The validity of the continuum limit in the gravitational N-body problem     

Ioannis V. Sideris 《Celestial Mechanics and Dynamical Astronomy》2004,90(1-2):147-162

This paper attempts to give quantitative as well as qualitative answers to the question of the analogy between smooth potentials and N-body systems. A number of simulations were performed in both integrable and nonintegrable smooth environments and their frozen N-body analogues, and comparisons were made using a number of different tools. The comparisons took place on both statistical and pointwise levels. The results of this study suggest that microscopic chaos associated with discreteness effects is always present in N-body configurations. This chaos is different from the macroscopic chaos which is associated with the bulk potential and persists even for very large N. Although the Lyapunov exponents of orbits evolving in N-body environments do not decrease as N increases, comparisons associated with the statistical properties, as well as with the power spectra of the orbits, affirm the existence of the continuum limit.  相似文献   

Analysis of Faults' Effect on the Stability of Surface Lignite Mining Areas Using the Distinct Element Method     

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   

Numerical Slope Stability Analysis of Deep Excavations Under Rainfall Infiltration     

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   

Petrography and geochemistry of the enriched basaltic shergottite Northwest Africa 2975          下载免费PDF全文

Qi He  Long Xiao  J. Brian Balta  Ioannis P. Baziotis  Weibiao Hsu  Yunbin Guan 《Meteoritics & planetary science》2015,50(12):2024-2044

We present a study of the petrology and geochemistry of basaltic shergottite Northwest Africa 2975 (NWA 2975). NWA 2975 is a medium‐grained basalt with subophitic to granular texture. Electron microprobe (EMP) analyses show two distinct pyroxene compositional trends and patchy compositional zoning patterns distinct from those observed in other meteorites such as Shergotty or QUE 94201. As no bulk sample was available to us for whole rock measurements, we characterized the fusion crust and its variability by secondary ion mass spectrometer (SIMS) measurements and laser ablation inductively coupled plasma spectroscopy (LA‐ICP‐MS) analyses as a best‐available proxy for the bulk rock composition. The fusion crust major element composition is comparable to the bulk composition of other enriched basaltic shergottites, placing NWA 2975 within that sample group. The CI‐normalized REE (rare earth element) patterns are flat and also parallel to those of other enriched basaltic shergottites. Merrillite is the major REE carrier and has a flat REE pattern with slight depletion of Eu, parallel to REE patterns of merrillites from other basaltic shergottites. The oxidation state of NWA 2975 calculated from Fe‐Ti oxide pairs is NNO‐1.86, close to the QFM buffer. NWA 2975 represents a sample from the oxidized and enriched shergottite group, and our measurements and constraints on its origin are consistent with the hypothesis of two distinct Martian mantle reservoirs: a reduced, LREE‐depleted reservoir and an oxidized, LREE‐enriched reservoir. Stishovite, possibly seifertite, and dense SiO₂ glass were also identified in the meteorite, allowing us to infer that NWA 2975 experienced a realistic shock pressure of ~30 GPa.  相似文献   

An agricultural flash flood loss estimation methodology: the case study of the Koiliaris basin (Greece), February 2003 flood   总被引：2，自引：1，他引：1  

Anthi-Eirini K. Vozinaki  George P. Karatzas  Ioannis A. Sibetheros  Emmanouil A. Varouchakis 《Natural Hazards》2015,79(2):899-920

  相似文献   

Fish farming enhances biomass and nutrient loss in Posidonia oceanica (L.) Delile     

Eugenia T. Apostolaki  Núria Marbà  Marianne Holmer  Ioannis Karakassis 《Estuarine, Coastal and Shelf Science》2009,81(3):390-400

Fish farming impact on the seasonal biomass, carbon and nutrient (nitrogen and phosphorus) balance of the endemic Mediterranean seagrass Posidonia oceanica was assessed in the Aegean Sea (Greece) in order to detect changes in magnitude and fate of seagrass production and nutrient incorporation with organic loading of the meadows. Phosphorus concentration in the leaves, rhizomes and roots was enhanced under the cages throughout the study. Standing biomass was diminished by 64% and carbon, nitrogen and phosphorus standing stock by 64%, 61% and 48%, respectively, under the cages in relation to those at the control. Seagrass production decreased by 68% and element (C, N, P) incorporation by 67%, 58% and 58%, respectively, under the cages. Leaf shedding was reduced by 81% and loss of elements (C, N, and P) through shedding by 82%, 74% and 72%, respectively, under the cages. Leaf and element (C, N, P) residual loss rate, accounting for grazing and mechanical breakage of leaves, was decreased by 79%, 85%, 100% and 96%, respectively, at the control station. At the control station, 13.98 g C m^?2 yr^?1, 1.91 g N m^?2 yr^?1 and 0.05 g P m^?2 yr^?1 were produced in excess of export and loss. In contrast, under the cages 12.69 g C m^?2 yr^?1, 0.31 g N m^?2 yr^?1 and 0.04 g P m^?2 yr^?1 were released from the meadow. Organic loading due to fish farm discharges transformed the seagrass meadow under the cages from a typical sink to a source of organic carbon and nutrients.  相似文献   

Mediterranean forest mapping using hyper-spectral satellite imagery   总被引：2，自引：0，他引：2  

Selma Etteieb  Mounir Louhaichi  Chariton Kalaitzidis  Ioannis Z. Gitas 《Arabian Journal of Geosciences》2013,6(12):5017-5032

Mediterranean forests are characterized by spatiotemporal heterogeneity that is associated with Mediterranean climate, floristic biodiversity and topographic variability. Satellite remote sensing can be an effective tool for characterizing and monitoring forest vegetation distribution within these fragmented Mediterranean landscapes. The heterogeneity of Mediterranean vegetation, however, often exceeds the resolution typical of most satellite sensors. Hyper-spectral remote sensing technology demonstrates the capacity for accurate vegetation identification. The objective of this research is to determine to what extent forest types can be discriminated using different image analysis techniques and spectral band combinations of Hyperion satellite imagery. This research mapped forest types using a pixel-based Spectral Angle Mapper (SAM), nearest neighbour and membership function classifiers of the object-oriented classification. Hyperion classification was done after reducing Hyperion data using nine selected band combinations. Results indicate that the selection of band combination while reducing the Hyperion dataset improves classification results for both the overall and the individual forest type accuracy, in particular for the selected optimum Hyperion band combination. One shortcoming is that the performance of the best selected band combination was superior in terms of both overall and individual forest type accuracy when applying the membership classifier of the object-oriented method compared to SAM and nearest neighbour classifiers. However, all techniques seemed to suffer from a number of problems, such as spectral similarity among forest types, overall low energy response of the Hyperion sensor, Hyperion medium spatial resolution and spatiotemporal and spectral heterogeneity of the Mediterranean ecosystem at multiple scales.  相似文献   

Yukawa-type potential effects in the anomalistic period of celestial bodies     

Ioannis Haranas  Omiros Ragos  Vasile Mioc 《Astrophysics and Space Science》2011,332(1):107-113

Several contemporary modified models of gravity predict the existence of a non-Newtonian Yukawa-type correction to the classical gravitational potential. We study the motion of a secondary celestial body under the influence of the corrected gravitational force of a primary. We derive two equations to approximate the periastron time rate of change and its total variation over one revolution (i.e., the difference between the anomalistic period and the Keplerian period) under the influence of the non-Newtonian radial acceleration. Kinematically, this influence produces apsidal motion. We performed numerical estimations for Mercury, for the companion star of the pulsar PSR 1913+16, and for the extrasolar Planet b of the star HD 80606. We also considered the case of the artificial Earth satellite GRACE-A, but the results present a low degree of reliability from a practical standpoint.  相似文献   

Extension of direct displacement‐based design methodology for bridges to account for higher mode effects     

Andreas J. Kappos  Konstantinos I. Gkatzogias  Ioannis G. Gidaris 《地震工程与结构动力学》2013,42(4):581-602

An improvement is suggested to the direct displacement‐based design (DDBD) procedure for bridges to account for higher mode effects, the key idea being not only the proper prediction of a target‐displacement profile through the effective mode shape method (wherein all significant modes are considered), but also the proper definition of the corresponding peak structural response. The proposed methodology is then applied to an actual concrete bridge wherein the different pier heights and the unrestrained transverse displacement at the abutments result in an increased contribution of the second mode. A comparison between the extended and the ‘standard’ DDBD is conducted, while further issues such as the proper consideration of the degree of fixity at the pier's top and the effect of the deck's torsional stiffness are also investigated. The proposed methodology and resulting designs are evaluated using nonlinear response‐history analysis for a number of spectrum‐compatible motions. Unlike the ‘standard’ DDBD, the extended procedure adequately reproduced the target‐displacement profile providing at the same time a good estimate of results regarding additional design quantities such as yield displacements, displacement ductilities, etc., closely matching the results of the more rigorous nonlinear response‐history analysis. However, the need for additional iterations clearly indicates that practical application of the proposed procedure is feasible only if it is fully ‘automated’, that is, implemented in a software package. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Integrated Use of Optical and Radar Satellite Data for Active Faults and Corresponding Displaced Landforms in Kozani Basin (Greece)     

Parcharidis Issaak  Nikolakopoulos Konstantinos  Serelis Konstantinos  Baskoutas Ioannis 《国际地球制图》2013,28(3):17-23

Abstract

The usefulness of integration of SAR (ERS-1) and Landsat TM data for study active faults and the corresponding displaced landforms in flat or almost flat areas has been demonstrated. The study area is the Kozani basin which in May 13, 1995 was affected by a strong earthquake (Ms=6.6). After co-registration and resampling the two data sets were merged to form a combined image. The combined image offers the spectral characteristics of the TM data with the spatial resolution and roughness sensitivity of SAR images. The merging method used was the IMS to RGB transform. The criteria and parameters examined were geomorphic features, drainage network analysis, slope processes, terrain analysis, and observations on spatial distribution of soil cover as well as linear features that correspond to fracture zones crossing the basin. The use of the combined image allowed us to identify tectonic terraces in the basin produced by activity of normal faults located in the adjacent relief zone.  相似文献