Reconstruction of the rose of directions from a digital microhologram of fibres

Digital holography makes it possible to acquire quickly the interference patterns of objects spread in a volume. The digital processing of the fringes is still too slow to achieve on line analysis of the holograms. We describe a new approach to obtain information on the direction of illuminated objects. The key idea is to avoid reconstruction of the volume followed by classical three-dimensional image processing. The hologram is processed using a global analysis based on autocorrelation. A fundamental property of diffraction patterns leads to an estimate of the mean geometric covariogram of the objects projections. The rose of directions is connected with the mean geometric covariogram through an inverse problem. In the general case, only the two-dimensional rose of the object projections can be reconstructed. The further assumption of unique-size objects gives access with the knowledge of this size to the three-dimensional direction information. An iterative scheme is suggested to reconstruct the three-dimensional rose in this special case. Results are provided on holograms of paper fibres.     

病“机”切勿乱投医——学会判断硬件故障

“电脑出故障了怎么办?”“当然是修啊”,“修!你会么?”“不会,但是我可以找‘电脑医院’啊!”这也许是我们对电脑故障最熟悉的一个解决方式,这样做没有问题,大部分情况都能让你的电脑“活蹦乱跳”地回到你的面前,你只需要付出维修费用即可。但是随着电脑维修的黑幕被揭发得越来越多,你还敢修么?知道什么叫“知己知彼”吗?如果你知道产生故障的可能部件,就不怕JS下“刀”太狠,因此我们有必要了解硬件故障的诊断和测试方法,电脑出了故障不用将整台机器都搬去了(当然最好是不出故障!),以后也许自己都能当上维修高手呢!,电脑的故障可以分为硬…     

Morphological modelling of three‐phase microstructures of anode layers using SEM images

A general method is proposed to model 3D microstructures representative of three‐phases anode layers used in fuel cells. The models are based on SEM images of cells with varying morphologies. The materials are first characterized using three morphological measurements: (cross‐)covariances, granulometry and linear erosion. They are measured on segmented SEM images, for each of the three phases. Second, a generic model for three‐phases materials is proposed. The model is based on two independent underlying random sets which are otherwise arbitrary. The validity of this model is verified using the cross‐covariance functions of the various phases. In a third step, several types of Boolean random sets and plurigaussian models are considered for the unknown underlying random sets. Overall, good agreement is found between the SEM images and three‐phases models based on plurigaussian random sets, for all morphological measurements considered in the present work: covariances, granulometry and linear erosion. The spatial distribution and shapes of the phases produced by the plurigaussian model are visually very close to the real material. Furthermore, the proposed models require no numerical optimization and are straightforward to generate using the covariance functions measured on the SEM images.     

Introduction to assembly features: an illustrated synthesis methodology

The article is an introduction to a new concept of assembly features able to support intelligent design and manufacturing of complex products. An assembly feature is defined as a generic solution referring to two groups of parts that need to be related by a relationship so as to solve a design problem. The concept of assembly feature encompasses the notions of design intent, technical function, technological solution and manufacturing process as well as it provides a justification for the use of part features. After a general introduction and a justification of the interest of assembly features, some guidelines are provided to show how assembly features can be characterized in any domain of application concerned with engineering design of assemblies. As an illustration of the proposed methodology, the concept is finally applied to the engineering phase of aeroplane design.     

INFLUENCE OF FLOW REGIMES ON TEMPERATURE HETEROGENEITIES WITHIN A SCRAPED SURFACE HEAT EXCHANGER

In industrial applications, fluids processed in scraped surface heat exchangers often show large temperature heterogeneities at the exchanger outlet. Our study deals with the thermal evolution of model fluids, Newtonian and non‐Newtonian in heating or cooling conditions and allows us to link the phenomena of appearance and disappearance of temperature heterogeneities with the changes in the flow pattern within the exchanger. Based on literature data dedicated to scraped surface heat exchangers as well as to annular spaces without blades, we have shown that thermally homogeneous products can be obtained when Taylor vortices appear in the exchanger. Studies done on the exchanger with and without blades show that the thermal behavior is basically the same for both geometries but with a difference in critical Taylor numbers value for change in heat transfer regime. The presence of blades promotes the appearance of instabilities at lower values of generalized Taylor number (Ta_g= 10 with blades; Ta_g= 39 without blades). It shows as well, that the value of critical Taylor number in scraped surface heat exchanger closely depends upon the flow‐rate even for very low values for Re_axg (Re_axg < <1).     

纵向通风隧道内火灾烟气流动的控制

讨论了纵向通风隧道火灾和相关烟气形成现象。利用计算机流体动力模型模拟烟气流动，获得可以与试验数据进行比较的预测结果。在Richardson数字基础上，采用了不同参考稳定值，结果发现，直接利用火灾热释放速率所获得的温度值会产生最有用的结果。试验结果与数值预测结果的比较发现，两者吻合较好。笔者验证了利用容积测定火源模拟火灾的情况。结果的准确性很大程度上取决于对墙和屋顶的热传递。     

Investigation des mécanismes de liaison impliqués dans la cohésion des compacts a usage cosmétique

La présence d'un pourcentage élevé de particules lamellaires dans les compacts à usage cosmétique les rend difficiles à compacter. La cohésion des particules de poudre n'est rendue possible que par la présence d'un liant de caractère lipophile. La détermination du bilan énergétique de compression ainsi que des mesures de dureté par indentation et de résistance mécanique des compacts mettent en évidence l'importance des propriétés rhéologiques et aussi du pourcentage auquel il est employé pour l'obtention de caractéristiques mécaniques optimales. Il est montré que les compacts cosmétiques de ce type sont un exemple d'un système de poudre humide compactée, différent en celà de ceux rencontrés dans d'autres branches de l'industrie (pharmacie, metallurgie, céramique…). Enfin, ces résultats permettent de conclure qu'une amélioration significative de la formulation passe par une bonne connaissance des propriétés rhéologiques du liant.     

Study of Composition of Leached Glass Surfaces by Photoelectron Spectroscopy

The effects of water attack on the surfaces of 2 bulk glasses, including changes with time of exposure to air after water exposure, were determined using X-ray photoelectron spectroscopy. Although the layer explored was extremely thin (∼30 Å), this nondestructive technique has potential for quantitative analysis. The results obtained for an industrial glass and an experimental nonresistant one are compared, i.e. the rapidity of ion exchange at the glass-water interface, fluctuation of Na content in the glass surface during water exposure, migration of Na through the SiO₂ surface layer, and nonmigration of Ca under the same conditions. The present results agree with those obtained by other workers from solution analysis and other surface-sensitive physical techniques. The surface of lead crystal glass exposed to dilute acetic acid was also studied.