29,050 research outputs found
Improved shape-signature and matching methods for model-based robotic vision
Researchers describe new techniques for curve matching and model-based object recognition, which are based on the notion of shape-signature. The signature which researchers use is an approximation of pointwise curvature. Described here is curve matching algorithm which generalizes a previous algorithm which was developed using this signature, allowing improvement and generalization of a previous model-based object recognition scheme. The results and the experiments described relate to 2-D images. However, natural extensions to the 3-D case exist and are being developed
Development of thermal stratification and destratification scaling concepts. Volume 1: Definition of thermal stratification scaling parameters and experimental investigations
The dimensionless parameters associated with the thermal stratification and pressure history of a heated container of liquid and its vapor were examined. The Modified Grashof number, the Fourier number, and an Interface number were parameterized using a single test liquid, Freon 113. Cylindrical test tanks with spherical dome end caps were built. Blanket heaters covered the tanks and thermocouples monitored the temperatures of the liquid, the ullage, the tank walls, and the foam insulation encapsulating the tank. A centrifuge was used for the 6 inch tank to preserve the same scaling parameter values between it and the larger tanks. Tests were conducted over a range of Gr* values and the degree of scaling was checked by comparing the dimensionless pressures and temperatures for each scaled pair of tests. Results indicate that the bulk liquid temperature, the surface temperature of the liquid, and the tank pressure can be scaled with the three dimensionless parameters. Some deviation was, however, found in the detailed temperature profiles between the scaled pairs of tests
Asymptotic Search for Ground States of SU(2) Matrix Theory
We introduce a complete set of gauge-invariant variables and a generalized
Born-Oppenheimer formulation to search for normalizable zero-energy asymptotic
solutions of the Schrodinger equation of SU(2) matrix theory. The asymptotic
method gives only ground state candidates, which must be further tested for
global stability. Our results include a set of such ground state candidates,
including one state which is a singlet under spin(9).Comment: 51 page
Lexicographic choice functions without archimedeanicity
We investigate the connection between choice functions and lexicographic probabilities, by means of the convexity axiom considered by Seidenfeld, Schervisch and Kadane (2010) but without imposing any Archimedean condition. We show that lexicographic probabilities are related to a particular type of sets of desirable gambles, and investigate the properties of the coherent choice function this induces via maximality. Finally, we show that the convexity axiom is necessary but not sufficient for a coherent choice function to be the infimum of a class of lexicographic ones
Generalized Supersymmetric Perturbation Theory
Using the basic ingredient of supersymmetry, we develop a simple alternative
approach to perturbation theory in one-dimensional non-relativistic quantum
mechanics. The formulae for the energy shifts and wave functions do not involve
tedious calculations which appear in the available perturbation theories. The
model applicable in the same form to both the ground state and excited bound
states, unlike the recently introduced supersymmetric perturbation technique
which, together with other approaches based on logarithmic perturbation theory,
are involved within the more general framework of the present formalism.Comment: 13 pages article in LaTEX (uses standard article.sty). No Figures.
Sent to Ann. Physics (2004
The nature of the long time decay at a second order transition point
We show that at a second order phase transition, of \phi^4 like system, a
necessary condition for streched exponential decay of the time structure factor
is obeyed. Using the ideas presented in this proof a crude estimate of the
decay of the structure factor is obtained and shown to yield stretched
exponential decay under very reasonable conditions.Comment: 7 page
Temporal Correlations and Persistence in the Kinetic Ising Model: the Role of Temperature
We study the statistical properties of the sum , that is the difference of time spent positive or negative by the
spin , located at a given site of a -dimensional Ising model
evolving under Glauber dynamics from a random initial configuration. We
investigate the distribution of and the first-passage statistics
(persistence) of this quantity. We discuss successively the three regimes of
high temperature (), criticality (), and low temperature
(). We discuss in particular the question of the temperature
dependence of the persistence exponent , as well as that of the
spectrum of exponents , in the low temperature phase. The
probability that the temporal mean was always larger than the
equilibrium magnetization is found to decay as . This
yields a numerical determination of the persistence exponent in the
whole low temperature phase, in two dimensions, and above the roughening
transition, in the low-temperature phase of the three-dimensional Ising model.Comment: 21 pages, 11 PostScript figures included (1 color figure
Hybrid simulations of lateral diffusion in fluctuating membranes
In this paper we introduce a novel method to simulate lateral diffusion of
inclusions in a fluctuating membrane. The regarded systems are governed by two
dynamic processes: the height fluctuations of the membrane and the diffusion of
the inclusion along the membrane. While membrane fluctuations can be expressed
in terms of a dynamic equation which follows from the Helfrich Hamiltonian, the
dynamics of the diffusing particle is described by a Langevin or Smoluchowski
equation. In the latter equations, the curvature of the surface needs to be
accounted for, which makes particle diffusion a function of membrane
fluctuations. In our scheme these coupled dynamic equations, the membrane
equation and the Langevin equation for the particle, are numerically integrated
to simulate diffusion in a membrane. The simulations are used to study the
ratio of the diffusion coefficient projected on a flat plane and the
intramembrane diffusion coefficient for the case of free diffusion. We compare
our results with recent analytical results that employ a preaveraging
approximation and analyze the validity of this approximation. A detailed
simulation study of the relevant correlation functions reveals a surprisingly
large range where the approximation is applicable.Comment: 12 pages, 9 figures, accepted for publication in Phys. Rev.
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