1,571 research outputs found
A comprehensive examination of the Eps Eri system -- Verification of a 4 micron narrow-band high-contrast imaging approach for planet searches
Due to its proximity, youth, and solar-like characteristics with a spectral
type of K2V, Eps Eri is one of the most extensively studied systems in an
extrasolar planet context. Based on radial velocity, astrometry, and studies of
the structure of its circumstellar debris disk, at least two planetary
companion candidates to Eps Eri have been inferred in the literature (Eps Eri
b, Eps Eri c). Some of these methods also hint at additional companions
residing in the system. Here we present a new adaptive optics assisted
high-contrast imaging approach that takes advantage of the favourable planet
spectral energy distribution at 4 microns, using narrow-band angular
differential imaging to provide an improved contrast at small and intermediate
separations from the star. We use this method to search for planets at orbits
intermediate between Eps Eri b (3.4 AU) and Eps Eri c (40 AU). The method is
described in detail, and important issues related to the detectability of
planets such as the age of Eps Eri and constraints from indirect measurements
are discussed. The non-detection of companion candidates provides stringent
upper limits for the masses of additional planets. Using a combination of the
existing dynamic and imaging data, we exclude the presence of any planetary
companion more massive than 3 Mjup anywhere in the Eps Eri system.
Specifically, with regards to the possible residual linear radial velocity
trend, we find that it is unlikely to correspond to a real physical companion
if the system is as young as 200 Myr, whereas if it is as old as 800 Myr, there
is an allowed semi-major axis range between about 8.5 and 25 AU.Comment: 11 pages, 8 figures, A&A accepte
Robust Vehicular Communications Using the Fast-Frequency-Hopping-OFDM Technology and the MIMO Spatial Multiplexing
Vehicle-to-Vehicle communication is one of the more emerging technologies in the 21st century from either the comfortable transportation or safer transportation point of view. Vehicle-to-Vehicle communication has one crucial factor, which is the huge information to be shared among vehicles, such as the position, the road data. In such situation, the accurate information sharing process is the most important factor in order to make the vehicles operating in the most feasible way. This work proposes a more robust vehicle communication system to make the existing vehicle transportation system more efficient. In this paper, we propose a fast frequency hopping orthogonal frequency division multiplexing to mitigate the Doppler spread effect on our previously published clustering benchmark. This benchmark contains both of a clustering weighting factor based stage and a multiparallel processing stage. This is in addition to modify the PHY layer of the existing IEEE 802.11p standard in order to impose Multiple Input Multiple Output for higher throughput purposes.The results show a noticeable stability compared to our previously published work. Furthermore, the results are almost exceeds the achieved results from the Lower-ID Distributed Clustering Algorithm (DCA) from both of the speed and communication range
Performance Study of Hybrid Spread Spectrum Techniques
This thesis focuses on the performance analysis of hybrid direct sequence/slow frequency hopping (DS/SFH) and hybrid direct sequence/fast frequency hopping (DS/FFH) systems under multi-user interference and Rayleigh fading. First, we analyze the performance of direct sequence spread spectrum (DSSS), slow frequency hopping (SFH) and fast frequency hopping (FFH) systems for varying processing gains under interference environment assuming equal bandwidth constraint with Binary Phase Shift Keying (BPSK) modulation and synchronous system. After thorough literature survey, we show that hybrid DS/FFH systems outperform both SFH and hybrid DS/SFH systems under Rayleigh fading and multi-user interference. Also, both hybrid DS/SFH and hybrid DS/FFH show performance improvement with increasing spreading factor and decreasing number of hopping frequencies
Prevention of Falls from Heights in Construction Using an IoT System Based on Fuzzy Markup Language and JFML
The main cause of fatal accidents in the construction sector are falls from height (FFH) and the inappropriate use of a harness is commonly associated with these fatalities. Traditional methods, such as onsite inspections, safety communication, or safety training, are not enough to mitigate accidents caused by FFH associated with a poor management in the use of a harness. Although some technological solutions for the automated monitoring of workers could improve safety conditions, their use is not frequent due to the particularities of construction sites: complexity, dynamic environments, outdoor workplaces, etc. Then, the integration of expert knowledge with technology is a key issue. Fuzzy logic systems (FLS) and Internet of Things (IoT) present many potential benefits, such as real-time decisions being made based on FLS and data from sensors. In the current research, the development and test of an IoT system integrated with the Java Fuzzy Markup Language Library for FLS, to support experts’ decision making in FFH, is proposed. The proposal was checked in four construction scenarios based on working conditions with different levels of risk of FFH and obtained promising results
Prevention of Falls from Heights in Construction Using an IoT System Based on Fuzzy Markup Language and JFML
The main cause of fatal accidents in the construction sector are falls from height (FFH)
and the inappropriate use of a harness is commonly associated with these fatalities. Traditional
methods, such as onsite inspections, safety communication, or safety training, are not enough to
mitigate accidents caused by FFH associated with a poor management in the use of a harness.
Although some technological solutions for the automated monitoring of workers could improve
safety conditions, their use is not frequent due to the particularities of construction sites: complexity,
dynamic environments, outdoor workplaces, etc. Then, the integration of expert knowledge with
technology is a key issue. Fuzzy logic systems (FLS) and Internet of Things (IoT) present many
potential benefits, such as real-time decisions being made based on FLS and data from sensors. In the
current research, the development and test of an IoT system integrated with the Java Fuzzy Markup
Language Library for FLS, to support experts’ decision making in FFH, is proposed. The proposal
was checked in four construction scenarios based on working conditions with different levels of risk
of FFH and obtained promising results.Universidad de Malaga
Plan Propio-Universidad de MalagaSpanish GovernmentEuropean Commission RTI2018-098371-B-I0
Monitoring Large Conservation Areas with Imaging Spectroscopy
Monitoring of large conservation areas has to be accomplished to fulfil the reporting commitment of the European FFH Directive. Aim of this project was to develop a new monitoring approach for area-wide mapping on a stand level. This approach was based on the combination of numerical methods in vegetation ecology with imaging spectroscopy.
The study took place in the FFH conservation area Murnauer Moos, Upper Bavaria. The imagery had been gathered using the imaging spectrometer HyMap™. In order to develop maps that include spatial information on vegetation types as well as on transitions, crisp field and image classifications were combined with fuzzy methods in field and image data analysis. With Non-metric Multidimensional Scaling (NMS) ordination technique for the pre-processing of vegetation data and Partial Least Squares (PLS) regression for extrapolation, we took account of occurring mixed stands and gradual vegetation transitions.
In contrast, crisp supervised image classifications are suited to assign clear categories, which are also needed in management practice. Certain emphasis was given to the different possibilities of ground data classification and endmember selection. Different applications of endmember determination to Spectral Angle Mapper (SAM) classification and Multiple Endmember Spectral Mixture Analysis (MESMA) were compared.
Synthesis maps for monitoring were produced that deliver two-fold information on pixel basis: vegetation type membership on the one side, stand position in the context of the continuous field of the vegetation on the other. Hence, ecotones can be monitored within habitats. This study shows that with the use of high spatial and spectral resolution of the imagery, this information is given in the same spatial detail for a large area, and the quality of the given details is measurable
Phospholipid dependency of membrane protein insertion by the Sec translocon
Membrane protein insertion into and translocation across the bacterial cytoplasmic membrane are essential processes facilitated by the Sec translocon. Membrane insertion occurs co-translationally whereby the ribosome nascent chain is targeted to the translocon via signal recognition particle and its receptor FtsY. The phospholipid dependence of membrane protein insertion has remained mostly unknown. Here we assessed in vitro the dependence of the SecA independent insertion of the mannitol permease MtlA into the membrane on the main phospholipid species present in Escherichia coli. We observed that insertion depends on the presence of phosphatidylglycerol and is due to the anionic nature of the polar headgroup, while insertion is stimulated by the zwitterionic phosphatidylethanolamine. We found an optimal insertion efficiency at about 30 mol% DOPG and 50 mol% DOPE which approaches the bulk membrane phospholipid composition of E. coli.</p
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