Metal-to-glass ratio and the Magneto-Impedance of glass-covered CoFeBSi microwires at high frequencies

High frequency [1-500 MHz] measurements of the Magneto-Impedance (MI) of glass-covered Co$_{69.4}$Fe$_{3.7}$B$_{15.9}$Si$_{11}$ microwires are carried out with various metal-to-wire diameter ratios. A twin-peak, anhysteretic behaviour is observed as a function of magnetic field. A maximum in $\Delta Z/Z$ appears at different values of the frequency $f$, 125, 140 and 85 MHz with the corresponding diameter ratio $p$ = 0.80, 0.55 and 0.32. We describe the measurement technique and interpret our results with a thermodynamic model that leads to a clearer view of the effects of $p$ on the maximum value of MI and the anisotropy field.Comment: 5 pages and 6 figure

Gestion de versions de formats avec Camlp4

National audienceLa gestion des changements de formats est un problème crucial de l'informatique : encore aujourd'hui, peu d'applications sont capables de lire des données sauvées dans un format d'une version antérieure ; en distribué, les versions de programmes devant communiquer entre eux sont de plus en plus hétérogènes, en particuliers dans les systèmes pair-à-pair. Dans ce papier, nous présentons une extension de syntaxe d'Objective-Caml en Camlp4 permettant de gérer plus efficacement les évolutions de formats, aussi bien dans les fichiers sauvegardés que dans les messages échangés dans un système distribué

A Novel Broadband Measurement Method for the Magnetoimpedance of Ribbons and Thin Films

A novel broad-band measurement method of the MI in thin films and ribbons is presented. It is based on the automated measurement of the reflection coefficient of a cell loaded with the sample. Illustrative results obtained with a permalloy multilayer thin film are presented and discussed.Comment: Paper submitted to International Conference on Magnetism (Rome 2003

Ocp-build: un gestionnaire de projets pour OCaml

National audienceDans ce papier, nous présentons ocp-build, un nouveau gestionnaire de projet pour OCaml [Leroy, X. The Objective Caml System : Documentation and User's Manual, 1996. With Damien Doligez, Jacques Garrigue, Didier Rémy, and Jérôme Vouillon. Availiable from http: //www.ocaml.org/.]. La gestion de projet -- description du projet et compilation -- a toujours été l'une des faiblesses de l'environnement de programmation d'OCaml. En effet, les règles de compilation d'un projet OCaml peuvent être complexes à mettre en oeuvre avec des outils classiques. ocp-build est une solution simple et facile d'accès à ce problème, il permet de décrire de façon concise un projet en terme de paquets et de fichiers sources, puis d'utiliser cette description pour compiler e ficacement le projet, ou le manipuler avec des outils de refactoring

Spying the World from your Laptop -- Identifying and Profiling Content Providers and Big Downloaders in BitTorrent

This paper presents a set of exploits an adversary can use to continuously spy on most BitTorrent users of the Internet from a single machine and for a long period of time. Using these exploits for a period of 103 days, we collected 148 million IPs downloading 2 billion copies of contents. We identify the IP address of the content providers for 70% of the BitTorrent contents we spied on. We show that a few content providers inject most contents into BitTorrent and that those content providers are located in foreign data centers. We also show that an adversary can compromise the privacy of any peer in BitTorrent and identify the big downloaders that we define as the peers who subscribe to a large number of contents. This infringement on users' privacy poses a significant impediment to the legal adoption of BitTorrent

Electromagnetic Sensors Based on Magnonic Crystals for Applications in the Fields of Biomedical and NDT

AbstractAn exploratory investigation of high sensitivity sensors based on magnonic crystals for the measurement of weak magnetic fields at room temperature is presented. The samples are YIG crystals on GGG substrate (Gadolinium-Gallium-Garnet) on which a periodic structure of shallow grooves are etched or gold stripes are deposited. The excitation of surface magnetostatic spin waves (MSSW) which should appear in these structures is obtained by means of microstrip transmission line or microstrip planar antenna.The measurement of the magnonic structure by complex transmission coefficient (S12) shows a significant shift in frequency of the maximum absorption peak related to magnonic band gap which depends on the magnitude of the DC magnetic bias field applied. It shows the possibility of magnonic high Q-value band gap implementation with respect to spin wave propagation band (GHz band) in magnonic crystals applied to spin waves detection of magnetic fields.The influence of the characteristics of the microstrip line or the microstrip antenna on sensor performance (sensitivity and resolution) is studied

Giant magnetoimpedance in Vitrovac amorphous ribbons over [0.3-400 MHz] frequency range

Giant magneto impedance (GMI) effect for as-cast Vitrovac$^{\textrm{\scriptsize\textregistered}}$ amorphous ribbons (Vacuumschmelze, Germany) in two configurations (parallel and normal to the ribbon axis) is studied over the frequency range [0.3-400 MHz] and under static magnetic fields -160 Oe $< H_{dc} <$+160 Oe. A variety of peak features and GMI ratio values, falling within a small field range, are observed and discussed.Comment: Paper submitted to International Conference on Magnetism 2003 (ICM Rome 2003