A new look at the controllability cost of linear evolution systems with a long gaze at localized data

We revisit the classical issue of the controllability/observability cost of linear first order evolution systems, starting with ODEs, before turning to some linear first order evolution PDEs in several space dimensions, including hyperbolic systems and pseudo-differential systems obtained by linearization in fluid mechanics. In particular we investigate the cost of localized initial data, and in the dispersive case, of initial data which are semi-classically microlocalized

Micro-end milling of NiTi biomedical alloys, burr formation and phase transformation

This paper focuses on burr formation in micro-end milling of two Nickel-Titanium shape memory alloys (SMA), an austenitic and a martensitic NiTi. Phase transformation during machining was also examined. The experimental design approach was used to study the effect of cutting parameters on burr formation. The studied parameters were cutting speed, feed per tooth, depth and width of cut, 20 machining strategy and initial material phase of the NiTi alloy. Different types of burrs were formed during micro-end milling of NiTi alloys; it was observed that top burrs are the most important. The height of top burrs can reach values close to those of the depth of cut. Burrs were observed and characterized using a Scanning Electron Microscope (SEM), confocal and optical microscopes. The affected layer under the machined surface, and phase transformation 25 were investigated by using SEM. The results of the analysis of variance showed a significant formation of burrs, deeply influenced by the feed per tooth and width of cut. An increase in the feed per tooth and a decrease of width of cut tend to decrease the height and width of the top burr. In a thin layer under the machined surface, phase transformation was observed for the martensitic NiTi

Combined RFID Tag Antenna for Recipients Containing Liquids

International audienceIn UHF RFID (radio frequency identification), passive tag antennascan be fixed on boxes or recipients where the nature and contentsmight vary. These variations strongly affect the antenna performance.A combined antenna is proposed to ensure an effective read-range for aplastic recipient containing water or not. Two separate antennas arefirst designed for the filled and unfilled cases, respectively, thencombined for a correct working in both configurations

Expérience de carbonisation de Vérignon

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Circularly polarised planar antenna excited by coplanar waveguide feedline

International audienceA circular patch antenna fed by a coplanar waveguide (CPW) line is proposed to obtain circular polarisation (CP). The CP results from the combined excitation of the patch by an inclined slot (integrated in the CPW feedline) and the CPW feedline termination. The asymmetrical characteristics of the excitation involve the excitation of both the odd and the even modes in the CPW line

Interaction of bone-dental implant with new ultra low modulus alloy using a numerical approach

International audienceAlthough mechanical stress is known as being a significant factor in bone remodeling, most implants are still made using materials that have a higher elastic stiffness than that of bones. Load transfer between the implant and the surrounding bones is much detrimental, and osteoporosis is often a consequence of such mechanical mismatch. The concept of mechanical biocompatibility has now been considered for more than a decade. However, it is limited by the choice of materials, mainly Ti-based alloys whose elastic properties are still too far from cortical bone. We have suggested using a bulk material in relation with the development of a new beta titanium-based alloy. Titanium is a much suitable biocompatible metal, and beta-titanium alloys such as metastable TiNb exhibit a very low apparent elastic modulus related to the presence of an orthorhombic martensite. The purpose of the present work has been to investigate the interaction that occurs between the dental implants and the cortical bone. 3D finite element models have been adopted to analyze the behaviour of the bone-implant system depending on the elastic properties of the implant, different types of implant geometry, friction force, and loading condition. The geometry of the bone has been adopted from a mandibular incisor and the surrounding bone. Occlusal static forces have been applied to the implants, and their effects on the bone-metal implant interface region have been assessed and compared with a cortical bone/ bone implant configuration. This work has shown that the low modulus implant induces a stress distribution closer to the actual physiological phenomenon, together with a better stress jump along the bone implant interface, regardless of the implant design

Étude et réalisation de antennes diélectriques pour les applications satellitaires et corps (BAN)

Dans cette thèse, on vise deux types d'applications de l antenne à résonateur diélectrique (DRA): 1) La réalisation d un élément rayonnant pour un réseau phasé embarqué sur un véhicule terrestre ou un avion. Cet élément de base requiert une couverture en élévation supérieure à celle des éléments imprimés pour permettre une poursuite typique comprise entre +-70. La couverture dans un cône large est assurée avec une bonne pureté de polarisation circulaire en alimentant l antenne à travers deux ouvertures à fente en H orthogonales parfaitement découplées en bande X. 2) La deuxième structure est destinée à la diversité d antennes dans le contexte des réseaux corporels embarqués ou Body Area Network (BAN). L antenne à diversité combine une antenne fente en boucle avec un DRA ce qui permet dans un espace compact de réaliser des diagrammes de type broadside et endfire respectivement. Les alimentations considérées sont de 2 types; Soit purement planaire (microruban et coplanaire) soit mixte en combinant une alimentation coaxiale et une alimentation coplanaire. Caractéristiques principales des antennes à résonateur diélectrique (DRA): Pour répondre aux attentes des utilisateurs en termes de débit, les systèmes de communication sans fils se tournent vers des fréquences de plus en plus élevées. La conséquence de cette montée en fréquence est notamment l augmentation des pertes au niveau des éléments conducteurs et donc une diminution de l efficacité globale des systèmes de communication. Dans ces circonstances, les DRA offre de meilleurs résultats par rapport à d'autres familles d'antennes à base d éléments métalliques. De plus, les DRA offrent des pertes diélectriques négligeables, elles sont peu sensibles aux variations de température et s intègrent facilement sur des technologies de fabrication planairesTechnologies such as direct broad cast satellite system (DBSS), Geosynchronous Earth Orbit (GEO) and Low Earth Orbit (LEO) satellite communications , global positioning system (GPS), high accuracy airborne navigation system and a large variety of radar systems demand for high level of antenna performance. Similar is the requirement for upcoming land based wireless systems such as cellular and indoor communication systems that is needed some more specific and additional features added to the antenna to compensate for the deficiencies encountered in system's performance. Though metallic antennas are capable enough to fulfil all the operational requirements, however at very high frequencies and under hostile temperature conditions they are constrained to face certain limitations. To avoid these constraints the performance of Dielectric Resonator Antennas (DRAs) is evaluated and their new applications are proposed. In the thesis, two types of antenna applications are sought :-First is for tracking and satellite applications that needs a larger aperture coverage in elevation plane. This coverage is realized with a good CP purity by proposing two ports dual linearly polarized DRA working at X-band. The DRA is excited by two orthogonal H-shaped aperture slots yielding two orthogonal polarizations in the broadside direction. A common impedance bandwidth of 5.9% and input port isolation of -35 dB are obtained. The broadside radiation patterns are found to be highly symmetric and stable with cross polarization levels -15dB or better over the entire matching frequency band. The maximum measured gain is found to be 2.5dBi at 8.4 GHz.- The 2nd type of antenna is a dual pattern diversity antenna to be used in the Body Area Network (BAN) context. This antenna combines a slot loop and DRA yielding broadside and end-fire radiation patterns respectively. Based upon the feeding techniques, the DG antenna is further divided into two categories one with planar feeds and the other with non-planar feeds (slot loop excited by planar CPW but DRA excited by vertical monopole) .Both types are successfully designed and measured upon body when configured into different propagation scenarios. The non-planar feeds antenna allows wider common impedance bandwidths than the planar feeds (4.95% vs 1.5%).In both cases, a maximum value of DG=9.5dB was achieved when diversity performance tests were carried out in rich fading environments. This value is close to the one (10 dB) theoretically reached in a pure Rayleigh environment and was obtained with efficiencies of 70% and 85% for the slot loop and the DRA respectively. Therefore, we conclude that these antennas could be used on the shoulders or the chest of professional clothes (firemen, policemen, soldier) where full planar integration is not a key issue but where the communication must be efficient in harsh environments and for various gestures, positions and scenariosPARIS-EST-Université (770839901) / SudocSudocFranceF