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61.
Abstract Between July 1974 and September 1975 aboard AEROS-B the electron temperature and the electron density have been measured by the Retarding Potential Analyses and the Impedance Probe respectively in the altitude range 200–870 km. Temperature and density fluctuations along satellite paths have been analysed by digital filtering. The large amount of data allows the mean fluctuations at different heights and latitude intervals to be evaluated. The resulting two-dimensional arrays are presented for some time periods. The global distributions show different patterns in the polar and equatorial regions, and seasonal variations. Mean temperature fluctuations and fluctuations of electron density in general occur simultaneously though with different amplitudes. At high latitudes a seasonal dependence in the strength of the fluctuations of both quantities was observed. 相似文献
62.
The groundwater flow in a fissured chalky environment at the northern border of the Paris Basin depends on several geological and hydrogeological parameters. Although the studied sector of the basin presents a homogeneous rock type, it is affected by a fracture network. In this type of environment, in which the permeability is low, the groundwater flow displays significant disruption, which is localized in the Fruges region (northern France). The interconnection of the discontinuities (network of fault and/or joints) is reliant on the structural control of groundwater flow through increases in the hydraulic connection between the unsaturated and the saturated zone. The methodology developed herein makes use of microstructural and regional analysis of the fracture patterns, and allowed consideration of the piezometric variations of the chalk aquifer during periods of low and high groundwater levels (April and October 2001) and a diagraphic representation of the estimated physical parameters (electrical resistivity). This enabled us to construct a ‘flow structure’ conceptual model in which we identify two types of faults: tight walls and flow paths that control the piezometric heads and the flow rate. Model validation was carried out on a similar sector. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
63.
The existing procedures for the selection of runout model parameters from back-analyses do not allow integrating different
types of runout criteria and generally lack a systematic approach. A new method based on receiver operating characteristic
(ROC) analyses and aimed at overcoming these limitations is herein proposed. The method consists of estimating discrete classifiers
for every runout simulation associated with a set of model parameters. The set of parameters that yields the best prediction
is selected using ROC metrics and space. The procedure is illustrated with the back-analyses of a rainfall-triggered debris
flow that killed 300–500 people in the Metropolitan Area of San Salvador in 1982. The selected model parameters are used to
estimate forward predictions for scenarios that correspond to different return periods. The proposed procedure may be useful
in the assessment of areas potentially affected by landslides. In turn, this information can be used in the production or
updating of land use plans and zonations, similar to that currently being carried out by the Office for Urban Planning of
the Metropolitan Area of San Salvador in El Salvador. 相似文献
64.
Geo-Characterization at selected accelerometric stations in Crete (Greece) and comparison of earthquake data recordings with EC8 elastic spectra 总被引:1,自引:0,他引:1
A. Savvaidis B. Margaris N. Theodoulidis V. Lekidis Ch. Karakostas C. Loupasakis D. Rozos P. Soupios M. -D. Mangriotis U. Dikmen Par. Tsangaratos E. Kokinou A. Vafidis Th. Rondoyanni I. Kalogeras S. Koutrakis A. Sarris N. Papadopoulos 《Central European Journal of Geosciences》2014,6(1):88-103
To estimate the seismic response according to Eurocode (EC8) and almost all other national codes, site conditions have to be properly characterized so that soil amplification and the corresponding peak ground motion can be calculated. In this work, different geophysical and geotechnical methods are combined in order to define the detailed ground conditions in selected sites of the Hellenic Accelerometric Network (HAN) in Crete. For this purpose, the geological information of the sites and shear wave velocity, calculated from surface wave measurements, is used. Additionally, ground acceleration data recorded through HAN have been utilized from intermediate depth earthquakes in the broader area of South Aegean Sea. Using the recorded ground motion data and the procedure defined in EC8, the corresponding elastic response spectrum is calculated for the selected sites. The resulting information is compared to the values defined in the corresponding EC8 spectrum for the seismic zone that includes the island of Crete. The comparison shows that accurate definition of ground type through geological, geotechnical and geophysical investigations is important. However, our current comparison focuses on the distribution of values rather than the absolute values of EC8-prescribed spectra, and the results should be considered in this context. 相似文献
65.
Prabhakara Prasad P. Satish Kumar K. Seshunarayana T. Rama Rao Ch. 《Arabian Journal of Geosciences》2014,7(7):2633-2639
Randomly distributed ground magnetic data sets, collected along parallel and closely spaced profiles, in small blocks, the blocks being separated/distributed widely over a large area, become, sometimes, unamenable for deriving a meaningful geological model. In such a situation, an approach of “Cumulative Total Intensity Magnetic Anomaly Field (CTIMAF)” has been devised to interpret the sparsely distributed magnetic data sets. A case history has been presented from the lead–zinc mineralized provenance of Ajabgarh Formation of Delhi Fold Belt in the northern part of Ajmer Town. Log-normalized radially averaged power spectrum was computed for the Cumulative Total Intensity Magnetic Anomaly data and depth to the basement is derived. The computed depth of 4.5 km is in good agreement with the Deep Seismic Studies. 相似文献
66.
Xavier Rodó Mercedes Pascual Francisco J. Doblas-Reyes Alexander Gershunov Dáithí A. Stone Filippo Giorgi Peter J. Hudson James Kinter Miquel-Àngel Rodríguez-Arias Nils Ch. Stenseth David Alonso Javier García-Serrano Andrew P. Dobson 《Climatic change》2013,118(3-4):625-640
The next generation of climate-driven, disease prediction models will most likely require a mechanistically based, dynamical framework that parameterizes key processes at a variety of locations. Over the next two decades, consensus climate predictions make it possible to produce forecasts for a number of important infectious diseases that are largely independent of the uncertainty of longer-term emissions scenarios. In particular, the role of climate in the modulation of seasonal disease transmission needs to be unravelled from the complex dynamics resulting from the interaction of transmission with herd immunity and intervention measures that depend upon previous burdens of infection. Progress is also needed to solve the mismatch between climate projections and disease projections at the scale of public health interventions. In the time horizon of seasons to years, early warning systems should benefit from current developments on multi-model ensemble climate prediction systems, particularly in areas where high skill levels of climate models coincide with regions where large epidemics take place. A better understanding of the role of climate extremes on infectious diseases is urgently needed. 相似文献
67.
68.
69.
Ch. Marqué P. Lantos J.M. Delouis C.E Alissandrakis 《Astrophysics and Space Science》2001,277(1-2):329-330
A filament eruption at decimetric wavelength is illustrated here, involving a quiescent filament seen in absorption. A CME
occurs in the vicinity of the event.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
70.
Ch. Skokos P. A. Patsis E. Athanassoula 《Monthly notices of the Royal Astronomical Society》2002,333(4):847-860
In this series of papers we investigate the orbital structure of three-dimensional (3D) models representing barred galaxies. In the present introductory paper we use a fiducial case to describe all families of periodic orbits that may play a role in the morphology of three-dimensional bars. We show that, in a 3D bar, the backbone of the orbital structure is not just the x1 family, as in two-dimensional (2D) models, but a tree of 2D and 3D families bifurcating from x1. Besides the main tree we have also found another group of families of lesser importance around the radial 3:1 resonance. The families of this group bifurcate from x1 and influence the dynamics of the system only locally. We also find that 3D orbits elongated along the bar minor axis can be formed by bifurcations of the planar x2 family. They can support 3D bar-like structures along the minor axis of the main bar. Banana-like orbits around the stable Lagrangian points build a forest of 2D and 3D families as well. The importance of the 3D x1-tree families at the outer parts of the bar depends critically on whether they are introduced in the system as bifurcations in z or in z˙ . 相似文献