129,921 research outputs found
First-principles study of Ce doped lanthanum silicate nitride phosphors: Neutral excitation, Stokes shift, and luminescent center identification
We study from first principles two lanthanum silicate nitride compounds,
LaSiN and LaSiN, pristine as well as doped with
Ce ion, in view of explaining their different emission color, and
characterising the luminescent center. The electronic structures of the two
undoped hosts are similar, and do not give a hint to quantitatively describe
such difference. The neutral excitation of the Ce
ions is simulated through a constrained density-functional theory method
coupled with a SCF analysis of total energies, yielding absorption
energies. Afterwards, atomic positions in the excited state are relaxed,
yielding the emission energies and Stokes shifts. Based on these results, the
luminescent centers in LaSiN:Ce and LaSiN:Ce are
identified. The agreement with the experimental data for the computed
quantities is quite reasonable and explains the different color of the emitted
light. Also, the Stokes shifts are obtained within 20\% difference relative to
experimental data.Comment: 12 pages, 10 figure
Monetary policy transparency and inflation persistence in a small open economy.
Using a New Keynesian small open economy model, we examine the effects of central bank transparency on inflation persistence. We have found that more opacity could reinforce the effect of persistent shocks on the level and variability of endogenous variables if the difference between the interest elasticity of domestic goods demand and the degree of trade openness is sufficiently large or sufficiently low, judging on structural parameters characterising the economy, the central bank preference and its initial degree of opacity. Our result implies that, under perfect capital mobility, a high degree of domestic financial development is a good reason for increasing transparency.Central bank’s transparency, open economy, inflation persistence.
Semi-classical Orthogonal Polynomial Systems on Non-uniform Lattices, Deformations of the Askey Table and Analogs of Isomonodromy
A -semi-classical weight is one which satisfies a particular
linear, first order homogeneous equation in a divided-difference operator
. It is known that the system of polynomials, orthogonal with
respect to this weight, and the associated functions satisfy a linear, first
order homogeneous matrix equation in the divided-difference operator termed the
spectral equation. Attached to the spectral equation is a structure which
constitutes a number of relations such as those arising from compatibility with
the three-term recurrence relation. Here this structure is elucidated in the
general case of quadratic lattices. The simplest examples of the
-semi-classical orthogonal polynomial systems are precisely those
in the Askey table of hypergeometric and basic hypergeometric orthogonal
polynomials. However within the -semi-classical class it is
entirely natural to define a generalisation of the Askey table weights which
involve a deformation with respect to new deformation variables. We completely
construct the analogous structures arising from such deformations and their
relations with the other elements of the theory. As an example we treat the
first non-trivial deformation of the Askey-Wilson orthogonal polynomial system
defined by the -quadratic divided-difference operator, the Askey-Wilson
operator, and derive the coupled first order divided-difference equations
characterising its evolution in the deformation variable. We show that this
system is a member of a sequence of classical solutions to the
-Painlev\'e system.Comment: Submitted to Duke Mathematical Journal on 5th April 201
The drag force in two-fluid models of gas-solid flows
Currently, the two most widespread methods for modelling the particulate phase in numerical simulations of gas-solid flows are discrete particle simulation (see, e.g., Mikami, Kamiya, & Horio, 1998), and the two-fluid approach, e.g., kinetic theory models (see, e.g., Louge, Mastorakos, & Jenkins, 1991). In both approaches the gas phase is described by a locally averaged Navier-Stokes equation and the two phases are usually coupled by a drag force. Due to the large density difference between the particles and the gas, inter-phase forces other than the drag force are usually neglected, so it plays a significant role in characterising the gas-solid flow. Yasuna, Moyer, Elliott, and Sinclair (1995) have shown that the solution of their model is sensitive to the drag coefficient. In general, the performance of most current models depends critically on the accuracy of the drag force formulation
Monetary policy transparency and inflation persistence in a small open economy
Using a New Keynesian small open economy model, we examine the effects of central bank transparency on inflation persistence. We have found that more opacity could reinforce the effect of persistent shocks on the level and variability of endogenous variables if the difference between the interest elasticity of domestic goods demand and the degree of trade openness is sufficient large or sufficiently low, judging on structural parameters characterising the economy, the central bank preference and its initial degree of opacity. Our result implies that, under perfect capital mobility, a high degree of domestic financial development is a good reason for increasing the transparency.Central bank’s transparency, open economy, inflation persistence, real exchange rate persistence
Does Union Membership Really Reduce Job Satisfaction?
We investigate the effect of union membership on job satisfaction. Whilst it is common to study the effects of union status on satisfaction treating individual membership as given, in this paper, we account for the endogenous selection induced by the sorting of workers into unionised jobs. Using linked employer-employee data from the 1998 British Workplace Employee Relations Survey, we address the question of how the membership decision is related to overall job satisfaction and to satisfaction with pay. Once the endogeneity of membership is accounted for, the marked difference in job satisfaction between unionised and non-unionised workers characterising raw data disappears, indicating that a selection effect, rather than a causal effect, explains the relationship.Job satisfaction, Trade unions, Linked employer-employee data
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