4,691 research outputs found
Evolution of the Dependence of Residual Lifetimes
We investigate the dependence properties of a vector of residual lifetimes by means of the copula associated with the conditional distribution function. In particular, the evolution of positive dependence properties (like quadrant dependence and total positivity) are analyzed and expressions for the evolution of measures of association are given
A note on drastic product logic
The drastic product is known to be the smallest -norm, since whenever . This -norm is not left-continuous, and hence it
does not admit a residuum. So, there are no drastic product -norm based
many-valued logics, in the sense of [EG01]. However, if we renounce standard
completeness, we can study the logic whose semantics is provided by those MTL
chains whose monoidal operation is the drastic product. This logic is called
in [NOG06]. In this note we justify the study of this
logic, which we rechristen DP (for drastic product), by means of some
interesting properties relating DP and its algebraic semantics to a weakened
law of excluded middle, to the projection operator and to
discriminator varieties. We shall show that the category of finite DP-algebras
is dually equivalent to a category whose objects are multisets of finite
chains. This duality allows us to classify all axiomatic extensions of DP, and
to compute the free finitely generated DP-algebras.Comment: 11 pages, 3 figure
Comment on "Recurrences without closed orbits"
In a recent paper Robicheaux and Shaw [Phys. Rev. A 58, 1043 (1998)]
calculate the recurrence spectra of atoms in electric fields with non-vanishing
angular momentum not equal to 0. Features are observed at scaled actions
``an order of magnitude shorter than for any classical closed orbit of this
system.'' We investigate the transition from zero to nonzero angular momentum
and demonstrate the existence of short closed orbits with L_z not equal to 0.
The real and complex ``ghost'' orbits are created in bifurcations of the
``uphill'' and ``downhill'' orbit along the electric field axis, and can serve
to interpret the observed features in the quantum recurrence spectra.Comment: 2 pages, 1 figure, REVTE
The dynamical mass of the young cluster W3 in NGC 7252: Heavy-Weight globular cluster or ultra compact dwarf galaxy ?
We have determined the dynamical mass of the most luminous stellar cluster
known to date, i.e. object W3 in the merger remnant galaxy NGC 7252. The
dynamical mass is estimated from the velocity dispersion measured with the
high-resolution spectrograph UVES on VLT. Our result is the astonishingly high
velocity dispersion of sigma=45 +- 5 km/s. Combined with the large cluster size
R_eff=17.5 +-1.8 pc, this translates into a dynamical virial mass for W3 of 8
+- 2 x 10^7 Msun. This mass is in excellent agreement with the value 7.2 x 10^7
Msun we previously estimated from the cluster luminosity M_V=-16.2 by means of
stellar M/L ratios predicted by Simple Stellar Population models (with a
Salpeter IMF) and confirms the heavy-weight nature of this object. This results
points out that the NGC 7252-type of mergers are able to form stellar systems
with masses up to ~ 10^8 Msun. We find that W3, when evolved to ~ 10 Gyr, lies
far from the typical Milky Way globular clusters, but appears to be also
separated from omegaCen in the Milky Way and G1 in M31, the most massive old
stellar clusters of the Local Group, because it is too extended for a given
mass, and from dwarf elliptical galaxies because it is much more compact for
its mass. Instead the aged W3 is amazingly close to the compact objects named
ultracompact dwarf galaxies (UCDGs) found in the Fornax cluster (Hilker et al.
1999; Drinkwater et al. 2000), and to a miniature version of the compact
elliptical M32. These objects start populating a previously deserted region of
the fundamental plane.Comment: 8 pages, 3 figures, A&A in pres
Effective temperatures of a heated Brownian particle
We investigate various possible definitions of an effective temperature for a
particularly simple nonequilibrium stationary system, namely a heated Brownian
particle suspended in a fluid. The effective temperature based on the
fluctuation dissipation ratio depends on the time scale under consideration, so
that a simple Langevin description of the heated particle is impossible. The
short and long time limits of this effective temperature are shown to be
consistent with the temperatures estimated from the kinetic energy and Einstein
relation, respectively. The fluctuation theorem provides still another
definition of the temperature, which is shown to coincide with the short time
value of the fluctuation dissipation ratio
Data-driven Bicycle Network Analysis Based on Traditional Counting Methods and GPS Traces from Smartphone
This research describes numerical methods to analyze the absolute transport demand of cyclists and to quantify the road network weaknesses of a city with the aim to identify infrastructure improvements in favor of cyclists. The methods are based on a combination of bicycle counts and map-matched GPS traces. The methods are demonstrated with data from the city of Bologna, Italy: approximately 27,500 GPS traces from cyclists were recorded over a period of one month on a volunteer basis using a smartphone application. One method estimates absolute, city-wide bicycle flows by scaling map-matched bicycle flows of the entire network to manual and instrumental bicycle counts at the main bikeways of the city. As there is a fairly high correlation between the two sources of flow data, the absolute bike-flows of the entire network have been correctly estimated. Another method describes a novel, total deviation metric per link which quantifies for each network edge the total deviation generated for cyclists in terms of extra distances traveled with respect to the shortest possible route. The deviations are accepted by cyclists either to avoid unpleasant road attributes along the shortest route or to experience more favorable road attributes along the chosen route. The total deviation metric indicates to the planner which road links are contributing most to the total deviation of all cyclists. In this way, repellant and attractive road attributes for cyclists can be identified. This is why the total deviation metric is of practical help to prioritize bike infrastructure construction on individual road network links. Finally, the map-matched traces allow the calibration of a discrete choice model between two route alternatives, considering distance, share of exclusive bikeway, and share of low-priority roads
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