1,461 research outputs found
A Time-Space Tradeoff for Triangulations of Points in the Plane
In this paper, we consider time-space trade-offs for reporting a triangulation of points in the plane. The goal is to minimize the amount of working space while keeping the total running time small. We present the first multi-pass algorithm on the problem that returns the edges of a triangulation with their adjacency information. This even improves the previously best known random-access algorithm
Develop and test fuel cell powered on-site integrated total energy system
Test results are presented for a 24 cell, two sq ft (4kW) stack. This stack is a precursor to a 25kW stack that is a key milestone. Results are discussed in terms of cell performance, electrolyte management, thermal management, and reactant gas manifolding. The results obtained in preliminary testing of a 50kW methanol processing subsystem are discussed. Subcontracting activities involving application analysis for fuel cell on site integrated energy systems are updated
A Protocol for Generating Random Elements with their Probabilities
We give an AM protocol that allows the verifier to sample elements x from a
probability distribution P, which is held by the prover. If the prover is
honest, the verifier outputs (x, P(x)) with probability close to P(x). In case
the prover is dishonest, one may hope for the following guarantee: if the
verifier outputs (x, p), then the probability that the verifier outputs x is
close to p. Simple examples show that this cannot be achieved. Instead, we show
that the following weaker condition holds (in a well defined sense) on average:
If (x, p) is output, then p is an upper bound on the probability that x is
output. Our protocol yields a new transformation to turn interactive proofs
where the verifier uses private random coins into proofs with public coins. The
verifier has better running time compared to the well-known Goldwasser-Sipser
transformation (STOC, 1986). For constant-round protocols, we only lose an
arbitrarily small constant in soundness and completeness, while our public-coin
verifier calls the private-coin verifier only once
The log-periodic-AR(1)-GARCH(1,1) model for financial crashes
This paper intends to meet recent claims for the attainment of more rigorous
statistical methodology within the econophysics literature. To this end, we
consider an econometric approach to investigate the outcomes of the
log-periodic model of price movements, which has been largely used to forecast
financial crashes. In order to accomplish reliable statistical inference for
unknown parameters, we incorporate an autoregressive dynamic and a conditional
heteroskedasticity structure in the error term of the original model, yielding
the log-periodic-AR(1)-GARCH(1,1) model. Both the original and the extended
models are fitted to financial indices of U. S. market, namely S&P500 and
NASDAQ. Our analysis reveal two main points: (i) the
log-periodic-AR(1)-GARCH(1,1) model has residuals with better statistical
properties and (ii) the estimation of the parameter concerning the time of the
financial crash has been improved.Comment: 17 pages, 4 figures, 12 tables, to appear in Europen Physical Journal
Treatment of Nongenital Warts
Topical salicylic acid, cryotherapy, and topical fluorouracil are effective for treating nongenital warts. (Strength of Recommendation [SOR]: A, based on a systematic review of randomized controlled trials [RCTs].) Fluorouracil is more expensive than salicylic acid and produces more adverse effects, such as pain and blisters. The combination of salicylic acid and cryotherapy may be better than either treatment alone, although salicylic acid may be more cost-effective than cryotherapy. Bleomycin and interferons should not be used to treat nongenital warts. (SOR: A, based on a meta-analysis.
Bifurcations and Chaos in the Six-Dimensional Turbulence Model of Gledzer
The cascade-shell model of turbulence with six real variables originated by
Gledzer is studied numerically using Mathematica 5.1. Periodic, doubly-periodic
and chaotic solutions and the routes to chaos via both frequency-locking and
period-doubling are found by the Poincar\'e plot of the first mode . The
circle map on the torus is well approximated by the summation of several
sinusoidal functions. The dependence of the rotation number on the viscosity
parameter is in accordance with that of the sine-circle map. The complicated
bifurcation structure and the revival of a stable periodic solution at the
smaller viscosity parameter in the present model indicates that the turbulent
state may be very sensitive to the Reynolds number.Comment: 19 pages, 12 figures submitted to JPS
Submodular Maximization Meets Streaming: Matchings, Matroids, and More
We study the problem of finding a maximum matching in a graph given by an
input stream listing its edges in some arbitrary order, where the quantity to
be maximized is given by a monotone submodular function on subsets of edges.
This problem, which we call maximum submodular-function matching (MSM), is a
natural generalization of maximum weight matching (MWM), which is in turn a
generalization of maximum cardinality matching (MCM). We give two incomparable
algorithms for this problem with space usage falling in the semi-streaming
range---they store only edges, using working memory---that
achieve approximation ratios of in a single pass and in
passes respectively. The operations of these algorithms
mimic those of Zelke's and McGregor's respective algorithms for MWM; the
novelty lies in the analysis for the MSM setting. In fact we identify a general
framework for MWM algorithms that allows this kind of adaptation to the broader
setting of MSM.
In the sequel, we give generalizations of these results where the
maximization is over "independent sets" in a very general sense. This
generalization captures hypermatchings in hypergraphs as well as independence
in the intersection of multiple matroids.Comment: 18 page
The quasi-periodic doubling cascade in the transition to weak turbulence
The quasi-periodic doubling cascade is shown to occur in the transition from
regular to weakly turbulent behaviour in simulations of incompressible
Navier-Stokes flow on a three-periodic domain. Special symmetries are imposed
on the flow field in order to reduce the computational effort. Thus we can
apply tools from dynamical systems theory such as continuation of periodic
orbits and computation of Lyapunov exponents. We propose a model ODE for the
quasi-period doubling cascade which, in a limit of a perturbation parameter to
zero, avoids resonance related problems. The cascade we observe in the
simulations is then compared to the perturbed case, in which resonances
complicate the bifurcation scenario. In particular, we compare the frequency
spectrum and the Lyapunov exponents. The perturbed model ODE is shown to be in
good agreement with the simulations of weak turbulence. The scaling of the
observed cascade is shown to resemble the unperturbed case, which is directly
related to the well known doubling cascade of periodic orbits
Stochastics theory of log-periodic patterns
We introduce an analytical model based on birth-death clustering processes to
help understanding the empirical log-periodic corrections to power-law scaling
and the finite-time singularity as reported in several domains including
rupture, earthquakes, world population and financial systems. In our
stochastics theory log-periodicities are a consequence of transient clusters
induced by an entropy-like term that may reflect the amount of cooperative
information carried by the state of a large system of different species. The
clustering completion rates for the system are assumed to be given by a simple
linear death process. The singularity at t_{o} is derived in terms of
birth-death clustering coefficients.Comment: LaTeX, 1 ps figure - To appear J. Phys. A: Math & Ge
Sublinear Estimation of Weighted Matchings in Dynamic Data Streams
This paper presents an algorithm for estimating the weight of a maximum
weighted matching by augmenting any estimation routine for the size of an
unweighted matching. The algorithm is implementable in any streaming model
including dynamic graph streams. We also give the first constant estimation for
the maximum matching size in a dynamic graph stream for planar graphs (or any
graph with bounded arboricity) using space which also
extends to weighted matching. Using previous results by Kapralov, Khanna, and
Sudan (2014) we obtain a approximation for general graphs
using space in random order streams, respectively. In
addition, we give a space lower bound of for any
randomized algorithm estimating the size of a maximum matching up to a
factor for adversarial streams
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