Search results for "Operation"
showing 10 items of 2969 documents
Evolution of correlation structure of industrial indices of U.S. equity markets
2013
We investigate the dynamics of correlations present between pairs of industry indices of US stocks traded in US markets by studying correlation based networks and spectral properties of the correlation matrix. The study is performed by using 49 industry index time series computed by K. French and E. Fama during the time period from July 1969 to December 2011 that is spanning more than 40 years. We show that the correlation between industry indices presents both a fast and a slow dynamics. The slow dynamics has a time scale longer than five years showing that a different degree of diversification of the investment is possible in different periods of time. On top to this slow dynamics, we als…
Quantifying the relationship between specialisation and reputation in an online platform
2022
AbstractOnline platforms implement digital reputation systems in order to steer individual user behaviour towards outcomes that are deemed desirable on a collective level. At the same time, most online platforms are highly decentralised environments, leaving their users plenty of room to pursue different strategies and diversify behaviour. We provide a statistical characterisation of the user behaviour emerging from the interplay of such competing forces in Stack Overflow, a long-standing knowledge sharing platform. Over the 11 years covered by our analysis, we represent the interactions between users and topics as bipartite networks. We find such networks to display nested structures akin …
The energy spectrum of cosmic rays beyond the turn-down around 1017 eV as measured with the surface detector of the Pierre Auger Observatory
2021
The successful installation, commissioning, and operation of the Pierre Auger Observatory would not have been possible without the strong commitment and effort from the technical and administrative staff in Malargüe. We are very grateful to the following agencies and organizations for financial support: Argentina – Comisión Nacional de Energía Atómica; Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Gobierno de la Provincia de Mendoza; Municipalidad de Malargüe; NDM Holdings and Valle Las Leñas; in gratitude for their continuing cooperation over land access; Australia – the Australian Research Council; Be…
A 1D coupled Schrödinger drift-diffusion model including collisions
2005
We consider a one-dimensional coupled stationary Schroedinger drift-diffusion model for quantum semiconductor device simulations. The device domain is decomposed into a part with large quantum effects (quantum zone) and a part where quantum effects are negligible (classical zone). We give boundary conditions at the classic-quantum interface which are current preserving. Collisions within the quantum zone are introduced via a Pauli master equation. To illustrate the validity we apply the model to three resonant tunneling diodes.
Particular features of ternary fission induced by polarized neutrons in the major actinidesU233,235andPu239,241
2016
Ternary fission in $(n,f)$ reactions was studied with polarized neutrons for the isotopes $^{233,235}\mathrm{U}$ and $^{239,241}\mathrm{Pu}$. A cold longitudinally polarized neutron beam was available at the High Flux Reactor of the Institut Laue-Langevin in Grenoble, France. The beam was hitting the fissile targets mounted at the center of a reaction chamber. Detectors for fission fragments and ternary particles were installed in a plane perpendicular to the beam. In earlier work it was discovered that the angular correlations between neutron spin and the momenta of fragments and ternary particles were very different for $^{233}\mathrm{U}$ or $^{235}\mathrm{U}$. These correlations could no…
SADE: The starspot and dynamo explorer
2003
We propose a mission called SADE, the Starspot And Dynamo Explorer, to study dynamo activity in nearby late-type stars. The onboard instruments will be a Ca-K telescope for magnetically dominated chromospheric emission, and an X-ray grazing incidence telescope to study coronal emission. We design the mission for a life-time of 15 years or longer to capture a full activity cycle for most solar-type stars. We aim to firmly establish the spectrum of the relation between chromospheric and coronal emission in late-type stars, and capture one or more stars going into or coming out of a Maunder type minimum. Operation costs will be kept to a minimum by automating mission operations to a maximum, a…
Topological Insulators in Ternary Compounds with a Honeycomb Lattice
2010
One of the most exciting subjects in solid state physics is a single layer of graphite which exhibits a variety of unconventional novel properties. The key feature of its electronic structure are linear dispersive bands which cross in a single point at the Fermi energy. This so-called Dirac cone is closely related to the surface states of the recently discovered topological insulators. The ternary compounds, such as LiAuSe and KHgSb with a honeycomb structure of their Au-Se and Hg-Sb layers feature band inversion very similar to HgTe which is a strong precondition for existence of the topological surface states. In contrast to graphene with two Dirac cones at K and K' points, these material…
Tailoring the electronic structure of half-metallic Heusler alloys
2009
We investigated element-specific magnetic moments and the spin-resolved unoccupied density of states (DOS) of polycrystalline ${\text{Co}}_{2}\text{Ti}Z$ $(Z=\text{Si},\text{ }\text{Ge},\text{ }\text{Sn},\text{ }\text{Sb})$, ${\text{Co}}_{2}{\text{Mn}}_{x}{\text{Ti}}_{1\ensuremath{-}x}\text{Si}$ and ${\text{Co}}_{2}{\text{MnGa}}_{1\ensuremath{-}x}{\text{Ge}}_{x}$ Heusler alloys using circular dichroism in x-ray absorption spectroscopy (XMCD). We find a small $(l0.03{\ensuremath{\mu}}_{B})$ Ti moment oriented antiparallel and a large $(g3{\ensuremath{\mu}}_{B})$ Mn moment oriented parallel to the Co moment of approximately $1{\ensuremath{\mu}}_{B}$ per atom in the investigated compounds. Orb…
The Heliospheric Imagers Onboard the STEREO Mission
2008
Mounted on the sides of two widely separated spacecraft, the two Heliospheric Imager (HI) instruments onboard NASA’s STEREO mission view, for the first time, the space between the Sun and Earth. These instruments are wide-angle visible-light imagers that incorporate sufficient baffling to eliminate scattered light to the extent that the passage of solar coronal mass ejections (CMEs) through the heliosphere can be detected. Each HI instrument comprises two cameras, HI-1 and HI-2, which have 20° and 70° fields of view and are off-pointed from the Sun direction by 14.0° and 53.7°, respectively, with their optical axes aligned in the ecliptic plane. This arrangement provides coverage over solar…
Symmetries and Symmetry Groups in Quantum Physics
2013
When one talks about discrete or continuous groups which are to describe symmetries of quantum systems, one must first identify the objects on which the elements of these groups are acting.