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931.
André Girard Jean Besson Renée Giraudet Louis Gramont 《Pure and Applied Geophysics》1978,117(3):381-394
Summary Spectrometric experiments performed, in November 1976, within the framework of the Latitude Survey Mission on board the NASA Convair 990 from Ames Research Center are briefly deseribed. The results presented concern odd nitrogen molecules, HCl and water vapor. In terms of vertical column density, HNO3 is predominant over NO+NO2 at all latitudes higher than 40 degrees. A seasonal variation of NO2 abundance is observed, with larger values in the summer hemisphere at high latitude. The mean zenith column density of HCl above 11 km is 1.5×1015 mol.cm–2, with no evidence for any seasonal or climatic variation. Local number densities as high as 1.4×1010 mol.cm–3 for HNO3 and 5.4×1014 mol.cm–3 for water vapor have been measured during the same flight near 11 km. 相似文献
932.
933.
934.
Atrazine, an herbicide widely used for selective control of grassy weeds in the fields where maize is grown, is a potential ground water contaminant in China and, consequently, there is interest in predicting its mobility in agricultural soils. In this study, we determined the nonequilibrium transport characteristics of atrazine in Shahe soil (Beijing sandy loam) using the advection-dispersion equation, and using a sensitivity analysis, we evaluated the contribution of the uncertainty in a given input parameter to the overall uncertainty in model results. The asymmetrical shape and tailing of the atrazine breakthrough curve (BTC) showed that atrazine was subject to nonequilibrium transport. The observed atrazine BTC was best fitted by the chemical nonequilibrium model with a nonlinear least-squares optimization approach. Results from the sensitivity analysis indicated that the retardation factor was the most sensitive parameter. Considering the reliability of the estimated parameters, the best fit to the atrazine BTC was obtained by fixing the retardation factor based on the linear distribution coefficient, and by calculating the dispersion coefficient from the bromide BTC and the average pore water velocity from the measured data; nonequilibrium parameters were the only unknown parameters that were optimized. Model verification procedures were based on best-fit parameters optimized from one soil column experiment and applied to simulate the transport of atrazine in the duplicate experiment. The results showed there was good agreement between measured and simulated concentrations for atrazine leaching in the soil column. 相似文献
935.
Paleomagnetic and rock magnetic study has been conducted on the Early Triassic red beds of Liujiagou Formation from Jiaocheng,
Shanxi Province. Hematite was shown as the main magnetic mineral. After eradicating an initial viscous component at room temperature
to ~100°C–200°C, thermal demagnetization shows that most samples contain two remanence components, intermediate-temperature
remanence component at 250°C–500°C and high-temperature component at 500°C–680°C. The intermediate-temperature component has
a negative fold test at the 95% confidence level. And the pole position of the intermediate-temperature component in geographic
coordinates is correlated with the Middle Jurassic reference pole of the North China Block (NCB) within the 95% confidence,
suggesting that it might be a remagnetization component acquired during the Yanshanian period. The high-temperature component
contains both reversal and normal polarities with positive fold test and C-level positive reversal test at the 95% confidence
level, which suggests that this high-temperature component can be regarded as primary magnetization. Comparison of this newly
obtained Early Triassic paleopole with the coeval mean pole of the Ordos Basin suggests that a locally relative rotation may
have happened between the Ordos and the Jiaocheng area of Shanxi Province. This rotation may be related with two faults: one
is Lishi big fault separating Ordos from Shanxi and the other is Jiaocheng big fault, which is situated in the southeast of
sampling locality and was still in motion during the Cenozoic. 相似文献
936.
Global tectonics and the plate motion obtained from the ITRF97 station velocity vectors 总被引:2,自引:0,他引:2
~~Global tectonics and the plate motion obtained from the ITRF97 station velocity vectors@马宗晋
@任金卫
@张进~~ 相似文献
937.
土壤墒情是反映一地土壤含水量多少的主要指标,墒情的好坏直接影响着农作物的生长。对于土壤墒情的计算和编报,曲沃县气象站经历了从完全的由人工查算计算编报,到用Basic语言编程计算编报,再到以后的Excel表格计算几个阶段。但这几种方法要么是计算量大,要么是界面不友好不易控制,要么是对操作计算机人员水平要求过高,稍不留心可能造成计算错误等多种不便。应用VFP语言可容易的编出具有Windows风格的程序,既方便操作,又能保证计算的精确度。 相似文献
938.
用sPn计算内蒙地震的震源深度 总被引:11,自引:6,他引:11
震源深度是地震定位的一个重要参数。本文讨论了用sPn测定震源深度的可能性。sPn对于测定地壳内震源深度具有重要意义。本文笔者利用记录到的sPn震相计算了2003年8月16日发生在我国内蒙地区地震的震源深度,并对该方法在日常工作中的应用进行了讨论。 相似文献
939.
Steve P. Schilling Paul E. Carrara Ren A. Thompson Eugene Y. Iwatsubo 《Quaternary Research》2004,61(3):325-329
The cataclysmic eruption of Mount St. Helens on May 18, 1980, resulted in a large, north-facing amphitheater, with a steep headwall rising 700 m above the crater floor. In this deeply shaded niche a glacier, here named the Amphitheater glacier, has formed. Tongues of ice-containing crevasses extend from the main ice mass around both the east and the west sides of the lava dome that occupies the center of the crater floor. Aerial photographs taken in September 1996 reveal a small glacier in the southwest portion of the amphitheater containing several crevasses and a bergschrund-like feature at its head. The extent of the glacier at this time is probably about 0.1 km2. By September 2001, the debris-laden glacier had grown to about 1 km2 in area, with a maximum thickness of about 200 m, and contained an estimated 120,000,000 m3 of ice and rock debris. Approximately one-third of the volume of the glacier is thought to be rock debris derived mainly from rock avalanches from the surrounding amphitheater walls. The newly formed Amphitheater glacier is not only the largest glacier on Mount St. Helens but its aerial extent exceeds that of all other remaining glaciers combined. 相似文献
940.