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.     

Parallel integral projection transform for straight electrode localization in 3-D ultrasound images

In surgical practice, small metallic instruments are frequently used to perform various tasks inside the human body. We address the problem of their accurate localization in the tissue. Recent experiments using medical ultrasound have shown that this modality is suitable for real-time visualization of anatomical structures as well as the position of surgical instruments. We propose an image-processing algorithm that permits automatic estimation of the position of a line-segment-shaped object. This method was applied to the localization of a thin metallic electrode in biological tissue. We show that the electrode axis can be found through maximizing the parallel integral projection transform that is a form of the Radon transform. To accelerate this step, hierarchical mesh-grid algorithm is implemented. Once the axis position is known, localization of the electrode tip is performed. The method was tested on simulated images, on ultrasound images of a tissue mimicking phantom containing a metallic electrode, and on real ultrasound images from breast biopsy. The results indicate that the algorithm is robust with respect to variations in electrode position and speckle noise. Localization accuracy is of the order of hundreds of micrometers and is comparable to the ultrasound system axial resolution.     

Ni based catalysts promoted with cerium used in the steam reforming of toluene for hydrogen production

Ni_xMg_6?xAl_1.8Ce_0.2 (with 0 ≤ x ≤ 6) mixed oxides catalysts were prepared by hydrotalcite route. All the oxides were calcined at 800 °C and characterized by different physico-chemical methods. The catalysts are then reduced before their use in the steam reforming of toluene. The XRD and TG/DTA confirmed the formation of the hydrotalcite structure for the non-calcined samples. The N₂ adsorption/desorption results revealed that all catalysts correspond to mesoporous materials. The study by temperature programmed reduction (H₂-TPR) showed that the reducibility of the catalysts is influenced by the nickel content. The CO₂-TPD results showed that the catalyst with high magnesium content present the highest basicity. The Ni₂Mg₄Al_1.8Ce_0.2 shows the best toluene conversion among all the catalysts and it was then compared to a non-promoted catalyst. The spent catalysts were characterized by TPO, TG/DTA and XRD and they didn't reveal any coke formation.     

Adaptive filtering in subbands using a weighted criterion

Transform-domain adaptive algorithms have been proposed to reduce the eigenvalue spread of the matrix governing their convergence, thus improving the convergence rate. However, a classical problem arises from the conflicting requirements between algorithm improvement requiring rather long transforms and the need to keep the input/output delay as small as possible, thus imposing short transforms. This dilemma has been alleviated by the so-called “short-block transform domain algorithms” but is still apparent. This paper proposes an adaptive algorithm compatible with the use of rectangular orthogonal transforms (e.g., critically subsampled, lossless, perfect reconstruction filter banks), thus allowing better tradeoffs between algorithm improvement, arithmetic complexity, and input/output delay. The method proposed makes a direct connection between the minimization of a specific weighted least squares criterion and the convergence rate of the corresponding stochastic gradient algorithm. This method leads to improvements in the convergence rate compared with both LMS and classical frequency domain algorithms     

Syngas production by the CO2 reforming of CH4 over Ni–Co–Mg–Al catalysts obtained from hydrotalcite precursors

The catalytic performance of the Ni, Co, Mg, and Al mixed-oxide solids, synthesized via hydrotalcite route, was investigated towards the dry reforming of methane for hydrogen production. The hydrotalcite structure was successfully obtained upon the synthesis. After calcination at 800 °C under an air flow, this structure was completely decomposed and the resulting oxides (Co_xNi_yMg_zAl₂800, x and y = 0; 1; 2; 3; 4, z = 2; 4, x + y + z = 6, x, y, and z are the molar ratios) were used as catalysts and were characterized using X-ray diffraction and Temperature-Programmed Reduction. The dry reforming of methane was carried out using a mixture of CH₄:CO₂ (1:1) after 2 h of reduction under an H₂ flow at 800 °C. Co₂Ni₂Mg₂Al₂800 showed the highest catalytic activity in the studied series, ascribable to an interaction between Ni and Co, which is optimal for such Co/Ni ratio. The post-reaction characterization of the catalytic samples by X-ray diffraction and Differential Scanning Calorimetry evidenced a better resistance towards carbon deposition for the catalysts where Co molar ratio is higher than Ni.     

Influence of chronic administration of L-DOPA on event-related desynchronization of mu rhythm preceding voluntary movement in Parkinson''s disease

Casein zymographic assays were performed to identify changes in mu-calpain and m-calpain activity in naive, sham-injured, and injured rat cortex at 15 minutes, 3 hours, 6 hours, and 24 hours after unilateral cortical impact brain injury. Cortical samples ipsilateral and contralateral to the site of injury were separated into cytosolic and total membrane fractions. Marked increases in mu-calpain activity in cytosolic fractions in the ipsilateral cortex occurred as early as 15 minutes, became maximal at 6 hours, and decreased at 24 hours to levels observed at 15 minutes after injury. A similar temporal profile of cytosolic mu-calpain activity in the contralateral cortex was observed, although the increases in the contralateral cortex were substantially lower than those in the ipsilateral cortex. Differences were also noted between cytosolic and total membrane fractions. The detection of a shift in mu-calpain activity to the total membrane fraction first occurred at 3 hours after traumatic brain injury and became maximal at 24 hours after traumatic brain injury. This shift in mu-calpain activity between the two fractions could be due to the redistribution of mu-calpain from the cytosol to the membrane. m-Calpain activity was detected only in cytosolic fractions. m-Calpain activity in cytosolic fractions did not differ significantly between ipsilateral and contralateral cortices, and increased in both cortices from 15 minutes to 6 hours after injury. Relative magnitudes of m-calpain versus mu-calpain activity in cytosolic fractions differed at different time points after injury. These studies suggest that traumatic brain injury can activate both calpain isoforms and that calpain activity is not restricted to sites of focal contusion and cell death at the site of impact injury but may represent a more global response to injury.     

Enzymic browning in apricots (Prunus armeniaca)

Enzymic browning in apricots (Prunus armeniaca L) was found to be catalysed by a catechol oxidase (o-diphenol oxidase) and a laccase (p-diphenol oxidase), both acting on catechin and chlorogenic acid as the natural substrates. The laccase was identified as such by substrate specificity tests and the effects of selective inhibitors. The enzymes were tightly bound to the fruit tissue and were inactivated by holding at 80°C for 10 min. The levels of phenolic compounds in healthy and rotted apricot tissue were compared by paper chromatography; the levels of catechin and chlorogenic acid were reduced in the rotted tissue.     

A genetic algorithm for vehicle routing with backhauling

In this paper, a greedy route construction heuristic for a vehicle routing problem with backhauling is described. This heuristic inserts customers one by one into the routes using a fixed a priori ordering of customers. Then, a genetic algorithm is used to identify an ordering that produces good routes. Numerical comparisons are provided with an exact algorithm and with other heuristic approaches.