scholarly journals J042043 High amplitude ultrasonic measurement technique using high frequency laminated transducers for crack tip

2012 ◽  
Vol 2012 (0) ◽  
pp. _J042043-1-_J042043-3
Author(s):  
Takumi KAMIMURA ◽  
Tetsuhiro ASAKURA ◽  
Tsuyoshi MTHARA ◽  
Hatsuzo TASHIRO
Keyword(s):  
Measurement Technique ◽  
High Frequency ◽  
Crack Tip ◽  
High Amplitude ◽  
Ultrasonic Measurement

scholarly journals Flame response to high-frequency oscillations in a cryogenic oxygen/hydrogen rocket combustor

2019 ◽  
Author(s):  
N. Fdida ◽  
J. Hardi ◽  
H. Kawashima ◽  
B. Knapp ◽  
M. Oschwald ◽  
...  
Keyword(s):  
High Frequency ◽  
Acoustic Resonance ◽  
High Amplitude ◽  
Operating Conditions ◽  
Test Facility ◽  
Response Analysis ◽  
Rocket Engines ◽  
Acoustic Oscillations ◽  
Spatially Resolved ◽  
Flame Response

Experiments presented in this paper were conducted with the BKH rocket combustor at the European Research and Technology Test Facility P8, located at DLR Lampoldshausen. This combustor is dedicated to study the effects of high magnitude instabilities on oxygen/hydrogen flames, created by forcing high-frequency (HF) acoustic resonance of the combustion chamber. This work addresses the need for highly temporally and spatially resolved visualization data, in operating conditions representative of real rocket engines, to better understand the flame response to high amplitude acoustic oscillations. By combining ONERA and DLR materials and techniques, the optical setup of this experiment has been improved to enhance the existing database with more highly resolved OH* imaging to allow detailed response analysis of the flame. OH* imaging is complemented with simultaneous visible imaging and compared to each other here for their ability to capture flame dynamics.

Vibrational Control of a 2-Link Mechanism

2020 ◽  
Author(s):  
Zakia Ahmed ◽  
Sevak Tahmasian ◽  
Craig A. Woolsey
Keyword(s):  
Translational Control ◽  
High Frequency ◽  
Horizontal Plane ◽  
High Amplitude ◽  
Torsional Stiffness ◽  
Physical Parameters ◽  
Vibrational Control ◽  
Link Mechanism ◽  
Torsional Damping ◽  
Fixed Input

Abstract This paper describes vibrational control and stability of a planar, horizontal 2-link mechanism using translational control of the base pivot. The system is a 3-DOF two-link mechanism that is subject to torsional damping, torsional stiffness, and is moving on a horizontal plane. The goal is to drive the averaged dynamics of the system to a desired configuration using a high-frequency, high-amplitude force applied at the base pivot. The desired configuration is achieved by applying an amplitude and angle of the input determined using the averaged dynamics of the system. We find the range of stable configurations that can be achieved by the system by changing the amplitude of the oscillations for a fixed input angle and oscillation frequency. The effects of varying the physical parameters on the achievable stable configurations are studied. Stability analysis of the system is performed using two methods: the averaged dynamics and averaged potential.

Follicle size and reproductive hormone profiles during a post-weaning altrenogest treatment in primiparous sows

2015 ◽  
Vol 27 (2) ◽  
pp. 304 ◽  
Author(s):  
J. J. J. van Leeuwen ◽  
M. R. T. M. Martens ◽  
J. Jourquin ◽  
M. A. Driancourt ◽  
A. Wagner ◽  
...  
Keyword(s):  
High Frequency ◽  
Fold Increase ◽  
High Amplitude ◽  
Daily Administration ◽  
Reproductive Hormone ◽  
Diurnal Pattern ◽  
Once Daily ◽  
Follicular Wave ◽  
Follicle Size ◽  
Low Amplitude

This study investigated the endocrine background of follicle size changes during post-weaning altrenogest treatment. altrenogest-treated sows received a 20-mg dosage daily at 8.00 a.m. from Day –1 to Day 14 after weaning. On Day –1, only 3/13 altrenogest-treated sows showed LH pulses compared with 8/8 control sows (P = 0.001). On Day 0, control sows showed a typical high frequency–low amplitude LH pattern, indicative for recruitment of oestrogenic follicles. In altrenogest-treated animals on Day 0, half of the sows showed high frequency–high amplitude pulses from 4–5 h after weaning. In altrenogest-treated sows, average follicle size increased from 3.1 ± 0.5 mm on Day 0 to 4.4 ± 0.6 mm on Day 5, then decreased to 3.7 ± 0.5 mm on Day 7 and stabilised thereafter. FSH and oestradiol (E2) concentrations showed a distinct diurnal pattern; high at 7.00 a.m. and low at 3.00 p.m. E2 concentrations (7.00 a.m.) showed a 2.5-fold increase from Day –1 to Day 2, and subsequently a 2-fold decline to reach a plateau at Day 8. FSH concentrations reached maximum levels by Day 5 and slowly declined afterwards. In conclusion, once-daily administration of altrenogest starting one day before weaning delays the weaning-induced increase in LH pulses. Although FSH and follicle size increase until Day 5 after weaning, follicle E2 production already decreased from Day 2 after weaning. Post-weaning altrenogest treatment thus results in a follicular wave of follicles that lose oestrogenic competence at Day 2 after weaning, presumably related to the changed LH dynamics during altrenogest treatment.

Active Vibration Control and Isolation for Micro-Machined Devices

2008 ◽  
Author(s):  
Seong Jin Kim ◽  
Chen Chen ◽  
George Flowers ◽  
Robert Dean
Keyword(s):  
High Frequency ◽  
Vibration Isolation ◽  
Active Vibration Control ◽  
Low Pressure ◽  
High Amplitude ◽  
Vibration Isolator ◽  
Mems Devices ◽  
Mechanical Vibrations ◽  
Mems Gyroscopes ◽  
Filter Structures

Some harsh environments contain high frequency, high amplitude mechanical vibrations. Unfortunately some very useful components, such as MEMS gyroscopes, can be very sensitive to these high frequency mechanical vibrations. Passive micromachined silicon lowpass filter structures (spring-mass-damper) have been demonstrated in recent years. However, the performance of these filter structures is typically limited by low damping. This is especially true if operated in low pressure environments, which is often the optimal operating environment for the attached device that requires vibration isolation. An active micromachined vibration isolator can be realized by combining a state sensor, and electrostatic actuator and feedback electronics with the passive isolator. Using this approach, a prototype active micromachined vibration isolator is realized and used to decrease the filter Q from approximately 135 to approximately 60, when evaluated in a low pressure environment. The physical size of these active isolators is suitable for use in or as packaging for sensitive electronic and MEMS devices, such as MEMS vibratory gyros.

Validation of fish length estimations from a high frequency multi-beam sonar (ARIS) and its utilisation as a field-based measurement technique

2019 ◽  
Vol 218 ◽  
pp. 59-68 ◽  
Author(s):  
Denham Cook ◽  
Karen Middlemiss ◽  
Peter Jaksons ◽  
William Davison ◽  
Alistair Jerrett
Keyword(s):  
Measurement Technique ◽  
High Frequency ◽  
Fish Length

An inkjet vision measurement technique for high-frequency jetting

2014 ◽  
Vol 85 (6) ◽  
pp. 065101 ◽  
Author(s):  
Kye-Si Kwon ◽  
Min-Hyuck Jang ◽  
Ha Yeong Park ◽  
Hyun-Seok Ko
Keyword(s):  
Measurement Technique ◽  
High Frequency ◽  
Vision Measurement

Vibrational Fatigue Analysis of a Strain Loading Using the Frequency and Wavelet Filtering Methods

2011 ◽  
Vol 462-463 ◽  
pp. 124-129
Author(s):  
Shahrum Abdullah ◽  
Edisah Putra Teuku ◽  
Zaki Nuawi Mohd. ◽  
Mohd. Nopiah Zulkifli
Keyword(s):  
High Frequency ◽  
Filter Design ◽  
High Amplitude ◽  
Morlet Wavelet ◽  
Wavelet Filtering ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Automotive Components ◽  
Low Pass ◽  
Low Amplitude

This paper presents a comparison work between the filtering methods of fatigue strain loadings using the frequency spectrum and the wavelet transform (WT), in which a raw loading signal can be simplified for purpose of simulation. For this reason, the Fast Fourier Transform (FFT) and the Morlet wavelet algorithms were used in order to transform the vibrational fatigue time series into the frequency domain signal, leading to the observation of the frequency characteristics of the signal. To retain high amplitude cycles in the FFT algorithm, a low pass filter technique was applied to remove the high frequency signals with small amplitude that are non-damaging. The departure of high frequency information smoothed the low amplitude cycles at high frequency events in the fatigue signal. The Butterworth filter was selected as the most efficient filter design as it retained most of the fatigue damage and also had the capability to remove 30 % of the original low amplitude cycles. On the other hand, the Morlet wavelet managed to remove 64 % of the original 59 second signal. This wavelet filtering method removed 34 % more than the similar procedure applied through the FFT approach. Hence, this fatigue data summarising algorithm can be used for studying the durability characteristics of automotive components.

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