TY  - JOUR
A1  - Förster, Saskia
A1  - Kaden, Klaus
A1  - Förster, Michael
A1  - Itzerott, Sibylle
T1  - Crop type mapping using spectral-temporal profiles and phenological information
JF  - Computers and electronics in agriculture
N2  - 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.
KW  - Crop type mapping
KW  - NDVI temporal profiles
KW  - Multi-temporal
KW  - Phenological correction
KW  - Agro-meteorological data
Y1  - 2012
U6  - https://doi.org/10.1016/j.compag.2012.07.015
SN  - 0168-1699
VL  - 89
IS  - 32
SP  - 30
EP  - 40
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Joshi, Siddharth
A1  - Pingel, Patrick
A1  - Grigorian, Souren
A1  - Panzner, Tobias
A1  - Pietsch, Ullrich
A1  - Neher, Dieter
A1  - Forster, Michael
A1  - Scherf, Ullrich
T1  - Bimodal temperature behavior of structure and mobility in high molecular weight p3ht thin films
N2  - 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.
Y1  - 2009
UR  - http://pubs.acs.org/journal/mamobx
U6  - https://doi.org/10.1021/Ma900021w
SN  - 0024-9297
ER  - 
TY  - JOUR
A1  - Yang, Xiao Hui
A1  - Jaiser, Frank
A1  - Neher, Dieter
A1  - Lawson, PaDreyia V.
A1  - Brédas, Jean-Luc
A1  - Zojer, Egbert
A1  - Güntner, Roland
A1  - Scanduicci de Freitas, Patricia
A1  - Forster, Michael
A1  - Scherf, Ullrich
T1  - Suppression of the keto-emission in polyfluorene light-emitting diodes : Experiments and models
N2  - 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
Y1  - 2004
SN  - 1616-301X
ER  -