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Dublin, Ireland

Dubois V.,CNRS Institute of Chemistry | Jannes G.,CNRS Institute of Chemistry | Jannes G.,ICHEC Inc
Applied Catalysis A: General | Year: 2014

2-Methyl-2-nitropropane hydrogenation proceeds along a rake scheme that may encompass homogeneous steps, reactions on the support and on the metallic phase as well. This complexity makes it useful as a test reaction. Reaction rates, selectivities and intermediate compounds accumulation provide experimental information on the modification of catalytic parameters such as support functionality and metallic dispersion. Experiments were carried out in homogeneous phase, on bare carbon supports, with mechanical mixtures of bare carbon supports and carbon-supported catalysts, and with catalysts prepared on modified supports. We have shown that hydrogen activation takes place on the metal and that organic reactants and intermediates may be activated on the metal and on the carbon support as well and may react with hydrogen available after spillover and jumpover migrations. © 2013 Elsevier B.V.

O'Sullivan J.,University College Dublin | Sweeney C.,University College Dublin | Nolan P.,ICHEC Inc | Gleeson E.,Met Eireann
International Journal of Climatology | Year: 2015

There is a paucity of dynamically downscaled climate model output at a high resolution over Ireland, of temperature projections for the mid-21st century. This study aims to address this shortcoming. A preliminary investigation of global climate model (GCM) data and high-resolution regional climate model (RCM) data shows that the latter exhibits greater variability over Ireland by reducing the dominance of the surrounding seas on the climate signal. This motivates the subsequent dynamical downscaling and analysis of the temperature output from three high-resolution (4-7 km grid size) RCMs over Ireland. The three RCMs, driven by four GCMs from CMIP3 and CMIP5, were run under different Special Report on Emissions Scenarios (SRES) and representative concentration pathway (RCP) future scenarios. Projections of mean and extreme temperature changes are considered for the mid-century (2041-2060) and assessed relative to the control period of 1981-2000. Analysis of the RCM data shows that annual mean temperatures are projected to rise between 0.4 and 1.8 °C above control levels by mid-century. On a seasonal basis, results differ by forcing scenario. Future summers have the largest projected warming under RCP 8.5, where the greatest warming is seen in the southeast of Ireland. The remaining two high emission scenarios (SRESs A1B and A2) project future winters to have the greatest warming, with almost uniform increases of 1.5-2 °C across the island. Changes in the bidecadal 5th and 95th percentile values of daily minimum and maximum temperatures, respectively, are also analysed. The greatest change in daily minimum temperature is projected for future winters (indicating fewer cold nights and frost days), a pattern that is consistent across all scenarios/forcings. An investigation into the distribution of temperature under RCP 8.5 shows a strong summer increase compounded by increased variability, and a winter increase compounded by an increase in skewness. © 2015 Royal Meteorological Society.

Farber R.,ICHEC Inc
Scientific Computing | Year: 2011

OpenCL and NVIDIA's CUDA are competing to become the common application platform for both GPU computing as well as x86 computers. The Portland Group (PGI) has introduced a native CUDA-x86 compiler that changes the decision-making process dramatically and makes CUDA a candidate for all. The PGI CUDA C/C++ compiler is a native compiler that transparently compiles CUDA to run on x86 systems even when a GPU is not present in the system. In 2012, the PGI compiler will be able to create a unified binary, which will simplify the software distribution process tremendously. On the other hand, OpenCL is an open, royalty-free standard for cross-platform, parallel programming of modern processors found in personal computers, servers and handheld/embedded devices. A strength of OpenCL is the flexibility it provides to support portability across multiple device types and configurations. OpenCL also offers an offline compilation capability that can be used to protect kernel source code, while it limits the execution to the precompiled devices.

Bull J.M.,University of Edinburgh | Reid F.,University of Edinburgh | McDonnell N.,ICHEC Inc
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

We present a set of extensions to an existing microbenchmark suite for OpenMP. The new benchmarks measure the overhead of the task construct introduced in the OpenMP 3.0 standard, and associated task synchronisation constructs. We present the results from a variety of compilers and hardware platforms, which demonstrate some significant differences in performance between different OpenMP implementations. © 2012 Springer-Verlag.

Sabatini R.,International School for Advanced Studies | Gorni T.,University of Modena and Reggio Emilia | Gorni T.,ICHEC Inc | De Gironcoli S.,International School for Advanced Studies | De Gironcoli S.,CNR Institute of Materials
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We present a simple revision of the VV10 nonlocal density functional by Vydrov and Van Voorhis for dispersion interactions. Unlike the original functional our modification allows nonlocal correlation energy and its derivatives to be efficiently evaluated in a plane wave framework along the lines pioneered by Román-Pérez and Soler. Our revised functional maintains the outstanding precision of the original VV10 in noncovalently bound complexes and performs well in representative covalent, ionic, and metallic solids. © 2013 American Physical Society.

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