88,704 research outputs found
Vortex configurations and metastability in mesoscopic superconductors
The vortex dynamics in mesoscopic superconducting cylinders with rectangular
cross section under an axially applied magnetic field is investigated in the
multivortex London regime. The rectangles considered range from a square up to
an infinite slab. The flux distribution and total flux carried by a vortex
placed in an arbitrary position of the sample is calculated analytically by
assuming Clem's solution for the vortex core. The Bean-Livingston energy
barrier is also analytically calculated in this framework. A Langevin algorithm
simulates the flux penetration and dynamical evolution of the vortices as the
external field is slowly cycled. The simulated magnetization process is
governed by metastable states. The magnetization curves are hysteretic, with
paramagnetic response in part of the downward branch, and present a series of
peaks corresponding to the entry or expulsion of a single vortex. For elongated
rectangles, the vortices arrange themselves into parallel vortex chains and an
additional modulation of the magnetization, corresponding to creation or
destruction of a vortex chain, comes out.Comment: 7 pages, 4 figures. Presented on the III European Conference on
Vortex Matter in Superconductors, Crete, 2003. To appear in Physica
A Nominal Theory of the Nominal Rate of Interest and the Price Level: Some Empirical Evidence
This paper aims to investigate the impact of the bond/money ratio on the nominal interest rate. The econometric model chosen fits a dynamic panel data for Canada, Japan and US over the period 1980-2006. We found empirical evidence that Ricardian Equivalence does not hold. The analysis indicates, for the three countries, that the bond/money ratio affects the nominal interest rate.Government debt, Ricardian equivalence, bond/money ratio.
Agent-oriented Modeling for Collaborative Learning Environments: A Peer-to-Peer Helpdesk Case Study
In this paper, we present the analysis and modelling of Help&Learn, an agent-based peer-to-peer helpdesk system to support extra-class interactions among students and teachers. Help&Learn expands the studentās possibility of solving problems, getting involved in a cooperative learning experience that transcends the limits of classrooms. To model Help&Learn, we have used Agent-Object-Relationship Modeling Language (AORML), an UML extension for agent-oriented information systems modeling. The aim of this research is two-fold. On one hand, we aim at modeling the variety of roles and the complexity of their interactions and activities within the Help&Learn system. On the other hand, we aim at showing the expressive power and the modeling strengths of AORML
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