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1.
The Euvoikos gulf, and the strait of Euripos therein, is a restricted embayment on the eastern coast of Greece having a significant, unusual tidal phenomenon and receiving some domestic, trade and industrial wastes from the town of Chalkis and several coastal industries. The purpose of the present work was to study the influence of the tidal current and the anthropogenic inputs on the distributions of several trace elements (namely, Pb, Cu, Zn, Cr, Fe, Mn and Ni) in the seawaters (as dissolved and particulate species) and the sea-bottom sediments. Thorough mixing, resuspension and transport of fine particles and direct discharges are the major mechanisms affecting the distribution patterns. 相似文献
2.
The magnitude M = 6-5 Coalinga earthquake of 2 May 1983 caused intense ground shaking throughout the epicentral region. Unanchored cylindrical ground supported tanks located at six sites within this oil producing area were damaged; damages included elephant's foot buckling at the base of three moderate sized tanks, joint rupture and top shell buckling in one large old rivetted tank, bottom plate rupture of a relatively new welded tank and damage to the floating roofs of 11 tanks. Also oil spilled over the top of many tanks and secondary damages occurred in pipe connections, ladders, etc. In this paper an estimate is made of the intensity of ground motion at each of the tank sites, based on strong motion records made during the main shock and the strongest aftershock. Then response parameters specified by current codes are correlated with the damages observed at each tank site. Based on this comparison, it is concluded that current U.S. practice under-estimates the sloshing response of tanks with floating roofs and does not adequately address the uplifting mechanism of unanchored ground supported tanks. 相似文献
3.
Tassos Bountis Thanos Manos Chris Antonopoulos 《Celestial Mechanics and Dynamical Astronomy》2012,113(1):63-80
We use probability density functions (pdfs) of sums of orbit coordinates, over time intervals of the order of one Hubble time, to distinguish weakly from strongly chaotic orbits in a barred galaxy model. We find that, in the weakly chaotic case, quasi-stationary states arise, whose pdfs are well approximated by q-Gaussian functions (with 1 <?q < 3), while strong chaos is identified by pdfs which quickly tend to Gaussians (q =?1). Typical examples of weakly chaotic orbits are those that ??stick?? to islands of ordered motion. Their presence in rotating galaxy models has been investigated thoroughly in recent years due to their ability to support galaxy structures for relatively long time scales. In this paper, we demonstrate, on specific orbits of 2 and 3 degree of freedom barred galaxy models, that the proposed statistical approach can distinguish weakly from strongly chaotic motion accurately and efficiently, especially in cases where Lyapunov exponents and other local dynamic indicators appear to be inconclusive. 相似文献
4.
George C. Manos Stergios A. Mitoulis Anastasios G. Sextos 《Bulletin of Earthquake Engineering》2012,10(3):1029-1047
Seismic design of isolated bridges involves conceptual, preliminary and detailed structural design. However, despite the variety of commercial software currently available for the analysis and design of such systems, conceptual and preliminary design can prove to be a non-straightforward procedure because of the sensitivity of bridge response on the initial decisions made by the designer of the location, number and characteristics of the bearings placed, as well as on a series of broader criteria such as serviceability, target performance level and cost-effectiveness of the various design alternatives. Given the lack of detailed design guidelines to ensure, at this preliminary stage, compliance with the above requirements, a “trial and error” procedure is typically followed in the design office to decide on the most appropriate design scheme in the number and location of the bearing systems; the latter typically based on engineering judgment to balance performance with cost. To this end, the particular research effort aims to develop a decision-making system for the optimal preliminary design of seismically isolated bridges, assumed to respond as single degree of freedom (SDOF) systems. The proposed decision-making process is based on the current design provisions of Eurocode 8, but is complemented by additional criteria set according to expert judgment, laboratory testing and recent research findings, while using a combined cost/performance criterion to select from a database of bearings available on the international market. Software is also developed for the implementation of the system. The paper concludes with the application, and essentially the validation of the methodology and software developed through more rigorous MDOF numerical analysis for the case of a real bridge. 相似文献
5.
Vlahogianni T Dassenakis M Scoullos MJ Valavanidis A 《Marine pollution bulletin》2007,54(9):1361-1371
Mussels are used as sentinel organisms and bioindicators to evaluate the toxic effects of chemical pollutants in marine organisms, especially heavy metals, representing an important tool for biomonitoring environmental pollution in coastal areas. Antioxidant defence enzymes play an important role in cellular antioxidant defence systems and protect from oxidative damage by reactive oxygen species (ROS). Indigenous mussels Mytilus galloprovincialis of the Saronikos Gulf of Greece were used for monitoring heavy metal pollution in three polluted sites in the area and in one unpolluted site. Seasonal variations of the activity of antioxidant defence enzymes, superoxide dismutase (SOD) and catalase (CAT), as well as lipid peroxidation (LP) were measured as biomarkers in a period of three years in relation to concentrations of trace metals in their gills and mantle and compared to mussels from an unpolluted sampling site. SOD activity increased at least 2 fold at the polluted sites when compared to the control site (the high activity was recorded in the spring time). CAT activity was increased 2-3 times at the polluted sites, with high activity in the winter and spring time, compared to the control site. LP concentration was twice higher at the polluted sites, following the same seasonal pattern. Trace metals contents in mussels collected at polluted sites were 3-4 fold higher compared to the control site and showed moderate variations along the months, with a winter maximum followed by a summer pre-spawning minimum matching the seasonal trends of temperature and salinity. Our results showed that metal pollution in the Elefsis Bay (the most polluted coastal area) causes relatively medium levels of oxidative stress in tissues of mussels due to cellular oxy-radical generation. This study, which is the first in the area, showed that seasonal variations of the activity of antioxidant defence enzymes and LP concentrations in mussels can be used as potential biomarkers of toxicity for long-term monitoring in marine coastal ecosystems. 相似文献
6.
Research of several years has confirmed the general aspect that the most acceptable model in quasars' nuclei is a rotating Kerr black hole.Assuming the Kerr type potential given by the equation:
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7.
George C. Manos 《地震工程与结构动力学》1991,20(12):1099-1114
This paper details the damage sustained by a number of wine tanks during the San Juan, Argentina, 1977 earthquake. The available ground motion information is used to compare the actual tank performance with that predicted. Two of the tanks examined were located quite near the two accelerographs that recorded the ground motion in the city of San Juan for the main shock. An empirical attenuation formula which describes the intensity of the shaking was derived for this earthquake and used in a quantitative evaluation of the performance of a number of other tanks. By correlating and comparing the observed performance of the anchors and what was predicted we see the predictions are upheld by the actual damage. When the anchoring system failed during the earthquake the tanks were rendered effectively unanchored. Consequently, the state of stress that results from their base uplift was then examined in conjunction with the tank wall stability approach proposed by the author, and seen to give results consistent with the observed tank wall performance. 相似文献
8.
The bulging observed on the wall of a ground supported cylindrical storage tank, located at the Chiba Experimental Station of the University of Tokyo, is investigated. This damage is correlated with a ground motion recording obtained very near the tank base during a moderately strong earthquake that occurred on September 25, 1980 not far from the Chiba Experimental Station. From this correlation the importance of the horizontal excitation in amplitude and direction is clearly established. In addition, good agreement can be seen between the predicted tank wall earthquake performance, derived by an empirical approach proposed by the first author, and the shell deformation observed at the Chiba Experimental Station. 相似文献
9.
A. Valavanidis Th. Vlachogianni S. Triantafillaki M. Dassenakis F. Androutsos M. Scoullos 《Estuarine, Coastal and Shelf Science》2008,79(4):733-739
Polycyclic aromatic hydrocarbons (PAHs) were identified and measured in surface seawater and in the tissues (gills and mantle) of indigenous black mussels, Mytilus galloprovincialis, collected from three coastal sites of Saronikos Gulf (Greece), a gulf that exhibits high levels of pollution. The total PAHs measured by spectrofluorometry in the surface seawater were found in the range of 425–459 ng L−1 at the most polluted sites 1 and 2 (Elefsis Bay–Salamis Island) and in the range of 103–124 ng L−1 at site 3 (Aegina Island). PAHs' sources in seawater were identified by application of specific PAH ratios, such as phenanthrene/anthracene and fluoranthene/pyrene. Levels of PAHs in soft tissues (gills and mantle) of indigenous mussels were much higher than those reported for seawater. Total PAH concentrations in mantle tissues were in the range of 1300–1800 ng g−1 dry weight (dw) tissue at sites 1 and 2 and approximately 380 ng g−1 dw at site 3. In gill tissues total PAH concentrations were in the range of 1480–2400 ng g−1 dw at sites 1 and 2 and approximately 430 ng g−1 dw at site 3. PAHs composition was dominated by two-, three- and four-ring compounds in seawater, where 17 different PAH compounds were identified and measured in mussel tissues. Mussels can be used as sentinel organisms to monitoring PAHs' contamination, since they concentrate PAHs from the surrounding water media and therefore making the chemical analysis simpler and less prone to error than that for water. In surface seawater possible weathering and photodegradation due to hot climates contribute to reduced PAHs concentrations. 相似文献
10.
The rapidly expanding industry of marine cage fish farming of sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) in the Mediterranean Sea over the last decade has often had damaging effects on the benthic aquatic environment near the fish farm installations. It has been observed that the food-remains, together with the pellets and metabolic products from fish, frequently form a “nepheloid” sediment layer covering large areas of the seabed. Under these conditions anoxia and/or hypoxia develop and affect benthic communities while the quality of the marine environment deteriorates for long periods, extending even beyond the life span of the fish farm itself. In most cases the affected areas act initially as sediment traps and in a second phase as secondary sources of organic carbon, nutrients and other substances.The aim of this paper is to explore the behaviour of such an affected area under different redox regimes by measuring the fluxes of ammonium, nitrite, nitrate, TDN, phosphate, TDP and silicate between the surface sediment and the overlying waters. To achieve this goal we constructed a prototype benthic chamber capable of sampling considerable quantities of affected undisturbed sediment along with its overlying water. The chamber was transported to the laboratory where simulation experiments reproducing the conditions occurring in nature, including the extreme ones, were carried out and studied carefully. The chamber allows the full and fine control of the dissolved oxygen concentration – and thus of the redox potential – as well as water temperature while subsamples of both water and sediment could be obtained and analysed for a series of chemical substances. The controlled laboratory chamber experiments reproduced four successional phases: 1) deoxygenation, 2) hypoxia, 3) reoxygenation and 4) anoxia.The results showed that even minor changes in the redox conditions at a relatively narrow zone near the water sediment interface have significant impacts on the concentrations of dissolved nitrogen, phosphorus and silicate compounds.With decreasing oxygen supply (phases 1, 2 and 4), the concentrations of ammonium, nitrite, TDN, phosphate, TDP and silicate rapidly increase, those of nitrate decrease. DON and DOP exhibit remarkable fluctuations.During reoxygenation (phase 3) the concentrations of ammonium stabilise, the nitrate concentration decreases while nitrite shows an increasing trend. Decreases in phosphate and silicate concentrations were also observed paralleled by TDP stabilization and DOP increasing trend. TDN shows a relatively small increase while the DON concentration fluctuates significantly. 相似文献
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