An experimental study of the transmission characteristics of pressure waves in the aorta

Transmission characteristics of sinusoidal pressure waves in aort

Nondestructive evaluation of wood properties by stress wave spectral analysis

The influence of selected properties on the propagation of stress waves in wood was investigated. Waveform analysis of the stress waves was performed using spectral analysis techhniques developed for stationary random processes. Information analyzed from the stress waves included wave velocity, energy spectra, and the frequency response function. Three wood properties investigated as to their influence on stress waves propagation were grain angle, moisture content, and weight loss caused by decay. Significant relationships between grain angle and the wave properties of velocity, amplitude gain, and total gain were obtained. Significant damping of the stress waves was observed at large grain angles and moisture content values above the fiber saturation point. No significant equations were found for consistent prediction of moisture content. The results of the decay study showed that as weight loss increased, the ratio of energy of the stress wave to that input to the specimen decreased for the perpendicular to grain case. Two approaches toward prediction of wood strength were investigated. The first method employed prediction of wood properties from the stress wave spectral characteristics. Known relationships between these wood properties and strength were then utilized. The second approach involved direct correlation of the stress wave spectral properties with strength. Significant correlatlons with strength were obtained using both approaches. Application of basic results are discussed as to their applicability toward development of an [sic] nondestructive evaluatlon (NOE) procedure for wood poles used in transmission line structures

Dispersion and attenuation of small artificial pressure waves in the aorta

Elastic behavior of canine aortae subjected to small sinusoidal pressure signal

Transcutaneous measurement of volume blood flow

Blood flow velocity measurements, using Doppler velocimeter, are described. The ability to measure blood velocity using ultrasound is derived from the Doppler effect; the change in frequency which occurs when sound is reflected or transmitted from a moving target. When ultrasound of the appropriate frequency is transmitted through a moving blood stream, the blood cells act as point scatterers of ultrasonic energy. If this scattered ultrasonic energy is detected, it is found to be shifted in frequency according to the velocity of the blood cells, nu, the frequency of the incident sound, f sub o, the speed of sound in the medium, c, and the angle between the sound beam and the velocity vector, o. The relation describing this effect is known as the Doppler equation. Delta f = 2 f sub o x nu x cos alpha/c. The theoretical and experimental methods are evaluated

Development of ultrasonic methods of hemodynamic measurements

A pulsed ultrasonic Doppler velocity meter which can be used (by modifying transducers) as a flowmeter for blood circulation was experimentally studied. Calculations and profiles of turbulent and laminar flow within blood vessels are shown. Graphs and charts of transducers are included

Development of ultrasonic methods for hemodynamic measurements

A transcutanous method to measure instantaneous mean blood flow in peripheral arteries of the human body was defined. Transcutanous and implanted cuff ultrasound velocity measurements were evaluated, and the accuracies of velocity, flow, and diameter measurements were assessed for steady flow. Performance criteria were established for the pulsed Doppler velocity meter (PUDVM), and performance tests were conducted. Several improvements are suggested

Transcutaneous measurement of blood velocity profiles and flow

A comprehensive report is presented of the application of a pulsed ultrasound Doppler velocity meter for transcutaneous measurement of time varying velocity, velocity profiles, and instantaneous flow in arteries of anaesthetized dogs. The procedure used to provide direct velocity and flow calibration using the Doppler equation is outlined. Typical transcutaneous recordings obtained from the femoral artery, abdominal aorta, and carotid artery are illustrated. The results compare favourably with data obtained by invasive means such as electromagnetic cuff flowmeters. The possibility of high resolution, non-invasive haemodynamic measurements on dogs is demonstrated and the application to conscious human subjects suggeste