scholarly journals Investigation on Methods of Determining the Grouting Quality of Embedded Rock Bolts Using High Frequency Guided Waves

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Peng Li ◽  
Changsuo Zhang ◽  
Guanlin Yang
Keyword(s):  
High Frequency ◽  
Guided Waves ◽  
Low Frequency ◽  
Guided Wave ◽  
Wave Frequency ◽  
Amplitude Ratios ◽  
Average Amplitude ◽  
Rock Bolts ◽  
Low Frequencies

Two experiments, with differing equipment setups, were used to test rock bolts, with differing structures and grouting qualities, using low frequency (20–200 kHz) and high frequency (700 kHz-3 MHz) guided waves to determine the effect of grouting quality on the propagating velocity of the guided waves. The results indicate that grouting quality has a significant effect on the velocity at which waves of low frequencies propagate through embedded rock bolts. As guided wave frequency increases, the sensitivity of the propagating velocity of guided waves to grouting quality decreases. Furthermore, the influence of grouting quality on propagating velocity becomes negligible once the frequency of the guided wave is greater than or equal to 1.0 MHz. An investigation was conducted to ascertain the feasibility of utilizing high frequency guided waves to determine the grouting quality of embedded rock bolts. Moreover, this study discusses a method of evaluating the grouting quality of embedded rock bolts using the peak ratios and average amplitude ratios of the high frequency guided waves. Through an analysis of the results of the abovementioned method, it was discovered that the optimal guided wave frequency is 2.65 MHz for the evaluation of 20 mm fully-embedded rock bolts because waves with this frequency have the largest average amplitude ratios.

scholarly journals High frequency guided wave ultrasound measurements using low-cost equipment

2021 ◽  
Vol 347 ◽  
pp. 00010
Author(s):  
Philip Loveday
Keyword(s):  
High Frequency ◽  
Low Cost ◽  
Mining Industry ◽  
Guided Wave ◽  
Rock Bolts ◽  
Low Frequencies ◽  
One Dimensional ◽  
Limited Budget ◽  
Theoretical Predictions ◽  
Ultrasound Testing

Guided wave ultrasound can be applied to inspect large volumes of structures from a single transducer location and is particularly effective in one-dimensional structures such as rods, pipes and rail. An application, which is of interest in South Africa, is the inspection rock bolts in the mining industry. The difficulty in inspecting embedded rods is that there is rapid attenuation of the signals with distance. While guided wave systems generally operate at low frequencies (20 kHz to 200 kHz), high frequency operation (1 MHz to 10 MHz) can offer some advantages when inspecting rock bolts. Guided wave ultrasound testing is complicated by multi-modal propagation and dispersion, which require the use of sophisticated excitation signals, which are not available in equipment designed for conventional ultrasonic testing. It was therefore necessary to develop a measurement setup and the approach taken was to use standard lab instruments wherever possible and to only purchase the items that are unique to this measurement, using the very limited budget available. The measurement setup was used to perform measurements on a rod and confirmed theoretical predictions. These measurements identified the frequencies where modes propagate with low attenuation and allow the attenuation to be quantified.

Dynamics of the processes in metal machining

1998 ◽  
Vol 2 ◽  
pp. 115-122
Author(s):  
Donatas Švitra ◽  
Jolanta Janutėnienė
Keyword(s):  
High Frequency ◽  
Machine Tools ◽  
Metal Cutting ◽  
Cutting Tool ◽  
Low Frequency ◽  
Metal Cutting Machine ◽  
Cutting Machine ◽  
Metal Machining

In the practice of processing of metals by cutting it is necessary to overcome the vibration of the cutting tool, the processed detail and units of the machine tool. These vibrations in many cases are an obstacle to increase the productivity and quality of treatment of details on metal-cutting machine tools. Vibration at cutting of metals is a very diverse phenomenon due to both it’s nature and the form of oscillatory motion. The most general classification of vibrations at cutting is a division them into forced vibration and autovibrations. The most difficult to remove and poorly investigated are the autovibrations, i.e. vibrations arising at the absence of external periodic forces. The autovibrations, stipulated by the process of cutting on metalcutting machine are of two types: the low-frequency autovibrations and high-frequency autovibrations. When the low-frequency autovibration there appear, the cutting process ought to be terminated and the cause of the vibrations eliminated. Otherwise, there is a danger of a break of both machine and tool. In the case of high-frequency vibration the machine operates apparently quiently, but the processed surface feature small-sized roughness. The frequency of autovibrations can reach 5000 Hz and more.

scholarly journals Earless toads sense low frequencies but miss the high notes

2017 ◽  
Vol 284 (1864) ◽  
pp. 20171670 ◽  
Author(s):  
Molly C. Womack ◽  
Jakob Christensen-Dalsgaard ◽  
Luis A. Coloma ◽  
Juan C. Chaparro ◽  
Kim L. Hoke
Keyword(s):  
High Frequency ◽  
Species Differences ◽  
Low Frequency ◽  
Auditory Brainstem ◽  
Low Frequencies ◽  
Hearing Sensitivity ◽  
Sensory Pathways ◽  
Airborne Sound ◽  
Vibrational Sensitivity ◽  
Species Specific

Sensory losses or reductions are frequently attributed to relaxed selection. However, anuran species have lost tympanic middle ears many times, despite anurans' use of acoustic communication and the benefit of middle ears for hearing airborne sound. Here we determine whether pre-existing alternative sensory pathways enable anurans lacking tympanic middle ears (termed earless anurans) to hear airborne sound as well as eared species or to better sense vibrations in the environment. We used auditory brainstem recordings to compare hearing and vibrational sensitivity among 10 species (six eared, four earless) within the Neotropical true toad family (Bufonidae). We found that species lacking middle ears are less sensitive to high-frequency sounds, however, low-frequency hearing and vibrational sensitivity are equivalent between eared and earless species. Furthermore, extratympanic hearing sensitivity varies among earless species, highlighting potential species differences in extratympanic hearing mechanisms. We argue that ancestral bufonids may have sufficient extratympanic hearing and vibrational sensitivity such that earless lineages tolerated the loss of high frequency hearing sensitivity by adopting species-specific behavioural strategies to detect conspecifics, predators and prey.

scholarly journals The Nature of the Stochastic Wind Forcing of ENSO

2018 ◽  
Vol 31 (19) ◽  
pp. 8081-8099 ◽  
Author(s):  
Antonietta Capotondi ◽  
Prashant D. Sardeshmukh ◽  
Lucrezia Ricciardulli
Keyword(s):  
El Niño ◽  
High Frequency ◽  
El Nino ◽  
Southern Oscillation ◽  
Low Frequency ◽  
Kelvin Waves ◽  
Wind Forcing ◽  
Alternative View ◽  
Low Frequencies ◽  
Wind Events

El Niño–Southern Oscillation (ENSO) is commonly viewed as a low-frequency tropical mode of coupled atmosphere–ocean variability energized by stochastic wind forcing. Despite many studies, however, the nature of this broadband stochastic forcing and the relative roles of its high- and low-frequency components in ENSO development remain unclear. In one view, the high-frequency forcing associated with the subseasonal Madden–Julian oscillation (MJO) and westerly wind events (WWEs) excites oceanic Kelvin waves leading to ENSO. An alternative view emphasizes the role of the low-frequency stochastic wind components in directly forcing the low-frequency ENSO modes. These apparently distinct roles of the wind forcing are clarified here using a recently released high-resolution wind dataset for 1990–2015. A spectral analysis shows that although the high-frequency winds do excite high-frequency Kelvin waves, they are much weaker than their interannual counterparts and are a minor contributor to ENSO development. The analysis also suggests that WWEs should be viewed more as short-correlation events with a flat spectrum at low frequencies that can efficiently excite ENSO modes than as strictly high-frequency events that would be highly inefficient in this regard. Interestingly, the low-frequency power of the rapid wind forcing is found to be higher during El Niño than La Niña events, suggesting a role also for state-dependent (i.e., multiplicative) noise forcing in ENSO dynamics.

Mind–body interactive qigong improves physical and mental aspects of quality of life in inpatients with stroke: A randomized control study

2019 ◽  
Vol 18 (8) ◽  
pp. 658-666 ◽  
Author(s):  
Ching-Hsiang Chen ◽  
Kuo-Sheng Hung ◽  
Yu-Chu Chung ◽  
Mei-Ling Yeh
Keyword(s):  
Quality Of Life ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
High Frequency ◽  
Standard Care ◽  
Low Frequency ◽  
Control Group ◽  
Subacute Stroke ◽  
Interactive Exercise

Background: Stroke, a medical condition that causes physical disability and mental health problems, impacts negatively on quality of life. Post-stroke rehabilitation is critical to restoring quality of life in these patients. Objectives: This study was designed to evaluate the effect of a mind–body interactive qigong intervention on the physical and mental aspects of quality of life, considering bio-physiological and mental covariates in subacute stroke inpatients. Methods: A randomized controlled trial with repeated measures design was used. A total of 68 participants were recruited from the medical and rehabilitation wards at a teaching hospital in northern Taiwan and then randomly assigned either to the Chan-Chuang qigong group, which received standard care plus a 10-day mind–body interactive exercise program, or to the control group, which received standard care only. Data were collected using the National Institutes of Health Stroke Scale, Hospital Anxiety and Depression Scale, Short Form-12, stroke-related neurologic deficit, muscular strength, heart rate variability and fatigue at three time points: pre-intervention, halfway through the intervention (day 5) and on the final day of the intervention (day 10). Results: The results of the mixed-effect model analysis showed that the qigong group had a significantly higher quality of life score at day 10 ( p<0.05) than the control group. Among the covariates, neurologic deficit ( p=0.04), muscle strength ( p=0.04), low frequency to high frequency ratio ( p=0.02) and anxiety ( p=0.04) were significantly associated with changes in quality of life. Conversely, heart rate, heart rate variability (standard deviation of normal-to-normal intervals, low frequency and high frequency), fatigue and depression were not significantly associated with change in quality of life ( p >0.05). Conclusions: This study supports the potential benefits of a 10-day mind–body interactive exercise (Chan-Chuang qigong) program for subacute stroke inpatients and provides information that may be useful in planning adjunctive rehabilitative care for stroke inpatients.

scholarly journals Effect of Closed-Loop Vibration Stimulation on Heart Rhythm during Naps

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4136 ◽  
Author(s):  
Sang Ho Choi ◽  
Heenam Yoon ◽  
Hyung Won Jin ◽  
Hyun Bin Kwon ◽  
Seong Min Oh ◽  
...  
Keyword(s):  
High Frequency ◽  
Closed Loop ◽  
Low Frequency ◽  
Heart Rhythm ◽  
Quality Of Sleep ◽  
Stimulation Condition ◽  
Term Basis ◽  
Stimulation System

Sleep plays a primary function for health and sustains physical and cognitive performance. Although various stimulation systems for enhancing sleep have been developed, they are difficult to use on a long-term basis. This paper proposes a novel stimulation system and confirms its feasibility for sleep. Specifically, in this study, a closed-loop vibration stimulation system that detects the heart rate (HR) and applies −n% stimulus beats per minute (BPM) computed on the basis of the previous 5 min of HR data was developed. Ten subjects participated in the evaluation experiment, in which they took a nap for approximately 90 min. The experiment comprised one baseline and three stimulation conditions. HR variability analysis showed that the normalized low frequency (LF) and LF/high frequency (HF) parameters significantly decreased compared to the baseline condition, while the normalized HF parameter significantly increased under the −3% stimulation condition. In addition, the HR density around the stimulus BPM significantly increased under the −3% stimulation condition. The results confirm that the proposed stimulation system could influence heart rhythm and stabilize the autonomic nervous system. This study thus provides a new stimulation approach to enhance the quality of sleep and has the potential for enhancing health levels through sleep manipulation.

Prediction of High Frequency Sonic Boom Noise Transmission Into Buildings Using a Hybrid Analytical-Ray Tracing Approach

2012 ◽  
Author(s):  
Joseph M. Corcoran ◽  
Marcel C. Remillieux ◽  
Ricardo A. Burdisso
Keyword(s):  
Ray Tracing ◽  
High Frequency ◽  
Acoustic Radiation ◽  
Low Frequency ◽  
Sonic Boom ◽  
Acoustic Transmission ◽  
Frequency Method ◽  
Low Frequencies ◽  
Sonic Booms ◽  
Acoustic Responses

As part of the effort to renew commercial supersonic flight, a predictive numerical tool to compute sonic boom transmission into buildings is under development. Due to the computational limitations of typical numerical methods used at low frequencies (e.g. Finite Element Method), it is necessary to develop a separate approach for the calculation of acoustic transmission and interior radiation at high frequencies. The high frequency approach can then later be combined with a low frequency method to obtain full frequency vibro-acoustic responses of buildings. An analytical method used for the computation of high frequency acoustic transmission through typical building partitions is presented in this paper. Each partition is taken in isolation and assumed to be infinite in dimension. Using the fact that a sonic boom generated far from the structure will approximate plane wave incidence, efficient analytical solutions for the vibration and acoustic radiation of different types of partitions are developed. This is linked to a commercial ray tracing code to compute the high frequency interior acoustic response and for auralization of transmitted sonic booms. Acoustic and vibration results of this high frequency tool are compared to experimental data for a few example cases demonstrating its efficiency and accuracy.

scholarly journals Pansharpening with a Gradient Domain GIF Based on NSST

Electronics ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 229
Author(s):  
Jiao Jiao ◽  
Lingda Wu
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Fusion Rule ◽  
Objective Evaluation ◽  
Data Sets ◽  
Multi Scale ◽  
Guided Image Filter ◽  
Gradient Domain ◽  
Spatial Quality

In order to improve the fusion quality of multispectral (MS) and panchromatic (PAN) images, a pansharpening method with a gradient domain guided image filter (GIF) that is based on non-subsampled shearlet transform (NSST) is proposed. First, multi-scale decomposition of MS and PAN images is performed by NSST. Second, different fusion rules are designed for high- and low-frequency coefficients. A fusion rule that is based on morphological filter-based intensity modulation (MFIM) technology is proposed for the low-frequency coefficients, and the edge refinement is carried out based on a gradient domain GIF to obtain the fused low-frequency coefficients. For the high-frequency coefficients, a fusion rule based on an improved pulse coupled neural network (PCNN) is adopted. The gradient domain GIF optimizes the firing map of the PCNN model, and then the fusion decision map is calculated to guide the fusion of the high-frequency coefficients. Finally, the fused high- and low-frequency coefficients are reconstructed with inverse NSST to obtain the fusion image. The proposed method was tested using the WorldView-2 and QuickBird data sets; the subjective visual effects and objective evaluation demonstrate that the proposed method is superior to the state-of-the-art pansharpening methods, and it can efficiently improve the spatial quality and spectral maintenance.

High-frequency neurons in the inferior colliculus that are sensitive to interaural delays of amplitude-modulated tones: evidence for dual binaural influences

1993 ◽  
Vol 70 (1) ◽  
pp. 64-80 ◽  
Author(s):  
R. Batra ◽  
S. Kuwada ◽  
T. R. Stanford
Keyword(s):  
Inferior Colliculus ◽  
High Frequency ◽  
Low Frequency ◽  
Sound Field ◽  
Low Frequencies ◽  
Contralateral Stimulation ◽  
Binaural Stimulation ◽  
Pure Tones ◽  
Ipsilateral Stimulation ◽  
Inferior Colliculi

1. Localization of sounds has traditionally been considered to be performed by a duplex mechanism utilizing interaural temporal differences (ITDs) at low frequencies and interaural intensity differences at higher frequencies. More recently, it has been found that listeners can detect ITDs at high frequencies if the amplitude of the sound varies and an ITD is present in the envelope. Here we report the responses of neurons in the inferior colliculi of unanesthetized rabbits to ITDs of the envelopes of sinusoidally amplitude-modulated (SAM) tones. 2. Neurons were studied extracellularly with glass-coated Pt-Ir or Pt-W microelectrodes. Their sensitivity to ITDs in the envelopes of high-frequency sounds (> or = 2 kHz) was assessed using SAM tones that were presented binaurally. The tones at the two ears had the same carrier frequency but modulation frequencies that differed by 1 Hz. This caused a cyclic variation in the ITD produced by the envelope. In this "binaural SAM" stimulus, the carriers caused no ITD because they were in phase. In addition to the binaural SAM stimulus, pure tones were used to investigate responses to ipsilateral and contralateral stimulation and the nature of the interaction during binaural stimulation. 3. Neurons tended to display one of two kinds of sensitivity to ITDs. Some neurons discharged maximally at the same ITD at all modulation frequencies > 250 Hz (peak-type neurons), whereas others were maximally suppressed at the same ITD (trough-type neurons). 4. At these higher modulation frequencies (> 250 Hz), the characteristic delays that neurons exhibited tended to lie within the range that a rabbit might normally encounter (+/- 300 microseconds). The peak-type neurons favored ipsilateral delays, which correspond to sounds in the contralateral sound field. The trough-type neurons showed no such preference. 5. The preference of peak-type neurons for a particular delay was sharper than that of trough-type neurons and was comparable to that observed in neurons of the inferior colliculus that are sensitive to delays of low-frequency pure tones. 6. At lower modulation frequencies (< 150 Hz) characteristic delays often lay beyond +/- 300 microseconds. 7. Increasing the ipsilateral intensity tended to shift the preferred delay ipsilaterally at lower (< 250 Hz), but not at higher, modulation frequencies. 8. When tested with pure tones, a substantial number of peak-type neurons were found to be excited by contralateral stimulation but inhibited by ipsilateral stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Modeling guided waves to constrain the velocity structure of the oceanic crust in the subduction zone of eastern Alaska

2020 ◽  
Author(s):  
Xiaoyu Guan ◽  
Yuanze Zhou ◽  
Takashi Furumura
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
High Frequency ◽  
Subduction Zones ◽  
Guided Waves ◽  
Velocity Structure ◽  
Guided Wave ◽  
S Wave ◽  
Arrival Times ◽  
Velocity Models

&lt;p&gt;Fitting subduction zone guided waves with synthetics is an ideal choice for studying the velocity structure of the oceanic crust. After an earthquake occurs in subduction zones, seismic waves can be trapped in the low-velocity oceanic crust and propagated as guided waves. The arrival time and frequency characteristics of the guided waves can be used to image the velocity structure of the oceanic crust. The analysis and modeling based on guided wave observations provide a rare opportunity to understand the velocity structure of the oceanic crust and the variations in oceanic crustal materials during the subduction process.&lt;/p&gt;&lt;p&gt;High-frequency guided waves have been observed in the subduction zone of eastern Alaska. On several sections, observed seismograms recorded by seismic stations show low-frequency (&lt;2Hz) onsets ahead of the main high-frequency (&gt;2Hz) guided waves. Differences in the arrival times and dispersion characteristics of seismic phases are related to the velocity structure of the oceanic crust, and the characteristics of coda waves are related to the distribution of elongated scatters in the oceanic crust. Through fitting the observed broadband waveforms and synthetics modeled with the 2-D FDM (Finite Difference Method), we obtain the preferred oceanic crustal velocity models for several sections in the subduction zone of eastern Alaska. The preferred models can explain the seismic phase arrival times, dispersions, and coda characteristics in the observed waveforms. With the obtained P- and S- wave models of velocity structures on several sections, the material compositions they represent are deduced, and the variations of oceanic crustal materials during subducting can be understood. This provides new evidence for studying the details of the subduction process in the subduction zone of eastern Alaska.&lt;/p&gt;

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