Remarks on high latitude air temperature ranges and solar activity     

Dr. Christos S. Zerefos  Prof. Dr. John Xanthakis 《Meteorology and Atmospheric Physics》1975,24(2):163-170

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A hybrid method for the vulnerability assessment of R/C and URM buildings   总被引：6，自引：1，他引：6  

Andreas J. Kappos  Georgios Panagopoulos  Christos Panagiotopoulos  Gregorios Penelis 《Bulletin of Earthquake Engineering》2006,4(4):391-413

The methodology followed by the Aristotle University (AUTh) team for the vulnerability assessment of reinforced concrete (R/C) and unreinforced masonry (URM) structures is presented. The paper focuses on the derivation of vulnerability (fragility) curves in terms of peak ground acceleration (PGA), as well as spectral displacement (s _d), and also includes the estimation of capacity curves, for several R/C and URM building types. The vulnerability assessment methodology is based on the hybrid approach developed at AUTh, which combines statistical data with appropriately processed (utilising repair cost models) results from nonlinear dynamic or static analyses, that permit extrapolation of statistical data to PGA’s and/or spectral displacements for which no data are available. The statistical data used herein are from earthquake-damaged greek buildings. An extensive numerical study is carried out, wherein a large number of building types (representing most of the common typologies in S. Europe) are modelled and analysed. Vulnerability curves for several damage states are then derived using the aforementioned hybrid approach. These curves are subsequently used in combination with the mean spectrum of the Microzonation study of Thessaloniki as the basis for the derivation of new vulnerability curves involving spectral quantities. Pushover curves are derived for all building types, then reduced to standard capacity curves, and can easily be used together with the S _d fragility curves as an alternative for developing seismic risk scenarios.  相似文献   

S-wave spectral analysis of the 1995 Kozani-Grevena (NW Greece) aftershock sequence     

Zafeiria Roumelioti  Anastasia Kiratzi  Nikos Theodoulidis  Christos Papaioannou 《Journal of Seismology》2002,6(2):219-236

S-wave spectral analysis is applied to 174 strong motion accelerationrecords to obtain the source parameters of 27 aftershocks(3.1 M_L 4.3) of the May 13, 1995, M_w 6.6,Kozani-Grevena (NW Greece) earthquake. The data are derived from atemporary network, of three-component digital accelerographs, deployedwithin the strongly affected area some days after the mainshock occurrence.Site effects were evident in the strong motion records at 3 out of the 4stations used, and a correction was applied to account for theoverestimation of seismic moment due to amplification of thelow-frequency part of the spectrum. The data from this analysis arecomplimented with previously obtained source parameters for earthquakesin Greece, in order to study the applicability of the empirical scalingrelations used so far, towards smaller magnitudes. In general, a goodcorrelation was observed in most cases, validating the use of empiricalrelations that are applicable to the Aegean area. Empirical relations aredetermined between seismic moment and seismic slip, as well as, betweenseismic moment and stress drop, applicable to small magnitude earthquakes(M_L < 4.3). Stress drop values were found to be relatively small,ranging from 2 to 41 bars, indicative of inter-plate environments. Thevalues of f_c and of f_max were found in good agreement withrelations based on observations from larger worldwide earthquakes.  相似文献   

A source study of the Thessaloniki (northern Greece) 1978 earthquake sequence   总被引：1，自引：0，他引：1  

Christos Soufleris  Gordon S. Stewart 《Geophysical Journal International》1981,67(2):343-358

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The time-latitude distribution of solar flares accompanied by type IV radio bursts during the period 1956 to 1969     

Michael D. Papagiannis  Christos S. Zerefos  Christos C. Repapis 《Solar physics》1972,27(1):208-216

A list of nearly 350 flares accompanied by type IV radio bursts by Krüger et al. (1971), which covers a period of 14 yr (1956–1969), was expanded to include all PCA and solar cosmic ray events during this entire period. This list, which includes practically all of the most energetic events during the maxima of two consecutive solar cycles, was used to investigate the latitudinal distribution of the above-mentioned flares, as well as of all PCA events, solar cosmic ray events and plage regions associated with them.Histograms of these occurences show clearly the appearance of two peaks in both solar maxima, which confirm the observations of Gnevyshev (1967). Latitudinal analysis of these histograms shows that in cycle 20 the two peaks are independent and their relative strength varies strongly with latitude. In cycle 19, however, this effect is not clearly evident, possibly because of the extremely high level of activity during this cycle. In both cycles, the second maximum shows the highest concentration of the most energetic events.During 1971–1972 visiting Professor of Astrophysics at the National University of Athens, Athens, Greece.  相似文献   

Circulation changes in the free atmosphere during proton events associated with type IV radio bursts     

Christos S. Zerefos 《Planetary and Space Science》1975,23(7):1035-1043

New evidence of statistically significant circulation changes in the lower stratosphere and in the middle and upper troposphere following Type IV Proton and Ground Level Events confirms some earlier findings of a relationship between solar activity and weather. The maximum 24-hr circulation changes appear to occur in the North Pacific-Alaskan area. A comparison between the effects that followed the flare sample used in this study with earlier results reported for less intense solar particle emission flare samples, implies that if these particles are responsible for triggering the atmospheric circulation in times of enhanced solar activity, their atmospheric effect is enhanced as we move to the more energetic solar proton events. The physical explanation of the results may possibly be found in numerical-experimental models. Some possible causes of the results are discussed.  相似文献   

Erratum to: A cervelleite-like mineral and other Ag-Cu-Te-S minerals [Ag2CuTeS and (Ag,Cu)2TeS] in gold-bearing veins in metamorphic rocks of the Cycladic Blueschist Unit, Kallianou, Evia Island, Greece     

Panagiotis Christos Voudouris  Paul G. Spry  Gregory Aarne Sakellaris  Constantinos Mavrogonatos 《Mineralogy and Petrology》2011,103(1-4):179-179

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Porting of a wildfire risk and fire spread application into a cloud computing environment     

Kostas Kalabokidis  Nikolaos Athanasis  Christos Vasilakos  Palaiologos Palaiologou 《International journal of geographical information science》2014,28(3):541-552

Effective wildfire management is an essential part of forest firefighting strategies to minimize damage to land resources and loss of human lives. Wildfire management tools often require a large number of computing resources at a specific time. Such computing resources are not affordable to local fire agencies because of the extreme upfront costs on hardware and software. The emerging cloud computing technology can be a cost- and result-effective alternative. The purpose of this paper is to present the development and the implementation of a state-of-the-art application running in cloud computing, composed of a wildfire risk and a wildfire spread simulation service. The two above applications are delivered within a web-based interactive platform to the fire management agencies as Software as a Service (SaaS). The wildfire risk service calculates and provides daily to the end-user maps of the hourly forecasted fire risk for the next 112 hours in high spatiotemporal resolution, based on forecasted meteorological data. In addition, actual fire risk is calculated hourly, based on meteorological conditions provided by remote automatic weather stations. Regarding the wildfire behavior simulation service, end users can simulate the fire spread by simply providing the ignition point and the projected duration of the fire, based on the HFire algorithm. The efficiency of the proposed solution is based on the flexibility to scale up or down the number of computing nodes needed for the requested processing. In this context, end users will be charged only for their consumed processing time and only during the actual wildfire confrontation period. The system utilizes both commercial and open source cloud resources. The current prototype is applied in the study area of Lesvos Island, Greece, but its flexibility enables expansion in different geographical areas.  相似文献   

Hydro-climatic change,conflict and security     

Giorgos Kallis  Christos Zografos 《Climatic change》2014,123(1):69-82

Climate change is likely to increase the frequency and intensity of water-related hazards on human populations. This has generated security concerns and calls for urgent policy action. However, the simplified narrative that links climate change to security via water and violent conflict is wanting. First, it is not confirmed by empirical evidence. Second, it ignores the varied character and implications of hydro-climatic hazards, the multi-faceted nature of conflict and adaptive action, and crucial intricacies of security. Integrating for the first time research and findings from diverse disciplines, we provide a more nuanced picture of the climate-water-security nexus. We consider findings from the transboundary waters, armed conflict, vulnerability, and political ecology literatures and specify the implications and priorities for policy relevant research. Although the social effects of future hydro-climatic change cannot be safely predicted, there is a good understanding of the factors that aggravate risks to social wellbeing. To reduce vulnerability, pertinent democratic and social/civil security institutions should be strengthened where they exist, and promoted where they are still absent.  相似文献   

Validation of satellite rainfall products for operational flood forecasting: the case of the Evros catchment     

Fotis Fotopoulos  Christos Makropoulos  Maria A. Mimikou 《Theoretical and Applied Climatology》2011,104(3-4):403-414

An extensive validation of two of the most popular and recently upgraded satellite rainfall products, 3B42 and 3B42RT, was performed over the Evros catchment in southeastern Europe using data recorded from January 2000 to April 2009. For conducting this validation study, the Climate Prediction Center's (CPC) ground data were used. The satellite data products were aggregated to daily time series, remapped to spatial resolution of 0.5°, validated against CPC, and intercompared using a variety of statistical indices and coefficients. After the validation process, all three data sets (CPC, 3B42, and 3B42RT) were separately fed in a statistical rainfall?Crunoff model, in order to predict the five major recorded flood events which occurred in the Evros catchment during the last decade. It has been found that post-calibration with ground data, which is present only in 3B42 product, is a necessity for operational flood forecasting and similar studies conducted in areas at mid-latitudes. Knowledge of rainfall events with small intensities is crucial for estimating the total rainfall height and drastically improves the skill of the satellite product.  相似文献