Modal structure of the Čerenkov second‐harmonic wave in optical fibers

1990 ◽  
Vol 67 (5) ◽  
pp. 2672-2674 ◽  
Author(s):  
K. Hayata ◽  
T. Sugawara ◽  
M. Koshiba
Keyword(s):  
Optical Fibers ◽  
Second Harmonic ◽  
Harmonic Wave ◽  
Modal Structure

scholarly journals Fatigue crack detection in pipes with multiple mode nonlinear guided waves

2018 ◽  
Vol 18 (1) ◽  
pp. 180-192 ◽  
Author(s):  
Ruiqi Guan ◽  
Ye Lu ◽  
Kai Wang ◽  
Zhongqing Su
Keyword(s):  
Fatigue Crack ◽  
Crack Detection ◽  
Guided Waves ◽  
Second Harmonic ◽  
Experimental Testing ◽  
Harmonic Wave ◽  
Guided Wave ◽  
Element Analysis ◽  
Fatigue Crack Detection ◽  
Wave Modes

This study elaborates fundamental differences in fatigue crack detection using nonlinear guided waves between plate and pipe structures and provides an effective approach for analysing nonlinearity in pipe structures. For this purpose, guided wave propagation and interaction with microcrack in a pipe structure, which introduced a contact acoustic nonlinearity, was analysed through a finite element analysis in which the material nonlinearity was also included. To validate the simulation results, experimental testing was performed using piezoelectric transducers to generate guided waves in a specimen with a fatigue crack. Both methods revealed that the second harmonic wave generated by the breathing behaviour of the microcrack in a pipe had multiple wave modes, unlike the plate scenario using nonlinear guided waves. Therefore, a proper index which considered all the generated wave modes due to the microcrack was developed to quantify the nonlinearity, facilitating the identification of microscale damage and further assessment of the severity of the damage in pipe structures.

Internal Resonating of Second-Harmonic Wave by Scanning Fundamental Cavity Length

1995 ◽  
Vol 34 (Part 2, No. 3B) ◽  
pp. L361-L364
Author(s):  
Wang-Long Zhou ◽  
Yusuke Mori ◽  
Takamoto Sasaki ◽  
Sadao Nakai
Keyword(s):  
Cavity Length ◽  
Second Harmonic ◽  
Harmonic Wave

Seeded second-harmonic generation in optical fibers: the effect of phase fluctuations

1991 ◽  
Vol 16 (4) ◽  
pp. 211 ◽  
Author(s):  
D. M. Krol ◽  
R. H. Stolen ◽  
H. W. K. Tom ◽  
M. M. Broer ◽  
K. T. Nelson ◽  
...  
Keyword(s):  
Second Harmonic Generation ◽  
Optical Fibers ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Phase Fluctuations

scholarly journals Wave Characteristics in Breaststroke Technique with and Without Snorkel Use

2013 ◽  
Vol 39 (1) ◽  
pp. 185-194 ◽  
Author(s):  
Ana Conceição ◽  
António J. Silva ◽  
José Boaventura ◽  
Daniel A. Marinho ◽  
Hugo Louro
Keyword(s):  
Normal Condition ◽  
Mass Velocity ◽  
Second Harmonic ◽  
Harmonic Wave ◽  
The Body ◽  
Swimming Velocity ◽  
Stroke Index ◽  
Stroke Length ◽  
Wave Characteristics ◽  
Second Wave

Abstract The purpose of this paper was to examine the characteristics of waves generated when swimming with and without the use of Aquatrainer® snorkels. Eight male swimmers performed two maximal bouts of 25 m breaststroke, first without the use of a snorkel (normal condition) and then using a snorkel (snorkel condition). The body landmarks, centre of the mass velocity, stroke rate, stroke length, stroke index, and Strouhal number (St) were quantified. Fourier analysis was conducted to determine the frequency, amplitude, and phase characteristics of the vertical undulations. We also determined the undulation period, the first and second harmonic wave percentage, and the contribution of these components to the power of each of the wave signals. The first wave harmonics had a frequency of 0.76 Hz (normal condition) and 0.78 Hz (snorkel condition), and the second wave harmonics had a frequency of 1.52 Hz (normal condition) and 1.56 Hz (snorkel condition). Under the normal conditions, the wave amplitude was higher on the vertex (0.72 m) and cervical (0.32 m) than that produced under snorkel conditions (0.71 m and 0.28 m, respectively). The lowest values were found in the hip (0.03 m in normal conditions, and 0.02 m in snorkel conditions) and in the trunk (0.06 m in normal conditions, and 0.04 m in snorkel conditions). It can be concluded that snorkel use seems to lead to slight changes in the biomechanical pattern in swimming velocity, as well as several stroke mechanical variables.

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