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811.
Aierken Sidike X.-M. Wang Alifu Sawuti H.-J. Zhu I. Kusachi N. Yamashita 《Physics and Chemistry of Minerals》2006,33(8-9):559-566
Natural calcite from Kuerle, Xinjiang, China, shows orange-red fluorescence when exposed to short-wave ultraviolet (UV) light (Hg 253.7 nm). Photoluminescence (PL) emission and excitation spectra of the calcite are observed at room temperature in detail. The PL emission spectrum under 208 nm excitation consists of three bands: two UV bands at 325 and 355 nm and an orange-red band at 620 nm. The three bands are ascribed to Pb2+, Ce3+ and Mn2+, respectively, as activators. The Pb2+ excitation band is observed at 243 nm, and the Ce3+ excitation band at 295 nm. The Pb2+ excitation band is also observed by monitoring the Ce3+ fluorescence, and the Pb2+ and Ce3+ excitation bands, in addition to six Mn2+ excitation bands, are also observed by monitoring the Mn2+ fluorescence. These indicate that four types of the energy transfer can occur in calcite through the following processes: (1) Pb2+ → Ce3+, (2) Pb2+ → Mn2+, (3) Ce3+ → Mn2+ and (4) Pb2+ → Ce3+ → Mn2+. 相似文献
812.
Residential RC framed structures suffered heavily during the 2001 Bhuj earthquake in Gujarat, India. These types of structures
also saw severe damage in other earthquakes such as the 1999 Kocaeli earthquake in Turkey and 921 Ji-Ji earthquake in Taiwan.
In this paper the seismic response of residential structures was investigated using physical modelling. Idealised soft storey
and top heavy, two degrees of freedom (2DOF) portal frame structures were developed and tested on saturated and dry sand models
at 25 g using the Schofield Centre 10-m Beam Centrifuge. It was possible to recreate observed field behaviour using these
models. As observed in many of the recent earthquakes, soft storey structures were found to be particularly vulnerable to
seismic loads. Elastic response spectra methods are often used in the design of simple portal frame structures. The seismic
risk of these structures can be significantly increased due to modifications such as removal of a column or addition of heavy
water tanks on the roof. The experimental data from the dynamic centrifuge tests on such soft storey or top-heavy models was
used to evaluate the predictions obtained from the response spectra. Response spectra were able to predict seismic response
during small to moderate intensity earthquakes, but became inaccurate during strong earthquakes and when soil structure interaction
effects became important. Re-evaluation of seismic risk of such modified structures is required and time domain analyses suggested
by building codes such as IBC, UBC or NEHRP may be more appropriate. 相似文献
813.
Gzhelian deposits established in Iran for the first time are described. They rest with a considerable hiatus on the Moscovian deposits constituting, along with Asselian strata, an integral carbonate succession of the Zaladu Formation in eastern Iran. The Zaladu Formation is correlative with the Vazhnan Formation of the Abadeh region (central Iran) and the Dorud Formation of the Elburz (Alborz) Mountains. An assemblage of Gzhelian fusulinids from the studied section is well comparable with the assemblage of the Ultradaixina bosbytauensis Zone distinguished in the uppermost Gzhelian of the Darvaz, Fergana, the Southern Urals, Donetsk Basin, and Carnic Alps. Two new species of the genus Schellwienia (Sch. anarakensis and Sch. stocklini) are described. Gzhelian and Asselian fusulinids found in the section are figured in two paleontological plates. 相似文献
814.
Seismic Hazards Assessment for Radioactive Waste Disposal Sites in Regions of Low Seismic Activity 总被引:4,自引:0,他引:4
Clark H. Fenton John Adams Stephen Halchuk 《Geotechnical and Geological Engineering》2006,24(3):579-592
A comparative tectonic quiescence and lack of earthquakes make the stable centres of continents attractive for siting long-term
radioactive waste storage facilities. The low rates of deformation in such regions, however, make it difficult to characterize
their long-term seismotectonic behaviour, leading to uncertain estimates for the very low probability hazard estimates required
by society. In an attempt to overcome the deficiency of both contemporary seismicity and paleoseismic data in central Canada,
we have used earthquake histories from regions with similar seismotectonic characteristics from around the world. Substituting
space for time, we estimate a long-term rate per 106 km2 of 0.004 magnitude ≥6 earthquakes per annum, of which 33–100% might rupture to the surface. 相似文献
815.
Breakthrough tailing has been observed during dye-tracing recovery tests in the Norville aquifer system (chalk), France. Karst-conduit flow and transport parameters were assessed using two different interpretative methods: the linear graphical method and the Chatwin method (implemented in the Qtracer2 program). The linear graphical method was used to model the observed tailing effects, which was explained by a second smaller delayed breakthrough curve. By comparing the results of tracer-test interpretation for the two methods, it was possible to relate the area of this second curve to the importance of turbulent flow in spring discharge. The more turbulent the flow, the less important the contribution of the second breakthrough curve and the tailing effect. The observed tailing could possibly be controlled by hydrodynamics to a greater extent than usually expected, the tailing effects being mostly attributed to diffusion phenomena. Tailing effects were expected to increase with discharge and the piezometric level, which would have resulted in overpressure in conduits, fissure flooding, etc. Instead, breakthrough tailing tended to disappear with increasing aquifer discharge, which would support the hypothesis of there being mostly hydrodynamic-controlled tailing effects instead of matrix- or fissure-diffusion.An erratum to this article can be found at 相似文献
816.
An 11-month observation of dissolved and particulate organic matter, chlorophyll a(Chl a), C18 Sep-Pak extractable hydrophobic dissolved organic matter (hDOM) fraction and associated dissolved trace metals (Cd,
Cu, V, Co, Ni, Mo, U) was performed in the Lot–Garonne River system. This system includes the Riou Mort, the Lot River and
the downstream reaches of the Garonne River and represents the fluvial transport path of trace metals between the major point
source of polymetallic pollution, located in the Riou Mort watershed and the Gironde estuary. Spatial and temporal variations
of dissolved and particulate organic carbon and Chl areflect the presence of different types of organic matter and their relation with the hDOM fraction. Maximum Chl a/POC ratios (up to 0.03), indicate intense phytoplankton production from March to May. In the Lot River (Temple), DOC and
POC concentrations were clearly higher and mean Chl a concentration (2.8 mg g−1) was about three times higher than those of the other sites. High Chl a/POC ratios suggest high phytoplankton activity with maxima in spring and late summer. In the Riou Mort River, very high POC
concentrations of up to 40 (mean: 20) occurred, whereas Chl a concentrations were relatively low indicating low phytoplankton activity. High, strongly variable DOC and POC concentrations
suggest important natural (Carboniferous soils, forests) or anthropogenic (e.g., former coal mines, waste areas, agriculture,
sewage) carbon sources within the small Riou Mort watershed. Despite high DOC concentrations in the Riou Mort River, hDOM
metal fractions were generally lower than those at the other sites. The general order of decreasing binding strength between
metals and the organic hydrophobic phase (Cu, U > Co, Ni > V, Mo > Cd) at all four sites was in good agreement with the Irving–William
series of transition element affinity towards organic ligands. Accordingly, the role of the hydrophobic phase in dissolved
Cd transport appeared to be negligible, whereas the hDOM–Cu fraction strongly contributed to dissolved Cu transport. 相似文献
817.
818.
Mercury speciation and mobilization in contaminated soils of the Valle del Azogue Hg mine (SE,Spain) 总被引:1,自引:0,他引:1
Hg mobilization from contaminated soils and mine wastes was the source of environmental contamination in the Valle del Azogue
mining area. We researched solid-phase speciation and aqueous mobility of Hg through Scanning electron microscopy-energy dispersive
X-ray spectroscopy and electron probe microanalysis analysis, solid-phase-Hg-thermo-desorption (SPTD) and laboratory column
experiments. We found that in contaminated soils and mine wastes, the predominant Hg species was cinnabar (HgS), mainly formed
from the weathering of Hg-rich pyrite, and metallic Hg (0) in the matrix, whereas in calcines and tailings the dominant species
was metallic Hg (0). The mobilization of Hg in the aqueous phase seems to have originated from the dissolution of elemental
Hg (0) present in soils and wastes, reaching concentrations of up to 67 μg l−1, and showing a higher long-term environmental potential risk, in addition to atmospheric emissions. 相似文献
819.
环境样品中痕量元素的化学形态分析Ⅱ.砷汞镉锡铅硒铬的形态分析 总被引:2,自引:6,他引:2
环境中元素的生物有效性和毒性依赖于其存在的化学形态。文章依据文献的有关报道介绍砷、汞、镉、锡、铅、硒和铬在环境中的分布、毒性及它们在环境样品如水、土壤、沉积物和生物体中的形态分析方法,包括分析物的保存、提取、分离和检测。引用文献120篇。 相似文献
820.
Georg Bergeton Larsen Stig Syndergaard Per Høeg Martin Bjært Sørensen 《GPS Solutions》2005,9(2):144-155
The Global Positioning System (GPS) radio occultation measurements obtained using the TurboRogue GPS receiver on the Danish satellite Ørsted have been processed using the single frequency method. Atmospheric profiles of refractivity and temperature are derived and validated against numerical weather prediction data from the European Centre for Medium-Range Weather Forecast (ECMWF). Results from the Ørsted GPS measurement campaign in February 2000 indicate that the single frequency method can provide retrievals with accuracy comparable to that of using two frequencies. From comparisons between measured dry temperature profiles and corresponding dry temperature profiles derived from ECMWF analysis fields, we find a mean difference of less than 0.5 K and a standard deviation of 2–4 K between 500 and 30 hPa in height. Above 30 hPa the impact of the ionosphere becomes more dominant and more difficult to eliminate using the single frequency method, and the results show degraded accuracy when compared to previous analysis results of occultation data from other missions using the dual frequency method. At latitudes less than 40° (denoted low latitudes), the standard deviation is generally smaller than at latitudes higher than 40° (denoted high latitudes). A small temperature bias is observed centered at 200 hPa for low latitudes and at 300 hPa for high latitudes. This indicates that the ECMWF analyses do not adequately resolve the tropopause temperature minimum. In the lowest part of the troposphere an observed warm bias is thought to be due to erroneous tracking of the GPS signal in cases of atmospheric multipath propagation. 相似文献