13,228 research outputs found
The correlation potential in density functional theory at the GW-level: spherical atoms
As part of a project to obtain better optical response functions for nano
materials and other systems with strong excitonic effects we here calculate the
exchange-correlation (XC) potential of density-functional theory (DFT) at a
level of approximation which corresponds to the dynamically- screened-exchange
or GW approximation. In this process we have designed a new numerical method
based on cubic splines which appears to be superior to other techniques
previously applied to the "inverse engineering problem" of DFT, i.e., the
problem of finding an XC potential from a known particle density. The
potentials we obtain do not suffer from unphysical ripple and have, to within a
reasonable accuracy, the correct asymptotic tails outside localized systems.
The XC potential is an important ingredient in finding the particle-conserving
excitation energies in atoms and molecules and our potentials perform better in
this regard as compared to the LDA potential, potentials from GGA:s, and a DFT
potential based on MP2 theory.Comment: 13 pages, 9 figure
Large-scale diversity estimation through surname origin inference
The study of surnames as both linguistic and geographical markers of the past
has proven valuable in several research fields spanning from biology and
genetics to demography and social mobility. This article builds upon the
existing literature to conceive and develop a surname origin classifier based
on a data-driven typology. This enables us to explore a methodology to describe
large-scale estimates of the relative diversity of social groups, especially
when such data is scarcely available. We subsequently analyze the
representativeness of surname origins for 15 socio-professional groups in
France
Implementation of mean-timing and subsequent logic functions on an FPGA
This article describes the implementation of a mean-timer and coincidence
logic on a Virtex-5 FPGA for trigger purposes in a particle physics experiment.
The novel feature is that the mean-timing and the coincidence logic are not
synchronized with a clock which allows for a higher resolution of approximately
400 ps, not limited by a clock frequency.Comment: 15 pages, 11 figure
The Quintuple Helix innovation model: Global warming as a challenge and driver for innovation
The Triple Helix innovation model focuses on university-industry-government relations. The Quadruple Helix embeds the Triple Helix by adding as a fourth helix the media-based and culture-based public and civil society. The Quintuple Helix innovation model is even broader and more comprehensive by contextualizing the Quadruple Helix and by additionally adding the helix (and perspective) of the natural environments of society. The Triple Helix acknowledges explicitly the importance of higher education for innovation. However, in one line of interpretation it could be argued that the Triple Helix places the emphasis on knowledge production and innovation in the economy so it is compatible with the knowledge economy. The Quadruple Helix already encourages the perspective of the knowledge society, and of knowledge democracy for knowledge production and innovation. In a Quadruple Helix understanding, the sustainable development of a knowledge economy requires a coevolution with the knowledge society. The Quintuple Helix stresses the necessary socioecological transition of society and economy in the twenty-first century; therefore, the Quintuple Helix is ecologically sensitive. Within the framework of the Quintuple Helix innovation model, the natural environments of society and the economy also should be seen as drivers for knowledge production and innovation, therefore defining opportunities for the knowledge economy. The European Commission in 2009 identified the socioecological transition as a major challenge for the future roadmap of development. The Quintuple Helix supports here the formation of a win-win situation between ecology, knowledge and innovation, creating synergies between economy, society, and democracy. Global warming represents an area of ecological concern, to which the Quintuple Helix innovation model can be applied with greater potential
Seebeck coefficients of half-metallic ferromagnets
In this report the Co2 based Heusler compounds are discussed as potential
materials for spin voltage generation. The compounds were synthesized by
arcmelting and consequent annealing. Band structure calculations were performed
and revealed the compounds to be half-metallic ferromagnets. Magnetometry was
performed on the samples and the Curie temperatures and the magnetic moments
were determined. The Seebeck coefficients were measured from low to ambient
temperatures for all compounds. For selected compounds high temperature
measurements up to 900 K were performed.Comment: accepted contribution o the Special Issue "Spin Caloritronics" of
Solid State Communication
- …