Active Ontology: An Information Integration Approach for Dynamic Information Sources

In this paper we describe an ontology-based information integration approach that is suitable for highly dynamic distributed information sources, such as those available in Grid systems. The main challenges addressed are: 1) information changes frequently and information requests have to be answered quickly in order to provide up-to-date information; and 2) the most suitable information sources have to be selected from a set of different distributed ones that can provide the information needed. To deal with the first challenge we use an information cache that works with an update-on-demand policy. To deal with the second we add an information source selection step to the usual architecture used for ontology-based information integration. To illustrate our approach, we have developed an information service that aggregates metadata available in hundreds of information services of the EGEE Grid infrastructure

Spin-phonon coupling and pressure effect in the superconductor LiFeAs : Lattice dynamics from first-principles calculations

The lattice dynamics and the effect of pressure on superconducting LiFeAs in both nonmagnetic (NM) and striped antiferromagnetic (SAF) phases are investigated using the plane-wave pseudopotential, density-functional-based method. While the obtained electron-phonon coupling $\lambda$ is very small for the NM calculation, the softening of phonon in the SAF phase may lead to a large increase in $\lambda$. In the SAF phase, strong anisotropy of the phonon softening in the Fe plane is found to arise from different spin orders in the $x$ and $y$ directions, indicating that the phonon softening is of spin-phonon coupling origin. For the SAF structure, the calculated variation trend of the electronic density of states and the phonon frequencies under pressure can explain a large negative pressure coefficient of $T_{c}$ in the LiFeAs compound.Comment: 2 figure

Periodic vortex shedding in the supersonic wake of a planar plate

Vortex sheets in the wake have been mainly studied in incompressible flows and in the transonic region. Heinemann et al. (1976) have shown that for the subsonic region the Strouhal number is nearly independent of the Mach number. Motallebi and Norbury (1981) have observed an increase in the Strouhal number in transonic supersonic flow at Mach numbers up to 1.25. The present investigation is concerned with an extension of the studies of vortex shedding to higher supersonic Mach numbers, taking into account questions regarding the possibility of a generation of stable von Karman vortex paths in the considered Mach number range. It is found that the vortex sheet observed in a supersonic wake behind a rough plate is only stable and reproducible in cases involving a certain surface roughness and certain aspects of trailing edge geometry

Grid Metadata Lifetime Control in ActOn

In the Semantic Grid, metadata, as first class citizens, should be maintained up to-date in a cost-effective manner. This includes maxi missing the automation of different aspects of the metadata lifecycle, managing the evolution and change of metadata in distributed contexts, and synchronizing adequately the evolution of all these related entities. In this paper, we introduce a semantic model and its operations which is designed for supporting dynamic metadata management in Active Ontology (Act On), a semantic information integration approach for highly dynamic information sources. Finally, we illustrate the Act On-based metadata lifetime control by EGEE examples

Evaluation of a novel sponge-submerged membrane bioreactor (SSMBR) for sustainable water reclamation

A novel sponge-submerged membrane bioreactor (SSMBR) to treat a high strength wastewater for water reclamation was developed in this study. The performance of this system was evaluated using two kinds of polyester-urethane sponges (coarse sponge with higher density S28-30/45R and fine sponge with lower density S16-18/80R) with sponge volume fraction of 10% and bioreactor MLSS of 10 g/L. The results indicated the addition of sponge in SMBR could increase sustainable flux (2 times for S28-30/45R and 1.4 times for S16-18/80R) and lower TMP development, thus significantly reduce membrane fouling. S28-30/45R gave rise in attached growth biomass and the removal efficiencies of DOC, COD and PO4-P whilst S16-18/80R had better performance in removing NH4-N. Although the SSMBR performed well for most of the trials, the superior recycled water quality was achieved when adding S28-30/45R and S16-18/80R together in SMBR with the ratio of 2:1 and without any pH adjustment during the operation. © 2007 Elsevier Ltd. All rights reserved

A game-theoretic model of private power production

Private power production has sprung up all around the world, especially in developing countries with rapidly increasing demands and shortage of finance. BOT arrangements have emerged as one of the most important options of private power production. Based on oligopoly theory, this paper proposes a Stackelberg game model between a BOT company and a utility where they negotiate a long-term energy contract. It is assumed that a host utility purchases electricity from a BOT company at its "avoided cost", and sells its electricity to end users at its average cost. Taking asymmetric pricing into account, our Stackelberg game model is transferred into a two-level optimization problem, and is then solved by an iterative algorithm.published_or_final_versio