Transducer Location Research Articles

Experimental investigation on the unsteady surface pressure fluctuation patterns over an airfoil

This article presents a comprehensive mapping of wall-pressure fluctuations over an airfoil under three different inflow conditions to shed light on some basic assumptions taken for granted for the recent aeroacoustic and aerodynamics experimental studies and in the noise prediction models. Unsteady and steady pressure measurements were performed over a heavily instrumented airfoil, which was exposed to smooth inflow, grid-generated turbulent inflow, and a smooth inflow with a tripping tape over the airfoil to explore the unsteady response of the airfoil for a broad range of angles of attack, 0°≤α≤20°. The results are presented in terms of non-dimensional pressure coefficient, root mean square non-dimensional pressure coefficient, frequency-energy content pattern map at isolated frequencies for the entire airfoil, and spectra of frequency-energy content at selected transducer locations. The results show that the unsteady airfoil response patterns for the tripped boundary layer and turbulence ingestion cases show a dramatic difference compared to the airfoil response patterns of the smooth inflow conditions. The response patterns differ across angles of attack, frequency, and between both sides of the airfoil. The results suggest a three-region pattern for the smooth inflow case, a two-region pattern for the tripped boundary layer case, and a two-region pattern for the turbulence ingestion case. Moreover, the results indicate that the presence of tripping may provide a flow with necessary statistical characteristics for the experimental rigs representing the full-scale application; however, it may misrepresent the frequency-dependent nature of the boundary layer.

Studies of Acceleration of the Human Body during Overturning and Falling from a Height Protected by a Self-Locking Device.

The use of individual fall protection equipment is one of the most commonly applied methods of protecting workers whose worksites are located above the floor level. The safety of the user in such a situation depends on both the proper selection and correct use of such equipment. Additionally, aspects such as minimizing the free-fall distance before the fall arrest, as well as quick notification of an accident and efficient rescue operation, are important factors influencing safety. This paper presents a new testing method for fall arrest equipment using a test stand consisting of the Hybrid III 50th Pedestrian ATD anthropomorphic manikin and measuring set with three-axis acceleration transducers. The proposed method and test stand were developed for the design and testing of new fall protection devices equipped with electronic detection and alarm systems, for which it is necessary to determine acceleration limits in order to determine the alarm threshold. The proposed method is based on the measurement of accelerations that occur during tipping and falling from the height of an anthropomorphic manikin secured by a self-locking device. Two places of attachment of the measuring set with a three-axis acceleration sensor were analyzed at the waist belt of the manikin (abdomen and back). Moreover, the self-locking device lanyard was attached to the two points of the safety harnesses (the front and back point). The aim of the research was to check whether the acceleration values depend on the places of attachment of the measuring and anchored system, as well as to determine their maximum values. Acceleration values corresponding to fall arrest and tipping were analyzed. Limits of acceleration have been established in order to determine the threshold of alarm triggering. The non-parametric Mann–Whitney U test was used to check whether the location of the three-axis acceleration transducer and the position of the self-locking device lanyard attachment affect the value of the recorded acceleration. For results of acceleration measurements when testing the behavior of the manikin during fall arrest, no statistically significant differences were found. For results of acceleration measurements when testing the tipping behavior of the manikin, statistically significant differences occurred. This means that during fall arrest, the location of the three-axis acceleration transducer and the position of the self-locking device lanyard attachment do not matter. This work is a continuation of previous research on accelerations characterizing human body positions occurring during normal physical activities (ADL—activities of daily living).

Fetal heartrate tracking system based on intensity of Doppler signal

Doppler-detected fetal heart rate (FHR) tracking is the primary testing method for assessing fetal well-being during antepartum care. However, owing to fetal movements or maternal position variations, the transducer on the abdomen can be displaced, changing the fetal heart location (FHL) and resulting in frequent signal losses and uninterpretable results. In this study, we present FHR monitoring system for continuously maintaining FHR measurements without specifying the location of the Doppler ultrasound transducer. An algorithm is developed to track the FHL based on the intensity of the received Doppler signal. The performance is evaluated by conducting underwater experiments using an object with repeated movements. The tracking error is 7.93° on the X-axis and 1.42° on the Y-axis. Even with those tracking errors, the FHR is continuously recorded. This system can be used to obtain heart rate records without manipulating the position of the transducer and losing the signal.

The feasibility study of XACT imaging for characterizing osteoporosis.

Osteoporosis is a progressive bone disease that is characterized by a decrease in bone mass and the deterioration in bone microarchitecture, which might be related to age and space travel. An unmet need exists for the development of novel imaging technologies to characterize osteoporosis. The purpose of our study is to investigate the feasibility of X-ray-induced acoustic computed tomography (XACT) imaging for osteoporosis detection. An in-house simulation workflow was developed to assess the ability of XACT for osteoporosis detection. To evaluate this simulation workflow, a three-dimensional digital bone phantom for XACT imaging was created by a series of two-dimensional micro-computed tomography (micro-CT) slices of normal and osteoporotic bones in mice. In XACT imaging, the initial acoustic pressure rise caused by the X-ray induce acoustic (XA) effect is proportional to bone density. First, region growing was deployed for image segmentation of different materials inside the bone. Then k-wave simulations were deployed to model XA wave propagation, attenuation, and detection. Finally, the time-varying pressure signals detected at each transducer location were used to reconstruct the XACT image with a time-reversal reconstruction algorithm. Through the simulated XACT images, cortical porosity has been calculated, and XA signal spectra slopes have been analyzed for the detection of osteoporosis. The results have demonstrated that osteoporotic bones have lower bone mineral density and higher spectra slopes. These findings from XACT images were in good agreement with porosity calculation from micro-CT images. This work explores the feasibility of using XACT imaging as a new imaging tool for Osteoporosis detection. Considering that acoustic signals are generated by X-ray absorption, XACT imaging can be combined with traditional X-ray imaging that holds potential for clinical management of osteoporosis and other bone diseases.

Eucalyptol prevents bleomycin-induced pulmonary fibrosis and M2 macrophage polarization

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrosing interstitial pneumonia with limited therapeutic options. Eucalyptol, a terpenoid oxide isolated from eucalyptus species, reportedly exhibits various biological activities such as anti-inflammatory and antioxidant effects. In the present study, we aimed to determine whether eucalyptol could alleviate bleomycin (BLM)-induced pulmonary fibrosis and inhibit interleukin (IL)-13-induced M2 macrophage polarization. Upon treatment with eucalyptol, BLM-induced pulmonary fibrosis and lung inflammation were significantly reduced. The pulmonary neutrophil accumulation and pulmonary permeability were inhibited and the expression of hydroxyproline, alpha-smooth muscle actin, and fibronectin was significantly down-regulated. Eucalyptol also markedly inhibited the expression of arginase-1, Ym-1, IL-13, and transforming growth factor (TGF)-β1, reduced the production of IL-13, IL-6, tumor necrosis factor (TNF)-α, and attenuated the activity of TGF-β1 in bronchoalveolar lavage fluid (BALF). Furthermore, the in vitro assay revealed that eucalyptol disturbed M2 macrophage polarization and reduced the macrophage-mediated secretion of the profibrotic factor TGF-β1. Eucalyptol inhibited the nuclear location of signal transducer and activator of transcription 6 (STAT6) and the phosphorylation of STAT6 and p38 mitogen-activated protein kinase (p38 MAPK), and reduced the expression of their downstream transcription factors, krupple-like factor 4 (KLF4) and peroxisome proliferator-activated receptor gamma (PPAR-γ). These findings indicated that eucalyptol alleviates BLM-induced pulmonary fibrosis by regulating M2 macrophage polarization, which, in turn, inhibits the activation of signaling molecules (e.g., STAT6 and p38 MAPK) and the expression of transcription factors (e.g., KLF4 and PPAR-γ). Thus, eucalyptol might be a potential therapeutic agent for IPF.

Verapamil inhibited the development of ureteral stricture by blocking CaMK II-mediated STAT3 and Smad3/JunD pathways.

Ureteral stricture (US) is a fibrotic process that leads to urinary tract obstruction and even kidney damage, with the characteristic of reduced extracellular matrix (ECM) degradation and increased collagen synthesis. Verapamil, as a calcium channel blocker, was reported to prevent scar formation. Our work aimed to investigate the biological effects and mechanism of verapamil in US. Fibroblasts were subjected to transforming growth factor-beta 1 (TGF-β1) to stimulate collagen synthesis, and the messenger ribonucleic acid (mRNA) and protein expressions in fibroblasts were assessed using quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. The location of phosphorylation-signal transducer and activator of transcription 3 (p-STAT3) and Jund proto-oncogene subunit (JunD) in fibroblasts were determined by immunofluorescence (IF). The binding relationship between signal transducer and activator of transcription 3 (STAT3) and collagen type I alpha1 (COL1A1)/collagen type III alpha 1 chain (COL3A1) and the binding relationship between JunD and tissue inhibitor of metalloproteinases-1 (TIMP-1) were verified by dual luciferase reporter gene and chromatin Immunoprecipitation (ChIP) assays. Herein, we found that verapamil could inhibit TGF-β1/Ca2 + ⁄calmodulin-dependent protein kinase II (CaMK II)-mediated STAT3 activation in fibroblasts, and STAT3 inhibition repressed collagen production. In addition, verapamil could inhibit TGF-β1/CaMK II-mediated Mothers against DPP homolog 3 (Smad3)/JunD pathway activation in fibroblasts, and JunD silencing inhibited TIMP1 (a matrix metalloproteinase inhibitor) expression. Our subsequent experiments revealed that STAT3 bound with COL1A1 promoter and COL3A1 promoter and activated their transcription, and JunD bound with TIMP1 promoter and activated its transcription. Moreover, as expected, STAT3 activation could eliminate the inhibitory effect of verapamil treatment on TGF-β1-induced collagen production in fibroblasts, and JunD overexpression reversed the inhibitory effect of verapamil treatment on TGF-β1-induced TIMP1 expression in fibroblasts. Verapamil inhibited collagen production and TIMP-1 expression in US by blocking CaMK II-mediated STAT3 and Smad3/JunD pathways.

A Body Navigation-Loaded Ultrasound Acquisition Technology: A Pilot Comparison with Conventional Ultrasound

Background: In conventional ultrasonography, the ultrasound image is not labeled with information on the location or orientation of the transducer. There is also no information on the parts of the body under examination. Objectives: This study aimed to investigate the efficacy of body navigation-loaded ultrasonography, including the real-time transducer location and the inspection site, compared to conventional ultrasound. Patients and Methods: After obtaining approval from the institutional review board, 29 healthy adult volunteers were prospectively enrolled in this study. One gastrointestinal radiologist performed an abdominal ultrasound, using an ultrasound navigation image convergence system, developed by the authors. Subsequently, an equivalent conventional ultrasound image set was prepared. Three radiologists independently evaluated the two ultrasound image sets for identifying the target organ (two points), transducer location (two points), and transducer orientation (one point). In a two-week interval, conventional ultrasound images were first analyzed, and then, body navigation-loaded images were examined. The score differences between the first and second evaluations were compared using Wilcoxon signed-rank test. The inter-rater agreement of the three reviewers was determined by measuring the Fleiss’ kappa value. Results: A total of 1,402 navigation-loaded ultrasound images were acquired in this study. The ultrasound operator carefully selected 203 images for analysis. The interpretation score of all three reviewers significantly increased for each examination in the second analysis using the body navigation-loaded ultrasound images (reviewer A, from 4.07 ± 1.56 to 4.79 ± 0.69; reviewer B, from 3.83 ± 1.59 to 4.49 ± 0.88; and reviewer C, from 3.43 ± 1.60 to 4.19 ± 1.01) (P < 0.0001). The inter-rater agreement of each examination also increased significantly in the second analysis using the body navigation-loaded ultrasound images (P < 0.0001). Conclusion: According to the results of this pilot study, the body navigation-loaded ultrasound technology can assist with a simple and objective interpretation of ultrasound images from organs.

Arterial Monitoring System Leveling Method, Transducer Location, and Accuracy of Blood Pressure Measurements.

Many critically ill patients have invasive arterial catheters inserted for blood pressure monitoring. Whether catheter leveling method and alternative transducer location affect the accuracy of blood pressure measurements is unknown. To determine whether the use of alternative transducer locations and visual alignment versus laser device leveling significantly affect the accuracy of blood pressure measurements. A convenience sample of 36 participants were randomly assigned to 1 of 3 experimental groups with different transducer locations: taped to the upper arm, next to the upper arm taped to a rolled cloth, or at the wrist. Participants served as their own controls; the control condition was having the transducer on the intravenous pole. Four blood pressure measurements were recorded for each patient (2 from each of the experimental and control conditions) using visual alignment and then laser device leveling. Only diastolic blood pressure (DBP) differed significantly between leveling methods (P = .01); no pressures differed significantly by transducer location. Covariate analysis indicated expected relationships between (1) age and DBP (P = .001), (2) Simplified Acute Physiology Score II and both DBP (P = .003) and mean arterial pressure (P = .03), and (3) duration of mechanical ventilation and DBP (P = .05). The findings indicate that any of the transducer locations evaluated may be useful in clinical prac-tice. Also, visual alignment rather than laser device leveling may be acceptable, except for DBP in the control location. More research is needed to strengthen these findings.

Spatial variation in mechanical properties along the sciatic and tibial nerves: An ultrasound shear wave elastography study

Ultrasound shear wave elastography has become a promising method in peripheral neuropathy evaluation. Shear wave velocity, a surrogate measure of stiffness, tends to increase in peripheral neuropathies regardless of etiology. However, little is known about the spatial variation in shear wave velocity of healthy peripheral nerves and how tensile loading is distributed along their course. Sixty healthy young adults were scanned using ultrasound shear wave elastography. Five regions of the sciatic (SciaticPROXIMAL, SciaticDISTAL) and tibial nerve (TibialPROXIMAL, TibialINTERMEDIATE, and TibialDISTAL) were assessed in two hip positions that alter nerve tension: 1) neutral in supine position; and 2) flexed at 90°. Knee and ankle remained in full-extension and neutral position. We observed spatial variations in shear wave velocity along the sciatic and tibial nerve (P < 0.0001). Shear wave velocities were significantly different between all nerve locations with the exception of SciaticDISTAL vs. TibialINTERMEDIATE (P = 0.999) and TibialPROXIMAL vs. TibialINTERMEDIATE (P = 0.708), and tended to increase in the proximal-distal direction at both upper and lower leg segments. Shear wave velocity increased with hip flexion (+54.3%; P < 0.0001), but the increase was not different among nerve locations (P = 0.233). This suggests that the increase in tensile loading with hip flexion is uniformally distributed along the nerve tract. These results highlight the importance of considering both limb position and transducer location for biomechanical and clinical assessments of peripheral nerve stiffness. These findings provide evidence about how tension is distributed along the course of sciatic and tibial nerves.

Differential evolution method to find optimal location of a single-element transducer for transcranial focused ultrasound therapy

Background and objectiveFocused ultrasound (FUS) has been receiving growing attention as a noninvasive brain stimulation tool because of its superior spatial specificity and depth penetrability. However, the large mismatch of acoustic properties between the skull and water can disrupt and shift the acoustic focus in the brain. In this paper, we present a numerical method to find the optimal location of a single-element FUS transducer, which creates focus on the target region. MethodsThe score function, representing the superposition of acoustic waves according to the relative phase difference and transmissibility, was defined based on time-reversal invariance of acoustic waves and depending on the spatial location of the transducer. The optimal location of the transducer was then determined using a differential evolution algorithm. To assess the proposed method, we conducted a forward simulation and compared the resulting focal location to the desired target point. We also performed experimental validation by measuring the acoustic pressure field through an ex vivo human skull in a water tank. ResultsThe numerical results indicated that the score function had a positive proportional relationship with the acoustic pressure at the target. Moreover, for the optimized transducer location, both the numerical and experimental results showed that the normalized acoustic pressure at the target was higher than 0.9. ConclusionsIn this study, we developed an optimization method to place a single-element transducer that effectively transmits acoustic energy to the targeted region in the brain. Our numerical and experimental results demonstrate that the proposed method can provide an optimal transducer location for safe and efficient FUS treatment.

Spatial Response Identification Enables Robust Experimental Ultrasound Computed Tomography.

Ultrasound computed tomography techniques have the potential to provide clinicians with 3-D, quantitative and high-resolution information of both soft and hard tissues such as the breast or the adult human brain. Their practical application requires accurate modeling of the acquisition setup: the spatial location, orientation, and impulse response (IR) of each ultrasound transducer. However, the existing calibration methods fail to accurately characterize these transducers unless their size can be considered negligible when compared with the dominant wavelength, which reduces signal-to-noise ratios below usable levels in the presence of high-contrast tissues such as the skull. In this article, we introduce a methodology that can simultaneously estimate the location, orientation, and IR of the ultrasound transducers in a single calibration. We do this by extending spatial response identification (SRI), an algorithm that we have recently proposed to estimate transducer IRs. Our proposed methodology replaces the transducers in the acquisition device with a surrogate model whose effective response matches the experimental data by fitting a numerical model of wave propagation. This results in a flexible and robust calibration procedure that can accurately predict the behavior of the ultrasound acquisition device without ever having to know where the real transducers are or their individual IR. Experimental results using a ring acquisition system show that SRI produces calibrations of significantly higher quality than standard methodologies across all transducers, both in transmission and in reception. Experimental full-waveform inversion (FWI) reconstructions of a tissue-mimicking phantom demonstrate that SRI generates more accurate reconstructions than those produced with standard calibration techniques.

Modeling, identification and optimization of damage deterioration in the bolted repaired metallic plate

The in situ detection of the damaged aluminum alloy plate with bolted patch is numerically and experimentally studied based on a surface-mounted piezoelectric ceramic lead zirconate titanate (PZT) elements. The contact effects between the bolts, repair patch and host structure are considered. The convergence analysis, range-frequency analysis and pretension force analysis are discussed. The numerical results are good agreement with those of the experiments. The damage identification indexes are introduced for damage detection. It indicates the numerical simulation is effective for the damage deterioration of bolted repaired structures. The location of the PZT transducer is discussed to optimize the process.

Erratum: Use of 3D Robotic Ultrasound for In Vivo Analysis of Mouse Kidneys.

An erratum was issued for:Use of 3D Robotic Ultrasound for In Vivo Analysis of Mouse Kidneys. An author name was updated, along with the Protocol and Representative Results. Thename of anauthor was updated from: Ryan C. Gesser to: Ryan C. Gessner Step 3.1 of the Protocol was updated from: Turn on the US machine and the heat lamp above the US platforms. Turn on the appropriate anesthesia valves for the corresponding US bays that will be used. to: Turn on the US machine and the switch for the internal heating element for the US bays. Turn on the appropriate anesthesia valves for the corresponding US bays that will be used. Figue 1 in the Representative Results was updated from: Figure 1: Ultrasound system and mouse placement. (A) Diagram of ultrasound system and location of transducers. (B) View of mice in supine position on ultrasound platform with heat lamp. (C) Example of region of interest (ROI)s in place for area of interest (kidneys) with animal IDs. Please click here to view a larger version of this figure. to: Figure 1: Ultrasound system and mouse placement. (A) Diagram of ultrasound system and location of transducers. (B) View of mice in supine position on ultrasound platform. (C) Example of region of interest (ROI)s in place for area of interest (kidneys) with animal IDs. Please click here to view a larger version of this figure.

Circumferential Variation of Noise at the Blade-Pass Frequency in a Turbocharger Compressor with Ported Shroud

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The ported shroud casing treatment for turbocharger compressors offers a wider operating flow range, elevated boost pressures at low compressor mass flow rates, and reduced broadband whoosh noise in spark-ignition internal combustion engine applications. However, the casing treatment elevates tonal noise at the blade-pass frequency (BPF). Typical rotational speeds of compressors employed in practice push BPF noise to high frequencies, which then promote multi-dimensional acoustic wave propagation within the compressor ducting. As a result, in-duct acoustic measurements become sensitive to the angular location of pressure transducers on the duct wall. The present work utilizes a steady-flow turbocharger gas stand featuring a unique rotating compressor inlet duct to quantify the variation of noise measured around the duct at different angular positions. The acoustic pressure transducers installed on the rotating duct record time-resolved in-duct acoustic pressure at different azimuthal locations while the compressor is held at a steady operating point. Acoustic measurements are performed across the flow range of a ported shroud compressor at three different rotational speeds. A comparison of sound pressure levels measured at different azimuthal locations reveals the significant contribution of high-frequency BPF noise to the variation in the acoustic pressure around the duct.&lt;/div&gt;&lt;/div&gt;

In-situ synchrotron X-ray imaging of ultrasound (US)-generated bubbles: Influence of US frequency on microbubble cavitation for membrane fouling remediation

Gaining an in-depth understanding of the characteristics and dynamics of ultrasound (US)--generated bubbles is crucial to effectively remediate membrane fouling. The goal of present study is to conduct in-situ visualization of US-generated microbubbles in water to examine the influence of US frequency on the dynamics of microbubbles. This study utilized synchrotron in-line phase contrast imaging (In-line PCI) available at the biomedical imaging and therapy (BMIT) beamlines at the Canadian Light Source (CLS) to enhance the contrast of liquid/air interfaces at different US frequencies of 20, 28 and 40 KHz at 60 Watts. A high-speed camera was used to capture 2,000 frames per second of the bubble cavitation generated in water under the ultrasound influence. Key parameters at the polychromatic beamlines were optimized to maximize the phase contrast of gas/liquid of the microbubbles with a minimum size of 5.5 µm. ImageJ software was used to analyze the bubble characteristics and their behavior under the US exposure including the microbubble number, size, and fraction of the total area occupied by the bubbles at each US frequency. Furthermore, the bubble characteristics over the US exposure time and at different distances from the transducer were studied. The qualitative and quantitative data analyses showed that the microbubble number or size did not change over time; however, it was observed that most bubbles were created at the middle of the frames and close to the US field. The number of bubbles created under the US exposure increased with the frequency from 20 kHz to 40 kHz (about 4.6 times). However, larger bubbles were generated at 20 kHz such that the average bubble radius at 20 kHz was about 6.8 times of that at 40 kHz. Microbubble movement/traveling through water was monitored, and it was observed that the bubble velocity increased as the frequency was increased from 20 kHz to 40 kHz. The small bubbles moved faster, and the majority of them traveled upward towards the US transducer location. The growth pattern (a correlation between the mean growth ratio and the exposure time) of bubbles at 20 kHz and 60 W was obtained by tracking the oscillation of 22 representative microbubbles over the 700 ms of imaging. The mean growth ratio model was also obtained.

Evaluation Methodology of a Smart Clothing Biomechanical Energy Harvesting System for Mountain Rescuers.

The article presents a methodology developed for the evaluation of biomechanical energy harvesting systems that permits avoiding long-duration outdoor tests while providing realistic input signals and preserving uniform conditions across repeated tests. It consists of two stages: transducer output signal recording and power conversion and storage system measurements. The proposed approach was applied to assess the usefulness of a commercial electromagnetic transducer for supplying a Global Positioning System (GPS) receiver used as an active component of a smart clothing dedicated for mountain rescuers. Electrical power yield measurements have been presented together with ergonomic tests results. They all involved diverse physical activities performed by mountain rescuers that simulated their true operations, but were conducted in a training room for the sake of standardization. By providing reliable data on the transducer’s performance under realistic use conditions, the proposed evaluation procedure revealed that the true energy yield was much smaller not only with respect to the manufacturer’s assertions, but also substantially lower than what was expected based on an independent review which used unrealistic and non-uniform excitations. On the other hand, ergonomics ratings given by potential end users were very high, which demonstrates that the evaluated transducer can still be useful for supplying active cloth components with a lower power demand. The study also revealed that transducer location and orientation strongly affect its performance, which must be taken into account at the first stage of the evaluation procedure. Moreover, physical activity type and conditions (such as motion speed and ground tilt) influence the output power and should be carefully considered when composing a typical case scenario for the second stage.

Optimization of Transducer Location for Novel Non-Intrusive Methodologies of Diagnosis in Diesel Engines

The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information.

High frequency guided wave ultrasound measurements using low-cost equipment

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.

A journey of wastewater to clean hydrogen: A perspective

A journey of wastewater to clean hydrogen: A perspective

Comparison of extraocular and intraocular pressure transducers for measurement of transient intraocular pressure fluctuations using continuous wireless telemetry

The optimal approach for continuous measurement of intraocular pressure (IOP), including pressure transducer location and measurement frequency, is currently unknown. This study assessed the capability of extraocular (EO) and intraocular (IO) pressure transducers, using different IOP sampling rates and duty cycles, to characterize IOP dynamics. Transient IOP fluctuations were measured and quantified in 7 eyes of 4 male rhesus macaques (NHPs) using the Konigsberg EO system (continuous at 500 Hz), 12 eyes of 8 NHPs with the Stellar EO system and 16 eyes of 12 NHPs with the Stellar IO system (both measure at 200 Hz for 15 s of every 150 s period). IOP transducers were calibrated bi-weekly via anterior chamber manometry. Linear mixed effects models assessed the differences in the hourly transient IOP impulse, and transient IOP fluctuation frequency and magnitude between systems and transducer placements (EO versus IO). All systems measured 8000–12,000 and 5000–6500 transient IOP fluctuations per hour > 0.6 mmHg, representing 8–16% and 4–8% of the total IOP energy the eye must withstand during waking and sleeping hours, respectively. Differences between sampling frequency/duty cycle and transducer placement were statistically significant (p < 0.05) but the effect sizes were small and clinically insignificant. IOP dynamics can be accurately captured by sampling IOP at 200 Hz on a 10% duty cycle using either IO or EO transducers.