemical Letters 2015年第9期26卷 1187-1190页

作者： ravi Shrivastava Jagjeet Kaur Govt.VYT PG Autonomous College

Di-barium magnesium silicate phosphors doped with europium and dysprosium were prepared under a weak reducing atmosphere.X-ray diffraction pattern of the sample was also done that confirmed the proper preparation of the *** electron microscope（SEM） images confirmed that the sample has regular surface and uniform grain size *** studies of phosphorescence decay of Ba2MgSi2O7：Eu^2＋,Dy^3＋ phosphors with different concentration of Dy^3＋ were *** phosphor with 0.5/1.5 mol%of Eu/Dy,exhibited optimum green color afterglow *** emission is expected to arise due to transition of Eu^2＋ ions from any of the sublevels of 4f^65d^1 configuration to ^8S（7/2） level of the 4f7 *** a suitable trap depth,the trap concentration is expected to be proportional to the concentration of Dy^3＋.These traps are responsible for holding the charge career for a reasonable time,subsequently for increasing the time of ***,optimum Dy3＊ concentration produces the longer afterglow duration with higher intensity of luminescence *** depth were also calculated using thermoluminescence glow curve which was indicative of formation of traps suitable for long afterglow.

关键词： Phosphorescence XRD Persistence luminescence Trapping center

A Review on Surface Stress-Based Miniaturized Piezoresistive SU-8 Polymeric Cantilever Sensors

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Nano-Micro Letters 2018年第2期10卷 198-238页

作者： Ribu Mathew A.ravi Sankar School of Electronics Engineering (SENSE) Vellore Institute of Technology (VIT) Chennai

In the last decade, microelectromechanical systems(MEMS) SU-8 polymeric cantilevers with piezoresistive readout combined with the advances in molecular recognition techniques have found versatile applications,especially in the field of chemical and biological *** to conventional solid-state semiconductor-based piezoresistive cantilever sensors, SU-8 polymeric cantilevers have advantages in terms of better sensitivity along with reduced material and fabrication cost. In recent times,numerous researchers have investigated their potential as a sensing platform due to high performance-to-cost ratio of SU-8 polymer-based cantilever sensors. In this article, we critically review the design, fabrication, and performance aspects of surface stress-based piezoresistive SU-8 polymeric cantilever sensors. The evolution of surface stress-based piezoresistive cantilever sensors from solid-state semiconductor materials to polymers, especially SU-8 polymer, is discussed in detail. Theoretical principles of surface stress generation and their application in cantilever sensing technology are also devised. Variants of SU-8 polymeric cantilevers with different composition of materials in cantilever stacks are explained. Furthermore, the interdependence of the material selection, geometrical design parameters, and fabrication process of piezoresistive SU-8 polymeric cantilever sensors and their cumulative impact on the sensor response are also explained in *** addition to the design-, fabrication-, and performancerelated factors, this article also describes various challenges in engineering SU-8 polymeric cantilevers as a universal sensing platform such as temperature and moisture vulnerability. This review article would serve as a guideline for researchers to understand specifics and functionality of surface stress-based piezoresistive SU-8 cantilever sensors.

关键词： SU-8 polymer Surface stress Biological sensor Cantilever Chemical sensor Piezoresistor Immobilization

Alkali activated slag-fly ash concrete incorporating precious slag as fine aggregate for rigid pavements

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Journal of Traffic and Transportation Engineering(English Edition) 2022年第1期9卷 78-92页

作者： Avinash Talkeri A.U.ravi Shankar Department of Civil Engineering National Institute of Technology KarnatakaSurathkalMangalore 575025India

This study aims to develop the alkali activated slag-fly ash concrete(AASFC) using precious slag(PS) ball as the fine aggregate. The slag-fly ash proportion, sodium silicate/sodium hydroxide(SS/SH) ratio and sodium hydroxide concentration are the prime variables. The fresh concrete properties like workability, setting time and the hardened concrete properties of AASFC developed under ambient curing were analyzed and similar way by replacing with fly ash(FA). The sodium hydroxide concentration of 8 M, 10 M and 12 M, SS/SH ratio of 1.0, 1.5 and 2.0, alkaline liquid to binder ratio of 0.35 and variation in slag-fly ash proportion as major inputs for mix design. The test results showed that, the fresh state of AASFC blend has a shorter setting time of 12-16 min, because of calcium mineral from the FA, the workability and setting time of AASFC mix was enhanced by the addition of the trisodium phosphate as a retarder. At the higher SS/SH extent, the workability and setting time exaggerated, whereas the increased FA content and sodium hydroxide concentration had a greater influence on the fresh state of concrete. Also, the sodium hydroxide concentration, SS/SH ratio and slag-fly ash proportion are the most inducing parameters on the workability, setting time and strength parameters of AASFC.

关键词： Road engineering Slag-fly ash proportion SS/SH ratio Molarity AASFC PS ball

Multivariable regression model for Fox depth correction factor

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Frontiers of Structural and Civil Engineering 2019年第1期13卷 103-109页

作者： ravi Kant MITTAL Sanket RAWAT Piyush BANSAL Department of Civil Engineering Birla Institute of Technology & SciencePilani 333031India Department of Civil and Environmental Engineering Virginia TechBlacksburgVA 24061USA

This paper presents a simple and efficient equation for calculating the Fox depth correction factor used in computation of settlement reduction due to foundation *** solution of Boussinesq theory was used originally to develop the Fox depth correction factor equations which were rather complex in *** equations were later simplified in the form of graphs and tables and referred in various international code of practices and standard texts for an unsophisticated and quick ***,these tables and graphs provide the factor only for limited values of the input variables and hence again complicates the process of automation of ***,this paper presents a non-linear regression model for the analysis of effect of embedment developed using "IBM Statistical Package for the Social Sciences" *** multiple iterations,the value of coefficient of determination is found to reach *** equation is straightforward,competent and easy to use for both manual and automated calculation of the Fox depth correction factor for wide range of input *** the developed equation,parametric study is also conducted in the later part of the paper to analyse the extent of effect of a particular variable on the Fox depth factor.

关键词： settlement embedment Fox depth correction factor regression multivariable

Improving the High Order Spectral Volume Formulation Using a Diffusion Regulator

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Communications in Computational Physics 2012年第6期12卷 247-260页

作者： ravi Kannan Zhijian Wang CFD Research Corporation 215Wynn DriveHuntsvilleAL 35805USA Iowa State University Howe HallAmesIA 50011USA

The concept of diffusion regulation(DR)was originally proposed by Jaisankar for traditional second order finite volume Euler *** was used to decrease the inherent dissipation associated with using approximate Riemann *** this paper,the above concept is extended to the high order spectral volume(SV)*** DR formulation was used in conjunction with the Rusanov flux to handle the inviscid flux *** experiments were conducted to compare and contrast the original and the DR *** experiments demonstrated(i)retention of high order accuracy for the new formulation,(ii)higher fidelity of the DR formulation,when compared to the original scheme for all orders and(iii)straightforward extension to Navier Stokes equations,since the DR does not interfere with the discretization of the viscous *** general,the 2D numerical results are very promising and indicate that the approach has a great potential for 3D flow problems.

关键词： Diffusion regulation spectral volume high-order Rusanov flux Navier Stokes equations

Takagi-Sugeno Fuzzy Regulator Design for Nonlinear and Unstable Systems Using Negative Absolute Eigenvalue Approach

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IEEE/CAA Journal of Automatica Sinica 2020年第2期7卷 482-493页

作者： ravi V.Gandhi Dipak M.Adhyaru Department of Electrical Engineering Indian Institute of Technology(IIT)GandhinagarGandhinagar 382355India Department of Instrumentation&Control Engineering Institute of TechnologyNirma UniversityAhmedabad-382481India

This paper introduces a Takagi-Sugeno(T-S)fuzzy regulator design using the negative absolute eigenvalue(NAE)approach for a class of nonlinear and unstable *** open-loop system is initially embodied by the traditional T-S fuzzy model and then,all closed-loop subsystems are combined using the proposed Max-Min operator in place of traditional weighted average operator from the controller side to lessen the coupling virtually and simplify the proposed regulator *** each virtually decoupled closed-loop subsystem,the composite regulators(i.e.,primary and secondary regulators)are designed by the NAE approach based on the enhanced eigenvalue *** Lyapunov function is utilized to guarantee the asymptotic stability of the overall T-S fuzzy control *** most popular and widely used nonlinear and unstable systems like the electromagnetic levitation system(EMLS)and the inverted cart pendulum(ICP)are simulated for the wide range of the initial conditions and the enormous variation in the *** transient and steady-state performance of the considered systems using the proposed design are analyzed in terms of the decay rate,settling time and integral errors as IAE,ISE,ITAE,and ITSE to validate the effectiveness of the proposed approach compared to the most popular and traditional parallel distributed compensation(PDC)approach.

关键词： Eigenvalue approach nonlinear and unstable systems stability analysis Takagi-Sugeno(T-S)fuzzy regulator