Continuous High Frequency Measurement Improves Understanding of High Frequency Torsional Oscillation in North America Land Drilling

2017 ◽  
Author(s):  
Z. Zhang ◽  
Y. Shen ◽  
W. Chen ◽  
J. Shi ◽  
W. Bonstaff ◽  
...  
Keyword(s):  
North America ◽  
High Frequency ◽  
Torsional Oscillation ◽  
Frequency Measurement

scholarly journals Gaining Insights in Loading Events for Wind Turbine Drivetrain Prognostics

2020 ◽  
Author(s):  
Pieter-Jan Daems ◽  
Y. Guo ◽  
S. Sheng ◽  
C. Peeters ◽  
P. Guillaume ◽  
...  
Keyword(s):  
High Frequency ◽  
Failure Modes ◽  
Measurement Data ◽  
Wind Farms ◽  
Frequency Measurement ◽  
Operating Conditions ◽  
Failure Data ◽  
The World ◽  
Operations And Maintenance ◽  
History Of

Abstract Wind energy is one of the largest sources of renewable energy in the world. To further reduce the operations and maintenance (O&M) costs of wind farms, it is essential to be able to accurately pinpoint the root causes of different failure modes of interest. An example of such a failure mode that is not yet fully understood is white etching cracks (WEC). This can cause the bearing lifetime to be reduced to 5–10% of its design value. Multiple hypotheses are available in literature concerning its cause. To be able to validate or disprove these hypotheses, it is essential to have historic high-frequency measurement data (e.g., load and vibration levels) available. In time, this will allow linking to the history of the turbine operating data with failure data. This paper discusses the dynamic loading on the turbine during certain events (e.g., emergency stops, run-ups, and during normal operating conditions). By combining the number of specific events that each turbine has seen with the severity of each event, it becomes possible to assess which turbines are most likely to show signs of damage.

scholarly journals High-Frequency Measurement of Ultrasound Using Flexural Ultrasonic Transducers

2018 ◽  
Vol 18 (13) ◽  
pp. 5238-5244 ◽  
Author(s):  
Andrew Feeney ◽  
Lei Kang ◽  
Steve Dixon
Keyword(s):  
High Frequency ◽  
Frequency Measurement ◽  
Ultrasonic Transducers

scholarly journals What do we know about Indonesian tropical lakes? Insights from high frequency measurement

2018 ◽  
Vol 118 ◽  
pp. 012024
Author(s):  
Arianto Budi Santoso ◽  
Endra Triwisesa ◽  
Muh. Fakhrudin ◽  
Eko Harsono ◽  
Hadiid Agita Rustini
Keyword(s):  
High Frequency ◽  
Frequency Measurement ◽  
Tropical Lakes

High-frequency measurement techniques for magnetic cores

1990 ◽  
Vol 5 (1) ◽  
pp. 41-53 ◽  
Author(s):  
V.J. Thottuvelil ◽  
T.G. Wilson ◽  
H.A. Owen
Keyword(s):  
High Frequency ◽  
Measurement Techniques ◽  
Frequency Measurement ◽  
Magnetic Cores

High-Frequency Seismic Wave Propagation in Northeastern North America

1990 ◽  
Vol 61 (3-4) ◽  
pp. 193-208 ◽  
Author(s):  
S. E. Hough ◽  
K. H. Jacob ◽  
L. Seeber
Keyword(s):  
North America ◽  
High Frequency ◽  
Characteristic Length ◽  
Body Waves ◽  
Eastern North America ◽  
Western North America ◽  
Energy Propagation ◽  
Length Scales ◽  
Near Surface ◽  
High Frequencies

Abstract A key element in the assessment of seismic hazard is the estimation of how energy propagation from a given earthquake is affected by crustal structure near the receiver and along the more distant propagation path. In this paper, we present data from a variety of sources in eastern North America recorded at epicentral distances of a few to 800 km, and characterize and interpret systematic features. Site effects have been classically considered in terms of amplification either within a sediment-filled valley or from a single topographic feature (Geli et al., 1988). We present evidence of high frequency (5–30 Hz) resonances observed in hard-rock recordings of both body waves and Lg waves, and suggest that site effect should be expanded regionally to include structural and topographic information over sufficiently large areas to include several wavelengths of any features that may interact with seismic waves in the frequency range of interest. A growing body of evidence suggests that ground motions at high frequencies recorded at large epicentral distances in eastern North America are controlled by resonance effects. We hypothesize that a fundamental difference between eastern and western North America spectra stems from a combination of differences in the character of topography and near-surface structure. Active tectonics of western North America gives rise to a complex crust that scatters seismic energy in a random manner and results in very effective attenuation of high frequencies. The older eastern North American crust contains scatterers that are more ordered, with characteristic length scales that give rise to resonance phenomena in the frequency band critical for earthquake hazard. We present preliminary analysis of topographic data from the Adirondack Mountains in New York that demonstrates the existence of characteristic length scales on the order of up to 1–3 kilometers. Features with these length scales will effectively scatter energy at frequencies in the 1 to 10 Hz range.

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