3,543 research outputs found
Modification of anatase TiO(001) surface electronic structure by Au impurity
We have used density functional theory calculations based on the projector
augmented wave method to investigate the electronic structure of
Au-incorporated anatase TiO(001) surface. Due to the coordination with
several level oxygens, Au atoms can be encapsulated inside TiO slab. Au is
adsorbed over the surface Ti--O bond, so called the bridge site on anatase
TiO(001)--11 surface. However, for 0.25 ML coverage, Au atoms
energetically prefer to stay at 0.64 {\AA} above the midpoint of the two
surface oxygens which is significantly closer to the surface layer. When
implanted inside the slab for full coverage, Au forms parallel metallic wires
inside TiO lattice where interlayer distances increase due to local
segregation. Au brings half-filled impurity states into the band gap leading to
metallization, in addition to other filled surface and impurity bands within
the gap. These Au-driven Fermi-level-pinning gap states are close to, or even
in some cases inside, the conduction band of the host slab. On the other hand,
if Au is substituted for the surface Ti atom, Fermi level falls lower in the
gap closer to the valence band top.Comment: 10 pages, 4 figure
Collider design issues based on proton-driven plasma wakefield acceleration
Recent simulations have shown that a high-energy proton bunch can excite
strong plasma wakefields and accelerate a bunch of electrons to the energy
frontier in a single stage of acceleration. It therefore paves the way towards
a compact future collider design using the proton beams from existing
high-energy proton machines, e.g. Tevatron or the LHC. This paper addresses
some key issues in designing a compact electron-positron linear collider and an
electron-proton collider based on existing CERN accelerator infrastructure
DFT study of noble metal impurities of TiO2(110)
Cataloged from PDF version of article.Atomic and electronic structures of TiO2(110) surface with possible adsorptional, substitutional and interstitial Au or Pt elemental impurities at full and one-sixth monolayer concentrations were investigated by density functional theory calculations using the projector augmented wave approach within the plane wave method. Relative thermodynamic stabilities of such phases have been discussed by means of their surface free energies. Our results suggest that tunable photocatalytic activity can be achieved on Pt atom admixed rutile (110) surface at low coverages
An collider based on proton-driven plasma wakefield acceleration
Recent simulations have shown that a high-energy proton bunch can excite
strong plasma wakefields and accelerate a bunch of electrons to the energy
frontier in a single stage of acceleration. This scheme could lead to a future
collider using the LHC for the proton beam and a compact electron
accelerator of length 170 m, producing electrons of energy up to 100 GeV. The
parameters of such a collider are discussed as well as conceptual layouts
within the CERN accelerator complex. The physics of plasma wakefield
acceleration will also be introduced, with the AWAKE experiment, a proof of
principle demonstration of proton-driven plasma wakefield acceleration, briefly
reviewed, as well as the physics possibilities of such an collider.Comment: 6 pages, 2 figures, to appear in the proceedings of the DIS 2014
Workshop, 28 April - 2 May, Warsaw, Polan
GEOSPATIAL BIG DATA ANALYTICS FOR SUSTAINABLE SMART CITIES
Growing urbanization cause environmental problems such as vast amount of carbon emissions and pollution all over the world.Smart Infrastructure and Smart Environment are two significant components of the smart city paradigm that can create opportunities for ensuring energy conservation, preventing ecological degradation, and using renewable energy sources. Since a great portion of the data contains location information, geospatial intelligence is a key technology for sustainable smart cities. We need a holistic framework for the smart governance of cities by utilizing key technological drivers such as big data, Geographic Information Systems (GIS), cloud computing, Internet of Things (IoT). Geospatial Big Data applications offer predictive data science tools such as grid computing and parallel computing for efficient and fast processing to build a sustainable smart city ecosystem. Effective management of big data in storage, visualization, analytics, and analysis stages can foster green building, green energy, and net zero targets of countries. Parallel computing systems have the ability to scale up analysis on geospatial big data platforms which is key for ocean, atmosphere, land, and climate applications. In this study, it is aimed to create the necessary technical infrastructure for smart city applications with a holistic big data management approach. Thus, a smart city model framework is developed for Smart Environment and Smart Governance components and performance comparison of Dask-GeoPandas and Apache Sedona parallel processing systems are carried out. Apache Sedona performed better on the performance test during read, write, join and clustering operations.</p
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