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181.
Investigation of waste disposal areas using electrical methods: a case study from Chania,Crete, Greece 总被引:1,自引:0,他引:1
Pantelis Soupios Ilias Papadopoulos Maria Kouli Irene Georgaki Filippos Vallianatos Eleni Kokkinou 《Environmental Geology》2007,51(7):1249-1261
A geophysical investigation of a landfill area was conducted as inextricable phase of a preliminary geotechnical, geological
and hydrogeological study of the area under investigation. Electrical resistivity tomography (ERT), one of the most promising
prospecting techniques mainly concerning its effective contribution to resolve several environmental problems, was applied
for the geophysical modeling. ERT is a robust imaging method the theory and implementation of which are well documented in
geophysical research literature. The survey site is located in Akrotirion Peninsula, about 7 km east of Chania city in Crete
I. The geological setting comprises Trypalion limestones, marly limestones and a clayed weathered layer. Cavities are also
identified at various scales which are recent tectono-karstic voids. Due to the above-mentioned geological singularity and
in the light of the requirement for an environmentally safe construction of the landfill, an ERT survey was carried out. Specifically,
seven geoelectrical tomographies were conducted reaching the prospecting depth of 36 m. The resulted images conduced, to overcome
geotechnical problems since the spatial distribution of karstic voids was determined, to plan the future sites for waste disposal
as the geological conditions were studied in detail and to reliably estimate the thickness of the already deposited wastes.
The resulted images were confirmed using available borehole logs and ambient noise measurements. 相似文献
182.
Anomaly analysis is used for various geophysics applications such as determination of geophysical structure's location and
border detections. Besides the classical geophysical techniques, artificial intelligence based image processing algorithms
have been found attractive for geophysical anomaly analysis. Recently, cellular neural networks (CNN) have been applied to
geophysical data and satisfactory results are reported. CNN provides fast and parallel computational capability for geophysical
image processing applications due to its filtering structure. The behavior of CNN is defined by two template matrices that
are adjusted by a properly supervised learning algorithm. After training stage for geophysical data, Bouguer anomaly maps
can be processed and analyzed sequentially. In this paper, CNN learning and processing capability have been improved, combining
Wavelet functions and backpropagation learning algorithms. The new architecture is denoted as Wavelet-Cellular Neural networks
(Wave-CNN) and it is employed to analyze Bouguer anomaly maps which are important to extract useful information in geophysics.
At first, Wave-CNN performance is tested on synthetic geophysical data, which are created by a computer environment. Then,
Bouguer anomaly maps of the Dumluca iron ore field have been analyzed and results are reported in comparison to real drilling
results. 相似文献
183.
In this paper, the adaptive chirplet decomposition combined with the Wigner-Ville transform and the empirical mode decomposition combined with the Hilbert transform are employed to process various non-stationary signals (strong ground motions and structural responses). The efficacy of these two adaptive techniques for capturing the temporal evolution of the frequency content of specific seismic signals is assessed. In this respect, two near-field and two far-field seismic accelerograms are analyzed. Further, a similar analysis is performed for records pertaining to the response of a 20-story steel frame benchmark building excited by one of the four accelerograms scaled by appropriate factors to simulate undamaged and severely damaged conditions for the structure. It is shown that the derived joint time–frequency representations of the response time histories capture quite effectively the influence of non-linearity on the variation of the effective natural frequencies of a structural system during the evolution of a seismic event; in this context, tracing the mean instantaneous frequency of records of critical structural responses is adopted.The study suggests, overall, that the aforementioned techniques are quite viable tools for detecting and monitoring damage to constructed facilities exposed to seismic excitations. 相似文献
184.
再论拟准检定法的原理、实施和应用 总被引:2,自引:0,他引:2
综合阐述了拟准检定法的原理和特点、研究思路。拟准检定法的关键是如何正确选择拟准观测,文章介绍了初选的复选拟准观测的实施要点。列举了拟准检定法在图相关情况下的相差检测,形变分析中的异常探测以及GPS相位观测的周跳检测和修复等方面的应用例子。 相似文献
185.
186.
SUI Haigang LI Deren 《地球空间信息科学学报》2001,4(3):29-34
1Currentchangedetectiontech niquesAutomaticchangedetectioninimagesofagivensceneacquiredatdifferenttimesisoneofthemostinterestingtopicsofimageprocessing .Itfindsim portantapplicationswithindifferentcontexts,rang ingfromvisualsurveillanceandvideocodingtot… 相似文献
187.
多窗谱分析方法及其在全球变暖研究中的应用 总被引:12,自引:0,他引:12
多窗谱分析方法是一种低方差、高分辨的谱分析方法 ,尤其适合于非线性气候系统中高噪声背景下弱信号、时频演变信号的诊断分析。文中简要地介绍了多窗谱分析方法的基本原理 ,并将其用于近 1 5 0 a来全球及南、北半球温度变化的研究。结果表明 :(1 )在温度呈线性变暖的背景趋势下 ,北半球、全球年平均温度还具有显著的 40~ 70 a的准周期低频振荡 ,它们与变暖过程中的波动性密切相关 ;(2 )年代际振荡信号在北半球温度序列中也相当明显 ,南半球则存在多种低于 5 a尺度的显著振荡周期 ,半球或全球 ENSO振荡分量、QBO周期信号的振幅都具有缓变包络的特性 ;(3 )与传统功率谱估计、最大熵谱估计结果的对比表明 ,多窗谱分析方法方法得到的谱估计分辨力高 ,稳定性强。 相似文献
188.
189.
190.
Evolution of accelerographs, data processing, strong motion arrays and amplitude and spatial resolution in recording strong earthquake motion 总被引:1,自引:0,他引:1
This paper presents a review of the advances in strong motion recording since the early 1930s, based mostly on the experiences in the United States. A particular emphasis is placed on the amplitude and spatial resolution of recording, which both must be ‘adequate’ to capture the nature of strong earthquake ground motion and response of structures. The first strong motion accelerographs had optical recording system, dynamic range of about 50 dB and useful life longer than 30 years. Digital strong motion accelerographs started to become available in the late 1970s. Their dynamic range has been increasing progressively, and at present is about 135 dB. Most models have had useful life shorter than 5–10 years. One benefit from a high dynamic range is early trigger and anticipated ability to compute permanent displacements. Another benefit is higher sensitivity and hence a possibility to record smaller amplitude motions (aftershocks, smaller local earthquakes and distant large earthquakes), which would augment significantly the strong motion databases. The present trend of upgrading existing and adding new stations with high dynamic range accelerographs has lead to deployment of relatively small number of new stations (the new high dynamic range digital instruments are 2–3 times more expensive than the old analog instruments or new digital instruments with dynamic range of 60 dB or less). Consequently, the spatial resolution of recording, both of ground motion and structural response, has increased only slowly during the past 20 years, by at most a factor of two. A major (and necessary) future increase in the spatial resolution of recording will require orders of magnitude larger funding, for purchase of new instruments, their maintenance, and for data retrieval, processing, management and dissemination. This will become possible only with an order of magnitude cheaper and ‘maintenance-free’ strong motion accelerographs. In view of the rapid growth of computer technology this does not seem to be (and should not be) out of our reach. 相似文献