31 research outputs found
Underground UHF-EM transillumination : a feasibility study
A feasibility study into the use of UHF-EM transillumination measurements in geophysics is presented. The electrical properties and absorption rates of common crustal materials are examined with the goal of identifying specific conditions under which sufficient material penetration at UHF frequencies is available.A prototype 445 MHz continuous-wave transillumination instrument designed for underground use is described. Test surveys, with this instrument, were conducted at the Big Nickel Mine in Sudbury, Ontario, to obtain a number of through-rock absorption rates. Estimated effective resistivities of between 500 and 1500 ohm-metres are determined from the survey data.Effective conductivities and permittivities from AC and DC electrical property measurements on geological samples from the mine site corroborate these transillumination survey results.The results of the field surveys indicate that the UHF-EM transillumination technique is a feasible and useful geophysical method
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Thickness dependence of piezo-bimorph adaptive mirror bending
A new generation of adaptive x-ray optics (AXO) is being installed on high-coherent-flux x-ray beamlines worldwide to correct and control the optical wavefront with sub-nm precision. These ultra-smooth mirrors achieve high reflectivities at glancing angles of incidence and can be hundreds of mm long. One type of adaptive x-ray mirror relies on piezoelectric ceramic strips which are segmented into channels and actuated to induce local, longitudinal bending, generating one-dimensional shape changes in the mirror substrate. A recently described mirror model uses a three-layer geometry with parallel actuators on the front and back surfaces of a thicker mirror substrate. By analogy to a solved problem in the thermal actuation of a tri-metal strip, we show that the achievable bending radius varies approximately as the square of the substrate thickness. We provide an analytic solution and simulate bending using a finite-element model
Scanning and Transmission Electron Microscopy of Tubular Structures Presumed to be Human Odontoblast Processes
Compositional Analysis of Local Redwares. Characterizing the Pottery Productions of 16 Workshops in Southern Quebec Dating from late 17th to late 19th century
International audienc
Compositional Analysis of Local Redwares. Characterizing the Pottery Productions of 16 Workshops in Southern Quebec Dating from late 17th to late 19th century
International audienc