35542
2012
2012
eng
30
40
11
32
89
article
Elsevier
Oxford
1
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Crop type mapping using spectral-temporal profiles and phenological information
Spatially explicit multi-year crop information is required for many environmental applications. The study presented here proposes a hierarchical classification approach for per-plot crop type identification that is based on spectral-temporal profiles and accounts for deviations from the average growth stage timings by incorporating agro-meteorological information in the classification process. It is based on the fact that each crop type has a distinct seasonal spectral behavior and that the weather may accelerate or delay crop development. The classification approach was applied to map 12 crop types in a 14,000 km(2) catchment area in Northeast Germany for several consecutive years. An accuracy assessment was performed and compared to those of a maximum likelihood classification. The 7.1% lower overall classification accuracy of the spectral-temporal profiles approach may be justified by its independence of ground truth data. The results suggest that the number and timing of image acquisition is crucial to distinguish crop types. The increasing availability of optical imagery offering a high temporal coverage and a spatial resolution suitable for per-plot crop type mapping will facilitate the continuous refining of the spectral-temporal profiles for common crop types and different agro-regions and is expected to improve the classification accuracy of crop type maps using these profiles.
Computers and electronics in agriculture
10.1016/j.compag.2012.07.015
0168-1699
wos:2011-2013
WOS:000311245300004
Foerster, S (reprint author), GFZ German Res Ctr Geosci, Helmholtz Ctr Potsdam, Sect Remote Sensing, D-14473 Potsdam, Germany., foerster@gfz-potsdam.de; kkaden@uni-potsdam.de; michael.foerster@tu-berlin.de; itzerott@gfz-potsdam.de
German Federal Ministry of Education and Research [0330227]
Saskia Förster
Klaus Kaden
Michael Förster
Sibylle Itzerott
eng
uncontrolled
Crop type mapping
eng
uncontrolled
NDVI temporal profiles
eng
uncontrolled
Multi-temporal
eng
uncontrolled
Phenological correction
eng
uncontrolled
Agro-meteorological data
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
31708
2009
2009
eng
article
1
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Bimodal temperature behavior of structure and mobility in high molecular weight p3ht thin films
We report a temperature dependent crystalline structure of spin-coated thin films of high molecular weight regioregular poly(3-hexylthiophene) (P3HT) (M-n similar to 30000 g/mol) and its correlation with charge carrier mobility. These investigations show a reversible change of the crystalline structure, where the interlayer lattice spacing (100)along the alkyl side chains continuously increases up to a temperature of about 220 degrees C; in contrast, the in-plane pi-pi distance reduces with increasing temperature. These changes in structure are reversible and can be repeated several times. The temperature-induced structural properties differ for thick and thin films, pointing to a surface/interface role in stabilization of the layer morphology. In contrast to the structural changes, the carrier mobility is rather constant in the temperature range from room temperature up to 100-120 degrees C, followed by a continuous decrease. For thick layers this drop is significant and the transistor performance almost vanishes at high temperature, however, it completely recovers upon cooling back to roorn temperature. The drop of the charge carrier mobility at higher temperatures is in contrast with expectations front the structural studies, considering the increase of crystalline fraction of the polycrystalline layer. our electrical measurements Underscore that the reduction of the macroscopic mobility is mostly caused by it pronounced decrease of the intergrain transport. The thermally induced crystallization along(100) direction and the creation of numerous small crystallites at the film-substrate interface reduce the number of long polymer chain, bridging crystalline domains, which ultimately limits the macroscopic charge transport.
http://pubs.acs.org/journal/mamobx
10.1021/Ma900021w
0024-9297
allegro:1991-2014
10108046
Macromolecules. - ISSN 0024-9297. - 42 (2009), 13, S. 4651 - 4660
Siddharth Joshi
Patrick Pingel
Souren Grigorian
Tobias Panzner
Ullrich Pietsch
Dieter Neher
Michael Forster
Ullrich Scherf
Institut für Physik und Astronomie
Referiert
15454
2004
2004
eng
article
1
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Suppression of the keto-emission in polyfluorene light-emitting diodes : Experiments and models
The spectral characteristics of polyfluorene (PF)-based light-emitting diodes (LEDs) containing a defined low concentration of either keto-defects or of the polymer poly(9.9-octylfuorene-co-benzothiadiazole) (F8BT) are preseneted. Both types of blend layers were tested in different device configurations with respect to the relative and absolute intensities of green blue emission components. It is shown that blending hole-transporting molecules into the emission layer at low concentration or incorporation of a suitable hole-transport layer reduces the green emission contribution in the electroluminescence (EL) spectrum of the PF:F8BT blend, which is similar to what is observed for the keto- containing PF layer. We conclude that the keto-defects in PF homopolymer layers mainly constitute weakly emissive electron traps, in agreement with the results of quantum-mechanical calculations
1616-301X
allegro:1991-2014
10104623
Advanced Functional Materials. - ISSN 1616-301X. - 14 (2004), 11, S. 1097 - 1104
Xiao Hui Yang
Frank Jaiser
Dieter Neher
PaDreyia V. Lawson
Jean-Luc Brédas
Egbert Zojer
Roland Güntner
Patricia Scanduicci de Freitas
Michael Forster
Ullrich Scherf
Institut für Physik und Astronomie
Referiert
Institut für Physik