281 research outputs found
Influence of Grassland Management and Grazing by Different Farm Animals on Animal Performance and Flora Alterations
The objectives of this study were to test the possibilities of using different farm animals for landscape care on extensive pasture, taking into account their particular performance, and to analyse alterations of the flora in consequence of grazing by different animals and various pasture management. Salers had the highest (836g/d) and Galloways (584g/d) the lowest live weight gain as compared with the other breeds (771g/d). Lambs had higher live weight when grazing together with cattle and horses (mixed grazing) than under one species grazing. The number of legume increased and that of grass decreased. Following 3 years the grazing animals effected an increase of plant numbers in order of: Horses 86%, Cattle 15%, Mixed grazing 14% and sheep no effect. The most success of increasing plant numbers was registered when combined grazing and mowing of pasture was used
Density of critical points for a Gaussian random function
Critical points of a scalar quantitiy are either extremal points or saddle
points. The character of the critical points is determined by the sign
distribution of the eigenvalues of the Hessian matrix. For a two-dimensional
homogeneous and isotropic random function topological arguments are sufficient
to show that all possible sign combinations are equidistributed or with other
words, the density of the saddle points and extrema agree. This argument breaks
down in three dimensions. All ratios of the densities of saddle points and
extrema larger than one are possible. For a homogeneous Gaussian random field
one finds no longer an equidistribution of signs, saddle points are slightly
more frequent.Comment: 11 pages 1 figure, changes in list of references, corrected typo
Scheduling Series-Parallel Orders Subject to 0/1-Communication Delays
We consider the problem P}&;| prec},cij&;{0,1}|κ of scheduling jobs with arbitrary processing times on sufficiently many parallel processors subject to series-parallel precedence constraints and 0/1-communication delays in order to minimize a regular performance measure κ. Such schedules without processor restrictions are used for generating approximate solutions for a restricted number of processors
Linking Dynamical and Thermal Models of Ultrarelativistic Nuclear Scattering
To analyse ultrarelativistic nuclear interactions, usually either dynamical
models like the string model are employed, or a thermal treatment based on
hadrons or quarks is applied. String models encounter problems due to high
string densities, thermal approaches are too simplistic considering only
average distributions, ignoring fluctuations. We propose a completely new
approach, providing a link between the two treatments, and avoiding their main
shortcomings: based on the string model, connected regions of high energy
density are identified for single events, such regions referred to as quark
matter droplets. Each individual droplet hadronizes instantaneously according
to the available n-body phase space. Due to the huge number of possible hadron
configurations, special Monte Carlo techniques have been developed to calculate
this disintegration.Comment: Complete paper enclosed as postscript file (uuencoded
Microcanonical Treatment of Hadronizing the Quark-Gluon Plasma
We recently introduced a completely new way to study ultrarelativistic
nuclear scattering by providing a link between the string model approach and a
statistical description. A key issue is the microcanonical treatment of
hadronizing individual quark matter droplets. In this paper we describe in
detail the hadronization of these droplets according to n-body phase space, by
using methods of statistical physics, i.e. constructing Markov chains of hadron
configurations.Comment: Complete paper enclosed as postscript file (uuencoded
Tropically convex constraint satisfaction
A semilinear relation S is max-closed if it is preserved by taking the
componentwise maximum. The constraint satisfaction problem for max-closed
semilinear constraints is at least as hard as determining the winner in Mean
Payoff Games, a notorious problem of open computational complexity. Mean Payoff
Games are known to be in the intersection of NP and co-NP, which is not known
for max-closed semilinear constraints. Semilinear relations that are max-closed
and additionally closed under translations have been called tropically convex
in the literature. One of our main results is a new duality for open tropically
convex relations, which puts the CSP for tropically convex semilinaer
constraints in general into NP intersected co-NP. This extends the
corresponding complexity result for scheduling under and-or precedence
constraints, or equivalently the max-atoms problem. To this end, we present a
characterization of max-closed semilinear relations in terms of syntactically
restricted first-order logic, and another characterization in terms of a finite
set of relations L that allow primitive positive definitions of all other
relations in the class. We also present a subclass of max-closed constraints
where the CSP is in P; this class generalizes the class of max-closed
constraints over finite domains, and the feasibility problem for max-closed
linear inequalities. Finally, we show that the class of max-closed semilinear
constraints is maximal in the sense that as soon as a single relation that is
not max-closed is added to L, the CSP becomes NP-hard.Comment: 29 pages, 2 figure
Molecular dynamics approach: from chaotic to statistical properties of compound nuclei
Statistical aspects of the dynamics of chaotic scattering in the classical
model of -cluster nuclei are studied. It is found that the dynamics
governed by hyperbolic instabilities which results in an exponential decay of
the survival probability evolves to a limiting energy distribution whose
density develops the Boltzmann form. The angular distribution of the
corresponding decay products shows symmetry with respect to angle. Time
estimated for the compound nucleus formation ranges within the order of
s.Comment: 11 pages, LaTeX, non
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