688 research outputs found
Strokes2Surface: Recovering Curve Networks From 4D Architectural Design Sketches
We present Strokes2Surface, an offline geometry reconstruction pipeline that
recovers well-connected curve networks from imprecise 4D sketches to bridge
concept design and digital modeling stages in architectural design. The input
to our pipeline consists of 3D strokes' polyline vertices and their timestamps
as the 4th dimension, along with additional metadata recorded throughout
sketching. Inspired by architectural sketching practices, our pipeline combines
a classifier and two clustering models to achieve its goal. First, with a set
of extracted hand-engineered features from the sketch, the classifier
recognizes the type of individual strokes between those depicting boundaries
(Shape strokes) and those depicting enclosed areas (Scribble strokes). Next,
the two clustering models parse strokes of each type into distinct groups, each
representing an individual edge or face of the intended architectural object.
Curve networks are then formed through topology recovery of consolidated Shape
clusters and surfaced using Scribble clusters guiding the cycle discovery. Our
evaluation is threefold: We confirm the usability of the Strokes2Surface
pipeline in architectural design use cases via a user study, we validate our
choice of features via statistical analysis and ablation studies on our
collected dataset, and we compare our outputs against a range of
reconstructions computed using alternative methods.Comment: 15 pages, 14 figure
Optical Pulse Dynamics in Active Metamaterials with Positive and Negative Refractive Index
We study numerically the propagation of two-color light pulses through a
metamaterial doped with active atoms such that the carrier frequencies of the
pulses are in resonance with two atomic transitions in the
configuration and that one color propagates in the regime of positive
refraction and the other in the regime of negative refraction. In such a
metamaterial, one resonant color of light propagates with positive and the
other with negative group velocity. We investigate nonlinear interaction of
these forward- and backward-propagating waves, and find self-trapped waves,
counter-propagating radiation waves, and hot spots of medium excitation.Comment: 9 pages, 6 figure
BIM in teaching â 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
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Homoclinic orbits and chaos in a second-harmonic generating optical cavity
We present two large families of Silnikov-type homoclinic orbits in a two mode-model that describes second-harmonic generation in a passive optical cavity. These families of homoclinic orbits give rise to chaotic dynamics in the model. 4 refs., 1 fig
Tsetse control and Gambian sleeping sickness ; implications for control strategy
Background Gambian sleeping sickness (human African trypanosomiasis, HAT) outbreaks are brought under control by case detection and treatment although it is recognised that this typically only reaches about 75% of the population. Vector control is capable of completely interrupting HAT transmission but is not used because it is considered too expensive and difficult to organise in resource-poor settings. We conducted a full scale field trial of a refined vector control technology to determine its utility in control of Gambian HAT. Methods and Findings The major vector of Gambian HAT is the tsetse fly Glossina fuscipes which lives in the humid zone immediately adjacent to water bodies. From a series of preliminary trials we determined the number of tiny targets required to reduce G. fuscipes populations by more than 90%. Using these data for model calibration we predicted we needed a target density of 20 per linear km of river in riverine savannah to achieve >90% tsetse control. We then carried out a full scale, 500 km(2) field trial covering two HAT foci in Northern Uganda to determine the efficacy of tiny targets (overall target density 5.7/km(2)). In 12 months, tsetse populations declined by more than 90%. As a guide we used a published HAT transmission model and calculated that a 72% reduction in tsetse population is required to stop transmission in those settings. Interpretation The Ugandan census suggests population density in the HAT foci is approximately 500 per km2. The estimated cost for a single round of active case detection (excluding treatment), covering 80% of the population, is US42,700. The case for adding this method of vector control to case detection and treatment is strong. We outline how such a component could be organised
On the dynamics of a nonlinear energy harvester with multiple resonant zones
The dynamics of a nonlinear vibration energy harvester for rotating systems is investigated analytically through harmonic balance, as well as by numerical analysis. The electromagnetic harvester is attached to a spinning shaft at constant speed. Magnetic levitation is used as the system nonlinear restoring force for broadening the resonant range of the oscillator. The system is modelled as a Duffing oscillator with linear frequency variation under static, as well as harmonic excitation. Behaviour charts and backbone curves are extracted for the fundamental harmonic response and validated against frequency response curves for selected cases, using direct numerical integration. It is found that variation in stiffness, together with asymmetric forcing, gives rise to a novel structure of multiple resonant zones, incorporating mono-stable and bi-stable dynamics. Contrary to previously considered bi-stable energy harvesters, cross-well oscillations are realized through a transition from single-well potential energy to double-well with forward frequency sweep. Furthermore, in-well_oscillations present a hardening behaviour, unlike the well-known softening in-well response of bi-stable Duffing oscillators. The analysis shows that the proposed system has multiple resonant responses to a frequency sweep, influenced by consecutive interacting backbone curves similar to a multi-modal system. This combined effect of the transition to bi-stable dynamics and the hardening in-well oscillations induces resonant response of the harvester over multiple distinct frequency ranges. Thus, the system exhibits a broadened frequency response, enhancing its energy harvesting potential
Non integrability of a self-gravitating Riemann liquid ellipsoid
We prove that the motion of a triaxial Riemann ellipsoid of homogeneous
liquid without angular momentum does not possess an additional first integral
which is meromorphic in position, impulsions, and the elliptic functions which
appear in the potential, and thus is not integrable. We prove moreover that
this system is not integrable even on a fixed energy level hypersurface.Comment: 14 pages, 8 reference
Radiation exposure to the population of Europe following the Chernobyl accident
On the occasion of the 20th anniversary of the Chernobyl accident an attempt has been made to evaluate the impact of the Chernobyl accident on the global burden of human cancer in Europe. This required the estimation of radiation doses in each of the 40 European countries. Dose estimation was based on the analysis and compilation of data either published in the scientific literature or provided by local experts. Considerable variability has been observed in exposure levels among the European populations. The average individual doses to the thyroid from the intake of 131I for children aged 1 y were found to vary from âŒ0.01 mGy in Portugal up to 750 mGy in Gomel Oblast (Belarus). Thyroid doses to adults were consistently lower than the doses received by young children. The average individual effective doses from external exposure and ingestion of long-lived radiocaesium accrued in the period 1986-2005 varied from âŒ0 in Portugal to âŒ10 mSv in Gomel Oblast (Belarus) and Bryansk Oblast (Russia). The uncertainties in the dose estimates were subjectively estimated on the basis of the availability and reliability of the radiation data that were used for dose reconstruction in each countr
Nonintegrability of the two-body problem in constant curvature spaces
We consider the reduced two-body problem with the Newton and the oscillator
potentials on the sphere and the hyperbolic plane .
For both types of interaction we prove the nonexistence of an additional
meromorphic integral for the complexified dynamic systems.Comment: 20 pages, typos correcte
Mass drug administration and beyond : how can we strengthen health systems to deliver complex interventions to eliminate neglected tropical diseases?
Achieving the 2020 goals for Neglected Tropical Diseases (NTDs) requires scale-up of Mass Drug Administration (MDA) which will require long-term commitment of national and global financing partners, strengthening national capacity and, at the community level, systems to monitor and evaluate activities and impact.
For some settings and diseases, MDA is not appropriate and alternative interventions are required. Operational research is necessary to identify how existing MDA networks can deliver this more complex range of interventions equitably.
The final stages of the different global programmes to eliminate NTDs require eliminating foci of transmission which are likely to persist in complex and remote rural settings. Operational research is required to identify how current tools and practices might be adapted to locate and eliminate these hard-to-reach foci.
Chronic disabilities caused by NTDs will persist after transmission of pathogens ceases. Development and delivery of sustainable services to reduce the NTD-related disability is an urgent public health priority.
LSTM and its partners are world leaders in developing and delivering interventions to control vector-borne NTDs and malaria, particularly in hard-to-reach settings in Africa. Our experience, partnerships and research capacity allows us to serve as a hub for developing, supporting, monitoring and evaluating global programmes to eliminate NTDs
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