118,136 research outputs found
Poderes del juez y remedios contractuales
No full textIl saggio esamina la progressiva incidenza del giudice sul contratt
Landsat MSS classification of fire fuel types in Wood Buffalo National Park, northern Canada
No full textJ1: Global Ecology & Biogeography Letters; M3: Article; Milne, David Franklin, Steven E. Wilson, Bradley A. Ghitter, Geoff Heathcott, Mark McCaffrey, Thomas M. Ow, Charlotte F. Y.; Source Information: Mar1994, Vol. 4 Issue 2, p33; Subject Term: FOREST fires; Author-Supplied Keyword: Canada (Wood Buffalo National Park); Author-Supplied Keyword: Forest fire; Author-Supplied Keyword: Fuel type classification; Author-Supplied Keyword: Landsat data; Number of Pages: 0p; Document Type: Articl
Pragmatic view of short-baseline neutrino oscillations
No full textWe present the results of global analyses of short-baseline neutrino oscillation data in 3+1, 3+2 and 3+1+1 neutrino mixing schemes. We show that the data do not allow us to abandon the simplest 3+1 scheme in favor of the more complex 3+2 and 3+1+1 schemes. We present the allowed region in the 3+1 parameter space, which is located at Δm412 between 0.82 and 2.19 eV2 at 3σ. The case of no oscillations is disfavored by about 6σ, which decreases dramatically to about 2σ if the Liquid Scintillating Neutrino Detector (LSND) data are not considered. Hence, new high-precision experiments are needed to check the LSND signal
Long–term information collection with energy harvesting wireless sensors: a multi–armed bandit based approach
No full textThis paper reports on the development of a multi–agent approach to long-term information collection in networks of energy harvesting wireless sensors. In particular, we focus on developing energy management and data routing policies that adapt their behaviour according to the energy that is harvested, in order to maximise the amount of information collected given the available energy budget. In so doing, we introduce a new energy management technique, based on multi–armed bandit learning, that allows each agent to adaptively allocate its energy budget across the tasks of data sampling, receiving and transmitting. By using this approach, each agent can learn the optimal energy budget settings that give it efficient information collection in the long run. Then, we propose two novel decentralised multi–hop algorithms for data routing. The first proveably maximises the information throughput in the network, but can sometimes involve high communication cost. The second algorithm provides near–optimal performance, but with reduced computational and communication costs. Finally, we demonstrate that, by using our approaches for energy management and routing, we can achieve a 120% improvement in long term information collection against state–of–the–art benchmarks
Prestige y 11-M : la vertebración política de la gestión de catástrofes
No full textBetween 2002 and 2004 Spain was jolted by two
big crisis scenarios with a very different nature but two common
characteristics. On one hand, they required an immediate response
of some magnitude and complex management. On the other, they both caused a very deep impact on Spanish society and politics.
Such two characteristics made them especially interesting in order to
analyzed multiple aspects related to decisionmaking
and “first
response” management as a reaction against catastrophes. We can
also withdraw several lessons about which factors and criteria are
employed by critical actors to evaluate crisis management and “first
response” as successful.
This article focuses on the lessons learned by analyzing two
singular events occurred in Spain and partly associated to very
Spanish civic culture keys and political dynamics. At the same time,
both of them have similar features and iconic meaning to other more
recent crisis occurred in other places around the world.
The first case studied is the crisis provoked by the accident of
the oil ship “Prestige”, drawn in November 2002, 130 miles away
from the Spanish coast in Galicia. It poured around 64.000 tones of
oil in the Atlantic Ocean. It provoked a huge ecological disaster
mainly in Galicia though to a great extent it reached 2.500Kms of
coastal line, from the North of Portugal to the South of France.
The second one is the terrorist attack of March 11th, 2004 in
Madrid. A cell of Islamist terrorists linked to Al Qaeda made explode
simultaneously ten bombs in train stations and suburban trains in
four different locations. More than 1.600 people were injured and
191 were killed.
The analysis of crisis management success criteria and
factors is framed in two competitive research projects 1 . Three
different qualitative research techniques are employed: (a) interviews
to critical actors involved in crisis management; (b) semistructured
questionnaires addressed to key informants; and (c) four workshops,
composed by experts, managers and decisionmakers
involved in
Prestige Oil Spill and M11
crisis. The method used is an original
and renewed version of the Nominal Group Technique (NGT). The
application of these techniques was complemented with the
information obtained out of other sources such as official reports,
press releases, articles and specialized monographs and some results
of the inquiries carried out by the Spanish Center of Sociological
Research (CIS
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
No full textIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
The generalized Liénard polynomial differential systems x'=y,y'= -g(x) - f (x)y with deg g = deg f 1 are not Liouvillian integrable
No full textAgraïments: The second author was supported by Portuguese National Funds through FCT - Fundação para a Ciência e a Tecnologia within the project PTDC/MAT/117106/2010 and by CAMGSD (PEst-OE/EEI/LA0009/2013)We prove the nonexistence of Liouvillian first integrals for the generalized Li\'enard polynomial differential systems of the form x' = y, y'=-g(x)-f(x)y, where g(x) and f(x) are arbitrary polynomials such that g = f 1
Multi–Armed Bandit Models for Efficient Long–Term Information Collection in Wireless Sensor Networks
No full textWe are entering a new age in the evolution of computer systems, in which pervasive computing technologies seamlessly interact with human users. These technologies serve people in their everyday lives at home and work by functioning invisibly in the background, creating a smart environment around them. For example, this could be an intelligent building or a smart traffic control system. Now, since such smart environments need information about their surroundings to function effectively, they rely first and foremost on sensory data from the real world. More accurately, this data is typically provided by wireless sensor networks, which are networks of small, autonomous sensor devices. The advantages of wireless sensor networks, such as flexibility, low cost and ease of deployment, have ensured they have gained significant attention from both researchers and manufacturers. However, due to the limited resource constraints of such sensors (e.g. hardware limitations, low computational capacity, or limited energy budget), there are still a number of significant and specific research challenges to be addressed in this domain. To overcome these challenges, we believe an efficient solution for long–term information collection in wireless sensor network should be able to fulfill the following requirements: (i) adaptivity to environmental changes; (ii) robustness and flexibility; (iii) computational feasibility; and (iv) limited use of communication. In more detail, wireless sensor networks are typically deployed in dynamic environments, we must take environmental changes into account, and thus, it must be able to adapt to those changes. Furthermore, since future changes of the environment are typically unknown a priori, we cannot accurately predict these changes. Thus, in order to efficiently adapt to the environment, a good solution must be on–line, so that it can quickly react to environmental changes. Besides, we must be aware of topological and physical changes (e.g. node or communication failures) as well. Finally, due to the limited resources of the sensors, communication and computational cost should not be significant, compared to the size of the network. Previous work of information collection in wireless sensor networks has typically focused on optimising data sampling, routing, information valuation and energy management in order to achieve efficient information collection. However, it usually fail to provide all of the aforementioned requirements. Specifically, existing solutions are typically not designed for long–term operation, since they cannot adapt to environmental changes. That is, they do not have the ability of modifying their behaviour so that they could efficiently adapt to the new characteristics of the environment. Other algorithms follow the concept of centralised control mechanism (i.e. a central unit is responsible for all the calculations and decision making). These solutions, however, are not robust and flexible, since the central unit may represent a computational bottleneck. Against this background, this transfer report focuses on the challenge of developing decentralised adaptive on–line algorithms for efficient long–term information collection in the wireless sensor network domain. In particular, we focus on developing energy management and information–centric data routing policies that adapt their behaviour according to the energy that is harvested, in order to achieve efficient performance. In so doing, we introduce two new energy management techniques, based on multi–armed bandit learning, that allow each sensor to adaptively allocate its energy budget across the tasks of data sampling, receiving and transmitting. These approaches are devised in order to deal with the following different situations: (i) when the sensors can harvest energy from the environment; and (ii) when energy harvesting from the environment is not possible. By using this approaches, each sensor can learn the optimal energy budget settings that gives it efficient information collection in the long run. In addition, we propose a novel decentralised algorithm for information–centric routing. In more detail, we first tackle the energy management problem with energy–harvesting sensors from the multi–armed bandit perspective. That is, we reduce the energy management problem to a non–stochastic multi–armed bandit model. Then through extensive simulations, we demonstrate that the performance of this approach outperforms other state–of–the–art non–learning algorithms. For the case of energy management with non–harvesting sensors, we show that existing multi–armed bandit models are not suitable for modelling this problem. Given this, we introduce a new bandit model, the budgeted multi–armed bandit with pulling cost, in order to efficiently tackle the energy management problem. Following this, we propose an epsilon–first approach for this new bandit problem, in which the first epsilon portion of the total budget is allocated to exploration (i.e. learning which actions are the most efficient). Finally, for the routing, we introduce an information–centric routing problem, the maximal information throughput routing problem. Existing routing algorithms, however, are not suitable to solve this problem. Thus, we devise a simple, but proveably optimal decentralised algorithm, that maximises the information throughput in the network
Large long-range F-F indirect spin-spin coupling constants. Prediction of measurable F-F couplings over a few nanometers
No full textLarge long-range indirect nuclear spin coupling constants are of great interest for quantum computers. But they are rarely observed and are usually considered very small, unless the coupled nuclear spins are proximate in space. Looking for counterexamples, we have calculated F−F couplings in four different series of acyclic hydrocarbons (alkanes, conjugated polyenes, conjugated polyynes, and cumulenes) where the coupled fluorine nuclei are separated by up to 11 bonds or 1.4 nm. The calculations were carried out at the level of the second-order polarization propagator approximation using locally dense basis sets. This approach has, in recent years, been shown to be particularly successful in reproducing indirect nuclear spin−spin couplings in organic molecules. We find that the F−F couplings in saturated alkanes diminish very quickly with the number of bonds between the coupled fluorine atoms, whereas in the conjugated polyenes and in particular polyynes the F−F couplings can be transmitted over much longer distances. We predict that the F−F coupling over 9 bonds or 1.1 nm is 12 Hz in (1E,3E,5E,7E)-1,8-difluoroocta-1,3,5,7-tetraene and the coupling over 11 bonds or 1.4 nm is 7 Hz in difluorodecapentayne. Analyzing the four Ramsey contributions, we find that the F−F couplings in the polyenes are dominated by the spin−dipolar term, which is known to be favored by π-electronic systems, whereas in the case of the polyynes the orbital paramagnetic terms make the largest contributions, although the spin−dipolar and the Fermi contact contributions are also significant.Fil: Provasi, Patricio Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura. Departamento de Física; ArgentinaFil: Aucar, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura. Departamento de Física; ArgentinaFil: Sauer, Stephan P. A.. Universidad de Copenhagen; Dinamarc
An experimental study on trailing edge crack detection for wind turbine blade using airfoil aerodynamic noise
No full textRecent decades have witnessed more and more wind turbines (WTs) being installed onshore and offshore. Health condition monitoring for WTs structures and components is increasingly becoming a compelling concern for stable power output and operational safety of a wind farm [1]. Blade damages seem to occur with a higher probability ahead of other components (e.g., gearbox and generator) damages [2]. After reviewing traditional damage detection approaches and their limitations [3], in this research a new non-contactable approach to detecting trailing edge (TE) damages is proposed based on airfoil aerodynamic noise measurements using a microphone array. In the experiment, four changeable TE parts with rectangular cracks (damaged width W of 0.2mm, 0.5mm, 1.0mm and 2.0mm) for a NACA0018 airfoil (chord C=200mm, span L=400mm) are designed and an example with W=0.2mm is shown in Fig.(a). The TEs with cracks have the same solid thickness as the baseline one (h_solid=0.76mm, standard NACA0018 airfoil TE thickness with chord of 200mm) but different dimensions of total TE thickness (h=W+h_solid). A phased microphone array with 64 microphones is used for acoustic measurement then beamforming is applied to extract TE noise and source power integration is performed within a 200×200mm2 region centred at TE midpoint [4][5]. Fig.(b) shows sound pressure levels (SPLs) L_p at the integrated region of four damaged cases as well as baseline with the frequency resolution of 10Hz under the freestream velocity U of 35m/s and geometrical angle of attack (AoA) alpha of 0º. The cases with smaller cracks show less remarkable tonal peaks compared with the one of W=2.0mm (~4dB); when the crack size is smaller the spectral peak broadens. These peaks or humps are attributed to the periodic vortex shedding from blunt TEs. Fig.(c) shows the SPL differences Delta L_p between the damaged cases and baseline; frequency is normalized as TE-thickness-based Strouhal number St. Local maxima of Lp are present at approximately St = 0.1 [6]. In the experiment, it is difficult to extract the spectral peaks or humps if the effective AoA (alpha*) [6] is more than 2.40º because the boundary layer on suction side becomes thicker and the asymmetry of boundary layers prevents coherent and periodic vortex shedding [7]. In Fig.(d), the discrete points are the St at peak L_p (St_peak) versus the ratio of TE thickness and averaged displacement thickness of pressure and suction sides (overline delta *) extracted from available cases (U=15m/s, 20m/s, 25m/s, 30m/s and 35m/s); the grey and blue curves are obtained from models reported in [6] with solid angle (Psi) of 20º and 23.76º (baseline solid angle), respectively. The points of St_peak versus thickness ratio show a good agreement with the prediction model [6]. This means that particularly for smaller cracks at the first stage of damaged process, the effect of solid angle can be neglected and considered as a minor and adjunctive factor. The TE thickness retrieved through the application of the model can be used as a prediction of the damage level. Additional data obtained from experiments with turbulent inflow will be presented to assess if the approach proposed is still feasible in more realistic turbulent inflow conditions. Keywords: wind turbine blade; trailing edge crack; damage detection; aerodynamic noise. Images: Link: https://s3-eu-west-1.amazonaws.com/static.vcongress.de/cms/forwind/paper/417dd783-7a7c-424d-a4d3- 55ce31fa41e1.png Description: (a) An example of NACA0018 airfoil with a TE crack of 0.2mm. (b) SPLs with resolution of 10Hz (U=35m/s and alpha=0º). (c) Corresponding SPL differences compared with baseline case normalized as peak St. (d) Relations of peak St and thickness ratio: discrete points are the experimental date; grey and black curves are prediction models Brooks et al. proposed with solid angle of 20º and 23.76º. References: [1] Tautz-Weinert, J. and Watson, S.J., 2016. Using SCADA data for wind turbine condition monitoring–a review. IET Renewable Power Generation, 11(4), pp.382-394. [2] Yang, W., Peng, Z., Wei, K. and Tian, W., 2016. Structural health monitoring of composite wind turbine blades: challenges, issues and potential solutions. IET Renewable Power Generation, 11(4), pp.411-416. [3] Du, Y., Zhou, S., Jing, X., Peng, Y., Wu, H. and Kwok, N., 2020. Damage detection techniques for wind turbine blades: A review. Mechanical Systems and Signal Processing, 141, p.106445. [4] Merino-Martínez, R., Carpio, A.R., Pereira, L.T.L., van Herk, S., Avallone, F., Ragni, D. and Kotsonis, M., 2020. Aeroacoustic design and characterization of the 3D-printed, open-jet, anechoic wind tunnel of Delft University of Technology. Applied Acoustics, 170, p.107504. [5] Carpio, A.R., Avallone, F., Ragni, D., Snellen, M. and van der Zwaag, S., 2020. Quantitative criteria to design optimal permeable trailing edges for noise abatement. Journal of Sound and Vibration, 485, p.115596. [6] Brooks, T.F., Pope, D.S. and Marcolini, M.A., 1989. Airfoil self-noise and prediction. [7] Moreau, D.J. and Doolan, C.J., 2016. Tonal noise production from a wall-mounted finite airfoil. Journal of Sound and Vibration, 363, pp.199-224
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