Showing papers on "Atmospheric pressure published in 1987"

Displacements of the Earth's surface due to atmospheric loading: Effects on gravity and baseline measurements

Abstract: Atmospheric mass loads and deforms the earth's crust. By performing a convolution sum between daily, global barometric pressure data and mass loading Green's functions, the time dependent effects of atmospheric loading, including those associated with short-term synoptic storms, on surface point positioning measurements and surface gravity observations are estimated. The response for both an oceanless earth and an earth with an inverted barometer ocean is calculated. Load responses for near-coastal stations are significantly affected by the inclusion of an inverted barometer ocean. Peak-to-peak vertical displacements are frequently 15-20 mm with accompanying gravity perturbations of 3-6 micro Gal. Baseline changes can be as large as 20 mm or more. The perturbations are largest at higher latitudes and during winter months. These amplitudes are consistent with the results of Rabbel and Zschau (1985), who modeled synoptic pressure disturbances as Gaussian functions of radius around a central point. Deformation can be adequately computed using real pressure data from points within about 1000 km of the station. Knowledge of local pressure, alone, is not sufficient. Rabbel and Zschau's hypothesized corrections for these displacements, which use local pressure and the regionally averaged pressure, prove accurate at points well inland but are, in general, inadequate within a few hundred kilometers of the coast.

Mass accommodation coefficient for HO2 radicals on aqueous particles

Abstract: The rate of reaction of gas phase HO2 radicals with a monodisperse, submicrometer aerosol was measured in a flow tube reactor at atmospheric pressure. At the relative humidity of the experiments (75%), the aerosol consisted of concentrated solution droplets of either LiNO3 or NH4HSO4. When the aerosol contained a sufficient amount of Cu(II) ions, reaction of HO2 with the aerosol was observed. The mass accommodation coefficient for HO2 on aqueous particles was determined to be greater than 0.2. This implies that in clouds HO2 mass transport will be limited by gas-phase diffusion and HO2 will be in equilibrium at the gas-liquid interface. Reactions of HO2 with Cu(I) and Cu(II) ions in submicrometer aerosols may have a significant role in converting atmospheric odd hydrogen radicals into H2O2.

Structure of high‐density amorphous water. I. X‐ray diffraction study

Abstract: X‐ray diffraction measurements up to momentum transfer q=16 A−1 were performed at atmospheric pressure on both the high‐density form of amorphous ice obtained by pressurization of crystalline ice Ih at 77 K up to 2 GPa and the low‐density form obtained by further heating. These two amorphous phases exhibit significant differences at the level of the second‐ and third‐nearest neighbors which involve a decrease of the O–O–O angle on compression at high pressure. Moreover, it is found that the low‐density form is quite similar to that obtained by vapor deposition on cooled substrates at 77 K.

Method and apparatus for surface treating of substrates

Abstract: A method for surface treating of thin substrates such as semiconductor wafers, wherein a semiconductor wafer formed with deep and minute trenches on its surface is horizontally placed on a spinner in a chamber with its trenched surface directed up, and then ultraviolet light is emitted to the surface of the wafer to dissolve impurities sticking in the trenches, and thereafter etchant is spouted from a nozzle to the trenched surface of the wafer being spinned about a vertical axis at a high speed, and next the inside of the chamber is rendered at a lower pressure than atmospheric pressure and the atmospheric pressure is recovered after the lapse of a predetermined time, and thus a series of these steps of etchant supplying, pressure reducing, and pressure recovering are carried out until the complete entrance of the etchant into the interior surfaces of the trenches is effected, so as to even or smooth the interior surfaces, and finally the wafer is treated with rinsing, and heating and drying.

Equations of properties as a function of temperature for seven fluids

Abstract: Equations are developed for property data of seven common fluids. These equations are useful in computer applications where it is desirable to determine properties without using tables or requiring the user to input data during the execution of programs. An equation is found that accurately approximates the variation of the fluid property data with temperature and is in a simple and convenient form. Equations are presented for the properties of the following fluids: air, liquid water, water vapor, carbon dioxide, Freon-12, engine oil, and mercury. The properties presented in equation form are: density, dynamic viscosity, constant pressure specific heat, thermal conductivity, and Prandtl number. Properties are presented for wide ranges of temperature and at atmospheric pressure.

Air support adjusting apparatus for seat of vehicle

Abstract: An apparatus for controlling air pressure of an onboard air support system of a vehicle comprising a pump connected to the air support for supplying or discharging the air to or from the air support, a pressure sensor in association with the air support for detecting the pressure thereof, a memory for storing present pressure values for the air support, a controller for generating pump operation control data on the basis of data derived from the detection output of the pressure sensor and data of the preset pressure value stored in the memory means, and a timer for determining the period during which the pump is to be operated on the basis of control data available from the controller, and producing a control signal supplied to said pump. Upon adjustment of the air pressure of the air support, the air pressure information inputted and stored previously is compared with the current air pressure, wherein the time for which the pump is operated is set in accordance with a difference resulting from the comparison, followed by operation of the pump.

Atmospheric pressure process for preparing pure cyclic esters

Abstract: This invention relates to an improved process for preparing highly pure cyclic esters by heating a polymer of the corresponding α-hydroxy acid or its ester or a copolymer of α-hydroxy acid or its ester and a thermally stable polyether in the presence of an inert gas at atmospheric pressure. The cyclic ester is carried from the reaction with the inert gas to a solvent system.

InGaAs-InP multiple quantum wells grown by atmospheric pressure metalorganic chemical vapor deposition

Abstract: The optical and structural properties of multiple quantum wells of InGaAs‐InP grown by atmospheric pressure metalorganic chemical vapor deposition are reported. Room‐temperature excitons are resolved for well widths from 50 to 200 A. Below 50 K, exciton linewidths, in absorption, of less than 10 meV are obtained. Absorbances for allowed valence to conduction subband transitions are found to be independent of well width, as expected in the two‐dimensional limit. A lower bound for the conduction‐band discontinuity of 235±20 meV is obtained.

High‐Pressure Phase Transitions in Zirconia and Yttria‐Doped Zirconia

Abstract: Raman spectroscopy has been utilized to characterize the phase transformations and transition pressures in pure and doped zirconia containing 3, 4, and 5 wt% Y/sub 2/O/sub 3/. The pressure-induced transformations were investigated to over 6 GPa (at room temperature) using a diamond anvil pressure cell. Pure zirconia single-crystal samples transformed to a ''new'' tetragonal phase (different from the one obtained at high temperatures at atmospheric pressure) at about 4 GPa. The pressure transformation, like the temperature transition, was reversible and exhibited an approximately 0.45-GPa hysteresis at room temperature. The 3 and 4 wt% Y/sub 2/O/sub 3/ crystals underwent a monoclinic (P2/sub 1/b) to tetragonal (P4/sub 2/nmc) phase transition similar to that observed at high temperatures. This phase change was found to be irreversible on releasing the pressure. The 5 wt% Y/sub 2/O/sub 3/ at atmospheric pressure consists of a tetragonal modification in a disordered cubic matrix; a gradual, but reversible, disordering transformation of the tetragonal precipitate takes place with pressure.

Differential pressure transmitter

Abstract: In a differential pressure transmitter, the respective measurement pressures are applied to a pair of barrier diaphragms respectively disposed on both side surfaces of a body, and movement of a sealed liquid caused by a differential pressure thereof is extracted as an electrical output by a differential pressure measuring pressure sensor provided by partitioning a sealing circuit. A sensor housing is manufactured independently of the body. The differential pressure measuring pressure sensor and a static pressure measuring pressure sensor for measuring a static pressure when applied with a measurement pressure applied to one of the pair of barrier diaphragms and a reference pressure such as an atmospheric pressure, are disposed in the housing. The housing is fixed to a housing mount portion of the body.

Experimental Study of the Effect of Gas Pressure on Arc Cathode Erosion and Redeposition in He, Ar, and SF6 from Vacuum to Atmospheric Pressure

Abstract: Experimental data on the erosion rates of a copper cathode in He, Ar, and SF6 from 10-6 to 760 torr are presented. The work performed by the cathodic-erosion plasma expanding against the gas is found experimentally to be constant, the volume of the expanding plasma cloud being linked to the gas pressure by the relation R3p = constant. These data agree with a redeposition model based on condensation of the metallic vapor produced by the arc on the cathode surface. The redeposited mass on the cathode is found to be proportional to the cube root of the gas mass density.

Alternatives to arsine: the atmospheric pressure organometallic chemical vapor deposition growth of GaAs using triethylarsenic

Abstract: Studies on the homoepitaxial growth of unintentionally doped GaAs by atmospheric pressure organometallic chemical vapor deposition using triethylarsenic and trimethylgallium have been carried out, and the effects of growth temperature, V/III ratio, and flow rate on film characteristics are reported. Mirrorlike epitaxial layers of n‐type GaAs were obtained at substrate temperatures of 540–650 °C and at V/III ratios of 6.7–11. The carrier concentrations for these films were approximately 1016–1017 cm−3, and from secondary ion mass spectroscopic analysis, the predominant epilayer impurities were determined to be both carbon and silicon.

Thermal-buble initiated breakdown characteristics of liquid helium and nitrogen at atmospheric pressure

Abstract: Experiments show that electric field promotes to form a vapor locking in a gap with a hot spot and in turn the formation of locked vapor produces the serious reduction of breakdown voltage. Especially it is argued that the dielectric strengh of liquid helium under serious hot spot conditions decreases below that for saturated gas.

A lidar system for measuring atmospheric pressure and temperature profiles

Abstract: The design and operation of a differential absorption lidar system capable of remotely measuring the vertical structure of tropospheric pressure and temperature are described. The measurements are based on the absorption by atmospheric oxygen of the spectrally narrowband output of two pulsed alexandrite lasers. Detailed laser output spectral characteristics, which are critical to successful lidar measurements, are presented. Spectral linewidths of 0.026 and 0.018 per cm for the lasers were measured with over 99.99 percent of the energy contained in three longitudinal modes.

The thermal conductivity of n-hexane, n-heptane, and n-decane by the transient hot-wire method

Abstract: New absolute measurements of the thermal conductivity of liquid n-hexane, n-heptane, and n-decane are reported. The measurements have been carried out in the temperature range 300–370 K at atmospheric pressure in a transient hotwire instrument. The accuracy of the measurements is estimated to be ±0.5%. The density dependence of the thermal conductivity of n-hexane and n-heptane is found to be well described by a universal equation for the hydrocarbons based on a rough hard-sphere model. The measurements of the three hydrocarbons studied are also employed to generate more accurate effective core volumes, which are the only parameters characteristic of the fluid required for the application of the proposed universal scheme.

Arsenic‐doped p‐CdTe layers grown by organometallic vapor phase epitaxy

Abstract: Arsenic‐doped CdTe layers have been grown by organometallic vapor phase epitaxy in an atmospheric pressure reactor using arsine as the dopant gas. Doping levels above 2×1017 cm−3 have been reproducibly obtained for the first time in an epitaxial growth system, with a doping uniformity of ±20% over 1.5×1.5 cm. This is a much higher level of doping than usually possible in bulk growth systems. The layers were characterized by photoluminescence measurements at 12 K and by Hall measurements as a function of temperature. The ionization energy of the As acceptor was found to be about 62±4 meV from transport measurements. It was also shown that the electronic activity of the As incorporated is a function of the dimethylcadmium to diethyltelluride partial pressure ratio in the gas phase.

Error Estimates for Passive Satellite Measurement of Surface Pressure Using Absorption in the A Band of Oxygen

Abstract: This paper investigates the feasibility of satellite remote sensing of surface pressure using radiometric measurements in the oxygen A band. It is shown out the primary sources of error are the uncertainties in the temperature profile, the surface reflection coefficient, and the aerosol loading. The impact of each of these errors upon the surface pressure is estimated. Pressure measurements to better than 2 hPa accuracy appear possible in principle over a wide range of surface reflectances if the temperature profile is known to an accuracy of 1 K, if the aerosol loading is known to an accuracy of 10%, and if instrumental noise can be limited to 0.1%. However, the calculations of this paper suggest that the radiometer must sample over extremely narrow spectral windows (1 cm−1) if this accuracy is to be achieved.

Formation and flow of gas bubbles in a pressurized bubble column with a single orifice or nozzle gas distributor

Abstract: The characteristics of gas bubbles in a 5 cm diameter bubble column equipped with a single orifice of 1,3 or 5 mm diameter were investigated under system pressure of 0.1-15 MPa. The formation of gas bubbles was strongly affected by the system pressure. Under high pressures a dispersed gas jet was formed at gas velocities where spherical gas bubbles would have been formed at atmospheric pressure. The critical gas velocity between the bubbling regime and the jetting regime was correlated with the liquid phase Weber number and the gas phase Reynolds number based on the gas velocity at the orifice. Bubble size and gas holdup in the main part of the bubble column were also affected by the bubble formation pattern at the distributor

Spark propagation mechanisms in ambient air at the surface of a charged dielectric. I: Experimental ― the main stages of the discharge

Abstract: The fast propagation (v≊106 ms−1) of an ionized and thermalized channel (ne≊1018 cm−3, T≊2.8×104 K) is studied in ambient air at atmospheric pressure, using gliding discharges produced over a charged dielectric slab. For surface voltages of about 100 kV, 1‐m‐long gliding sparks follow a straight line without any preionization of the gas. In this way, the discharges can be investigated with full diagnostics, including measurements of the current and of the propagation velocity, recording of the light emission (electronic image converter, spectroscopy, Lichtenberg figures), holographic interferometry of the spark channels, and detection of transient electric fields by capacitive probes. The various measurements are synchronized from optical fiber devices located close to the sparks. The study shows that the thermalized spark channel is produced by the three following stages: (a) a predischarge stage where the electron temperature Te≊2 eV is much greater than the gas temperature T0<1500 K; (b) a transient ar...

Drive unit for medical pump

Abstract: A fluid isolator is used to separate a drive gas from a drive air. A pulsation in the air pressure is produced to drive a balloon pump placed within the aorta through the drive gas. The gas pressure on the secondary side is determined as the air pressure applied to the primary side of the isolator is a positive pressure, and the quantity of gas on the secondary side is automatically regulated in accordance with a result of such determination. The gas pressure may be controlled so as to coincide with a target value, or alternatively, the quantity of gas may be controlled in accordance with a difference between the gas pressure and the blood pressure of a physical body.

Influence of Ambient Air Pressure on Pressure-Swirl Atomization

Abstract: The spray characteristics of six simplex atomizers are examined in a pressure vessel using a standard light diffraction technique. Attention is focused on the effects of liquid properties, nozzle flow number, spray cone angle, and ambient air pressure on mean drop size and drop-size distribution. For all nozzles and all liquids it is found that continuous increase in air pressure above the normal atmospheric value causes the SMD to first increase up to a maximum value and then decline. An explanation for this characteristic is provided in terms of the measurement technique employed and the various competing influences on the overall atomization process. The basic effect of an increase in air pressure is to improve atomization, but this trend is opposed by contraction of the spray angle which reduces the relative velocity between the drops and the surrounding air, and also increases the possibility of droplet coalescence.Copyright © 1987 by ASME

Upwelling in the liquid region surrounding the keyhole in penetration welding with a laser

Abstract: In penetration welding with a laser, the pressure in the keyhole is in excess at atmospheric pressure. A pressure gradient related to this is produced in the liquid region surrounding it, with the result that there is a flow parallel to the axis of the laser. The velocity of this flow is found as a function of the material constants, and the volume flow rate calculated. From this it is possible to construct an estimate of the elevation or depression of the surface of the weld. the shape of the surface cross section is discussed, and some deductions made about the pressure distribution in the liquid metal.

Use of the microwave-induced nitrogen discharge at atmospheric pressure as an ion source for elemental mass spectrometry

Abstract: A microwave-induced nitrogen discharge at atmospheric pressure (MINDAP) is used as the ion source for elemental mass spectrometry (MS) and compared to the use of the inductively coupled plasma (ICP). Optimization studies are presented to illustrate the dependence of signals on various instrumental parameters. Detection limits determined for five elements range from 3 to 22 ng/mL, somewhat higher than those determined with an ICP and the same mass spectrometer system. The background mass spectrum from the MINDAP is dominated by NO/sup +/; oxide and hydroxide ion ratios are higher than for ICP-MS. The linear dynamic range is similar to that in ICP-MS, but interferences caused by concomitant elements are much worse in MINDAP-MS.

Chemical Species and Temperature Profiles of Laminar Dichloromethane-Methane-Air Flames.I. Variation of Chlorine/ Hydrogen Loading

Abstract: Gas samples have been extracted from laminar atmospheric pressure CH2 CI2-CH4 -air flat flames using uncooled quartz probes with 0.05 to 0.10 mm orifices. The samples ( 50torr total pressure) were analyzed by gas chromatography for a number of major C1 and C2 hydrocarbons, chlorinated hydrocarbons and CO, CO2, O2 CH4 N2and H2 Temperatures were obtained throughout the reaction zone and into the postflame region using Pt-Pt (13 percent Rh) uncoated thermocouples with typical bead diameters of 0.15 mm. Measurements of species concentrations (major and minor stable products) along with temperatures are provided as a function of vertical distance above the burner for three separate flames with Cl/ H ratios of 0.060, 0.33 and 0.72 for φ 0.80. All intermediate species (with the exception of CHC13) are observed to fall below detectable limits when the CH2 CI2 concentration is less than 1 percent of its initial value. Peak values of major intermediates are presented as a function of Cl/ H ratio. In additi...

Method and device for pumping out vapours and/or vaporous mixtures and/or gas-vapour mixtures or similar media

Abstract: A method for pumping out vapours and/or vaporous mixtures and/or gas-vapour mixtures and/or similar media in two or more stages from at least one receiver by evacuation is to be developed further so that a final pressure of less than 10 hPa, and preferably in the range 10 hPa to 10 hPa, can easily be achieved, and that it is also ensured that the vapours and/or vaporous mixtures and/or gas-vapour mixtures or similar media can be compressed to atmospheric pressure and pumped, even if partial condensation occurs. This is achieved by having the one or more first, vacuum-producing pumping-out stages (A1) followed by one or more second pumping-out stages (A2) that compress to atmospheric pressure so that the one or more first pumping-out stages or the space surrounding these is pumped out by the one or more second pumping-out stages to below a pressure corresponding to the dew point of the respective medium to be pumped out.