530 research outputs found
Probing the isospin dependent mean field and nucleon nucleon cross section in the medium by the nucleon emissions
We study the isospin effects of the mean field and two-body collision on the
nucleon emissions at the intermediate energy heavy ion collisions by using an
isospin dependent transport theory. The calculated results show that the
nucleon emission number depends sensitively the isospin effect of
nucleon nucleon cross section and weakly on the isospin dependent mean field
for neutron-poor system in higher beam energy region . In particular, the
correlation between the medium correction of two-body collision and the
momentum dependent interaction enhances the dependence of nucleon emission
number on the isospin effect of nucleon nucleon cross section.
On the contrary, the ratio of the neutron proton ratio of the gas phase to
the neutron proton ratio of the liquid phase, i.e., the degree of isospin
fractionation depends sensitively on the
isospin dependent mean field and weakly on the isospin effect of two-body
collision for neutron-rich system in the lower beam energy region. In this
case, and are the probes for
extracting the information about the isospin dependent nucleon nucleon cross
section in the medium and the isospin dependent mean field,respectively.Comment: 4 pages,4 figure
The Demand for Current Public Expenditure in Fiji: Theory and Empirical Results
The purpose of this paper is to analyse government expenditure in Iran using annual time series data for the period 1963-2000. Various theories of the size of government are reviewed and a distinction is made between economic/structural determinants and institutional determinants. Categorising the theories of government expenditure in this way suggests the application of non-nested tests as a mechanism whereby the relative importance of the two broad theoretical categories can be determined. The empirical results, indicating "double rejection", reveal that neither the economic/structural determinants nor the institutional determinants alone are sufficient to explain government expenditure in Iran. A comprehensive, incorporating explanatory variables from both models provides a robust explanation of the data. This paper presents the first empirical estimates of the own-price elasticity of the demand, and income elasticity of the demand, for current government expenditures in Iran
Economic Mobility: Is the American Dream Alive and Well?
Draws on research analysis to outline what economic mobility is, why it matters in today's economy, and why it is important for policy makers to focus on mobility as part of the ongoing national economic debate
Colloidal diffusion and hydrodynamic screening near boundaries
The hydrodynamic interactions between colloidal particles in small ensembles are measured at varying distances from a no-slip surface over a range of inter-particle separations. The diffusion tensor for motion parallel to the wall of each ensemble is calculated by analyzing thousands of particle trajectories generated by blinking holographic optical tweezers and by dynamic simulation. The Stokesian
Dynamics simulations predict similar particle dynamics. By separating the dynamics into three classes of modes: self, relative and collective diffusion, we observe qualitatively different behavior depending on the relative magnitudes of the distance of the ensemble from the wall and the inter-particle separation. A simple picture of the pair-hydrodynamic interactions is developed, while many-body-hydrodynamic interactions give rise to more complicated behavior. The results demonstrate that the
effect of many-body hydrodynamic interactions in the presence of a wall is much richer than the single
particle behavior and that the multiple-particle behavior cannot be simply predicted by a superposition of pair interactions
Developments in Retirement Provision: Global Trends and Lessons from Australia and the US
Retirement systems should be conceived of as long-term financial contracts under which workers' contributions today are exchanged for benefits paid to the elderly tomorrow. Such contracts are said to be well-managed if the transactions are handled in an affordable, reliable, and efficient manner. Yet all pension systems are forced to operate under a multitude of constraints including participants' ability and willingness to save; the availability of assets with which to convert current saving into future retirement benefits; the limitations of imperfect capital markets; political influences imposed by stakeholders; county macroeconomic conditions; and as we are becoming increasingly aware, global business cycles. If pensions are to continue to meet the needs of an aging world, it is imperative to prepare for emerging challenges as these systems evolve through time. In these remarks we first show how global demographic change is driving pension change throughout the world. Next we describe and compare developments in old-age provision over the last decade in Australia and the United States, and outline the key issues facing retirement systems in both nations. There are many differences between the experiences of the two countries, but as we shall show there are also common themes. Finally we identify key pension reform design issues facing Australia and the US in the upcoming decades.
"Regulating Healthcare Technologies and Medical Supplies: A Comparative Overview"
A complex relationship exists among EU regulations, current national practices and rules, institutional capacities to implement regulatory adjustments and the legacy of past health and regulatory policy and traditions. However, there is little empirical information on medical devices policy, the medical devices industry, and the assurance of medical device safety and usage. Drawing on a review of the secondary literature and on-going field work, the evidence suggests that the current mix of statecentric and self-regulatory traditions will be as important in determining the implementation and final outcomes of EU-rules as the new rules themselves. EU directives redesign rules, but they do not necessarily lead to institutional change, create institutional capacities, or alter old practices in the short term. Neither EU directives nor national regulatory adjustments determine the "man-machine/skill-experience" interface which is shaped and influenced by local medical traditions and the acceptance of these traditions by local publics
Hydrodynamic interactions of spherical particles in Poiseuille flow between two parallel walls
We study hydrodynamic interactions of spherical particles in incident
Poiseuille flow in a channel with infinite planar walls. The particles are
suspended in a Newtonian fluid, and creeping-flow conditions are assumed.
Numerical results, obtained using our highly accurate Cartesian-representation
algorithm [Physica A xxx, {\bf xx}, 2005], are presented for a single sphere,
two spheres, and arrays of many spheres. We consider the motion of freely
suspended particles as well as the forces and torques acting on particles
adsorbed at a wall. We find that the pair hydrodynamic interactions in this
wall-bounded system have a complex dependence on the lateral interparticle
distance due to the combined effects of the dissipation in the gap between the
particle surfaces and the backflow associated with the presence of the walls.
For immobile particle pairs we have examined the crossover between several
far-field asymptotic regimes corresponding to different relations between the
particle separation and the distances of the particles from the walls. We have
also shown that the cumulative effect of the far-field flow substantially
influences the force distribution in arrays of immobile spheres. Therefore, the
far-field contributions must be included in any reliable algorithm for
evaluating many-particle hydrodynamic interactions in the parallel-wall
geometry.Comment: submitted to Physics of Fluid
AFRILEX 2002: 7th international conference of the African Association for Lexicography: Culture and dictionaries: programme and abstracts
Extended ASP tableaux and rule redundancy in normal logic programs
We introduce an extended tableau calculus for answer set programming (ASP).
The proof system is based on the ASP tableaux defined in [Gebser&Schaub, ICLP
2006], with an added extension rule. We investigate the power of Extended ASP
Tableaux both theoretically and empirically. We study the relationship of
Extended ASP Tableaux with the Extended Resolution proof system defined by
Tseitin for sets of clauses, and separate Extended ASP Tableaux from ASP
Tableaux by giving a polynomial-length proof for a family of normal logic
programs P_n for which ASP Tableaux has exponential-length minimal proofs with
respect to n. Additionally, Extended ASP Tableaux imply interesting insight
into the effect of program simplification on the lengths of proofs in ASP.
Closely related to Extended ASP Tableaux, we empirically investigate the effect
of redundant rules on the efficiency of ASP solving.
To appear in Theory and Practice of Logic Programming (TPLP).Comment: 27 pages, 5 figures, 1 tabl
- …