6,010 research outputs found
Auxiliary Signal-Based Distance Protection in Inverter-Dominated Power Systems
Power system protection schemes today rely on currents rising by several
orders of magnitude when faults occur. In inverter-dominated power systems, a
fault current might be just a few percent larger than normal, making fault
detection more difficult. One solution is for the inverter to slightly perturb
its output current and/or voltage, i.e., to inject an auxiliary signal, so as
to make the system's behavior under faults easier to distinguish from normal.
In this paper, we optimize auxiliary signals for fault detection with distance
relays. We begin with a standard auxiliary signal design problem for generic
static systems. We use duality to reformulate the problem as a bilinear
program, which we solve using the convex-concave procedure. We implement the
framework in an example based on distance protection, in which the auxiliary
signal is negative sequence current
Extended WKB method, resonances and supersymmetric radial barriers
Semiclassical approximations are implemented in the calculation of position
and width of low energy resonances for radial barriers. The numerical
integrations are delimited by t/T<<8, with t the period of a classical particle
in the barrier trap and T the resonance lifetime. These energies are used in
the construction of `haired' short range potentials as the supersymmetric
partners of a given radial barrier. The new potentials could be useful in the
study of the transient phenomena which give rise to the Moshinsky's diffraction
in time.Comment: 12 pages, 4 figures, 3 table
The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB stars
Context: The commonly used extinction laws of Cardelli et al. (1989) have
limitations that, among other issues, hamper the determination of the effective
temperatures of O and early B stars from optical+NIR photometry. Aims: We aim
to develop a new family of extinction laws for 30 Doradus, check their general
applicability within that region and elsewhere, and apply them to test the
feasibility of using optical+NIR photometry to determine the effective
temperature of OB stars. Methods: We use spectroscopy and NIR photometry from
the VLT-FLAMES Tarantula Survey and optical photometry from HST/WFC3 of 30
Doradus and we analyze them with the software code CHORIZOS using different
assumptions such as the family of extinction laws. Results: We derive a new
family of optical+NIR extinction laws for 30 Doradus and confirm its
applicability to extinguished Galactic O-type systems. We conclude that by
using the new extinction laws it is possible to measure the effective
temperatures of OB stars with moderate uncertainties and only a small bias, at
least up to E(4405-5495) ~ 1.5 mag.Comment: Accepted for publication in A&A. Revised version corrects language
and fixes typos (one of them caught by David Nicholls). Figure 4 has poor
quality due to the size restrictions imposed by arXi
Exploring wind direction and SO2 concentration by circular-linear density estimation
The study of environmental problems usually requires the description of
variables with different nature and the assessment of relations between them.
In this work, an algorithm for flexible estimation of the joint density for a
circular-linear variable is proposed. The method is applied for exploring the
relation between wind direction and SO2 concentration in a monitoring station
close to a power plant located in Galicia (NW-Spain), in order to compare the
effectiveness of precautionary measures for pollutants reduction in two
different years.Comment: 17 pages, 7 figures, 2 table
How to achieve a healthier and more sustainable europe by 2040 according to the public? Results of a five-country questionnaire survey
The aim of this paper is to understand public preferences for several future scenarios of achieving a healthier, more equitable and sustainable Europe, which differ in the way the society is organized (individualistically vs. collectively) and in the driving sector (public vs. private). To achieve this aim, we conducted a questionnaire survey using representative samples for five European countries in 2018. About three thousand respondents chose among the four scenarios presented within four different contexts (green spaces, active mobility, energy-efficient housing, food consumption) or none of them. A majority of people in the five European countries were ready to accept one of the scenarios. We found significant differences in preferences according to socioeconomic backgrounds and values of respondents. People above 35 years old, those who were less educated, and those in the lowest household income tertile were less supportive of all scenarios. The heterogeneity in preferences associated with differences in socioeconomic backgrounds was larger for the scenario in which society is organized individualistically and driven by the private sector. Smaller distinctions were found in case of the scenario in which society is organized collectively and is driven by the public sector. Departing from social psychological theories, we examine the role of altruistic, biospheric, egoistic, hedonic, and security values. People with stronger biospheric values were more likely to accept scenarios, particularly those which are driven by the public sector and where there is more collective organisation. Those with a more egoistic value orientation were more likely to have higher preferences for scenarios where the private sector had a dominant role. The policy implications, in terms of the selection and framing of policy measures to enhance public support, are discussed.info:eu-repo/semantics/publishedVersio
An oligofluorene truxene based distributed feedback laser for biosensing applications
The first example of an all-organic oligofluorene truxene based distributed feedback laser for the detection of a specific protein–small molecule interaction is reported. The protein avidin was detected down to View the MathML source1μgmL−1 using our biotin-labelled biosensor platform. This interaction was both selective and reversible when biotin was replaced with desthiobiotin. Avidin detection was not perturbed by Bovine Serum Albumin up to View the MathML source50,000μgmL−1. Our biosensor offers a new detection platform that is both highly sensitive, modular and potentially re-usable
Application and validation of the notch master curve in medium and high strength structural steels
This paper applies and validates the Notch master curve in two ferritic steels with medium (steel S460M) and high (steel S690Q) strength. The Notch master curve is an engineering tool that allows the fracture resistance of notched ferritic steels operating within their corresponding ductile-to-brittle transition zone to be estimated. It combines the Master curve and the Theory of critical distances in order to take into account the temperature and the notch effect respectively, assuming that both effects are independent. The results, derived from 168 fracture tests on notched specimens, demonstrate the capability of the Notch master curve for the prediction of the fracture resistance of medium and high strength ferritic steels operating within their ductile-to-brittle transition zone and containing notches
MLP: a MATLAB toolbox for rapid and reliable auditory threshold estimation
In this paper, we present MLP, a MATLAB toolbox enabling auditory
thresholds estimation via the adaptive Maximum Likelihood procedure proposed
by David Green (1990, 1993). This adaptive procedure is particularly appealing for
those psychologists that need to estimate thresholds with a good degree of accuracy
and in a short time. Together with a description of the toolbox, the current text
provides an introduction to the threshold estimation theory and a theoretical
explanation of the maximum likelihood adaptive procedure. MLP comes with a
graphical interface and it is provided with several built-in, classic psychoacoustics
experiments ready to use at a mouse click
Modeling approach to regime shifts of primary production in shallow coastal ecosystems
Pristine coastal shallow systems are usually dominated by extensive meadows
of seagrass species, which are assumed to take advantage of nutrient supply
from sediment. An increasing nutrient input is thought to favour phytoplankton,
epiphytic microalgae, as well as opportunistic ephemeral macroalgae that
coexist with seagrasses. The primary cause of shifts and succession in the
macrophyte community is the increase of nutrient load to water; however
temperature plays also an important role. A competition model between rooted
seagrass (Zostera marina), macroalgae (Ulva sp), and phytoplankton has been
developed to analyse the succession of primary producer communities in these
systems. Successions of dominance states, with different resilience
characteristics, are found when modifying the input of nutrients and the
seasonal temperature and light intensity forcing.Comment: 33 pages, including 10 figures. To appear in Ecological Complexit
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