Search results for "Pressure"
showing 10 items of 4493 documents
Optical activation of a silicon vibrating sensor
1986
The operation of a micromachined silicon vibrating sensor with both optical excitation and optical interrogation is reported. The proper locations at which the optical excitation should be applied for optimum excitation of different modes of resonance are described.
Testing the concentric-disk tension infiltrometer for field measurement of soil hydraulic conductivity
2010
Abstract The concentric-disk tension infiltrometer (CDTI) may be used to simultaneously measure the confined ( K c ) and the unconfined ( K u ) soil hydraulic conductivity, but it has received little testing. Comparison between K c and K u can be affected by the calculation approach applied to analyze unconfined steady-state infiltration rates. The objectives of this investigation were to: i) establish the effect of the calculation approach on the estimates of K u ; and ii) compare the K c and K u values measured by the CDTI. A clay soil, a structureless sandy loam soil, and a sandy loam soil with a relatively high gravel content were sampled using a disk of radius equal to 107.5 mm, compri…
Effect of the loading rate on ultimate strength of composites. Application: Pressure vessel slow burst test
2013
International audience; The strength of unidirectional elastic fibre composites is shown to depend on the loading rate as the viscoelastic nature of the matrix results in a fall in breaking load as the rate is reduced. The simulation of the accumulation of fibre breaks leading to failure, takes into account all physical phenomena involved fibre failure, including the stochastic nature of fibre strength, stress transfer through the matrix between reinforcements, interfacial debonding and the viscoelastic nature of the matrix. The kinetics of composite failure are seen to involve the initial formation of random fibre breaks which at higher loads coalesce into clusters of broken fibres. The ra…
Pressure effect investigations on spin-crossover coordination compounds
2018
International audience; The piezochromic properties of spin-crossover complexes have been recognized for a long time, with increasing pressure favouring the low spin state due to its smaller volume and therefore shifting the spin equilibrium towards higher temperatures and accelerating the relaxation at a given temperature. However, the interpretation and quantification of pressure-induced changes have been several times compromised by the relatively poor and incomplete spectral and structural information provided by the detection methods or due to the experimental difficulties related to the need for hydrostatic conditions at low temperatures. The present review is therefore primarily focu…
Anisotropic and non-heterogeneous continuum percolation in titanium oxynitride thin columnar films
2002
International audience; We report the percolation behaviour of the conductivity of titanium oxynitride films grown by low-pressure metal-organic chemical vapour deposition, composed of TiNxOy mixed with TiO2. The usual DC parameters (t, s and Φc), obtained from the effective media theory equations, are compared to the universal values (s = sun while t < tun because of the film anisotropy). This is the first example of an electrical continuum percolation applied to columnar films with chemically similar conducting and insulating units (non-heterogeneous percolation) whose mixing is based upon the growth temperature during the film growth.
Investigation of the hemodynamic flow conditions and blood-induced stresses inside an abdominal aortic aneurysm by means of a SPH numerical model.
2019
The estimation of blood flow-induced loads occurring on the artery wall is affected by uncertainties hidden in the complex interaction of the pulsatile flow, the mechanical parameters of the artery, and the external support conditions. To circumvent these difficulties, a specific tool is developed by combining the aorta displacements measured by an electrocardiogram-gated-computed tomography angiography, with the blood velocity field computed by a smoothed particle hydrodynamics (SPH) numerical model. In the present work, the SPH model has been specifically adapted to the solution of the 3D Navier-Stokes equations inside a domain with boundaries of prescribed motion. Images of the abdominal…
High-pressure melting curves of the transition metals Cu, Ni, Pd, and Pt
2013
Melting curves of Cu, Ni, Pd, and Pt were measured in a laser-heated diamond-anvil cell up to 43, 52, 28, and 28 GPa, respectively. The obtained results are compared with previous studies. In particular, the measurements made in Cu are in agreement with the literature. In Pt the experiments are consistent with $Z$ method calculations indicating that earlier measurements probably underestimate the melting temperature of Pt at high pressure. Cu, Pd, and Pt show a qualitative similar melting behavior. In the case of Ni, experiments confirm that it has a low melting slope of 28 K/GPa. Ni is the only transition metal of groups 10 and 11 of the Periodic Table that shows such a slope since the oth…
Laser Ultrasonic Testing for Estimation of Adhesion of Al2O3Plasma Sprayed Coatings
2001
Abstract The aim of the present study was to investigate the possibility of using a laser ultrasonic technique for the estimation of the adhesion of ceramic coatings, deposited onto metallic substrates by thermal spraying techniques. For this purpose, a pulsed Nd : YAG laser (λ = 1064 nm, 14 ns) was used to irradiate Al2O3 coatings, of different thickness (30–350 µm), deposited onto stainless steel substrates by atmospheric plasma spraying. The laser generated ultrasonic waves were in situ recorded at the epicentre using a laser heterodyne interferometer. The acoustic waveforms were correlated with the interaction between the pulsed laser radiation and the coated metal, taking into account …
Random Copolymers: Their Solution Thermodynamics as Compared with That of the Corresponding Homopolymers
2008
Vapor pressure data (at 50 °C) of solutions of poly(methyl methacrylate) [PMMA], polystyrene [PS], and poly(styrene-ran-methyl methacrylate) [P(S-ran-MMA)], with different weight fractions f of styrene units, in either CHCl3, acetone [AC], methyl acetate [MeAc], or toluene [TL] were evaluated with respect to the dependence of the Flory−Huggins interaction parameter χ on polymer concentration and on f. For all solutions under investigation, χ varies considerably with the composition of the mixture, and only for four of them [CHCl3/PS, AC/PMMA, MeAc/PS, and TL/P(S-ran-MMA) f = 0.5] is this dependence linear; another four systems exhibit a minimum [CHCl3/PMMA, CHCl3/P(S-ran-MMA) f = 0.5, TL/PM…
(Ga,In)P nanowires grown without intentional catalyst
2015
Abstract We have grown (Ga,In)P nanowires through the MOCVD method without a intentional catalyst. The organometallic precursor triethylgallium ( ( C 2 H 5 ) 3 Ga ) , used as Ga source, is transported by the N 2 gas carrier to the reactor chamber where reacts with the InP vapor pressure producing the nanowires. Two different reactor pressures (70 and 740 Torr) were used leading to nanowires with different In contents. The nanowires are straight or wool-like and exhibit a twinned structure. They emit an intense orange to red color visible even to the naked eyes. Interface tunneling process at Ga 1 − x In x P / Ga 1 − y In y P interfaces ( x ≠ y ) is proposed to explain this efficient light e…