The Experts below are selected from a list of 61620 Experts worldwide ranked by ideXlab platform
Sylvain Crovisier - One of the best experts on this subject based on the ideXlab platform.
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essential hyperbolicity and homoclinic bifurcations a dichotomy phenomenon mechanism for diffeomorphisms
Inventiones Mathematicae, 2015Co-Authors: Sylvain Crovisier, Enrique R PujalsAbstract:We prove that any diffeomorphism of a Compact Manifold can be approximated in the \(C^1\) topology by another diffeomorphism exhibiting a homoclinic bifurcation (a homoclinic tangency or a heterodimensional cycle) or by one which is essentially hyperbolic (has a finite number of transitive hyperbolic attractors with open and dense basin of attraction).
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partial hyperbolicity far from homoclinic bifurcations
Advances in Mathematics, 2011Co-Authors: Sylvain CrovisierAbstract:Abstract We prove that any diffeomorphism of a Compact Manifold can be C 1 -approximated by a diffeomorphism which exhibits a homoclinic bifurcation (a homoclinic tangency or a heterodimensional cycle) or by a diffeomorphism which is partially hyperbolic (its chain-recurrent set splits into partially hyperbolic pieces whose centre bundles have dimensions less or equal to two). We also study in a more systematic way the central models introduced in Crovisier (in press) [10] .
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essential hyperbolicity and homoclinic bifurcations a dichotomy phenomenon mechanism for diffeomorphisms
arXiv: Dynamical Systems, 2010Co-Authors: Sylvain Crovisier, Enrique R PujalsAbstract:We prove that any diffeomorphism of a Compact Manifold can be approximated in topology C1 by another diffeomorphism exhibiting a homoclinic bifurcation (a homoclinic tangency or a heterodimensional cycle) or by one which is essentially hyperbolic (it has a finite number of transitive hyperbolic attractors with open and dense basin of attraction).
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the c 1 generic diffeomorphism has trivial centralizer
Publications Mathématiques de l'IHÉS, 2009Co-Authors: Christian Bonatti, Sylvain Crovisier, Amie WilkinsonAbstract:Answering a question of Smale, we prove that the space of C 1 diffeomorphisms of a Compact Manifold contains a residual subset of diffeomorphisms whose centralizers are trivial.
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the centralizer of a c 1 generic diffeomorphism is trivial
Electronic Research Announcements, 2008Co-Authors: Christian Bonatti, Sylvain Crovisier, Amie WilkinsonAbstract:Answering a question of Smale, we prove that the space of C 1 dieomorphisms of a Compact Manifold contains a residual subset of dieomorphisms whose centralizers are trivial.
Michael M Ohadi - One of the best experts on this subject based on the ideXlab platform.
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additive manufacturing of Compact Manifold microchannel heat exchangers utilizing direct metal laser sintering
Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, 2019Co-Authors: Hadi Keramati, Fabio Battaglia, Martinus Arie, Farah Singer, Michael M OhadiAbstract:Direct Metal Laser Sintering is a metal additive manufacturing technique which uses a laser to fuse metal powders, layer by layer to form a 3D object. In this study, Direct Metal Laser Sintering is used to fabricate Compact high temperature Manifold-microchannel heat exchangers. Compared to the state of the art heat exchangers, Manifold-microchannel heat exchangers have been proven to yield superior performances. However, fabrication of Manifold-microchannel heat exchangers using conventional fabrication methods is a challenge due to their complex geometry. Additive manufacturing processes, like Direct Metal Laser Sintering, allow fabricating the Manifold-microchannel heat exchanger as a single component, which significantly simplify its production process. In order to fully utilize the performance potential of Manifold-microchannel heat exchangers, small fins (0.1-0.2 mm) and channels (0.2-0.3 mm) are required. In this study, three different machines were used to study the effect of geometries and printing parameters, such as laser power, powder size, and layer thickness, on the fins and channel size of the fabricated microchannel heat exchangers. A comprehensive study has been performed to achieve fin thickness as small as 0.110 mm. Pressure containment tests were also performed to evaluate the minimum base thickness that can hold the designed pressure. A $3^{\prime\prime}\times 3^{\prime\prime}\times 3^{\prime\prime}$ size microchannel heat exchangers was then successfully fabricated with straight fins of 0.133 mm out of Maraging Steel, and a $4^{\prime\prime}\times 4^{\prime\prime}\times 4^{\prime\prime}$ size microchannel heat exchangers was successfully fabricated with fin size of 0.22mm out of Inconel 718. The results thus pave the way for more advancements in optimized additive manufacturing of next-generation heat exchangers.
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development of an additive manufacturing enabled Compact Manifold microchannel heat exchanger
Applied Thermal Engineering, 2019Co-Authors: Ratnesh Tiwari, Rohit S Andhare, Amir Shooshtari, Michael M OhadiAbstract:Abstract This paper discusses the design and performance characterization of a Compact tubular Manifold microchannel heat exchanger. The purpose of this study was to explore the role of more precise flow distribution in the heat exchanger utilizing an additively manufactured Manifold for single-phase flow under low to moderate heat flux conditions. The heat exchanger uses a commercially available enhanced tube having a fin structure on its outer surface and helical pattern of grooves (rifling structure) on the inner bore of the tube. A 3D printed Manifold made of ABS plastic was used to properly distribute the flow on the shell-side of the heat exchanger. Water was used as the working fluid for both shell and tube-sides. Single-phase experimental tests showed an overall heat transfer coefficient of 22,000 W / ( m 2 K ) and shell-side heat transfer coefficient of 45,000 W / ( m 2 K ) for the shell-side and tube-side water flow rates of 82 g / s and 806 g / s , respectively. The shell-side heat transfer coefficient was found to be an order of magnitude higher than that found in typical shell and tube and plate-type heat exchangers.
Francesca Antoci - One of the best experts on this subject based on the ideXlab platform.
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on the spectrum of the laplace beltrami operator for p forms for a class of warped product metrics
Advances in Mathematics, 2004Co-Authors: Francesca AntociAbstract:We explicitly compute the essential spectrum of the Laplace–Beltrami operator for p-forms for the class of warped product metrics dσ2=y2ady2+y2bdθ∂M2, where y is a boundary defining function on a Compact Manifold with boundary M.
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on the spectrum of the laplace beltrami operator for p forms for a class of warped product metrics
arXiv: Spectral Theory, 2003Co-Authors: Francesca AntociAbstract:We explicitely compute the essential spectrum of the Laplace-Beltrami operator for $p$-forms for the class of warped product metrics $d\sigma^2= y^{2a}dy^2 + y^{2b}d\theta_{\partial M}^2$, where $y$ is a boundary defining function on a Compact Manifold with boundary $M$.
Reinhard Alkofer - One of the best experts on this subject based on the ideXlab platform.
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solving coupled dyson schwinger equations on a Compact Manifold
Annals of Physics, 2006Co-Authors: C S Fischer, Burghard Gruter, Reinhard AlkoferAbstract:Abstract We present results for the gluon and ghost propagators in SU (N) Yang–Mills theory on a four-torus at zero and non-zero temperatures from a truncated set of Dyson–Schwinger equations. When compared to continuum solutions at zero temperature sizeable modifications due to the finite volume of the Manifold, especially in the infrared, are found. Effects due to non-vanishing temperatures T , on the other hand, are minute for T
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solving coupled dyson schwinger equations on a Compact Manifold
arXiv: High Energy Physics - Phenomenology, 2005Co-Authors: C S Fischer, Burghard Gruter, Reinhard AlkoferAbstract:We present results for the gluon and ghost propagators in SU(N) Yang--Mills theory on a four-torus at zero and nonzero temperatures from a truncated set of Dyson-Schwinger equations. When compared to continuum solutions at zero temperature sizeable modifications due to the finite volume of the Manifold, especially in the infrared, are found. Effects due to non-vanishing temperatures T, on the other hand, are minute for T < 250 MeV.
Andrei A Agrachev - One of the best experts on this subject based on the ideXlab platform.
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well posed infinite horizon variational problems on a Compact Manifold
Proceedings of the Steklov Institute of Mathematics. Volume 268 Issue 1 2010 Pages 17-31, 2010Co-Authors: Andrei A AgrachevAbstract:We give an effective sufficient condition for a variational problem with infinite horizon on a Compact Riemannian Manifold M to admit a smooth optimal synthesis, i.e., a smooth dynamical system on M whose positive semi-trajectories are solutions to the problem. To realize the synthesis, we construct an invariant Lagrangian subManifold (well-projected to M) of the flow of extremals in the cotangent bundle T*M. The construction uses the curvature of the flow in the cotangent bundle and some ideas of hyperbolic dynamics.
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well posed infinite horizon variational problems on a Compact Manifold
arXiv: Optimization and Control, 2009Co-Authors: Andrei A AgrachevAbstract:We give an effective sufficient condition for a variational problem with infinite horizon on a Compact Riemannian Manifold M to admit a smooth optimal synthesis, i. e. a smooth dynamical system on M whose positive semi-trajectories are solutions to the problem. To realize the synthesis we construct a well-projected to M invariant Lagrange subManifold of the extremals' flow in the cotangent bundle T*M. The construction uses the curvature of the flow in the cotangent bundle and some ideas of hyperbolic dynamics.