Improvement of grain-size analyses using the automated SEDIGRAPH 5100

The method of analysing fine grained sediments is discussed and an improved technique using a water-glycerol solution of known density instead of water is proposed. Inaccuracies resulting from wet sieving may contribute to explain the observed difference between the pipette method and the Sedigraph 5100 analyses

Применение нейросетевых технологий для измерений параметров вибрации объектов с неплоской поверхностью

Было проведено компьютерное моделирование электродинамической системы интерференционного измерителя параметров вибраций объектов с неплоской поверхностью. Показано, что применение нейросетевых технологий позволяет использовать интерференционный метод для измерения параметров перемещений объектов с неплоской поверхностью. Полученные результаты обработки данных компьютерного моделирования свидетельствуют об эффективности практического применения нейронных сетей для обработки сигналов трёхзондового интерференционного сверхвысокочастотного измерителя.Було проведено комп'ютерне моделювання електродинамічної системи інтерференційного вимірювача параметрів вібрацій об'єктів з неплоскою поверхнею. Показано, що застосування нейромережевих технологій дозволяє використовувати інтерференційний метод для вимірювання параметрів переміщень об'єктів з неплоскою поверхнею. Отримані результати обробки даних комп'ютерного моделювання свідчать про ефективність практичного застосування нейронних мереж для обробки сигналів тризондового інтерференційного надвисокочастотного вимірювача.An electrodynamical system of an interference vibration meter for objects with a non-planar surface is simulated using a computer. It is shown that neural technologies allow to use an interference method for measuring parameters of the moving objects with a non-planar surface. The results obtained of processing data of a computer simulation show the effectiveness of the practical application of neural networks for processing signals of the trisounder interference microwave meter

A log-normal spectral analysis of inorganic grain-size distributions from a Canadian boreal lake core: Towards refining depositional process proxy data from high latitude lakes

Better methods for interpreting grain size spectra will enhance current understanding of past transport–depositional processes. A high-resolution inorganic grain-size dataset has been measured from a freeze core extracted from ‘Alberta Lake E’ a boreal fresh water lake 40 km east of the Athabasca Oil Sands in north-eastern Alberta, Canada. The grain-size spectra are remarkably consistent throughout the core, exhibiting a structure comprising six persistent grain-size distributions below ca 250 μm, plus a rare medium-sand distribution. Automated deconvolution of the grain-size spectra produced poor results. Constraining the modes of two of the distributions produced deconvolution solutions that were statistically excellent and consistent with the structure of each spectrum. Statistical analysis of the ‘constrained’ solutions indicates that deconvolution successfully extracted independent grain-size populations. Conversely, the multimodal spectra generate traditional measures (for example, mean grain size) that are inconsistent combinations of different individual populations, and thus are poor proxies of transport–depositional processes. Alberta Lake E is situated in a boreal wetland landscape where sediment delivery is dominated by overland flow transport during spring melt. This context means that the Alberta Lake E grain-size spectra can be interpreted to reflect: (i) a bedload component transported during short-duration high discharge events that reflect the intensity of the melt; and (ii) a finer suspended load component representing material whose magnitude is controlled by the volume of the spring melt. Stratigraphically, bedload and suspended load populations demonstrate different short-wavelength and long-wavelength cyclicity, suggesting that spring melt is likely to be driven by cyclic external forcing factors. The links between the grain-size spectra and spring melt have potential for generating proxy records that better capture the external controls over spring melt in boreal systems, and the risks associated with these energetic hydrodynamics. This is exemplified by the coarsest Alberta Lake E distributions, which indicate that more intense spring melt dynamics occurred in pre-historical times

Propriétés spectrales des opérateurs de Toeplitz

La première partie de la thèse réunit des résultats classiques sur l’espace de Hardy, les espaces modèles et l’espace de Bergman. Puis sur cette base, nous exposons des travaux relatifs aux opérateurs de Toeplitz, en particulier, nous présentons la description du spectre et du spectre essentiel de ces opérateurs sur l’espace de Hardy et de Bergman. La première partie de notre recherche tire son inspiration de deux faits établis pour un opérateur de Toeplitz T. Premièrement, sur l’espace de Hardy, la norme de T, la norme essentielle de T et la norme infinie du symbole de T sont égales. Nous étudions ce cas d’égalité sur l’espace de Bergman pour les opérateurs de Toeplitz à symbole quasihomogène et radial. Deuxièmement, sur l’espace de hardy, le spectre et le spectre essentiel sont fortement liés à l’image du symbole de T. Nous étudions le cas d’égalité entre le spectre et l’image essentielle du symbole pour les symboles quasihomogènes et radials. Pour répondre à ces deux questions, nous utilisons la transformée de Berezin, les coefficients de Mellin et la moyenne du symbole. La dernière partie de la thèse s’interesse au théorème de Szegö qui donne un lien entre les valeurs propres d’une suite de matrices de Toeplitz de taille n, et le symbole de cette suite de matrice. Nous donnons un résultat du même type sur l’espace de Bergman pour les symboles harmoniques sur le disque et continus sur le cercle. Enfin, nous étudions une généralisation de ce théorème en compressant l’opérateur de Toeplitz sur une suite d’espaces modèles de dimension finie.This thesis deals with the spectral properties of the Toeplitz operators in relation to their associated symbol. In the first part, we give some classical results about Hardy space, model spaces and Bergman space. Afterwards, we expose some results about Toeplitz operator on the Hardy space. In particular, we discuss their spectrum and essential spectrum. Our work is inspired from two facts which have been proved on the Hardy space. First, considering a Toeplitz operator T, the norm, essential norm, spectral radius of T and the supremum of its symbol are equal. Secondly, on the Hardy space, spectrum, essential spectrum and essential range are strongly related. We answer the question of the equality between the norms, the spectral radius and the supremum of the symbol and between spectrum and essential range on the Bergman space. We look at these two properties on the Bergman space when the symbol is radial or quasihomogeneous. We answer these questions using the Berezin transform, the Mellin coefficients and the mean value of the symbol. The last part deals with the classical Szegö theorem which underline a link between the eigenvalues of a Toeplitz matrix sequence and its symbol. We give a result of the same type on Bergman space considering harmonic symbol wich have a continuous extension. We give a generalization, considering the sequence of the compressions of a Toeplitz operator on a sequence of model spaces

Sur la minéralogie de la fraction lourde et des alluvions sableuses des pertuis charentais (pertuis d'Antioche et pertuis breton)

National audienc

Sur la minéralogie de la fraction lourde des alluvions sableuses des pertuis charentais (pertuis d'Antioche et pertuis breton)

Barusseau J. P. Sur la minéralogie de la fraction lourde des alluvions sableuses des pertuis charentais (pertuis d'Antioche et pertuis breton). In: Bulletin de l'Association française pour l'étude du quaternaire, vol. 4, n°2, 1967. pp. 135-143