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71.
水文时间系列周期分析方法探讨 总被引:15,自引:2,他引:15
以分析广东省降水周期变化规律为例,探讨了最大熵谱方法在提取水文时间系列的主次周期上以及小波变换方法在分析水文时间系列的多时间尺度演变规律上的应用。由计算结果分析得到广东省降水过程主要存在的周期特性和旱涝变化趋势,为广东省降水趋势预测提供了重要信息。 相似文献
72.
Hsueh-Yu Lu 《Environmental Geology》2007,51(6):1029-1041
A new method has been developed to estimate the hydraulic conductivity in unconsolidated aquifers. The method uses bulk geochemical
compositions correlated with hydraulic conductivities measured by pumping tests. The concept is based on a general rule that
hydraulic conductivity is principally controlled by grain-size distribution and particle shape,both of which relate to mineralogical
composition. Using a MINLITH algorithm, normative mineralogical compositions can be derived from bulk geochemical compositions
economically and expediently, and then correlated to the hydraulic conductivity determined by pumping tests in the field.
In this study, 202 sediment samples from nine unconsolidated aquifers were analyzed by X-ray fluorescence. Although hydraulic
conductivity does not show a definite relationship with geochemical compositions, it does demonstrate a linear logarithmic
equation to the content of normative earthy minerals. However, linear regressed equations should not be applied to aquifers
composed of medium to coarse sand and gravel sizes due to interference from lithic fragments. In addition, this equation tends
to overestimate hydraulic conductivity possibly because the effect of compaction is ignored in this study. 相似文献
73.
原子荧光光谱分析环境样品中砷锑铋汞易出现的问题及解决方法 总被引:2,自引:0,他引:2
针对原子荧光光谱法测试砷锑铋汞中易出现的仪器空白不稳定、样品制备及仪器污染等问题,总结出相应的解决方法。 相似文献
74.
On May 28, 1998, a moderate size earthquake of mb 5.5 occurred offshore the northwestern part of Egypt (latitude 31.45°N and
longitude 27.64°E). It was widely felt in the northern part of Egypt. Being the largest well-recorded event in the area for
which seismic data from the global digital network are available, it provides an excellent opportunity to study the tectonic
process and present day stress field occurring along the offshore Egyptian coast. The source parameters of this event are
determined using three different techniques: modeling of surface wave spectral amplitudes, regional waveform inversion, and
teleseismic body waveform inversion. The results show a high-angle reverse fault mechanism generally trending NNW–SSE. The
P-axis trends ENE–WSW consistently with the prevailed compression stress along the southeastern Hellenic arc and southwestern
part of the Cyprean arc. This unexpected mechanism is most probably related to a positive inversion of the NW trending offshore
normal faults and confirms an extension of the back thrusting effects towards the African margin. The estimated focal depth
ranges from 22 to 25 km, indicating a lower crustal origin earthquake owing to deep-seated tectonics. The source time function
indicates a single source with rise time and total rupture duration of 2 and 5 s, respectively. The seismic moment (M
o) and the moment magnitude (M
w) determined by the three techniques are 1.03 × 1017 Nm, 5.28; 1.24 × 1017 Nm, 5.33; and 1.68 × 1017 Nm, 5.42; respectively. The calculated fault radius, stress drop, and the average dislocation assuming a circular fault model
are 7.2 km, 0.63 Mpa, and 0.11 m, respectively. 相似文献
75.
A statistical analysis of the peak acceleration demands for nonstructural components (NSCs) supported on a variety of stiff and flexible inelastic regular moment‐resisting frame structures with periods from 0.3 to 3.0 s exposed to 40 far‐field ground motions is presented. Peak component acceleration (PCA) demands were quantified based on the floor response spectrum (FRS) method without considering dynamic interaction effects. This study evaluated the main factors that influence the amplification or decrease of FRS values caused by inelasticity in the primary structure in three distinct spectral regions namely long‐period, fundamental‐period, and short‐period region. The amplification or decrease of peak elastic acceleration demands depends on the location of the NSC in the supporting structure, periods of the component and building, damping ratio of the component, and level of inelasticity of the supporting structure. While FRS values at the initial modal periods of the supporting structure are reduced due to inelastic action in the primary structure, the region between the modal periods experiences an increase in PCA demands. A parameter denoted as acceleration response modification factor (Racc) was proposed to quantify this reduction/increase in PCA demands. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
76.
77.
WEI Heli LIU Qinghong XU Qingshan ZHAO Fengsheng SONG Zhengfang 《Acta Meteorologica Sinica》2001,15(2):249-256
Infrared solar spectra on clear days were measured automatically by an infrared solar spectrometer(ISS) with 0.4 cm-1 resolution developed by us.A line-by line(LBL) computation method was used to calculate theoretical atmospheric absorption.In the wavelength range of 3.410-3.438 μm.the absorption is mainly due to atmospheric methane and water vapor.Columnatmospheric methane was retrieved from the recorded infrared solar spectra.The seasonal variation of column atmospheric methane in Hefei has been obtained from the measuremental data of nearly 18 months since the April of 1997.and found that it is similar to that of background data.The instruments.principles of measurement and some of results were introduced,and the results are also discussed briefly in the paper. 相似文献
78.
In recent years, more and more studies are focused on the performance in seismic design instead of the strength of structures. People have realized that the structure deformation (displacement) can describe the damage more properly and directly than the strength (force). The displacement design spectra need to be constructed within more wide range of the period and the damping for the displacement-based seismic design. 相似文献
79.
80.
氢化物发生—原子荧光光谱法测定煤样中的硒 总被引:6,自引:2,他引:6
采用氢化物发生原子荧光光谱法测定了煤样中的总Se。煤样选用高压闷罐强酸消解的方法进行处理,所得消解液经6mol/L HCl将Se(Ⅵ)还原为Se(Ⅳ),然后进行测定。标准工作曲线的线性范围为0-400μg/L Se,检测限为0.4μg/L Se。用标准参考物质煤飞灰对方法进行了验证,所得总Se含量与标准值相符,对ω为10^-6级Se的4次测定,RSD≤4.5%。 相似文献