Showing papers on "Atmospheric pressure published in 1968"

A Search for X Rays from Helium and Air Discharges at Atmospheric Pressure

Abstract: X‐ray production in wide‐gap helium and air discharges was investigated using calibrated film‐badge detectors. Helium discharges were found to produce x rays with average energies in the range <11 to 13 keV. The energies were independent of applied electric field for average E/p ratios between 35 and 140 V/cm·Torr. X‐ray intensities were proportional to the atomic number of the electrode material. No evidence for similar x‐ray production was found in air discharges.

Effect of pressure on ionization equilibria in water at 25°C

Abstract: A simpler equation than that proposed by Owen and Brinkley in 1941 is shown to be satisfactory for the calculation of the pressure dependence of the dissociation constant to approximately 2000 bars, from density and compressibility measurements on solutions. As a corollary, an accurate graphical method is proposed for the evaluation of standard partial molal volume and compressibility changes on ionization at atmospheric pressure (Δtext-decoration:overlineV∘1 and text-decoration:overlineκ∘1), from dissociation constant against pressure data. text-decoration:overlineV∘1 and text-decoration:overlineκ∘1 values for a wide range of acid-base equilibria are tabulated, and an approximately linear relationship between these thermodynamic function changes is demonstrated. This observation may be useful for predicting the effect of pressure on ionization equilibria for which Δtext-decoration:overlineV∘1 but not text-decoration:overlineκ∘1 data are available.

Raman Spectrum of α Quartz at High Pressures

Abstract: Raman spectra of single crystals of α quartz at pressures as high as 40 kbar are reported The frequencies of the Raman lines located at 128, 207, 265, 464, 697, 795, and 807 cm−1 at atmospheric pressure increase with increasing pressure by about 06, 18, 05, 09, 08, 08, and 08 cm−1·kbar−1, respectively, with a probable accuracy of about 20% due to an uncertainty about the pressure scale These frequencies of the α‐quartz spectrum also are significantly sensitive to temperature The frequencies of all other Raman lines of α quartz, except three at 145, 450, and 509 cm−1 that could not be studied, are independent of pressure

Excimer Emission of Naphthalene, Anthracene, and Phenanthrene Crystals Produced by Very High Pressures

Abstract: Fluorescence spectra of ultrapure crystals of naphthalene, anthracene, and phenanthrene have been studied at pressures as great as 50 kbar. These spectra exhibit complex irreversible effects superimposed upon the expected reversible shifts in the energies of the normal fluorescence spectra. The irreversible effects include a loss of the intensity of the normal fluorescence with increasing pressure and the almost simultaneous appearance of a broad, featureless emission at energies about 3000–6000 cm−1 lower than that of the normal fluorescence. This emission is assigned as the fluorescence of excimers formed upon optical excitation of the crystals under high pressure. The crystals continue to exhibit this excimer fluorescence after the pressure is reduced to atmospheric pressure, but the irreversible effects can be removed by thermal annealing of the crystal at atmospheric pressure. The irreversibility is attributed to trapping of pairs of molecules in an excimer‐like orientation as a crystal defect after they lose the excitation energy of the excimer. These defects then act as traps for excitation energy in the crystal. Other possible interpretations of the irreversible effects are discussed.

Continental shelf waves off Oregon

Abstract: A statistical search for continental shelf waves of several days' periods has been performed on Oregon sea level records. Daily mean sea level at three locations, atmospheric pressure, and winds for winter and summer 100-day records have been analyzed by standard correlation and spectral analysis techniques. The summer atmospheric pressure and sea level spectra have peaks at 0.1 and 0.3 cycles per day (cpd). The sea level records have been adjusted for a one-to-one isostatic barometric factor, yet there remains a strong coupling between atmospheric pressure and sea level at frequencies of 0.1 and 0.35 cpd in the summer. Computations from cross spectra give a barometric factor of about −1.2 cm/mb. The cross-spectral analysis indicates a wave at 0.1 cpd moving to the south with the atmospheric pressure systems and a wave at 0.35 cpd moving to the north as a free continental shelf wave. The wave phenomenon at 0.35 cpd is consistent with the theory of continental shelf waves and with similar observations on the Australian shelf.

Liquefaction process for gas mixtures by means of fractional condensation

Abstract: A process for the liquefaction of gas mixtures by at least two open partial cycles with different boiling points includes premixing the gas mixture with the cycle media and by means of a compressor bringing it to an elevated pressure and subjecting it to a fractional condensation where the cycle media and the more difficulty boiling mixture constituents are precipitated as liquid fractions in separators. The liquid fraction of the first separator is divided into two partial streams. The first stream, which forms the first partial cycle, after expansion to an average pressure gives off coolness from cycle gas and gas mixture to be liquefied to the mixture streaming to the first separator and again conducts back to the compressor. The second stream is deep-cooled, expanded to about atmospheric pressure and admixed to the last cycle medium streaming back to the compressor. Furthermore, it is proceeded with the compressor of the subsequent separator accordingly, the expansion of the first partial streams occurring at average pressure until finally the liquid precipitating in the last separator after cooling of itself and expanding to about atmospheric pressure, gives off coolness to the gas mixture to be liquefied and to the other separated cycle media and is again conducted to the compressor.

Spectroscopic Observations on Induction‐Coupled Plasma Flames in Air and Argon

Abstract: Plasma flames in argon and air have been maintained at atmospheric pressure by rf induction in a 100‐mm‐wide quartz tube for extended times with only forced air required for tube cooling. For air, a rotational temperature of 6300°K at the central point of the induction zone was determined from intensity ratios of both sextet components and unresolved sextets in the 0, 0 band of the N2(2+) system. Absolute intensity measurements in this band and in the 0, 0 band of the N2+(1−) system yielded probabilities of 1.34×107 sec−1±14% for the C 3πu→B 3πg transition and 1.15×107 sec−1±14% for the B 2Σu+→X 2Σg+ transition, which agree well with values in the literature. Under the assumption of local thermal equilibrium (LTE) in the plasma, radial temperature distributions at the coil midsection were derived for both systems. Results agree within 7%, which supports the validity of the above values for transition probabilities and indicates that deviations from LTE are less than 10%. Average electron densities were de...

Effect of Pressure on the Magnetic and Electrical Transition Point of the NiAs-Type NiS

Abstract: In order to study the nature of the first-order antiferromagnetic transition in NiS the electrical resistivity in the vicinity of the transition point has been investigated at the hydrostatic pressures up to 7 kbar. The transition has characteristics of semiconductive-metallic transformation. The transition point, observed at 230°K at atmospheric pressure, is lowered as the hydrostatic pressure is increased, with the rate ( d T t / d P )=-(6.0±0.3) deg./kbar. The transition can be described in terms of the electronic rearrangement in d -orbitals of nickel atoms between localized-collective electronic states.

Radiation from High‐Pressure Plasmas

Abstract: If the temperature dependence of the total radiation source strength and the continuum radiation source strength of a gas are known, the contribution of the line radiation can be determined. The investigation of the line factor L shows that it is independent of pressure over a wide temperature and pressure range. Therefore, to determine the total radiation source strength of a gas at high pressure, one need calculate only the continuum radiation at high pressure and use the measured or calculated line factor of the gas at atmospheric pressure. This method was applied to argon and the total radiation source strength u=F (temperature, pressure), in the range 9000≤T≤15 000°K and 1≤p≤100 atm was determined using the existing values measured at 1 atm.

Ultrahigh‐Frequency Discharge in Atmospheric‐Pressure Gas

Abstract: A 2469 MHz discharge was generated at an open end of a coaxial waveguide, through which atmospheric‐pressure gas flowed. Argon served as a plasma‐forming gas, hydrogen and calcium as probe elements for the measurement of electron density and gas temperature, respectively, and sodium as a seed for increasing electron density. The density of excited hydrogen atoms, the excitation temperature, the electron density, the ionization temperature, and the gas temperature were measured at operating powers of 50, 200, and 400 W. The plasma in the close vicinity of the electrode (0 to 0.5 mm from the terminus of the inner conductor) was not in the local thermal equilibrium at any power level investigated, independently of the sodium seeding. At a distance between 1 and 3 mm from the electrode, on the contrary, the nonseeded plasma approached the local thermal equilibrium when the power was increased, while the seeded plasma exhibited a deviation from the local thermal equilibrium. The deviation from the local therma...

Measurement of atmospheric surface pressure with a satellite-borne laser

Abstract: A laser system operating in the oxygen A band (near 0.76 mu) can be used to measure surface pressure by determining absorptance inside and outside of the bands. An accuracy of 10 mbar may require thirty pulses, using a 1-m(2) receiver. A systems analysis shows that internal noise is negligible and that background is not serious, even in daylight. As compared with the corresponding method using the sun, the laser method can be used at night, can discriminate cloud vs surface reflections, and may be able to determine altitude, pressure, and temperature at selected points in the atmosphere. An early test in a manned orbiting satellite is proposed. If successful, the method will have important applications to the projected Global Atmospheric Research Program, to cloud studies, and to oceanography.

The effects of entrapped air and barometric fluctuations on the drainage of porous mediums

Abstract: A theory was developed for transient drainage of porous mediums taking into consideration the air that is entrapped within the flow region. The theory is based on the soil moisture diffusion equation with modifications made to include the effect of the entrapped air and the effect of changes in pressure due to barometric fluctuations. The theory was tested on a one-dimensional flow sand model, and the results were compared with results obtained from a numerical solution of the developed equation. The theory and experiments show that barometric fluctuations have little effect on a draining column containing entrapped air when the column is open to the atmosphere at both ends. However, when the column is closed at the bottom, an increase in atmospheric pressure lowers the position of the water table, whereas a decrease in atmospheric pressure raises the water table. Both the experiments and the developed theory show a much greater change in the position of the water table with atmospheric pressure than a previous steady-state theory.

Observation of superradiant laser action in spark discharges in air at atmospheric pressure

Abstract: Superradiant, stimulated emission at 3371 A has been observed from spark discharges in air at atmospheric pressure. This emission corresponds to transitions in the second positive band system of molecular nitrogen. Duration of the emitted laser pulse is about 0.6 nsec and peak power output is about 2 W.

Decompression sickness: a review.

Abstract: Work in compressed air is a dangerous activity, whether it is carried on under water in a conventional diving suit, in self-contained breathing apparatus or in a diving bell, or in relatively dry conditions in a caisson or an underwater tunnel. Surprisingly large numbers of men have worked at one time or another in compressed air in tunnels or caissons and it is the dangers which arise to the health of these men that are considered here. When a tunnel is driven through water-logged strata or through porous ground under a river, the open end of the tunnel must be sealed off and air pumped in to balance the hydrostatic pressure, should there be any danger of water flooding in and bringing with it unmanageable quantities of silt or sand. A pier of a bridge may be constructed in deep water by means of a caisson (Fr. caisse, a box), which is a compressed air chamber in which a gang of men excavate foundations. In both tunnels and caissons men come and go through an air lock and must be compressed on entering and decompressed at the end of the work period. Although working conditions in these circumstances have much improved over the last 6o years, our understanding of the reactions of the human body to atmospheric pressures greater than the normal and of the pathogenesis of decompression sickness is still insufficient to prevent illness completely. In engineering practice it is customary for working pressure to be expressed as gauge pressure in pounds per square inch (p.s.i.g.) which is the pressure over and above the normal atmospheric pressure of I4-7 p.S.i. (I 03 kg./cm.2). For certain calculations absolute pressure (gauge pressure plus atmospheric pressure) is used, and for clarity it must always be stated whether gauge or absolute pressure is referred to. In naval practice it is usual to think in terms of feet of sea water, each 33 feet of depth corresponding to about one atmosphere or approximately I5 p.s.i. Sometimes the unit of pressure used is the atmosphere (atm.). On the

Change of dislocation density in aluminium and lithium fluoride after annealing near the melting point under hydrostatic pressure

Abstract: This paper describes an experimental investigation of the change in etch-pit density (ρ) in aluminium and lithium fluoride crystals after anneals of varying duration (up to 10 h) near the melting point, either without pressure or under hydrostatic pressures of up to 10 kbar. It is found that, when the temperature is high enough (near the melting point), the action of pressure promotes lowering of the etch-pit density after the anneal. For instance, in the case of aluminium, the reduction in ρ after a 10 h anneal at 630° C under a pressure of 10 kbar is 100 times greater than under the same conditions without pressure. But for 550° C annealing temperature, the influence of pressure on change in ρ is already insignificant. In the case of lithium fluoride, annealing at 810° C (6 h) under a pressure of 8 kbar diminishes ρ by a factor of 30. At 750° C, the application of 8 kbar pressure reduces ρ only by a factor of 5 compared with atmospheric pressure. The effect of pressure, and its temperature dependence, is qualitatively explained in the following way. Under pressure near the melting point, the microcracks, which always exist in solids, are healed (i.e. sintered). The inner surfaces of these microcracks serve as sources and sinks for Schottky vacancies. Therefore, during the establishment of an equilibrium vacancy concentration, when the microcracks are healed, dislocations begin to act as vacancy sources (or sinks) and this results in the acceleration of their climb and consequential annihilation (i.e. a reduction in dislocation density). The comparison of literature data on dislocation density (N) in pure aluminium samples cooled (after anneal) at different rates, and of etch-pit density for similarly treated aluminium samples shows that, under our experimental conditions, ρ and N coincide in order of magnitude.

Pressure Dependence of Transitions and Relaxations in Polytetrafluoroethylene

Abstract: The ultrasonic absorption and linear thermal expansion behavior of polytetrafluoroethylene in a hydrostatic high pressure vessel (piston and compound cylinder type) capable of achieving 16,000 kg/cm2 are measured in the temperature from -30°C to 200°C and in the pressure from 1 atm. to 5,000 kg/cm2. Ultrasonic (5 Mc/s carrier frequency) attenuation maxima at atmospheric pressure are found at about -12°C, 30°C, 50°C, 130°C and 140°C, and pressure dependence of these maxima is found as about 10, 9, 28, 13, and 25 degrees per 1,000 kg/cm2, respectively. From these facts and the dispersion map, the third, fourth and fifth peaks indicate important informations of existence of segmental motion in amorphous regions (primary dispersion), crystalline dispersion and grain-boundary dispersion, respectively. By a thermodynamical consideration and the thermal expansion behavior, the second peak is defined as the one due to the 30°C transition.

Effect of Low Pressures on the Room Temperature Transitions of Polytetrafluoroethylene.

Abstract: Between approximately 20 and 30 °C at atmospheric pressure, polytetrafluoroethylene exhibits a phase (denoted as IV), which has not been observed in P-V-T measurements at pressures above 108 Nm-2 (1 Kilobar). Data are presented to resolve this phase in the temperature range 0 to 50 °C and the pressure range 0 to 0.686 × 108 Nm-2. The II-IV (20 °C) transition pressure increases with temperature according to the equation P = (-820 + 26.9t + 0.68t 2) × 105 and the IV-I (30 °C) transition according to the equation P = (- 91-57.8t + 1.99t 2) × 105 suggesting a possible triple point near 2.6 × 108 Nm-2 and 54 °C. However, the IV-I transition probably cannot be resolved by volume measurements at pressures above 2 × 108 Nm-2 because its volume of transition is small and the two transitions overlap. The enthalpies of the transitions are calculated for different pressures and some thermodynamic properties of phase IV are determined indirectly. It is shown that, if the effect of volume change is subtracted, random reversals of the hand of the helical conformation of the molecule can account for appreciable fractions of the enthalpy and corresponding entropy change for the combined transitions at atmospheric pressure.

γ Radiolysis of Liquids at High Pressures. VI. Hydrogen‐Atom Reactions in Aqueous 0.8N H2SO4 Solutions

Abstract: The competition between Reactions [1] and [2], H + S→no H2, H + RH→H2 + R, in aqueous 0.8N H2SO4 solutions was studied at 20° over the applied pressure range of 0–6.34 kbar by measurement of G(H2) from the gamma‐irradiated solutions. With O2 as S, in aerated solutions, relative specific rates k10 / k20 were determined at atmospheric pressure for methanol, glucose, glycerol, ethanol, and isopropanol as RH. From the pressure dependence of k1 / k2 and an estimated ΔV1‡ = 1.6 ml mole−1 for S ≡ O2, values of ΔV2‡ in the range −5.5 to −6.7 ml mole−1 are obtained for the five H donors. The average value ΔV2‡ = − 5.9 ml mole−1 is taken as characteristic for Reaction [2]. Values of k10 / k20 at atmospheric pressure also were determined for four deaerated 0.8N H2SO4 solutions: (1) RH ≡ glucose and S ≡ benzyl alcohol; (2) RH ≡ glucose and S ≡ BrCH2COOH; (3) RH ≡ S ≡ acetone; (4) RH ≡ S ≡ ClCH2COOH. Because little or no pressure dependence of G(H2) and, therefore, of k1 / k2 was observed with these four solutions, ΔV...

Enhancing low-temperature flow properties of fuel oil

Abstract: The response of a middle distillate petroleum fuel oil, boiling within the range of about 250* to about 670* F. at atmospheric pressure and containing normal paraffinic hydrocarbons within the range of about n-decane and n-hexacosane to the addition of a flow-improving additive such as a copolymer of ethylene, is improved by adding to the fuel oil a paraffinic distillate fraction, obtained from a crude petroleum, the said fraction boiling at atmospheric pressure within the range of about 450* to about 950* F. and containing normal paraffins higher than nhexacosane and as high as n-tetracontane, C40H82.

Radiation studies of arc heated nitrogen, oxygen, and argon plasmas.

Abstract: : This report presents continuum radiation and line radiation measurements for nitrogen, oxygen, and argon covering wavelength ranges from the vacuum ultraviolet to the infrared for a selection of pressures and temperatures. A mechanically constricted dc arc was used as the radiation source. Nitrogen continuum data at 1 and 2 atmospheres is reported for wavelengths from 700 to 37,000 A and temperatures from 9,000 to 13,500 K. The spectral data have been treated analytically to separate the radiation from electron-neutral atom and electron-positive ion collisions, and comparison is made with the theory of Burgess and Seaton for the positive ion recombination radiation. Values of the ratio, R, by which this theory differs from our experimental results are given as a function of wavelength. A subtraction of the positive ion radiation from the total continuum yields the contribution from the neutral atom, from which was extracted the approximate absorption edges of the nitrogen negative ion and an estimate of the photo-detachment cross section. Earlier data reported for the argon continuum at atmospheric pressure has been improved by a reinterpretation of the temperature measurement. New argon continuum intensities at 5 atmospheres pressure and 12,300 K are reported. (Author)

A Magnetostrictive Load Cell for Use under High Hydrostatic Pressures

Abstract: A load cell utilizing magnetostrictive strain gauges which is suitable for measuring loads up to 300 kg in tensile testing of materials under high hydrostatic pressures up to 15000 kg/cm2 is described. Temperature and pressure variations during tensile testing can be completely compensated by the use of a dummy gauge. The calibration of the load cell under pressure is performed by a coil spring which is calibrated at atmospheric pressure. The calibration curves under pressures up to 13400 kg/cm2 and 200 kg agree with the atmospheric calibration curve within 2%.

Laser-Produced Sparks in a 200-kG Magnetic Field

Abstract: Laser‐produced sparks in air, butane, and helium at atmospheric pressure have been studied in a 200‐kG magnetic field. The influence of the magnetic field on the breakdown threshold, on the visible radiation emitted by the plasma, and on the plasma expansion has been investigated.

Root beer postmix drink dispenser

Abstract: A carbonated postmix drink dispenser in which syrup under pressure is jetted through carbonated water under pressure to a zone of atmospheric pressure while the major portion of the carbonated water is segregated under pressure and aerated with minute air particles as it is expanded by CO2 ebullitions at atmospheric pressure prior to final mixing with the major portion of the syrup.

Reducing electrolytic sludge formation

Abstract: Method and apparatus for decreasing sludging in a stannous-tin electrolyte used in continuous-strip electroplating by continuous deaeration of the electrolyte which removes gases absorbed when the electrolyte is exposed to ambient atmosphere and by decreasing the opportunity for the electrolyte to absorb oxygen. A barometric leg, or other suitable pressure isolation means, is arranged to separate the path for continuous replenishment of electrolyte into an atmospheric pressure loop and a subatmospheric pressure loop. Desorption performance and efficiency is increased by operation at or below the vapor pressure of the electrolyte at the operating temperature for the system and by use of a vapor condenser on the vacuum side of the deaeration means used. Improved results are obtained by providing an inert gas shield during collection of electrolyte splash-over and carryout from the plating cells and also by injection of an inert gas into the electrolyte after deaeration and prior to exposure of the electrolyte to ambient atmosphere. The inert gas steps operate to reduce the opportunity for oxygen absorption.