Investigating the influence of the constituent materials on the performance of periodic piezoelectric composite arrays

This paper describes a theoretical investigation into the influence of the constituent materials on periodic composite array transducer performance. A finite element (FE) model, configured in PZFlex, is used to analyze the performance of a wedge coupled array transducer operating into a steel component. Here, the improvements offered by new single crystal piezoelectric materials are compared to standard PZT‐based configurations. In addition, new passive polymer materials, possessing low longitudinal loss and high shear loss, are evaluated for their potential to significantly reduce inter‐element mechanical cross talk. The FE results illustrate the potential for the next generation of array transducers incorporating these new materials and this is highlighted in the A‐scan predictions from simulated defects

In situ diagnostics and prognostics of solder fatigue in IGBT modules for electric vehicle drives

This paper proposes an in situ diagnostic and prognostic (D&P) technology to monitor the health condition of insulated gate bipolar transistors (IGBTs) used in EVs with a focus on the IGBTs' solder layer fatigue. IGBTs' thermal impedance and the junction temperature can be used as health indicators for through-life condition monitoring (CM) where the terminal characteristics are measured and the devices' internal temperature-sensitive parameters are employed as temperature sensors to estimate the junction temperature. An auxiliary power supply unit, which can be converted from the battery's 12-V dc supply, provides power to the in situ test circuits and CM data can be stored in the on-board data-logger for further offline analysis. The proposed method is experimentally validated on the developed test circuitry and also compared with finite-element thermoelectrical simulation. The test results from thermal cycling are also compared with acoustic microscope and thermal images. The developed circuitry is proved to be effective to detect solder fatigue while each IGBT in the converter can be examined sequentially during red-light stopping or services. The D&P circuitry can utilize existing on-board hardware and be embedded in the IGBT's gate drive unit

Application of pulsed power generated high power ultrasound to waste comminution and the recovery of metals

The disposal of waste materials is an increasing burden on industry across the world. In order to address this problem, the development of viable technologies and recycling paths is required. Often it is necessary to process waste to reduce its size (comminution) or to allow the recovery of high value components entrapped in waste. This paper describes the application of high power ultrasound (HPU), generated using pulsed power techniques, to two waste products: glass and stainless steel slag

Anesthesia for liver transplantation from a maastricht category 4 non-heart-beating donor -A case report-

Great improvements in patient selection, surgical techniques, perioperative care, and immunosuppression have been made for the optimization of liver transplantation. To increase the number of organs available for liver transplantation, transplant centers have used marginal donors, split livers, living donors, or non-heart-beating donors (NHBDs). Despite recent enthusiasm for NHBDs in liver transplantation, warm ischemic injury to recovered organs has been an obstacle for the wide acceptance of NHBD. In the present case, we have conducted a liver transplantation from a Maastricht Category 4 NHBD. Warm ischemic time was 20 minutes and cold ischemic time was 5 hour 43 minutes. Consequently, the liver was successfully transplanted into the recipient

The moderating effect of success importance on the relationship between listening demand and listening effort

A common element of the psychophysiological research on listening effort is the focus on listening demand as determinant of effort. The paper discusses preceding studies and theorizing on effort to show that the link between listening demand and listening effort is moderated by various variables. Moreover, I will present a recent study that examined the joint effect of listening demand and success importance on effort-related cardiovascular reactivity in an auditory discrimination task. Results for pre-ejection period reactivity—an indicator of sympathetic activity—supported the hypothesis that the relationship between listening demand and listening effort is moderated by other variables: Pre-ejection period reactivity was higher in the high-demand-high-success-importance condition than in the other three conditions. This new finding as well as the findings of previous research on effort suggest that a broader perspective on the determinants of listening effort is warranted

Relations between self-reported daily-life fatigue, hearing status and pupil dilation during a speech perception in noise task

Objective: people with hearing impairment are likely to experience higher levels of fatigue due to effortful listening in daily communication. This hearing-related fatigue might not only constrain their work performance, but also result in withdrawal from major social roles. Therefore, it is important to understand the relationships between fatigue, listening effort, and hearing impairment, by examining the evidence from both subjective and objective measurements. The aim of the present study was to investigate these relationships by assessing subjectively measured daily-life fatigue (self-report questionnaires) and objectively measured listening effort (pupillometry) in both normally-hearing and hearing-impaired participants. Design: twenty-seven normally-hearing and 19 age-matched participants with hearing impairment were included in this study. Two self-report fatigue questionnaires: Need For Recovery and Checklist Individual Strength were given to the participants before the test session to evaluate the subjectively measured daily fatigue. Participants were asked to perform a speech reception threshold test with single-talker masker targeting a 50% correct response criterion. The pupil diameter was recorded during the speech processing, and we used peak pupil dilation as the main outcome measure of the pupillometry. Results: No correlation was found between subjectively measured fatigue and hearing acuity, nor was a group difference found between the normally-hearing and the hearing-impaired participants on the fatigue scores. A significant negative correlation was found between self-reported fatigue and peak pupil dilation. A similar correlation was also found between Speech Intelligibility Index required for 50% correct and peak pupil dilation. Multiple regression analysis showed that factors representing 'hearing acuity' and 'self-reported fatigue' had equal and independent associations with the peak pupil dilation during the speech in noise test. Less fatigue and better hearing acuity were associated with a larger pupil dilation. Conclusions: To the best of our knowledge, this is the first study to investigate the relationship between a subjective measure of daily-life fatigue and an objective measure of pupil dilation, as an indicator of listening effort. These findings help to provide an empirical link between pupil responses, as observed in the laboratory, and daily life fatigue