Mines ParisTech

About: Mines ParisTech is a education organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Microstructure. The organization has 6564 authors who have published 11676 publications receiving 359898 citations. The organization is also known as: École nationale supérieure des mines de Paris & École des mines de Paris.

Semigroup Kernels on Measures

Abstract: We present a family of positive definite kernels on measures, characterized by the fact that the value of the kernel between two measures is a function of their sum. These kernels can be used to derive kernels on structured objects, such as images and texts, by representing these objects as sets of components, such as pixels or words, or more generally as measures on the space of components. Several kernels studied in this work make use of common quantities defined on measures such as entropy or generalized variance to detect similarities. Given an a priori kernel on the space of components itself, the approach is further extended by restating the previous results in a more efficient and flexible framework using the "kernel trick". Finally, a constructive approach to such positive definite kernels through an integral representation theorem is proved, before presenting experimental results on a benchmark experiment of handwritten digits classification to illustrate the validity of the approach.

Speciation of organotins in environmental samplesby SPME-GC: comparison of four specific detectors: FPD, PFPD, MIP-AES andICP-MS

Abstract: The performances of four specific detectors used for the speciation of butyl- and phenyltin compounds after solid phase microextraction (SPME) and gas chromatography (GC) separation are evaluated. A flame photometric detector (FPD), a pulsed flame photometric detector (PFPD), a microwave induced plasma atomic emission spectrometer (MIP-AES) and an inductively coupled plasma mass spectrometer (ICP-MS) were used. The principle of PFPD, a new generation of FPD, is presented. The original transfer line used between GC and ICP-MS is detailed. The high SPME preconcentration allows very low limits of detection (LOD) to be reached (less than 500 pg l−1 Sn for all the detectors). Sensitivity, linearity and selectivity of the different detectors are also discussed. As expected, ICP-MS is the most sensitive (LOD ranged from 0.6 to 20 pg l−1 Sn) but the cheapest PFPD is also of significant interest. The analytical procedure is applied to the determination of organotins in two different reference materials: a sediment (PACS 2) and a fish tissue (NIES 11). These different examples show that the detection of ultra-trace tin species is now possible in natural samples using a combination of SPME and GC with a specific detector.

Influence of screw profile and extrusion conditions on the microstructure of polypropylene/organoclay nanocomposites

Abstract: Direct melt mixing in a twin screw extruder is a simple and classical technique for preparing nanocomposites by dispersing organoclay in a thermoplastic matrix. In this paper, we focus on organoclay/polypropylene nanocomposites, using maleated polypropylene as compatibilizer. The objective of the work is to characterize the influence of screw profile and processing conditions on the microstructure of the nanocomposite (intercalation and exfoliation). Different screw profiles, more or less severe in terms of mixing elements, have been investigated. For each profile, different processing conditions (feed rate, screw speed) have been tested. Samples were collected both at die exit and all along the screw profiles and analyzed (X-ray diffraction and rheometry). Numerical simulations have been performed to quantify the thermomechanical treatment experienced by the material inside the extruder. For all profiles and operating conditions, a mixed intercalated/ exfoliated structure has been observed. Exfoliation increases linearly with the ratio of screw speed to feed rate, but is more important for the less severe profile. Except at low feed rate, intercalation and exfoliation do not change a lot along the screw profile. In many cases, the final microstructure is already obtained after the melting zone of the extruder.

Global complete observability and output-to-state stability imply the existence of a globally convergent observer

Abstract: In this paper we consider systems which are globally completely observable and output-to-state stable. The former property guarantees the existence of coordinates such that the dynamics can be expressed in observability form. The latter property guarantees the existence of a state norm observer and therefore nonlinearities bounding function and local Lipschitz bound. Both allow us to build an observer from an approximation of an exponentially attractive invariant manifold in the space of the system state and an output driven dynamic extension. The state of this observer has the same dimension as the state to be observed. Its main interest is to provide convergence to zero of the estimation error within the domain of definition of the solutions.