Adapting LPGP to plan with deadlines

This paper describes two approaches that enable the AI Planner LPGP to reason about domains with exogenous events and goals with duration: the first investigates how such domains may be encoded using the planning domain definition language PDDL2.1 level 3, while the second involves directly modifying LPGP. Both approaches have been tested in a number of domains and conclusions are drawn about the relative merits of the two approaches

Time-dependent current density functional theory on a lattice

A rigorous formulation of time-dependent current density functional theory (TDCDFT) on a lattice is presented. The density-to-potential mapping and the ${\cal V}$-representability problems are reduced to a solution of a certain nonlinear lattice Schr\"odinger equation, to which the standard existence and uniqueness results for nonliner differential equations are applicable. For two versions of the lattice TDCDFT we prove that any continuous in time current density is locally ${\cal V}$-representable (both interacting and noninteracting), provided in the initial state the local kinetic energy is nonzero everywhere. In most cases of physical interest the ${\cal V}$-representability should also hold globally in time. These results put the application of TDCDFT to any lattice model on a firm ground, and open a way for studying exact properties of exchange correlation potentials.Comment: revtex4, 9 page

Self-adjoint subspace extensions of nondensely defined symmetric operators

AbstractThe self-adjoint subspace extensions of a possibly nondensely defined symmetric operator in a Hilbert space are characterized in terms of “generalized boundary conditions.

JAPARA - A Java parallel random number generator library for high-performance computing

Copyright © 2004 IEEERandom number generators are one of the most common numerical library functions used in scientific applications. The standard random number generator provided within Java is fine for most purposes, however it does not adequately meet the needs of large-scale scientific applications, such as Monte Carlo simulations. Previous work has addressed some of these problems by extending the standard Random API in Java and providing an implementation that includes a choice of several different generator algorithms. One issue that was not addressed in this work was concurrency. Implementations of the standard Java random number generator use synchronized methods to support the use of the generator across multiple Java threads, however this is a sequential bottleneck for parallel applications. Here we present a proposal for further extending the standard API to support parallel generation of random number streams, which we have implemented in JAPARA, a Java Parallel Random Number Generator Library for high-performance computing.P. D. Coddington, A. J. Newel

Nonequilibrium effects of anisotropic compression applied to vortex lattices in Bose-Einstein condensates

We have studied the dynamics of large vortex lattices in a dilute-gas Bose-Einstein condensate. While undisturbed lattices have a regular hexagonal structure, large-amplitude quadrupolar shape oscillations of the condensate are shown to induce a wealth of nonequilibrium lattice dynamics. When exciting an m = -2 mode, we observe shifting of lattice planes, changes of lattice structure, and sheet-like structures in which individual vortices appear to have merged. Excitation of an m = +2 mode dissolves the regular lattice, leading to randomly arranged but still strictly parallel vortex lines.Comment: 5 pages, 6 figure

Experimental studies of equilibrium vortex properties in a Bose-condensed gas

We characterize several equilibrium vortex effects in a rotating Bose-Einstein condensate. Specifically we attempt precision measurements of vortex lattice spacing and the vortex core size over a range of condensate densities and rotation rates. These measurements are supplemented by numerical simulations, and both experimental and numerical data are compared to theory predictions of Sheehy and Radzihovsky [17] (cond-mat/0402637) and Baym and Pethick [25] (cond-mat/0308325). Finally, we study the effect of the centrifugal weakening of the trapping spring constants on the critical temperature for quantum degeneracy and the effects of finite temperature on vortex contrast.Comment: Fixed minor notational inconsistencies in figures. 12 pages, 8 figure

Bridging the gap between the semantic web and existing network services

©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.This paper presents an overview of a mechanism for bridging the gaps between the Semantic Web data and services, and existing network-based services that are not semantically-annotated or do not meet the requirements of Semantic Web-based applications. The Semantic Web is a relatively new set of technologies that mutually interoperate well but often require mediation, translation or wrapping to interoperate with existing network-based services. Seen as an extension of network-based services and the WWW, the Semantic Web constitutes an expanding system that can require significant effort to integrate and develop services while still providing seamless service to users. New components in a system must interoperate with the existing components and their use of protocols and shared data must be structurally and semantically equivalent. The new system must continue to meet the original system requirements as well as providing the new features or facilities. We propose a new model of network services using a knowledge-based approach that defines services and their data in terms of an ontology that can be shared with other components.Nickolas J. G. Falkner, Paul D. Coddington, Andrew L. Wendelbor

Compilation of XSLT into dataflow graphs for web service composition

Copyright © 2006 IEEEOur current research into programming models for parallel Web services composition is targeted at providing mechanisms for obtaining higher throughput for large scale compute and data intensive programs that delegate part of their computation to services, and making it easier to develop such applications. The ability to invoke multiple service calls at one time on different machines enables different portions of the program to be executed concurrently. We are addressing this through an implementation of an existing functional language, XSLT. Our implementation uses a dataflow execution model, and includes a compiler to build dataflow graphs from XSLT source code. This paper describes the execution model used to obtain parallelism and compose Web services, as well as the compilation process used to create the dataflow graphs. Our aim with this paper is to present the design of our system and demonstrate that XSLT provides a suitable model for distributed execution and parallel composition of Web services.Peter M. Kelly, Paul D. Coddington, and Andrew L. Wendelbor