Measurements of some dielectric and electrolytic properties of pyrex brand glass

Not availabl

On the scattering of torsional elastic waves from axisymmetric defects in coated pipes

This is the post-print version of the Article - Copyright @ 2012 ElsevierLong range ultrasonic testing is now a well established method for examining in-service degradation in pipelines. In order to protect pipelines from the surrounding environment it is common for viscoelastic coatings to be applied to the outer surface. These coatings are, however, known to impact on the ability of long range ultrasonic techniques to locate degradation, or defects, within a coated pipe. The coating dissipates sound energy travelling along the pipe, attenuating both the incident and reflected signals making responses from defects difficult to detect. This article aims to investigate the influence of a viscoelastic coating on the ability of long range ultrasonic testing to detect a defect in an axisymmetric pipe. The article focuses on understanding the behaviour of the fundamental torsional mode and quantifying the effect of bitumen coatings on reflection coefficients generated by axisymmetric defects. Reflection coefficients are measured experimentally for coated and uncoated pipes and compared to theoretical predictions generated using numerical mode matching and a hybrid finite element technique. Good agreement between prediction and measurement is observed for uncoated pipes, and it is shown that the theoretical methods presented here are fast and efficient making them suitable for studying long pipe runs. However, when studying coated pipes agreement between theory and prediction is observed to be poor for predictions based on those bulk acoustic properties currently reported in the literature for bitumen. Good agreement is observed only after conducting a parametric study to identify more appropriate values for the bulk acoustic properties. Furthermore, the reflection coefficients obtained for the fundamental torsional mode in a coated pipe show that significant sound attenuation is present over relatively short lengths of coating, thus quantifying those problems commonly encountered with the use of long range ultrasonic testing on coated pipes in the field

Water waves over a time-dependent bottom: Exact description for 2D potential flows

Two-dimensional potential flows of an ideal fluid with a free surface are considered in situations when shape of the bottom depends on time due to external reasons. Exact nonlinear equations describing surface waves in terms of the so called conformal variables are derived for an arbitrary time-evolving bottom parameterized by an analytical function. An efficient numerical method for the obtained equations is suggested.Comment: revtex4, 7 pages, 19 EPS figures; corrected version with more numerical result

Study of passenger subjective response to ideal and real-vehicle vibration environments

The stimulus received by subjects tested on the passenger ride quality apparatus (PRQA) is defined. Additional analyses on the data collected from field tests using buses, were conducted to assess the relation between subjective ratings of ride quality and vibrations measured on the buses, and to better define the vibration stimulus measured in the field. The relation of subjective evaluation of simulations of bus rides produced by the DRQA to subjective evaluations of the actual bus rides is discussed. The relative contribution of the seat and floor vibration to human comfort in a simulated aircraft ride environment is discussed along with the determination of equal comfort curves through magnitude estimation

Mode-matching without root-finding: Application to a dissipative silencer

This article presents an analytic mode-matching approach suitable for modelling the propagation of sound in a two-dimensional, three-part, ducting system. The approach avoids the need to the find roots of the characteristic equation for the middle section of the duct (the component) and is readily applicable to a broad class of problems. It is demonstrated that the system of equations, derived via analytic mode-matching, exhibits certain features which ensure that they can be re-cast into a form that is independent of the roots of the characteristic equation for the component. The precise details of the component are irrelevant to the procedure; it is required only that there exists an orthogonality relation, or similar, for the eigenmodes corresponding to the propagating wave-forms in this region. The method is applied here to a simple problem involving acoustic transmission through a dissipative silencer of the type commonly found in heating ventilation and air-conditioning (HVAC) ducts. With reference to this example, the silencer transmission loss is computed, and the power balance for the silencer is investigated and is shown to be an identity that is necessarily satisfied by the system of equations, regardless of the level of truncation

Preliminary investigation of effects of exposure to sulfur hexafluoride on tensile and yield strengths of aluminum and steel

Effects of sulfur hexafluoride on tensile and yield strengths of aluminum and steel with application to exhaust gases from rocket engine

A Modified Hypersensitization Procedure for Eastman Kodak I-Z Spectroscopic Plates

Modified hypersensitization procedure for Eastman Kodak I-Z spectroscopic plate

Quasi-planar steep water waves

A new description for highly nonlinear potential water waves is suggested, where weak 3D effects are included as small corrections to exact 2D equations written in conformal variables. Contrary to the traditional approach, a small parameter in this theory is not the surface slope, but it is the ratio of a typical wave length to a large transversal scale along the second horizontal coordinate. A first-order correction for the Hamiltonian functional is calculated, and the corresponding equations of motion are derived for steep water waves over an arbitrary inhomogeneous quasi-1D bottom profile.Comment: revtex4, 4 pages, no figure

Movements of ice in Central Labrador-Ungava

À l'aide d'analyses statistiques de l'orientation des galets dans les formations glaciaires et de l'étude des formes mineures d'érosion glaciaire (roches moutonnées, stries, fissures de pression), l'auteur décrit les modalités de la dernière déglaciation dans la région de Schefferville. — La convergence des formes glaciaires dans cette région est imputable soit au fait qu'elle était, au cours de la dernière glaciation, un centre de dispersion de la glace, soit au fait qu'elle était, lors de la déglaciation, à cause des facteurs topographiques locaux, une zone occupée tardivement par des culots de glace. Ainsi, si l'écoulement de la glace s'effectuait, de façon générale, depuis des directions à composante ouest, ceci n'est pas le cas dans toute la région. Localement, comme aux alentours du lac Kivivic, la morphologie glaciaire se caractérise surtout par des formes de décrépitude créées par des culots de glace au cours des stades finaux de la dernière déglaciation