La théorie variation des rayons complexes pour le calcul des vibrations moyennes fréquences

A new approach named the "Variational Theory of Complex Rays" is introduced for computing the vibrations of elastic structures weakly damped in the medium frequency range. Emphasis has been placed here on the most fundamental aspects. The effective quantities (elastic energy, vibration intensity ...) are evaluated after computing a small system of equations which does not derive from a finite element dicretization of the structure. Numerical examples related to plates show the interest and the possibilities ofthe VTRC

Etude du comportement statique et dynamique d'un pieu isolé implanté dans le sable par éléments finis

info:eu-repo/semantics/nonPublishe

Some Synchronization Issues in OSPF Routing

A routing protocol such as OSPF has a cyclic behavior to regularly update its view of the network topology. Its behavior is divided into periods. Each period produces a flood of network information messages. We observe a regular activity in terms of messages exchanges and filling of receive buffers in routers. This article examines the consequences of possible overlap of activity between periods, leading to a buffer overflow. OSPF allows “out of sync ” flows by considering an initial delay (phase). We study the optimum calculation of these offsets to reduce the load, while maintaining a short period to ensure a protocol reactive to topology changes. Such studies are conducted using a simulated Petri net model. A heuristic for determining initial delays is proposed. A core network in Germany serves as illustration.

Combination of ERDA, FTIR spectroscopy and NanoSIMS for the characterization of hydrogen incorporation in natural diamonds

International audienceHydrogen is a volatile element involved in several geological processes ranging from rock weakening to the initiation of tectonic plates. Because it is present in diamond, the investigation of hydrogen content in natural diamonds could provide valuable information. Such studies are scarce despite hydrogen being among the main impurities in their structure. Using Elastic Recoil Detection Analysis, Fourier Transform Infrared spectroscopy and Nanoscale Secondary Ions Mass Spectrometry, we analyzed the incorporation of hydrogen in three diamonds growth habits: octahedral, cuboid and fibrous. Up to 25 wt. ppm of hydrogen was measured in some samples, placing hydrogen as the second most abundant impurity in natural diamonds after nitrogen and before boron. Comparison between the three methods indicates a difference in the main mode of hydrogen incorporation depending on the growth habit. Hydrogen is more readily incorporated in the fibrous and cuboid habits compared to the octahedral one. We also show that the incorporation of hydrogen is not correlated with the incorporation of nitrogen. Results suggest no chemical equilibration of hydrogen by diffusion through geological times and also confirm that not all hydrogen may be infrared active