690 research outputs found
Nonlinear supratransmission in multicomponent systems
A method is proposed to solve the challenging problem of determining the
supratransmission threshold (onset of instability of harmonic boundary driving
inside a band gap) in multicomponent nonintegrable nonlinear systems. It is
successfully applied to the degenerate three-wave resonant interaction in a
birefringent quadratic medium where the process generates spatial gap solitons.
No analytic expression is known for this model showing the broad applicability
of the method to nonlinear systems.Comment: 4 pages, 3 figure
Four-dimensional ultrafast electron microscopy of phase transitions
Reported here is direct imaging (and diffraction) by using 4D ultrafast electron microscopy (UEM) with combined spatial and temporal resolutions. In the first phase of UEM, it was possible to obtain snapshot images by using timed, single-electron packets; each packet is free of space–charge effects. Here, we demonstrate the ability to obtain sequences of snapshots ("movies") with atomic-scale spatial resolution and ultrashort temporal resolution. Specifically, it is shown that ultrafast metal–insulator phase transitions can be studied with these achieved spatial and temporal resolutions. The diffraction (atomic scale) and images (nanometer scale) we obtained manifest the structural phase transition with its characteristic hysteresis, and the time scale involved (100 fs) is now studied by directly monitoring coordinates of the atoms themselves
BIM in teaching — lessons learned from exploratory study
Building Information Technology bears promise to bring
integration into fragmented AEC industry, as well as large
potentials for optimization and management of building performance
along life cycle. However, the adoption in Central
Europe is much slower than in the USA or Scandinavia; the
designers and planners are sceptical about BIM benefits. In
order to build up capabilities and thus support BIM adoption
in the practice, BIM skills have be built up already in university
teaching. This endeavour is the central aim of the BIM_sustain
project accomplished at the Vienna University of Technology.
In winter term 2012/13 and winter term 2013/14 we accomplished
interdisciplinary BIM-supported design labs with
student participants from architecture, civil engineering and
building science. The teams used different modelling and simulation
software constellations for building design and analysis.
The software-constellations were evaluated in terms of BIMinteroperability,
and the design process was documented by
means of time and activity assessment, surveys on team performance,
process satisfaction and technology acceptance and
focus group interviews. In this paper we will present the results
of the evaluation of both courses and analyse the differences
resulting from the different course design in the two consequent
terms. The first course was dominated by the issue of
interfaces, whereas the second course, where better functioning
software combinations in terms of data transfer were used,
was dominated by the issues related to the collaboration and
teamwork. Our results are not only informative for the configuration
of interdisciplinary BIM-supported university teaching,
but can be derived for the practice as well, especially in the
areas of project management, software usage, modelling conventions
or incentive systems
Autonomous gathering of livestock using a multi-functional sensor network platform
In this paper we develop algorithms and hardware for the autonomous gathering of cattle. We present a comparison of three different autonomous gathering algorithms that employ sound and/or electric stimuli to guide the cattle. We evaluate these algorithms in simulation by extending previous behavioral simulations for cattle. We implemented one of these algorithms and present data from experiments in which cattle were equipped with sensor nodes that allowed cueing with sound and electric stimuli. We discuss the minimum requirements for algorithms and hardware for autonomous gathering
The anatomy of a horizontally impacted maxillary wisdom tooth
A completely horizontally impacted upper third molar was revealed after routine
dissection of a 62-year-old human cadaver of a Caucasian male. The molar
was penetrating into the maxillary sinus and there was antral dehiscence of its
bony alveolus. The bony alveolus was immediately in front of the greater palatine
canal contents, and the bottom of the alveolus was dehiscent towards
the greater palatine foramen. Within the greater palatine canal and foramen
the greater palatine artery was duplicated and the nerve was found. Such antral
relations of an impacted upper third molar predispose to oroantral communications
if extraction is performed, while the close neurovascular relations
represent a risk factor for postextractional haemorrhage and neurosensory disturbances
and must be borne in mind when deciding on or performing the
extraction. (Folia Morphol 2008: 67: 154–156
Multilinear Wavelets: A Statistical Shape Space for Human Faces
We present a statistical model for D human faces in varying expression,
which decomposes the surface of the face using a wavelet transform, and learns
many localized, decorrelated multilinear models on the resulting coefficients.
Using this model we are able to reconstruct faces from noisy and occluded D
face scans, and facial motion sequences. Accurate reconstruction of face shape
is important for applications such as tele-presence and gaming. The localized
and multi-scale nature of our model allows for recovery of fine-scale detail
while retaining robustness to severe noise and occlusion, and is
computationally efficient and scalable. We validate these properties
experimentally on challenging data in the form of static scans and motion
sequences. We show that in comparison to a global multilinear model, our model
better preserves fine detail and is computationally faster, while in comparison
to a localized PCA model, our model better handles variation in expression, is
faster, and allows us to fix identity parameters for a given subject.Comment: 10 pages, 7 figures; accepted to ECCV 201
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