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- Boström, Anders E, 1951, et al.
(författare)
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Acoustics of an obstacle inside a reactive silencer
- 1983
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Ingår i: Journal of Sound and Vibration. - 1095-8568 .- 0022-460X. ; 87, s. 603-619
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Tidskriftsartikel (refereegranskat)abstract
- The transmission and reflection coefficients of sound in a cylindrical duct containing several discontinuities are investigated. A building-block method, which gives the transmission and reflection coefficients for a complex system from those of the parts, is applied to bifurcations, sudden area changes with or without extended inlets, and spherical obstacles (which may be lossy). In some cases the solution can be interpreted in terns of multiple reflections. When the length between the discontinuities are small it is important to include also non-propagating modes, and this is especially true when the sudden area change is obtained from the area change with extended inlet in the limit of vanishing inlet. For an expansion chamber (a portion of the duct with a larger radius) with or without an obstacle and with or without inlets a number of numerical results with variation in frequency are presented. Numerical results for the various building-block elements of the expansion chamber are also considered.
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| 2. |
- Nilsson, Holger, 1956, et al.
(författare)
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Extent of structurally reduced venous distensibility in rats.
- 1981
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Ingår i: Clinical science (London, England : 1979). - 0143-5221. ; 61 Suppl 7
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Tidskriftsartikel (refereegranskat)abstract
- 1. Venous pressure--volume relations were studied in maximally vasodilated whole-body preparations after cardiac arrest, as well as in fully vasodilated, perfused hindquarter preparations of spontaneously hypertensive rats (SHR) and normotensive controls. Central venous pressures were measured also in the anaesthetized animals before cardiac arrest. 2. Central venous pressure in intact, anaesthetized SHR was 1.9 +/- 0.20 mmHg compared with 0.75 +/- 0.25 in controls (P less than 0.001). 3. In both preparations SHR showed a nearly 20% reduction in venous compliance, whereas calculated 'unstressed' volumes (volumes at zero transmural pressure) were largely equal in SHR and controls. 4. SHR capacitance vessels thus appear to have a structurally reduced wall distensibility of about 10% with no change in overall size. It probably reflects a structural adaptation to a modest increase of average transmural pressure that also affects the low-pressure side.
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