171 research outputs found
Variational Monte-Carlo studies of Gossamer Superconductivity
We use a partially Gutzwiller projected BCS d-wave wavefunction with an
antiferromagentic weighting factor to study the ground state phase diagram of a
half filled Hubbard-Heisenberg model in a square lattice with nearest neighbor
hopping and a diagonal hopping . The calculations are carried out by
using variational Monte Carlo method which treats the Gutzwiller projection
explicitly. At large on-site Coulomb interaction , the ground state is
antiferromagnetic. As decreases, the ground state becomes superconducting
and eventually metallic. The phase diagram is obtained by extensive
calculations. As compared to the strong effect of , the phase boundaries
turn out to be less sensitive to . The result is consistent with the
phase diagram in layered organic conductors, and is compared to the earlier
mean field result based on the Gutzwiller approximation.Comment: 5 pages, 4 figure
A Discipline-Spanning Overview of Action Research and Its Implications for Technology and Innovation Management
The iterative and learning character of action research is particularly beneficial for exploring complex socio-technical problems in technology and innovation management (TIM). In this respect, action research allows both rigorous and relevant research due to parallel solving of real-world problems, capability building, and gaining scientific insights. However, the use of action research within TIM research is surprisingly limited. Action research also is not a homogeneous research methodology since each research discipline, such as education and organizational science, has its own action research streams, which are often only loosely linked. A systematic overview of those action research traditions and specific best practices is still missing, which complicates a systematic transfer and use of action research in TIM. This article addresses this essential gap by building a cross-disciplinary overview of action research streams based on a bibliometric analysis using Scopus. The analysis includes relevant disciplines with action research traditions, their development over time, and the most influential journals, authors, institutions, and countries. Along with this discipline-spanning analysis, the article investigates particular TIM benefits and challenges of action research. The two key contributions of this article are: 1) a discipline-spanning overview of action research and its evolution and 2) an analysis of its implications for TIM research. These contributions build the basis for strengthening the use of action research in TIM. In the medium-term, action research has the capacity to link academia and industry more closely and, in doing so, assists important endeavours of translating more of our research outcomes into practice
Developing Design Methods - A Conceptual Requirement Framework
Design methods can provide valuable support in structuring and solving complex product design problems. However, the application and the transfer of methods from academia to industry is limited. To date, research has tended to focus on solving this through improved method selection, method adaptation and training. The development of design methods itself has attracted surprisingly low attention. This paper closes this gap and adds a quite new perspective of systematic requirement management of method development. However, the variety of methods, method users and application contexts is a key challenge and does not allow for a universal set of requirements. Thus, this paper transfers the concept of solution-neutral requirements frameworks, which are established in product design, to method development. The framework is derived from analysing and structuring different requirements found in literature. Different requirement sub-/categories allow for accommodating the varying levels of detail of requirements. The framework works like a checklist and helps design researchers to consider the most important requirement categories, which subsequently can be detailed project-specifically
RECAP – A Framework to Support Structured Reflection in Engineering Projects
Reflection is understood as an integral part of designing and design processes. Despite the high relevance and an ongoing discussion about agile engineering, we found that reflection is rarley established in industrial practice. There is a need for an approach structuring the wide range of levels, stakeholders, objects and timing of reflections. The introduced RECAP framework is an important step towards a guideline (heuristic) for reflection in engineering projects. Based on the four dimensions objectives, stakeholders, objects, and processes it supports structured planning of reflection
Directional ordering of fluctuations in a two-dimensional compass model
A classical realization of directional coupling in two dimension of the effective orbital-orbital interaction in the Mott insulating phase of the transition metal oxides (TMO) was presented. The model exhibited partial orbital ordering in the form of directional ordering of fluctuation at low temperatures stabilized by an entropy gap. The directional ordering was necessarily accompanied by a lattice distortion and the bond length in horizontal and vertical directions became unequal when the couplings of the orbital isosopin to lattice modes were included. Analysis shows that the compass model has a low temperature phase which exhibited long-ranged correlations in the directions of fluctuations in both isospin and lattice spaces.published_or_final_versio
Modulares Projektportfoliomanagement – Eine Vision zur Beherrschung komplexer Projektlandschaften
Die Festschrift für Wolfgang Kersten zum 60. Geburtstag enthält 41 Beiträge, die seine Schüler und Schülerinnen, Kolleginnen und Kollegen sowie Freunde ihm zu Ehren gewidmet haben
Internet-of-Things-Enabled Smart Bed Rail for Application in Hospital Beds
This article presents an atypical offline based LoRaWAN application for use in hospital settings, where the ability to maintain network connectivity during internet connection disruption is paramount. A prototype bed rail is demonstrated, providing advanced functionality compared to traditional bed rails. The manufactured prototype provides data to a nurses station reliably and operates under battery backup. The power consumption of the system under different transmission intervals was tested, allowing appropriate battery sizing for different applications to be specified accurately. It is expected that a single LoRaWAN gateway will be able to cover bed rails across an entire modern hospital, allowing minimal infrastructure cost to implement the device or application in a rapidly deployed field hospital.</jats:p
The mineralogy, geometry and mass-loss history of IRAS 16342-3814
We present the 2-200 um Infrared Space Observatory (ISO) spectrum and 3.8-20
um ISAAC and TIMMI2 images of the extreme OH/IR star IRAS 16342-3814. Amorphous
silicate absorption features are seen, together with crystalline silicate
absorption features up to almost 45 um. No other OH/IR star is known to have
crystalline silicate features in absorption up to these wavelengths. This
suggests that IRAS 16342-3814 must have, or recently had, an extremely high
mass-loss rate. Preliminary radiative transfer calculations suggest that the
mass-loss rate may be as large as 10^{-3} Msun/yr. The 3.8 um ISAAC image shows
a bipolar reflection nebula with a dark equatorial waist or torus, similar to
that seen in optical Hubble Space Telescope (HST) images. The position angle of
the nebula decreases significantly with increasing wavelength, suggesting that
the dominant source of emission changes from scattering to thermal emission.
Still, even up to 20 um the nebula is oriented approximately along the major
axis of the nebula seen in the HST and ISAAC images, suggesting that the torus
must be very cold, in agreement with the very red ISO spectrum. The 20 um image
shows a roughly spherically symmetric extended halo, approximately 6'' in
diameter, which is probably due to a previous phase of mass-loss on the AGB,
suggesting a transition from a (more) spherically symmetric to a (more) axial
symmetric form of mass-loss at the end of the AGB. We estimate the maximum dust
particle sizes in the torus and in the reflection nebula to be 1.3 and 0.09 um
respectively. The size of the particles in the torus is large compared to
typical ISM values, but in agreement with high mass-loss rate objects like AFGL
4106 and HD161796. We discuss the possible reason for the difference in
particle size between the torus and the reflection nebula.Comment: Accepted for publication by A&
Trans-Atlantic exchanges have shaped the population structure of the Lyme disease agent Borrelia burgdorferi sensu stricto
The origin and population structure of Borrelia burgdorferi sensu stricto (s.s.), the agent of Lyme disease, remain obscure. This tick-transmitted bacterial species occurs in both North America and Europe. We sequenced 17 European isolates (representing the most frequently found sequence types in Europe) and compared these with 17 North American strains. We show that trans-Atlantic exchanges have occurred in the evolutionary history of this species and that a European origin of B. burgdorferi s. s. is marginally more likely than a USA origin. The data further suggest that some European human patients may have acquired their infection in North America. We found three distinct genetically differentiated groups: i) the outgroup species Borrelia bissettii, ii) two divergent strains from Europe, and iii) a group composed of strains from both the USA and Europe. Phylogenetic analysis indicated that different genotypes were likely to have been introduced several times into the same area. Our results demonstrate that irrespective of whether B. burgdorferi s. s. originated in Europe or the USA, later trans-Atlantic exchange(s) have occurred and have shaped the population structure of this genospecies. This study clearly shows the utility of next generation sequencing to obtain a better understanding of the phylogeography of this bacterial species
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