Changes of macrofaunal functional composition at sedimentary habitats in the vicinity of fish farms     

Nafsika Papageorgiou  Kalliopi Sigala  Ioannis Karakassis   《Estuarine, Coastal and Shelf Science》2009,83(4):561-568

The relationship of functional diversity and composition was studied in gradients of organically enriched sediments from four Mediterranean fish farms. Within-functional trait diversity was also used to examine the functional redundancy of specific functional traits. Characteristics considered to respond to different geochemical conditions of the sediment were chosen for the traits list of that organism and were classified into ecological and morphological traits. Each trait was split up into several categories chosen to encompass the range of possible attributes of all species. The abundance of species possessing the same code was summed for each sample. Functional codes analyses differentiated between the sediment types and the TOC states, confirming the sensitivity of the functional characteristics to the geochemistry of the sediment. Changes in species number and abundance in the compared sites determined the shifts of the functional processes and not the presence or absence of individual traits. The important functional codes for the homogeneity within the examined habitats were fewer in the disturbed areas indicating that the functioning of these ecosystems is significantly reduced.  相似文献   

Accidental eccentricity in symmetric buildings due to wave passage effects arising from near‐fault pulse‐like ground motions          下载免费PDF全文

Yenan Cao  George P. Mavroeidis  Kristel C. Meza‐Fajardo  Apostolos S. Papageorgiou 《地震工程与结构动力学》2017,46(13):2185-2207

This article investigates the characteristics of the accidental eccentricity in symmetric buildings due to torsional response arising from wave passage effects in the near‐fault region. The soil–foundation–structure system is modeled as a symmetric cylinder placed on a rigid circular foundation supported on an elastic halfspace and subjected to obliquely incident plane SH waves simulating the action of near‐fault pulse‐like ground motions. The translational response is computed assuming that the superstructure behaves as a shear beam under the action of translational and rocking base excitations, whereas the torsional response is calculated using the mathematical formulation proposed in a previous study. A broad range of properties of the soil–foundation–structure system and ground motion input are considered in the analysis, thus facilitating a detailed parametric investigation of the structural response. It is demonstrated that the normalized accidental eccentricity is most sensitive to the pulse period (T_P) of the near‐fault ground motions and to the uncoupled torsional‐to‐translational fundamental frequency ratio (Ω) of the structure. Furthermore, the normalized accidental eccentricities due to simplified pulse‐like and broadband ground motions in the near‐fault region are computed and compared against each other. The results show that the normalized accidental eccentricity due to the broadband ground motion is well approximated by the simplified pulse for longer period buildings, while it is underestimated for shorter period buildings. For symmetric buildings with values of Ω commonly used in design practice, the normalized accidental eccentricity due to wave passage effects is less than the typical code‐prescribed value of 5%, except for buildings with very large foundation radius. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

On the date of construction of Lechaion,western harbor of ancient Corinth,Greece     

S. Stiros  P. Pirazzoli  R. Rothaus  S. Papageorgiou  J. Laborel  M. Arnold 《Geoarchaeology》1996,11(3):251-263

Lechaion, the western harbor of ancient Corinth, was an artificial harbor excavated in a marshy area and connected to the open sea through a channel with revetment walls. It was probably the most important harbor of this type in antiquity, and one of the most important harbors in Greece for more than one millennium. Yet, the date of construction of this harbor is a matter of debate; 600 B.C., ca. 44 B.C., and A.D. 350 are the most probable dates. Geomorphological and biological investigations, in combination with AMS radiocarbon dating of exposed marine shells found in the walls of the channel leading to the inner basin of the harbor indicate that the channel was open to the sea before a seismic land uplift that probably occurred sometime in the fifth to third century B.C. These data indicate that the construction of the harbor began in ca. 600 B.C., the period of Corinthian expansion to the Ionian Sea and southern Italy. © 1996 John Wiley & Sons, Inc.  相似文献