Generation Of Pressure Pulses Research Articles

Cross-correlation between vagal afferent impulses from pulmonary mechanoreceptors and high-frequency inflation (HFI) and deflation (HFD) in rabbits

The effects of high-frequency airway inflation (HFI) and high-frequency airway deflation (HFD) generated by a triangular pressure pulse generator on pulmonary mechanoreceptors were examined. The cross-correlograms between vagal afferent impulses from the slowly adapting (SAR) and the rapidly adapting receptors (RAR) and the HFI or the HFD pulses were analysed. HFI stimulated SAR and RAR and HFD stimulated RAR, but inhibited SAR. The time lag of the mode in the correlogram between SAR and HFI was shorter than that of the mode in the correlogram between RAR and HFI. The span of the mode and the trough of SAR was shorter than the span of the mode of RAR. This may indicate that the time to peak of the generator potential of RAR is longer than that of SAR.

An investigation into the breaking-down of water-in-oil type emulsions by means of pulsed voltage

Demulsification by means of a high pressure pulse generator is superior to demulsification by an AC generator. For the emulsions used in liquid membrane separation, we found that when the frequency used was 500 Hz, demulsification was carried out more efficiently than when the frequency was 50 Hz. High-speed photography showed the coalescing time to be less than 1 1500 s. It was also observed that water droplets in emulsions have an inherent vibration and this is believed to promote the coalescence of the particles.

Study on the High Pressure Generation by Means of Oil Hammer : 1st Report, Fundamental Properties of Repeated High Pressure Generator

A technique of hydraulic pressure pulse series generation by means of oil hammer is discussed. It is confirmed experimentally that a stable pressure pulse series can be obtained in a pipe, one end of which is attached to a rotary valve which controls a flow to be periodically off and on. The results of numerical calculation show good agreement with the experimental results. The pulse pressure is amplified by a booster piston, and the amplified pressure in the booster chamber runs up to about 140MPa at a frequency of 15.2Hz. It is expected that the frequency of the pulse series can be heightened by adopting a shorter pipe and the pulse pressure can be raised by increasing the amplifing ratio of the booster piston. The technique of pressure pulse generation applying an oil hammer is practical enough for generating a high frequency and high pressure pulse series.

Response of Liquid Lithium Layers to Neutron and X-Ray Pulses

Many inertial confinement fusion reactors will employ liquid lithium to breed tritium, to remove heat from reactor vessels, and to protect the interior walls of the vessel. Heat loads on the liquid lithium will consist of intense pulses that are short in comparison to hydrodynamic and thermal relaxation times and therefore will generate pressure pulses and/or pressure waves. The generation process is investigated analytically and numerically. Analytic solutions are derived for liquid blankets with thicknesses comparable to the neutron energy deposition depth contained between two structural shells and for free surface layers with thicknesses much smaller than the depth of neutron energy deposition. Results indicate that the amplitudes of the neutron-generated pressure waves are comparable to the mean pressure rise that would be obtained if the energy were deposited so slowly and uniformly that the waves did not develop. Numerically investigated are pressure pulses in lithium layers, which are initially at the vapor pressure. Results indicate that rapid heating occurs at constant specific volume (isochorically) and therefore results in a sharp and intense pressure rise. However, the resulting pressure wave dissipates after propagating only a few millimetres through the layer if the lithium contains any fraction of the vapor phase.

Fluid actuated acoustic pulse generator

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Analysis of Pressure Pulse Generation Due to Gas Release from Failed Fuel Pins in a Liquid-Metal Fast Breeder Reactor

A model for the analysis of pressure pulse generation due to sudden gas release from failed pins in a liquid-metal fast breeder reactor is presented. The predictions of the model are compared to experimental data on sudden gas release in the ducts of the Experimental Breeder Reactor II. The predicted magnitudes of pressure pulses are in good agreement with the experimental observations. The predicted pressure pulse, however, seems to decay at a faster rate than the experimentally observed rate. The effects of the pin internal pressure upon rupture, the rupture area, and the amount of compressed gas are studied parametrically. The pressure pulse magnitude is found to be more sensitive to the internal pin pressure upon rupture than to either the rupture area or the compressed gas volume.

Interaction of aortic and carotid sinus baroreceptors: effect of activation times.

Changes in pulse-wave velocity were simulated by changing the relative timing between aortic and carotid sinus barorecptor activity in anesthetized rabbits and dogs. In the rabbit, electrical stimulation was used to vary the timing; in the dog, it was also varied by perfusing the carotid sinuses with externally generated pressure pulses that could be triggered in any portion of the cardiac cycle. Changing the relative delay between aortic and carotid sinsus nerve stimulation did not result in variations of blood pressure or heart rate in the rabbit. Varing the time of electrical stimulation of the carotid sinus nerve caused at most 5 mmHg change of blood pressure in the dog. Delay-related heart-rate changes could be usually observed only when the stimulus consisted of short, high-intensity bursts. When the carotid sinus was externally perfused with pulses of pressure, only one out of five dogs showed delay-related variations in blood pressure (3mmHg) and heart rate (6 beats/min). It is concluded that variations in pulse-wave velocity are unlikely to play a significant role in acute cardiovascular control.

Transient Pressure Attenuation by Nonlinear, Resilient, Cylindrical Scatterers

Temporal convolution techniques [T. L. Geers, J. Acoust. Soc. Amer. 51, 1640–1651 (1972)] are used to obtain solutions for the problem of transient acoustic scattering by nonlinear cylindrical scatterers. These scatterers behave like cavities during the initial stages of motion, but then offer increasing dilatational resistance with increasing deformation. In contrast to the results of previous studies [M. L. Baron, J. Appl. Mech. 24, 501–505 (1957) and J. Appl. Mech. 28, 135–136 (1961)], it is found that such “modified cavities” are indeed capable of effective transient pressure attenuation in the surrounding fluid without the generation of unacceptable pressure pulses at later times. Parameter studies for plane, step-exponential incident waves are performed to establish suitable ranges for the modified cavity stiffness parameters.

Assisted circulation: The pressure pulse generator

Assisted circulation: The pressure pulse generator

An assisting computerized pulse generator

A new hydraulically actuated pressure pulse generator has been developed with very fast response times, along with a new blood-handling pump in which inertial losses are balanced against the pressure drops. This has lowered the hemolysis of blood to a great extent. The servomechanism along with an automated control system, which has combined nine circulatory variables, has enabled this null timing point to be achieved, cycle after cycle. Thus, postsystolic myocardial augmentation can be achieved in determinable fashion and pressure work load of the heart can be lowered.

POSTSYSTOLIC MYOCARDIAL AUGMENTATION: CLINICAL APPLICATIONS UTILIZING THE PRESSURE PULSE GENERATOR.

THE DEMONSTRATION of the importance of accurate phasing in an arterioarterial system where the attempt is made to reduce the pressure-work load of the heart by withdrawing blood during the natural systole and reinjecting it during diastole was made in 1960 with the development of postsystolic myocardial augmentation.1,2The theoretical, experimental, and clinical results obtained with the apparatus originally described have been so encouraging that now a completely automated system has been devised. Theory of Operation The pressure pulse generator is a device to generate a repetitive pulsatile pressure pulse wave. The timing of the pressure pulse wave is electronically controlled to maintain a precise phase relationship with the natural pulse pressure from the heart. During cardiac systole the heart ejects blood from the left ventricle into the aorta; in this action the heart exerts force to overcome the resistance to flow in the arterial tree. Under circumstances where