5,044 research outputs found
Workbench spatial quality : spatial quality through stakeholder participation : lessons learnt from the city of Amersfoort
EAGLE 2006 – Multi-purpose, multi-angle and multi-sensor in-situ and airborne campaigns over grassland and forest
EAGLE2006 - an intensive field campaign - was carried out in the Netherlands from the 8th until the
18th of June 2006. Several airborne sensors - an optical imaging sensor, an imaging microwave
radiometer, and a flux airplane – were used and extensive ground measurements were conducted over
one grassland (Cabauw) site and two forest sites (Loobos & Speulderbos) in the central part of the
Netherlands, in addition to the acquisition of multi-angle and multi-sensor satellite data. The data set is
both unique and urgently needed for the development and validation of models and inversion
algorithms for quantitative surface parameter estimation and process studies. EAGLE2006 was led by
the Department of Water Resources of the International Institute for Geo-Information Science and
Earth Observation and originated from the combination of a number of initiatives coming under
different funding. The objectives of the EAGLE2006 campaign were closely related to the objectives of
other ESA Campaigns (SPARC2004, Sen2Flex2005 and especially AGRISAR2006). However, one
important objective of the campaign is to build up a data base for the investigation and validation of the
retrieval of bio-geophysical parameters, obtained at different radar frequencies (X-, C- and L-Band)
and at hyperspectral optical and thermal bands acquired over vegetated fields (forest and grassland). As
such, all activities were related to algorithm development for future satellite missions such as Sentinels
and for satellite validations for MERIS, MODIS as well as AATSR and ASTER thermal data
validation, with activities also related to the ASAR sensor on board ESA’s Envisat platform and those
on EPS/MetOp and SMOS. Most of the activities in the campaign are highly relevant for the EU
GEMS EAGLE project, but also issues related to retrieval of biophysical parameters from MERIS and
MODIS as well as AATSR and ASTER data were of particular relevance to the NWO-SRON EcoRTM
project, while scaling issues and complementary between these (covering only local sites) and global
sensors such as MERIS/SEVIRI, EPS/MetOP and SMOS were also key elements for the SMOS cal/val
project and the ESA-MOST DRAGON programme. This contribution describes the mission objectives
and provides an overview of the airborne and field campaigns
Lorentz violation in neutron and allowed nuclear beta decay
We explore the possibility that the weak interaction violates Lorentz, and in
particular rotational, invariance in neutron and allowed nuclear beta decay. A
broad class of Lorentz-violating effects is considered, in which the standard
propagator of the W-boson acquires an additional Lorentz-violating tensor. The
general decay rate for allowed beta decay that incorporates such a modified
propagator is derived. The resulting Lorentz-violating signals are discussed
for the different types of beta-decay transitions, Fermi, Gamow-Teller, and
mixed. We study the implications of our formalism for dedicated beta-decay
experiments. We give a short overview of the few relevant experiments that have
been performed or are ongoing.Comment: 23 pages; added reference
Limits on Lorentz violation in neutral-Kaon decay
The KLOE collaboration recently reported bounds on the directional dependence
of the lifetime of the short-lived neutral kaon K_S with respect to the cosmic
microwave background dipole anisotropy. We interpret their results in a general
framework developed to probe Lorentz violation in the weak interaction. In this
approach a Lorentz-violating tensor \chi_{\mu\nu} is added to the standard
propagator of the W boson. We derive the K_S decay rate in a naive tree-level
model and calculate the asymmetry for the lifetime. By using the KLOE data the
real vector part of \chi_{\mu\nu} is found to be smaller than 10^-2. We briefly
discuss the theoretical challenges concerning nonleptonic decays.Comment: Presented at the Sixth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 17-21, 2013
Prospect of creating a composite fermi/bose superfluid
We show that composite fermi/bose superfluids can be created in cold-atom
traps by employing a Feshbach resonance or coherent photoassociation. The
bosonic molecular condensate created in this way implies a new fermion pairing
mechanism associated with the exchange of fermion pairs between the molecular
condensate and an atomic fermion superfluid. We predict macroscopically
coherent, Josephson-like oscillations of the atomic and molecular populations
in response to a sudden change of the molecular energy, and suggest that these
oscillations will provide an experimental signature of the pairing.Comment: Rejected by PR
Nuclear beta decay with Lorentz violation
We consider the possibility of Lorentz-invariance violation in weak-decay
processes. We present a general approach that entails modifying the W-boson
propagator by adding a Lorentz-violating tensor to it. We describe the effects
of Lorentz violation on nuclear beta decay in this scenario. In particular we
show the expression for a first-forbidden transition with a spin change of two.
Using data from an old experiment on the rotational invariance of yttrium-90,
we derive several bounds on the Lorentz-violating parameters of the order of
10^(-6)-10^(-8).Comment: 4 pages; presented at the Sixth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 17-21, 2013; Added reference
Symmetry violations in nuclear and neutron decay
The role of decay as a low-energy probe of physics beyond the
Standard Model is reviewed. Traditional searches for deviations from the
Standard Model structure of the weak interaction in decay are discussed
in the light of constraints from the LHC and the neutrino mass. Limits on the
violation of time-reversal symmetry in decay are compared to the strong
constraints from electric dipole moments. Novel searches for Lorentz symmetry
breaking in the weak interaction in decay are also included, where we
discuss the unique sensitivity of decay to test Lorentz invariance. We
end with a roadmap for future -decay experiments.Comment: Accepted for publication in Rev. Mod. Phys. 86 pages, 13 figure
Testing Lorentz invariance in orbital electron capture
Searches for Lorentz violation were recently extended to the weak sector, in
particular neutron and nuclear decay [1]. From experiments on forbidden
-decay transitions strong limits in the range of -
were obtained on Lorentz-violating components of the -boson propagator [2].
In order to improve on these limits strong sources have to be considered. In
this Brief Report we study isotopes that undergo orbital electron capture and
allow experiments at high decay rates and low dose. We derive the expressions
for the Lorentz-violating differential decay rate and discuss the options for
competitive experiments and their required precision.Comment: accepted for publication as a Brief Report in Physical Review
Strategies for Improving Semi-automated Topic Classification of Media and Parliamentary documents
Since 1995 the techniques and capacities to store new electronic data and to make it available to many persons have become a common good. As of then, different organizations, such as research institutes, universities, libraries, and private companies (Google) started to scan older documents and make them electronically available as well. This has generated a lot of new research opportunities for all kinds of academic disciplines. The use of software to analyze large datasets has become an important part of doing research in the social sciences. Most academics rely on human coded datasets, both in qualitative and quantitative research. However, with the increasing amount of datasets and the complexity of the questions scholars pose to the datasets, the quest for more efficient and effective methods is now on the agenda. One of the most common techniques of content analysis is the Boolean key-word search method. To find certain topics in a dataset, the researcher creates first a list of keywords, added with certain parameters (AND, OR etc.). All keys are usually grouped in families and the entire list of keys and groups is called the ontology. Then the keywords are searched in the dataset, retrieving all documents containing the specified keywords. The online newspaper dataset, LexisNexis, provides the user with such a Boolean search method. However, the Boolean key-word search is not always satisfying in terms of reliability and validity. For that reason social scientists rely on hand-coding. Two projects that do so are the congressional bills project (www.congressionalbills.org ) and the policy agenda-setting project (see www.policyagendas.org ). They developed a topic code book and coded various different sources, such as, the state of the union speeches, bills, newspaper articles etcetera. The continuous improving automated coding techniques, and the increasing number of agenda setting projects (in especially European countries), however, has made the use of automated coding software a feasible option and also a necessity
Retrieval of canopy component temperatures through Bayesian inversion of directional thermal measurements
Evapotranspiration is usually estimated in remote sensing from single temperature value representing both soil and vegetation. This surface temperature is an aggregate over multiple canopy components. The temperature of the individual components can differ significantly, introducing errors in the evapotranspiration estimations. The temperature aggregate has a high level of directionality. An inversion method is presented in this paper to retrieve four canopy component temperatures from directional brightness temperatures. The Bayesian method uses both a priori information and sensor characteristics to solve the ill-posed inversion problem. The method is tested using two case studies: 1) a sensitivity analysis, using a large forward simulated dataset, and 2) in a reality study, using two datasets of two field campaigns. The results of the sensitivity analysis show that the Bayesian approach is able to retrieve the four component temperatures from directional brightness temperatures with good success rates using multi-directional sensors (Srspectra˜0.3, Srgonio˜0.3, and SrAATSR˜0.5), and no improvement using mono-angular sensors (Sr˜1). The results of the experimental study show that the approach gives good results for high LAI values (RMSEgrass=0.50 K, RMSEwheat=0.29 K, RMSEsugar beet=0.75 K, RMSEbarley=0.67 K); but for low LAI values the results were unsatisfactory (RMSEyoung maize=2.85 K). This discrepancy was found to originate from the presence of the metallic construction of the setup. As these disturbances, were only present for two crops and were not present in the sensitivity analysis, which had a low LAI, it is concluded that using masked thermal images will eliminate this discrepanc
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