27,591 research outputs found
A direct helicopter EM sea ice thickness inversion, assessed with synthetic and field data
Accuracy and precision of helicopter electromagneticHEM sounding are the essential parameters for HEM seaicethickness profiling. For sea-ice thickness research, thequality of HEM ice thickness estimates must be better than10 cm to detect potential climatologic thickness changes.Weintroduce and assess a direct, 1D HEM data inversion algorithmfor estimating sea-ice thickness. For synthetic qualityassessment, an analytically determined HEM sea-ice thicknesssensitivity is used to derive precision and accuracy. Precisionis related directly to random, instrumental noise, althoughaccuracy is defined by systematic bias arising fromthe data processing algorithm. For the in-phase component ofthe HEM response, sensitivity increases with frequency andcoil spacing, but decreases with flying height. For small-scaleHEM instruments used in sea-ice thickness surveys, instrumentalnoise must not exceed 5 ppm to reach ice thicknessprecision of 10 cm at 15-m nominal flying height. Comparableprecision is yielded at 30-m height for conventional explorationHEM systems with bigger coil spacings. Accuracylosses caused by approximations made for the direct inversionare negligible for brackish water and remain better than10 cm for saline water. Synthetic precision and accuracy estimatesare verified with drill-hole validated field data fromEast Antarctica, where HEM-derived level-ice thicknessagrees with drilling results to within 4%, or 2 cm
Study on integration of silver-zinc battery improvements Interim technical report, 1 Jan. - 30 Jun. 1970
Components and single cell design for five cell silver zinc batter
Study on integration of silver-zinc battery improvements Interim technical report, 1 Mar. 1969 - 31 Dec. 1969
Research and development in silver zinc batteries for aerospace us
Optimal control of electromagnetic field using metallic nanoclusters
The dielectric properties of metallic nanoclusters in the presence of an
applied electromagnetic field are investigated using non-local linear response
theory. In the quantum limit we find a non-trivial dependence of the induced
field and charge distribution on the spatial separation between the clusters
and on the frequency of the driving field. Using a genetic algorithm, these
quantum functionalities are exploited to custom-design sub-wavelength lenses
with a frequency controlled switching capability.Comment: accepted for publication in New Journal of Physic
Detection of Prolonged Diapause of Northern Corn Rootworm in Michigan (Coleoptera: Chrysomelidae)
Prolonged diapause of northern corn rootworm, while known from other Midwestern states, has not previously been reported in Michigan. Populations of northern corn rootworm, (Diabrotica barberi) from two first-year corn fields in Genesee County, Michigan were examined for prolonged egg diapause. Pro- longed diapause was suspected in these populations due to an unusually high proportion of northern versus western corn rootworms in these fields. Eggs obtained from females collected at these sites were reared in the laboratory for two years. The presence of the prolonged diapause trait was confirmed in one population by eggs which hatched following two simulated winters (7.3%). None of the eggs m the second population hatched following the second chill period, however, some eggs in this population remained in apparent diapause at the end of two years. The potential for using observed population shifts in favor of D. barberi as an early warning of the expansion of prolonged diapause in a population is discussed
Chord Label Personalization through Deep Learning of Integrated Harmonic Interval-based Representations
The increasing accuracy of automatic chord estimation systems, the
availability of vast amounts of heterogeneous reference annotations, and
insights from annotator subjectivity research make chord label personalization
increasingly important. Nevertheless, automatic chord estimation systems are
historically exclusively trained and evaluated on a single reference
annotation. We introduce a first approach to automatic chord label
personalization by modeling subjectivity through deep learning of a harmonic
interval-based chord label representation. After integrating these
representations from multiple annotators, we can accurately personalize chord
labels for individual annotators from a single model and the annotators' chord
label vocabulary. Furthermore, we show that chord personalization using
multiple reference annotations outperforms using a single reference annotation.Comment: Proceedings of the First International Conference on Deep Learning
and Music, Anchorage, US, May, 2017 (arXiv:1706.08675v1 [cs.NE]
The dust SED in the dwarf galaxy NGC 1569: Indications for an altered dust composition?
We discuss the interpretation of the dust SED from the mid-infrared to the
millimeter range of NGC 1569. The model developed by D\'esert et al. (1990)
including three dust components (Polyaromatic Hydrocarbons, Very Small Grains
and big grains) can explain the data using a realistic interstellar radiation
field and adopting an enhanced abundance of VSGs. A simple three-temperature
model is also able to reproduce the data but requires a very low dust
temperature which is considered to be unlikely in this low-metallicity
starburst galaxy. The high abundance of Very Small Grains might be due to large
grain destruction in supernova shocks. This possibility is supported by ISO
data showing that the emission at 14.3 m, tracing VSGs, is enhanced with
respect to the emission at 6.7 m and 850 m in regions of high star
formation.Comment: 4 pages, conference proceedings paper, "The Spectral Energy
Distribution of Gas-Rich Galaxies: Confronting Models with Data", Heidelberg,
4-8 Oct. 2004, eds. C.C. Popescu & R.J. Tuffs, AIP Conf. Ser., in pres
Highly erosive glaciers on Mars - the role of water
International audiencePolewards of 30 • in each hemisphere, the surface of Mars hosts a suite of landforms reminiscent of glacial landscapes on Earth. Amongst these landforms are: 1) Viscous Flow Features (VFF), which resemble glaciers on Earth and are thought to contain large volumes of water ice, 2) martian gullies which are km-scale features resembling water-eroded gullies on Earth and 3) arcuate ridges thought to be moraines from previous glaciations. Gullies have been long-associated with a surface unit originally called "pasted-on terrain" and now often called the "latitude dependant mantle". Arcuate ridges are often found at the base of hillslopes with gullies, but are also found on hillslopes with pasted-on terrain and no gullies. We have found a systematic lowering of the slope of the bedrock exposure located topographically above the pasted-on terrain whether that same slope hosts gullies or not. The lowered bedrock exposures display a different surface texture from bedrock exposed on other parts of the crater wall and from fresh crater walls-it appears fragmented and has reduced relief. Using 1-m-digital elevation models from the High Resolution Imaging Science Experiment (HiRISE) we compared the slopes of eight "eroded" craters and seven unmodified craters. We estimated their age using the crater size-frequency distribution of small craters on their ejecta blankets. From this information we calculated bedrock retreat rates for the eroded craters and found they were up to ∼103 m Myr-1-equivalent to erosion rates of wet-based glaciers on Earth. This is several orders of magnitude higher than previous estimates of erosion by VFF (10-2-101 m Myr-1), which themselves are roughly equivalent to cold-based glaciers on Earth. Such erosion rates are sufficient to erase previously existing landforms, such as martian gullies. We hypothesise, therefore, that the pasted-on terrain is a glacial deposit, overturning its previous interpretation as an airfall deposit of ice nucleated on dust. We maintain the interpretation of the arcuate ridges as moraines, but further conclude that they are likely the result of glaciotectonic deformation of sub-marginal and proglacial sediment in the presence of sediment pore-water. We do not support the generation of large quantities of glacial meltwater because it would have broken-up and degraded the arcuate ridges and pasted-on terrain an produced a suite of landforms (e.g., hummocky moraine, lacustrine forms, outwash plains, eskers) which are not observed
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