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131.
希尔伯特—黄变换(Hilbert-Huang transform,HHT)是一种新的适合非平稳和非线性信号的分析方法,由于地震信号一般呈现出非平稳与非线性特性,因此HHT非常适合地震信号的分析。本文首先介绍了HHT中关于经验模态分解(Empirical Mode Decomposition,EMD)的实现过程,在此基础上分析了几种基于EMD获得本征模态函数(Intrinsic Mode Functions,IMF)来计算瞬时频率的算法,其中利用了两个采样间隔瞬时频率的平均来计算瞬时频率,较好地反映了地震信号频率成分随时间变化的特征。将该方法应用于四川东北部某地区海相碳酸盐岩地层三维地震叠后偏移数据处理,提取"三瞬"地震属性,与传统的希尔伯特变换提取的"三瞬"地震属性进行对比,结果表明基于HHT的"三瞬"地震属性结果具有更高的分辨率,IMF2的瞬时相位能够较好地刻画台地边缘生物礁相,IMF2的瞬时频率亦具有较好的分带性。将IMF2的"三瞬"地震属性与钻井等资料结合分析,能够更好地识别沉积相的分布。 相似文献
132.
多分量勘探相比常规纵波勘探而言有许多的优势,PP/PS联合AVO分析和反演是强而有效的储层识别方法。在本文中,我们推导了更精确的转换波AVO反射系数公式;并在入射角小于30度时进行了进一步简化,其对于转换波AVO分析和反演而言更加简单有效。基于该近似,我们进行了PP/PS联合AVO反演。实际资料的实例表明,反演得到的纵横波速度比可很好地识别岩性及油气。反演得到的流体因子和泊松比等其他属性在储层处也显示出明显异常,效果显著。 相似文献
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地质样品正构烷烃组分分离纯化的部分问题探究 总被引:3,自引:3,他引:0
用实验室自配的标准正构烷烃样品分别经硅胶或氧化铝柱层析后发现,等量溶剂洗脱的情况下硅胶对长链正构烷烃无吸附而氧化铝具有一定吸附性。进一步通过用植物样品测试4种层析柱填充方法,发现不论是只用氧化铝填充还是上部硅胶下部氧化铝和上部氧化铝下部硅胶,都会对长链正构烷烃产生一定的吸附,且这种吸附效果随着碳链的增长而增强。在实验条件下,当碳链加长到C36时,用硅胶加氧化铝填充层析柱的吸附量已达到20%左右,而只用氧化铝填充层析柱的吸附量则高达50%。故建议对研究高碳数正构烷烃的地质样品组分提取时用单一的硅胶柱层析方法。同时,实验显示对于一些杂质多的正构烷烃样品经过尿素络合后比络合前"干净"得多。18个黄土-古土壤和植物样品平均回收率为50%左右,经过尿素络合后的样品正构烷烃各组分相对含量基本不会发生改变,也不会产生明显的同位素分馏效应。因此在进行非正构组分干扰较大的正构烷烃各组分相对含量或同位素分析时,可以选择尿素络合的方法来将其纯化。 相似文献
135.
We present δDwax values from different forms of plants and soils, and δDsw values from soil water along the northern slope of Mount Taibai, China. The results show a highly negative linear correlation of the δDwax values for soils with altitude (R2 0.74) and we observed the same correlation for δDsw values of soil water with altitude (R2 0.68). The δDwax of living plants behaves like the soil, but does not exhibit a significant linear correlation with altitude (R2 0.11). The δDwax values of woody plants and grasses also show a similar trend with respect to altitude with significant and no linear correlation, respectively (R2 0.50 for woody plants and 0.17 for grass), which suggest that the “altitude effect” can not be well documented for the δDwax values of living plants, which may be due to differences in plant type and/or evapotranspiration controlled by the plant microclimate. The εwax-sw values of woody plants, grasses and soil show minor fluctuations with altitude. However, the εwax-sw and δDwax values of woody plants are roughly 51‰ and 50‰ more positive, respectively, than those of grasses, suggesting that an “altitude effect” could be documented in the δDwax of woody plants and grasses, with each responding independently to changes in precipitation along the altitude transect. Additionally, the εwax-sw values of soil are relatively constant with altitude, suggesting that the altitudinal change in the proportions between woody plant and grass input to soils will likely change the relationship between the δDwax values of soil n-alkanes and altitude. 相似文献
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Guofeng Zhu Tao Pu Yuanqing He Peiji Shi Tao Zhang Wei Wei Hewen Niu 《Environmental Earth Sciences》2013,70(6):2807-2816
The present study investigated the chemical composition of summer precipitation at different altitudes in Yulong Snow Mountain, hoping to obtain some basic information about the chemical characteristics of precipitation. A couple of precipitation samples at different altitudes in the Yulong Snow Mountain area in southeastern China were collected from July 26 to July 31, 2005 for chemical analyses. Sea-salt tracer analysis showed that Cl? and Na+ had high proportion from marine sources, while the other ions mainly were from non-marine sources. Statistics showed that the cation concentrations ranged from 0.51 to 5.26 mg L?1 and anion concentrations ranged from 0.99 to 4.90 mg L?1. Further analysis showed that terrestrial ions, especially from the proximal terrestrial sources, largely affected the ion concentrations in precipitation. Ion concentrations of precipitation were correlated significantly with local atmospheric circulation at altitude 2,950–4,800 m, and also correlated closely with human activities at altitude 2,400–2,950 m. Limestone, the majority of local rocks, caused high cation concentrations in precipitation, such as Ca2+ and Mg2+. The majority of vapors in the region came from the Indian Ocean whereas parts came from the eastern Pacific. The inorganic ions in precipitation increased significantly in the Yulong Snow Mountain area during this century. Compared with most of the high altitude Mountains in China, the precipitations in the Yulong Snow Mountain area had higher concentrations of inorganic ions and low acidic ion concentrations. The conclusions can provide a basis for study of regional climate characteristics, environment and ecological characteristics of Yulong Snow Mountain area. 相似文献
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V. Mishin Z. Pu L. Sapronova A. Bazarzhapov Yu. Kuz’minykh X. Cao H. Zhang 《Geomagnetism and Aeronomy》2009,49(8):1193-1198
The maps of the field-aligned current (FAC) density distribution in the ionosphere obtained by the TIM-2 magnetogram inversion
technique are used to investigate the August 27, 2001 substorm. The open magnetic flux Ψ and intensity J of the substorm current wedge (SCW) have been determined with a step of 1–5 min. The substorm onsets are divided into two
types, PSR (plasma sheet reconnection) and TLR (tail lobe reconnection). The fast expansion tailward of the PSR region is
described as the transition from PSR to PSR+TLR. Assuming that the SCW FACs flow down into the ionosphere from the edges of
the disruption region of the cross-tail dawn-dusk current, several parameters of the disruption region have been estimated.
The disrupted magnetic field has been found to be ∼5% of the undisrupted one for PSR and ∼95% for PSR+TLR. The disturbance
power Q for PSR is an order of magnitude lower than that for PSR+TLR. The abrupt growth of Q during the transition from PSR to PSR+TLR is observed over the entire SCW area from its near-Earth part to the midtail and
distant tail. 相似文献