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Full-Text Articles in Physical Sciences and Mathematics

Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis Jul 2009

Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis

Faculty of Engineering - Papers (Archive)

An unusual concept for a simple and inexpensive terahertz source is presented: unpeeling adhesive tape. The observed spectrum of this terahertz radiation exhibits a peak at 2 THz and a broader peak at 18 THz. The radiation is not polarized. The mechanism of terahertz radiation is tribocharging of the adhesive tape and subsequent discharge, possibly bremsstrahlung with absorption or energy density focusing during the dielectric breakdown of a gas. The accompanying optical emission is also a consequence of tribocharging.


Strategic Approaches For Management Of Risk In Geomechanics, R. Chowdhury, P. Flentje Oct 2008

Strategic Approaches For Management Of Risk In Geomechanics, R. Chowdhury, P. Flentje

Faculty of Engineering - Papers (Archive)

This paper outlines the challenges facing geomechanics and advocates some strategies for dealing with these challenges. Advancement of geomechanics and its application in the past may be seen in a historical context as serving the needs of society such as the development of infrastructure and natural resources. The needs of society are changing rapidly due to population growth, increasing urbanisation and globalisation. Climate change poses specially challenges, the impacts increasing with time. Therefore, development of new strategies is essential. For example, greater attention should be given to the development of interdisciplinary approaches. It is vitally important that systematic methods be …


Transport And Magnetic Critical Current In Superconducting Mgb2 Wires, J. Horvat, W. K. Yeoh, J. H. Kim, S. X. Dou Jan 2008

Transport And Magnetic Critical Current In Superconducting Mgb2 Wires, J. Horvat, W. K. Yeoh, J. H. Kim, S. X. Dou

Faculty of Engineering - Papers (Archive)

Direct comparison of the magnetic and transport critical current density (Jc) for the same pieces of copper-sheathed MgB2 wires shows a large discrepancy in magnitude and field dependence of the two. The value of magnetic Jc can differ from the value of transport Jc by a factor of 10 or more. This discrepancy does not occur merely because of the difference in the voltage at which the magnetic and transport Jc are measured, but mainly because of the specific microstructure of MgB2. Such microstructure results in superconducting screening on at least two different length-scales, despite the absence of weak links …