131,333 research outputs found
Michaelides (D.), The Mosaic and Marble Floors
No full textMorand Isabelle. Michaelides (D.), The Mosaic and Marble Floors. In: Revue des Études Anciennes. Tome 101, 1999, n°3-4. pp. 601-603
Michaelides (D.), The Mosaic and Marble Floors
No full textMorand Isabelle. Michaelides (D.), The Mosaic and Marble Floors. In: Revue des Études Anciennes. Tome 101, 1999, n°3-4. pp. 601-603
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On the accuracy of van der Waals inclusive density-functional theory exchange-correlation functionals for ice at ambient and high pressures
No full textDensity-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [B. Santra, J. Klimeš, D. Alfè, A. Tkatchenko, B. Slater, A. Michaelides, R. Car, and M. Scheffler, Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure ice phases pose they should be used in future benchmark studies of simulation methods for water
Reconciling Versioning and Context in Hypermedia Structure Servers
No full textContextual structure servers and versioning servers share a similar goal in allowing different views on a stored structure according to the viewer’s perspective. In this paper we argue that a generic contextual model can be used to facilitate versioning. In order to prove our hypothesis we have drawn on our experiences with OHP-Version to extend FOHM’s contextual model
Semantic annotation in ubiquitous healthcare skills-based learning environments
No full textThis paper describes initial work on developing a semantic annotation system for the augmentation of skills-based learning for Healthcare. Scenario driven skills-based learning takes place in an augmented hospital ward simulation involving a patient simulator known as SimMan. The semantic annotation software enables real-time annotations of these simulations for debriefing of the students, student self study and better analysis of the learning approaches of mentors. A description of the developed system is provided with initial findings and future directions for the work.<br/
Binding of hydrogen on benzene, coronene, and graphene from quantum Monte Carlo calculations
No full textQuantum Monte Carlo calculations with the diffusion Monte Carlo (DMC) method have been used to compute the binding energy curves of hydrogen on benzene, coronene, and graphene. The DMC results on benzene agree with both Moller-Plessett second order perturbation theory (MP2) and coupled cluster with singles, doubles, and perturbative triples [CCSD(T)] calculations, giving an adsorption energy of similar to 25 meV. For coronene, DMC agrees well with MP2, giving an adsorption energy of similar to 40 meV. For physisorbed hydrogen on graphene, DMC predicts a very small adsorption energy of only 5 +/- 5 meV. Density functional theory (DFT) calculations with various exchange-correlation functionals, including van der Waals corrected functionals, predict a wide range of binding energies on all three systems. The present DMC results are a step toward filling the gap in accurate benchmark data on weakly bound systems. These results can help us to understand the performance of current DFT based methods, and may aid in the development of improved approaches. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3569134
On Hyperstructure and Musical Structure
No full textIn this paper we report on an ongoing investigation into the relationship between musical structure and hyperstructure, based on a series of open hypermedia systems research projects that have featured case studies involving musical content. We provide a general overview of the intersection between hypermedia and musical structure, drawing also on ideas from narrative structure. Through the example systems we consider techniques for building hyperstructure from musical structure and, conversely, building musical structure from hyperstructure. Additionally we describe an experiment in the sonification of hyperstructure
The Collaborative Semantic Grid
No full textGrid and Semantic Web technologies both enable heterogeneous resources to be joined up to achieve new functionality and capability, and their combined effectiveness has been demonstrated through a number of ‘Semantic Grid’ projects. These typically apply Semantic Web technologies in Grid applications, in a datagrid or within the Grid middleware. In this paper we suggest how both approaches also support distributed collaborative endeavours, and explore their combined role. We illustrate this ‘Collaborative Semantic Grid’ through a number of case studies, and contemplate the changing nature of collaboration as these technologies evolve
Design of experiments for models involving profile factors
No full textIn the traditional design of experiments, it is assumed that each run of the experiment involves the application of a treatment, consisting of static settings of the controllable factors. The objective of this work is to extend the usual optimal experimental design paradigm to modern experiments where the settings of factors are functions. Such factors are known as profile factors, or as dynamic factors. For these new experiments, the design problem is to identify optimal experimental conditions to vary the profile factors in each run of the experiment.In general, functions are infinite dimensional objects. The latter produces challenges in estimation and design. To face the challenges, a new methodology using basis functions is developed. Primary focus is given on the B-spline basis system, due to its computational efficiency and useful properties. The methodology is applied to a functional linear model, and expanded to a functional generalised linear model, reducing the problem to an optimisation of basis coefficients. Special cases, including combinations of profile and scalar factors, interactions, and polynomial effects, are taken into consideration.The methodology is demonstrated through multiple examples, aiming to find A- and D- optimal experimental designs. The sensitivity of optimal experimental conditions to changes in the settings of the profile factors and the functional parameters is extensively investigated. Bayesian optimal designs are identified through the addition of roughness penalties to penalise the complicated functions. The latter contributes in identifying the connection between the frequentist and the Bayesian approaches
Benchmarking the performance of density functional theory and point charge force fields in their description of sI methane hydrate against diffusion Monte Carlo.
No full textHigh quality reference data from diffusion Monte Carlo calculations are presented for bulk sI methane hydrate, a complex crystal exhibiting both hydrogen-bond and dispersion dominated interactions. The performance of some commonly used exchange-correlation functionals and all-atom point charge force fields is evaluated. Our results show that none of the exchange-correlation functionals tested are sufficient to describe both the energetics and the structure of methane hydrate accurately, while the point charge force fields perform badly in their description of the cohesive energy but fair well for the dissociation energetics. By comparing to ice [Formula: see text], we show that a good prediction of the volume and cohesive energies for the hydrate relies primarily on an accurate description of the hydrogen bonded water framework, but that to correctly predict stability of the hydrate with respect to dissociation to ice [Formula: see text] and methane gas, accuracy in the water-methane interaction is also required. Our results highlight the difficulty that density functional theory faces in describing both the hydrogen bonded water framework and the dispersion bound methane
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