Search results for "Speed of sound"
showing 10 items of 34 documents
Experimental investigation of the effect of moisture on the acoustic properties of lightweight substrates used in green envelopes
2021
International audience; Substrates are used in green walls and roofs to supply air and water to the roots of the growing plants. These substrates are porous with micropores which store water and macropores which facilitate drainage and air entry. Effect of moisture on acoustic absorption is studied for two lightweight substrates: coir dust and perlite. Measurement of dry and moistened substrates are conducted to evaluate their effective speed of sound, attenuation, characteristic impedance, compressibility and density between 100 Hz and 1000 Hz using an impedance tube and the three microphone-two load method. Effect of moisture on these quantities is found to depend strongly upon the intera…
Speed of sound measurements in mandibular and phalangeal bone during growth
2001
The micromechanical and elastic properties of bone, its structural maturity and, indirectly, mineral density are important factors for the planning and assessment of orthodontic and/or jaw orthopaedic treatment. This clinical study was undertaken to evaluate age-related changes in the anterior mandibular body. The speed of sound (SOS) has demonstrated age dependency in various peripheral bones and has been proposed as an alternative method for investigating bone parameters without the use of radiation. The ultrasound transmission velocity was measured in 184 healthy subjects (93 females, 91 males; mean age 17.6 +/- 13.7 years). According to the statistical analysis, the data did not reveal …
Density, Viscosity, and Sound Speed of Bis(trifluoromethylsulfonyl)imide-Based Ionic Liquids + 1-Propanol Mixtures
2015
The density, viscosity, and speed of sound of three mixtures formed by 1-propanol and an ionic liquid were measured in a temperature range of 278.15–338.15 K. All measurements were made at atmospheric pressure and covered the entire range of miscible compositions. The three ionic liquids have the same anion but differ in the cation: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim][NTf2], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][NTf2], and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [hmim][NTf2]. The experimental data allowed calculate the molar volume and isentropic compressibility of the mixture and their respective exces…
Molecular Dynamics Study of Copper and Aluminum under Mechanical Strain
1998
AbstractMechanical properties of copper and aluminum have been studied using finite temperature molecular dynamics simulations. Atomic interactions have been described by a many-atom effective medium potential, which takes into account interactions up to third neighbors. The computed elastic constants showed good agreement with experimental data. Encouraged by these results the model was applied to study fracture in copper. Systems with a grain boundary and an initial cut serving as a crack seed have been studied. In the first case, crack nucleation and propagation took place exclusively at the grain boundary. In the second case, dislocation propagation was observed in one of the <110>…
Molecular-dynamics study of copper with defects under strain
1998
Mechanical properties of copper with various types of defects have been studied with the molecular-dynamics method and the effective-medium theory potential both at room temperature and near zero temperature. The loading has been introduced as constant rate straining and the dynamics of the process region of fracture is purely Newtonian. With the model three types of defects were studied: point defects, grain boundary, and an initial void serving as a crack seed. Point defects were seen to decrease the system strength in terms of fracture stress, fracture strain, and elastic modulus. Due to random microstructure, highly disordered systems turned out to be isotropic, which on the other hand …
Free-surface flows solved by means of SPH schemes with numerical diffusive terms
2010
A novel system of equations has been defined which contains diffusive terms in both the continuity and energy equations and, at the leading order, coincides with a standard weakly-compressible SPH scheme with artificial viscosity. A proper state equation is used to associate the internal energy variation to the pressure field and to increase the speed of sound when strong deformations/compressions of the fluid occur. The increase of the sound speed is associated to the shortening of the time integration step and, therefore, allows a larger accuracy during both breaking and impact events. Moreover, the diffusive terms allows reducing the high frequency numerical acoustic noise and smoothing …
Ultrasonic and Volumetric Properties of 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate Ionic Liquid with 2-Propanol or Tetrahydrofuran at Seve…
2011
Densities and speeds of sound of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate mixtures with 2-propanol and tetrahydrofuran (THF), as well as of the pure components, have been measured over the whole range of compositions at T = (278.15 to 328.15) K and P = (101 ± 2) kPa. From these experimental data, the excess molar volume, excess speed of sound, and excess isentropic compressibility have been calculated and fitted to an extended version of the Redlich–Kister equation, which takes into account the dependence on composition and temperature simultaneously. The Prigogine–Flory–Patterson theory has also been used to explain the behavior of these systems.
Exact spherically-symmetric inhomogeneous model withnperfect fluids
2011
We present the exact equations governing the dynamics of a spherically-symmetric inhomogeneous model with n decoupled and non-comoving perfect fluids. Thanks to the use of physically meaningful quantities we write the set of 3+2n equations in a concise and transparent way. The n perfect fluids can have general equations of state, thus making the model extremely flexible to study a large variety of cosmological and astrophysical problems. As applications we consider a model sourced by two non-comoving dust components and a cosmological constant, and a model featuring dust and a dark energy component with negligible speed of sound.
Maximizing phonon thermal conductance for ballistic membranes
2007
At low temperatures, phonon scattering can become so weak that phonon transport becomes ballistic. We calculate the ballistic phonon conductance G for membranes using elasticity theory, considering the transition from three to two dimensions. We discuss the temperature and thickness dependence and especially concentrate on the issue of material parameters. For all membrane thicknesses, the best conductors have, counter-intuitively, the lowest speed of sound.
Volumetric and Ultrasonic Studies of 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate Ionic Liquid with Methanol, Ethanol, 1-Propanol, and Water…
2007
The speed of sound and density of mixtures of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim][triflate]) with methanol, ethanol, 1-propanol, and water, as well as of the pure components have been experimentally measured over the whole range of compositions at T = (278.15 to 338.15) K and atmospheric pressure. From these experimental data, the excess molar volume, excess isentropic compressibility, and excess speed of sound have been calculated and fitted to an extended version of the Redlich−Kister equation, which takes into account the dependence on composition and temperature simultaneously. The Prigogine−Flory−Patterson theory has also been used to explain the behavior of t…