318 research outputs found
Rooftop rainwater harvesting for Mombasa: Scenario development with image classification and water resources simulation
Mombasa faces severe water scarcity problems. The existing supply is unable to satisfy the demand. This article demonstrates the combination of satellite image analysis and modelling as tools for the development of an urban rainwater harvesting policy. For developing a sustainable remedy policy, rooftop rainwater harvesting (RRWH) strategies were implemented into the water supply and demand model WEAP (Water Evaluation and Planning System). Roof areas were detected using supervised image classification. Future population growth, improved living standards, and climate change predictions until 2035 were combined with four management strategies. Image classification techniques were able to detect roof areas with acceptable accuracy. The simulated annual yield of RRWH ranged from 2.3 to 23 million cubic meters (MCM) depending on the extent of the roof area. Apart from potential RRWH, additional sources of water are required for full demand coverage. © 2017 by the authors.DAA
The Voice of Bats: How Greater Mouse-eared Bats Recognize Individuals Based on Their Echolocation Calls
Echolocating bats use the echoes from their echolocation calls to perceive their
surroundings. The ability to use these continuously emitted calls, whose main
function is not communication, for recognition of individual conspecifics might
facilitate many of the social behaviours observed in bats. Several studies of
individual-specific information in echolocation calls found some evidence for
its existence but did not quantify or explain it. We used a direct paradigm to
show that greater mouse-eared bats (Myotis myotis) can easily
discriminate between individuals based on their echolocation calls and that they
can generalize their knowledge to discriminate new individuals that they were
not trained to recognize. We conclude that, despite their high variability,
broadband bat-echolocation calls contain individual-specific information that is
sufficient for recognition. An analysis of the call spectra showed that
formant-related features are suitable cues for individual recognition. As a
model for the bat's decision strategy, we trained nonlinear statistical
classifiers to reproduce the behaviour of the bats, namely to repeat correct and
incorrect decisions of the bats. The comparison of the bats with the model
strongly implies that the bats are using a prototype classification approach:
they learn the average call characteristics of individuals and use them as a
reference for classification
Increasing robustness of handwriting recognition using character N-Gram decoding on large lexica
Offline handwriting recognition systems often include a decoding step, that is retrieving the most likely character sequence from the underlying machine learning algorithm. Decoding is sensitive to ranges of weakly predicted characters, caused e.g. by obstructions in the scanned document. We present a new algorithm for robust decoding of handwriting recognizer outputs using character n-grams. Multidimensional hierarchical subsampling artificial neural networks with Long-Short-Term-Memory cells have been successfully applied to offline handwriting recognition. Output activations from such networks, trained with Connectionist Temporal Classification, can be decoded with several different algorithms in order to retrieve the most likely literal string that it represents. We present a new algorithm for decoding the network output while restricting the possible strings to a large lexicon. The index used for this work is an n-gram index with tri-grams used for experimental comparisons. N-grams are extracted from the network output using a backtracking algorithm and each n-gram assigned a mean probability. The decoding result is obtained by intersecting the n-gram hit lists while calculating the total probability for each matched lexicon entry. We conclude with an experimental comparison of different decoding algorithms on a large lexicon
SPHERES, J\"ulich's High-Flux Neutron Backscattering Spectrometer at FRM II
SPHERES (SPectrometer with High Energy RESolution) is a third-generation
neutron backscattering spectrometer, located at the 20 MW German neutron source
FRM II and operated by the Juelich Centre for Neutron Science. It offers an
energy resolution (fwhm) better than 0.65 micro-eV, a dynamic range of +-31
micro-eV, and a signal-to-noise ratio of up to 1750:1.Comment: 12 pages, 7 figures, 2 tables. Supplemental material consists of 3
pages, 2 figures, 2 table
Design and implementation of an illumination system to mimic skyglow at ecosystem level in a large-scale lake enclosure facility
Light pollution is an environmental stressor of global extent that is growing exponentially in area and intensity. Artificial skyglow, a form of light pollution with large range, is hypothesized to have environmental impact at ecosystem level. However, testing the impact of skyglow at large scales and in a controlled fashion under in situ conditions has remained elusive so far. Here we present the first experimental setup to mimic skyglow at ecosystem level outdoors in an aquatic environment. Spatially diffuse and homogeneous surface illumination that is adjustable between 0.01 and 10 lx, resembling rural to urban skyglow levels, was achieved with white light-emitting diodes at a large-scale lake enclosure facility. The illumination system was enabled by optical modeling with Monte-Carlo raytracing and validated by measurements. Our method can be adapted to other outdoor and indoor skyglow experiments, urgently needed to understand the impact of skyglow on ecosystems
Spin orthogonality catastrophe in two-dimensional antiferromagnets and superconductors
We compute the spectral function of a spin S hole injected into a
two-dimensional antiferromagnet or superconductor in the vicinity of a magnetic
quantum critical point. We show that, near van Hove singularities, the problem
maps onto that of a static vacancy carrying excess spin S. The hole creation
operator is characterized by a new boundary anomalous dimension and a vanishing
quasiparticle residue at the critical point. We discuss possible relevance to
photoemission spectra of cuprate superconductors near the anti-nodal points.Comment: (v1) 4 pages, 2 figures; field theory afficionados - see also
cond-mat/0011233; (v2) added figure of Monte Carlo data; (v3) corrected typo
Skin Barrier Development Depends on CGI-58 Protein Expression during Late-Stage Keratinocyte Differentiation
Adipose triglyceride lipase (ATGL) and its coactivator comparative gene identification-58 (CGI-58) are limiting in cellular triglyceride catabolism. Although ATGL deficiency is compatible with normal skin development, mice globally lacking CGI-58 die postnatally and exhibit a severe epidermal permeability barrier defect, which may originate from epidermal and/or peripheral changes in lipid and energy metabolism. Here, we show that epidermis-specific disruption of CGI-58 is sufficient to provoke a defect in the formation of a functional corneocyte lipid envelope linked to impaired ω-O-acylceramide synthesis. As a result, epidermis-specific CGI-58-deficient mice show severe skin dysfunction, arguing for a tissue autonomous cause of disease development. Defective skin permeability barrier formation in global CGI-58-deficient mice could be reversed via transgenic restoration of CGI-58 expression in differentiated but not basal keratinocytes suggesting that CGI-58 is essential for lipid metabolism in suprabasal epidermal layers. The compatibility of ATGL deficiency with normal epidermal function indicated that CGI-58 may stimulate an epidermal triglyceride lipase beyond ATGL required for the adequate provision of fatty acids as a substrate for ω-O-acylceramide synthesis. Pharmacological inhibition of ATGL enzyme activity similarly reduced triglyceride-hydrolytic activities in wild-type and CGI-58 overexpressing epidermis implicating that CGI-58 participates in ω-O-acylceramide biogenesis independent of its role as a coactivator of epidermal triglyceride catabolism
Local Electronic Structure of a Single Magnetic Impurity in a Superconductor
The electronic structure near a single classical magnetic impurity in a
superconductor is determined using a fully self-consistent Koster-Slater
algorithm. Localized excited states are found within the energy gap which are
half electron and half hole. Within a jellium model we find the new result that
the spatial structure of the positive-frequency (electron-like) spectral weight
(or local density of states), can differ strongly from that of the negative
frequency (hole-like) spectral weight. The effect of the impurity on the
continuum states above the energy gap is calculated with good spectral
resolution for the first time. This is also the first three-dimensional
self-consistent calculation for a strong magnetic impurity potential.Comment: 13 pages, RevTex, change in heuristic picture, no change in numerical
result
Local Electronic Structure of Defects in Superconductors
The electronic structure near defects (such as impurities) in superconductors
is explored using a new, fully self-consistent technique. This technique
exploits the short-range nature of the impurity potential and the induced
change in the superconducting order parameter to calculate features in the
electronic structure down to the atomic scale with unprecedented spectral
resolution. Magnetic and non-magnetic static impurity potentials are
considered, as well as local alterations in the pairing interaction. Extensions
to strong-coupling superconductors and superconductors with anisotropic order
parameters are formulated.Comment: RevTex source, 20 pages including 22 figures in text with eps
Quantum impurity dynamics in two-dimensional antiferromagnets and superconductors
We present the universal theory of arbitrary, localized impurities in a
confining paramagnetic state of two-dimensional antiferromagnets with global
SU(2) spin symmetry. The energy gap of the host antiferromagnet to spin-1
excitations, \Delta, is assumed to be significantly smaller than a typical
nearest neighbor exchange. In the absence of impurities, it was argued in
earlier work (Chubukov et al. cond-mat/9304046) that the low-temperature
quantum dynamics is universally and completely determined by the values of
\Delta and a spin-wave velocity c. Here we establish the remarkable fact that
no additional parameters are necessary for an antiferromagnet with a dilute
concentration of impurities, n_{imp} - each impurity is completely
characterized by a integer/half-odd-integer valued spin, S, which measures the
net uncompensated Berry phase due to spin precession in its vicinity. We
compute the impurity-induced damping of the spin-1 collective mode of the
antiferromagnet: the damping occurs on an energy scale \Gamma= n_{imp} (\hbar
c)^2/\Delta, and we predict a universal, asymmetric lineshape for the
collective mode peak. We argue that, under suitable conditions, our results
apply unchanged (or in some cases, with minor modifications) to d-wave
superconductors, and compare them to recent neutron scattering experiments on
YBCO by Fong et al. (cond-mat/9812047). We also describe the universal
evolution of numerous measurable correlations as the host antiferromagnet
undergoes a quantum phase transition to a Neel ordered state.Comment: 36 pages, 12 figures; added reference
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