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721.
Yuri D Zakharov Alexander M Popov Galina I Buryi 《中国地质大学学报(英文版)》2005,16(3):219-230
INTRODUCTION LateOlenekianandAnisianmarinedepositsin SouthPrimoryewerefirststudiedbyD.L.Ivanov,thechiefofageologicalteammakingreconnaissance workfortheconstructionofthetrans Siberianrail road.HecollectedEarlyandMiddleTriassicam monoidsonRussianIsland.Arep… 相似文献
722.
G. R. Adhikari A. I. Theresraj R. N. Gupta 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(2):79-92
Various methods of transducer mounting provide varying degrees of coupling between the transducer and the measurement surface. The influence of four of these methods on vibration measurements was studied. For this purpose, the first transducer was placed freely on a horizontal surface, the second one was 'sandbagged', the third one was 'spiked' and the fourth one was completely buried in soil. These transducers were mounted side by side and ground vibrations were monitored for 14 blasts at an opencast coal mine.
Ground vibrations in terms of peak particle velocity, peak vector sum and frequency with different mounting methods were analysed. Assuming the data of the buried transducer as the most acceptable one, relative values of other transducers were determined and plotted. For the given tolerance for instrumental and human errors, anomalous readings were found in some cases. The waveforms of the buried transducer were then compared with those of others. Clear distortion in the waveforms or a very low correlation coefficient between two waveforms was suspected poor coupling.
The results indicate that decoupling is most likely with the surface transducer. However, the sandbagged and spiked transducers are also prone to decoupling. Decoupling can result in higher or lower ground vibration. Therefore, burial should be the preferred method for mounting of transducers in soil. 相似文献
Ground vibrations in terms of peak particle velocity, peak vector sum and frequency with different mounting methods were analysed. Assuming the data of the buried transducer as the most acceptable one, relative values of other transducers were determined and plotted. For the given tolerance for instrumental and human errors, anomalous readings were found in some cases. The waveforms of the buried transducer were then compared with those of others. Clear distortion in the waveforms or a very low correlation coefficient between two waveforms was suspected poor coupling.
The results indicate that decoupling is most likely with the surface transducer. However, the sandbagged and spiked transducers are also prone to decoupling. Decoupling can result in higher or lower ground vibration. Therefore, burial should be the preferred method for mounting of transducers in soil. 相似文献
723.
Development of an integrated conceptual model for the rational management of the transboundary Nestos River, Greece 总被引:1,自引:0,他引:1
This paper provides a detailed analysis of the geologic, hydrologic and hydrogeologic characteristics of Nestos River basin,
which is formed within the Greek mountainous part of the river. The quantitative analysis was mainly based on the data of
the river flow in different gauging points across the rivercourse as well as on the data of groundwater discharge from karst
springs of the mountainous area while important conclusions were made regarding the hydraulic connection between the surface
waters of the river and the groundwater of the karst aquifers of the basin. The qualitative analysis has shown that the quality
of both surface waters and groundwaters of the investigated basin is high, whereas, no sources of contamination were indicated
during this research. The possible effects of the two large dams of Platanovrisi and Thesavros are also analysed as they strongly
affect the quantitative and qualitative regime of the river delta. 相似文献
724.
We estimate the absolute intensity of the Hα emission line in M17 based on spectroscopic observations with the 70 cm telescope of the Fesenkov Astrophysical Institute and the 1.25 m telescope of the Sternberg Astronomical Institute’s Crimean Laboratory. The visual extinction, A v , is derived for about 250 regions in the nebula via a comparison of the optical (Hα) and radio (21 cm continuum) emissions. The A v values for the eastern, optically bright, part of the nebula are 2–6m. For the western part, which is covered by a dark cloud, the extinction is A v = 7?14.5m. We derived I(Hα)/I([NII] λ6584) ratios and estimated the degree of ionization of nitrogen in the nebula; we find that most nitrogen is in the [NIII] state. 相似文献
725.
High-resolution historical records from Pettaquamscutt River basin sediments: 2. Pb isotopes reveal a potential new stratigraphic marker 总被引:2,自引:0,他引:2
Ana Lúcia Lima Bridget A. Bergquist Matthew K. Reuer Francis O. Dudas Timothy I. Eglinton 《Geochimica et cosmochimica acta》2005,69(7):1813-1824
A high-resolution record of Pb deposition in Rhode Island over the past 250 yr was constructed using a sediment core from the anoxic Pettaquamscutt River basin. The sedimentary Pb concentration record shows the well-described maximum associated with leaded gasoline usage in the United States. Diminished Pb variability during recorded periods of local industrial activity (1735 to 1847) supports the greater importance of regional atmospheric lead transport vs. local inputs. The Pb isotopic composition at this site shows a clear maximum in anthropogenic 206Pb/207Pb in the mid-1800s. Similar peaks have also been observed in sediments from Chesapeake Bay and the Great Lakes, suggesting a common source. Possible causes for this event include mining and smelting of Pb ores in the Upper Mississippi Valley district, which accounted for almost all Pb production in the United States in that period. The timing of this event can provide an important stratigraphic marker for sediments deposited in the past 200 yr in the Northeastern United States. The downcore profile of anthropogenic 206Pb/207Pb provides a classic example of how changes in the mixture of ores for production of tetraethyl lead caused a regional-scale shift in the sedimentary record, and suggests that coal could have played a secondary role in Pb emissions after 1920. 相似文献
726.
Ana Lúcia Lima J. Bradford Hubeny John W. King Timothy I. Eglinton 《Geochimica et cosmochimica acta》2005,69(7):1803-1812
Cesium-137 derived from the explosion of the Chernobyl reactor in 1986 was preserved in anoxic sediments from a coastal environment in southern Rhode Island. Although the radioactive plume was detected in surface air samples at several locations in the United States, this is the first known record of a Chernobyl 137Cs peak in sediments from North America. The inventory of Chernobyl 137Cs that was preserved in the Pettaquamscutt River is small compared to European counterparts and should only be detectable for the next 15-20 yr. However, the presence of two 137Cs peaks (1963 and 1987) identifies a well-dated segment of the sediment column that could be exploited in understanding the decomposition and preservation of terrestrial and aquatic organic matter. Different methods for calculating the 210Pb chronology were also evaluated in this study and checked against independent varve counting. The end result is a detailed chronology of a site well suited for reconstruction of historical records of environmental change. 相似文献
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Izvestiya, Physics of the Solid Earth - Abstract—The influence of the relief on baric tilts is studied. Main attention is focused on two-dimensional problem. It is assumed that variations of... 相似文献