Temporal patterns of glass eel migration (Anguilla anguilla L. 1758) in relation to environmental factors in the Western Greek inland waters     

Spyridoula Zompola  George Katselis  Constantin Koutsikopoulos  Yannis Cladas 《Estuarine, Coastal and Shelf Science》2008

Glass eel migration of the European eel Anguilla anguilla (L., 1758) in the eastern Mediterranean is poorly known despite the increasing state of anxiety for the future of the stock. In the present study, glass eel migration was investigated from October 1999 to April 2000, using experimental fishery with fyke nets, in two coastal systems along the western Greece (Ionian Sea): at the Sagiada marsh in the delta area of Kalamas River and at the mouth of Alfios River. The main period of the glass eel entrance was from December to March and the migration pattern was similar to those observed along the Atlantic coast of southwestern Europe. The variance of daily glass eel catches between the two studied sites was significantly different. The univariate and bivariate time series spectral analysis showed that glass eel short-term freshwater migration: (1) consisted of waves with periods from 5 to 40 days and (2) was correlated with environmental factors such as water temperature, atmospheric pressure, rainfall and moonlight. The observed differences between the two sites reveal the importance of the inland ecosystem characteristics.  相似文献   

The solar service of the National Observatory of Athens     

Constantin J. Macris 《Solar physics》1967,2(1):125-128

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Flood risk perception along the Lower Danube river,Romania     

Iuliana Armas  Radu Ionescu  Cristina Nenciu Posner 《Natural Hazards》2015,79(3):1913-1931

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Avalonian and Cadomian terranes in North Dobrogea,Romania     

Ion Balintoni  Constantin Balica  Antoneta Seghedi  Mihai N. Ducea 《Precambrian Research》2010

The North Dobrogea orogen is a collage of dismembered terrane fragments between the Moesian platform and East European craton (Baltica). It records Alpine and Variscan deformation, magmatism and metamorphism. Its basement comprises three metamorphic complexes (Boclugea, Megina and Orliga) that are separated by tectonic boundaries. Detrital zircon U/Pb ages suggest the Boclugea and Orliga complexes represent two peri-Gondwanan terranes of Avalonian and Cadomian affinities, respectively. The new data clarify the original relationships between the North Dobrogea terranes, and Baltica and Moesia platform.  相似文献   

Sliding response of gravity dams including vertical seismic accelerations     

Constantin?ChristopoulosEmail author  Pierre?Léger  André?Filiatrault 《地震工程与工程振动(英文版)》2003,2(2):189-200

Seismic safety assessment of gravity dams has become a major concern in many regions of the world while the effects of vertical seismic accelerations on the response of structures remain poorly understood. This paper first investigates the effect of including vertical accelerations in the sliding response analysis of gravity dams subjected to a range of historical ground motion records separated in two groups according to their source-to-site distance. Analyses showed that the incidence of vertical accelerations on the sliding response of gravity dams is significantly higher for near-source records than for farsource records. The pseudo-static 30% load combination rule, commonly used in practice to account for the non-simultaneous occurrence of the peak horizontal and vertical accelerations, yielded good approximations of the minimum safety factors against sliding computed from time-history analyses. A method for empirically estimating the vertical response spectra based on horizontal spectra, accounting for the difference in frequency content and amplitudes between the two components is investigated. Results from analyses using spectrum compatible horizontal and vertical synthetic records also approximated well the sliding response of a gravity dam subjected to series of simultaneous horizontal and vertical historical earthquake records.  相似文献   

On the possibilities of using the power spectrum in some geological and geophysical problems     

Radu Botezatu 《Mathematical Geology》1970,2(3):303-305

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The mm wave outbursts of November 1 and 2, 1968     

Michael Anastassiades  Constantin Macris 《Solar physics》1969,10(1):188-195

On November 1 and 2, 1968 two flares of importance 2b associated with the active region = S15°, L = 173° presented particular activity in the mm band. The outburst of November 1 in the mm wavelength band was of the gradual rise and fall type, while 24 hours later, the outburst of November 2 was of the sudden increase type with flux increase of the order of 4000 units. In the cm band the flare of November 1 produced a flux increase greater than in the mm band, while on November 2 the flare produced a series of outbursts with gradually increasing maxima, but much lower than the mm flux increase. It is reported that generally the peak flux decreases with increasing wavelength. The outburst of November 2 follows this rule but it is exactly the opposite for the sudden increase outburst produced by the November 1 flare. As to whether an increased brightness produces a higher mm or cm flux increase, available observations are not sufficient to make a firm statement.  相似文献   

Le développement du potentiel dans le cas d'une densité lisse     

Constantin Kholchevnikov 《Celestial Mechanics and Dynamical Astronomy》1972,6(2):214-220

The potential of a body of revolution is expanded in a series of spherical functions. It is proved that for a body of smooth structure the coefficients of expansion decrease in a power law.

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Horseshoes and nonintegrability in the restricted case of a spinless axisymmetric rigid body in a central gravitational field     

Radu Balan 《Celestial Mechanics and Dynamical Astronomy》1995,63(1):59-79

The purpose of this paper is to study the motion of a spinless axisymmetric rigid body in a Newtonian field when we suppose the motion of the center of mass of the rigid body is on a Keplerian orbit. In this case the system can be reduced to a Hamiltonian system with configuration space of a two-dimensional sphere. We prove that the restricted planar motion is analytical nonintegrable and we find horseshoes due to the eccentricity of the orbit. In the caseI ₃/I ₁>4/3, we prove that the system on the sphere is also analytical nonintegrable.On leave from the Polytechnic Institute of Bucharest, Romania.  相似文献   

Macroseismic field of the March 4, 1977 Vrancea earthquake     

C. Radu  G. Polonic  I. Apopei 《Tectonophysics》1979,53(3-4)

The macroseismic field of the Vrancea earthquake of March 4, 1977, characterized by the following parameters : H = 19h 21m 56s, ø = 45.8°N, γ = 26.8° E, h = 95 Km, M = 7.2, I = VIIIMSK has been analyzed. The following problems were studied : area and shape of the isoseismals of intensity III–VIII ; elongation of the isoseismal ellipses and decrease of intensity with distance. The results confirm our previous studies (Radu and Apopei, 1978) of strong intermediate earthquakes, but render evidence for some peculiarities in the seismic intensity attenuation as well.  相似文献