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Search Results: 1 - 10 of 894 matches for " Arvind Santhanakrishnan "
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Broad Leaves in Strong Flow
Laura Miller,Arvind Santhanakrishnan
Physics , 2013,
Abstract: Flexible broad leaves are thought to reconfigure in the wind and water to reduce the drag forces that act upon them. Simple mathematical models of a flexible beam immersed in a two-dimensional flow will also exhibit this behavior. What is less understood is how the mechanical properties of a leaf in a three-dimensional flow will passively allow roll up into a cone shape and reduce both drag and vortex induced oscillations. In this fluid dynamics video, the flows around the leaves are compared with those of simplified sheets using 3D numerical simulations and physical models. For some reconfiguration shapes, large forces and oscillations due to strong vortex shedding are produced. In the actual leaf, a stable recirculation zone is formed within the wake of the reconfigured cone. In physical and numerical models that reconfigure into cones, a similar recirculation zone is observed with both rigid and flexible tethers. These results suggest that the three-dimensional cone structure in addition to flexibility is significant to both the reduction of vortex-induced vibrations and the forces experienced by the leaf.
Leaf roll-up and aquaplaning in strong winds and floods
Laura Miller,Gregory Herschlag,Arvind Santhanakrishnan
Physics , 2008,
Abstract: Flexible plants, fungi, and sessile animals are thought to reconfigure in the wind and water to reduce the drag forces that act upon them. In strong winds, for example, leaves roll up into cone shapes that reduce flutter and drag when compared to paper cut-outs with similar shapes and flexibility. During flash floods, herbaceous broad leaves aquaplane on the surface of the water which reduces drag. Simple mathematical models of a flexible beam immersed in a two-dimensional flow will also reconfigure in flow. What is less understood is how the mechanical properties of a two-dimensional leaf in a three-dimensional flow will passively allow roll up and aquaplaning. In this study, we film leaf roll-up and aquaplaning in tree and vine leaves in both strong winds and water flows.
A numerical study of the effects of bell pulsation dynamics and oral arms on the exchange currents generated by the upside-down jellyfish Cassiopea spp
Christina Hamlet,Arvind Santhanakrishnan,Laura A. Miller
Physics , 2010,
Abstract: Mathematical and experimental studies of the flows generated by jellyfish have focused primarily on mechanisms of swimming. More recent work has also considered the fluid dynamics of feeding from currents generated during swimming. Here the benthic lifestyle of the upside down jellyfish (Cassiopea spp.) is capitalized upon to explore the fluids dynamics of feeding uncoupled from swimming. A mathematical model is developed to capture the fundamental characteristics of the motion of the unique concave bell shape. Given the prominence of the oral arms, this structure is included and modeled as a porous layer that perturbs the flow generated by bell contractions. The immersed boundary method is used to solve the fluid-structure interaction problem. Velocity fields obtained from live organisms using digital particle image velocimetry were used to validate the numerical simulations. Parameter sweeps were used to numerically explore the effects of changes in pulse dynamics and the properties of the oral arms independently. Numerical experiments allow the opportunity to examine physical effects and limits within and beyond the biologically relevant range to develop a better understanding of the system. The presence of the prominent oral arm structure in the field of flow increased the flux of new fluid from along the substrate to the bell. The numerical simulations also showed that the presence of pauses between bell expansion and the next contraction alters the flow of the fluid over the bell and through the oral arms.
Aerodynamics of the Smallest Flying Insects
Laura A. Miller,Steven Harenber,Ty Hedrick,Alice Robinson,Arvind Santhanakrishnan,Audrey Lowe
Physics , 2011,
Abstract: We present fluid dynamics videos of the flight of some of the smallest insects including the jewel wasp, \textit{Ampulex compressa}, and thrips, \textit{Thysanoptera} spp. The fruit fly, \textit{Drosophila melanogaster}, is large in comparison to these insects. While the fruit fly flies at $Re \approx 120$, the jewel wasp flies at $Re \approx 60$, and thrips flies at $Re \approx 10$. Differences in the general structures of the wakes generated by each species are observed. The differences in the wakes correspond to changes in the ratio of lift forces (vertical component) to drag forces (horizontal component) generated.
U(2) invariant squeezing properties of pair coherent states
Physics , 2002, DOI: 10.1016/S0375-9601(02)00663-1
Abstract: The U(2) invariant approach is delineated for the pair coherent states to explore their squeezing properties. This approach is useful for a complete analysis of the squeezing properties of these two-mode states. We use the maximally compact subgroup U(2) of Sp(4,R) to mix the modes, thus allowing us to search over all possible quadratures for squeezing. The variance matrix for the pair coherent states turns out to be analytically diagonalisable, giving us a handle over its least eigenvalue, through which we are able to pin down the squeezing properties of these states. In order to explicitly demonstrate the role played by U(2) transformations, we connect our results to the previous analysis of squeezing for the pair coherent states.
Quantum Entanglement and Quantum Computational Algorithms
Physics , 2000, DOI: 10.1007/s12043-001-0130-9
Abstract: The existence of entangled quantum states gives extra power to quantum computers over their classical counterparts. Quantum entanglement shows up qualitatively at the level of two qubits. We show that if no entanglement is envolved then whatever one can do with qubits can also be done with classical optical systems. We demonstrate that the one- and the two-bit Deutsch-Jozsa algorithm does not require entanglement and can be mapped onto a classical optical scheme. It is only for three and more input bits that the DJ algorithm requires the implementation of entangling transformations and in these cases it is impossible to implement this algorithm classically.
Structure, Composition and Diversity of Horticulture Trees and Agricultural Crops Productivity under Traditional Agri-Horticulture System in Mid Hill Situation of Garhwal Himalaya, India  [PDF]
Arvind Bijalwan
American Journal of Plant Sciences (AJPS) , 2012, DOI: 10.4236/ajps.2012.34057
Abstract: Productivity of agricultural crops under traditional agri-hortculture system alongwith structure, composition and diversity of fruit trees and shrub species in mid hill situation of Garhwal Himalaya, India between 1000 to 2000 m asl during summer and winter seasons on northern and southern aspect were studied. The tree density, composition and diversity in the system varied depending upon aspect, landholding and requirements of the farmers. A total of 12 fruit tree species were recorded in agri-horticulture system; of which 4 trees were common in northern and southern aspect and 6 trees were only noticed in northern aspect while 2 in the southern. The apple tree (Malus domestica) was recorded to be dominant fruit tree species with highest IVI values on both northern and southern aspect with prime preference by the farmers for high additional economic return in agri-horticulture system. Among the shrubs, the 6 shrub species were recorded on the northern aspect whereas there number was 16 on southern aspect. The agricultural crop diversity was higher on the northern aspect in summer and winter season. The average annual productivity of grain under agri-horticulture system recorded 1106 kg·ha–1·year–1 on northern aspect and 1122 kg·ha–1·year–1 on southern with a reduction of 34.56% and 38.29% compared to the sole agriculture crops. The aspect and season also played significantly role in grain, straw and biological productivity of agricultural crops present in agri-horticulture and sole cropping systems. In general there was reduction in yield of agricultural crops under fruit trees but this reduction is supplemented by fruit production which support and sustain the rural community of this hilly region.
Study on Performance and Emission Characteristics of a Compression Ignition Engine Fueled with Diesel-2 Ethoxy Ethyl Acetate Blends  [PDF]
R. Senthil, M. Kannan, B. Deepanraj, V. Nadanakumar, S. Santhanakrishnan, P. Lawrence
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.311141
Abstract: Diesel engines are the major contributors of various types of air polluting gases like carbon monoxide, oxides of nitrogen, smoke, etc. Improvement of fuel properties is essential for suppression of Diesel pollutant emissions along with the optimization of design factors and after treatment equipment. Studies conducted in the past have shown that a significant reduction were obtained in the emissions using oxygenates. This paper investigates the performance and emission characteristics of a direct injection Diesel engine fueled with 2 Ethoxy Ethyl Acetate (EEA) blends. Different fuel blends which contain 5%, 10% and 15% of EEA were prepared and the effect of these blends on performance and emissions were studied on a single cylinder direct injection Diesel engine. The blends were tested under different load conditions and the result showed that EEA blended fuels improves the performance of the engine and reduce the emission level significantly.
Diet Composition of the Barn Owl Tyto alba (Aves: Tytonidae) and Spotted Owlet Athene brama (Aves: Strigidae) Coexisting in an Urban Environment
A. Mohamed Samsoor Ali, R. Santhanakrishnan
Podoces , 2012,
Abstract: The comparative diet of the Barn OwlTyto alba and the Spotted Owlet Athene brama were studied in an urban habitat of Madurai District, Tamil Nadu, Southern India, during January–December 2008. Regurgitated pellets of these two owl species were analysed to understand their dietary composition. The diet of the Barn Owl mainly comprised small mammals such as Suncus murinus(51.9%) and Rattus rattus(28.6%), while the diet of the Spotted Owlet comprised mostly arthropods (84.9%); Coleoptera (40.9%) and Orthoptera (32.4%). Food niche overlap between the Barn Owl and the Spotted Owlet in overall diet was 6.5%,which indicated very low degree of overlap.
Identification of Source of Rumors in Social Networks with Incomplete Information
Alireza Louni,Anand Santhanakrishnan,K. P. Subbalakshmi
Computer Science , 2015,
Abstract: Rumor source identification in large social networks has received significant attention lately. Most recent works deal with the scale of the problem by observing a subset of the nodes in the network, called sensors, to estimate the source. This paper addresses the problem of locating the source of a rumor in large social networks where some of these sensor nodes have failed. We estimate the missing information about the sensors using doubly non-negative (DN) matrix completion and compressed sensing techniques. This is then used to identify the actual source by using a maximum likelihood estimator we developed earlier, on a large data set from Sina Weibo. Results indicate that the estimation techniques result in almost as good a performance of the ML estimator as for the network for which complete information is available. To the best of our knowledge, this is the first research work on source identification with incomplete information in social networks.
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