Showing papers on "Atmospheric pressure published in 1977"

Sound absorption in sea water

Abstract: An equation for sound absorption in Lyman and Fleming sea water (S= 35‰, pH=8) is presented as a function of frequency. temperature, and pressure. It represents the contributions to absorption due to boric acid, magnesium sulfate, and water. The pressure effect on sound absorption by magnesium sulfate is treated in more detail than Schulkia and March did. The equation is based on the laboratory work at atmospheric pressure by Simmons for MgSo4 and boric acid, on the pressure work by Fisher in 0.5m MgSO4 solutions, and on pressure work by Litovitz and Carnevale in pure water. For frequencies from 10 to 400 kHz up to pressures of 500 atm the absorption is substantially lower than that calculated from the Schulkin and Marsh equation. The pressure results are in good agreement with field data obtained by Bezdek. [Work supported by Office of Naval Research.]

The influence of barometric‐pressure variations on gravity

Abstract: Summary. The superconducting gravimeter has been used to measure the influence of barometric pressure on gravity in the frequency range 0.1–10 cycles/day. These measurements show that the incoherent barometric fluctuations are the major cause of random fluctuations in local gravity and account for much of the ‘noise’ on our gravimeter records. A simple model has been constructed which adequately explains the response of gravity to the local pressure fluctuations. These measurements also show a response to the global atmospheric tides at S1 and S2 which is much larger than the response to local fluctuations. Although this behaviour is most likely due to the response of the world-wide oceans to the atmospheric tides, no theoretical model has yet been constructed.

The Effect of Pressure on the Mechanical Properties of Polymers

Abstract: Stress relaxation measurements were made as a function of temperature and hydrostatic pressure on two lightly filled elastomers (Hypalon 40 and Viton B), one highly filled elastomer (Neoprene WB), and on an EPDM rubber. The latter was not piezorheologioally simple. The lightly filled elastomers showed piezorheologically simple behavior, i.e. their response curves under different hydrostatic pressures could be superposed empirically by a simple horizontal shift along the logarithmic axis. The filled elastomer was piezorheologically simple only in the rubbery region and in the beginning of the transition region. The dependence of the empirical shift distances, log a_p , on P could not be described by either the Ferry-Stratton or the Bueche-O'Reilly equation. By considering the bulk modulus to be linearly related to pressure, a new equation has been developed for log a_(T,P) which describes the pressure dependence well and contains the WLF equation as a limiting case. Published data on the response of poly(vinyl chloride) under superposed hydrostatic pressure are shown to obey the new equation also. The theoretical importance of the new equation lies in the fact that combination of the usual isobaric measurements at atmospheric pressure as function of temperature with isothermal measurements as function of pressure allows, in principle, all the molecular parameters required by the free volume theory to be determined unambiguously.

Pressure and temperature dependence of the longitudinal proton relaxation times in supercooled water to −87 °C and 2500 bar

Abstract: The longitudinal proton relaxation times T1 of the water protons have been determined at 100.1 MHz in the temperature range from +20 to −87 °C and up to pressures of 2500 bar. At temperatures below +10 °C, the T1 isotherms exhibit a maximum at pressures between 1.5 and 2 kbar. While at +10 and 0 °C, T1 rises by ∼10% from its atmospheric pressure value, this maximum becomes much more pronounced between −20 and −45 °C. In this region application of pressure increases T1 by ∼100%. The isobars at 2 kbar and above run through a minimum at −76 °C, indicating that at this temperature ωτϑ?1 and that the proton relaxation rate cannot be described by the extreme narrowing condition below ∼−40 °C. The experimental T1 data and the τϑ values derived at 2 kbar could be treated by a sum of two exponentials. While the smaller activation energies derived from this fit of 3.44±0.17 kcal mole−1 is independent of pressure, the higher activation energy decreases from 13±0.65 kcal mole−1 at atmospheric pressure to 9.3±0.5 kcal mole−1 around 1 kbar and then remains independent of pressure to 2.5 kbar. The data are qualitatively discussed in terms of a random hydrogen‐bond network.

A high‐pressure x‐ray study of Nylon 11

Abstract: An x‐ray diffraction study of Nylon 11 was carried out at high pressures and high temperatures. Careful measurements made on both wet and dry samples at atmospheric pressure indicated that the structure of Nylon 11 suggested by Slichter was not quite correct. Some distortion of the planar conformation causes a shortening of the c repeat distance from the value required for a fully extended conformation. The compressibility of the crystal lattice at higher pressures up to 20 kbar was studied and related to the anisotropic bonding present in the structure. A crystal transition at atmospheric pressure previously unreported was observed to occur at 95 °C, the triclinic structure (α phase) changing to a pseudohexagonal structure. The influence of pressure on this transition was studied. It was found that the increase in transition temperature with pressure dTt/dP (∼15 K/kbar) was greater than the melting temperature increase with pressure dTm/dP (∼9 K/kbar). A pressure‐temperature phase diagram for Nylon 11 wa...

Rate constants for the reaction of OH radicals with ethylene over the temperature range 299–425 °K

Abstract: Absolute rate constants for the reaction of OH radicals with ethylene have been determined, using a flash photolysis–resonance fluorescence technique, over the temperature range 299–425 °K at total pressures of 25–663 torr of argon. The rate constants k2 were observed to be pressure dependent below ∼225 torr total pressure, in agreement with other recent studies. The rate constants were independent of total pressure over the range 225–663 torr of argon, and the Arrhenius expression obtained from data over this pressure range was k2=2.18×10−12 e(770±300)/RT cm3 molecule−1⋅sec−1 with a value at 299 °K of k2= (7.85±0.79) ×10−12 cm3 molecule−1⋅sec−1. This room temperature high pressure rate constant is in good agreement with a recent relative rate determination carried out at atmospheric pressure.

Occultation of epsilon Geminorum by Mars. II. The structure and extinction of the Martian upper atmosphere.

Abstract: The occultation of Epsilon Geminorum by Mars on April 8, 1976, was observed at three wavelengths and 4-ms time resolution with the 91-cm telescope aboard NASA's G. P. Kuiper Airborne Observatory. Temperature, pressure, and number-density profiles of the Martian atmosphere were obtained for both the immersion and emersion events. Within the altitude range 50-80 km above the mean surface, the mean temperature is about 145 K, and the profiles exhibit wavelike structures with a peak-to-peak amplitude of 35 K and a vertical scale of about 20 km. The ratio of the refractivity of the atmosphere at 4500 A and 7500 A is consistent with the atmospheric composition measured by Viking 1. From the 'central flash' - a bright feature in the light curve midway between immersion and emersion - an optical depth at 4500 A of 3.3 + or - 1.7 per km atm (about 0.23 per equivalent Martian air mass) is found for the atmosphere about 25 km above the mean surface near the south polar region. This large value and its weak wavelength dependence rule out Rayleigh scattering as the principal cause of the observed extinction.

Behavior of volatiles in Mars' polar areas: A model incorporating new experimental data

Abstract: A model has been developed to explain the north polar water vapor results obtained by the Viking orbiter Mars atmospheric water detector; it has also been used to compute the thickness of seasonally deposited CO2 frost, the variation of the total atmospheric pressure, and wind velocities due to mass motions associated with CO2 condensation. A north polar water ice thickness in excess of 1 m and an ice albedo a of 0.34(+0.06,-0.03) are inferred from a comparison of the model and experimental data. The model results confirm an earlier conclusion that the atmosphere over the ice is saturated. It is suggested that concentration of the atmospheric inert gases in the polar region, combined with local topography and arctic circulation patterns, could be responsible for the south remnant cap not being at the south pole

The viscosity of five gaseous hydrocarbons

Abstract: The paper presents new data on the viscosity of CH4, C2H4, C2H6, C3H8, and C4H10 at atmospheric pressure and in the temperature range 25–200°C. The measurements were absolute and were performed in an oscillating‐disk instrument. The results fit into the extended law of corresponding states of Kestin, Ro, and Wakeham. The scaling constants σ and e for each gas which assure such a fit are calculated in the paper.

A Semiempirical Equation of State for Polymer Melts

Abstract: An explicit reduced equation of state is developed by combining results of the hole'theory with a semitheoretical expression for the temperature dependence of the reduced Tait parameter B which is found to be in good agreement with experiment. This approach circumvents the implicit character of the theoretical equations. Two procedures are explored to derive for a given system the PVT surface and the compressional energy and entropy changes from the corresponding reduced functions. One rests on the usual superposition of experimental and analytical isotherms and isobars. The other, and more approximate method, utilizes a correlation between the scaling temperatures, pressures, and volumes obtained previously, and requires only experimental data at atmospheric pressure and a single temperature above the glass transition (Tg) or the melting temperature (Tm). The good agreement between experiment and theory noted previously is shown to extend to the semiempirical relationships. Finally, internal pressure data for oligomers and polymers at atmospheric pressure and encompasing a wide range of reduced temperatures are examined. The ensemble of data can be described by simple power relationships between the internal energy and the density. The exponents, however, depart significantly from the van der Waal's value of unity.

Process for recovering a solvent vapor

Abstract: The present invention is a process for recovering solvent vapor which comprises absorbing solvent vapor in a first absorbing liquid, and subsequently stripping the solvent vapor to regenerate the first absorbing liquid. The stripped solvent vapor may be reabsorbed in a second absorbing liquid. The second absorbing liquid may be under greater than atmospheric pressure. Regenerating the first absorbing liquid may occur at pressures only slightly below atmospheric pressure, i.e., a low vacuum, by recycling the absorbing liquid to a regenerator. Because the regenerating process does not require the use of a high vacuum, the gas recovery apparatus may be more economically constructed and operated.

A spectroscopic study of a high-frequency, inductively-coupled ArH2S plasma

Abstract: An inductively coupled argon plasma working at atmospheric pressure and having a small amount of H2S (0.5%) added was studied. Physical parameters such as electron density and ionization temperature were determined by measuring the Stark broadening of the Hβ line and 5495 Ar(I) line. The excitation temperature was measured from Ti and Fe injected into the plasma. These results indicate that LTE does not prevail in this kind of source. The spectrum of sulfur was studied in the 4180–6060 A range. New and known lines of sulfur are given.

Vacuum actuated pressurized fluid dispenser

Abstract: A dispenser device which has the contents under pressure so that they can be dispensed by actuating a valve similar to an aerosol unit. The contents are maintained under pressure by using a movable piston element driven by external air pressure against the contents which are contained in an enclosure within an evacuated vessel. The dispenser can be filled and sealed at atmospheric pressure and normal temperature and activated by evacuating the unit.

Volume Properties of Binary Mixtures of Water with 2‐Propanol

Abstract: The density and the ultrasonic velocity are measured at atmospheric pressure on binary mixtures of water with 2-propanol. The measurements are made at various concentrations of the components and at the temperatures 20°C and 25°C. - The experimental data are discussed with reference to the unique properties of water as a solvent, and with particular emphasis on the possibility that structural changes are introduced in water by solute molecules.

Air pressure differential energy system

Abstract: An air pressure differential energy generation system comprises a stack for conduction of air from a high to a low atmospheric pressure level. A vapor injection device within the stack provides a method of filling the stack at least in part with water vapor. A heat exchanger is provided at the high atmospheric pressure end of the stack. A turbine is coupled to the heat exchanger and is impelled by warmed air. An electrical generator is coupled to the turbine to provide electrical power.

Miniaturized atmospheric pressure nitrogen laser

Abstract: A compact, low-cost atmospheric pressure UV nitrogen laser employing photoionization stabilization techniques is described. The device yields peak output power of 200 kW in subnanosecond pulses. Average output power is 200 mW at a repetition rate of 1.7 kHz.

Pitch bonded carbon electrode

Abstract: This invention relates to the production of chemical pitch by stripping under reduced pressure steam cracker tar to obtain a pitch having an initial boiling point of between 350° C and 400° C at atmospheric pressure, heat soaking the pitch at 360° to 420° C in the absence of air or oxygen at sub-atmospheric to 4 atmospheres absolute and stripping under reduced pressure the soaked pitch to obtain a product having a minimum softening point (R and B) of 75° C. This pitch can be mixed with coke to make electrodes especially suitable for aluminium production.

Effect of cross‐linking on hydrostatic creep of epoxy

Abstract: Samples of epoxy having three different degrees of crosslinking were subjected to several constant values of hydrostatic pressure ranging from 1000 psi to 80 ksi. Each period of constant pressure was followed by a period at atmospheric pressure. A continuing decrease in volume (creep), as measured by axial strain at constant pressure, was observed for pressures of 10 ksi and greater. The creep strain was recovered immediately upon pressure removal. Reapplication of pressure after a short period at atmospheric pressure resulted in the same creep behavior as that resulting from the first pressure. The least cross-linked epoxy had the smallest creep rate and the smallest compressibility. These observations are consistent with the view that the leapt cross-linked epoxy would be the most compact and have the least voids at points of cross-linking.

Direct measurement of the lifetimes of the 3B1 state of sulfur dioxide in air at atmospheric pressure.

Abstract: The lifetimes of SO/sub 2/ phosphorescence in air were measured using a single photon counting instrument. The lifetime of the /sup 3/B/sub 1/ state proved to be longer than expected from extrapolation of previous low pressure data to atmospheric conditions. This paper was noted to be the first report of pressure saturation of intersystem crossing of gases. (DDA)

Non vacuum soft x-ray lithographic source

Abstract: A source of electrons or charged particles is contained in a baffled enclosure at less than atmospheric pressure. The source projects the electrons or charged particles to strike a target with a velocity which generates soft x-rays. The target is in a chamber at substantially atmospheric pressure in a gaseous environment which is only slightly dispersive and absorptive of the soft x-rays. Access to this chamber is provided to insert a mask and substrate for lithographing by the soft x-rays.

Pneumatic system for smoothing discharge pressure from air

Abstract: A pneumatic system consisting of an air pump, air-passage switching means, operating components and air pipes connecting those together. This pneumatic system features improvements in a pressure smoothing means for smoothing a surge pressure discharged from an air pump in the pneumatic system, which pressure smoothing means is built in the pneumatic system between the air pump and the air-passage switching means. The pressure smoothing means includes an air chamber having an air inlet and an air outlet, and means for increasing and decreasing the volume of the air passage defined between the aforesaid air inlet and outlet, commensurate to the surging discharge pressure from the air pump, i.e., in response to the surge pressure of the air being admitted in the air chamber. This pressure smoothing means is provided with a pressure receiving plate which is displaced under the air pressure being introduced into the air chamber, whereby the volume of the air passage defined within the air chamber may be adjusted.