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71.
John Wilson Stewart Fotheringham Gary Hunter Jochen Albrecht 《Transactions in GIS》2007,11(4):479-481
72.
Ming?FangEmail author Bruce?A.?Albrecht Virendra?P.?Ghate Pavlos?Kollias 《Boundary-Layer Meteorology》2014,150(3):341-360
Comprehensive, ground-based observations from the US Department of Energy Atmospheric Radiation Measurements program Southern Great Plains site are used to study the variability of turbulence forcings and cloud-scale turbulence structures in a continental stratocumulus cloud. The turbulence observations are made from an upward facing cloud (35 GHz) Doppler radar. Cloud base and liquid water path are characterized using a lidar at the surface and a microwave radiometer. The turbulence characterizations are compared and contrasted with those observed in marine stratocumulus clouds. During the 16-h observation period used in this study the cloud-base and cloud-top heights evolve with time and changes in liquid water path observed by the radiometer are consistent with variations in cloud depth. Unlike marine stratocumulus clouds, a diurnal cycle of cloud thickness and liquid water path is not observed. The observed surface latent, sensible, and virtual sensible heat fluxes and the radiative fluxes exhibit a diurnal cycle with values increasing from sunrise to afternoon and decreasing afterwards. During the night, the sensible heat, virtual sensible heat and the net radiative fluxes at the surface are slightly negative. Solar radiative heating prevails in the cloud layer during the day and strong radiative cooling exists at cloud top even during the day. Unlike marine stratocumulus, surface heating described by the convective velocity scale \(W_\mathrm{s}^{*}\) and cloud-top cooling described by \(W_\mathrm{r}^{*}\) are both important in driving the in-cloud turbulence during the day, whereas cloud-top cooling is the exclusive contributor during the night. The combined \(W_\mathrm{s}^{*}\) and \(W_\mathrm{r}^{*}\) (the total velocity scale \(W_\mathrm{t}^{*})\) provides a useful way to track the evolution of the turbulence structure in the cloud. The variance of the radar-measured radial velocity, which is related to resolved turbulence, follows the diurnal cycle and is consistent with the total velocity scale \(W_\mathrm{t}^{*}\) variations. It is higher during the day and lower during the night, which is contrary to that in marine stratocumulus. The \(W_\mathrm{t}^{*}\) values are lowest around sunset when the radiative cooling is also small due to upper-level clouds observed above the low-level stratus. The vertical distribution of the variance results from the surface heating during the day and cloud-top cooling during the night. The squared spectrum width, which is related to turbulence structures within the radar sampling volume (unresolved turbulence) also follows the diurnal cycle. Its vertical distribution indicates that the unresolved turbulence more closely relates to the processes near cloud top. Turbulence in the cloud requires about an hour to respond to the external forcings of surface heating and cloud-top radiative cooling. Positive skewness prevails during the day and negative skewness prevails at night with a sharp transition around sunset. Resolved turbulence dominates near cloud base whereas unresolved turbulence dominates near cloud top. The turbulence characteristics and variability defined in this study can be used to evaluate the time evolution of turbulence structures in large eddy simulation forced by surface and cloud-top radiative forcings. 相似文献
73.
Regional mean sea level changes in the German Bight are considered. Index time series derived from 15 tide gauge records are
analysed. Two different methods for constructing the index time series are used. The first method uses arithmetic means based
on all available data for each time step. The second method uses empirical orthogonal functions. Both methods produce rather
similar results for the time period 1924–2008. For this period, we estimate that regional mean sea level increased at rates
between 1.64 and 1.74 mm/year with a 90% confidence range of 0.28 mm/year in each case. Before 1924, only data from a few
tide gauges are available with the longest record in Cuxhaven ranging back till 1843. Data from these tide gauges, in particular
from Cuxhaven, thus receive increasingly more weight when earlier years are considered. It is therefore analysed to what extent
data from Cuxhaven are representative for the regional sea level changes in the German Bight. While this cannot be clarified
before 1924, it is found that this is not the case from 1924 onwards when changes in Cuxhaven can be compared to that derived
from a larger data set. Furthermore, decadal variability was found to be substantial with relatively high values towards the
end of the analysis period. However, these values are not unusual when compared to earlier periods. 相似文献
74.
Robert G. Mann Seb Oliver Ruth Carballo Alberto Franceschini Michael Rowan-Robinson Alan F. Heavens Maria Kontizas David Elbaz Anastasios Dapergolas Evanghelos Kontizas Gian Luigi Granato Laura Silva Dimitra Rigopoulou J. Ignacio Gonzalez-Serrano Aprajita Verma Steve Serjeant reas Efstathiou Paul P. van der Werf 《Monthly notices of the Royal Astronomical Society》2002,332(3):549-574
75.
Leonhard Ganzer Viktor Reitenbach Dieter Pudlo Daniel Albrecht Arron Tchouka Singhe Kilian Nhungong Awemo Joachim Wienand Reinhard Gaupp 《Acta Geotechnica》2014,9(1):39-47
The feasibility of CO2 storage and enhanced gas recovery (EGR) effects in the mature Altmark natural gas field in Central Germany has been studied in this paper. The investigations were comprehensive and comprise the characterization of the litho- and diagenetic facies, mineral content, geochemical composition, the petrophysical properties of the reservoir rocks with respect to their potential reactivity to CO2 as well as reservoir simulation studies to evaluate the CO2 wellbore injectivity and displacement efficiency of the residual gas by the injected CO2. The Rotliegend sediments of the Altmark pilot injection area exhibit distinct mineralogical, geochemical, and petrophysical features related to litho- and diagenetic facies types. The reservoir rock reactivity to CO2 has been studied in autoclave experiments and associated effects on two-phase transport properties have been examined by means of routine and special core analysis before and after the laboratory runs. Dissolution of calcite and anhydrite during the short-term treatments leading to the enhancements of permeability and porosity as well as stabilization of the water saturation relevant for CO2 injection have been observed. Numerical simulation of the injection process and EGR effects in a sector of the Altmark field coupled with a wellbore model revealed the possibility of injecting the CO2 gas at temperatures as low as 10 °C and pressures around 40 bar achieving effective inflow in the reservoir without phase transition in the wellbore. The small ratio of injected CO2 volume versus reservoir volume indicated no significant EGR effects. However, the retention and storage capacity of CO2 will be maximized. The migration/extension of CO2 varies as a function of heterogeneity both in the layers and in the reservoir. The investigation of CO2 extension and pressure propagation suggested no breakthrough of CO2 at the prospective production well during the 3-year injection period studied. 相似文献
76.
77.
Jim Braun Jon Dumm Francesco De Palma Chad Finley Albrecht Karle Teresa Montaruli 《Astroparticle Physics》2008,29(4):299-305
Neutrino telescopes are moving steadily toward the goal of detecting astrophysical neutrinos from the most powerful galactic and extragalactic sources. Here we describe analysis methods to search for high energy point-like neutrino sources using detectors deep in the ice or sea. We simulate an ideal cubic kilometer detector based on real world performance of existing detectors such as AMANDA, IceCube, and ANTARES. An unbinned likelihood ratio method is applied, making use of the point spread function and energy distribution of simulated neutrino signal events to separate them from the background of atmospheric neutrinos produced by cosmic ray showers. The unbinned point source analyses are shown to perform better than binned searches and, depending on the source spectral index, the use of energy information is shown to improve discovery potential by almost a factor of two. 相似文献
78.
Kalin Kouzmanov Robert Moritz Albrecht von Quadt Massimo Chiaradia Irena Peytcheva Denis Fontignie Claire Ramboz Kamen Bogdanov 《Mineralium Deposita》2009,44(6):611-646
Vlaykov Vruh–Elshitsa represents the best example of paired porphyry Cu and epithermal Cu–Au deposits within the Late Cretaceous
Apuseni–Banat–Timok–Srednogorie magmatic and metallogenic belt of Eastern Europe. The two deposits are part of the NW trending
Panagyurishte magmato-tectonic corridor of central Bulgaria. The deposits were formed along the SW flank of the Elshitsa volcano-intrusive
complex and are spatially associated with N110-120-trending hypabyssal and subvolcanic bodies of granodioritic composition.
At Elshitsa, more than ten lenticular to columnar massive ore bodies are discordant with respect to the host rock and are
structurally controlled. A particular feature of the mineralization is the overprinting of an early stage high-sulfidation
mineral assemblage (pyrite ± enargite ± covellite ± goldfieldite) by an intermediate-sulfidation paragenesis with a characteristic
Cu–Bi–Te–Pb–Zn signature forming the main economic parts of the ore bodies. The two stages of mineralization produced two
compositionally different types of ores—massive pyrite and copper–pyrite bodies. Vlaykov Vruh shares features with typical
porphyry Cu systems. Their common geological and structural setting, ore-forming processes, and paragenesis, as well as the
observed alteration and geochemical lateral and vertical zonation, allow us to interpret the Elshitsa and Vlaykov Vruh deposits
as the deep part of a high-sulfidation epithermal system and its spatially and genetically related porphyry Cu counterpart,
respectively. The magmatic–hydrothermal system at Vlaykov Vruh–Elshitsa produced much smaller deposits than similar complexes
in the northern part of the Panagyurishte district (Chelopech, Elatsite, Assarel). Magma chemistry and isotopic signature
are some of the main differences between the northern and southern parts of the district. Major and trace element geochemistry
of the Elshitsa magmatic complex are indicative for the medium- to high-K calc-alkaline character of the magmas. 87Sr/86Sr(i) ratios of igneous rocks in the range of 0.70464 to 0.70612 and 143Nd/144Nd(i) ratios in the range of 0.51241 to 0.51255 indicate mixed crustal–mantle components of the magmas dominated by mantellic signatures.
The epsilon Hf composition of magmatic zircons (+6.2 to +9.6) also suggests mixed mantellic–crustal sources of the magmas.
However, Pb isotopic signatures of whole rocks (206Pb/204Pb = 18.13–18.64, 207Pb/204Pb = 15.58–15.64, and 208Pb/204Pb = 37.69–38.56) along with common inheritance component detected in magmatic zircons also imply assimilation processes of
pre-Variscan and Variscan basement at various scales. U–Pb zircon and rutile dating allowed determination of the timing of
porphyry ore formation at Vlaykov Vruh (85.6 ± 0.9 Ma), which immediately followed the crystallization of the subvolcanic
dacitic bodies at Elshitsa (86.11 ± 0.23 Ma) and the Elshitsa granite (86.62 ± 0.02 Ma). Strontium isotope analyses of hydrothermal
sulfates and carbonates (87Sr/86Sr = 0.70581–0.70729) suggest large-scale interaction between mineralizing fluids and basement lithologies at Elshitsa–Vlaykov
Vruh. Lead isotope compositions of hydrothermal sulfides (206Pb/204Pb = 18.432–18.534, 207Pb/204Pb = 15.608–15.647, and 208Pb/204Pb = 37.497–38.630) allow attribution of ore-formation in the porphyry and epithermal deposits in the Southern Panagyurishte
district to a single metallogenic event with a common source of metals. 相似文献
79.
Maarten Haest Philippe Muchez Stijn Dewaele Adrian J. Boyce Albrecht von Quadt Jens Schneider 《Mineralium Deposita》2009,44(5):505-522
The Dikulushi Cu–Ag vein-type deposit is located on the Kundelungu Plateau, in the southeastern part of the Democratic Republic
of Congo (D.R.C.). The Kundelungu Plateau is situated to the north of the Lufilian Arc that hosts the world-class stratiform
Cu–Co deposits of the Central African Copperbelt. A combined petrographic, fluid inclusion and stable isotope study revealed
that the mineralisation at Dikulushi developed during two spatially and temporally distinct mineralising episodes. An early
Cu–Pb–Zn–Fe mineralisation took place during the Lufilian Orogeny in a zone of crosscutting EW- and NE-oriented faults and
consists of a sequence of sulphides that precipitated from moderate-temperature, saline H2O–NaCl–CaCl2-rich fluids. These fluids interacted extensively with the country rocks. Sulphur was probably derived from thermochemical
reduction of Neoproterozoic seawater sulphate. Undeformed, post-orogenic Cu–Ag mineralisation remobilised the upper part of
the Cu–Pb–Zn–Fe mineralisation in an oxidising environment along reactivated and newly formed NE-oriented faults in the eastern
part of the deposit. This mineralisation is dominated by massive Ag-rich chalcocite that precipitated from low-temperature
H2O–NaCl–KCl fluids, generated by mixing of moderate- and low-saline fluids. The same evolution in mineralisation assemblages
and types of mineralising fluids is observed in three other Cu deposits on the Kundelungu Plateau. Therefore, the recognition
of two distinct types of (vein-type) mineralisation in the study area has a profound impact on the exploration in the Kundelungu
Plateau region. The identification of a Cu–Ag type mineralisation at the surface could imply the presence of a Cu–Pb–Zn–Fe
mineralisation at depth. 相似文献
80.
Managing Ontong Java: Social institutions for production and governance of atoll resources in Solomon Islands 总被引:2,自引:2,他引:0
Tim Bayliss-Smith Katherine V. Gough reas Egelund Christensen Søren Pilgaard Kristensen 《Singapore journal of tropical geography》2010,31(1):55-69
This paper explores the changing nature of social institutions and organizations for resource management on Ontong Java and their central role in maintaining livelihoods. Using detailed field data for three time periods, 1970–72, 1986 and 2006–07, and drawing on earlier secondary data, a longitudinal analysis of changes in governance and livelihoods is undertaken. Increased exploitation of marine resources has widened the resource base and increased people's access to goods and services. Following the ban in 2005 on the bêche-de-mer trade, however, livelihoods have reverted to being more subsistence oriented. For almost two decades after 1978, a communal organization, the Area Council, succeeded in regulating exploitation of the atoll's marine resources to ensure sustainable use, but in the 1990s it collapsed. In addition there was a paralysis of institutions that had once settled land disputes. This failure of atoll governance is a greater threat to future 'sustainability' than the usual processes that are invoked for atolls and small islands generally. As the Solomon Islands state is also failing, we argue that local institutions and organizations have a vital role to play in managing access to resources and the future of livelihoods on Ontong Java atoll. 相似文献