On convergence in the methods of Strat and of Smith for Shape from Shading

We study the convergence of two iterative Shape from Shading methods: the methods of Strat and of Smith. We try to determine the spectral radius of the Jacobian matrix of each iteration at any possible fixed point. We show that the method of Strat diverges for any image containing at least four pixels forming a square, any reflectance map and any relative weight between the irradiance term and the integrability term. An example is provided, in which divergence occurs after a large number of iterations, even if the reconstructed surface approaches the real surface after only a few iterations. We show then by a similar way that the method of Smith diverges for any image containing at least nine pixels forming a square, any reflectance map and any relative weight between the irradiance term and the smoothing term.     

Combined decrease of sulphur,nitrogen, hydrogen and total oxygen in only one secondary steelmaking operation

The development of a matured metallurgical process allows the reduction of the sulphur, nitrogen, hydrogen and total oxygen content to the lowest values in only one secondary metallurgical step during treatment in a ladle tank degassing unit. By careful adjustment of a lime-saturated ladle top slag at the beginning of the vacuum treatment, it is possible to obtain a desulphurization degree of more than 95%. The process of nitrogen removal by a stirring gas can be described with a dynamic model in excellent agreement with plant trials. The nitrogen content after vacuum treatment depends mainly on the nitrogen content before vacuum, the stirring gas quantity and the sulphur content. The achievable hydrogen contents mainly depend on the stirring gas quantity and dehydrogenisation can be described by the same model used for denitrogenisation. By a cleanliness stirring after the vacuum treatment under a nearly SiO₂-free-, lime-alumina slag, saturated with lime, the total-oxygen content can be lowered to less than 20 ppm.     

Distribution of projection angles for single-axis-tilt electron microscope tomography of extended thin planar specimens

An optimized distribution of tilt angles for tomography of specimens of non-circular cross-section is derived and tested with reconstructions of a phantom model.     

Analysis of planar structures by an integral approach using entiredomain trial functions

In this paper, a method based on an integral formulation with an excitation term is presented. The particularities of this approach lie in the utilization of entire domain trial functions and in the characterization of the coupling effect due to the excitation mechanism. The trial functions are taken as the TE-TM modes of a waveguide whose cross section corresponds to the shape of the discontinuity. The trial functions are computed and stored in the memory, then the study of complex planar structures becomes easy. A complete study is proposed, including the analysis of the coupling mechanism due to the source interaction and the characterization of higher order modes influence. This work is followed by two applications: a multiaxial discontinuity (bend discontinuity) in microstrip and in CPW. The computed results have been compared with data furnished by the literature. A good accuracy has been obtained     

The Influence of C60 Powders On Cultured Human Leukocytes

In order to check its possible acute toxicity, C₆₀ was incorporated into living human phagocytes. It was observed that C₆₀ has no influence on the survival of human leukocytes.     

Vector Quantization-Based Motion Field Segmentation under the Entropy Criterion

This paper proposes a segmentation of block-based motion fields under the constraint of the entropy criterion. The segmentation is performed by a vector quantization technique which associates the segmentation pattern to an element of a codebook. Optimization of the bit rate as a trade-off between motion and segmentation on the one hand and prediction error on the other hand is addressed. An estimation of the amount of information to code the displaced frame difference is derived, making it possible to control the segmentation process. Simulation results show the efficiency of the segmentation method combined with the entropy criterion in a video coding scheme.     

Generalizing database relational algebra for the treatment of incomplete or uncertain information and vague queries

This paper deals with relational databases which are extended in the sense that fuzzily known values are allowed for attributes. Precise as well as partial (imprecise, uncertain) knowledge concerning the value of the attributes are represented by means of [0,1]-valued possibility distributions in Zadeh's sense. Thus, we have to manipulate ordinary relations on Cartesian products of sets of fuzzy subsets rather than fuzzy relations. Besides, vague queries whose contents are also represented by possibility distributions can be taken into account. The basic operations of relational algebra, union, intersection, Cartesian product, projection, and selection are extended in order to deal with partial information and vague queries. Approximate equalities and inequalities modeled by fuzzy relations can also be taken into account in the selection operation. Then, the main features of a query language based on the extended relational algebra are presented. An illustrative example is provided. This approach, which enables a very general treatment of relational databases with fuzzy attribute values, makes an extensive use of dual possibility and necessity measures.     

Propriétés de la Surface d'un Film de Polyéthylène Modifiée par Greffage d'un Oligomère Acrylique

The grafting of a liquid acrylic derivative (2-methylenepentane-1,5-dicarboxylic acid diethylester) on the surface of a polyethylene film (HD) was carried out in the presence of benzoylperoxide. The wettability of the surface was investigated with respect to the adhesion properties against aluminium and compared with those of a film of polyethylene grafted in mass with acrylic acid. The mobility of the surface grafted chains may cause the differences in the observed comportment.     

Choix entre les différentes méthodes quadratiques d’estimation du spectre de puissance

Quadratic estimators of power spectra are compared, for a given total observation range, by using the matrix of the associated quadratic form. Considering the case of smooth spectra, it is shown that the smallest variance for a given resolution is achieved if this matrix is Toeplitz. From the estimation and the computation points of view, a detailed comparison is made between two types of estimation schemes. The first is composed of methods equivalent to the smoothing of a single periodogram; the second reduces to the very popular Welch method (averaging of several short, modified periodograms). Our presentation makes clear the choice of parameters and should prevent errors, common mainly when dealing with short records.