1,106 research outputs found

    Seismicity of Algeria from 1365 to 2013: Maximum Observed Intensity Map (MOI2014)

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    Algeria is one of the most seismically active areas in the Medi- terranean basin. The available catalogs reported numerous de- structive earthquakes striking different regions, such as Algiers (1365, maximum observed intensity Io X; 1716, Io X; Ambraseys and Vogt, 1988), Oran (1790, Io X; Lopez Mari- nas and Salord, 1990), Djidjelli (1856, Io IX; Ambraseys, 1982), Orléansville (1854, Ms 6.7; Rothé, 1950), El Asnam (1980, Ms 7.3; Yielding et al., 1989), Constantine (1985, M s 5.9; Ousadou et al., 2013), Tipasa-Chenoua (1989, M s 6.0; Bounif et al., 2003), Mascara (1994, M s 6.0; Ayadi et al., 2002), and Zemmouri (2003, Mw 6.8; Harbi, Maouche, Ousadou, et al., 2007; Ayadi et al., 2008). This seismicity is related to the collision between the African and Eurasian plates and is lo- cated within the Tell Atlas of Algeria along the plate boundary zone. Two periods that are related to the installation of the Algerian seismic network are identified from the seismic cata- log of Algeria: the pre-1910 and post-1910 periods

    Linear semigroups with coarsely dense orbits

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    Let SS be a finitely generated abelian semigroup of invertible linear operators on a finite dimensional real or complex vector space VV. We show that every coarsely dense orbit of SS is actually dense in VV. More generally, if the orbit contains a coarsely dense subset of some open cone CC in VV then the closure of the orbit contains the closure of CC. In the complex case the orbit is then actually dense in VV. For the real case we give precise information about the possible cases for the closure of the orbit.Comment: We added comments and remarks at various places. 14 page

    Van der Waals induced polarization of molecules adsorbed on small metallic spheres : anisotropy and nonlocality effects

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    The calculation of Van der Waals induced polarization of molecules interacting with small metallic spheres is based on the spherical-tensor theory by using the response field susceptibility of the sphere. The first Euler angle appearing in the expression giving this polarization exhibits the anisotropy of the molecule. In order to illustrate the non locality and anisotropy effects as well as the importance of the metallic sphere curvature on the induced polarization magnitudes, we present numerical results for typical systems (HF, HCl) on (Ag, Al and Cu).The calculation of Van der Waals induced polarization of molecules interacting with small metallic spheres is based on the spherical-tensor theory by using the response field susceptibility of the sphere. The first Euler angle appearing in the expression giving this polarization exhibits the anisotropy of the molecule. In order to illustrate the non locality and anisotropy effects as well as the importance of the metallic sphere curvature on the induced polarization magnitudes, we present numerical results for typical systems (HF, HCl) on (Ag, Al and Cu)

    Trigonometric Sutherland systems and their Ruijsenaars duals from symplectic reduction

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    Besides its usual interpretation as a system of nn indistinguishable particles moving on the circle, the trigonometric Sutherland system can be viewed alternatively as a system of distinguishable particles on the circle or on the line, and these 3 physically distinct systems are in duality with corresponding variants of the rational Ruijsenaars-Schneider system. We explain that the 3 duality relations, first obtained by Ruijsenaars in 1995, arise naturally from the Kazhdan-Kostant-Sternberg symplectic reductions of the cotangent bundles of the group U(n) and its covering groups U(1)×SU(n)U(1) \times SU(n) and R×SU(n){\mathbb R}\times SU(n), respectively. This geometric interpretation enhances our understanding of the duality relations and simplifies Ruijsenaars' original direct arguments that led to their discovery.Comment: 34 pages, minor additions and corrections of typos in v

    Temporal fluctuations of current surface density in a triangular lattice

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    In this paper, we examine the effect of the temporal fluctuation current correlation in the surface diffusion process in a triangular lattice, in the framework of the lattice gas model. Our calculations are per found in small circular surfaces equivalent to the probe areas in the scanning microscopy experiments. We have found that the correlation function, in the non- interacting case, follows the law Öp . In the presence of repulsive interactions between mobile particles, it behaves like Öp exp(8γp). We have also calculated the collective diffusion coefficient by the linear response theory and by the characteristic time method, which reflect clearly the order-disorder effect on the diffusion.In this paper, we examine the effect of the temporal fluctuation current correlation in the surface diffusion process in a triangular lattice, in the framework of the lattice gas model. Our calculations are per found in small circular surfaces equivalent to the probe areas in the scanning microscopy experiments. We have found that the correlation function, in the non- interacting case, follows the law Öp . In the presence of repulsive interactions between mobile particles, it behaves like Öp exp(8γp). We have also calculated the collective diffusion coefficient by the linear response theory and by the characteristic time method, which reflect clearly the order-disorder effect on the diffusion

    Naturalistic Affective Expression Classification by a Multi-Stage Approach Based on Hidden Markov Models

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    In naturalistic behaviour, the affective states of a person change at a rate much slower than the typical rate at which video or audio is recorded (e.g. 25fps for video). Hence, there is a high probability that consecutive recorded instants of expressions represent a same affective content. In this paper, a multi-stage automatic affective expression recognition system is proposed which uses Hidden Markov Models (HMMs) to take into account this temporal relationship and finalize the classification process. The hidden states of the HMMs are associated with the levels of affective dimensions to convert the classification problem into a best path finding problem in HMM. The system was tested on the audio data of the Audio/Visual Emotion Challenge (AVEC) datasets showing performance significantly above that of a one-stage classification system that does not take into account the temporal relationship, as well as above the baseline set provided by this Challenge. Due to the generality of the approach, this system could be applied to other types of affective modalities

    Space-time variation of ciliates related to environmental factors in 15 nearshore stations of the Gulf of Gabes

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    Diversity and structure of ciliate communities in the Gulf of Gabes (Tunisia) were investigated based on a survey of 15 nearshore stations along 237 Km, by monthly sampling over a 1-year. Ciliated protozoa were identified to genus and/or species level and enumerated. Statistic tools were used to explain the ciliates assemblage. High ciliates species richness from 133 taxa was recorded, including new records of 76 species. This study showed a longitudinal distribution of ciliate communities, which are organized in northern stations (from Tabia to Harbor of Gabes) and southern stations (from Zarrat to Jabiat Haj Ali). The number of taxa increased significantly in northern stations but decreased in the southern. This distribution was mainly influenced by the salinity and phytoplankton abundance. Ciliate taxa were grouped into fives size-classes: 15-30 µm, 30-50 µm, 50-100 µm, 100-200 µm and >200 µm. In terms of abundance, most abundant size groups were small ciliates (15-30 μm) accounted from 15 to 79 %, while the greatest biomass contribution came from the 50-100 μm size classes. We thus conclude high diversity of ciliates communities that showed a geographical distribution influenced by abiotic and biotic factors along the coast of Gulf of Gabes
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