924 research outputs found
Effect of layer thickness on thermal properties of multilayer thin films produced by PVD
Cr/CrN/CrAlN, CrN/CrAlN and Cr/CrN thin layers were deposited by PVD (Physical Vapor Deposition). The multilayers were obtained from the combined deposition of different layers Cr, CrN and CrAlN thick films on on AISI4140 steel and silicon substrates at 200 °C, and evaluated with respect to fundamental properties such as structure and thermal properties. Cr, CrN and CrAlN single layers were also prepared for comparison purposes. The structural and morphological properties of PVD layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS + WDS microanalyses, stresses were determined by the Newton’s rings methods using the Stoney’s equation and surface hardening and hardness profiles were evaluated by micro hardness measurements. The XRD data and HRTEM showed that both the Cr/CrN, CrN/CrAlN and Cr/CrN/CrAlN multilayer coatings exhibited B1NaCl structure with a prominent reflection along (200) plane, and CrAlN sub-layer microstructures composed of nanocrystallites uniformly embedded in an amorphous matrix. The innovation of this work was to use the thickness of three different coating types to determine the thermal properties. Furthermore, an empirical equation was developed for the thermal properties variations with temperature of AISI4140 steel coated with different multilayer coatings. The thermal conductivity of CrAlN single layered was lower than the multilayer and the bulk material AISI4140. Moreover, the influences of structure and composition of the multilayer coatings on the thermal properties are discussed. The thermal conductivity of nanoscale thin film is remarkably lower than that of bulk materials because of its various size effects.The authors wish to thank the Regional Council of Burgundy and EGIDE for their financial support, and also the technical staff of the Arts et Métiers ParisTech of Cluny: especially Romaric Masset and Pierre-Michel Barbier for the samples preparation
AN ANALYSIS OF IODINE DEFICIENCY DISORDER AND ERADICATION STRATEGIES IN THE HIGH ATLAS MOUNTAINS OF MOROCCO
Food Consumption/Nutrition/Food Safety, Health Economics and Policy,
Homogenization of the one-dimensional wave equation
We present a method for two-scale model derivation of the periodic
homogenization of the one-dimensional wave equation in a bounded domain. It
allows for analyzing the oscillations occurring on both microscopic and
macroscopic scales. The novelty reported here is on the asymptotic behavior of
high frequency waves and especially on the boundary conditions of the
homogenized equation. Numerical simulations are reported
Photothermal heterodyne imaging of individual nonfluorescent nanoclusters and nanocrystals
We introduce a new, highly sensitive, and simple heterodyne optical method
for imaging individual nonfluorescent nanoclusters and nanocrystals. A 2 order
of magnitude improvement of the signal is achieved compared to previous
methods. This allows for the unprecedented detection of individual small
absorptive objects such as metallic clusters (of 67 atoms) or nonluminescent
semiconductor nanocrystals. The measured signals are in agreement with a
calculation based on the scattering field theory from a photothermal-induced
modulated index of refraction profile around the nanoparticle
Optimal Multi-Modes Switching Problem in Infinite Horizon
This paper studies the problem of the deterministic version of the
Verification Theorem for the optimal m-states switching in infinite horizon
under Markovian framework with arbitrary switching cost functions. The problem
is formulated as an extended impulse control problem and solved by means of
probabilistic tools such as the Snell envelop of processes and reflected
backward stochastic differential equations. A viscosity solutions approach is
employed to carry out a finne analysis on the associated system of m
variational inequalities with inter-connected obstacles. We show that the
vector of value functions of the optimal problem is the unique viscosity
solution to the system. This problem is in relation with the valuation of firms
in a financial market
Effect of layer thickness on thermal properties of multilayer thin films produced by PVD
Cr/CrN/CrAlN, CrN/CrAlN and Cr/CrN thin layers were deposited by PVD (Physical Vapor Deposition). The multilayers were obtained from the combined deposition of different layers Cr, CrN and CrAlN thick films on on AISI4140 steel and silicon substrates at 200 °C, and evaluated with respect to fundamental properties such as structure and thermal properties. Cr, CrN and CrAlN single layers were also prepared for comparison purposes. The structural and morphological properties of PVD layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS + WDS microanalyses, stresses were determined by the Newton’s rings methods using the Stoney’s equation and surface hardening and hardness profiles were evaluated by micro hardness measurements. The XRD data and HRTEM showed that both the Cr/CrN, CrN/CrAlN and Cr/CrN/CrAlN multilayer coatings exhibited B1NaCl structure with a prominent reflection along (200) plane, and CrAlN sub-layer microstructures composed of nanocrystallites uniformly embedded in an amorphous matrix. The innovation of this work was to use the thickness of three different coating types to determine the thermal properties. Furthermore, an empirical equation was developed for the thermal properties variations with temperature of AISI4140 steel coated with different multilayer coatings. The thermal conductivity of CrAlN single layered was lower than the multilayer and the bulk material AISI4140. Moreover, the influences of structure and composition of the multilayer coatings on the thermal properties are discussed. The thermal conductivity of nanoscale thin film is remarkably lower than that of bulk materials because of its various size effects.The authors wish to thank the Regional Council of Burgundy and EGIDE for their financial support, and also the technical staff of the Arts et Métiers ParisTech of Cluny: especially Romaric Masset and Pierre-Michel Barbier for the samples preparation
Tribological and electrochemical performances of Cr/CrN and Cr/CrN/CrAlN multilayer coatings deposited by RF magnetron sputtering
CrN/CrAlN and Cr/CrN/CrAlN multilayers were grown with dual RF magnetron sputtering. The application of these multilayers will be wood machining of green wood. That is why ball-on-disc and electrochemical tests in NaCl aqueous solution were realized to elucidate the tribological and corrosion behavior of these coatings as they will be exposed to wear and corrosion during wood machining process. The samples/alumina and samples/WC coupling showed different wear mechanisms. The 300 nm thick Cr/CrN/CrAlN multilayer demonstrated the best tribological behavior and corrosion resistance. The influence of growth defects on corrosion resistance has been shown
Gestion péri opératoire d’un paragangliome rétro-péritonéal
Nous rapportons l'observation d'un patient âgé de 62 ans qui présente des douleurs abdominales avec une masse du flanc droit. Les explorations morphologiques ainsi que les données biologiques ont permis de faire le diagnostic d'un paragangliome secrétant. Les particularités diagnostiques ainsi que la gestion périopératoire sont envisagées
Early-career paleoscientists meet in the mountains of Aragon
Three days prior to the 5th PAGES Open Science Meeting (OSM), 80 ambitious early-career scientists (PhD students and postdoctoral researchers) met in the restored village of Morillo de Tou, Spain. The remote setting in the Pyrenees, the old style buildings constructed of turbidites, and the clear and sunny weather made this place an inspiring location to discuss past climate, environment and human interactions. Despite some grumblings about cold coffee served in small cups, the conference was a high-energy affair that promoted connections
Diammonium trisÂ[hexaÂaquaÂmagnesium(II)] tetraÂkisÂ[hydrogenphosphate(III)], (NH4)2[Mg(H2O)6]3(HPO3)4
The framework of the title compound is made up of discrete Mg(H2O)6 octa¬hedra, and HPO3 and NH4 tetra¬hedra, which are organized in planes parallel to (010). Strong hydrogen bonding between the building units stabilizes the structure. The hydrogenphosphate(III) tetra¬hedra, the ammonium tetra¬hedron and one of the two Mg atoms lie on positions with m symmetry, whereas the second Mg atom is located on a position with 2/m symmetry
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