232 research outputs found
Thermoelectrics of Interacting Nanosystems -- Exploiting Superselection instead of Time-Reversal Symmetry
Thermoelectric transport is traditionally analyzed using relations imposed by
time-reversal symmetry, ranging from Onsager's results to fluctuation relations
in counting statistics. In this paper, we show that a recently discovered
duality relation for fermionic systems -- deriving from the fundamental
fermion-parity superselection principle of quantum many-particle systems --
provides new insights into thermoelectric transport. Using a master equation,
we analyze the stationary charge and heat currents through a weakly coupled,
but strongly interacting single-level quantum dot subject to electrical and
thermal bias. In linear transport, the fermion-parity duality shows that
features of thermoelectric response coefficients are actually dominated by the
average and fluctuations of the charge in a dual quantum dot system, governed
by attractive instead of repulsive electron-electron interaction. In the
nonlinear regime, the duality furthermore relates most transport coefficients
to much better understood equilibrium quantities. Finally, we naturally
identify the fermion-parity as the part of the Coulomb interaction relevant for
both the linear and nonlinear Fourier heat. Altogether, our findings hence
reveal that next to time-reversal, the duality imposes equally important
symmetry restrictions on thermoelectric transport. As such, it is also expected
to simplify computations and clarify the physical understanding for more
complex systems than the simplest relevant interacting nanostructure model
studied here.Comment: 38 pages (23 main paper, 15 appendix), 8 figure
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High-Speed Curtain Recoating for Stereolithography
The University of Leuven uses a liquid curtain recoating system for resin deposition in
stereolithography. This system deposits new liquid layers of photo-polymer by means of a liquid
curtain travelling over the build vat. Experiments have been carried out to increase the speed of the
liquid curtain while depositing a layer. Speeds up to 1.2 m/s, and accelerations up to 1 g have been
tested successfully, meaning that it is possible to coat high-quality layers of 75 µm thickness with
this recoating technique. However, the curtain restores too slowly after acceleration. This paper
discusses possible reasons and tries to formulate adequate solutions. Possible solutions consist in
controlling small pressure differences in the curtain’s neighbourhood. A solution to this problem
is necessary, as to make the travelling length of the curtain, and so the machine length acceptable
with respect to the dimensions of the build vat.Mechanical Engineerin
Anisotropic bulk and planar Heisenberg ferromagnets in uniform, arbitrarily oriented magnetic fields
Today, further downscaling of mobile electronic devices poses serious
problems, such as energy consumption and local heat dissipation. In this
context, spin wave majority gates made of very thin ferromagnetic films may
offer a viable alternative. However, similar downscaling of magnetic thin films
eventually enforces the latter to operate as quasi-two dimensional magnets, the
magnetic properties of which are not yet fully understood, especially those
related to anisotropies and external magnetic fields in arbitrary directions.
To this end, we have investigated the behaviour of an easy-plane and easy-axis
anisotropic ferromagnet -- both in two and three dimensions -- subjected to a
uniform magnetic field, applied along an arbitrary direction. In this paper, a
spin-1/2 Heisenberg Hamiltonian with anisotropic exchange interactions is
solved using double-time temperature-dependent Green's functions and the
Tyablikov decoupling approximation. We determine various magnetic properties
such as the Curie temperature and the magnetization as a function of
temperature and the applied magnetic field, discussing the impact of the
system's dimensionality and the type of anisotropy. The magnetic reorientation
transition taking place in anisotropic Heisenberg ferromagnets is studied in
detail. Importantly, spontaneous magnetization is found to be absent for
easy-plane two-dimensional spin systems with short range interactions
E-CLOUD, the open microgrid in existing network infrastructure
peer reviewedThe main goal of the E-Cloud, as with every microgrid, is to maximize the consumption of energy produced locally. To reach this goal, based on consumption profiles of customers willing to participate in the E-cloud and given some local restrictions (e.g. wind turbines cannot be put everywhere), an optimal mix of green generation sources (in kW) and local storage (in kWh) needs to be computed.
Then according to this computation, the required generating units and storage device are installed. A repartition mechanism grants the customer a share of the generated electricity and storage capacity. These shares are either computed offline, or dynamically adapted on line. The project will test two models: either the DSO or a producer owns and operates the storage device.
Two flows of information (real-time for operation of the storage facility and ex-post for its settlement) are needed to correctly manage the E-Cloud and to ensure correct information exchange with the wholesale market. These information flows are completed thanks to a forecast that provides members of the E-Cloud the full capability to anticipate and obtain the maximum benefits of the local generation.
The expected benefits for the customer are a reduction of their electricity bill by a minimum of 10%. Societal benefits should also arise: 1) easing the technical integration of renewables’ generation embedded in the distribution network, and 2) avoids extra investment on the DSO network. The E-Cloud may also ensure new revenue for the DSO thanks to new services provided to the E-Cloud community
Orbital bleeding in rats while under diethylether anaesthesia does not influence telemetrically determined heart rate, body temperature, locomotor and eating activity when compared with anaesthesia alone
The question addressed was whether orbital bleeding in rats, while under diethylether anaesthesia, affects their locomotor activity, body core temperature, heart rate rhythm and eating pattern. Roman High Avoidance (RHA) and Roman Low Avoidance (RLA) rats were used to enhance generalization of the results. Orbital bleeding when the rats were under diethylether anaesthesia was compared with diethylether anaesthesia alone. To take into account any effects of handling, the rats were also subjected to sham anaesthesia. The RHA rats urinated more during anaesthesia, needed more time to recover from the anaesthesia and showed a greater endocrine stress response to diethylether anaesthesia when compared with the RLA rats. During anaesthesia, the RHA rats showed a greater fall of body temperature and bradycardia than did the RLA rats. Diethylether anaesthesia reduced locomotor activity in the RHA rats, but had no effect in the RLA rats. In neither RHA nor RLA rats did anaesthesia plus orbital puncture, versus anaesthesia alone, influence body temperature, heart rate rhythm, locomotor and eating activity. The lack of effect of orbital puncture occurred both in the short term (within 2 h) and long term (within 48 hours) and thus this study indicates that orbital puncture had, at least with respect to variables measured in the present study, no effect superimposed on that of diethylether anaesthesia
Mobile Robot Localization using Panoramic Vision and Combinations of Feature Region Detectors
IEEE International Conference on Robotics and Automation (ICRA 2008, Pasadena, California, May 19-23, 2008), pp. 538-543.This paper presents a vision-based approach for
mobile robot localization. The environmental model is topological. The new approach uses a constellation of different types of affine covariant regions to characterize a place. This type of representation permits a reliable and distinctive environment modeling. The performance of the proposed approach is evaluated using a database of panoramic images from different rooms. Additionally, we compare different combinations of complementary feature region detectors to find the one that achieves the best results. Our experimental results show promising results for this new localization method. Additionally, similarly to what happens with single detectors, different combinations exhibit different strengths and weaknesses depending on the situation, suggesting that a context-aware method to combine
the different detectors would improve the localization results.This work was partially supported by USC Women in Science and Engineering (WiSE), the FI grant from the Generalitat de Catalunya, the European Social Fund, and the MID-CBR project grant TIN2006-15140-C03-01 and FEDER funds and the grant 2005-SGR-00093
FORMAT - Building an original methodology for Technology Forecasting through researchers exchanges between industry and academia
AbstractThe paper presents an overview of the FORMAT methodology, an approach for technological forecasting capable of satisfying the need of manufacturing industries to better support decision-making processes in planning corporate strategies for R&D. The methodology has been developed within the FORMAT consortium, gathering partners from both industry and academia in a Marie-Curie EU funded project of the 7th Framework Programme - IAPP PEOPLE. The methodology is intentionally shaped as a generic one, so as to foster its adoption by the wider audience, but it suggests the adoption of several TRIZ techniques and models to support the forecast. Its exemplary application in the field of forming technologies for domestic refrigerators aims at showing its potential and viability in a real industrial context. The paper is supplemented by a case study in the white goods manufacturing (forming techniques for the inner liners of domestic refrigerators)
The mid-twentieth century Baby Boom and the changing educational gradient in Belgian cohort fertility
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