Marion E. Unwin

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This paper is concerned with modeling ultrasonic wave propagation in epoxy materials to better understand NDE procedures and to provide reliable input to more complex models of guided wave propagation in layered structures. Different physical models are considered in the context of how well they simulate the (known) linear relationship between bulk wave(More)
Ultrasonic imaging of biofilms in water is difficult due to the very low contrast in acoustic impedance between the biofilm and water. In this paper, biofilms exposed to moist air are scanned through the substrate in order to obtain echoes from the biofilm/air interface. A 50 MHz scanning system was used to scan 1 mm x 1 mm areas of biofilms in a 10 microm(More)
AIMS This study evaluated the effect of protozoan movement and grazing on the topography of a dual-bacterial biofilm using both conventional light microscopy and a new ultrasonic technique. METHODS AND RESULTS Coupons of dialysis membrane were incubated in Chalkley's medium for 3 days at 23 degrees C in the presence of bacteria (Pseudomonas aeruginosa and(More)
This paper focuses on the analysis of frame jitter and the impact of data acquisition architecture on the associated disturbances to the acquired record. Frame jitter leads to the same random shift of all samples in an acquired record. It results in errors in the estimates of time intervals, and makes consecutive records slightly incoherent compromising(More)
Proportionality between the ultrasonic wave attenuation coefficient in epoxies and other polymers and frequency is a commonly observed but little understood phenomenon. How it is ultimately explained will depend on the breadth of the frequency range over which it is significant. This paper presents results of experiments to measure loss in a single epoxy(More)
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