These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

A Method for Calculating Viscosity and Thermal Conductivity of a Helium-Xenon Gas Mixture  

NASA Technical Reports Server (NTRS)

A method for calculating viscosity and thermal conductivity of a helium-xenon (He-Xe) gas mixture was employed, and results were compared to AiResearch (part of Honeywell) analytical data. The method of choice was that presented by Hirschfelder with Singh's third-order correction factor applied to thermal conductivity. Values for viscosity and thermal conductivity were calculated over a temperature range of 400 to 1200 K for He-Xe gas mixture molecular weights of 20.183, 39.94, and 83.8 kg/kmol. First-order values for both transport properties were in good agreement with AiResearch analytical data. Third-order-corrected thermal conductivity values were all greater than AiResearch data, but were considered to be a better approximation of thermal conductivity because higher-order effects of mass and temperature were taken into consideration. Viscosity, conductivity, and Prandtl number were then compared to experimental data presented by Taylor.

Johnson, Paul K.

2006-01-01

2

Monte Carlo simulation study of the Fano factor, w value, and energy resolution for the absorption of soft x rays in xenon{endash}neon gas mixtures  

SciTech Connect

Xenon gas proportional-scintillation counters (GPSC) have many applications in the detection of soft x rays where their energy resolution, R, is comparable to solid-state detectors when large window areas are required. However, R is known to deteriorate for energies E{sub xr} below 2{endash}3 keV due to electron loss to the entrance window. Since the addition of a lighter noble gas increases the absorption depth, we have investigated the use of Xe{endash}Ne gas mixtures at atmospheric pressure as detector fillings. The results of a Monte Carlo simulation study of the Fano factor, F, the w value, and the intrinsic energy resolution, R=2.36(Fw/E{sub xr}){sup 1/2}, are presented for Xe{endash}Ne mixtures and pure Xe and Ne. The results show that the addition of Ne to Xe reduces the intrinsic energy resolution R but this never compensates for the reduction in scintillation yield in GPSC applications, implying that the instrumental energy resolution R will only improve with the addition of Ne when electron loss to the window in pure Xe is significant. The simulation reproduces the photoionization process of the Xe and Ne atoms, the vacancy cascade decay of the residual ions, and the elastic and inelastic scattering of electrons by the gas atoms. The contribution of energy and charge transfer mechanisms such as Penning, associative, and transfer ionization is discussed in detail. It is shown that Penning and associative ionization are the crucial indirect ionization processes which determine the behavior of F and w at low concentrations of Xe. The importance of the nonmetastable Ne states is also assessed. {copyright} 2001 American Institute of Physics.

Santos, F. P.; Dias, T. H. V. T.; Rachinhas, P. J. B. M.; Conde, C. A. N.; Stauffer, A. D.

2001-06-15

3

TOF electron drift measurements in xenon difluoride (XeF2) and hydrogen sulfide (H2S) gas mixtures  

Microsoft Academic Search

Sensitive, high-temporal-resolution, time-of-flight (TOF) drift measurements yielding the drift velocity, longitudinal diffusion, and a new, higher order diffusion coefficient have been obtained in the gases XeF2 and H2S. These gases are of interest because of their potential as lasing constituents when combined with the highly energetic (8.5 MJ\\/kg) hydrogen azide (HN3) gas. Kinetic studies indicate that a hybrid electrochemical laser

C. A. Denman; L. A. Schlie

1989-01-01

4

Gas mixtures for X-ray proportional counters  

NASA Astrophysics Data System (ADS)

Results are presented which detail the performance of proportional counters when filled with a wide variety of argon- and xenon-based gas mixtures. It is shown that alternative gas mixtures can offer considerable advantages in the counters. The mixtures of argon plus 10 percent propane and xenon plus 10 percent propylene look particularly attractive in terms of operating voltage and energy resolution. The quench gas CO2 returns the poorest results in all areas except aging.

Ramsey, B. D.; Agrawal, P. C.

1988-01-01

5

Oriented xenon hydride molecules in the gas phase  

Microsoft Academic Search

The production of the xenon hydride molecules HXeX with X = I and Cl in the gas phase is reviewed. These molecules are generated by the photolysis of the hydrogen halide HI and HCl molecules on the surface of large xenon Xen clusters. Molecular dynamics simulations show that the flexible H atoms react with the heavy XeX moiety and form

Udo Buck; Michal Fárník

2006-01-01

6

Hyperpolarized xenon NMR and MRI signal amplification by gas extraction  

PubMed Central

A method is reported for enhancing the sensitivity of NMR of dissolved xenon by detecting the signal after extraction to the gas phase. We demonstrate hyperpolarized xenon signal amplification by gas extraction (Hyper-SAGE) in both NMR spectra and magnetic resonance images with time-of-flight information. Hyper-SAGE takes advantage of a change in physical phase to increase the density of polarized gas in the detection coil. At equilibrium, the concentration of gas-phase xenon is ?10 times higher than that of the dissolved-phase gas. After extraction the xenon density can be further increased by several orders of magnitude by compression and/or liquefaction. Additionally, being a remote detection technique, the Hyper-SAGE effect is further enhanced in situations where the sample of interest would occupy only a small proportion of the traditional NMR receiver. Coupled with targeted xenon biosensors, Hyper-SAGE offers another path to highly sensitive molecular imaging of specific cell markers by detection of exhaled xenon gas. PMID:19805177

Zhou, Xin; Graziani, Dominic; Pines, Alexander

2009-01-01

7

Hyperpolarized xenon relaxation times in perfluorocarbon emulsion and plasma mixtures  

Microsoft Academic Search

Hyperpolarized xenon (Hyp-129Xe) has great potential in perfusion, blood flow and functional investigations of organs beyond the lungs. Injection of xenon in a dissolved carrier would be the best delivery method for this purpose. The blood substitute perfluorooctyl bromide (PFOB) emulsion is the leading candidate as a carrier. To assess the suitability of PFOB emulsion as a Hyp-129Xe carrier, spectra

Albert R. Cross; Dan McPhee; Dale Stevens; Mark McDonald; Giles E. Santyr

2000-01-01

8

Separation of gas mixtures by thermoacoustic waves.  

SciTech Connect

Imposing sound on a binary gas mixture in a duct separates the two gases along the acoustic-propagation axis. Mole-fraction differences as large as 10% and separation fluxes as high as 0.001 M-squared c, where M is Mach number and c is sound speed, are easily observed. We describe the accidental discovery of this phenomenon in a helium-xenon mixture, subsequent experiments with a helium-argon mixture, and theoretical developments. The phenomenon occurs because a thin layer of the gas adjacent to the wall is immobilized by viscosity while the rest of the gas moves back and forth with the wave, and the heat capacity of the wall holds this thin layer of the gas at constant temperature while the rest of the gas experiences temperature oscillations due to the wave's oscillating pressure. The oscillating temperature gradient causes the light and heavy atoms in the gas to take turns diffusing into and out of the immobilized layer, so that the oscillating motion of the wave outside the immobilized layer tends to carry light-enriched gas in one direction and heavy-enriched gas in the opposite direction. Experiment and theory are in very good agreement for the initial separation fluxes and the saturation mole-fraction differences.

Swift, G. W. (Gregory W.); Geller, D. A. (Drew A.)

2001-01-01

9

Diffusion NMR methods applied to xenon gas for materials study.  

PubMed

We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack. PMID:12807139

Mair, R W; Rosen, M S; Wang, R; Cory, D G; Walsworth, R L

2002-12-01

10

Diffusion NMR methods applied to xenon gas for materials study  

NASA Technical Reports Server (NTRS)

We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack. c2002 John Wiley & Sons, Ltd.

Mair, R. W.; Rosen, M. S.; Wang, R.; Cory, D. G.; Walsworth, R. L.

2002-01-01

11

Gas-phase silicon micromachining with xenon difluoride  

NASA Astrophysics Data System (ADS)

Xenon difluoride is a gas phase, room temperature, isotropic silicon etchant with extremely high selectivity to many materials commonly used in microelectromechancial systems, including photoresists, aluminum, and silicon dioxide. Using a simple vacuum system, the effects of etch aperture and loading were explored for etches between 10 and 200 micrometers . Etch rates as high as 40 micrometers /minute were observed. Initial characteriation of wafer surface temperature during the etch indicates tens of degrees of self-heating, which is known to cause substantial decrease in etch rate.

Chang, Floy I.; Yeh, Richard; Lin, Gisela; Chu, Patrick B.; Hoffman, Eric G.; Kruglick, Ezekiel J.; Pister, Kristofer S. J.; Hecht, Michael H.

1995-09-01

12

Characteristic parameters of xenon near its liquid-gas critical point Yves Garrabos and Carole Lecoutre  

E-print Network

Characteristic parameters of xenon near its liquid-gas critical point Yves Garrabos and Carole the singular behaviors of the isothermal compressibility of xenon along the critical isochore. The validity range and the Ising nature of the crossover description are discussed in terms of a single scale

Boyer, Edmond

13

Ionization and scintillation response of high-pressure xenon gas to alpha particles  

E-print Network

High-pressure xenon gas is an attractive detection medium for a variety of applications in fundamental and applied physics. In this paper we study the ionization and scintillation detection properties of xenon gas at 10 bar pressure. For this purpose, we use a source of alpha particles in the NEXT-DEMO time projection chamber, the large scale prototype of the NEXT-100 neutrinoless double beta decay experiment, in three different drift electric field configurations. We measure the ionization electron drift velocity and longitudinal diffusion, and compare our results to expectations based on available electron scattering cross sections on pure xenon. In addition, two types of measurements addressing the connection between the ionization and scintillation yields are performed. On the one hand we observe, for the first time in xenon gas, large event-by-event correlated fluctuations between the ionization and scintillation signals, similar to that already observed in liquid xenon. On the other hand, we study the field dependence of the average scintillation and ionization yields. Both types of measurements may shed light on the mechanism of electron-ion recombination in xenon gas for highly-ionizing particles. Finally, by comparing the response of alpha particles and electrons in NEXT-DEMO, we find no evidence for quenching of the primary scintillation light produced by alpha particles in the xenon gas.

NEXT Collaboration; V. Álvarez; F. I. G. M. Borges; S. Cárcel; S. Cebrián; A. Cervera; C. A. N. Conde; T. Dafni; J. Díaz; M. Egorov; R. Esteve; P. Evtoukhovitch; L. M. P. Fernandes; P. Ferrario; A. L. Ferreira; E. D. C. Freitas; V. M. Gehman; A. Gil; A. Goldschmidt; H. Gómez; J. J. Gómez-Cadenas; D. González-Díaz; R. M. Gutiérrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; I. G. Irastorza; M. A. Jinete; L. Labarga; A. Laing; I. Liubarsky; J. A. M. Lopes; D. Lorca; M. Losada; G. Luzón; A. Marí; J. Martín-Albo; T. Miller; A. Moiseenko; F. Monrabal; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muñoz Vidal; H. Natal da Luz; G. Navarro; M. Nebot-Guinot; D. Nygren; C. A. B. Oliveira; R. Palma; J. Pérez; J. L. Pérez Aparicio; J. Renner; L. Ripoll; A. Rodríguez; J. Rodríguez; F. P. Santos; J. M. F. dos Santos; L. Segui; L. Serra; D. Shuman; A. Simón; C. Sofka; M. Sorel; J. F. Toledo; A. Tomás; J. Torrent; Z. Tsamalaidze; D. Vázquez; J. F. C. A. Veloso; R. Webb; J. T White; N. Yahlali

2012-11-19

14

A technique for administering xenon gas anesthesia during surgical procedures in mice.  

PubMed

Carrying out invasive procedures in animals requires the administration of anesthesia. Xenon gas offers advantages as an anesthetic agent compared with other agents, such as its protection of the brain and heart from hypoxia-induced damage. The high cost of xenon gas has limited its use as an anesthetic in animal experiments, however. The authors designed and constructed simple boxes for the induction and maintenance of xenon gas and isoflurane anesthesia in small rodents in order to minimize the amount of xenon gas that is wasted. While using their anesthesia delivery system to anesthetize pregnant mice undergoing caesarean sections, they measured the respiratory rates of the anesthetized mice, the survival of the pups and the percentages of oxygen and carbon dioxide within the system to confirm the system's safety. PMID:25333593

Ruder, Arne Mathias; Schmidt, Michaela; Ludiro, Alessia; Riva, Marco A; Gass, Peter

2014-10-21

15

Gas mixtures for spark gap closing switches  

DOEpatents

Gas mixtures for use in spark gap closing switches comprised of fluorocarbons and low molecular weight, inert buffer gases. To this can be added a third gas having a low ionization potential relative to the buffer gas. The gas mixtures presented possess properties that optimized the efficiency spark gap closing switches. 6 figs.

Christophorou, L.G.; McCorkle, D.L.; Hunter, S.R.

1987-02-20

16

Separation of gas mixtures by centrifugation  

NASA Technical Reports Server (NTRS)

Magnetohydrodynamic (MHD) centrifuge utilizing electric currents and magnetic fields produces a magnetic force which develops supersonic rotational velocities in gas mixtures. Device is superior to ordinary centrifuges because rotation of gas mixture is produced by MHD force rather than mechanical means.

Park, C.; Love, W. L.

1972-01-01

17

Gas-Mixture Cryocoolers Optimization: Theory & Experiment  

Microsoft Academic Search

The use gas mixture cryocoolers can be widely applied in spacecraft under 300-20K. The advantages of such mixtures are three-fold: (1) High reliability, (2) low noise level, and (3) application over the temperature range. Until recently the range we are addressing has been validated only theoretically. The results are based on calculations of gas-mixture properties and counter-flow heat exchangers. We

V. T. Arkhipov; V. F. Getmanets; Yu. I. Gorpinko; O. V. Yevdokimova; V. V. Yakuba; M. P. Lobko; H. Stears

1999-01-01

18

Radioactive 133Xenon Gas-Filled Balloon to Prevent Restenosis Dosimetry, Efficacy, and Safety Considerations  

Microsoft Academic Search

Background—Ionizing radiation administered intraluminally via catheter-based systems using solid and sources or liquid-filled balloons has shown reduction in the neointima formation after injury in the porcine model. We propose a novel system that uses a 133-Xenon (133Xe) radioactive gas-filled balloon catheter system. Methods and Results—Overstretch balloon injury was performed in the coronary arteries of 33 domestic pigs. A novel 133

Marc Apple; Ron Waksman; Rosanna C. Chan; Yoram Vodovotz; Jana Fournadjiev; Bill G. Bass

19

Membrane selective separation of binary gas mixtures  

Microsoft Academic Search

A general approach to solving a conjugate problem of mass transfer in the separation of binary gas mixtures in selectively\\u000a permeable membrane elements with allowance for the external convective and intramembrane diffusion resistances is suggested.

V. I. Baikov; N. V. Primak

2007-01-01

20

Absorption of Gas Phase Contaminant Mixtures.  

National Technical Information Service (NTIS)

This project seeks to study the effect of multiple gas-vapor mixtures on the activated carbon adsorption breakthrough time and pattern. Activated carbon cartridges used for respiratory protection are tested in most cases for a single component at relative...

C. Lungu

2004-01-01

21

Separation of gas mixtures by supported complexes  

Microsoft Academic Search

The goal of this program is to determine the feasibility of solvent-dissolved coordination complexes for the separation of gas mixtures under bench-scale conditions. In particular, mixtures such as low-Btu gas are examined for CO and Hâ separation. Two complexes, Pdâ(dpm)âBrâ and Ru(CO)â(PPhâ)â, were examined in a bench-scale apparatus for the separation of binary (CO-Nâ or Hâ-Nâ) and quinary (Hâ, CO,

D. A. Nelson; M. A. Lilga; R. T. Hallen; S. E. Lyke

1986-01-01

22

Cryogenic system with GM cryocooler for krypton, xenon separation from hydrogen-helium purge gas  

NASA Astrophysics Data System (ADS)

In the thorium molten salt reactor (TMSR), fission products such as krypton, xenon and tritium will be produced continuously in the process of nuclear fission reaction. A cryogenic system with a two stage GM cryocooler was designed to separate Kr, Xe, and H2 from helium purge gas. The temperatures of two stage heat exchanger condensation tanks were maintained at about 38 K and 4.5 K, respectively. The main fluid parameters of heat transfer were confirmed, and the structural heat exchanger equipment and cold box were designed. Designed concentrations after cryogenic separation of Kr, Xe and H2 in helium recycle gas are less than 1 ppb.

Chu, X. X.; Zhang, M. M.; Zhang, D. X.; Xu, D.; Qian, Y.; Liu, W.

2014-01-01

23

Separation of gas mixtures including hydrogen  

SciTech Connect

A process is described of separating a gas mixture comprising at least three components into three different fractions by pressure swing adsorption, comprising repeatedly performing a cycle including: passing said gas mixture sequentially through first and second adsorptive regions on each of which a second component of the mixture is more strongly adsorbed than a first component, but less strongly adsorbed than a third component; withdrawing a first fraction enriched in said first component from the downstream end of the second adsorptive region; stopping admission of the said gas mixture to the first adsorptive region; withdrawing a second fraction enriched in the second component from the downstream end of the first adsorptive region and from the upstream end of the second adsorptive region into a common pipeline; and withdrawing a third fraction enriched in the third component from the upstream end of the first adsorptive region.

Krishnamurthy, R.; Lerner, S.L.; Shukla, Y.; Stokley, A.G.

1993-08-10

24

Improved gas mixtures for gas-filled radiation detectors  

DOEpatents

Improved binary and ternary gas mixtures for gas-filled radiation detectors are provided. The components are chosen on the basis of the principle that the first component is one molecular gas or mixture of two molecular gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a noble gas having a very small cross section at and below about 1.0 eV, whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electric field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Christophorou, L.G.; McCorkle, D.L.; Maxey, D.V.; Carter, J.G.

1980-03-28

25

Gas mixtures for gas-filled particle detectors  

DOEpatents

Improved binary and tertiary gas mixtures for gas-filled particle detectors are provided. The components are chosen on the basis of the principle that the first component is one gas or mixture of two gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a gas (Ar) having a very small cross section at and below aout 0.5 eV, whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electron field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Christophorou, Loucas G. (Oak Ridge, TN); McCorkle, Dennis L. (Knoxville, TN); Maxey, David V. (Knoxville, TN); Carter, James G. (Oak Ridge, TN)

1980-01-01

26

Gas mixtures for gas-filled radiation detectors  

DOEpatents

Improved binary and ternary gas mixtures for gas-filled radiation detectors are provided. The components are chosen on the basis of the principle that the first component is one molecular gas or mixture of two molecular gases having a large electron scattering cross section at energies of about 0.5 eV and higher, and the second component is a noble gas having a very small cross section at and below about 1.0 eV, whereby fast electrons in the gaseous mixture are slowed into the energy range of about 0.5 eV where the cross section for the mixture is small and hence the electron mean free path is large. The reduction in both the cross section and the electron energy results in an increase in the drift velocity of the electrons in the gas mixtures over that for the separate components for a range of E/P (pressure-reduced electric field) values. Several gas mixtures are provided that provide faster response in gas-filled detectors for convenient E/P ranges as compared with conventional gas mixtures.

Christophorou, Loucas G. (Oak Ridge, TN); McCorkle, Dennis L. (Knoxville, TN); Maxey, David V. (Knoxville, TN); Carter, James G. (Knoxville, TN)

1982-01-05

27

A novel 83mKr tracer method for characterizing xenon gas and cryogenic distillation systems  

NASA Astrophysics Data System (ADS)

The radioactive isomer 83mKr, has many properties that make it very useful for various applications. Its low energy decay products, like conversion, shake-off and Auger electrons as well as X- and ?-rays are used for calibration purposes in neutrino mass experiments and direct dark matter detection experiments. Thanks to the short half-life of 1.83 h and the decay to the ground state 83Kr, one does not risk contamination of any low-background experiment with long-lived radionuclides. In this paper, we present a new approach, using 83mKr as a radioactive tracer in noble gases. A method of doping 83mKr, into xenon gas and its detection, using special custom-made detectors, based on a photomultiplier tube, is described. Two applications of this method are presented: firstly, it can be used to characterize the particle flow inside of gas routing systems and determine the circulation speed of gas particles inside of a gas purification system for xenon. Secondly, it is used for rapid estimating of the separation performance of a distillation system.

Rosendahl, S.; Bokeloh, K.; Brown, E.; Cristescu, I.; Fieguth, A.; Huhmann, C.; Lebeda, O.; Levy, C.; Murra, M.; Schneider, S.; V'enos, D.; Weinheimer, C.

2014-10-01

28

The NEXT experiment: A high pressure xenon gas TPC for neutrinoless double beta decay searches  

E-print Network

Neutrinoless double beta decay is a hypothetical, very slow nuclear transition in which two neutrons undergo beta decay simultaneously and without the emission of neutrinos. The importance of this process goes beyond its intrinsic interest: an unambiguous observation would establish a Majorana nature for the neutrino and prove the violation of lepton number. NEXT is a new experiment to search for neutrinoless double beta decay using a radiopure high-pressure xenon gas TPC, filled with 100 kg of Xe enriched in Xe-136. NEXT will be the first large high-pressure gas TPC to use electroluminescence readout with SOFT (Separated, Optimized FuncTions) technology. The design consists in asymmetric TPC, with photomultipliers behind a transparent cathode and position-sensitive light pixels behind the anode. The experiment is approved to start data taking at the Laboratorio Subterr\\'aneo de Canfranc (LSC), Spain, in 2014.

D. Lorca; J. Martín-Albo; F. Monrabal; for the NEXT Collaboration

2012-10-15

29

An automated multidimensional preparative gas chromatographic system for isolation and enrichment of trace amounts of xenon from ambient air.  

PubMed

The monitoring of radioactive xenon isotopes is one of the principal methods for the detection of nuclear explosions in order to identify clandestine nuclear testing. In this work, a miniaturized, multiple-oven, six-column, preparative gas chromatograph was constructed in order to isolate trace quantities of radioactive xenon isotopes from ambient air, utilizing nitrogen as the carrier gas. The multidimensional chromatograph comprised preparative stainless steel columns packed with molecular sieves, activated carbon, and synthetic carbon adsorbents (e.g., Anasorb®-747 and Carbosphere®). A combination of purification techniques--ambient adsorption, thermal desorption, back-flushing, thermal focusing, and heart cutting--was selectively optimized to produce a well-defined xenon peak that facilitated reproducible heart cutting and accurate quantification. The chromatographic purification of a sample requires approximately 4 h and provides complete separation of xenon from potentially interfering components (such as water vapor, methane, carbon dioxide, and radon) with recovery and accuracy close to 100%. The preparative enrichment process isolates and concentrates a highly purified xenon gas fraction that is suitable for subsequent ultra-low-level ?-, ß/?-spectroscopic or high-resolution mass spectrometric measurement (e.g., to monitor the gaseous fission products of nuclear explosions at remote locations). The Xenon Processing Unit is a free-standing, relatively lightweight, and transportable system that can be interfaced to a variety of sampling and detection systems. It has a relatively inexpensive, rugged, and compact modular (19-inch rack) design that provides easy access to all parts for maintenance and has a low power requirement. PMID:21347675

Larson, Tuula; Östman, Conny; Colmsjö, Anders

2011-04-01

30

Is xenon eldest?  

NASA Technical Reports Server (NTRS)

It is well known that the solubility of noble gases in magmas decreases with increasing atomic weight. Xenon, the weightiest of the stable noble gases, is the least soluble atmospheric gas in magma. It is not unreasonable to suppose that the noble gases should have degassed from (or equilibrated with) a bubbling mantle in order of increasing solubility, such that xenon was the most rapidly degassed and helium the least. The apparent relative ages of the famous radiogenic noble gas isotopes agrees, at least qualitatively, with this premise. When atmospheric loss processes are assigned their proper place, several long-standing xenonological puzzles become added evidence for xenon's relative antiquity. Xenon being the afore-mentioned sense the oldest atmospheric gas, will have been most greatly subject to escape, be it impact-driven or EUV-driven. Nonradiogenic xenon's pronounced isotopic fractionation has already been attributed to escape; why it should be more fractionated than krypton would be assigned to xenon's greater atmospheric age. The small atmospheric inventory of xenon relative to the other nonradiogenic noblegases, known as the 'missing xenon' problem, could easily be explained by differential escape. The relatively tiny atmospheric inventories of the radiogenic daughter products of 129 Iodine and 244 Plutonium, both much smaller than would be expected from the inferred abundances of the parents in meteorites, offer a third and fourth data to support the hypothesis that Earth has lost most of its xenon.

Zahnle, K.

1994-01-01

31

arXiv:1106.1812v1[physics.ins-det]9Jun2011 A Xenon Gas Purity Monitor for EXO  

E-print Network

words: xenon, electronegative ion, purification, tungsten oxide, argon, space charge 1. Introduction of the GPM is discussed along with the interactions of oxygen and other impurities with the GPM's tungsten locations in the EXO-200 xenon gas system, and they have proved useful during the commissioning phase

Gratta, Giorgio

32

IGNITION IMPROVEMENT OF LEAN NATURAL GAS MIXTURES  

SciTech Connect

This report describes work performed during a thirty month project which involves the production of dimethyl ether (DME) on-site for use as an ignition-improving additive in a compression-ignition natural gas engine. A single cylinder spark ignition engine was converted to compression ignition operation. The engine was then fully instrumented with a cylinder pressure transducer, crank shaft position sensor, airflow meter, natural gas mass flow sensor, and an exhaust temperature sensor. Finally, the engine was interfaced with a control system for pilot injection of DME. The engine testing is currently in progress. In addition, a one-pass process to form DME from natural gas was simulated with chemical processing software. Natural gas is reformed to synthesis gas (a mixture of hydrogen and carbon monoxide), converted into methanol, and finally to DME in three steps. Of additional benefit to the internal combustion engine, the offgas from the pilot process can be mixed with the main natural gas charge and is expected to improve engine performance. Furthermore, a one-pass pilot facility was constructed to produce 3.7 liters/hour (0.98 gallons/hour) DME from methanol in order to characterize the effluent DME solution and determine suitability for engine use. Successful production of DME led to an economic estimate of completing a full natural gas-to-DME pilot process. Additional experimental work in constructing a synthesis gas to methanol reactor is in progress. The overall recommendation from this work is that natural gas to DME is not a suitable pathway to improved natural gas engine performance. The major reasons are difficulties in handling DME for pilot injection and the large capital costs associated with DME production from natural gas.

Jason M. Keith

2005-02-01

33

ADIABATIC THERMAL EXPLOSION OF A GAS–SOLID MIXTURE  

Microsoft Academic Search

The critical conditions of the adiabatic explosion problem of a gas–solid (dusty gas) mixture is presented. The definitions used for the homogeneous gas to determine criticality are used here for the gas–solid mixture. This work showed that the classical definition of the critical point can be adopted and modified to determine the critical condition in ?–? and ?–? domains. It

SAAD A. EL-SAYED

2004-01-01

34

Xenon Isotope Releases from Buried Transuranic Waste  

Microsoft Academic Search

Xenon is an inert rare gas produced as a fission product in nuclear reactors and through spontaneous fission of some transuranic isotopes. Thus, xenon will be released from buried transuranic waste. Two complementary methods are used to measure xenon isotopes: radiometric analysis for short-lived radioxenon isotopes and mass spectrometry for detection of stable xenon isotopes. Initial measurements near disposal facilities

P. E. Dresel; S. R. Waichler; B. M. Kennedy; J. C. Hayes; J. I. McIntyre; J. R. Giles; A. J. Sondrup

2004-01-01

35

Effects of xenon gas on generation and propagation of shock waves in the cavity of excimer laser  

NASA Astrophysics Data System (ADS)

High repetition rate excimer lasers are expected for wide industrial application. The power of excimer laser, however, decreases rapidly in a higher repetition rate operation. Shock or acoustic waves, which are caused by the periodic pulse discharge, may limit the repetition rate of an excimer laser up to 2.5 kHz. Such waves cause inhomogeneity of gas density in the discharge region of the excimer laser. In high repetition rate operation this inhomogeneity remains at the next discharge. Arcing may be generated by this inhomogeneity and the homogeneous excitation of the laser gas is obstructed. Although these phenomena have been reported, the research for the effects of shock waves has remained insufficient. And the relation between these shock waves and discharge phenomena has not been clarified. To resolve this problem, we developed a scaling model chamber of a UV preionized excimer laser cavity with windows for flow visualization. We report the first result by using this model and Schlieren technique in a pure helium gas case. In our experiment three types of shock waves are found in the discharge cavity. Those shock waves are generated from the boundary of the main discharge area, from sparking pin gaps, and from the main electrode surfaces. In this study we focus on the effect of xenon gas on the generation and the propagation of shock waves. Components of the Xe-Cl excimer laser gas are helium, xenon, and hydrogen chloride. In those gases xenon has the largest molecular weight of 131.29. So we conclude xenon plays an important role in the shock wave propagation and in discharge phenomenon.

Kosugi, Shinichiroh; Maeno, Kazuo; Honma, Hiroki

1993-05-01

36

THEORETICAL STUDY ON THE INTERACTION BETWEEN XENON AND POSITIVE SILVER CLUSTERS IN GAS PHASE AND ON THE (001) CHABAZITE SURFACE  

SciTech Connect

A systematic study on the adsorption of xenon on silver clusters in the gas phase and on the (001) surface of silver-exchanged chabazite is reported. Density functional theory at the B3LYP level with the cluster model was employed. The results indicate that the dominant part of the binding is the {sigma} donation, which is the charge transfer from the 5p orbital of Xe to the 5s orbital of Ag and is not the previously suggested d{sub {pi}}-d{sub {pi}} back-donation. A correlation between the binding energy and the degree of {sigma} donation is found. Xenon was found to bind strongly to silver cluster cations and not to neutral ones. The binding strength decreases as the cluster size increases for both cases, clusters in the gas-phase and on the chabazite surface. The Ag{sup +} cation is the strongest binding site for xenon both in gas phase and on the chabazite surface with the binding energies of 73.9 and 14.5 kJ/mol, respectively. The results also suggest that the smaller silver clusters contribute to the negative chemical shifts observed in the {sup 129}Xe NMR spectra in experiments.

Hunter, D.

2009-03-16

37

Barium Ion Extraction and Identification from Laser Induced Fluorescence in Gas for the Enriched Xenon Observatory  

NASA Astrophysics Data System (ADS)

The scientific community is increasingly interested in neutrinoless double beta decay. A potential measurement of the decay rate would determine the neutrino mass and would be sensitive to some extensions of the Standard Model of particle physics. Unfortunately, the decay rate is very low and competes with natural and cosmogenic radioactivity. This thesis presents a technique that eliminates such background events. It is performed by observing the barium ion daughter from the double beta decay of xenon-136 using laser induced fluorescence. The technique is very complex and requires an excellent understanding of the barium ion spectroscopy and its chemistry in the vicinity of other molecules. Such a technique will become a unique advantage over other neutrinoless double beta decay experiments, especially if the neutrino mass is low. This thesis describes three main topics. The first one describes simulations of ionizing electrons in xenon to determine the size of a gas phase detector for a neutrinoless double beta decay measurement. It has been determined that a meter size detector would contain most electron tracks. Then, it describes the design of two barium ion sources, one relying on electric discharges across two electrodes and the other one using a high energy pulsed laser. From those sources, the spectroscopy of barium ions was studied. The branching ratio of the 62S1/2 -- ---6 2P1/2 transition was found to be 74 +/- 4%. By adding argon in the chamber, the lineshift of the transition due to collisions was found to be -132 MHz/torr while the broadening rate was 23 MHz/torr. Finally, the most interesting topic is the production of doubly charged barium ions using an electrospray source. From it, ions were extracted to vacuum in a mass spectrometer and charge conversion was achieved using triethylamine. The efficiency of the conversion of Ba+ to Ba ++ was almost 100%, with a cross-section between 1.69 x 10 -18 m2 and 2.21 x 10-18 m 2 without forming any molecules.

Rollin, Etienne

38

Structural transition in mixed hydrates of xenon and krypton as a function of gas composition  

SciTech Connect

Six samples of mixed hydrates of structure I former Xe and structure II former Kr were prepared from gas mixtures in which the concentration of Xe varied from 1 to 24 mol %. The structures and compositions of the hydrates were studied by X-ray diffraction, NMR, and calorimetry. In all cases, there was significant enrichment of Xe in the hydrate phase. The structure of the mixed hydrate changed from structure II to structure I when the initial concentration of Xe in the gas mixture was 5 mol % or more. The results show that the structure of the mixed hydrate is primarily determined by the component having the larger Cf, where C is the Langmuir constant and f the partial fugacity.

Handa, Y.P.; Ratcliffe, C.I.; Ripmeester, J.A.; Tse, J.S. (National Research Council of Canada, Ottawa, Ontario (Canada))

1990-05-17

39

Optimization of Dual-Energy Xenon-CT for Quantitative Assessment of Regional Pulmonary Ventilation  

PubMed Central

Objective Dual-energy X-ray computed tomography (DECT) offers visualization of the airways and quantitation of regional pulmonary ventilation using a single breath of inhaled xenon gas. In this study we seek to optimize scanning protocols for DECT xenon gas ventilation imaging of the airways and lung parenchyma and to characterize the quantitative nature of the developed protocols through a series of test-object and animal studies. Materials and Methods The Institutional Animal Care and Use Committee approved all animal studies reported here. A range of xenon-oxygen gas mixtures (0, 20, 25, 33, 50, 66, 100%; balance oxygen) were scanned in syringes and balloon test-objects to optimize the delivered gas mixture for assessment of regional ventilation while allowing for the development of improved three-material decomposition calibration parameters. Additionally, to alleviate gravitational effects on xenon gas distribution, we replaced a portion of the oxygen in the xenon/oxygen gas mixture with helium and compared gas distributions in a rapid-prototyped human central-airway test-object. Additional syringe tests were performed to determine if the introduction of helium had any effect on xenon quantitation. Xenon gas mixtures were delivered to anesthetized swine in order to assess airway and lung parenchymal opacification while evaluating various DECT scan acquisition settings. Results Attenuation curves for xenon were obtained from the syringe test objects and were used to develop improved three-material decomposition parameters (HU enhancement per percent xenon: Within the chest phantom: 2.25 at 80kVp, 1.7 at 100 kVp, and 0.76 at 140 kVp with tin filtration; In open air: 2.5 at 80kVp, 1.95 at 100 kVp, and 0.81 at 140 kVp with tin filtration). The addition of helium improved the distribution of xenon gas to the gravitationally non-dependent portion of the airway tree test-object, while not affecting quantitation of xenon in the three-material decomposition DECT. 40%Xe/40%He/20%O2 provided good signal-to-noise, greater than the Rose Criterion (SNR > 5), while avoiding gravitational effects of similar concentrations of xenon in a 60%O2 mixture. 80/140-kVp (tin-filtered) provided improved SNR compared with 100/140-kVp in a swine with an equivalent thoracic transverse density to a human subject with body mass index of 33. Airways were brighter in the 80/140 kVp scan (80/140Sn, 31.6%; 100/140Sn, 25.1%) with considerably lower noise (80/140Sn, CV of 0.140; 100/140Sn, CV of 0.216). Conclusion In order to provide a truly quantitative measure of regional lung function with xenon-DECT, the basic protocols and parameter calibrations needed to be better understood and quantified. It is critically important to understand the fundamentals of new techniques in order to allow for proper implementation and interpretation of their results prior to wide spread usage. With the use of an in house derived xenon calibration curve for three-material decomposition rather than the scanner supplied calibration and a xenon/helium/oxygen mixture we demonstrate highly accurate quantitation of xenon gas volumes and avoid gravitational effects on gas distribution. This study provides a foundation for other researchers to use and test these methods with the goal of clinical translation. PMID:23571834

Fuld, Matthew K.; Halaweish, Ahmed; Newell, John D.; Krauss, Bernhard; Hoffman, Eric A.

2013-01-01

40

30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.  

...containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6...containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the...

2014-07-01

41

30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.  

Code of Federal Regulations, 2012 CFR

...containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6...containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the...

2012-07-01

42

30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.  

Code of Federal Regulations, 2010 CFR

...containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6...containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the...

2010-07-01

43

30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.  

Code of Federal Regulations, 2013 CFR

...containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6...containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the...

2013-07-01

44

30 CFR 75.1106-6 - Exemption of small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures.  

Code of Federal Regulations, 2011 CFR

...containing nonflammable or nonexplosive gas mixtures. 75.1106-6 Section 75.1106-6...containing nonflammable or nonexplosive gas mixtures. Small low pressure gas cylinders containing nonflammable or nonexplosive gas mixtures, which provide for the...

2011-07-01

45

Formation of Structured Water and Gas Hydrate by the Use of Xenon Gas in Vegetable Tissue  

NASA Astrophysics Data System (ADS)

Freezing is a valuable technique for food preservation. However, vegetables are known to be softening remarkably after freezing and thawing process. It is expected to find alternative technique instead of freezing. Recently, the application of structured water and/or gas hydrate had been attempted to prolong the preservation of vegetable. In this study, the formation process of structure water and/or gas hydrate in pure water and carrot tissue was investigated by using NMR relaxation times, T1 and T2, of which applying condition was up to 0.4MPa and 0.8MPa at 5oC. Under the pressure of 0.4MPa, no gas hydrate was appeared, however, at 0.8MPa, formation of gas hydrate was recognized in both water and carrot tissue. Once the gas hydrate formation process in carrot tissue started, T1 and T2 increased remarkably. After that, as the gas hydrate developed, then T1 and T2 turned to decrease. Since this phenomenon was not observed in pure water, it is suggested that behavior of NMR relaxation time just after the formation of gas hydrate in carrot tissue may be peculiar to compartment system such as inter and intracellular spaces.

Ando, Hiroko; Suzuki, Toru; Kawagoe, Yoshinori; Makino, Yoshio; Oshita, Seiichi

46

Electrical Breakdown in a Martian Gas Mixture  

NASA Technical Reports Server (NTRS)

The high probability for dust interactions during Martian dust storms and dust devils combined with the cold, dry climate of Mars most likely result in airborne dust that is highly charged. On Earth, potential gradients up to 5 kV/m have been recorded and in some cases resulted in lightning. Although the Martian atmosphere is not conducive to lightning generation, it is widely believed that electrical discharge in the form of a corona occurs. In order to understand the breakdown of gases, Paschen measurements are taken which relate the minimum potential required to spark across a gap between two electrodes. The minimum potential is plotted versus the pressure-distance value for electrodes of a given geometry. For most gases, the potential decreases as the pressure decreases. For CO2, the minimum in the curve happens to be at Mars atmospheric pressures (5-7 mm Hg) for many distances and geometries. However, a very small amount (<0.1%) of mixing gases radically changes the curve, as noted by Leach. Here, we present the first experimental results of a Paschen curve for a Mars gas mixture compared with 100% pure CO2.

Buhler, C. R.; Calle, C. I.; Nelson, E.

2003-01-01

47

A novel $^{83\\mathrm{m}}$Kr tracer method for characterizing xenon gas and cryogenic distillation systems  

E-print Network

The radioactive isomer $^{83\\mathrm{m}}$Kr has many properties that make it very useful for various applications. Its low energy decay products, like conversion, shake-off and Auger electrons as well as X- and $\\gamma$-rays are used for calibration purposes in neutrino mass experiments and direct dark matter detection experiments. Thanks to the short half-life of 1.83 h and the decay to the ground state $^{83}$Kr, one does not risk contamination of any low-background experiment with long- lived radionuclides. In this paper, we present two new applications of $^{83\\mathrm{m}}$Kr. It can be used as a radioactive tracer in noble gases to characterize the particle flow inside of gas routing systems. A method of doping $^{83\\mathrm{m}}$Kr into xenon gas and its detection, using special custom-made detectors, based on a photomultiplier tube, is described. This technique has been used to determine the circulation speed of gas particles inside of a gas purification system for xenon. Furthermore, 83m Kr can be used to...

Rosendahl, S; Brown, E; Cristescu, I; Fieguth, A; Huhmann, C; Lebeda, O; Levy, C; Murra, M; Schneider, S; Vénos, D; Weinheimer, C

2014-01-01

48

High-pressure Xenon Gas Electroluminescent TPC Concept for Simultaneous Searches for Neutrino-less Double Beta Decay & WIMP Dark Matter  

NASA Astrophysics Data System (ADS)

Xenon is an especially attractive candidate for both direct WIMP and 0- decay searches. Although the current trend has exploited the liquid phase, gas phase xenon offers some remarkable performance advantages for energy resolution, topology visualization, and discrimination between electron and nuclear recoils. The NEXT-100 experiment, now beginning construction in the Canfranc Underground Laboratory, Spain, will operate at 12 bars with 100 kg of ^136Xe for the 0- decay search. I will describe recent results with small prototypes, indicating that NEXT-100 can provide about 0.5% FWHM energy resolution at the decay 2457.83 keV Q-value, as well as rejection of -rays by topology. However, sensitivity goals for WIMP dark matter and 0- decay searches indicate the need for ton-scale active masses; NEXT-100 provides the springboard to reach this scale with xenon gas. I describe a scenario for performing both searches in a single high-pressure ton-scale xenon gas detector, without significant compromise to either. In addition, -- even in a single, ton-scale, high-pressure xenon gas TPC, an intrinsic sensitivity to the nuclear recoil direction may exist -- plausibly offering an advance of more than two orders of magnitude relative to current low-pressure TPC concepts. I argue that, in an era of deepening fiscal austerity, such a dual-purpose detector may be possible, at acceptable cost, within the time frame of interest, and deserves our collective attention.

Nygren, David

2013-04-01

49

Gas hydrate formation from hydrogen\\/carbon dioxide and nitrogen\\/carbon dioxide gas mixtures  

Microsoft Academic Search

Gas hydrates from CO2\\/N2 and CO2\\/H2 gas mixtures were formed in a semi-batch stirred vessel at constant pressure and temperature of 273.7K. These mixtures are of interest to CO2 separation and recovery from flue gas and fuel gas, respectively. During hydrate formation the gas uptake was determined and the composition changes in the gas phase were obtained by gas chromatography.

Praveen Linga; Rajnish Kumar; Peter Englezos

2007-01-01

50

Inferential determination of various properties of a gas mixture  

DOEpatents

Methods for inferentially determining various properties of a gas mixture, when the speed of sound in the gas is known at an arbitrary temperature and pressure. The method can be applied to natural gas mixtures, where the known parameters are the sound speed, temperature, pressure, and concentrations of any dilute components of the gas. The method uses a set of reference gases and their calculated density and speed of sound values to estimate the density of the subject gas. Additional calculations can be made to estimate the molecular weight of the subject gas, which can then be used as the basis for heating value calculations. The method may also be applied to inferentially determine density and molecular weight for gas mixtures other than natural gases.

Morrow, Thomas B. (San Antonio, TX); Behring, II, Kendricks A. (Torrance, CA)

2007-03-27

51

Large scale high pressure jet fires involving natural gas and natural gas\\/hydrogen mixtures  

Microsoft Academic Search

A series of six large scale high pressure jet fires were conducted using natural gas and natural gas\\/hydrogen mixtures. Three tests involved natural gas and three involved a mixture of natural gas and hydrogen containing approximately 24% by volume hydrogen. For each fuel, the three tests involved horizontal releases from 20, 35 and 50mm diameter holes at a gauge pressure

B. J. Lowesmith; G. Hankinson

52

Composition for absorbing hydrogen from gas mixtures  

DOEpatents

A hydrogen storage composition is provided which defines a physical sol-gel matrix having an average pore size of less than 3.5 angstroms which effectively excludes gaseous metal hydride poisons while permitting hydrogen gas to enter. The composition is useful for separating hydrogen gas from diverse gas streams which may have contaminants that would otherwise render the hydrogen absorbing material inactive.

Heung, Leung K. (Aiken, SC); Wicks, George G. (Aiken, SC); Lee, Myung W. (Aiken, SC)

1999-01-01

53

Stripping and depressurization of solids and gas mixture  

Microsoft Academic Search

This patent describes an apparatus for stripping and depressurizing fine particles mixed with gas discharged from a vessel operated at elevated temperature and pressure conditions. It comprises means for receiving and conveying the mixture from the vessel, the means for receiving and conveying extending downwardly from the vessel. The means having upper and lower ends; means for selectively injecting gas

Dewitz

1990-01-01

54

Reduced viscosity interpreted for fluid/gas mixtures  

NASA Technical Reports Server (NTRS)

Analysis predicts decrease in fluid viscosity by comparing pressure profile of fluid/gas mixture with that of power-law fluid. Fluid is taken to be viscous, non-Newtonian, and incompressible; the gas to be ideal; the flow to be inertia-free, isothermal, and one dimensional. Analysis assists in design of flow systems for petroleum, coal, polymers, and other materials.

Lewis, D. H.

1981-01-01

55

Optical pumping and xenon NMR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

Raftery, M.D.

1991-11-01

56

Optical pumping and xenon NMR  

SciTech Connect

Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping {sup 129}Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the {sup 131}Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

Raftery, M.D.

1991-11-01

57

Gas sampling system for reactive gas-solid mixtures  

DOEpatents

An apparatus and method for sampling gas containing a reactive particulate solid phase flowing through a duct and for communicating a representative sample to a gas analyzer. A sample probe sheath 32 with an angular opening 34 extends vertically into a sample gas duct 30. The angular opening 34 is opposite the gas flow. A gas sampling probe 36 concentrically located within sheath 32 along with calibration probe 40 partly extends in the sheath 32. Calibration probe 40 extends further in the sheath 32 than gas sampling probe 36 for purging the probe sheath area with a calibration gas during calibration.

Daum, Edward D. (Alliance, OH); Downs, William (Alliance, OH); Jankura, Bryan J. (Mogadore, OH); McCoury, Jr., John M. (Mineral City, OH)

1990-01-01

58

Gas sampling system for reactive gas-solid mixtures  

DOEpatents

An apparatus and method for sampling a gas containing a reactive particulate solid phase flowing through a duct and for communicating a representative sample to a gas analyzer. A sample probe sheath 32 with an angular opening 34 extends vertically into a sample gas duct 30. The angular opening 34 is opposite the gas flow. A gas sampling probe 36 concentrically located within sheath 32 along with calibration probe 40 partly extend in the sheath 32. Calibration probe 40 extends further in the sheath 32 than gas sampling probe 36 for purging the probe sheath area with a calibration gas during calibration.

Daum, Edward D. (Alliance, OH); Downs, William (Alliance, OH); Jankura, Bryan J. (Mogadore, OH); McCoury, Jr., John M. (Mineral City, OH)

1989-01-01

59

Reversible sorption of nitrogen and xenon gas by the guest-free zeolite tris( o-phenylenedioxy)cyclotriphosphazene (TPP)  

Microsoft Academic Search

The sorption of nitrogen at 77K and xenon at 298K by the guest-free zeolite tris(o-phenylenedioxy)cyclotriphosphazene (TPP) was investigated. Xenon atoms show a remarkable affinity to the trigonal cavity of TPP by occupying about 90% of these sites at the pressure of about 100kPa. Efficient sorption originates from a van der Waals type complex of xenon in the ?-electron-rich environment given

G. Couderc; T. Hertzsch; N.-R. Behrnd; K. Krämer; J. Hulliger

2006-01-01

60

Acoustics and precondensation phenomena in gas-vapor saturated mixtures  

NASA Astrophysics Data System (ADS)

Starting from fundamental hydrodynamics and thermodynamics equations for thermoviscous fluids, a new modeling procedure, which is suitable to describe acoustic propagation in gas mixtures, is presented. The model revises the boundary conditions which are appropriate to describe the condensation-evaporation processes taking place on a solid wall when one component of the mixture approaches saturation conditions. The general analytical solutions of these basic equations now give a unified description of acoustic propagation in an infinite, semi-infinite, or finite medium, throughout and beyond the boundary layers. The solutions account for the coupling between acoustic propagation and heat and concentration diffusion processes, including precondensation on the walls. The validity of the model and its predictive capability have been tested by a comparison with the description available in the literature of two particular systems (precondensation of propane and acoustic attenuation in a duct filled with an air-water vapor saturated mixture). The results of this comparison are discussed to clarify the relevance of the various physical phenomena that are involved in these processes. The model proposed here might be useful to develop methods for the acoustic determination of the thermodynamic and transport properties of gas mixtures as well as for practical applications involving gas and gas-vapor mixtures like thermoacoustics and acoustics in wet granular or porous media.

Guianvarc'h, C.; Bruneau, M.; Gavioso, R. M.

2014-02-01

61

Characterization of Gas Mixtures for Ultra-Light Drift Chambers  

NASA Astrophysics Data System (ADS)

Low pressure helium/hydrocarbons mixtures are a key ingredient for next generation ultra-light drift chambers. Besides the obvious advantage of limiting the contribution to the momentum measurement due to multiple scattering, the operation at low pressure allows for a broad range of the drift chamber working parameters like drift velocity, diffusion, specific ionization and gas gain. Low pressure operation is of particular advantage for experiments where the tracking detector operates in vacuum. We present our campaign to characterize electron drift, primary ionization yield, gas gain, stability and the relative spatial resolution in helium based mixtures at absolute pressures down to 100 mbar.

Cascella, M.; Grancagnolo, F.; Mazzotta, P.; Miccoli, A.; Panareo, M.; Spedicato, M.; Tassielli, G.

2014-03-01

62

Trapping of gas mixtures by amorphous water ice.  

PubMed

Our studies on gas trapping in amorphous water ice at 24-100 K were extended, by using mixtures of CH4, CO, N2, and Ar, rather than single gases. In 1:1 gas:(water vapor) mixtures, the competition among these gases on the available sites in the ice showed that the trapping capacity for the various gases is determined not only by the structure and dynamics of the ice, but is also influenced by the gas itself. Whereas at 24-35 K all four gases are trapped in the ice indiscriminantly, at 50-75 K there is a clear enhancement, in the order of CH4 > CO > N2 > or approximately Ar. This order is influenced by the gas-water interaction energy, the size of the trapped gas atom or molecule, the type of clathrate-hydrate formed (I or II) and, possibly, other factors. It seems that the gas can be trapped in the amorphous ice in several different locations, each being affected in a different way by the deposition temperature and gas composition. Once a gas atom or molecule is trapped in a specific location, it is predestined to emerge in one of eight different temperature ranges, which are associated with changes in the ice. The experimentally observed enhancements, together with the findings on the gas composition of comet Halley, might enable an estimation of the gas composition in the region of comet formation. PMID:9945502

Bar-Nun, A; Kleinfeld, I; Kochavi, E

1988-10-15

63

Shear viscosity of a hadronic gas mixture  

E-print Network

We discuss in detail the shear viscosity coefficient eta and the viscosity to entropy density ratio eta/s of a hadronic gas comprised of pions and nucleons. In particular, we study the effects of baryon chemical potential on eta and eta/s. We solve the relativistic quantum Boltzmann equations with binary collisions (pi pi, pi N, and NN) for a state slightly deviated from thermal equilibrium at temperature T and baryon chemical potential mu. The use of phenomenological amplitudes in the collision terms, which are constructed to reproduce experimental data, greatly helps to extend the validity region in the T-mu plane. The total viscosity coefficient eta(T,mu)=eta^pi + eta^N increases as a function of T and mu, indirectly reflecting energy dependences of binary cross sections. The increase in mu direction is due to enhancement of the nucleon contribution eta^N while the pion contribution eta^pi diminishes with increasing mu. On the other hand, due to rapid growth of entropy density, the ratio eta/s becomes a decreasing function of T and mu in a wide region of the T-mu plane. In the kinematical region we investigated T T_c. There is a nontrivial structure at low temperature and at around normal nuclear density. We examine its possible interpretation as the liquid-gas phase transition.

Kazunori Itakura; Osamu Morimatsu; Hiroshi Otomo

2007-11-07

64

Xenon ionization detector for digital radiography  

Microsoft Academic Search

Xenon gas x-ray detectors have been used successfully in CT scanners; however, they have been found to be unsuitable for digital radiography. We have designed and built a new type of xenon x-ray detector array and tested its suitability for digital radiography. The detector consists of two parallel plates separated by a 0.5-mm gap, filled with xenon gas at a

D. J. Drost; A. Fenster

1982-01-01

65

Analysis of multicomponent gas mixture flows with partial chemical equilibrium  

Microsoft Academic Search

Diffusion equations and the corresponding transfer equations with effective transfer coefficients are derived using new unknown functions (linear combinations of diffusion fluxes and of concentrations) for reactive gas mixture flows with partial chemical equilibrium. The diffusion differential equations for rapid independent reactions degenerate into algebraic equations of detailed chemical equilibrium. The component formation sources on the right-hand sides of the

O. N. Suslov; E. I. Fateeva

1996-01-01

66

Method of scrubbing acid gases from gas mixtures  

SciTech Connect

A process for scrubbing acid gases, especially carbon dioxide, from gas mixtures with an aqueous amine solution serving as the scrubbing liquid in which hexamethylene diamine serves as the amine. The concentration of the hexamethylene diamine in the aqueous solution is 5 to 40% by weight, preferably 25 to 35% by weight.

Beran, F.; Gerhards, H.J.; Kohler, P.; Lassmann, E.

1981-07-21

67

Corrosion behaviors of inconel 617 in hydrogen base gas mixture  

NASA Astrophysics Data System (ADS)

The corrosion behavior of Inconel 617, a candidate for the structural material of heat exchanger in the high temperature gas-cooled reactor (HTGR), has been investigated at elevated temperatures in the hydrogen base gas mixture (80 pct H2 + 15 pct CO + 5 pct CO2). This gas mixture simulates the reducing gas in the direct steel making system that uses heat from HTGR in Japan. This gas has relatively high oxidizing and carburizing potentials. In the temperature range of 650 to 1000 °C Inconel 617 oxidized to form a Cr2O3 scale containing titanium oxide. The activation energy for this process is estimated to be 50 to 60 kcal/mol. The time dependence of the growth of the surface oxide scale was parabolic. The aluminum in Inconel 617 was internally oxidized. The time dependence of the internal oxidation was noticed to obey a 0.4 power rate law. Carburization was noticed at 650 and 900 °C. At 900 °C, carbides containing Si, Ti, and Mo precipitated beneath the oxide scale for gas exposure times up to 200 h. After 200 h, the formation and growth of the surface scale suppresses carburization. The thermodynamic analysis of gas atmosphere proposed by Gurry could be applied successfully to the experimental results. Some inconsistency existed mainly because of the scale formation and direct gas-metal interactions.

Shikama, Tatsuo; Tanabe, Tatsuhiko; Fujitsuka, Masakazu; Kitajima, Masahiro; Yoshida, Heitaro; Watanabe, Ryoji

1980-09-01

68

Electrochemical separation and concentration of hydrogen sulfide from gas mixtures  

DOEpatents

A method of removing sulfur oxides of H.sub.2 S from high temperature gas mixtures (150.degree.-1000.degree. C.) is the subject of the present invention. An electrochemical cell is employed. The cell is provided with inert electrodes and an electrolyte which will provide anions compatible with the sulfur containing anions formed at the anode. The electrolyte is also selected to provide inert stable cations at the temperatures encountered. The gas mixture is passed by the cathode where the sulfur gases are converted to SO.sub.4 -- or, in the case of H.sub.2 S, to S--. The anions migrate to the anode where they are converted to a stable gaseous form at much greater concentration levels (>10X). Current flow may be effected by utilizing an external source of electrical energy or by passing a reducing gas such as hydrogen past the anode.

Winnick, Jack (Atlanta, GA); Sather, Norman F. (Naperville, IL); Huang, Hann S. (Darian, IL)

1984-10-30

69

METEORITIC KRYPTON AND BARIUM VERSUS THE GENERAL ISOTOPIC ANOMALIES IN METEORITIC XENON  

Microsoft Academic Search

General isotopic anomalies in meteoritic xenon are described in detail. ; Where superior isotopic analyses exist, the xenon anomalies appear to be the same ; for all meteorites. In other cases there is fair evidence that the xenon ; examined is a mixture of meteoritic and contaminating atmospheric xenon. Two ; superior krypton analyses for carbonaceous chondrites show no anomalies

D. Krummenacher; C. M. Merrihue; R. O. Pepin; J. H. Reynolds

1962-01-01

70

Gas adsorption and gas mixture separations using mixed-ligand MOF material  

DOEpatents

A method of separating a mixture of carbon dioxiode and hydrocarbon gas using a mixed-ligand, metal-organic framework (MOF) material having metal ions coordinated to carboxylate ligands and pyridyl ligands.

Hupp, Joseph T. (Northfield, IL); Mulfort, Karen L. (Chicago, IL); Snurr, Randall Q. (Evanston, IL); Bae, Youn-Sang (Evanston, IL)

2011-01-04

71

Numerical studies of hypersonic binary gas-mixture flows near a sphere  

E-print Network

Numerical studies of hypersonic binary gas-mixture flows near a sphere V.V. Riabov 1 Diffusive] to study the flow. In the present study, diffusive effects in hypersonic flows of binary gas-mixtures near

Riabov, Vladimir V.

72

Modeling of non-thermal plasma in flammable gas mixtures  

NASA Astrophysics Data System (ADS)

An idea of using plasma-assisted methods of fuel ignition is based on non-equilibrium generation of chemically active species that speed up the combustion process. It is believed that gain in energy consumed for combustion acceleration by plasmas is due to the non-equilibrium nature of discharge plasma, which allows radicals to be produced in an above-equilibrium amount. Evidently, the size of the effect is strongly dependent on the initial temperature, pressure, and composition of the mixture. Of particular interest is comparison between thermal ignition of a fuel-air mixture and non-thermal plasma initiation of the combustion. Mechanisms of thermal ignition in various fuel-air mixtures have been studied for years, and a number of different mechanisms are known providing an agreement with experiments at various conditions. The problem is -- how to conform thermal chemistry approach to essentially non-equilibrium plasma description. The electric discharge produces much above-equilibrium amounts of chemically active species: atoms, radicals and ions. The point is that despite excess concentrations of a number of species, total concentration of these species is far below concentrations of the initial gas mixture. Therefore, rate coefficients for reactions of these discharge produced species with other gas mixture components are well known quantities controlled by the translational temperature, which can be calculated from the energy balance equation taking into account numerous processes initiated by plasma. A numerical model was developed combining traditional approach of thermal combustion chemistry with advanced description of the plasma kinetics based on solution of electron Boltzmann equation. This approach allows us to describe self-consistently strongly non-equilibrium electric discharge in chemically unstable (ignited) gas. Equations of pseudo-one-dimensional gas dynamics were solved in parallel with a system of thermal chemistry equations, kinetic equations for charged particles (electrons, positive and negative ions), and with the electric circuit equation. The electric circuit comprises power supply, ballast resistor connected in series with the discharge and capacity. Rate coefficients for electron-assisted reactions were calculated from solving the two-term spherical harmonic expansion of the Boltzmann equation. Such an approach allows us to describe influence of thermal chemistry reactions (burning) on the discharge characteristics. Results of comparison between the discharge and thermal ignition effects for mixtures of hydrogen or ethylene with dry air will be reported. Effects of acceleration of ignition by discharge plasma will be analyzed. In particular, the role of singlet oxygen produced effectively in the discharge in ignition speeding up will be discussed.

Napartovich, A. P.; Kochetov, I. V.; Leonov, S. B.

2008-07-01

73

49 CFR 173.305 - Charging of cylinders with a mixture of compressed gas and other material.  

Code of Federal Regulations, 2013 CFR

...false Charging of cylinders with a mixture of compressed gas and other material...305 Charging of cylinders with a mixture of compressed gas and other material. (a) Detailed requirements. A mixture of a compressed gas and any...

2013-10-01

74

49 CFR 173.305 - Charging of cylinders with a mixture of compressed gas and other material.  

Code of Federal Regulations, 2012 CFR

...false Charging of cylinders with a mixture of compressed gas and other material...305 Charging of cylinders with a mixture of compressed gas and other material. (a) Detailed requirements. A mixture of a compressed gas and any...

2012-10-01

75

49 CFR 173.305 - Charging of cylinders with a mixture of compressed gas and other material.  

Code of Federal Regulations, 2011 CFR

...false Charging of cylinders with a mixture of compressed gas and other material...305 Charging of cylinders with a mixture of compressed gas and other material. (a) Detailed requirements. A mixture of a compressed gas and any...

2011-10-01

76

Understanding the response behavior of potentiometric gas sensors for non-equilibrium gas mixtures  

SciTech Connect

Many applications of gas sensors require concentration measurements of reactive gases in mixtures that are out of thermodynamic equilibrium. These applications include: hydrogen and hydrocarbon fuel gas sensors operating in ambient air for explosion hazard detection, carbon monoxide detection in ambient air for health protection, combustion efficiency sensors for stoichiometry control, and nitric oxide sensors for air pollution monitoring. Many potentiometric and amperometric electrochemical sensor technologies have been developed for these applications. A class of the potentiometric sensors developed for gas mixtures are the non-Nerstian sensors. This presentation defines a categorization and theoretical analysis of three distinct electrochemical processes that can produce a non-Nernstian sensor response.

Garzon, F. H. (Fernando H.); Mukundan, R. (Rangachary); Brosha, E. L. (Eric L.)

2002-01-01

77

High-Calorific Gas Mixtures Produced from Biomass  

NASA Astrophysics Data System (ADS)

Investigations in the field of processing of different types of biomass into high calorific gas fuel are carried out in the Joint Institute for High Temperatures of RAS. Design of technology for effective processing of low-grade solid fuel to gas mixtures which can be used as fuel for power plants is rather actual problem both in the view of natural resources conservation and in the view of the development of autonomous energy unit for thermal and electric power supply. The experimental data on quantity and composition of the gaseous products formed in the process of peat pyrolysis are presented at various operating parameters of the process. It is shown that as a result of peat pyrolysis and the subsequent cracking of emanating products at temperature 1,000 °C it is possible to receive 1.4 m3 of gas with specific caloricity 11.7 MJ/m3 per 1 kg of original raw material.

Kosov, Valentin; Kosov, Vladimir; Sinelschikov, Vladimir; Zaichenko, Victor

78

Method for the simultaneous preparation of Radon-211, Xenon-125, Xenon-123, Astatine-211, Iodine-125 and Iodine-123  

DOEpatents

A method for simultaneously preparing Radon-211, Astatine-211, Xenon-125, Xenon-123, Iodine-125 and Iodine-123 in a process that includes irradiating a fertile metal material then using a one-step chemical procedure to collect a first mixture of about equal amounts of Radon-211 and Xenon-125, and a separate second mixture of about equal amounts of Iodine-123 and Astatine-211.

Mirzadeh, Saed (East Setauket, NY); Lambrecht, Richard M. (Quogue, NY)

1987-01-01

79

Xenon Additives Detection in Helium Micro-Plasma Gas Analytical Sensor  

NASA Astrophysics Data System (ADS)

Electron energy spectra of Xe atoms at He filled micro-plasma afterglow gas analyzer were observed using Collisional Electron Spectroscopy (CES) method [1]. According to CES, diffusion path confinement for characteristic electrons makes it possible to measure electrons energy distribution function (EEDF) at a high (up to atmospheric) gas pressure. Simple geometry micro-plasma CES sensor consists of two plane parallel electrodes detector and microprocessor-based acquisition system providing current-voltage curve measurement in the afterglow of the plasma discharge. Electron energy spectra are deduced as 2-nd derivative of the measured current-voltage curve to select characteristic peaks of the species to be detected. Said derivatives were obtained by the smoothing-differentiating procedure using spline least-squares approximation of a current-voltage curve. Experimental results on CES electron energy spectra at 10-40 Torr in pure He and in admixture with 0.3% Xe are discussed. It demonstrates a prototype of the new miniature micro-plasma sensors for industry, safety and healthcare applications. [1]. A.A.Kudryavtsev, A.B.Tsyganov. US Patent 7,309,992. Gas analysis method and ionization detector for carrying out said method, issued December 18, 2007.

Tsyganov, Alexander; Kudryavtsev, Anatoliy; Mustafaev, Alexander

2012-10-01

80

Binary and ternary gas mixtures for use in glow discharge closing switches  

DOEpatents

Highly efficient binary and ternary gas mixtures for use in diffuse glow discharge closing switches are disclosed. The binary mixtures are combinations of helium or neon and selected perfluorides. The ternary mixtures are combinations of helium, neon, or argon, a selected perfluoride, and a small amount of gas that exhibits enhanced ionization characteristics. These mixtures are shown to be the optimum choices for use in diffuse glow discharge closing switches by virtue of the combined physio-electric properties of the mixture components.

Hunter, Scott R. (Oak Ridge, TN); Christophorou, Loucas G. (Oak Ridge, TN)

1990-01-01

81

Comparison of SF6\\/N2 and SF6\\/CO 2 gas mixtures as alternatives to SF6 gas  

Microsoft Academic Search

The interest in SF6 gas mixtures has been re-ignited in recent years by the issue of the greenhouse effect of the SF6 gas, and most research work is now focused on a SF6\\/N2 gas mixture, which is suitable for application in electrical apparatus with slightly non-uniform fields. This paper presents a comparison of SF6\\/N2 and SF6\\/CO2 gas mixtures with a

Y. Qiu; E. Kuffel

1999-01-01

82

Two-phase argon and xenon avalanche detectors based on Gas Electron Multipliers  

E-print Network

We study the performance of two-phase avalanche detectors based on Gas Electron Multipliers (GEMs) and operated in an electron-avalanching mode in Ar and Xe. Emission, gain, energy resolution and stability characteristics of the detectors were studied. Rather high gains, reaching 5000, and stable operation for several hours were observed in the two-phase Ar avalanche detector using a triple-GEM multiplier. The signals induced by X-rays, beta-particles and gamma-rays were successfully recorded. Preliminary results were obtained in the two-phase Xe avalanche detector: the maximum gain of the triple-GEM in two-phase Xe and Xe+2%CH4 was about 200. The results obtained are relevant in the field of two-phase detectors for dark matter searches, coherent neutrino scattering, PET and digital radiography.

Bondar, A; Grebenuk, A; Pavlyuchenko, D; Snopkov, R; Tikhonov, Yu A

2006-01-01

83

Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry.  

PubMed

Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance. PMID:25325339

Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

2014-01-01

84

Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry  

PubMed Central

Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance. PMID:25325339

Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

2014-01-01

85

Anticonvulsant effect of xenon on neonatal asphyxial seizures.  

PubMed

Xenon, a monoatomic gas with very high tissue solubility, is a non-competitive inhibitor of N-methyl-D-aspartate (NMDA) glutamate receptor, has antiapoptotic effects and is neuroprotective following hypoxic ischaemic injury in animals. Xenon may be expected to have anticonvulsant effects through glutamate receptor blockade, but this has not previously been demonstrated clinically. We examined seizure activity on the real time and amplitude integrated EEG records of 14 full-term infants with perinatal asphyxial encephalopathy treated within 12 h of birth with 30% inhaled xenon for 24 h combined with 72 h of moderate systemic hypothermia. Seizures were identified on 5 of 14 infants. Seizures stopped during xenon therapy but recurred within a few minutes of withdrawing xenon and stopped again after xenon was restarted. Our data show that subanaesthetic levels of xenon may have an anticonvulsant effect. Inhaled xenon may be a valuable new therapy in this hard-to-treat population. PMID:23572341

Azzopardi, Denis; Robertson, Nicola J; Kapetanakis, Andrew; Griffiths, James; Rennie, Janet M; Mathieson, Sean R; Edwards, A David

2013-09-01

86

Operation of microstrip gas counters with DME-based gas mixtures  

NASA Astrophysics Data System (ADS)

This paper reports on the operation of MicroStrip Gas Counters (MSGC) with several dimethylether (DME)-based gas mixtures. We present measurements of signal amplitude, detection efficiency and spatial resolution for minimum ionizing particles. We also show measurements of electron drift velocity and transverse diffusion coefficient in the counting gases considered. These results are discussed regarding the use of MSGC's for tracking at high-energy physics experiments that have to deal with high particle rates.

Bouhali, O.; Udo, F.; Van Doninck, W.; Van Lancker, L.; Vander Velde, C.; Vanlaer, P.; Zhukov, V.; Beaumont, W.; Beckers, T.; De Troy, J.; Van Dyck, C.; Verbeure, F.

87

10 CFR 504.8 - Prohibitions against excessive use of petroleum or natural gas in mixtures-certifying powerplants.  

Code of Federal Regulations, 2011 CFR

...excessive use of petroleum or natural gas in mixtures-certifying powerplants. 504.8...excessive use of petroleum or natural gas in mixtures—certifying powerplants. ...the reasonable fuel efficiency of the mixture. This authority is contained in...

2011-01-01

88

10 CFR 504.8 - Prohibitions against excessive use of petroleum or natural gas in mixtures-certifying powerplants.  

...excessive use of petroleum or natural gas in mixtures-certifying powerplants. 504.8...excessive use of petroleum or natural gas in mixtures—certifying powerplants. ...the reasonable fuel efficiency of the mixture. This authority is contained in...

2014-01-01

89

10 CFR 504.8 - Prohibitions against excessive use of petroleum or natural gas in mixtures-certifying powerplants.  

Code of Federal Regulations, 2013 CFR

...excessive use of petroleum or natural gas in mixtures-certifying powerplants. 504.8...excessive use of petroleum or natural gas in mixtures—certifying powerplants. ...the reasonable fuel efficiency of the mixture. This authority is contained in...

2013-01-01

90

10 CFR 504.8 - Prohibitions against excessive use of petroleum or natural gas in mixtures-certifying powerplants.  

Code of Federal Regulations, 2012 CFR

...excessive use of petroleum or natural gas in mixtures-certifying powerplants. 504.8...excessive use of petroleum or natural gas in mixtures—certifying powerplants. ...the reasonable fuel efficiency of the mixture. This authority is contained in...

2012-01-01

91

10 CFR 504.8 - Prohibitions against excessive use of petroleum or natural gas in mixtures-certifying powerplants.  

Code of Federal Regulations, 2010 CFR

...excessive use of petroleum or natural gas in mixtures-certifying powerplants. 504.8...excessive use of petroleum or natural gas in mixtures—certifying powerplants. ...the reasonable fuel efficiency of the mixture. This authority is contained in...

2010-01-01

92

49 CFR 173.305 - Charging of cylinders with a mixture of compressed gas and other material.  

Code of Federal Regulations, 2010 CFR

...See § 173.301.) For mixtures, the liquid portion of the liquefied compressed gas at 131 °F. plus any additional liquid or solid must not completely fill the...mixtures. Mixtures containing compressed gas or gases including...

2010-10-01

93

On studies of 3He and isobutane mixture as neutron proportional counter gas  

NASA Astrophysics Data System (ADS)

The performance of neutron detectors filled with 3He+iC 4H 10 (isobutane) gas mixtures has been studied and compared with the performance of detectors filled with 3He+Kr gas mixtures. The investigations are made to determine suitable concentration of isobutane in the gas mixture to design neutron proportional counters and linear position sensitive neutron detectors (1-D PSDs). Energy resolution, range of proportionality, plateau and gas gain characteristics are studied for various gas mixtures of 3He and isobutane. The values for various gas constants are determined by fitting the gas gains to Diethorn and Bateman's equations and their variation with isobutane concentration in the fill gas mixture is studied.

Desai, S. S.; Shaikh, A. M.

2006-02-01

94

SAFETY OF HYDROGEN/NATURAL GAS MIXTURES BY PIPELINES: ANR FRENCH PROJECT HYDROMEL  

E-print Network

1 SAFETY OF HYDROGEN/NATURAL GAS MIXTURES BY PIPELINES: ANR FRENCH PROJECT HYDROMEL H�brard, J.1 linked with Hydrogen/Natural gas mixtures transport by pipeline, the National Institute of Industrial scenario, i.e. how the addition of a quantity of hydrogen in natural gas can increase the potential

Boyer, Edmond

95

Aerobic fitness in patients with fibrositis. A controlled study of respiratory gas exchange and 133-xenon clearance from exercising muscle  

SciTech Connect

Aerobic fitness was evaluated in 25 women with fibrositis, by having them exercise to volitional exhaustion on an electronically braked cycle ergometer. Compared with published standards, greater than 80% of the fibrositis patients were not physically fit, as assessed by maximal oxygen uptake. Compared with matched sedentary controls, fibrositis patients accurately perceived their level of exertion in relation to oxygen consumption and attained a similar level of lactic acidosis, as assessed by their respiratory quotient and ventilatory threshold. Exercising muscle blood flow was estimated by 133-xenon clearance in a subgroup of 16 fibrositis patients and compared with that in 16 matched sedentary controls; the fibrositis patients exhibited reduced 133-xenon clearance. These results indicate a need to include aerobic fitness as a matched variable in future controlled studies of fibrositis and suggest that the detraining phenomenon may be of relevance to the etiopathogenesis of the disease.

Bennett, R.M.; Clark, S.R.; Goldberg, L.; Nelson, D.; Bonafede, R.P.; Porter, J.; Specht, D.

1989-04-01

96

Fermion-fermion interaction in a dilute gas-mixture Bose condensate  

SciTech Connect

A mixture of a one-component Bose gas and two-component Fermi gas is considered at temperatures at which the Bose gas is completely condensed. Two fermions in such a mixture can interact with each other exchanging bosons from the condensate or supercondensate. The interaction potential, a change in the effective mass, the decay, and fermion spectrum are calculated in this quantum Fermi-Bose mixture.

Mogilyuk, T. I., E-mail: 5taras@mail.ru [National Research Centre Kurchatov Institute (Russian Federation)

2011-11-15

97

Quantitative Fourier transform infrared analysis of gas phase cigarette smoke and other gas mixtures  

SciTech Connect

A new method for the analysis of selected components in complex gas mixtures has been developed utilizing a relatively inexpensive Fourier transform infrared spectrometer and a continuous flow gas cell. The method was used to monitor nitric oxide and nitrogen dioxide concentrations in cigarette smoke with time. Using multivariate least-square regression analysis, it is possible to simultaneously quantitate both NO and NO{sub 2}, even in the presence of overlapping peaks. Using this method, the oxidation of nitric oxide in the presence of isoprene in cigarette smoke and in a model system was followed with time. The method also can be applied to other compounds in smoke or to any other gaseous mixture.

Cueto, R.; Church, D.F.; Pryor, W.A. (Louisiana State Univ., Baton Rouge (USA))

1989-03-01

98

Binary and ternary gas mixtures for use in glow discharge closing switches  

DOEpatents

Highly efficient binary and ternary gas mixtures for use in diffuse glow discharge closing switches are disclosed. The binary mixtures are combinations of helium or neon and selected perfluorides. The ternary mixtures are combinations of helium, neon, or argon, a selected perfluoride, and a small amount of gas that exhibits enhanced ionization characteristics. These mixtures are shown to be the optimum choices for use in diffuse glow discharge closing switches by virtue if the combines physio-electric properties of the mixture components. 9 figs.

Hunter, S.R.; Christophorou, L.G.

1988-04-27

99

Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures  

SciTech Connect

A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

Aines, Roger D.

2013-03-12

100

Flammability of selected heat resistant alloys in oxygen gas mixtures  

SciTech Connect

Within recent years, the use of oxygen has increased in applications where elevated temperatures and corrosion may be significant factors. In such situations, traditional alloys used in oxygen systems will not be adequate. Where alternative alloys must be utilized, based upon environmental requirements, it is essential that they may be characterized with respect to their ignition and combustion resistance in oxygen. Promoted ignition and promoted ignition-combustion are terms which have been used to describe a situation where a substance with low oxygen supports the combustion of a compatibility ignites and more ignition resistant material. In this paper, data will be presented on the promoted ignition-combustion behavior of selected heat resistant engineering alloys that may be considered for gaseous oxygen applications in severe environments. In this investigation, alloys have been evaluated via both flowing and static (fixed volume) approaches using a rod configuration. Oxygen-nitrogen gas mixtures with compositions ranging from approximately 40 to 99.7% oxygen at pressures of 3.55 to 34.6 MPa were used in the comparative studies.

Zawierucha, R.; McIlroy, K.; Million, J.F. [Praxair, Inc., Tonawanda, NY (United States)

1995-12-31

101

Response of tomato plants to simulated landfill gas mixtures  

SciTech Connect

The roots of tomato plants were fumigated with simulated refuse-generated gas mixtures at levels of methane (CH/sub 4/), carbon dioxide (CO/sub 2/), and oxygen (O/sub 2/) previously measured in the atmospheres of landfill cover soils associated with poor growth or death of plants. A concentration of 18% CO/sub 2/ or greater, exceeded in almost 30% of thirty-two landfills examined throughout the US, caused reduced growth and visible symptoms on tomato after 1 wk, regardless of O/sub 2/ level. Doubling the CO/sub 2/ level to that encountered in a typical local site (Edgeboro Landfill) resulted in more severe symptom development and the subsequent death of plants. Methane, in concentrations of 20% and above, found in more than 25% of the landfills visited, while not observed to be toxic per se; was associated with drastic O/sub 2/ depletion in the soil atmosphere, which activity was believed to be the cause of the plant decline.

Arthur, J.J.; Leone, I.A.; Flower, F.B.

1985-01-01

102

Metastable sound speed in gas-liquid mixtures  

NASA Technical Reports Server (NTRS)

A new method of calculating speed of sound for two-phase flow is presented. The new equation assumes no phase change during the propagation of an acoustic disturbance and assumes that only the total entropy of the mixture remains constant during the process. The new equation predicts single-phase values for the speed of sound in the limit of all gas or all liquid and agrees with available two-phase, air-water sound speed data. Other expressions used in the two-phase flow literature for calculating two-phase, metastable sound speed are reviewed and discussed. Comparisons are made between the new expression and several of the previous expressions -- most notably a triply isentropic equation as used, a triply isentropic equation as used, among others, by Karplus and by Wallis. Appropriate differences are pointed out and a thermodynamic criterion is derived which must be satisfied in order for the triply isentropic expression to be thermodynamically consistent. This criterion is not satisfied for the cases examined, which included two-phase nitrogen, air-water, two-phase parahydrogen, and steam-water. Consequently, the new equation derived is found to be superior to the other equations reviewed.

Bursik, J. W.; Hall, R. M.

1979-01-01

103

Two-dimensional simulation of the development of an inhomogeneous volume discharge in a Ne/Xe/HCl gas mixture  

SciTech Connect

The kinetic processes accompanying plasma column formation in an inhomogeneous discharge in a Ne/Xe/HCl gas mixture at a pressure of 4 atm were investigated by using a two-dimensional model. Two cathode spots spaced by 0.7 cm were initiated by distorting the cathode surface at local points, which resulted in an increase in the field strength in the cathode region. Three regimes differing in the charging voltage, electric circuit inductance, and electric field strength at the local cathode points were considered. The spatiotemporal distributions of the discharge current; the electron density; and the densities of excited xenon atoms, HCl(v = 0) molecules in the ground state, and HCl(v > 0) molecules in vibrational levels were calculated. The development of the discharge with increasing the electron density from 10{sup 4} to 10{sup 16} cm{sup -3} was analyzed, and three characteristic stages in the evolution of the current distribution were demonstrated. The width of the plasma column was found to depend on the energy deposited in the discharge. The width of the plasma column was found to decrease in inverse proportion to the deposited energy due to spatiotemporal variations in the rates of electron production and loss. The calculated dependences of the cross-sectional area of the plasma column on the energy deposited in the discharge agree with the experimental results.

Bychkov, Yu. I., E-mail: bych-yu@yandex.ru; Yampolskaya, S. A.; Yastremskii, A. G. [Russian Academy of Sciences, Institute of High Current Electronics, Siberian Branch (Russian Federation)

2013-05-15

104

Two-dimensional simulation of the development of an inhomogeneous volume discharge in a Ne/Xe/HCl gas mixture  

NASA Astrophysics Data System (ADS)

The kinetic processes accompanying plasma column formation in an inhomogeneous discharge in a Ne/Xe/HCl gas mixture at a pressure of 4 atm were investigated by using a two-dimensional model. Two cathode spots spaced by 0.7 cm were initiated by distorting the cathode surface at local points, which resulted in an increase in the field strength in the cathode region. Three regimes differing in the charging voltage, electric circuit inductance, and electric field strength at the local cathode points were considered. The spatiotemporal distributions of the discharge current; the electron density; and the densities of excited xenon atoms, HCl( v = 0) molecules in the ground state, and HCl( v > 0) molecules in vibrational levels were calculated. The development of the discharge with increasing the electron density from 104 to 1016 cm-3 was analyzed, and three characteristic stages in the evolution of the current distribution were demonstrated. The width of the plasma column was found to depend on the energy deposited in the discharge. The width of the plasma column was found to decrease in inverse proportion to the deposited energy due to spatiotemporal variations in the rates of electron production and loss. The calculated dependences of the cross-sectional area of the plasma column on the energy deposited in the discharge agree with the experimental results.

Bychkov, Yu. I.; Yampolskaya, S. A.; Yastremskii, A. G.

2013-05-01

105

Xenon and other volatile anesthetics change domain structure in model lipid raft membranes.  

PubMed

Inhalation anesthetics have been in clinical use for over 160 years, but the molecular mechanisms of action continue to be investigated. Direct interactions with ion channels received much attention after it was found that anesthetics do not change the structure of homogeneous model membranes. However, it was recently found that halothane, a prototypical anesthetic, changes domain structure of a binary lipid membrane. The noble gas xenon is an excellent anesthetic and provides a pivotal test of the generality of this finding, extended to ternary lipid raft mixtures. We report that xenon and conventional anesthetics change the domain equilibrium in two canonical ternary lipid raft mixtures. These findings demonstrate a membrane-mediated mechanism whereby inhalation anesthetics can affect the lipid environment of transmembrane proteins. PMID:24299622

Weinrich, Michael; Worcester, David L

2013-12-19

106

Venus, Earth, Xenon  

NASA Astrophysics Data System (ADS)

Xenon has been regarded as an important goal of many proposed missions to Venus. This talk is intended to explain why. Despite its being the heaviest gas found in natural planetary atmospheres, there is more evidence that Xe escaped from Earth than for any element apart from helium: (i) Atmospheric Xe is very strongly mass fractionated (at about 4% per amu) from any known solar system source. This suggests fractionating escape that preferentially left the heavy Xe isotopes behind. (ii) Xe is underabundant compared to Kr, a lighter noble gas that is not strongly mass fractionated in air. (iii) Radiogenic Xe is strongly depleted by factors of several to ~100 compared to the quantities expected from radioactive decay of primordial solar system materials. In these respects Xe on Mars is similar to Xe on Earth, but with one key difference: Xe on Mars is readily explained by a simple process like hydrodynamic escape that acts on an initially solar or meteoritic Xe. This is not so for Earth. Earth's Xe cannot be derived by an uncontrived mass fractionating process acting on any known type of Solar System Xe. Earth is a stranger, made from different stuff than any known meteorite or Mars or even the Sun. Who else is in Earth's family? Comets? We know nothing. Father Zeus? Data from Jupiter are good enough to show that jovian Xe is not strongly mass-fractionated but not good enough to determine whether Jupiter resembles the Earth or the Sun. Sister Venus? Noble gas data from Venus are incomplete, with Kr uncertain and Xe unmeasured. Krypton was measured by several instruments on several spacecraft. The reported Kr abundances are discrepant and were once highly controversial. These discrepancies appear to have been not so much resolved as forgotten. Xenon was not detected on Venus. Upper limits were reported for the two most abundant xenon isotopes 129Xe and 132Xe. From the limited data it is not possible to tell whether Venus's affinities lie with the solar wind, or with the chondrites, with Earth, or with none of the above. Modern spacecraft mass spectrometers are at least 100-fold more sensitive to noble gases. Sending such an instrument to Venus may be the last best hope for decrypting what Earth's noble gases have been trying to tell us.

Zahnle, K. J.

2013-12-01

107

Mixtures  

NSDL National Science Digital Library

Mixtures allows exploration of percents through two piles of colored and uncolored chips. The user must decide how many chips to color to create the desired percentage of colored chips compared to the total pile. Mixtures is one of the Interactivate assessment explorers.

108

Xenon recirculation-purification with a heat exchanger  

Microsoft Academic Search

Liquid-xenon based particle detectors have been dramatically growing in size during the last years, and are now exceeding the one-ton scale. The required high xenon purity is usually achieved by continuous recirculation of xenon gas through a high-temperature getter. This challenges the traditional way of cooling these large detectors, since in a thermally well insulated detector, most of the cooling

K. L. Giboni; E. Aprile; B. Choi; T. Haruyama; R. F. Lang; K. E. Lim; A. J. Melgarejo; G. Plante

2011-01-01

109

The Krypton and Xenon Contents of Atmospheric Air  

Microsoft Academic Search

The proportion of krypton and xenon in dry air has been measured by a method using distillation and low-temperature gas-chromatography for the isolation of krypton and xenon. The separation has been controlled by the use of radioactive 85Kr tracer. The krypton content of dry air is 1\\\\cdot 139 ± 0\\\\cdot 01 × 10-6 by volume. The xenon content of dry

E. Glueckauf; G. P. Kitt

1956-01-01

110

Kinetic Effects in Spherical Expanding Flows of Binary-Gas Mixtures  

E-print Network

Kinetic Effects in Spherical Expanding Flows of Binary-Gas Mixtures Vladimir V. Riabov Rivier,3 was used to study the flow structure. Kinetic effects influence the shock-wave thickness, species.53). REFERENCES 1. Bird, G. A., Molecular Gas Dynamics and the Direct Simulation of Gas Flows, 1st ed., Oxford

Riabov, Vladimir V.

111

GAS CHROMATOGRAPHIC RETENTION PARAMETERS DATABASE FOR REFRIGERANT MIXTURE COMPOSITION MANAGEMENT  

EPA Science Inventory

Composition management of mixed refrigerant systems is a challenging problem in the laboratory, manufacturing facilities, and large refrigeration machinery. Ths issue of composition management is especially critical for the maintenance of machinery that utilizes zeotropic mixture...

112

10 CFR 504.7 - Prohibition against excessive use of petroleum or natural gas in mixtures-electing powerplants.  

Code of Federal Regulations, 2011 CFR

...excessive use of petroleum or natural gas in mixtures-electing powerplants. 504.7 ...excessive use of petroleum or natural gas in mixtures—electing powerplants. (a...financially feasible for a unit to use a mixture of petroleum or natural gas...

2011-01-01

113

10 CFR 504.7 - Prohibition against excessive use of petroleum or natural gas in mixtures-electing powerplants.  

Code of Federal Regulations, 2012 CFR

...excessive use of petroleum or natural gas in mixtures-electing powerplants. 504.7 ...excessive use of petroleum or natural gas in mixtures—electing powerplants. (a...financially feasible for a unit to use a mixture of petroleum or natural gas...

2012-01-01

114

10 CFR 504.7 - Prohibition against excessive use of petroleum or natural gas in mixtures-electing powerplants.  

Code of Federal Regulations, 2010 CFR

...excessive use of petroleum or natural gas in mixtures-electing powerplants. 504.7 ...excessive use of petroleum or natural gas in mixtures—electing powerplants. (a...financially feasible for a unit to use a mixture of petroleum or natural gas...

2010-01-01

115

10 CFR 504.7 - Prohibition against excessive use of petroleum or natural gas in mixtures-electing powerplants.  

...excessive use of petroleum or natural gas in mixtures-electing powerplants. 504.7 ...excessive use of petroleum or natural gas in mixtures—electing powerplants. (a...financially feasible for a unit to use a mixture of petroleum or natural gas...

2014-01-01

116

10 CFR 504.7 - Prohibition against excessive use of petroleum or natural gas in mixtures-electing powerplants.  

Code of Federal Regulations, 2013 CFR

...excessive use of petroleum or natural gas in mixtures-electing powerplants. 504.7 ...excessive use of petroleum or natural gas in mixtures—electing powerplants. (a...financially feasible for a unit to use a mixture of petroleum or natural gas...

2013-01-01

117

Quantitative analysis of multi-component gas mixture based on AOTF-NIR spectroscopy  

NASA Astrophysics Data System (ADS)

Near Infrared (NIR) spectroscopy analysis technology has attracted many eyes and has wide application in many domains in recent years because of its remarkable advantages. But the NIR spectrometer can only be used for liquid and solid analysis by now. In this paper, a new quantitative analysis method of gas mixture by using new generation NIR spectrometer is explored. To collect the NIR spectra of gas mixtures, a vacuumable gas cell was designed and assembled to Luminar 5030-731 Acousto-Optic Tunable Filter (AOTF)-NIR spectrometer. Standard gas samples of methane (CH 4), ethane (C IIH 6) and propane (C 3H 8) are diluted with super pure nitrogen via precision volumetric gas flow controllers to obtain gas mixture samples of different concentrations dynamically. The gas mixtures were injected into the gas cell and the spectra of wavelength between 1100nm-2300nm were collected. The feature components extracted from gas mixture spectra by using Partial Least Squares (PLS) were used as the inputs of the Support Vector Regress Machine (SVR) to establish the quantitative analysis model. The effectiveness of the model is tested by the samples of predicting set. The prediction Root Mean Square Error (RMSE) of CH 4, C IIH 6 and C 3H 8 is respectively 1.27%, 0.89%, and 1.20% when the concentrations of component gas are over 0.5%. It shows that the AOTF-NIR spectrometer with gas cell can be used for gas mixture analysis. PLS combining with SVR has a good performance in NIR spectroscopy analysis. This paper provides the bases for extending the application of NIR spectroscopy analysis to gas detection.

Hao, Huimin; Zhang, Yong; Liu, Junhua

2007-12-01

118

Recovering Residual Xenon Propellant for an Ion Propulsion System  

NASA Technical Reports Server (NTRS)

Future nuclear-powered Ion-Propulsion- System-propelled spacecraft such as Jupiter Icy Moon Orbiter (JIMO) will carry more than 10,000 kg of xenon propellant. Typically, a small percentage of this propellant cannot be used towards the end of the mission because of the pressure drop requirements for maintaining flow. For large missions such as JIMO, this could easily translate to over 250 kg of unusable xenon. A proposed system, the Xenon Recovery System (XRS), for recovering almost all of the xenon remaining in the tank, would include a cryopump in the form of a condenser/evaporator that would be alternatively cooled by a radiator, then heated electrically. When the pressure of the xenon in the tank falls below 0.7 MPa (100 psia), the previously isolated XRS will be brought online and the gas from the tank would enter the cryopump that is initially cooled to a temperature below saturation temperature of xenon. This causes xenon liquefaction and further cryopumping from the tank till the cryopump is full of liquid xenon. At this point, the cryopump is heated electrically by small heaters (70 to 80 W) to evaporate the liquid that is collected as high-pressure gas (<7 MPa; 1,000 psia) in an intermediate accumulator. Check valves between the tank and the XRS prevent the reverse flow of xenon during the heating cycle. The accumulator serves as the high-pressure source of xenon gas to the Xenon Feed System (XFS) downstream of the XRS. This cycle is repeated till almost all the xenon is recovered. Currently, this system is being baselined for JIMO.

Ganapathi, Gani; Skakkottai, P.; wu, Jiunn Jeng

2006-01-01

119

Phase Equilibria for a Complex Mixture-Coal Gas-At Low Temperatures and High Pressures  

Microsoft Academic Search

No extensive investigations of the phase equilibria of complex mixtures at low temperatures and high pressures have hitherto been reported. In the present paper the coal-gas system has been studied, the apparatus employed by Ruhemann for the study of the vapour-liquid equilibria in binary mixtures has been modified and is described in detail. The pressure-composition curve of methane-ethylene mixtures has

C. S. Chow

1948-01-01

120

Gravity-induced density and concentration profiles in binary mixtures near gas–liquid critical lines  

Microsoft Academic Search

We have calculated gravity-induced density and concentration gradients using scaled equations of state fashioned after that of Leung and Griffiths for binary mixtures near gas–liquid critical lines. The mixtures considered here are those of helium-3 and helium-4 and of carbon dioxide and ethane. Our calculations show that the density profiles for both mixtures in any proportion of the components are

R. F. Chang; J. M. H. Levelt Sengers; T. Doiron; J. Jones

1983-01-01

121

Proportional counters aged anode wire recovering using an 80%CF4 + 20%CO2 gas mixture  

E-print Network

A technique to recover a gas proportional counter having an aged anode wire using a glow discharge in an 80%CF4 + 20%CO2 gas mixture has been developed and tested. Studies of aging effects were carried out under sustained irradiation by an intense 90Sr ?-source of the straw proportional counters operated with a 60%Ar + 30%CO2 + 10%CF4 gas mixture. Special attention was paid to the aging mechanism of the anode wires. Our experience showed that using a given gas mixture the swelling of the anode wires is a typical mode of aging that leads to degradation of the gas gain. The proposed method of recovery provided a complete restoration of the gas gain and the signal amplitude in the damaged zone of the wire. SEM/XEM analysis confirmed successful cleaning WOx deposits from the wire surface. The application of this method to recover the aged gaseous detectors in real experimental conditions is discussed.

Gavrilov, Gennady; Conti, Richard; Fetisov, Andrey; Maysuzenko, Dmitry; Shvecova, Natalia; Vakhtel, Victor

2011-01-01

122

The unsteadiness of shock waves propagating through gas-particle mixtures  

Microsoft Academic Search

A shock wave which is incident onto a gas-particle mixture or initiated within such a mixture needs a certain distance to reach a constant velocity. This effect is due to the inertia and the heat capacity of the particles. In general the shock wave is decelerated and the frozen pressure jump is decaying.

M. Sommmerfeld

1985-01-01

123

Experiments and analyses on shock waves propagating through a gas-particle mixture  

Microsoft Academic Search

The structure and behavior of shock waves propagating through a gas and solid particle mixture are studied by shock-tube experiments and by two methods of wave analysis. The shock waves concerned are incident on the mixture dispersed uniformly in the downstream part of the driven section. Pressures and shock velocities are measured under the condition that the particle loading ratio

E. Outa; K. Tajima; H. Morii

1976-01-01

124

A Xenon Condenser with a Remote Liquid Storage Vessel  

E-print Network

We describe the design and operation of a system for xenon liquefaction in which the condenser is separated from the liquid storage vessel. The condenser is cooled by a pulse tube cryocooler, while the vessel is cooled only by the liquid xenon itself. This arrangement facilitates liquid particle detector research by allowing easy access to the upper and lower flanges of the vessel. We find that an external xenon gas pump is useful for increasing the rate at which cooling power is delivered to the vessel, and we present measurements of the power and efficiency of the apparatus. Key words: Xenon, Condenser, Recirculation pump

S. Slutsky A; Y. -r. Yen A; H. Breuer A; A. Dobi A; C. Hall A; T. Langford A; D. Leonard A; L. J. Kaufman A; V. Strickl; N. Voskanian A

125

Method and apparatus for perforating at cutting with a solid fueled gas mixture  

SciTech Connect

A method for cutting pipe casings and concrete liners or perforating the same and localized portions of surrounding strata in an earth bore is set forth wherein a gas phase cutting or perforating jet mixture of fluorine and nitrogen trifluoride is delivered to the cutting or perforation site from the decomposition of a solid, normally stable, perfluoroammonium salt. An appropriate apparatus for delivering the gas mixture of fluorine and nitrogen trifluoride from the salt is also disclosed.

Woytek, A.J.; Lileck, J.T.; Steigerwalt, E.J.

1984-05-08

126

Atomically detailed models of gas mixture diffusion through CuBTC membranes  

Microsoft Academic Search

Metal–organic frameworks are intriguing crystalline nanoporous materials that have potential applications in adsorption-based and membrane-based gas separations. We describe atomically detailed simulations of gas adsorption and diffusion in CuBTC that have been used to predict the performance of CuBTC membranes for separation of H2\\/CH4, CO2\\/CH4 and CO2\\/H2 mixtures. CuBTC membranes are predicted to have higher selectivities for all three mixtures

Seda Keskin; Jinchen Liu; J. Karl Johnson; David S. Sholl

2009-01-01

127

Measured Gas Concentrations and Flow Properties in SiH4-H2 Mixtures  

NASA Astrophysics Data System (ADS)

Each gas concentration in silane-hydrogen (SiH4-H2) gas mixtures was measured using a diaphragm gauge and a quartz friction pressure gauge (D- and Q-gauges). At constant pressures of 0.13-1.3 kPa, the Q-gauge pressure readings depended on the densities of SiH4 and H2. Therefore, the dependence of the Q-gauge pressure readings on the partial pressures of SiH4 could be used to measure the concentrations of these gases in the gas mixtures. The relative SiH4 density in the flow of gas mixtures was higher than the SiH4 flow rate ratio, indicating that the flow of the mixtures was intermediate between molecular and viscous. The viscosities of the gas mixtures estimated from the pressure-normalized Q-gauge pressures were compared with the calculations by Wilke's equation, with the finding that the viscosity of the gas mixture can be derived using the present measurement.

Suzuki, Atsushi; Nonaka, Hidehiko

2008-05-01

128

Post-Launch Performance Characterization of the Xenon Feed System on Deep Space One  

Microsoft Academic Search

Propulsion for the Deep Space One @SI) spacecraft is provided by a xenon ion engine. Xenon is stored in a supercritical state and is delivered as a low pressure gas to the thruster and two cathodes (called the main cathode and neutralizer) by a Xenon Feed System (XFS). This mission requires tight constraints on thruster performance, which in turn requires

Gani B. Ganapathi; Carl S. Engelbrecht

129

Terrestrial and Martian weathering signatures of xenon components in shergottite mineral separates  

Microsoft Academic Search

Xenon-isotopic ratios, step-heating release patterns, and gas concentrations of mineral separates from Martian shergottites Roberts Massif (RBT) 04262, Dar al Gani (DaG) 489, Shergotty, and Elephant Moraine (EET) 79001 lithology B are reported. Concentrations of Martian atmospheric xenon are similar in mineral separates from all meteorites, but more weathered samples contain more terrestrial atmospheric xenon. The distributions of xenon from

J. A. Cartwright; K. D. Ocker; S. A. Crowther; R. Burgess; J. D. Gilmour

2010-01-01

130

Separation of Methane and Carbon Dioxide Gas Mixtures by Pressure Swing Adsorption  

Microsoft Academic Search

Two pressure swing adsorption processes for separation of methane and carbon dioxide gas mixtures are described. One process simultaneously produces a high purity CH4 and a high purity CO2 product with high recoveries of both components from the feed gas. The other process only produces a high purity CH4 product with high recovery. Test data for these processes are reported

Shivaji Sircar

1988-01-01

131

Process for scrubbing of NO and/or SO sub 2 from gas mixtures  

SciTech Connect

This patent describes a process for removal of, an atmospheric pollutant from a gas. The atmospheric pollutant being at least one of NO{sub {ital x}} and SO{sub 2}. It comprises: contacting the gas mixture with a scrubbing agent so as to remove the at least one of NO{sub {ital x}} and SO{sub 2} from the gas, the scrubbing agent including iron(II) ions and a substantially water-free nonaqueous solvent and wherein the nonaqueous solvent is selected from the group consisting of dimethyl sulfoxide, phosphoric or phosphonic esters, a compound of a formula given in the patent, or mixtures thereof.

Lassmann, E.; Helmling, R.; Beran, F.

1990-01-01

132

Exploring interaction effects in two-component gas mixtures using orthogonal signal correction of ultrasound pulses  

NASA Astrophysics Data System (ADS)

Within Sweden and the EU, an increased use of biogas gas and natural gas is encouraged to decrease emission of carbon dioxide. To support more effective manufacturing, distribution, and consumption of energy gases, new methods for the measurement of the calorimetric value or the gas composition are needed. This paper presents a method to extract and visualize variations in ultrasound pulse shape, caused by interaction effects between the constituents of a two-component gas mixture. The method is based on a combination of principal component analysis and orthogonal signal correction. Pulse-echo ultrasound experiments on mixtures of oxygen and ethane in the concentration range from 20% to 80% ethane show that the extracted information could be correlated with the molar fraction of ethane in the mixture. .

Carlson, Johan E.; Martinsson, Pär-Erik

2005-05-01

133

Phase equilibria in the system Ne-Xe at high pressures I. Gas-gas equilibrium and the critical line up to 20 kbar  

Microsoft Academic Search

The phase behaviour of the system neon-xenon has been studied in a diamond anvil cell at pressures up to 20kbar. By visual observation of the mixtures, the phase transition of the homogeneous gas phase to fluid-fluid equilibrium has been detected as a function of pressure and temperature, with an overall composition ranging from 14% to 53% xenon. The measurements reveal

L. C. van den Bergh; J. A. Schouten; N. J. Trappeniers

1985-01-01

134

Proton irradiation of simple gas mixtures: Influence of irradiation parameters  

NASA Technical Reports Server (NTRS)

In order to get information about the influence of irradiation parameters on radiolysis processes of astrophysical interest, methane gas targets were irradiated with 6.5 MeV protons at a pressure of 1 bar and room temperature. Yields of higher hydrocarbons like ethane or propane were found by analysis of irradiated gas samples using gas chromatography. The handling of the proton beam was of great experimental importance for determining the irradiation parameters. In a series of experiments current density of the proton beam and total absorbed energy were shown to have a large influence on the yields of produced hydrocarbons. Mechanistic interpretations of the results are given and conclusions are drawn with regard to the chemistry and the simulation of various astrophysical systems.

Sack, Norbert J.; Schuster, R.; Hofmann, A.

1990-01-01

135

Measurement of nitrogen content in a gas mixture by transforming the nitrogen into a substance detectable with nondispersive infrared detection  

DOEpatents

A method of determining the amount of nitrogen in a gas mixture. The constituent gases of the mixture are dissociated and transformed to create a substance that may measured using nondispersive infrared adsorption techniques.

Owen, Thomas E. (Helotes, TX); Miller, Michael A. (San Antonio, TX)

2010-08-24

136

Study on the recovery of hydrogen from refinery (hydrogen + methane) gas mixtures using hydrate technology  

Microsoft Academic Search

A novel technique for separating hydrogen from (H2 + CH4) gas mixtures through hydrate formation\\/dissociation was proposed. In this work, a systematic experimental study was performed\\u000a on the separation of hydrogen from (H2 + CH4) feed mixtures with various hydrogen contents (mole fraction x = 40%–90%). The experimental results showed that the hydrogen content could be enriched to as high

XiuLin Wang; GuangJin Chen; LanYing Yang; LinWei Zhang

2008-01-01

137

Remote monitoring of multi-gas mixtures by passive standoff Fourier transform infrared radiometry.  

PubMed

The passive remote monitoring of multi-gas mixtures was experimentally investigated using Fourier transform infrared (FT-IR) radiometry. The spectral radiance data were collected using a dual-port radiometrically balanced interferometer for a variety of multi-gas plumes at a standoff distance of 60 m. Two basic sets of mixtures were studied. The first set corresponded to mixtures consisting of three gases with no overlapping spectral bands (C(2)H(2), C(2)H(4), and R14). The second set corresponded to mixtures of three gases having significant spectral overlap (C(2)H(4), R114, and R134a). For each mixture the flow rates of individual constituents were adjusted to yield specific constituent optical-density (CL) ratios. These ratios were compared to the optical-density ratios retrieved from the measured infrared radiance spectra. Results of this study indicated that for both sets of multi-gas mixtures the optical-density ratios retrieved by the passive remote monitoring technique were in good agreement with those derived from the release flow rates, provided that a simple correction scheme was introduced to compensate for the limited accuracy of the fast radiance model implemented in the monitoring algorithm. PMID:17650375

Thériault, Jean-Marc; Puckrin, Eldon; Lavoie, Hugo

2007-06-01

138

Heat Transfer and Pressure Drop in Concentric Annular Flows of Binary Inert Gas Mixtures  

NASA Technical Reports Server (NTRS)

Studies of heat transfer and pressure drop of binary inert gas mixtures flowing through smooth concentric circular annuli, tubes with fully developed velocity profiles, and constant heating rate are described. There is a general lack of agreement among the constant property heat transfer correlations for such mixtures. No inert gas mixture data exist for annular channels. The intent of this study was to develop highly accurate and benchmarked pressure drop and heat transfer correlations that can be used to size heat exchangers and cores for direct gas Brayton nuclear power plants. The inside surface of the annular channel is heated while the outer surface of the channel is insulated. Annulus ratios range 0.5 < r* < 0.83. These smooth tube data may serve as a reference to the heat transfer and pressure drop performance in annuli, tubes, and channels having helixes or spacer ribs, or other surfaces.

Reid, R. S.; Martin, J. J.; Yocum, D. J.; Stewart, E. T.

2007-01-01

139

Two-phase turbine engines. [using gas-liquid mixture accelerated in nozzles  

NASA Technical Reports Server (NTRS)

A description is given of a two-phase turbine which utilizes a uniform mixture of gas and liquid accelerated in nozzles of the types reported by Elliott and Weinberg (1968). The mixture acts directly on an axial flow or tangential impulse turbine or is separated into gas and liquid streams which operate separately on a gas turbine and a hydraulic turbine. The basic two-phase cycles are examined, taking into account working fluids, aspects of nozzle expansion, details of turbine cycle operation, and the effect of mixture ratio variation. Attention is also given to two-phase nozzle efficiency, two-phase turbine operating characteristics and efficiencies, separator turbines, and impulse turbine experiments.

Elliott, D. G.; Hays, L. G.

1976-01-01

140

Separation of gas mixtures using a range of zeolite membranes: A molecular-dynamics study  

NASA Astrophysics Data System (ADS)

Gas separation efficiencies of three zeolite membranes (Faujasite, MFI, and Chabazite) have been examined using the method of molecular dynamics. Our investigation has allowed us to study the effects of pore size and structure, state conditions, and compositions on the permeation of two binary gas mixtures, O2/N2 and CO2/N2. We have found that for the mixture components with similar sizes and adsorption characteristics, such as O2/N2, small-pore zeolites are not suited for separations, and this result is explicable at the molecular level. For mixture components with differing adsorption behavior, such as CO2/N2, separation is mainly governed by adsorption and small-pore zeolites separate such gases quite efficiently. When selective adsorption takes place, we have found that, for species with low adsorption, the permeation rate is low, even if the diffusion rate is quite high. Our results further indicate that loading (adsorption) dominates the separation of gas mixtures in small-pore zeolites, such as MFI and Chabazite. For larger-pore zeolites such as Faujasite, diffusion rates do have some effect on gas mixture separation, although adsorption continues to be important. Finally, our simulations using existing intermolecular potential models have replicated all known experimental results for these systems. This shows that molecular simulations could serve as a useful screening tool to determine the suitability of a membrane for potential separation applications.

Jia, W.; Murad, S.

2005-06-01

141

CO2 + N2O mixture gas hydrate formation kinetics and effect of soil minerals on mixture-gas hydrate formation process  

NASA Astrophysics Data System (ADS)

CO2 mitigation is one of the most pressing global scientific topics in last 30 years. Nitrous oxide (N2O) is one of the main greenhouse gases (GHGs) defined by the Kyoto Protocol and its global warming potential (GWP) of one metric ton is equivalent to 310 metric tons of CO2. They have similar physical and chemical properties and therefore, mixture-gas (50% CO2 + 50% N2O) hydrate formation process was studied experimentally and computationally. There were no significant research to reduce N20 gas and we tried to make hydrate to mitigate N20 and CO2 in same time. Mixture gas hydrate formation periods were approximately two times faster than pure N2O hydrate formation kinetic in general. The fastest induction time of mixture-gas hydrate formation observed in Illite and Quartz among various soil mineral suspensions. It was also observed that hydrate formation kinetic was faster with clay mineral suspensions such as Nontronite, Sphalerite and Montmorillonite. Temperature and pressure change were not significant on hydrate formation kinetic; however, induction time can be significantly affected by various chemical species forming under the different suspension pHs. The distribution of chemical species in each mineral suspension was estimated by a chemical equilibrium model, PHREEQC, and used for the identification of hydrate formation characteristics in the suspensions. With the experimental limitations, a study on the molecular scale modeling has a great importance for the prediction of phase behavior of the gas hydrates. We have also performed molecular dynamics computer simulations on N2O and CO2 hydrate structures to estimate the residual free energy of two-phase (hydrate cage and guest molecule) at three different temperature ranges of 260K, 273K, and 280K. The calculation result implies that N2O hydrates are thermodynamically stable at real-world gas hydrate existing condition within given temperature and pressure. This phenomenon proves that mixture-gas could be efficiently applied to CO2 sequestration at potential sites and further investigations must be conducted to identify possible effects frequently found in natural geological environments and geo-environmental conditions at the site affecting the hydrate formation kinetics.

Enkh-Amgalan, T.; Kyung, D.; Lee, W.

2012-12-01

142

The influence of recent heat transfer data on gas mixtures /He-Ar, H2-CO2/ on closed cycle gas turbines  

NASA Astrophysics Data System (ADS)

Previous studies have been made on the composition of an optimal working fluid for closed cycle gas turbines. Those studies were based on the assumption that the objective could be achieved by mixing helium with a gas of higher molecular weight. The results of those calculations, based on heat transfer data of pure gases and air, indicated the possibility of significant cost advantages of gas mixtures relative to pure helium. Recent heat transfer measurements of low Prandtl number gas mixtures indicate that existing scaling laws for normal Prandtl number (approximately 0.7) gases do not adequately represent the heat transfer characteristic of these gas mixtures. In this paper the influence of these gas mixture heat transfer data on closed cycle gas turbine coolers, recuperators, and heat source exchangers is presented. The characteristic dimensions (flow area, surface area, and length) of these heat exchangers utilizing pure gases and gas mixtures are compared.

Pierce, B. L.

1980-03-01

143

On dynamics of imploding shock waves in a mixture of gas and dust particles  

E-print Network

In this paper, the generalized analytical solutions for one-dimensional adiabatic flow behind the imploding shock waves propagating in a dusty gas are obtained using the geometrical shock dynamics theory. The dusty gas is assumed to be a mixture of a perfect gas and spherically small solid particles, in which solid particles are continuously distributed. Shock jump relations given by Anand for a dusty gas are taken into consideration to explore the effects due to an increase in (i) the propagation distance from the centre of convergence, (ii) the mass fraction of solid particles in the mixture and (iii) the ratio of the density of solid particles to the initial density of the gas, on the shock velocity, pressure, temperature, density, velocity of mixture, speed of sound, adiabatic compressibility of mixture and the change-in-entropy across the shock front. The results provided a clear picture of whether and how the presence of solid particles influences the flow field behind the imploding shock front.

Anand, R K

2014-01-01

144

Process and installation for purification of the helium contained in a mixture of gas  

SciTech Connect

The present invention relates to a process and an installation for purification of the helium contained in a mixture of gas, employing a pre-treatment unit to retain the impurities such as water, carbon dioxide gas and heavy organic compounds, and at least one reactor of the chromatographic type located downstream of said pre-treatment unit, said process comprising the following steps of: (a) adjusting the pressure of the mixture of gas until the working pressure of the phase of adsorption is obtained, this pressure being between 10 and 30 bars, and preferably 12 to 15 bars; (b) taking the temperature of the mixture of gas at the outlet of said pre-treatment unit until it is located in the range -15/sup 0/ C./-35/sup 0/ C., and preferably -25/sup 0/ C.; (c) and sending the mixture of gas into the reactor and passing it through an absorbent, which is constituted by a microporous charcoal whose pores are of dimensions less than or equal to 20 A.

Avon, M.F.; Markarian, G.R.

1984-04-24

145

On dynamics of imploding shock waves in a mixture of gas and dust particles  

NASA Astrophysics Data System (ADS)

In this paper, the generalized analytical solutions for one-dimensional adiabatic flow behind the imploding shock waves propagating in a dusty gas are obtained using the geometrical shock dynamics theory. The dusty gas is assumed to be a mixture of a perfect gas and spherically small solid particles, in which solid particles are continuously distributed. Shock jump relations given by Anand for a dusty gas are taken into consideration to explore the effects due to an increase in (i) the propagation distance from the centre of convergence, (ii) the mass fraction of solid particles in the mixture and (iii) the ratio of the density of solid particles to the initial density of the gas, on the shock velocity, pressure, temperature, density, velocity of mixture, speed of sound, adiabatic compressibility of mixture and the change-in-entropy across the shock front. The results provided a clear picture of whether and how the presence of solid particles influences the flow field behind the imploding shock front.

Anand, R. K.

2014-10-01

146

Modeling of the gas-phase chemistry in C-H-O gas mixtures for diamond chemical vapor deposition  

NASA Astrophysics Data System (ADS)

The boundaries of the diamond deposition region in the C-H-O (Bachmann) atomic phase composition diagram have been reproduced successfully for 38 different C, H, and O containing gas mixtures using the CHEMKIN computer package, together with just two criteria—a minimum mole fraction of methyl radicals [CH3] and a limiting value of the [H]/[C2H2] ratio. The diamond growth/no-growth boundary coincides with the line along which the input mole fractions of C and O are equal. For every gas mixture studied, no-growth regions are found to coincide with a negligible (<10-10) mole fraction of CH3 radicals, while for gas mixtures lying within the diamond growth region the CH3 mole fraction is ˜10-7. Each no-growth?diamond growth boundary is seen to be accompanied by a 2-3 order of magnitude step in CH3 mole fraction. The boundary between diamond and nondiamond growth is less clearly defined, but can be reproduced by assuming a critical, temperature dependent [H]/[C2H2] ratio (0.2, in the case that Tgas=2000 K) that reflects the crucial role of H atoms in the etching of nondiamond phases. The analysis allows prediction of the composition process window for good quality diamond growth for all stable input gas mixtures considered in this study.

Petherbridge, James R.; May, Paul W.; Ashfold, Michael N. R.

2001-05-01

147

Non-self-sustained electric discharge in oxygen gas mixtures: singlet delta oxygen production  

Microsoft Academic Search

The possibility of obtaining a high specific input energy in an electron-beam sustained discharge ignited in oxygen gas mixtures O2 : Ar : CO (or H2) at the total gas pressures of 10-100 Torr was experimentally demonstrated. The specific input energy per molecular component exceeded ~6 kJ l-1 atm-1 (150 kJ mol-1) as a small amount of carbon monoxide was

A. A. Ionin; Yu M. Klimachev; A. A. Kotkov; I. V. Kochetov; A. P. Napartovich; L. V. Seleznev; D. V. Sinitsyn; G. D. Hager

2003-01-01

148

Thermodiffusiophoresis of a small volatile aerosol particle in a polyatomic gas mixture  

NASA Astrophysics Data System (ADS)

The thermodiffusiophoretic motion of convex particles in an N-component polyatomic gas mixture is investigated theoretically, with no constraints imposed on the relative directions of the temperature and concentration gradients. Results obtained for a spherical particle in a single-component polyatomic gas (nitrogen) for different values of the accommodation coefficient agree to within 15 percent with the results based on the classical Deriagin-Bakanov-Waldman theory.

Ialamov, Iu. I.; Markov, M. G.; Shchukin, E. R.

149

Hovering performance of hummingbirds in hyperoxic gas mixtures.  

PubMed

Hummingbirds evolved during a period of decline in atmospheric oxygen concentration and currently encounter varying levels of oxygen availability along their elevational distribution. We tested the hypothesis that inspiration of hyperoxic gas increases hummingbird hovering performance when birds are simultaneously challenged aerodynamically. We measured the maximum duration of hovering flight while simultaneously monitoring the rate of oxygen consumption of ruby-throated hummingbirds (Archilochus colubris) in low-density heliox that was either normoxic (21% O2) or hyperoxic (35% O2). As air density decreased below 0.85 kg x m(-3), hummingbirds hovered significantly longer in hyperoxia than in normoxia, but the air density at which the birds could no longer sustain hovering flight was independent of oxygen concentration. At low air densities in hyperoxia flight trials, hummingbirds appeared to increase their rate of oxygen consumption relative to flight sequences at equivalent densities in normoxia trials, but these differences were not significant. We tested the hypothesis that hummingbirds can discriminate between environments that differ in oxygen concentration. In another density-reduction experiment, hummingbirds were allowed to choose between artificial feeders infused with either normoxic or hyperoxic gases. The hypothesis was not supported because birds failed to associate oxygen concentration with a particular feeder independently of air density. Supplemental oxygen thus yields increased hovering duration at intermediate air densities, but the minimum density at which birds can fly is limited exclusively by aerodynamic considerations. PMID:11441043

Altshuler, D L; Chai, P; Chen, J S

2001-06-01

150

Removal of carbon dioxide from gas mixtures by wollastonite  

NASA Astrophysics Data System (ADS)

Wollastonite synthesis and decomposition were analyzed from the viewpoint of thermodynamics (using the TERRA software). It is shown that wollastonite synthesis from limestone and silica takes place at a minimum content of nitrogen (10-5 N2) with a release of carbon dioxide. The synthesis temperature is T ? 560 K. Wollastonite is decomposed in the presence of flue gas (4N2) with limestone and silica formation and burial of carbon dioxide in the form of CaCO3(c). Wollastonite decomposition temperature is T ? 420 K. The cyclic reciprocating process for complete removal of carbon dioxide by wollastonite is suggested. Four strokes of the reciprocating system with the fixed temperatures of wollastonite decomposition (T=300 K) and wollastonite synthesis (T=560 K) are presented. Total energy consumption (T = 560 K) is ? I ? 130 kJ/mole, 30 % of energy is spent for heating and 70 % of energy is spent for chemical reaction. This is comparable with the heat of CO2 solution in ethanolamin.

Engelsht, V. S.; Muratalieva, V. Zh.

2013-09-01

151

Research and Development Work Concerning the Separation of Helium from Gas Mixtures by SiO2 Composite Membranes.  

National Technical Information Service (NTIS)

Methods for the selective separation of helium from natural gas as an alternative to natural gas liquefaction was investigated. Composite membranes were examined for their usefulness for the separation of helium from a methane helium mixture. These compos...

W. Kreiger, P. Wiessart

1982-01-01

152

Application of compressibility factors for high ratio carbon dioxide-methane gas mixtures  

Microsoft Academic Search

Compressibility factors for a high-ratio COâ-natural gas mixture, measured in a visual PVT cell, are compared with other experimental data and values calculated with 2 correlations. The correlations diverge from the experimental results near the critical region. Discussion includes how compressibility factors effect compressor cylinder sizing and related horsepower requirements. Also discussed are the factors used in monitoring reservoir performance

C. J. Fesmire; R. M. Dicharry; R. Simon; F. H. Vorhis

1974-01-01

153

Method and apparatus for perforating at cutting with a solid fueled gas mixture  

Microsoft Academic Search

A method for cutting pipe casings and concrete liners or perforating the same and localized portions of surrounding strata in an earth bore is set forth wherein a gas phase cutting or perforating jet mixture of fluorine and nitrogen trifluoride is delivered to the cutting or perforation site from the decomposition of a solid, normally stable, perfluoroammonium salt. An appropriate

A. J. Woytek; J. T. Lileck; E. J. Steigerwalt

1984-01-01

154

Molecular dynamics simulation of helium–argon gas mixture under various wall conditions  

Microsoft Academic Search

As computational capabilities increase, molecular dynamics (MD) simulations become important tools of simulating reality. These simulations are especially useful for compressible gas mixture problems. In this study, binary diffusion of helium and argon was examined using a hard-sphere MD simulation method. For the sake of computational speed, low spacing ratios were chosen. Binary mass diffusion of gases in two equally

Ilyas Kandemir; Fatih Erdogan Sevilgen

2008-01-01

155

EVALUATION OF THE EFFICIENCY OF INDUSTRIAL FLARES: H2S GAS MIXTURES AND PILOT ASSISTED FLARES  

EPA Science Inventory

The report is the fourth in a series on a research program which will result in quantification of emissions from, and efficiencies of, industrial flares. The report gives test data on the combustion efficiency and destruction efficiency of (1) gas mixtures containing H2S, and (2)...

156

Clathrate hydrate equilibrium data for the gas mixture of carbon dioxide and nitrogen in the  

E-print Network

1 Clathrate hydrate equilibrium data for the gas mixture of carbon dioxide and nitrogen Department, CNRS-UMR 5307 LGF, 158 cours Fauriel, 42023 St Etienne, FRANCE. ABSTRACT Carbon dioxide the mole fraction of CO2 in the carbon dioxide + nitrogen + cyclopentane mixed hydrate phase, both defined

Paris-Sud XI, Université de

157

Ignition of a Combustible Mixture by a Hot Unsteady Gas Jet  

Microsoft Academic Search

The study of the ignition of a combustible mixture induced by means of an unsteady gas jet, at an initial temperature ranging from 700 to 3000 K, requires the construction of an original test facility which consists of a shock tube connected to a combustion chamber via an injector. With this new experimental setup, the ignition conditions of hydrogen-air (

N. DJEBAILI; R. LISBET; G. DUPRE; C. PAILLARD

1995-01-01

158

Electron drift velocity and Townsend coefficient in DME-based gas mixtures  

NASA Astrophysics Data System (ADS)

Drift velocity and Townsend coefficients in pure DME, Ar-DME (50/50) and (80/20) and Ne-DME (50/50) and (80/20) mixtures have been measured for high and very high electric fields. The use of a modified pulsed Townsend technique allowed the study of electron transport close to the steady breakdown field of the gas.

Oettinger, Eva; Hildebrandt, Malte; Schmidt, Bernhard

159

Implementation of Ultrasonic Sensing for High Resolution Measurement of Binary Gas Mixture Fractions  

E-print Network

We describe an ultrasonic instrument for continuous real-time analysis of the fractional mixture of a binary gas system. The instrument is particularly well suited to measurement of leaks of a high molecular weight gas into a system that is nominally composed of a single gas. Sensitivity ultrasonic leak detection systems are also described. Although development of the described systems was motivated by the requirements of an evaporative fluorocarbon cooling system, the instrument is applicable to the detection of leaks of many other gases and to proce...

Bates, Richard; Berry, Stephane; Bitadze, Alexander; Bonneau, Pierre; Bousson, Nicolas; Boyd, George; Bozza, Gennaro; Crespo-Lopez, Olivier; Da Riva, Enrico; Degeorge, Cyril; Deterre, Cecile; DiGirolamo, Beniamino; Doubek, Martin; Favre, Gilles; Godlewski, Jan; Hallewell, Gregory; Hasib, Ahmed; Katunin, Sergey; Langevin, Nicolas; Lombard, Didier; Mathieu, Michel; McMahon, Stephen; Nagai, Koichi; Pearson, Benjamin; Robinson, David; Rossi, Cecilia; Rozanov, Alexandre; Strauss, Michael; Vitek, Michal; Vacek, Vaclav; Zwalinski, Lukasz

2014-01-01

160

Electron-beam sustained discharge in oxygen gas mixtures: singlet delta oxygen production for oxygen-iodine laser  

Microsoft Academic Search

Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressure up to 100 Torr were experimentally studied. The pulsed discharge in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amount of carbon monoxide or hydrogen, the

Mikhail P. Frolov; Gordon D. Hager; Andrei A. Ionin; Yurii M. Klimachev; Igor V. Kochetov; Andrei A. Kotkov; John K. McIver; Anatolii P. Napartovich; Yurii P. Podmar'kov; Leonid V. Seleznev; Dmitrii V. Sinitsyn; Nikolai P. Vagin; Nikolay N. Yuryshev

2004-01-01

161

Electric properties, spectroscopy, and singlet delta oxygen yield of electron-beam sustained discharge in oxygen gas mixtures  

Microsoft Academic Search

Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressures up to 100 Torr was experimentally studied in large excitation volume (~18 liter). The discharge in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amount of

Michail P. Frolov; Gordon D. Hager; Andrei A. Ionin; Yurii M. Klimachev; Igor V. Kochetov; Andrei A. Kotkov; Jack McIver; Anatolii P. Napartovich; Yurii P. Podmar'kov; Leonid V. Seleznev; Dmitrii V. Sinitsyn; Nikolai P. Vagin; Nikolai N. Yuryshev

2004-01-01

162

Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches  

DOEpatents

An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.

Christophorou, L.G.; Hunter, S.R.

1988-06-28

163

Electrochemical separation and concentration of sulfur containing gases from gas mixtures  

DOEpatents

A method of removing sulfur oxides of H.sub.2 S from high temperature gas mixtures (150.degree.-1000.degree. C.) is the subject of the present invention. An electrochemical cell is employed. The cell is provided with inert electrodes and an electrolyte which will provide anions compatible with the sulfur containing anions formed at the anode. The electrolyte is also selected to provide inert stable cations at the temperatures encountered. The gas mixture is passed by the cathode where the sulfur gases are converted to SO.sub.4.sup.= or, in the case of H.sub.2 S, to S.sup.=. The anions migrate to the anode where they are converted to a stable gaseous form at much greater concentration levels (>10X). Current flow may be effected by utilizing an external source of electrical energy or by passing a reducing gas such as hydrogen past the anode.

Winnick, Jack (3805 Woodrail-on-the-Green, Columbia, MO 65201)

1981-01-01

164

Liquid xenon scintillation spectrometer  

NASA Astrophysics Data System (ADS)

A liquid xenon scintillation detector has been worked out. Liquid xenon fills up a volume 27 mm diameter by 12-30 mm long inside a quartz cylinder with a teflon reflector. Both ends of the cylinder are sealed with photomultipliers with quartz windows. The energy resolution of the detector was found to be of the same order of magnitude as NaI(Tl) crystals for the energy 120 KeV. However, the resolution increases for the higher energies and comes up to 15% for 662 KeV. The reasons of such deterioration of resolution with increasing energy are discussed.

Barabanov, I. R.; Gavrin, V. N.; Pshukov, A. M.

1987-02-01

165

Ionization and scintillation of nuclear recoils in gaseous xenon  

E-print Network

Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

Renner, J; Goldschmidt, A; Matis, H S; Miller, T; Nakajima, Y; Nygren, D; Oliveira, C A B; Shuman, D; Álvarez, V; Borges, F I G; Cárcel, S; Castel, J; Cebrián, S; Cervera, A; Conde, C A N; Dafni, T; Dias, T H V T; Díaz, J; Esteve, R; Evtoukhovitch, P; Fernandes, L M P; Ferrario, P; Ferreira, A L; Freitas, E D C; Gil, A; Gómez, H; Gómez-Cadenas, J J; González-Díaz, D; Gutiérrez, R M; Hauptman, J; Morata, J A Hernando; Herrera, D C; Iguaz, F J; Irastorza, I G; Jinete, M A; Labarga, L; Laing, A; Liubarsky, I; Lopes, J A M; Lorca, D; Losada, M; Luzón, G; Marí, A; Martín-Albo, J; Martínez, A; Moiseenko, A; Monrabal, F; Monserrate, M; Monteiro, C M B; Mora, F J; Moutinho, L M; Vidal, J Muñoz; da Luz, H Natal; Navarro, G; Nebot-Guinot, M; Palma, R; Pérez, J; Aparicio, J L Pérez; Ripoll, L; Rodríguez, A; Rodríguez, J; Santos, F P; Santos, J M F dos; Seguí, L; Serra, L; Simón, A; Sofka, C; Sorel, M; Toledo, J F; Tomás, A; Torrent, J; Tsamalaidze, Z; Veloso, J F C A; Villar, J A; Webb, R C; White, J; Yahlali, N

2014-01-01

166

Ionization and scintillation of nuclear recoils in gaseous xenon  

E-print Network

Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

J. Renner; V. M. Gehman; A. Goldschmidt; H. S. Matis; T. Miller; Y. Nakajima; D. Nygren; C. A. B. Oliveira; D. Shuman; V. Álvarez; F. I. G. Borges; S. Cárcel; J. Castel; S. Cebrián; A. Cervera; C. A. N. Conde; T. Dafni; T. H. V. T. Dias; J. Díaz; R. Esteve; P. Evtoukhovitch; L. M. P. Fernandes; P. Ferrario; A. L. Ferreira; E. D. C. Freitas; A. Gil; H. Gómez; J. J. Gómez-Cadenas; D. González-Díaz; R. M. Gutiérrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; F. J. Iguaz; I. G. Irastorza; M. A. Jinete; L. Labarga; A. Laing; I. Liubarsky; J. A. M. Lopes; D. Lorca; M. Losada; G. Luzón; A. Marí; J. Martín-Albo; A. Martínez; A. Moiseenko; F. Monrabal; M. Monserrate; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muñoz Vidal; H. Natal da Luz; G. Navarro; M. Nebot-Guinot; R. Palma; J. Pérez; J. L. Pérez Aparicio; L. Ripoll; A. Rodríguez; J. Rodríguez; F. P. Santos; J. M. F. dos Santos; L. Seguí; L. Serra; A. Simón; C. Sofka; M. Sorel; J. F. Toledo; A. Tomás; J. Torrent; Z. Tsamalaidze; J. F. C. A. Veloso; J. A. Villar; R. C. Webb; J. White; N. Yahlali

2014-09-09

167

A Xenon Condenser with a Remote Liquid Storage Vessel  

E-print Network

We describe the design and operation of a system for xenon liquefaction in which the condenser is separated from the liquid storage vessel. The condenser is cooled by a pulse tube cryocooler, while the vessel is cooled only by the liquid xenon itself. This arrangement facilitates liquid particle detector research by allowing easy access to the upper and lower flanges of the vessel. We find that an external xenon gas pump is useful for increasing the rate at which cooling power is delivered to the vessel, and we present measurements of the power and efficiency of the apparatus.

S. Slutsky; Y. -R. Yen; H. Breuer; A. Dobi; C. Hall; T. Langford; D. S. Leonard; L. J. Kaufman; V. Strickland; N. Voskanian

2009-07-13

168

The structure of variable property, compressible mixing layers in binary gas mixtures  

NASA Technical Reports Server (NTRS)

We present the results of a study of the structure of a parallel compressible mixing layer in a binary mixture of gases. The gases included in this study are hydrogen (H2), helium (He), nitrogen (N2), oxygen (02), neon (Ne) and argon (Ar). Profiles of the variation of the Lewis and Prandtl numbers across the mixing layer for all thirty combinations of gases are given. It is shown that the Lewis number can vary by as much as a factor of eight and the Prandtl number by a factor of two across the mixing layer. Thus assuming constant values for the Lewis and Prandtl numbers of a binary gas mixture in the shear layer, as is done in many theoretical studies, is a poor approximation. We also present profiles of the velocity, mass fraction, temperature and density for representative binary gas mixtures at zero and supersonic Mach numbers. We show that the shape of these profiles is strongly dependent on which gases are in the mixture as well as on whether the denser gas is in the fast stream or the slow stream.

Kozusko, F.; Grosch, C. E.; Jackson, T. L.; Kennedy, Christipher A.; Gatski, Thomas B.

1996-01-01

169

A study of non-flammable gas mixture for resistive plate counter  

SciTech Connect

The RPC (resistive plate counter) has good time and position resolution. These factors make it an attractive candidate for trigger system at collider experiment. The standard gas mixtures (Ar+iso-C{sub 4}H{sub 10}+Freon) used in RPC are very flammable when leaked into air. In view of safety issue, the authors have studied non-flammable gas of Ar+CO{sub 2}+iso-C{sub 4}H{sub 10}+Freon as a function of ratio Ar:CO{sub 2} allowed in non-flammable gas mixtures for the RPC with ABS electrodes. The basic performance of the various mixtures have been measured; singles (untriggered) count rate, detection efficiency and charge spectra versus operating voltage. They have found a set of non-flammable mixtures of the kind of AR+CO{sub 2}+Freon contained less than {approximately}8.4% of iso-C{sub 4}H{sub 10} for K{sub L}/muon counter of KEK B-factory at KEK.

Takamatsu, H.; Hoshi, Y. [Tohoku-gakuin Univ., Tagajo (Japan)] [Tohoku-gakuin Univ., Tagajo (Japan); Abe, K. [Tohoku Univ., Sendai (Japan)] [and others] [Tohoku Univ., Sendai (Japan); and others

1996-06-01

170

Monte Carlo Simulation of Electron Swarm Parameters in the SF6/CF4 Gas Mixtures  

NASA Astrophysics Data System (ADS)

We use a binary gas mixture Monte Carlo simulation model to calculate the electron transport parameters in SF6/CF4 mixtures in uniform electric fields. Electron collision cross section sets are assembled on the basis of the critical survey of Christophorou et al. [J. Phys. Chem. Ref. Data 25 (1996) 1341] for CF4 and Itoh et al. [J. Phys. D 21 (1988) 922] for SF6. The electron swarm parameters studied here are electron drift velocity, effective ionization coefficient and the ratio of longitudinal diffusion coefficient to mobility for the density-reduced electric field strength (E/N) in the range of 140? E/N? 600 Td (1 Td = 10-17 V cm2); the SF6 contents in the gas mixtures are 0, 20, 50, and 100%. The differences between the present calculated and measured values of Urquijo et al. [J. Phys. D 36 (2003) 3132] do not exceed the overall measured uncertainties for the parameters. To our knowledge, only Urquijo et al. [J. Phys. D 36 (2003) 3132] have measured the electron swarm parameters in SF6/CF4 gas mixtures by a pulsed Townsend technique; however, simulation results have scarcely been reported.

Liu, Xueli; Xiao, Dengming

2007-04-01

171

Purging means and method for Xenon arc lamps  

NASA Technical Reports Server (NTRS)

High pressure Xenon short-arc lamp with two reservoirs which are selectively connectable to the lamp's envelope is described. One reservoir contains an absorbent which will absorb both Xenon and contaminant gases such as CO2 and O2. The absorbent temperature is controlled to evacuate the envelope of both the Xenon and the contaminant gases. The temperature of the absorbent is then raised to desorb only clean Xenon while retaining the contaminant gases, thereby clearing the envelope of the contaminant gases. The second reservoir contains a gas whose specific purpose is, to remove the objectional metal film which deposits gradually on the interior surface of the lamp envelope during normal arc operation. The origin of the film is metal transferred from the cathode of the arc lamp by sputtering or other gas transfer processes.

Miller, C. G. (inventor)

1973-01-01

172

Evolution of ideal gas mixtures confined in an insulated container by two identical pistons  

NASA Astrophysics Data System (ADS)

We study the quasistatic adiabatic expansion of monatomic-diatomic ideal gas mixtures bounded by identical pistons and obtain closed form expressions for the temperature of the gas as a function of the time. We find that the temperature decreases as an inverse power of the time for large times, with the exponent as a function of the monatomic to diatomic gas ratio. The piston speeds increase from zero to a maximum value determined by the heat capacity of the gas and the masses of the pistons. Plots of the temperature and piston speed versus the logarithm of the time show points of inflection, which are interpreted as signaling the onset of steady state behavior. These points shift to later times as the monatomic to diatomic gas ratio is varied from purely monatomic to purely diatomic.

Amor, Rumelo C.; Esguerra, Jose Perico H.

2010-09-01

173

Measurement of gas-compressibility factor data for natural gas and synthetic-gas components and their mixtures. Final report, April 1983December 1985  

Microsoft Academic Search

Over 2700 independent, highly accurate compressibility-factor measurements were made on natural and synthetic gas components and their mixtures. Accurate second virial coefficients were determined for pure gases and mixtures and interaction second virial coefficients obtained. These already have been used to test the Phase I OU\\/GRI correlation and to improve low-pressure representation in the Phase II work to extend and

R. T. Ellington; K. E. Starling; M. J. Hill; J. L. Savidge; K. H. Kumar

1986-01-01

174

Implementation of Ultrasonic Sensing for High Resolution Measurement of Binary Gas Mixture Fractions  

PubMed Central

We describe an ultrasonic instrument for continuous real-time analysis of the fractional mixture of a binary gas system. The instrument is particularly well suited to measurement of leaks of a high molecular weight gas into a system that is nominally composed of a single gas. Sensitivity < 5 × 10?5 is demonstrated to leaks of octaflouropropane (C3F8) coolant into nitrogen during a long duration (18 month) continuous study. The sensitivity of the described measurement system is shown to depend on the difference in molecular masses of the two gases in the mixture. The impact of temperature and pressure variances on the accuracy of the measurement is analysed. Practical considerations for the implementation and deployment of long term, in situ ultrasonic leak detection systems are also described. Although development of the described systems was motivated by the requirements of an evaporative fluorocarbon cooling system, the instrument is applicable to the detection of leaks of many other gases and to processes requiring continuous knowledge of particular binary gas mixture fractions. PMID:24961217

Bates, Richard; Battistin, Michele; Berry, Stephane; Bitadze, Alexander; Bonneau, Pierre; Bousson, Nicolas; Boyd, George; Bozza, Gennaro; Crespo-Lopez, Olivier; Riva, Enrico Da; Degeorge, Cyril; Deterre, Cecile; DiGirolamo, Beniamino; Doubek, Martin; Favre, Gilles; Godlewski, Jan; Hallewell, Gregory; Hasib, Ahmed; Katunin, Sergey; Langevin, Nicolas; Lombard, Didier; Mathieu, Michel; McMahon, Stephen; Nagai, Koichi; Pearson, Benjamin; Robinson, David; Rossi, Cecilia; Rozanov, Alexandre; Strauss, Michael; Vitek, Michal; Vacek, Vaclav; Zwalinski, Lukasz

2014-01-01

175

KEY COMPARISON: International comparison CCQM-K54: Primary standard gas mixtures of hexane in methane  

NASA Astrophysics Data System (ADS)

The aim of this comparison is to evaluate the gravimetry and purity verification of gas mixtures prepared by introducing a liquid into a gas cylinder. This type of preparation is well known from, e.g., ethanol in nitrogen/air (CCQM-K4), and n-hexane in synthetic natural gas (CCQM-K16). The choice for n-hexane in methane is based on the relevance of natural gas primary standard mixtures and higher hydrocarbons in synthetic natural gas (for, e.g., dew point calibrations). Furthermore, n-hexane is relatively straightforward to analyse using a GC/FID (gas chromatograph equipped with a flame ionisation detector) with good repeatability. Eight laboratories participated. After the data evaluation, the result of one laboratory was eliminated to arrive at a consistent subset. The quality of the fitted line was not overly good, leading to small discrepancies in the degrees-of-equivalence calculated for three other laboratories. Only four laboratories are consistent with the KCRV. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

van der Veen, Adriaan M. H.; Chander, Hima; Ziel, Paul R.; Wessel, Rob M.; de Leer, Ed W. B.; Smeulders, Damian; Besley, Laurie; Kato, Kenji; Watanabe, Takuro; Seog Kim, Jin; Woo, Jin-Chun; Bae, Hyun Kil; Doo Kim, Yong; Pérez Castorena, Alejandro; Rangel Murillo, Francisco; Serrano Caballero, Victor M.; Ramírez Nambo, Carlos; de Jesús Avila Salas, Manuel; Konopelko, Leonid A.; Popova, Tatjana A.; Pankratov, V. V.; Kovrizhnih, M. A.; Kuzmina, T. A.; Efremova, O. V.; Kustikov, Yury A.; Milton, Martin J. T.; Vargha, Gergely; Guenther, Frank R.; Rhoderick, George C.

2010-01-01

176

Requirements for Xenon International  

SciTech Connect

This document defines the requirements for the new Xenon International radioxenon system. The output of this project will be a Pacific Northwest National Laboratory (PNNL) developed prototype and a manufacturer-developed production prototype. The two prototypes are intended to be as close to matching as possible; this will be facilitated by overlapping development cycles and open communication between PNNL and the manufacturer.

Hayes, James C.; Ely, James H.

2013-09-26

177

Two-Dimensional Gas-Phase Separations Coupled to Mass Spectrometry for Analysis of Complex Mixtures  

SciTech Connect

Ion mobility spectrometry (IMS) has been explored for decades, and its versatility in separation and identification of gas-phase ions, including in isomeric mixtures, is well established. Recently, field asymmetric waveform IMS (FAIMS) has been gaining acceptance in similar applications. Coupled to mass spectrometry (MS), both IMS and FAIMS have shown the potential for broad utility in proteomics and other biological analyses. A major attraction of these separations is extremely high speed, exceeding that of condensed-phase alternatives by orders of magnitude. However, modest separation peak capacities have limited the utility of FAIMS and IMS for analyses of complex mixtures. We report 2-D gas-phase separations that join FAIMS to IMS, in conjunction with high-resolution and accuracy time-of-flight MS. Evaluation of FAIMS/IMS/TOF performance using a protein mixture tryptic digest reveals high orthogonality between FAIMS and IMS dimensions, and hence the benefit of FAIMS filtering prior to IMS/MS. The effective overall peak capacities are {approx}500 for FAIMS/IMS separations, and {approx}106 for 3-D FAIMS/IMS/MS analyses of tryptic peptides. Implementation of FAIMS/IMS and IMS/MS interfaces using electrodynamic ion funnels greatly improves sensitivity, making FAIMS/IMS/MS a potential platform for ultrahigh-throughput analyses of complex mixtures.

Tang, Keqi; Li, Fumin; Shvartsburg, Alexandre A.; Strittmatter, Eric F.; Smith, Richard D.

2005-10-01

178

Study of thermite mixture consolidated by the cold gas dynamic spray process  

NASA Astrophysics Data System (ADS)

The present study focused on the cold gas dynamic spray process for manufacturing porosity free, finely structured energetic materials with high reactivity and structural integrity. The experiments have focused the reaction between the aluminium and metal oxide, such as Al-CuO system. The consolidation of the materials used the cold gas dynamic spray technique, where the particles are accelerated to high speeds and consolidated via plastic deformation upon impact. Reactive composites are formed in arbitrary shapes with close to zero porosity and without any reactions during the consolidation phase. Reactivity of mixtures has been investigated through flame propagation analysis on cold sprayed samples and compacted powder mixture. Deflagration tests showed the influence of porosity on the reactivity.

Bacciochini, A.; Maines, G.; Poupart, C.; Akbarnejad, H.; Radulescu, M.; Jodoin, B.; Zhang, F.; Lee, J. J.

2014-05-01

179

Limits to flight energetics of hummingbirds hovering in hypodense and hypoxic gas mixtures.  

PubMed

Hovering hummingbirds offer a model locomotor system for which analyses of both metabolism and flight mechanics are experimentally tractable. Because hummingbirds exhibit the highest mass-specific metabolic rates among vertebrates, maximum performance of hovering flight represents the upper limit of aerobic locomotion in vertebrates. This study evaluates the potential constraints of flight mechanics and oxygen availability on maximum flight performance. Hummingbird flight performance was manipulated non-invasively using air and gas mixtures which influenced metabolism via variable oxygen partial pressure and/or altered flight mechanics via variable air densities. Limits to the locomotor capacity of hovering ruby-throated hummingbirds (Archilochus colubris) were unequivocally indicated by aerodynamic failure in either air/helium or air/heliox mixtures. Air/helium mixtures are hypodense and hypoxic; failure to sustain hovering flight occurred at 63% of the density of sea-level air and at an oxygen concentration of 12%. Air/heliox mixtures are hypodense but normoxic; failure in hovering occurred at 47% of sea-level air density. Thus, hummingbirds demonstrated considerable power reserves in hovering flight as well as hypoxic tolerance. In air/helium mixtures, hovering was limited by oxygen supply and not by flight mechanics. Birds hovering in air/helium mixtures increased their mechanical power output but not their rate of oxygen consumption. By contrast, birds hovering in air/heliox mixtures increased both mechanical performance and metabolic expenditure. Under hypoxia, hovering hummingbirds demonstrated non-negligible, but still limited, capacities for anaerobic metabolism and/or oxygen storage. Depending on the physical context, hummingbird flight performance can therefore be limited by oxygen availability or by flight aerodynamics. PMID:8896366

Chai, P; Dudley, R

1996-10-01

180

Inhomogeneity of density fields behind a shock wave propagating in a dust-gas mixture  

Microsoft Academic Search

The paper deals with the effect of the formation of the rho-layer, a narrow zone with an increased concentraion of solid particles, behind a shock wave propagating in a homogeneous dust-gas mixture. A mathematical model describing this mechanical effect is developed, and a physical mechanism explaining this phenomenon is proposed. The effect of rho-layer formation is then discussed with reference

V. P. Korobeinikov; V. V. Markov; L. I. Sedov; I. S. Men'shov

1989-01-01

181

Viscous-shock-layer solutions for turbulent flow of radiating gas mixtures in chemical equilibrium  

NASA Technical Reports Server (NTRS)

The viscous-shock-layer equations for hypersonic laminar and turbulent flows of radiating or nonradiating gas mixtures in chemical equilibrium are presented for two-dimensional and axially-symmetric flow fields. Solutions were obtained using an implicit finite-difference scheme and results are presented for hypersonic flow over spherically-blunted cone configurations at freestream conditions representative of entry into the atmosphere of Venus. These data are compared with solutions obtained using other methods of analysis.

Anderson, E. C.; Moss, J. N.

1975-01-01

182

Viscous shock layer solutions for turbulent flow of radiating gas mixtures in chemical equilibrium  

NASA Technical Reports Server (NTRS)

The viscous shock layer equations for hypersonic laminar and turbulent flows of radiating or nonradiating gas mixtures in chemical equilibrium are presented for two-dimensional and axially symmetric flow fields. Solutions are obtained using an implicit finite difference scheme and results are presented for hypersonic flow over spherically blunted cone configurations at free stream conditions representative of entry into the atmosphere of Venus. These data are compared with solutions obtained using other methods of analysis.

Anderson, E. C.; Moss, J. N.

1975-01-01

183

Combustion gas and NO emission characteristics of hazardous waste mixture particles in a fixed bed  

Microsoft Academic Search

Experiments with fixed-bed incinerators were carried out to model the combustion characteristics and gas emission characteristics\\u000a of hazardous waste mixture particles in a grate furnace. The results indicate that combustion can be divided into three stages:\\u000a ignition, main combustion and combustion completion stage. According to the various concentrations of O2, CO2 and CO, the main combustion stage can be subdivided

Ling Tao; Guangbo Zhao; Rui Sun

2011-01-01

184

Possibility of analyzing deuterium-tritium gas mixtures using a time-of-flight mass spectrometer  

Microsoft Academic Search

The use of a time-of-flight mass spectrometer, whose ion source and detector operate in a synchronous regime, is proposed\\u000a for the chemical and isotope analysis of gas mixtures containing radioactive tritium. The experiments performed confirm that\\u000a the detector background current caused by tritium ? electrons scarcely influences the signal-to-noise ratio and does not diminish the accuracy of analyses.

N. N. Aruev; A. V. Kozlovskii; I. L. Fedichkin; G. L. Saksaganski

1997-01-01

185

Electron interaction cross sections for a low-temperature 'plasma-like' gas mixture  

NASA Astrophysics Data System (ADS)

Electron interaction cross sections for species found in low-temperature industrial plasma environments are a crucial component to allow for accurate modeling of those plasmas. However, such data are still rarely reported in the literature, due to the complexities of working with such highly reactive species in a laboratory. Here, absolute differential cross section measurements for a 'plasma-like' gas mixture, containing CF3I, CF3, I2, I and C2F6, are reported.

Hargreaves, L. R.; Brunton, J. R.; Brunger, M. J.; Buckman, S. J.

2010-12-01

186

FIRE SUPPRESSION EFFICIENCY OF BROMOALKENE\\/NITROGEN GAS MIXTURES AS TOTAGFLOODING AGENTS  

Microsoft Academic Search

The tire suppression efiiciencies of I-bromo-I-propene I nitrogen and 2-bromo-3,3,3 trifluoro-I-propene I nitrogen gas mixtures as total-flooding agents were studied by a cup-burner method. It was shown that addition of small amounts of I-bromo-I-propene and 2-bromo-3,3,3 trifluoro-I-propene to nitrogen can improve the suppression effectiveness of the inert gas by 34 and 64% respectively. An arrangement for mixing organic compounds with

Yong Zou; Nader Vahdat; Michelle M. Collins

187

Process and catalyst for converting synthesis gas to liquid hydrocarbon mixture  

DOEpatents

Synthesis gas containing CO and H.sub.2 is converted to a high-octane hydrocarbon liquid in the gasoline boiling point range by bringing the gas into contact with a heterogeneous catalyst including, in physical mixture, a zeolite molecular sieve, cobalt at 6-20% by weight, and thoria at 0.5-3.9% by weight. The contacting occurs at a temperature of 250.degree.-300.degree. C., and a pressure of 10-30 atmospheres. The conditions can be selected to form a major portion of the hydrocarbon product in the gasoline boiling range with a research octane of more than 80 and less than 10% by weight aromatics.

Rao, V. Udaya S. (Monroeville, PA); Gormley, Robert J. (Pittsburgh, PA)

1987-01-01

188

The incorporation and migration of a single xenon atom in ceria  

NASA Astrophysics Data System (ADS)

The behavior of xenon gas is crucial for the performance of nuclear fuel materials. We report molecular statics calculation results for the characteristics of a single xenon atom in cerium oxide, a non-radioactive surrogate of uranium dioxide. A variety of possible xenon incorporation sites, including the octahedral interstitial position, single-Ce-vacancy clusters, and double-Ce-vacancy clusters were considered. The binding energies and corresponding xenon incorporation energies were computed to reveal the preferred xenon positions in ceria. Different migration mechanisms of single xenon atoms were found to be involved with various incorporation sites. The energy barriers of all possible migration pathways were calculated. Only the mobility of single xenon atoms in the double-Ce-vacancy sites, which is due to the vacancy-assisted xenon migration, can account for the xenon diffusivity implied by bubble formation observed in experiments. The results also validated the role of ceria as a reliable surrogate of uranium dioxide in studies involving xenon gas.

Miao, Yinbin; Chen, Wei-Ying; Oaks, Aaron; Mo, Kun; Stubbins, James F.

2014-06-01

189

Plasma nitriding using high H2 content gas mixtures for a cavitation erosion resistant steel  

NASA Astrophysics Data System (ADS)

Plasma nitriding using high H2 content gas mixtures in CA-6NM martensitic stainless steel was studied in the present work. Nitriding was performed in H2 + N2 gas mixtures for 5, 10 and 20% N2, in volume, at 773 K (500 °C), during 2 h. Changes in the surface morphology and nitrided layer constitution were characterized by SEM, XRD, roughness analysis, and nanoindentation technique. Cavitation erosion behavior of the nitrided samples was also investigated by means of a 20 kHz ultrasonic vibrator. The study was emphasized for the three first cavitation stages (incubation, acceleration, and maximum erosion rate stage) of the cumulative erosion-time curve. Results indicate that the gas mixture nitrogen content strongly influences the phases' formation and its distribution on the nitrided layer. Better cavitation erosion resistance which was attributed to the finer and more homogeneous distribution of the nitrided layer phases was verified for samples treated at 5% N2. Otherwise, worse cavitation erosion behavior for samples nitrided at 20% N2 is supposed to be due to the formation of multiphase compound layer constituted by Fe4N + Fe2-3N + CrN, which can infer residual stress in treated surface.

Allenstein, A. N.; Lepienski, C. M.; Buschinelli, A. J. A.; Brunatto, S. F.

2013-07-01

190

The Genesis solar xenon composition and its relationship to planetary xenon signatures  

NASA Astrophysics Data System (ADS)

The fluence and isotopic composition of solar wind xenon have been determined from silicon collector targets flown on the NASA Genesis mission. A protocol was developed to extract gas quantitatively from samples of ?9-25 mm2, and xenon measured using the RELAX mass spectrometer. The fluence of implanted solar wind xenon is 1.202(87) × 106 atoms 132Xe cm-2, which equates to a flux of 5.14(21) × 106 atoms 132Xe cm-2 year-1 at the L1 point. This value is in good agreement with those reported in other studies. The isotopic composition of the solar wind is consistent with that extracted from the young lunar regolith and other Genesis collector targets. The more precise xenon isotopic data derived from the Genesis mission confirm models of relationships among planetary xenon signatures. The underlying composition of Xe-Q is mass fractionated solar wind; small, varying contributions of Xe-HL and 129Xe from 129I decay are present in reported meteorite analyses. In contrast, an s-process deficit is apparent in Xe-P3, which appears to have been mass fractionated to the same extent as Xe-Q from a precursor composition, suggesting similar trapping mechanisms. Solar wind xenon later evolved by the addition of ?1% (at 132Xe) of s-process xenon to this precursor. As an alternative model to a single source reservoir for Xe-P3, we propose that trapping of xenon onto carbonaceous carriers has been an ongoing process across galactic history, and that preparation of the residues in which Xe-P3 has been identified preferentially preserves longer lived host phases; a higher proportion of these sample xenon isotopic compositions from earlier in galactic chemical evolution, allowing the s-process deficit to become apparent. The relationships among SW-Xe, Xe-Q and Xe-P3 predict that the 124Xe/132Xe ratio for the solar wind is 0.00481(6).

Crowther, S. A.; Gilmour, J. D.

2013-12-01

191

Optical absorption method of natural gas component analysis in real time. Part II. Analysis of mixtures of arbitrary composition  

NASA Astrophysics Data System (ADS)

The present paper continues the presentation of the results of studies started in [1]. The referred paper reports the development of the optical method for component analysis of natural gas mixtures with different compositions, allowing conducting measurements in real time. The method is based on the measurement of the absorption coefficients for the analyzed gas mixture at several wavelengths within the infrared region of the spectrum (7-14 ?m), with the selected number and values of wavelengths depending on the category of the gas mixture. The resulting accuracy of the determination of the main components of gas mixtures including methane, ethane, propane, butane, pentane and carbon dioxide is sufficient for the use of the developed method for the monitoring of the component composition of natural gas in pipelines.

Kireev, S. V.; Podolyako, E. M.; Simanovsky, I. G.; Shnyrev, S. L.

2012-10-01

192

Prospects for Barium Tagging in Gaseous Xenon  

NASA Astrophysics Data System (ADS)

Tagging events with the coincident detection of a barium ion would greatly reduce the background for a neutrino-less double beta decay search in xenon. This paper describes progress towards realizing this goal. It outlines a source that can produce large quantities of Ba++ in gas, shows that this can be extracted to vacuum, and demonstrates a mechanism by which the Ba++ can be efficiently converted to Ba+ as required for laser identification.

Sinclair, D.; Rollin, E.; Smith, J.; Mommers, A.; Ackeran, N.; Aharmin, B.; Auger, M.; Barbeau, P. S.; Benitez-Medina, C.; Breidenbach, M.; Burenkov, A.; Cook, S.; Coppens, A.; Daniels, T.; DeVoe, R.; Dobi, A.; Dolinski, M. J.; Donato, K.; Fairbank, W., Jr.; Farine, J.; Giroux, G.; Gornea, G.; Graham, K.; Gratta, G.; Green, M.; Hagemann, C.; Hall, C.; Hall, K.; Hallman, D.; Hargrove, C.; Herrin, S.; Kaufman, L. K.; Leonard, D. S.; LePort, F.; Mackay, D.; MacLennan, R.; Mong, B.; Montero Díez, M.; Müller, A. R.; Neilson, R.; Niner, E.; Odian, A.; O'Sullivan, K.; Ouellet, C.; Piepke, A.; Pocar, A.; Prescott, C. Y.; Pushkin, K.; Rowson, P. C.; Slutsky, S.; Stekhanov, V.; Twelker, K.; Voskanian, N.; Vuilleumier, J.-L.; Wichoski, U.; Wodin, J.; Yang, L.; Yen, Y.-R.

2011-08-01

193

Converging xenon shock waves driven by megagauss magnetic fields  

SciTech Connect

We attempted to implode a conducting metal linear at high velocity, and our failure to do so led to switching, or rapidly transferring the field from pushing an aluminum conductor to snow-plowing a half-atmosphere of xenon gas. We successfully initiated convergent xenon gas shocks with the use of a magnetohydrodynamic switch and coaxial high-explosive, flux-compression generators. Principal diagnostics used to study the imploding xenon gas were /sup 133/Xe radioactive tracers, continuous x-ray absorption, and neutron output. We compressed the xenon gas about five to sixfold at a velocity of 10 cm/..mu..s at a radius of 4 cm. The snowplow efficiency was good; going from 13- to 4-cm radius, we lost only about 20% of the mass. The temperature of the imploded sheath was determined by mixing deuterium with the xenon and measuring the neutron output. Using reasonable assumptions about the amount, density, and uniformity of the compressed gas, we estimate that we reached temperatures as high as 155 eV. Energy-loss mechanisms that we encountered included wall ablation and Taylor instabilities of the back surface.

Shearer, J.W.; Steinberg, D.J.

1986-07-01

194

Perceptual Characterization and Analysis of Aroma Mixtures Using Gas Chromatography Recomposition-Olfactometry  

PubMed Central

This paper describes the design of a new instrumental technique, Gas Chromatography Recomposition-Olfactometry (GC-R), that adapts the reconstitution technique used in flavor chemistry studies by extracting volatiles from a sample by headspace solid-phase microextraction (SPME), separating the extract on a capillary GC column, and recombining individual compounds selectively as they elute off of the column into a mixture for sensory analysis (Figure 1). Using the chromatogram of a mixture as a map, the GC-R instrument allows the operator to “cut apart" and recombine the components of the mixture at will, selecting compounds, peaks, or sections based on retention time to include or exclude in a reconstitution for sensory analysis. Selective recombination is accomplished with the installation of a Deans Switch directly in-line with the column, which directs compounds either to waste or to a cryotrap at the operator's discretion. This enables the creation of, for example, aroma reconstitutions incorporating all of the volatiles in a sample, including instrumentally undetectable compounds as well those present at concentrations below sensory thresholds, thus correcting for the “reconstitution discrepancy" sometimes noted in flavor chemistry studies. Using only flowering lavender (Lavandula angustifola ‘Hidcote Blue’) as a source for volatiles, we used the instrument to build mixtures of subsets of lavender volatiles in-instrument and characterized their aroma qualities with a sensory panel. We showed evidence of additive, masking, and synergistic effects in these mixtures and of “lavender' aroma character as an emergent property of specific mixtures. This was accomplished without the need for chemical standards, reductive aroma models, or calculation of Odor Activity Values, and is broadly applicable to any aroma or flavor. PMID:22912722

Johnson, Arielle J.; Hirson, Gregory D.; Ebeler, Susan E.

2012-01-01

195

Adiabatic temperature changes of magma-gas mixtures during ascent and eruption  

USGS Publications Warehouse

Most quantitative studies of flow dynamics in eruptive conduits during volcanic eruptions use a simplified energy equation that ignores either temperature changes, or the thermal effects of gas exsolution. In this paper we assess the effects of those simplifications by analyzing the influence of equilibrium gas exsolution and expansion on final temperatures, velocities, and liquid viscosities of magma-gas mixtures during adiabatic decompression. For a given initial pressure (p1), temperature (T1) and melt composition, the final temperature (Tf) and velocity (Umax) will vary depending on the degree to which friction and other irreversible processes reduce mechanical energy within the conduit. The final conditions range between two thermodynamic end members: (1) Constant enthalpy (dh=0), in which Tf is maximal and no energy goes into lifting or acceleration; and (2) constant entropy (ds=0), in which Tf is minimal and maximum energy goes into lifting and acceleration. For ds=0, T1=900 ??C and p1=200 MPa, a water-saturated albitic melt cools by ???200 ??C during decompression, but only about 250 ??C of this temperature decrease can be attributed to the energy of gas exsolution per se: The remainder results from expansion of gas that has already exsolved. For the same T1 and p1, and dh=0, Tf is 10-15 ??C hotter than T1 but is about 10-25 ??C cooler than Tf in similar calculations that ignore the energy of gas exsolution. For ds=0, p1=200 MPa and T1= 9,000 ??C, assuming that all the enthalpy change of decompression goes into kinetic energy, a water-saturated albitic mixture can theoretically accelerate to ???800 m/s. Similar calculations that ignore gas exsolution (but take into account gas expansion) give velocities about 10-15% higher. For the same T1, p1 = 200 MPa, and ds = 0, the cooling associated with gas expansion and exsolution increases final melt viscosity more than 2.5 orders of magnitude. For dh = 0, isenthalpic heating decreases final melt viscosity by about 0.7 orders of magnitude. Thermal effects of gas exsolution are responsible for less than 10% of these viscosity changes. Isenthalpic heating could significantly reduce flow resistance in eruptive conduits if heat generation were concentrated along conduit walls, where shearing is greatest. Isentropic cooling could enhance clast fragmentation in near-surface vents in cases where extremely rapid pressure drops reduce gas temperatures and chill the margins of expanding pyroclasts.

Mastin, L.G.; Ghiorso, M.S.

2001-01-01

196

Adiabatic temperature changes of magma-gas mixtures during ascent and eruption  

NASA Astrophysics Data System (ADS)

Most quantitative studies of flow dynamics in eruptive conduits during volcanic eruptions use a simplified energy equation that ignores either temperature changes, or the thermal effects of gas exsolution. In this paper we assess the effects of those simplifications by analyzing the influence of equilibrium gas exsolution and expansion on final temperatures, velocities, and liquid viscosities of magma-gas mixtures during adiabatic decompression. For a given initial pressure (p1), temperature (T1) and melt composition, the final temperature (Tf) and velocity (umax) will vary depending on the degree to which friction and other irreversible processes reduce mechanical energy within the conduit. The final conditions range between two thermodynamic end members: (1) constant enthalpy (dh=0), in which Tf is maximal and no energy goes into lifting or acceleration; and (2) constant entropy (ds=0), in which Tf is minimal and maximum energy goes into lifting and acceleration. For ds=0, T1=900 °C and p1=200 MPa, a water-saturated albitic melt cools by 200 °C during decompression, but only about 250 °C of this temperature decrease can be attributed to the energy of gas exsolution per se: the remainder results from expansion of gas that has already exsolved. For the same T1 and p1, and dh=0, Tf is 10-15 °C hotter than T1 but is about 10-25 °C cooler than Tf in similar calculations that ignore the energy of gas exsolution. For ds=0, p1=200 MPa and T1=9,000 °C, assuming that all the enthalpy change of decompression goes into kinetic energy, a water-saturated albitic mixture can theoretically accelerate to 800 m/s. Similar calculations that ignore gas exsolution (but take into account gas expansion) give velocities about 10-15% higher. For the same T1, pI=200 MPa, and ds=0, the cooling associated with gas expansion and exsolution increases final melt viscosity more than 2.5 orders of magnitude. For dh=0, isenthalpic heating decreases final melt viscosity by about 0.7 orders of magnitude. Thermal effects of gas exsolution are responsible for less than 10% of these viscosity changes. Isenthalpic heating could significantly reduce flow resistance in eruptive conduits if heat generation were concentrated along conduit walls, where shearing is greatest. Isentropic cooling could enhance clast fragmentation in near-surface vents in cases where extremely rapid pressure drops reduce gas temperatures and chill the margins of expanding pyroclasts.

Mastin, Larry; Ghiorso, Mark

2001-02-01

197

Carburization and gas reactions of hydrocarbon-nitrogen mixtures at 850 °C and 925 °C  

NASA Astrophysics Data System (ADS)

Rates of carburization of low-carbon steel by CH4, C2H2, C2H4, C2H6, and C3H8 in N2 have been measured gravimetrically at 850 °C and 925 °C. Methane appears to be the slowest and acetylene the fastest carburizing agent among the hydrocarbons tested. Hydrogen enhances the rates of carburizing of all hydrocarbons, probably by removing adsorbed oxygen from the steel surface. At high H2/CH4 ratios, H2 will decarburize steel at 925 °C. All hydrocarbons, including CH2, are also involved in gas phase reactions. These reactions may lead to the formation of soot at carburizing temperatures. Sooting is inhibited by the addition of H2 to hydrocarbon-nitrogen gas mixtures. Acetylene appears to be a key intermediate for the formation of soot as the final product of hydrocarbon reactions in the gas phase.

Kaspersma, Jelle H.; Shay, Robert H.

1982-06-01

198

Measurement of adiabatic burning velocity in natural gas-like mixtures  

SciTech Connect

Experimental measurements of the adiabatic burning velocities were carried out for natural gas-like mixtures burning in air over a range of equivalence ratios at atmospheric pressure. Effect of CO{sub 2} dilution up to 60%, N{sub 2} dilution up to 40% and 25% enrichment of ethane on burning velocity of methane-air flames were studied. Heat flux method with setup similar to that of [K.J. Bosschaart, L.P.H. de Goey, Detailed analysis of the heat flux method for measuring burning velocity, Combustion and Flame 132 (2003) 170-180] was used for measurement of burning velocities. Initially experiments were done for methane-air and ethane-air mixtures at various equivalence ratios and the results were in good agreement with published data in the literature. Computations were performed using PREMIX code with GRI 3.0 reaction mechanism for all the mixtures. Predicted flame structures were used to the explain the effect of N{sub 2} and CO{sub 2} dilution on burning velocity of methane-air flames. Peak burning velocity for CH{sub 4}/CO{sub 2}-air mixtures occur near to {phi} = 1.0. (author)

Ratna Kishore, V.; Duhan, Nipun; Ravi, M.R.; Ray, Anjan [Department of Mechanical Engineering, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110 016 (India)

2008-10-15

199

Combustion of bulk density powder mixtures in a coflow of inert gas: 6*(Fe 2 O 3 + 2Al) + 30% Al 2 O 3 mixtures  

Microsoft Academic Search

Investigated was the combustion of bulk density (Fe2O3 + 2Al) + 30% Al2O3 mixtures in a coflow of inert gas (Ar) in the presence\\/absence of blowing agents (borax, baking soda) and applied pressure\\u000a difference ?P. The results have been rationalized in terms of the conduction-convection theory for combustion in heterogeneous systems.

G. B. Brauer; A. G. Tarasov; B. S. Seplyarskii

2009-01-01

200

78 FR 41768 - Chemical Substances and Mixtures Used in Oil and Gas Exploration or Production; TSCA Section 21...  

Federal Register 2010, 2011, 2012, 2013

...EPA-HQ-OPPT-2011-0683; FRL-9339-4] Chemical Substances and Mixtures Used in Oil and Gas Exploration...petitioned EPA under section 21 of the Toxic Substances Control Act (TSCA) to use: TSCA section...exploration and production (E&P) chemical substances and mixtures to maintain certain...

2013-07-11

201

Catalytic decomposition of methane and methane\\/CO 2 mixtures to produce synthesis gas and nanostructured carbonaceous material  

Microsoft Academic Search

Methane and CO2 are the main components of biogas; therefore its direct conversion into a higher added value gas as syn-gas (mixture of CO and H2) is a very interesting alternative for the valorisation of such renewable resource. In this work, firstly a thermodynamic analysis of the decomposition of CH4:CO2 mixtures at different temperatures and CH4:CO2 ratios simulating the biogas

J. L. Pinilla; S. de Llobet; I. Suelves; R. Utrilla; M. J. Lázaro; R. Moliner

2011-01-01

202

Explosive limits and its container factors of polybasic explosive mixture gas containing H 2 , CH 4 and CO  

Microsoft Academic Search

Explosive characteristics of polybasic explosive mixture gas are systematically researched. Over 28000 experimental data have\\u000a been obtained from 1278 effective experiments. The paper probes into the concentration explosive limits and the container\\u000a factors of polybasic explosive mixture gas which contains H2, CH4 and CO. It has worked out the sufficient and necessary condition for branch-chain explosion and the unified expression

Hu Yaoyuan; Zhou Bangzhi; Yang Yuanfa; Li Yong; Zhu Kaihan

2002-01-01

203

Precision measurement of timing RPC gas mixtures with laser-beam induced electrons  

NASA Astrophysics Data System (ADS)

The main goals of a new test facility at Helmholtz-Zentrum Dresden-Rossendorf are precision measurements of the electron drift velocity and the Townsend coefficient of gases at atmospheric pressure in the strongest ever used homogenous electrical fields and the search for new RPC gas mixtures to substitute the climate harmful Freon. Picosecond UV laser pulses were focused into a sub-millimeter gas gap to initialize a defined tiny charge. These gaps are formed by electrodes of low-resistive ceramics or high-resistive float glass. The charge multiplication occurs in a strong homogeneous electric field of up to 100 kV/cm. Electron-ion pairs were generated in a cylindrical micro-volume by multi-photon ionization. The laser-pulse repetition rate ranges from 1 Hz to a few kHz. The RPC time resolution has been measured for different gases. First results of the Townsend coefficient at 100 kV/cm show a strong disagreement between the present measurement and Magboltz simulations for the typical timing RPC gas mixture C2F4H2/SF6/i-C4H10, while the measured electron drift velocities are in a good agreement with the model predictions.

Naumann, L.; Siebold, M.; Kaspar, M.; Kämpfer, B.; Kotte, R.; Laso Garcia, A.; Löser, M.; Schramm, U.; Wüstenfeld, J.

2014-10-01

204

Probing gas motions in the intra-cluster medium: a mixture model approach  

NASA Astrophysics Data System (ADS)

Upcoming high spectral resolution telescopes, particularly Astro-H, are expected to finally deliver firm quantitative constraints on turbulence in the intra-cluster medium (ICM). We develop a new spectral analysis technique which exploits not just the line width but the entire line shape, and show how the excellent spectral resolution of Astro-H can overcome its relatively poor spatial resolution in making detailed inferences about the velocity field. The spectrum is decomposed into distinct components, which can be quantitatively analysed using Gaussian mixture models. For instance, bulk flows and sloshing produce components with offset means, while partial volume-filling turbulence from the active galactic nucleus (AGN) or galaxy stirring leads to components with different widths. The offset between components allows us to measure gas bulk motions and separate them from small-scale turbulence, while component fractions and widths constrain the emission weighted volume and turbulent energy density in each component. We apply mixture modelling to a series of analytic toy models as well as numerical simulations of clusters with cold fronts and AGN feedback, respectively. From Markov chain Monte Carlo and Fisher's matrix estimates which include line blending and continuum contamination, we show that the mixture parameters can be accurately constrained with Astro-H spectra: at an ˜10 per cent level when components differ significantly in width, and an ˜1 per cent level when they differ significantly in the mean value. We also study error scalings and use information criteria to determine when a mixture model is preferred. Mixture modelling of spectra is a powerful technique which is potentially applicable to other astrophysical scenarios.

Shang, Cien; Oh, S. Peng

2012-11-01

205

High-accuracy P-p-T measurements of pure gas and natural gas like mixtures using a compact magnetic suspension densimeter  

E-print Network

sinker magnetic suspension densimeter has been used first to determine densities of pure component�s densities for which very reliable data are available. After validating its performance, the densities of four light natural gas mixtures, containing...

Ejaz, Saquib

2007-09-17

206

A computer program for calculation of spectral radiative properties of gas mixtures  

NASA Technical Reports Server (NTRS)

A computer code is described whereby calculations of radiative properties of gas mixtures may be made. The program is arranged so that distinct radiative processes for each species are computed in individual subroutines. Provision is made for calculating radiative properties in nonequilibrium situations - separate rotational, vibrational, and electronic temperatures may be used. These features should provide a flexibility not currently available in such programs. The basic equations and the program listing in FORTRAN 4 language are presented. Sample calculations are given for high temperature air and carbon dioxide and are compared to calculations made with previously developed programs.

Nealy, J. E.

1975-01-01

207

Lasing characteristics of gas mixtures involving UFG: Application to nuclear pumping of lasers  

NASA Technical Reports Server (NTRS)

Intense blue-green fluorescence from a structured band centered at lambda approximately 484 nm was observed from Ar, CF3I and NF3 gas mixtures excited by an electron beam. This emission was tentatively assigned to the E yields A transition of the iodine monofluoride (IF) molecule. The fluorescence efficiency of the IF(E yields A) band and the IF (E) state radiative lifetime were estimated to be approximately 6% and 15 ns, respectively. The emission band structure, the short IF(E) radiative lifetime and the Franck-Condon shift between the E and A states suggest that IF is an attractive candidate for a blue-green laser.

Verdeyen, J. T.; Eden, J. G.

1980-01-01

208

Quenching of Particle-Gas Combustible Mixtures Using Electric Particulate Suspension (EPS) and Dispersion Methods  

NASA Technical Reports Server (NTRS)

A cooperative study is being carried out between Iowa State University and McGill University. The new study concerns wall and particle quenching effects in particle-gas mixtures. The primary objective is to measure and interpret flame quenching distances, flammability limits, and burning velocities in particulate suspensions. A secondary objective is to measure particle slip velocities and particle velocity distribution as these influence flame propagation. Two suspension techniques will be utilized and compared: (1) electric particle suspension/EPS; and (2) flow dispersion. Microgravity tests will permit testing of larger particles and higher and more uniform dust concentrations than is possible in normal gravity.

Colver, Gerald M.; Goroshin, Samuel; Lee, John H. S.

2001-01-01

209

XENON-133 IN CALIFORNIA, NEVADA, AND UTAH FROM THE CHERNOBYL ACCIDENT (JOURNAL VERSION)  

EPA Science Inventory

The accident at the Chernobyl nuclear reactor in the USSR introduced numerous radioactive nuclides into the atmosphere, including the noble gas xenon-133. EPA's Environmental Monitoring Systems Laboratory, Las Vegas, NV, detected xenon-133 from the Chernobyl accident in air sampl...

210

INTEGRAL AND SPECTRAL CHARACTERISTICS OF ATON STATIONARY PLASMA THRUSTER OPERATING ON KRYPTON AND XENON  

Microsoft Academic Search

The integral characteristics of an ATON (1) stationary plasma thruster operating on xenon and krypton are investigated. It is shown that, with krypton, the thrust at the same mass flow rate of the working gas is greater and the efficiency is somewhat lower than those with xenon. An efficiency of ~60% was achieved with krypton for the specific impulse attaining

A. I. Bugrova; A. I. Morozov; A. S. Lipatov; A. M. Bishaev; V. K. Kharchevnikov; M. V. Kozintseva

211

High pressure and temperature optical flow cell for Near-Infra-Red spectroscopic analysis of gas mixtures  

NASA Astrophysics Data System (ADS)

A new optical flow cell with a new optical arrangement adapted for high pressures and temperatures using glass fibres to connect light source, cell, and spectrometer has been developed, as part of a larger project comprising new methods for in situ analysis of bio and hydrogen gas mixtures in high pressure and temperature applications. The analysis is based on measurements of optical, thermo-physical, and electromagnetic properties in gas mixtures with newly developed high pressure property sensors, which are mounted in a new apparatus which can generate gas mixtures with up to six components with an uncertainty of composition of as little as 0.1 mol. %. Measurements of several pure components of natural gases and biogases to a pressure of 20 MPa were performed on two isotherms, and with binary mixtures of the same pure gases at pressures to 17.5 MPa. Thereby a new method of analyzing the obtained spectra based on the partial density of methane was investigated.

Norton, C. G.; Suedmeyer, J.; Oderkerk, B.; Fieback, T. M.

2014-05-01

212

Effects of temperature on the carbonation of flue gas desulphurization gypsum using a CO2/N2 gas mixture.  

PubMed

The carbonation of flue gas desulphurization (FGD) gypsum using a CO2/N2 gas mixture was investigated to study the feasibility of using the flue gas directly in the gypsum carbonation. The effect of the reaction temperature on the carbonation reaction and the carbonation conversion efficiency of the samples were considered. In this study, the carbonation conversion efficiency was calculated using a new method for decreasing the error range from a sample containing unreacted gypsum. The carbonation reaction at 40°C was nearly twice as fast as the reaction at room temperature. In addition, the carbonation conversion efficiency at 40°C (96%) was nearly the same as that at room temperature. However, the efficiency decreased significantly with temperature, especially above 60°C. It can, therefore, be concluded that the direct use of flue gas in gypsum carbonation is most feasible at 40°C. The temperature of carbonation strongly affected the CaCO3 polymorphs and the morphological characteristics. Calcite with various shapes was the dominant (40-90%) phase at all temperatures. At temperatures below 40°C, spherical-shaped vaterite was pronounced, while needle-flower-shaped aragonite was dominant at temperatures above 80°C. PMID:25409589

Lee, Myung Gyu; Ryu, Kyung Won; Chae, Soo Chun; Jang, Young Nam

2015-01-01

213

Richtmyer-Meshkov instability in dilute gas-particle mixtures with re-shock  

NASA Astrophysics Data System (ADS)

The Richtmyer-Meshkov instability (RMI) is investigated in a dilute gas-particle mixture using three-dimensional numerical simulations. This work extends an earlier two-dimensional study [S. Ukai, K. Balakrishnan, and S. Menon, "On Richtmyer-Meshkov instability in dilute gas-particle mixtures," Phys. Fluids 22, 104103 (2010)] to a larger parameter space consisting of variations in the mass loading and the particle size as well as considering both single-mode and multi-mode interface initializations. In addition, the effect of the presence of particles on re-shock RMI is also investigated. Single-phase numerical predictions of the mixing layer growth-rate are shown to compare well to both experimental and theoretical results. In a dilute gas-particle mixture, the initial growth-rate of RMI shows similar trends compared to previous work; however, the current numerical predictions show that there is an observable increase, not previously predicted, in the growth of the mixing layer at higher mass loadings. For the range of cases considered, an increase as much as 56% is observed. This increase is attributed to additional vorticity production in the mixing layer resulting from inter-phase momentum coupling. Moreover, the presence of particles introduces a continuous drag on the gas-phase resulting in a delay in the time at which re-shock occurs. This delay, which is observed to be as much as 6%, is largest for higher initial mass loadings and smaller particle radii and has a corresponding effect on both the growth-rate of the mixing-layer after re-shock and the final width of the mixing layer. A new semi-analytical correlation is developed and verified against the numerical data to predict the re-shocked RMI growth-rate in dilute gas-particle flows. The correlation shows that the re-shock RMI growth-rate is linearly proportional to the velocity jump at re-shock, the molecular mixing fraction, and the multi-phase Atwood number. Depending on the initial mass loading and particle radii, the re-shock RMI growth-rates were observed to be reduced by as much as 48% in some cases with variations of around 26% in the width of the mixing layer after re-shock.

Schulz, J. C.; Gottiparthi, K. C.; Menon, S.

2013-11-01

214

Transport Properties of He-N{sub 2} Binary Gas Mixtures for CBC Space Applications  

SciTech Connect

In order to reduce the size and mass of the single-shaft turbo-machines, with little impact on the size of the heat transfer components in the CBC loop, He-Xe binary mixture with a molecular weight of 40 g/mole has been the working fluid of choice in space nuclear reactor power systems with Close Brayton Cycle (CBC) for energy conversion. This working fluid is also a suitable coolant for the fission reactors heat source designed with fast neutron energy spectra. For space nuclear reactors with thermal neutron energy spectra, however, the high capture neutron cross-section of Xe will reduce the beginning-of-life excess reactivity of the reactor, decreasing its effective operation lifetime. In addition, the neutron activation of Xe in the reactor will introduce a radioactivity source term in the CBC loop. Alternative working fluids with no activation concerns and comparable performance are N{sub 2} and the binary mixtures of He-N{sub 2}. This paper calculates the transport properties of these working fluids and compares their values to those of noble gas binary mixtures at the temperatures and pressures expected in CBC space reactor power system applications. Also investigated is the impact of using these working fluids on the pressure losses, heat transfer coefficient, and the aerodynamic loading of the blades in the CBC turbo-machines.

Tournier, Jean-Michel P.; El-Genk, Mohamed S. [Institute for Space and Nuclear Power Studies and Chemical and Nuclear Engineering Department, University of New Mexico, Albuquerque, NM 87131 (United States)

2008-01-21

215

WIMP Detection Using Liquid Xenon  

NASA Astrophysics Data System (ADS)

The missing mass 'Dark Matter' problem of the Universe is one of the most important questions facing the moden physics and astronomy. This thesis work developed the Liquid Xenon technology to detect the SUSY ark matter. The background rejection principle was tested and many technical problem are studied, including the purification of the liquid xenon to yield both long electron lifetime and long xenon scintillation light attenuation length, and xenon recoil scintillation efficiency measurement. The detector design and construction are studied. Finally a two phase xenon detector was realized for the future dark matter experiment. The key working principle is the use of proportional scintillation and electro-luminescence to detector the ionization components, which is different between background and recoil signals. The two phase test results shown that a detector energy threshold as low as 10keV can be achieved.

Wang, Hanguo

216

Finding the composition of gas mixtures by a phthalocyanine-coated QCM sensor array and an artificial neural network  

Microsoft Academic Search

This paper presents a system, which is made of an array of eight phthalocyanine-coated QCM sensors and an ANN to find the corresponding composition of a gas mixture. The digital data collected from the sensor responses were preprocessed by a sliding window algorithm, and then used to train a three layer ANN to determine the gas compositions. The system is

A. Özmen; F. Tekce; M. A. Ebeo?lu; C. Ta?alt?n; Z. Z. Öztürk

2006-01-01

217

Method of gas mixtures discrimination based on sensor array, temporal response and data driven approach.  

PubMed

This work presents a method of gas mixtures discrimination. The principal concept of the method is to apply measurement data provided by a combination of sensors at single time point of their temporal response as input of the discrimination models. The pattern data combinations are selected for classes of target gases based on the criterion of 100% efficient discrimination. Combinations of sensors and time points, which provide pattern data combinations in course or repeated measurements, are encoded in the form of addresses. The designer of sensor system is responsible for their selection and they are included in the software of the final instrument. The study of the method involved the discrimination of gas mixtures composed of air and single chemical: hexane, ethanol, acetone, ethyl acetate and toluene. Two sensor arrays were utilized. Each consisted of six TGS sensors of the same type. The dynamic operation of sensors was employed. As an example the stop-flow mode was chosen. The work provides the evidence of the existence of sensor combinations and time points, which are successful in discrimination of studied classes of target gases. The persistence of addresses was discussed considering the ability of sensor array to recognize analytes, variability of repeated measurement results, number of repeated measurements and a twin sets of sensors. Altogether, the validity of the method was demonstrated. PMID:21147337

Szczurek, A; Maciejewska, M; Flisowska-Wiercik, B

2011-01-15

218

Measurement of gas-compressibility factor data for natural gas and synthetic gas components and their mixtures. Annual report, April 1983March 1984  

Microsoft Academic Search

The objective of this contract is to obtain high accuracy data on natural and synthetic gas components and, especially, mixtures to supply needs of GRI super-compressibility correlation project. These are in addition to data from other labs. A Burnett-type P-V-T cell has been set up with auxiliaries and calibrated by use of the best nitrogen data available. The internally consistent

R. T. Ellington; K. E. Starling; K. H. Kumar; V. Oswal; T. Pham

1984-01-01

219

Xenon Recirculation-Purification with a Heat Exchanger  

E-print Network

Liquid-xenon based particle detectors have been dramatically growing in size during the last years, and are now exceeding the one-ton scale. The required high xenon purity is usually achieved by continuous recirculation of xenon gas through a high-temperature getter. This challenges the traditional way of cooling these large detectors, since in a thermally well insulated detector, most of the cooling power is spent to compensate losses from recirculation. The phase change during recondensing requires five times more cooling power than cooling the gas from ambient temperature to -100C (173 K). Thus, to reduce the cooling power requirements for large detectors, we propose to use the heat from the purified incoming gas to evaporate the outgoing xenon gas, by means of a heat exchanger. Generally, a heat exchanger would appear to be only of very limited use, since evaporation and liquefaction occur at zero temperature difference. However, the use of a recirculation pump reduces the pressure of the extracted liquid, forces it to evaporate, and thus cools it down. We show that this temperature difference can be used for an efficient heat exchange process. We investigate the use of a commercial parallel plate heat exchanger with a small liquid xenon detector. Although we expected to be limited by the available cooling power to flow rates of about 2 SLPM, rates in excess of 12 SLPM can easily be sustained, limited only by the pump speed and the impedance of the flow loop. The heat exchanger operates with an efficiency of (96.8 +/- 0.5)%. This opens the possibility for fast xenon gas recirculation in large-scale experiments, while minimizing thermal losses.

K. L. Giboni; E. Aprile; B. Choi; T. Haruyama; R. F. Lang; K. E. Lim; A. J. Melgarejo; G. Plante

2011-03-04

220

Determination of time-course change rate for arterial xenon using the time course of tissue xenon concentration in xenon-enhanced computed tomography  

SciTech Connect

In calculating tissue blood flow (TBF) according to the Fick principle, time-course information on arterial tracer concentration is indispensable and has a considerable influence on the accuracy of calculated TBF. In TBF measurement by xenon-enhanced computed tomography (Xe-CT), nonradioactive xenon gas is administered by inhalation as a tracer, and end-tidal xenon is used as a substitute for arterial xenon. There has been the assumption that the time-course change rate for end-tidal xenon concentration (Ke) and that for arterial xenon concentration (Ka) are substantially equal. Respiratory gas sampling is noninvasive to the patient and Ke can be easily measured by exponential curve fitting to end-tidal xenon concentrations. However, it is pointed out that there would be a large difference between Ke and Ka in many cases. The purpose of this work was to develop a method of determining the Ka value using the time course of tissue xenon concentration in Xe-CT. The authors incorporated Ka into the Kety autoradiographic equation as a parameter to be solved, and developed a method of least-squares to obtain the solution for Ka from the time-course changes in xenon concentration in the tissue. The authors applied this method of least-squares to the data from Xe-CT abdominal studies performed on 17 patients; the solution for Ka was found pixel by pixel in the spleen, and its Ka map was created for each patient. On the one hand, the authors obtained the average value of the Ka map of the spleen as the calculated Ka (Ka{sub calc}) for each patient. On the other hand, the authors measured Ka (Ka{sub meas}) using the time-course changes in CT enhancement in the abdominal aorta for each patient. There was a good correlation between Ka{sub calc} and Ka{sub meas} (r=0.966, P<0.0001), and these two Ka values were close to each other (Ka{sub calc}=0.935xKa{sub meas}+0.089). This demonstrates that Ka{sub calc} would be close to the true Ka value. Accuracy of TBF by Xe-CT can be improved with use of the average value of the Ka map of an organ like the spleen that has a single blood supply (only arterial inflow)

Sase, Shigeru; Takahashi, Hideaki; Ikeda, Hiroki; Kobayashi, Minoru; Matsumoto, Nobuyuki; Suzuki, Michihiro [Anzai Medical Co., Ltd., 3-9-15 Nishi-Shinagawa, Shinagawa-ku, Tokyo 141-0033 (Japan); Department of Internal Medicine, Division of Gastroenterology and Hepatology, School of Medicine, St. Marianna University, 2-16-1 Miyamae-ku, Sugao, Kawasaki 216-5811 (Japan)

2008-06-15

221

Xenon-enhanced CT imaging of local pulmonary ventilation  

NASA Astrophysics Data System (ADS)

We are using the unique features of electron beam CT (EBCT) in conjunction with respiratory and cardiac gating to explore the use of non-radioactive xenon gas as a pulmonary ventilation contrast agent. The goal is to construct accurate and quantitative high-resolution maps of local pulmonary ventilation in humans. We are evaluating xenon-enhanced computed tomography in the pig model with dynamic tracer washout/dilution and single breath inhalation imaging protocols. Scanning is done via an EBCT scanner which offers 50 msec scan aperture speeds. CT attenuation coefficients (image gray scale value) show a linear increase with xenon concentration (r equals 0.99). We measure a 1.55 Hounsfield Unit (HU) enhancement (kV equals 130, mA equals 623) per percentage increase in xenon gas concentration giving an approximately 155 HU enhancement with 100% xenon gas concentration as measured in a plexiglass super-syringe. Early results indicate that a single breath (from functional residual capacity to total lung capacity) of 100% xenon gas provides an average 32 +/- 1.85 (SE) HU enhancement in the lung parenchyma (maximum 50 HU) and should not encounter unwanted xenon side effects. However, changes in lung density occurring during even short breath holds (as short as 10 seconds) may limit using a single breath technique to synchronous volumetric scanning, currently possible only with EBCT. Preliminary results indicate close agreement between measured regional xenon concentration-time curves and theoretical predictions for the same sample. More than 10 breaths with inspirations to as high as 25 cmH2O airway pressure were needed to clear tracer from all lung regions and some regions had nearly linear rather than mono-exponential clearance curves. When regional parenchymal xenon concentration-time curves were analyzed, vertical gradients in ventilation and redistribution of ventilation at higher inspiratory flow rates were consistent with known pulmonary physiology. We present here a works in progress, showing results from two pigs illustrating the high resolution and detailed regional information obtainable with careful attention to cardiac and respiratory gating during a multi-breath washout period.

Tajik, Jehangir K.; Tran, Binh Q.; Hoffman, Eric A.

1996-04-01

222

The breast feeding mother and xenon anaesthesia: four case reports. Breast feeding and xenon anaesthesia  

PubMed Central

Background Four nursing mothers consented to anaesthesia for urgent surgery only on condition that their ability to breast feed would not be impaired. Methods Following induction of general anaesthesia with propofol and remifentanil, 65-69% xenon supplemented with remifentanil was used as an inhalational anaesthetic for maintenance. Results After finishing surgery the women could be extubated between 2:52 and 7:22 minutes. The women were fully alert just minutes after extubation and spent about 45 minutes in the recovery room before discharge to a regular ward. They resumed regular breast feeding some time later. The propofol concentration in the blood was measured after 0, 30, 90, and 300 minutes and in the milk after 90 and 300 minutes. Just 90 minutes after extubation, the concentration of propofol in the milk was limited (> 3 mg/l) so that pharmacological effects on the babies were excluded after oral intake. Also, no traces of xenon gas were found in the maternal milk at any time. After propofol induction and maintenance of anaesthesia with xenon in combination with a water-soluble short-acting drug like remifentanil, the concentration of propofol in maternal milk is low (> 3 mg/l 90 min after anesthesia) and harmless after oral intake. Conclusions These results, as well as the rapid elimination and absence of metabolism of xenon, are of great interest to nursing mothers. General anaesthesia with propofol for induction only, combined with remifentanil and xenon for maintenance, has not yet been described in breast feeding mothers. PMID:20167123

2010-01-01

223

Low-pressure inductive gas discharges in Ar, Kr, He and Ar+Hg mixture  

NASA Astrophysics Data System (ADS)

This paper presents results of theoretical and experimental investigations of high-frequency (HF) inductive gas discharges in Ar, Kr, He and Ar+Hg mixture in the pressure area of 0.1-10 Torr. The HF inductive discharges are known as effective sources of spectral lines. Our estimations predict that due to the skin-effect, high-frequency inductive discharge should have more high line intensity if compare with a DC discharge in the related conditions. The intensities of the Ar, Kr, He and Hg spectral lines in visible region are measured at a wide range of gas pressures varying the HF generator current. Tomographic reconstructions of spatial profiles of emitting mercury atoms in Ar+Hg discharge are performed. A stationary self-consistent model of high-frequency inductive discharge is developed including detailed kinetics of the excited atomic states. Based on the developed model, the spatial profiles of atoms in excited levels and emission properties of the discharge plasma are calculated. The detailed comparative analysis of the experimental and theoretical curves has been performed. We make the conclusion that numerical results are in good agreement with the experimental data. The obtained results - dependencies of the line intensities versus gas pressure and HF generator current - are discussed.

Denisova, Natalia; Gita, Revalde; Atis, Skudra

2009-10-01

224

Influence of gas temperature on self-sustained volume discharge characteristics in working mixtures of a repetitively pulsed COIL  

NASA Astrophysics Data System (ADS)

The influence of gas temperature on the characteristics of a self-sustained volume discharge was studied in the working mixtures of a chemical oxygen - iodine laser with pulsed electricdischarge production of iodine atoms. In experiments, laser working mixtures were modelled by the mixture of air and iodide C2H5I. It was established that mixture heating is accompanied by an increase in the voltage across the discharge plasma and by a decrease in the discharge current. By varying the temperature of the mixture with the iodine content of ~2.7% and initial pressure p=12 Torr from 22 °C to 96 °C, the current amplitude falls by ~12%, and at the instant corresponding to a maximal current the voltage raises by ~22%. Such a change in the discharge characteristics is explained by a higher rate of electron attachment to vibrationally excited iodide molecules at elevated temperatures.

Aksinin, V. I.; Antsiferov, S. A.; Velikanov, S. D.; Kazantsev, S. Yu; Kalinovskii, V. V.; Konovalov, V. V.; Kononov, I. G.; Mikhalkin, V. N.; Podlesnykh, S. V.; Sevryugin, I. V.; Firsov, K. N.

2014-02-01

225

Limiting field strength and electron swarm coefficients of the CF3I-SF6 gas mixture  

NASA Astrophysics Data System (ADS)

We have measured the electron drift velocity, longitudinal diffusion, and the effective ionization coefficients in the gaseous mixture of CF3I-SF6 over the density-normalized electric field intensity E/N, from 375 to 500 Td (1 Td = 10-17 V cm2). A pulsed Townsend technique was used. Overall, the gas mixture compositions were varied from 50 to 90% CF3I. We have found that the limiting field strength E/Nlim of the CF3I-SF6 mixture is superior to that of CF3I-N2, and always higher than that of SF6. Moreover, over the whole mixture range, the range of the limiting field strength for the CF3I-SF6 mixture is 360-437 Td, these limits corresponding for pure SF6 and CF3I, respectively.

de Urquijo, J.; Mitrani, A.; Ruíz-Vargas, G.; Basurto, E.

2011-08-01

226

Inductively coupled plasma etching of hafnium-indium-zinc oxide using chlorine based gas mixtures  

NASA Astrophysics Data System (ADS)

We report the etching characteristics of a stacked hafnium-indium-zinc oxide (HIZO) with a photoresist using the gas mixture of chlorine and argon (Cl2/Ar). The etching behaviors of HIZO have been investigated in terms of a source power, a bias power and a chamber pressure. As the concentration of Cl2 was increased compared to pure Ar, the etch rate of HIZO film was found slightly different from that of indium-zinc oxide (IZO) film. Moreover, to investigate the etching mechanism systematically, various inspections were carried out such as atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) depending on the portion of Cl2. Additionally, we compared the etching mechanism of HIZO film with IZO film to confirm the difference of chemical bonds caused by the influence of hafnium doping.

Choi, Yong-Hee; Jang, Ho-Kyun; Jin, Jun-Eon; Joo, Min-Kyu; Piao, Mingxing; Shin, Jong Mok; Kim, Jae-Sung; Na, Junhong; Kim, Gyu Tae

2014-04-01

227

Effects of flow rate and gas mixture on the welfare of weaned and neonate pigs during gas euthanasia.  

PubMed

The objectives of this study were to assess efficacy and welfare implications of gas euthanasia when applied to weaned and neonate pigs. Parameters associated with welfare, which were measured before loss of consciousness, included open-mouth breathing, ataxia, righting response, and escape attempts. Two age groups (weaned and neonate) were assessed in 9 gas treatments arranged in a 2 × 4 factorial design, with 2 gas types (CO2 = 100% CO2 and 50:50 = 50:50 CO2:argon) and 4 flow rates (box volume exchange/min: slow = 20%; medium = 35%; fast = 50%; prefill = prefilled followed by 20%) and a control treatment in which ambient air was passed through the box. Pig pairs (10/treatment) were placed in a modified Euthanex AgPro system (Euthanex Corp., Palmer, PA). Behavioral and physiological responses were observed directly and from video recordings for latency, duration, prevalence (percent of pigs affected), and frequency (number of occurrences/pig). Data were analyzed as linear mixed models or with a Cox proportional hazard model as appropriate. Piglet pair was the experimental unit. For the weaned pig, welfare was superior with CO2 relative to 50:50 within 1 or more flow rates on the basis of reduced duration of open-mouth breathing, duration of ataxia, frequency of escape attempts, and duration and frequency of righting response (P < 0.05). No measured parameters indicated superior welfare with the use of 50:50, whereas latencies to loss of posture and last movement favored CO2 (P < 0.05). Faster flow rates were associated with reduced (P < 0.05) duration or frequency of open-mouth breathing, ataxia, and righting response, as well as superior (P < 0.05) indicators of efficacy, including latencies to loss of posture, gasping, and last movement, relative to slower flow rates. Weaned pigs were more likely to defecate (P < 0.01), display nasal discharge (P < 0.05), and display longer (P < 0.001) latencies to loss of posture and last movement than neonates. Duration of ataxia was the only parameter for which neonates were superior (P < 0.01) to weaned pigs during euthanasia. As such, a 50:50 CO2:argon gas mixture and slower flow rates should be avoided when euthanizing weaned or neonate pigs with gas methods. Neonate pigs succumb to the effects of gas euthanasia quicker than weaned pigs and display fewer signs of distress. PMID:24664567

Sadler, L J; Hagen, C D; Wang, C; Widowski, T M; Johnson, A K; Millman, S T

2014-02-01

228

Corona inception voltage in statorettes with various gas-solid dielectric systems  

NASA Technical Reports Server (NTRS)

Corona inception voltage was calculated and measured for three statorettes in several gases and gas mixtures at pressures from 50.8 to 1270 torr. In helium the corona inception voltage was lowest, and in air it was highest. In argon and mixtures of helium and xenon the corona inception voltage was between that of air and helium. Correlation between experimental and calculated data was good.

Bollenbacher, G.; Kempke, E. E., Jr.

1972-01-01

229

Measurement of activity coefficients of mixtures by head-space gas chromatography: general procedure.  

PubMed

Head-space gas chromatography (HS-GC) is an applicable method to perform vapor-liquid equilibrium measurements and determine activity coefficients. However, the reproducibility of the data may be conditioned by the experimental procedure concerning to the automated pressure-balanced system. The study developed in this work shows that a minimum volume of liquid in the vial is necessary to ensure the reliability of the activity coefficients since it may become a parameter that influences the magnitude of the peak areas: the helium introduced during the pressurization step may produce significant variations of the results when too small volume of liquid is selected. The minimum volume required should thus be evaluated prior to obtain experimentally the concentration in the vapor phase and the activity coefficients. In this work, the mixture acetonitrile-toluene is taken as example, requiring a sample volume of more than 5mL (about more than 25% of the vial volume). The vapor-liquid equilibrium and activity coefficients of mixtures at different concentrations (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 molar fraction) and four temperatures (35, 45, 55 and 70°C) have been determined. Relative standard deviations (RSD) lower than 5% have been obtained, indicating the good reproducibility of the method when a sample volume larger than 5mL is used. Finally, a general procedure to measure activity coefficients by means of pressure-balanced head-space gas chromatography is proposed. PMID:23809803

Luis, Patricia; Wouters, Christine; Van der Bruggen, Bart; Sandler, Stanley I

2013-08-01

230

A photochemical answer to the 'xenon paradox'  

NASA Astrophysics Data System (ADS)

Xenon is depleted by one order of magnitude relative to other volatile elements when normalized to the chondritic composition. Furthermore, atmospheric xenon is far more enriched in the heavy isotopes relatively to chondritic and solar compositions (3-4%.amu-1) than atmospheric krypton (< 1%.amu-1). This discrepancy, known as the 'xenon paradox', has led to sophisticated models of atmospheric evolution coupled with mantle geodynamics (Pepin, 1991; Tolstikhin and Marty, 1998) and cometary contributions (Dauphas, 2003; Owen et al., 1992) that could explain terrestrial noble gas patterns under ad hoc conditions during the building stages of the Earth, no more than ~200 Ma following the beginning of solar system formation. Yet, xenon having an isotopic composition intermediate between the atmospheric and the chondritic ones has been recently documented in Archean (?3 Ga-old) sedimentary rocks (Pujol et al., 2011), suggesting that isotopic fractionation of Xe occurred over a much longer period of time than previously thought, during the Hadean and the Archean eons. In that case, assuming a Rayleigh type isotope evolution for atmospheric Xe requires an enrichment fractionation factor of 1.3% in heavy isotopes for Xe remaining in the atmosphere. This is clearly within the range of values observed in laboratory experiments aimed at trapping and fractionating Xe isotopes in solids, which is only effective upon ionization (Marrocchi et al., 2011; Kuga et al., 2012). We report here a possibility for explaining the 'xenon paradox' through interaction of the Hadean/Archean atmosphere with EUV light from the young Sun. By using a new photochemical model, we have found out that atmospheric Xe depletion and enrichment in heavy Xe isotopes could be achieved by EUV photoionization deep enough in the atmosphere to allow the preferential implantation of the heavier Xe isotopes in organic aerosols, the formation of which is itself triggered by UV photochemistry. Most of the ionized Xe would have escaped from the atmosphere into space by hydrodynamic escape (Zahnle, 2011). We have established that this mechanism specifically affected Xe and was particularly effective during the Hadean/Archean times, since the irradiation flux was expected to be orders of magnitude higher than today (Ribas et al., 2010). Dauphas (2003), Icarus 165, 326-339. Kuga et al. (2012), #2347 Goldschmidt 2012 Marrocchi et al. (2011), GCA 75, 6255-6266. Owen et al. (1992), Nature 358, 43-46. Pepin (1991), Icarus 92, 1-79. Pujol et al. (2011), Earth Planet. Sci. Lett. 308, 298-306. Ribas et al. (2010), Astrophys. J. 714, 384-395. Srinivasan, (1976), Earth Planet. Sci. Lett. 31, 129-141. Tolstikhin and Marty (1998), Chem. Geol. 147, 27-52. Zahnle (2011), #2241 Goldschmidt 2011

Hébrard; Marty, B.

2012-12-01

231

Standardization of xenon-127 and measurement of photon emission intensities.  

PubMed

Xenon-127 was standardized by internal gas counting using three proportional counters in a differential arrangement to eliminate edge effects. The detection efficiency of the proportional counters was calculated by considering the cascade of events following the electron capture and associated gamma transitions. Activity per unit volume was measured with 0.7% relative standard uncertainty. Gamma-ray spectrometry was performed and absolute photon emission intensities were derived. This study shows that (127)Xe could be a surrogate for (133)Xe for the calibration of remote radio-xenon monitoring stations. PMID:24360861

Rodrigues, M; Lépy, M-C; Cassette, P; Mougeot, X; Bé, M M

2014-05-01

232

Supersonic Flow of Chemically Reacting Gas-Particle Mixtures. Volume 2: RAMP - A Computer Code for Analysis of Chemically Reacting Gas-Particle Flows  

NASA Technical Reports Server (NTRS)

A computer program written in conjunction with the numerical solution of the flow of chemically reacting gas-particle mixtures was documented. The solution to the set of governing equations was obtained by utilizing the method of characteristics. The equations cast in characteristic form were shown to be formally the same for ideal, frozen, chemical equilibrium and chemical non-equilibrium reacting gas mixtures. The characteristic directions for the gas-particle system are found to be the conventional gas Mach lines, the gas streamlines and the particle streamlines. The basic mesh construction for the flow solution is along streamlines and normals to the streamlines for axisymmetric or two-dimensional flow. The analysis gives detailed information of the supersonic flow and provides for a continuous solution of the nozzle and exhaust plume flow fields. Boundary conditions for the flow solution are either the nozzle wall or the exhaust plume boundary.

Penny, M. M.; Smith, S. D.; Anderson, P. G.; Sulyma, P. R.; Pearson, M. L.

1976-01-01

233

Gas-particle partitioning of semivolatile organic compounds (SOCs) on mixtures of aerosols in a smog chamber.  

PubMed

The partitioning behavior of a set of diverse SOCs on two and three component mixtures of aerosols from different sources was studied using smog chamber experimental data. A set of SOCs of different compound types was introduced into a system containing a mixture of aerosols from two or more sources. Gas and particle samples were taken using a filter-filter-denuder sampling system, and a partitioning coefficient Kp was estimated using Kp = Cp/(CgTSP). Particle size distributions were measured using a differential mobility analyzer and a light scattering detector. Gas and particle samples were analyzed using GCMS. The aerosol composition in the chamber was tracked chemically using a combination of signature compounds and the organic matter mass fraction (f(om)) of the individual aerosol sources. The physical nature of the aerosol mixture in the chamber was determined using particle size distributions, and an aggregate Kp was estimated from theoretically calculated Kp on the individual sources. Model fits for Kp showed that when the mixture involved primary sources of aerosol, the aggregate Kp of the mixture could be successfully modeled as an external mixture of the Kp on the individual aerosols. There were significant differences observed for some SOCs between modeling the system as an external and as an internal mixture. However, when one of the aerosol sources was secondary, the aggregate model Kp required incorporation of the secondary aerosol products on the preexisting aerosol for adequate model fits. Modeling such a system as an external mixture grossly overpredicted the Kp of alkanes in the mixture. Indirect evidence of heterogeneous, acid-catalyzed reactions in the particle phase was also seen, leading to a significant increase in the polarity of the resulting aerosol mix and a resulting decrease in the observed Kp of alkanes in the chamber. The model was partly consistent with this decrease but could not completely explain the reduction in Kp because of insufficient knowledge of the secondary organic aerosol composition. PMID:14524443

Chandramouli, Bharadwaj; Jang, Myoseon; Kamens, Richard M

2003-09-15

234

Hugoniot measurements of double-shocked precompressed dense xenon plasmas.  

PubMed

The current partially ionized plasmas models for xenon show substantial differences since the description of pressure and thermal ionization region becomes a formidable task, prompting the need for an improved understanding of dense xenon plasmas behavior at above 100 GPa. We performed double-shock compression experiments on dense xenon to determine accurately the Hugoniot up to 172 GPa using a time-resolved optical radiation method. The planar strong shock wave was produced using a flyer plate impactor accelerated up to ?6 km/s with a two-stage light-gas gun. The time-resolved optical radiation histories were acquired by using a multiwavelength channel optical transience radiance pyrometer. Shock velocity was measured and mass velocity was determined by the impedance-matching methods. The experimental equation of state of dense xenon plasmas are compared with the self-consistent fluid variational calculations of dense xenon in the region of partial ionization over a wide range of pressures and temperatures. PMID:23368058

Zheng, J; Chen, Q F; Gu, Y J; Chen, Z Y

2012-12-01

235

Hugoniot measurements of double-shocked precompressed dense xenon plasmas  

NASA Astrophysics Data System (ADS)

The current partially ionized plasmas models for xenon show substantial differences since the description of pressure and thermal ionization region becomes a formidable task, prompting the need for an improved understanding of dense xenon plasmas behavior at above 100 GPa. We performed double-shock compression experiments on dense xenon to determine accurately the Hugoniot up to 172 GPa using a time-resolved optical radiation method. The planar strong shock wave was produced using a flyer plate impactor accelerated up to ˜6 km/s with a two-stage light-gas gun. The time-resolved optical radiation histories were acquired by using a multiwavelength channel optical transience radiance pyrometer. Shock velocity was measured and mass velocity was determined by the impedance-matching methods. The experimental equation of state of dense xenon plasmas are compared with the self-consistent fluid variational calculations of dense xenon in the region of partial ionization over a wide range of pressures and temperatures.

Zheng, J.; Chen, Q. F.; Gu, Y. J.; Chen, Z. Y.

2012-12-01

236

Calibration of the XENON100 Time Projection Chamber  

NASA Astrophysics Data System (ADS)

The XENON Dark Matter Experiment aims at the direct detection of dark matter Weakly Interacting Massive Particles (WIMPs) with dual phase (liquid/gas) xenon time projection chambers. Following the successful performance of the XENON10, we have designed and built a new detector with a total Xe mass of 170 kg, and with 100 times less background. The XENON100 detector is currently undergoing commissioning at the Gran Sasso Underground Laboratory. The calibration of the detector with gamma sources and with low energy neutrons is essential to determine the response to electron and nuclear recoils, and their discrimination based on the ratio of ionization to scintillation, as well as on event positioning and scattering-multiplicity within the active liquid volume. External gamma sources used for the XENON100 calibration include Cs-137, Co-57 and Co-60. An external Am-Be source is used for irradiation by neutrons. Additionally, we have been testing mixing Kr-83m (tau=12.6 hr, 18 and 32 keV electrons and 13 keV x-rays) into the LXe target, as internal source of low energy electron recoils. We discuss how different detector performance parameters such as light yield and electron lifetime can be inferred from these calibrations and show how the spatial dependence of some other parameters (light collection efficiency for example) can be obtained. We also present comparisons of results from calibrations with Monte Carlo simulations.

Lim, Kyungeun

2009-05-01

237

Modeling Xenon Purification Systems in a Laser Inertial Fusion Engine  

NASA Astrophysics Data System (ADS)

A Laser Inertial Fusion Engine (LIFE) is a proposed method to employ fusion energy to produce electricity for consumers. However, before it can be built and used as such, each aspect of a LIFE power plant must first be meticulously planned. We are in the process of developing and perfecting models for an exhaust processing and fuel recovery system. Such a system is especially essential because it must be able to recapture and purify expensive materials involved in the reaction so they may be reused. One such material is xenon, which is to be used as an intervention gas in the target chamber. Using Aspen HYSYS, we have modeled several subsystems for exhaust processing, including a subsystem for xenon recovery and purification. After removing hydrogen isotopes using lithium bubblers, we propose to use cryogenic distillation to purify the xenon from remaining contaminants. Aspen HYSYS allows us to analyze predicted flow rates, temperatures, pressures, and compositions within almost all areas of the xenon purification system. Through use of Aspen models, we hope to establish that we can use xenon in LIFE efficiently and in a practical manner.

Hopkins, Ann; Gentile, Charles

2011-11-01

238

Single Ion Trapping for the Enriched Xenon Observatory  

SciTech Connect

In the last decade, a variety of neutrino oscillation experiments have established that there is a mass difference between neutrino flavors, without determining the absolute neutrino mass scale. The Enriched Xenon Observatory for neutrinoless double beta decay (EXO) will search for the rare decays of xenon to determine the absolute value of the neutrino mass. The experiment uses a novel technique to minimize backgrounds, identifying the decay daughter product in real time using single ion spectroscopy. Here, we describe single ion trapping and spectroscopy compatible with the EXO detector. We extend the technique of single ion trapping in ultrahigh vacuum to trapping in xenon gas. With this technique, EXO will achieve a neutrino mass sensitivity of {approx_equal} .010 eV.

Waldman, Samuel J.; /Stanford U., Phys. Dept. /SLAC; ,

2006-03-28

239

Hydrogen generation in a microhollow cathode discharge in high-pressure ammonia-argon gas mixtures  

NASA Astrophysics Data System (ADS)

We explored the feasibility of using a single flow-through microhollow cathode discharge (MHCD) as a non-thermal plasma source for hydrogen (H2) production for portable fuel cell applications. The MHCD device consisted of two thin metal electrodes separated by a mica spacer with a single-hole, roughly 100 [mu]m in diameter, through all three layers. The efficiency of the MHCD reactor for H2 generation from NH3 was analyzed by monitoring the products formed in the discharge in a mass spectrometer. Using a gas mixture of up to 10% NH3 in Ar at pressures up to one atmosphere, the MHCD reactor achieved a maximum ammonia conversion of slightly more than 20%. The overall power efficiency of the MHCD reactor reached a peak value of about 11%. The dependence of NH3 conversion and power efficiency on the residence time of the gas in the MHCD plasma was studied. Experiments using pulsed excitation of the MHCD plasma indicated that pulsing can increase the power efficiency. Design and operating criteria are proposed for a microplasma-based H2 generator that can achieve a power efficiency above the break-even point, i.e., a microplasma reactor that requires less electrical power to generate and maintain the plasma than the power that can be obtained from the conversion of the H2 generated in the microplasma reactor.

Qiu, H.; Martus, K.; Lee, W. Y.; Becker, K.

2004-04-01

240

[Correction of the functional state of deck aviation pilots by the course of inhalation of therapeutic doses of xenon during long march].  

PubMed

The article deals with efficiency of the course of O2-Xe inhalation for correction of the functional state of deck aviation pilots in a long march. The course was shown to stabilize vagosympathetic balance in organism, to compensate functioning and to retain reserve of the cardiovascular system that resulted in significant psychoemotional animation attested by self-appreciation, amelioration and cheerfulness, and weakening of reactive anxiety. These observations point to applicability of xenon-based gas mixtures to correction of the pilot's functional state in the most intensive periods of service. Guidelines for broad adoption of the method by military medicine have been developed. PMID:21970037

Bubeev, Iu A; Kal'manov, A S; Kotrovskaia, T I

2011-01-01

241

On Richtmyer-Meshkov instability in dilute gas-particle mixtures  

NASA Astrophysics Data System (ADS)

Richtmyer-Meshkov instability (RMI) in gas-particle mixtures is investigated both numerically and analytically. The linear amplitude growth rate for a RMI in a two-phase mixture is derived by using a dusty gas formulation for small Stokes number (St ?1.0), and it is shown that the problem can be characterized by mass loading and St. The model predictions are compared with numerical results under two conditions, i.e., a shock wave hitting (1) a perturbed species interface of air and SF6 surrounded by uniformly distributed particles, and (2) a perturbed shape particle cloud in uniform air. In the first case, the interaction between the instability of the species perturbation and the particles is investigated. The multiphase growth model accurately predicts the growth rates when St ?1.0, and the amplitude growth normalized by the two-phase RMI velocity shows good agreement with the single-phase RMI growth rate as well. It is also shown that the two-phase model results are in accordance with the growth rates obtained from the simulations even for cases corresponding to St ?10. However, for St ?10, particles do not follow the RMI motion, and the RMI growth rate agrees with the original Richtmyer's model [R. D. Richtmyer, "Taylor instability in shock acceleration of compressible fluids," Commun. Pure Appl. Math. 13, 297 (1960)]. Preferential concentration of particles are observed around the RMI roll-ups at late times when St is of order unity, whereas when St ?1.0, the particles respond rapidly to the flow, causing them to distribute within the roll-ups. In the second problem, the two-phase RMI growth model is extended to study whether a perturbed dusty gas front shows RMI-like growth due to the impact of a shock wave. When St ?1.0, good agreement with the multiphase model is again seen. Moreover, the normalized growth rates are very close to the single-phase RMI growth rates even at late times, which suggest that the two-phase growth model is applicable to this type of perturbed shape particle clouds as well. However, when St is close to unity or larger (St >1.0), the particles do not experience impulsive acceleration but rather a continuous one, which results in exponential growth rates as seen in a Rayleigh-Taylor instability.

Ukai, Satoshi; Balakrishnan, Kaushik; Menon, Suresh

2010-10-01

242

Detection of a CO and NH3 gas mixture using carboxylic acid-functionalized single-walled carbon nanotubes  

PubMed Central

Carbon nanotubes (CNT) are extremely sensitive to environmental gases. However, detection of mixture gas is still a challenge. Here, we report that 10 ppm of carbon monoxide (CO) and ammonia (NH3) can be electrically detected using a carboxylic acid-functionalized single-walled carbon nanotubes (C-SWCNT). CO and NH3 gases were mixed carefully with the same concentrations of 10 ppm. Our sensor showed faster response to the CO gas than the NH3 gas. The sensing properties and effect of carboxylic acid group were demonstrated, and C-SWCNT sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective detection method of CO and NH3 mixture gas. PMID:23286690

2013-01-01

243

On the gas-gas equilibria of second kind of nonpolar fluid binary mixtures from a hard-sphere EXP-6 molecular model  

NASA Astrophysics Data System (ADS)

The phase behavior of a molecular-based model of nonpolar binary mixtures is investigated by the application of thermodynamic perturbation theory. The pair potential interaction model is represented as a reference system of equal size hard-spheres perturbed by the exponential-6 potential. It is found that the qualitative behavior of gas-gas immiscibility of second kind is very much sensitive to the hardness of the potential (ratio of the hard sphere diameter to the size parameter of the perturbation). Calculated theoretical phase diagrams are compared with results from Monte Carlo simulations in the Gibbs ensemble performed for this model mixture.

Zarragoicoechea, G. J.; Scalise, O. H.

1997-09-01

244

Observation and applications of single-electron charge signals in the XENON100 experiment  

E-print Network

The XENON100 dark matter experiment uses liquid xenon in a time projection chamber (TPC) to measure xenon nuclear recoils resulting from the scattering of dark matter Weakly Interacting Massive Particles (WIMPs). In this paper, we report the observation of single-electron charge signals which are not related to WIMP interactions. These signals, which show the excellent sensitivity of the detector to small charge signals, are explained as being due to the photoionization of impurities in the liquid xenon and of the metal components inside the TPC. They are used as a unique calibration source to characterize the detector. We explain how we can infer crucial parameters for the XENON100 experiment: the secondary-scintillation gain, the extraction yield from the liquid to the gas phase and the electron drift velocity.

E. Aprile; M. Alfonsi; K. Arisaka; F. Arneodo; C. Balan; L. Baudis; B. Bauermeister; A. Behrens; P. Beltrame; K. Bokeloh; A. Brown; E. Brown; S. Bruenner; G. Bruno; R. Budnik; J. M. R. Cardoso; W. -T. Chen; B. Choi; A. P. Colijn; H. Contreras; J. P. Cussonneau; M. P. Decowski; E. Duchovni; S. Fattori; A. D. Ferella; W. Fulgione; F. Gao; M. Garbini; C. Ghag; K. -L. Giboni; L. W. Goetzke; C. Grignon; E. Gross; W. Hampel; R. Itay; F. Kaether; G. Kessler; A. Kish; J. Lamblin; H. Landsman; R. F. Lang; M. Le Calloch; C. Levy; K. E. Lim; Q. Lin; S. Lindemann; M. Lindner; J. A. M. Lopes; K. Lung; T. Marrodan Undagoitia; F. V. Massoli; A. J. Melgarejo Fernandez; Y. Meng; M. Messina; A. Molinario; J. Naganoma; K. Ni; U. Oberlack; S. E. A. Orrigo; E. Pantic; R. Persiani; F. Piastra; G. Plante; N. Priel; A. Rizzo; S. Rosendahl; J. M. F. dos Santos; G. Sartorelli; J. Schreiner; M. Schumann; L. Scotto Lavina; M. Selvi; P. Shagin; H. Simgen; A. Teymourian; D. Thers; O. Vitells; H. Wang; M. Weber; C. Weinheimer

2013-11-05

245

Prediction of Volumetric Properties ( p-v-T) of Natural Gas Mixtures Using Extended Tao-Mason Equation of State  

Microsoft Academic Search

A statistical-mechanical-based equation of state (EOS) for pure substances, the Tao-Mason equation of state, is successfully extended to prediction of the (p-v-T) properties of fourteen natural gas mixtures at temperatures from 225 K to 483 K and pressures up to 60.5 MPa. This work shows that the Tao-Mason equation of state for multicomponent natural gas is predictable with minimal input

Hajir Karimi; Fakhri Yousefi; Mohammad Mehdi Papari

2011-01-01

246

Automation of gas chromatography instruments. Part I. Automated peak identification in the chromatograms of standard test mixtures  

Microsoft Academic Search

The evaluation of the chromatogram recorded during the gas chromatographic analysis of a standard test mixture is of importance in the assessment of the performance of the underlying GC system. Automated evaluation is essential in the development of software that can be used in systems that can perform totally automated analysis. In this study, an algorithm for automated peak identification

Hai Du; Martin J. Stillman

1997-01-01

247

Combustion of Cr 2 O 3 + Al powder mixtures in a coflow of inert gas: 5. Effect of green density  

Microsoft Academic Search

Combustion of Cr2O3 + Al powder mixtures in a coflow of inert gas (Ar) was investigated upon variation in green density in the presence\\/absence\\u000a of blowing agents (borax, baking soda). The results were rationalized in terms of the convection-conduction theory for combustion\\u000a in heterogeneous condensed systems.

B. S. Seplyarskii; G. B. Brauer; A. G. Tarasov

2009-01-01

248

Aerodynamic Separation Effect on Gas and Isotope Mixtures Induced by Invasion of the Free Jet Shock Wave Structure  

Microsoft Academic Search

The shock wave system of the underexpanded free jet, in a region where the pressure is in the range of 10?2 up to 1 torr, is partly invaded by background molecules, these latter being pumped and carried by the supersonic flow. When a gas mixture is introduced into the nozzle chamber and outside the shock barrel, this aspiration acts very

Roger Campargue

1970-01-01

249

Biotreatment of a gas-phase volatile mixture from fibreglass and composite manufacturing industries.  

PubMed

Acetone, toluene and styrene (ATS) are representative air pollutants emanating during the production process in fibreglass and composite manufacturing industries. In this study, the performance of a steady-state biofilter inoculated with the fungus Sporothrix variecibatus was tested at different empty bed residence times (EBRTs), and at different inlet concentrations of ATS, corresponding to total pollutant loading rates ranging from 30 to 490 gm(-3)hour(-1). Styrene was somewhat better removed (47-100%) in the biofilter than acetone (34-100%) and toluene (42-100%), with maximum elimination capacities (EC(max)) of 108, 72 and 144 gm(-3)hour(-1), for ATS, respectively. Besides, it was observed that, although increasing the concentration of ATS decreased their removal, the presence of toluene also decreased the EC(max) of both acetone and toluene in the ternary mixture. During transient operations, the biofilter was subjected to intermittent shutdown and re-start operations where the gas-phase pollutant flow was stopped for either 5 or 16d. It was observed that, for longer shutdown periods (16d), the biofilter required nearly 8-10d to reach similar removal patterns to those observed before the shutdown phase. Batch biodegradation tests were conducted, using Sporothrix-like microorganisms present in the leachate of the biofilter, with a mixture of ATS as the sole carbon source. Complete removal of ATS was observed within the test period of 168 hours. Styrene was degraded faster, with a specific substrate utilization rate of 0.9 mg styrenemg biomass(-1)hour(-1), followed by toluene (0.6) and acetone (0.44). The effectiveness of the biofilter to reach high total EC (321.3 gm(-3)hour(-1)), and withstand transient operations shows the robustness of this fungal-bioreactor and its suitability to handle emissions from a fibreglass and composite manufacturing industry. PMID:21911090

Rene, Eldon R; Montes, María; Veiga, María C; Kennes, Christian

2011-12-15

250

The fate of xenon-131 from iodine-131 absorbed on the silver zeolite samplers  

NASA Astrophysics Data System (ADS)

The purpose of this study was to investigate whether xenon-131, the decay daughter of I-131, was retained in or escaped from the silver zeolite cartridge after iodine-131 had been adsorbed in the cartridge. Currently, silver zeolite cartridges are used in the nuclear power industry to adsorb the radioactive iodine gas in sampling lines because of their high retention efficiency for gaseous iodine but not for noble gases. If xenon-131 is desorbed and escapes from the silver zeolite cartridge, the surfaces originally occupied by iodine-131 in the silver zeolite cartridge may be vacant and thus available to adsorb other iodine gas molecules. The reusability of silver zeolite cartridges may reduce the sampling cost and radioactive waste volume and also preserve the silver resource. A silver zeolite cartridge containing only iodine-131 of known activity in a cartridge holder was connected with a blank charcoal cartridge in another cartridge holder. The end of each cartridge holder was sealed so the diffusion of xenon was contained in a closed system. Radioactive xenon-131 m, the daughter of iodine-131, was used as an indicator for stable xenon-131. The absence or presence of xenon-131m on the charcoal cartridge was used to determine if xenon-131 was desorbed from the silver zeolite cartridge. A NaI scintillator was used to detect iodine-131 and a HPGe detector was used to detect xenon- 131 m. The desorption fraction of xenon-133 from the silver zeolite cartridge was found to be 0.66 +/- 4.3% and the retention fraction of xenon-133 in the charcoal cartridge was found to be 0.61 +/- 7.5%. Xenon-131m was frequently present in the charcoal cartridge. This showed that xenon131 was desorbed and escaped from the initial occupied sites in the silver zeolite cartridge after iodine-131 decayed. The amount of xenon-131m escaping from the silver zeolite cartridge fluctuated from day to day. This is thought to be due to what is known as the tunnel blocking effect. This effect has been described in the literature and involves the random location of xenon-131m atoms in the microscopic infrastructure of the silver zeolite.

Wang, Wei-Hsung

2000-09-01

251

The kinetics of gas-liquid metal reactions involving levitated drops. Carburization and decarburization of molten iron in CoCo2 gas mixtures at high pressures  

Microsoft Academic Search

The kinetics of decarburization and carburization of levitated molten iron-carbon alloy drops at 1650? in CO-CO2 gas mixtures\\u000a were studied at a pressure of 40 atm. The results showed that, under the experimental conditions used, the rates were controlled\\u000a by transport in the gas phase (decarburization) or by mixed transport control (carburization). The levitated drops behaved\\u000a as static spherical particles

N. H. El-kaddah; D. G. C. Robertson

1978-01-01

252

Supersonic flow of chemically reacting gas-particle mixtures. Volume 1: A theoretical analysis and development of the numerical solution  

NASA Technical Reports Server (NTRS)

A numerical solution for chemically reacting supersonic gas-particle flows in rocket nozzles and exhaust plumes was described. The gas-particle flow solution is fully coupled in that the effects of particle drag and heat transfer between the gas and particle phases are treated. Gas and particles exchange momentum via the drag exerted on the gas by the particles. Energy is exchanged between the phases via heat transfer (convection and/or radiation). Thermochemistry calculations (chemical equilibrium, frozen or chemical kinetics) were shown to be uncoupled from the flow solution and, as such, can be solved separately. The solution to the set of governing equations is obtained by utilizing the method of characteristics. The equations cast in characteristic form are shown to be formally the same for ideal, frozen, chemical equilibrium and chemical non-equilibrium reacting gas mixtures. The particle distribution is represented in the numerical solution by a finite distribution of particle sizes.

Penny, M. M.; Smith, S. D.; Anderson, P. G.; Sulyma, P. R.; Pearson, M. L.

1976-01-01

253

FAST TRACK COMMUNICATION: Effects of reducing interferers in a binary gas mixture on NO2 gas adsorption using carbon nanotube networked films based chemiresistors  

NASA Astrophysics Data System (ADS)

Analysis of binary gas mixtures using chemiresistors based on carbon nanotubes (CNTs) networked films has been performed for chemical detection up to a sub-ppm level. The effects of individual interfering analytes of reducing H2S and NH3 gases on oxidizing NO2 gas adsorption in CNTs tangled films are considered. The CNTs are grown by plasma-enhanced chemical vapour deposition technology onto inexpensive alumina substrates, coated by cobalt nanosized catalyst. Charge transfer between adsorbed gas molecules and CNT networks, characterized by a semiconducting p-type electrical transport, occurs depending on opposite trend in the sensor response to the electron-donating interfering gases (H2S, NH3) and target electron-withdrawing NO2 gas causing a compensation of the charge transport, upon given working conditions. This compensated exchange of electrical charge affects the limit of detection of the targeted NO2 gas sensed in different real-world binary gas mixtures of reducing interferers of H2S and NH3. In addition, the functionalization of the CNT films with Au nanoclusters enhanced the sensitivity of the chemiresistor and tuned the compensation of electrical charge crossover in the selected binary oxido-reducing mixtures.

Penza, M.; Rossi, R.; Alvisi, M.; Signore, M. A.; Serra, E.

2009-04-01

254

Radiation-induced reactions of CO?H 2 gas mixtures over various solid catalysts  

NASA Astrophysics Data System (ADS)

Studies have been carried out of radiation-induced reactions of CO?H 2 gas mixtures in the presence of various solid catalysts in order to find possibilities of synthesizing organic raw materials from CO?H 2 by radiation for the future. The solid catalysts studied include Fischer-Tropsch catalyst (Fe?Cu supported by diatomaceous earth), titania(TiO 2), and silica gel. Analysis of the reaction products over Fischer-Tropsch catalyst or semiconductors such as TiO 2 and ZnO?Cr 2O 3 reveals that these solid catalysts do not sensitize the radiation chemical reaction of CO?H 2 but show the secondary effects on the reaction so as to induce the hydrogenation of olefins produced by the catalytic reaction and of aldehydes produced in gas phase by radiation. On the other hand, silica gel and other insulators such as alumina have been found to exhibit high catalytic activity in the formation of hydrocarbons from CO?H 2 under electron beam irradiation at 300°C. It has been shown experimentally that secondary reactions between H 2 and carbonaceous solid produced from CO make a substantial contribution to the formation of hydrocarbons from CO?H 2 over silica gel. In an attempt to find the role of silica gel in the reaction to produce hydrocarbons, radiation-induced reactions have been studied of H 2 with the carbonaceous solid that had been produced by irradiation of CO in the absence of solid catalyst, over TiO 2, or over silica gel. The results indicate that silica gel not only enhances the yields of CO 2 and carbonaceous solid from CO but also promotes hydrogenation reactions of the carbonaceous solid under electron beam irradiation.

Nagai, S.; Arai, H.; Hatada, M.

255

Studies of Helium Based Gas Mixtures Using a Small Cell Drift Chamber  

SciTech Connect

An international collaboration is currently working on the construction and design of an asymmetric B Factory at the Stanford Linear Accelerator Center that will be ready to collect data in 1999. The main physics motivation for such a facility is to test the description and mechanism of CP violation in the Standard Model of particle physics and provide insight into the question of why more matter than antimatter is observed in the universe today. In particular, this experiment will measure CP violation in the decay of B mesons. In the early stages of this effort, the Canadian contingent proposed to build the central tracking chamber for the BaBar detector. Presently, a prototype drift chamber is in operation and studies are being performed to test some of the unique features of drift chamber design dictated by the conditions of the experiment. Using cosmic muons, it is possible to study tracking and pattern recognition in the prototype chamber, and therefore calculate the efficiency and spatial resolution of the prototype chamber cells. These performance features will be used to test whether or not the helium-based gas mixtures proposed for the BaBar drift chamber are a viable alternative to the more traditional argon-based gases.

Heise, Jaret; /British Columbia U.

2006-07-07

256

Dynamic Characteristics of SF6-N2-CO2 Gas Mixtures in DC Discharge Process  

NASA Astrophysics Data System (ADS)

Dynamic characteristics of discharge particles are described within the framework of a two-dimensional photoionization-hydrodynamic numerical model for the discharge process of SF6-N2-CO2 gas mixtures at atmospheric pressure, under a uniform DC applied field. The finite difference—flux corrected transport (FD-FCT) algorithm is used in the numerical implementation for improving the accuracy and efficiency. Then the tempo-spatial distributions of the gap—space electric field and electron velocity are calculated from the microscopic mechanism, and the dynamic behaviors of charged particles are obtained in detail. Meanwhile, the tempo—spatial critical point of the avalanche-to-streamer in this model is discovered, and several microscopic parameters are also investigated. The results showed that the entire gap discharge process can be divided into two phases of avalanche and streamer according to Raether-Meek criterion; the electron density within the discharge channel is lower compared to that of positive and negative ions; space charge effect is a dominant factor for the distortion of spatial electric field, making the discharge channel expand toward both electrodes faster; photoionization provides seed electrons for a secondary electron avalanche, promoting the formation and development speed of the streamer.

Zheng, Dianchun; Wang, Jia; Chen, Chuntian; Zhao, Dawei; Zhang, Chunxi; Yang, Jiaxiang

2014-09-01

257

Enhanced technique for measuring collisional quenching rate coefficients in rare-gas mixtures  

SciTech Connect

We set forth an improved technique for the investigation of collisional quenching in high-pressure rare-gas mixtures, which relies on the absorption probing measurements of the decay rates of the excited states of these gases in the afterglow of a fast electron beam discharge. We determined more precisely the rate coefficients of the plasmochemical reactions Xe* + Xe + Ar {yields} Xe{sub 2}* and Xe*+Ar {yields} products + Ar for the metastable (6s[3/2]{sub 2}{sup 0}) and resonance (6s[3/2]{sub 1}{sup 0}) levels of atomic Xe investigated in our earlier work. The rate coefficients for the reactions Xe(6s[3/2]{sub 2}{sup 0}) + 2Ar {yields} ArXe* + Ar((7.2{+-}1.4)x10{sup -36} cm{sup 6} s{sup -1}) and Xe(6s[3/2]{sub 1}{sup 0}) + 2Ar {yields} ArXe*((5.3{+-}2.4)x10{sup -36} cm{sup 6} s{sup -1}) were measured for the first time. (active media)

Zayarnyi, D A; L'dov, A Yu; Kholin, I V [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2011-02-28

258

Gas-phase ion chemistry of NF3/SO2 mixtures  

NASA Astrophysics Data System (ADS)

The gas-phase ion chemistry of NF3/SO2 mixtures has been investigated by ion trap mass spectrometry and theoretical calculations. SO+ and SO2+ react efficiently with NF3 giving F(SO)+ and F(SO2)+. CAD experiments and thermochemical considerations support the exclusive formation of the sulfur-fluorine cations FSO+ and FSO2+. NF2+ is unreactive toward SO2, and NF3+ undergoes exclusively the efficient charge transfer. On the other hand, NF+ activates the OSO bond, with formation of SO+ and NO+. DFT and coupled cluster calculations indicate that these ionic products arise from a SO+-(FNO) ion-dipole complex, which dissociates into SO+ and FNO or NO+ and FSO. This intermediate is more stable than NF+ and SO2 by nearly 60 kcal mol-1. We have also located a less stable sulfur-nitrogen complex FNSO2+, whose formation explains the less efficient observed charge transfer between NF+ and SO2. The only observed negative ion-molecule reaction is the formation of FSO2- from the reaction between SO2- and NF3. Our investigated processes may be of interest for the plasma and the atmospheric chemistry of NF3, one of the gaseous compounds most extensively used in the electronic industry to perform etching and cleaning processes.

Antoniotti, Paola; Rabezzana, Roberto; Turco, Francesca; Borocci, Stefano; Bronzolino, Nicoletta; Grandinetti, Felice

2007-10-01

259

Dust and gas mixtures with multiple grain species - a one-fluid approach  

NASA Astrophysics Data System (ADS)

We derive the single-fluid evolution equations describing a mixture made of a gas phase and an arbitrary number of dust phases, generalizing the approach developed by Laibe & Price. A generalization for continuous dust distributions as well as analytic approximations for strong drag regimes is also provided. This formalism lays the foundation for numerical simulations of dust populations in a wide range of astrophysical systems while avoiding limitations associated with a multiple-fluid treatment. The usefulness of the formalism is illustrated on a series of analytical problems, namely the DUSTYBOX, DUSTYSHOCK and DUSTYWAVE problems as well as the radial drift of grains and the streaming instability in protoplanetary discs. We find physical effects specific to the presence of several dust phases and multiple drag time-scales, including non-monotonic evolution of the differential velocity between phases and increased efficiency of the linear growth of the streaming instability. Interestingly, it is found that under certain conditions, large grains can migrate outwards in protoplanetary discs. This may explain the presence of small pebbles at several hundreds of astronomical units from their central star.

Laibe, Guillaume; Price, Daniel J.

2014-10-01

260

Temporal Characteristics of Emission of Working Mixtures of a HgBr/HgCl Excimer Lamp  

NASA Astrophysics Data System (ADS)

Results of a study of temporal characteristics of the emission of gas-discharge plasma of atmospheric pressure in multicomponent mixtures (mercury dibromide and dichloride with helium and additions of molecular nitrogen and xenon) of working media of HgBr/HgCl excimer lamps are presented. Gas-discharge plasma was produced and components of the working mixture were excited by high-frequency barrier and surface discharges occurring simultaneously. The repetition rate of the pumping pulse and its duration are 1000 Hz and ˜100 ns, respectively. It is found that the amplitude and the length of emission pulses and their trailing edge are modified in HgBr2: HgCl2: Xe: He and HgBr2: HgCl2: N2: He mixtures when xenon and molecular nitrogen are added, as compared to a HgBr2: HgCl2: He mixture. Regularities observed in temporal characteristics of gas-discharge plasma emission are discussed.

Malinin, A. N.; Gu?van, N. N.; Shimon, L. L.; Polyak, A. V.; Zubrilin, N. G.; Shchedrin, A. I.

2001-12-01

261

Multidimensional gas chromatography with electron capture detection for the determination of toxic congeners in polychlorinated biphenyl mixtures  

SciTech Connect

A multidimensional gas chromatographic technique is suggested as a tool for effective separation of polychlorinated biphenyl (PCB) congeners which cannot be separated on a single SE 54 or other column. Two capillary columns are arranged in series, such that the second column receives only small preselected fractions eluting from the first column. The technique offers complete separation and increased sensitivity. The possibilities of the technique are demonstrated for toxic PCB congeners which were quantitated accurately for the first time in Clophen and Aroclor commercial mixtures and a seal blubber extract. The relative concentrations differed considerably between blubber extract and the commercial mixtures.

Duinker, J.C.; Schulz, D.E.; Petrick, G.

1988-03-01

262

Working process study of a novel scroll type multiphase pump for the transportation of gas-liquid mixtures  

NASA Astrophysics Data System (ADS)

A novel scroll type multiphase pump was proposed to transport gas-liquid two-phase mixture. There is a pressure unloading gap from compression chambers to the discharge port by constructing scroll wrap profile with variational meshing clearance in this scroll multiphase pump. In the working process when the volume of working chamber decreases, the pressure of gas-liquid mixtures increases gradually, at the same time small amounts of gas-liquid mixture are pushed to the discharge port from compression chambers through the pressure unloading gap. Therefore, this multiphase pump has an advantage of unloading pressure method automatically, and the frequently problem of liquid impacting in volume multiphase pump is solved. The safety and reliability of volumetric multiphase pump are improved, and the scope of multiphase pump of the gas-liquid ratio is expanded. The working process and the performance characteristics of scroll multiphase pump were analyzed too, and the generation method of scroll wrap profile with variational meshing clearance was investigated. The equations of the profile were obtained, and the changing principle of the working volume and the meshing clearance were analyzed. The geometric theory of scroll multiphase pump was formed. All of that lay the theoretical foundation for engineering design of this novel scroll.

Wang, J.; Zha, H. B.; Zhang, X. H.; Zhang, D. H.

2012-11-01

263

Separating Mixtures  

NSDL National Science Digital Library

Students learn how to classify materials as mixtures, elements or compounds and identify the properties of each type. The concept of separation of mixtures is also introduced since nearly every element or compound is found naturally in an impure state such as a mixture of two or more substances, and it is common that chemical engineers use separation techniques to separate mixtures into their individual components. For example, the separation of crude oil into purified hydrocarbons such as natural gas, gasoline, diesel, jet fuel and/or lubricants.

National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

264

Global characteristics of an ATON stationary plasma thruster operating with krypton and xenon  

Microsoft Academic Search

The global characteristics of an ATON stationary plasma thruster operating on xenon and krypton are investigated. It is shown\\u000a that, with krypton, the thrust at the same mass flow rate of the working gas is greater and the efficiency is somewhat lower\\u000a than those with xenon. An efficiency of ?60% was achieved with krypton for the specific impulse attaining 3000

A. I. Bugrova; A. S. Lipatov; A. I. Morozov; L. V. Solomatina

2002-01-01

265

Pulsed-field-gradient measurements of time-dependent gas diffusion  

NASA Technical Reports Server (NTRS)

Pulsed-field-gradient NMR techniques are demonstrated for measurements of time-dependent gas diffusion. The standard PGSE technique and variants, applied to a free gas mixture of thermally polarized xenon and O2, are found to provide a reproducible measure of the xenon diffusion coefficient (5.71 x 10(-6) m2 s-1 for 1 atm of pure xenon), in excellent agreement with previous, non-NMR measurements. The utility of pulsed-field-gradient NMR techniques is demonstrated by the first measurement of time-dependent (i.e., restricted) gas diffusion inside a porous medium (a random pack of glass beads), with results that agree well with theory. Two modified NMR pulse sequences derived from the PGSE technique (named the Pulsed Gradient Echo, or PGE, and the Pulsed Gradient Multiple Spin Echo, or PGMSE) are also applied to measurements of time dependent diffusion of laser polarized xenon gas, with results in good agreement with previous measurements on thermally polarized gas. The PGMSE technique is found to be superior to the PGE method, and to standard PGSE techniques and variants, for efficiently measuring laser polarized noble gas diffusion over a wide range of diffusion times. Copyright 1998 Academic Press.

Mair, R. W.; Cory, D. G.; Peled, S.; Tseng, C. H.; Patz, S.; Walsworth, R. L.

1998-01-01

266

Xenon NMR studies of dynamics and exchange in zeolites  

SciTech Connect

We have found, despite earlier reports to the contrary, that for many microporous solids with one-dimensional channels (ZSM-12, ALPO-5, VPI-5, SSZ-24) the chemical shift has an anisotropic component. For ALPO-11, a detailed model has been developed which accounts for the loading-dependent chemical shift in terms of intraparticle exchange of statistical distributions of xenon atoms with 0, 1 or 2 nearest neighbors. A similar model can be applied to ZSM-12 up to moderate loadings. At higher loading levels 2D exchange methods show that interparticle exchange occurs as well. The same approach was used to study interparticle exchange in X and Y zeolite mixtures, exchange amongst zeolite clusters of up to 8 xenon atoms in the supercages of AgA zeolite, and main channel - side pocket exchange in mordenite. The parameters derived are directly relevant to the understanding of sorption and diffusion processes in zeolites.

Moudrakovski, I.L.; Ratcliffe, C.I.; Ripmeester, J.A. [Steacie Institute for Molecular Sciences, Ottawa, Ontario (Canada)

1996-10-01

267

Influence of balance gas mixture on decomposition of dimethyl sulfide in a wire-cylinder pulse corona reactor  

Microsoft Academic Search

The influence of balance gas mixture on decomposition of dimethyl sulfide was investigated experimentally by a wire-cylinder pulse corona reactor at room temperature. A new type of high voltage pulse generator with a thyratron switch and a Blumlein pulse-forming network was used in the experiments. The experiments were conducted at a fixed pulse frequency of 100pps. The DMS decomposition efficiency

Jie Chen; Qingfa Su; Hua Pan; Jianwen Wei; Xuming Zhang; Yao Shi

2009-01-01

268

Method of and apparatus for measuring the mean concentration of thoron and/or radon in a gas mixture  

DOEpatents

A method of and an apparatus for detecting and accurately measuring the mean concentrations of .sup.222 Rn and .sup.220 Tn in a gas mixture, such as the ambient atmosphere in a mine, is provided. The apparatus includes an alpha target member which defines at least one operative target surface and which is preferably fabricated from a single piece of an alpha particle sensitive material. At least one portion of the operative target surface is covered with an alpha particle filter. The uncovered and filter covered operative surface is exposed to the gas mixture containing the .sup.222 Rn and .sup.220 Tn. In the radioactive decay series of these isotopes the maximum kinetic energy emitted by the alpha decay of .sup.222 Rn is about 1.1 MeV less than the maximum kinetic energy emitted by the alpha decay of a .sup.220 Tn. The alpha particle filter has a predetermined mass per unit area of the covered portion of the operative target surface that prevents penetration of alpha particles which originate from .sup.222 Rn decay, but which allows passage therethrough of the maximum kinetic energy alpha particles from .sup.220 Tn decay. Thus, a count of the alpha particle tracks in the uncovered portion of the target member is proportional to the mean concentration of sum of .sup.222 Rn and .sup.220 Tn in the gas mixture, while the count of alpha tracks in the target member under the filter is proportional to the concentration of only the .sup.220 Tn in the gas mixture.

Lucas, Henry (P.O. Box 1454, Sedona, AZ 86336)

1990-01-01

269

Numerical Prediction of Radiation Measurements Taken in the X2 Facility for Mars and Titan Gas Mixtures  

NASA Technical Reports Server (NTRS)

Thermochemical relaxation behind a normal shock in Mars and Titan gas mixtures is simulated using a CFD solver, DPLR, for a hemisphere of 1 m radius; the thermochemical relaxation along the stagnation streamline is considered equivalent to the flow behind a normal shock. Flow simulations are performed for a Titan gas mixture (98% N2, 2% CH4 by volume) for shock speeds of 5.7 and 7.6 km/s and pressures ranging from 20 to 1000 Pa, and a Mars gas mixture (96% CO2, and 4% N2 by volume) for a shock speed of 8.6 km/s and freestream pressure of 13 Pa. For each case, the temperatures and number densities of chemical species obtained from the CFD flow predictions are used as an input to a line-by-line radiation code, NEQAIR. The NEQAIR code is then used to compute the spatial distribution of volumetric radiance starting from the shock front to the point where thermochemical equilibrium is nominally established. Computations of volumetric spectral radiance assume Boltzmann distributions over radiatively linked electronic states of atoms and molecules. The results of these simulations are compared against experimental data acquired in the X2 facility at the University of Queensland, Australia. The experimental measurements were taken over a spectral range of 310-450 nm where the dominant contributor to radiation is the CN violet band system. In almost all cases, the present approach of computing the spatial variation of post-shock volumetric radiance by applying NEQAIR along a stagnation line computed using a high-fidelity flow solver with good spatial resolution of the relaxation zone is shown to replicate trends in measured relaxation of radiance for both Mars and Titan gas mixtures.

Palmer, Grant; Prabhu, Dinesh; Brandis, Aaron; McIntyre, Timothy J.

2011-01-01

270

Sparkover Characteristics in CF3I Gas and CF3I/N2 Gas Mixture under Non-uniform Field Gaps  

NASA Astrophysics Data System (ADS)

A steep-front square pulse voltage generator, which has a rise time of 16ns, a dumping factor less than 2.5% after 10?s duration and a peak value of 200kV, is successfully used to survey the V-t characteristics in nanosecond range. The V-t characteristics of CF3I, SF6, CF3I/N2 and SF6/N2 gas mixtures under non-uniform field gaps by using the steep-front square pulse voltage. When the field utilization factor are measured less than 0.38, the sparkover voltage of CF3I is lower than that of SF6. On the contrary, when the field utilization factor is more than 0.38, the sparkover voltage of CF3I is higher than that of SF6. The corona inception voltage calculated by using Schumann's criteria and compared with measured one. The V-t characteristics for a uniform field gap in CF3I/N2 gas mixture containing N2 gas of 40% are equivalent to those in pure SF6 gas. The synergism for appears when CF3I gas is mixed with N2 gas.

Takeda, Toshinobu; Matsuoka, Shigeyasu; Kumada, Akiko; Hidaka, Kunihiko

271

Terrestrial and Martian weathering signatures of xenon components in shergottite mineral separates  

NASA Astrophysics Data System (ADS)

Xenon-isotopic ratios, step-heating release patterns, and gas concentrations of mineral separates from Martian shergottites Roberts Massif (RBT) 04262, Dar al Gani (DaG) 489, Shergotty, and Elephant Moraine (EET) 79001 lithology B are reported. Concentrations of Martian atmospheric xenon are similar in mineral separates from all meteorites, but more weathered samples contain more terrestrial atmospheric xenon. The distributions of xenon from the Martian and terrestrial atmospheres among minerals in any one sample are similar, suggesting similarities in the processes by which they were acquired. However, in opaque and maskelynite fractions, Martian atmospheric xenon is released at higher temperatures than terrestrial atmospheric xenon. It is suggested that both Martian and terrestrial atmospheric xenon were initially introduced by weathering (low temperature alteration processes). However, the Martian component was redistributed by shock, accounting for its current residence in more retentive sites. The presence or absence of detectable 129Xe from the Martian atmosphere in mafic minerals may correspond to the extent of crustal contamination of the rock's parent melt. Variable contents of excess 129Xe contrast with previously reported consistent concentrations of excess 40Ar, suggesting distinct sources contributed these gases to the parent magma.

Cartwright, J. A.; Ocker, K. D.; Crowther, S. A.; Burgess, R.; Gilmour, J. D.

2010-08-01

272

High Pressure XENON Gamma-Ray Spectrometers for Field Use  

SciTech Connect

This project explored a new concept for high-pressure xenon ionization chambers by replacing the Frisch grid with coplanar grid electrodes similar to those used in wide bandgap semiconductor gamma-ray spectrometers. This work is the first attempt to apply the coplanar grid anode design in a gas ionization chamber in order to achieve to improved energy resolution. Three prototype detectors, two cylindrical and one parallel plate configurations, were built and tested. While the detectors did not demonstrate energy resolutions as good as other high pressure xenon gamma-ray spectrometers, the results demonstrated that the concept of single polarity charge sending using coplanar grid electrodes will work in a gas detector.

David K. Wehe; Zong He; Glenn K. Knoll

2004-02-16

273

ANALYTICAL METHOD FOR MEASURING TOTAL PROTIUM AND TOTAL DEUTERIUM IN A GAS MIXTURE CONTAINING H2, D2,AND HD VIA GAS CHAROMATOGRAPHY  

SciTech Connect

The most common analytical method of identifying and quantifying non-radioactive isotopic species of hydrogen is mass spectrometry. A low mass, high resolution mass spectrometer with adequate sensitivity and stability to identify and quantify hydrogen isotopes in the low ppm range is an expensive, complex instrument. A new analytical technique has been developed that measures both total protium (H) and total deuterium (D) in a gas mixture containing H{sub 2}, D{sub 2}, and HD using an inexpensive micro gas chromatograph (GC) with two molecular sieve columns. One column uses D{sub 2} as the carrier gas and the other uses H{sub 2} as the carrier gas. Laboratory tests have shown that when used in this configuration the GC can measure both total protium and total deuterium each with a detection and quantification limit of less than 20 ppm.

Sessions, H

2007-08-07

274

Radiant flash pyrolysis of biomass using a xenon flashtube  

Microsoft Academic Search

Biomass materials, including lignin, redwood, corn cob, Calotropis Procera, Leucaena wood, Kraft paper, newsprint, cow manure, D-glucose, and D-cellobiose, were pyrolyzed in vacuum by the visible radiant flux emitted from a Xenon flashtube. The flux density exceeded 8 kW\\/cm² during the 1 ms flash. Sirup yields were low (avg 25%), while the gas yield was high (avg 32%). The gaseous

Mark Willard Hopkins; Michael Jerry Antal; Jack G. Kay

1984-01-01

275

Variation of density with composition for natural gas mixtures in the supercritical region  

E-print Network

. Jacobsen, ?GRI High Accuracy Natural Gas Equation of State GRI-91/0184,? Gas Research Insitute, Chicago, (1991). Ting, V. C., L. L. Schexnayder, and D. B. Congkling, ?On-Site Flow Calibration of Turbine Meters for Natural Gas Custody Transfer,? Proc.... Jacobsen, ?GRI High Accuracy Natural Gas Equation of State GRI-91/0184,? Gas Research Insitute, Chicago, (1991). Ting, V. C., L. L. Schexnayder, and D. B. Congkling, ?On-Site Flow Calibration of Turbine Meters for Natural Gas Custody Transfer,? Proc...

Widia

2004-11-15

276

Characteristics of a cylindrical collector mirror for laser-produced xenon plasma soft X-rays and improvement of mirror lifetime by buffer gas  

NASA Astrophysics Data System (ADS)

The focusing characteristics of a ruthenium-coated cylindrical mirror were investigated on the basis of its ability to collect and focus broadband 5-17-nm soft X-rays emitted from a laser-produced plasma. Based on the plasmas spectral intensity distribution and the reflectivity function of the mirror, we defined the optimum position of the integrated cylindrical mirror at which the X-ray energy flux transported and focused through the mirror was maximum. A minimum spot diameter of 22 mm at a distance of approximately 200 mm from a soft X-ray source was confirmed. The maximum intensity of the collected soft X-rays was 1.3 mJ/cm2 at the center of the irradiation zone. Thus, the irradiation intensity was improved by approximately 27 times when compared to that of 47 ?J/cm2 without the mirror. The debris sputtering rate on the reflection surface of the mirror can be reduced to 1/110 by argon gas at 11 Pa, while the attenuation rate of the soft X-rays due to absorption by the buffer gas can be suppressed to less than 10% at the focal point. The focusing property of the mirror is expected to be maintained for 3000 h or longer without significant degradation for a 100 W/320 pps laser shot if the ruthenium layer is thicker than 10 ?m. These results suggest that a stand-alone broadband soft X-ray processing system can be realized by using laser-produced plasma soft X-rays.

Inoue, Tomoaki; Mochizuki, Takayasu; Miyamoto, Shuji; Masuda, Kazuya; Amano, Sho; Kanda, Kazuhiro

2012-12-01

277

Effect of hydrogen ratio on plasma parameters of N{sub 2}-H{sub 2} gas mixture glow discharge  

SciTech Connect

A dc plane glow discharge in a nitrogen-hydrogen (N{sub 2}-H{sub 2}) gas mixture has been operated at discharge currents of 10 and 20 mA. The electron energy distribution function (EEDF) at different hydrogen concentrations is measured. A Maxwellian EEDF is found in the positive column region, while in both cathode fall and negative glow regions, a non-Maxwellian one is observed. Langmuir electric probes are used at different axial positions, gas pressures, and hydrogen concentrations to measure the electron temperature and plasma density. The electron temperature is found to increase with increasing H{sub 2} concentration and decrease with increasing both the axial distance from the cathode and the mixture pressure. At first, with increasing distance from the cathode, the ion density decreases, while the electron density increases; then, as the anode is further approached, they remain nearly constant. At different H{sub 2} concentrations, the electron and ion densities decrease with increasing the mixture pressure. Both the electron and ion densities slightly decrease with increasing H{sub 2} concentration.

El-Brulsy, R. A.; Abd Al-Halim, M. A.; Abu-Hashem, A. [Benha University, Physics Department, Faculty of Science (Egypt); Rashed, U. M. [Alazhar University, Physics Department, Faculty of Science (Egypt); Hassouba, M. A. [Benha University, Physics Department, Faculty of Science (Egypt)

2012-05-15

278

Slow flows of a vapor-gas mixture with large density and temperature variations in the near-continuum regime  

NASA Astrophysics Data System (ADS)

A binary mixture of a vapor and a noncondensable gas in contact with the boundary made of the condensed phase (liquid or solid) of the vapor is considered in the following situation: the amount of the noncondensable gas contained in the system is of the same order of magnitude as that of the vapor; the temperature variation along the boundary may be large; the boundary is at rest, and there is no flow at infinity when an infinite domain is considered; and the Knudsen number is small (i.e., near-continuum regime). Slow steady flows (with Mach number of the order of Knudsen number, or equivalently, with Reynolds number of the order of unity) of the mixture, mainly caused by evaporation and condensation of the vapor on the boundary, are investigated on the basis of kinetic theory. The basic system used in this work is the fluid-dynamic-type system that was derived systematically from the Boltzmann system in a previous paper [S. Takata and K. Aoki, Transp. Theor. Stat. Phys. 30, 205 (2001); erratum, Transp. Theor. Stat. Phys. 31, 289 (2002)] in connection with the ghost effect, and it is solved numerically by a finite-volume method. Some additional computation using the direct simulation Monte Carlo method, based on the original Boltzmann system, is also performed for comparison. The behavior of the mixture in the continuum limit in which the Knudsen number vanishes is discussed with special interest in the ghost effect.

Laneryd, Carl-Johan Tor; Aoki, Kazuo; Takata, Shigeru

2007-10-01

279

Removal of particle matter from dust-vapor-gas mixture in condenser with inclined tubes  

NASA Astrophysics Data System (ADS)

The article presents results of the research of particulate matter and droplets removal on inclined tubes of the flue gas cleaning condenser in the process of vapor condensation of vapor-and-gas emissions from kraft pulp production.

Romanova, L. V.; Gogonin, I. I.

2012-03-01

280

Xenon preconditioning: molecular mechanisms and biological effects  

PubMed Central

Xenon is one of noble gases and has been recognized as an anesthetic for more than 50?years. Xenon possesses many of the characteristics of an ideal anesthetic, but it is not widely applied in clinical practice mainly because of its high cost. In recent years, numerous studies have demonstrated that xenon as an anesthetic can exert neuroprotective and cardioprotective effects in different models. Moreover, xenon has been applied in the preconditioning, and the neuroprotective and cardioprotective effects of xenon preconditioning have been investigated in a lot of studies in which some mechanisms related to these protections are proposed. In this review, we summarized these mechanisms and the biological effects of xenon preconditioning. PMID:23305274

2013-01-01

281

Low-temperature normal-pressure CVD of carbon nanotubes from CO + H2 gas mixture: Thermodynamic analysis and experimental observation  

NASA Astrophysics Data System (ADS)

It has been shown that the deposition of carbon nanotubes from CO could take place at very low temperatures by adding hydrogen to the gas mixture. Adding hydrogen significantly changes the nature of the chemical vapor deposition process. It has been demonstrated that at a certain ratio CO : H2 this gas mixture on the one hand could be used for the deposition of carbon structures at low temperatures and on the other hand for the etching of carbon structures at high temperatures. Thus, the same gas mixture can be both a source of carbon and its etchant depending on temperature. We have also demonstrated that carbon nanotubes of good quality without impurities of amorphous carbon, soot or graphite can be formed from the gas mixture of CO + H2 at low temperatures.

Mironov, A. E.; Gromov, D. G.; Gavrilov, S. A.; Galperin, V. A.

2013-01-01

282

Dynamic mean field theory for lattice gas models of fluid mixtures confined in mesoporous materials.  

PubMed

We present the extension of dynamic mean field theory (DMFT) for fluids in porous materials (Monson, P. A. J. Chem. Phys. 2008, 128, 084701) to the case of mixtures. The theory can be used to describe the relaxation processes in the approach to equilibrium or metastable equilibrium states for fluids in pores after a change in the bulk pressure or composition. It is especially useful for studying systems where there are capillary condensation or evaporation transitions. Nucleation processes associated with these transitions are emergent features of the theory and can be visualized via the time dependence of the density distribution and composition distribution in the system. For mixtures an important component of the dynamics is relaxation of the composition distribution in the system, especially in the neighborhood of vapor-liquid interfaces. We consider two different types of mixtures, modeling hydrocarbon adsorption in carbon-like slit pores. We first present results on bulk phase equilibria of the mixtures and then the equilibrium (stable/metastable) behavior of these mixtures in a finite slit pore and an inkbottle pore. We then use DMFT to describe the evolution of the density and composition in the pore in the approach to equilibrium after changing the state of the bulk fluid via composition or pressure changes. PMID:24102541

Edison, J R; Monson, P A

2013-11-12

283

Surface tension, coexistence curve, and vapor pressure of binary liquid-gas mixtures  

NASA Astrophysics Data System (ADS)

The objective of this paper is to present measurements of the vapor pressure, capillary coefficient, and refractive index of four binary mixtures, CO2-SF6, R14-SF6, SF6-R13B1, and SF6-R22, at liquid-vapor equilibrium at different average concentrations. The measuring temperature range covered the entire liquid-vapor region from the triple line up to the critical point. The capillary coefficient was determined by means of the capillary rise method; the refractive index, by measuring the angle of refraction of a light beam passing through a prism and the sample. In order to obtain the liquid-vapor densities of pure substances the Lorentz-Lorenz relation can be used. However, in applying this relation to calculate the liquid-vapor densities of a mixture, one may need the concentrations of both the liquid and the vapor phase, which are, for the most part, quite different from the average concentration of the mixture. Calculating the concentrations of both fluid phases with the aid of an equation of state and comparing with measurements, we could show that the molar refraction coefficient of the mixtures can be simply determined from the average concentration and the molar refraction coefficients of their pure components. The surface tension of the mixtures could then be calculated from the measured capillary coefficient and the refractive index with the aid of the Lorentz-Lorenz relation.

Do, V. T.; Straub, J.

1986-01-01

284

Effects of breathing a normoxic He-O2 gas mixture on exercise tolerance and VO2 max.  

PubMed

The purpose of these experiments was to compare the effects of breathing air (79% N2-21% O2) and a normoxic helium oxygen gas mixture (He-O2) (79% He-21% O2) on maximal oxygen uptake (VO2 max) and work tolerance during both incremental and high-intensity constant load exercise. First, eight subjects underwent two separate short incremental cycle ergometer exercise tests until the subject could not maintain the desired power output. Second, four subjects exercised to exhaustion on two separate occasions at a constant exercise intensity (100% VO2 max). Each exercise protocol required the subject to breathe air on one test and a normoxic He-O2 mixture on an additional occasion. Data analysis revealed higher (P less than 0.05) minute ventilations, an increased time to exhaustion, and a greater VO2 max during He-O2 breathing in both exercise conditions. Small but significant (P less than 0.05) differences existed in the percent hemoglobin saturated with O2 (% SO2) at exercise demands greater than 120 W during the incremental experiment and during each minute of the constant load test with He-O2 giving the higher value. These data support the hypothesis that breathing a normoxic He-O2 gas mixture during exercise elevates VO2 max and increases exercise tolerance. Further, although it appears that breathing a He-O2 mixture results in higher %SO2 during intense exercise, the increase in arterial O2 content is small and probably does not fully account for the higher VO2 max observed under these conditions. PMID:3759302

Powers, S K; Jacques, M; Richard, R; Beadle, R E

1986-08-01

285

Selective Adsorption of CO2 from Light Gas Mixtures Using a Structurally Dynamic Porous Coordination Polymer**  

SciTech Connect

The selective adsorption of CO{sub 2} from mixtures with N{sub 2}, CH{sub 4}, and N{sub 2}O in a dynamic porous coordination polymer (see monomer structure) was evaluated by ATR-FTIR spectroscopy, GC, and SANS. All three techniques indicate highly selective adsorption of CO{sub 2} from CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} mixtures at 30 C, with no selectivity observed for the CO{sub 2}/N{sub 2}O system.

Kristi L. Kauffman, Jeffrey T. Culp, Andrew J. Allen, Laura Espinal, Winnie Wong-Ng, Thomas D.

2010-01-01

286

Gas dynamic aspects of silicon thin layers deposition using excitation of a free jet of the working gas mixture by an electron beam  

SciTech Connect

A film of microcrystalline silicon ({mu}c-Si:H) deposited at low temperature is a promising material for thin-film silicon solar cells with high efficiency and high stability. To deposit silicon thin films with high deposition rate and high quality, a novel gas-jet deposition method has been developed. The paper is devoted to experimental and numerical study of the method from the gas dynamic point of view. A numerical model of the flow field of the working gas mixture in the device was developed that provides predictions of the film thickness distribution over the substrate surface and was found to describe the measured data satisfactory. The model may be used to optimize the operating parameters of the device.

Skovorodko, P. A.; Sharafutdinov, R. G.; Shchukin, V. G.; Konstantinov, V. O. [CJSC Institute of Plasma Chemical Technologies, 630090, Novosibirsk (Russian Federation) and Kutateladze Institute of Thermophysics, 630090, Novosibirsk (Russian Federation)

2012-11-27

287

Removal of mixtures of acetaldehyde and propionaldehyde from waste gas in packed column with immobilized activated sludge gel beads.  

PubMed

The removal of mixed acetaldehyde and propionaldehyde as a model of the binary contaminants in waste gas was studied in the packed column containing the immobilized activated sludge gel beads together with the hollow plastic balls developed for the removal of a single aldehyde in the previous work. The rate of each aldehyde biodegradation by the gel beads in the aldehydes mixture was expressed by the Michaelis-Menten type rate equation with an inhibitory term due to the other coexistent aldehyde. The kinetic parameters involved were found to be the same as those determined previously for biodegradation of a single aldehyde. A model for prediction of removal of each aldehyde in the packed column was developed assuming that each aldehyde dissolved in the aqueous phase within the gel bead was biodegraded according to the above rate equation with no mass transfer effect. The packed column was stable and efficient for removal of the binary aldehydes mixture with a very low pressure drop for gas flow due to a reduced gel beads bed compaction by the hollow plastic balls. Removal of each aldehyde decreased with increasing the inlet aldehyde concentrations since each biodegradation rate itself approached asymptotically the maximum one with increase in each aldehyde concentration. The observed removals for each aldehyde in the aldehydes mixture agreed well with those calculated from the design equations developed. The contact efficiency of gel beads with the waste gas stream was estimated to be the same value of 0.24 as in the previous work, supporting that the efficiency was specific to the geometrical and physical properties of the packed column used. PMID:11356366

Ibrahim, M A.; Mizuno, H; Yasuda, Y; Fukunaga, K; Nakao, K

2001-07-01

288

Investigation of nonstationary shock waves in gas-liquid mixtures of bubble structure  

Microsoft Academic Search

Consideration is given to the possibility of constructing an adequate model for the dynamic behavior of a two-phase mixture of a liquid with bubbles. A cell representation is used to obtain a precise condition (the generalized Rayleigh-Lamb equation) for the simultaneous deformation of the two phases. In a numerical study of a 50% solution of glycerin in water containing bubbles

A. A. Gubaidullin; A. I. Ivandaev; R. I. Nigmatulin

1978-01-01

289

Experimental Investigation on High-pressure, High-temperature Viscosity of Gas Mixtures  

E-print Network

, and mixtures of CO2 and methane measured to take into account of the fact that the concentration of non-hydrocarbons increase significantly in HPHT reservoir. The recorded measured data were then used to evaluate the reliability of the most commonly used...

Davani, Ehsan

2012-02-14

290

Experimental measurement of the effective diffusion and thermodiffusion coefficients for binary gas mixture in porous media  

Microsoft Academic Search

Thermodiffusion or Soret effect, corresponding to a mass flux caused by a temperature gradient applied to fluid mixture, has been taken into account in many porous media applications, particularly in chemical engineering and geophysics. In the literature, the effective macro-scale diffusion coefficients are now well established, while uncertainty remains concerning the relationship between the effective thermodiffusion coefficient and micro-scale parameters

H. Davarzani; M. Marcoux; P. Costeseque; M. Quintard

2010-01-01

291

Perfluorocarbon emulsions as intravenous delivery media for hyperpolarized xenon.  

PubMed

The use of perfluorooctyl bromide (PFOB) emulsions as delivery media for hyperpolarized xenon has been investigated. Emulsion droplet size was controlled by varying the content of egg yolk phospholipid (EYP), which served as an emulsifier. Hyperpolarized 129Xe nuclear magnetic resonance (NMR) spectra of the dissolved gas were obtained. The NMR spectra were found to be correlated strongly with the emulsion droplet size distribution. The NMR line width is determined by xenon exchange between the PFOB droplets and the aqueous environment. Our findings show that, in a 1.5-Tesla field, relatively narrow 129Xe NMR spectra are obtained for droplet sizes larger than 5 microm. Preliminary results on animal models show that PFOB emulsions have potential as hyperpolarized 129Xe carriers for in vivo magnetic resonance applications. PMID:10204864

Wolber, J; Rowland, I J; Leach, M O; Bifone, A

1999-03-01

292

Development, implementation, and evaluation of accurate natural gas mixture models. Final report, June 1992June 1995  

Microsoft Academic Search

DETAIL and GROSS characterization methods outlined in the 2nd edition of AGA Report No. 8 and ISO 12213 were developed, documented, and implemented in this work. This includes FORTRAN computer programs which can be obtained on diskette from the American Gas Association. Natural gas compressibility factor data which are consistent with new PVT reference data were used to establish the

S. W. Beyerlein; E. W. Lemmon

1995-01-01

293

Measurement of the Vaporization Enthalpy of Complex Mixtures by Correlation-Gas Chromatography. The  

E-print Network

on the development of fuels that, when heated, undergo endothermic decomposition to yield secondary products whose and hydrogen is an example of an endothermic reaction identified in early investiga- tions of endothermic fuels the condensed phase to the gas phase. The endothermicity of the gas-phase dehydrogenation of methylcyclohexanes2

Chickos, James S.

294

A numerical program for steady-state flow of magma-gas mixtures through vertical eruptive conduits  

USGS Publications Warehouse

This report presents a model that calculates flow properties (pressure, vesicularity, and some 35 other parameters) as a function of vertical position within a volcanic conduit during a steady-state eruption. The model idealizes the magma-gas mixture as a single homogeneousfluid and calculates gas exsolution under the assumption of equilibrium conditions. These are the same assumptions on which classic conduit models (e.g. Wilson and Head, 1981) have been based. They are most appropriate when applied to eruptions of rapidly ascending magma (basaltic lava-fountain eruptions, and Plinian or sub-Plinian eruptions of intermediate or silicic magmas) that contains abundant nucleation sites (microlites, for example) for bubble growth.

Mastin, Larry G.; Ghiorso, Mark S.

2000-01-01

295

Comparisoin between mass spectrometry and Haldane technique in analysing O2 and CO2 concentrations in air gas mixtures.  

PubMed

We have evaluated a mass spectrometer for use as a gas analyser in air gas mixtures. Simultaneous determinations of O2 and CO2 concentrations with both the mass spectrometer and the Haldane technique were done in ninety-nine different samples of expired air from ordinary laboratory experiments. The mean differences (+/- SD) between the two techniques for O2 and CO2 concentrations were 0.003% (+/- 0.049%), and 0.001% (+/- 0.045%) absolute values, respectively, (P greater than 0.05 for both), r values being 0.996 for O2 and 0.994 for CO2. There was a drift in the apparatus, which decreased with operating time. Proper calibration is necessary for accurate readings. A cost-benefit balance is made. PMID:663551

Hallbäck, I; Karlsson, E; Ekblom, B

1978-05-01

296

Numerical study of the structure flow of the gas-vapor mixture in a channel with injection of water droplets  

NASA Astrophysics Data System (ADS)

Mathematical modeling algorithm for the numerical analysis of the dynamics and evaporation of the water droplet which is injected into a gas-vapor flow is offered. The algorithm was tested with the help of the problem solution about a viscous fluid flow in a plane channel of constant cross section. It was shown that the proposed mathematical model and implementation algorithm are adequate to the physics of the investigated process. It was shown that the proposed mathematical model and implementation algorithm are adequate to the physics of the investigated process. Results of numerical study of the flow structure of the gas-vapor mixture in the channel with injection of water droplet under varying the initial droplet parameters are given.

Maslov, Eugene; Zharova, Irina; Borisov, Boris; Fedotova, Natalya

2014-08-01

297

Measurement of Binary Diffusion Coefficients for Neon-Argon Gas Mixtures Using a Loschmidt Cell Combined with Holographic Interferometry  

NASA Astrophysics Data System (ADS)

The paper reports on experimental binary diffusion coefficient data of neon-argon gas mixtures. Measurements were performed in the temperature range between 293.15 K and 333.15 K and for pressures between 1 bar and 10 bar over almost the whole composition range using a Loschmidt diffusion cell combined with holographic interferometry. The thermostated Loschmidt cell is divided into two half-cells, which can be separated and connected by a sliding plate. Prior to the measurements, two different pure gases are filled into the two half-cells. After starting the diffusion process, the temporal change of the partial molar densities, or rather of the refractive index of the gases, is detected in both half-cells using two holographic interferometers. With this apparatus, the temperature, pressure, and concentration dependence of the binary diffusion coefficient can be determined. The relative uncertainty of a diffusion measurement is between 0.4 % and 1.4 % depending on the pressure. The experimental data are compared with data from the literature and with new theoretical data based on quantum-mechanical ab initio calculations combined with the kinetic theory of gases. Due to a systematic error, the concentration dependence determined in the upper half-cell shows deviations from the theoretical values and from most of the literature data. The concentration, temperature, and pressure dependence obtained from the data from the lower half-cell, however, are in very good agreement with available data. The product of the binary gas diffusion coefficient and the molar density of the gas mixture shows no significant dependence on pressure for the studied neon-argon noble gas system.

Kugler, T.; Jäger, B.; Bich, E.; Rausch, M. H.; Fröba, A. P.

2013-01-01

298

Separation of hydrocarbon gas mixtures using phenolic resin-based carbon membranes  

Microsoft Academic Search

Carbon membranes are prepared by the carbonisation of a thin film of phenolic resin deposited on the inner face of an alumina tube. Air oxidative treatments at temperatures in the range of 75–350°C, prior to carbonisation (pre-oxidation) or after carbonisation (post-oxidation) were tested in order to improve the separation characteristics of carbon membranes when used with hydrocarbon mixtures such as

Antonio B. Fuertes; Ivan Menendez

2002-01-01

299

Adsorptive separation of CO2\\/CH4\\/CO gas mixtures at high pressures  

Microsoft Academic Search

The major objective of this communication is to compare the performance of three metal–organic frameworks (MOFs): CuBTC, MIL-101, and Zn(bdc)dabco, with that of NaX zeolite for selective adsorption of CO2 from mixtures containing CH4 and CO in a pressure swing adsorption (PSA) unit operating at pressures ranging to 60 bar. Data on the pure component adsorption isotherms in the published

R. Krishna

2012-01-01

300

Reactions of xenon with iridium- and Osmiumhexafluoride.  

PubMed

Xenon and Iridiumhexafluoride react at temperatures above room temperature forming XeF+IrF6-. In presence of SbF5 FXe+IrSbF11- is formed. Xenon and Osmiumhexafluoride form in solution a blue charge transfer complex that cannot be isolated as a solid. PMID:24169702

Tamadon, Farhad; Seidel, Stefan; Seppelt, Konrad

2013-01-01

301

Experimental and simulation studies of iron oxides for geochemical fixation of CO2-SO2 gas mixtures  

USGS Publications Warehouse

Iron-bearing minerals are reactive phases of the subsurface environment and could potentially trap CO2-SO2 gas mixtures derived from fossil fuel combustion processes by their conversion to siderite (FeCO 3) and dissolved sulfate. Changes in fluid and mineral compositions resulting from reactions, involving the co-injection of SO2 with CO2 were observed both theoretically and experimentally. Experiments were conducted with a natural hematite (??-Fe2O3) sample. A high pressure-high temperature apparatus was used to simulate conditions in geologic formations deeper than 800 m, where CO2 is in the supercritical state. Solid samples were allowed to react with a NaCl-NaOH brine and SO2-bearing CO2-dominated gas mixtures. The predicted equilibrium mineral assemblage at 100??C and 250 bar became hematite, dawsonite (NaAl(OH)2CO3), siderite (FeCO 3) and quartz (SiO2). Experimentally, siderite and dawsonite, derived from the presence of kaolinite (Al2Si 2O5(OH)4) in the parent material, were present in residual solids at longer reaction time intervals, which agreed well with results from the modelling work. ?? 2011 Published by Elsevier Ltd.

Garcia, S.; Rosenbauer, R. J.; Palandri, J.; Maroto-Valer, M. M.

2011-01-01

302

PILOT STUDY: International comparison CCQM-P41 Greenhouse gases. 2. Direct comparison of primary standard gas mixtures  

NASA Astrophysics Data System (ADS)

In this second part of this study, primary standard gas mixtures (PSMs) as used for calibrations for the greenhouse gases carbon dioxide and methane have been compared. The nominal amount-of-substance fraction levels were 365 µmol/mol for carbon dioxide and 1.8 µmol/mol for methane. The matrix was synthetic air, simulated by a mixture of nitrogen, oxygen (209 mmol/mol) and argon (9.3 mmol/mol). The measurements took place in the spring of 2003. In the protocol, it was foreseen to have the PSMs produced for this study in a small range, enabling regression analysis on the data to assess the consistency of the gas mixtures. The direct comparison of the PSMs shows agreement for carbon dioxide at 365 µmol/mol nominal within 0.52 µmol/mol (0.14% relative) standard uncertainty. One cylinder lies between the 95% and 99% boundaries of the regression line, and after removing this cylinder from the dataset the standard deviation of the x-residuals reduces to 0.18 µmol/mol (0.05% relative). This value for the standard deviation is substantially greater than the stated standard uncertainties for several cylinders. The standard deviation of the x-residuals for methane at 1.8 µmol/mol nominal is 0.011 µmol/mol. Main text. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCQM.

van der Veen, Adriaan M. H.; Brinkmann, Freek N. C.; Arnautovic, Mile; Besley, Laurie; Heine, Hans-Joachim; Lopez Esteban, Teresa; Sega, Michela; Kato, Kenji; Seog Kim, Jin; Perez Castorena, Alejandro; Rakowska, Agata; Milton, Martin J. T.; Guenther, Frank R.; Francey, R.; Dlugokencky, E.

2007-01-01

303

Influence of balance gas mixture on decomposition of dimethyl sulfide in a wire-cylinder pulse corona reactor.  

PubMed

The influence of balance gas mixture on decomposition of dimethyl sulfide was investigated experimentally by a wire-cylinder pulse corona reactor at room temperature. A new type of high voltage pulse generator with a thyratron switch and a Blumlein pulse-forming network was used in the experiments. The experiments were conducted at a fixed pulse frequency of 100pps. The DMS decomposition efficiency as well as energy yield was investigated using varying oxygen concentration (0.6-21.0%), humidity (0-1.0%) and different balance gas (air, N(2), Ar). Breakdown voltage of DMS in Ar is lower than that of DMS in N(2), both of which are proportional to the gas pressures. The conversion of DMS in Ar is more efficient than that in N(2) and air at a fixed peak voltage. In addition, it is found that 5% oxygen is the optimum concentration in decomposition of DMS, due to higher conversion of DMS and relatively fewer yields of by products, such as O(3), NO(x) and SO(2). The highest DMS removal efficiency where the energy yield was 1.24mgkJ(-1) was achieved with the gas stream containing 0.3% H(2)O in air. PMID:19162296

Chen, Jie; Su, Qingfa; Pan, Hua; Wei, Jianwen; Zhang, Xuming; Shi, Yao

2009-04-01

304

Emission Spectra of Working Mixtures of a HgBr/HgCl Excimer Lamp  

NASA Astrophysics Data System (ADS)

A study of emission spectra of a gas-discharge plasma produced in a HgBr/HgCl excimer lamp, which is filled with multicomponent working mixtures at atmospheric pressure (HgBr2 and HgCl2 with additions of molecular nitrogen and xenon), are reported. A gas-discharge plasma was produced by high-frequency (pulses ˜100 ns long with a repetition rate of up to 2000 Hz) barrier and surface discharges, which took place simultaneously. Emission of HgBr* and HgCl* excimer molecules, the second positive system of molecular oxygen, and helium and xenon lines in the UV, visible, and IR spectral regions was observed. The strongest emission of HgBr* and HgCl* molecules (the emission intensities were in the ratio 10:1) was observed in the HgBr2: HgCl2: N2: He mixture. Regularities in spectral and integrated characteristics of gas-discharge plasma emission are discussed.

Malinin, A. N.; Gu?van, N. N.; Shimon, L. L.

2000-12-01

305

SAFE OPERATION OF NATURAL GAS APPLIANCES FUELED WITH HYDROGEN\\/NATURAL GAS MIXTURES (PROGRESS OBTAINED IN THE NATURALHY-PROJECT)  

Microsoft Academic Search

Considering the transition towards the hydrogen economy, dependent on hydrogen penetration scenario, the cost of a new hydrogen pipeline infrastructure in Europe may amount to several thousands of billions of EURO's. Therefore, the examination of the potential contribution of the existing natural gas assets is a practical and logical first step. As the physical and chemical properties of hydrogen differ

De Vries; O. Florisson; G. C. Tiekstra

306

Increase of passenger car engine efficiency with low engine-out emissions using hydrogen–natural gas mixtures: A thermodynamic analysis  

Microsoft Academic Search

In this study a state of the art passenger car natural gas engine was optimised for hydrogen natural gas mixtures and high exhaust gas recirculation (EGR) rates in the part load domain. With optimal combinations of spark timing (ST) and EGR rate the achievements are significant efficiency increase with substantially lower engine-out NOx while total unburned hydrocarbons or CO-engine-out emissions

P. Dimopoulos; C. Rechsteiner; P. Soltic; C. Laemmle; K. Boulouchos

2007-01-01

307

Xenon Gamma Detector Project Support  

SciTech Connect

This project provided funding of $48,500 for part of one year to support the development of compressed xenon spectrometers at BNL. This report describes upgrades that were made to the existing detector system electronics during that period, as well as subsequent testing with check sources and Special Nuclear Materials. Previous testing of the equipment extended only up to the energy of 1.3 MeV, and did not include a spectrum of Pu-239. The new electronics allowed one-button activation of the high voltage ramp that was previously controlled by manual adjustments. Mechanical relays of the charging circuit were replaced by a tera-ohm resistor chain and an optical switch. The preamplifier and shaping amplifier were replaced by more modern custom designs. We found that the xenon purity had not been degraded since the chamber was filled 10 years earlier. The resulting spectra showed significantly better resolution than sodium iodide spectra, and could be analyzed quite effectively by methods using peak area templates.

Vanier,P.E.; Forman, L.

2008-04-01

308

Properties of Gas Mixtures and Their Use in Mixed-Refrigerant Joule-Thomson Refrigerators  

NASA Astrophysics Data System (ADS)

The Joule-Thomson (J-T) effect has been widely used for achieving low temperatures. In the past few years, much progress has been made in better understanding the working mechanism of the refrigeration method and in developing prototypes for different applications. In this talk, there are three aspects of our research work to be discussed. First, some special thermal properties of the mixtures for achieving liquid nitrogen temperature range will be presented. Secondly, some important conclusions from the optimization of various mixed-refrigerant J-T cycles such as a simple J-T cycle and an auto-cascade mixed-refrigerant J-T cycle will be presented. Moreover, an auto-cascade, mixed-refrigerant J-T refrigerator with a special mixture capable of achieving about 50K will be mentioned. Finally, various prototypes based on the mixed-refrigerant refrigeration technology will be described. These applications include miniature J-T cryocoolers for cooling infrared detectors and high-temperature superconducting devices, cryosurgical knife for medical treatment, low-temperature refrigerators for biological storage and so forth. The on-going research work and unanswered questions for this technology will be also discussed.

Luo, E.; Gong, M.; Wu, J.; Zhou, Y.

2004-06-01

309

Device for two-dimensional gas-phase separation and characterization of ion mixtures  

DOEpatents

The present invention relates to a device for separation and characterization of gas-phase ions. The device incorporates an ion source, a field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer, an ion mobility spectrometry (IMS) drift tube, and an ion detector. In one aspect of the invention, FAIMS operating voltages are electrically floated on top of the IMS drift voltage. In the other aspect, the FAIMS/IMS interface is implemented employing an electrodynamic ion funnel, including in particular an hourglass ion funnel. The present invention improves the efficiency (peak capacity) and sensitivity of gas-phase separations; the online FAIMS/IMS coupling creates a fundamentally novel two-dimensional gas-phase separation technology with high peak capacity, specificity, and exceptional throughput.

Tang, Keqi (Richland, WA); Shvartsburg, Alexandre A. (Richland, WA); Smith, Richard D. (Richland, WA)

2006-12-12

310

Performance of a cryogenic system prototype for the XENON1T Detector  

E-print Network

We have developed an efficient cryogenic system with heat exchange and associated gas purification system, as a prototype for the XENON1T experiment. The XENON1T detector will use about 3 ton of liquid xenon (LXe) at a temperature of 175K as target and detection medium for a dark matter search. In this paper we report results on the cryogenic system performance focusing on the dynamics of the gas circulation-purification through a heated getter, at flow rates above 50 Standard Liter per Minute (SLPM). A maximum flow of 114 SLPM has been achieved, and using two heat exchangers in parallel, a heat exchange efficiency better than 96% has been measured.

Elena Aprile; Ran Budnik; Bin Choi; Hugo Contreras; Karl Giboni; Luke Goetzke; Rafael Lang; Kyungeun Lim; Antonio melgarejo; Petr Shagin

2012-08-09

311

Viscoelastiticy and shear thinning near the critical point of xenon  

NASA Astrophysics Data System (ADS)

The critical point is the exact combination of pressure and temperature at which a fluid is balanced between the states of liquid and gas. Everyday experience gives no hint of the unusual nature of the critical point because familiar fluids such as air and water are far from their critical temperatures. Understanding the critical point is essential for an understanding of fluids in general because the near-critical behavior is universal. Properly scaled, fluids as dissimilar as air and water have near-critical thermodynamic properties (e.g. heat capacity) and transport properties (e.g. viscosity) that are similar. Sufficiently close to the critical point, theory predicts the similarities to be exact. This talk will describe two measurements of the viscosity of xenon that were made very close (<1 mK) to xenon's critical point (289 K, 5.8 MPa). The first experiment measured the viscosity increase caused by near-critical conditions. It revealed that, close to the critical point, xenon is partly elastic: It can stretch as well as flow. The second experiment, planned for July 2002, will look for the shear-rate-induced viscosity decrease predicted by theory. Such "viscoelasticity" and "shear-thinning" are ordinarily seen only in much more complicated fluids such as polymer solutions. Slowly relaxing fluctuations cause both phenomena. The first experiment found that the time scale for viscoelasticity was 2.0 times slower than predicted. Preliminary results for shear thinning from the second experiment will be reported. Both experiments were designed to operate in the microgravity provided by the Space Shuttle. We required microgravity because Earth's gravity compresses any fluid near its critical point. Near its critical point, a layer of xenon as thin as 1 mm collapses under its own weight until the density at the bottom is 8% greater than at the top. The density difference distorts the data. Conducting the experiments on the Space Shuttle reduces the density difference by a factor of 100.

Berg, R.; Yao, M.; Moldover, M.; Zimmerli, G.

312

Sound Absorption in Molecular Gas Mixtures: Master Equation for Rotational and Vibrational Excitation, Relaxation, and Energy Transfer  

NASA Astrophysics Data System (ADS)

Laboratory sound absorption measurements provide much of what we know about the vibrational kinetics of air mixtures, forming the core basis for retrieving the altitude profile of water in the mesosphere from infrared emissions between 6.3 and 6.9 ?m. Here we show that sound-absorption and laser-excitation experiments follow exactly the same kinetics, reflect the same underlying reaction rates, and can be vulnerable to similar ambiguities. This has not been obvious because the literature lacks a consistent prescription for calculating the sound absorption frequency spectrum from the reaction rate coefficients. We have developed the first general theoretical formalism for calculating the absolute magnitude of sound absorption per-unit-length, versus sound frequency, for any number of collisional excitation, relaxation, and energy transfer processes, for any mixture of atomic and molecular gases. This new formalism, and the computer code that implements it, provide the first systematic means for inferring collisional rate coefficients from sound absorption measurements in which more than one rotational or vibrational mode is active, such as N2/O2/H2O/CO2 gas mixtures in the laboratory and the atmosphere. When a sound wave travels through a gas, the alternating compression and expansion cycles heat and cool the gas. If the acoustic frequency roughly matches the rate of vibrational relaxation, then the effective vibrational temperature lags behind the translational temperature and the energy in the sound wave is attenuated. The measured frequency of maximum absorption is proportional to the vibrational relaxation rate. In the simplest laser-based experiment, we excite a single molecular level and record its exponential time decay, with the vibrational relaxation rate being proportional to the decay frequency. In both experiments we derive the relaxation rate coefficient from the linear graph versus gas pressure. The technical problem is that any mixture of molecular gases will have more than one relaxation time constant. Thus we write the chemical kinetics master equation as (1) (d/dt) Nm = ?npq [ - kmn?pq Nm Nn + kpq?mn Np Nq ] which has the well-known time-dependent solution given by (2) Nm(t) = ?n Cmn exp(-?n t) where the ?n values are the decay frequencies and the Cmn coefficients depend on how the gas was initially excited. What we have contributed is the frequency-dependent sound absorption solution to Equation (1): (3) cvint(?) = ?nk Wn / (1 + i ?/?n) where cvint(?) is the complex heat capacity (per molecule), ? is the circular sound frequency, 2?f, the ?n are the calculated decay frequencies [as in Equation (2)] and k Wn is the real effective heat capacity for decay mode n. As pointed out by Landau and Teller [Phys. Z. Sowjet. 10, 34-43 (1936)], for a simple case when the decay modes correspond to vibrational modes, Wn is the ordinary heat capacity of the vibrational mode. In the more complicated case involving one or more reversible energy-transfer steps, e.g., water and oxygen, the vibrational modes and the decay modes do not correspond to each other, and we need to use the rate coefficients in Equation (1) to calculate both ?n and Wn.

Huestis, D. L.

2008-12-01

313

Time evolution of discharge current and light intensity in a PDP with Ne-H2 gas mixtures  

NASA Astrophysics Data System (ADS)

In previously published papers [G. Musa et al., Rom. Rep. Phys. 49, 195 (1997); G. Musa et al., Eur. Phys. J. Appl. Phys. 4, 165 (1998)] we reported a drastic change of time evolution of the barrier discharge current at the addition of hydrogen to neon filling gas of the discharge device. Both, discharge current and discharge emitted light durations increase at least five times. We established that the main explanation of the above mentioned behavior consists in the negative-positive ion recombination, process which has one of the largest known cross section [M.A. Lieberman and A.J. Lichtenberg, Principles of plasma discharges and material processing (John Wiley & Sons, N.Y., 1994)]. The first condition to have negative-positive ions recombination is to use as filling gas of the discharge device an electronegative electropositive gas mixture [G. Musa et al., ESCAMPIG-16, Grenoble France, 2002, Vol. 2, p. 29; G. Musa et al., J. Phys. D: Appl. Phys. 18, 2119 (1985); A. Baltog et al., Contrib. Plasma Phys. 40, 537 (2000); G. Musa and A. Baltog, Contrib. Plasma Phys. 43, 210 (2003)]. Additional conditions must be fulfilled in order to ensure enough density of negative ions necessary for such a recombination process. An increased “consumption” of electrons is necessary to produce needed negative ions. Consequently, the wall polarization process is slowing down with subsequent increase of the light emission and discharge current duration. Possible use of this increase of light emission at electronegative gas addition to the filling gas neon as a mean to increase the discharge light generation efficiency is considered.

Musa, G.; Baltog, A.; Ciobotaru, L. C.; Chiru, P.; Lungu, C. P.; Raiciu, E.; Ricard, A.

2004-12-01

314

Improvement of xenon purification system using a combination of a pulse tube refrigerator and a coaxial heat exchanger  

E-print Network

We have developed a compact cryogenic system with a pulse tube refrigerator and a coaxial heat exchanger. This liquefaction-purification system not only saves the cooling power used to reach high gaseous recirculation rate, but also reduces the impurity level with high speed. The heat exchanger operates with an efficiency of 99%, which indicates the possibility for fast xenon gas recirculation in a highpressurized large-scale xenon storage with much less thermal losses.

Chen, Wan-Ting; Cussonneau, J -P; Donnard, J; Duval, S; Lemaire, O; Calloch, M Le; Ray, P Le; Mohamad-Hadi, A -F; Morteau, E; Oger, T; Scotto-Lavina, L; Stutzmann, J -S; Thers, D; Briend, P; Haruyama, T; Mihara, S; Tauchi, T

2012-01-01

315

Variable composition hydrogen\\/natural gas mixtures for increased engine efficiency and decreased emissions  

Microsoft Academic Search

It is well known that adding hydrogen to natural gas extends the lean limit of combustion and that in this way extremely low emission levels can be obtained: even the equivalent zero emission vehicle (EZEV) requirements can be reached. The emissions reduction is especially important at light engine loads. In this paper results are presented for a GM V8 engine.

R. Sierens; E. Rosseel

2000-01-01

316

Discharge stabilization studies of CO laser gas mixtures in quasi-steady supersonic flow  

NASA Technical Reports Server (NTRS)

Experiments were conducted to study the applicability of a double discharge stabilization scheme in conditions appropriate for high energy CO lasers in supersonic flows. A Ludwieg tube impulse flow facility and a ballasted capacitor bank provided essentially steady flow and discharge conditions (d.c.) for times longer than ten electrode length-flow transit times. Steady, arc-free, volume discharges were produced in a Mach 3 test cavity using an auxiliary discharge to stabilize the main discharge in N2 and He/CO mixture. A signigicant result is the lack of observed plasma E/N changes in response to auxiliary discharge current changes. Also, where glow discharges were obtained, the energy loading achieved was very much less than the threshold level required for laser operation.

Srinivasan, G.; Smith, J. A.

1976-01-01

317

Stability of hypersonic reacting stagnation flow of a detonatable gas mixture by dynamical systems analysis  

SciTech Connect

The stability characteristics of the reacting hypersonic flow of the fuel/oxidizer mixture in the stagnation region of a blunt body are studied. The conditions for oscillations of the combustion front are assumed to be determined mainly by the flow conditions at the stagnation region. The density at the stagnation region is assumed to be constant at hypersonic flow conditions. By assuming a simplified flow model, the time dependent flow equations, including the heat addition due to the chemical reactions, are reduced to a second-order nonlinear differential equation for the instantaneous temperature. The solutions are analyzed assuming a one-step chemical reaction with zero-order and first-order processes using dynamical systems methods. These methods are used to determine the stability boundaries in terms of the flow and chemical reaction parameters. It is shown that the zero-order reaction has nonperiodic solutions that may lead to explosion whereas the first-order and higher-order reactions may have periodic solutions indicating oscillations. The zero-order analysis also reaffirms the requirements for a minimum size blunt body for the establishment of a detonation (in agreement with classical detonation theory) and the first-order analysis indicates a minimum body size for establishment of oscillations. The oscillation frequencies are calculated using the small perturbation approximation for the temperature oscillations. These frequencies are compared with results from published data on spheres and hemisphere cylindrical bodies fired into hydrogen-oxygen and acetylene oxygen mixtures. Very good agreement is found between the measured and calculated results.

Tivanov, G.; Rom, J. [Technion-Israel Inst. of Tech., Haifa (Israel)] [Technion-Israel Inst. of Tech., Haifa (Israel)

1995-12-01

318

Two fluid dust and gas mixtures in SPH: A semi-implicit approach  

E-print Network

A method to avoid the explicit time integration of small dust grains in the two fluid gas/dust smoothed particle hydrodynamics (SPH) approach is proposed. By assuming a very simple exponential decay model for the relative velocity between the gas and dust components, all the effective characteristics of the drag force can be reproduced. A series of tests has been performed to compare the accuracy of the method with analytical and explicit integration results. We find that the method performs well on a wide range of tests, and can provide large speed ups over explicit integration when the dust stopping time is small. We have also found that the method is much less dissipative than conventional explicit or implicit two-fluid SPH approaches when modelling dusty shocks.

Loren-Aguilar, Pablo

2014-01-01

319

High pressure laser plasma studies. [energy pathways in He-Ar gas mixtures at low pressure  

NASA Technical Reports Server (NTRS)

The operation of a nuclear pumped laser, operating at a wavelength of 1.79 micron m on the 3d(1/2-4p(3/2) transition in argon with helium-3 as the majority gas is discussed. The energy pathways in He-Ar gas were investigated by observing the effects of varying partial pressures on the emissions of levels lying above the 4p level in argon during a pulsed afterglow. An attempt is made to determine the population mechanisms of the 3d level in pure argon by observing emission from the same transition in a high pressure plasma excited by a high energy electron beam. Both collisional radiative and dissociative recombination are discussed.

Wells, W. E.

1980-01-01

320

Observations of columnal recombination in the ionization tracks of energetic heavy nuclei in an argon-methane gas mixture  

NASA Technical Reports Server (NTRS)

Measurements of ionization signals resulting from the passage of energetic heavy nuclei through a gas mixture consisting of 95 mol percent Ar plus 5 mol percent CH4, at an absolute pressure of 3 atm are presented. The measurements take place under a uniform electric field perpendicular to the ionization track. The signals were compared to the calculated energy losses, with an assumption of proportionality between energy loss rate and ionization rate. Significant deviations from proportionality are found for energy loss rate grater than about 3000 MeV sq cm/g, while fractional deviations are found to be proportional to the energy loss rate (dE/dx) exp m, where m is equal to about two. These results are attributed to the columnal recombination.

Wiedenbeck, Mark E.

1990-01-01

321

Low-pressure plasma-etching of bulk polymer materials using gas mixture of CF4 and O2  

NASA Astrophysics Data System (ADS)

In this study, we have proposed a low-pressure reactive ion etching of bulk polymer materials with a gas mixture of CF4 and O2, and have achieved precise fabrication of poly(methyl methacrylate) (PMMA) and perfluoroalkoxy (PFA) bulk polymer plates with high-aspect-ratio and narrow gap array structures, such as, pillar, frustum, or cone, on a nano/micro scale. The effects of the etching conditions on the shape and size of each pillar were evaluated by changing etching duration and the size/material of etching mask. The fabricated PMMA array structures indicate possibilities of optical waveguide and nanofiber array. PFA cone array structures showed super-hydrophobicity without any chemical treatments. Also, polystyrene-coated silica spheres were used as an etching mask for the pillar array structure formation to control the gap between pillars.

Nabesawa, Hirofumi; Hiruma, Takaharu; Hitobo, Takeshi; Wakabayashi, Suguru; Asaji, Toyohisa; Abe, Takashi; Seki, Minoru

2013-11-01

322

In-line calibration of Raman systems for analysis of gas mixtures of hydrogen isotopologues with sub-percent accuracy.  

PubMed

Highly accurate, in-line, and real-time composition measurements of gases are mandatory in many processing applications. The quantitative analysis of mixtures of hydrogen isotopologues (H2, D2, T2, HD, HT, and DT) is of high importance in such fields as DT fusion, neutrino mass measurements using tritium ?-decay or photonuclear experiments where HD targets are used. Raman spectroscopy is a favorable method for these tasks. In this publication we present a method for the in-line calibration of Raman systems for the nonradioactive hydrogen isotopologues. It is based on precise volumetric gas mixing of the homonuclear species H2/D2 and a controlled catalytic production of the heteronuclear species HD. Systematic effects like spurious exchange reactions with wall materials and others are considered with care during the procedure. A detailed discussion of statistical and systematic uncertainties is presented which finally yields a calibration accuracy of better than 0.4%. PMID:23320553

Schlösser, Magnus; Seitz, Hendrik; Rupp, Simone; Herwig, Philipp; Alecu, Catalin Gabriel; Sturm, Michael; Bornschein, Beate

2013-03-01

323

Thermodynamic properties of arbitrary perfect gas mixtures at low pressures and high temperatures  

Microsoft Academic Search

Atmospheric entry flights, combusting flows, experiments in high-enthalpy wind tunnels, CFD simulation of high-velocity, high-temperature flow fields, are a number of areas in which the thermodynamic properties of gases at high temperatures must be correctly computed because of their important influence on the flow field. For low-density applications (up to about 10 times the normal density), the gas properties can

2000-01-01

324

The effective ionization coefficients and electron drift velocities in gas mixtures of CF3I with N2 and CO2 obtained from Boltzmann equation analysis  

NASA Astrophysics Data System (ADS)

The electron swarm parameters including the density-normalized effective ionization coefficients (?-?)/N and the electron drift velocities Ve are calculated for a gas mixture of CF3I with N2 and CO2 by solving the Boltzmann equation in the condition of a steady-state Townsend (SST) experiment. The overall density-reduced electric field strength is from 100 Td to 1000 Td (1 Td = 10-17 V·cm2), while the CF3I content k in the gas mixture can be varied over the range from 0% to 100%. From the variation of (?-?)/N with the CF3I mixture ratio k, the limiting field strength (E/N)lim for each CF3I concentration is derived. It is found that for the mixtures with 70% CF3I, the values of (E/N)lim are essentially the same as that for pure SF6. Additionally, the global warming potential (GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of application in the gas insulation of power equipment.

Deng, Yun-Kun; Xiao, Deng-Ming

2013-03-01

325

Luminescence characteristics of Xe{sub 2}Cl excimer molecules under pumping the dense Xe-CCl{sub 4} gas mixtures with a pulsed electron beam  

SciTech Connect

Temporal and spectral characteristics of the luminescence of dense Xe-CCl{sub 4} gas mixtures of different composition, excited by a 5-ns pulsed electron beam, were measured. The energy of the electrons amounted to 150 keV and the electron beam current pulse amplitude was 5 A. The gas mixtures were used containing Xe (38-700 Torr) and CCl{sub 4} (0.03-0.3 Torr). The studies were performed within the wavelength range 200-1200 nm using a MAYA-2000Pro diffraction grating spectrometer and a RIGOL DS 5022 ME fast digital oscilloscope. The luminescence lifetimes of the excimer molecules XeCl* (band with {lambda}{sub max} = 308 nm) and Xe{sub 2}Cl* (band with {lambda}{sub max} = 486 nm) were measured, as well as the constants of quenching by the components of the gas mixture for Xe{sub 2}Cl* molecules. A model of plasma-chemical processes for dense Xe-CCl{sub 4} gas mixtures with a very low content of the CCl{sub 4} donor is proposed. It is shown that in such 'poor' mixtures Xe{sub 2}Cl* molecules are mainly produced as a result of recombination of the Xe{sub 2}{sup +} and Cl{sup -} ions. (active media)

Mis'kevich, A I; Jinbo, Guo [National Research Nuclear University 'Moscow Engineering Physics Institute', Moscow (Russian Federation)] [National Research Nuclear University 'Moscow Engineering Physics Institute', Moscow (Russian Federation)

2013-05-31

326

Zeolite screening for the separation of gas mixtures containing SO2, CO2 and CO.  

PubMed

We used a combination of experiments and molecular simulations to investigate at the molecular level the effects of zeolite structure on the adsorption and diffusion of sulfur dioxide, carbon dioxide and carbon monoxide as well as separation processes of their mixtures. Our study involved different zeolite topologies and revealed numerous structure-property trends depending on the temperature and pressure conditions. Sulfur dioxide, which has the strongest interactions with zeolites due to its size and polarity, showed the largest adsorption across investigated temperatures and pressures. Our results indicate that structures with channel-type pore topology and low pore volume are the most promising for selective adsorption of sulfur dioxide over carbon dioxide and carbon monoxide under room conditions, while structures with higher pore volume exhibit better storage capacity at higher pressure. Our results emphasize the need for considering both adsorption and diffusion processes in the selection of the optimal structure for a given separation process. Our findings help to identify the best materials for effective separation processes under realistic operating conditions. PMID:24691937

Matito-Martos, I; Martin-Calvo, A; Gutiérrez-Sevillano, J J; Haranczyk, M; Doblare, M; Parra, J B; Ania, C O; Calero, S

2014-10-01

327

Torsional rheometer for granular materials slurries and gas-solid mixtures and related methods  

DOEpatents

A torsional rheometer apparatus for determining rheological properties of a specimen is provided. A stationary plate and a rotatable plate are in generally coaxial position and structured to receive a specimen there between. In one embodiment, at least one of the plates and preferably both have roughened specimen engaging surfaces to serve to reduce undesired slippage between the plate and the specimen. A motor is provided to rotate the rotatable plate and a transducer for monitoring forces applied to the stationary plate and generating output signals to a computer which determines the desired rheological properties are provided. In one embodiment, the roughened surfaces consist of projections extending toward the specimen. Where granular material is being evaluated, it is preferred that the roughness of the plate is generally equal to the average size of the granular material being processed. In another embodiment, an air-solid mixture is processed and the roughened portions are pore openings in the plates. Air flows through the region between the two pore containing plates to maintain the solid materials in suspension. In yet another embodiment, the base of the stationary plate is provided with a deformable capacitance sensor and associated electronic means. 17 figs.

Rajagopal, C.; Rajagopal, K.R.; Yalamanchili, R.C.

1997-03-11

328

Development of proton-conducting membranes for separating hydrogen from gas mixtures  

SciTech Connect

Thin and dense ceramic membranes fabricated from mixed protonic/electronic conductors can provide a simple, efficient means of separating hydrogen from gas streams and offer an alternative to existing methods of hydrogen recovery. Because mixed electronic/protonic conductors internally transport not only hydrogen (and thus provide the means to separate hydrogen from other gaseous components) but also electrons, hydrogen separation could be achieved in a non-Galvanic mode of operation (i.e., without the need for external electrodes, circuitry, and/or power supply). To be suitable as a hydrogen-permeable membrane, a material must exhibit sufficiently high electronic and protonic conductivities, and these conductivities must be approximately equal to one another to maximize hydrogen permeation through the material. In addition, the material must have sufficient mechanical integrity to withstand normal operating stresses and must be chemically stable under a wide range of gas atmospheres. This talk summarizes results obtained in Argonne`s effort to develop material for use as a hydrogen separation membrane. The transport properties of BaCe{sub 0.95}Y{sub 0.05}O{sub 3{minus}{alpha}} (5%-BCY) and SrCe{sub 0.95}Y{sub 0.05}O{sub 3{minus}{alpha}} (5%-SCY) were characterized by impedance spectroscopy, gas permeation, and open-cell voltage measurements. In this presentation, the authors describe the materials selection, synthesis, characterization, and performance evaluation of mixed-conducting dense ceramic membranes for hydrogen separation applications.

Balachandran, U.; Guan, J.; Dorris, S.E. [Argonne National Lab., IL (United States). Energy Technology Div.; Liu, M. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering

1997-09-01

329

Development of an atmospheric dispersion model for heavier-than-air-gas mixtures, volume 1  

NASA Astrophysics Data System (ADS)

The mathematical modeling techniques which have been used to predict atmospheric dispersion of heavy gases are reviewed and critiqued. These dispersion processes are characterized by three regimes or phases: near-field, negative buoyancy-dominated flow regime, intermediate-field, stably stratified shear flow regime, and far-field, passive turbulent diffusion regime. Mathematical models of laboratory and natural gravity currents are used to describe the negative buoyancy-dominated regime flow and dilution processes. The model concepts are consistent with the limiting passive behavior of demonstrated air pollution models. An interactive computer model for heavy gas dispersion (DEGADIS) is developed.

Havens, J. A.; Spicer, T. O.

1985-02-01

330

Analysis of polyaromatic hydrocarbon mixtures with laser ionization gas chromatography/mass spectrometry  

SciTech Connect

Excimer laser induced multiphoton ionization has been utilized for ion generation in capillary gas chromatography/mass spectrometry and the technique applied to the separation and detection of polyaromatic hydrocarbons. Detection limits as low as 200 fg and linearity over a range of 5 x 10/sup +4/ were obtained for the polyaromatic hydrocarbons examined. Multiphoton ionization mass spectra were dominated by parent ions. Selective ionization based upon small differences in ionization potentials has been demonstrated for coeluting chrysene and triphenylene. Instrumental parameters have been investigated to assess improvements in sensitivity.

Rhodes, G.; Opsal, R.B.; Meek, J.T.; Reilly, J.P.

1983-02-01

331

Microdischarges of xenon sustained by microwaves: Determination of scaling laws  

SciTech Connect

The threshold conditions to maintain millimeter and submillimeter-size discharges of xenon with microwaves are experimentally determined. The threshold electric field required to sustain the plasma is reported as a function of gas pressure. The influence of the size of the dielectric cell in which the discharge is produced is also shown. The scaling laws are deduced from the threshold electric field measurements, assuming a few additional simplifying assumptions. The results are compared with data obtained with argon discharges sustained by surface waves in capillary tubes and the hypotheses assumed for the calculations are discussed.

Lacoste, A.; Maulat, O.; Latrasse, L.; Arnal, Y.; Pelletier, J. [Laboratoire Elaboration par Procedes Magnetiques (EPM), UPR CNRS 9033 ENSHMG, BP 95, 38402 Saint Martin d'Heres Cedex (France)

2005-04-04

332

Experimental evidence on interaction between xenon and bovine serum albumin  

NASA Astrophysics Data System (ADS)

Xenon gas interacts with bovine serum albumin (BSA) dissolved in a physiological buffer solution. The fluorescence quenching related to the Trp emission is reversible and depends linearly on the time of saturation by Xe. The most probable site of this interaction is Trp212. The common emission of all BSA fluorophores is also influenced by Xe but this quenching is more complex and suggests: (i) at least two sites occupied by Xe and related to the Tyr and Trp residues; (ii) structural variations of BSA induced by the Xe guest atoms.

Wo?oszyn, ?ukasz; Ilczyszyn, Marek; Ilczyszyn, Maria M.

333

Combustion of ultrafine coal/water mixtures and their application in gas turbines: Final report  

SciTech Connect

The feasibility of using coal-water fuels (CWF) in gas turbine combustors has been demonstrated in recent pilot plant experiments. The demands of burning coal-water fuels with high flame stability, complete combustion, low NO/sub x/ emission and a resulting fly ash particle size that will not erode turbine blades represent a significant challenge to combustion scientists and engineers. The satisfactory solution of these problems requires that the variation of the structure of CWF flames, i.e., the fields of flow, temperature and chemical species concentration in the flame, with operating conditions is known. Detailed in-flame measurements are difficult at elevated pressures and it has been proposed to carry out such experiments at atmospheric pressure and interpret the data by means of models for gas turbine combustor conditions. The research was carried out in five sequential tasks: cold flow studies; studies of conventional fine-grind CWF; combustion studies with ultrafine CWF fuel; reduction of NO/sub x/ emission by staged combustion; and data interpretation-ignition and radiation aspects. 37 refs., 61 figs., 9 tabs.

Toqan, M.A.; Srinivasachar, S.; Staudt, J.; Varela, F.; Beer, J.M.

1987-10-01

334

Martian atmospheric xenon contents of Nakhla mineral separates: implications for the origin of elemental mass fractionation  

Microsoft Academic Search

Analyses of mineral separates from Nakhla reveal that Martian atmosphere-derived xenon is present in olivine and pyroxene in concentrations close to that of the bulk meteorite, and at elevated concentrations in mesostasis. We argue that neither aqueous alteration nor adsorption followed by shock incorporation are plausible mechanisms for incorporating this gas component into the meteorite, and suggest trapping occurred on

J. D Gilmour; J. A Whitby; G Turner

1999-01-01

335

Interplay of defect cluster and the stability of xenon in uranium dioxide from density functional calculations  

NASA Astrophysics Data System (ADS)

Self-defect clusters in bulk matrix might affect the thermodynamic behavior of fission gases in nuclear fuel such as uranium dioxide. With first-principles local spin-density approximation plus U calculations and taking xenon as a prototype, we find that the influence of oxygen defect clusters on the thermodynamics of gas atoms is prominent, which increases the solution energy of xenon by a magnitude of 0.5 eV, about 43% of the energy difference between the two lowest lying states at 700 K. Calculation also reveals a thermodynamic competition between the uranium vacancy and trivacancy sites to incorporate xenon in hyperstoichiometric regime at high temperatures. The results show that in hypostoichiometric regime neutral trivacancy sites are the most favored position for diluted xenon gas, whereas in hyperstoichiometric condition they prefer to uranium vacancies even after taking oxygen self-defect clusters into account at low temperatures, which not only confirms previous studies but also extends the conclusion to more realistic fuel operating conditions. The observation that gas atoms are ionized to a charge state of Xe+ when at a uranium vacancy site due to strong Madelung potential implies that one can control temperature to tune the preferred site of gas atoms and then the bubble growth rate. A solution to the notorious metastable states difficulty that frequently encountered in density functional theory plus U applications, namely, the quasiannealing procedure, is also discussed.

Geng, Hua Y.; Chen, Ying; Kaneta, Yasunori; Kinoshita, Motoyasu; Wu, Q.

2010-09-01

336

New concepts for a gaseous Xenon detector for double beta decay  

NASA Astrophysics Data System (ADS)

Xenon gas is an attractive medium for the search for neutrinoless double beta decay because it offers the possibility of reasonable energy resolution, event topology reconstruction, very high intrinsic purity and background rejection through the identification of the daughter barium ion. This talk explores recent developments in the conceptual design of such a detector.

Sinclair, D.; Exo Collaboration

2010-01-01

337

Direct comparison of a Xenon and a solid state CT detector system: Measurements under working conditions  

Microsoft Academic Search

Measurements of various image quality parameters were carried out with two different detector systems in an otherwise unchanged medical computed tomography (CT) scanner. As all other components of the scanner and the image reconstruction system remained identical, the authors were able to quantify the difference in performance between a xenon gas ionization detector and a new solid-state scintillation detector in

Theobald Fuchs; Marc Kachelriess; Willi A. Kalender

2000-01-01

338

Transportable Xenon Laboratory (TXL-1) Operations Manual  

SciTech Connect

The Transportable Xenon Laboratory Operations Manual is a guide to set up and shut down TXL, a fully contained laboratory made up of instruments to identify and measure concentrations of the radioactive isotopes of xenon by taking air samples and analyzing them. The TXL is housed in a standard-sized shipping container. TXL can be shipped to and function in any country in the world.

Thompson, Robert C.; Stewart, Timothy L.; Willett, Jesse A.; Woods, Vincent T.

2011-03-07

339

The XENON100 Dark Matter Experiment  

SciTech Connect

The XENON100 experiment is searching for WIMPs, which are particles that may consist dark matter. It is located in the underground laboratory of Gran Sasso (LNGS) in Italy at a depth of {approx}3600 m.w.e.. The experiment description, its performance and the expected background based on Monte Carlo simulations and material screening along with the projected sensitivities of the experiment are presented. In addition, a brief description of the upgrade XENON100 detector is given.

Tziaferi, E. [Physics Institute, University of Zuerich, Winterthurerstr. 190, Zuerich (Switzerland)

2010-06-23

340

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) enables high-resolution non-invasive observation of the anatomy and function of intact organisms. However, previous MRI reporters of key biological processes tied to gene expression have been limited by the inherently low molecular sensitivity of conventional 1H MRI. This limitation could be overcome through the use of hyperpolarized nuclei, such as in the noble gas xenon, but previous reporters acting on such nuclei have been synthetic. Here, we introduce the first genetically encoded reporters for hyperpolarized 129Xe MRI. These expressible reporters are based on gas vesicles (GVs), gas-binding protein nanostructures expressed by certain buoyant microorganisms. We show that GVs are capable of chemical exchange saturation transfer interactions with xenon, which enables chemically amplified GV detection at picomolar concentrations (a 100- to 10,000-fold improvement over comparable constructs for 1H MRI). We demonstrate the use of GVs as heterologously expressed indicators of gene expression and chemically targeted exogenous labels in MRI experiments performed on living cells.

Shapiro, Mikhail G.; Ramirez, R. Matthew; Sperling, Lindsay J.; Sun, George; Sun, Jinny; Pines, Alexander; Schaffer, David V.; Bajaj, Vikram S.

2014-07-01

341

Measurement of Xenon Viscosity as a Function of Low Temperature and Pressure  

NASA Technical Reports Server (NTRS)

The measurement of xenon gas viscosity at low temperatures (175-298 K) and low pressures (350 torr-760 torr) has been performed in support of Hall Thruster testing at NASA Lewis Research Center. The measurements were taken using the capillary flow technique. Viscosity measurements were repeatable to within 3%. The results in this paper are in agreement with data from Hanley and Childs and suggest that the data from Clarke and Smith is approximately 2% low. There are no noticeable pressure effects on xenon absolute viscosity for the pressure range from 350 torr to 760 torr.

Grisnik, Stanley P.

1998-01-01

342

The inactivation of Chlorella spp. with dielectric barrier discharge in gas-liquid mixture  

NASA Astrophysics Data System (ADS)

The inactivation of Chlorella spp. with high voltage and frequency pulsed dielectric barrier discharge in hybrid gas-liquid reactor with a suspension electrode was studied experimentally. In the hybrid gas-liquid reactor, a steel plate was used as high voltage electrode while a quartz plate as a dielectric layer, another steel plate placing in the aqueous solution worked as a whole ground electrode. A suspension electrode is installed near the surface of solution between high voltage and ground electrode to make the dielectric barrier discharge uniform and stable, the discharge gap was between the quartz plate and the surface of the water. The effect of peak voltage, treatment time, the initial concentration of Chlorella spp. and conductivity of solution on the inactivation rate of Chlorella spp. was investigated, and the inactivation mechanism of Chlorella spp. preliminarily was studied. Utilizing this system inactivation of Chlorella spp., the inactivation rate increased with increasing of peak voltage, treatment time and electric conductivity. It was found that the inactivation rate of Chlorella spp. arrived at 100% when the initial concentration was 4 × 106 cells mL-1, and the optimum operation condition required a peak voltage of 20 kV, a treatment time of 10 min and a frequency of 7 kHz. Though the increasing of initial concentration of the Chlorella spp. contributed to the addition of interaction probability between the Chlorella spp. and O3, H2O2, high-energy electrons, UV radiation and other active substances, the total inactivation number raise, but the inactivation rate of the Chlorella spp. decreased.

Song, Dan; Sun, Bing; Zhu, Xiaomei; Yan, Zhiyu; Liu, Hui; Liu, Yongjun

2013-03-01

343

Progress on the Characterization of the Yale ``PIXeY'' Two-Phase Xenon Detector  

NASA Astrophysics Data System (ADS)

PIXeY (Particle Identification in Xenon at Yale) is a two-phase (liquid/gas) xenon prototype detector with 3-kg active mass. The two-phase xenon technology has many applications that include gamma-ray imaging, neutrinoless double beta decay searches, and dark matter searches. PIXeY was built to optimize energy resolution and gamma/neutron discrimination, with a number of technological improvements over previous work. Parallel-wire grids, which control the drift and proportional-scintillation fields, are optimized both for light collection efficiency and field uniformity. High quantum efficiency Hamamatsu R8778 PMTs, high-reflectivity Teflon walls, and charge-light anti-correlation techniques are also incorporated. PIXeY will serve as a platform for future improvements, including multiple optical volumes and single wire readout for R&D on gamma-ray imaging and track-imaging studies. The latest progress on the detector will be presented.

Destefano, Nicholas; Gai, Moshe; McKinsey, Daniel; Bernard, Ethan; Cahn, Sidney; Curioni, Alessandro; Edwards, Blair; Kachulis, Christopher; Larsen, Nicole; Lyashenko, Alexey; Nikkel, James; Skin, Yunchang; Wahl, Christopher; Young, Alexander

2012-10-01

344

The gas phase FTIR studies of chloroform + B and halothane + B (B = TMA, FCD3) mixtures  

NASA Astrophysics Data System (ADS)

An infrared and ab initio (MP2/6-311++G(2d,2p)) study of complexes of chloroform (Cl3CH(D)) and halothane (CHClBrCF3) with weak - methyl fluoride (FCD3) and strong - trimethylamine (N(CH(D)3)3tbnd TMA) proton acceptors in the gas phase near the room temperature is presented. The so called blue shifting hydrogen bond has been identified in the former case and the formation of conventional H-bond with the red frequency shift of CH stretching vibration of the proton donors was observed in the latter case. An attempt of temperature spectroscopic measurements has been made for the systems studied to estimate the formation energy. In the case of Cl3CD…N(CH3)3 complex this value equals -23(2) kJ/mol. The results obtained in ab inito calculations generally agree with those obtained in IR spectroscopic measurements, however they overestimate the frequency shift caused by the complex formation, especially in the case of the red-shifting H-bonds. Possible origin of such overestimation is discussed shortly.

Rutkowski, K. S.; Melikova, S. M.; Asfin, R. E.; Czarnik-Matusewicz, B.; Rospenk, M.

2014-08-01

345

NATURE OF UNRESOLVED COMPLEX MIXTURE IN SIZE-DISTRIBUTED EMISSIONS FROM RESIDENTIAL WOOD COMBUSTION AS MEASURED BY THERMAL DESORPTION-GAS CHROMATOGRAPHY-MASS SPECTROMETRY  

EPA Science Inventory

In this study, the unresolved complex mixture (UCM) in size resolved fine aerosol emissions from residential wood combustion (RWC) is examined. The aerosols are sorted by size in an electrical low-pressure impactor (ELPI) and subsequently analyzed by thermal desorbtion/gas chroma...

346

Stirring Up an Elastic Fluid: Critical Viscosity of Xenon-2 (CVX-2)  

NASA Technical Reports Server (NTRS)

Whipped cream stays in place even when turned upside down. Yet it readily flows through the nozzle of a spray can to reach the dessert plate. This demonstrates the phenomenon of shear thinning that is important to many industrial and physical processes. Paints, film emulsions, and other complex solutions that are highly viscous under normal conditions but become thin and flow easily under shear forces. A simple fluid, such as water, does not exhibit shear thinning under normal conditions. Very close to the liquid-vapor critical point, where the distinction between liquid and vapor disappears, the fluid becomes more complex and is predicted to display shear thinning. At the critical point, xenon atoms interact over long distances in a classical model of cooperative phenomena. Physicists rely on this system to learn how long-range order arises. The Critical Viscosity of Xenon Experiment (CVX-2) will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Although it does not easily combine with other chemicals, its viscosity at the critical point can be used as a model for a range of fluids. Viscosity originates from the interactions of individual molecules. It is so complicated that, except for the simplest gas, it cannot be calculated accurately from theory. Tests with critical fluids can provide key data, but are limited on Earth because critical fluids are highly compressed by gravity. CVX-2 employs a tiny metal screen vibrating between two electrodes in a bath of critical xenon. The vibrations and how they dampen are used to measure viscosity. CVX flew on STS-85 (1997), where it revealed that, close to the critical point, the xenon is partly elastic: it can 'stretch' as well as flow. For STS-107, the hardware has been enhanced to determine if critical xenon is a shear-thinning fluid.

Berg, Robert F.; Moldover, Michael R.; Zimmerli, Gregory A.; Motil, Susan M. (Technical Monitor)

2002-01-01

347

Equation of state and ideal-gas heat capacity of a gaseous mixture of 1,1,1,2-tetrafluoroethane, pentafluoroethane, and difluoromethane  

SciTech Connect

The authors present the gas-phase equation of state and ideal-gas heat capacity of a ternary mixture of 1,1,1,2-tetrafluoroethane (35%), pentafluoroethane (30%), and difluoromethane (35%) for temperatures between 260 and 453 K and pressures between 0.05 and 7.7 MPa. These results were based on two very different measurement techniques. The first technique measured the gas density of the mixture in a Burnett apparatus from 313 to 453 K and from 0.2 to 7.7 MPa. The second technique deduced the gas density and ideal-gas heat capacity from high-accuracy speed-of-sound measurements in the mixture at temperatures between 260 and 400 K and at pressures between 0.05 and 1.0 MPa. The data from the two techniques were analyzed together to obtain an equation of state that reproduced the densities from the Burnett technique with a fractional RMS deviation of 0.038%, and it also reproduced the sound speeds with a fractional RMS deviation of 0.003%. Finally, the results are compared to a predictive model based on the properties of the pure fluids.

Hurly, J.J.; Schmidt, J.W.; Gillis, K.A. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1997-05-01

348

Determination of nitrogen dioxide in air compressed gas mixtures by quantitative tunable diode laser absorption spectrometry and chemiluminescence detection  

SciTech Connect

Tunable diode laser absorption spectrometry (TDLAS) and chemiluminescence detection (CD) were both employed for the determination of seven NO/sub 2//air compressed gas mixtures in the 2.3-2500 ppm (by mole) concentration range. In the diode laser determinations, they employed a variety of different measurement and calibration approaches based upon direct absorption and second harmonic detection. Such redundancy enabled them to carry out a careful analysis thus minimizing systematic errors. After HNO/sub 3/ was accounted for, measured in all but one cylinder examined, the TDLAS and CD NO/sub 2/ determinations were generally found to agree to better than 3%. Fourier transform infrared absorption spectrometry was also employed in the determination of one particular cylinder, the nominal 2500 ppm cylinder. The resulting NO/sub 2/ determination was within 0.2% of that obtained by TDLAS. However, a small remaining discrepancy on the order of 5-8% was still observed between these two results and those determined by CD even after HNO/sub 3/ was accounted for. Further studies pointed to the presence of an additional nitrogen-containing compound in this cylinder.

Fried, A.; Sams, R.; Dorko, W.; Elkins, J.W.; Cai, Z.

1988-03-01

349

Investigating of electrons bunching in a Penning trap and accelerating process for CO2 gas mixture active medium  

E-print Network

In the presence of an active medium incorporated in a Penning trap, the moving electrons can become bunched, as they get enough energy, they escape the trap forming an optical injector. These bunched electrons can enter next PASER section filled with the same active medium to be accelerated. In this paper, electron dynamics in the presence of gas mixture active medium incorporated in a penning trap is analyzed by developing an idealized 1D model. We further evaluate the energy exchange occurring as the train of electrons traversing the next PASER section. The results show that the oscillating electrons can be bunched at the resonant frequency of the active medium. The influence of the trapped time and the population inversion are analyzed, which shows that the longer the electrons are trapped, the more energy from the medium the accelerated electrons get, and with the increase of the population inversion, the decelerated electrons virtually unchanged but the accelerated electrons more than double their peak e...

Tian, Xiu-fang; Jia, Qika

2014-01-01

350

Characterisation and fingerprinting of PCBs in flue gas and ash from waste incineration and in technical mixtures.  

PubMed

Congener patterns of mono- to deca-chlorinated biphenyls (PC1-10B) were evaluated in (a) waste incineration flue gases collected in the post-combustion zone of a laboratory-scale fluidized-bed reactor, (b) ashes from two different MSW incineration plants, and (c) published data of eight Aroclor formulations. The congener patterns of the flue gases, ashes, and Aroclor mixtures clearly differed from each other, likely reflecting differences in formation pathways. The flue gas congener patterns were largely dominated by the least chlorinated congeners, whereas the ashes displayed more evenly distributed patterns. The most abundant congeners indicated a preference for 3,3',4,4'-oriented substitution, which may be related to de novo-type formation involving perylene. Principal component analysis confirmed that congener patterns differed among the three matrices and also distinguished flue gases collected at 200 °C from those collected at 300 °C and 450 °C. This distinction could be partly explained by the degree of chlorination, although the substitution status of the ortho-position, and substitution in the 3,3',4,4'-positions also seemed to be influential. Injecting biphenyl into the post-combustion zone of the reactor did not alter the patterns, indicating that availability of the backbone structure is not a limiting factor for PCB formation. PMID:21885088

Jansson, Stina; Lundin, Lisa; Grabic, Roman

2011-10-01

351

The bidirectional character of O2 concentration in pulsed dielectric barrier discharges in O2/N2 gas mixtures  

NASA Astrophysics Data System (ADS)

This paper presents experimental results on the influence of O2 on the characteristics of dielectric barrier discharges (DBDs) at one and at half atmospheric pressure. Gas mixtures of 0.1–10?vol?% O2 in N2 were investigated, as well as in virtually pure N2. Electrical data, simultaneous streak and intensified charge-coupled device images were recorded in pulsed driven dielectric barrier discharges of 0.8?mm gap in a single filament arrangement. The O2 concentration is shown to have a significant impact on the electrical characteristics, the temporal DBD development and its breakdown inception. Higher O2 concentrations (above 0.1?vol?%) led to an ignition delay, a shorter discharge duration, increased discharge radius, higher discharge current maxima and larger velocities of the cathode directed streamers. For O2 concentrations below 0.01?vol?%—i.e. nearly pure nitrogen—some of these effects were reversed. Moreover, the effects were more pronounced at a pressure of 0.5?bar compared to 1?bar. This result can be explained by the pressure dependent decay and recombination processes of positive nitrogen and oxygen ions.

Höft, H.; Kettlitz, M.; Weltmann, K.-D.; Brandenburg, R.

2014-11-01

352

Output gas stream composition from methane saturated coal during injection of nitrogen, carbon dioxide, a nitrogen–carbon dioxide mixture and a hydrogen–carbon dioxide mixture  

Microsoft Academic Search

Proven global methane reserves can be increased from 177Tm3 to 210–308Tm3 (+19 to 74%) if 50% of global coalbed methane resources are deemed producible. As primary recovery methods for CBM produce at most 50% of the methane present, there is considerable interest in enhancing recovery by gas injection. It is not clear which composition of the injection gas is most

Patrick van Hemert; Karl-Heinz A. A. Wolf; E. Susanne J. Rudolph

353

Spectroscopic diagnostics of barrier-discharge plasma in mixtures of cadmium diiodide vapor with gases  

NASA Astrophysics Data System (ADS)

The spectral characteristics of the emission of atmospheric-pressure gas-discharge plasma in mixtures of cadmium diiodide vapor with gases (Ne, Ar, Kr, Xe, and N2) were investigated along with the time characteristics of the voltage and current. The gas-discharge plasma was produced and excited by a barrier discharge at a repetition rate of sine voltage pulses of up to 140 kHz. The discharge emission was analyzed in the spectral range 200 900 nm with a high resolution (0.05 nm). Radiation from exciplex CdI(B-X) molecules and excimer I2* molecules was revealed, as well as the atomic lines of cadmium, iodine, and inert gases. In a mixture with xenon, radiation from exciplex molecules XeI(B-X, B-A) was also found. This radiation prevailed in the spectra at mixture temperatures up to 150°C. The further increase of the temperature leads to the prevalence of the CdI(B-X) radiation. It was found that the most intense CdI(B-X) radiation is observed in mixtures CdI2/Xe(N2)/Ne. Regularities in the spectral characteristics of the emission of the gas-discharge plasma are discussed.

Guivan, M. M.; Malinin, A. N.

2007-02-01

354

Simulating film condensation of steam from steam-gas mixtures with different compositions on the outer surface of vertical tubes used in a heat exchanger  

NASA Astrophysics Data System (ADS)

A mathematical model of heat-and mass transfer processes in surface-type heat exchangers that use mixtures of steam with various noncondensable gases as heat carriers is presented. The results of numerical calculations are compared with experimental data reported in the literature. It is shown that the thermal-physical properties of the noncondensable component in a steam-gas mixture have an essential effect on the distribution of concentrations and temperatures over the heat exchanger length and on the heat flux transferred in it.

Dudnik, N. M.; Garyaev, A. B.

2010-06-01

355

Discovery potential of xenon-based neutrinoless double beta decay experiments in light of small angular scale CMB observations  

NASA Astrophysics Data System (ADS)

The South Pole Telescope (SPT) has probed an expanded angular range of the CMB temperature power spectrum. Their recent analysis of the latest cosmological data prefers nonzero neutrino masses, with ?m? = (0.32±0.11) eV. This result, if confirmed by the upcoming Planck data, has deep implications on the discovery of the nature of neutrinos. In particular, the values of the effective neutrino mass m?? involved in neutrinoless double beta decay (??0?) are severely constrained for both the direct and inverse hierarchy, making a discovery much more likely. In this paper, we focus in xenon-based ??0? experiments, on the double grounds of their good performance and the suitability of the technology to large-mass scaling. We show that the current generation, with effective masses in the range of 100 kg and conceivable exposures in the range of 500 kg·year, could already have a sizeable opportunity to observe ??0? events, and their combined discovery potential is quite large. The next generation, with an exposure in the range of 10 ton·year, would have a much more enhanced sensitivity, in particular due to the very low specific background that all the xenon technologies (liquid xenon, high-pressure xenon and xenon dissolved in liquid scintillator) can achieve. In addition, a high-pressure xenon gas TPC also features superb energy resolution. We show that such detector can fully explore the range of allowed effective Majorana masses, thus making a discovery very likely.

Gómez-Cadenas, J. J.; Martín-Albo, J.; Muñoz Vidal, J.; Peña-Garay, C.

2013-03-01

356

Equation of State for thermodynamic equilibrium of gas mixtures and brines to allow simulation of the effects of impurities in CO2 storage  

NASA Astrophysics Data System (ADS)

Comprehensive understanding and prediction of chemical, reactive processes during and following injection of CO2 in depleted gas reservoirs and saline aquifers is important for the assessment of the performance and impacts of planned and existing Carbon Capture and Storage (CCS) projects. Over the last decade significant improvements have been made in numerical modelling of the complex, coupled processes involved. Among the many remaining issues where progress is still called for, is the consistent simulation of impacts of gas mixtures. In particular the presence of 'impurities' or 'co-contaminants' in the injected CO2 stream that are retained from the original flue-gases, such as H2S, SO2, have the potential, upon dissolution in the pore water, to alter aqueous and water-mineral reactions. Moreover, presence of these and other injected or in-situ (CH4) gases affect CO2 solubility and thermodynamic properties of the fluid and gas phases, which, in turn, impact transport processes. To be able to evaluate the impact of gas mixtures on these processes, a new non-iterative Equation of State (EOS) has been developed which allows accurate and efficient modelling of thermodynamic equilibrium of gas mixtures and brines over a large range of pressure, temperature and salinity conditions. Presently the model includes CO2, SO2, H2S, CH4 and N2. This model is based on equating the chemical potentials in the system, using the modified Redlich-Kwong EOS to calculate the fugacity of the gas phase. Preliminary analysis shows, for instance, that CO2 solubility is most sensitive to CH4 admixture and least sensitive to the presence of SO2 in the injected gas mixture. The model design/approach will be outlined. Furthermore, the model performance will be illustrated with respect to experimental data from literature and other EOS's. In further work we aim to use this EOS in coupled flow and chemical reactive-transport simulations to investigate the impact of gas mixtures for CO2 storage.

Ziabakhshganji, Z.; Kooi, H.

2012-04-01

357

Characterisation of NEXT-DEMO using xenon K? X-rays  

NASA Astrophysics Data System (ADS)

The NEXT experiment aims to observe the neutrinoless double beta decay of 136Xe in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ionization. Understanding the response of the detector is imperative in achieving a consistent and well understood energy measurement. The abundance of xenon K-shell X-ray emission during data taking has been identified as a multitool for the characterisation of the fundamental parameters of the gas as well as the equalisation of the response of the detector. The NEXT-DEMO prototype is a ~ 1.5 kg volume TPC filled with natural xenon. It employs an array of 19 PMTs as an energy plane and of 256 SiPMs as a tracking plane with the TPC light tube and SiPM surfaces being coated with tetraphenyl butadiene (TPB) which acts as a wavelength shifter for the VUV scintillation light produced by xenon. This paper presents the measurement of the properties of the drift of electrons in the TPC, the effects of the EL production region, and the extraction of position dependent correction constants using K? X-ray deposits. These constants were used to equalise the response of the detector to deposits left by gammas from 22Na.

Lorca, D.; Martín-Albo, J.; Laing, A.; Ferrario, P.; Gómez-Cadenas, J. J.; Álvarez, V.; Borges, F. I. G.; Camargo, M.; Cárcel, S.; Cebrián, S.; Cervera, A.; Conde, C. A. N.; Dafni, T.; Díaz, J.; Esteve, R.; Fernandes, L. M. P.; Ferreira, A. L.; Freitas, E. D. C.; Gehman, V. M.; Goldschmidt, A.; Gómez, H.; González-Díaz, D.; Gutiérrez, R. M.; Hauptman, J.; Hernando Morata, J. A.; Herrera, D. C.; Irastorza, I. G.; Labarga, L.; Liubarsky, I.; Losada, M.; Luzón, G.; Marí, A.; Martínez-Lema, G.; Martínez, A.; Miller, T.; Monrabal, F.; Monserrate, M.; Monteiro, C. M. B.; Mora, F. J.; Moutinho, L. M.; Muñoz Vidal, J.; Nebot-Guinot, M.; Nygren, D.; Oliveira, C. A. B.; Pérez, J.; Pérez Aparicio, J. L.; Renner, J.; Ripoll, L.; Rodríguez, A.; Rodríguez, J.; Santos, F. P.; dos Santos, J. M. F.; Seguí, L.; Serra, L.; Shuman, D.; Simón, A.; Sofka, C.; Sorel, M.; Toledo, J. F.; Torrent, J.; Tsamalaidze, Z.; Veloso, J. F. C. A.; Webb, R.; White, J. T.; Yahlali, N.

2014-10-01

358

Xenon behavior in TiN: A coupled XAS/TEM study  

NASA Astrophysics Data System (ADS)

Titanium nitride is a refractory material that is being considered as an inert matrix in future Generation IV nuclear reactors, in particular in relation to the Gas-cooled Fast Reactor. The main role of this matrix would be to act as a barrier against the release of fission products, in particular gaseous ones like xenon. This release phenomenon will be enhanced by high temperatures expected in the fuel vicinity: 1200 °C under normal conditions, and up to 1800 °C under accidental conditions. It is therefore necessary to investigate the behavior of volatile fission products in TiN under high temperature and irradiation. Indeed, these basic data are very useful to predict the volatile fission products released under these extreme conditions. Our previous work has shown that Xe introduced by ion implantation in sintered TiN tends to be released as a result of annealing, due to a transport mechanism towards the sample surface. The aim of the present work is to determine under which physical state Xe is in TiN. Xenon was first introduced using ion implantation at 800 keV in TiN samples obtained by hot pressing at several concentrations ranging from 0.4 to 8 at.%. Secondly, samples were annealed at high temperature, from 1000 °C to 1500 °C. Xe was then characterized by X-ray Absorption Spectroscopy and Transmission Electron Microscopy. The formation of intragranular xenon bubbles was demonstrated, and the xenon concentration which is sufficient to form bubbles is found to be lower than 0.4 at.% under our experimental conditions. These bubbles were found unpressurised at 15 K. Their size increases with the temperature and the local xenon concentration. For the highest xenon concentrations, a mechanism involving the formation of a Xe interconnected bubble network is proposed to explain Xe massive release observed by Rutherford Backscattering Spectrometry experiments.

Bès, R.; Gaillard, C.; Millard-Pinard, N.; Gavarini, S.; Martin, P.; Cardinal, S.; Esnouf, C.; Malchère, A.; Perrat-Mabilon, A.

2013-03-01

359

Reflectance of polytetrafluoroethylene for xenon scintillation light  

NASA Astrophysics Data System (ADS)

Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet (VUV) wavelength region (? ?175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work, we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived, and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Other fluoropolymers, namely, ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and perfluoro-alkoxyalkane (PFA) were also measured.

Silva, C.; Pinto da Cunha, J.; Pereira, A.; Chepel, V.; Lopes, M. I.; Solovov, V.; Neves, F.

2010-03-01

360

Reflectance of polytetrafluoroethylene for xenon scintillation light  

SciTech Connect

Gaseous and liquid xenon particle detectors are being used in a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as electrical insulator and as a light reflector to improve the efficiency of detection of scintillation photons. However, xenon emits in the vacuum ultraviolet (VUV) wavelength region ({lambda}{approx_equal}175 nm) where the reflecting properties of PTFE are not sufficiently known. In this work, we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived, and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples ranges from about 47% to 66% for VUV light. Other fluoropolymers, namely, ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and perfluoro-alkoxyalkane (PFA) were also measured.

Silva, C.; Pinto da Cunha, J.; Pereira, A.; Chepel, V.; Lopes, M. I.; Solovov, V.; Neves, F. [Department of Physics, LIP-Coimbra, University of Coimbra, P-3004 516 Coimbra (Portugal)

2010-03-15

361

Amino acid formation induced by high-power laser in CO 2/CO-N 2-H 2O gas mixtures  

NASA Astrophysics Data System (ADS)

In a mixture of molecular gases with compositions (CO 2-N 2-H 2O and CO-N 2-H 2O) and total pressure close to that of the Earth's early atmospheres, a centimeter-sized plasma was created by focusing a single 85-J, 450-ps near-infrared laser pulse in a center of 15-L gas cell. Chemical consequences of the laser-produced plasma generation in such a mixture were investigated using high-performance liquid chromatography with mass-spectrometric detection (HPLC/MS). Amino acids were identified in the reaction mixture containing CO 2 as well as in that one based on CO, both exposed to 10 laser shots.

Civiš, Svatopluk; Juha, Libor; Babánková, Dagmar; Cva?ka, Josef; Frank, Ota; Jehli?ka, Jan; Králiková, Božena; Krása, Josef; Kubát, Pavel; Muck, Alexandr; Pfeifer, Miroslav; Skála, Ji?í; Ullschmied, Ji?í

2004-03-01

362

Coupled gas flow/solid dynamics model for predicting the formation of fracture patterns in gas well simulation experiments. [Propellant mixture used instead of explosives to fracture rock surrounding borehole  

SciTech Connect

A two-dimensional finite element model for predicting fracture patterns obtained in high energy gas fracture experiments is presented. In these experiments, a mixture of propellants is used instead of explosives to fracture the rock surrounding the borehole. The propellant mixture is chosen to tailor the pressure pulse so that multiple fractures emanate from the borehole. The model allows the fracture pattern and pressure pulse to be calculated for different combinations of propellant mixture, in situ stress conditions, and rock properties. The model calculates the amount of gas generated by the burning propellants using a burn rate given by a power law in pressure. By assuming that the gas behaves as a perfect gas and that the flow down the fractures is isothermal, the loss of gas from the borehole due to flow down the cracks is accounted for. The flow of gas down the cracks is included in an approximate manner by assuming self-similar pressure profiles along the fractures. Numerical examples are presented and compared to three different full-scale experiments. Results show a good correlation with the experimental data over a wide variety of test parameters. 9 reference, 10 figures, 3 tables.

Taylor, L.M.; Swenson, D.V.; Cooper, P.W.

1984-07-01

363

Mixing of equations of state for xenon-deuterium using density functional theory  

SciTech Connect

We report on a theoretical study of equation of state (EOS) properties of fluid and dense plasma mixtures of xenon and deuterium to explore and illustrate the basic physics of the mixing of a light element with a heavy element. Accurate EOS models are crucial to achieve high-fidelity hydrodynamics simulations of many high-energy-density phenomena, for example inertial confinement fusion and strong shock waves. While the EOS is often tabulated for separate species, the equation of state for arbitrary mixtures is generally not available, requiring properties of the mixture to be approximated by combining physical properties of the pure systems. Density functional theory (DFT) at elevated-temperature is used to assess the thermodynamics of the xenon-deuterium mixture at different mass ratios. The DFT simulations are unbiased as to elemental species and therefore provide comparable accuracy when describing total energies, pressures, and other physical properties of mixtures as they do for pure systems. The study focuses on addressing the accuracy of different mixing rules in the temperature range 1000-40 000 K for pressures between 100 and 600 GPa (1-6 Mbar), thus, including the challenging warm dense matter regime of the phase diagram. We find that a mix rule taking into account pressure equilibration between the two species performs very well over the investigated range.

Magyar, Rudolph J.; Mattsson, Thomas R. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2013-03-15

364

Prediction of thermodynamic properties of natural gas mixtures using 10 equations of state including a new cubic two-constant equation of state  

Microsoft Academic Search

In this contribution, 10 equations of state (EoSs) are used to predict the thermo-physical properties of natural gas mixtures. One of the EoSs is proposed in this work. This EoS is obtained by matching the critical fugacity coefficient of the EoS to the critical fugacity coefficient of methane. Special attention is given to the supercritical behavior of methane as it

Kh. Nasrifar; O. Bolland

2006-01-01

365

Effect of switching gas inlet position on the performance of a polyurethane biofilter under transient loading for the removal of benzene, toluene and xylene mixtures  

Microsoft Academic Search

The performance of a polyurethane (PU) biofilter was evaluated using different operating modes (unidirectional flow (UF) and flow-directional switching (FDS) operations) under transient loading conditions (intermittent and shutdown). Gas mixtures containing benzene, toluene and xylene (BTX) were employed as model gases. Quantitative real-time PCR methods were used for targeting the tmoA gene responsible for BTX degradation and estimating density of

Eun-Hee Lee; Hee Wook Ryu; Kyung-Suk Cho

2011-01-01

366

Polycrystalline silicon carbide films deposited by low-power radio-frequency plasma decomposition of SiF4CF4-H2 gas mixtures  

Microsoft Academic Search

Polycrystalline silicon carbide thin films have been deposited on amorphous substrates by radio-frequency plasma-assisted decomposition of tetrafluoro silane, tetrafluoro methane, and hydrogen gas mixtures using low-power density and deposition temperatures. The material is shown to possess the ?-SiC structure using transmission electron microscopy. It has highly visible transmittance and exhibits bands due to silicon carbide as well as fluorine bonded

Gautam Ganguly; Subal C. De; Swati Ray; A. K. Barua

1991-01-01

367

11/04/02 L. Henn-Lecordier AVS 2002 MS MoA6 1 Monitoring and control of binary gas mixtures  

E-print Network

11/04/02 L. Henn-Lecordier ­ AVS 2002 ­ MS MoA6 1 Monitoring and control of binary gas mixtures from solid phase MOCVD sources using an acoustic sensor L. Henn-Lecordier, G. Rubloff, J. Kidder, College Park, MD, 20742 http://www.isr.umd.edu/~rubloff #12;11/04/02 L. Henn-Lecordier ­ AVS 2002 ­ MS Mo

Rubloff, Gary W.

368

Anticipatory control of xenon in a pressurized water reactor  

SciTech Connect

A method is described for automatically dampening xenon-135 spatial transients in the core of a pressurized water reactor having control rods which regulate reactor power level, comprising the steps of: measuring the neutron flu in the reactor core at a plurality of axially spaced locations on a real-time, on-line basis; repetitively generating from the neutron flux measurements, on a point-by-point basis, signals representative of the current axial distribution of xenon-135, and signals representative of the current rate of change of the axial distribution of xenon-135; generating from the xenon-135 distribution signals and the rate of change of xenon distribution signals, control signals for reducing the xenon transients; and positioning the control rods as a function of the control signals to dampen the xenon-135 spatial transients.

Impink, A.J. Jr.

1987-02-10

369

Atomistic study of stability of xenon nanoclusters in uranium oxide  

SciTech Connect

Density-functional theory calculations of the xenon incorporation energies in point defects in urania have been done in order to fit empirical potentials. With this set of parameters, we have considered the incorporation of xenon in small and extended defects such as planar interstitials, grain boundaries, faceted, and spherical voids. The results show that xenon atoms are more likely to aggregate than to be homogeneously distributed in the urania grains. SIGMA5 grain boundary and spherical shape voids are the most favorable defects of xenon atom incorporation. The presence of xenon atoms in nanovoids affects their shape. The energy gain to aggregate xenon atoms into clusters saturates for cluster sizes of about 15-20 Schottky defects. This demonstrates that medium size defects are just as favorable as big size defects for xenon incorporation.

Chartier, A.; Van Brutzel, L. [DEN, Service de Chimie Physique, CEA, F-91191 Gif-sur-Yvette (France); Freyss, M. [DEN, Service d'Etudes et de Simulation du Comportement des Combustibles, CEA, F-13108 Saint-Paul lez Durance (France)

2010-05-01

370

XENON: a 1 tonne Liquid Xenon Experiment for a Sensitive Dark Matter Search  

E-print Network

XENON is a novel liquid xenon experiment concept for a sensitive dark matter search using a 1-tonne active target, distributed in an array of ten independent time projection chambers. The design relies on the simultaneous detection of ionization and scintillation signals in liquid xenon, with the goal of extracting as much information as possible on an event-by-event basis, while maintaining most of the target active. XENON is expected to have effective and redundant background identification and discrimination power, higher than 99.5%, and to achieve a very low threshold, on the order of 4 keV visible recoil energy. Based on this expectation and the 1-tonne mass of active xenon, we project a sensitivity of 0.0001 events/kg/day, after 3 yr operation in an appropriate underground location. The XENON experiment has been recently proposed to the National Science Foundation (NSF) for an initial development phase leading to the development of the 100 kg unit module.

E. Aprile; E. A. Baltz; A. Curioni; K-L. Giboni; C. J. Hailey; L. Hui; M. Kobayashi; K. Ni; W. W. Craig; R. J. Gaitskell; U. Oberlack; T. Shutt

2002-07-31

371

DFT-MD simulations of shocked Xenon  

NASA Astrophysics Data System (ADS)

Xenon is not only a technologically important element used in laser technologies, jet propulsion and dental anesthesia, but it is also arguably the simplest material in which to study the metal-insulator transition at high pressure. Because of its closed shell electronic configuration, Xenon is often assumed to be chemically inert, interacting almost entirely through the van der Waals interaction, and at liquid density, is typically modeled well using Leonard-Jones potentials. However, such modeling has a limited range of validity as Xenon is known to form compounds at normal conditions and likely exhibits considerably more chemistry at higher densities when hybridization of occupied orbitals becomes significant. In this talk, we present DFT-MD simulations of shocked liquid Xenon with the goal of developing an improved equation of state. The relative importance of the van der Waals interaction compared to other Coulomb interactions is considered, and estimates of the relative accuracy of various density functionals are quantified. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Magyar, Rudolph J.; Mattsson, Thomas R.

2009-03-01

372

Xenon fluorides show potential as fluorinating agents  

NASA Technical Reports Server (NTRS)

Xenon fluorides permit the controlled addition of fluorine across an olefinic double bond. They provide a series of fluorinating agents that permit ready separation from the product at a high purity. The reactions may be carried out in the vapor phase.

Chernick, C. L.; Shieh, T. C.; Yang, N. C.

1967-01-01

373

Preliminary Measurements of the Xenon Triple Point  

NASA Astrophysics Data System (ADS)

Ever since the construction and definition of the highly successful International Temperature Scale of 1990 (ITS-90), one severe deficiency of the scale has been recognized, without a reliable remedy. The problem is the fact that the only then available high-quality fixed point between the argon triple point and the water triple point was the mercury triple point, which unfortunately is situated rather closely to the water triple point, thus having an extremely strong influence on the interpolation function of SPRTs in the range. Already before 1990, measurements on possible fixed points better placed in this temperature range have been investigated, such as the triple points of krypton and xenon. However, results have been rather elusive, mainly regarding the rather large melting range of their transition. A turning point was the 2005 paper from the National Research Council (NRC, Canada), where it was established that the relatively high content of krypton was the culprit for the large melting range of the xenon transitions published previously. Indeed, measurements on a xenon sample with very low krypton content produced a very high-quality plateau, of the same level as other ITS-90 fixed points. However, no follow-up measurements have been reported, and thus neither have comparison measurements been reported. Shortly, after the appearance of the NRC paper, Istituto Nazionale di Ricerca Metrologica (INRIM, Italy) acquired a batch of the same high-purity xenon as used by NRC with the aim of preparing a few sealed cells with it and trying to reproduce the NRC results. However, with the start of the Neon Project (Euromet Project 770), the realization of these intentions had to be postponed until now. Last December, three cells of different design have been filled with this high-quality xenon and preliminary results of the measurements on the triple point are reported.

Steur, P. P. M.; Giraudi, D.

2014-04-01

374

Accurate Measurements and Modeling of the PpT Behavior of Pure Substances and Natural Gas-Like Hydrocarbon Mixtures  

E-print Network

Exclusion volume, constant in Redlich-Kwong EoS, intermediate coefficient for calculation of second virial coefficient of mixture B Second virial coefficient c Intermediate coefficient for calculation of third virial coefficient of mixture C... and powerful enough to predict thermodynamic properties to the lowest achievable experimental uncertainties. 1.3. Equations of State An equation of state (EoS) is a model that correlates the properties of substances, such as the volumetric (P?...

Mantilla, Ivan

2012-10-19

375

Influence of the cathode composition on the performance of high pressure short arc xenon lamps  

NASA Astrophysics Data System (ADS)

Thoriated tungsten has been widely used as a cathode material in arc lamps. The addition of thorium reduces the work function of tungsten and allows the cathode to operate at a lower temperature. However, most of the studies on thoriated cathodes were done either for welding arcs or for metal halide lamps, where reactions with the ambient gas could contribute to the cathode erosion. In the case of completely inert, high-purity xenon gas and highly collisional arc plasma, the differences in performance of thoriated and non-thoriated cathodes are mainly material-based. In this talk we will discuss how 2% ThO2 addition to tungsten cathodes changes the lifetime, ignition performance, and stability of xenon lamps.

Minayeva, Olga B.; Doughty, Douglas A.

2006-10-01

376

Multiple-ionization of xenon atoms by positron impact  

NASA Technical Reports Server (NTRS)

Previously the cross sections were measured for positronium formation and single ionization by positron impact for He and H2. With the same apparatus, slightly modified, the single and multiple ionization of xenon is now investigated. The principle of the method is the detection of ion and positron in time correlation which allows the discrimination of positronium formation (whereby the positron vanishes) and the destinction of single, double and triple impact ionization (which lead to different ion flight times from the gas target to the ion detector). By using secondary electrons from the positron moderator, similar measurements were performed on electron impact ionization. By comparing with literature values for electron multiple ionization cross sections, the detection-probability ratios were determined for the differently charged ions.

Kruse, Georg; Quermann, Andreas; Raith, Wilhelm; Sinapius, Guenther

1990-01-01

377

Improved resolution of hydrocarbon structures and constitutional isomers in complex mixtures using Gas Chromatography-Vacuum Ultraviolet-Mass Spectrometry (GC-VUV-MS)  

SciTech Connect

Understanding the composition of complex hydrocarbon mixtures is important for environmental studies in a variety of fields, but many prevalent compounds cannot be confidently identified using traditional gas chromatography-mass spectrometry (GC-MS) techniques. This work uses vacuum-ultraviolet (VUV) ionization to elucidate the structures of a traditionally"unresolved complex mixture" by separating components by GC retention time, tR, and mass-to-charge ratio, m/Q, which are used to determine carbon number, NC, and the number of rings and double bonds, NDBE. Constitutional isomers are resolved based on tR, enabling the most complete quantitative analysis to date of structural isomers in an environmentally-relevant hydrocarbon mixture. Unknown compounds are classified in this work by carbon number, degree of saturation, presence of rings, and degree of branching, providing structural constraints. The capabilities of this analysis are explored using diesel fuel, in which constitutional isomer distribution patterns are shown to be reproducible between carbon numbers and follow predictable rules. Nearly half of the aliphatic hydrocarbon mass is shown to be branched, suggesting branching is more important in diesel fuel than previously shown. The classification of unknown hydrocarbons and the resolution of constitutional isomers significantly improves resolution capabilities for any complex hydrocarbon mixture.

Aerosol Dynamics Inc; Aerodyne Research, Inc.,; Tofwerk AG, Thun; Isaacman, Gabriel; Wilson, Kevin R.; Chan, Arthur W. H.; Worton, David R.; Kimmel, Joel R.; Nah, Theodora; Hohaus, Thorsten; Gonin, Marc; Kroll, Jesse H.; Worsnop, Doug R.; Goldstein, Allen H.

2011-09-13

378

Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Films by Dielectric Barrier Discharge in TiCl4/O2/N2 Gas Mixtures  

NASA Astrophysics Data System (ADS)

Low-pressure dielectric barrier discharge (DBD) TiCl4/O2 and N2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A homemade large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15°. Compared to titanium oxide films deposited in TiCl4/O2 gas mixtures, those in TiCl4/O2/N2 gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O2/N2 gas mixtures with the addition of 50% N2 and 20% TiCl4 is still smaller than 20°, while that of undoped titanium oxide films is larger than 64° when they are measured after one week. The low-pressure TiCl4/O2 plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film's fragmentation due to the over-high film stress. Optical emission spectra (OES) of TiCl4/O2 DBD plasmas at various power supply driving frequencies are presented.

Niu, Jinhai; Zhang, Zhihui; Fan, Hongyu; Yang, Qi; Liu, Dongping; Qiu, Jieshan

2014-07-01

379

Research and Development Work Concerning the Separation of Helium from Gas Mixtures by SiO sub 2 Composite Membranes.  

National Technical Information Service (NTIS)

The demand for helium is continuously rising, so that methods for the selective separation of helium from natural gas are gaining increasing importance as an alternative to natural gas liquefaction. Composite membranes were examined for their usefulness f...

W. Krieger, P. Wiesert

1982-01-01

380

A PROCEDURE FOR ESTABLISHING TRACEABILITY OF GAS MIXTURES TO CERTAIN NATIONAL BUREAU OF STANDARDS STANDARD REFERENCE MATERIALS  

EPA Science Inventory

This procedure includes the specifications and requirements that must be followed by gas manufacturers during the preparation of compressed cylinder gas Certified Reference Materials (CRM). A CRM is a certified gas standard prepared at a concentration that does not exceed + or - ...

381

MOFs for CO2 capture and separation from flue gas mixtures: the effect of multifunctional sites on their adsorption capacity and selectivity.  

PubMed

Microporous metal-organic frameworks (MOFs) have attracted tremendous attention because of their versatile structures and tunable porosity that allow almost unlimited ways to improve their properties and optimize their functionality, making them very promising for a variety of important applications, especially in the adsorption and separation of small gases and hydrocarbons. Numerous studies have demonstrated that MOFs with multifunctional groups, such as open metal sites (OMSs) and Lewis basic sites (LBSs), interact strongly with carbon dioxide and are particularly effective in its capture and separation from binary mixtures of CO(2) and N(2). In this feature article, we briefly review the current state of MOF development in this area, with an emphasis on the effect of multifunctional groups on the selectivity and capacity of MOFs for the CO(2) capture from flue gas mixtures. PMID:23150882

Zhang, Zhijuan; Zhao, Yonggang; Gong, Qihan; Li, Zhong; Li, Jing

2013-01-25

382

The final LDRD report for the project entitled: {open_quotes}Enhanced analysis of complex gas mixtures by pattern recognition of microsensor array signals{close_quotes}  

SciTech Connect

Microsensors do not have the selectivity to chemical species available in large laboratory instruments. This project employed arrays of catalytically gated silicon microsensors with different catalysts to create data streams which can be analyzed by pattern recognition programs. One of the most significant accomplishments of the program was the demonstration of that mixtures of H{sub 2} with the oxidants NO{sub x} and O{sub 2} could distinguished from one another by the use of different catalytic metals on the Sandia Robust Hydrogen (SRH) sensors and the newly developed pattern recognition algorithm. This sensor system could be used to identify explosive gas mixtures and analyze exhaust streams for pollution control.

Hughes, R.C.; Osbourn, G.C.

1996-09-01

383

Xenon ion propulsion for orbit transfer  

NASA Technical Reports Server (NTRS)

The status of critical ion propulsion system elements is reviewed. Electron bombardment ion thrusters for primary propulsion have evolved to operate on xenon in the 5-10 kW power range. Thruster efficiencies of 0.7 and specific impulse values of 4000 s have been documented. The baseline thruster currently under development by NASA LeRC includes ring-cusp magnetic field plasma containment and dished two-grid ion optics. Based on past experience and demonstrated simplifications, power processors for these thrusters should have approximately 500 parts, a mass of 40 kg, and an efficiency near 0.94. Thrust vector control, via individual thruster gimbals, is a mature technology. High pressure, gaseous xenon propellant storage and control schemes, using flight qualified hardware, result in propellant tankage fractions between 0.1 and 0.2. In-space and ground integration testing has demonstrated that ion propulsion systems can be successfully integrated with their host spacecraft.

Rawlin, V. K.; Patterson, M. J.; Gruber, R. P.

1990-01-01

384

Versatile power supply circuit for xenon flashlamps  

NASA Astrophysics Data System (ADS)

A simple, versatile power supply designed to control xenon flashlamps is described. The circuit is configured to utilize an N-channel enhanced metal-oxide-semiconductor field effect transistor (MOSFET), taking the place of commonly used triggering devices such as a silicon controlled rectifier (SCR), or triac. Incorporation of the MOSFET permits flexible control of flash duty cycle and frequency by applying one signal to the transistor's gate. The circuit's versatility is demonstrated using an 8.3-W xenon flashlamp as an excitation source for a photodiode array based HPLC fluorescence detector. A detailed description of the power supply circuit is given, along with information on interfacing the circuit and the photodiode array.

Wegrzyn, Jeff; Patonay, Gabor; Warner, Isiah; Ford, Michael

1989-01-01

385

Xenon preconditioning reduces brain damage from neonatal asphyxia in rats  

Microsoft Academic Search

Xenon attenuates on-going neuronal injury in both in vitro and in vivo models of hypoxic–ischaemic injury when administered during and after the insult. In the present study, we sought to investigate whether the neuroprotective efficacy of xenon can be observed when administered before an insult, referred to as ‘preconditioning’. In a neuronal–glial cell coculture, preexposure to xenon for 2 h

Daqing Ma; Mahmuda Hossain; Garry K J Pettet; Yan Luo; Ta Lim; Stanislav Akimov; Robert D Sanders; Nicholas P Franks; Mervyn Maze

2006-01-01

386

Design and Performance of the XENON10 Dark Matter Experiment  

Microsoft Academic Search

XENON10 is the first two-phase xenon time projection chamber (TPC) developed\\u000awithin the XENON dark matter search program. The TPC, with an active liquid\\u000axenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground\\u000alaboratory (LNGS) in Italy, and operated for more than one year, with excellent\\u000astability and performance. Results from a dark matter search

E. Aprile; J. Angle; F. Arneodo; L. Baudis; A. Bernstein; A. Bolozdynya; P. Brusov; L. C. C. Coelho; C. E. Dahl; L. DeViveiros; A. D. Ferella; L. M. P. Fernandes; S. Fiorucci; R. J. Gaitskell; K. L. Giboni; R. Gomez; R. Hasty; L. Kastens; J. Kwong; J. A. M. Lopes; N. Madden; A. Manalaysay; A. Manzur; D. N. McKinsey; M. E. Monzani; K. Ni; U. Oberlack; J. Orboeck; D. Orlandi; G. Plante; R. Santorelli; J. M. F. dos Santos; P. Shagin; T. Shutt; P. Sorensen; S. Schulte; E. Tatananni; C. Winant; M. Yamashita

2010-01-01

387

Identification of the components of aldoses in a tautomeric equilibrium mixture as their trimethylsilyl ethers by capillary gas chromatography  

Microsoft Academic Search

Equilibrium tautomers of aldopentoses (arabinose, ribose, xylose and lyxose) and aldohexones (allose, altrose, gulose, idose and talose) have been analyzed as their trimethyl-silyl ethers by capillary GC. Pentoses were separated on SE-54 and hexoses on OV-225. The four components of the tautomer equilibrium mixture have been identified using GC\\/MS and NMR data.

M. Paez; I. Martínez-Castro; J. Sanz; A. Olano; A. Garcia-Raso; F. Saura-Calixto

1987-01-01

388

The influence of different volume ratios of He and Ar in shielding gas mixture on the power waste parameters for Nd:YAG and CO2 laser welding  

NASA Astrophysics Data System (ADS)

In this paper, we numerically solve the Saha equations to drive the number densities of electrons and ions, the degrees of ionization of the plasma as well as the refractive indices and the inverse Bremsstrahlung absorption coefficients as a function of temperature for a variety of volume ratios of the (He+Ar) mixtures. Furthermore, the heat transfer equation was solved to determine the plasma temperature. The effect of shielding gas volume ratios on the power waste parameters was estimated during long pulse Nd:YAG and CW CO2 laser welding accompanying the experimental verification.

Hosseini Motlagh, N. S.; Parvin, P.; Jandaghi, M.; Torkamany, M. J.

2013-12-01

389

Effects of hydrogen dilution of silane\\/methane gas mixtures on growth and structure of aSi 1?xC x:H alloys  

Microsoft Academic Search

In this paper we have studied amorphous hydrogenated silicon-carbon, a-Si1?xCx:H, films grown by ultra high vacuum plasma enhanced chemical vapor deposition in undiluted and hydrogen diluted SiH4+CH4 gas mixtures, having energy gap in the range 2.1–3.2 eV. The films have been characterized in optical properties by transmittance-reflectance spectroscopy. The elemental composition has been determined by Rutherford back-scattering and elastic recoil

F. Demichelis; F Giorgis; C. F Pirri

1995-01-01

390

A plan for directional dark matter sensitivity in high-pressure xenon detectors through the addition of wavelength shifting gaseous molecules  

NASA Astrophysics Data System (ADS)

Xenon is an especially attractive candidate for both direct WIMP and 0??? decay searches. Although the current trend has exploited the liquid phase, the gas phase xenon offers remarkable performance advantages for: energy resolution, topology visualization, and discrimination between electron and nuclear recoils. The NEXT-100 experiment, now under construction in the Canfranc Underground Laboratory, Spain, will operate at ~ 15 bars with 100 kg of 136Xe for the 0??? decay search. We will describe recent results with small prototypes, indicating that NEXT-100 can provide about 0.5% FWHM energy resolution at the decay's Q value (2457.83 keV), as well as rejection of ?-rays with topological cuts. However, sensitivity goals for WIMP dark matter and 0??? decay searches indicate the probable need for ton-scale active masses. NEXT-100 provides the springboard to reach this scale with xenon gas. We describe a scenario for performing both searches in a single, high-pressure, ton-scale xenon gas detector, without significant compromise to either. In addition, even in a single ton-scale, high-pressure xenon gas TPC, an intrinsic sensitivity to the nuclear recoil direction may exist. This plausibly offers an advance of more than two orders of magnitude relative to current low-pressure TPC concepts. We argue that, in an era of deepening fiscal austerity, such a dual-purpose detector may be possible at acceptable cost, within the time frame of interest, and deserves our collective attention.

Gehman, V. M.; Goldschmidt, A.; Nygren, D.; Oliveira, C. A. B.; Renner, J.

2013-10-01

391

Atmospheric Krypton and Xenon Measurements from Mars Science Laboratory  

NASA Astrophysics Data System (ADS)

The heavy noble gases krypton and xenon are important tracers of planetary processes from accretion to differentiation and to atmospheric escape. Their abundance and stable isotopic ratios are also indicative of sources as well. The Sample Analysis at Mars (SAM) investigation on the Curiosity rover has measured the Martian atmosphere and reported on the volume mixing ratio of its major constituents (Mahaffy et al., 2013). Here we report the abundance and isotopic ratios of Kr and Xe in the atmosphere of Mars as obtained by semi-static operation of the SAM quadrupole mass spectrometer. Viking provided the first in situ detection of these gases (Owen et al, 1977), suggesting upper limits of 300 ppb for Kr and 80 ppb for Xe, based upon calibration gases with terrestrial isotopic abundances. The abundances of individual isotopes as well as their ratios to one another have been derived from martian meteorite samples by many investigators (e.g., Becker & Pepin, 1984; Bogard & Garrison, 1998). The SAM heavy noble gas data complement the argon isotopic data reported in Mahaffy et al., 2013. Becker, R. H., & Pepin, R. O. (1984). The case for a Martian origin of the shergottites: Nitrogen and noble gases in EETA 79001. Earth and Planetary Science Letters, 69(2), 225-242. Bogard, D. D., & Garrison, D. H. (1998). Relative abundances of argon, krypton, and xenon in the Martian atmosphere as measured in Martian meteorites. Geochimica et cosmochimica acta, 62(10), 1829-1835. Mahaffy, et al., (2013) Abundance and isotopic composition of gases in the martian atmosphere from the Curiosity rover. Science 341, 263-266 Owen, T. et al.,(1977). The composition of the atmosphere at the surface of Mars. Journal of Geophysical research, 82(28), 4635-4639.

Conrad, P. G.; Malespin, C. A.; Franz, H.; Manning, H. L.; Trainer, M. G.; Wong, M. H.; Brunner, A.; Atreya, S. K.; Pepin, R. O.; Jones, J. H.; Owen, T. C.; Mahaffy, P. R.

2013-12-01

392

Characterisation of NEXT-DEMO using xenon K$_?$ X-rays  

E-print Network

The NEXT experiment aims to observe the neutrinoless double beta decay of $^{136}$Xe in a high pressure gas TPC using electroluminescence (EL) to amplify the signal from ionization. Understanding the response of the detector is imperative in achieving a consistent and well understood energy measurement. The abundance of xenon k-shell x-ray emission during data taking has been identified as a multitool for the characterisation of the fundamental parameters of the gas as well as the equalisation of the response of the detector. The NEXT-DEMO prototype is a ~1.5 kg volume TPC filled with natural xenon. It employs an array of 19 PMTs as an energy plane and of 256 SiPMs as a tracking plane with the TPC light tube and SiPM surfaces being coated with tetraphenyl butadiene (TPB) which acts as a wavelength shifter for the VUV scintillation light produced by xenon. This paper presents the measurement of the properties of the drift of electrons in the TPC, the effects of the EL production region, and the extraction of position dependent correction constants using K$_{\\alpha}$ X-ray deposits. These constants were used to equalise the response of the detector to deposits left by gammas from $^{22}$Na.

NEXT Collaboration; D. Lorca; J. Martín-Albo; A. Laing; P. Ferrario; J. J. Gómez-Cadenas; V. Álvarez; F. I. G. Borges; M. Camargo; S. Cárcel; S. Cebrián; A. Cervera; C. A. N. Conde; T. Dafni; J. Díaz; R. Esteve; L. M. P. Fernandes; A. L. Ferreira; E. D. C. Freitas; V. M. Gehman; A. Goldschmidt; H. Gómez; D. González-Díaz; R. M. Gutiérrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; I. G. Irastorza; L. Labarga; I. Liubarsky; M. Losada; G. Luzón; A. Marí; G. Martínez-Lema; A. Martínez; T. Miller; F. Monrabal; M. Monserrate; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muñoz Vidal; M. Nebot-Guinot; D. Nygren; C. A. B. Oliveira; J. Pérez; J. L. Pérez Aparicio; J. Renner; L. Ripoll; A. Rodríguez; J. Rodríguez; F. P. Santos; J. M. F. dos Santos; L. Seguí; L. Serra; D. Shuman; A. Simón; C. Sofka; M. Sorel; J. F. Toledo; J. Torrent; Z. Tsamalaidze; J. F. C. A. Veloso; R. Webb; J. T. White; N. Yahlali

2014-07-15

393

Excimer emission from pulsed microhollow cathode discharges in xenon  

SciTech Connect

Direct current (dc) microhollow cathode discharge (MHCD) is an intense source for excimer radiation in vacuum ultraviolet at a wavelength of 172 nm in a high pressure xenon (Xe) gas. The concentration of precursors for the excimer formation, i.e., excited and ionized gas atoms, increases significantly by applying high voltage pulse onto the dc MHCD over the pulse duration range from 20 to 100 ns. The intensity of the excimer emission for the voltage pulse of 20 ns duration exceeds that of the emission intensity obtained from the same MHCD operated only in the dc mode, by one order of magnitude. In addition, the emission intensity increases by one order of magnitude over the pulse duration range from 20 to 100 ns. It can be assumed that the emission intensity of the MHCD source increases as long as the duration of the high voltage pulse is shorter than the electron relaxation time. For the high voltage pulse of 100 ns duration, the emission intensity has been found to be further enhanced by a factor of three when the gas pressure is increased from 200 to 800 mbar.

Lee, B.-J.; Nam, S. H. [Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of)] [Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of); Rahaman, H. [CSIR–CEERI Pilani, Rajasthan 333031 (India)] [CSIR–CEERI Pilani, Rajasthan 333031 (India); Iberler, M.; Jacoby, J. [Institute of Applied Physics, Goethe University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)] [Institute of Applied Physics, Goethe University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany); Frank, K. [Physics Department 1, University of Erlangen – Nuremberg, 91058 Erlangen (Germany)] [Physics Department 1, University of Erlangen – Nuremberg, 91058 Erlangen (Germany)

2013-12-15

394

Temporal changes in absolute atom densities in H2 and N2 mixture gas plasmas by surface modifications of reactor wall  

NASA Astrophysics Data System (ADS)

Real time vacuum ultraviolet absorption spectroscopic (VUVAS) measurements revealed that temporal changes in absolute atom densities in H2 and N2 mixture gas (H2/N2) plasmas were affected by the conditions of the reactor inner wall-surface made of anodically-oxidized aluminum. Depending on preceding processes prior to the H2/N2 plasma process, N and H atom densities decreased for a nitrided wall surface, while no change occurred for a hydrogenated surface. Thus, the process history was revealed in the loss-properties of atoms on the reactor wall-surfaces. Suppressing the temporal variations in the gas-phase atom density is crucially important for realizing the precise control of the material processing with a high reproducibility.

Suzuki, Toshiya; Takeda, Keigo; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru

2014-05-01

395

Design of oil-free simple turbo type 65 K/6 KW helium and neon mixture gas refrigerator for high temperature superconducting power cable cooling  

NASA Astrophysics Data System (ADS)

For the requirement of HTS facility cooling, we propose oil-free simple turbo-type refrigerator. The working gas is a helium and neon mixture. Two single-stage turbo compressors and two expansion turbines are applied to the cycle. The rotor consists of the compressor impeller, turbine impeller and driving motor, and is supported by foil type gas bearing. The refrigerator requires two rotating machines with excellent reliability and compactness, and the motor power required is 72.5 kW for a refrigeration load of 6 kW. For the cooling of power cable, sub-cooled pressurized liquid nitrogen and a circulation pump must be provided. If the estimated distance between inter-cooling stations is quite long, for example 5 km, plural refrigerators may be set up on one cooling station.

Saji, N.; Asakura, H.; Yoshinaga, S.; Ishizawa, T.; Miyake, A.; Obata, M.; Nagaya, S.

2002-05-01

396

Complex mixture analysis based on gas chromatography-mass spectrometry with time array detection using a beam deflection time-of-flight mass spectrometer.  

PubMed

A beam deflection time-of-flight mass spectrometer was developed in conjunction with an integrating transient recorder to provide time array detection, permitting high mass spectral scan file acquisition rates for complex mixture analysis by capillary gas chromatography-mass spectrometry (GC-MS). Results are presented for the analysis of a urinary organic acid mixture by GC-MS at a scan file acquisition rate of 10 scan files per second (sf/s), showing the advantages of such data collection in the deconvolution of partially resolved components. The reconstructed total ion current (RTIC) chromatogram available from data acquired at this scan file generation rate is shown to be comparable to the profile obtained from a flame ionization detector in representing the chromatography performed under identical experimental parameters. The RTIC chromatogram available from the database obtained at 10 sf/s is compared with that available from a database obtained at 1 sf/s, the latter representing that scan rate typically used with most GC-MS instruments. The advantages of the higher scan file acquisition rate in representing the chromatographic profile and in allowing mass spectral data to be obtained for components in the complex mixture that are unresolved chromatographically are discussed. PMID:1560100

Schultz, G A; Chamberlin, B A; Sweeley, C C; Watson, J T; Allison, J

1992-01-31

397

The missing modes of self-organization in cathode boundary layer discharge in xenon  

NASA Astrophysics Data System (ADS)

Self-organized pattern formation has been previously observed in cathode boundary layer discharges (CBLDs) in high-purity xenon gas at pressures ranging from about 60 Torr to atmospheric pressure. However, certain modes predicted by the COMSOL multiphysics simulation were never observed. In this paper, using the same reactor design, we managed to fine tune the discharge current into regions that were not fully explored before. Two new self-organized patterns were observed, at the verge of the extinguishing of the self-organization. One pattern was a perfect ring that was detached from the dielectric walls. The other pattern was a series elongated spots arranged along a circle. Both patterns were preferably observed at pressures ranging from 60 to 120 Torr. The observation of these patterns may open up new discussions to the self-organized pattern formation in CBLD in xenon.

Zhu, WeiDong; Niraula, Prajwal

2014-10-01

398

Inactivation factors of spore-forming bacteria using low-pressure microwave plasmas in an N2 and O2 gas mixture  

NASA Astrophysics Data System (ADS)

In this study, we investigated the inactivation characteristics of Geobacillus stearothermophilus spores under different plasma exposure conditions using low-pressure microwave plasma in nitrogen, oxygen and an air-simulated (N2:O2=4:1) gas mixture. The microwave-excited surface-wave plasma discharges were produced at low pressure by a large volume device. The directly plasma-exposed spores, up to 106 populations, were successfully inactivated within 15, 10 and 5 min of surface-wave plasma treatment using nitrogen, oxygen and an air-simulated gas mixture, respectively, as working gases within the temperature of 75 °C. The contribution of different inactivation factors was evaluated by placing different filters (e.g. a LiF plate, a quartz plate and a Tyvek® sheet) as indirect exposure of spores to the plasma. It was observed that optical emissions (including vacuum UV (VUV)/UV) play an important role in the inactivation process. To further evaluate the effect of VUV/UV photons, we placed an evacuated isolated chamber, inside which spores were set, into the main plasma chamber. The experimental results show that the inactivation time by VUV/UV photons alone, without working gas in the immediate vicinity of the spores, is longer than that with working gas. This suggests that the VUV/UV emission is responsible not only for direct UV inactivation of spores but also for generation of reactive neutral species by photoexcitation. The scanning electron microscopy images revealed significant changes in the morphology of directly plasma-exposed spores but no change in the spores irradiated by VUV/UV photons only.

Singh, M. K.; Ogino, A.; Nagatsu, M.

2009-11-01

399

Characterisation and fingerprinting of PCBs in flue gas and ash from waste incineration and in technical mixtures  

Microsoft Academic Search

Congener patterns of mono- to deca-chlorinated biphenyls (PC1–10B) were evaluated in (a) waste incineration flue gases collected in the post-combustion zone of a laboratory-scale fluidized-bed reactor, (b) ashes from two different MSW incineration plants, and (c) published data of eight Aroclor formulations.The congener patterns of the flue gases, ashes, and Aroclor mixtures clearly differed from each other, likely reflecting differences

Stina Jansson; Lisa Lundin; Roman Grabic

2011-01-01

400

Initiation of explosive processes in hydrogen-containing gas mixtures by a multijet flow of detonation products  

Microsoft Academic Search

Explosive regimes initiated by interaction of a detonation wave with a permeable screen are studied experimentally. Possible\\u000a explosive regimes that may form behind the screen are found to be detonation, deflagration-to-detonation transition, quasisteady\\u000a system consisting of the shock wave and the flame front, and decaying shock wave with the flame lagging behind it. The effect\\u000a of the mixture sensitivity and

S. V. Khomik; S. P. Medvedev; B. E. Gel’fand

2010-01-01

401

Monitoring complex trace-gas mixtures by long-path laser absorption spectrometry. [in long duration manned mission closed environments  

NASA Technical Reports Server (NTRS)

Laser-based spectrophotometric methods, which have been proposed for the detection of trace concentrations of gaseous contaminants, include Raman and passive radiometry. The paper discusses a simple long-path laser absorption method which is capable of resolving complex mixtures of closely related trace contaminants at ppm levels. A number of species were selected which are most likely to accumulate in closed environments, such as submarines or long-duration manned space flights. Absorption coefficients at CO2 laser wavelengths were measured, accurate to + 3 per cent or better, for each of these species. This data base was then used to determine the presence and concentration of the contaminants in prepared mixtures of 12 to 15 gases. Computer programs have been developed which will permit a real-time analysis of the monitored atmosphere. Minimum detectable concentrations for individual species are generally in the ppm range, and are not seriously degraded by interferences even in complex mixtures. Estimates of the dynamic range of this monitoring technique for various system configurations and comparison with other methods of analysis are discussed

Green, B. D.; Steinfeld, J. I.

1976-01-01

402

Corrosion of 310 stainless steel in H2-H2O-H2S gas mixtures: Studies at constant temperature and fixed oxygen potential  

NASA Technical Reports Server (NTRS)

Corrosion of SAE 310 stainless steel in H2-H2O-H2S gas mixtures was studied at a constant temperature of 1150 K. Reactive gas mixtures were chosen to yield a constant oxygen potential of approximately 6 x 10 to the minus 13th power/cu Nm and sulfur potentials ranging from 0.19 x 10 to the minus 2nd power/cu Nm to 33 x 10 to the minus 2nd power/cu Nm. The kinetics of corrosion were determined using a thermobalance, and the scales were analyzed using metallography, scanning electron microscopy, and energy dispersive X-ray analysis. Two corrosion regimes, which were dependent on sulfur potential, were identified. At high sulfur potentials (p sub S sub 2 less than or equal to 2.7 x 10 to the minus 2nd power/cu Nm) the corrosion rates were high, the kinetics obeyed a linear rate equation, and the scales consisted mainly of sulfide phases similar to those observed from pure sulfication. At low sulfur potentials (P sub S sub 2 less than or equal to 0.19 x 10 to the minus 2nd power/cu Nm) the corrosion rates were low, the kinetics obeyed a parabolic rate equation, and scales consisted mainly of oxide phases.

Rao, D. B.; Jacob, K. T.; Nelson, H. G.

1981-01-01

403

The effect of gas mixture of post-oxidation on structure and corrosion behavior of plasma nitrided AISI 316 stainless steel  

NASA Astrophysics Data System (ADS)

In this research, microstructure and corrosion properties of plasma nitriding and post-oxidation treated AISI 316 austenitic stainless steel have been studied. The plasma nitriding treatment was carried out at 450 °C for 5 h in a D.C. plasma setup with a gas mixture of 25% N2-75% H2 followed by post-oxidation in gas mixtures of O2/H2: 1/3, 1/5, 1/9 and 1/12 for 30 min. The treated samples were characterized by SEM, XRD and roughness testing. Potentiodynamic and cyclic polarization tests were also employed to evaluate the corrosion resistance of the samples. The results showed that plasma nitriding treatment decreases corrosion resistance of the steel substrate. However, post-oxidizing treatment improves both uniform and pitting corrosion resistances of the nitrided specimens. This effect was most pronounced by post-oxidizing at lower O2/H2 ratios due to the development of magnetite as a more dense oxide phase over the modified layer.

Karimzadeh, N.; Moghaddam, E. G.; Mirjani, M.; Raeissi, K.

2013-10-01

404

Correlations for determining thermodynamic properties of hydrogen-helium gas mixtures at temperatures from 7,000 to 35,000 K  

NASA Technical Reports Server (NTRS)

Simple relations for determining the enthalpy and temperature of hydrogen-helium gas mixtures were developed for hydrogen volumetric compositions from 1.0 to 0.7. These relations are expressed as a function of pressure and density and are valid for a range of temperatures from 7,000 to 35,000 K and pressures from 0.10 to 3.14 MPa. The proportionality constant and exponents in the correlation equations were determined for each gas composition by applying a linear least squares curve fit to a large number of thermodynamic calculations obtained from a detailed computer code. Although these simple relations yielded thermodynamic properties suitable for many engineering applications, their accuracy was improved significantly by evaluating the proportionality constants at postshock conditions and correlating these values as a function of the gas composition and the product of freestream velocity and shock angle. The resulting equations for the proportionality constants in terms of velocity and gas composition and the corresponding simple realtions for enthalpy and temperature were incorporated into a flow field computational scheme. Comparison was good between the thermodynamic properties determined from these relations and those obtained by using a detailed computer code to determine the properties. Thus, an appreciable savings in computer time was realized with no significant loss in accuracy.

Zoby, E. V.; Gnoffo, P. A.; Graves, R. A., Jr.

1976-01-01

405

Flow pattern changes influenced by variation of viscosities of a heterogeneous gas-liquid mixture flow in a vertical channel  

SciTech Connect

In the steady-state flow of a heterogeneous mixture such as an air-liquid mixture, the velocity and void fraction are space- and time-dependent parameters. These parameters are the most fundamental in the analysis and description of a multiphase flow. The determination of flow patterns in an objective way is extremely critical, since this is directly related to sudden changes in spatial and temporal changes of the random like characteristic of concentration. Flow patterns can be described by concentration signals in time, amplitude, and frequency domains. Despite the vital importance and countless attempts to solve or incorporate the flow pattern phenomena into multiphase models, it has still been a very challenging topic in the scientific community since the 1940's and has not yet reached a satisfactory solution. This paper reports the experimental results of the impact of fluid viscosity on flow patterns for two-phase flow. Two-phase flow was created in laboratory equipment using air and liquid as phase medium. The liquid properties were changed by using variable concentrations of glycerol in water mixture which generated a wide-range of dynamic viscosities ranging from 1 to 1060 MPa s. The in situ spatial concentration vs. liquid viscosity and airflow velocity of two-phase flow in a vertical ID=50.8 mm pipe were measured using two concomitant computer-aided measurement systems. After acquiring data, the in situ special concentration signals were analyzed in time (spatial concentration and RMS of spatial concentration vs. time), amplitude (PDF and CPDF), and frequency (PSD and CPSD) domains that documented broad flow pattern changes caused by the fluid viscosity and air velocity changes. (author)

Keska, Jerry K.; Hincapie, Juan; Jones, Richard [Department of Mechanical Engineering, University of Louisiana at Lafayette (United States)

2011-02-15

406

Mixture Experiments  

SciTech Connect

A mixture experiment involves combining two or more components in various proportions or amounts and then measuring one or more responses for the resulting end products. Other factors that affect the response(s), such as process variables and/or the total amount of the mixture, may also be studied in the experiment. A mixture experiment design specifies the combinations of mixture components and other experimental factors (if any) to be studied and the response variable(s) to be measured. Mixture experiment data analyses are then used to achieve the desired goals, which may include (i) understanding the effects of components and other factors on the response(s), (ii) identifying components and other factors with significant and nonsignificant effects on the response(s), (iii) developing models for predicting the response(s) as functions of the mixture components and any other factors, and (iv) developing end-products with desired values and uncertainties of the response(s). Given a mixture experiment problem, a practitioner must consider the possible approaches for designing the experiment and analyzing the data, and then select the approach best suited to the problem. Eight possible approaches include 1) component proportions, 2) mathematically independent variables, 3) slack variable, 4) mixture amount, 5) component amounts, 6) mixture process variable, 7) mixture of mixtures, and 8) multi-factor mixture. The article provides an overview of the mixture experiment designs, models, and data analyses for these approaches.

Piepel, Gregory F.

2007-12-01

407

Evidence of charge exchange pumping in calcium-xenon system  

NASA Technical Reports Server (NTRS)

Charge exchange between xenon ions and calcium atoms may produce an inversion between the 5s or 4d and 4p energy levels of the calcium ions. A low power flowing xenon plasma seeded with calcium was utilized to determine if charge exchange or electron collisions populate the 5s and 4d levels Ca(+). Line intensity ratios proportional to the density ratios n5s/n4p and n4d/n4p were measured. From the dependence of these intensity ratios on power input to the xenon plasma it was concluded that charge exchange pumping of the 5s and 4d levels predominates over electron collisional pumping of these levels. Also, by comparing intensity ratios obtained using argon and krypton in place of xenon with those obtained in xenon the same conclusion was made.

Chubb, D. L.

1973-01-01

408

Enhancing Solution-State NMR with Laser-Polarized Xenon  

NASA Astrophysics Data System (ADS)

We report measurements of the polarization transfer from laser-polarized ^129Xe to molecules in various solutions at room temperature. We have shownfootnote G. Navon, Y.-Q. Song, T. Rõõm, S. Appelt, R.E. Taylor, and A. Pines, Science 271, 1848(1996). that the nuclear dipolar couplings between xenon and protons in solution, modulated by their diffusional motion, are responsible for the transfer of the nuclear spin polarization from xenon to molecules when specific binding does not occur. However, when xenon does bind to molecules in solution-even temporarily-the coupling can be much stronger and the polarization transfer can be more efficient. We report measurements of the polarization transfer from xenon to several solutes, in particular, to ?-cyclodextrin whose coupling to xenon is found to be two orders of magnitude stronger than the diffusive couplings alone.

Goodson, B. M.; Song, Y.-Q.; Taylor, R. E.; Laws, D. D.; Pines, A.; Navon, G.

1997-03-01

409

Etching Silicon Films With Xenon Difluoride  

NASA Technical Reports Server (NTRS)

Microscopic circuit structures prepared for probing. Xenon difluoride removes relatively large amounts of silicon from integratedcircuit or solar-cell structures while leaving SiO2, Si3N4, Al2O3, and other compounds intact. In Etching Apparatus, solid XeF2 sublimated in vacuum, then allowed to flow over sample at controlled rate and pressure. Wafer etched from back to expose SiO2 and Al layers for spectroscopic analysis of SiO2/Al interface. Using XeF2 technique, silicon wafer with oxide layer reduced in thickness from standard 300 micrometer to as little as 10 nanometer without adversely affecting oxide.

Hecht, M. H.

1986-01-01

410

Xenon isotopic composition of the Mid Ocean Ridge Basalt (MORB) source  

NASA Astrophysics Data System (ADS)

Although convection models do not preclude preservation of smaller mantle regions with more pristine composition throughout Earth's history, it has been widely assumed that the moon forming giant impact likely homogenizes the whole mantle following a magma ocean that extended all the way to the bottom of the mantle. Recent findings of tungsten and xenon heterogeneities in the mantle [1,2,3,4], however, imply that i) the moon forming giant impact may not have homogenized the whole mantle and ii) plate tectonics was inefficient in erasing early formed compositional differences, particularly for the xenon isotopes. Therefore, the xenon isotope composition in the present day mantle still preserves a memory of early Earth processes. However, determination of the xenon isotopic composition of the mantle source is still scarce, since the mantle composition is overprinted by post-eruptive atmospheric contamination in basalts erupted at ocean islands and mid ocean ridges. The xenon composition of the depleted upper mantle has been defined by the gas rich sample, 2?D43 (also known as "popping rock"), from the North Atlantic (13° 469`N). However, the composition of a single sample is not likely to define the composition of the upper mantle, especially since popping rock has an "enriched" trace element composition. We will present Ne, Ar and Xe isotope data on MORB glass samples with "normal" helium isotope composition (8±1 Ra) from the Southeast Indian Ridge, the South Atlantic Ridge, the Sojourn Ridge, the Juan de Fuca, the East Pacific Rise, and the Gakkel Ridge. Following the approach of [1], we correct for syn- and post-eruptive atmosphere contamination, and determine the variation of Ar and Xe isotope composition of the "normal" MORB source. We investigate the effect of atmospheric recycling in the variation of MORB mantle 40Ar/36Ar and 129Xe/130Xe ratios, and attempt to constrain the average upper mantle argon and xenon isotopic compositions. [1] Mukhopadhyay, Nature 2012; [2] Tucker et al., EPSL (in review); [3] Moreira et al., Nature 1998 [4] Touboul et al., Science 2012.

Peto, M. K.; Mukhopadhyay, S.

2012-12-01

411

Optimisation of a laser-plasma soft X-ray source excited in a pulsed xenon jet  

SciTech Connect

A 'clean' (debris-free) pulsed soft X-ray (12.5-25 nm) source excited by nanosecond neodymium laser pulses in a pulsed xenon jet was optimised. The source efficiency in the {lambda} < 15 nm range is improved due to the weakening of photoabsorption in the peripheral regions of the gas jet in going over to the supersonic regime of xenon gas flow into vacuum, as well as due to the laser beam focusing onto the plateau edge in the radial gas density profile nearest to the observer. The source efficiency at 13.5 nm is 0.22% into a solid angle of 2{pi} sr into a 0.5 nm band. (laser plasma)

Levashov, V E; Mednikov, Konstantin N; Pirozhkov, A S; Ragozin, Evgenii N [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2006-06-30

412

The contribution of gas-phase reactions in the Pt-catalyzed conversion of ethane-oxygen mixtures  

SciTech Connect

This paper presents an analysis of the oxidative dehydrogenation of ethane on platinum-containing monoliths. The purpose of the work is to make a quantitative assessment of the extent to which homogeneous gas-phase reactions contribute to the overall conversion of the ethane. In making the analysis, extensive use is made of kinetic information obtained and compiled by A.M. Dean and associates for elementary homogeneous reaction steps and by L.D. Schmidt and associates for elementary surface reactions. A critical part of the analysis is concerned with accounting for the heat effects and for the reactor temperature gradient resulting therefrom. This is absolutely essential for meeting the objective of this investigation. The rise in temperature as the gases proceed through the reactor is responsible for a very substantial contribution of homogeneous gas-phase reactions in the chemical transformation occurring. one can view the process as a sequential one in which ethane is first oxidized on the platinum surface to CO, CO{sub 2} and H{sub 2}O in the front region of the monolith. The formation of these products causes a substantial temperature increase that drives the dehydrogenation of ethane to ethylene (and acetylene) in the gas phase. The heat required to sustain these endothermic reactions in the tail end of the reaction zone is supplied by exothermic gas-phase oxidation reactions that form additional H{sub 2}O and CO. Overall, the system can be viewed as one in which the catalyst initiates gas-phase chemistry through the acceleration of exothermic reactions at the front of the reactor which increase the downstream temperature to the point where gas-phase reactions occur readily.

Huff, M.C.; Androulakis, I.P.; Sinfelt, J.H.; Reyes, S.C.

2000-04-01

413

Development of an atmospheric dispersion model for heavier-than-air gas mixtures. Volume 2. Laboratory calm air heavy gas dispersion experiments. Final report, September 1980-May 1985  

SciTech Connect

Laboratory experimental instantaneous releases of right-circular-cylindrical volumes of heavy gas (Freon-12/air) with initial volumes ranging from 0.034 to 0.531 cu m and specific gravities ranging from 2.2 to 4.2 are described. Releases with initial height-to-diameter ratios of 0.4, 1.0, and 1.57 are reported. The heavy-gas flow field surrounding the release is described by time series of gas concentration at various radial and vertical coordinates with respect to release center. Measurements of the gravity-current velocities are determined from time-of-onset of measured gas concentration. Calm-air instantaneous heavy-gas releases are demonstrated to scale with a characteristic length cube root of V/sub i/ where V/sub i/ is the initial volume, and a characteristic time (V/sub i/ to the 1/6 power)/(sq root of the reduced gravitational acceleration). The scaled laboratory releases predict the gravity-spreading and dilution process occurring during the buoyancy-dominated flow phase of the 2000 cu/m Freon/air instantaneous releases conducted by the British Health and Safety Executive at Thorney Island, UK. The gravity spread and dilution data are used to validate the buoyancy-dominated flow submodel which is incorporated in DEGADIS, the general-purpose heavy-gas dispersion model developed for the Coast Guard.

Havens, J.A.; Spicer, T.O.

1985-05-01

414

Experimental aspects of combined NOx and SO2 removal from flue-gas mixture in an integrated wet scrubber-electrochemical cell system.  

PubMed

The objective of this work was to study the effect of some operating conditions on the simultaneous removal of NO(x) and SO2 from simulated NO-SO2-air flue-gas mixtures in a scrubber column. The gaseous components were absorbed into 6M HNO3 electrolyte in the scrubber in a counter-current mode, and were oxidatively removed by the Ag(II) mediator oxidant electrochemically generated in an electrochemical cell set-up. The integration of the electrochemical cell with the scrubber set-up ensured continuous regeneration of the Ag(II) mediator and its repeated reuse for NO(x) and SO2 removal purpose, thereby avoiding: (1) the usage of chemicals continuously for oxidation and (2) the production of secondary waste. The influences of packing material (raschig glass rings, raschig poly(vinylidene) fluoride rings, Jaeger tri-pack perfluoroalkoxy spheres), feed concentrations of NO and SO2 (100-400 ppm NO and 100-400 ppm SO2), superficial gas velocity (0.061-0.61ms(-1)) and liquid velocity (0.012-0.048 ms(-1)) were investigated. The raschig glass rings with high surface area provided highest NO removal efficiency. NO and NO(x) showed decreasing abatement at higher feed concentrations. The removal of nitrogen components was faster and also greater, when SO2 co-existed in the feed. Whereas the gas flow rate decreased the removal efficiency, the liquid flow rate increased it for NO and NOx. The flow rate effects were analyzed in terms of gas/liquid residence time and superficial liquid velocity/superficial gas velocity ratio. SO2 removal was total under all conditions. PMID:19500817

Chandrasekara Pillai, K; Chung, Sang Joon; Raju, T; Moon, Il-Shik

2009-07-01

415

High-pressure autoignition of natural gas\\/air mixtures and the problem of engine knock. Topical report  

Microsoft Academic Search

Although increases in compression ratio can improve the efficiency of most internal combustion engines, including those fueled by natural gas, the onset of engine knock provides an upper limit to the compression ratio at which the engine can be operated. The chemical factors involved in autoignition and knock in these engines are reviewed in the report and those operating parameters

C. K. Westbrook; W. J. Pitz

1987-01-01

416

Molecular Theory and Computer Simulation Studies of Natural and Synthetic Gas Mixtures. Final Report, July 1, 1991-December 31, 1993.  

National Technical Information Service (NTIS)

FTIR and FT Raman spectroscopic measurements have been shown to provide an important new technique for the study of the formation, kinetics and inhibition of gas hydrates. Important advantages of these methods are (1) being non-invasive, they enable in-si...

K. E. Gubbins

1993-01-01

417

Formation of a hydrogen plasma from an incandescently heated hydrogen-catalyst gas mixture with an anomalous afterglow duration  

Microsoft Academic Search

We report the generation of a plasma of hydrogen and certain alkali ions as recorded via EUV spectroscopy and the hydrogen Balmer and alkali line emissions in the visible range. Typically, a hydrogen plasma is generated and the emission of extreme ultraviolet light from hydrogen gas is achieved via a discharge at high voltage, a high power inductively-coupled plasma, or

Randell L. Mills; Takeyoshi Onuma; Ying Lu

2001-01-01

418

Measurements of the equations of state and spectrum of nonideal xenon plasma under shock compression  

SciTech Connect

Experimental equations of state on generation of nonideal xenon plasma by intense shock wave compression was presented in the ranges of pressure of 2-16 GPa and temperature of 31-50 kK, and the xenon plasma with the nonideal coupling parameter {Gamma} range from 0.6-2.1 was generated. The shock wave was produced using the flyer plate impact and accelerated up to {approx}6 km/s with a two-stage light gas gun. Gaseous specimens were shocked from two initial pressures of 0.80 and 4.72 MPa at room temperature. Time-resolved spectral radiation histories were recorded by using a multiwavelength channel pyrometer. The transient spectra with the wavelength range of 460-700 nm were recorded by using a spectrometer to evaluate the shock temperature. Shock velocity was measured and particle velocity was determined by the impedance matching methods. The equations of state of xenon plasma and ionization degree have been discussed in terms of the self-consistent fluid variational theory.

Zheng, J.; Gu, Y. J.; Chen, Z. Y.; Chen, Q. F. [National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, P.O. Box 919-102, Mianyang, Sichuan (China)

2010-08-15

419

Measurements of the equations of state and spectrum of nonideal xenon plasma under shock compression.  

PubMed

Experimental equations of state on generation of nonideal xenon plasma by intense shock wave compression was presented in the ranges of pressure of 2-16 GPa and temperature of 31-50 kK, and the xenon plasma with the nonideal coupling parameter ? range from 0.6-2.1 was generated. The shock wave was produced using the flyer plate impact and accelerated up to ?6?km/s with a two-stage light gas gun. Gaseous specimens were shocked from two initial pressures of 0.80 and 4.72 MPa at room temperature. Time-resolved spectral radiation histories were recorded by using a multiwavelength channel pyrometer. The transient spectra with the wavelength range of 460-700 nm were recorded by using a spectrometer to evaluate the shock temperature. Shock velocity was measured and particle velocity was determined by the impedance matching methods. The equations of state of xenon plasma and ionization degree have been discussed in terms of the self-consistent fluid variational theory. PMID:20866920

Zheng, J; Gu, Y J; Chen, Z Y; Chen, Q F

2010-08-01

420

Synthesis of ZrO{sub 2} in molten salt mixtures: Control of the evolved gas and the oxide texture  

SciTech Connect

The authors investigated a mixture of KNO{sub 3}-NaNO{sub 3}-Na{sub 2}CO{sub 3} as a reaction medium for the preparation of ZrO{sub 2}. The formation of ZrO{sub 2} in molten nitrate can be considered as an acid-base reaction in which the zirconium salt plays the role of an acid and the melt anions that of a base. The higher reactivity of the carbonate ion in comparison to that of nitrate could modify the reaction mechanism, and different physico-chemical properties of the resulting solid could be expected. Carbonate may also act as a textural modifier similarly to preparations performed in aqueous media. 20 refs.

Afanasiev, P.; Geantet, C.; Lacroix, M.; Breysse, M. [Institut de Recherches sur la Catalyse, Villeurbanne (France)] [Institut de Recherches sur la Catalyse, Villeurbanne (France)

1996-08-01

421

Raman spectroscopic characterization of gas mixtures. II. Quantitative composition and pressure determination of the CO2-CH4 system  

USGS Publications Warehouse

Raman spectral parameters were determined for the v1 band of CH4 and the v1 and 2v2 bands (Fermi diad) of CO2 in pure CO2 and CO2-CH4 mixtures at pressures up to 700 bars and room temperature. Peak position, area, height, and width were investigated as functions of pressure and composition. The peak positions of the CH4 and CO2 bands shift to lower relative wavenumbers as fluid pressure is increased. The peak position of the lower-wavenumber member of the Fermi diad for CO2 is sensitive to fluid composition, whereas the peak positions of the CH4 band and the upper Fermi diad member for CO2 are relatively insensitive in the CO2-CH4 system. The magnitude of the shifts in each of the three peak positions (as a function of pressure) is sufficient to be useful as a monitor of fluid pressure. The relative molar proportions in a CO2-CH4 mixture may be determined from the peak areas: the ratio of the peak areas of the CH4 band and the CO2 upper Fermi diad member is very sensitive to composition, whereas above about 100 bars, it is insensitive to pressure. Likewise, the peak height ratio is very sensitive to composition but also to fluid pressure. The individual peak widths of CO2 and CH4, as well as the ratios of the widths of the CH4 peak to the CO2 peaks are a sensitive function of pressure and, to a lesser extent, composition. Thus, upon determination of fluid composition, the peak width ratios may be used as a monitor of fluid pressure. The application of these spectral parameters to a suite of natural CO2-CH4 inclusions has yielded internally-consistent, quantitative determinations of the fluid composition and density.

Seitz, J. C.; Pasteris, J. D.; Chou, I. -M.

1996-01-01

422

Simultaneous quantification of Aroclor mixtures in soil samples by gas chromatography/mass spectrometry with solid phase microextraction using partial least-squares regression.  

PubMed

Multivariate partial least-squares (PLS) method was applied to the quantification of two complex polychlorinated biphenyls (PCBs) commercial mixtures, Aroclor 1254 and 1260, in a soil matrix. PCBs in soil samples were extracted by headspace solid phase microextraction (SPME) and determined by gas chromatography/mass spectrometry (GC/MS). Decachlorinated biphenyl (deca-CB) was used as internal standard. After the baseline correction was applied, four data representations including extracted ion chromatograms (EIC) for Aroclor 1254, EIC for Aroclor 1260, EIC for both Aroclors and two-way data sets were constructed for PLS-1 and PLS-2 calibrations and evaluated with respect to quantitative prediction accuracy. The PLS model was optimized with respect to the number of latent variables using cross validation of the calibration data set. The validation of the method was performed with certified soil samples and real field soil samples and the predicted concentrations for both Aroclors using EIC data sets agreed with the certified values. The linear range of the method was from 10?gkg(-1) to 1000?gkg(-1) for both Aroclor 1254 and 1260 in soil matrices and the detection limit was 4?gkg(-1) for Aroclor 1254 and 6?gkg(-1) for Aroclor 1260. This holistic approach for the determination of mixtures of complex samples has broad application to environmental forensics and modeling. PMID:25216382

Zhang, Mengliang; Harrington, Peter de B

2015-01-01

423

129Xe NMR as a probe of the dynamics of gas confined in porous Vycor.  

PubMed

We use 129Xe NMR to probe the diffusion of xenon gas in the porous network of Vycor glass, by monitoring its relaxation properties. When the mean free path of the diffusing gas is larger than the pore size (Knudsen conditions), both 129Xe chemical shifts and relaxation rates are sensitive to the confinement of xenon gas within a porous solid. The influence of both temperature and xenon pressure are recorded on the 129Xe chemical shifts and relaxation rates, in order to characterise the xenon/Vycor interactions. Monte Carlo (MC) and Molecular Dynamics (MD) simulations, using a numerical model of Vycor, are required to interpret the relaxation properties of xenon. MD simulations clearly establish the occurrence of confined diffusion of xenon within Vycor, related to the geometry of this porous media. This work shows the potentiality of NMR relaxation to obtain dynamical information on the diffusion within porous media. PMID:8970126

Pasquier, V; Levitz, P; Tinet, D; Delville, A

1996-01-01

424

Oxidation-chlorination of binary Ni-Cr alloys in flowing Ar-O2-Cl2 gas mixtures at 1200 K  

NASA Technical Reports Server (NTRS)

Nickel-chromium alloys are resistant to oxidation because of the selective oxidation of chromium to form a protective Cr2O3 scale. In chlorine-containing environments, volatile corrosion products can also be formed. The mixed oxidation-chlorination of Ni-4.5Cr, Ni-13.8Cr, and Ni-26.5Cr (by weight) alloys in Ar-O2-Cl2 gas mixtures is investigated using thermogravimetric analysis and atmospheric-pressure-sampling mass spectrometry, followed by examination of the corrosion products using scanning electron microscopy and X-ray diffraction analysis. The overall kinetics of the corrosion are affected by the relative amounts of oxides and chlorides formed and the composition of the oxide corrosion products.

Mcnallan, M. J.; Lee, Y. Y.; Chang, Y. W.; Jacobson, N. S.; Doychak, J.

1991-01-01

425

Development of vinylic and acetylenic functionalized structures based on high permeable glassy polymers as membrane materials for gas mixtures separation  

NASA Astrophysics Data System (ADS)

There are several challenging separation problems in industries which can be solved with the help of membrane technologies. It is the case for instance of the purification of gas energy carriers (i.e. H2, CH4) from CO2 as well as the CO2 recovery from flue gas. Glassy polymers containing trimethylsilyl residues like poly(1-trimethylsilyl-1-propyne) [PTMSP] and polyvinyltrimethylsilane [PVTMS] are known to exhibit good membrane properties for gas separation. This paper reports two ways of improving their performances based on the controlled introduction of selective groups - alkyl imidazomium salts (C4I) and polyethyleneglycol (M-PEG)- able to enhance CO2 selectivity. CO2 Isotherm sorption data and permeability measurements have shown that the membrane performances could be significantly improved when C4I and M-PEG were introduced as residues covalently bounded to the main polymer chain. Moreover the introduced bromine reactive centres could also be used to induce chemical crosslinking giving rise to more resistant and stable membranes to organic vapours. With the C4I groups, the CO2 sorption could be enhanced by a factor 4.4.

Roizard, D.; Kiryukhina, Y.; Masalev, A.; Khotimskiy, V.; Teplyakov, V.; Barth, D.

2013-03-01

426

On the effect of gas mixture non-homogeneity and pre-ignition turbulence on gas explosions in high density congested industrial facilities  

Microsoft Academic Search

The consequences of vapour cloud explosions are dependent on many factors, such as gas cloud size, fuel reactivity, ignition location, degree of congestion and degree of confinement. In case of a realistic release there are, however, two additional factors that affect the outcome of an explosion, viz. turbulence generated by the release itself or by wind and the non-homogeneity of

Kees van Wingerden; Brian Wilkins

427

Quantification of complex polycyclic aromatic hydrocarbon mixtures in standard reference materials using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.  

PubMed

This research is the first to quantify complex PAH mixtures in NIST SRMs using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/ToF-MS), with and without extract cleanup, and reports previously unidentified PAH congeners in the NIST SRMs. We tested a novel, high orthogonality GC column combination (LC-50×NSP-35), as well as with a commonly used column combination (Rtx-5ms×Rxi-17) for the quantification of a complex mixture of 85 different PAHs, including parent (PAHs), alkyl- (MPAHs), nitro- (NPAHs), oxy- (OPAHs), thio- (SPAHs), bromo- (BrPAHs), and chloro-PAHs (ClPAHs) in extracts from two standard reference materials: NIST SRM1650b (diesel particulate matter), with cleanup and NIST SRM1975 (diesel particulate extract), with and without extract cleanup. The LC-50×NSP-35 column combination resulted in an average absolute percent difference of 33.8%, 62.2% and 30.8% compared to the NIST certified PAH concentrations for NIST SRM1650b, NIST SRM1975 with cleanup and NIST SRM1975 without cleanup, while the Rtx-5ms×Rxi-17 resulted in an absolute percent difference of 38.6%, 67.2% and 79.6% for NIST SRM1650b, NIST SRM1975 with cleanup and NIST SRM1975 without cleanup, respectively. This GC×GC/ToF-MS method increases the number of PAHs detected and quantified in complex environmental extracts using a single chromatographic run. Without clean-up, 7 additional compounds were detected and quantified in NIST SRM1975 using the LC-50×NSP-35 column combination. These results suggest that the use of the LC-50×NSP-35 column combination in GC×GC/ToF-MS not only results in better chromatographic resolution and greater orthogonality for the separation of complex PAH mixtures, but can also be used for the accurate quantification of complex PAH mixtures in environmental extracts, such as diesel particulate matter, without silica gel cleanup. PMID:23932031

Manzano, Carlos; Hoh, Eunha; Simonich, Staci L Massey

2013-09-13

428

Viscosity of Xenon Examined in Microgravity  

NASA Technical Reports Server (NTRS)

Why does water flow faster than honey? The short answer, that honey has a greater viscosity, merely rephrases the question. The fundamental answer is that viscosity originates in the interactions between a fluid s molecules. These interactions are so complicated that, except for low-density gases, the viscosity of a fluid cannot be accurately predicted. Progress in understanding viscosity has been made by studying moderately dense gases and, more recently, fluids near the critical point. Modern theories predict a universal behavior for all pure fluids near the liquid-vapor critical point, and they relate the increase in viscosity to spontaneous fluctuations in density near this point. The Critical Viscosity of Xenon (CVX) experiment tested these theories with unprecedented precision when it flew aboard the Space Shuttle Discovery (STS-85) in August 1997. Near the critical point, xenon is a billion times more compressible than water, yet it has about the same density. Because the fluid is so "soft," it collapses under its own weight when exposed to the force of Earth s gravity - much like a very soft spring. Because the CVX experiment is conducted in microgravity, it achieves a very uniform fluid density even very close to the critical point. At the heart of the CVX experiment is a novel viscometer built around a small nickel screen. An oscillating electric field forces the screen to oscillate between pairs of electrodes. Viscosity, which dampens the oscillations, can be calculated by measuring the screen motion and the force applied to the screen. So that the fluid s delicate state near the critical point will not be disrupted, the screen oscillations are set to be both slow and small.

Zimmerli, Gregory A.; Berg, Robert F.; Moldover, Michael R.

1999-01-01