162,283 research outputs found
Vibrational wavenumber analysis of a fluid-filled pipe in an elastic medium for leak detection
No full textWavenumber prediction and measurement of axisymmetric waves in buried fluid-filled pipes: inclusion of shear coupling at a lubricated pipe/soil interface
No full textAcoustic methods have been widely used to detect water leaks in buried fluid-filled pipes, and these technologies also have the potential to locate buried pipes and cables. Relatively predictable for metal pipes, there is considerably more uncertainty with plastic pipes, as the wave propagation behaviour becomes highly coupled between the pipe wall, the contained fluid and surrounding medium. Based on the fully three-dimensional effect of the surrounding soil, pipe equations for n=0 axisymmetric wave motion are derived for a buried, fluid-filled pipe. The characteristics of propagation and attenuation are analysed for two n=0 waves, the s=1 wave and s=2 wave, which correspond to a predominantly fluid-borne wave and a compressional wave predominantly in the shell, respectively. At the pipe/soil interface, two extreme cases may be considered in order to investigate the effects of shear coupling: the “slip” condition representing lubricated contact; and the “no slip” condition representing compact contact. Here, the “slip” case is considered, for which, at low frequencies, analytical expressions can be derived for the two wavenumbers, corresponding to the s=1 and s=2 waves. These are both then compared with the situations in which there is no surrounding soil and in which the pipe is surrounded by fluid only, which cannot support shear. It is found that the predominant effect of shear at the pipe/soil interface is to add stiffness along with damping due to radiation. For the fluid-dominated wave, this causes the wavespeed to increase and increases the wave attenuation. For the shell-dominated wave there is little effect on the wavespeed but a marked increase in wave attenuation. Comparison with experimental measurements confirms the theoretical finding
Special issue "Culture and Cognition". Cognitive Neuroscience
No full textThere is increasing interest in the nature and both environmental and cognitive origins of culturally associated differences in a range of behaviors. This special issue of Cognitive Neuroscience presents six empirical papers investigating diverse categories of potential culturally related effects as well as a review article, all of which provide timely updates of the current state of knowledge in this area
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Axisymmetric wave propagation in fluid-filled pipes: wavenumber measurements in in-vacuo and buried pipes
No full textDetection of water leaks in buried distribution pipes using acoustic methods is common practice in many countries. Correlation techniques are widely used in leak detection, but for these to be effective, the propagation wave speeds and wave attenuation must be known. Relatively predictable for metal pipes, these are largely unknown for the newer plastic pipes, being highly dependent on the pipe wall properties and the surrounding medium. In a previous paper a theoretical model of a buried fluid-filled pipe to predict both wavespeed and attenuation was presented; the aim of the work in this paper is to validate this model experimentally. Wavenumber measurements, encompassing both wavespeed and wave attenuation are made on a water-filled pipe in vacuo and on a buried water-filled pipe. In general, the measurements show good agreement with the theoretical predictions
Lumbar spine motion palpation compared with objective interverteral motion analysis: preliminary findings
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Murder on the mountain: author talk with Peter J. Wosh
No full textAuthor talk by Peter J. Wosh on May 5th, 2022, on his book, "Murder on the Mountain: crime, passion, and punishment in gilded age New Jersey.
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