A noncontact ultrasonic platform for structural inspection

Miniature robotic vehicles are receiving increasing attention for use in nondestructive testing (NDE) due to their attractiveness in terms of cost, safety, and their accessibility to areas where manual inspection is not practical. Conventional ultrasonic inspection requires the provision of a suitable coupling liquid between the probe and the structure under test. This necessitates either an on board reservoir or umbilical providing a constant flow of coupling fluid, neither of which are practical for a fleet of miniature robotic inspection vehicles. Air-coupled ultrasound offers the possibility of couplant-free ultrasonic inspection. This paper describes the sensing methodology, hardware platform and algorithms used to integrate an air-coupled ultrasonic inspection payload into a miniature robotic vehicle platform. The work takes account of the robot's inherent positional uncertainty when constructing an image of the test specimen from aggregated sensor measurements. This paper concludes with the results of an automatic inspection of a aluminium sample

Zur Berechnung der Matrizen beim Wasserstoffatom

Für die Matrixkomponenten der Koordinaten x, y, z sind von P. Epstein für das Wasserstoffatom hei Separation in Polar- und parabolischen Koordinaten (Zeeman- und Starkeffekt) allgemeine Formeln aufgestellt worden, die im folgenden auf einfache Weise (auch bei Berücksichtigung des kontinuierlichen Spektrums) abgeleitet werden sollen

Some diseases involving the eye and the skin

Diseases involving the skin and the eye are so numerous that only certain selected aspects can be considered here. For a complete list the reader is rejerred to a review by Beerman et al.' Those abnormalities to be discussed here. and which may present to ophthalmologists, are divided into two broad groups: (a) skin conditions that may be limited to the eye and eyelids, and (b) systemic diseases with skin and eye manifestations

Simulation of ultrasonic lamb wave generation, propagation and detection for an air coupled robotic scanner

A computer simulator, to facilitate the design and assessment of a reconfigurable, air-coupled ultrasonic scanner is described and evaluated. The specific scanning system comprises a team of remote sensing agents, in the form of miniature robotic platforms that can reposition non-contact Lamb wave transducers over a plate type of structure, for the purpose of non-destructive evaluation (NDE). The overall objective is to implement reconfigurable array scanning, where transmission and reception are facilitated by different sensing agents which can be organised in a variety of pulse-echo and pitch-catch configurations, with guided waves used to generate data in the form of 2-D and 3-D images. The ability to reconfigure the scanner adaptively requires an understanding of the ultrasonic wave generation, its propagation and interaction with potential defects and boundaries. Transducer behaviour has been simulated using a linear systems approximation, with wave propagation in the structure modelled using the local interaction simulation approach (LISA). Integration of the linear systems and LISA approaches are validated for use in Lamb wave scanning by comparison with both analytic techniques and more computationally intensive commercial finite element/difference codes. Starting with fundamental dispersion data, the paper goes on to describe the simulation of wave propagation and the subsequent interaction with artificial defects and plate boundaries, before presenting a theoretical image obtained from a team of sensing agents based on the current generation of sensors and instrumentation

A note on tidal friction

The Moon\u27s gravitational torque on the ocean tide has been computed on the basis of Dietrich\u27s cotidal charts. The result is -4.5 × 1023 dynes cm as compared to Heiskanen\u27s (1921) value of -2.9 × 1023 dynes cm based on Sterneck\u27s (1920) charts. Both values are subject to great uncertainty. The observed deceleration of the Moon implies a torque of (-3.9 ± 1.0) × 1023 dyne cm, which is consistent with both foregoing calculations. It is concluded that the deceleration of the Moon\u27s orbital motion and the associated deceleration of the Earth\u27s rotation may be due to oceanic tidal dissipation...

Canadian railway museums and visitor attraction

Canadian museums with operating railways constitute special places, and over the past five years they have seen a marked increase in historic preservation work. If this work is to continue these museums, run by volunteer organizations, must be able to increase the numbers of visitors to their sites. Two research questions were investigated, one more objective and scientific, the other more subjective and humanistic: How do such special places function, especially with respect to their market area? And, what sort of sense of place do they create? The first question considers what draws visitors initially; the second question, what brings them back. The data was gathered through inspection and interviews at six major operating railway museums across Canada. It was found that museums divided into two groups. Type A museums have a “tourist” market area, while type B museums are used by day-trippers. Visitors, too, divide into two groups. One group comprises the hands-on, rail-buff types whereas the other group consists mainly of those who appreciate history and museums. The findings of this study have both applied and theoretical aspects. By determining the major factors that influence and motivate visitors, the museums should be able to attract more people and become more viable. By investigating short-term visits, our understanding of place and sense of place is expanded

Temperature and Magnetic Field Dependencies of Condon Domain Phase in Lifschitz-Kosevich-Shoenberg Approximation

The temperature and magnetic field behavior of non-uniform diamagnetic phase of strongly correlated electron gas at the conditions of dHvA effect is analyzed. It is shown, that in the framework of Lifschitz-Kosevich-Shoenberg approximation the magnetic induction splitting, as well as the range of existence of Condon domains, are characterized by strong dependencies on temperature, magnetic field and impurities of the sample.Comment: 7 pages, 7 figure

Synthetic aperture guided wave imaging using a mobile sensor platform

This oral session at conference looks at synthetic aperture guided wave imaging using a mobile sensor platfor