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排序方式: 共有113条查询结果,搜索用时 31 毫秒
81.
Lentas Konstantinos Gkarlaouni Charikleia G. Kalligeris Nikos Melis Nikolaos S. 《Bulletin of Earthquake Engineering》2022,20(2):819-851
Bulletin of Earthquake Engineering - We study the major MW = 7.0, 30 October 2020, Samos earthquake and its aftershocks, by calculating improved locations using differential travel times and... 相似文献
82.
Al Heib Marwan Zevgolis Ioannis E. Theocharis Alexandros I. Koukouzas Nikolaos C. Coccia Stella 《Geotechnical and Geological Engineering》2022,40(3):1307-1321
Geotechnical and Geological Engineering - Mining operations can drastically affect the stability of nearby areas. A representative case for this has been the Mavropigi mine, a part of an open-pit... 相似文献
83.
Deliveris Alexandros V. Theocharis Alexandros I. Koukouzas Nikolaos C. Zevgolis Ioannis E. 《Geotechnical and Geological Engineering》2022,40(8):4023-4039
Geotechnical and Geological Engineering - Rainfall leads to the deterioration of slope stability conditions, while intense rainfall has been commonly associated with landslides on natural or... 相似文献
84.
The relationship between altitude of meteorological stations and average monthly and annual precipitation 总被引:2,自引:0,他引:2
Markos Gouvas Nikolaos Sakellariou Fotios Xystrakis 《Studia Geophysica et Geodaetica》2009,53(4):557-570
The aim of this study was to prove that altitudinal variability of average monthly and annual precipitation is better summarised
when the altitude observed within a radius of several kilometres around a meteorological station is taken into consideration,
instead of the altitude of the station itself. The use of the variable Z′, which combines the altitude of the closest mountain
with its distance from the station, is compared against the use of altitude alone in simple linear and multiple quadratic
regression equations for the altitudinal interpolation of precipitation over Greece. The data-set comprised precipitation
observations from 516 meteorological stations. The comparison between the two variables is discussed on the basis of the resulting
determination coefficients (R2) and standard errors of estimate (S). For all seasons, except summer, it was found that the variable Z′ improves the predictive
ability of the regression equations, thus showing its potential for further use in interpolation procedures. 相似文献
85.
Nikolaos Athanasiadis Spassimir Tonkov Juliana Atanassova Elissaveta Bozilova 《Journal of Paleolimnology》2000,24(3):331-342
A palynological investigation was conducted on two cores with Holocene sediments collected from the northeastern littoral part of the border Lake Doirani in northern Greece. The radiocarbon dates indicated that the analyzed sediments accumulated during the last 5000 yrs. The pollen-stratigraphic record revealed the environmental changes in the catchment area, starting from a natural undisturbed landscape to one modified by increasing anthropogenic influences. The tree vegetation dominated by Quercus woods in the lowlands and byPinus, Abies, and Fagus at higher altitudes, lasted for the period 2900 - 830 cal. B.C. Subsequently it was replaced by xerothermic herb and tree vegetation as a result of intensive human activity - and farming and stock-breeding. The accumulation of sediments with more sand and gravel in historical time was the result of increased erosion. 相似文献
86.
Nikolaos Efthimiou 《水文科学杂志》2019,64(9):1095-1116
The study aims to investigate the effect of soil properties delineation on erosion modelling. To that end, the soil attributes of the Venetikos River catchment, northwestern Greece, are described using two pedological datasets, i.e. field samples and classification maps. The goal is to select the most appropriate for the accurate estimation of erosion. The Revised Morgan-Morgan-Finney (RMMF) model is developed per base map (annual or multi-annual), keeping all other parameters unchanged. Modelled sediment yield (SY) values are validated against “observed” ones, calculated utilizing the sediment rating curve methodology. Overall, the classification maps approach (164.35 t km-2 year?1) performed better than the soil samples one (82.97 t km-2 year?1), displaying higher convergence to the synthetic SY (548.9 t km-2 year?1). The discrepancy among approaches is attributed to the different computation methodologies (thus pedological background) used. Both approximations successfully identified the high-risk erosion areas. The same conclusions arose from the multi-annual application of the model. 相似文献
87.
Optimal multi-step collocation: application to the space-wise approach for GOCE data analysis 总被引:5,自引:3,他引:2
Collocation is widely used in physical geodesy. Its application requires to solve systems with a dimension equal to the number
of observations, causing numerical problems when many observations are available. To overcome this drawback, tailored step-wise
techniques are usually applied. An example of these step-wise techniques is the space-wise approach to the GOCE mission data
processing. The original idea of this approach was to implement a two-step procedure, which consists of first predicting gridded
values at satellite altitude by collocation and then deriving the geo-potential spherical harmonic coefficients by numerical
integration. The idea was generalized to a multi-step iterative procedure by introducing a time-wise Wiener filter to reduce
the highly correlated observation noise. Recent studies have shown how to optimize the original two-step procedure, while
the theoretical optimization of the full multi-step procedure is investigated in this work. An iterative operator is derived
so that the final estimated spherical harmonic coefficients are optimal with respect to the Wiener–Kolmogorov principle, as
if they were estimated by a direct collocation. The logical scheme used to derive this optimal operator can be applied not
only in the case of the space-wise approach but, in general, for any case of step-wise collocation. Several numerical tests
based on simulated realistic GOCE data are performed. The results show that adding a pre-processing time-wise filter to the
two-step procedure of data gridding and spherical harmonic analysis is useful, in the sense that the accuracy of the estimated
geo-potential coefficients is improved. This happens because, in its practical implementation, the gridding is made by collocation
over local patches of data, while the observation noise has a time-correlation so long that it cannot be treated inside the
patch size. Therefore, the multi-step operator, which is in theory equivalent to the two-step operator and to the direct collocation,
is in practice superior thanks to the time-wise filter that reduces the noise correlation before the gridding. The criteria
for the choice of this filter are investigated numerically. 相似文献
88.
Nikolaos Andronikidis Eleni Kokinou Antonios Vafidis Evangelos Kamberis Emmanouil Manoutsoglou 《Marine Geophysical Researches》2018,39(4):475-490
Seismic reflection data and bathymetry analyses, together with geological information, are combined in the present work to identify seabed structural deformation and crustal structure in the Western Mediterranean Ridge (the backstop and the South Matapan Trench). As a first step, we apply bathymetric data and state of art methods of pattern recognition to automatically detect seabed lineaments, which are possibly related to the presence of tectonic structures (faults). The resulting pattern is tied to seismic reflection data, further assisting in the construction of a stratigraphic and structural model for this part of the Mediterranean Ridge. Structural elements and stratigraphic units in the final model are estimated based on: (a) the detected lineaments on the seabed, (b) the distribution of the interval velocities and the presence of velocity inversions, (c) the continuity and the amplitudes of the seismic reflections, the seismic structure of the units and (d) well and stratigraphic data as well as the main tectonic structures from the nearest onshore areas. Seabed morphology in the study area is probably related with the past and recent tectonics movements that result from African and European plates’ convergence. Backthrusts and reverse faults, flower structures and deep normal faults are among the most important extensional/compressional structures interpreted in the study area. 相似文献
89.
90.
Influence of frequency‐dependent soil–structure interaction on the fragility of R/C bridges
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Bridge performance under earthquake loading can be significantly influenced by the interaction between the structure and the supporting soil. Even though the frequency dependence of the interaction mentioned in this study has long been documented, the simplifying assumption that the dynamic stiffness is dominated by the mean or predominant excitation frequency is still commonly made, primarily as a result of the associated numerical difficulties when the analysis has to be performed in the time domain. This study makes use of the advanced lumped parameter models recently developed 1 in order to quantify the impact of the assumption on the predicted fragility of bridges mentioned in this study. This is achieved by comparing the predicted vulnerability for the case of a reference, well studied, actual bridge using both conventional, frequency‐independent, Kelvin–Voigt models and the aforementioned lumped parameter formulation. Analysis results demonstrate that the more refined consideration of frequency dependence of soil–structure interaction at the piers and the abutments of a bridge not only leads to different probabilities of failure for given intensity measures but also leads to different hierarchy and distribution of damage within the structure for the same set of earthquake ground motions even if the overall probability of exceeding a given damage state is the same. The paper concludes with the comparative assessment of the effect for different soil conditions, foundation configurations, and ground motion characteristics mentioned in this study along with the relevant analysis and design recommendations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献