San Diego, CA, United States
San Diego, CA, United States

Time filter

Source Type

Uren V.,University of Sheffield | Uren V.,Open University Milton Keynes | Sabou M.,Open University Milton Keynes | Motta E.,Open University Milton Keynes | And 4 more authors.
International Journal of Metadata, Semantics and Ontologies | Year: 2010

Evaluations of semantic search systems are generally small scale and ad hoc due to the lack of appropriate resources such as test collections, agreed performance criteria and independent judgements of performance. By analysing our work in building and evaluating semantic tools over the last five years, we conclude that the growth of the semantic web led to an improvement in the available resources and the consequent robustness of performance assessments. We propose two directions for continuing evaluation work: the development of extensible evaluation benchmarks and the use of logging parameters for evaluating individual components of search systems. Copyright © 2010 Inderscience Enterprises Ltd.


Tasaki K.,Mitsubishi Chemical Holdings America | Goldberg A.,Accelrys Software Inc. | Winter M.,University of Munster
Electrochimica Acta | Year: 2011

Density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations have been performed to gain insight into the difference in cycling behaviors between the ethylene carbonate (EC)-based and the propylene carbonate (PC)-based electrolytes in lithium-ion battery cells. DFT calculations of the lithium solvation, Li+(S)i (S = EC or PC; i = 1-4) with and without the presence of the counter anion showed that the desolvation energy to remove one solvent molecule from the first solvation shell of the lithium ion was significantly reduced by as much as 70 kcal mol-1 (293.08 kJ mol-1) in the presence of the counter anion, suggesting the lithium ion is more likely to be desolvated at high salt concentrations. The thermodynamic stability of the ternary graphite intercalation compounds, Li+(S)iC72, in which Li+(S)i was inserted into a graphite cell, was also examined by DFT calculations. The results suggested that Li+(EC) iC72 was more stable than Li+(PC) iC72 for a given i. Furthermore, some of Li +(PC)iC72 were found to be energetically unfavorable, while all of Li+(EC)i=1-4C72 were stable, relative to their corresponding Li+(S)i in the bulk electrolyte. In addition, the interlayer distances of Li +(PC)iC72 were more than 0.1 nm longer than those of Li+(EC)iC72. MD simulations were also carried out to examine the solvation structures at a high salt concentration of LiPF6: 2.45 mol kg-1. The results showed that the solvation structure was significantly interrupted by the counter anions, having a smaller solvation number than that at a lower salt concentration (0.83 mol kg-1). We propose that at high salt concentrations, the lithium desolvation may be facilitated due to the increased contact ion pairs so as to form a stable ternary GIC with less solvent molecules without destruction of graphite particles, followed by solid-electrolyte-interface film formation reactions. The results from both DFT calculations and MD simulations are consistent with the recent experimental observations. © 2011 Elsevier Ltd. All rights reserved.


Tasaki K.,Mitsubishi Group | Goldberg A.,Accelrys Software Inc. | Liang J.-J.,Accelrys Software Inc. | Winter M.,University of Munster
ECS Transactions | Year: 2011

Density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations have been performed to gain insight into the difference in cycling behaviors between the ethylene carbonate (EC)-based and the propylene carbonate (PC)-based electrolytes in lithium-ion battery cells. DFT calculations for the ternary graphite intercalation compounds (Li +(S) iCn: S=EC or PC), in which the solvated lithium ion Li +(S) i (i=1-3) was inserted into a graphite cell, suggested that Li +(EC) iC n was more stable than Li +(PC) iC n in general. In addition, MD simulations were carried out to examine the solvation structures at a high salt concentration: 2.45 mol kg -1. The results showed that the solvation structure was significantly interrupted by the counter anions, having a smaller solvation number than that at a lower salt concentration (0.83 mol kg -1). The results from both DFT calculations and MD simulations are consistent with the recent experimental observations. ©The Electrochemical Society.


Gao J.,Stevens Institute of Technology | Zheng Y.,Stevens Institute of Technology | Fitzgerald G.B.,Accelrys Software Inc. | De Joannis J.,Accelrys Software Inc. | And 3 more authors.
Journal of Physical Chemistry C | Year: 2014

Mo carbide nanoparticles supported on ZSM-5 zeolites are promising catalysts for methane dehydroaromatization. For this and other applications, it is important to identify the structure and anchoring sites of Mo carbide nanoparticles. In this work, structures of Mo2Cx (x = 1, 2, 3, 4, and 6) and Mo4Cx (x = 2, 4, 6, and 8) nanoparticles are identified using a genetic algorithm with density functional theory (DFT) calculations. The ZSM-5 anchoring sites are determined by evaluating infrared vibrational spectra for surface OH groups before and after Mo deposition. The spectroscopic results demonstrate that initial Mo oxide species preferentially anchors on framework Al sites and partially on Si sites on the external surface of the zeolite. In addition, Mo oxide deposition causes some dealumination, and a small fraction of Mo oxide species anchor on extraframework Al sites. Anchoring modes of Mo carbide nanoparticles are evaluated with DFT cluster calculations and with hybrid quantum mechanical and molecular mechanical (QM/MM) periodic structure calculations. Calculation results suggest that binding through two Mo atoms is energetically preferable for all Mo carbide nanoparticles on double Al-atom framework sites and external Si sites. On single Al-atom framework sites, the preferential binding mode depends on the particle composition. The calculations also suggest that Mo carbide nanoparticles with a C/Mo ratio greater than 1.5 are more stable on external Si sites and, thus, likely to migrate from zeolite pores onto the external surface of the zeolite. Therefore, in order to minimize such migration, the C/Mo ratio for zeolite-supported Mo carbide nanoparticles under hydrocarbon reaction conditions should be maintained below 1.5. © 2014 American Chemical Society.


Tasaki K.,Mitsubishi Chemical United States | Goldberg A.,Accelrys Software Inc. | Liang J.-J.,Accelrys Software Inc. | Winter M.,University of Munster
Materials Research Society Symposium Proceedings | Year: 2011

Density functional theory (DFT) calculations and classical molecular dynamics (MD) simulations have been performed to gain insight into the difference in cycling behaviors between the ethylene carbonate (EC)-based and the propylene carbonate (PC)-based electrolytes in lithium-ion battery cells. DFT calculations for the ternary graphite intercalation compounds (Li +(S) iC n: S=EC or PC), in which the solvated lithium ion Li +(S) i (i=1-3) was inserted into a graphite cell, suggested that Li +(EC) iC n was more stable than Li +(PC) iC n in general. Furthermore, Li +(PC) 3C n was found to be energetically unfavorable, while Li +(PC) 2C n was stable, relative to their corresponding Li +(PC) i in the bulk electrolyte. The calculations also revealed severe structural distortions of the PC molecule in Li +(PC) 3C n, suggesting a rapid kinetic effect on PC decomposition reactions, as compared to decompositions of EC. In addition, MD simulations were carried out to examine the solvation structures at a high salt concentration: 2.45 mo kg -1. The results showed that the solvation structure was significantly interrupted by the counter anions, having a smaller solvation number than that at a lower salt concentration (0.83 mol kg -1). We propose that at high salt concentrations, the lithium desolvation may be facilitated due to the increased contact ion pairs, so that a stable ternary GIC with less solvent molecules can be formed without the destruction of graphite particles, followed by solid-electrolyte-interface film formation reactions. The results from both DFT calculations and MD simulations are consistent with the recent experimental observations. © 2011 Materials Research Society.


Harding J.A.,Loughborough University | Swarnkar R.,Accelrys Software Inc.
International Journal of Production Research | Year: 2013

Research into moderators, which support collaborative teams by proactively making team members aware of actions or potential problems which may affect them, began in the 1990s, in the context of supporting collaborations during concurrent engineering projects. This paper provides a background to the evolution of moderators and explores their role in supporting virtual organisations. A collaboration moderator (CM) is an evolution of earlier moderators and is capable of behaving differently for different types of users and therefore caters for the varying requirements of individual users depending on the roles they have in the collaborations. This paper describes the architecture and components of a CM from an implementation perspective. Prototype CMs have been developed during the EU-funded SYNERGY project, and two use cases for which the prototype CMs were implemented as a service (a Pre-Creation use case and an Operational use case) are also discussed in this paper. © 2013 Taylor & Francis.

Loading Accelrys Software Inc. collaborators
Loading Accelrys Software Inc. collaborators