Electronics Cooling Fan Noise Prediction

Using the finite volume CFD software FLUENT, one fan was studied at a given flow rate (1.5m3/min) for three different operational rotating speeds : 2,000, 2,350 and 2,700 rpm. The turbulent air flow analysis predicts the acoustic behavior of the fan. The best fan operating window, i.e. the one giving the best ratio between noise emissions and cooling performance, can then be determined. The broadband noise acoustic model is used. As the computation is steady state, a simple Multiple Reference Frame model (MRF, also known as stationary rotor approach) is used to represent the fan. This approach is able to capture the effects of the flow non-uniformity at the fan inlet together with their impact on the fan performance. Furthermore, it is not requiring a fan curve as an input to the model. When compared to the available catalog data the simulation results show promising qualitative agreement that may be used for fan design and selection purposes.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Criteria for and extrapolation in overstress models

Accelerated life test models, criteria for model selection, and extrapolation in overstress model

Nearly Antiferromagnetic Fermi Liquids: A Progress Report

I describe recent theoretical and experimental progress in understanding the physical properties of the two dimensional nearly antiferromagnetic Fermi liquids (NAFL's) found in the normal state of the cuprate superconductors. In such NAFL's, the magnetic interaction between planar quasiparticles is strong and peaked at or near the commensurate wave vector, $Q \equiv (\pi,\pi)$. For the optimally doped and underdoped systems, the resulting strong antiferromagnetic correlations produce three distinct magnetic phases in the normal state: mean field above $T_{cr}$, pseudoscaling between $T_{cr}$ and $T_*$, and pseudogap below $T_*$. I present arguments which suggest that the physical origin of the pseudogap found in the quasiparticle spectrum below $T_{cr}$ is the formation of a precursor to a spin-density-wave-state, describe the calculations based on this scenario of the dynamical spin susceptibility, Fermi surface evolution, transport, and Hall effect, and summarize the experimental evidence in its support.Comment: LATEX + PS figures. To appear in the proceedings of the Euroconference on "Correlations in Unconventional Quantum Liquids," Evora, Portugal, October 199

Thermal stability of titanium hydride thin films

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Local hydrogen environments in Gd 1− x Fe x thin films amorphous alloys from effusion experiments

International audienceThin films of hydrogenated Gd,-XFeX (0.25 =%< 0.90) amorphous-alloys were prepared by reactive evaporation. Effusion experiments, showing several hydrogen release peaks, allowed us to describe the site distribution of hydrogen in these alloys. The different local environments correspond to tetrahedral sites and the stability of these sites increases with the number of rare-earth neighbors

Gravitational wave forms for a three-body system in Lagrange's orbit: parameter determinations and a binary source test

Continuing work initiated in an earlier publication [Torigoe et al. Phys. Rev. Lett. {\bf 102}, 251101 (2009)], gravitational wave forms for a three-body system in Lagrange's orbit are considered especially in an analytic method. First, we derive an expression of the three-body wave forms at the mass quadrupole, octupole and current quadrupole orders. By using the expressions, we solve a gravitational-wave {\it inverse} problem of determining the source parameters to this particular configuration (three masses, a distance of the source to an observer, and the orbital inclination angle to the line of sight) through observations of the gravitational wave forms alone. For this purpose, the chirp mass to a three-body system in the particular configuration is expressed in terms of only the mass ratios by deleting initial angle positions. We discuss also whether and how a binary source can be distinguished from a three-body system in Lagrange's orbit or others.Comment: 21 pages, 3 figures, 1 table; text improved, typos corrected; accepted for publication in PR

Improvement of the stability under illumination of a-Si:H films elaborated by ion-beam-assisted evaporation using a hydrogen–argon plasma

International audienceHydrogenated amorphous silicon films were deposited by ion-beam-assisted evaporation using a hydrogen-argon plasma. The influence of the substrate temperature was studied. Light induced photoconductivity decay measurements showed that high stability materials can be obtained under well defined conditions. By combined infrared spectrometry and thermal desorption spectrometry experiments, it was demonstrated that microstructure has a great influence on the stability against light induced defects

Densification of amorphous silicon prepared by hydrogen‐ion‐beam‐assisted evaporation

International audienceHydrogenated amorphous silicon films were deposited by ion-beam-assisted evaporation onto substrates maintained at 120 °C. The influence of the substrate bias was studied. By combined infrared spectrometry and thermal desorption spectrometry experiments, it is inferred that the bombardment of the growing a-Si:H film by energetic hydrogen ions produces a densification of the material without modification of the Si:H bonding

Growth and characterization studies of Fe 4 N thin films prepared by ion beam assisted evaporation

International audienceThin films of iron nitrides have been prepared using an ion beam assisted evaporation method. X-ray diffraction and Mössbauer spectrometry show that the films generally consist in a mixture of Fe and Fe 4 N phases. For high source powers and temperatures higher than 300 °C it was possible to obtain the pure Fe 4 N phase

Intense visible photoluminescence in amorphous SiOx and SiOx:H films prepared by evaporation

International audienceVisible photoluminescence PL can be observed in a-SiO x and a-SiO x :H alloys prepared by evaporation of SiO in ultrahigh vacuum and under a flow of hydrogen ions, respectively. The hydrogen and oxygen bonding is studied by infrared spectrometry. The hydrogen stability is followed by thermal desorption spectrometry experiments. The evolution of the PL with annealing treatments shows that the PL can be attributed to a quantum confinement effect in a-Si clusters embedded in the matrix of a-SiO x. Hydrogen does not greatly contribute to the PL efficiency and to the thermal evolution of the a-Si clusters