29,934 research outputs found
Precision heat forming of tetrafluoroethylene tubing
An invention that provides a method of altering the size of tetrafluoroethylene tubing which is only available in limited combination of wall thicknesses and diameter are discussed. The method includes the steps of sliding the tetrafluoroethylene tubing onto an aluminum mandrel and clamping the ends of the tubing to the mandrel by means of clamps. The tetrafluorethylene tubing and mandrel are then placed in a supporting coil which with the mandrel and tetrafluorethylene tubing are then positioned in a insulated steel pipe which is normally covered with a fiber glass insulator to smooth out temperature distribution therein. The entire structure is then placed in an event which heats the tetrafluorethylene tubing which is then shrunk by the heat to the outer dimension of the aluminum mandrel. After cooling the aluminum mandrel is removed from the newly sized tetrafluorethylene tubing by a conventional chemical milling process
Directed Random Markets: Connectivity determines Money
Boltzmann-Gibbs distribution arises as the statistical equilibrium
probability distribution of money among the agents of a closed economic system
where random and undirected exchanges are allowed. When considering a model
with uniform savings in the exchanges, the final distribution is close to the
gamma family. In this work, we implement these exchange rules on networks and
we find that these stationary probability distributions are robust and they are
not affected by the topology of the underlying network. We introduce a new
family of interactions: random but directed ones. In this case, it is found the
topology to be determinant and the mean money per economic agent is related to
the degree of the node representing the agent in the network. The relation
between the mean money per economic agent and its degree is shown to be linear.Comment: 14 pages, 6 figure
Time--Evolving Statistics of Chaotic Orbits of Conservative Maps in the Context of the Central Limit Theorem
We study chaotic orbits of conservative low--dimensional maps and present
numerical results showing that the probability density functions (pdfs) of the
sum of iterates in the large limit exhibit very interesting
time-evolving statistics. In some cases where the chaotic layers are thin and
the (positive) maximal Lyapunov exponent is small, long--lasting
quasi--stationary states (QSS) are found, whose pdfs appear to converge to
--Gaussians associated with nonextensive statistical mechanics. More
generally, however, as increases, the pdfs describe a sequence of QSS that
pass from a --Gaussian to an exponential shape and ultimately tend to a true
Gaussian, as orbits diffuse to larger chaotic domains and the phase space
dynamics becomes more uniformly ergodic.Comment: 15 pages, 14 figures, accepted for publication as a Regular Paper in
the International Journal of Bifurcation and Chaos, on Jun 21, 201
Non-Canonical Perturbation Theory of Non-Linear Sigma Models
We explore the O(N)-invariant Non-Linear Sigma Model (NLSM) in a different
perturbative regime from the usual relativistic-free-field one, by using
non-canonical basic commutation relations adapted to the underlying O(N)
symmetry of the system, which also account for the non-trivial (non-flat)
geometry and topology of the target manifold.Comment: 11 pages, 1 figure, LaTe
D-branes with Lorentzian signature in the Nappi-Witten model
Lorentzian signature D-branes of all dimensions for the Nappi-Witten string
are constructed. This is done by rewriting the gluing condition for
the model chiral currents on the brane as a well posed first order differential
problem and by solving it for Lie algebra isometries other than Lie algebra
automorphisms. By construction, these D-branes are not twined conjugacy
classes. Metrically degenerate D-branes are also obtained.Comment: 22 page
Physical interpretation of NUT solution
We show that the well-known NUT solution can be correctly interpreted as
describing the exterior field of two counter-rotating semi-infinite sources
possessing negative masses and infinite angular momenta which are attached to
the poles of a static finite rod of positive mass.Comment: 7 pages, 1 figure, submitted to Classical and Quantum Gravit
Householdsâ Financial Vulnerability
Householdsâ financial vulnerability determines householdsâ default risk. Financial stability could be affected by householdsâ behavior under stressful macroeconomic conditions. Householdsâ financial vulnerability depends on their indebtedness levels and on the fragility of their income sources to be able to fulfill their obligations. The main source of householdsâ uncertainty comes from labor income generation, which is critically determined by unemployment. Heterogeneity of indebtedness levels and of income uncertainty calls for microeconomic analysis. This paper uses panel data survival analysis to estimate the probability of job loss at the individual level. Using semi-parametric methods, a significant heterogeneity is found for the impact of aggregate unemployment among individuals. Monte Carlo simulations are run to assess households financial stress and then to estimate aggregate debt at risk under high unemployment rate scenarios. Since the majority of debt is held by those with lower levels of income vulnerability, it is found that financial stability is not significantly affected by high unemployment levels.
Stabilized mixed approximation of axisymmetric Brinkman flows
This paper is devoted to the numerical analysis of an augmented finite element approximation of the axisymmetric Brinkman equations. Stabilization of the variational formulation is achieved by adding suitable Galerkin least-squares terms, allowing us to transform the original problem into a formulation better suited for performing its stability analysis. The sought quantities (here velocity, vorticity, and pressure) are approximated by RaviartâThomas elements of arbitrary order k â„ 0, piecewise continuous polynomials of degree k + 1, and piecewise polynomials of degree k, respectively. The well-posedness of the resulting continuous and discrete variational problems is rigorously derived by virtue of the classical BabuĆĄkaâBrezzi theory. We further establish a priori error estimates in the natural norms, and we provide a few numerical tests illustrating the behavior of the proposed augmented scheme and confirming our theoretical findings regarding optimal convergence of the approximate solutions
Polyakov loop in chiral quark models at finite temperature
We describe how the inclusion of the gluonic Polyakov loop incorporates large
gauge invariance and drastically modifies finite temperature calculations in
chiral quark models after color neutral states are singled out. This generates
an effective theory of quarks and Polyakov loops as basic degrees of freedom.
We find a strong suppression of finite temperature effects in hadronic
observables triggered by approximate triality conservation (Polyakov cooling),
so that while the center symmetry breaking is exponentially small with the
constituent quark mass, chiral symmetry restoration is exponentially small with
the pion mass. To illustrate the point we compute some low energy observables
at finite temperature and show that the finite temperature corrections to the
low energy coefficients are suppressed due to color average of the
Polyakov loop. Our analysis also shows how the phenomenology of chiral quark
models at finite temperature can be made compatible with the expectations of
chiral perturbation theory. The implications for the simultaneous center
symmetry breaking-chiral symmetry restoration phase transition are also
discussed.Comment: 24 pages, 8 ps figures. Figure and appendix added. To appear in
Physical Review
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