10 MHz Thin-Film PZT-Based Flexible PMUT Array: Finite Element Design and Characterization.

Piezoelectric micromachined ultrasound transducers (PMUT) incorporating lead zirconate titanate PbZr0.52Ti0.48O3 (PZT) thin films were investigated for miniaturized high-frequency ultrasound systems. A recently developed process to remove a PMUT from an underlying silicon (Si) substrate has enabled curved arrays to be readily formed. This research aimed to improve the design of flexible PMUT arrays using PZFlex, a finite element method software package. A 10 MHz PMUT 2D array working in 3-1 mode was designed. A circular unit-cell was structured from the top, with concentric layers of platinum (Pt)/PZT/Pt/titanium (Ti) on a polyimide (PI) substrate. Pulse-echo and spectral response analyses predicted a center frequency of 10 MHz and bandwidth of 87% under water load and air backing. A 2D array, consisting of the 256 (16 × 16) unit-cells, was created and characterized in terms of pulse-echo and spectral responses, surface displacement profiles, crosstalk, and beam profiles. The 2D array showed: decreased bandwidth due to protracted oscillation decay and guided wave effects; mechanical focal length at 2.9 mm; 3.7 mm depth of field for -6 dB; and -55.6 dB crosstalk. Finite element-based virtual prototyping identified figures of merit-center frequency, bandwidth, depth of field, and crosstalk-that could be optimized to design robust, flexible PMUT arrays.

Implementation of a frailty screening programme and Geriatric Assessment Service in a nephrology centre: a quality improvement project.

INTRODUCTION: The aims of this quality improvement project were to: (1) proactively identify people living with frailty and CKD; (2) introduce a practical assessment, using the principles of the comprehensive geriatric assessment (CGA), for people living with frailty and chronic kidney disease (CKD) able to identify problems; and (3) introduce person-centred management plans for people living with frailty and CKD. METHODS: A frailty screening programme, using the Clinical Frailty Scale (CFS), was introduced in September 2018. A Geriatric Assessment (GA) was offered to patients with CFS ≥ 5 and non-dialysis- or dialysis-dependent CKD. Renal Frailty Multidisciplinary Team (MDT) meetings were established to discuss needs identified and implement a person-centred management plan. RESULTS: A total of 450 outpatients were screened using the CFS. One hundred and fifty patients (33%) were screened as frail. Each point increase in the CFS score was independently associated with a hospitalisation hazard ratio of 1.35 (95% CI 1.20-1.53) and a mortality hazard ratio of 2.15 (95% CI 1.63-2.85). Thirty-five patients received a GA and were discussed at a MDT meeting. Patients experienced a median of 5.0 (IQR 3.0) problems, with 34 (97%) patients experiencing at least three problems. CONCLUSIONS: This quality improvement project details an approach to the implementation of a frailty screening programme and GA service within a nephrology centre. Patients living with frailty and CKD at risk of adverse outcomes can be identified using the CFS. Furthermore, a GA can be used to identify problems and implement a person-centred management plan that aims to improve outcomes for this vulnerable group of patients.

Evaluation of near-surface stress distributions in dissimilar welded joint by scanning acoustic microscopy.

This paper presents the results from a set of experiments designed to ultrasonically measure the near surface stresses distributed within a dissimilar metal welded plate. A scanning acoustic microscope (SAM), with a tone-burst ultrasonic wave frequency of 200 MHz, was used for the measurement of near surface stresses in the dissimilar welded plate between 304 stainless steel and low carbon steel. For quantitative data acquisition such as leaky surface acoustic wave (leaky SAW) velocity measurement, a point focus acoustic lens of frequency 200 MHz was used and the leaky SAW velocities within the specimen were precisely measured. The distributions of the surface acoustic wave velocities change according to the near-surface stresses within the joint. A three dimensional (3D) finite element simulation was carried out to predict numerically the stress distributions and compare with the experimental results. The experiment and FE simulation results for the dissimilar welded plate showed good agreement. This research demonstrates that a combination of FE simulation and ultrasonic stress measurements using SAW velocity distributions appear promising for determining welding residual stresses in dissimilar material joints.