Showing papers on "Pressure measurement published in 1983"

Noninvasive determination of systolic, diastolic and end-systolic blood pressure in neonates, infants and young children: Comparison with central aortic pressure measurements

Abstract: Noninvasive determinations of systolic and diastolic blood pressure using the oscillometric method for pressure measurement were combined with externally recorded axillary pulse tracings to estimate end-systolic pressure in 32 neonates, infants and young children. Results were compared with central aortic pressure measurements made at the time of central aortic catheter placement. Studies were performed in patients aged 1 day to 48 months who weighed 0.9 to 18.1 kg. A wide range of systolic (41 to 141 mm Hg), diastolic (22 to 73 mm Hg) and end-systolic (30 to 111 mm Hg) pressure values were found. The mean absolute pressure differences and percent errors (pressure difference divided by central aortic pressure) were 1.8 mm Hg and 2.5% for systolic, 0.8 mm Hg and 0.8% for diastolic and 1.4 mm Hg and 2.1% for end-systolic pressure. No correlation was noted between percent error and age, weight, heart rate, cardiac index or systemic vascular resistance. The ability to perform reliable noninvasive pressure measurements should prove invaluable for clinical and research purposes. In addition, this method of end-systolic blood pressure determination enables sensitive indexes of left ventricular contractility to be measured noninvasively in small children.

A clinical comparison of subdural screw pressure measurements with ventricular pressure.

Abstract: ✓ Simultaneous recordings of intracranial pressure (ICP) from a single-lumen subdural screw and a ventricular catheter were compared in 10 patients with severe head injury. Forty-one percent of the readings corresponded within the same 10 mm Hg ranges, while 13% of the screw pressure measurements were higher and 46% were lower than the associated ventricular catheter measurements. In 10 other patients, also with severe head injury, pressure measurements obtained with the Leeds-type screw were similarly compared with ventricular fluid pressure. Fifty-eight percent of the dual pressure readings corresponded, while 15% of the screw measurements were higher and 27% were lower than the ventricular fluid pressure, within 10-mm Hg ranges. It is concluded that subdural screws may give unreliable results, particularly by underestimating the occurrence of high ICP.

Field Measurements of Annular Pressure and Temperature During Primary Cementing

Abstract: This paper measures pressure and temperature in the annulus of 7 wells during cementing operations in order to investigate the causes of fluid migration behind the casing after primary cementing. It explains that sensors were attached to the outside of the casing as it was run into each well, and a logging cable, also clamped to the casing, was used to bring data from the sensors to the surface. It was found that pressure in a cement column in a well normally begins to decline shortly after the pumping of the cement is completed; that the effectiveness of applied surface pressure to prevent the pressure decline in cement depends on the rate at which the gel strength of the cement develops; that annular pressure measurements indicate fluid entering the wellbore when the cement pressure drops to pore pressure in a zone and stabilizes at this value before the cement sets; that pressure sensors can detect fluid communication in the annulus when the well is perforated, squeeze cemented, or acidized; that the top of cement at the completion of pumping can be estimated from pressure data; that the volume of mud bypassed by the cement can approximate the volume of themore » hole in excess of bit size; that the time of the final setting of the cement at different depths in a well can be detected by annular temperature measurements; and that cement generally sets from the bottom of the wellbore upward.« less

Seven-hole cone probes for high angle flow measurement Theory and calibration

Abstract: A non-nulling seven-hole conical pressure probe capable of measuring flow conditions at angles up to 75 deg relative to its axis is described. The theoretical rationale of the seven-hole probe is developed and the calibration procedure outlined. Three-variable third-order polynomial functions are used to represent local values of relative flow angles, total pressure, and total minus static pressure. These flow properties are determined explicitly from measured probe pressures. Flow angles are determined within 2.5 deg and Mach number within 0.05 with 95% certainty. The probe can be used in subsonic compressible and incompressible flows.

Measurement of the eardrum impedance of human ears

Abstract: The determination of an acoustical impedance requires measurements of pressure and volume velocity. As no direct method is available for measuring velocity in an ear canal, a technique was developed which is based on pure pressure measurements. The ear canal is used as a measuring tube, the area function of which is also deduced from the pressure measurements. High-frequency measurements in living subjects involve many sources of errors. A criterion for deciding if a good measurement has been made is given. The technique of measurements is described, regarding both the use of probe tube microphones and the computer aided data recording. Finally, the results are presented, and some comments are given. A reliable interpretation of the results seems to be impossible because of lack of our knowledge of the middle ear function at high frequencies.

Pressure measurements on twin vertical tails in buffeting flow

Abstract: Buffeting pressures were measured on the vertical tail surfaces of a 13% F-15 model in a low-speed wind tunnel. Test variables included dynamic pressure, aircraft angle of attack, vertical tail incidence, and rudder deflection. Pressure transducers were flush mounted on rigid and flexible tails. Steady and unsteady pressures were obtained from the transducers at levels as low as 0.1% full scale. The steady pressures were integrated for aerodynamic coefficients and the unsteady pressures were reduced to spectral densities. The pressures are maximum at approximately 22 deg angle of attack and are significantly affected by tail flexibility.

Innovative Air Data System for the Space Shuttle Orbiter

Abstract: The Shuttle entry air data system (SEADS) embodies a flush orifice concept, where, in principle, the Orbiter fuselage functions both as a pitot-static probe and as a differential pressure flow direction sensor. The surface pressure distribution is sampled at an array of orifices on the Orbiter forebody. A digital batch filter, based on a minimum variance criterion, is used to fit a mathematical pressure model to the measured pressures. Forebody pressures are modeled as functions of a four-dimensional "aerodynamic state vector." The filter optimizes the state vector estimate from which standard air data parameters are then derived. Results from simulations, wind tunnel, and flight tests are presented.

High‐frequency temperature and pressure probe for unsteady compressible flows

Abstract: A 3‐mm‐diam, dual hot‐wire aspiring probe is described which can simultaneously measure total temperature and total pressure in an unsteady high‐speed gas flow. The probe consists of two coplanar constant temperature hot wires at different overheat ratios operated in a 1.5‐mm‐diam channel with a choked exit. Thus, the constant Mach number flow by the wires is influenced only by free‐stream total temperature and pressure. The probe design is a compromise between the conflicting requirements of spatial resolution, frequency response, and angular sensitivity. The dc temperature accuracy of the probe is about 1% while the resolution is 0.3%. Frequency response of the present design is dc to 20 kHz.

Differential absorption lidar technique for measurement of the atmospheric pressure profile.

Abstract: A new two-wavelength lidar technique for remotely measuring the pressure profile using the trough absorption region between two strong lines in the oxygen A band is described. The theory of integrated vertical path, differential ranging, and horizontal-path pressure measurements is given, with methods to desensitize and correct for temperature effects. The properties of absorption troughs are described and shown to reduce errors due to laser frequency jitter by up to two orders of magnitude. A general analysis, including laser bandwidth effects, demonstrates that pressure measurements with an integrated-vertical-path technique are typically fifty times more accurate than with a differential ranging technique. Simulations show 0.1-0.3 percent accuracy for ground and Shuttle-based pressure-profile and surface-pressure experiments.

Gold as a reliable internal pressure calibrant at high temperatures

Abstract: Energy‐dispersive x‐ray diffraction measurements on a mixture of powdered NaCl and Au were carried out at high temperatures up to 600 °C (at atmospheric pressure) and also at simultaneously high temperatures and high pressures (to 425 °C and 10.2 GPa). A modified diamond‐anvil high pressure cell with a mini resistance‐wire heater was used in conjunction with the synchrotron radiation at the Stanford Synchrotron Radiation Laboratory. The temperature of the sample was measured directly by a precalibrated Pt‐Pt 10% Rh thermocouple adjacent to the sample. The pressure of the sample was determined by measuring the molar volume changes in NaCl and deriving the pressure through an equation of state. The measured thermal expansion from 25 °C up to 600 °C for NaCl and Au at 1 atm can be expressed by second‐order polynomials: V/V0(NaCl)=1+(1.08±0.05)×10−4 (T−25)+(7.5±1.1)×10−8 (T−25)2 and V/V0(Au) =1+(4.26±0.85)×10−5 (T−25)+(5.0±20)×10−9 (T−25)2, where T is in °C. These results are in excellent agreement with previ...

Piezoelectric transducer notably for pressure measurement

Abstract: In a pressure transducer of the piezoelectric type, a resonator (10) is made up of a pellet (16) mounted inside an element designed to be subjected to the action of a pressure on its exterior face (18). The pellet (16) and the element (12) are cut in the same quartz block, using a cut which provides two vibration modes. The forces resulting from the external pressure are transmitted to the edge of the pellet (16) by connecting bridges (22, 23) whose orientation is chosen so that one of the vibration modes has maximum sensitivity to the forces while the other mode has a practically zero sensitivity.

A system for measurements of micturition urethral cross-sectional areas and pressures.

Abstract: A system for the measurement of urethral urinary stream cross-sectional areas and pressures is described. The system consists of: (1) A 4 French gauge probe with electrodes for the electrical impedance measurement of cross-sectional areas and side-holes for pressure measurements (2) an electrical field generator and impedance detecting section and (3) a side-hole perfusion and pressure measuring part.

Reflection from elastic discontinuities

Abstract: Elastic mismatching is studied by an impulse technique. Elastic mismatches are created by joining two latex rubber tubes of the same internal diameter but different wall thickness. A short duration pressure impulse is generated at the entrance of the water-filled tube system and the transmission characteristics of the impulse are determined from a series of measurements along the tube system using a catheter-tip pressure manometer. This technique enables the magnitude and phase change of the reflection at the elastic discontinuity to be obtained. A number of tube combinations are examined and in all cases a good agreement is shown between the measured reflection coefficient and the value calculated theoretically.

Dynamic-pressure measurements using an electronically scanned pressure module

Abstract: Frequency response was measured for different lengths and diameters of tubing between a sinusoidal pressure source and a pressure sensing module from an electronically scanned pressure measuring system. Measurements were made for straight runs of both steel and vinyl tubing. For steel tubing, measured results are compared with results calculated by using equations developed by Tijdeman and Bergh. Measurements were also made with a bend in the vinyl tubing at the module. In addition, measurements were made with two coils placed in the tubing near the middle of the run.

Unsteady Three-Dimensional Turbine Aerodynamics

Abstract: High response aerodynamic measurements were made in a large scale, axial, flow turbine model to study the unsteadiness and three dimensionality of the flow. High response velocity vector and total pressure data were acquired. A comparison was made of the results of phase lock, averaging both raw and reduced data (voltages and velocities). The velocity vector measurements showed that there were strong radial flows present as well as significant periodic changes in the flow field due to relative rotor and vane positions. Random, periodic, and total unsteadiness levels were computed from the instantaneous and phase lock averaged velocity data. Time averaged data were compared with an inviscid two-dimensional calculation. A comparison was also made of time averaged total pressure measurements obtained from high response and low response (steady-state) probes.Copyright © 1982 by ASME

Accurate determination of the vapor pressure of potassium using optical absorption.

Abstract: The vapor pressure of potassium has been measured in absorption using a CW tunable laser and calibrated against the accurate radiative lifetime of the 4s-4p doublet of potassium. An accurate value of 20,850 + or - 30 cal/mol for the heat of vaporization (from the liquid phase) at the melting point was determined.

Nonintrusive Pressure Measurements with Laser-Induced Iodine Fluorescence

Abstract: Laser-induced fluorescence from iodine molecules seeded into a flowfield is shown to provide the capability for the nonintrusive measurement of pressure with both spatial and temporal resolution. It is shown theoretically that, in the limit of high pressure, fluorescence from iodine, excited at linecenter by a tunable, narrow-band­ width laser, is inversely proportional to pressure and insensitive to other flowfield variables. The high­ pressure limit is shown to apply for pressures greater than about 150 Torr in an iodine-seeded flowfield. Data col­ lected in a static cell and in an underexpanded-jet flow­ field verify the theoretical prediction. A photographic negative is shown to record two-dimensional pressure distributions directly when exposed by fluorescence from a sheet of laser radiation. Iodine transitions which are optimum for pressure measurement and accessible with a tunable dye laser are identified. The effect of fluid velocity on the linecenter fluorescence signal is evalu­ ated. Preliminary measurements in a non-steady flow demonstrate that the technique can be used to resolve pressure fluctuations on the order of 1% at frequencies up to a few kHz with good spatial resolution.

Multicolor laser altimeter for barometric measurements over the ocean: theoretical.

Abstract: It is noted that the optical path length from a satellite to the earth's surface strongly depends on the atmospheric pressure along the propagation path. The theoretical basis of a surface pressure measurement technique, which uses a two-color laser altimeter to observe the change with wavelength in the optical path length from a satellite to the ocean surface, is evaluated. The statistical characteristics of the ocean-reflected pulses and the expected measurement accuracy are analyzed in terms of the altitude parameters. The results show that it is feasible to obtain a pressure accuracy of a few millibars.

Abnormal treating pressures in MHF treatments

Abstract: Abnormal treating pressures are observed during massive hydraulic fracturing (MHF) treatments in the Mesa Verde formation of the Piceance Basin, Colorado. Data from three widely separated wells and in several zones per well all show a pressure increase during MHF treatments which the authors call ''pressure growth''. This pressure growth is at least semi-permanent. The elevated instantaneous shut-in pressures do not return to initial values over periods of several days. The magnitude of this pressure growth is highly variable. When its value is less than about 2300 psi the MHF treatments are usually completed and results are obtained which are within normal expectations. When its value exceeds 2300 psi, sandout occurs and the fracture length estimated from production data is much less than that calculated using crack propagation models. Temperature logs indicate little or only modest vertical extension of the fractures above the perforations. These data, along with sandouts, point to a large increase in width of the fractures in response to pressure growth. One possible cause of pressure growth is fracture branching. A multiplicity of branches could produce a plastic-like effect. Laboratory measurements have ruled out plasticity as the cause. The stress-strain behavior of the rock is similar tomore » that of rocks where no pressure growth occurs. Pressure growth seems to be dependent on both pumping rate and fluid viscosity. Thus, there is some hope for its mitigation through treatment design. Also, pressure growth appears to correlate negatively with pay zone quality. This suggests that the phenomenon can be exploited as a fluid diversion technique.« less

The Real-Time Calculation of Accurate Bottomhole Fracturing Pressure From Surface Measurements Using Measured Pressures as a Base

Abstract: This paper stresses the importance of a knowledge of bottomhole pressure behavior to the mechanics and control of hydraulic fracturing. It discusses the implementation of a reference string for purposes of pressure measurement and lists the hazards such a string confronts and also poses for injection fluids such as crosslinked gels. It presents methods for forecasting bottomhole pressure behavior which take into account the injection rate, sand concentration, and base gel friction, and a method for sensing and averaging these data quite rapidly.

Combined pressure gauge-transmitter

Abstract: A Bourdon tube adapted for connection to a source of fluid pressure operates both a mechanically driven gauge pointer and an optical-electronic transmitter for providing operatively parallel output signals corresponding to values of pressure incurred by the fluid source. Simultaneously operative from the displaceable end of the Bourdon tube are both a mechanical movement for effecting amplified displacement of the pointer relative to a dial plate and an opaque vane displaceable within the transmitter between a photoemitter and a pair of photosensors. Circuitry in the transmitter responsive to discrete changes in light interruption between the vane and one of the photosensors emits a signal current corresponding to the pressure value at any given position of the vane.

Cross spectra between temperature and pressure in a constant area duct downstream of a combustor

Abstract: The feasibility of measuring pressure temperature cross spectra and coherence and temperature-temperature cross spectra and coherence at spatially separated points along with pressure and temperature auto-spectra in a combustion rig was investigated. The measurements were made near the inlet and exit of a 6.44 m long duct attached to a J-47 combustor. The fuel used was Jet A. The cross spectra and coherence measurements show the pressure and temperature fluctuations correlate best at low frequencies. At the inlet the phenomena controlling the phase relationship between pressure and temperature could not be identified. However, at the duct exit the phase angle of the pressure is related to the phase angle of the temperature by the convected flow time delay.

Measurement of interface pressures

Abstract: Sustained or elevated pressures acting on the skin and superficial tissues are a major factor in the initiation of pressure sores. Numerous devices have been developed to measure the interface pressure between patients and support surfaces. Some of the more successful devices are described and their suitability for research and clinical use critically examined. It is suggested that simple inflatable sensors are suitable for routine clinical use. The clinical importance and usefulness of pressure measurements is discussed.

Nonintrusive pressure measurement

Abstract: Pressure within a cylindrical shell (10) is measured by generating acoustic waves in the shell in a manner which minimizes the propagation of any appreciable vibrational energy to its mechanical supports. The mode of the generated vibration is chosen from among the banded resonance vibrations which can be generated in a cylindrical shell (10), the chosen banded resonance having an even number of longitudinally extending nodes parallel to the portion of the shell within which the vibration exists. Stress variation in the cylindrical shell due to the contained pressure causes a change in the banded resonant frequency which is monitored as a measure of the pressure.

The frequency response of external transducer blood pressure measurement systems: a theoretical and experimental study

Abstract: An electrical transmission line model of the class of blood pressure measurement systems that consists of a needle, or cannula, a manometer line and a transducer, is described. Transducer compliance and manometer line compliance and hysteresis losses of systems have been determined experimentally, and viscous resistance and inertance components have been calculated. Correlations between observed and theoretical frequency responses, predicted using these parameters, have shown the theory to be adequate to at least 100 Hz. The model is a useful tool for predicting the best frequency response that may be expected of a particular measurement system.

Resistor network simulation method for a vacuum system in a molecular flow region

Abstract: A simulation method to obtain the pressure distribution in a complex vacuum system has been proposed. The method introduces a new concept with regard to the function of each component of the vacuum system. The vacuum pump is regarded as a ‘‘vacuum resistor’’ connected at one side to the perfect vacuum. The gas source is regarded as a pressure generator connected to the vacuum. The conducting pipe is regarded as a vacuum resistor between the above elements. The vacuum sides of the pump element and the gas source element are assumed to be connected together by an imaginary route, and thus the vacuum system can be regarded as a closed vacuum circuit network. Such a vacuum circuit network may be replaced by an electric circuit network of a simulator for the vacuum system. The simulator was employed for the high vacuum system of an electron microscope in order to obtain the pressure distribution. The results obtained were in good agreement with the actually measured pressure distribution.