Showing papers on "Total pressure published in 1984"

Electron attachment to the perfluoroalkanes n‐CNF2N+2 (N=1–6) using high pressure swarm techniques

Abstract: The electron attachment rate constants and negative ion formation mechanisms for six perfluoroalkanes [n‐CNF2N+2(N=1–6)] have been studied in a high pressure swarm experiment within the mean electron energy range from thermal energy (≊0.04 eV) to ≊4.9 eV. These experiments were performed over a total gas number density range of 3.2×1019 to 3.9×1020 cm−3 using N2 and argon as buffer gases. Dissociative electron attachment was found to be the only negative ion formation process for CF4 and C2F6. For C3F8, n‐C4F10, and n‐C5F12 the electron attachment rate constant measurements exhibited a large total pressure dependence which was strongest for C3F8 and decreased with increasing size of the perfluoroalkane molecule. These measurements have been interpreted as electron attachment by parent negative ion formation due to three‐body stabilization processes of the initially excited, short‐lived (5×10−11 s <τ<10−8 s) parent anion. The lifetimes of these transient parent anions have been found to depend on the natur...

Low‐temperature pressure variations in a self‐clamping pressure cell

Abstract: A simple method is described that permits a consistent determination of thermally induced pressure variations in a piston‐cylinder, self‐clamping pressure cell at temperatures less than ambient. Significant pressure changes are found to be present even for T<75 K. It is also shown that the pressure coefficient of resistance of a manganin‐wire gauge is, to within experimental uncertainty, independent of temperature over the range 0

Pressure and temperature dependence of the reaction NO2 + NO3 + M yields N2O5 + M

Abstract: The pressure and temperature dependences of the reaction NO2 + NO3 + M which yields N2O5 + M are investigated by using the flash photolysis/visible absorption technique in which the pseudo-first-order decay of NO3 is monitored as a function of total pressure (20-700 torr), diluent gas (M = He and N2), and temperature (236-358 K). The reaction is found to be in the falloff region in the 20-700 torr pressure range with collision efficiencies increasing in the order He less than N2. Falloff parameters are obtained by fitting the experimental data to the falloff equation of Troe and co-workers. The expression for k1(N2 concentration, T) is obtained and compared with the evaluations presented in the NASA (DeMore, 1983) and CODATA (Baulch et al., 1982) reviews of kinetic data for atmospheric chemistry. Both evaluations are based on N2O5 thermal decomposition data coupled with estimates of the equilibrium constant. The significance of the reactions for atmospheric chemistry rests not only on their rates but on the extent to which they result in a permanent sink for NOX.

Deposition and diffusion source control means and method

Abstract: The uniformity and reproducibility of doped, deposited, or etched layers formed in a reaction chamber (38) by a reactant derived in part from a solid or liquid reactant source (34), through which a carrier gas (29) flows, is improved by dynamically adjusting the carrier gas flow so that the ratio of the partial pressure of the reactant and the partial pressure of the carrier gas in the source chamber (33) remains substantially constant. This is conveniently accomplished by measuring the instantaneous source temperature therefrom, and then dynamically adjusting the carrier gas flow into the system to keep the total pressure of the reactant vapor plus carrier gas mixture (35) in the source chamber (33) at a predetermined value.

Wall shear measurements by electrochemical probe for gas-liquid two-phase flow in vertical duct

Abstract: For over 40 years, gas-liquid two-phase flows have been very important in the field of industrial sciences as their heat and mass transfer properties, particularly in chemical, oil and nuclear engineering. These flows are usually classified according to the relative configuration of the two phases, mainly by geometrical and visual criteria (bubble, slug, annular flows, etc.). To better understand the transport phenomena in these rather complicated flows, we need more experimental data, among which is the momentum transferred to the wall by the shear stress. Usually this quantity is indirectly obtained from overall measurements (total pressure drop, average void fraction, etc.). In vertical ducts, the pressure loss by friction is small compared with the total pressure drop and the pressure loss by gravity (weight of the fluid column); therefore, a small error concerning these two terms may involve a considerable uncertainty for the friction. This leads to the interest on the direct measurement of the local wall shear stress. The electrochemical technique using probes mounted flush to the wall appeared to be convenient for that purpose.

Electron diffraction studies of supersonic jets. VII. Liquid and plastic crystalline carbon tetrachloride

Abstract: Carbon tetrachloride at 3–11 mol % in neon carrier produces clusters of CCl4 molecules in flow through a Laval nozzle. Electron diffraction patterns of the clusters formed at a total pressure below 2.5 bar are intermediate between x‐ray diffraction patterns of bulk liquid CCl4 and neutron patterns of the amorphous material formed by condensation at 10 K. Strong, sharp interference features at low angle imply appreciable long range order, perhaps beyond 50 A, in the clusters, whose temperatures are about 210 K. When carrier partial pressure is increased beyond 2.6 bar, clusters begin to exhibit crystallinity. Crystallites belong to the rhombohedral plastic‐crystalline phase Ib, a=14.27 A and α=90.0°.

Radiation Pressure and the Stability of Broad-Line Region Clouds

Abstract: We discuss two constraints on the existence and stability of quasar emission-line gas. The case of a constant pressure photoionized cloud in pressure equilibrium with a surrounding hot gas is considered. We show that the radiation pressure of the internally generated line emission makes a significant contribution to the total pressure in standard broad-line region models, and that models with either a higher ionization parameter or lower gas density are dominated by radiation pressure and hence unstable. Further, clouds with ionization parameters lower than the standard value cannot be supported by any hot gas which is heated only by the observed radiation field. The result is a strict limit on the range of parameters which permit the existence of the observed emission-line gas. These results offer a natural explanation for the similarities among emission-line spectra of active galactic nuclei.

The gas-phase decomposition of methylsilane. Part I. Mechanism of decomposition under shock-tube conditions

Abstract: The gas-phase decompositions of methylsilane and methylsilane-d3 have been investigated in a single-pulse shock tube at 4700 torr total pressure in the temperature range of 1125–1250 K. For CH3SiD3 at 1200 K three primary steps occur in the homogeneous decomposition with efficiencies in parentheses: , , and . For CH3SiH3 at 1200 K the primary CH4 elimination efficiency is 0.09 while the total primary H2 elimination efficiency is 0.91. Minor product formations of C2H4, acetylene, dimethylsilane, and SiH4 are discussed.

Intense laser generation from an atomic-fluorine laser

Abstract: An intensive generation of radiation from a discharge-pumped atomic-fluorine gas laser is reported. A peak power exceeding 330 kW and a total energy of more than 2 mJ is obtained for a number of lines in the red, using a NF3∶He (1∶100) gas mixture at total pressure of 500 Torr. The circuitry optimization is described and the conditions for effective operation of the atomic-fluorine laser are discussed. The temporal and the spectral characteristics of the laser emission are also presented.

Flow measuring traverse probe

Abstract: A traverse probe for insertion transversely with respect to the direction of bulk flow of an air or gas stream to sense and average a traverse of the static pressure and separately to sense and average a traverse of the combination of static and velocity pressure or total pressure of the stream. The probe includes along its length a spaced set of total pressure ports in the tube wall substantially aligned with the direction of flow in the zone of positive total pressure at the tube wall facing the direction of flow and first and second spaced sets of static pressure ports in the tube wall, one set aligned in each of the zones of static pressure only that lie at the tube wall adjacent to and on each side of the zone of positive total pressure. The set of total pressure ports is aligned on the bisector of the included angle between the sets of static pressure ports where the included angle is in the range of about 78°-80° for useful probe diameters.

Apparatus for and method of operating quadrupole mass spectrometers in the total pressure mode

Abstract: This invention relates to a method of operating quadrupole mass spectrometers with only an RF potential applied to the filter rods so that the spectrometer operates to pass all ions above a particular value of m/e. In practice, spectrometers operated in this way usually show a marked loss in transmission efficiency for ions of high m/e when operated with an RF potential low enough to pass ions of m/e<10, and the invention overcomes this defect by providing a method of switching the RF potential between two or more values at which ions of different ranges of m/e values are efficiently transmitted, and combining the output signals at each value to give a resultant signal more accurately proportional to the number of ions formed in the source of the spectrometer, irrespective of their m/e values. The invention can be used to improve the accuracy of total pressure measurement using a conventional residual gas analyzing mass spectrometer, eliminating the need for additional pressure gauges.

Efficient conversion of CO + H2 into acetylene at atmospheric pressure using a graphite-based catalyst

Abstract: A 3 : 1 mixture of H2 : CO (total pressure 1 atm) is converted with ca. 20% efficiency and ca. 95% selectivity into acetylene at 100°C over a catalyst generated by partially de-intercalating a (first stage) sandwich compound C9FeCl3 with potassium naphthalenide: the catalyst maintains its performance for several days under these conditions.

Low-pressure study of the HO2 + HO2 reaction at 298 K

Abstract: The rate constant for the reaction HO2 + HO2 yields H2O2 + O2 was measured at 298 K and 1 torr total pressure of helium by using the discharge flow technique. A quadrupole mass spectrometer was used to detect HO2 in conjunction with in situ long-path ultraviolet absorption which was used for calibration. A value of 1.5 + or - 0.4 x 10 to the -12th per molecule/s was obtained for k1 where the rate constant is defined by the relation -d(HO2)/dt = 2K1(HO2)HO2.

Improved Statistical Analysis Method for Prediction of Maximum Inlet Distortion

Abstract: : This report presents the results of an investigation to develop an analytical method which predicts the maximum pressure distortion level and provides a synthesized pressure distortion map at the entrance to the turbine engine compression system. The method uses inlet total pressure statistical properties and a random number process to predict the most probable maximum pressure distortion and pressure distortion map. The validity of the method is demonstrated by comparing predicted maximum distortion levels and pressure contour maps with measured peak distortion levels and pressure contour maps obtained from analog screening of inlet pressure data. Keywords include: Time-variant distortion inlet analysis, and Inlet-engine compatibility statistical method.

Pressure measurements in a full-scale fly ash silo

Abstract: SUMMARY In cooperation with the Danish electrical power supply organizations Elkraft and Elsam, test series have been carried out in a circular fly ash bin with a diameter of 16 m and a height of 28 m. The bin is emptied by an arrangement that causes sector-wise fluidizing inthe slightly inclined bottom. This silo has been equipped with 19 pressure cells to measure the total pressure, and the same number of pore pressure cells were made and mounted in accordance with theoretical and experimental results developed at the Department of Structural Engineering, Technical University of Denmark. An interpretation of the test results shows that two types of flow field can exist, depending on certain conditions: one with mass flow and an almost rotationally symmetric pressure distribution, and one with partial funnel flow and a non-uniform pressure distribution. During flow it has been observed that the flow field can suddenly change between these two types. Such changes have been found to be connected with a con...

Apparatus for measuring fluid flow rate in a two-phase fluid stream

Abstract: A pitot tube type apparatus (10) is specifically adapted for measuring fluid flow rate in a gas flow containing entrained liquid droplets. The probe (20) includes first and second probe means (22,24) which are interconnected through pressure transmitting lines (12,14) to a pressure differential indicator (16). The first probe means (22) has a total pressure sampling port (21) opening directly upstream into the gas flow. The second probe means (24) has a static pressure sampling port (25) opening normal to the gas flow at a location downstream of the total pressure sampling port (21). A flat plate (30) is mounted to the first probe means and extends therealong in the plane of the static pressure sampling port (25) to a point adjacent and downstream of the static pressure sampling port so as to cause the boundary layer to be established over the static pressure sampling port (25). The ports (21,25) are also sized to be substantially greater than the size of the liquid droplets entrained in the gas. A flow of blow-back gas is intermittently passed through the transmitting lines to clear the lines and the probe means of any accumulating liquid.

Residual gas analysis in a SEM

Abstract: SUMMARY It is shown that a clean (hydrocarbon partial pressure 0·1 times 10−6 Pa) high vacuum (total pressure 5 times 10−5 Pa) is obtainable in the specimen chamber of a scanning electron microscope by relatively inexpensive means.

Transmission of pressure into the human limb from pneumatic splints

Abstract: The anterior compartment of the leg of 4 volunteers was used to study the transmission of externally applied pressure into a limb. The pressure from a pneumatic splint was found to be transmitted directly into the leg and was found to be added to the resting intramuscular pressure. The median inflation pressure of such a splint applied by trained ambulance personnel was 25 mm Hg (range 15–36 mm Hg). When the resting intramuscular pressure was raised experimentally, either by voluntary muscular contraction or venous engorgement, numerical addition of externally applied pressure was again observed. A moderate rise in compartment pressure commonly occurs after injury. Due care should be taken in the use of pneumatic splints or compressive dressings as the total pressure generated within a limb may be sufficient to induce ischaemia.

Calculation of deposition conditions for Si3N4 from a SiL4-NH3 gas phase (L=H, Cl, Br, CH)

Abstract: Deposition conditions yielding silicon nitride are calculated for a set of initial gaseous systems, by complex thermodynamic equilibria computations. The influence of temperature, total pressure and reactant gas ratios on the composition and yield of the condensed phase are shown for SiH4/NH3, SiCl4/NH3, SiBr4/NH3, Si(CH3)4/NH3 and SiH4/ CH4/NH3 systems. The interest of such calculations is to give an efficient approach for experimental studies of vapour-deposition systems.

Using the modulating ion current gauge for total pressure measurements below 10−10 Torr without errors caused by electron‐stimulated ion desorption

Abstract: Total pressure measurements below 10−10 Torr, in an active residual gas, were made using a special hot‐cathode ionization gauge, without errors caused by electron‐stimulated ion desorption. The gauge can separate the two ion signals, i.e., the signal created from gas phase molecules and that from electron‐stimulated ion desorption, by using a new modulation and amplification system. In order to verify this separation effect, experiments were made with oxygen and nitrogen introduction in the 10−10 Torr range.

Electron attachment to the perfluoroalkanes n-cnf2n+2(n = 1-6) using high-pressure swarm techniques

Abstract: The electron attachment rate constants and negative ion formation mechanisms for six perfluoroalkanes [n‐CNF2N+2(N=1–6)] have been studied in a high pressure swarm experiment within the mean electron energy range from thermal energy (≊0.04 eV) to ≊4.9 eV. These experiments were performed over a total gas number density range of 3.2×1019 to 3.9×1020 cm−3 using N2 and argon as buffer gases. Dissociative electron attachment was found to be the only negative ion formation process for CF4 and C2F6. For C3F8, n‐C4F10, and n‐C5F12 the electron attachment rate constant measurements exhibited a large total pressure dependence which was strongest for C3F8 and decreased with increasing size of the perfluoroalkane molecule. These measurements have been interpreted as electron attachment by parent negative ion formation due to three‐body stabilization processes of the initially excited, short‐lived (5×10−11 s <τ<10−8 s) parent anion. The lifetimes of these transient parent anions have been found to depend on the natur...

Rod-type detection terminal for measuring flow speed of fluid

Abstract: PURPOSE:To improve characteristics for general purpose and durability, by providing the 1st and 2nd sensors on the part inserting into a fluid transport pipe of a rod-type member which is pushed into a streamline of the pipe and transmitting detected signals of total pressure of the 1st sensor and static pressure of the 2nd sensor to the outside of the pipe. CONSTITUTION:The plural number of the 1st pressure/electric current transmitter S1 for total pressure detection and the 2nd pressure/electric current transmitter S2 for static pressure detection are provided to an insertion part 2A of a rod-type member 2 vertically by a streamline in a fluid transport pipe 1. It is constituted so that each electric current of both transmitters S1, S2 is transmitted from the part 2A to the outside of the pipe 1 through the member 2.

Device for measuring air flow rate

Abstract: PURPOSE:To detect the flow rate of air accurately in various duct pipes, by providing a bypass air path in a duct, yielding a bypass flow by the pressure difference between a total pressure pipe and a static pressure pipe, and detecting the bypass rate by a hot wire type flowmeter. CONSTITUTION:A static pressure pipe 21 is communicated to one end of a bypass air path 20, wherein a hot wire type resistor 23 is provided. The other end thereof is communicated to a total pressure pipe 22, which is opened in the air blowing direction in a duct through opening parts 25. A bypass controlling means 28, which controls and regulates the amount of bypass air, is provided. A bridge circuit output signal controlling means 30 is connected to a hot wire type resistor 23 and can adjust the output signal of a bridge circuit built in a box 29. The initial adjustment at the time of starting operation is performed by the bypass flow rate controlling means 28 or the output signal controlling means 30. Thus the measured value of the flow rate can be corrected, and the flow rate can be measured accurately.

Performance of Gas-Atomized Spray Scrubbers at High Pressure

Abstract: A large number of pressurized coal gasification processes being developed propose to use venturi scrubbers for particulate removal at high pressures. Theoretical predictions based on venturi scrubber performance models indicate that particle collection efficiency will decrease severely in these high gas pressure applications. An exploratory theoretical and experimental program was performed to study the effect of gas pressure on venturi scrubber performance. Experiments were done on a 0.47 m3/s (1000 acfm) pilot scale venturi scrubber. Particle collection performance was determined as a function of scrubber pressure drop for venturi scrubbers operating In the range of 1-10 atm total pressure. Experimental results confirmed that the particle collection efficiency of venturi scrubbers decreases for a given scrubber pressure drop as total gas pressure Is increased. To achieve the same particle collection efficiency, the pressure drop across a venturi scrubber operated at 10 atm Is about 10 times that of the ...