Thermal reaction of SiC films with tungsten and tungsten–rhenium alloys

Solid-state reactions between SiC films and W–xRe (x = 0, 5 and 25 at%) substrates on thermal annealing between 1673 K and 1873 K for various durations have been investigated. SiC coatings were deposited on metallic wires by hot filament chemical vapour deposition (HFCVD) from a gas mixture of tetramethylsilane (TMS) and hydrogen at 1373 K under normal pressure. The interface zones were characterized using scanning electron and optical microscopies, X-ray diffraction and electron microprobe microanalysis. All analyses reveal that SiC reacts with substrates. Various metal silicides and carbides were formed in layered reaction and the presence of these phases was confirmed by electron probe microanalysis. The effects of rhenium on the reactivity were established by the determination of growth kinetics deducted from the thicknesses of reaction zones as a function of annealing time. It has been found that an increase in the diffusion kinetics and activation energy with the quantity of rhenium in the tungsten wire.     

Resolution-independent characteristic scale dedicated to satellite images.

We study the problem of finding the characteristic scale of a given satellite image. This feature is defined so that it does not depend on the spatial resolution of the image. This is a different problem than achieving scale invariance, as often studied in the literature. Our approach is based on the use of a linear scale space and the total variation (TV). The critical scale is defined as the one at which the normalized TV reaches its maximum. It is shown experimentally, both on synthetic and real data, that the computed characteristic scale is resolution independent.     

Metals in Biotechnology: Cr-Driven Stereoselective Reduction of Conjugated C=C Double Bonds

Elemental metals are shown to be suitable sacrificial electron donors to drive the stereoselective reduction of conjugated C=C double bonds using Old Yellow Enzymes as catalysts. Both direct electron transfer from the metal to the enzyme as well as mediated electron transfer is feasible, although the latter excels by higher reaction rates. The general applicability of this new chemoenzymatic reduction method is demonstrated, and current limitations are outlined.     

Object removal from complex videos using a few annotations

Computational Visual Media - We present a system for the removal of objects from videos. As input, the system only needs a user to draw a few strokes on the first frame, roughly delimiting the...     

From conventional ac flash-sintering of YSZ to hyper-flash and double flash

Flash-sintering experiments were performed on conventional 8 mol% Y₂O₃-doped ZrO₂. By varying the initial power spike, the steady state limited current density, the flash duration and furnace temperature, various microstructures corresponding to different sintering stages were observed. It is shown that operating the flash-sintering under the power dissipation regime may lead to microstructure heterogeneity. Under a quasi-adiabatic regime a better homogeneity is obtained. The major part of the shrinkage strain occurs within a short time interval of about 1 s, after the incubatory period. The remaining part appears to be a conventional shrinkage process induced by Joule heating. Hyper-flashes were performed over this short time interval, yielding relative densities up to 90%. Additional flashes can be subsequently applied up to full density. It is stressed that densification is not an absolute quality parameter in the optimization of the experimental conditions; inappropriate conditions may lead to fairly dense but brittle materials.     

Controller reduction with closed loop H infinity performance constraints: A QFT perspective

Assume that an initial stabilizing controller K₀₍s₎, which satisfies various closed loop frequency domain specifications, has been a priori synthesized using, e.g. H infinity control, mu synthesis techniques or closed loop convex synthesis. Remembering that the order of K₀₍s₎ is typical y at least equal to the order of the plant to be controlled, the aim of this paper is to find a stabilizing reduced order controller, which also satisfies the performance specifications and which moreover minimizes the open loop bandwidth. To this aim, the structured singular value mu is used to translate at each frequency closed loop frequency domain specifications into requirements on the frequency response of the controller. The principle of our reduction method is thus very close to the original idea of the SISO QFT design approach, except that the problem of translating closed loop frequency domain specifications into open loop ones is much more complex in the MIMO case. The problem reduces to the issue of finding a controller, whose frequency response belongs at each frequency to a template. The convexity of these templates greatly facilitates the practical realization of the controller. As a final point, the method is successfully applied to a standard H problem, which is extracted from the mu Analysis and Synthesis Toolbox of Matlab, namely the synthesis of an autopilot for the space shuttle.