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981.
Four-level Dahan downhole recordings are used to investigate site amplification due to the near-surface structure. The downhole array is installed at the depths of 0 m (surface), 50, 100 and 200 m. Eight sets of data presenting well-separated incident and reflected waves (from the free surface) are selected to analyse the site amplification. Five techniques of spectral ratios have been tested to determine the most reliable way to estimate site response. The superior one is the ratio of Root-Mean-Square (RMS) Fourier amplitude spectra, because it has the minimum number of pseudopeaks. However, the pseudopeaks can be further reduced by omitting those ratios with small denominators. Results show that the amplification factors are nearly uniform at the depths of 50 and 100 m, where their values fall between one and two. This factor is frequency-dependent at the surface and in the range from two to five under 6 Hz. These results agree well with those from time-domain analyses and the transmission-coefficient estimation except that the latter overestimates the amplification factor of the surface station. This suggests that the shallow velocity structure provided by the geotechnical survey might be underestimated. Numerical modelling also supports the underestimation of velocity at near surface since the synthetic SH waves based on a modified velocity model can match these observations well. 相似文献
982.
基于凸集投影算法的超分辨率图像重建技术 总被引:6,自引:0,他引:6
图像的空间分辨率是评价图像质量的一个关键性指标,也是图像应用中举足轻重的一个参数。然而在图像获取的过程中,诸多因素均会导致图像质量的下降或退化。解决这一问题的一种有效办法就是超分辨率图像重建技术,介绍了超分辨率图像重建技术,对其两种主要的方法进行了分析,给出了凸集投影算法的步骤并通过实验数据进行了图像重建的验证。 相似文献
983.
I. C. Lemmer 《Mathematical Geology》1986,18(7):605-623
The theory of mononodal variography developed in the preceeding paper is checked against a simulated deposit consisting of 60,500 grade values, called Stanford II. In the case of this deposit at least, assumptions underlying the concept of mononodal variography are borne out accurately. In particular, a linear relationship does exist indeed between indicator and grade variogram values of Stanford II at corresponding lags. Furthermore, such grade-indicator plots, and the information deduced from them, are robust under reduction of data at the mononodal cutoff. The method thus has predictive potential for grade variograms of highly variant deposits. Forecasting a grade variogram from the associated mononodal indicator variogram and grade-indicator plot is illustrated. Agreement with the experimental variogram is shown to be excellent.This paper is based in part on a PhD thesis submitted to the Department of Applied Earth Sciences, Stanford University, Stanford, California 94305, in 1984 (unpublished). 相似文献
984.
Long-Term Earthquake Clustering 总被引:22,自引:0,他引:22
985.
986.
Distinguishing Carbonate Reservoir Pore Facies with Nuclear Magnetic Resonance Measurements 总被引:1,自引:0,他引:1
Characterization of carbonate rocks may involve identifying the important pore types which are present. In the past, this
task has required detailed petrographic analysis of many core samples. Here, we describe a method which uses nuclear magnetic
resonance (NMR) measurements to reduce the amount of petrographic analysis needed for porosity typing of carbonate reservoir
rocks.
For a rock sample which has been measured with NMR, our method decomposes the log(T2) spectrum into at most three Gaussian-shaped components and gives a set of nine parameters. Two characteristic quantities
having geological significance are extracted from the nine parameters. Values of the two quantities are compared with a reference
set, established from samples having both NMR and petrographic evaluations of porosity types. We use a Bayesian approach to
the classification of the dominant porosity type.
Tests of our method on 103 samples show a correct prediction in 60 to 90 percent of the samples. The lower success rate was
obtained for samples with five porosity types from three fields; the higher success rate obtained with samples with three
porosity types from one well. The use of geologically significant quantities extracted from the decomposition gives comparable
success rate to those obtained using a standard, non-geological approach such as canonical variates. 相似文献
987.
针对一类具有未知对象和外部干扰输入的多输入多输出非线性系统提出了一种自适应鲁棒控制方案。该方案采用小波网络辨识未知非线性对象并使用高增益观测器估计不能直接测量的系统状态。理论分析证明了一定的假设条件下闭环系统半全局稳定,所设计控制器不仅可保证闭环系统的所有信号半全局一致有界,而且使得系统的输出渐近跟踪有界的期望轨迹到一小邻域。仿真结果也充分表明该方法的可行性和有效性。 相似文献
988.
989.
废光谱感光板用自来水浸泡,剥离的乳胶经氢氧化钠和双氧水溶解后,在微酸性溶液中加入锌粉置换出银,银沉淀经过滤和硼砂与碳酸钠的混合熔剂熔炼后得到成品银锭。采用建立的方案提取废光谱感光板中成品银的纯度达到95.4%,工艺操作简便,成本低、环境污染小。 相似文献
990.
Gravity data are the results of gravity force field interaction from all the underground sources. The objects of detection
are always submerged in the background field, and thus one of the crucial problems for gravity data interpretation is how
to improve the resolution of observed information. The wavelet transform operator has recently been introduced into the domain
fields both as a filter and as a powerful source analysis tool. This paper studied the effects of improving resolution of
gravity data with wavelet analysis and spectral method, and revealed the geometric characteristics of density heterogeneities
described by simple shaped sources. First, the basic theory of the multiscale wavelet analysis and its lifting scheme and
spectral method were introduced. With the experimental study on forward simulation of anomalies given by the superposition
of six objects and measured data in Songliao plain, Northeast China, the shape, size and depth of the buried objects were
estimated in the study. Also, the results were compared with those obtained by conventional techniques, which demonstrated
that this method greatly improves the resolution of gravity anomalies.
Translated from Progress in Geophysics, 2007, 22(1): 112–120 [译自: 地球物理学进展] 相似文献