Parametric investigation of a transducer for guided wave applications

The use of dry-coupled thickness-shear piezoelectric transducers for the generation of ultrasonic guided waves in Non Destructive Testing is well established in industry. The control of guided waves can be supported by designing transducers that achieve a uniform excitation over frequency and contact area. It is necessary to control the wave modes generated such that only modes with characteristics useful for inspection are transmitted and received. Recent research has identified the need to improve the ultrasonic performance in terms of amplitude and signal-to-noise ratio of guided waves via the miniaturization of the transducers. The influence of the geometry of the transducer on the generation of guided waves needs to be investigated. It is well known that the geometry of the transducers influences the normal modes of the ultrasonic transducers, which in turn can influence their ability to excited ultrasonic guided waves. However, the influence of transducer geometry on ultrasonic performance is still not completely understood: mode coupling and the presence of satellite modes might be detrimental for the generation of guided waves. These requirements drive the testing of design changes in terms of geometry and shape of the electrodes to improve the ultrasonic performance of the aforementioned transducers. The transducer is analysed both numerically (by Finite Element Analysis) and experimentally (with Laser Vibrometry) to offer a characterisation of existing piezoelectric elements. It is shown that a change in the actuation area of the transducer leads to a significant difference in the ultrasonic output

Experimental and numerical analysis of a transducer for the generation of guided waves

Dry-coupled thickness-shear transducers represent one of the most common ways to excite guided waves for the inspection of tubular and plate-like structures. Although already established in industry, some features of these transducers need to be studied, i.e. the uniformity of vibration, the modes excitability and the transmission of ultrasonic energy into the inspected structure. In particular, due to the dispersive behaviour of guided waves and the mode coupling these transducers require a precise characterization to guarantee a uniform in-plane vibration. A numerical and experimental characterization of the assembly has been carried out to assess the influence of the elements of the assembly into the uniformity of vibration. The outcome of the results in terms of mode-shape, displacement pattern and resonance frequencies is discussed to predict useful design changes to enhance the ultrasonic performance of these transducers

Characterisation of the vibration of an ultrasonic transducer for guided wave applications

Dry-coupled thickness-shear piezoelectric transducers are typically used to excite guided waves in plate-like or tubular structures in the frequency range of 20-150 kHz. The dispersive behaviour of guided waves and the excitation of unwanted wave modes require a precise tuning of the excitation frequency to facilitate effective inspection. A natural frequency analysis of a typical piezoelectric transducer has been performed to identify the shape of vibration in the frequency range indicated. Moreover, an experimental analysis of the vibration of the piezoelectric element through a scanning laser Doppler Vibrometer has been conducted. The numerical and experimental results agree in indicating no longitudinal mode is present up to 94 kHz. Experiments also has shown that the higher the frequency the higher the longitudinal component of displacement

How to Do Things Without Words: Infants, utterance-activity and distributed cognition

Clark and Chalmers (1998) defend the hypothesis of an ‘Extended Mind’, maintaining that beliefs and other paradigmatic mental states can be implemented outside the central nervous system or body. Aspects of the problem of ‘language acquisition’ are considered in the light of the extended mind hypothesis. Rather than ‘language’ as typically understood, the object of study is something called ‘utterance-activity’, a term of art intended to refer to the full range of kinetic and prosodic features of the on-line behaviour of interacting humans. It is argued that utterance activity is plausibly regarded as jointly controlled by the embodied activity of interacting people, and that it contributes to the control of their behaviour. By means of specific examples it is suggested that this complex joint control facilitates easier learning of at least some features of language. This in turn suggests a striking form of the extended mind, in which infants’ cognitive powers are augmented by those of the people with whom they interact

Integrating team science into interdisciplinary graduate education: an exploration of the SESYNC Graduate Pursuit

Complex socio-environmental challenges require interdisciplinary, team-based research capacity. Graduate students are fundamental to building such capacity, yet formal opportunities for graduate students to develop these capacities and skills are uncommon. This paper presents an assessment of the Graduate Pursuit (GP) program, a formal interdisciplinary team science graduate research and training program administered by the National Socio-Environmental Synthesis Center (SESYNC). Quantitative and qualitative assessment of the program’s first cohort revealed that participants became significantly more comfortable with interdisciplinary research and team science approaches, increased their capacity to work across disciplines, and were enabled to produce tangible research outcomes. Qualitative analysis of four themes—(1) discipline, specialization, and shared purpose, (2) interpersonal skills and personality, (3) communication and teamwork, and (4) perceived costs and benefits—encompass participants’ positive and negative experiences and support findings from past assessments. The findings also identify challenges and benefits related to individual personality traits and team personality orientation, the importance of perceiving a sense of autonomy and independence, and the benefit of graduate training programs independent of the university and graduate program environment

A compact system for intraoperative specimen imaging based on edge illumination x-ray phase contrast

A significant number of patients receiving breast-conserving surgery (BCS) for invasive carcinoma and ductal carcinoma in situ (DCIS) may need reoperation following tumor-positive margins from final histopathology tests. All current intraoperative margin assessment modalities have specific limitations. As a first step towards the development of a compact system for intraoperative specimen imaging based on edge illumination x-ray phase contrast, we prove that the system\u27s dimensions can be reduced without affecting imaging performance. We analysed the variation in noise and contrast to noise ratio (CNR) with decreasing system length using the edge illumination x-ray phase contrast imaging setup. Two-(planar) and three-(computed tomography (CT)) dimensional imaging acquisitions of custom phantoms and a breast tissue specimen were made. Dedicated phase retrieval algorithms were used to separate refraction and absorption signals. A \u27single-shot\u27 retrieval method was also used, to retrieve thickness map images, due to its simple acquisition procedure and reduced acquisition times. Experimental results were compared to numerical simulations where appropriate. The relative contribution of dark noise signal in integrating detectors is significant for low photon count statistics acquisitions. Under constant exposure factors and magnification, a more compact system provides an increase in CNR. Superior CNR results were obtained for refraction and thickness map images when compared to absorption images. Results indicate that the \u27single-shot\u27 acquisition method is preferable for a compact CT intraoperative specimen scanner; it allows for shorter acquisition times and its combination of the absorption and refraction signals ultimately leads to a higher contrast. The first CT images of a breast specimen acquired with the compact system provided promising results when compared to those of the longer length system

A compact system for intraoperative specimen imaging based on edge illumination x-ray phase contrast

“This is an author-created, un-copyedited version of an article accepted for publication/published in Physics in Medicine & Biology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6560/ab4912

A communal catalogue reveals Earth's multiscale microbial diversity

Our growing awareness of the microbial world's importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth's microbial diversity.Peer reviewe