Development of the HEFT and NuSTAR focusing telescopes     

Fiona A. Harrison  Finn E. Christensen  William Craig  Charles Hailey  Wayne Baumgartner  C. M. H. Chen  James Chonko  W. Rick Cook  Jason Koglin  Kristin-Kruse Madsen  Michael Pivavoroff  Steven Boggs  David Smith 《Experimental Astronomy》2005,20(1-3):131-137

Hard X-ray/soft gamma-ray astrophysics is on the verge of a major advance with the practical realization of technologies capable of efficiently focusing X-rays above 10 keV. Hard X-ray focusing telescopes can achieve orders of magnitude improvements in sensitivity compared to the instruments based on coded apertures and collimated detectors that have traditionally been employed in this energy band. Compact focal planes enable high-performance detectors with good spectral resolution to be employed in efficient, low-background configurations. We have developed multilayer coated grazing incidence optics and solid state Cadmium Zinc Telluride focal plane systems for the High Energy Focusing Telescope (HEFT) balloon-borne experiment, and for the Nuclear Spectroscopic Telescope Array (NuSTAR) Small Explorer satellite. In this paper we describe the technologies, telescope designs, and performance of both experiments.  相似文献   

Origin of channel systems in the Upper Cretaceous Chalk Group of the Paris Basin   总被引：1，自引：0，他引：1  

Estela V. Esmerode  Finn Surlyk 《Marine and Petroleum Geology》2009,26(8):1338-1349

The Upper Cretaceous Chalk Group of the Anglo-Paris Basin is known to show wedging beds and channel-like features which disrupt the quietly deposited pelagic chalk that covered most of NW Europe in the Late Cretaceous. Two-D reflection seismic data from the Brie region, SE of Paris, show the presence of at least two distinct intra-chalk discordant reflections: a Top Santonian and a Mid-Campanian reflection. These reflections are in places associated with up to 120-m-deep channel-like structures trending preferentially N–S and NW–SE. The Mid-Campanian reflection is also sporadically associated with a massive secondary dolomite layer, the thicknesses of which may reach 110 m. Diagenesis does not seem to account for the formation of the discordant reflections, as there is neither a one-to-one relationship between the dolomite and discordant reflections, nor are there signs of systematic collapse of the Cenozoic succession over the channel-like features as a result of intra-chalk dissolution. Both reflections correlate with indurated chalk layers and hardgrounds, and represent real unconformities. The Mid-Campanian reflection is furthermore associated with a stratigraphic hiatus. A submarine origin is suggested due to the uninterrupted deep-marine chalk facies below and above both unconformities, and the unrealistically large sea-level drop of more than 200 m, which would be necessary for subaerial exposure of the central Paris Basin during the Campanian. The channels are oriented parallel to the margins of the basin, and important bathymetric elements which could induce erosion by slope failure are not observed. The channels are thus interpreted as having formed by strong, mainly slope-parallel bottom currents. Major channeling events are common in the Chalk Group throughout NW Europe and represent palaeoceanographic re-organization of bottom currents, probably driven by changes in sea level and water temperature.  相似文献   

In Memoriam Per-Anders Persson     

Roger Holmberg  Finn Ouchterlony 《Fragblast: International Journal for Blasting and Fragmentation》2001,5(4):197-199

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Simulation of liquefaction beneath an impermeable surface layer     

N. Yoshida  W. D. L. Finn   《Soil Dynamics and Earthquake Engineering》2000,19(5)

A joint element is proposed, which can simulate the three phases of behaviour of an impermeable layer over a liquefied sand layer. The analysis tracks the post-liquefaction reconsolidation of the sand, the simultaneous development of a water film between the layers and the settlements resulting from the subsequent drainage of the water film. The element is incorporated in a finite element program, which can be used to simulate the behaviour of layered systems. The effectiveness of the program is demonstrated by simulation of the performance of a model soil deposit of two layers in a centrifuge test.  相似文献   

Climate change impacts and adaptations: lessons learned from the greater Zambeze River Valley and beyond     

Channing Arndt  Finn Tarp 《Climatic change》2015,130(1):1-8

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Metallographic cooling rates of group IIF iron meteorites     

Kaare L. RASMUSSEN  Henning HAACK  Finn ULFF‐M LLER 《Meteoritics & planetary science》2001,36(7):883-896

Abstract— Metallographic cooling rates have been calculated for all five members of the iron meteorites group IIF using two different techniques. We have determined cooling rates of ～5 °C/Ma based on Ni profiles through the taenite rim enclosing kamacite spindles. Ni profiles through the kamacite phase are less precise cooling rate indicators, but suggest a cooling rate of ～1 °C/Ma within an order of magnitude at lower temperatures (360–400 °C). Based on the kamacite bandwidth and the Ni profiles through the taenite, we estimate that the kamacite nucleated 130–200 °C below the temperature predicted from the phase diagram. The size of and the distance between the large kamacite spindles is found to be consistent with the thermal history that we have determined on the basis of Ni profiles in kamacite and taenite. We find that previously published kamacite bandwidth cooling rates for the five group IIF members are most likely in error because of the presence of large schreibersite spindles in some kamacite spindles and because undercooling of kamacite was ignored. Contrary to previous workers we find that the metallographic cooling rates are consistent with cooling in a common core.  相似文献   

Water level and atmospheric humidity history of Lake Ichkeul (northern Tunisia) during the last 3000 years     

Asma Ben Hamad  Finn A. Viehberg  Afef Khadraoui  Chahira Zaïbi  Yasser Trabelsi  Gloria H. Mouanga  Martin R. Langer  Habib Abida  Fekri Kamoun 《Arabian Journal of Geosciences》2018,11(12):316

Changes in paleoecology and climate of northern Tunisia during the last 3000 years were reconstructed based on the flood history interpreted from a 172-cm sediment core of Lake Ichkeul (NW Tunisia). Seven wet/dry episodes were identified based on biological (ostracods, foraminifera and mollusks) and biotic indices (H and E index, species richness and abundance). These proxy-based environmental changes were supported by correspondence analyses (CAs) and ecophenotypic responses of the brackish taxon Cyprideis torosa in addition to a grain-size study. Two dry episodes were identified in the lower (EP1) and upper (EP7) parts of the core. These were marked by the dominance of the brackish ostracod C. torosa. High water salinity was indicated by the presence of the brackish ostracod Loxoconcha elliptica, the foraminifer Ammonia sp. and lagoonal mollusks. The occurrence of the freshwater ostracods Ilyocypris sp., Herpetocypris sp., Dawinula stevensoni and Limnocythere inopinata was associated with high species richness and ecophenotypic changes of C. torosa valves indicating lower salinity during three major wet episodes (EP2, EP4, and EP6). The ecological and environmental changes, occurring between 3050 and 50 cal. year BP, are most likely linked to an increase of fluvial inputs which are also recognized in several other Mediterranean lakes. The humid episodes were interrupted by two saline periods (EP3 and EP5) during which freshwater ostracod assemblages declined, diversity indices dropped to the lowest values, and fine-grained sediments became dominant. The top of the core is characterized by the remarkable dominance of L. elliptica coupled with C. torosa, the absence of freshwater ostracods, and the changes in grain-size sediment parameters which are most likely the result of anthropogenic activities. The changes in hydrochemistry and sedimentology were attributed to the deepening of the Bizerte navigation canal, main wadis damming, and Tinja sluice construction which mostly occurred in the XX^th century.  相似文献   

Submarine landslide tsunamis: how extreme and how likely?     

Carl B. Harbitz  Finn Løvholt  Hilmar Bungum 《Natural Hazards》2014,72(3):1341-1374

A number of examples are presented to substantiate that submarine landslides have occurred along most continental margins and along several volcano flanks. Their properties of importance for tsunami generation (i.e. physical dimensions, acceleration, maximum velocity, mass discharge, and travel distance) can all gain extreme values compared to their subaerial counterparts. Hence, landslide tsunamis may also be extreme and have regional impact. Landslide tsunami characteristics are discussed explaining how they may exceed tsunamis induced by megathrust earthquakes, hence representing a significant risk even though they occur more infrequently. In fact, submarine landslides may cause potentially extreme tsunami run-up heights, which may have consequences for the design of critical infrastructure often based on unjustifiably long return periods. Giant submarine landslides are rare and related to climate changes or glacial cycles, indicating that giant submarine landslide tsunami hazard is in most regions negligible compared to earthquake tsunami hazard. Large-scale debris flows surrounding active volcanoes or submarine landslides in river deltas may be more frequent. Giant volcano flank collapses at the Canary and Hawaii Islands developed in the early stages of the history of the volcanoes, and the tsunamigenic potential of these collapses is disputed. Estimations of recurrence intervals, hazard, and uncertainties with today’s methods are discussed. It is concluded that insufficient sampling and changing conditions for landslide release are major obstacles in transporting a Probabilistic Tsunami Hazard Assessment (PTHA) approach from earthquake to landslide tsunamis and that the more robust Scenario-Based Tsunami Hazard Assessment (SBTHA) approach will still be most efficient to use. Finally, the needs for data acquisition and analyses, laboratory experiments, and more sophisticated numerical modelling for improved understanding and hazard assessment of landslide tsunamis are elaborated.  相似文献   

Dynamic characteristics of a base isolated building from ambient vibration measurements and low level earthquake shaking   总被引：3，自引：0，他引：3  

C. E. Ventura  W. D. Liam Finn  J. -F. Lord  N. Fujita 《Soil Dynamics and Earthquake Engineering》2003,23(4):313-322

Ambient vibration tests were conducted on a base-isolated apartment building in Takamatsu, Japan, to determine the mode shapes and the associated natural frequencies and damping ratios at very low levels of excitation. The latest developments in signal analysis for modal decomposition are used to analyze the ambient response data. A finite element model of the building and isolators was calibrated and refined using the experimental results from the ambient vibration tests. This model was then used to simulate the recorded response of the building under excitation from a small earthquake. The finite element model, calibrated by ambient vibration data and the low level of earthquake shaking, provides the starting point for modelling the non-linear response of the building when subjected to strong shaking.  相似文献   

Quaternary coastline evolution of Lake Ohrid (Macedonia/Albania)     

Nadine Hoffmann  Klaus Reicherter  Christoph Grützner  Jochen Hürtgen  Andreas Rudersdorf  Finn A. Viehberg  Martin Wessels 《Central European Journal of Geosciences》2012,4(1):94-110

Lake Ohrid (between FYR of Macedonia and Albania), situated in an active tectonic region of the Balkanides, is characterized by N ?? S trending active faults. To reconstruct the Holocene shoreline evolution we investigated the coastline using sediment cores and geophysical methods to image sedimentary and tectonic structures. We revealed areas of differing sedimentation regimes. The plains north and south of the lake are dominated by clastic input related to climate variations and uplift/erosion, whereas the steep western and eastern margins are controlled by recent tectonics. Furthermore, no evidence for a much higher lake-level during the Holocene was found in the plains north and south of the lake, except rare temporary floodings. This is supported by mappings of the limestone cliffs around Lake Ohrid, which yielded no evidence for abrasional platforms or notches as indicators for past highstands.  相似文献