Determination of wave intensity in flexible tubes using measured diameter and velocity

Wave intensity analysis (WIA) was introduced 25 years ago for the study of arterial wave travel and has since been established as a powerful tool for the investigation of cardio-vascular interaction. Despite the complex mathematical derivation of the method, the implementation is simple. As a time-domain technique, WIA enables the direct association between waves and events during the cardiac cycle. Furthermore, it enables the separation of the pressure (or diameter), velocity and wave intensity waveforms into their forward and backward components, and provides a means for the determination of the timing and magnitude of waves of different origins. Hemodynamic questions at several locations along the vascular tree have been investigated with WIA. Part 2 of this review will focus on the physiological and clinical findings to which WIA has contributed, through clinical and in vivo studies in the ventricles and in the coronary and carotid arteries.

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An Investigation Into the Post-Stable Behavior of a Tube Array in Cross-Flow

Journal of Pressure Vessel Technology ◽

10.1115/1.3265704 ◽

1989 ◽

Vol 111 (4) ◽

pp. 457-465

Author(s):

J. H. Lever ◽

G. Rzentkowski

Keyword(s):

Flow Velocity ◽

Cross Flow ◽

Elastic Stability ◽

Critical Flow Velocity ◽

Tube Arrays ◽

Pitch Ratio ◽

Velocity Increments ◽

The Subject ◽

Flexible Tubes

In the experimental determination of fluid-elastic stability thresholds in tube arrays, the critical flow velocity is normally approached from below. Once large amplitude whirling motions are initiated, however, the system often does not retrace the response curve as flow velocity is reduced. This hysteresis behavior has been the subject of a recent investigation utilizing a newly constructed wind tunnel facility at Memorial University. The post-stable response of a 1.375-pitch ratio parallel triangular array was first generated under steady flow conditions, with positive velocity increments to just beyond the threshold, then velocity reductions in steps back to stable amplitude levels. It was found that an array with 7 central flexible tubes displayed a fairly broad hysteresis loop, while the same array with only a single flexible tube displayed no hysteresis. The transition from steady stable response levels to steady unstable response levels was then investigated using two types of transient excitation: tube displacement and flow velocity. The effect of increasing tube damping was also investigated.

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Using wave intensity analysis to determine local reflection coefficient in flexible tubes

Journal of Biomechanics ◽

10.1016/j.jbiomech.2016.06.004 ◽

2016 ◽

Vol 49 (13) ◽

pp. 2709-2717 ◽

Cited By ~ 7

Author(s):

Ye Li ◽

Kim H. Parker ◽

Ashraf W. Khir

Keyword(s):

Reflection Coefficient ◽

Wave Intensity ◽

Intensity Analysis ◽

Wave Intensity Analysis ◽

Flexible Tubes

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Galactic orbits of stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900105340 ◽

1966 ◽

Vol 25 ◽

pp. 93-97

Author(s):

Richard Woolley

Keyword(s):

Globular Cluster ◽

Potential Field ◽

High Velocity ◽

Velocity Vector ◽

Variable Stars ◽

The Sun ◽

Proper Motions ◽

Rr Lyrae ◽

The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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Distance to SN 1987A and the LMC

Symposium - International Astronomical Union ◽

10.1017/s0074180900118959 ◽

1999 ◽

Vol 190 ◽

pp. 549-554

Author(s):

Nino Panagia

Keyword(s):

Angular Size ◽

Large Magellanic Cloud ◽

Magellanic Cloud ◽

Light Curves ◽

Distance Modulus ◽

Absolute Size ◽

Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

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International determination of the total motion of the pole

Symposium - International Astronomical Union ◽

10.1017/s0074180900177824 ◽

1961 ◽

Vol 13 ◽

pp. 29-41

Author(s):

Wm. Markowitz

Keyword(s):

Secular Motion ◽

The Future

A symposium on the future of the International Latitude Service (I. L. S.) is to be held in Helsinki in July 1960. My report for the symposium consists of two parts. Part I, denoded (Mk I) was published [1] earlier in 1960 under the title “Latitude and Longitude, and the Secular Motion of the Pole”. Part II is the present paper, denoded (Mk II).

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Time and Latitude in South Africa

International Astronomical Union Colloquium ◽

10.1017/s0252921100026816 ◽

1972 ◽

Vol 1 ◽

pp. 27-38

Author(s):

J. Hers

Keyword(s):

South Africa ◽

Cape Town ◽

Astronomical Observations ◽

Royal Observatory ◽

The Republic ◽

Astronomical Determination ◽

Limited Accuracy ◽

Better Than

In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.

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