Correction of ozone influence on TOA radiance

An accurate atmospheric correction (AC) of Earth remote-sensing data in the spectral region 450–800 nm has to account for the ozone gas absorption influence. Usual operational AC codes employ a fixed ozone concentration corresponding to a climatologic average for a certain region and season, e.g. the mid-latitude summer atmosphere of the Moderate Resolution Atmospheric Transmission (MODTRAN) code. The reasons for a fixed ozone column are that ozone does not vary rapidly on a spatial and temporal scale, and additionally, the look-up table (LUT) size for AC is already big. This means that another degree of freedom for the ozone parameter would dramatically increase the size of the LUT database and the time required for LUT interpolation. In order to account for this effect, we use already existing LUTs that were calculated for a certain ozone reference level, e.g. an ozone column of g = 330 Dobson Units (DU) for MODTRAN’s mid-latitude summer atmosphere. Then the deviation of the top-of-atmosphere (TOA) radiance ΔL(g) from the reference level L(g = 330) is calculated as a function of solar and view geometries. The calculation is performed for a set of 36 wavelengths in the ozone-sensitive spectrum (450–800 nm) and five ozone columns. The last step computes the linear regression coefficients for each wavelength and geometry. The results are stored in a small table (11 kB). It is shown that the ozone influence is accurately accounted for by multiplying the modelled radiance L(g = 330) with a factor depending on g and wavelength yielding TOA radiance relative errors smaller than 0.5% for a wide range of ozone concentrations between 180 and 500 DU. Selected examples of a sensitivity study of the ozone effect on the retrieval of water constituents demonstrate the need to account for ozone in the AC step.     

Spectral and radiometric requirements for the airborne thermal imaging spectrometer ARES

ARES (Airborne Reflective/Emissive Spectrometer) is an airborne imaging spectrometer for remote sensing of land surfaces covering the wavelength regions 0.45–2.45?µm and 8–13?µm with 160 channels. The instrument is being built by Integrated Spectronics, financed by DLR and GFZ, and will be available to the scientific community from 2005 on.

This contribution presents the design of the thermal spectrometer covering the 8–13?µm region with 32 channels of 150?nm bandwidth while a separate paper treats the instrument specifications in the solar reflective region. The spectro‐radiometric design is based on scientific requirements derived from application scenarios comprising vegetation, soils of different compositions, and mineral exploration. The corresponding emissivity spectra are input for a simulation model that calculates at‐sensor radiance spectra, resamples them with the channel‐specific response functions, adds different amounts of sensor noise to the signal, and performs a retrieval to get the corresponding noisy surface emissivity spectra. The results of the simulation study indicate that a spectral wavelength accuracy of 3?nm and a sensor noise equivalent temperature of 0.05–0.1?K are required for an accurate retrieval of emissivity spectra.     

Correction of cirrus effects in Sentinel-2 type of imagery

Optical satellite images are often contaminated with cirrus clouds. Thin cirrus can be detected with a channel at 1.38 μm, and an established cirrus removal method exists for visible/near-infrared (VNIR) channels in atmospheric window regions, which was demonstrated with Moderate Resolution Imaging Spectrometer (MODIS) data. This contribution addresses open issues of cirrus correction for Sentinel-2 type of instruments, that is, future spaceborne sensors such as Sentinel-2 or similar instruments. These issues are (i) an extension of the existing technique to account for cirrus during the water vapour retrieval (channel at 0.94 μm) and surface reflectance calculation to avoid reflectance artefacts at 0.94 μm, (ii) a discussion of options concerning cirrus removal in the short-wave infrared (SWIR, channels at 1.6 and 2.2 μm) region and (iii) an analysis of channel parallax (view angle) requirements to achieve a high-quality cirrus removal.     

Mixed-ion linear actuation behaviour of polypyrrole

The linear actuation of polypyrrole (PPy) films polymerized at 0.85 V (versus Ag-wire) and −27 °C in propylene carbonate solutions of tetrabutylammonium trifluoromethanesulfonate (TBACF₃SO₃) was investigated in the same monomer-free electrolyte. The actuation properties were evaluated by electrochemomechanical deformation measurements (ECMD) during cyclic voltammetry and potential step experiments. The ECMD response revealed mixed-ion actuation behaviour for the film, namely the polymer film actuation was dominated by cation movement at potentials less than 0 V and anion movement at potentials greater than 0 V, with film lengthening seen at both potential extremes. It was found that the ratio of cathodic to anodic actuation can be modulated by the scan rate. Longer-term actuation (50 potential steps from −1 V to 0 V, or from 0 V to +1 V), indicated better film stability when cycled in the anodic region. Changing the electropolymerisation potential to a higher value of 1.2 V led to a modification in ECMD characteristics for the PPy/CF₃SO₃ films.     

Messung und Theorie der Wandschubspannung bei Zweiphasenströmung im Rohr

Zusammenfassung Im allgemeinen gilt es als selbstverst?ndlich, da? ein durch ein Rohr str?mendes Medium auf die Rohrwand eine Schubspannung in Richtung der Str?mung übertr?gt. Aus Versuchen und überlegungen geht jedoch hervor, da? bei Zweiphasenstr?mungen im Schwerefeld auf Grund der Vorg?nge an der Wand die Schubspannung u. U. der Hauptstromrichtung entgegengerichtet ist. Auch ergibt sich, da? die dynamisch, d. h. unter Einflu? der Reibung gemessene F?rderh?he einer Pumpe h?her als die hydrostatisch berechnete sein kann. VDI Mitteilung aus dem Institut für kalorische Apparate und K?ltetechnik der Eidgen?ssischen Technischen Hochschule Zürich Herrn Prof. Dr. phil.E. Justi zur Vollendung seines 60. Geburtstags gewidmet.     

Project organization and contract management

The conceptual set-up of project organizations before tendering and contracting and their development and review during contract fulfilment is much more than a primitive art, today. The project organization can be designed and tailored to the actual objectives, phase, services, works, contract partners, and environmental conditions. Highly qualified organizational work is adequate to the important tasks of quality assurance and to using human talents and effort effectively.     

The influence of the die and floating plug geometry on the drawing process of tubing

Nowadays, the development of tube drawing process with a floating plug technique has moved our limit up to the production of thick-walled tubes; production of which still belongs to marginal techniques which are different from drawing of standard tubes. The submitted paper is basically a survey of research in fundamental characteristics of tube drawing with a floating plug with the aim to summarize some important results from the theory, which have not yet been published in any English publication. The purpose of this survey is to fill the gap in English literature to promote transfer and exploitation of knowledge. Research in fundamental characteristics was further developed and conditions under which it is possible to draw thick-walled tubes are defined. Confirmed possibility of thick-walled tubes drawing with support provided by a floating plug having negative overlap is the result of theoretical study and practical verification, which enables further moving of drawing process limit.     

An assessment of discretizations for convection-dominated convection–diffusion equations

The performance of several numerical schemes for discretizing convection-dominated convection–diffusion equations will be investigated with respect to accuracy and efficiency. Accuracy is considered in measures which are of interest in applications. The study includes an exponentially fitted finite volume scheme, the Streamline-Upwind Petrov–Galerkin (SUPG) finite element method, a spurious oscillations at layers diminishing (SOLD) finite element method, a finite element method with continuous interior penalty (CIP) stabilization, a discontinuous Galerkin (DG) finite element method, and a total variation diminishing finite element method (FEMTVD). A detailed assessment of the schemes based on the Hemker example will be presented.     

Three-dimensional Visualization of the Magnetic Microstructure in Bulk Fe-6.6 Pct Si

Magnetic materials such as Fe-Si alloys are magnetized by the rearrangement of their magnetic microstructure and domain wall motion. Understanding magnetic microstructures in the interior of a ferromagnet is essential for the control and reduction of energy losses in electrical devices. The three-dimensional magnetic microstructure of solids is still unknown due to the lack of an appropriate observation technique, and the magnetic domain wall structure inside a ferromagnet has never been observed with sufficiently high resolution. The first observation of the 3D magnetic microstructure of an Fe-6.6 pct Si alloy with a high spatial resolution is reported. The domain walls known to exist inside positive anisotropy cubic materials, i.e., the 180-deg domain walls and the 90-deg domain walls, were analyzed for the first time. The structure and orientation of the domain walls were found to be very different from the prediction of current theoretic models.