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991.
C. B. Winkelmann E. Collin Yu. M. Bunkov H. Godfrin 《Journal of Low Temperature Physics》2004,135(1-2):3-14
We report systematic measurements of the response of a Vibrating Wire Resonator (VWR) in normal and superfluid liquid 3He. Special attention has been paid to the hydrodynamic regime of the superfluid B-phase, where the response parameters of the VWR do not follow a simple law. We show that a simple interpolation between the region where first order slip-corrections can be applied and the ballistic regime is insufficient. Measuring an empirical effective viscosity, we propose a temperature calibration method which allows the use of VWRs as a secondary thermometer at intermediate and high pressures in the temperature range 0.2 T c < T < 50 mK. 相似文献
992.
A. Hernández O. Arés C. Hart D. Domínguez H. Pastoriza A. Butera 《Journal of Low Temperature Physics》2004,135(1-2):119-122
The response of mesoscopic superconductors to an ac magnetic field is investigated both experimentally and with numerical simulations. We study small square samples with dimensions of the order of the penetration depth. We obtain the ac susceptibitity χ=χ′+iχ″ at microwave frequencies as a function of the dc magnetic field H dc. We find that the dissipation, given by x″, has a non monotonous behavior in mesoscopic samples. In the numerical simulations we obtain that the dissipation increases before the penetration of vortices and then it decreases abruptly after vortices have entered, the sample. This is verified experimentally, where we find that χ″ has strong oscillations as a function of H dc in small squares of Pb. 相似文献
993.
Flux pinning characteristics have been investigated for the Nb x Ti100-x /Nb(x = 65, 50 and 28) and Nb 28 Ti 72/Nb 65 Ti 35 superconductor(S)/superconductor(S′) multilayers. The maximum of the pinning force F p⊥ max perpendicular to the layer plane as a function of the structure modulation length λ has a peak in the quasi-two-dimensional region (λ~20 nm). The maximum. values of the F p⊥ max versus λ curve are proportional to the difference of the GL coherence length (ξ GL ) between the superconductive sublayers S and S′. The results suggest that the large F p⊥ max in the S/S′ multilayer is caused by the repulsive pinning force due to Nb layers with larger ξ GL . 相似文献
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997.
Damage detection of CFRP using fiber Bragg gratings 总被引:1,自引:0,他引:1
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Toughness variation of non-notched poly(acrylonitrile-butadiene-styrene) (ABS) subjected to uniaxial fatigue loading was investigated. The experiments were conducted by applying fatigue loading to strip specimens first, from which dog-bone specimens were machined. The dog-bone specimens were tested to measure the strain for the on-set of fracture, named cracking strain here, thus to monitor the toughness change due to the fatigue loading.The test results showed that the fatigue loading caused the toughness drop in ABS, even before any visible crack was developed. Damage development and fracture behavior were then analyzed using scanning electron microscopy (SEM). The SEM analysis revealed that damage zones, not cracks, were initiated during the fatigue loading, and were the main cause of the toughness drop. Mechanisms for the damage initiation include matrix crazing and debonding of small rubber particles; however, large rubber particles remained intact. Based on the results, a deformation model is proposed for the damage zone initiation, which provides an explanation for the toughness change under the fatigue loading. 相似文献