47,748 research outputs found
USING LAND AS A CONTROL VARIABLE IN DENSITY-DEPENDENT BIOECONOMIC MODELS
The bioeconomic analysis of endangered species without consumptive values can be problematic when analysed with density-dependent models that assume a fixed environment size. Most bioeconomic models use harvest as a control variable, yet when modelling non-harvestable species, frequently the only variable under control of conservationists is the quantity of habitat to be made available. The authors explore the implications of this in a model developed to analyse the potential population recovery of New Zealand's yellow-eyed penguin. The penguin faces severe competition with man for the terrestrial resources required for breeding and has declined in population to perilously low levels. The model was developed to estimate the land use required for recovery and preservation of the species and to compare the results to current tourism-driven conservation efforts. It is demonstrated that land may serve as a useful control variable in bioeconomic models and that such a model may be useful for determining whether sufficient incentives exist to preserve a species. However, the model may generate less useful results for providing a specific estimate of the optimal allocation of land to such a species.Land Economics/Use,
Costly Enforcement of Property Rights and the Coase Theorem
We examine a setting in which property rights are initially ambiguously defined. Whether the parties go to court to remove the ambiguity or bargain and settle privately, they incur enforcement costs. When the parties bargain, a version of the Coase theorem holds. Despite the additional costs of going to court, other ex post ine.ciencies, and the absence of incomplete information, however, going to court may be an equilibrium or ex ante Pareto-superior over settlement; this is especially true in dynamic settings whereby a court decision saves on future enforcement costs. When the parties do not negotiate and go to court the Coase theorem ceases to hold, and a simple rule for the initial assignment of rights maximizes net surplus.
BIOECONOMIC MODELLING OF ENDANGERED SPECIES CONSERVATION
Resource /Energy Economics and Policy,
Tridiagonalized GUE matrices are a matrix model for labeled mobiles
It is well-known that the number of planar maps with prescribed vertex degree
distribution and suitable labeling can be represented as the leading
coefficient of the -expansion of a joint cumulant of traces of
powers of an -by- GUE matrix. Here we undertake the calculation of this
leading coefficient in a different way. Firstly, we tridiagonalize the GUE
matrix in the manner of Trotter and Dumitriu-Edelman and then alter it by
conjugation to make the subdiagonal identically equal to . Secondly, we
apply the cluster expansion technique (specifically, the
Brydges-Kennedy-Abdesselam-Rivasseau formula) from rigorous statistical
mechanics. Thirdly, by sorting through the terms of the expansion thus
generated we arrive at an alternate interpretation for the leading coefficient
related to factorizations of the long cycle . Finally, we
reconcile the group-theoretical objects emerging from our calculation with the
labeled mobiles of Bouttier-Di Francesco-Guitter.Comment: 42 pages, LaTeX, 17 figures. The present paper completely supercedes
arXiv1203.3185 in terms of methods but addresses a different proble
Understanding the assembly of Kepler's compact planetary systems
The Kepler mission has recently discovered a number of exoplanetary systems,
such as Kepler-11 and Kepler-32, in which ensembles of several planets are
found in very closely packed orbits (often within a few percent of an AU of one
another). These compact configurations present a challenge for traditional
planet formation and migration scenarios. We present a dynamical study of the
assembly of these systems, using an N-body method which incorporates a
parametrized model of planet migration in a turbulent protoplanetary disc. We
explore a wide parameter space, and find that under suitable conditions it is
possible to form compact, close-packed planetary systems via traditional
disc-driven migration. We find that simultaneous migration of multiple planets
is a viable mechanism for the assembly of tightly-packed planetary systems, as
long as the disc provides significant eccentricity damping and the level of
turbulence in the disc is modest. We discuss the implications of our preferred
parameters for the protoplanetary discs in which these systems formed, and
comment on the occurrence and significance of mean-motion resonances in our
simulations.Comment: 12 pages, 4 figures, 2 tables. Accepted for publication in Monthly
Notices of the Royal Astronomical Societ
On high-order pressure-robust space discretisations, their advantages for incompressible high Reynolds number generalised Beltrami flows and beyond
An improved understanding of the divergence-free constraint for the
incompressible Navier--Stokes equations leads to the observation that a
semi-norm and corresponding equivalence classes of forces are fundamental for
their nonlinear dynamics. The recent concept of {\em pressure-robustness}
allows to distinguish between space discretisations that discretise these
equivalence classes appropriately or not. This contribution compares the
accuracy of pressure-robust and non-pressure-robust space discretisations for
transient high Reynolds number flows, starting from the observation that in
generalised Beltrami flows the nonlinear convection term is balanced by a
strong pressure gradient. Then, pressure-robust methods are shown to outperform
comparable non-pressure-robust space discretisations. Indeed, pressure-robust
methods of formal order are comparably accurate than non-pressure-robust
methods of formal order on coarse meshes. Investigating the material
derivative of incompressible Euler flows, it is conjectured that strong
pressure gradients are typical for non-trivial high Reynolds number flows.
Connections to vortex-dominated flows are established. Thus,
pressure-robustness appears to be a prerequisite for accurate incompressible
flow solvers at high Reynolds numbers. The arguments are supported by numerical
analysis and numerical experiments.Comment: 43 pages, 18 figures, 2 table
Development of a real-time aeroperformance analysis technique for the X-29A advanced technology demonstrator
The X-29A advanced technology demonstrator has shown the practicality and advantages of the capability to compute and display, in real time, aeroperformance flight results. This capability includes the calculation of the in-flight measured drag polar, lift curve, and aircraft specific excess power. From these elements many other types of aeroperformance measurements can be computed and analyzed. The technique can be used to give an immediate postmaneuver assessment of data quality and maneuver technique, thus increasing the productivity of a flight program. A key element of this new method was the concurrent development of a real-time in-flight net thrust algorithm, based on the simplified gross thrust method. This net thrust algorithm allows for the direct calculation of total aircraft drag
Urban and regional land use analysis: CARETS and census cities experiment package
The author has identified the following significant results. Successful tentative calibration permits computer programs to be written to convert Skylab thermal tapes into line-printed graymaps showing actual surface radiation temperature distributions at the time of imaging. The calibrations will be further checked when atmospheric soundings are available. Success of Skylab calibration suggests that satellite are feasible platforms for thermal scanning and provide a much broader geographical field of view than is possible with airborne platforms
Helicopter gust response characteristics including unsteady aerodynamic stall effects
The results of an analytical study to evaluate the general response characteristics of a helicopter subjected to various types of discrete gust encounters are presented. The analysis employed was a nonlinear coupled, multi-blade rotorfuselage analysis including the effects of blade flexibility and unsteady aerodynamic stall. Only the controls-fixed response of the basic aircraft without any aircraft stability augmentation was considered. A discussion of the basic differences between gust sensitivity of fixed and rotary wing aircraft is presented. The effects of several rotor configuration and aircraft operating parameters on initial gust-induced load factor and blade vibratory stress and pushrod loads are discussed
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