On the control of uncertain impulsive systems: approximate stabilization and controlled invariance

The problems of stabilization and controlled invariance of a fairly wide class of uncertain hybrid systems is considered. Uncertainty enters in the form of a disturbance input that can affect both the continuous and the discrete dynamics. A method for designing piecewise constant, feedback controllers for this class of systems is developed. In the case of controlled invariance, the controller ensures that the state of the system remains arbitrarily close to a desired set over an arbitrarily long time horizon. In the case of stabilization, the controller ensures approximate exponential convergence of the runs of the closed loop system to the zero level set of a Lyapunov function.     

Neutronic characterization of the MEGAPIE target

The MEGAPIE project aimed to design, build and operate a liquid metal spallation neutron target of about 1 MW beam power in the SINQ facility at the Paul Scherrer Institut (Villigen, Switzerland). This project is an important step in the roadmap towards the demonstration of the accelerator driven system (ADS) concept and high power liquid metal targets in general. Following the design phase, an experimental program was defined to provide a complete characterization of the facility by performing a “mapping” of the neutron flux at different points, from the center of the target to the beam lines. The neutronic performance of the target was studied using different experimental techniques with the goals of validating the Monte Carlo codes used in the design of the target; additionally, the performance was compared with the solid lead targets used before and after the MEGAPIE experiment.     

Thermal stability of SiC Schottky diode anode and cathode metalisations after 1000 h at 350 °C

The thermal stability of two commercially available silicon carbide Schottky diode types has been evaluated following a 1000 h non-biased storage test under vacuum at 350 °C. The Ti-based Schottky (Anode) contact shows excellent stability over the duration of the test with less than 5% change in either extracted Schottky barrier height or ideality values. The Al die attach metalisation on the anode also shows no evidence of degradation after the test. However, a considerable change in series resistance was observed for both diode types, with up to a factor of 100 measured for one of the diodes. The primary early failure mode is related to degradation of the NiAg Ohmic (cathode) die attach metalisation. Demixing of the NiAg alloy, leading to Ag agglomeration is proposed to be the underlying degradation mechanism involved resulting in delamination of the die attach metalisation and the corresponding series resistance increase.     

Characterization of reactively sputtered permeation barrier materials on polymer substrates

Transparent permeation barrier layers are not only used for food packaging but are also needed to encapsulate flexible electronic devices. Magnetron sputtering allows the deposition of high quality oxide barrier layers with a low water vapor and oxygen permeation. This paper compares different metal oxide layers which are deposited onto a polyethylene terephthalate (PET) film using a reactive dual magnetron sputtering process. The oxides of aluminum, silicon, titanium, zinc and a zinc-tin alloy are compared regarding their permeation barrier, structural and surface properties to determine the relationship between the layer structure and the gas permeation. Thereby, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the morphology and surface structure of the layers and X-ray diffraction analysis (XRD) was used to determine the solid state phase.Cross-section images taken with SEM show a very compact structure for both aluminum oxide and zinc-tin oxide layers. These materials also have the lowest water vapor permeation compared to all other materials. Zinc oxide and titanium oxide layers both exhibit a columnar structure. Zinc oxide is polycrystalline and has a surprising low water vapor and oxygen permeation. In contrast to that the amorphous titanium oxide layers show a high water vapor and oxygen permeation which is not decreasing with an increasing layer thickness above 40 nm.     

Crystal growth of bullet-shaped magnetite in magnetotactic bacteria of the Nitrospirae phylum

Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth''s magnetic field lines. MTB have been suggested as being one of the most ancient biomineralizing metabolisms on the Earth and they represent a fundamental model of intracellular biomineralization. Moreover, the determination of their specific crystallographic signature (e.g. structure and morphology) is essential for palaeoenvironmental and ancient-life studies. Yet, the mechanisms of MTB biomineralization remain poorly understood, although this process has been extensively studied in several cultured MTB strains in the Proteobacteria phylum. Here, we show a comprehensive transmission electron microscopy (TEM) study of magnetic and structural properties down to atomic scales on bullet-shaped magnetites produced by the uncultured strain MYR-1 belonging to the Nitrospirae phylum, a deeply branching phylogenetic MTB group. We observed a multiple-step crystal growth of MYR-1 magnetite: initial isotropic growth forming cubo-octahedral particles (less than approx. 40 nm), subsequent anisotropic growth and a systematic final elongation along [001] direction. During the crystal growth, one major {111} face is well developed and preserved at the larger basal end of the crystal. The basal {111} face appears to be terminated by a tetrahedral–octahedral-mixed iron surface, suggesting dimensional advantages for binding protein(s), which may template the crystallization of magnetite. This study offers new insights for understanding magnetite biomineralization within the Nitrospirae phylum.     

Terahertz Real-Time Imaging Uncooled Arrays Based on Antenna-Coupled Bolometers or FET Developed at CEA-Leti

Journal of Infrared, Millimeter, and Terahertz Waves - Sensitive and large-format terahertz focal plane arrays (FPAs) integrated in compact and hand-held cameras that deliver real-time terahertz...     

Driving an electric vehicle. A sociological analysis on pioneer users

In most of the western countries, car is the prevalent means of transport for local mobility. At the same time, sensitivity to environmental issues is increasing, correlated to the consciousness that carbon dioxide emissions have to be reduced. In regard to these two trends (individual mobility and public opinions favourable to a reduction of carbon emissions), energy-efficient vehicles will probably develop in the future—car manufacturers actually prepare new offers for the mass market. Comparable cases have occurred during the last decades—probably more modest but full of learning: some local authorities have promoted innovations based on electric vehicles in the 1990s, and some people have chosen this kind of cars for their daily travels. This article deals with these pioneers (This article comes from a communication at the ECEEE Summer Study, June 2009, Panel 6: Energy efficiency in transport and mobility.). Reporting studies carried out in 2006 and 2008, we intend to identify the reasons of this innovative modal choice, to show the difficulties that electric vehicle drivers then encountered and to analyse the patterns of use that governed their mobility and their use of electric vehicles.