1,987 research outputs found
Curve Reconstruction, the Traveling Salesman Problem, and Menger's Theorem on Length
We give necessary and sufficient regularity conditions under which the curve reconstruction problem is solved by a traveling salesman tour or path, respectively. For the proof we have to generalize a theorem of Menger [12], [13] on arc lengt
The Quantity Theory Revisited: A New Structural Approach
While the long run relation between money and inflation is well established, empirical evidence on the adjustment to the long run equilibrium is very heterogeneous. In this paper we show, that the development of US consumer price inflation between 1960Q1 and 2005Q4 is strongly driven by money overhang. To this end, we use a multivariate state space framework that substantially expands the traditional vector error correction approach. This approach allows us to estimate the persistent components of velocity and GDP. A sign restriction approach is subsequently used to identify the structural shocks to the signal equations of the state space model, that explain money growth, inflation and GDP growth. We also account for the possibility that measurement error exhibited by simple-sum monetary aggregates causes the consequences of monetary shocks to be improperly identified by using a Divisia monetary aggregate. Our findings suggest that when the money is measured using a reputable index number, the quantity theory holds for the United States.Divisia money, state space decomposition, sign restrictions
Simultaneous Implicit Surface Reconstruction and Meshing
We investigate an implicit method to compute a piecewise linear representation of a surface from a set of sample points. As implicit surface functions we use the weighted sum of piecewise linear kernel functions. For such a function we can partition Rd in such a way that these functions are linear on the subsets of the partition. For each subset in the partition we can then compute the zero level set of the function exactly as the intersection of a hyperplane with the subset
Morphology of ledge patterns during step flow growth of metal surfaces vicinal to fcc(001)
The morphological development of step edge patterns in the presence of
meandering instability during step flow growth is studied by simulations and
numerical integration of a continuum model. It is demonstrated that the kink
Ehrlich-Schwoebel barrier responsible for the instability leads to an invariant
shape of the step profiles. The step morphologies change with increasing
coverage from a somewhat triangular shape to a more flat, invariant steady
state form. The average pattern shape extracted from the simulations is shown
to be in good agreement with that obtained from numerical integration of the
continuum theory.Comment: 4 pages, 4 figures, RevTeX 3, submitted to Phys. Rev.
Correlations in nano-scale step fluctuations: comparison of simulation and experiments
We analyze correlations in step-edge fluctuations using the
Bortz-Kalos-Lebowitz kinetic Monte Carlo algorithm, with a 2-parameter
expression for energy barriers, and compare with our VT-STM line-scan
experiments on spiral steps on Pb(111). The scaling of the correlation times
gives a dynamic exponent confirming the expected step-edge-diffusion
rate-limiting kinetics both in the MC and in the experiments. We both calculate
and measure the temperature dependence of (mass) transport properties via the
characteristic hopping times and deduce therefrom the notoriously-elusive
effective energy barrier for the edge fluctuations. With a careful analysis we
point out the necessity of a more complex model to mimic the kinetics of a
Pb(111) surface for certain parameter ranges.Comment: 10 pages, 9 figures, submitted to Physical Review
Bounds on the k-neighborhood for locally uniform sampled surfaces
Given a locally uniform sample set P of a smooth surface S. We derive upper and lower bounds on the number k of nearest neighbors of a sample point p that have to be chosen from P such that this neighborhood contains all restricted Delaunay neighbors of p. In contrast to the trivial lower bound, the upper bound indicates that a sampling condition that is used in many computational geometry proofs is quite reasonable from a practical point of view
Tube Width Fluctuations in F-Actin Solutions
We determine the statistics of the local tube width in F-actin solutions,
beyond the usually reported mean value. Our experimental observations are
explained by a segment fluid theory based on the binary collision approximation
(BCA). In this systematic generalization of the standard mean-field approach
effective polymer segments interact via a potential representing the
topological constraints. The analytically predicted universal tube width
distribution with a stretched tail is in good agreement with the data.Comment: Final version, 5 pages, 4 figure
Bounds on the k-neighborhood for locally uniform sampled surfaces
Given a locally uniform sample set P of a smooth surface S. We derive upper and lower bounds on the number k of nearest neighbors of a sample point p that have to be chosen from P such that this neighborhood contains all restricted Delaunay neighbors of p. In contrast to the trivial lower bound, the upper bound indicates that a sampling condition that is used in many computational geometry proofs is quite reasonable from a practical point of view
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