15,807 research outputs found
Using emission standards under incomplete compliance
Using the case study of water pollution in the Flemish textile industry, we discuss three empirical questions concerning the use of emission standards. We find that the Becker result ("maximal fine / minimal inspection") does not hold if we include rule making, implementation and enforcement costs into the model. There is a balance between the fine and the inspection variables. Making enforcement more stringent does not mean to put the fine levels as high as possible and only then increase the inspections. We have also shown that is extremely important to have correct estimates of people's willingness to pay for environmental improvement. These WTP estimates determine in great part the optimal environmental strategy and its associated optimal monitoring and enforcement policy. Moreover, it really pays off to optimise the monitoring and enforcement strategy associated with an emission standard. This optimisation does not necessarily mean that monitoring and enforcement should be as stringent as possible. It is often possible to obtain the desired result by some intermediate value of the monitoring and enforcement parameters. This is due to the balancing of costs and benefits associated with monitoring and enforcement.Environmental Law; Illegal behaviour; Enforcement of Law
Modelling of the radiative properties of an opaque porous ceramic layer
Solid Oxide Fuel Cells (SOFCs) operate at temperatures above 1,100 K where radiation effects can be significant. Therefore, an accurate thermal model of an SOFC requires the inclusion of the contribution of thermal radiation. This implies that the thermal radiative properties of the oxide ceramics used in the design of SOFCs must be known. However, little information can be found in the literature concerning their operating temperatures. On the other hand, several types of ceramics with different chemical compositions and microstructures for designing efficient cells are now being tested. This is a situation where the use of a numerical tool making possible the prediction of the thermal radiative properties of SOFC materials, whatever their chemical composition and microstructure are, may be a decisive help. Using this method, first attempts to predict the radiative properties of a lanthanum nickelate porous layer deposited onto an yttria stabilized zirconium substrate can be reported
Valid Asymptotic Expansions for the Maximum Likelihood Estimator of the Parameter of a Stationary, Gaussian, Strongly Dependent Process
We establish the validity of an Edgeworth expansion to the distribution of the maximum likelihood estimator of the parameter of a stationary, Gaussian, strongly dependent process. The result covers ARFIMA type models, including fractional Gaussian noise. The method of proof consists of three main ingredients: (i) verification of a suitably modified version of Durbin's (1980) general conditions for the validity of the Edgeworth expansion to the joint density of the log-likelihood derivatives; (ii) appeal to a simple result of Skovgaard (1986) to obtain from this an Edgeworth expansion for the joint distribution of the log-likelihood derivatives; (iii) appeal to and extension of arguments of Bhattacharya and Ghosh (1978) to accomplish the passage from the result on the log-likelihood derivatives to the result for the maximum likelihood estimators. We develop and make extensive use of a uniform version of Dahlhaus's (1989) Theorem 5.1 on products of Toeplitz matrices; the extension of Dahlhaus's result is of interest in its own right. A small numerical study of the efficacy of the Edgeworth expansion is presented for the case of fractional Gaussian noise.Edgeworth expansions, long memory processes, ARFIMA models
Anharmonic stabilization of the high-pressure simple cubic phase of calcium
The phonon spectrum of the high-pressure simple cubic phase of calcium, in
the harmonic approx- imation, shows imaginary branches that make it
mechanically unstable. In this letter, the phonon spectrum is recalculated
using density-functional theory (DFT) ab initio methods fully including
anharmonic effects up to fourth order at 50 GPa. Considering that perturbation
theory cannot be employed with imaginary harmonic frequencies, a variational
procedure based on the Gibbs- Bogoliubov inequality is used to estimate the
renormalized phonon frequencies. The results show that strong quantum
anharmonic effects make the imaginary phonons become positive even at zero
temperature so that the simple cubic phase becomes mechanically stable, as
experiments suggest. Moreover, our calculations find a superconducting Tc in
agreement with experiments and predict an anomalous behavior of the specific
heat.Comment: 5 pages, 3 figure
The Bose-Hubbard model on a triangular lattice with diamond ring-exchange
Ring-exchange interactions have been proposed as a possible mechanism for a
Bose-liquid phase at zero temperature, a phase that is compressible with no
superfluidity. Using the Stochastic Green Function algorithm (SGF), we study
the effect of these interactions for bosons on a two-dimensional triangular
lattice. We show that the supersolid phase, that is known to exist in the
ground state for a wide range of densities, is rapidly destroyed as the
ring-exchange interactions are turned on. We establish the ground-state phase
diagram of the system, which is characterized by the absence of the expected
Bose-liquid phase.Comment: 6 pages, 10 figure
Asymptotic Properties of Approximate Bayesian Computation
Approximate Bayesian computation allows for statistical analysis in models
with intractable likelihoods. In this paper we consider the asymptotic
behaviour of the posterior distribution obtained by this method. We give
general results on the rate at which the posterior distribution concentrates on
sets containing the true parameter, its limiting shape, and the asymptotic
distribution of the posterior mean. These results hold under given rates for
the tolerance used within the method, mild regularity conditions on the summary
statistics, and a condition linked to identification of the true parameters.
Implications for practitioners are discussed.Comment: This 31 pages paper is a revised version of the paper, including
supplementary materia
Local Density of the Bose Glass Phase
We study the Bose-Hubbard model in the presence of on-site disorder in the
canonical ensemble and conclude that the local density of the Bose glass phase
behaves differently at incommensurate filling than it does at commensurate one.
Scaling of the superfluid density at incommensurate filling of and
on-site interaction predicts a superfluid-Bose glass transition at
disorder strength of . At this filling the local density
distribution shows skew behavior with increasing disorder strength.
Multifractal analysis also suggests a multifractal behavior resembling that of
the Anderson localization. Percolation analysis points to a phase transition of
percolating non-integer filled sites around the same value of disorder. Our
findings support the scenario of percolating superfluid clusters enhancing
Anderson localization near the superfluid-Bose glass transition. On the other
hand, the behavior of the commensurate filled system is rather different. Close
to the tip of the Mott lobe () we find a Mott insulator-Bose
glass transition at disorder strength of . An analysis of
the local density distribution shows Gaussian like behavior for a wide range of
disorders above and below the transition.Comment: 12 pages, 14 figure
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