Showing papers on "Pressure measurement published in 1975"

Abnormal Formation Pressure

Abstract: Abnormal formation pressure requires a seal; without a seal pressures would equalize to normal hydrostatic. Abnormal pressures originate from several interrelated processes, but temperature change appears to be the principal cause. Both epeirogenic movements with associated erosion and deposition and long-term changes in climate can alter the temperature of a sealed formation at depth. Abnormal pressure resulting from temperature change caused by change of overburden thickness must be corrected for inherited pressure and change of hydrostatic pressure related to elevation difference. Osmosis, precipitation, or solution by trapped pore fluid and carbonization effects are minor in comparison with temperature effects. Overburden stress cannot cause abnormally high pressure at present drilling depths. The loss of porosity with depth in all sedimentary rocks appears to be a chemical process rather than mechanical compression. Pressure differentials between wells may indicate ambiguously either no fluid flow (wherein the pressure difference is maintained by a seal) or flow (wherein the pressure drop is from fluid friction in the permeable medium). A relatively small amount of flow across a seal can equalize pressures, retarding further flow. The fluid expelled as a result of loss of porosity during geologic time also flows at a low rate. The geologist concerned with pressure problems must be aware of (1) the many variables involved in subsurface pressures, (2) the low number and ambiguity of pressure measurements, (3) the need to establish what constitutes "normal" pressure to determine abnormal pressure, and (4) the possibility of uniqueness in any field situation.

Pressure responsive fluid collection system

Abstract: A collection system having a vacuum source in flow communication with a closed fluid collection vessel which is in flow communication with an inlet conduit disposed to apply the vacuum to non-gaseous fluids. The non-gaseous fluids to be collected are ingested through the inlet conduit through an inlet port to the closed collection vessel where they are retained. The collection vessel is kept at a negative gauge pressure through an outlet port connecting the collection vessel to the vacuum source. A variable restriction means is provided at one point between the outlet port and the vacuum source for reducing the cross-sectional area available for flow. The restriction means is responsive to the pressure differential across it and thus tends to reduce gas flow through the system in response to increasing differential pressure.

Observation of the Temperature and Pressure Changes During the 30 June 1973 Solar Eclipse

Abstract: Atmospheric pressure, temperature and wind speed were measured at the ground in Chinguetti, Mauritania, during the 1973 solar eclipse. The pressure measurements were intended to determine if barometric pressure changes were caused by the eclipse, but they produced a null result because of local weather conditions. Eclipse-induced temperature changes were measured continuously at altitudes of 0.3, 6.75 and 13.5 m. The maximum temperature changes were 3.5°C at the lowest level and 2.5°C at the two upper levels. The wind decreased by approximately 4.5 m s−1.

Piezo-optic measuring transducer and accelerometer, pressure gauge, dynamometer, and thermometer based thereon

Abstract: A piezo-optic measuring transducer is disclosed herein and an accelerometer, a pressure gauge, a dynamometer, and a thermometer based thereon. The piezo-optic measuring transducer comprises two polarization-optical channels. Each of these channels includes the following components arranged in series downstream the luminous flux produced by a light source: a polarizer, an elastic element which is common to both channels and sensitive to stress variations therein caused by a variation in the measurand, an analyzer, and a photocell. Both channels are provided with a means for varying the intensity of the luminous flux incident upon one of the photocells which intensity variation is opposite in polarity to that in the luminous flux incident upon the other photocell. Both photocells are arranged in a differential relationship with the difference in the electrical signals produced thereby being representative of the measurand. An accelerometer, a pressure gauge, a dynamometer, and a thermometer can be provided on the basis of said transducer.

Prediction of maximum expiratory flow rate from area-transmural pressure curve of compressed airway

Abstract: The site of greatest airway deformation in dog lungs was located during maximum expiratory flow by use of tantalum bronchography, fiberoptic bronchoscopy, and airway pressure measurements. A series of area vs. transmural pressure curves for each of these segments of the airway was produced after stepwise changes in transmural pressure. Measurements of area were made using cinephotography to elucidate the effect of time on airway compliance. The maximum flow rate was calculated using the t = 0.1 s compliance curve of the airway. An equation was derived so that maximum flow (V) could be calculated from the area (A) and transmural pressure (Ptm) of the flow-limiting segment. This equation, V = K-A square root of Ptm, implied that if V were constant then A must vary as Ptm-1/2. It was demonstrated that the area-transmural pressure curve of the flow-limiting segment showed this relationship between A and Ptm and that the flow calculated from this equation and the data from the A-Ptm curve gave flows identical to those measured during maximum expiration. The phenomena of effort-independent flow and negative effort dependence are also explained in terms of the area-transmural pressure curve of the flow-limiting segment.

Gain characteristics of a multiatmosphere UV-preionized CO 2 laser

Abstract: The small-signal gain of a transverse-discharge UV-preionized CO 2 laser has been investigated at pressures in the 1-15-atm range. Measurements were carded out on the P(18) and R(16) lines of both the 10.4- and 9.4-μm bands, and data on the pressure dependence of the peak gain and gain rise time are presented. The results demonstrate that small-signal gains in excess of 5-percent cm-1are readily obtained at pressures of ∼ 12 atm and confirm that the relaxation times of the energy levels relevant to laser action scale inversely with pressure. In addition, it is found that the gain of both R branches increases more rapidly with pressure than that of the P branches, while there are indications that the 9.4- and 10.4-μm gain values become comparable at pressures of ∼ 15 atm. The experimental results have been compared with the dependence of gain on pressure predicted by a relatively simple theoretical model. On the basis of this model it is found that the experimentally determined gain rises more rapidly with pressure than one would expect and a number of possible reasons for this discrepancy are discussed.

Non-invasive nuclear device for communicating pressure inside a body to the exterior thereof

Abstract: A non-invasive nuclear device for communicating pressure inside a body to the exterior, such as from within the cranium, bladder or vena cava, of an animal or human, the device including a housing having an interior communicating through a conduit of deformable metallic material with a fluid pressure sensing device positioned within the body portion being monitored, the housing being mounted on the body adjacent the body portion being monitored, a shaped mass of radioactive material together with radiation shield means being disposed within the housing interior together with urging means for producing a predetermined shielding relationship between the radioactive mass and the shield means, the radioactive mass being supported on the urging means for guide movement relative to the shield means and the sensed pressure being exerted through a pressure transmitting fluid flowing within the deformable metal conduit against the urging means for modifying the shielding relationship between the radioactive mass and the shield means proportionally with a change in fluid pressure in the body cavity thereby producing a radioactive output from the radioactive mass corresponding to the magnitude of the fluid pressure in the body position being monitored together with an ambient pressure sensing device mounted on the housing for applying ambient pressure through a pressure transmitting fluid to the urging means in opposition to the sensed body cavity pressure to compensate for changes in ambient pressure.

The high pressure PVT properties of deuterium oxide

Abstract: The high pressure isothermal compressibilities of deuterium oxide from 5 to 100 °C and 0 to 1000 bars applied or gauge pressure were determined from sound speed data. These compressibilities were used to derive an equation of state of the form V0P/(V0 − VP) = B + A1P + A2P2, where V0 and VP are the specific volumes at an applied pressure of zero and P; and B, A1, and A2 are polynomial functions of temperature. The compressibilities derived from this equation of state are consistent with those derived from the sound speed data to ±0.016×10−6 bar−1 over the entire pressure and temperature range (this is equivalent to ∼0.2 m sec−1 in sound speed). The 1 atm sound‐derived compressibilities agree on the average to ±0.06×10−6 bar−1 with the direct measurements of Millero and Lepple. The P–V–T data from the sound‐derived equation are compared with the high pressure work of Bridgman, Kesselman, Juza et al., and Emmet and Millero. Good agreement (average deviation of ±28×10−6 cm3 g−1) was found with the recent spe...

Pressure measuring method and apparatus with digital readout

Abstract: A pressure-measuring apparatus and method is described for providing a digital readout of the intra-ocular pressure of an eye. The apparatus comprises a transducer for applanating the cornea of an eye and providing a variable output proportional to pressure as the transducer is applied to the cornea. Electronic means responsive to a change in the output of the transducer is coupled to the transducer for providing a digital readout of the pressure sensed by the transducer when there is a change in the slope of the output of the transducer and the change in the slope has a predetermined polarity and exceeds a predetermined rate. Means are also provided for simultaneously displaying at least four digital readouts of pressure corresponding to four successive pressure measurements. The multiple readouts permit an operator to use the lowest of the four readouts as an accurate measure of intra-ocular pressure when the measurements are taken from a given eye.

Reliability of a capacitance manometer in the range 2×10−4−5×10−6 Torr

Abstract: A capacitance manometer has been tested and compared to the method of volumetric pressure division using helium as a working gas in the range 2×10−4−5×10−6 Torr. The results show that the unit tested was linear to the lowest pressures utilized, and the two methods were in agreement to about 0.6% plus 4×10−7 Torr, in addition to the errors introduced by the least count of the capacitance manometer’s digital readout. Argon and air gave similar results.

Effects of transducer flushness on fluctuating surface pressure measurements

Abstract: The installation flushness of pressure transducers has been found to strongly influence the quality of fluctuating surface pressure data in supersonic-attached turbulent boundary-layer flow. A systematic investigation of the effects of flushness on surface pressure fluctuations beneath a 4-in.-thick boundary layer was conducted in a supersonic wind tunnel at Mach numbers of 1.68, 2.0, and 2.5. Flushness effects on transducer signal amplitude, power spectral density, coherence, and narrowband convection velocity was evaluated. Results show that a very slightly protruding transducer produces adverse effects on the desired pressure fluctuation measurements, whereas a submerged transducer produces small effects. Indications are that a more viable method for enhancing the uniformity and spatial correlation of fluctuating surface pressure data can be achieved by deliberately submerging transducers beneath a surface orifice about 0.010 in. deep.

A Note on the Transition Observations on an Axisymmetric Body and Some Related Fluctuating Wall Pressure Measurements

Abstract: Boundary layer transition on an axisymmetric body up to Reynolds number of 1.26 × 106 was observed by schlieren method of flow visualization developed for water tunnel use. The spectrum of the flush mounted pressure transducer signal showed a dominant frequency to exist at transition and further, this frequency was in close agreement with the predicted critical frequency by Smith’s approximate method of transition calculation based on linear stability theory.

Inflator valve with pressure gauge and safety regulator

Abstract: An improvement in an inflator valve, pressure gauge, and automatic pressure-responsive relief valve, all of which are combined into an integral hand-held and operated device for use in high pressure inflating applications.

An Experiment to Determine Nose Tip Transition with Fluctuating Pressure Measurements

Abstract: Theme A accurate assessment of the altitude at which nose tip boundary-layer transition onset occurs is required to design and evaluate the heat protection system of high performance re-entry vehicles. Theoretical approaches to the transition phenomena are lacking, consequently the re-entry vehicle designer has relied almost exclusively on experimental data. Although transition onset has been determined on the frustum of R/V's in both ground and flight test experiments, and nose tip transition has been obtained and detected in ground tests with thermal instrumentation, there is a noticeable lack of transition detection techniques based on pressure measurements for the nose tip region. The purpose of this paper is to present the results of an exploratory ground test program to assess possible flight pressure instrumentation concepts to detect nose tip transition for full scale R/V flight test applications. l Specific ground test objectives were: a) to determine the feasibility of detecting nose tip transition by fluctuating pressure measurements using a miniaturized solid-state pressure transducer, and b) to demonstrate that the solid-state pressure sensor can make both steady-state and fluctuating pressure measurements simultaneously in a wind tunnel test for possible flight test application. Simultaneous fluctuating and steady-state pressure measurements were made and transition could be detected on the nose tip frustum 3.3 nose radii aft of the stagnation point. Transition onset was not detected at more forward stations possibly due to a porous nose.

Absorption coefficients in highly transparent solids: barothermal theory for cylindrical configurations

Abstract: The development of highly transparent solids requires improved methods to measure very low absorption coefficients at laser wavelengths. For the case in which a laser beam passes through a weakly absorbing solid that is surrounded by a confined, nonabsorbing gas, the temperature profiles in the solid and the temperature and pressure profiles in the gas have been calculated. Our calculations suggest that sufficient heat transfers from the solid into the gas to produce an easily detected pressure rise in the gas.

Borehole pressure measurement

Abstract: A pressure measurement system particularly suited to use in boreholes uses a pressure source at the surface to supply a test fluid through a small tube to a large downhole chamber having a fluid port on its bottom side. The test fluid displaces borehole fluid from the chamber after which the pressure of the test fluid is measured at the surface, thereby indicating the pressure of the borehole fluid.

Mass flowmeter for a gaseous medium, for example air

Abstract: A mass flowmeter for gas wherein the absolute pressure at and the pressure differential across a laminar restriction are measured with diaphragms and multiplied, each diaphragm having at least one surface resistance element acting as a strain gauge, the resistance element having a resistance inversely proportional to temperature. The diaphragms and resistance elements are preferably semiconductors.

Pressure measurement sheet and method of using the same

Abstract: A pressure measurement sheet comprises a support and a layer containing microcapsules provided thereon, wherein the ratio of the number average wall thickness (δ) to the volume average particle diameter (D) of the microcapsules lies in the range: δ/D = about 1.5 × 10 - 3 to about 3.0 × 10 - 2 . A method of measuring pressure by the use of the pressure measurement sheet described above comprising the steps of contacting the pressure measurement sheet with the area to be measured, applying pressure to form color and determining the applied pressure from changes in optical densities or hues, where the color is formed through contact under pressure between a layer containing microcapsules and a layer containing an adsorbent.

Magnetic forces and the surface instability in ferromagnetic fluids

Abstract: Ferromagnetic fluids are a colloidal suspension of subdomain iron particles dispersed in a carrier fluid. Experiments were performed to determine the pressure exerted by the fluid in a uniform and a gradient magnetic field. The pressure measurements were not the same as predicted by the continuum theory. An expression for the pressure jump at the surface of the fluid was proposed for the particular ferromagnetic fluid used based on the experimental measurements. This pressure jump was then used to predict the shape of the surface of the ferrofluid that results when a magnetic field is applied normal to an initially flat ferrofluid surface (ferrofluid spike). An expression for the radius of the shape ρ as a function of its distance from the base z, ρ=ρ (z), was calculated and compared to an enlarged photograph of the particular shape. In the region ρ≳0, a simple analytical solution was found. When ρ is zero or in the region close to zero, surface tension must be included and a numerical solution was necessary to determine the profile.

Thermal transpiration correction of hydrogen equilibrium pressure measurements in metal/hydrogen solution

Abstract: Experimentally determined results on the measurement of hydrogen equilibrium pressure as a function of hydrogen concentration and temperature in α-titanium have been corrected for thermal transpiration effects in the apparatus. An empirical relationship, which accurately describes the transitional thermal transpiration region over which the effect is diminishing in magnitude with increasing hydrogen pressure, has been developed. This relationship is both simpler in form and more convenient in application than earlier derived correction factors.

Brain Tissue Pressure Gradients in Experimental Infarction Recorded by Multiple Wick-Type Transducers1

Abstract: The wick catheter, applied to brain tissue pressure measurements by BROCK (1), appears to be a reliable device to measure the regional brain tissue pressure, based on our experience of implantation of about 150 wicks in 55 experimental animals.

Water and concentrate supply valves for proportioning mixer-dispenser

Abstract: A portable mixing-dispensing device having a manual flow control valve means between a ventable flow control chamber and a solution-proportioning chamber, and a manual feed valve between the proportioning device and a source of concentrate supplied at a negative gauge pressure, same including means to selectively coordinate the operation of the valves. The feed valve serves also as an anti-backflow check valve for the concentrate supplied under a negative gauge pressure as well as maintaining the prime thereof without dilution when concentrate is not being supplied to the mixing chamber. A translucent concentrate supply tube readily visible from above the mixing chamber serves as a visual check as to the prime of the concentrate.

Temperature compensated pressure limited gauge

Abstract: A temperature compensated pressure limited gauge is provided having a bourdon tube pressure sensing element. The coil is connected to a sealed cavity and has a predetermined quantity of fluid such as oil calibrated into the gauge. A solid cylinder or block of material is located within the cavity and has a relatively low volumetric thermal expansion characteristic relative to that of the fluid and of the gauge housing about the cavity. The dimensions of the block of material and housing cavity are such that their relative expansions are capable of compensating for any volumetric changes of the fluid throughout the applicable temperature range of the pressure gauge. Accordingly, a temperature compensation feature is provided that renders the pressure gauge independent of ambient thermal conditions. A fitting is included in the gauge to provide fluidic communication with the cavity. The fitting is adapted to be connected to a source of pressure to be monitored and further includes a diaphragm and a stop or limit member adjacent the diaphragm. The diaphragm separates the predetermined quantity of fluid in the pressure gauge from that of the source of pressure that is being monitored, while at the same time transmitting any changes in pressure to the fluid in the sealed cavity. The stop or limit member provides a maximum limit to the pressure that is capable of being transmitted via the diaphragm movement to the coil and thereby, protects the gauge from any destructive overload.

Novel method for measuring total pressure of fuel gas in hollow, glass Microshell pellets

Abstract: A sampling technique has been developed that permits direct, rapid, and accurate determination of the pressure inside gas‐filled, hollow, glass Microshell pellets.

Automatically controlled microreactor - coupled to chromatograph having flow, pressure and temp. controls

Abstract: Experimental investigation of catalytic reactions is carried out in microreactor. Accurate metering of liquids is achieved by measuring their flow in control capillary with constant pressure drop. Gas is fed from cylinder to regulator with spring tensioned diaphragm, this giving an outlet pressure pi. There is a pressure backloading from this via a solenoid valve and manometer to the other side of the diaphragm and a similar signal is fed forward to two other regulators. The manometer controls opening of the solenoid valve and a purge valve. The spring on the first regulator has a screw adjustment. Gas then feeds forward via the regulator finishing with a pressure (p + p2). (P is press. at reactor; p2 pi). Top of capillary is at pressure (p + p1), so difference is controlled at (pi-p2). This allows flow to be measured. Liquid is injected into gas stream and combined stream enters heating capillary. This together with reactor plus regulator and sampler are in temp. controlled enclosure. The gas then enters the reactor which has 2ml. capacity and is filled with catalyst. Pressure across it is controlled so that outlet pressure is p. The reactor is of steel with electric heating and suitable insulation. The still gaseous reaction products than pass to sampler which on a time cycle which injects a sample into carrier gas stream which then enters separation column followed by detector and flow controller. The carrier gas can be taken from container via regulators if suitable, or an independent supply can be used. Regulator ensures that a constant pressure is maintained even when a sample is being injected.

Cold cathode vacuum gauging system

Abstract: A vacuum gauging system of the cold cathode type is provided for measuring the pressure of a plurality of separate vacuum systems, such as in a gas centrifuge cascade. Each casing is fitted with a gauge tube assembly which communicates with the vacuum system in the centrifuge casing. Each gauge tube contains an anode which may be in the form of a slender rod or wire hoop and a cathode which may be formed by the wall of the gauge tube. The tube is provided with an insulated high voltage connector to the anode which has a terminal for external connection outside the vacuum casing. The tube extends from the casing so that a portable magnet assembly may be inserted about the tube to provide a magnetic field in the area between the anode and cathode necessary for pressure measurements in a cold cathode-type vacuum gauge arrangement. The portable magnetic assembly is provided with a connector which engages the external high voltage terminal for providing power to the anode within in the gauge tube. Measurement is made in the same manner as the prior cold cathode gauges in that the current through the anode to the cathode is measured as an indication of the pressure. By providing the portable magnetic assembly, a considerable savings in cost, installation, and maintenance of vacuum gauges for pressure measurement in a gas centrifuge cascade is realizable.

Experimentally determined rocket-exhaust flowfield in a constrictivetube launcher

Abstract: Pressure histories have been obtained during a flight test program in which a 6.0-in (15.2-cm) diameter rocket was launched from instrumented tube launchers whose cross section varied. Pressure measurements were used to define the flow mechanisms characterizing the underexpanded, supersonic rocket exhaust flow in the constrictive tube launcher. As the exhaust flow impinged on the constriction, the local pressure rose immediately, resulting in a pressure gradient in the annular region between the rocket and the launcher wall and, hence, the blowby flow. Later, when the rocket exhausted into the large-diameter forward tube, the flow was choked by the constrictive change in cross section and a normal shock wave was generated in the forward tube. Neither the geometry of the constriction nor the presence of vent ports significantly affected the pressure distribution in the launcher.