Affected depth and effective reactivity in porous thermal protection materials for atmospheric re-entry

International audienceAffected depth and effective reactivity in porous thermal protection materials for atmospheric re-entr

Comparing comprehension of a long text read in print book and on Kindle: Where in the text and when in the story?

Digital reading devices such as Kindle differ from paper books with respect to the kinesthetic and tactile feedback provided to the reader, but the role of these features in reading is rarely studied empirically. This experiment compares reading of a long text on Kindle DX and in print. Fifty participants (24 years old) read a 28 page (∼1 h reading time) long mystery story on Kindle or in a print pocket book and completed several tests measuring various levels of reading comprehension: engagement, recall, capacities to locate events in the text and reconstructing the plot of the story. Results showed that on most tests subjects performed identically whatever the reading medium. However, on measures related to chronology and temporality, those who had read in the print pocket book, performed better than those who had read on a Kindle. It is concluded that, basically comprehension was similar with both media, but, because kinesthetic feedback is less informative with a Kindle, readers were not as efficient to locate events in the space of the text and hence in the temporality of the story. We suggest that, to get a correct spatial representation of the text and consequently a coherent temporal organization of the story, readers would be reliant on the sensorimotor cues which are afforded by the manipulation of the book.publishedVersio

Comparaison entre les déformations représentatives de l'indentation Vickers et de l'indentation sphérique Comparison between representative deformations in Vickers indentation and spherical indentation

National audienceThe application of the concept of the representative strain is often used in the stress-strain curve determination from indentation test. A new methodology for determining the representative strain for spherical and for Vickers indentation is presented in this article. The results obtained from this methodology show that there is no universal value of representative strain independent of the mechanical parameters of materials indented by Vickers indentation and spherical indentation. It is also shown that the representative strain, obtained by Vickers or by spherical indentation, is much lower when it is obtained from the relationship between the applied force and the penetration depth, F-h, rather than from the relationship between the applied force and the contact radius, F-a. By choosing the same representative strain value in spherical indentation and in Vickers indentation, the results show that the same constraint factor is obtained. Hence, it is possible to determine a perfect analogy between the two types of indentation. For Vickers indentation, the values of the calculated representative strains show that simultaneous measurement of relationships F-a and F-h allows to characterize the hardening law with two unknown parameters. In the case of the spherical indentation, the identification of a material hardening law from simultaneous measurements relationships F-a and F-h should lead to a more accurate determination of the stress-strain curve

Identification of the hardening law of materials with spherical indentation using the average representative strain for several penetration depths

International audienceThe identification of plastic properties with spherical indentation has been the subject of many studies in last decades. In the present work, a new method for the determination of the hardening law of materials using the load-displacement curve of a spherical indentation test is proposed. This method is based on the use of an average representative strain. The advantage of the proposed average representative strain is that it is strictly obtained from the material response to the indentation test. By using various values of penetration depth, the proposed method gives the range of strain for which the hardening law is precisely identified and allows determining a confidence domain that takes into account experimental imprecision and material heterogeneity. The influence of penetration depth and the error formula on the identified Hollomon hardening law are discussed in the present study. The present study clarifies many problems that were observed in previous studies such as the uniqueness solution and the sensitivity of the indentation test to the plastic parameters of the Hollomon hardening law

Revue bibliographique sur la caractérisation mécanique des matériaux utilisant la déformation représentative en indentation sphérique Literature review on mechanical characterization of materials using a representative strain in spherical indentation

National audienceThe instrumented indentation provides access to several mechanical properties of materials, leading in particular to the knowledge of their hardening law. In front of the lack of a standard procedure, many techniques have been proposed in recent decades. The present work is a literature review on the methods of mechanical characterization based on the instrumented indentation, and using a representative strain. There are two families of methods. The first, based on the Meyer hardness, includes methods of conducting hardness tests with different loads and determine, from the hardness and measuring the radius of the corresponding imprint, a representative deformation and the corresponding stress leading to the construction of the work hardenning curve "point by point" of the tested material. The second includes the methods giving the 2 plastic parameters of the Hollomon law that minimize the difference between the experimental indentation F(h) curve, and a model based on a representative deformation, linking the measured quantities (F, h) and the parameters of the Hollomon law. Each family of methods has advantages and disadvantages that should be known for choosing the most suitable method to the studied case and thus makes best use of instrumented indentation testing

Influence of sample thickness and experimental device configuration on the spherical indentation of AISI 1100 steel

International audienceMost instrumented indentation theoretical studies and models consider bulk sample geometry, which implies no influence on the indentation response. In the particular case of thin samples, our previous studies have shown that the thickness has an influence on the experimental device behaviour as well as on the sample and material response. This work is a numerical and experimental illustration of this particularity. Spherical macroindentation tests are performed on AISI 1100 steel samples of thicknesses varying from 10 to 0.55 mm. Experimental and numerical results are compared. Experimental limitations are investigated and solutions to obtain results which are independent of the sample thickness and curvature are proposed. We show that the proposed solution, which is the object of an international patent, leads to a reliable identification of the material mechanical properties of thin and moderately bent samples

Correlation between homogeneous propane pyrolysis and pyrocarbon deposition

International audiencePyrocarbon deposition through propane pyrolysis is studied in a 1-D hot-wall CVD furnace. The gas-phase pyrolysis is modelled with a partially reduced kinetic mechanism leading to polycyclic aromatic compounds (PAHs). The C2-C4 and C3 reaction paths are in competition for benzene formation. There is also an independent C3-C5 path leading to naphthalene. The gas-phase concentrations are correlated with experimental data including in-situ FTIR spectra intensities, pyro- carbon deposition rates, and pyrocarbon nanotextures. Rough Laminar pyrocarbon deposition appears to be more related to PAHs than Smooth Laminar pyrocarbon

Experimentation of ‘Link for Health’, a new Telehealth application in Cochin Hospital, France

Orange and Cochin Hospital have experimented ‘Link for Health’, a new Telehealth application in the Department of Oncology of Cochin Hospital, France.This new application allows a complete Telehealth service combining mobile application, sensors and questionnaires to return by internet to healthcare team.The purpose of this paper is to analyse and experiment the effectiveness of the Telehealth service, in oral and intravenous anti-cancer therapy to improve clinical and process outcomes.Results were analysed in terms of benefits for the patients and the hospital team

Kinetic modeling of gas-phase decomposition of propane : correlation with pyrocarbon deposition

International audienceA chemical kinetic model for gas-phase pyrolysis of propane has been set up, partially reduced, and validated against FTIR measurements in a tubular hot-wall reactor at P = 2 kPa, and T = 900 to 1400 K. It confirms the notion of "maturation" from propane to lighter hydrocarbons, the to aromatic compounds and PAHs. The gas-phase composition above the substrate has been correlated to pyrocarbon deposition rates and to the deposit nanostructure. It is confirmed that the growth of the rough laminar (RL) form would be related to heavier gaseous species than for the smooth laminar (SL) form

Comparing Optical-Flow Based Methods for Quantification of Myocardial Deformations on RT3D Ultrasound

This paper presents a new homogeneity measure for variational segmentation with multiple level set functions. We propose to modify the quadratic homogeneity measure to trade off the convexity of the function against a faster rate of convergence. We tested in two series of experiments the performance of this new homogeneity force at converging to appropriate partitioning of brain MRI data sets, over a large range of image spatial resolution and image quality, in terms of tissue homogeneity and contrast