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In situ investigations on forces and power consumption during flow forming process
Ravi J. Bhatt,Harit K. Raval 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.3
Flow forming is used to manufacture high precision seamless components for aerospace and defence industries. The typical applications are rocket missile case, cartridge case, rocket nose cones etc. In flow forming, the deformable workpiece is placed over rigid mandrel and rigid roller(s) deform it under contact zone. There are two approaches used for production i.e. forward and reverse. In forward approach, the roller feed and deformation direction are same. Whereas in reverse approach, the roller feed and deformation directions are opposite. The power consumption during the process is an important aspect to foster energy efficient production environment. Also, forces encountered on the tool (Roller) are also crucial aspect in order to design tooling for different material and geometrical conditions. Based on literature review and industrial survey, it was observed that online force and power measurement are quite difficult in commercial machines. Hence, experimental and numerical studies have been carried out on force(s) and power consumption to promote environment conscious manufacturing. Design of experiment (DOE) approach was used to reduce experimental runs. Taguchi L 36 design was used to conduct experiments. Three levels of three operating variables like speed, feed and reduction percentage along with two levels of two roller parameters like attack angle and nose radius were considered during the study. It was observed that speed and feed are the most important factors which are influencing the power consumption. Even, roller attack angle, nose radius and reduction percentage are mainly affecting force(s). Also, the results of experiments and simulations are found in good accordance.
Micro and macro in the dynamics of dilute polymer solutions: Convergence of theory with experiment
J. Ravi Prakash 한국유변학회 2009 Korea-Australia rheology journal Vol.21 No.4
Recent developments in dilute polymer solution rheology are reviewed, and placed within the context of the general goals of predicting the complex flow of complex fluids. In particular, the interplay between the use of polymer kinetic theory and continuum mechanics to advance the microscopic and the macroscopic description, respectively, of dilute polymer solution rheology is delineated. The insight that can be gained into the origins of the high Weissenberg number problem through an analysis of the configurational changes undergone by a single molecule at various locations in the flow domain is discussed in the context of flow around a cylinder confined between flat plates. The significant role played by hydrodynamic interactions as the source of much of the richness of the observed rheological behaviour of dilute polymer solutions is highlighted, and the methods by which this phenomenon can be incorporated into a macroscopic description through the use of closure approximations and multiscale simulations is discussed.
Micro and macro in the dynamics of dilute polymer solutions: Convergence of theory with experiment
Prakash, J. Ravi The Korean Society of Rheology 2009 Korea-Australia rheology journal Vol.21 No.4
Recent developments in dilute polymer solution rheology are reviewed, and placed within the context of the general goals of predicting the complex flow of complex fluids. In particular, the interplay between the use of polymer kinetic theory and continuum mechanics to advance the microscopic and the macroscopic description, respectively, of dilute polymer solution rheology is delineated. The insight that can be gained into the origins of the high Weissenberg number problem through an analysis of the configurational changes undergone by a single molecule at various locations in the flow domain is discussed in the context of flow around a cylinder confined between flat plates. The significant role played by hydrodynamic interactions as the source of much of the richness of the observed rheological behaviour of dilute polymer solutions is highlighted, and the methods by which this phenomenon can be incorporated into a macroscopic description through the use of closure approximations and multi scale simulations is discussed.
Kim, H.J.,Suh, S.M.,Rao, S.S.,Punnoose, D.,Tulasivarma, C.V.,Gopi, Chandu.V.V.M.,Kundakarla, N.,Ravi, S.,Durga, I.K. Elsevier Sequoia 2016 Journal of Electroanalytical Chemistry Vol.777 No.-
<P>To make quantum dot-sensitized solar cells (QDSSCs) more attractive, it is necessary for the power conversion efficiency (PCE) to be comparable to those of other emerging solar cells. Currently, copper sulfide (CuS) and nickel sulfide (NiS) are commonly used counter electrodes (CEs) in high-efficiency QDSSCs because of their low toxicity, environmental compatibility, and superior electrocatalytic activity in the presence of polysulfide electrolyte. For the first time, novel CuS/NiS electrodes were prepared by facile chemical bath deposition method. This article describes the effect of NiS layer on CuS film for preventing the recombination process to enhance the performance of QDSSCs. Under one sun illumination, the CE with the optimized CuS/NiS composite film exhibits higher short-circuit current density (J(sc)), open-circuit voltage (V-oc), and PCE of 12.47 mA cm(-2), 0.599 V, and 4.19%, respectively. These values are much higher than those of bare CuS (2.73%), NiS (1.82%), and Pt CEs (1.16%). This enhancement is mainly attributed to the improved surface morphology, higher sulfur atomic percentage with Cu vacancies, rapid electron transport, and lower electron recombination rate for the polysulfide electrolyte. Characterization with, cyclic voltammetry, and Tafel polarization was performed to study the reasons for efficient CE performance. (C) 2016 Elsevier B.V. All rights reserved.</P>
Bundy, Jacob J,Chick, Jeffrey Forris Beecham,Hage, Anthony N,Srinivasa, Ravi N,Chaudhary, Neeraj,Srinivasa, Rajiv N,Vadlamudi, Venu,Gemmete, Joseph J BMJ Publishing Group Ltd. 2018 Journal of neurointerventional surgery Vol.10 No.12
<P><B>Purpose</B></P><P>To describe the stroke-related Twitter network through analysis of the #Stroke hashtag.</P><P><B>Materials and methods</B></P><P>621 653 tweets containing the #Stroke hashtag were analyzed from 20 March 2012 to 31 January 2018. Twitter activity metrics, engagement, user characteristics, content analysis, and network analysis were obtained using the healthcare social media analytics platform, Symplur Signals.</P><P><B>Results</B></P><P>The number of users, the number of impressions, and the number of tweets containing the #Stroke hashtag increased by an annual average of 64.9%, 87.7%, and 89.2% over the past 6 years from 20 March 2012 to 31January 2018. 69 371 tweets (11.2%) contained novel content and 48 568 tweets (7.8%) related to patient care. 181 120 (29.1%) tweets contained at least one image and 436 132 tweets (70.2%) contained links to outside resources. Stroke prevention, diabetes, and atrial fibrillation were commonly discussed topics. With regard to engagement, there were 259 438 retweets (41.7%), 366 561 mentions (59.0%), and 8549 replies (1.4%). Physicians and patients authored 52 197 (8.4%) and 41 822 (6.7%) tweets, respectively. Advocate organizations, patients, and non-healthcare individuals most frequently used the #Stroke hashtag on Twitter.</P><P><B>Conclusion</B></P><P>The use of the #Stroke hashtag on Twitter has grown significantly over the 6-year study period. The majority of the discussions were held between stroke support groups and non-healthcare-related individuals, with discussion content centering around stroke prevention, stroke symptoms, associated medical conditions, and treatment options.</P>
Ravi, N.,Hsien-Hsin Liao,Jungkunz, A. F.,Han Ho Song,Gerdes, J. C. IEEE 2012 IEEE control systems magazine Vol.32 No.4
<P>The 21st century has brought with it a strong push in the automotive industry to develop energy technologies that can better address the global challenges posed by the depletion of finite fossil fuel resources and the pollution caused by using these fossil fuels as an energy resource. The two key words dominating automotive powertrain research today, therefore, are efficiency and emissions-There is a strong push for cars that burn less fuel and emit fewer pollutants. Some of the technologies in the spotlight include fuel cells, batteries, hybrid powertrains, and advanced IC engine strategies. Though fuel cells and battery technologies are very promising in the long-term future, they are currently more expensive and less practical than hybrid and advanced combustion engine strategies and are expected to remain so in the near future. In addition, technological advances that have made electronic control systems ubiquitous in todays automobiles have enabled combustion strategies that would not have been possible even a decade ago. One such advanced engine strategy that presents significant opportunities for reduced emissions and higher efficiencies is homogeneous charge compression ignition (HCCI).</P>
On solutions of a generalized neutral logistic differential equation
Ravi P. Agarwal,J´ozef Bana´s,Reza Mollapourasl,T. Gnana Bhaskar 장전수학회 2010 Advanced Studies in Contemporary Mathematics Vol.20 No.2
We study a generalized neutral logistic differential equation with deviating argument. Using the classical Banach contraction principle on an equivalent nonlinear functional integral equation we establish the existence of a unique solution in a certain function space. A few examples along with a numerical solutions are presented.
On constant--sign solutions of a system of discrete equations
Ravi P. Agarwal,Donal O'Regan,Patricia J. Y. Wong 한국전산응용수학회 2004 Journal of applied mathematics & informatics Vol.14 No.-
Abstract. We consider the following system of discrete equations ui(k) = N X `=0 gi(k, `)fi(`, u1(`), u2(`), · · · , un(`)), k 2 {0, 1, · · · , T}, 1 i n where T N > 0, 1 i n. Existence criteria for single, double and multiple constant-sign solutions of the system are established. To illustrate the generality of the results obtained, we include applications to several well known boundary value problems. The above system is also extended to that on {0, 1, · · ·} ui(k) = 1 X `=0 gi(k, `)fi(`, u1(`), u2(`), · · · , un(`)), k 2 {0, 1, · · ·}, 1 i n for which the existence of constant-sign solutions is investigated. AMS Mathematics Subject Classification : 39A12