Solar-Blind Diamond Detectors for Lyra, the Solar VUV Radiometer on Board Proba II     

A. Benmoussa  J.-F. Hochedez  W. K. Schmutz  U. SchÜhle  M. NeslÁdek  Y. Stockman  U. Kroth  M. Richter  A. Theissen  Z. Remes  K. Haenen  V. Mortet  S. Koller  J. P. Halain  R. Petersen  M. Dominique  M. D’Olieslaeger 《Experimental Astronomy》2003,16(3):141-148

Fabrication, packaging and experimental results on the calibration of metal-semiconductor-metal (MSM) photodetectors made on diamond are reported. LYRA (Lyman- RAdiometer onboard PROBA-2) will use diamond detectors for the first time in space for a solar physics instrument. A set of measurement campaigns was designed to obtain the XUV-to-VIS responsivity of the devices and other characterizations. The measurements of responsivity in EUV and VUV spectral ranges (40–240 nm) have been carried out by the Physkalisch-Technische Bundesanstalt (PTB) in Germany at the electron storage ring BESSY II. The longer wavelength range from 210 to 1127 nm was measured with monochromatic light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a photoresponse which lie in the 35–65 mA/W range at 200 nm (corresponding to an external quantum efficiency of 20–40%) and indicate a visible rejection ratio (200–500 nm) higher than four orders of magnitude.  相似文献   

PGE distribution in massive sulfides from the PACMANUS hydrothermal field, eastern Manus basin, Papua New Guinea: implications for PGE enrichment in some ancient volcanogenic massive sulfide deposits     

Jan Pašava  Anna Vymazalová  Sven Petersen  Peter Herzig 《Mineralium Deposita》2006,41(2):201-202

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Rapid evolution of a jet streak circulation in a pre-convective environment     

P. J. Kocin  L. W. Uccellini  R. A. Petersen 《Meteorology and Atmospheric Physics》1986,35(3):103-138

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Verification of the pollutant transport model ‘MODIS’ using EPRI plains site data from a tall stack     

G. Petersen  D. Eppel  H. Grassl 《Boundary-Layer Meteorology》1987,41(1-4):265-277

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Modelling of hydrocyclone performance based on spray profile analysis     

J. S. J. van Deventer  D. Feng  K. R. P. Petersen  C. Aldrich 《International Journal of Mineral Processing》2003,70(1-4):183-203

Spray profile measurements can be used to calculate the underflow rate, and consequently, be related to hydrocyclone performance. The flow geometry of the spray discharge is found to arise from velocity patterns at the outlet orifice. Through a videographic example of an industrial hydrocyclone, it is shown that underflow profiles are typically parabolic, a feature which is indicative of the velocity at which the fluid exits. The inclusion of gravity in this model clearly highlights deficiencies in currently used models. Moreover, an intimate knowledge of factors affecting the profiles of the underflow of a cyclone is essential for the correct interpretation of videographic images. Subsequently, image data are used to estimate outlet velocities, which give an excellent insight into various fluid mechanical phenomena that are not appreciated by analysing basic operational variables. The exit velocities are used to calculate underflow rates, which are related to mass recovery in the underflow.  相似文献   

Magnetic properties and Mössbauer spectra of urban atmospheric particulate matter: a case study from Munich, Germany     

A. R. Muxworthy  E. Schmidbauer  N. Petersen 《Geophysical Journal International》2002,150(2):558-570

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The role of roadcuts, quarries, and other artificial exposures in geomorphology education     

James F. Petersen 《Geomorphology》2002,47(2-4)

Quarries and roadcuts are time-honored stopping points on geoscience field trips. Artificial exposures are good field sites for learning because of their accessibility, and the potential range of features they present for first-hand examination. On undergraduate-level field excursions, site discussions typically center on stratigraphic unit identification, correlation, depositional environments, paleontology, facies relationships, lithology, mineralogy, and/or structural features. It is rare (in my experience) for geomorphologic features and relationships to be the focus of attention, or even to receive more than passing mention. Yet, roadcuts and quarries offer much potential for learning about basic landform features, forms, and processes. This paper, with illustrated examples, discusses five general characteristics, present in artificial exposures, that offer opportunities for learning about geomorphology. (1) Roadcuts and quarries expose cross sections, not only of structure, but also of landforms, illustrating relationships between subsurface geology and the surface landscape. (2) The faces of roadcuts and quarries are anthropomorphic landforms of relatively well-known age and original form, two qualities that provide opportunities for discussing erosional modification over time. (3) These sites are generally nodes of intense geomorphic activity, useful for directly observing landform processes and their effects. The intensity of degradational and depositional processes at artificial exposures often produces (4) landform miniatures, and (5) landform analogs, both providing instructional examples or illustrations of geomorphic features. In addition to their utility to other geoscience sub-disciplines, roadcuts and quarries also offer important opportunities for students to learn about basic geomorphologic concepts, processes, and forms.  相似文献   

Seismo-acoustic signals associated with degassing explosions recorded at Shishaldin Volcano,Alaska, 2003–2004     

Tanja Petersen  Stephen R. McNutt 《Bulletin of Volcanology》2007,69(5):527-536

In summer 2003, a Chaparral Model 2 microphone was deployed at Shishaldin Volcano, Aleutian Islands, Alaska. The pressure sensor was co-located with a short-period seismometer on the volcano’s north flank at a distance of 6.62 km from the active summit vent. The seismo-acoustic data exhibit a correlation between impulsive acoustic signals (1–2 Pa) and long-period (LP, 1–2 Hz) earthquakes. Since it last erupted in 1999, Shishaldin has been characterized by sustained seismicity consisting of many hundreds to two thousand LP events per day. The activity is accompanied by up to ∼200 m high discrete gas puffs exiting the small summit vent, but no significant eruptive activity has been confirmed. The acoustic waveforms possess similarity throughout the data set (July 2003–November 2004) indicating a repetitive source mechanism. The simplicity of the acoustic waveforms, the impulsive onsets with relatively short (∼10–20 s) gradually decaying codas and the waveform similarities suggest that the acoustic pulses are generated at the fluid–air interface within an open-vent system. SO₂ measurements have revealed a low SO₂ flux, suggesting a hydrothermal system with magmatic gases leaking through. This hypothesis is supported by the steady-state nature of Shishaldin’s volcanic system since 1999. Time delays between the seismic LP and infrasound onsets were acquired from a representative day of seismo-acoustic data. A simple model was used to estimate source depths. The short seismo-acoustic delay times have revealed that the seismic and acoustic sources are co-located at a depth of 240±200 m below the crater rim. This shallow depth is confirmed by resonance of the upper portion of the open conduit, which produces standing waves with f=0.3 Hz in the acoustic waveform codas. The infrasound data has allowed us to relate Shishaldin’s LP earthquakes to degassing explosions, created by gas volume ruptures from a fluid–air interface.  相似文献   

In-situ registration of oxygen utilization at sediment-water interfaces     

H.P. Hansen  K. Grasshoff  J. Petersen 《Marine Chemistry》1980,10(1):47-54

A polyacrylic dome was anchored over natural sediments, enclosing a water volume of 0.125 m³ over an area of 0.45 m² of sediment. A vertical convection was produced in the dome, by means of a small pump, to prevent formation of gradients. Oxygen partial pressure and temperature were measured at 20-min intervals by an automatic data system and stored on magnetic tape in digitized form. After some days the system was recovered. The data were read by a microprocessor system, interpreted, listed and plotted against time. Chemical and hydrographic data, from a sample taken at the location of the experiment at the instant it was started, were used as calibration data to calculate oxygen utilization of the sediments in the Kiel Bight.  相似文献   

Self-reversal of remanent magnetization in basalts due to partially oxidized titanomagnetites     

David Krása  Valera P. Shcherbakov  Thomas Kunzmann  Nikolai Petersen 《Geophysical Journal International》2005,162(1):115-136

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