Polymer chain dynamics in solution probed with a fluorescence blob model

This Account describes a new fluorescence tool that characterizes the chain dynamics of polymers in solution. This new tool, coined the fluorescence blob model (FBM), is employed to analyze the fluorescence decays of polymers randomly labeled with pyrene. The FBM yields the number of monomers making up a blob (Nblob) where a blob is the volume probed by an excited pyrene. By establishing a relationship between Nblob and the lifetime of pyrene used as an internal clock, the FBM provides previously unavailable information about polymer chain dynamics and opens new venues of research, which are described in this Account.     

Models and hybrid methods for the onshore wells maintenance problem

Workover rigs are used in onshore basins but they are often in limited number and they may not attend all the maintenance requests. We consider here the problem of scheduling the rigs over a time horizon in order to minimize the total oil loss due to the idle production states. Three mixed integer linear models are proposed. The first one improves an existing scheduling-based formulation. The second one uses an open vehicle routing approach and the third one is an extended model for which a column generation strategy is developed. Several improvements are presented as well as two heuristics coupled with column generation. To our knowledge, the first optimal values for medium-size instances of the problem are presented in this paper. The results show the potential of the column generation and its interest in a practical context.     

Decision-Feedback Equalization for Pulse-Position Modulation

In this paper, we propose a minimum mean squared error (MMSE) decision feedback equalizer (DFE) for pulse position modulated (PPM) signals in the presence of intersymbol interference (ISI). While traditional uses of PPM may not have had ISI, PPM is increasingly being considered for use in situations where ISI is an issue, such as high-performance optical communication systems and ultrawideband communications. First, we review previous work on the subject which used the zero-forcing criterion under strict assumptions about the channel and equalizer lengths. Then, we derive a computationally efficient MMSE equalizer which removes these restrictions, and is suitable for use with training-based stochastic gradient-descent algorithms. Finally, we demonstrate the performance of the proposed equalizer with simulations.     

On Blind Equalization of Biorthogonal Signaling

Motivated by increasing interest in energy efficient modulations, we provide the first look at adaptive equalization of biorthogonal signaling. While this modulation has historically been considered only for use in narrowband systems without intersymbol interference (ISI), recent attention has been given to its use in ISI channels. Due to the fact that biorthogonal modulation (BOM) results in a source that is not i.i.d., however, classical blind adaptive equalization techniques cannot be directly applied to equalization of BOM signals. We first examine minimum mean-squared error (MMSE) and least mean squares (LMS)-based equalizers, and identify some peculiarities that arise in equalization of BOM signals when compared to more traditional modulations like binary phase shift keying (BPSK). Next, we present two novel blind algorithms for the adaptive equalization of BOM signals: LTBOMB and TROMBONE. We discuss the convergence properties of these algorithms, and demonstrate their performance with numerical simulations     

A fast exact least mean square adaptive algorithm

A general block formulation of the least-mean-square (LMS) algorithm for adaptive filtering is presented. This formulation has an exact equivalence with the original LMS algorithm; hence it retains its convergence properties, while allowing a reduction in arithmetic complexity, even for very small block lengths. Working with small block lengths is interesting from an implementation point of view (large blocks result in large memory and large system delay) and allows a significant reduction in the number of operations. Tradeoffs between a number of operations and a convergence rate are obtainable by applying certain approximations to a matrix involved in the algorithm. Hence, the usual block LMS appears as a special case, which explains its convergence behavior according to the type of input signal (correlated or uncorrelated)     

Adaptive solution for blind identification/equalization usingdeterministic maximum likelihood

A deterministic maximum likelihood (DML) approach is presented for the blind channel estimation problem. It is first proposed in a block version, which consists of iterating two steps, each one solving a least-squares problem either in the channel or in the symbols. In the noiseless case and under certain conditions, this algorithm gives the exact channel and the exact symbol vector with a finite number of samples. It is shown that even if the DML method has a single global minimum, the proposed iterative procedure can converge to spurious local minima. This problem can be detected (under some channel diversity conditions) by using a numerical test that is proposed in the paper. Based on these considerations, we extend the maximum likelihood block algorithm (MLBA) to recursive implementations [maximum likelihood recursive algorithm (MLRA)]. The MLRA is able to track variations of the system by the introduction of an exponential forgetting factor in the DML criterion. The link between the adaptive algorithm and a soft decision feedback equalizer (SDFE) is emphasized. Low-complexity versions of the recursive and adaptive algorithm are presented     

An asymmetric watermarking method

This paper presents an asymmetric watermarking method as an alternative to classical direct sequence spread spectrum and watermarking Costa (1983) schemes techniques. This new method provides a higher security level against malicious attacks threatening watermarking techniques used for a copy protection purpose. This application, which is quite different from the classical copyright enforcement issue, is extremely challenging as no public algorithm is yet known to be secure enough, and some proposed proprietary techniques have been already hacked. Our method is thus an attempt toward the proof that the Kerckhoff's (1883) principle can be stated in the copy protection framework.     

Analyse thermique d''un mur composite soumis sur une face a une variation en creneaux de la temperature

An analytical method [1] improves the separation of variables technique to solve the problem of transient heat conduction in a composite wall with constant properties; each eigenvalue is the same for all slabs in the wall. The case of an intermittent working of a furnace is considered with two types of wall. Those walls have the same overall thermal resistance and practically the same overall thermal capacitance. One of them is completely made of ceramic fibers. For each wall the influence of the arrangement of the different slabs between the hot and cold surfaces on the heat fluxes which pass through them is considered. It is said that the ceramic fibers wall is not the best to spare energy.     

Filtre intégré à transferts récursifs

A new fully integrated mos frequency filter is suggested, using passive charge routing structure. The principle of operation, the synthesis procedure, and the first experimental results are discussed. This new device has to be compared with finite impulse CCD-filters and switched capacitor filters. Large improvements are expected in terms of silicon area and power consumption. Finally, this solution should be of large economical interest for digital communications.