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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

Near Optimal PID Controllers for the Biped Robot While Walking on Uneven Terrains

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International Journal of Automation and computing 2018年第6期15卷 689-706页

作者： ravi kumar Mandava Pandu Ranga Vundavilli School of Mechanical Sciences Indian Institute of Technology (IIT) Bhubaneswar

The execution of the gaits generated with the help of a gait planner is a crucial task in biped locomotion. This task is to be achieved with the help of a suitable torque based controller to ensure smooth walk of the biped robot. It is important to note that the success of the developed proportion integration differentiation （PID） controller depends on the selected gains of the controller. In the present study, an attempt is made to tune the gains of the PID controller for the biped robot ascending and descending the stair case and sloping surface with the help of two non-traditional optimization algorithms, namely modified chaotic invasive weed optimization （MCIWO） and particle swarm optimization （PSO） algorithms. Once the optimal PID controllers are developed, a simulation study has been conducted in computer for obtaining the optimal tuning parameters of the controller of the biped robot. Finally, the optimal gait angles obtained by using the best controller are fed to the real biped robot and found that the biped robot has successfully negotiated the said terrains.

关键词： Biped robot staircase sloping surface proportion integration differentiation (PID) controller modified chaotic invasive weed optimization (MCIWO) & particle swarm optimization (PSO) algorithm.

Sand-polished Kapton film and aluminum as source of electron transfer triboelectric nanogenerator through vertical contact separation mode

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International Journal of Smart and Nano Materials 2020年第1期11卷 38-46页

作者： ravi kumar Cheedarala Jung Il Song Research Institute of Mechatronics Department of Mechanical EngineeringChangwon National UniversityUichang-guChangwon CityS.Korea

Contact electrification is a direct triboelectrification method for producing current through charge transfer when two different differentiated materials have brought into *** the first time,we developed a simple triboelectric nanogenerator(TENG)where the electronic charges were realized through contact separation mode between sand-polished Kapton(SPK)and Al ***,we demonstrated the energetic interfacial contact between these surfaces and observed satisfactory output *** novel SPK-TENG produced 40 V and 2.8μA,of open-circuit voltages(V_(oc))and short-circuit currents(Isc)at 4 Hz,***,the SPK-TENG was dramatically increased up the performance of TENG,up to 40% of V_(oc) and 42% of I_(sc),with respect to the Kapton film because the mobility of electrons is very high on the device surface compared to the other pristine Kapton *** fabricated SPK-TENGs were good candidates for satisfying the need for alternative contact separation mode TENGs.

关键词： Kapton contactelectrification K-Al TENG SPK-Al TENGs electron transfer mechanism

Processing and characterization of polymer precursor derived silicon oxycarbide ceramic foams and compacts

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Journal of Advanced Ceramics 2013年第4期2卷 318-324页

作者： Srinivasan NEDUNCHEZHIAN ravindran SUJITH ravi kumar Materials Processing Section Department of Metallurgical and Materials EngineeringIndian Institute of Technology MadrasChennai 600036Tamil NaduIndia

This work focused on the fabrication of silicon oxycarbide ceramic(SiOC)foams as well as dense compacts using poly(hydridomethylsiloxane)(PHMS)as a polymer *** room-temperature cross-linking of PHMS was achieved by the addition of 1,4-diazabicyclo[2.2.2]octane(DABCO)with the release of hydrogen gas as a *** resulted in self-blowing of the polymer precursor at room temperature and thereby offered the possibility of producing SiOC foams without the need of any external blowing *** also reported the fabrication of crack-free silicon oxycarbide compacts by cold compaction and pyrolysis route using polyvinyl alcohol(PVA)as a processing ***-shaped pellets were pyrolysed at 1300℃in argon atmosphere with a ceramic yield of approximately 85%.Increased resistance to phase separation and crystallization up to 1400℃was attributed to the presence of large volume fraction of free carbon in the material which was confirmed by Raman spectroscopy.

关键词： silicon oxycarbide foams 1,4-diazabicyclo[2.2.2]octane(DABCO) self-blown polymer poly(hydridomethylsiloxane)(PHMS)

Wide-Angle Scanning Antennas for Millimeter-Wave 5G Applications

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Engineering 2022年第4期8卷 60-71页

作者： Raj Mittra Abdelkhalek Nasri ravi kumar Arya Electrical and Computer Engineering University of Central FloridaOrlandoFL 32816USA Electrical and Computer Engineering Department Faculty of EngineeringKing Abdulaziz UniversityJeddah 21589Saudi Arabia Department of Electronics and Communication Engineering National Institute of Technology DelhiDelhi 110040India

The fifth generation(5G)network communication systems operate in the millimeter waves and are expected to provide a much higher data rate in the multi-gigabit range,which is impossible to achieve using current wireless services,including the sub-6 GHz *** this work,we briefly review several existing designs of millimeter-wave phased arrays for 5G applications,beginning with the low-profile antenna array designs that either are fixed beam or scan the beam only in one *** then move on to array systems that offer two-dimensional(2D)scan capability,which is highly desirable for a majority of 5G ***,in the main body of the paper,we discuss two different strategies for designing scanning arrays,both of which circumvent the use of conventional phase shifters to achieve beam *** note that it is highly desirable to search for alternatives to conventional phase shifters in the millimeter-wave range because legacy phase shifters are both lossy and costly;furthermore,alternatives such as active phase shifters,which include radio frequency amplifiers,are both expensive and *** this backdrop,we propose two different antenna systems with potential for the desired 2D scan performance in the millimeter-wave *** first of these is a Luneburg lens,which is excited either by a 2D waveguide array or by a microstrip patch antenna array to realize 2D scan ***,for second design,we turn to phased-array designs in which the conventional phase shifter is replaced by switchable PIN diodes or varactor diodes,inserted between radiating slots in a waveguide to provide the desired phase shifts for ***,we discuss several approaches to enhance the gain of the array by modifying the conventional array *** describe novel techniques for realizing both one-dimensional(1D)and 2D scans by using a reconfigurable metasurface type of panels.

关键词： Luneburg lens Scanning arrays Millimeter-wave antennas Switchable phase shifters Reconfigurable metasurfaces

Spatial distribution of fossil fuel derived CO_(2) over India using radiocarbon measurements in crop plants

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Journal of Environmental Sciences 2023年第2期124卷 19-30页

作者： Rajveer Sharma ravi kumar Kunchala Sunil Ojha Pankaj kumar Satinath Gargari Sundeep Chopra Inter University Accelerator Centre New Delhi 110067India Centre for Atmospheric Sciences Indian Institute of Technology DelhiNew Delhi 110016India

Examining the contribution of fossil fuel CO_(2) to the total CO_(2) changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifically developing *** radiocarbon represents an important observational constraint and utilized to trace fossil fuel derived CO_(2)(CO_(2ff))in the *** the first time,we have presented a detailed analysis on the spatial distribution of fossil fuel derived CO_(2)(CO_(2ff))over India using radiocarbon(Δ14C)measurements during three-year *** shows that theΔ14C values are varying between 29.33‰ to-34.06‰ across India in the year 2017,where highest value belongs to a location from Gujarat while lowest value belongs to a location from *** on the14C patterns,spatial distributions of CO_(2ff) mole fractions have been determined over India and the calculated values of CO_(2ff) mole fractions are varying between 4.85 ppm to 26.59 ppm across *** is also noticed that the highest CO_(2ff) mole fraction is observed as 26.59 ppm from a site in ***_(2ff) mole fraction values from four high altitude sites are found to be varied between 4.85 ppm to 14.87 *** of sampling different crop plants from the same growing season and different crop plant organs(grains,leaves,stems)on theΔ14C and CO_(2ff) have been *** and intra seasonal variations in theΔ14C and CO_(2ff) mole fractions have also been analyzed from a rural location(Dholpur,Rajasthan).

关键词： Carbon dioxide Crop plants Fossil fuel CO_(2) Radiocarbon measurements

Emissions analysis on second generation biodiesel

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Frontiers of Environmental Science & Engineering 2017年第1期11卷 53-58页

作者： Yuvarajan Devarajan ravi kumar Jayabal Devanathan Ragupathy Harish Venu Department of Mechanical Engineering Vel Tech Dr. RR & Dr. SR Technical University Chennai 600062 India Department of Mechanical Engineering Jeppiaar Institute of Technology Chennai 631604 India Department of Mechanical Engineering Anna University Chennai 600025 India

This work investigates the effect of adding pentanol with biodiesel derived from cashew nut shell on its emissions characteristics is conducted in stationery diesel engine. The main purpose of this work is intended to reduce the emissions by fuelling biodiesel derived from cashew nut shell and the pentanol blends. Cashew nut shell biodiesel is prepared by transesterification process. Oxygenated additive used in the work is Pentanol. The experiment is con-ducted using four test fuels such-as, biodiesel derived from cashew nut shell （CNSBD）, a fuel containing 90% cashew nut shell biodiesel and 10% pentanol （CNSBD90P 10）, a fuel containing 80% cashew nut shell biodiesel and 20% pentanol （CNSBDSOP20） and neat diesel. Experimental work concluded that by adding 10% of pentanol to cashew nut shell biodiesel 10.1%, 2.6%, 5.1% and 2.1%reduction in CO, HC, NOx and Smoke emissions were observed respectively. Further by fueling with these blends, no modifications in engines were required.

关键词： Pentanol Biodiesel Emissions

Magnetizations and magneto-transport properties of Ni-doped PrFeO_3 thin films

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Chinese Physics B 2014年第4期23卷 608-615页

作者： Feroz A.Mir S.K.Sharma ravi kumar University Science Instrumentation Center University of Kashmir Instituto de Fisica Gleb Wataghin Universidade Estadual de Campinas (UNICAMP) CMSE National Institute of Technology

The present study reports the magnetizations and magneto-transport properties of PrFel_xNixO3 thin films grown by pulsed laser ablation technique on LaA103 snbstrates. From DC M/H plots of these films, weak ferromagnetism or ferrimagnetism behaviors are observed. With Ni substitution, reduction in saturation magnetization is also seen. With Ni doping, variations in saturation field （Hs）, coercive field （Hc）, Weiss temperature （0）, and effective magnetic moment （Pelf） are seen. A small change of magnetoresitance with application of higher field is observed. Various essential parameters like density of state （Nf） at Fermi level, Mott＇s characteristic temperature （To）, and activation energy （Ea） in the presence of and in the absence of magnetic field are calculated. The present observed magnetic properties are related to the change of Fe-O bond length （causing an overlap between the oxygen p orbital and iron d orbital） and the deviation of the Fe-O-Fe angle from 180~. Reduction of magnetic domain after Ni doping is also explored to explain the present observed magnetic behavior of the system. The influence of doping on various transport properties in these thin films indicates a distortion in the lattice structure and single particle band width, owing to stress-induced reduction in unit cell volume.

关键词： thin films magnetization ferromagnetism ferrimagnetism magneto-transport and distortion

SRN-LEACH: an energy-efficient leach protocol with random number stabilisation for WSNs

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Journal of Control and Decision 2023年第1期10卷 82-89页

作者： ravi kumar Sanapala Srineevasa Rao Duggirala Department of Electronics and Communication Engineering Jawaharlal Nehru Technological UniversityHyderabadTelanganaIndia

The power supplies of wireless sensor networks (WSNs) are not replaceable orrechargeable forsensors. For reducing the communication protocols’ impact onthe sensor network’s energy dissipation,various protocols or mechanisms havebeen proposed. Therefore, this article proposesa stable random number-basedLEACH protocol to stabilize the random number generation toimprove the CHselection efficiency. The wireless sensor network’s average node energy (ANE)ismultiplied by the random number that relies on the nodes’ energy. A nodegrade algorithm(NGA) based relay selection is introduced for inter andintracluster communication for energy efficiencyenhancement. The proposed NGA calculates the grade of a node using residual energy,distance from CHs,and its traffic parameters. Based on the simulation results, the proposedSRN-LEACH protocol shows superior performance as compared to existing protocolsincludingreduced energy dissipation, improved communication quality, andNLT. The proposed methodattains a minimum average delay of 0.136ms, 0.95% PDR, 148kbps TP rate, and 98% NLT.

关键词： Wireless sensor networks LEACH protocol cluster head average node energy node grade algorithm relay selection

Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints

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Geoscience Frontiers 2014年第1期5卷 25-41页

作者： D.C.Mishra M.ravi kumar National Geophysical Research Institute (CSIR) Gravity GroupHyderabad 500007 India Indian Institute of Geomagnetism Navi Mumbai 410218 India

The Aravalli-Delhi and Satpura Mobile Belts （ADMB and SMB） and the Eastern Ghat Mobile Belt （EGMB） in India form major Proterozoic mobile belts with adjoining cratons and contemporary basins. The most convincing features of the ADMB and the SMB have been the crustal layers dipping from both sides in opposite directions, crustal thickening （ -45 km） and high density and high conductivity rocks in upper/ lower crust associated with faults/thrusts. These observations indicate convergence while domal type re- flectors in the lower crust suggest an extensional rifting phase. In case of the SMB, even the remnant of the subducting slab characterized by high conductive and low density slab in lithospheric mantle up to - 120 km across the Purna-Godavari river faults has been traced which may be caused by fluids due to metamorphism. Subduction related intrusives of the SMB south of it and the ADMB west of it suggest N-S and E-W directed convergence and subduction during Meso-Neoproterozoic convergence. The simultaneous E-W conver- gence between the Bundelkhand craton and Marwar craton （Western Rajasthan） across the ADMB and the N-S convergence between the Bundelkhand craton and the Bhaodara and Dharwar cratons across the SMB suggest that the forces of convergence might have been in a NE SW direction with E-W and N-S compo- nents in the two cases, respectively. This explains the arcuate shaped collision zone of the ADMB and the SMB which are connected in their western part. The Eastern Ghat Mobile Belt （EGMB） also shows signatures orE -W directed Meso Neoproterozoic convergence with East Antarctica similar to ADMB in north India. Foreland basins such as Vindhyan （ADMB-SMB）, and Kurnool （EGMB） Supergroups of rocks were formed during this convergence. Older rocks such as Aravalli （ADMB）, Mahakoshal-Bijawar （SMB）, and Cuddapah （EGMB） Supergroups of rocks with several basic/ultrabasic intrusives along these mobile belts, plausibly formed during an earlier episode of rifting during

关键词： Indian Shield Convergence Collision Rifting Geophysical anomalies