Implicit reconstruction by zooming

This paper presents a new method to infer 3D information using a static camera equipped with a zoom-lens. The modelling algorithm does not required any explicit calibration model and the computations involved are straightforward. This approach uses several images of accurate regular grids placed on a micrometric table, as calibration process . The basic idea is to compute a local transformation that allows to establish a relationship between a distorted grid detected on the CCD matrix and the real one located in front of the camera . This relationship takes automatically into account all distortion phenomena and allows to obtain reconstruction results much more accurate than previous works in the same field . A complete experiment on real data is provided and shows that it is possible to compute 3D information from a zooming image set even if data are close to the optical axis .Cet article présente une nouvelle méthode permettant d'inférer des informations tridimensionnelles à l'aide d'une caméra statique munie d'un zoom. L'algorithme de modélisation ne nécessite aucun modèle explicite de calibrage et met en oeuvre plusieurs images de grilles régulières et précises formant un espace métrique particulier. Une transformation locale permet d'établir une relation entre l'image distordue d'une grille détectée sur la matrice CCD et une grille réelle située devant la caméra. Cette relation prend automatiquement en compte les phénomènes de distorsion optique et permet d'obtenir des résultats de reconstruction bien meilleurs que ceux obtenus jusqu'à présent en reconstruction axiale par zoom. De plus, la méthode présentée permet de calibrer l'objectif sur une gamme importante de distances focales sans changer d'objet de calibrage. Une expérimentation complète sur des données réelles est présentée et montre qu'il est possible de reconstruire des objets 3D à partir d'une séquence d'images de zoom même si ces données sont proches de l'axe optique

Electrons elastically backscattered from Al, Ag and Au samples

International audienc

Les thermes romains de Treignes (campagnes 1980 et 1981): rapport préliminaire

c.r. Ch. LEVA, dans Publ. trim. d’informations du Centre Interdisciplinaire de Recherches Aériennes, 5e année, 1982-1, pp. 9-10. Vie Archéologique, 2e année, n°4, mars 1982, p. 35info:eu-repo/semantics/publishe

La fortification protohistorique d’Olloy-sur-Viroin

info:eu-repo/semantics/publishe

Logiciel de gestion de banques de donnees terminologiques

CNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Nanofiltration of nonionic surfactants: effect of the molecular weight cutoff and contact angle on flux behavior

Nonionic surfactants are widely used in industry, and large amounts of wastewater containing nonionic surfactants are produced each year. Nanofiltration (NF) is a possible option to purify these waters, reducing the overall water consumption and enhancing biological purification. However, the flux behavior of NF during purification of wastewaters containing nonionic surfactants is not well understood. NF tests were performed with both synthetic solutions and real wastewaters containing nonionic surfactants from carpet rinsing. When a membrane with a relatively high molecular weight cutoff (MWCO) was chosen, flux decreased to a level lower than that with most ultrafiltration membranes. When a low MWCO was chosen, flux either increased above pure water flux when a relatively hydrophobic membrane was chosen or decreased when a relatively hydrophilic membrane was chosen. NF thus seems feasible to reduce water usage in industrial processes involving nonionic surfactants when a proper membrane is selected. It appeared that flux is controlled by three mechanisms: first, the narrowing of membrane pores through adsorption of monomers when the MWCO is comparable or larger than the monomer size, causing flux decline; second, an improved wettability of the membrane surface through adsorption of monomers on hydrophobic groups, causing flux to increase above pure water flux; third, a decreased wettability through adsorption of monomers on hydrophilic groups, causing flux decline. The nonionic surfactant concentration, MWCO, and membrane's hydrophilicity determine which mechanism is dominant.Geert Cornelis, Katleen Boussu, Bart Van der Bruggen, Ilse Devreese and Carlo Vandecasteel

Performance evaluation of microfiltration with electrocoagulation and chemical coagulation pretreatment

ne of the significant parameters to be considered for evaluating the process and economic viability of crosssflow microfiltration (MF) is flux stability. The MF economics are dependent on the flux decay through the membrane caused by membrane fouling. This work aims to evaluate the performance of MF by electro and chemical coagulation as pretreatments. The performance of MF was found to be sensitive to pH of feed solution, coagulant dosing and generation time. Acrylonitrile butadiene styrene (ABS) MF membrane of pore size 0.4 μm was used in this study. Without pretreatment normalised flux declined by 94% after 160 min of MF operation using model wastewater. However with pretreatments, the MF flux was significantly improved. The optimum performance for MF with both electro and chemical coagulation pretreatments occurred at isoelectric point where the highest removal of organic and turbidity was observed. With chemical coagulation under optimum conditions (30 mg/l alum dose and pH 6.5), MF did not experience any flux decline. MF performed better with chemical coagulation compared to electrocoagulation (EC). Also organic matter removal was found to be more for chemical coagulation than for EC