陆上地震技术新进展

先进的地震采集和处理技术已经应用于陆上。一种高保真度、高分辨率集成式单传感器系统目前已在陆上使用。该技术的出现标志着在勘探、开发和生产应用方面取得了重大进展。     

Electrical behaviour of fractal nanosized tin dioxide films prepared by electrodeposition for gas sensing applications

An original electrochemical process to prepare SnO₂ gas sensors is detailed and correlated to electrical behaviour under gas environment. In particular conditions, Tin material was electrodeposited on insulating substrate to form a thin film principally composed of a single layer of individual nanoaggregates (5-10 nm in size). After tin electrodeposition, these supported aggregates were oxidised at air or pressurized oxygen to induce the formation of a fractal SnO₂ film. From these resulting active films, electrical measurements were carried out in ethanol and 300 ppm CO atmospheres. The results show, a sensitivity of 400% at 227 °C in the ethanol case with a response time of 140 s. When the temperature of electrical measurements increases, response and recovery times decrease. However, the sensing amplitude was not modified (Sensitivity around 4) between 250 and 300 °C. In the case of CO, the sensor presented a typical response with a factor of about 2.5 at 250 °C. A fractal dimension between 1.4 and 1.6 is found for fractal-shaped samples allowing an increase of specific surface in contact with gases. However, its does not effect sensitivity, which depends mainly on grain size.     

Geht Ihr Smartphone fremd?

Smartphones haben sich l?ngst als praktische Allesk?nner durchgesetzt und sind aus dem Unternehmensalltag nicht mehr wegzudenken. Genauso unerl?sslich wie das allgegenw?rtige Nutzen ihrer vielf?ltigen Funktionen ist aber auch ihre Absicherung geworden. Der folgende Beitrag stellt die wichtigsten Angriffsvektoren vor, die für eine Unternehmensabsicherung berücksichtigt werden sollten, um die Kontrolle über die genutzten Informationen zu behalten.     

Orthonormal Vector Sets Regularization with PDE's and Applications

We are interested in regularizing fields of orthonormal vector sets, using constraint-preserving anisotropic diffusion PDE's. Each point of such a field is defined by multiple orthogonal and unitary vectors and can indeed represent a lot of interesting orientation features such as direction vectors or orthogonal matrices (among other examples). We first develop a general variational framework that solves this regularization problem, thanks to a constrained minimization of -functionals. This leads to a set of coupled vector-valued PDE's preserving the orthonormal constraints. Then, we focus on particular applications of this general framework, including the restoration of noisy direction fields, noisy chromaticity color images, estimated camera motions and DT-MRI (Diffusion Tensor MRI) datasets.     

Microarchitected Stretching‐Dominated Mechanical Metamaterials with Minimal Surface Topologies

Historically, the creation of lightweight, yet mechanically robust, materials have been the most sought‐after engineering pursuit. For that purpose, research efforts are dedicated to finding pathways to emulate and mimic the resilience offered by natural biological systems (i.e., bone and wood). These natural systems evolved over time to provide the most attainable structural efficiency through their architectural characteristics that can span over multiple length scales. Nature‐inspired man‐made cellular metamaterials have effective properties that depend largely on their topology rather than composition and are hence remarkable candidates for a wide range of application. Despite their geometrical complexity, the fabrication of such metamaterials is made possible by the emergence of advanced fabrication techniques that permit the fabrication of complex architectures down to the nanometer scale. In this work, we report the fabrication and mechanical testing of nature‐inspired, mathematically created, micro‐architected, cellular metamaterials with topologies based on triply periodic minimal surfaces (TPMS) with cubic symmetries fabricated through direct laser writing two‐photon lithography. These TPMS‐based microlattices are sheet/shell‐ and strut‐based metamaterials with high geometrical complexity. Interestingly, results show that TPMS sheet‐based microlattices follow a stretching‐dominated mode of deformation, and further illustrate their mechanical superiority over the traditional and well‐known strut‐based microlattices and microlattice composites. The TPMS sheet‐based polymeric microlattices exhibited mechanical properties superior to other micrloattices comprising metal‐ and ceramic‐coated polymeric substrates and, interestingly, are less affected by the change in density, which opens the door for fabricating ultralightweight materials without much sacrificing mechanical properties.

     

Flood monitoring using microwave passive remote sensing (AMSR-E) in part of the Brahmaputra basin,India

In this work, Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E) signatures were analysed over some critical sites in Lakhimpur District in Brahmaputra basin, India, characterized by a high frequency of flooding events. The site is mostly covered by paddy fields. Results obtained were compared with water level measurements in three stations close to the main channel of the river. Information about surface temperature, which allowed us to estimate the emissivity, was also available. Investigations were carried out at the C, X, and K_a bands of the AMSR-E channel. A multi-frequency analysis indicated that the X band would represent a good compromise between resolution and sensitivity requirements, while at the C band the resolution was too coarse and at the K_a band the signatures were affected by raindrops. Samples collected during rain were eliminated using techniques based on the 89.0 GHz channel. However, even after this correction, the K_a band showed poor sensitivity due to higher attenuation by vegetation. The correlations between different pairs of variables, viz. polarization index (PI), water level (WL), and fractional water surface area (F _WS), were also investigated. At the X band, the water level was better correlated with the PI than with emissivity and other parameters defined in the literature. The correlation was good in cases of slow variation in WL. In cases of sudden variation in the river, the PI followed the variations with some time delay related to the propagation of water within the covered AMSR-E pixel.     

p53-dependent ceramide response to genotoxic stress

Both p53 and ceramide have been implicated in the regulation of growth suppression. p53 has been proposed as the "guardian of the genome" and ceramide has been suggested as a "tumor suppressor lipid. " Both molecules appear to regulate cell cycle arrest, senescence, and apoptosis. In this study, we investigated the relationship between p53 and ceramide. We found that treatment of Molt-4 cells with low concentrations of actinomycin D or gamma-irradiation, which activate p53-dependent apoptosis, induces apoptosis only in cells expressing normal levels of p53. In these cells, p53 activation was followed by a dose- and time-dependent increase in endogenous ceramide levels which was not seen in cells lacking functional p53 and treated similarly. Similar results were seen in irradiated L929 cells whereby the p53-deficient clone was significantly more resistant to irradiation and exhibited no ceramide response. However, in p53-independent systems, such as growth suppression induced by TNF-alpha or serum deprivation, ceramide accumulated irrespective of the upregulation of p53, indicating that p53 regulates ceramide accumulation in only a subset of growth-suppressive pathways. Finally, ceramide did not increase p53 levels when used at growth-suppressive concentrations. Also, when cells lacking functional p53, either due to mutation or the expression of the E6 protein of human papilloma virus, were treated with exogenous ceramide, there was equal growth suppression, cell cycle arrest, and apoptosis as compared with cells expressing normal p53. These results indicate that p53 is unlikely to function "downstream" of ceramide. Instead, they suggest that, in situations where p53 performs a critical regulatory role, such as the response to genotoxic stress, it functions "upstream" of ceramide. These studies begin to define a relationship between these two pathways of growth inhibition.     

A hybrid electronic-density-functional/molecular-dynamics simulation scheme for multiscale simulation of materials on parallel computers: applications to silicon and alumina

In hybrid electronic-density-functional/molecular-dynamics schemes, a total system is partitioned in real space into the quantum-mechanical (QM) region treated by the electronic-density-functional theory and the molecular dynamics (MD) region in which atoms are interacting through the empirical inter-atomic potential. In the former hybrid scheme [Ogata et al. Comput. Phys. Commun. 149 (2002) 30], appropriate selection of QM atoms for seamless coupling between the QM and MD regions is limited in Si systems, and applications of the scheme to other materials are difficult. Novel hybrid scheme that is free from the limitation and applicable to both Si and alumina systems, is presented.     

Speed control of automotive diesel engines

This paper deals with Diesel engine control. More precisely, a model-based approach is considered to stabilise engine speed around a defined value. The model taken into account is nonlinear and contains explicitly the expression of fuel conversion efficiency. In general in the literature, this experimentally obtained quantity is modelled with either a polynomial or an exponential form (see for instance Younes, R. (1993). Elaboration d’un modèle de connaissance du moteur diesel avec turbocompresseur à géométrie variable en vue de l’optimisation de ses émissions. Ecole Centrale de Lyon; Omran, R., Younes, R., Champoussin, J., & Outbib, R. (2011). New indicated mean effective pressure (IMEP) model for predicting crankshaft movement. Energy Conversion and Management, 52, 3376–3382). This paper focuses on engine speed feedback stabilisation when fuel conversion efficiency is modelled with an exponential form, which is more suitable for automative applications. Simulation results are proposed to highlight the closed-loop control performances.