Ultra Wide X-Band Microwave Imaging of Concealed Weapons and Explosives Using 3D-SAR Technique

In order to detect and image concealed weapons and explosives, an electromagnetic imaging tool with its related signal processing is presented. The aim is to penetrate clothes and to find personal-born weapons and explosives under clothes. The chosen UWB frequency range covers the whole X-band. The frequency range is justified after transmission measurements of numerous clothes that are dry or slightly wet. The apparatus and the 3D near-field SAR processor are described. A strategy for contour identification is presented with results of some simulants of weapon and explosive. A conclusion is drawn on the possible future of this technique

Sound production in red-bellied piranhas (<i>Pygocentrus nattereri</i>, Kner): an acoustical, behavioural and morphofunctional study

Piranhas are known to be sound-producing animals. Nevertheless, the biological significance of piranha calls remains unclear because sounds have been recorded only when specimens were held by hand or trapped in a gill net. These sounds are generated by rapid contractions of sonic muscles that insert on a broad tendon surrounding ventrally the cranial sac of the swimbladder. The piranha swimbladder is thought to play an important role in sound production as an impedance-matching device and as a resonator. However, the vibratory capacities of the cranial and caudal sacs and the exact role of both sacs in sound production remain poorly understood. In this study, three sounds were each associated to a specific behaviour. The first sound (type 1) was produced during frontal display; it had numerous pulses and lasted 140!±17 ms, with a fundamental frequency of 120±4 Hz. It corresponded to the sound made by hand-held fishes. The second sound (type 2) was produced during circling and fighting behaviour; it was a single pulse lasting 36±8 ms, with a fundamental frequency of 43±10 Hz. The third sound (type 3) corresponded to chasing behaviour and comprised three to four pulses, each lasting 3±1 ms, with a fundamental frequency of 1739±18 Hz. Using a laser vibrometer to study the swimbladder displacement when stimulated at different frequencies, it was demonstrated that the first two sounds corresponded to the swimbladder mechanism. By contrast, the third sound was associated with the jaw mechanism. The vibrometer indicated that the swimbladder is a highly damping structure, simply copying the sonic muscle contraction rate. This study provides two interesting insights. First, it shows the relationships between three kinds of piranha sound and three specific behaviours. Second, using muscle stimulation at different rates, it shows which simultaneous conditions are required for production of sound in this species. Swimbladder calls were produced by a muscle contraction rate of approximately 100 Hz because this periodicity allowed the swimbladder to vibrate. At this frequency range, the contraction–relaxation cycles of the swimbladder muscles engendered wall displacements that had short amplitudes and with only a small variability between them

Aspects of sound communication in the pearlfish <i>Carapus boraborensis</i> and <i>Carapus homei</i> (Carapidae)

Several species of Carapidae are known to have symbiotic relationships with marine invertebrates. The two most common species in Moorea (French Polynesia), Carapus boraborensis and Carapus homei, undergo conspecific and heterospecific encounters in the same holothurian host during which they produce sounds. Another characteristic of these fish lies in their abilities to produce sounds. The objective of this study was dual: (1) to seek if there was a sexual difference in the sounds produced by C. boraborensis; (2) to seek if there was a difference in the sound emissions between heterospecific and conspecific encounters. In each trial, sounds were only recorded when one individual entered the sea cucumber that was already occupied. In encounters, sounds were structured in regular pulse emissions whose pulse lengths and periods allowed to significantly distinguish each species, as well as both sexes in C. boraborensis. In the latter species, results show for the first time that temporal features of the emitted sounds can have a functional importance in sex identification. In heterospecific encounters, sounds were reduced 68% of the time to a single pulse emission and there was a modification in the pulse length of each species: it shortens in C. homei and it lengthens in C. boraborensis. It highlights that both carapids are able to adapt their sounds to the facing species. Because a modification of the sound appears to be done at the first emission, it is supposed that recognition precedes the sound emission

Soil evolution and plant communities on coastal dunes near Veracruz, Mexico

En climat tropical les dunes côtières peuvent, dans certaines situations protégées des vents dominants, se fixer et évoluer rapidement (Parker-Nance et al., 1991; Amundson et Temblack, 1981). Dans ces conditions se forment des sols profonds sablo-argileux brun-rouge sur lesquels croît une forêt tropicale. Sur la station biologique de La Mancha, Veracruz, des recherches furent entreprises afin de vérifier si les paramètres qui influencent le développement de la forêt sur les dunes sont liés aux sols et à leurs réserves minérales (Kellman et Roulet, 1990; Kellman, 1990). Mais la grande variété des groupements végétaux de cette zone ne semble pas se calquer sur la répartition des sols. Une étude intégrée de la géomorphologie (fig. 2), de la pédologie (fig. 4) et des groupements végétaux (tabl. II) confirme que le sable a partout la même origine, à la fois marine et continentale volcanique, mais la lithologie des dépôts a été bouleversée par des mouvements tectoniques récents (fig. 10). Les sols présentent, côte à côte ou en superposition, des horizons anciens de sable très altéré avec des horizons de sable peu évolué. La végétation a elle aussi subi des bouleversements, mais d'origine anthropique. Actuellement les espèces se concentrent en îlots qui colonisent à nouveau les sites favorables. Cette colonisation suit deux orientations distinctes qui se calquent sur les conditions actuelles d'évolution du sol. La première tend à former un bush arbustif d'espèces à couvert permanent de feuilles coriacées, la seconde tend à former des îlots de forêt tropicale avec des arbres à port élevé et un grand nombre d'espèces associées. L'étude minéralogique des sols montre que les deux types de colonisation se répartissent sur des milieux totalement différents. Le premier est hydromorphe. Le substrat sableux est soumis à une calcitisation prononcée (fig. 4) sous un pH élevé et de fortes concentrations en Ca et Mg. La formation d'argile, un mélange smectite et chlorite (fig. 5 et 6), reste très limitée. Le second milieu est bien drainé, les carbonates tendent à disparaître du profil et un horizon B sablo-argileux bien structuré (fig. 7), à smectite (Beidellite) associée à de faibles quantités d'illite (fig. 9) et à des oxydes de fer, se développe. Les situations des horizons brun-rouge, en relation avec la présence passée ou actuelle de la forêt, tendent à montrer que cette évolution est dépendante du couvert végétal et de l'activité biologique liés à la forêt. En effet elle ne s'observe pas en dehors des foyers de régénération forestière. (Résumé d'auteur

Choice, sorting and ranking in aerial conflict management

International audienceIn the Air Traffic control, many decisions must be taken, quickly. Due to the increase of traffic, these decisions are more and more numerous. It is possible to propose some assistance tools to air traffic controllers in order to help them to make decisions. For that purpose we need to understand how the controllers make these decisions. This paper proposes a knowledge acquisition approach composed of three steps: an analysis of the decision-making process, a multiple criteria methodology, and interviews in order to obtain information, and to develop models. The last part of this paper presents the results we expect to obtain with appropriate interviews and analyse

A universal optical all-fiber omnipolarizer

Wherever the polarization properties of a light beam are of concern, polarizers and polarizing beamsplitters (PBS) are indispensable devices in linear-, nonlinear-and quantum-optical schemes. By the very nature of their operation principle, transformation of incoming unpolarized or partially polarized beams through these devices introduces large intensity variations in the fully polarized outcoming beam(s). Such intensity fluctuations are often detrimental, particularly when light is post-processed by nonlinear crystals or other polarization-sensitive optic elements. Here we demonstrate the unexpected capability of light to self-organize its own state-of-polarization, upon propagation in optical fibers, into universal and environmentally robust states, namely right and left circular polarizations. We experimentally validate a novel polarizing device-the Omnipolarizer, which is understood as a nonlinear dual-mode polarizing optical element capable of operating in two modes-as a digital PBS and as an ideal polarizer. Switching between the two modes of operation requires changing beam's intensity

The mean circulation of the southwestern Mediterranean Sea: Algerian Gyres

This is a study about the general circulation of the southwestern Mediterranean Sea based on observations of currents carried out in the southwestern Mediterranean Sea in the framework of the Mass Transfer and Ecosystem Response (MATER) program (EEC/MAST3 program). From July 1997 to August 2002, profiling floats (MEDPROF experiment), isobaric floats (LIWEX experiment), and moored current meters (ELISA experiment) give evidence of two large-scale barotropic cyclonic circulations, the here-called Western and Eastern Algerian Gyres, centered around [3730′N, 230′E] and [3830′N, 600′E], respectively. These gyres have typical horizontal scales of 100–300 km and are characterized by orbital velocities of about 5 cm/s corresponding to rotational periods of about 4 months. They are strongly related to the bottom topography of the basin and to the planetary vorticity gradient: closed f/H isocontours (f is the planetary vorticity, H the water depth) correspond to the locations of the gyres and favor such circulations as free geostrophic modes. A linear and barotropic model is used to investigate the possibility of wind driving, but the results suggest that the wind stress is not responsible for establishing such circulations. The boundary currents flowing along the continental slope of Africa, Sardinia, and the Balearic Islands are proposed to be the main drivers of these gyres

A propos du rôle du lait et du colostrum dans la Physiopathologie de l’Ictère grave du muleton nouveau-né

Bessis M., Millot P. A propos du lait et du colostrum dans la physiopathologie de l'Ictère grave du Muleton nouveau-né. In: Bulletin de l'Académie Vétérinaire de France tome 102 n°7, 1949. pp. 291-295