Relativistic disturbances in a finite elastic rod in an electromagnetic field

Summary The paper is concerned with the investigation of the disturbances of a finite elastic rod within the framework of relativistic mechanics of continua and of relativistic electrodynamics under specified boundary conditions.     

Beach erosion along the coastline of Alexandria, Egypt

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Comparison of Kansas Data with High-resolution Large-eddy Simulation Fields

The surface layer of an atmospheric boundary layer (ABL) is most accessible to field measurements and hence its ensemble-mean structure has been well established. The Kansas field measurements were the first detailed study of this layer, providing numerous benchmark statistical profiles for a wide range of stability states. Large-eddy simulation (LES), in contrast, is most suitable for studying the mixed layer of the ABL where the energy-containing range of the vertical velocity field is well resolved. In the surface layer, typical large-eddy simulations barely resolve the energy-containing vertical-velocity fields and hence do not provide sufficient data for a detailed analysis.We carried out a nested-mesh simulation of a moderately convective ABL (-z_i/L = 8) in which the lower 6% of the boundary layer had an effective grid resolution of 512³. We analyze the LES fields above the 6th vertical grid level (z = 23 m) where the vertical velocity field has a well formed inertial subrange, for a detailed comparison with the Kansas results. Various terms in the budgets of turbulent kinetic energy, temperature variance, Reynolds stress, temperature flux, and some higher order moments are compared. The agreement is generally quite good; however, we do observe certain discrepancies, particularly in the terms involving pressure fluctuations.     

Modeling of the Removal of Arsenic Species from Simulated Groundwater Containing As,Fe, and Mn: A Neural Network Based Approach

The present paper deals with the modeling of the removal of total arsenic As(T), trivalent arsenic As(III), and pentavalent arsenic As(V) from synthetic solutions containing total arsenic (0.167–2.0 mg/L), Fe (0.9–2.7 mg/L), and Mn (0.2–0.6 mg/L) in a batch reactor using Fe impregnated granular activated charcoal (GAC‐Fe). Mass ratio of As(III) and As(V) in the solution was 1:1. Multi‐layer neural network (MLNN) has been used and full factorial design technique has been applied for the selection of input data set. The developed models are able to predict the adsorption of arsenic species with an error limit of ?0.3 to +1.7%. Combination of MLNN with design of experiment has been able to generalize the MLNN with less number of experimental points.     

Hydrochemical characterization of groundwater using multivariate statistical analysis: the Maritime Djeffara shallow aquifer (Southeastern Tunisia)

Worldwide, groundwater resources have been considered as the main sources of drinking, domestic uses, industrial and agriculture water demands, especially in arid and semiarid regions. Accordingly, the monitoring of the groundwater quality based on different tools and methods becomes a necessity. The aim of this study was to apply several approaches to assess the water quality and to define the main hydrochemical process which affect groundwater of the Maritime Djeffara shallow aquifer. In addition to the hydrochemical approach, two multivariate statistical analyses, hierarchical clusters analysis (HCA) and principal component analysis (PCA), were carried out to identify the natural and the anthropogenic processes affecting groundwater chemistry. Hydrochemical approach, based on 47 analyzed groundwater samples, shows that most of samples present a sulfate to mixed chloride, with sodi-potassic tendency facies. According to their chemically composition, the HCA revealed three different groups (C1, C2 and C3) according to their electrical conductivity (EC) values: C1 (average EC = 4500 µS/cm), C2 (average EC = 7040 µS/cm) and C3 (average EC = 9767 µS/cm). Furthermore, PCA results show two principal factors account 84.05% of the total variance: (1) F1 represents the natural component, and (2) F2 symbolizes the anthropic component. Moreover, the groundwater quality map of the Maritime Djeffara shows three categories: suitable, doubtful and unsuitable water for irrigation. These different results should be taken to protect water resources in arid and semiarid regions, especially at the alluvial coastal regions. Also, they help to make a suitable planning to manage and protect the groundwater resources.     

Petrography and geochemistry of the Middle Miocene Gebel El Rusas sandstones,Eastern Desert,Egypt: Implications for provenance and tectonic setting

Petrography and bulk rock geochemistry of the Middle Miocene sandstones of the lower and upper members of Gebel El Rusas Formation along the Egyptian Red Sea Coastal plain, have been investigated to determine the provenance, tectonic setting, and weathering condition of this formation. The Lower Member is formed mainly of sandstones and conglomerates with clay interbeds. The Upper Member is more calcareous and formed mainly of sandstones and limestones with marls and clays intercalations. Petrographically, the Lower Member sandstones are mostly immature and classified as arkoses with an average framework composition of \(\hbox {Q}_{66}\hbox {F}_{29}\hbox {R}_{5}\), and the Upper Member sandstones are partly submature (more quartzose, less feldspathic) and classified as subarkoses with an average framework composition of \(\hbox {Q}_{80}\hbox {F}_{17}\hbox {R}_{3}\). The Gebel El Rusas sandstones are enriched in Sr, Ba, Zr and Rb and depleted in Co and U, as compared to UCC. The chemical index of alteration (CIA) values suggest moderate weathering conditions. The geochemistry results revealed that the Gebel El Rusas sandstones were derived from felsic-granitic source rocks and deposited in a passive margin of a synrift basin. The inferred tectonic setting for Middle Miocene Gebel El Rusas sandstones in the study area is consistent with the regional geology of the Eastern Desert of Egypt during Middle Miocene.     

Provenance of coastal dune sands along Red Sea,Egypt

Texture, mineralogy, and major and trace element geochemistry of 26 coastal dune sand samples were studied to determine the provenance and tectonic environment of two dune fields close to the beaches of Safaga (SF) and Quseir (QS) at the Egyptian Red Sea coast. Onshore winds generate fine, moderate, moderately-well to well-sorted, coarse-skewed to near-symmetrical dune sands with mesokurtic distributions. Winds pick up and transport grains from nearby beach sands and alluvial deposits into a wide Red Sea coastal plain at the border of the beach. The mineralogical (Qt–Ft–Lt) and geochemical composition of the sands, indicate that SF and QS coastal dune sands are mature and influenced by quartz-rich sands. The average CIA values in SF and QS coastal dune sands are low relative to the range of the PAAS, suggesting an arid climate and a low intensity of chemical weathering. The SF and QS coastal dune sand samples are plotted in the recycled orogen and partly in craton interior fields suggesting recycled older sedimentary and partly metamorphic-plutonic sources. The high content of quartz with shell debris and carbonates in coastal dune sands support the recycled sedimentary beach and alluvial sand sources. The dominance of heavy minerals like amphiboles (hornblende) and biotite in the coastal dune sands also supports the effect of metamorphic-plutonic source rocks. The new tectonic discriminant-function diagrams suggest that the coastal dune sands were deposited in a passive margin of a synrift basin. The results provide a good evidence for the extension in the Red Sea rift system during Oligocene-post Pliocene, which is consistent with the general geology of Egypt.     

Does a ‘two-stream’ flow model apply to wakes of large bodies in space?

Structural patterns of ion and electron currents observed on the wake axes of the Ariel J and the Gemini 10 space vehicles are re-examined, together with relevant theoretical and laboratory ‘simulation’, studies. Some insight into existingin-situ data is provided. The possibility that ‘converging-stream’ models describe structural features of current enhancements in the wake region of large spacecraft is discussed.     

Apport de la gravimétrie à l’étude des structures effondrées du Nord-Est de la Tunisie: implications hydrogéologiques

Résumé

Cette étude basée sur l’analyse des données gravimétriques a pour but d’améliorer la connaissance des structures effondrées du Nord-Est de la Tunisie. La carte de l’anomalie résiduelle a d’abord été calculée à partir de la carte de l’anomalie de Bouguer en enlevant un gradient régional. La résiduelle calculée fournit des informations sur la variation de la densité dans les bassins sédimentaires de l’Oued Chafrou-Khlidia, de Mornag et de Grombalia. Afin de mettre en évidence les différentes structures géologiques (failles, bassins, etc.) dans le secteur d’étude, différentes techniques (gradient vertical, gradient horizontal, prolongement vers le haut, déconvolution d’Euler) ont été appliquées à la carte gravimétrique des structures effondrées du Nord-Est de la Tunisie. Les résultats obtenus ont permis de dresser une carte structurale présentant le système de failles responsable de la structuration de la zone d’étude. Cette carte constitue un document très utile pour orienter les recherches hydrogéologiques futures qui seront menées dans ces plaines.

Editeur Z.W. Kundzewicz

Citation Ouerghi, S., Rebai, N., Gabtni, H., Farhat, B., et Bouaziz, S., 2013. Apport de la gravimétrie à l’étude des structures effondrées du Nord-Est de la Tunisie: implications hydrogéologiques. Hydrological Sciences Journal, 58 (6), 1361–1373.