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This paper introduces an improved image processing method usable in capacitive imaging applications. Standard capacitive imaging tends to prefer amplitude-based images over the use of phase due to better signal-to-noise ratios. The new approach exploits the best features of both types of information by combining them to form clearer images, hence improving both defect detection and characterization in non-destructive evaluation. The methodology is demonstrated and optimized using a benchmark sample. Additional experiments on glass fibre composite sample illustrate the advantages of the technique.

Acoustic metamaterials constructed from conventional base materials can exhibit exotic phenomena such as negative refractive index, extraordinary transmission-absorption and sub-wavelength imaging. These are typically achieved by combining geometrical and resonance effects. Holey-structured acoustic metamaterials have already shown potential for sub-wavelength acoustic imaging in air, where it is relatively simple to achieve the required difference in acoustic impedance needed to create resonances within the holes. However, the use of polymers for metamaterial operation in water is difficult, due to the much lower difference in acoustic impedance between water and the many polymers used, for example, in additive manufacturing. Hence, metals are commonly used. Here we show that this can be overcome by trapping air layers so that they surround each water-filled channel, making sub-wavelength imaging in water possible. The operation of such a Trapped air design is confirmed at 200-300 kHz ultrasonic frequencies via both finite element modelling and experimental measurements in a water tank. It is also shown quantitatively that the trapped air design outperforms its metal counterpart. The results indicate a way forward for exploiting additive-manufacturing for realising acoustic metamaterials in water at ultrasonic frequencies., Comment: 29 pages, 14 figures

This article described an experiment using group procedures as a means of training faculty members and student peer-helpers to conduct student advisement in a college setting with entering freshmen. Results suggested that the group process can assist in overcoming certain limitations of more traditional faculty-student advisement activities by expanding the range of topics and concerns dealt with, utilizing the group process as a partial substitute for professional counseling services, and providing a basic reference group in which students can share ideas, feelings and concerns before they become crises. Group advisement procedures were used as a method of integrating the student personnel and academic functions of the college for the overall benefit of student, faculty, and student personnel administrators. (Author)