IMPULSIVE EXCITATION OF ACOUSTIC VIBRATIONS IN APPLES FOR FIRMNESS DETERMINATION

1990 ◽  
Vol 33 (4) ◽  
pp. 1353-1359 ◽  
Author(s):  
P. Armstrong ◽  
H. R. Zapp ◽  
G. K. Brown
Keyword(s):  
Acoustic Vibrations ◽  
Impulsive Excitation

Magnetic Field Distribution in Aperture of TEM Horn Antenna for Close Proximity RF Immunity Test by Impulsive Excitation Wave

2020 ◽  
Vol 140 (12) ◽  
pp. 601-602
Author(s):  
Gen Kawakami ◽  
Ken Kawamata ◽  
Shinobu Ishigami ◽  
Takeshi Ishida ◽  
Katsushige Harima ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Horn Antenna ◽  
Magnetic Field Distribution ◽  
Excitation Wave ◽  
Impulsive Excitation ◽  
Close Proximity ◽  
Tem Horn

Graphic method for assessing the margins of resistance to acoustic vibrations in the chambers of rocket engines by combustion noise

2020 ◽  
pp. 15-21
Author(s):  
R.A. Tsarapkin ◽  
V.N. Ivanov ◽  
V.I. Biryukov
Keyword(s):  
Rocket Engine ◽  
Spectral Characteristics ◽  
Combustion Process ◽  
Combustion Noise ◽  
Rocket Engines ◽  
Acoustic Vibrations ◽  
Statistical Regression ◽  
Unknown Parameters ◽  
Damping Decrement ◽  
Resonance Frequencies

An experimental method is proposed for estimating the damping decrements of pressure fluctuations in the combustion chambers of forced rocket engines. The method is based on the statistical processing of noise pressure pulsations in the vicinity of natural resonance frequencies for normal modes of acoustic vibrations of the reaction volume and the subsequent prediction of the instability of the combustion process relative to acoustic vibrations. Based on the theory of statistical regression for multidimensional experimental data, the problem of predicting unknown parameters of sample distributions is solved by asymptotic determination of the correlation coefficient of the damping decrement of pressure vibrations through optimal linear predictors and the Kolmogorov distribution. Keywords rocket engine, combustion chamber, acoustic vibrations, combustion noise, spectral characteristics, Kolmogorov criterion, damping decrement. [email protected]

Ultrafast dynamic reflectivity of vanadium pentoxide

2008 ◽  
Vol 23 (2) ◽  
pp. 308-311 ◽  
Author(s):  
Gregory J. Taft ◽  
Matthew T. Newby ◽  
Joel J. Hrebik ◽  
Marshall Onellion ◽  
Thomas F. George ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Vanadium Pentoxide ◽  
Linear Polarization ◽  
Laser Pulses ◽  
Acoustic Vibrations ◽  
Frequency Oscillation ◽  
Ultrafast Dynamic ◽  
Transverse Acoustic ◽  
Wave Numbers ◽  
Lower Frequency Oscillation

The ultrafast dynamic reflectivity of vanadium pentoxide is measured using 40 fs pulses from a self-mode-locked Ti:sapphire laser. The laser pulses excite acoustic vibrations at wave numbers of 145 and 103 cm−1. The amplitudes of the induced oscillations depend strongly on the orientation between the linear polarization of the laser pulses and the crystal axes, with the largest oscillations observed for an orientation of 45°. The higher-frequency oscillation is induced immediately upon arrival of the laser pulse, while the lower-frequency oscillation appears a few picoseconds later. The oscillations persist for approximately 10 ps after the arrival of the pulse. The oscillations are attributed to transverse acoustic modes propagating along the a-axis of the crystal.

Investigation of the Influence of Ultrasound Action on Diffusion Processes in an Explosion-Welded Bimetal System Cu-Al during Heat Treatment

2021 ◽  
Vol 410 ◽  
pp. 306-312
Author(s):  
Oleg V. Slautin ◽  
Dmitriy V. Pronichev ◽  
Evgeniy V. Kuz’min
Keyword(s):  
Heat Treatment ◽  
Composite Material ◽  
Diffusion Zone ◽  
Diffusion Processes ◽  
Intermetallic Phases ◽  
Layered Composite ◽  
Acoustic Vibrations ◽  
Fixed Temperature ◽  
Eutectic Transformation ◽  
Ultrasound Action

The influence of ultrasound on the main regularities of the formation and growth of the diffusion zone at the interlayer boundary of an explosion-welded layered composite material of Al-Cu systems is investigated. It is proved that the effect of ultrasound contributes to the reduction of the latent period of the nucleation of intermetallic phases at the interlayer boundary, lowers the temperature of the beginning of the eutectic transformation (by about 10 ° C), but at the same time does not affect the phase composition of the diffusion zone as a result of homogeneous reactions at the boundary of contact of solids. It has been established that the thickness of the diffusion zone, with the duration of the supplied acoustic vibrations, ensures the absence of cracks in the diffusion zone, leading to delamination of the material, increases by 30-40% at a fixed temperature of intense diffusion.

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