Showing papers on "Atmospheric pressure published in 1986"

AFGL atmospheric constituent profiles (0-120km)

Abstract: : An atmospheric data base consisting of volume mixing ratios (o0 to 12okm) for twenty eight (28) minor and trace gases has been assembled for use with spectral radiance transmittance models. Six references atmospheres, each defining temperature, pressure and density as a function of altitude (selected from the U.S. Standard Supplements, 1966 and the U.S. Standard Atmosphere, 1976) provide a range of climatological choices. Analogous zonal-mean descriptions for 2O, O3, N2O, CO, and CH4 have been subsequently adapted from satellite data and/or dynamical-photochemical analyses. The remaining species are defined by single profiles, usually appropriate for U.S. Standard conditions. Because the entire profile set is preferentially based on available measurements, explicit photochemical consistency between the different species has not been maintained. Keywords: ATMOSPHERIC CONSTITUENTS; TEMPERATURE PROFILES; MODEL ATMOSPHERES.

The dimensions and dynamics of volcanic eruption columns

Abstract: Eruption columns can be divided into three regimes of physical behaviour. The basal gas thrust region is characterized by large velocities and decelerations and is dominated by momentum. This region is typically a few hundred metres in height and passes upwards into a much higher convective region where buoyancy is dominant. The top of the convective region is defined by the level of neutral density (heightHB) where the column has a bulk density equal to the surrounding atmosphere. Above this level the column continues to ascend to a heightHT due to its momentum. The column spreads horizontally and radially outwards between heightHT andHB to form an umbrella cloud. Numerical calculations are presented on the shape of eruption columns and on the relationships between the heightHB and the mass discharge rate of magma, magma temperature and atmospheric temperature gradients. Spreading rate of the column margins increases with height principally due to the decrease in the atmospheric pressure. The relationship between column height and mass discharge rate shows good agreement with observations. The temperature inversion above the tropopause is found to only have a small influence on column height and, eruptions with large discharge rates can inject material to substantially greater heights than the inversion level. Approximate calculations on the variation of convective velocities with height are consistent with field data and indicate that columns typically ascend at velocities from a few tens to over 200 m/s. In very large columns (greater than 30 km) the calculated convective velocities approach the speed of sound in air, suggesting that compressibility effects may become important in giant columns. Radial velocities in the umbrella region where the column is forced laterally into the atmosphere can be substantial and exceed 55 m/s in the case of the May 18th Mount St. Helens eruption. Calculations on motions in this region imply that it plays a major role in the transport of coarse pyroclastic fragments.

Photochemistry of the Atmospheres of Mars and Venus

Abstract: 1 Chemical Composition and Structure of the Martian Atmosphere.- 1.1 Carbon Dioxide and Atmospheric Pressure.- 1.2 CO and O2 Mixing Ratios.- 1.3 Ozone.- 1.4 Water Vapor.- 1.5 Composition of the Upper Atmosphere as Determined from Airglow Spectroscopy.- 1.6 Mass Spectrometric Measurements of the Atmospheric Composition.- 1.7 Ionospheric Composition.- 1.8 Temperature Profile of the Lower Atmosphere.- 1.9 Temperature of the Upper Atmosphere.- 1.10 Eddy Diffusion Coefficient.- 2 Photochemistry of the Martian Atmosphere.- 2.1 Ionosphere.- 2.2 Photochemistry of Nitrogen.- 2.3 H2 Dissociation and Escape of Atomic Hydrogen.- 2.4 Nonthermal Escape and Isotopic Composition of Oxygen and Nitrogen.- 2.5 Dissociation of C02: Atomic Carbon in the Upper Atmosphere.- 2.6 Diffusion and Photolysis of Water Vapor.- 2.7 Photochemistry of the Lower Atmosphere (Global Average Conditions).- 2.8 Diurnal Variations of Minor Components in the Low Latitude Atmosphere.- 2.9 Latitudinal Distribution of Ozone in Different Seasons.- 2.10 Seasonal Variations of Atmospheric Composition at a Latitude of 65 N.- 3 Chemical Composition and Structure of the Yenusian Atmosphere and Cloud Layer.- 3.1 Properties of Aerosol in the Upper Part of the Cloud Layer Deduced from Polarization Measurements.- 3.2 Interpretation of Spectroscopic Measurements of Escaping Radiation.- 3.3 Spectroscopy in Visible and Infrared Ranges.- 3.4 Remote Sounding of Water Vapor and Carbon Monoxide in Far Infrared and Microwave Regions. Radio Spectrum.- 3.5 Optical Measurements in the 0.45-1.2 ?m Range from Venera Landers.- 3.6 Mass Spectrometric and Gas Chromatographic Measurements in the Lower Atmosphere.- 3.7 Physical Characteristics of the Cloud Layer.- 3.8 Ultraviolet Absorption in the Cloud Layer.- 3.9 Investigation of a Cloud Layer Elemental Composition by X-Ray Fluorescent Spectroscopy in the Region of 1 to 20 A (0.6-13 keV).- 3.10 Summary of the Data on the Tropospheric and Cloud Layer Composition.- 3.11 The Upper Atmosphere.- 3.12 Ionosphere.- 3.13 Temperature, Eddy Mixing, Atmospheric Dynamics, and Lightning.- 4 Photochemistry of the Venusian Atmosphere.- 4.1 Day Side Ionosphere.- 4.2 Nighttime Ionosphere.- 4.3 Metastable Species in the Venusian Ionosphere. Nitric Oxide, Atomic Nitrogen, and Atomic Carbon.- 4.4 Light Components of the Upper Atmosphere (H, H2, He). "Hot" Atoms and Nonthermal Escape of H, He, and O.- 4.5 Thermospheric Models.- 4.6 Lightning and Lower Atmospheric Chemistry. Nitric Oxide in the Lower Atmosphere.- 4.7 Lower Atmospheric and Surface Rock Compositions (0 - 50 km).- 4.8 Neutral Atmospheric Photochemistry Above 50 km. Main Problems, Previous Results, Main Chemical Reactions.- 4.9 Radiative Transfer and Aerosol Transport in the Cloud Laye.- 4.10 Boundary Conditions.- 4.11 Atmospheric Composition at 50 to 200 km (Results of Calculations).- 4.12 O2 1.27 m and O (1D) 630 nm Airglow. Photolytic Rates.- 4.13 The Influence of Some Reaction Rate Coefficients on the Results of Calculations.- 4.14 Photochemistry of the Venusian Mesosphere as Considered by Winick and Stewart (1980).- 4.15 Analysis of Atmospheric Photochemistry on Venus by Yung and DeMore (1982).- 4.16 Loss of Water from Venus and Its Atmospheric Evolution.- 4.17 Conclusions.- References.

Effects of Ambient Pressure on the Instability of a Liquid Boiling Explosively at the Superheat Limit

Abstract: The effect of ambient pressure on the dynamical behaviour of a single droplet (1-2 mm diameter) of volatile liquid boiling explosively at the limit of superheat is studied experimentally and theoretically. In a series of experiments it is shown that the evaporative instability, observed earlier by Shepherd & Sturtevant (1982) during the rapid vapourization of butane droplets at atmospheric pressure, is suppressed at high pressure. Three other fluids (pentane, isopentane, and ether) are tested to establish the generality of the instability and other transient processes previously observed. Direct evidence is obtained showing that during violently unstable boiling small liquid particles are torn from the liquid-vapour interface. This ejection of fine droplets from the evaporating surface produces a mass flux orders of magnitude greater than that characteristic of ordinary boiling. Raising the ambient pressure lowers the superheat attained at the superheat limit, which decreases the vapourization rate. At high pressure boiling consists of normal slow vapourization from a smooth interface. Observed bubble growth rates show reasonable agreement with theory. At intermediate pressures a transitional regime of stability occurs in which a drop initially vapourizes stably for several milliseconds while incipient instability waves develop on the evaporating interface. When only a small amount of liquid remains in the drop in the shape of a thin cap, heat transfer from the surrounding hot host fluid initiates violent boiling at the edge of the liquid cap. The subsequent rapid vapourization generates a radiated pressure field two orders of magnitude larger than during stable boiling, and sets the bubble into violent oscillation. The bubble is subject to the Rayleigh-Taylor instability and rapidly disintegrates into a cloud of small bubbles. Lowering the ambient pressure decreases the time delay between nucleation and onset of unstable boiling. For example, in ether at atmospheric pressure the instability is triggered less than 8 µsec after nucleation, shortly after the smooth vapour bubble contacts the droplet surface. Heterogeneous nucleation spreads out along the surface of the drop while disturbances (with a length scale of 100 µm) distort the unstably evaporating interface within the drop, substantially enhancing the vapourization rate. At early times, droplets torn from the evaporating surface evaporate before the instability-driven jet impinges upon the surrounding fluid, bulging the bubble surface. The last portion of liquid in a drop boils particularly violently and droplets ejected from the evaporating interface at this time remain intact to splatter the bubble surface. At subatmospheric pressures the most rapid vapourization occurs and temperature gradients within a drop produce spatial variations in vapourization rate. The Landau mechanism for the instability of laminar flames is adapted to the case of evaporation to investigate the effects of variable ambient pressure. A spherical version of the theory, applicable before the vapour bubble contacts the droplet surface, predicts absolute stability at atmospheric pressure. At later times the spherical constraint is inappropriate and planar theory yields results in general agreement with observation. Differences in fluid properties make some fluids more prone to instability than others. The product of the maximum growth rate with the time interval the interface is predicted to be linearly unstable measures the susceptibility to instability. For practical estimates it is suggested that a value of 3 of this parameter be taken as the lower limit for instability. The sensitivity of the instability to temperature suggests that small temperature nonuniformities may be responsible for quantitative departures of the behaviour from predictions.

Photoionization in air with ion mobility spectrometry using a hydrogen discharge lamp

Abstract: An ion mobility spectrometer (IMS) suitable for operation in air at atmospheric pressure using direct gaseous photoionization (PI) was demonstrated by using an on-axis mounted 10.2-eV hydrogen discharge lamp (lambda/sub max/ 121.5 nm). Penetration of UV photons into air in PI-IMS was determined by using product ion intensity and analyte location as 15 mm from the lamp window. Spectra were obtained for ten organic compounds and were simple with one to three peaks. Detection limits in PI-IMS ranged from 0.1 to 50 ppb directly without any sample preconcentration and working ranges were 1000-10,000. Detection limits were similar to those for conventional chemical ionization but working ranges were improved 100- to 1000-fold. Operation of PI-IMS in nitrogen with on-axis placement of the discharge lamp was complicated by penetration of photons > 2 cm through the Bradbury-Nielson shutter leading to analyte ionization in the drift region. Use of nitrogen as a drift gas was possible with the lamp placed perpendicular to gas flow. However, sensitivity and limits of detection were better with the on-axis design in air since ionization volumes were 7.1 cm/sup 3/ for the on-axis mount but only 4.0 cm/sup 3/ for the side-mount.

Atmospheric pressure ionization mass spectrometer

Abstract: An atmospheric pressure ionization mass spectrometer which comprises an ion source for ionizing a sample gas, a low pressure region provided with a mass filter and a collector therein, a differential pumping region provided between the ion source and the low pressure region and with electrodes provided on the side of the ion source and on the side of the low pressure region, respectively, and a pressure-gradient electrode means for dissociation and removal of cluster ions, as connected to the electrode on the side of the ion source among the electrodes provided in the differential pumping region is disclosed.

Dual air pressure cycle to produce low purity oxygen

Abstract: In a process for the production of an oxygen-enriched air product, feed air is fed to the main heat exchangers at two pressures. The high pressure feed air from the main exchanger is partially condensed to vaporize the oxygen-enriched air product. This partially condensed feed air is separated with the vapor phase being warmed and expanded to supply refrigeration and subsequently being fed to the low pressure fractionation section, and the liquid phase being used to reflux both the high pressure and low pressure fractionation sections of a double distillation column. The low pressure feed air from the main heat exchangers is fed to the high pressure fractionation section. The high pressure fractionation section condenser is used to provide reboiler duty to the low pressure fractionation section.

Techniques for determining thermal conductivity and heat capacity under hydrostatic pressure

Abstract: The paper describes a method for measuring the pressure dependence of the thermal conductivity and the heat capacity of hard materials and single crystals. Two parallel metal strips are evaporated onto a flat surface of the specimen, one being used as a heater, the other as a resistance thermometer. The appropriate theoretical expression for a specimen in a liquid medium is fitted to the temperature, sampled at constant time intervals. The thermophysical properties of the liquid high‐pressure medium are taken from hot‐wire experiments. The procedure has been thoroughly tested at atmospheric pressure using an MgO crystal and glass as specimens and liquids of different characteristics in lieu of high‐pressure medium. The accuracy attainable was found to be 3% or better, the standard deviation of the measurements being about 0.3%. The potential of the system was demonstrated by measurements on single‐crystal MgO under pressures up to 1 GPa.

Growth of ultrapure InP by atmospheric pressure organometallic vapor phase epitaxy

Abstract: We report the growth and characterization of ultrapure InP using trimethylindium and phosphine by atmospheric pressure organometallic vapor phase epitaxy (APOMVPE). The 77 K mobility of 131 000 cm2 /V s is the highest ever obtained by APOMVPE and among the highest ever measured for InP using any growth technique. The low‐temperature photoluminescence measurements reveal that impurity reduction occurs at higher growth temperatures.

The High-Tc Superconducting State of β-(BEDT-TTF)2I3 at Atmospheric Pressure: Bulk Superconductivity and Metastability

Abstract: The AC susceptibility study of β-(BEDT-TTF)2I3 reveals that the high-Tc metastable superconducting state which can be stabilized at atmospheric pressure after a particular pressure-temperature cycling procedure, exhibits bulk superconductivity resembling very closely that of the high-Tc state, which is stabilized above 1 kbar. Annealing experiments show that the high-Tc state remains stable at low temperature as long as the annealing temperature does not exceed 125 K.

Optical properties of InGaAs‐InP single quantum wells grown by atmospheric pressure metalorganic chemical vapor deposition

Abstract: Low‐temperature photoluminescence and photoconductivity studies of high quality InGaAs‐InP quantum wells grown by metalorganic chemical vapor deposition at atmospheric pressure are reported. The best luminescence linewidth obtained for a 100‐A well is found to be 7.9 meV. The residual line broadening is discussed in terms of interface fluctuations, and is compared directly with structural properties as determined by high resolution lattice imaging transmission electron microscopy.

Evidence for anomalous pressure dependence of the spontaneous strain in PbTiO3

Abstract: The a and c lattice parameters of tetragonal PbTiO3 have been measured by X-ray diffraction techniques, using a diamond-anvil cell, up to a pressure of 6.35(5) GPa at room temperature. The a lattice parameter is found to show a small expansion with pressure up to approximately 1.7 GPa, beyond which da/dP then becomes negative (as is more usual). The compressibility is highly anisotropic: between atmospheric pressure and 6.35 GPa the c parameter is compressed more than ten times as much as the a parameter. The spontaneous strain, z12/=(c/a-1)12/, exhibits significantly anomalous behaviour: the magnitude of d(z12/)/dP decreases with pressure, from -3.4(2)*10-2 GPa-1 at low pressures to about -1.3*10-2 GPa-1 at 6.0 GPa. There is some evidence that this can be interpreted as a discontinuity in the behavior of PbTiO3 at approximately 1.7 GPa, close to the pressure where da/dP passes through zero.

Pyrolyzing plastic or rubber wastes

Abstract: Pyrolytic reprocessing of plastic, rubber, or other hydrocarbon materials in which the resultant pyrolysis gas is brought in a cooling stage to a temperature just above the freezing point of water and to a pressure of approximately 0.8 to 1.4 bar of overpressure. The resultant condensate is then separated and heated to a normal storage temperature and the super atmospheric pressure on the condensate reduced to atmospheric pressure. The gas produced thereby comprising C 4 hydrocarbon compounds is supplied to the pyrolysis process as special product gas. By means of this provision, the proportion of aromatic compounds in the pyrolysis gas is raised substantially.

Kinetics of the OH + CO reaction under atmospheric conditions

Abstract: A pulsed laser photolysis-pulsed laser-induced fluorescence technique is used to directly measure the temperature, pressure, and H2O concentration dependence on k1 in air. K1 is found to increase linearly with increasing pressure at pressures of not greater than 1 atm, and the pressure dependence of k1 at 299 K is the same in N2 buffer gas as in O2 buffer gas. The rate constant in the low-pressure limit and the slope of the k1 versus pressure dependence are shown to be the same at 262 K as at 299 K. The present results significantly reduce the current atmospheric model uncertainties in the temperature dependence under atmospheric conditions, in the third body efficiency of O2, and in the effect of water vapor on k1.

Atomic emission spectrometry with a reduced-pressure afterglow extracted from an inductively coupled plasma

Abstract: The inductively coupled plasma (ICP) has proven to be an excellent excitation source for elemental analysis of solutions by atomic emission spectrometry (AES). One reason for the success of the ICP is that volatilization and atomization interferences are minimal because the analyte is efficiently atomized in the high-temperature, atmospheric pressure environment. It seems that such an environment is essential for proper dissociation of analytes from sample particles such as those generated by solution nebulization. In a conventional ICP the analyte atoms then continue through the axial channel where they are excited and ionized at atmospheric pressure. In some ways, the observation of ICP emission at reduced pressure might offer potential advantages in that line widths should be sharper than from an atmospheric pressure source. The same experimental techniques for sampling the ICP for mass spectrometry (MS) should also be useful for AES at reduced pressures. In fact, in ICP-MS the initial extraction process is often accompanied by emission of visible radiation from inside the first vacuum chamber. In addition to potential analytical applications, the observation of emission spectra from such an afterglow could also provide fundamental information about processes occurring during the extraction step, which would be useful for furthermore » improvements in ICP-MS. In this communication the authors report for the first time the results of initial investigations that indicate the feasibility of using an analytical ICP at atmospheric pressure for atomization while observing atomic emission spectra at reduced pressure as the analyte species are extracted into a vacuum chamber.« less

Thermal insulating material.

Abstract: A thermal insulating material comprising layers of thin walled hollow glass or plastic tubes (18) stacked together so that their longitudinal axes are perpendicular to the direction of heat flow. The tubes are preferably elliptical in cross-section with the larger axes of the ellipse also being aligned in a plane perpendicular to the direction of heat flow. The tubes may be sealed at each end or open; if sealed they may contain air or a low conductivity gas at atmospheric pressure or less than atmospheric pressure. In preferred embodiments the internal surface of the tubes are coated with a reflective material.

The growth and characteristics of device quality InP/Ga 1-x In x As y P 1-y double heterostructures by atmospheric pressure MOVPE using trimethylindium

Abstract: We report on recent developments of the atmospheric pressure OMVPE of InP and InxGa1-xASyP1-y using trimethylindium, trimethylgallium, phosphine and arsine. The use of diffuser organometallic sources significantly increased the accuracy of quaternary composition control. This control was achieved in the whole range of quaternary light emitting wavelengths from 1.20 micrometers up to the ternary GaInAs limit. The influence of the carrier gas was further investigated: device-quality heterostructures were obtained for either of the three carrier gases hydrogen, helium and argon. The experimental conditions for growing quaternaries with a given composition agree well with a simple model. This work has permitted the realization of 1.3 micrometer laser heterostructures with low threshold current density.

Remote measurement of surface pressure using absorption in the oxygen A-band.

Abstract: A simple technique is described that measures the atmospheric absorption in the oxygen A-band near 0.76 μm. A narrow interference filter is tilted so that its passband scans through the two branches of the absorption band. By viewing the direct solar beam a differential absorption measurement of the mass of oxygen in the optical path is obtained which is then compared to surface pressure. A transmittance model is described which gives results that agree well with the measurements. The model is also used to investigate the possible extension of the technique to a satellite-borne instrument for estimating surface pressure.

Valve manifold for a differential pressure transmitter

Abstract: A valve manifold (18) between a main flow line (10) and a differential pressure transmitter (24) having a body (40) with a bore (48) in which three spherical ball valve members (72, 74, 76) are mounted for rotation among run, zero and calibration positions. A low pressure calibrating port (28) and a high pressure calibrating port (46) are controlled by calibration valve member (76). Low pressure calibrating port (28) is connected to a source of a predetermined low pressure calibrating fluid and high pressure calibrating fluid port (46) is connected to a source of a predetermined high pressure calibrating fluid to calibrate transmitter (24) between any desired low pressure and high pressure ranges. Low pressure calibrating port (28) and high pressure calibrating port (46) may be selectively connected to atmospheric pressure if desired and the calibrating fluids may be controlled from a remote control site (26).

Methods and apparatus for steam sterilization

Abstract: Methods and apparatus for steam sterilization in which goods are conditioned by removing air and heated to a desired temperature in a chamber. The goods are subjected to a plurality of pressure pulses at above atmospheric pressure by alternate pressurization and venting of the chamber to atmospheric pressure. At the beginning of the process and following pressurization pulses, at or slightly above atmospheric pressure air is flushed from the chamber with steam prior to pressurization. Upon removal of air from the load and the chamber sterilizing environment, the chamber is pressurized until a selected pressure related sterilization temperature is reached. After a timed exposure period, the sterilizing chamber is vented to atmospheric pressure and a vacuum is created in the sterilizing chamber to dry the load.

Investigation of high pressure solid propellant combustion chemistryusing emission spectroscopy

Abstract: A survey of the chemiluminescent emission in the range from 280 and 800 nm from the flames of ammonium perchlorate (AP)and HMX-based solid propellants has been performed at pressures from atmospheric to 7 MPa (1000 psig). The AP propellant flame showed the emission of CH, CN, NH, and OH at atmospheric pressure (under nitrogen), as well as emission from several trace impurities such as Na, K, and Ca. As the pressure was increased, the banded molecular emission of all molecules except OH was rapidly obscured by a continuum that spanned the range 350-550 nm. In contrast, the HMX propellant showed CN, NH, and OH emission at pressures up to 7 MPa. CH emission was not detected in the HMX flame at any pressure; C2 emission was not detected in either propellant flame. Spatial intensity distributions of emitting species were obtained, showing OH and atomic emission spatially distributed throughout the propellant flame and CN and NH emission confined to the region near the surface.

Monochromatic calculations of atmospheric radiative transfer due to molecular line absorption

Abstract: Sensitivity studies related to the effects of line cutoff, spectral resolution, and temperature and pressure interpolations in radiative transfer have been performed so that a data set of absorption coefficients for water vapor, CO2, and O3 may be created efficiently. Results show that computations of absorption coefficients are affected only slightly by cutting a line off at a wave number 190 times the Lorentz half width from the center, or equivalently, cutting off 0.33 percent of the line intensity from the wings. To achieve a relative cooling rate error smaller than 2 percent, it is sufficient to precompute the absorption coefficient at three temperatures (210, 250, and 290 K) and 19 pressures with Delta (log 10 p) = 0.2. The absorption coefficient at other conditions can be interpolated linearly with pressure and exponentially with a quadratic in temperature. For the spectral resolution the absorption coefficients can be adequately computed at 0.01, 0.002, 0.005, and 0.025/cm intervals in the thermal water vapor, the CO2 and O3 bands, and the solar water vapor bands, respectively, which limits the error to only a few percent in the cooling and heating rates. Using the precomputed absorption coefficients, repeated monochromatic calculations of atmospheric heating/cooling rates for radiation model developments and for comparison with less detailed calculations are no longer difficult.

Fuel cell device

Abstract: A fuel-cell device according to this invention comprises switching valves which open at the time of the urgent stop of the device or the suspension of electric power and which are arranged outside a cell vessel, first and second differential pressure detectors which detect the differential pressures of an excess fuel pressure and an excess air pressure with respect to a nitrogen pressure in the cell vessel respectively, and first and second pressure controllers which control the opening and closing operations of a fuel differential pressure control valve and an air differential pressure control valve in response to the outputs of the first and second differential pressure detectors respectively.