Blind separation of vibration signals and source change detection – Application to machine monitoring

The paper presents a new approach for machine vibration analysis and health monitoring combining blind source separation (BSS) and change detection in source signals. So, the problem is transferred from the original space of the measurements to the space of independent sources, where the reduced number of components is going to simplify the monitoring problem while the change detection methods are going to be applied for scalar signals. The assessment of the approach on a real machine is presented in this paper.     

Isotopic fingerprint of the middle Olt River basin,Romania

One of the most important tributaries of the Danube River in Romania, the Olt River, was characterized in its middle catchment in terms of the isotopic composition using continuous flow–isotope ratio mass spectrometry (CF–IRMS). Throughout a period of 10 months, from November 2010 to August 2011, water samples from the Olt River and its more important tributaries were collected in order to investigate the seasonal and spatial isotope patterns of the basin waters. The results revealed a significant difference between the Olt River and its tributaries, by the fact that the Olt River waters show smaller seasonal variations in the stable isotopic composition and are more depleted in ¹⁸O and ²H. The waters present an overall enrichment in heavy isotopes during the warm seasons.     

Solving inverse scattering problems in biological samples by quantitative phase imaging

Quantitative phase imaging (QPI), a method that precisely recovers the wavefront of an electromagnetic field scattered by a transparent, weakly scattering object, is a rapidly growing field of study. By solving the inverse scattering problem, the structure of the scattering object can be reconstructed from QPI data. In the past decade, 3D optical tomographic reconstruction methods based on QPI techniques to solve inverse scattering problems have made significant progress. In this review, we highlight a number of these advances and developments. In particular, we cover in depth Fourier transform light scattering (FTLS), optical diffraction tomography (ODT), and white‐light diffraction tomography (WDT).

     

General tridiagonal random matrix models, limiting distributions and fluctuations

In this paper we discuss general tridiagonal matrix models which are natural extensions of the ones given in Dumitriu and Edelman (J. Math. Phys. 43(11): 5830–5847, 2002; J. Math. Phys. 47(11):5830–5847, 2006). We prove here the convergence of the distribution of the eigenvalues and compute the limiting distributions in some particular cases. We also discuss the limit of fluctuations, which, in a general context, turn out to be Gaussian. For the case of several random matrices, we prove the convergence of the joint moments and the convergence of the fluctuations to a Gaussian family. The methods involved are based on an elementary result on sequences of real numbers and a judicious counting of levels of paths.     

Sub-Lagrangians and sub-Hamiltonians on affine bundles

In this paper, sub-Lagrangians and sub-Hamiltonians are defined on anchored affine bundles as a natural extension of sub-Riemannian metrics. A duality considered between regular sub-Lagrangians and sub-Hamiltonians, gives the same solution of the Euler–Lagrange and Hamilton equations. Using the Pontryagin maximum principle, we prove that a similar situation of sub-Riemannian minimizers is encountered in this case, i.e., for a positive-definite sub-Lagrangian (sub-Hamiltonian), the locally arc-minimizing curves are either regular ones (as solutions of the Euler–Lagrange and Hamilton equations) or abnormal minimizers. Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 61, Optimal Control, 2008.     

Influence of the Comonomer on the Dissociation of Some Alternating Maleic Acid Copolymers

Five alternating copolymers of maleic acid with N-vinylpyrrolidone, vinyl acetate, styrene, 2-vinylnaphthalene, and vinyl cyclohexane were used in order to study the influence of the comonomer on the polyelectrolyte behavior. The dissociation of the maleic acid copolymers was investigated by electrochemical methods in pure water and in the presence of supporting electrolytes. The conformational modifications during the dissociation were directly investigated by viscosimetry and fluorescence probing. The shape of the potentiometric and conductometric titration curves was influenced by the comonomer structure. In salt-free solution, only the first dissociation step was observed. The addition of univalent counterions permitted the evidencing of the second ionization step only for the copolymers with hydrophilic comonomers, but the addition of divalent counterions permitted the evidencing of the second ionization step for all five copolymers. The apparent dissociation constants increase with the increase of the comonomer hydrophobicity. A conformational transition was evidenced especially in the case of the maleic acid-2-vinylnaphthalene copolymer.