Connectivity and stock composition of loggerhead turtles foraging on the North African continental shelf (Central Mediterranean): implications for conservation and management          下载免费PDF全文

Sami Karaa  Fulvio Maffucci  Imed Jribi  Marco Alberto Bologna  Marco Borra  Elio Biffali  Mohamed Nejmeddine Bradai  Sandra Hochscheid 《Marine Ecology》2016,37(5):1103-1115

The loggerhead turtle, Caretta caretta, is a highly migratory species with a complex life cycle that involves a series of ontogenetic habitat shifts and migrations. Understanding the links amongst nesting populations and foraging habitats is essential for the effective management of the species. Here we used mixed stock analysis to examine the natal origin of loggerhead turtles foraging on the North African continental shelf off Tunisia, one of the most important Mediterranean neritic habitats. An 815‐bp fragment of the mitochondrial DNA control region was sequenced from 107 individuals sampled from 2007 to 2009. No temporal variation in haplotype frequencies was detected. Juveniles (n = 87) and adults (n = 23) exhibited weak but significant genetic differentiation that resulted in different stock compositions. Libya was the main source population but the proportion of turtles from this rookery was higher in adults (median = 80%) than in juveniles (median = 35%). Western Greece was the second most important contributing population. Juvenile stock composition derived from mixed stock analysis and the estimates produced by numerical simulation of hatchling dispersion in the Mediterranean Sea were significantly correlated, supporting the recent theory that loggerheads imprint on possible future neritic habitats during the initial phase of their life. This association was not significant for adults, suggesting that other factors contribute to shaping their distribution. Overall, our results show that human activities on the South Tunisian continental shelf pose an immediate threat to the survival of the Libyan rookery.  相似文献   

An investigation on the formation of submerged bar under surges in sandy coastal region   总被引：1，自引：0，他引：1  

Mustafa DEMRC  M.Sami AKZ 《中国海洋工程》2012,26(3):535-546

Cross-shore sediment transport rate exposed to waves is very important for coastal morphology,the design of marine structures such as seawalls,jetties,breakwaters etc,and the prevention of coastal erosion and accretion due to on-off shore sediment transportation.In the present study,the experiments on cross-shore sediment transport are carried out in a laboratory wave channel with initial beach slopes of 1/8,1/10 and 1/15.By using the regular waves with different deep-water wave steepnesses generated by a pedal-type wave generator,the geometrical characteristics of beach profiles under storm conditions and the parameters affecting on-off shore sediment transport are investigated for the beach materials with medium diameters of d50=0.25,0.32,0.45,0.62 and 0.80 mm.The offshore bar geometric characteristics are the horizontal distances from the shoreline to the bar beginning(Xb),crest(Xt),and ending(Xs) points,the depth from the bar crest to the still water level(ht),and the bar volume(Vbar).The experimental results have indicated that when the deep-water steepness(H0/L0) increased,the net movement to seaside increased.With the increasing wave steepness,the bars moved to widen herewith the vertical distances from still water level to the bar beginning(Xb),crest(Xt) and ending(Xs) points and the horizontal distances from the coast line to the bar beginning,crest and ending points increased.It was also shown from experimental results that the horizontal distances from the bar beginning and ending points to the coast line increased with the decrease of the beach slope.The experimental results obtained from this study are compared with previous experimental work and found to be of the same magnitude as the experimental measurements and followed the expected basic trend.  相似文献   

Electrical Resistivity Tomography (ERT) Applied to Karst Carbonate Aquifers: Case Study from Amdoun,Northwestern Tunisia     

Belgacem Redhaounia  Batobo Ountsche Ilondo  Hakim Gabtni  Khomsi Sami  Mourad Bédir 《Pure and Applied Geophysics》2016,173(4):1289-1303

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A method for non-parametric damage detection through the use of neural networks     

Mitsuru Nakamura  Sami F. Masri  Anastassios G. Chassiakos  Thomas K. Caughey 《地震工程与结构动力学》1998,27(9):997-1010

A neural network-based approach is presented for the detection of changes in the characteristics of structure-unknown systems. The approach relies on the use of vibration measurements from a ‘healthy’ system to train a neural network for identification purposes. Subsequently, the trained network is fed comparable vibration measurements from the same structure under different episodes of response in order to monitor the health of the structure. The methodology is applied to actual data obtained from ambient vibration measurements on a steel building structure that was damaged under strong seismic motion during the Hyogo-Ken Nanbu Earthquake of 17 January 1995. The measurements were done before and after repairs to the damaged frame were made. A neural network is trained with data after the repairs, which represents ‘healthy’ condition of the building. The trained network, which is subsequently fed data before the repairs, successfully identified the difference between the damaged storey and the undamaged storey. Through this study, it is shown that the proposed approach has the potential of being a practical tool for a damage detection methodology applied to smart civil structures. © 1998 John Wiley & Sons, Ltd.  相似文献   

Combination of FEM and CMA‐ES algorithm for transmissivity identification in aquifer systems          下载免费PDF全文

Hassan Smaoui  Lahcen Zouhri  Sami Kaidi  Erick Carlier 《水文研究》2018,32(2):264-277

In this paper, we propose a coupling of a finite element model with a metaheuristic optimization algorithm for solving the inverse problem in groundwater flow (Darcy's equations). This coupling performed in 2 phases is based on the combination of 2 codes: This is the HySubF‐FEM code (hydrodynamic of subsurface flow by finite element method) used for the first phase allowing the calculation of the flow and the CMA‐ES code (covariance matrix adaptation evolution strategy) adopted in the second phase for the optimization process. The combination of these 2 codes was implemented to identify the transmissivity field of groundwater by knowing the hydraulic head in some point of the studied domain. The integrated optimization algorithm HySubF‐FEM/CMA‐ES has been validated successfully on a schematic case offering an analytical solution. As realistic application, the integrated optimization algorithm HySubF‐FEM/CMA‐ES was applied to a complex groundwater in the north of France to identify the transmissivity field. This application does not use zonation techniques but solves an optimization problem at each internal node of the mesh. The obtained results are considered excellent with high accuracy and fully consistent with the hydrogeological characteristics of the studied aquifer.However, the various numerical simulations performed in this paper have shown that the CMA‐ES algorithm is time‐consuming. Finally, the paper concludes that the proposed algorithm can be considered as an efficient tool for solving inverse problems in groundwater flow.  相似文献   

Coupling of phytoplankton and ciliate biomasses to environmental factors along the north coast of Sfax (Tunisia,Eastern Mediterranean Sea)     

Amira Rekik  Jannet Elloumi  Zaher Drira  Sami Maalej  Habib Ayadi 《Water Resources》2017,44(6):849-863

The phytoplankton and ciliate biomasses coupled with environmental factors were investigated in 15 transects in north coasts of Sfax (Tunisia, Eastern Mediterranean Sea) in July 2007. The phytoplankton biomass was dominated by Bacillariophyceae (89.66%), followed by Dinophyceae (10.07%), Coccolithophorideae (0.96%), Cyanobacteriae (0.21%), Chlorophyceae (0.03%) and Euglenophyceae (0.01%). Coscinodiscus sp. (93.26%) was the most abundant species of Bacillariophyceae group and associated with a high nutrient availability. Ciliate biomass was highly variable, with a large dominance of Spirotrichea, up to 96.2%. Biomass followed distinct patterns because of differences in the observed organism biovolumes. The spatial distribution of the ciliates biomass seems to be dependent on environmental factors and probably on their capacity to exploit a wide range of food resources including phytoplankton. The pollution generated by the phosphate-treating manufactory influenced the spatial phytoplankton and ciliate community’s distribution and their diversity along the north coast of Sfax.  相似文献   

The orientations of molecular clouds in the outer Galaxy: evidence for the scale of the turbulence driver?     

Sami Dib  C. Jakob Walcher  Mark Heyer  Edouard Audit  Laurent Loinard 《Monthly notices of the Royal Astronomical Society》2009,398(3):1201-1206

Supernova (SN) explosions inject a considerable amount of energy into the interstellar medium (ISM) in regions with high-to-moderate star formation rates. In order to assess whether the driving of turbulence by supernovae is also important in the outer Galactic disc, where the star formation rates are lower, we study the spatial distribution of molecular cloud (MC) inclinations with respect to the Galactic plane. The latter contains important information on the nature of the mechanism of energy injection into the ISM. We analyse the spatial correlations between the position angles (PAs) of a selected sample of MCs (the largest clouds in the catalogue of the outer Galaxy published by Heyer et al). Our results show that when the PAs of the clouds are all mapped to values into the  [0°, 90°]  interval, there is a significant degree of spatial correlation between the PAs on spatial scales in the range of 100–800 pc. These scales are of the order of the sizes of individual SN shells in low-density environments such as those prevailing in the outer Galaxy and where the metallicity of the ambient gas is of the order of the solar value or smaller. These findings suggest that individual SN explosions, occurring in the outer regions of the Galaxy and in likewise spiral galaxies, albeit at lower rates, continue to play an important role in shaping the structure and dynamics of the ISM in those regions. The SN explosions we postulate here are likely associated with the existence of young stellar clusters in the far outer regions of the Galaxy and the ultraviolet emission and low levels of star formation observed with the Galaxy Evolution Explorer (GALEX) satellite in the outer regions of local galaxies.  相似文献   

An overview of the Late Cretaceous-Eocene positive inversions and Oligo-Miocene subsidence events in the foreland of the Tunisian Atlas: Structural style and implications for the tectonic agenda of the Maghrebian Atlas system   总被引：4，自引：0，他引：4  

Sami Khomsi  Mohamed Ghazi Ben Jemia  Chokri Maherssi  Riadh Mezni 《Tectonophysics》2009,475(1):38-207

Structural interpretation of surface and subsurface data in the Eastern foreland basins of Tunisia, allows us to recognize positive inversion structures, i.e. related to compressional events, expressed and recorded in the Paleogene sedimentary pile of the Atlas domain. These episodes are followed by a period of relative tectonic quiescence during Oligocene-Early Miocene with development of extensional structures with slightly tilted panels, grabens and locally the development of listric normal faults branched at depth on “décollement” levels.Comparison of the seismic interpretations and field data collected along the South Atlas Front as well as in the Atlas belt, allows us to propose a tectonic scenario at the scale of Eastern Tunisia Atlas. In particular, we emphasise the role of the so-called “Atlas event” (Middle-Late Eocene), which was initially defined in Algeria but poorly outlined in Tunisia. We will show that the tectonic agenda defined in Eastern Tunisia is consistent with the one proposed elsewhere in the Maghreb allowing us to propose a unified view of the geodynamic evolution of the whole Atlas system during this period.The negative inversion recorded during Oligocene-Early Miocene along with the occurrence of synsedimentary normal faults are related to an increase of the subsidence rate in the frame of continuous shortening coeval to basin formation in the front of the Atlas. The whole Oligo-Miocene evolution results from two different mechanisms: flexuration in the front of the Atlas and the onset of the extension of the Pantelleria-Linosa-Malta rift system of central Mediterranean, which attained a climax stage later during Pliocene-Quaternary.  相似文献   

Numerical modeling of wave–mud interaction using projection method     

Kourosh Hejazi  Mohsen Soltanpour  Saeideh Sami 《Ocean Dynamics》2013,63(9-10):1093-1111

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Minimum principle and related numerical scheme for simulating initial flow and subsequent propagation of liquefied ground     

Sami Montassar  Patrick de Buhan 《国际地质力学数值与分析法杂志》2005,29(11):1065-1086

The problem of predicting the evolution of liquefied ground, modelled as a viscoplastic material, is addressed by combining a minimum principle for the velocity field, which characterizes such an evolution, and a time step integration procedure. Two different numerical schemes are then presented for the finite element implementation of this minimum principle, namely, the regularization technique and the decomposition‐co‐ordination method by augmented Lagrangian. The second method, which proves more accurate and efficient than the first, is finally applied to simulate the incipient flow failure and subsequent spreading of a liquefied soil embankment subject to gravity. The strong influence of liquefied soil residual shear strength on reducing the maximum amplitude of the ground displacement is particularly emphasized in such an analysis. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献