39 research outputs found

    La résilience des organisations locales en situation post-conflit

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    Coral cavernous angiomas in a child

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    Dural-based cavernous angiomas are rare intracranial vascular lesions. Most of the reported cases are located in the middle cranial fossa, and those located outside the middle fossa are even more uncommon. Thus far, only 3 pediatric cases have been reported and all of them were found outside the middle fossa of a neonate. We would like to add the fourth pediatric case of a dural-based cavernous angioma located in the posterior fossa of a 5-year-old boy.link_to_subscribed_fulltex

    Surface Characterization of Material Using Rayleigh Velocity Measurement in the Broad-Band Mode

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    The surface damage of materials can be characterized by measuring the variation of the Rayleigh wave velocity. There is also a need to study the effect of the anisotropy and the gradient of the damage versus the depth. The acoustic microscopy using broad-band pulses is one of the methods which can produce interesting results in a simple and fast way. In this case, the Rayleigh velocity can be also obtained through a time of flight measurement. In order to have a sufficient separation between the different components of the reflected echoes, it is necessary to properly select the geometrical and acoustical parameters, and that requires a sufficient comprehension of the phenomena. One of the challenge of this technique is to be able to perform time measurements with the necessary accuracy. We will show also that it is possible to extract conventional V(z) curves for a given frequency.</p

    Microstructural Characterization of Materials by a Rayleigh Wave Analysis

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    It is well known that material characteristics properties such as anisotropy, grain size, damage, roughness, can affect the Rayleigh wave propagating on a sample surface. The acoustic microscopy using broad-band pulses is one of the methods which can generate Rayleigh waves in a simple way. The acoustic energy generated by a transducer in the coupling medium reaches the sample surface and is partially reflected into an axial echo and converted into a Rayleigh wave at the Rayleigh critical angle θR. With an impulse excitation, these two echoes are resolved in time. In this case, the Rayleigh velocity can be also obtained through a time of flight measurement. One of the challenge of this technique is to be able to perform time measurements with the necessary accuracy in order to detect shifts in the material properties.</p

    Signcryption in Hierarchical Identity Based Cryptosystem

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    It is well known that material characteristics properties such as anisotropy, grain size, damage, roughness, can affect the Rayleigh wave propagating on a sample surface. The acoustic microscopy using broad-band pulses is one of the methods which can generate Rayleigh waves in a simple way. The acoustic energy generated by a transducer in the coupling medium reaches the sample surface and is partially reflected into an axial echo and converted into a Rayleigh wave at the Rayleigh critical angle θR. With an impulse excitation, these two echoes are resolved in time. In this case, the Rayleigh velocity can be also obtained through a time of flight measurement. One of the challenge of this technique is to be able to perform time measurements with the necessary accuracy in order to detect shifts in the material properties

    Sobrevivencia campesina en ecosistemas de altura

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    Le cas Pilahuin, prétend interpréter une réalité sociale comme conséquence historique d'un processus productif dépendant des formes d'appropriation de la terre (hacienda traditionnelle) et démontrer en quoi consiste une stratégie de survie dans une zone écologiquement inhospitalière de la Cordillière des Andes équatoriennes. Ce travail ouvre des pistes fondamentales qui devraient être prises en compte pour préparer les études de faisabilité des projets de développement dans les zones d'économie paysanne de montagne dans la région andin
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