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排序方式: 共有433条查询结果,搜索用时 15 毫秒
101.
102.
Hydrogeological Decision Analysis: 1. A Framework 总被引:6,自引:0,他引:6
R. Allan Freeze Joel Massmann Leslie Smith Tony Sperling Bruce James 《Ground water》1990,28(5):738-766
103.
I. L. Jones Volker Heine Maurice Leslie Geoffrey D. Price 《Physics and Chemistry of Minerals》1990,17(3):238-245
The technique of calculating lattice dissociation energies using static, minimum lattice energy, ionic models has been extended to allow for multiple occupancy of the ionic sites. A particular lattice site can have a fraction x of an ionic species A and a fraction y of an ionic species B, where the position of each can be relaxed separately along with the unit cell dimensions until an equilibrium is reached. Various degrees of long and short range order can be modelled. This technique has been applied to the mineral sillimanite, Al2SiO5, to calculate the effect on the lattice energy of (Al, Si) ordering over the tetrahedral sites. It is found using this method that (Al, Si) ordering with space group Pbmn stabilizes the material by 29.25 kcal/mol (Aliv-O-Aliv), with respect to the completely disordered material. 相似文献
104.
This article describes a new general circulation model (GCM) developed jointly by The University of New South Wales (UNSW)
and the University of Hamburg. The model is versatile in that it can be run as a medium-range (1 to 15 days) global numerical
weather prediction (NWP) model; as an extended range (15 to 30 days) NWP model; and as a GCM for periods extending from seasons,
through annual and decadal periods, and beyond. The model can be coupled with ocean models that vary in complexity from simple
"swamp" oceans to complex ocean GCMs. The atmospheric GCM also has a number of novel features, particularly in the numerical
integration scheme which is a high-order, mass-conserving, semi-implicit semi-Lagrangian scheme, thereby removing the stability
restriction on the time-step and allowing efficient long-term integrations. The emphasis here will be on demonstrating that
the new model performs effectively on the usual measures of skill (statistics such as mean errors, root-mean-square errors
and anomaly correlations) in several standard applications upon which new models usually are assessed. These applications
include medium range weather forecasts out to 10 days on a daily basis over a one year period; a limited 10-year simulation
climatology, prediction of atmospheric anomalies using SST anomalies in an El Nino year; and an alternative two-way approach
to regional modelling (the "down-scaling problem") made possible because the unconditional stability of the semi-implicit,
semi-Lagrangian formulation permits large variations in grid spacing without changing the time step size. Finally, the model
is run on a variety of parallel computing platforms and it is shown that near-linear speed-up can be attained. This is significant
for both medium range NWP and very long-term GCM integrations.
Received: 28 February 1996 / Accepted: 30 July 1996 相似文献
105.
Groundwater Discharge as a Source of Dissolved Carbon and Greenhouse Gases in a Subtropical Estuary 总被引:1,自引:0,他引:1
Groundwater may be highly enriched in dissolved carbon species, but its role as a source of carbon to coastal waters is still poorly constrained. Exports of deep and shallow groundwater-derived dissolved carbon species from a small subtropical estuary (Korogoro Creek, Australia, latitude ?31.0478°, longitude 153.0649°) were quantified using a radium isotope mass balance model (233Ra and 224Ra, natural groundwater tracers) under two hydrological conditions. In addition, air-water exchange of carbon dioxide and methane in the estuary was estimated. The highest carbon inputs to the estuary were from deep fresh groundwater in the wet season. Most of the dissolved carbon delivered by groundwater and exported from the estuary to the coastal ocean was in the form of dissolved inorganic carbon (DIC; 687 mmol m?2 estuary day?1; 20 mmol m?2 catchment day?1, respectively), with a large export of alkalinity (23 mmol m?2 catchment day?1). Average water to air flux of CO2 (869 mmol m?2 day?1) and CH4 (26 mmol m?2 day?1) were 5- and 43-fold higher, respectively, than the average global evasion in estuaries due to the large input of CO2- and CH4-enriched groundwater. The groundwater discharge contribution to carbon exports from the estuary for DIC, dissolved organic carbon (DOC), alkalinity, CO2, and CH4 was 22, 41, 3, 75, and 100 %, respectively. The results show that CO2 and CH4 evasion rates from small subtropical estuaries surrounded by wetlands can be extremely high and that groundwater discharge had a major role in carbon export and evasion from the estuary and therefore should be accounted for in coastal carbon budgets. 相似文献
106.
107.
Records of palaeo‐sea level and eruption duration in a coastal tuff ring,Jeju Island,Korea
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Phreatomagmatic volcanoes and their sedimentary products can preserve high‐resolution records of earth surface processes because of their high deposition rate. Songaksan, Jeju Island, Korea, is a phreatomagmatic volcano, which erupted c. 3.7 ka BP in a coastal setting. Its tuff ring preserves a record of intertidal to supratidal facies transition in the basal part, which reveals the position of palaeo‐high‐tide level for at least 13 high‐tide events, and a record of a storm‐surge event in the middle part of the tuff ring, which lasted approximately three tidal cycles. Based on these features, the phreatomagmatic eruption of Songaksan is estimated to have taken place over a month. The sea level at the time was almost identical to that at present. This study shows that coastal phreatomagmatic volcanoes can preserve high‐resolution records of eruption duration and palaeo‐sea level, and can provide accurately levelled and dated data points to the Quaternary sea‐level curve. 相似文献
108.
Leslie Hebb Larry Petro Holland C. Ford David R. Ardila Ignacio Toledo Dante Minniti David A. Golimowski Mark Clampin 《Monthly notices of the Royal Astronomical Society》2007,379(1):63-72
We present high-cadence, high-precision multiband photometry of the young, M1Ve, debris disc star, AU Microscopii. The data were obtained in three continuum filters spanning a wavelength range from 4500 to 6600 Å, plus Hα, over 28 nights in 2005. The light curves show intrinsic stellar variability due to star-spots with an amplitude in the blue band of 0.051 mag and a period of 4.847 d. In addition, three large flares were detected in the data which all occur near the minimum brightness of the star. We remove the intrinsic stellar variability and combine the light curves of all the filters in order to search for transits by possible planetary companions orbiting in the plane of the nearly edge-on debris disc. The combined final light curve has a sampling of 0.35 min and a standard deviation of 6.8 mmag. We performed Monte Carlo simulations by adding fake transits to the observed light curve and find with 95 per cent significance that there are no Jupiter mass planets orbiting in the plane of the debris disc on circular orbits with periods, P ≤ 5 d. In addition, there are no young Neptune like planets (with radii 2.5 times smaller than the young Jupiter) on circular orbits with periods, P ≤ 3 d. 相似文献
109.
110.
Natural Hazards - This research is focused on identifying urban sprawl pattern and extent in two rapidly growing major Ghanaian cities (Accra and Kumasi) and how urban expansion affected heat... 相似文献