Calibration facility for airborne imaging spectrometers     

Peter Gege  Jochen Fries  Peter Haschberger  Paul Schtz  Horst Schwarzer  Peter Strobl  Birgit Suhr  Gerd Ulbrich  Willem Jan Vreeling 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(4):387-397

A new facility designed to perform calibration measurements of airborne imaging spectrometers was established at the German Aerospace Center (DLR) in Oberpfaffenhofen. This Calibration Home Base (CHB) is optimized to characterize radiometrically, spectrally, and geometrically the APEX (Airborne Prism Experiment) imaging spectrometer, which is currently being developed under the authority of the European Space Agency (ESA). It however can be used for other optical sensors as well. Computer control of major laboratory equipment allows automation of time consuming measurements. In APEX configuration (wavelength range: 380 to 2500 nm, instantaneous field of view: 0.48 mrad, field of view: ±14) spectral measurements can be performed to a wavelength uncertainty of ±0.15 nm, geometric measurements at increments of 0.0017 mrad across track and 0.0076 mrad along track, and radiometric measurements to an uncertainty of ±3% relative to national standard. The CHB can be adapted to similar sensors (including those with thermal infrared detectors) by exchanging the monochromator’s lamp, the gratings and the filters, and by adjusting the distance between the sensor and folding mirror.  相似文献   

Reply on ‘Sequence stratigraphy of an argillaceous,deepwater basin plain succession: Vischkuil Formation (Permian), Karoo Basin,South Africa’ from van der Merwe,Flint and Hodgson (Marine and Petroleum Geology, 2010, 27, 321–333)     

Willem C. van der Merwe  Stephen S. FlintDavid M. Hodgson 《Marine and Petroleum Geology》2010

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Neoichnology and implications for stratigraphy of reworked Upper Oligocene oysters,Antigua, West Indies     

Stephen K. Donovan  David A.T. Harper  Roger W. Portell  Willem Renema 《Proceedings of the Geologists' Association. Geologists' Association》2014

The Late Oligocene oyster Hyotissa antiguensis (Brown) is locally common in the Antigua Formation of Hughes Point, eastern Antigua, Lesser Antilles; it was not commonly bored at that time. Its valves and shells are robust, and reworked into the shallow water near-shore environment in Antigua; it could potentially be incorporated into younger rocks. Its neoichnology includes clues that would facilitate identification of these oysters as reworked fossils. The suite of modern borings found in these specimens includes common Caulostrepsis taeniola Clarke, Gastrochaenolites isp. cf. G. turbinatus Kelly and Bromley and Entobia isp., and rare Oichnus simplex Bromley and Rogerella? isp. The latter three taxa are limited to oyster shell substrates. Of the common ichnotaxa, Caulostrepsis and Gastrochaenolites are particularly prominent in limestone clasts and limestone cemented to oyster shells, which would be an indicator of reworking if found in a post-Oligocene lithified deposit. Caulostrepsis and Gastrochaenolites are relatively less common in oyster shells and valves, and in many specimens are seen to terminate against the shell. Entobia is the only common boring limited to the shell substrate. The fidelity of preservation of modern borings is also superior in limestone clasts. This suite of borings is comparable with those found in the Neogene of the Antillean region.  相似文献   

Building pit dewatering: application of transient analytic elements     

Zaadnoordijk WJ 《Ground water》2006,44(1):106-110

Analytic elements are well suited for the design of building pit dewatering. Wells and drains can be modeled accurately by analytic elements, both nearby to determine the pumping level and at some distance to verify the targeted drawdown at the building site and to estimate the consequences in the vicinity. The ability to shift locations of wells or drains easily makes the design process very flexible. The temporary pumping has transient effects, for which transient analytic elements may be used. This is illustrated using the free, open-source, object-oriented analytic element simulator Tim(SL) for the design of a building pit dewatering near a canal. Steady calculations are complemented with transient calculations. Finally, the bandwidths of the results are estimated using linear variance analysis.  相似文献   

Comment on `Tectono‐sedimentary evolution of lower to middle Miocene halfgraben basins related to an extensional detachment fault (western Crete,Greece)' by M. Seidel,E. Seidel and B. Stöckhert     

Douwe J. J. Van Hinsbergen  Willem‐Jan Zachariasse  Anne R. Fortuin 《地学学报》2008,20(5):414-416

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Megamasers: Molecular Diagnostics of the Nuclear Ism     

Willem A. Baan  Hans-R. Klöckner 《Astrophysics and Space Science》2005,295(1-2):263-275

Molecular emissions are powerful tracers of intense heating and star-formation processes in galactic nuclei. In this paper we consider the characteristics of molecular Megamaser emission among the population of (Ultra-) Luminous Infrared Galaxies that are powered by intense star-formation or accretion onto a massive compact object. In addition, we consider the systematic behavior of the line emission of high-density tracer molecules. An evolutionary scenario is presented for ULIRGs that may explain the molecular line ratios observed in the population of FIR galaxies.  相似文献   

The effect of a northward shift in the southern hemisphere westerlies on the global ocean     

Willem P. Sijp  Matthew H. England 《Progress in Oceanography》2008,79(1):1-19

We examine the effect of a northward shift in the position of the southern hemisphere subpolar westerly winds (SWWs) on the vertical and horizontal distribution of temperature and salinity in the world ocean. A northward shift of the SWWs causes a latitudinal contraction of the subpolar gyres in the southern hemisphere (SH). In the Indian and Pacific, this leads to subsurface warming in the subtropical thermocline. As the southern margins of the gyres move into latitudes characterised by warmer surface air temperature (SAT), the layers at mid-depth below 400 m depth become ventilated by warmer water. We characterize the approximation of the ventilated thermocline in our coarse resolution model using a set of passive tracer experiments, and illustrate how the northward shift in the SWWs causes an equatorward shift in the latitude of origin of water ventilating layers deeper than 400 m in the Indian and Pacific, leaving the total surface ventilation of the upper 1200 m unchanged. In contrast, the latitudinal constraint on the Antarctic Circumpolar Current posed by the Drake Passage causes a cooling and freshening throughout the Atlantic thermocline; here, subsurface thermocline water originates from higher latitudes under the wind shift. On longer timescales Atlantic cooling and freshening is reinforced by a reduction in North Atlantic Deep Water (NADW) formation and surface salinification of the Indian and Pacific Oceans. In effect, the latitude of zero wind stress curl in the SWWs regulates the relative importance of the “cold water route” via the Drake Passage and the “warm water route” associated with thermocline water exchange via the Indian Ocean. Thus, a more northward location of the SWWs corresponds with a reduced salinity contrast between the Indian/ Pacific Oceans and the Atlantic. This results in reduced NADW formation. Also, a more northward location of the SWWs facilitates the injection of cool fresh Antarctic Intermediate Water into the South Atlantic subtropical gyre. Beyond these changes, on a millennial timescale, the deep ocean warms throughout the water column in response to the wind shift. Global salinity stratification also becomes less stable, as more saline water remains at the surface and accumulates in the Indian and Pacific thermocline. The freshening of the deep ocean reflects a reduced stirring of the global ocean due to reduced net circulation arising from a misalignment between the westerlies and the topographically constrained ACC. Our results lend support to the idea that a more equatorward location of the SWW maximum during glacial climates contributed to cooler and fresher conditions in the Atlantic, inhibiting NADW.  相似文献   

Persistence of Artemisia steppe in the Tangra Yumco Basin,west-central Tibet,China: despite or in consequence of Holocene lake-level changes?     

Sabine Miehe  Georg Miehe  Jacqueline F. N. van Leeuwen  Claudia Wrozyna  Willem O. van der Knaap  La Duo  Torsten Haberzettl 《Journal of Paleolimnology》2014,51(2):267-285

The closed Tangra Yumco Basin underwent the strongest Quaternary lake-level changes so far recorded on the Tibetan Plateau. It was hitherto unknown what effect this had on local Holocene vegetation development. A 3.6-m sediment core from a recessional lake terrace at 4,700 m a.s.l., 160 m above the present lake level of Tangra Yumco, was studied to reconstruct Holocene flooding phases (sedimentology and ostracod analyses), vegetation dynamics and human influence (palynology, charcoal and coprophilous fungi analyses). Peat at the base of the profile proves lake level was below 4,700 m a.s.l. during the Pleistocene/Holocene transition. A deep-lake phase started after 11 cal ka BP, but the ostracod record indicates the level was not higher than ~4,720 m a.s.l. (180 m above present) and decreased gradually after the early Holocene maximum. Additional sediment ages from the basin suggest recession of Tangra Yumco from the coring site after 2.6 cal ka BP, with a shallow local lake persisting at the site until ~1 cal ka BP. The final peat formation indicates drier conditions thereafter. Persistence of Artemisia steppe during the Holocene lake high-stand resembles palynological records from west Tibet that indicate early Holocene aridity, in spite of high lake levels that may have resulted from meltwater input. Yet pollen assemblages indicate humidity closer to that of present potential forest areas near Lhasa, with 500–600 mm annual precipitation. Thus, the early mid-Holocene humidity was sufficient to sustain at least juniper forest, but Artemisia dominance persisted as a consequence of a combination of environmental disturbances such as (1) strong early Holocene climate fluctuations, (2) inundation of habitats suitable for forest, (3) extensive water surfaces that served as barriers to terrestrial diaspore transport from refuge areas, (4) strong erosion that denuded the non-flooded upper slopes and (5) increasing human influence since the late glacial.  相似文献   

Dynamic Development of Hydrofracture     

Irfan Ghani  Daniel Koehn  Renaud Toussaint  Cees Willem Passchier 《Pure and Applied Geophysics》2013,170(11):1685-1703

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Observations, Effects and Real Time Assessment of the March 11, 2011 Tohoku-oki Tsunami in New Zealand     

Jose C. Borrero  Rob Bell  Claudia Csato  Willem DeLange  Derek Goring  S. Dougal Greer  Vernon Pickett  William Power 《Pure and Applied Geophysics》2013,170(6-8):1229-1248

The great Tohoku-oki earthquake of March 11, 2011 generated a devastating tsunami in the near field as well as substantial far-field effects throughout the Pacific Ocean. In New Zealand, the tsunami was widely observed and instrumentally recorded on an extensive array of coastal tidal gauges and supplemented by current velocity data from two sites. While the tsunami's first arrival was on the morning of March 12 in New Zealand, the strongest effects occurred throughout that afternoon and into the following day. Tsunami effects consisted primarily of rapid changes in water level and associated strong currents that affected numerous bays, harbors, tidal inlets and marine facilities, particularly on the northern and eastern shores of the North Island. The tsunami caused moderate damage and significant overland flooding at one location. The tsunami signal was clearly evident on tide gauge recordings for well over 2 days, clearly illustrating the extended duration of far field tsunami hazards. Real time analysis and modelling of the tsunami through the night of March 11, as the tsunami crossed the Pacific, was used as a basis for escalating the predicted threat level for the northern region of New Zealand. A comparison to recorded data following the tsunami shows that these real time prediction models were accurate despite the coarse near-shore bathymetry used in the assessment, suggesting the efficacy of such techniques for future events from far-field sources.  相似文献