The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Zixiang Xiong - One of the best experts on this subject based on the ideXlab platform.
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the sum rate bound for a new class of quadratic gaussian multiterminal source coding problems
IEEE Transactions on Information Theory, 2012Co-Authors: Yang Yang, Zixiang XiongAbstract:In this paper, we show tightness of the Berger-Tung (BT) sum-rate bound for a new class of quadratic Gaussian multiterminal (MT) source coding problems dubbed bi-eigen equal-variance with equal distortion (BEEV-ED), where the L × L source covariance matrix has equal diagonal elements with two distinct eigenvalues, and the L target distortions are equal. Let K (K <; L) be the number of repetitions of the larger eigenvalue, the BEEV covariance structure allows us to connect K i.i.d. virtual Gaussian sources with the L given MT sources via an L × K semiorthogonal transform whose rows have equal Euclidean norm plus additive i.i.d. Gaussian noises, resulting in the two sets of sources being mutually conditional i.i.d. By relating the given MT source coding problem to a generalized Gaussian CEO problem with the K virtual sources as remote sources and the L MT sources as observations, we obtain a lower bound on the MT sum-rate, and show its achievability by BT schemes under the equal distortion constraints. Our BEEV-ED class of quadratic Gaussian MT source coding problems subsumes both the positive-Symmetric Case considered by Wagner et al. and the negative-Symmetric Case. Other examples, including a subclass of sources with BE circulant Symmetric covariance matrices and equal distortion constraints, are also provided to highlight tightness of the sum-rate bound.
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code design for quadratic gaussian multiterminal source coding the Symmetric Case
International Symposium on Information Theory, 2009Co-Authors: Yifu Zhang, Yang Yang, Zixiang XiongAbstract:Whereas the theory and practice of two-terminal quadratic Gaussian multiterminal (MT) source coding is complete, the theory with more than two terminals is only partial, with the sum-rate limit only known in the Symmetric Case where all sources are positively Symmetric and all target distortions equal. This paper proposes the first code design for quadratic Gaussian MT source coding in this Symmetric setup. The aim is to approach corner points of the rate region via TCQ for quantization and LDPC codes for Slepian-Wolf compression. We provide high-rate analysis of our code design. Simulations with three and four terminals show a very small sum-rate loss.
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the supremum sum rate loss of quadratic gaussian direct multiterminal source coding
Information Theory and Applications, 2008Co-Authors: Yang Yang, Zixiang XiongAbstract:Wagner et al. recently characterized the rate region for the quadratic Gaussian two-terminal source coding problem. They also show that the Berger-Tung sum-rate bound is tight in the Symmetric Case, where all sources are positively Symmetric and all target distortions are equal. This work studies the sum-rate loss of quadratic Gaussian direct multiterminal source coding. We first give the minimum sum-rate for joint encoding of Gaussian sources in the Symmetric Case, we than show that the supremum of the sum-rate loss due to distributed encoding in this Case is 1/2 log2 5/4 = 0.161 b/s when L = 2 and increases in the order of radic(L)/2 log2 e b/s as the number of terminals L goes to infinity. The supremum sum-rate loss of 0.161 b/s in the Symmetric Case equals to that in general quadratic Gaussian two-terminal source coding without the Symmetric assumption. It is conjectured that this equality holds for any number of terminals.
Yang Yang - One of the best experts on this subject based on the ideXlab platform.
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the sum rate bound for a new class of quadratic gaussian multiterminal source coding problems
IEEE Transactions on Information Theory, 2012Co-Authors: Yang Yang, Zixiang XiongAbstract:In this paper, we show tightness of the Berger-Tung (BT) sum-rate bound for a new class of quadratic Gaussian multiterminal (MT) source coding problems dubbed bi-eigen equal-variance with equal distortion (BEEV-ED), where the L × L source covariance matrix has equal diagonal elements with two distinct eigenvalues, and the L target distortions are equal. Let K (K <; L) be the number of repetitions of the larger eigenvalue, the BEEV covariance structure allows us to connect K i.i.d. virtual Gaussian sources with the L given MT sources via an L × K semiorthogonal transform whose rows have equal Euclidean norm plus additive i.i.d. Gaussian noises, resulting in the two sets of sources being mutually conditional i.i.d. By relating the given MT source coding problem to a generalized Gaussian CEO problem with the K virtual sources as remote sources and the L MT sources as observations, we obtain a lower bound on the MT sum-rate, and show its achievability by BT schemes under the equal distortion constraints. Our BEEV-ED class of quadratic Gaussian MT source coding problems subsumes both the positive-Symmetric Case considered by Wagner et al. and the negative-Symmetric Case. Other examples, including a subclass of sources with BE circulant Symmetric covariance matrices and equal distortion constraints, are also provided to highlight tightness of the sum-rate bound.
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code design for quadratic gaussian multiterminal source coding the Symmetric Case
International Symposium on Information Theory, 2009Co-Authors: Yifu Zhang, Yang Yang, Zixiang XiongAbstract:Whereas the theory and practice of two-terminal quadratic Gaussian multiterminal (MT) source coding is complete, the theory with more than two terminals is only partial, with the sum-rate limit only known in the Symmetric Case where all sources are positively Symmetric and all target distortions equal. This paper proposes the first code design for quadratic Gaussian MT source coding in this Symmetric setup. The aim is to approach corner points of the rate region via TCQ for quantization and LDPC codes for Slepian-Wolf compression. We provide high-rate analysis of our code design. Simulations with three and four terminals show a very small sum-rate loss.
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the supremum sum rate loss of quadratic gaussian direct multiterminal source coding
Information Theory and Applications, 2008Co-Authors: Yang Yang, Zixiang XiongAbstract:Wagner et al. recently characterized the rate region for the quadratic Gaussian two-terminal source coding problem. They also show that the Berger-Tung sum-rate bound is tight in the Symmetric Case, where all sources are positively Symmetric and all target distortions are equal. This work studies the sum-rate loss of quadratic Gaussian direct multiterminal source coding. We first give the minimum sum-rate for joint encoding of Gaussian sources in the Symmetric Case, we than show that the supremum of the sum-rate loss due to distributed encoding in this Case is 1/2 log2 5/4 = 0.161 b/s when L = 2 and increases in the order of radic(L)/2 log2 e b/s as the number of terminals L goes to infinity. The supremum sum-rate loss of 0.161 b/s in the Symmetric Case equals to that in general quadratic Gaussian two-terminal source coding without the Symmetric assumption. It is conjectured that this equality holds for any number of terminals.
Jose M Rico - One of the best experts on this subject based on the ideXlab platform.
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branch reconfiguration of bricard linkages based on toroids intersections plane Symmetric Case
Journal of Mechanisms and Robotics, 2018Co-Authors: P C Lopezcustodio, Jian S Dai, Jose M RicoAbstract:This paper for the first time reveals a set of special plane-Symmetric Bricard linkages with various branches of reconfiguration by means of intersection of two generating toroids, and presents a complete theory of the branch reconfiguration of the Bricard plane-Symmetric linkages. An analysis of the intersection of these two toroids reveals the presence of coincident conical singularities, which lead to design of the plane-Symmetric linkages that evolve to spherical 4R linkages. By examining the tangents to the curves of intersection at the conical singularities, it is found that the linkage can be reconfigured between the two possible branches of spherical 4R motion without disassembling it and without requiring the usual special configuration connecting the branches. The study of tangent intersections between concentric singular toroids also reveals the presence of isolated points in the intersection, which suggests that some linkages satisfying the Bricard plane-symmetry conditions are actually structures with zero finite degrees-of-freedom (DOF) but with higher instantaneous mobility. This paper is the second part of a paper published in parallel by the authors in which the method is applied to the line-Symmetric Case.
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branch reconfiguration of bricard linkages based on toroids intersections line Symmetric Case
Journal of Mechanisms and Robotics, 2018Co-Authors: P C Lopezcustodio, Jian S Dai, Jose M RicoAbstract:This paper for the first time investigates a family of line-Symmetric Bricard mechanisms by means of two generated toroids and reveals their intersection that leads to a set of special Bricard mechanisms with various branches of reconfiguration. The discovery is made in the concentric toroid-toroid intersection. By manipulating the construction parameters of the toroids any possible bifurcation point is explored. This leads to the common bi-tangent planes that present singularities in the intersection set. The study reveals the presence of Villarceau and secondary circles in the toroids intersection. Therefore, a way to reconfigure the Bricard linkage to two different types of Bennett mechanism is uncovered. Further a linkage with two Bricard and two Bennett motion branches is explored. In addition, the paper reveals the Altmann linkage as a member of the family of special line-Symmetric Bricard linkages studied in this paper.
Remigio Russo - One of the best experts on this subject based on the ideXlab platform.
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the liouville theorem for the steady state navier stokes problem for axially Symmetric 3d solutions in absence of swirl
Journal of Mathematical Fluid Mechanics, 2015Co-Authors: Mikhail V Korobkov, Konstantin Pileckas, Remigio RussoAbstract:We study the Navier–Stokes equations of steady motion of a viscous incompressible fluid in \({\mathbb{R}^{3}}\). We prove that there are no nontrivial solution of these equations defined in the whole space \({\mathbb{R}^{3}}\) for axially Symmetric Case with no swirl (the Liouville theorem). Also we prove the conditional Liouville type theorem for axial Symmetric solutions to the Euler system.
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the existence theorem for steady navier stokes equations in the axially Symmetric Case
Annali Della Scuola Normale Superiore Di Pisa-classe Di Scienze, 2015Co-Authors: Mikhail V Korobkov, Konstantin Pileckas, Remigio RussoAbstract:We study the nonhomogeneous boundary value problem for the Navier-Stokes equations of steady motion of a viscous incompressible fluid in a bounded three-dimensional domain with multiply connected boundary. We prove that this problem has a solution in some axially Symmetric Cases, in particular, when all components of the boundary intersect the axis of symmetry.
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steady navier stokes system with nonhomogeneous boundary conditions in the axially Symmetric Case
Comptes Rendus Mecanique, 2012Co-Authors: Mikhail V Korobkov, Konstantin Pileckas, Remigio RussoAbstract:Abstract The nonhomogeneous boundary value problem for the steady Navier–Stokes equations is studied in a three-dimensional axially Symmetric bounded domain with multiply connected Lipschitz boundary. We assume that the boundary value is axially Symmetric. Our results imply, in particular, the existence of the solution with arbitrary large fluxes over the connected components of the boundary, provided that all these components intersect the axis of the symmetry. The proof uses the Bernoulli law for a weak solution to the Euler equations and the one-side maximum principle for the total head pressure corresponding to this solution.
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the existence theorem for steady navier stokes equations in the axially Symmetric Case
arXiv: Mathematical Physics, 2011Co-Authors: Mikhail V Korobkov, Konstantin Pileckas, Remigio RussoAbstract:We study the nonhomogeneous boundary value problem for Navier-Stokes equations of steady motion of a viscous incompressible fluid in a three-dimensional bounded multiply connected domain. We prove that this problem has a solution in some axially Symmetric Cases, in particular, when all components of the boundary intersect the axis of symmetry.
Saeed Rastgoo - One of the best experts on this subject based on the ideXlab platform.
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quantum scalar field in quantum gravity the propagator and lorentz invariance in the spherically Symmetric Case
General Relativity and Gravitation, 2011Co-Authors: Rodolfo Gambini, Jorge Pullin, Saeed RastgooAbstract:We recently studied gravity coupled to a scalar field in spherical symmetry using loop quantum gravity techniques. Since there are local degrees of freedom one faces the “problem of dynamics”. We attack it using the “uniform discretization technique”. We find the quantum state that minimizes the value of the master constraint for the Case of weak fields and curvatures. The state has the form of a direct product of Gaussians for the gravitational variables times a modified Fock state for the scalar field. In this paper we do three things. First, we verify that the previous state also yields a small value of the master constraint when one polymerizes the scalar field in addition to the gravitational variables. We then study the propagators for the polymerized scalar field in flat space-time using the previously considered ground state in the low energy limit. We discuss the issue of the Lorentz invariance of the whole approach. We note that if one uses real clocks to describe the system, Lorentz invariance violations are small. We discuss the implications of these results in the light of Hořava’s Gravity at the Lifshitz point and of the argument about potential large Lorentz violations in interacting field theories of Collins et al.
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quantum scalar field in quantum gravity the vacuum in the spherically Symmetric Case
Classical and Quantum Gravity, 2009Co-Authors: Rodolfo Gambini, Jorge Pullin, Saeed RastgooAbstract:We study gravity coupled to a scalar field in spherical symmetry using loop quantum gravity techniques. Since this model has local degrees of freedom, one has to face 'the problem of dynamics', that is, diffeomorphism and Hamiltonian constraints that do not form a Lie algebra. We tackle the problem using the 'uniform discretization' technique. We study the expectation value of the master constraint and argue that among the states that minimize the master constraint is one that incorporates the usual Fock vacuum for the matter content of the theory.
