On-line compositional controller synthesis for AGV

This paper deals with the on-line design of a supervisor to coordinate an automated guided vehicle (AGV) fleet. This supervisor ensures the system safety (no collision) and a good coordination between vehicles (no blocking situations). It is the so-called Wonham-Ramadge supervisor, it is the least restrictive, and ensures controllability and nonblocking. We propose a compositional procedure to resolve this problem allowing an efficient on-line synthesis. A calculation on the fly is made at every attribution of a new mission for an AGV, to actualize the supervisor and adapt it to the new situation. This compositional approach allows to increase the number of AGV taken on compared to the monolithic approach. We show on some tests the efficiency of this method for the on-line synthesis of supervisor to coordinate a fleet of mobile robots for real cases.     

Revealing determinant factors for early breast cancer recurrence by decision tree

Early breast cancer recurrence is indicative of poor response to adjuvant therapy and poses threats to patients’ lives. Most existing prediction models for breast cancer recurrence are regression-based models and difficult to interpret. We apply a Decision Tree algorithm to the clinical information of a cohort of non-metastatic invasive breast cancer patients, to establish a classifier that categorizes patients based on whether they develop early recurrence and on similarities of their clinical and pathological diagnoses. The classifier predicts for whether a patient developed early disease recurrence; and is estimated to be about 70% accurate. For an independent validation cohort of 65 patients, the classifier predicts correctly for 55 patients. The classifier also groups patients based on intrinsic properties of their diseases; and for each subgroup lists the disease characteristics in a hierarchal order, according to their relevance to early relapse. Overall, it identifies pathological nodal stage, percentage of intra-tumor stroma and components of TGFβ-Smad signaling pathway as highly relevant factors for early breast cancer recurrence. Since most of the disease characteristics used by this classifier are results of standardized tests, routinely collected during breast cancer diagnosis, the classifier can easily be adopted in various research and clinical settings.     

LBM based flow simulation using GPU computing processor

Graphics Processing Units (GPUs), originally developed for computer games, now provide computational power for scientific applications. In this paper, we develop a general purpose Lattice Boltzmann code that runs entirely on a single GPU. The results show that: (1) simple precision floating point arithmetic is sufficient for LBM computation in comparison to double precision; (2) the implementation of LBM on GPUs allows us to achieve up to about one billion lattice update per second using single precision floating point; (3) GPUs provide an inexpensive alternative to large clusters for fluid dynamics prediction.     

Discrete nonlinear observers for inertial navigation

We derive an exact deterministic nonlinear observer to compute the continuous state of an inertial navigation system based on partial discrete measurements, the so-called strap-down problem. Nonlinear contraction is used as the main analysis tool, and the hierarchical structure of the system physics is systematically exploited. The paper also discusses the use of nonlinear measurements, such as distances to time-varying reference points.     

Influence of the 316 L stainless steel interface on the stability and barrier properties of plasma fluorocarbon films

Coatings are known to be one of the more suited strategies to tailor the interface between medical devices and the surrounding cells and tissues once implanted. The development of coatings and the optimization of their adhesion and stability are of major importance. In this work, the influence of plasma etching of the substrate on a plasma fluorocarbon ultrathin coating has been investigated with the aim of improving the stability and the corrosion properties of coated medical devices. The 316 L stainless steel interface was subjected to two different etching sequences prior to the plasma deposition. These plasma etchings, with H(2) and C(2)F(6) as gas precursors, modified the chemical composition and the thickness of the oxide layer and influenced the subsequent polymerization. The coating properties were evaluated using flat substrates submitted to deformation, aging into aqueous medium and corrosion tests. X-ray photoelectron spectroscopy (XPS), time of flight-secondary ion mass spectrometry (ToF-SIMS), ellipsometry, and atomic force microscopy (AFM) were performed to determine the effects of the deformation and the aging on the chemistry and morphology of the coated samples. Analyses showed that plasma etchings were essential to promote reproducible polymerization and film growth. However, the oxide layer thinning due to the etching lowered the corrosion resistance of the substrate and affected the stability of the interface. Still, the deformed samples did not exhibited adhesion and cohesion failure before and after the aging.     

Multi-level analysis of low-cost Z-pinned composite joints: Part 2: Joint behaviour

In the framework of the E-U program ALCAS (Advanced Low-Cost Aircraft Structure), a new Z-pinning technique was developed by EADS Innovation Works. This technology was used to manufacture low-cost Z-pinned junction demonstrators (L and T shaped specimens) typical of aeronautical structures. In order to understand load transfer mechanisms in this kind of assembly, a multi-level analysis was performed. In the first part of this study, tension and shear pin behaviour was investigated as well as pin pull-out from neat resin or laminate. An analytical model was proposed to predict the maximum load capability of a single pin for an insertion depth of less than 8 mm which correspond to the usual technology. Now, in this second part, we demonstrate that the behaviour of the junction under pull-out, shear and unfolding is globally homothetic to the mechanical behaviour of a pin. This study provides the basis for a pre-sizing methodology for Z-pinned junctions under complex loading.     

A method for assessing the impact of product development on the company

Because of competitiveness, the problem of product and production system developments is becoming increasingly current. From the point of view of products and production systems, companies must have tools to redesign, analyse, choose and manage their developments. After analysing which tools and methods exist in the scientific literature, we present in this paper a general method for assessing the impact of product development on the company. This method can be applied for each criterion that the company wants to analyse (delay, cost, organization, resources, quality, etc); we choose here the delay criterion. The method features four steps. The first step aims to characterize the case study by representing it with generic parameters. The second step offers the construction of a matrix model (called a static model) in order to categorize the product developments. The third step proposes the construction of a Temporized Coloured Petri Net model (called a dynamic model) and the fourth step simulates this model in order to obtain the expected result: the assessment of impact of the product development. At the end of the paper, we propose a case study on a roller tapered bearing manufacturer-- the Timken company.     

Fast-grown CdS quantum dots: Single-source precursor approach vs microwave route

A cross-disciplinary protocol of characterization by joint techniques enables one to closely compare chemical and physical properties of CdS quantum dots (QDs) grown by single source precursor methodology (SSPM) or by microwave synthetic route (MWSR). The results are discussed in relation with the synthesis protocols. The QD average sizes, reproducible as a function of the temperatures involved in the growth processes, range complementarily in 2.8–4.5 nm and 4.5–5.2 nm for SSPM and MWSR, respectively. Hexagonal and cubic structures after X-ray diffraction on SSPM and MWSR grown CdS QDs, respectively, are tentatively correlated to a better crystalline quality of the latter with respect to the further ones, suggested by (i) a remarkable stability of the MWSR grown QDs after exposure to air during several days and (ii) no evidence of their fragmentation during mass spectrometry (MS) analyses, after a fair agreement between size dispersities obtained by transmission electron microscopy (TEM) and MS, in contrast with the discrepancy found for the SSPM grown QDs. Correlatively, a better optical quality is suggested for the MWSR grown QDs by the resolution of n > 1 excitonic transitions in their absorption spectra. The QD average sizes obtained by TEM and deduced from MS are in overall agreement. This agreement is improved for the MWSR grown QDs, taking into account a prolate shape of the QDs also observed in the TEM images. For both series of samples, the excitonic responses vs the average sizes are consistent with the commonly admitted empirical energy-size correspondence. A low energy PL band is observed in the case of the SSPM grown QDs. Its decrease in intensity with QD size increase suggests a surface origin tentatively attributed to S vacancies. In the case of the MWSR grown QDs, the absence of this PL is tentatively correlated to an absence of S vacancies and therefore to the stable behavior observed when the QDs are exposed to air.     

Tower shadow modelization with helicoidal vortex method

The helicoidal vortex model developed by the author is compared with data of the National Renewable Energy Laboratory (NREL) Unsteady Aerodynamics Experiment (UAE). The B Sequence has been used for this purpose. It corresponds to the “downwind configuration” where the blades cross the tower shadow. Several cases have been analyzed with wind speeds of V = 5, 7, 10 and 12 m/s and yaw angles of up to 30°. The results indicate that the modelization of the tower shadow gives good results in the range of applicability of the vortex model, at a low computer cost, and demonstrates further the versatility of this approach.     

DRYING OF SUGAR BEET FIBER WITH HOT AIR OR SUPERHEATED STEAM

A comparative study of drying thin layers of sugar beet fiber with hot air or with superheated steam in a specially designed pilot dryer is reported. Our present interests are focused on drying rate and on the quality of the dried product. Steam superheated at 130-150°C yields 90 % of dry matter (DM), however steam condensation on the cold product at the beginning of the process may penalize the drying time. The color of the fiber is not modified until reaching 80 % DM. Drying with air heated at temperatures lying in the 40 to 105°C range does not alter the white color up to 90 % DM. The water retention capacity of the original fiber, 14 g water/g DM remains unchanged whatever drying agent is used. The scaling up of the primary hot air drying set up to a ten times larger experimental dryer introduce no modification of drying time, water retention capacity or fiber color. Thick layer drying experiments permit to define parameters of a belt dryer for an industrial fiber processing plant.