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101.
Non-Axisymmetric Oscillation of Acoustically Levitated Water Drops at Specific Frequencies 下载免费PDF全文
A category of non-axisymmetric oscillations of acoustically levitated water drops was observed. These oscillations can be qualitatively described by superposing a sectorial oscillating term upon the initial oblate shape resulting from the effect of acoustic radiation pressure. The oscillation frequencies are around 25 Hz for the 2-lobed mode and exactly 50 Hz for the 3- and 4-1obed modes. These oscillations were excited by the disturbance from the power supply. For the same water drop, higher mode oscillations were observed with more oblate initial shape, indicating that the eigenfrequencies of these non-axisymmetric oscillations decrease with increasing initial distortion. The maximum velocity and acceleration within the oscillating drop can attain 0.3 m·s^-1 and 98.7 m·s^-2 respectively, resulting in strong fluid convection and enhanced heat and mass transfer. 相似文献
102.
Bruno Frka-Petesic Jean-François Berret Régine Perzynski Olivier Sandre 《Journal of magnetism and magnetic materials》2009,321(7):667-670
Mixing in aqueous solutions polyelectrolyte-neutral block copolymers with oppositely charged species, spontaneously forms stable core-shell complexes, which are electrostatically driven. We report here on the structural and orientational properties of such mixed magnetic nanoclusters made of magnetic iron oxide nanoparticles (MNPs) and polyelectrolyte-neutral block copolymers. Small angle neutron scattering and transmission electron microscopy experiments allows to probe the inner-core nanoparticle organization, leading to an average interparticle distance and confirming the hierarchical internal structure of the clusters. Thanks to the MNP optical anisotropy, we also probe the under-magnetic field orientational properties of the core-shell clusters and their dynamical rotational relaxation. 相似文献
103.
We consider the feasibility of an experiment to measure the string parameter α′. The proposal relies on the stringy prediction that low-energy electrodynamics is described by a Born–Infeld Lagrangian. 相似文献
105.
Y. Zhang C. K. Kim K. J. B. Lee Y. Park 《The European physical journal. E, Soft matter》2009,29(3):345-349
High auditory sensitivity, sharp frequency selectivity, and spontaneous otoacoustic emissions are signatures of active amplification
of the cochlea. The human ear can also detect very large amplitude sounds without being damaged, as long as the exposed time
is not too long. The outer hair cells are believed to be the best candidate for the active force generator of the mammalian
cochlea. In this paper, we propose a new model for the basilar membrane oscillation which describes both an active and a protective
mechanism by employing an energy depot concept and a critical velocity of the basilar membrane. The compressive response of
the basilar membrane at the characteristic frequency and the dynamic response to the stimulation are consistent with the experimental
results. Although our model displays a Hopf bifurcation, our braking mechanism results in a hyper-compressive response to
intense stimuli which is not generically observed near a Hopf bifurcation. Asymmetry seen in experimental recordings between
the onset and the offset of the basilar membrane response to a sound burst is also observed in this model. 相似文献
106.
F. G. Mitri 《The European physical journal. E, Soft matter》2009,28(4):469-478
The partial wave series for the scattering of a high-order Bessel beam (HOBB) of acoustic quasi-standing waves by an air bubble
and fluid spheres immersed in water and centered on the axis of the beam is applied to the calculation of the acoustic radiation
force. A HOBB refers to a type of beam having an axial amplitude null and an azimuthal phase gradient. Radiation force examples
obtained through numerical evaluation of the radiation force function are computed for an air bubble, a hexane, a red blood
and mercury fluid spheres in water. The examples were selected to illustrate conditions having progressive, standing and quasi-standing
waves with appropriate selection of the waves’ amplitude ratio. An especially noteworthy result is the lack of a specific
vibrational mode contribution to the radiation force determined by appropriate selection of the HOBB parameters. 相似文献
107.
108.
Christophe Lethien Christophe Loyez Jean-Pierre Vilcot Michael Bocquet 《Optics Communications》2009,282(24):4706-4715
A radio over fiber system using the fluorinated based polymer multimode fibers (PMMF) is presented in this paper for the enhancement of the indoor coverage of the multiband orthogonal frequency division multiplexing ultra-wideband standard (MB-OFDM UWB) inside a building. A preliminary part related the cost analysis owing to glass and polymer multimode fiber deployment inside a fiber network is reported. The study of the physical properties of the polymer optical fibers (core diameter, numerical aperture, differential mode delays, modal bandwidth…) is firstly performed in order to effectively exhibit the potentialities and the robustness of such fibers to be used in a low cost radio over fiber system. The DMD measurements of four fluorinated based polymer optical fiber are reported. The designed system operates at 850 nm with commercial off the shelf (COTS) devices combined to the intensity modulation/direct detection technique. The opportunity of using polymer fibers and COTS components to improve the indoor coverage of the MB-OFDM UWB standard is so reported by the measurement of the Error Vector Magnitude or the Relative Constellation Error variation as a function of the system parameters (RF power, optical attenuation, fiber length…) as well as the compliance of the eye diagram with the mask testing. By the way, the transmission performance of both 200 and 480 Mbps signals is demonstrated over up to 200 m link length of polymer multimode fibers: transmission penalties are quantified by relative constellation error with values under the standard requirements. A comparative study with classical OM2 50 μm based glass multimode fiber having the same bandwidth/length product than the PMMF is done. 相似文献
109.
Using ab initio techniques we have calculated the electron energy loss near edge structure (ELNES) of a new high pressure phase of boron (γ‐B28) and the structurally similar allotrope, α‐B12. The total ELNES spectra are presented as weighted sums of the site specific spectra of the constituent non‐equivalent B atoms. The five different non‐equivalent B sites in γ‐B28 all show rich ELNES spectra and their similarities and differences to the simpler α‐B12 case are detailed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
110.
The aim of this study is to compare water vapour sorption isotherms on various mesoporous materials in their pristine state and after silanisation. Commonly the pristine state is regarded as hydrophilic and the silanised one as hydrophobic. Water vapour sorption experiments are discussed for a highly ordered nanoporous aluminium oxide with straight cylindrical channels of ca. 25 nm diameter and for various controlled porous glasses (CPGs) with disordered pores in the range of 13 nm diameter. The water sorption isotherms exhibit in both cases a hysteresis over the entire humidity range. At higher humidities the pristine materials show capillary condensation whereas for the silanised samples this phase transition does not occur or even a loss of water is recorded as for the silanised Al2O3. Surprisingly, for the silanised Al2O higher water uptake is observed in the low humidity region. Application of the excess surface work (ESW) method delivers a reduced structural component in the long range interaction of the water molecules with a hydrophobic surface. Inverse gas chromatography studies of the silanised CPGs result in an increased short range dispersive part of the surface energy with the increasing degree of silanisation. 相似文献