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1

Application of Xenon in Gas Mixture for Drift Proportional Chambers.  

National Technical Information Service (NTIS)

A method for increasing the gas amplification coefficient in drift proportional chambers at the expense of using a gas mixtures with xenon additions is considered. One of such mixtures comprises 86% Ar + 7% CO sub 2 + 7% Xe. The main Advantages of such mi...

V. K. Gorbunov V. A. Krasnov A. B. Kurepin V. I. Razin A. I. Reshetin

1979-01-01

2

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

3

Physiologic implications of adding small amounts of carbon dioxide to the gas mixture during inhalation of xenon  

Microsoft Academic Search

In addition to being a physiologically active tracer of CBF, xenon (Xe) in subanesthetic concentrations produces a relatively mild lowering of carbon dioxide (CO2) in the blood and elevation of transcranial Doppler (TCD) velocity. The addition of small concentrations of CO2 (0.4–1.2%) to the inhaled mixture produced no measurable effect on end tidal (Pet) CO2 or TCD velocity. Cerebral blood

E. C. Marks; H. Yonas; M. H. Sanders; J. T. Love; C. Maxwell; S. Schimmerman

1992-01-01

4

Description and commissioning of NEXT-MM prototype: first results from operation in a Xenon-Trimethylamine gas mixture  

NASA Astrophysics Data System (ADS)

A technical description of NEXT-MM and its commissioning and first performance is reported. Having an active volume of ~ 35 cm drift × 28 cm diameter, it constitutes the largest Micromegas-read TPC operated in Xenon ever constructed, made by a sectorial arrangement of the 4 largest single wafers manufactured with the Microbulk technique to date. It is equipped with a suitably pixelized readout and with a sufficiently large sensitive volume ( ~ 23 l) so as to contain long ( ~ 20 cm) electron tracks. First results obtained at 1 bar for Xenon and Trymethylamine (Xe-(2%)TMA) mixture are presented. The TPC can accurately reconstruct extended background tracks. An encouraging full-width half-maximum of 11.6 % was obtained for ~ 29 keV gammas without resorting to any data post-processing.

Álvarez, V.; Aznar, F.; Borges, F. I. G. M.; Calvet, D.; Cárcel, S.; Castel, J.; Cebrián, S.; Cervera, A.; Conde, C. A. N.; Dafni, T.; Dias, T. H. V. T.; Díaz, J.; Druillole, F.; Egorov, M.; Esteve, R.; Evtoukhovitch, P.; Fernandes, L. M. P.; Ferrario, P.; Ferreira, A. L.; Ferrer-Ribas, E.; Freitas, E. D. C.; Gehman, V. M.; Gil, A.; Giomataris, I.; Goldschmidt, A.; Gómez, H.; Gómez-Cadenas, J. J.; González-Díaz, D.; Gutiérrez, R. M.; Hauptman, J.; Hernando Morata, J. A.; Herrera, D. C.; Iguaz, F. J.; Irastorza, I. G.; Jinete, M. A.; Labarga, L.; Laing, A.; Le Coguie, A.; Liubarsky, I.; Lopes, J. A. M.; Lorca, D.; Losada, M.; Luzón, G.; Marí, A.; Martín-Albo, J.; Martínez, A.; Martínez-Lema, G.; Miller, T.; Moiseenko, A.; Mols, J. P.; Monrabal, F.; Monteiro, C. M. B.; Mora, F. J.; Moutinho, L. M.; Muñoz Vidal, J.; Natal da Luz, H.; Navarro, G.; Nebot-Guinot, M.; Nygren, D.; Oliveira, C. A. B.; Palma, R.; Pérez, J.; Pérez Aparicio, J. L.; Renner, J.; Ripoll, L.; Rodríguez, A.; Rodríguez, J.; Santos, F. P.; dos Santos, J. M. F.; Segui, L.; Serra, L.; Shuman, D.; 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. T.; Yahlali, N.

2014-03-01

5

Preliminary performance of a 4.97-inch radial turbine operating in a Brayton power system with a helium-xenon gas mixture  

NASA Technical Reports Server (NTRS)

The performance characteristics of the Brayton-rotating-unit's 4.97-inch radial turbine were investigated with the turbine part of a power conversion system. The following system parameters were varied: turbine inlet temperature from 1200 to 1600 F, compressor inlet temperature from 60 to 120 F, compressor outlet pressure from 20 to 45 psia, and shaft speed from 90-110 percent of rated speed (36000 rpm). The working fluid of the system was a gas mixture of helium-xenon with a nominal molecular weight of 83.8. Test results indicate that changes in system conditions have little effect on the turbine efficiency. At the design turbine inlet temperature of 1600 F and compressor inlet temperature of 80 F, an average turbine efficiency of 91 percent was obtained.

Leroy, M. J., Jr.; Ream, L. W.; Curreri, J. S.

1971-01-01

6

Purification of krypton-xenon mixture from fluorine-containing gases  

NASA Astrophysics Data System (ADS)

Active alumina was used to purify krypton-xenon mixtures from fluorine-containing gases (tetrafluoromethane and sulfur hexafluoride). At 580°C, the admixtures are converted into aluminum trifluoride, with their content in the test gas mixture reducing from hundreds of ppm to 0.1 ppm or even below.

Adamov, V. S.; Yatkin, V. A.

2007-06-01

7

The effect of reusing laser gas on the fission-fragment pumped 1.73 {mu}m atomic xenon laser output  

SciTech Connect

Fission-fragment pumped 1.73 {mu}m atomic xenon laser output was measured without changing the laser gas mixture before each reactor pulse. For a Ar/Xe gas mixture at 260 Torr and 0.3 percent xenon, no degradation in laser output was noted for five reactor pulses.

Hebner, G.A.

1994-08-01

8

Purification of gas mixtures  

Microsoft Academic Search

The invention concerns a process for the purification of a hydrogen-containing gas mixture comprising up to 45% by volume of hydrogen, together with carbon oxides, hydrogen cyanide and impurities including nitrogen oxides and\\/or oxygen. The process comprises passing the gas over a sulphur-resistant hydrogenation catalyst at a temperature of from 120 to 250\\/sup degrees\\/ C and at a pressure of

A. D. Engelbrecht; G. J. Houten

1982-01-01

9

Numerical model of an ac plasma display panel cell in neon-xenon mixtures  

Microsoft Academic Search

We present a self-consistent 1D model of the discharge initiated in an ac plasma display panel cell. The model is based on a two-moments fluid description of electron and ion transport, coupled with Poisson’s equation, and with a set of kinetic equations characterizing the evolution of the population of excited states leading to UV emission in neon-xenon mixtures. Results are

J. Meunier; Ph. Belenguer; J. P. Boeuf

1995-01-01

10

Experimental determination of tetrafluoromethane and hexafluoroethane accumulation in khrom-3 krypton–xenon mixture producing equipment  

Microsoft Academic Search

Experimental data are provided on perfluorocarbon accumulation from atmospheric air in an industrial facility in Ukraine in\\u000a the process of air treatment in a modern air-fractionating plant with production of krypton–xenon mixture. Comparison of the\\u000a obtained data with the calculated values supports the proposition put forward by these authors regarding the crucial contribution\\u000a of adsorption processes to the final outcome

V. L. Bondarenko; N. P. Losyakov; V. B. Vorotyntsev; V. A. Mamrenko; Ya. V. Dzyuzyura; A. A. Vinnik

2010-01-01

11

Krypton assay in xenon at the ppq level using a gas chromatographic system and mass spectrometer  

NASA Astrophysics Data System (ADS)

We have developed a new method to measure krypton traces in xenon at unprecedented low concentrations. This is a mandatory task for many near-future low-background particle physics detectors. Our system separates krypton from xenon using cryogenic gas chromatography. The amount of krypton is then quantified using a mass spectrometer. We demonstrate that the system has achieved a detection limit of 8 ppq (parts per quadrillion) and present results of distilled xenon with krypton concentrations below 1 ppt.

Lindemann, Sebastian; Simgen, Hardy

2014-02-01

12

Optical absorption and fluorescence studies in high pressure cesium-xenon mixtures  

Microsoft Academic Search

The pressure and temperature dependent absorption and fluorescence spectra of the cesium-xenon (CsXe) molecule have been examined. In contrast to previous investigations of the alkali-rare gas molecules, cesium atomic states that have weakly allowed optical transitions have been studied and have been shown to form excimer levels that are attractive for application as potential dissociation lasers. In particular, the (Cs[7^{2}S]Xe)*

J. G. Eden; B. E. Cherrington; J. T. Verdeyen

1976-01-01

13

Systematic error in isotopic analysis of noble gas mixtures  

Microsoft Academic Search

Analyses of known standard mixtures of helium-neon, helium-argon, and helium-xenon, show significant biases in measured ratio which change with sample (inlet) pressure. Bias magnitude appears dependent on component partial pressure and not total sample pressure. Quantitative gas analysis assumes a linear relationship between measured ion current, I\\/sub i\\/, and partial pressure, PP\\/sub i\\/, of a corresponding component in the inlet

Ellefson

1981-01-01

14

A xenon gas proportional scintillation counter with a UV-sensitive large-area avalanche photodiode  

Microsoft Academic Search

The performance characteristics of a xenon gas proportional scintillation counter comprising a large-area avalanche photodiode with enhanced ultraviolet sensitivity were evaluated. By integrating the photodiode within the xenon gas envelope of the scintillator, the intervening quartz window was eliminated. Energy resolutions of 7.8% and 4.4% were measured for 5.9- and 22.1-keV X-rays, respectively. The results demonstrate that large-area avalanche photodiodes

J. A. M. Lopes; J. M. F. dos Santos; R. E. Morgado; C. A. N. Conde

2001-01-01

15

Investigations of Buffer-Gases Role in Xenon and Halogen Excimer Mixtures  

NASA Astrophysics Data System (ADS)

Excimer- is an acronym in use for the excited dimmer, molecule which does not exist in the ground state but only in an excited state. This paper presents the role of the buffer-gas atoms (Ar, Ne, He), in the (Cl2/I2 Xe) excimer radiation emission mechanisms. The same buffer-gas produced a different effect on the excimer emission intensity: the neon and argon addition to xenon/chlorine/iodine had a negative effect while the helium and neon addition had a positive effect. The Penning reactions play an important role in the excimer radiation generation in connection with the gas-buffer addition and the halogen ionization potential value. The measurements are performed using a dielectric barrier discharge (DBD) at moderate pressure in a panel, respectively classic coaxial geometry.

Ciobotaru, L. C.; Porosnicu, C.

2010-10-01

16

TEA laser gas mixture optimization  

SciTech Connect

The topographical plot of an optimized parameter, such as pulse energy or peak power, on the gas mixture plane is presented as a useful aid in realizing optimum mixtures of helium, carbon dioxide, and nitrogen, for operation of CO/sub 2/ TEA lasers. A method for generating such a plot is discussed and an example is shown. The potential benefits of this graphical technique are also discussed.

Lipchak, W.M.; Luck, C.F.

1982-11-01

17

Monte Carlo simulation of electron trajectories in high pressure xenon gas  

Microsoft Academic Search

A Monte Carlo calculation was developed to simulate electron trajectories in high pressure gas. In this report we discuss the calculation and some of the results relevant for the design of a high pressure xenon gas time projection chamber suitable for double beta decay experiment. Our calculation is quite general and can be extended towards a larger range of gas

M. Z. Iqbal; B. M. G. O'Callaghan; H. T. Wong

1987-01-01

18

Secondary avalanches in gas mixtures  

NASA Astrophysics Data System (ADS)

Avalanche development in gas-based detectors relies not only on direct ionisation but also on excitation of noble gas atoms. Some quencher molecules can be ionised when they collide with excited atoms, a process on which we reported earlier [1]. Alternatively, excited atoms can decay by photon emission. If these photons are insufficiently absorbed by the quencher, yet capable of ionising, then they may escape from the avalanche region and start secondary avalanches. This process, called photon feedback, leads to an over-exponential increase of the gas gain which limits the working range. In this paper, we derive photon feedback parameters from published gain measurements for several gas mixtures and fit these parameters in a model which describes their dependence on the quencher concentration and the pressure.

?ahin, Özkan; Tapan, ?lhan; Veenhof, Rob

2013-08-01

19

Nuclear excited xenon flashlamp  

SciTech Connect

The optical emissions of nuclear excited Xenon plasmas were investigated to determine basic parameters important to photolytic pumping of lasers. Gas mixtures of Helium-3 and Xenon were irradiated in the steady state mode in the University of Florida Training Reactor at neutron flux levels of about 10/sup 12//cm/sup 2/.s, generating a power density in the gas of approximately 3 milliwatts/cm/sup 3/. Optical emissions from the gas were primarily due to Xe/sub 2/* band emission at 172 nm with a few Xell lines in the visible and ir. Energy transfer from the /sup 3/He(n,p)T reaction to the Xe/sub 2/* 172 nm band was 67.0% +- 10%. High pressure gas mixtures (4 atm.) of Helium-3 and Xenon were irradiated in the pulse mode (250 ..mu..s FWHM) at the fast burst reactor at the Aberdeen Pulsed Radiation Facility at thermal neutron flux levels of about 10/sup 17//cm/sup 2/.s, generating a power density in the gas of about 1 kilowatt/cm/sup 3/. Optical emissions from the gas extended from the vacuum ultraviolet through the visible to the infrared, resembling a discharge excited lamp with a current density of about 1500 amp./cm/sup 2/. Such a lamp could pump a Neodymium YAG or liquid laser.

Cox, J.D.

1982-01-01

20

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.

Christophorou, Loucas G. (Oak Ridge, TN); McCorkle, Dennis L. (Knoxville, TN); Hunter, Scott R. (Oak Ridge, TN)

1988-01-01

21

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

22

Condensing from Vapor-Gas Mixtures.  

National Technical Information Service (NTIS)

Designing condensers for vapor-gas mixtures is far more complex than for vapors alone. This simplified design method eliminates the old trial-and-error procedures. Condensation of vapor from a vapor-gas mixture where the gas does not condense is quite dif...

F. Votta

1964-01-01

23

Physiological response of rats to delivery of helium and xenon: implications for hyperpolarized noble gas imaging  

NASA Technical Reports Server (NTRS)

The physiological effects of various hyperpolarized helium and xenon MRI-compatible breathing protocols were investigated in 17 Sprague-Dawley rats, by continuous monitoring of blood oxygen saturation, heart rate, EKG, temperature and endotracheal pressure. The protocols included alternating breaths of pure noble gas and oxygen, continuous breaths of pure noble gas, breath-holds of pure noble gas for varying durations, and helium breath-holds preceded by two helium rinses. Alternate-breath protocols up to 128 breaths caused a decrease in oxygen saturation level of less than 5% for either helium or xenon, whereas 16 continuous-breaths caused a 31.5% +/- 2.3% decrease in oxygen saturation for helium and a 30.7% +/- 1. 3% decrease for xenon. Breath-hold protocols up to 25 s did not cause the oxygen saturation to fall below 90% for either of the noble gases. Oxygen saturation values below 90% are considered pathological. At 30 s of breath-hold, the blood oxygen saturation dropped precipitously to 82% +/- 0.6% for helium, and to 76.5% +/- 7. 4% for xenon. Breath-holds longer than 10 s preceded by pre-rinses caused oxygen saturation to drop below 90%. These findings demonstrate the need for standardized noble gas inhalation procedures that have been carefully tested, and for continuous physiological monitoring to ensure the safety of the subject. We find short breath-hold and alternate-breath protocols to be safe procedures for use in hyperpolarized noble gas MRI experiments. Copyright 2000 John Wiley & Sons, Ltd.

Ramirez, M. P.; Sigaloff, K. C.; Kubatina, L. V.; Donahue, M. A.; Venkatesh, A. K.; Albert, M. S.; ALbert, M. S. (Principal Investigator)

2000-01-01

24

Searching for neutrinoless double beta decay with gas-xenon TPCs: R&D for next  

NASA Astrophysics Data System (ADS)

The search for neutrinoless double beta (??0?) decay is fundamental to probe the character of neutrinos and to determine the their mass. Several experiments in this field are using different techniques in order to achieve good energy resolution (<= 1%), very low background contamination (~ 10-4 counts/(keV.kg. y)) and large target mass (> 100 kg), that are required for that research. Natural xenon consists almost 9% of 136Xe, a possible ??0? emitter and can be easily enriched. A xenon TPC can provide the excellent energy resolution moreover, in a gaseous phase, the signature of the decay given by the two electrons can be detected reducing considerable the background. The NEXT collaboration aims to build a pressurized gaseous detector of about 100 kg of enriched xenon to be operated at the Canfranc Underground Laboratory in Spain. An extensive R&D has been carried out by the collaboration in the last two years with several prototypes, investigating both energy resolution and tracking capabilities in xenon gas.

Santorelli, Roberto; NEXT Collaboration

2012-04-01

25

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

26

Generation of soft x-ray radiation by laser irradiation of a gas puff xenon target  

NASA Astrophysics Data System (ADS)

Plasmas produced from laser-irradiated gas puff xenon targets, created by pulsed injection of xenon with high-pressure solenoid valve, offer the possibility of realizing a debrisless x-ray point source for the x-ray lithography applications. In this paper we present results of the experimental investigations on the x-ray generation from a gas puff xenon target irradiated with nanosecond high-power laser pulses produced using two different laser facilities; a Nd:glass laser operating at 1.06 micrometers , which generated 10-15 J pulses in 1 ns FWHM, and Nd:glass slab laser, producing pulses of 10 ns duration with energy reaching 12 J for a 0.53 micrometers wavelength or 20 J for 1.05 micrometers . To study the x-ray emission different x-ray diagnostic methods have been used. X-ray spectra were registered using a flat CsAP crystal spectrograph with an x-ray film or a curved KAP crystal spectrograph with a convex curvature coupled to an x-ray CCD readout detector. X-ray images have been taken using pinhole cameras with an x-ray film or a CCD array. X-ray yield was measured with the use of semiconductor detectors (silicon photodiodes or diamond photoconductors).

Fiedorowicz, Henryk; Bartnik, Andrzej; Szczurek, Miroslaw; Parys, Piotr; Celliers, Peter; Da Silva, Luiz B.; Mrowka, Stanley J.; Dane, C. Brent; Matthews, Dennis L.; Abate, Joseph A.

1995-09-01

27

Viscosity Prediction for Natural Gas Mixtures  

Microsoft Academic Search

The viscosity of multicomponent natural gas-mixtures containing hydrocarbons (C1 through C7) is predicted by modifying a previously published dilute-gas viscosity model and extending its applicability to a wide range of temperature and pressure conditions including liquid and gas states. Nitrogen, oxygen, carbon dioxide, and helium are also included among components of mixtures for which published viscosity data are available. The

Z. Shan; R. T Jacobsen; S. G. Penoncello

2001-01-01

28

Fitting formula for the injection volume of a gas chromatograph for radio-xenon sampling in the lower troposphere.  

PubMed

GC is usually used for xenon concentration and radon removal in the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty. In a gas chromatograph, the injection volume is defined to calculate the column capacity. In this paper, the injection volume was investigated and a fitting formula for the injection volume was derived and discussed subsequently. As a consequence, the xenon injection volume exponentially decreased with the column temperature increased, but exponentially increased as the flow rate increased. PMID:24659471

Shu-Jiang, Liu; Zhan-Ying, Chen; Shi-Lian, Wang; Yin-Zhong, Chang; Qi, Li; Yuan-Qing, Fan; Yun-Gang, Zhao; Huai-Mao, Jia; Xin-Jun, Zhang; Jun, Wang

2014-06-01

29

Structural Plasticity of the Phage P22 Tail Needle gp26 Probed with Xenon Gas  

SciTech Connect

The tail needle, gp26, is a highly stable homo-trimeric fiber found in the tail apparatus of bacteriophage P22. In the mature virion, gp26 is responsible for plugging the DNA exit channel, and likely plays an important role in penetrating the host cell envelope. In this article, we have determined the 1.98 A resolution crystal structure of gp26 bound to xenon gas. The structure led us to identify a calcium and a chloride ion intimately bound at the interior of alpha-helical core, as well as seven small cavities occupied by xenon atoms. The two ions engage in buried polar interactions with gp26 side chains that provide specificity and register to gp26 helical core, thus enhancing its stability. Conversely, the distribution of xenon accessible cavities correlates well with the flexibility of the fiber observed in solution and in the crystal structure. We suggest that small internal cavities in gp26 between the helical core and the C-terminal tip allow for flexible swinging of the latter, without affecting the overall stability of the protein. The C-terminal tip may be important in scanning the bacterial surface in search of a cell-envelope penetration site, or for recognition of a yet unidentified receptor on the surface of the host.

Olia, A.; Casjens, S; Cingolani, G

2009-01-01

30

Collapsing Radiative Shocks in Xenon Gas on the Omega Laser  

NASA Astrophysics Data System (ADS)

A number of astrophysical systems involve radiative shocks that collapse spatially in response to energy lost through radiation, producing thin shells believed to be Vishniac unstable. We report experiments intended to study such collapsing shocks. The Omega laser drives a thin slab of material at >100 km/s through Xe gas. Simulations predict a collapsed layer in which the density reaches 45 times initial density. X-ray backlighting techniques have yielded images of a collapsed shock compressed to <1/25 its initial thickness (45 ?m) at a speed of ˜100 km/s when the shock has traveled 1.3 mm. Optical depth before and behind the shock is important for comparison to astrophysical systems. This research was sponsored by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Research Grants DE-FG52-03NA00064, DE-FG53-2005-NA26014, and other grants and contracts.

Reighard, A. B.; Glendinning, S. G.; Knauer, J.; Bouquet, S.; Koenig, M.

2005-10-01

31

Radioxenon production through neutron irradiation of stable xenon gas  

SciTech Connect

The Spectral Deconvolution Analysis Tool (SDAT) software was developed to improve counting statistics and detection limits for nuclear explosion radionuclide measurements. SDAT utilizes spectral deconvolution spectroscopy techniques and can analyze both ?-? coincidence spectra for radioxenon isotopes and high-resolution HPGe spectra from aerosol monitors. The deconvolution algorithm of the SDAT requires a library of ?-? coincidence spectra of individual radioxenon isotopes to determine isotopic ratios in a sample. In order to get experimentally produced spectra of the individual isotopes we have irradiated enriched samples of 130Xe, 132Xe, and 134Xe gas with a neutron beam from the TRIGA reactor at The University of Texas. The samples produced were counted in an Automated Radioxenon Sampler/Analyzer (ARSA) style ?-? coincidence detector. The spectra produced show that this method of radioxenon production yields samples with very high purity of the individual isotopes for 131mXe and 135Xe and a sample with a substantial 133mXe to 133Xe ratio.

Haas, Derek A.; Biegalski, Steven R.; Foltz Biegalski, Kendra M.

2009-12-01

32

New gas mixtures suitable for rare event detection using a Micromegas-TPC detector  

NASA Astrophysics Data System (ADS)

The aim of the presented work was to develop further techniques based on a Micromegas-TPC, in order to reach a high gas gain with good energy resolution, and to search for gas mixtures suitable for rare event detection. This paper focuses on Xenon, which is convenient for the search of neutrinoless double beta decay in 136Xe, and CF4, suitable for dark matter searches and the study of solar and reactor neutrinos. Various configurations of the Micromegas plane were investigated and are described. Gains of 105 and energy resolutions of 35-65% at 6 keV have been achieved.

Ounalli, L.; Vuilleumier, J.-L.; Schenker, D.; Vuilleumier, J.-M.

2009-01-01

33

Shock wave structure in gas mixtures  

Microsoft Academic Search

The problem of shock wave structure in a binary gas mixture with largely different molecular masses is investigated on the basis of equations of two-velocity, two-temperature gas dynamics. Reference is made to results obtained in a previous study (Ruev et al., 1986), and some new results are presented. It is shown, in particular, that the equations of two-velocity, two-temperature gas

G. A. Ruev; V. M. Fomin; M. Sh. Shavaliev

1990-01-01

34

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

NASA Astrophysics Data System (ADS)

Neutrinoless double beta decay (??0?) 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 Subterráneo de Canfranc (LSC), Spain, in 2014.

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

2013-08-01

35

NEXT, high-pressure xenon gas experiments for ultimate sensitivity to Majorana neutrinos  

NASA Astrophysics Data System (ADS)

In this paper we describe an innovative type of Time Projection Chamber (TPC), which uses high-pressure xenon gas (HPXe) and electroluminescence amplification of the ionization charge as the basis of an apparatus capable of fully reconstructing the energy and topological signature of rare events. We will discuss a specific design of such HPXe TPC, the NEXT-100 detector, that will search for ??0? events using 100-150 kg of xenon enriched in the isotope 136Xe. NEXT-100 is currently under construction, after completion of an accelerated and very successful R&D period. It will be installed at the Laboratorio Subterr&aposaneo de Canfranc (LSC), in Spain. The commissioning run is expected for late 2013 or early 2014. We will also present physics arguments that suggest that the HPXe technology can be extrapolated to the next-to-next generation (e.g, a fiducial mass of 1 ton of target), which will fully explore the Majorana nature of the neutrino if the mass hierarchy is inverse.

Gómez-Cadenas, J. J.; Martín-Albo, J.; Monrabal, F.

2012-11-01

36

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

37

Iodine Mass Transfer from Xenon-Iodine Mixed Gas Bubble to Liquid Sodium Pool, (II) Development of Analytical Model  

Microsoft Academic Search

Iodine mass transfer in a xenon-iodine mixed gas bubble rising through a liquid sodium pool is analyzed on the basis of a diffusion model applied to the first short stage just after the bubble generation and a convection model applied to the successive stage. In the diffusion model, production of sodium iodide aerosols and generation of the heat caused by

Shinya MIYAHARA; Norihiko SAGAWA

1996-01-01

38

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

39

Transfer phenomena in reacting gas mixtures  

NASA Technical Reports Server (NTRS)

In considering transfer phenomena in reacting gas mixtures, the following topics are discussed: (1) dynamics of paired collisions; (2) Enskog method for solving the Boltzmann equation, taking into account inelastic collisions; (3) use of the variation principle for approximate solutions; (4) computations of inelastic bracketed expressions; (5) calculation of collision integrals; and (6) formulas for transfer coefficients.

Alekseyev, B. V.

1972-01-01

40

Initiation of Detonation in Various Gas Mixtures.  

National Technical Information Service (NTIS)

For the transition of a flame to a detonation the initiation distance, X(o), and the initiation time, t(D), have been measured for various detonable gas mixtures, and from these two quantities the Oppenheim velocity, V(Opp) = X(D)/t(D) has been obtained. ...

D. Pawel H. Vasatko H. G. Wagner P. J. Van Tiggelen

1970-01-01

41

X-ray emission of a xenon gas jet plasma diagnosed with Thomson scattering.  

PubMed

We present the results of a benchmark experiment aimed at validating recent calculation techniques for the emission properties of medium and high-Z multicharged ions in hot plasmas. We use space- and time-resolved M-shell x-ray spectroscopy of a laser-produced gas jet xenon plasma as a primary diagnostic of the ionization balance dynamics. We perform measurements of the electron temperature, electron density, and average charge state by recording simultaneous spectra of ion acoustic and electron plasma wave Thomson scattering. A comparison of the experimental x-ray spectra with calculations performed ab initio with a non-local-thermodynamic-equilibrium collisional-radiative model based on the superconfiguration formalism, using the measured plasma parameters, is presented and discussed. PMID:12006034

Chenais-Popovics, C; Malka, V; Gauthier, J-C; Gary, S; Peyrusse, O; Rabec-Le Gloahec, M; Matsushima, I; Bauche-Arnoult, C; Bachelier, A; Bauche, J

2002-04-01

42

Mesoscale Backtracking by Means of Atmospheric Transport Modeling of Xenon Plumes Measured by Radionuclide Gas Stations  

NASA Astrophysics Data System (ADS)

The monitoring of atmospheric radioactive xenon concentration is performed for nuclear safety regulatory requirements. It is also planned to be used for the detection of hypothetical nuclear tests in the framework of the Comprehensive nuclear-Test-Ban Treaty (CTBT). In this context, the French Atomic Energy Commission designed a high sensitive and automated fieldable station, named SPALAX, to measure the activity concentrations of xenon isotopes in the atmosphere. SPALAX stations were set up in Western Europe and have been operated quite continuously for three years or more, detecting principally xenon-133 and more scarcely xenon-135, xenon-133m and xenon-131m. There are around 150 nuclear power plants in the European Union, research reactors, reprocessing plants, medical production and application facilities releasing radioactive xenon in normal or incidental operations. A numerical study was carried out aiming to explain the SPALAX measurements. The mesoscale Atmospheric Transport Modelling involves the MM5 suite (PSU- NCAR) to predict the wind fields on nested domains, and FLEXPART, a 3D Lagrangian particle dispersion code, used to simulate the backward transport of xenon plumes detected by the SPALAX. For every event of detection, at least one potential xenon source has a significant efficiency of emission. The identified likely sources are located quite close to the SPALAX stations (some tens of kilometres), or situated farther (a few hundreds of kilometres). A base line of some mBq per cubic meter in xenon-133 is generated by the nuclear power plants. Peaks of xenon-133 ranging from tens to hundreds of mBq per cubic meter originate from a radioisotope production facility. The calculated xenon source terms required to obtain the SPALAX measurements are discussed and seem consistent with realistic emissions from the xenon sources in Western Europe.

Armand, P. P.; Achim, P.; Taffary, T.

2006-12-01

43

Separation of gas mixtures by supported complexes  

SciTech Connect

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 H/sub 2/ separation. Two complexes, Pd/sub 2/(dpm)/sub 2/Br/sub 2/ and Ru(CO)/sub 2/(PPh/sub 3/)/sub 3/, were examined in a bench-scale apparatus for the separation of binary (CO-N/sub 2/ or H/sub 2/-N/sub 2/) and quinary (H/sub 2/, CO, CO/sub 2/, CH/sub 4/, and N/sub 2/) mixtures. The separation of CO-N/sub 2/ was enhanced by the presence of the palladium complex in the 1,1,2-trichloroethane (TCE) solvent, especially at high gas and low liquid rates. The five-component gas mixture separation with the palladium complex in TCE provided quite unexpected results based on physical solubility and chemical coordination. The complex retained CO, while the solvent retained CO/sub 2/, CH/sub 4/, and N/sub 2/ to varying degrees. This allowed the hydrogen content to be enhanced due to its low solubility in TCE and inertness to the complex. Thus, a one-step, hydrogen separation can be achieved from gas mixtures with compositions similar to that of oxygen-blown coal gas. A preliminary economic evaluation of hydrogen separation was made for a system based on the palladium complex. The palladium system has a separation cost of 50 to 60 cents/MSCF with an assumed capital investment of $1.60/MSCF of annual capacity charged at 30% per year. This assumes a 3 to 4 year life for the complex. Starting with a 90% hydrogen feed, PSA separation costs are in the range of 30 to 50 cents/MSCF. The ruthenium complex was not as successful for hydrogen or carbon monoxide separation due to unfavorable kinetics. The palladium complex was found to strip hydrogen gas from H/sub 2/S. The complex could be regenerated with mild oxidants which removed the sulfur as SO/sub 2/. 24 refs., 26 figs., 10 tabs.

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

1986-08-01

44

Development of a Custom CRDS-based Trace Gas Analyzer for Argon and Xenon  

NASA Astrophysics Data System (ADS)

Noble liquid-based dark matter detectors are sensitive to parts-per-billion (ppb) concentrations of impurities of O2, N2, and H2O, which reduce the scintillation light yield and disrupt the ionization signal. In order to achieve an optimal light yield and collection of the ionization signal, DARKSIDE is designing a cryogenic distillation unit to achieve large quantities of depleted argon with a purity at sub-ppb levels. Critical to the success of the depleted argon dark matter detector will be the development of a system capable of analyzing these impurities at the sub-ppb level. A trace gas analyzer based on cw-Cavity Ring-Down Spectroscopy (CRDS) technology is being built at Black Hills State University that exceeds the current limits of commercially available systems. CRDS involves measuring the decay rate of the intensity of monochromatic light transmitted at the mirrors enclosing a cavity filled with a sample of gas. By comparing the decay rates for light at a resonance frequency of the contaminant of interest with that of light slightly off-resonance, a direct measurement of the amount of absorbing material (the contaminant) is obtained. Designed to measure ultra-low levels of elemental impurities, the BHSU system will be critical to such experiments as DARKSIDE and other dark matter searches based on liquid argon and xenon.

Keeter, K. J.; Durben, D.; Zehfus, M.; Galbiati, C.; Mei, D.; Sun, Y.; Alton, A.

2010-03-01

45

Investigation of the combined adsorption of krypton, xenon, and water vapor of the off-gas of atomic power stations  

Microsoft Academic Search

A radiochromatogra phic system of purifying the off-gas from the short-lived krypton, xenon, and iodine nuclides is presently used in Russian atomic power stations and in foreign atomic power stations equipped with the aid of the USSR. The basic elements of the system are filter-adsorbers filled with activated carbon and a drying unit [1-3]. Dynamic adsorption and radioactive decay in

I. E. Nakhutin; D. V. Ochkin; S. A. Tret'yak

1980-01-01

46

Micro-CT imaging of rat lung ventilation using continuous image acquisition during xenon gas contrast enhancement.  

PubMed

We measured ventilation (V) in seven anesthetized, mechanically ventilated, supine Wistar rats. Images of the whole lung were continuously acquired using a dynamic, flat-panel volumetric micro-computed tomography (micro-CT) scanner during ventilation with a xenon/oxygen (Xe-O(2)) gas mixture. Forty time-resolved volumes consisting of eighty 0.45-mm-thick slices (covering the entire lung) were acquired in 40 s, using a gantry rotation rate of one rotation per second. The animals were ventilated at a respiratory rate of 60 breaths/min, matching the gantry rotation rate, and imaged without suspending ventilation. A previously published theoretical model was modified slightly and used to calculate the whole lung ventilation from volumes of interest generated by seeded region growing. Linear regression of calculated whole lung ventilation volumes vs. expected tidal volumes yielded a slope of 1.12 +/- 0.11 (slope +/- SE) and a y-intercept of -1.56 +/- 0.42 ml (y-intercept +/- SE) with 95% confidence intervals of 0.83 to 1.40 and -2.6 to -0.5 ml, respectively. The same model was used to calculate the regional ventilation in axial slices for each animal. Voxels were fit to the model to yield a map of V, which displayed an anterior/posterior gravitational gradient of (-3.9 +/- 1.8) x 10(-6) mlxs(-1)xcm(-1) for slices immediately superior to the diaphragm and (-6.0 +/- 2.4) x 10(-6) mlxs(-1)xcm(-1) for slices at the midlevel of the heart (mean +/- SD). Thus continuous Xe-enhanced computed tomography enables the noninvasive determination of regional V with the temporal and spatial resolution necessary for rats. PMID:17690202

Lam, Wilfred W; Holdsworth, David W; Du, Louise Y; Drangova, Maria; McCormack, David G; Santyr, Giles E

2007-11-01

47

HDT mixtures treatment strategies by gas chromatography  

SciTech Connect

Gas phase chromatographic processes are of interest for the separation of hydrogen isotopes from an HDT mixture. For a certain quantity, they are very competitive and present several benefits. Nevertheless no active packing material allows to have simultaneously good enrichment performances for tritium production and high decontamination capabilities for HD gases. The influence of the packing material is first described in this article. Then two specific processes (TCAP and Reverse Chromatography), each well adapted to perform one target, are presented. Finally, the problematic to propose an optimized treatment scheme associating these two processes is formulated. (authors)

Laquerbe, C.; Contreras, S.; Demoment, J. [Commissariat a l'Energie Atomique - CEA/Valduc, F-21121 Is sur Tille (France)

2008-07-15

48

The narrow pulse approximation and long length scale determination in xenon gas diffusion NMR studies of model porous media  

NASA Technical Reports Server (NTRS)

We report a systematic study of xenon gas diffusion NMR in simple model porous media, random packs of mono-sized glass beads, and focus on three specific areas peculiar to gas-phase diffusion. These topics are: (i) diffusion of spins on the order of the pore dimensions during the application of the diffusion encoding gradient pulses in a PGSE experiment (breakdown of the narrow pulse approximation and imperfect background gradient cancellation), (ii) the ability to derive long length scale structural information, and (iii) effects of finite sample size. We find that the time-dependent diffusion coefficient, D(t), of the imbibed xenon gas at short diffusion times in small beads is significantly affected by the gas pressure. In particular, as expected, we find smaller deviations between measured D(t) and theoretical predictions as the gas pressure is increased, resulting from reduced diffusion during the application of the gradient pulse. The deviations are then completely removed when water D(t) is observed in the same samples. The use of gas also allows us to probe D(t) over a wide range of length scales and observe the long time asymptotic limit which is proportional to the inverse tortuosity of the sample, as well as the diffusion distance where this limit takes effect (approximately 1-1.5 bead diameters). The Pade approximation can be used as a reference for expected xenon D(t) data between the short and the long time limits, allowing us to explore deviations from the expected behavior at intermediate times as a result of finite sample size effects. Finally, the application of the Pade interpolation between the long and the short time asymptotic limits yields a fitted length scale (the Pade length), which is found to be approximately 0.13b for all bead packs, where b is the bead diameter. c. 2002 Elsevier Sciences (USA).

Mair, R. W.; Sen, P. N.; Hurlimann, M. D.; Patz, S.; Cory, D. G.; Walsworth, R. L.

2002-01-01

49

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Because xenon near the critical point will collapse under its own weight, experiments on Earth (green line) are limited as they get closer (toward the left) to the critical point. CVX in the microgravity of space (red line) moved into unmeasured territory that scientists had not been able to reach.

2001-01-01

50

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The sample cell at the heart of CVX-2 will sit inside a thermostat providing three layers of insulation. The cell itself comprises a copper body that conducts heat efficiently and smoothes out thermal variations that that would destroy the xenon's uniformity. Inside the cell, the oscillating screen viscometer element is supported between two pairs of electrodes that deflect the screen and then measure screen motion.

2001-01-01

51

Noble Gas Xenon Is a Novel Adenosine Triphosphate-sensitive Potassium Channel Opener  

PubMed Central

Background Adenosine triphosphate-sensitive potassium (KATP) channels in brain are involved in neuroprotective mechanisms. Pharmacologic activation of these channels is seen as beneficial, but clinical exploitation by using classic K+ channel openers is hampered by their inability to cross the blood–brain barrier. This is different with the inhalational anesthetic xenon, which recently has been suggested to activate KATP channels; it partitions freely into the brain. Methods To evaluate the type and mechanism of interaction of xenon with neuronal-type KATP channels, these channels, consisting of Kir6.2 pore-forming subunits and sulfonylurea receptor-1 regulatory subunits, were expressed in HEK293 cells and whole cell, and excised patch-clamp recordings were performed. Results Xenon, in contrast to classic KATP channel openers, acted directly on the Kir6.2 subunit of the channel. It had no effect on the closely related, adenosine triphosphate (ATP)-regulated Kir1.1 channel and failed to activate an ATP-insensitive mutant version of Kir6.2. Furthermore, concentration–inhibition curves for ATP obtained from inside-out patches in the absence or presence of 80% xenon revealed that xenon reduced the sensitivity of the KATP channel to ATP. This was reflected in an approximately fourfold shift of the concentration causing half-maximal inhibition (IC50) from 26 ± 4 to 96 ± 6 ?m. Conclusions Xenon represents a novel KATP channel opener that increases KATP currents independently of the sulfonylurea receptor-1 subunit by reducing ATP inhibition of the channel. Through this action and by its ability to readily partition across the blood–brain barrier, xenon has considerable potential in clinical settings of neuronal injury, including stroke.

Bantel, Carsten; Maze, Mervyn; Trapp, Stefan

2010-01-01

52

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Shear thirning will cause a normally viscous fluid -- such as pie filling or whipped cream -- to deform and flow more readily under high shear conditions. In shear thinning, a pocket of fluid will deform and move one edge forward, as depicted here.

2001-01-01

53

Improved Coward explosive triangle for determining explosibility of mixture gas  

Microsoft Academic Search

It is very important to determine the explosibility of the mixture gas in the coal mine sealed area after a gas explosion occurred. If the combustible mixture gas has high explosive tendency, the potential re-occurring explosion would cause rescue workers’ death when they proceed with their rescue operations in the accident mine. Therefore, no one is allowed to go down

Jian-wei Cheng; Sheng-qiang Yang

2011-01-01

54

Nonlinear Reflection of Sound Wave in Gas Mixture (Abstract Only).  

National Technical Information Service (NTIS)

Propagation of sound through a mixture of light gas and heavy gas is examined for the possibility of total reflection as a result of energy transfer from incident wave to reflected wave during their nonlinear interaction. The binary gas mixture is assumed...

A. M. Dykhne S. V. Pokrovskiy

1987-01-01

55

Process of removing hydrogen sulfide from gas mixtures  

Microsoft Academic Search

This patent describes a process for selectively removing hydrogen sulfide from a gas mixture. It comprises: treating a gas mixture comprising natural gas, hydrogen sulfide and carbon dioxide with an aqueous medium containing an effective amount of an inorganic water soluble metal sodium nitrite, the aqueous medium being buffered to a pH of about 5.5 or greater.

E. E. Burnes; K. Bhatia

1989-01-01

56

Pulmonary Perfusion and Xenon Gas Exchange in Rats: MR Imaging with Intravenous Injection of Hyperpolarized 129Xe1  

PubMed Central

Purpose: To develop and demonstrate a method for regional evaluation of pulmonary perfusion and gas exchange based on intravenous injection of hyperpolarized xenon 129 (129Xe) and subsequent magnetic resonance (MR) imaging of the gas-phase 129Xe emerging in the alveolar airspaces. Materials and Methods: Five Fischer 344 rats that weighed 200—425 g were prepared for imaging according to an institutional animal care and use committee—approved protocol. Rats were ventilated, and a 3-F catheter was placed in the jugular (n = 1) or a 24-gauge catheter in the tail (n = 4) vein. Imaging and spectroscopy of gas-phase 129Xe were performed after injecting 5 mL of half-normal saline saturated with 129Xe hyperpolarized to 12%. Corresponding ventilation images were obtained during conventional inhalation delivery of hyperpolarized 129Xe. Results: Injections of 129Xe-saturated saline were well tolerated and produced a strong gas-phase 129Xe signal in the airspaces that resulted from 129Xe transport through the pulmonary circulation and diffusion across the blood-gas barrier. After a single injection, the emerging 129Xe gas could be detected separately from 129Xe remaining in the blood and was imaged with an in-plane resolution of 1 × 1 mm and a signal-to-noise ratio of 25. Images in one rat revealed a matched ventilation-perfusion deficit, while images in another rat showed that xenon gas exchange was temporarily impaired after saline overload, with recovery of function 1 hour later. Conclusion: MR imaging of gas-phase 129Xe emerging in the pulmonary airspaces after intravenous injection has the potential to become a sensitive and minimally invasive new tool for regional evaluation of pulmonary perfusion and gas exchange. Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/2513081550/DC1

Driehuys, Bastiaan; Moller, Harald E.; Cleveland, Zackary I.; Pollaro, James; Hedlund, Laurence W.

2009-01-01

57

Xenon filled silicon germanium thermoelectric generators  

NASA Technical Reports Server (NTRS)

An analysis is presented that shows the desirability and feasibility of using a xenon fill in the initial stages of operation of a silicon-germanium radioisotope thermoelectric generator to be used in outer-planetary exploration. The xenon cover gas offers protection against oxidation and against material sublimation, and allows the generator to deliver required power throughout the prelaunch and launch phases. The protective mechanisms afforded by the xenon cover gas and the mechanization of a xenon supply system are also discussed.

Dewinter, F.

1972-01-01

58

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of liquid xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. Resembling a tiny bit of window screen, the oscillator at the heart of CVX-2 will vibrate between two pairs of paddle-like electrodes. The slight bend in the shape of the mesh has no effect on the data. What counts are the mesh's displacement in the xenon fluid and the rate at which the displacement dampens. The unit shown here is encased in a small test cell and capped with a sapphire windown to contain the xenon at high pressure.

2001-01-01

59

A note on the biological activity of the noble gas compound xenon trioxide.  

NASA Technical Reports Server (NTRS)

Comparison of xenon trioxide for toxicity in the few common oxidants using three bioassays. On a molar basis XeO3 and HOCl were similar, but XeO3 was less active than expected when comparisons were based on normality.

Siegel, S. M.; Smith, C. W.

1972-01-01

60

In situ measurements of krypton in xenon gas with a quadrupole mass spectrometer following a cold-trap at a temporarily reduced pumping speed  

NASA Astrophysics Data System (ADS)

A new method for measuring trace amounts of krypton in xenon using a cold trap with a residual gas analyzer has been developed, which achieves an increased sensitivity by temporarily reducing the pumping speed while expending a minimal amount of xenon. By partially closing a custom built butterfly valve between the measurement chamber and the turbomolecular pump, a sensitivity of 40 ppt has been reached. This method has been tested on an ultra-pure gas sample from Air Liquide with an unknown intrinsic krypton concentration, yielding a krypton concentration of 330±200 ppt.

Brown, E.; Rosendahl, S.; Huhmann, C.; Weinheimer, C.; Kettling, H.

2013-02-01

61

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

62

Novel Sorbent Development and Evaluation for the Capture of Krypton and Xenon from Nuclear Fuel Reprocessing Off-Gas Streams  

SciTech Connect

The release of volatile radionuclides generated during Used Nuclear Fuel reprocessing in the US will most certainly need to be controlled to meet US regulatory emission limits. A US DOE sponsored Off-Gas Sigma Team has been tasked with a multi-lab collaborative research and development effort to investigate and evaluate emissions and immobilization control technologies for the volatile radioactive species generated from commercial Used Nuclear Fuel (UNF) Reprocessing. Physical Adsorption technology is a simpler and potential economical alternative to cryogenic distillation processes that can be used for the capture of krypton and xenon and has resulted in a novel composite sorbent development procedure using synthesized mordenite as the active material. Utilizing the sorbent development procedure, INL sigma team members have developed two composite sorbents that have been evaluated for krypton and xenon capacities at ambient and 191 K temperature using numerous test gas compositions. Adsorption isotherms have been generated to predict equilibration and maximum capacities enabling modeling to support process equipment scale-up.

Troy G. Garn; Mitchell R. Greenhalgh; Jack D. Law

2013-10-01

63

Novel Sorbent Development and Evaluation for the Capture of Krypton and Xenon from Nuclear Fuel Reprocessing Off-Gas Streams  

SciTech Connect

The release of volatile radionuclides generated during Used Nuclear Fuel reprocessing in the US will most certainly need to be controlled to meet US regulatory emission limits. A US DOE sponsored Off-Gas Sigma Team has been tasked with a multi-lab collaborative research and development effort to investigate and evaluate emissions and immobilization control technologies for the volatile radioactive species generated from commercial Used Nuclear Fuel (UNF) Reprocessing. Physical Adsorption technology is a simpler and potential economical alternative to cryogenic distillation processes that can be used for the capture of krypton and xenon and has resulted in a novel composite sorbent development procedure using synthesized mordenite as the active material. Utilizing the sorbent development procedure, INL sigma team members have developed two composite sorbents that have been evaluated for krypton and xenon capacities at ambient and 191 K temperature using numerous test gas compositions. Adsorption isotherms have been generated to predict equilibration and maximum capacities enabling modeling to support process equipment scale-up.

Troy G. Garn; Mitchell R. Greenhalgh; Jack D. Law

2013-09-01

64

Chemical recognition of gases and gas mixtures with terahertz waves  

NASA Astrophysics Data System (ADS)

A time-domain chemical-recognition system for classifying gases and analyzing gas mixtures is presented. We analyze the free induction decay exhibited by gases excited by far-infrared (terahertz) pulses in the time domain, using digital signal-processing techniques. A simple geometric picture is used for the classification of the waveforms measured for unknown gas species. We demonstrate how the recognition system can be used to determine the partial pressures of an ammonia-water gas mixture.

Jacobsen, R. H.; Mittleman, D. M.; Nuss, M. C.

1996-12-01

65

Gas-Phase and Surface Reactions in Xenon Lamp-Assisted Organometallic Vapor-Phase Epitaxy of ZnSe  

NASA Astrophysics Data System (ADS)

In this paper, the influence of xenon lamp irradiation on gas-phase and surface reactions in organometallic vapor-phase epitaxy of ZnSe on GaAs is investigated. The irradiation only to the gas phase scarcely influences the growth rate, while irradiation to the growth surface is essential for growth rate enhancement. Numbers of incident photons and those of adhered molecules are found to be of the same order, i.e., most photons irradiated onto the substrate are associated with the epitaxial growth. The above experimental results strongly suggest that incident photons enhance some surface reactions, resulting in higher growth rates and lower growth temperatures compared with those reactions occuring under no irradiation.

Fujita, Shizuo; Takeuchi, Fumiyo Y.; Fujita, Shigeo

1988-11-01

66

THE RECOVERY OF URANIUM FROM GAS MIXTURE  

Microsoft Academic Search

A method of separating uranium from a mixture of uranium hexafluoride ; and other gases is described that comprises bringing the mixture into contact ; with anhydrous calcium sulfate to preferentially absorb the uranium hexafluoride ; on the sulfate. The calcium sulfate is then leached with a selective solvent for ; the adsorbed uranium. (AEC)

Jury

1964-01-01

67

Theoretical studies of pressure broadening of alkali-metal-rare-gas mixtures.  

NASA Astrophysics Data System (ADS)

Pressure broadening is investigated for alkali-metal atoms perturbed by rare gas atoms at high density. Quasi-molecular vibrational and rotational structures appear in the the far-wing spectra. Their importance to understanding energy transport in the gas and also the use of satellite structures as a diagnostic of gas conditions are explored. In the quasi-static limit, the pair-wise interacting alkali-metal atoms and rare gas atoms are treated as quasi-molecules and the far-wings of the broadened spectra are modeled as molecular radiation, calculated quantum-mechanically utilizing critically evaluated molecular data. We also extend our quantum-mechanical approach to a unified theory which can explain not only the far wings but also the core of the broadened lines. Our results are compared with experimental results for sodium-xenon gas mixtures and their relevance to high-pressure sodium lamps will be considered. This research has been carried out in collaboration with OSRAM SYLVANIA Inc. and is supported in part by the NSF.

Chung, H.-K.; Shurgalin, M.; Babb, J. F.

1999-10-01

68

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

69

New approach in direct-simulation of gas mixtures  

NASA Technical Reports Server (NTRS)

Results are reported for an investigation of a new direct-simulation Monte Carlo method by which energy transfer and chemical reactions are calculated. The new method, which reduces to the variable cross-section hard sphere model as a special case, allows different viscosity-temperature exponents for each species in a gas mixture when combined with a modified Larsen-Borgnakke phenomenological model. This removes the most serious limitation of the usefulness of the model for engineering simulations. The necessary kinetic theory for the application of the new method to mixtures of monatomic or polyatomic gases is presented, including gas mixtures involving chemical reactions. Calculations are made for the relaxation of a diatomic gas mixture, a plane shock wave in a gas mixture, and a chemically reacting gas flow along the stagnation streamline in front of a hypersonic vehicle. Calculated results show that the introduction of different molecular interactions for each species in a gas mixture produces significant differences in comparison with a common molecular interaction for all species in the mixture. This effect should not be neglected for accurate DSMC simulations in an engineering context.

Chung, Chan-Hong; De Witt, Kenneth J.; Jeng, Duen-Ren

1991-01-01

70

A nonflammable gas mixture for plastic limited streamer tubes  

Microsoft Academic Search

The gas mixtures presently used in plastic limited streamer tubes (``Iarocci tubes'' or LSTs) have a high hydrocarbon content and are very flammable when mixed with air, posing a potential safety hazard in modern large underground experiments. The SLD Warm Iron Calorimeter group has therefore made an extensive investigation of nonflammable ternary mixtures based on CO2. Ar and various hydrocarbons.

A. C. Benvenuti; L. Piemontese; A. Calcaterra; R. de Sangro; P. de Simone; I. Peruzzi; M. Piccolo; W. Busza; S. L. Cartwright; J. I. Friedman; S. Fuess; S. Gonzalez; T. Hansl-Kozanecka; H. W. Kendall; T. Lyons; L. S. Osborne; L. Rosenson; U. Schneekloth; F. E. Taylor; R. Verdier; D. Williams; J. M. Yamartino; N. Bacchetta; D. Bisello; A. Castro; M. Loreti; L. Pescara; J. Wyss; B. Alpat; R. Battiston; G. M. Bilei; R. dell'Orso; G. Mantovani; M. Pauluzzi; M. Scarlatella; L. Servoli; M. Carpinelli; R. Castaldi; C. Vannini; P. G. Verdini; R. L. Messner; R. W. Zdarko; J. R. Johnson

1989-01-01

71

Velocity limitations in coaxial plasma gun experiments with gas mixtures  

Microsoft Academic Search

The velocity limitations found in many crossed field plasma experiments with neutral gas present were studied for binary mixtures of H2, He, N2, O2, Ne, and Ar. The apparatus used was a coaxial plasma gun with an azimuthal magnetic bias field. The discharge parameters were chosen so that the plasma was weakly ionized. In some of the mixtures it was

I. Axnaes

1976-01-01

72

Dielectric Strengths of New Gases and Gas Mixtures.  

National Technical Information Service (NTIS)

It is emphasized that the most effective gaseous dielectrics are gas mixtures with components chosen on the basis of fundamental physicochemical knowledge, especially on low-energy electron-molecule interactions. On the basis of such lnowledge, especially...

D. R. James L. G. Christophorou R. Y. Pai M. O. Pace R. A. Mathis

1978-01-01

73

Critical Viscosity of Xenon  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2001 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure that is placed inside a pressure canister. A similar canister holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (not shown) of the National Institutes of Standards and Technology, Gaithersburg, MD. This is a detail view of MSFC 0100143.

2001-01-01

74

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

75

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

76

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

77

A Decade of Xenon Chemistry  

ERIC Educational Resources Information Center

Presents reactions for the formation of xenon compounds and compounds of the other inert gases. Provides bonding and structure theories for noble gas compounds and speculates on possible applications. (GS)

Moody, G. J.

1974-01-01

78

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

79

Adsorption equilibria of binary gas mixtures on graphitized carbon black.  

PubMed

Adsorption equilibria for binary gas mixtures (methane-carbon dioxide, methane-ethane, and carbon dioxide-ethane) on the graphitized carbon black STH-2 were measured by the open flow method at 293.2 K. The experimental pressure range was (0 to 1.6) MPa. The extended Langmuir (EL) model and the ideal adsorption solution theory (IAST) have been adopted to predict the equilibria of binary gas mixtures. The results indicate that gas mixtures adsorbed on the homogeneous surface of STH-2 exhibit the nonideal behavior, which is mainly induced by adsorbate-adsorbate interactions. The real adsorption solution theory (RAST) has been used to analyze the property of the adsorbed mixtures. The activity coefficients have been correlated with the Wilson equation. The investigation demonstrates that the nonideality of adsorbed phase is completely dissimilar with the bulk liquid phase. The adsorption of the heavier component would benefit the adsorption of the lighter component. PMID:22191667

Li, Ming; Xu, Erling; Wang, Tingliang; Liu, Juan

2012-02-01

80

Xenon gas flow patterns evaluated by high-speed multi-row detector CT  

NASA Astrophysics Data System (ADS)

Regional lung ventilation can be measured via Xenon-enhanced computed tomography (Xe-CT) by determining washin (WI) and washout (WO) rates of stable Xe. It has been assumed that WI = WO, ignoring Xe solubility in blood and tissue and then other geometric isssues. We test this by measuring WO-WI in lung by Xe-CT. Also, we investigate the effect of tidal volume (TV) and end inspiratory (EI) vs end expiratory (EE) scan gating on WO and WI measurements. 3 anesthetized, supine sheep were scanned using multidetector-row computed tomography (MDCT). Imaging was gated to both EE and EI during a WI (33 breaths) and WO (20 breaths) maneuver using 55% Xe for WI and room air for WO. Time constants (TCs) of Xe WI and WO were obtained by exponential fitting. WO and WI TCs were compared: 1) apex and base 2) dependent, middle, and nondependent 3) EE and EI 4) three TVs. The vertical gradient of WO-WI showed WO > WI in dependent vs non-dependent regions. WO-WI in both dependent and nondependent region at the lung base and apex was larger when measured at EE compared to EI. As TV increases, the global WO-WI difference decreased. TV showed greater influence on WO than WI. Xe WO was longer than WI possibly reflecting Xe solubility in blood and tissue. Higher TVs and gating to EE provided greater effects on WO than WI TCs which may relate to the number of partial volumed conducting airways contributing to the regional voxel-based measures. We conclude that WO mode is more susceptible to errors caused by either xenon solubility or tidal volume than WI mode and EE scanning may more accurately reflect alveolar ventilation.

Chon, Deokiee; Beck, Ken C.; Shikata, Hidenori; Saba, Osama I.; Simon, Brett A.; Won, Chulho; Hoffman, Eric A.

2004-04-01

81

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

82

Variable hard-sphere model for gas mixture  

Microsoft Academic Search

The variable hard-sphere model of Bird, which is used in simulating molecular collisions in pure gas, is extended so that it is applicable to the collisions in gas mixture. The constant in the model is determined from the coefficient of diffusion.

Kenichi Nanbu

1990-01-01

83

Transport phenomena in a reactive quaternary gas mixture  

Microsoft Academic Search

Quaternary gas mixtures which undergo a binary and reversible chemical reaction of the type A+B?C+D are analyzed within the framework of Boltzmann equation in order to investigate the effects caused by the reactions on the transport coefficients. The gas system is considered close to chemical equilibrium, a state in which the affinity has a small value characterizing the final stage

Adriano W. Silva; Giselle M. Alves; Gilberto M. Kremer

2007-01-01

84

High severity pyrolysis of shale and petroleum gas oil mixtures  

Microsoft Academic Search

Light gas oil and heavy gas oil from Paraho shale oil and their mixtures with a petroleum light gas oil were pyrolyzed in the presence of steam at 880-900°C and contact times between 60 and 90 ms in a nonisothermal bench-scale pyrolysis reactor. Blending of petroleum LGO into the shale oil feeds provided product yields that were the weighted linear

Harry P. Leftin; David S. Newsome

1986-01-01

85

Critical Viscosity of Xenon investigators  

NASA Technical Reports Server (NTRS)

Dr. Dr. Robert F. Berg (right), principal investigator and Dr. Micheal R. Moldover (left), co-investigator, for the Critical Viscosity of Xenon (CVX/CVX-2) experiment. They are with the National Institutes of Standards and Technology, Gaithersburg, MD. The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 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 chemicals.

2001-01-01

86

Tortuosity measurement and the effects of finite pulse widths on xenon gas diffusion NMR studies of porous media  

NASA Technical Reports Server (NTRS)

We have extended the utility of NMR as a technique to probe porous media structure over length scales of approximately 100-2000 microm by using the spin 1/2 noble gas 129Xe imbibed into the system's pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We utilized Pulsed Gradient Spin Echo NMR measurements of the time-dependent diffusion coefficient, D(t), of the xenon gas filling the pore space to study further the measurements of both the pore surface-area-to-volume ratio, S/V(p), and the tortuosity (pore connectivity) of the medium. In uniform-size glass bead packs, we observed D(t) decreasing with increasing t, reaching an observed asymptote of approximately 0.62-0.65D(0), that could be measured over diffusion distances extending over multiple bead diameters. Measurements of D(t)/D(0) at differing gas pressures showed this tortuosity limit was not affected by changing the characteristic diffusion length of the spins during the diffusion encoding gradient pulse. This was not the case at the short time limit, where D(t)/D(0) was noticeably affected by the gas pressure in the sample. Increasing the gas pressure, and hence reducing D(0) and the diffusion during the gradient pulse served to reduce the previously observed deviation of D(t)/D(0) from the S/V(p) relation. The Pade approximation is used to interpolate between the long and short time limits in D(t). While the short time D(t) points lay above the interpolation line in the case of small beads, due to diffusion during the gradient pulse on the order of the pore size, it was also noted that the experimental D(t) data fell below the Pade line in the case of large beads, most likely due to finite size effects.

Mair, R. W.; Hurlimann, M. D.; Sen, P. N.; Schwartz, L. M.; Patz, S.; Walsworth, R. L.

2001-01-01

87

Apparatus for determining thermal-diffusion coefficients in gas mixtures  

Microsoft Academic Search

A description is given of the construction of, and the technique of measuring separation effects in a single-stage thermal-diffusion apparatus. For the separation analysis, use is made of the dependence of the viscosity of gas mixtures on composition. Results are presented of a determination of the coefficient of thermal diffusion of a He\\/N2 mixture in the pressure range 0. 0005–0.

L. S. Kotousov; A. V. Panyushkin

1965-01-01

88

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

89

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

90

Recent nuclear pumped laser results. [gas mixtures and laser plasmas  

NASA Technical Reports Server (NTRS)

Recent direct nuclear pumped laser research has concentrated on experiments with three gas mixtures (Ne-N2, He-Ne-O2, and He-Hg). One mixture has been made to lase and gain has been achieved with the other two. All three of these mixtures are discussed with particular attention paid to He-Hg. Of interest is the 6150-angstroms ion transition in Hg(+). The upper state of this transition is formed directly by charge transfer and by Penning ionization.

Miley, G. H.; Wells, W. E.; Akerman, M. A.; Anderson, J. H.

1976-01-01

91

Lattice Boltzmann model for thermal binary-mixture gas flows.  

PubMed

A lattice Boltzmann model for thermal gas mixtures is derived. The kinetic model is designed in a way that combines properties of two previous literature models, namely, (a) a single-component thermal model and (b) a multicomponent isothermal model. A comprehensive platform for the study of various practical systems involving multicomponent mixture flows with large temperature differences is constructed. The governing thermohydrodynamic equations include the mass, momentum, energy conservation equations, and the multicomponent diffusion equation. The present model is able to simulate mixtures with adjustable Prandtl and Schmidt numbers. Validation in several flow configurations with temperature and species concentration ratios up to nine is presented. PMID:23767654

Kang, Jinfen; Prasianakis, Nikolaos I; Mantzaras, John

2013-05-01

92

IGNITION IMPROVEMENT OF LEAN NATURAL GAS MIXTURES  

Microsoft Academic Search

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,

Jason M. Keith

2005-01-01

93

Calculation of excess potentials of binary gas mixtures  

Microsoft Academic Search

The paper presents a simple method for calculating the excess potentials of binary gas mixtures, which does not require the determination of temperature effects, but uses only data on diffusion coefficients, thermal conductivity, thermal diffusivity, and specific heat. Activity coefficients and their concentration derivatives were calculated for 13 gas mixtures (Ne-Ar, He-Ar, He-Kr, He-Xe, Ne-20-Ne-22, H2-He, CH4-CH3Cl, Ne-N2O, N2O-Kr, N2-CO2,

L. S. Kotousov; A. N. Sviridov

1977-01-01

94

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

95

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

96

Trapping of gas mixtures by amorphous water ice  

NASA Technical Reports Server (NTRS)

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.

Bar-Nun, A.; Kleinfeld, I.; Kochavi, E.; Owen, T. (Principal Investigator)

1988-01-01

97

Transport phenomena in a reactive quaternary gas mixture  

Microsoft Academic Search

Quaternary gas mixtures which undergo a binary and reversible chemical reaction of the type A+B&rlhar2;C+D are analyzed within the framework of Boltzmann equation in order to investigate the effects caused by the reactions on the transport coefficients. The gas system is considered close to chemical equilibrium, a state in which the affinity has a small value characterizing the final stage

Adriano W. Silva; Giselle M. Alves; Gilberto M. Kremer

2007-01-01

98

Xenon-Sensitized Radiolysis of Propane.  

National Technical Information Service (NTIS)

The xenon-sensitized radiolysis of propane was investigated in the presence and absence of small amounts of ion and free radical interceptors. From an analysis of mixtures of deuterated propanes and a knowledge of radical disproportionation yields in the ...

L. I. Bone L. W. Sieck J. H. Futrell

1965-01-01

99

Theory of gas sensors: response of an electrochemical sensor to multi-component gas mixtures  

Microsoft Academic Search

A first-principles model of the operation of an electrochemical metal oxide gas sensor had been previously used to analyze the response when the sensor was exposed to a simple gas mixture (e.g. O2\\/CO\\/CO2). Here, the model is extended to study the sensor response to a complex gas mixture containing two reducing gases e.g. O2\\/CO\\/CO2\\/H2\\/H2O. In a first version, it is

A. D. Brailsford; M. Yussouff; E. M. Logothetis

1996-01-01

100

Heat Conductivity of Polyatomic and Polar Gases and Gas Mixtures  

Microsoft Academic Search

A theory is presented which can be used for the practical calculation of the heat conductivity of polyatomic and polar gases and gas mixtures. For pure gases, the results are based on the Wang Chang—Uhlenbeck equations and involve no approximations, provided that a suitable definition of an internal diffusion coefficient is employed. This is compared with the known results for

L. Monchick; A. N. G. Pereira; E. A. Mason

1965-01-01

101

Process for the Removal of Sulphur Compounds from Gas Mixtures.  

National Technical Information Service (NTIS)

A process is described for the removal of sulphur compounds, especially H2S, from gas mixtures by scrubbing with a physical solvent which after the absorption of the sulphur compounds is regenerated and re-used. To improve the absorption and desorption of...

K. Baur P. Haeussinger L. Fruhstorfer H. J. Neubert

1986-01-01

102

Shock-wave structure in a gas mixture  

Microsoft Academic Search

The basic relationships for strong discontinuity and shock-wave structure in a gas mixture are developed on the basis of Struminskii's (1974) equations. Attention is given to the case when viscosity and thermal conductivity are present only in the forces of interaction between components. Results are presented for weak shock waves.

G. A. Ruev; V. M. Fomin; N. N. Ianenko

1981-01-01

103

Bobylev-Krook-Wu Modes for Multicomponent Gas Mixtures  

NASA Astrophysics Data System (ADS)

Exact invariant solutions of the spatially uniform Boltzmann equations, the so-called Bobylev-Krook-Wu modes, are presented in the explicit form for an arbitrary N-species gas mixture. The corresponding necessary and sufficient conditions imposed on the molecular parameters are formulated. The completeness of the results obtained is supported by the rigorous group analysis of the Boltzmann equations.

Grigoryev, Yu. N.; Meleshko, S. V.

1998-07-01

104

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

105

Laser beam characterization of the ATLAS RPC gas mixture  

NASA Astrophysics Data System (ADS)

A measurement of the electrons drift velocity in C 2H 2F 4-based gas mixture has been performed and results have been compared with calculations. Primary ionization is induced in the gas via double photon ionization process by mean of a pulsed Nitrogen laser. The results of the drift velocity, obtained at room temperature and normal pressure, are presented as a function of the electric field strength. To perform the measurements we used a small sized RPC prototype with a 2 mm gas gap delimited by 2mm-thick linseed-oil-treated bakelite plates with resistivity of about 1.71×10? cm at 20°C.

Chiodini, G.; Coluccia, M. R.; Gorini, E.; Grancagnolo, F.; Primavera, M.

2007-10-01

106

Approximate Thermodynamics State Relations in Partially Ionized Gas Mixtures  

SciTech Connect

In practical applications, the thermodynamic state relations of partially ionized gas mixtures are usually approximated in terms of the state relations of the pure partially ionized constituent gases or materials in isolation. Such approximations are ordinarily based on an artificial partitioning or separation of the mixture into its constituent materials, with material k regarded as being confined by itself within a compartment or subvolume with volume fraction {alpha}k and possessing a fraction {beta}k of the total internal energy of the mixture. In a mixture of N materials, the quantities {alpha}k and {beta}k constitute an additional 2N--2 independent variables. The most common procedure for determining these variables, and hence the state relations for the mixture, is to require that the subvolumes all have the same temperature and pressure. This intuitively reasonable procedure is easily shown to reproduce the correct thermal and caloric state equations for a mixture of neutral (non-ionized) ideal gases. Here we wish to point out that (a) this procedure leads to incorrect state equations for a mixture of partially ionized ideal gases, whereas (b) the alternative procedure of requiring that the subvolumes all have the same temperature and free electron density reproduces the correct thermal and caloric state equations for such a mixture. These results readily generalize to the case of partially degenerate and/or relativistic electrons, to a common approximation used to represent pressure ionization effects, and to two-temperature plasmas. This suggests that equating the subvolume electron number densities or chemical potentials instead of pressures is likely to provide a more accurate approximation even in nonideal plasma mixtures.

Ramshaw, J D

2003-12-30

107

Fast and robust gas identification system using an integrated gas sensor technology and Gaussian mixture models  

Microsoft Academic Search

Among the most serious limitations facing the success of future consumer gas identification systems are the drift problem and the real-time detection due to the slow response of most of today's gas sensors. This paper shows that the combination of an integrated sensor array and a Gaussian mixture model permits success in gas identification problems. An integrated sensor array has

Sofiane Brahim-Belhouari; Amine Bermak; Minghua Shi; Philip C. H. Chan

2005-01-01

108

Perturbation of the Maxwellian distribution in chemically reacting gas mixtures  

NASA Technical Reports Server (NTRS)

Chemically reacting gas mixtures are considered for the case in which inelastic collisions occur significantly less frequently than elastic ones. The first approximation of the general solution of the Boltzmann equation is developed and is shown to contain an additional scaler term. The concentration, the mean mass velocity, and the temperature of the mixture are determined and the rate of reaction in the first approximation is formulated. Tables are presented which give reaction rate values obtained by both the first and second approximation for different activation energies. The tables show that the first approximation is sufficient for practical purposes for calculating the reaction rate.

Alekseyev, B. V.; Yanovskiy, V. R.

1972-01-01

109

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

2011-01-04

110

Fast sound in a dense helium argon gas mixture  

NASA Astrophysics Data System (ADS)

By means of inelastic neutron scattering we measure the dynamic structure factors S( k, ?) for a dense 4He 7540Ar 25 gas mixture (total number density n = 13 nm -3, p = 370 bar) and for pure He ( n = 12.1 nm -3, p = 350 bar) at T = 160 K for wavenumbers 2 ? k ? 5 nm -1. For both samples C( k, ?) = ?2S( k, ?) shows clear maxima at the same frequency ? = c Hek with cHe = 970 m/s the sound velocity in pure He, much larger than the sound velocity cmix = 635 m/s of 4He 7540Ar 25, thus directly confirming the existence of fast sound oscillations in the mixture, due to the light He particles alone. Molecular dynamics simulations and kinetic theory calculations for corresponding Lennard-Jones and hard sphere mixtures, respectively, indicate that the experimental C( k, ?) of 4He 7540Ar 25 is almost completely due to fast sound.

Smorenburg, H. E.; Crevecoeur, R. M.; de Schepper, I. M.

1996-02-01

111

Third-harmonic generation in xenon in a pulsed jet and a gas cell  

Microsoft Academic Search

We report experimental studies of harmonic generation in Xe using a 1064 nm Nd-YAG laser. Third-harmonic conversion is observed in a positively dispersive medium, using a tight-focusing geometry. The intensity of third-harmonic generation in a gas cell varies much more steeply with the laser intensity than a cubic law. The reason for the breaking of the phase matching condition is

A. L'Huillier; L. A. Lompré; M. Ferray; X. F. Li; G. Mainfray; C. Manus

1988-01-01

112

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

113

Rapid heating of gas/small particle mixture  

SciTech Connect

The concept of using a mixture of particles and air as a medium to absorb radiative energy has been proposed for various applications. In this paper, carbon particles mixed with gas form a medium that absorbs radiation from sources such as concentrated solar energy. A single-particle, two-temperature model is used to study the transient temperature of the particle/gas mixture as it undergoes a constant pressure expansion process. The results indicate that for particles smaller than 1 ..mu..m in diameter, the surrounding air can be heated as quickly as the particles, while for particles larger than 1 mm in diameter, the air temperature stays relatively unchanged and the particles are heated to a very high temperature.

Wang, K.Y.; Yuen, W.W.

1987-05-01

114

Morphological transitions in partially gas-fluidized granular mixtures  

SciTech Connect

Experiments were conducted to investigate pattern formation during the defluidization of a partially fluidized bimodal granular mixture. Partial fluidization occurs when the system is driven at gas velocities that are insufficient to fluidize all of the constituent particles. Over time, the granular mixture evolves into a variety of patterns depending on the concentrations of large and small particles and the gas velocity. We show how vertically oriented pipes, containing large particles, grow at the interface between the fluidized and static zones. The heterogeneities in the permeability field focus the flow, causing localized fluidization, which in turn localizes the sedimentation of the large particles segregating the system. We discuss how the interplay between heterogeneities in material properties, fluid flow and fluid induced deformation may be relevant to a variety of geological processes.

Anders Nermoen; Christophe Raufaste; Simon Daniel deVillers; Espen Jettestuen; Paul Meakin; Dag Kristian Dysthe

2010-06-01

115

Plasma polymerization of an ethylene-nitrogen gas mixture  

NASA Technical Reports Server (NTRS)

A procedure has been developed whereby nitrogen can be incorporated into an organic film from an ethylene-nitrogen gas mixture using an internal electrode capacitively coupled radio frequency reactor. The presence of nitrogen has been shown directly by infrared transmittance spectra and electron spectroscopic chemical analysis data, and further indirect evidence was provided by dielectric measurements and by the reverse osmosis properties of the film. Preparation of a nitrogen containing film did not require vapor from an organic nitrogen containing liquid monomer. Some control over the bonding and stoichiometry of the polymer film was provided by the added degree of freedom of the nitrogen partial pressure in the gas mixture. This new parameter strongly affected the dielectric properties of the plasma polymerized film and could affect the reverse osmosis behavior.

Hudis, M.; Wydeven, T.

1975-01-01

116

Rapid heating of gas/small-particle mixture  

SciTech Connect

The concept of using a mixture of particles and air as a medium to absorb radiative energy has been proposed for various applications. In this paper, carbon particles mixed with gas form a medium that absorbs radiation from sources such as concentrated solar energy. A single-particle, two-temperature model is used to study the transient temperature of the particle/gas mixture as it undergoes a constant pressure expansion process. The results indicate that for particles smaller than 1 ..mu..m in diameter, the surrounding air can be heated as quickly as the particles, while for particles larger than 1 mm in diameter, the air temperature stays relatively unchanged and the particles are heated to a very high temperature. The effect of scattering from the particles is also examined, revealing that such a contribution is insignificant for small particles.

Wang, K.Y.; Yuen, W.W.

1986-02-01

117

Fast sound in a dense helium argon gas mixture  

Microsoft Academic Search

By means of inelastic neutron scattering we measure the dynamic structure factors S(k, ?) for a dense 4He7540Ar25 gas mixture (total number density n = 13 nm?3, p = 370 bar) and for pure He (n = 12.1 nm?3, p = 350 bar) at T = 160 K for wavenumbers 2 ? k ? 5 nm?1. For both samples C(k,

H. E. Smorenburg; R. M. Crevecoeur; I. M. de Schepper

1996-01-01

118

Composition dependence of ion-transport coefficients in gas mixtures  

NASA Technical Reports Server (NTRS)

Simple momentum-transfer theory for the composition dependence of ion mobilities and diffusion coefficients in gas mixtures at arbitrary field strengths is corrected and extended, and compared with a similar theory based on momentum and energy transfer, and with results based on direct solution of the Boltzmann equation by Kihara's method. Final equations are recommended for predicting composition dependences, given only results on ion mobilities and diffusion coefficients in the pure component gases.

Whealton, J. H.; Mason, E. A.; Robson, R. E.

1974-01-01

119

Composition dependence of ion transport coefficients in gas mixtures  

NASA Technical Reports Server (NTRS)

A simple momentum-transfer theory for the composition dependence of ion mobilities and diffusion coefficients in gas mixtures at arbitrary field strengths is corrected, extended, and compared with a similar theory based on momentum and energy transfer, and with results based on direct solution of the Boltzmann equation by Kihara's method. Final equations are recommended for predicting composition dependences, given only results on ion mobilities and diffusion coefficients in the pure component gases.

Whealton, J. H.; Mason, E. A.; Robson, R. E.

1973-01-01

120

Breakdown field strength of unitary attaching gases and gas mixtures  

Microsoft Academic Search

A model is presented, which yields the breakdown field strength for space-chargefree configurations and the corona onset voltage\\u000a for conditions with space charges in unitary, attaching gases and gas mixtures. It is entirely based on a physical description.\\u000a Therefore, it does not require form parameters to be adjusted by comparison with experiments. It only necessitates the knwoledge\\u000a of a set

K. P. Brand; J. Kopainsky

1979-01-01

121

Numerical simulation for explosion wave propagation of combustible mixture gas  

Microsoft Academic Search

A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and\\u000a ignition positions on the propagation law of explosion wave for hydrogen and methane-based combustible mixture gas. In the\\u000a code, Young’s technique was employed to track the interface between the explosion products and air, and combustible function\\u000a model was adopted to simulate ignition process. The

Cheng Wang; Jian-guo Ning; Tian-bao Ma

2008-01-01

122

Generation of radio frequency induced metastable xenon as a gain medium for diode pumped rare gas laser systems  

NASA Astrophysics Data System (ADS)

The pursuit of novel, hybrid methods of achieving lasing from the rare gases has recently been a topic of interest in the field of high energy laser systems. This investigation presents the construction and execution of an experimental setup designed to generate metastable xenon (Xe*) to determine its potential to perform as a high power laser gain medium in a similar capacity as the alkali metals in Diode Pumped Alkali Lasers. A capacitively coupled radio frequency discharge was used to light plasma from naturally abundant xenon, thus exciting the 6s[3/2]2 metastable state. The metastable xenon was probed with a tunable diode laser at 882.2 and 904.8 nanometers, and absorption was detected to verify the presence of Xe* atoms. The absorption profiles are reported with in-depth calculations of the isotope shift and hyperfine structure of each absorption line. Preliminary calculations for the properties of the proposed laser system are also presented.

Andreozzi, Jacqueline Marie

123

Nuclear reactor excitation of XeF laser gas mixtures  

SciTech Connect

Kinetic studies of the XeF laser system and other laser media have been studied under low-power (several kW/cc), long-pulse (100 to 200 microseconds) pumping conditions using fission-fragment pumping. Results include the measurement of fluorescence from excited states of KrF, N/sub 2//sup +/, and XeF and optical gain near 351 nm in gas mixtures containing Xe, NF/sub 3/, and a rare gas. Sandia's fast-pulse reactor facility (SPR III) was used for these experiments, in which a cell containing the gas mixtures is irradiated with thermalized neutrons. Energy deposition in the gas occurs through the interaction of energetic charged particles produced by neutron-induced fission events. Two pumping modes have been examined. One mode uses /sup 3/He as the rare gas, where charged particles from the /sup 3/He(n,p)/sup 3/H reaction excite the medium. Another mode uses fission fragments from /sup 235/U, which is coated on thin ceramic substrates, as the source of excitation. 7 refs., 10 figs.

Rice, J.K.; Hays, G.N.; Neal, D.R.; McArthur, D.A.; Alford, W.J.

1986-01-01

124

Nuclear reactor excitation of XeF laser gas mixtures  

NASA Astrophysics Data System (ADS)

Kinetic studies of the XeF laser system and other laser media have been studied under low-power (several kW/cu cm), long-pulse (100-200 microsec) pumping conditions using fission-fragment pumping. Results include the measurement of fluorescence from excited states of KrF, N2(+), and XeF and optical gain near 351 nm in gas mixtures containing Xe, NF3, and a rare gas. Sandia's fast-pulse reactor facility (SPR III) was used for these experiments, in which a cell containing the gas mixtures is irradiated with thermalized neutrons. Energy deposition in the gas occurs through the interaction of energetic charged particles produced by neutron-induced fission events. Two pumping modes have been examined. One mode uses He-3 as the rare gas, where charged particles from the He-3 (n,p) H-3 reaction excite the medium. Another mode uses fission fragments from U-235, which is coated on thin ceramic substrates, as the source of excitation.

Rice, James K.; Hays, Gerald N.; Neal, Daniel R.; McArthur, David A.; Alford, William J.

125

Magnetic resonance imaging of convection in laser-polarized xenon  

NASA Technical Reports Server (NTRS)

We demonstrate nuclear magnetic resonance (NMR) imaging of the flow and diffusion of laser-polarized xenon (129Xe) gas undergoing convection above evaporating laser-polarized liquid xenon. The large xenon NMR signal provided by the laser-polarization technique allows more rapid imaging than one can achieve with thermally polarized gas-liquid systems, permitting shorter time-scale events such as rapid gas flow and gas-liquid dynamics to be observed. Two-dimensional velocity-encoded imaging shows convective gas flow above the evaporating liquid xenon, and also permits the measurement of enhanced gas diffusion near regions of large velocity variation.

Mair, R. W.; Tseng, C. H.; Wong, G. P.; Cory, D. G.; Walsworth, R. L.

2000-01-01

126

Application of Two Phase (Liquid/Gas) Xenon Gamma-Camera for the Detection of Special Nuclear Material and PET Medical Imaging  

SciTech Connect

The McKinsey group at Yale has been awarded a grant from DTRA for the building of a Liquid Xenon Gamma Ray Color Camera (LXe-GRCC), which combines state-of-the-art detection of LXe scintillation light and time projection chamber (TPC) charge readout. The DTRA application requires a movable detector and hence only a single phase (liquid) xenon detector can be considered in this case. We propose to extend the DTRA project to applications that allow a two phase (liquid/gas) xenon TPC. This entails additional (yet minimal) hardware and extension of the research effort funded by DTRA. The two phase detector will have better energy and angular resolution. Such detectors will be useful for PET medical imaging and detection of special nuclear material in stationary applications (e.g. port of entry). The expertise of the UConn group in gas phase TPCs will enhance the capabilities of the Yale group and the synergy between the two groups will be very beneficial for this research project as well as the education and research projects of the two universities. The LXe technology to be used in this project has matured rapidly over the past few years, developed for use in detectors for nuclear physics and astrophysics. This technology may now be applied in a straightforward way to the imaging of gamma rays. According to detailed Monte Carlo simulations recently performed at Yale University, energy resolution of 1% and angular resolution of 3 degrees may be obtained for 1.0 MeV gamma rays, using existing technology. With further research and development, energy resolution of 0.5% and angular resolution of 1.3 degrees will be possible at 1.0 MeV. Because liquid xenon is a high density, high Z material, it is highly efficient for scattering and capturing gamma rays. In addition, this technology scales elegantly to large detector areas, with several square meter apertures possible. The Yale research group is highly experienced in the development and use of noble liquid detectors for astrophysics, most recently in the XENON10 experiment. The existing facilities at Yale are fully adequate for the completion of this project. The facilities of the UConn group at the LNS at Avery Point include a (clean) lab for detector development and this group recently delivered an Optical Readout TPC (O-TPC) for research in Nuclear Astrophysics at the TUNL in Duke University. The machine shop at UConn will be used (free of charge) for producing the extra hardware needed for this project including grids and frames.

McKinsey, Daniel Nicholas [Yale University] [Yale University

2013-08-27

127

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

128

Production of Samples of Individual Radioxenon Isotopes Through Neutron Irradiation of Stable Xenon Gas  

SciTech Connect

The Spectral Deconvolution Analysis Tool (SDAT) software was developed to improve counting statistics and detection limits for nuclear explosion radionuclide measurements. SDAT utilizes spectral deconvolution spectroscopy techniques and can analyze both ?-? coincidence spectra for radioxenon isotopes and high-resolution HPGe spectra from aerosol monitors. The deconvolution algorithm of the SDAT requires a library of ?-? coincidence spectra of individual radioxenon isotopes to determine isotopic ratios in a sample. In order to get experimentally produced spectra of the individual isotopes we have irradiated enriched samples of 130Xe, 132Xe, and 134Xe gas with a neutron beam from the TRIGA reactor at The University of Texas. The samples produced were counted in an Automated Radioxenon Sampler/Analyzer (ARSA) style ?-? coincidence detector. The spectra produced show that this method of radioxenon production yields samples with very high purity of the individual isotopes for 131mXe and 135Xe and a sample with a substantial 133mXe to 133Xe ratio.

Haas, Derek A.; Biegalski, Steven R.; Foltz Biegalski, Kendra M.

2008-09-23

129

Process for testing a xenon gas feed system of a hollow cathode assembly  

NASA Technical Reports Server (NTRS)

The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma, at voltages of less than 20 Volts.

Patterson, Michael J. (Inventor); Verhey, Timothy R. R. (Inventor); Soulas, George C. (Inventor)

2004-01-01

130

Superconducting cable cooling system by helium gas and a mixture of gas and liquid helium  

Microsoft Academic Search

Thermally contacting, oppositely streaming cryogenic fluid streams in the same enclosure in a closed cycle that changes from a cool high pressure helium gas to a cooler reduced pressure helium fluid comprised of a mixture of gas and boiling liquid so as to be near the same temperature but at different pressures respectively in go and return legs that are

John W

1977-01-01

131

Superconducting cable cooling system by helium gas and a mixture of gas and liquid helium  

Microsoft Academic Search

Thermally contacting, oppositely streaming cryogenic fluid streams in the same enclosure in a closed cycle that changes from a cool high pressure helium gas to a cooler reduced pressure helium fluid are comprised of a mixture of gas and boiling liquid so as to be near the same temperature but at different pressures respectively in go and return legs that

1977-01-01

132

Quantitative Fourier Transform Infrared Analysis of Gas Phase Cigarette Smoke and Other Gas Mixtures  

Microsoft Academic Search

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

Rafael Cueto; Daniel R. Church; William A. Piyor

1989-01-01

133

Developing Automated Gas Recovery System for SF6/N2 Insulation Gas Mixtures  

NASA Astrophysics Data System (ADS)

We have already three gas insulated power lines in service applying SF6/N2 gas mixtures, the two in Europe and the rest in South Asia. To cope with the global warming issue on gas insulated power apparatus, we have been investigating the recovery of SF6 from those apparatus. This paper describes an automated gas recovery method that secures SF6 gas concentration in the recovered gas at a high and desired level. The gas mixtures investigated contain 5 - 20 vol. % of SF6 in N2. We adopt a membrane method to separate the two gas species, in which two membrane separators are connected in cascade. There are several factors that affect the concentration of SF6 in the recovered gas. As the concentration greatly depends on recovery gas flow speed, we control the speed by using a piezo-valve. For driving the piezo-valve, we use a voltage regulator together with an infrared gas concentration online monitor. This link allows PID control of the SF6 gas recovery system. Successful operation results of this automated system, as well as the basic recovering characteristics of the cascaded system, are demonstrated after a brief review on gas recovery methods.

Yamamoto, Osamu; Michishita, Makoto; Kinouchi, Masayuki

134

Remote sensing of high temperature H2O CO2 CO mixture with a correlated k-distribution fictitious gas method and the single-mixture gas assumption  

NASA Astrophysics Data System (ADS)

Infrared spectra of high temperature H2O CO2 CO mixtures are calculated using narrow band models in order to simulate hot jet signature at long distance. The correlated k-distribution with fictitious gas (CKFG) approach generally gives accurate data in such situations (especially for long atmospheric paths) but results in long computation time in cases involving mixtures of gases. This time may be reduced if the mixture is treated as a single gas (single-mixture gas assumption, SMG). Thus the lines of the single-mixture gas are assigned to the fictitious gases. In this study, the accuracy of two narrow band models is evaluated. The first narrow band model considers one single-mixture gas and no fictitious gas (CK-SMG) whereas the second model accounts for one single-mixture gas and three fictitious gases (CKFG-SMG). Both narrow band models are compared with reference spectra calculated with a line-by-line (LBL) approach. As expected, the narrow band accuracy is improved by the fictitious gas (FG) assumption particularly when long atmospheric paths are involved. Concerning the SMG assumption, it may lead to an underestimation of about 10% depending on the variation of the gas mixture composition ratio. Nevertheless, in most of realistic situations the SMG assumption results in negligible errors and may be used for remote sensing of plume signature.

Caliot, C.; Le Maoult, Y.; El Hafi, M.; Flamant, G.

2006-11-01

135

Investigation of plasma-dust structures in He-Ar gas mixture  

SciTech Connect

The paper reports on the first experiments with plasma-dust formations in dc gas discharge plasma for a He-Ar mixture. It is shown that the choice of light and heavy gases for the mixture suppresses ion heating in electric field under the conventional conditions of experiments and results in a supersonic jet with high Mach numbers. Distribution functions for drifting ions in the gas mixture are calculated for various mixture concentrations, electric field strengths, and gas pressures.

Maiorov, S. A. [A.M. Prokhorov General Physics Institute of Russian Academy of Sciences, Moscow (Russian Federation); Ramazanov, T. S.; Dzhumagulova, K. N.; Jumabekov, A. N.; Dosbolayev, M. K. [Al Farabi Kazakh National University, IETP, Tole bi 96a, Almaty, 050012 (Kazakhstan)

2008-09-15

136

Critical Viscosity of Xenon team  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure (at left) that is placed inside a pressure canister. A similar canister (right) holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (not shown) of the National Institutes of Standards and Technology, Gaithersburg, MD.

2001-01-01

137

Critical Viscosity of Xenon team  

NASA Technical Reports Server (NTRS)

The Critical Viscosity of Xenon Experiment (CVX-2) on the STS-107 Research 1 mission in 2002 will measure the viscous behavior of xenon, a heavy inert gas used in flash lamps and ion rocket engines, at its critical point. The thermostat for CVX sits inside the white cylinder on a support structure (at left) that is placed inside a pressure canister. A similar canister (right) holds the electronics and control systems. The CVX-2 arrangement is identical. The principal investigator is Dr. Robert F. Berg (left) of the National Institutes of Standards and Technology, Gaithersburg, MD.

2001-01-01

138

Slurried solid media for simultaneous water purification and carbon dioxide removal from gas mixtures  

DOEpatents

A slurried solid media for simultaneous water purification and carbon dioxide removal from gas mixtures includes the steps of dissolving the gas mixture and carbon dioxide in water providing a gas, carbon dioxide, water mixture; adding a porous solid media to the gas, carbon dioxide, water mixture forming a slurry of gas, carbon dioxide, water, and porous solid media; heating the slurry of gas, carbon dioxide, water, and porous solid media producing steam; and cooling the steam to produce purified water and carbon dioxide.

Aines, Roger D.; Bourcier, William L.; Viani, Brian

2013-01-29

139

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

140

Separation of SF6 from gas mixtures using gas hydrate formation.  

PubMed

This study aims to examine the thermodynamic feasibility of separating sulfur hexafluoride (SF(6)), which is widely used in various industrial fields and is one of the most potent greenhouse gases, from gas mixtures using gas hydrate formation. The key process variables of hydrate phase equilibria, pressure-composition diagram, formation kinetics, and structure identification of the mixed gas hydrates, were closely investigated to verify the overall concept of this hydrate-based SF(6) separation process. The three-phase equilibria of hydrate (H), liquid water (L(W)), and vapor (V) for the binary SF(6) + water mixture and for the ternary N(2) + SF(6) + water mixtures with various SF(6) vapor compositions (10, 30, 50, and 70%) were experimentally measured to determine the stability regions and formation conditions of pure and mixed hydrates. The pressure-composition diagram at two different temperatures of 276.15 and 281.15 K was obtained to investigate the actual SF(6) separation efficiency. The vapor phase composition change was monitored during gas hydrate formation to confirm the formation pattern and time needed to reach a state of equilibrium. Furthermore, the structure of the mixed N(2) + SF(6) hydrate was confirmed to be structure II via Raman spectroscopy. Through close examination of the overall experimental results, it was clearly verified that highly concentrated SF(6) can be separated from gas mixtures at mild temperatures and low pressure conditions. PMID:20704207

Cha, Inuk; Lee, Seungmin; Lee, Ju Dong; Lee, Gang-woo; Seo, Yongwon

2010-08-15

141

Atmospheric xenon radioactive isotope monitoring.  

PubMed

The Comprehensive Nuclear Test Ban Treaty (CTBT) organisation is implementing a world-wide monitoring network in order to check that the State Signatories comply with the treaty. One of the monitoring facilities consists of an atmospheric noble gas monitoring equipment. According to the requirements annexed in the treaty, the French Atomic Energy Commission (CEA) developed a device, called SPALAX, which automatically extracts xenon from ambient air and makes in situ measurements of the activities of four xenon radioisotopes (131mXe, 133mXe, 133Xe, 135Xe). The originality of this device is noticeable essentially in the gas sample processing method: thanks to the coupling of a gas permeator and of a noble gas specific adsorbent, it can selectively extract and concentrate xenon to more than 3 x 10 E6. This process is carried out continuously without cryogenic cooling, without any regeneration time. The detection of the xenon radioactive isotopes is done automatically by high spectral resolution gamma spectrometry, a robust technology well-suited for on-field instrumentation. In the year 2000, a prototype was involved in an international evaluation exercise directed by the CTBT organisation (CTBTO). This exercise demonstrated that the SPALAX equipment perfectly met the requirements of the CTBTO for such systems. On the basis of the continuous 24-h resolution record of the atmospheric xenon radioactive isotopes concentrations, the SPALAX system also demonstrated that ambient levels of 133Xe can fluctuate quickly from less than the detection limit to over 40 x 10(-3) Bq m(-3). In order to build an industrial version of this equipment, the CEA entered into a partnership with a French engineering company (S.F.I., Marseille, France), which is now able to produce an industrial version of SPALAX, i.e. more compact and more efficient than the prototypes. The 133Xe minimum detectable concentration is 0.15 x 10(-3) Bq m(-3) air per 24 h sampling cycle. PMID:15162864

Fontaine, J P; Pointurier, F; Blanchard, X; Taffary, T

2004-01-01

142

10 CFR 503.38 - Permanent exemption for certain fuel mixtures containing natural gas or petroleum.  

Code of Federal Regulations, 2010 CFR

...permanent mixtures exemption for the use of a mixture of solar energy (including wind, tide, and other intermittent sources) and petroleum or natural gas, where: (1) Solar energy will account for at least 20 percent of the total...

2010-01-01

143

Process and apparatus for cooling and\\/or liquefying a gas or a gas mixture  

Microsoft Academic Search

A new process developed by Institut Francais du Petrole, des Carburants et Lubrifiants for cooling or liquefying natural gas greatly reduces the number of compressors and heat exchangers required, and also considerably lowers the necessary heat-exchanger surface area and the flow rate of the cooling fluid found in conventional processes. IFP's process consists of compressing a mixture of gaseous constituents

Rojey

1975-01-01

144

Traceable reference gas mixtures for sulfur-free natural gas odorants.  

PubMed

The first reference gas mixtures of sulfur-free natural gas odorants that are traceable to the International System of Units (SI) have been produced and their compositions validated. These mixtures, which contain methyl acrylate and ethyl acrylate at amount fractions between 1.1 and 2.1 ?mol mol(-1), can be used to underpin measurements of sulfur-free odorants, which are increasingly being used to odorize natural gas in transmission networks as they have less harmful properties than traditional sulfur-containing odorants. The reference gas mixtures produced have been shown to be stable in passivated aluminum cylinders for at least 8 months and have been validated (to within 6% or less) by interlaboratory measurements at three National Measurement Institutes. The stability of methyl acrylate and ethyl acrylate in gas sampling bags has been investigated, and the challenges of analyzing 2-ethyl-3-methylpyrazine, which is used as a stabilizer in sulfur-free odorants, are also briefly discussed. PMID:24882216

Brown, Andrew S; van der Veen, Adriaan M H; Arrhenius, Karine; Downey, Michael L; Kühnemuth, Daniel; Li, Jianrong; Ent, Hugo; Culleton, Lucy P

2014-07-01

145

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

146

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

147

Pathway to Cryogen Free Production of Hyperpolarized Krypton-83 and Xenon-129  

PubMed Central

Hyperpolarized (hp) 129Xe and hp 83Kr for magnetic resonance imaging (MRI) are typically obtained through spin-exchange optical pumping (SEOP) in gas mixtures with dilute concentrations of the respective noble gas. The usage of dilute noble gases mixtures requires cryogenic gas separation after SEOP, a step that makes clinical and preclinical applications of hp 129Xe MRI cumbersome. For hp 83Kr MRI, cryogenic concentration is not practical due to depolarization that is caused by quadrupolar relaxation in the condensed phase. In this work, the concept of stopped flow SEOP with concentrated noble gas mixtures at low pressures was explored using a laser with 23.3 W of output power and 0.25 nm linewidth. For 129Xe SEOP without cryogenic separation, the highest obtained MR signal intensity from the hp xenon-nitrogen gas mixture was equivalent to that arising from 15.5±1.9% spin polarized 129Xe in pure xenon gas. The production rate of the hp gas mixture, measured at 298 K, was 1.8 cm3/min. For hp 83Kr, the equivalent of 4.4±0.5% spin polarization in pure krypton at a production rate of 2 cm3/min was produced. The general dependency of spin polarization upon gas pressure obtained in stopped flow SEOP is reported for various noble gas concentrations. Aspects of SEOP specific to the two noble gas isotopes are discussed and compared with current theoretical opinions. A non-linear pressure broadening of the Rb D1 transition was observed and taken into account for the qualitative description of the SEOP process.

Six, Joseph S.; Hughes-Riley, Theodore; Stupic, Karl F.; Pavlovskaya, Galina E.; Meersmann, Thomas

2012-01-01

148

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

DOEpatents

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

149

Mutual Diffusion Coefficient in Binary Mixtures and the Lattice Gas Model  

Microsoft Academic Search

A modification of the elementary kinetic theory of a gas mixture in terms of the lattice gas model is proposed. It is assumed that molecules of components of the mixture are spherical and close in size. In calculating the diffusion flux of molecules through a selected plane, instead of the mean thermal velocity of molecules, the mean relative velocity of

Yu. K. Tovbin

2005-01-01

150

Experimental and theoretical characterization of a multi-wavelength DBD-driven exciplex lamp operated with mercury bromide/rare gas mixtures  

NASA Astrophysics Data System (ADS)

Emission spectra from an atmospheric-pressure dielectric barrier discharge (DBD) with HgBr2/He or HgBr2/Xe/Kr mixtures, as well as the electrical characteristics, were investigated at repetition frequencies of sinusoidal voltage pulses up to 125 kHz. In the spectra, the study revealed radiation from HgBr(B-X, C-X) exciplex molecules, atomic lines of mercury and rare gases, and in mixtures with xenon, radiation of XeBr(B-X, B-A) exciplex molecules. Regularities in the spectral characteristics of the radiation from the gas-discharge plasma were discussed. The electron energy distribution function, the specific energy lost in the processes involving electrons, the electron temperature and density, and the rate constants of elastic and inelastic electron scattering by the components of the working mixture were calculated as functions of the reduced field E/N. The high-frequency atmospheric-pressure barrier discharge in mixtures of mercury dibromide with gases can be used in multi-wavelength exciplex lamps, operating in the UV and visible regions.

Guivan, Mykola M.; Malinina, Antonina A.; Brablec, Antonin

2011-06-01

151

Chemically-bound xenon in fibrous silica.  

PubMed

High-level quantum chemical calculations reported here predict the existence and remarkable stability, of chemically-bound xenon atoms in fibrous silica. The results may support the suggestion of Sanloup and coworkers that chemically-bound xenon and silica account for the problem of "missing xenon" (by a factor of 20!) from the atmospheres of Earth and Mars. So far, the host silica was assumed to be quartz, which is in contradiction with theory. The xenon-fibrous silica molecule is computed to be stable well beyond room temperature. The calculated Raman spectra of the species agree well with the main features of the experiments by Sanloup et al. The results predict computationally the existence of a new family of noble-gas containing materials. The fibrous silica species are finite molecules, their laboratory preparation should be feasible, and potential applications are possible. PMID:24807740

Kalinowski, Jaroslaw; Räsänen, Markku; Gerber, R Benny

2014-05-21

152

Condensed xenon scintillators  

Microsoft Academic Search

Liquid and solid xenon were investigated as scintillator media for the detection of charged particles. The LET dependence of the integral light output was studied over a wide range of ionization densities using alpha and beta particles and heavy ions of 1.4 MeV\\/amu. For solid xenon, scintillation decay times were measured by the delayed single-photon method. For liquid xenon, a

W. Baum; S. Gotz; H. Heckwolf; P. Heeg; M. Mutterer; J. P. Theobald

1988-01-01

153

Strange xenon in Jupiter  

Microsoft Academic Search

Jupiter's helium-rich atmosphere contains xenon with excess136Xe and the ratio of r-products more closely resembles “strange” xenon (Xe-X, alias Xe-HL) seen in carbonaceous chondrites\\u000a than xenon seen in the solar wind (SW-Xe). The linkage of primordial helium with Xe-X, as seen on a microscopic scale in meteorites,\\u000a apparently extended across planetary distances in the solar nebula, This is expected if

O. Manuel; K. Windler; A. Nolte; L. Johannes; J. Zirbel; D. Ragland

1998-01-01

154

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

155

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

156

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

157

Steady-state temperature distribution within a Brayton rotating unit operating in a power conversion system using helium-xenon gas  

NASA Technical Reports Server (NTRS)

The Brayton rotating unit (BRU), consisting of a turbine, an alternator, and a compressor, was tested as part of a Brayton cycle power conversion system over a side range of steady state operating conditions. The working fluid in the system was a mixture of helium-xenon gases. Turbine inlet temperature was varied from 1200 to 1600 F, compressor inlet temperature from 60 to 120 F, compressor discharge pressure from 20 to 45 psia, rotative speed from 32 400 to 39 600 rpm, and alternator liquid-coolant flow rate from 0.01 to 0.27 pound per second. Test results indicated that the BRU internal temperatures were highly sensitive to alternator coolant flow below the design value of 0.12 pound per second but much less so at higher values. The armature winding temperature was not influenced significantly by turbine inlet temperature, but was sensitive, up to 20 F per kVA alternator output, to varying alternator output. When only the rotational speed was changed (+ or - 10% of rated value), the BRU internal temperatures varied directly with the speed.

Johnsen, R. L.; Namkoong, D.; Edkin, R. A.

1971-01-01

158

Gas-phase detonation propagation in mixture composition gradients.  

PubMed

The propagation of detonations through several fuel-air mixtures with spatially varying fuel concentrations is examined numerically. The detonations propagate through two-dimensional channels, inside of which the gradient of mixture composition is oriented normal to the direction of propagation. The simulations are performed using a two-component, single-step reaction model calibrated so that one-dimensional detonation properties of model low- and high-activation-energy mixtures are similar to those observed in a typical hydrocarbon-air mixture. In the low-activation-energy mixture, the reaction zone structure is complex, consisting of curved fuel-lean and fuel-rich detonations near the line of stoichiometry that transition to decoupled shocks and turbulent deflagrations near the channel walls where the mixture is extremely fuel-lean or fuel-rich. Reactants that are not consumed by the leading detonation combine downstream and burn in a diffusion flame. Detonation cells produced by the unstable reaction front vary in size across the channel, growing larger away from the line of stoichiometry. As the size of the channel decreases relative to the size of a detonation cell, the effect of the mixture composition gradient is lessened and cells of similar sizes form. In the high-activation-energy mixture, detonations propagate more slowly as the magnitude of the mixture composition gradient is increased and can be quenched in a large enough gradient. PMID:22213660

Kessler, D A; Gamezo, V N; Oran, E S

2012-02-13

159

A 650 J e-beam-pumped atomic xenon laser  

SciTech Connect

The atomic xenon laser has been scaled from the 80 J per pulse output energy level reported to 650 J, using a large two-sided {ital e}-beam-pumped device. The extraction volume dimensions were 0.5 m {center dot} 0.65 m {center dot} 3 m. The gas was pumped at a temporally and spatially averaged rate of 70 kW/cm{sup 3}, and the spatially averaged specific input energy was 115 J/L. An aluminum rear reflector and an uncoated, fused silica output coupler were aligned to form a plane-parallel optical resonator. Output energy measurements were made with a full-aperture calorimeter, and the temporal pulse shape of the 1.7 {mu}m laser radiation was recorded with a spectrally filtered germanium photodiode. The device was operated with argon-xenon gas mixtures at pressures ranging from 20 to 40 psia at a temperature of 23{degrees} C, and the xenon mole fraction was empirically optimized. The maximum output energy of 650 J was obtained at an intrinsic efficiency (output energy divided by energy deposited in gas) of 0.57%. A higher efficiency of 0.85% was achieved by using a shorter {ital e}-beam pulse, at a reduced laser output energy of 495 J. Laser output which began shortly after the start of the {ital e}-beam pulse continued well beyond the termination of that pulse, decaying at an exponential rate with an {ital e}-fold time of 1.8 {mu}s. A possible explanation for the observed laser pulse shape is discussed.

Litzenberger, L.N.; Trainor, D.W.; McGeoch, M.W. (Avco-Everett Research Lab., Everett, MA (USA))

1990-09-01

160

Remote analysis of gas mixtures using an optical parametric oscillator based lidar system  

Microsoft Academic Search

A scheme for lidar measurements of multicomponent gas mixtures in the mid-IR region using a newly developed fast-switching, frequency-agile optical parametric oscillator (OPO) system combined with multivariate statistical methods has been implemented and tested. The scheme adopted was able to predict the composition of the remote hydrocarbon gas mixture within the uncertainty of the pre-determined gas composition.

P. Weibring; C. Abrahamsson; M. Sjoholm; J. N. Smith; H. Edner; S. Svanberg

2003-01-01

161

Measurement of Excess Functions of Binary Gas Mixtures Adsorbed in Zeolites by Adsorption Calorimetry  

Microsoft Academic Search

Adsorption equilibria and heats of adsorption were measured for mixtures of ethylene and ethane on NaX at 298 K. The pure-component isosteric heat of adsorption of ethane increases with loading due to gas-gas interactions; the heat of adsorption of ethylene is approximately constant with loading because of a balance between cooperative interactions and gas-solid energetic heterogeneity. This mixture, which is

Flor Siperstein; Raymond J. Gorte; Alan L. Myers

1999-01-01

162

Pure SF6 and SF6-N2 mixture gas hydrates equilibrium and kinetic characteristics.  

PubMed

Sulfur hexafluoride (SF6), whether pure or mixed with inexpensive inert gas, has been widely used in a variety of industrial processes, but it is one of the most potent greenhouse gases. For this reason, it is necessary to separate and/or collect it from waste gas streams. In this study, we investigated the pure SF6 and SF6-N2 mixture gas hydrates formation equilibrium aswell asthe gas separation efficiency in the hydrate process. The equilibrium pressure of SF6-N2 mixture gas was higher than that of pure SF6 gas. Phase equilibrium data of SF6-N2 mixture gas was similar to SF6 rather than N2. The kinetics of SF6-N2 mixture gas was controlled by the amount of SF6 at the initial gas composition as well as N2 gas incorporation into the S-cage of structure-II hydrate preformed by the SF6 gas. Raman analysis confirmed the N2 gas incorporation into the S-cage of structure-II hydrate. The compositions in the hydrate phase were found to be 71, 79, 80, and 81% of SF6 when the feed gas compositions were 40, 65, 70, and 73% of SF6, respectively. The present study provides basic information for the separation and purification of SF6 from mixed SF6 gas containing inert gases. PMID:19921885

Lee, Eun Kyung; Lee, Ju Dong; Lee, Hyun Ju; Lee, Bo Ram; Lee, Yoon Seok; Kim, Soo Min; Park, Hye Ok; Kim, Young Seok; Park, Yeong-Do; Kim, Yang Do

2009-10-15

163

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.

164

Adsorptive Separation of Krypton-85 in Reprocessing Plant in Consideration of Gas Impurities and a Xenon-Preseparation.  

National Technical Information Service (NTIS)

After loading at low temperatures and following desorption on activated charcoal krypton is separated out of waste gas. In a compact pilot plant a high degree of retention is achieved. The components in waste gas like methane, carbondioxid, laughing gas a...

G. Assmann

1986-01-01

165

Preliminary performance of the Brayton 4.25 inch radial compressor operating in a helium xenon gas mixture  

NASA Technical Reports Server (NTRS)

Compressor performance was mapped during the Brayton cycle power system testing. The range of testing included three shaft speeds: the design speed of 36,000 rpm, 10 percent overspeed (39,600 rpm), and 10 percent underspeed (32,400 rpm). A range of compressor inlet temperatures from 60 F to 120 F and discharge pressures from 20 to 45 psia were included. The effects of turbine inlet temperatures (from 1200 F to 1600 F) on the compressor were also studied. The data presented include plots of weight flow, compressor pressure ratio, efficiency, and temperature-rise ratio.

Asadourian, A. S.; Hecker, T. P.; Kruchowy, R.

1971-01-01

166

Detailed investigation on the neon-xenon mixture as filling gas for mercury-free fluorescent lamps  

Microsoft Academic Search

Summary form only given. The conventional fluorescent lamp is a low-pressure mercury discharge device with a phosphor coating that converts ultraviolet light into visible light. Since mercury is toxic, it represents an environmental hazard and suggests a need for mercury-free light sources. Many years ago, several investigations were carried out in an endeavour to use inert gases as a substitute

H. Sarroukh; E. Robert; C. Cachoncinlle; R. Viladrosa; G. Pousse; J. M. Pouvesle

2001-01-01

167

Calculation of the relative speed of sound in a gas mixture.  

PubMed

Since the frequency spectrum of a voice signal is directly dependent on the velocity of sound, studies of speech spectra include the problem of calculating the speed of sound in the gas mixture being used. A computer program written in BASIC has been developed to calculate the speed of sound relative to air in various diving gas mixtures. In addition, a set of tables available as a separate technical report has been generated using this program. These tables are designed to provide a standard reference for reporting spectral shifts in speech due to different gas mixtures under normal diving conditions. PMID:1226588

Ackerman, M J; Maitland, G

1975-12-01

168

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

169

Gas build-up in a domestic property following releases of methane\\/hydrogen mixtures  

Microsoft Academic Search

The results of large scale experiments to study gas accumulation within a ventilated enclosure representing a domestic room are presented. Gas was released vertically upwards at a pressure typical of that experienced in a domestic environment from hole sizes representative of leaks and breaks in pipes. The released gas composition was either methane or a methane\\/hydrogen mixture containing up to

B. J. Lowesmith; G. Hankinson; C. Spataru; M. Stobbart

2009-01-01

170

[Distribution of a hypoxic gas mixture by retro-pollution of a medical gas distribution system].  

PubMed

The authors report a case of retropollution through the defective gas mixer of a Logic O4T-IMV ventilator (Ohmeda) located in the recovery room. Due to a defective check valve inside the mixer, medical air entered into the oxygen pipeline when the O2 pressure decreased below the pressure inside the medical air pipeline. This incident resulted in episodes of hypoxic gas mixture delivery in the operating theatre, when nitrous oxide was associated with oxygen polluted with medical air. The occurrence of such an incident, rarely described so far, requires the association of several factors. It can be recognized without delay with the continuous use of an oxygen analyser. PMID:7733527

Gorce, P; Crisan, A; Gondret, R; Viallard, M L; Clergue, F

1994-01-01

171

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...

172

Irreversible Processes in a Universe modelled as a mixture of a Chaplygin gas and radiation  

Microsoft Academic Search

The evolution of a Universe modelled as a mixture of a Chaplygin gas and\\u000aradiation is determined by taking into account irreversible processes. This\\u000amixture could interpolate periods of a radiation dominated, a matter dominated\\u000aand a cosmological constant dominated Universe. The results of a Universe\\u000amodelled by this mixture are compared with the results of a mixture whose\\u000aconstituents

G. M. Kremer

2003-01-01

173

Binary Gas Mixtures of Light Helium to Intensify Laminar Forced Convection in Round Tubes  

NASA Astrophysics Data System (ADS)

This paper addresses potential heat transfer enhancement of laminar gaseous flows inside tubes with constant wall temperatures. The goal is to investigate the capabilities of certain binary gas mixtures of light helium as the primary gas with nitrogen, oxygen, carbon dioxide, methane, sulfur hexafluoride and tetrafluoromethane as the secondary heavier gases. The velocity of the binary gas mixtures is fully established and the temperature develops from a uniform value. The thermophysical properties of the binary gas mixtures depend on the molar gas composition in the w-domain [0, 1]. The two case studies involve a low mean bulk temperature of 300 K and the other a high mean bulk temperature of 600 K, both sharing 1 atm. The two target parameters for analysis and design are the maximum heat transfer rate and the pressure drop at the optimal molar gas composition.

Campo, Antonio; Chikh, Salah; Papari, Mohammad; Mobinipouya, Mahammad

2007-11-01

174

Rapid helium-air analyzer can measure other binary gas mixtures  

NASA Technical Reports Server (NTRS)

Instrument comprised of an ionization pressure gage and a diaphragm pressure gage consisting of strain gages to make a four-arm bridge, and a ratiometer is constructed for analyzing gas mixtures. The ratio of the outputs of the two gages is proportional to the mixture composition.

Melfi, L. T.; Wood, G. M.; Yeager, P. R.

1964-01-01

175

Flash Pyrolysis of New Mexico sub-Bituminous Coal in Helium-Methane Gas Mixtures.  

National Technical Information Service (NTIS)

A New Mexico sub-bituminous coal was flash pyrolyzed in gas mixtures of helium and methane at 1000 sup 0 C and 50 psi in an 1-in. I.D. entrained down-flow tubular reactor. The mixture contained 0 to 40% helium in methane. Under tested experimental conditi...

M. S. Sundaram P. T. Fallon M. Steinberg

1986-01-01

176

Statistical collision model for Monte Carlo simulation of polyatomic gas mixture  

Microsoft Academic Search

A formal derivation of the direct simulation technique of solution to the Boltzmann equation for a mixture of polyatomic gases is presented. A phenomenological model for binary collisions in a gas mixture having continuous internal energy is then developed. The model is based on the relaxation concept applied to individual collisions and interpreted statistically in a manner suitable to Monte

C. Borgnakke; P. S. Larsen

1975-01-01

177

Viscous-Shock-Layer Solutions for Turbulent Flow of Radiating Gas Mixtures in Chemical Equilibrium.  

National Technical Information Service (NTIS)

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 f...

E. C. Anderson J. N. Moss

1975-01-01

178

Viscous Shock Layer Solutions for Turbulent Flow of Radiating Gas Mixtures in Chemical Equilibrium.  

National Technical Information Service (NTIS)

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 fi...

E. C. Anderson J. N. Moss

1975-01-01

179

Electron--ion recombination in gas mixtures of helium, nitrogen, and carbon dioxide  

SciTech Connect

A study has been conducted to determine the electron--ion recombination rates in gas mixtures of helium, nitrogen, and carbon dioxide. Measurements were made as functions of electric field strength, gas pressure, and gas composition. In gas mixtures containing only nitrogen and carbon dioxide, the rates were dependent on pressure. This dependence is interpreted as being due to the separate effects of two- and three-body recombination processes. No pressure dependence was observed for mixtures containing helium. In such mixtures, two-body recombination appears to be dominant. Moreover the addition of relatively low concentrations of helium to the discharge leads to a dramatic change in the bulk recombination rate. Two possible explanations for this observation are suggested.

Littlewood, I.M.; Cornell, M.C.; Nygaard, K.J.

1984-08-01

180

Xenon migration behaviour in titanium nitride  

NASA Astrophysics Data System (ADS)

Titanium nitride is one of the inert matrixes proposed to surround the fuel in gas cooled fast reactor (GFR) systems. These reactors operate at high temperature and necessitate refractory materials presenting a high chemical stability and good mechanical properties. A total retention of the most volatile fission products, such as Xe, I or Cs, by the inert matrix is needed during the in pile process. The thermal migration of xenon in TiN was studied by implanting 800 keV Xe ++ ions in sintered samples at an ion fluence of 5 × 10 15 cm -2. Annealing was performed at temperatures ranging from 1673 to 1923 K for 1 and 3 h. Xenon concentration profiles were studied by Rutherford backscattering spectrometry (RBS) using 2.5 MeV ?-particles. The migration behaviour of xenon corresponds to a gas migration model. It is dominated by a surface directed transport with a slight diffusion component. The mean activation energy corresponding to the diffusion component was found to be 2.2 ± 0.3 eV and corresponds to the Brownian motion of xenon bubbles. The directed Xe migration can be interpreted in term of bubble transport using Evans model. This last process is mostly responsible for xenon release from TiN.

Gavarini, S.; Toulhoat, N.; Peaucelle, C.; Martin, P.; Mende, J.; Pipon, Y.; Jaffrezic, H.

2007-05-01

181

Oxygen sensor for monitoring gas mixtures containing hydrocarbons  

DOEpatents

A gas sensor measures O.sub.2 content of a reformable monitored gas containing hydrocarbons H.sub.2 O and/or CO.sub.2, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system.

Ruka, Roswell J. (Pittsburgh, PA); Basel, Richard A. (Pittsburgh, PA)

1996-01-01

182

Oxygen sensor for monitoring gas mixtures containing hydrocarbons  

DOEpatents

A gas sensor measures O{sub 2} content of a reformable monitored gas containing hydrocarbons, H{sub 2}O and/or CO{sub 2}, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system. 4 figs.

Ruka, R.J.; Basel, R.A.

1996-03-12

183

Rarefied gas flow of binary mixtures through long channels with triangular and trapezoidal cross sections  

Microsoft Academic Search

The flow of binary gas mixtures through long micro-channels with triangular and trapezoidal cross sections is investigated\\u000a in the whole range of the Knudsen number. The flow is driven by pressure and concentration gradients. The McCormack kinetic\\u000a model is utilized to simulate the rarefied flow of the gas mixture, and the kinetic equations are solved by an upgraded discrete\\u000a velocity

Lajos Szalmas; Dimitris Valougeorgis

2010-01-01

184

Method for the adsorptive removal of hydrogen sulfide from gas mixtures  

Microsoft Academic Search

A method is disclosed for the adsorptive removal of HâS from gas mixtures in C-containing adsorption agents with 1-80 bar pressures and regeneration, employing pressure lowering and\\/or temperature change and simultaneous rinsing with an at most negligibly absorbable component of the gas mixture. A carbon molecular sieve of fossil and\\/or bituminous fuel is used, with for pore diameter less than

Kd. Henning; B. Harden; J. Klein

1984-01-01

185

Shock-wave structure in a ternary disparate-mass gas mixture  

Microsoft Academic Search

Navier-Stokes level equations of three-fluid hydrodynamics are presented for ternary gas mixture consisting of heavy molecules of two species with near masses and light molecules. It is shown that in flows of such mixtures there may arise the large relative diffusion velocity and temperature-difference between heavy species due to the influence of light gas. The equations are applied to study

G. A. Ruev; V. M. Fomin; M. Sh. Shavaliev

1991-01-01

186

Determination of concentrations in ternary and quaternary molecular gas mixtures using femtosecond Raman spectroscopy  

Microsoft Academic Search

Measurements of concentrations in gas mixtures of three and four molecular components are presented. They rely on a femtosecond time-resolved pump-probe technique based on Raman-induced polarization spectroscopy. The rotational time response of the molecular gas mixture is measured as a function of the pump-probe time delay. No selective frequency tunability is needed as the molecular rotational spectra are excited within

H. Tran; B. Lavorel; O. Faucher; R. Saint-Loup; P. Joubert

2002-01-01

187

Operation of the multigap resistive plate chamber using a gas mixture free of flammable components  

Microsoft Academic Search

We have investigated the operation of the multigap resistive plate chamber (MRPC) for the ALICE-TOF system with a gas mixture free of flammable components. Two different gas mixtures, with and without iso-C4H10 have been used to measure the performance of the MRPC. The efficiency, time resolution, total charge, and the fast to total charge ratio have been found to be

A. N. Akindinov; A. Alici; P. Antonioli; S. Arcelli; M. Basile; G. Cara Romeo; L. Cifarelli; F. Cindolo; A. De Caro; S. De Pasquale; A. Di Bartolomeo; M. Fusco Girard; V. Golovine; M. Guida; D. Hatzifotiadou; A. B. Kaidalov; D. H. Kim; D. W. Kim; S. M. Kisselev; G. Laurenti; K. Lee; S. C. Lee; E. Lioublev; M. L. Luvisetto; A. Margotti; A. N. Martemiyanov; R. Nania; F. Noferini; P. Otiougova; A. Pesci; O. Pinazza; P. A. Polozov; E. Scapparone; G. Scioli; S. B. Sellitto; F. Semeria; A. V. Smirnitski; M. M. Tchoumakov; E. Usenko; G. Valenti; K. G. Voloshin; M. C. S. Williams; B. V. Zagreev; C. Zampolli; A. Zichichi

2004-01-01

188

Operation of the Multigap Resistive Plate Chamber using a gas mixture free of flammable components  

NASA Astrophysics Data System (ADS)

We have investigated the operation of the Multigap Resistive Plate Chamber (MRPC) for the ALICE-TOF system with a gas mixture free of flammable components. Two different gas mixtures, with and without iso-C 4H 10 have been used to measure the performance of the MRPC. The efficiency, time resolution, total charge, and the fast to total charge ratio have been found to be comparable.

Akindinov, A. N.; Alici, A.; Antonioli, P.; Arcelli, S.; Basile, M.; Cara Romeo, G.; Cifarelli, L.; Cindolo, F.; De Caro, A.; De Pasquale, S.; Di Bartolomeo, A.; Fusco Girard, M.; Golovine, V.; Guida, M.; Hatzifotiadou, D.; Kaidalov, A. B.; Kim, D. H.; Kim, D. W.; Kisselev, S. M.; Laurenti, G.; Lee, K.; Lee, S. C.; Lioublev, E.; Luvisetto, M. L.; Margotti, A.; Martemiyanov, A. N.; Nania, R.; Noferini, F.; Otiougova, P.; Pesci, A.; Pinazza, O.; Polozov, P. A.; Scapparone, E.; Scioli, G.; Sellitto, S. B.; Semeria, F.; Smirnitski, A. V.; Tchoumakov, M. M.; Usenko, E.; Valenti, G.; Voloshin, K. G.; Williams, M. C. S.; Zagreev, B. V.; Zampolli, C.; Zichichi, A.

2004-10-01

189

Operation of the multigap resistive plate chamber using a gas mixture free of flammable components  

NASA Astrophysics Data System (ADS)

We have investigated the operation of the multigap resistive plate chamber (MRPC) for the ALICE-TOF system with a gas mixture free of flammable components. Two different gas mixtures, with and without iso-C 4H 10 have been used to measure the performance of the MRPC. The efficiency, time resolution, total charge, and the fast to total charge ratio have been found to be comparable.

Akindinov, A. N.; Alici, A.; Antonioli, P.; Arcelli, S.; Basile, M.; Cara Romeo, G.; Cifarelli, L.; Cindolo, F.; De Caro, A.; De Pasquale, S.; Di Bartolomeo, A.; Fusco Girard, M.; Golovine, V.; Guida, M.; Hatzifotiadou, D.; Kaidalov, A. B.; Kim, D. H.; Kim, D. W.; Kisselev, S. M.; Laurenti, G.; Lee, K.; Lee, S. C.; Lioublev, E.; Luvisetto, M. L.; Margotti, A.; Martemiyanov, A. N.; Nania, R.; Noferini, F.; Otiougova, P.; Pesci, A.; Pinazza, O.; Polozov, P. A.; Scapparone, E.; Scioli, G.; Sellitto, S. B.; Semeria, F.; Smirnitski, A. V.; Tchoumakov, M. M.; Usenko, E.; Valenti, G.; Voloshin, K. G.; Williams, M. C. S.; Zagreev, B. V.; Zampolli, C.; Zichichi, A.

2004-10-01

190

Operation of the Multigap Resistive Plate Chamber using a gas mixture free of flammable components  

Microsoft Academic Search

We have investigated the operation of the Multigap Resistive Plate Chamber (MRPC) for the ALICE-TOF system with a gas mixture free of flammable components. Two different gas mixtures, with and without iso-C4H10have been used to measure the performance of the MRPC. The efficiency, time resolution, total charge, and the fast to total charge ratio have been found to be comparable.

A. N. Akindinov; A. Alici; P. Antonioli; S. Arcelli; M. Basile; G. Cara Romeo; L. Cifarelli; F. Cindolo; A. De Caro; S. De Pasquale; A. Di Bartolomeo; M. Fusco Girard; V. Golovine; M. Guida; D. Hatzifotiadou; A. B. Kaidalov; D. H. Kim; D. W. Kim; S. M. Kisselev; G. Laurenti; K. Lee; S. C. Lee; E. Lioublev; M. L. Luvisetto; A. Margotti; A. N. Martemiyanov; R. Nania; F. Noferini; P. Otiougova; A. Pesci; O. Pinazza; P. A. Polozov; E. Scapparone; G. Scioli; S. B. Sellitto; F. Semeria; A. V. Smirnitski; M. M. Tchoumakov; E. Usenko; G. Valenti; K. G. Voloshin; M. C. S. Williams; B. V. Zagreev; C. Zampolli; A. Zichichi

2004-01-01

191

Microwave Determination of Water Mole Fraction in Humid Gas Mixtures  

NASA Astrophysics Data System (ADS)

A small volume (65 cm3) gold-plated quasi-spherical microwave resonator has been used to measure the water vapor mole fraction x w of H2O/N2 and H2O/air mixtures. This experimental technique exploits the high precision achievable in the determination of the cavity microwave resonance frequencies and is particularly sensitive to the presence of small concentrations of water vapor as a result of the high polarizability of this substance. The mixtures were prepared using the INRIM standard humidity generator for frost-point temperatures T fp in the range between 241 K and 270 K and a commercial two-pressure humidity generator operated at a dew-point temperature between 272 K and 291 K. The experimental measurements compare favorably with the calculated molar fractions of the mixture supplied by the humidity generators, showing a normalized error lower than 0.8.

Cuccaro, R.; Gavioso, R. M.; Benedetto, G.; Madonna Ripa, D.; Fernicola, V.; Guianvarc'h, C.

2012-09-01

192

Measurements of laminar burning velocities for natural gas-hydrogen-air mixtures  

SciTech Connect

Laminar flame characteristics of natural gas-hydrogen-air flames were studied in a constant-volume bomb at normal temperature and pressure. Laminar burning velocities and Markstein lengths were obtained at various ratios of hydrogen to natural gas (volume fraction from 0 to 100%) and equivalence ratios (f from 0.6 to 1.4). The influence of stretch rate on flame was also analyzed. The results show that, for lean mixture combustion, the flame radius increases with time but the increasing rate decreases with flame expansion for natural gas and for mixtures with low hydrogen fractions, while at high hydrogen fractions, there exists a linear correlation between flame radius and time. For rich mixture combustion, the flame radius shows a slowly increasing rate at early stages of flame propagation and a quickly increasing rate at late stages of flame propagation for natural gas and for mixtures with low hydrogen fractions, and there also exists a linear correlation between flame radius and time for mixtures with high hydrogen fractions. Combustion at stoichiometric mixture demonstrates the linear relationship between flame radius and time for natural gas-air, hydrogen-air, and natural gas-hydrogen-air flames. Laminar burning velocities increase exponentially with the increase of hydrogen fraction in mixtures, while the Markstein length decreases and flame instability increases with the increase of hydrogen fractions in mixture. For a fixed hydrogen fraction, the Markstein number shows an increase and flame stability increases with the increase of equivalence ratios. Based on the experimental data, a formula for calculating the laminar burning velocities of natural gas-hydrogen-air flames is proposed. (author)

Huang, Zuohua; Zhang, Yong; Zeng, Ke; Liu, Bing; Wang, Qian; Jiang, Deming [State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an (People's Republic of China)

2006-07-15

193

Xenon Feed System Progress.  

National Technical Information Service (NTIS)

This paper reports on Moog's efforts to support the design, development, assembly and test of an electric propulsion xenon feed system for a flight technology demonstration program. Major accomplishments include: (1) Utilization of the Moog Proportional F...

J. K. Barbaritis P. T. King

2006-01-01

194

Electron temperature and density measurement of tungsten inert gas arcs with Ar-He shielding gas mixture  

NASA Astrophysics Data System (ADS)

The diagnostics of atmospheric welding plasma is a well-established technology. In most cases the measurements are limited to processes using pure shielding gas. However in many applications shielding gas is a mixture of various components including metal vapor in gas metal arc welding (GMAW). Shielding gas mixtures are intentionally used for tungsten inert gas (TIG) welding in order to improve the welding performance. For example adding Helium to Argon shielding gas allows the weld geometry and porosity to be influenced. Yet thermal plasmas produced with gas mixtures or metal vapor still require further experimental investigation. In this work coherent Thomson scattering is used to measure electron temperature and density in these plasmas, since this technique allows independent measurements of electron and ion temperature. Here thermal plasmas generated by a TIG process with 50% Argon and 50% Helium shielding gas mixture have been investigated. Electron temperature and density measured by coherent Thomson scattering have been compared to the results of spectroscopic measurements of the plasma density using Stark broadening of the 696.5 nm Argon spectral line. Further investigations of MIG processes using Thomson scattering technique are planned.

Kühn-Kauffeldt, M.; Marques, J.-L.; Forster, G.; Schein, J.

2013-10-01

195

Direct nuclear excitation of a He-3 - CO2 gas mixture  

NASA Technical Reports Server (NTRS)

Probe measurements using a continuous wave CO2 laser have been carried out on a He-3 - CO2 gas mixture directly excited by the He-3(n,p)H-3 reaction. At a gas pressure of 1 atm and thermal neutron flux up to 10 to the 17th n/sq cm sec, total extinction of the probe beam was observed. Addition of N2 to the gas mixture (up to 20%) produced a media such as is used in electric discharge CO2 lasers. However, this mixture produced the same results as the He-3 - CO2 mixture. Absorption of the laser beam indicates that with direct nuclear excitation, it is the lower laser level which is excited. Therefore direct nuclear pumping of a CO2 laser does not appear feasible.

Jalufka, N. W.

1981-01-01

196

Direct nuclear excitation of a He-3 - CO2 gas mixture  

NASA Astrophysics Data System (ADS)

Probe measurements using a continuous wave CO2 laser have been carried out on a He-3 - CO2 gas mixture directly excited by the He-3(n,p)H-3 reaction. At a gas pressure of 1 atm and thermal neutron flux up to 10 to the 17th n/sq cm sec, total extinction of the probe beam was observed. Addition of N2 to the gas mixture (up to 20%) produced a media such as is used in electric discharge CO2 lasers. However, this mixture produced the same results as the He-3 - CO2 mixture. Absorption of the laser beam indicates that with direct nuclear excitation, it is the lower laser level which is excited. Therefore direct nuclear pumping of a CO2 laser does not appear feasible.

Jalufka, N. W.

1981-08-01

197

Effect of various gas mixtures on plasma cleaned ceramics. Final report. [Electronic components  

Microsoft Academic Search

Activated gas plasma cleaning efficiencies of various gas mixtures were studied for the preparation of ceramic parts. Differences in the ease of removal of organic residue are shown by Auger analyses for the various gases. A reduction in plasma process time is shown to be possible, and gases are compared with oxygen on the basis of cleaning efficiency. The plasma

1979-01-01

198

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

Federal Register 2010, 2011, 2012, 2013

...Substances and Mixtures Used in Oil and Gas Exploration or Production; TSCA...manufacturers and processors of oil and gas exploration and production (E...geologic formations, such as shale rock, allowing enhanced natural gas or oil recovery. Since...

2013-07-11

199

Solution of the Boltzmann kinetic equation for the relaxation of a gas mixture  

NASA Technical Reports Server (NTRS)

The temporal behavior is considered of a quiescent mixture of gases of different temperatures with spatially uniform distribution. The process of heating a cold gas by a hot gas is treated on the basis of the Boltzmann kinetic equation. The mixture is assumed to be composed of absolutely hard smooth spheres, and the initial distribution functions for each gas is taken to the Maxwellian. With such a choice of initial distribution functions, it is shown that the solution of the Boltzmann kinetic equation depends only on the velocity modulus and the time.

Rykov, V. A.; Chukanova, T. I.

1972-01-01

200

Pressurised xenon as scintillator for gamma spectroscopy  

NASA Astrophysics Data System (ADS)

Detectors based on liquid or gas xenon have been used and are in use for a number of applications, in particular for the detection of gamma rays. Xenon is a well-suited medium for gamma spectroscopy thanks to its high atomic number and, consequently, large cross-section for photo-electric absorption. This paper presents experimental studies of high pressure xenon as a scintillator, with the aim of developing a gamma ray detector for the detection of Special Nuclear Materials (SNM). The first goal was to study the dependence of the light yield and of the energy resolution on the thermodynamic conditions. We present preliminary results from an optimised version of the detector.

Resnati, F.

2013-09-01

201

Xenon Tetrafluoride: Reaction with Aqueous Solutions  

Microsoft Academic Search

Xenon tetrafluoride reacts with water to yield xenon, oxygen, hydrofluoric acid, and a very soluble species containing xenon. Evaporation of the solution yields a white, crystalline substance which has been identified as xenon (VI) oxide, XeO3.

Stanley M. Williamson; Charles W. Koch

1963-01-01

202

XENON TETRAFLUORIDE: REACTION WITH AQUEOUS SOLUTIONS  

Microsoft Academic Search

Xenon tetrafluoride reacts with water to yield xenon, oxygen, ; hydrofluoric acid, and a very soluble species containing xenon. Evaporation of ; the solution yields a white, crystalline substance which was identified as xenon ; (VI) oxide, XeOâ. (auth);

S. M. Williamson; C. W. Koch

1963-01-01

203

Tortuosity measurement and the effects of finite pulse widths on xenon gas diffusion NMR studies of porous media  

Microsoft Academic Search

We have extended the utility of NMR as a technique to probe porous media structure over length scales of ;100 -2000 mm by using the spin 1\\/2 noble gas 129Xe imbibed into the system's pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We utilized Pulsed Gradient Spin Echo

R. W. Maira; M. D. Hurlimann; P. N. Sen; S. Patz; R. L. Walsworth

204

Air gas dynamic spraying of powder mixtures: Theory and application  

Microsoft Academic Search

The radial injection gas dynamic spray (RIGDS) technology of powder coatings deposition was considered for this work. A coating\\u000a was created by injecting powders with variable compositions into a supersonic air jet and depositing powder on the substrate.\\u000a This study describes the preliminary analysis of an air gas dynamic spray method realized by a portable RIGDS apparatus with\\u000a a radial

R. Gr. Maev; V. Leshchynsky

2006-01-01

205

Spatial separation of components of gas mixtures and isotopes in a free supersonic jet  

SciTech Connect

The results of an experimental investigation of a method of gas-dynamic separation, spatial separation of the components of gas mixtures and isotopes when they are injected into a jet of light carrier gas (hydrogen or helium), are presented. The density of the supersonic jet is investigated by drawing off gas with a skimmer into the high-vacuum space of a mass spectrometer. The main characteristic of the gas-dynamic separating element, namely, the dependence of the enrichment factor on the fraction of the component being selected, is found for the following mixtures: argon--helium, nitrogen--oxygen (air), and sulfur isotopes in the compound SF/sub 6/. An attempt to increase the enrichment factor in a gas-dynamic system by using selective laser excitation of the molecules is described.

Kusner, Y.; Nikolaev, G.; Prikhod'ko, V.

1981-09-01

206

Laser absorption spectroscopy - Method for monitoring complex trace gas mixtures  

NASA Technical Reports Server (NTRS)

A frequency stabilized CO2 laser was used for accurate determinations of the absorption coefficients of various gases in the wavelength region from 9 to 11 microns. The gases investigated were representative of the types of contaminants expected to build up in recycled atmospheres. These absorption coefficients were then used in determining the presence and amount of the gases in prepared mixtures. The effect of interferences on the minimum detectable concentration of the gases was measured. The accuracies of various methods of solution were also evaluated.

Green, B. D.; Steinfeld, J. I.

1976-01-01

207

Influence of the gas mixture temperature on the efficiency of synthesis gas production from ethanol in a nonequilibrium plasma  

NASA Astrophysics Data System (ADS)

The mechanism behind the plasma conversion of a mixture of ethanol vapor, water vapor, air, and carbon dioxide CO2 in the nonequilibrium plasma of a tornado discharge is studied. The influence of the CO2 flow rate, the current through the discharge, and the gas temperature in the discharge on the concentrations of molecular hydrogen and carbon monoxide CO is studied. Comparison between the concentrations of the gaseous mixture's main components at the output from the reactor obtained experimentally and by numerical simulation shows that the adopted kinetic mechanism adequately describes the plasma kinetics in the mixture.

Tsymbalyuk, A. N.; Levko, D. S.; Chernyak, V. Ya.; Martysh, E. V.; Nedybalyuk, O. A.; Solomenko, E. V.

2013-08-01

208

Some possibilities of using gas mixtures other than air in aerodynamic research  

NASA Technical Reports Server (NTRS)

A study is made of the advantages that can be realized in compressible-flow research by employing a substitute heavy gas in place of air. The present report is based on the idea that by properly mixing a heavy monatomic gas with a suitable heavy polyatomic gas, it is possible to obtain a heavy gas mixture which has the correct ratio of specific heats and which is nontoxic, nonflammable, thermally stable, chemically inert, and comprised of commercially available components. Calculations were made of wind-tunnel characteristics for 63 gas pairs comprising 21 different polyatomic gases properly mixed with each of three monatomic gases (argon, krypton, and zenon).

Chapman, Dean R

1956-01-01

209

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) [Helotes, TX; Miller, Michael A. (San Antonio, TX) [San Antonio, TX

2010-08-24

210

Inflammable Gas Mixture Detection with a Single Catalytic Sensor Based on the Electric Field Effect  

PubMed Central

This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%.

Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng

2014-01-01

211

Inflammable gas mixture detection with a single catalytic sensor based on the electric field effect.  

PubMed

This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%. PMID:24717635

Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng

2014-01-01

212

Nonequilibrium Molecular Dynamics Simulation of Transport of Gas Mixtures in Nanopores  

NASA Astrophysics Data System (ADS)

The results of the first nonequilibrium molecular dynamics simulation of transport of a gas mixture through a carbon nanopore, in the presence of an external chemical potential gradient, are reported. While the structure of the pore walls and the composition of the mixture have essentially no effect on the separation factor, the temperature of the system and the pore size strongly influence it. The results are in qualitative agreement with the new experimental data that are presented in this Letter.

Xu, Lifang; Sedigh, Mehran G.; Sahimi, Muhammad; Tsotsis, Theodore T.

1998-04-01

213

Nonequilibrium Molecular Dynamics Simulation of Transport of Gas Mixtures in Nanopores  

NASA Astrophysics Data System (ADS)

We report the results of the first nonequilibrium Molecular Dynamics simulation of transport of a gas mixture through a carbon nanopore in the presence of an external chemical potential gradient. While the structure of the pore walls and the composition of the mixture have essentially no effect on the separation factor, the temperature of the system and the pore size strongly influence the results. The results are in qualitative agreement with the new experimental data that are reported here.

Xu, Lifang; Sedigh, Mehran G.; Sahimi, Muhammad; Tsotsis, Theodore T.

1998-03-01

214

Degradation of ZnS:Cu,Al,Au phosphor powder in different gas mixtures  

Microsoft Academic Search

The ZnS:Cu,Al,Au (P22G) phosphor powder was bombarded by an electron beam in an O2 ambient, Ar ambient and other mixture of gases. These gases consisted of mixtures of O2 and COx, and O2, COx and Ar gas. Auger electron spectroscopy (AES) was used to monitor changes in the surface composition of the P22G phosphor during electron bombardment. When the P22G

S. H Chen; A. P Greeff; H. C Swart

2004-01-01

215

Sound speed models for a noncondensible gas-steam-water mixture  

SciTech Connect

An analytical expression is derived for the homogeneous equilibrium speed of sound in a mixture of noncondensible gas, steam, and water. The expression is based on the Gibbs free energy interphase equilibrium condition for a Gibbs-Dalton mixture in contact with a pure liquid phase. Several simplified models are discussed including the homogeneous frozen model. These idealized models can be used as a reference for data comparison and also serve as a basis for empirically corrected nonhomogeneous and nonequilibrium models.

Ransom, V.H.; Trapp, J.A.

1984-01-01

216

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

217

Passive remote monitoring of multi-gas mixtures by FTIR radiometry  

NASA Astrophysics Data System (ADS)

The passive remote monitoring of multi-gas vapour mixtures by FTIR spectroscopy is investigated experimentally. The spectral radiance data were collected with the CATSI interferometer for a variety of multi-gas plumes at a distance of 60 m. Two basic sets of mixtures were studied. The first set corresponds to mixtures formed of three gases with no overlapping spectral bands (C2H2, C2H4 and R14). The second set corresponds to mixtures formed of three gases having overlapping spectral bands (C2H4, R114 and R134a). For each mixture the flow rates of individual constituents were adjusted to yield specific constituent CL ratios. These ratios are compared to the CL ratios retrieved from infrared radiance spectra. Results of this study indicate that for both sets of multi-gas mixtures the CL ratios retrieved by the passive remote monitoring technique agree well with those derived from the release flow rates. This good level of agreement was achieved by introducing a simple correction scheme to compensate for the limited accuracy of the fast radiance model implemented in the GASEM monitoring algorithm.

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

2005-11-01

218

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

219

Mixing in Wave Processes Propagating in Gas Mixtures (Review)  

Microsoft Academic Search

A review is made of up-to-date investigations in the field of physicomathematical modeling of mixing of solid particles with high-velocity gas flows arising under the action on shock waves, compression waves, and expansion waves on unstable dust deposits on the boundaries of channels or plates and in cavities, as well as on free clouds of particles. In particular, experiments in

A. V. Fedorov

2004-01-01

220

Reduction of titania by methane-hydrogen-argon gas mixture  

SciTech Connect

Reduction of titania using methane-containing gas was investigated in a laboratory fixed-bed reactor in the temperature range 1,373 to 1,773 K. The reduction production product is titanium oxycarbide, which is a solid solution of TiC and TiO. At 1,373 K, the formation rate of TiC is very slow. The rate and extent of reaction increase with increasing temperature to 1,723 K. A further increase in temperature to 1,773 K does not affect the reaction rate and extent. An increase in methane concentration to 8 vol pct favors the reduction process. A further increase in methane concentration above 8 vol pct causes excessive carbon deposition, which has a negative effect on the reaction rate. Hydrogen partial pressure should be maintained above 35 vol pct to depress the cracking of methane. Addition of water vapor to the reducing gas strongly retards the reduction reaction, even at low concentrations of 1 to 2 vol pct. Carbon monoxide also depresses the reduction process, but its effect is significant only at higher concentrations, above 10 vol pct.

Zhang, G.; Ostrovski, O.

2000-02-01

221

A Study for Health Hazard Evaluation of Methylene Chloride Evaporated from the Tear Gas Mixture  

PubMed Central

This study explored the health hazard of those exposed to methylene chloride by assessing its atmospheric concentration when a tear gas mixture was aerially dispersed. The concentration of methylene chloride ranged from 311.1-980.3 ppm (geometric mean, 555.8 ppm), 30 seconds after the dispersion started. However, the concentration fell rapidly to below 10 ppm after dispersion was completed. The concentration during the dispersion did not surpass the National Institute for Occupational Safety and Health 'immediately dangerous to life or health' value of 2,300 ppm, but did exceed the American Conference of Governmental Industrial Hygienists excursion limit of 250 ppm. Since methylene chloride is highly volatile (vapor pressure, 349 mmHg at 20?), the postdispersion atmospheric concentration can rise instantaneously. Moreover, the o-chlorobenzylidenemalononitrile formulation of tear gas (CS gas) is an acute upper respiratory tract irritant. Therefore, tear gas mixtures should be handled with delicate care.

Chung, Eun-Kyo; Yi, Gwang-Yong; Chung, Kwang-Jae; Shin, Jung-Ah; Lee, In-Seop

2010-01-01

222

Variable-temperature cryogenic trap for the separation of gas mixtures  

NASA Technical Reports Server (NTRS)

The paper describes a continuous variable-temperature U-shaped cold trap which can both purify vacuum-line combustion products for subsequent stable isotopic analysis and isolate the methane and ethane constituents of natural gases. The canister containing the trap is submerged in liquid nitrogen, and, as the gas cools, the gas mixture components condense sequentially according to their relative vapor pressures. After the about 12 min required for the bottom of the trap to reach the liquid-nitrogen temperature, passage of electric current through the resistance wire wrapped around the tubing covering the U-trap permits distillation of successive gas components at optimal temperatures. Data on the separation achieved for two mixtures, the first being typical vacuum-line combustion products of geochemical samples such as rocks and the second being natural gas, are presented, and the thermal behavior and power consumption are reported.

Des Marais, D. J.

1978-01-01

223

[Electroencephalogram, informational saturation of electroencephalogram, and bispectral index during xenon anesthesia for laparoscopic operations].  

PubMed

The depth of xenon anesthesia was never evaluated by modern methods of EEG monitoring, and hence, we studied changes in EEG, INEEG, and BIS during different stages of xenon narcosis and evaluated the possibility of using these values as criteria of xenon anesthesia adequacy. The study was carried out in 60 patients during laparoscopic operations on abdominal organs. The patients were divided into 2 groups receiving different gas anesthetics (xenon or nitric oxide). The results indicate that xenon monoanesthesia caused dose-dependent changes in the native and treated EEG; xenon is a good inhalation anesthetic providing adequate anesthesia for little traumatic operations even in case of mononarcosis; INEEG and BIS monitoring during xenon anesthesia allows an objective evaluation of its depth. PMID:12221874

Likhvantsev, V V; Volovik, A G; Petrov, O V; Sitnikov, A V; Subbotin, V V

2002-01-01

224

Ionization efficiency studies for xenon ions with thesuperconducting ECR ion source VENUS  

SciTech Connect

Ionization efficiency studies for high charge state xenon ions using a calibrated gas leak are presented. A 75% enriched {sup 129}Xe gas leak with a gas flow equivalent to 5.11p{mu}A was used in all the measurements. The experiments were performed at the VENUS (Versatile ECR ion source for Nuclear Science) ion source for 18 GHz, 28 GHz and double frequency operation. Overall, total ionization efficiencies close to 100% and ionization efficiencies into a single charge state up to 22% were measured. The influence of the biased disk on the ionization efficiency was studied and the results were somewhat surprising. When the biased disk was removed from the plasma chamber, the ionization efficiency was dramatically reduced for single frequency operation. However, using double frequency heating the ionization efficiencies achieved without the biased disk almost matched the ionization efficiencies achieved with the biased probe. In addition, we have studied the influence of the support gas on the charge state distribution of the xenon ions. Either pure oxygen or a mixture of oxygen and helium were used as support gases. The addition of a small amount of helium can increase the ionization efficiency into a single charge state by narrowing the charge state distribution. Furthermore by varying the helium flow the most efficient charge state can be shifted over a wide range without compromising the ionization efficiency. This is not possible using only oxygen as support gas. Results from these studies are presented and discussed.

Leitner, Daniela; Lyneis, Claude M.; Todd, DamonS.; Tarvainen,Olli

2007-06-05

225

Recognizing indoor formaldehyde in binary gas mixtures with a micro gas sensor array and a neural network  

NASA Astrophysics Data System (ADS)

Low-concentration formaldehyde (HCHO) together with ethanol/toluene/acetone/?-pinene (as an interference gas of HCHO) is detected with a micro gas sensor array, composed of eight tin oxide (SnO2) thin film gas sensors with Au, Cu, Pt or Pd metal catalysts. The characteristics of the multi-dimensional signals from the eight sensors are evaluated. A multilayer neural network with an error backpropagation (BP) learning algorithm, plus the principal component analysis (PCA) technique, is implemented to recognize these indoor volatile organic compounds (VOC). The results show that the micro gas sensor array, plus the multilayer neural network, is very effective in recognizing 0.06 ppm HCHO in single gas component and in binary gas mixtures, toluene/ethanol/?-pinene with small relative error.

Lv, Pin; Tang, Zhenan; Wei, Guangfen; Yu, Jun; Huang, Zhengxing

2007-09-01

226

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.; Haas, Derek A.; Harper, Warren W.; Heimbigner, Tom R.; Hubbard, Charles W.; Humble, Paul H.; Madison, Jill C.; Morris, Scott J.; Panisko, Mark E.; Ripplinger, Mike D.; Stewart, Timothy L.

2013-09-26

227

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

228

Enhanced IR hollow cathode laser in a 3He Ne gas mixture  

NASA Astrophysics Data System (ADS)

An experimental and theoretical study on 3He-Ne and 4He-Ne helical hollow cathode lasers is presented. Enhanced laser operation on the near IR NeI lines is observed when the natural isotope 4He is substituted by the lighter isotope 3He. A four-fold increase in the laser output power and a three-fold increase in the laser gain for the strongest NeI 1.1523 µm line is measured in the 3He-Ne gas mixture compared to the 4He-Ne gas mixture. On the basis of the theoretical analysis done by means of a non-stationary kinetic model for the negative glow plasma of 3He-Ne and 4He-Ne hollow cathode lasers, a study on the changes in the particle kinetics is carried out and an explanation of the experimental results is proposed. In the 3He-Ne mixture the electron temperature is lower than in the 4He-Ne mixture, while the gas temperature is higher. As a result the helium triplet metastable density and the rate constant for excitation transfer to neon atoms are higher in the 3He-Ne mixture. The lower laser level de-excitation due to intra-multiplet mixing of 2p1-10levels by 3He atoms is more efficient.

Stefanova, M. S.; Pramatarov, P. M.; Karelin, A. V.

2005-09-01

229

Analysis of gas-phase polycyclic aromatic hydrocarbon mixtures by laser-induced fluorescence  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence (LIF) is a viable technique for qualitative and quantitative analysis of polycyclic aromatic hydrocarbons (PAH). An analytical tool for a nearly continuous analysis of gas-phase PAH based on LIF was designed and built. The author's intention is to further analyse complex mixtures containing PAH such as tar from gasification processes. This paper deals with measurements of individual PAH-components and mixtures thereof. Comparison of results and calibration of selected PAH-species was performed with on-line gas chromatography/mass spectrometry (GC/MS). A multiple linear regression approach is applied to LIF-spectra of mixtures from selected components at known concentrations in various combinations. It can be demonstrated that this approach opens the possibility to determine the concentration of PAH species in the gas phase at elevated temperatures within×20% accuracy. This is true if LIF-spectra of the individual species for specified concentrations in the PAH mixture are known beforehand. It will be further discussed how results change if substances being present in the mixture remain unconsidered in the calculations.

Sun, Renhui; Zobel, Nico; Neubauer, York; Cardenas Chavez, Christian; Behrendt, Frank

2010-12-01

230

Understanding and Designing Field Asymmetric Waveform Ion Mobility Spectrometry Separations in Gas Mixtures  

SciTech Connect

Field Asymmetric waveform Ion Mobility Spectrometry (FAIMS) has significant potential for post-ionization separations in conjunction with MS analyses. FAIMS exploits the fact that ion mobilities in gases depend on the electric field in a manner specific to each ion, which allows one to fractionate ion mixtures. Nearly all previous work has used pure gases, for which FAIMS fundamentals are understood reasonably well. However, experiments in gas mixtures like N2/CO2 have uncovered unexpected phenomena that remained unexplained. Here we introduce a universal model for FAIMS separations in mixtures, derived from the formalisms that determine high-field mobilities in heteromolecular gases. Overall, the theoretical findings are consistent with the data in N2/CO2, though quantitative discrepancies remain. As a control, modeled results for N2/O2 fit Blanc's law, in agreement with measurements. Calculations for He/N2 are broadly consistent with observations, and show why adding He to the working gas enhances FAIMS performance. We predict spectacular non-Blanc effects in mixtures of extremely disparate gases such as He/CO2, which could improve the peak capacity and sensitivity of technique. Understanding the FAIMS operation in gas mixtures will enable rational design of media for both targeted and global analyses.

Shvartsburg, Alexandre A.; Tang, Keqi; Smith, Richard D.

2004-12-15

231

Characterization and control of exhaust gas from diesel engine firing coal-water mixture  

SciTech Connect

Exhaust from the GE-TS single cylinder diesel engine, fitted with hardened metal, and diamond-tipped metal fuel injection nozzles, and firing coal-water mixture (CWM) has been characterized with respect to gas composition, particulate size distribution, and particulate filtration characteristics. The measured flue gas compositions are roughly in keeping with results from combustion calculations. The time variations of the hydrocarbon, CO, and NO{sub x} concentrations are also understood in terms of known reaction mechanisms.

Samuel, E.A.; Gal, E.; Mengel, M.; Arnold, M.

1990-03-01

232

Characterization and control of exhaust gas from diesel engine firing coal-water mixture  

SciTech Connect

Exhaust from the GE-TS single cylinder diesel engine, fitted with hardened metal, and diamond-tipped metal fuel injection nozzles, and firing coal-water mixture (CWM) has been characterized with respect to gas composition, particulate size distribution, and particulate filtration characteristics. The measured flue gas compositions are roughly in keeping with results from combustion calculations. The time variations of the hydrocarbon, CO, and NO[sub x] concentrations are also understood in terms of known reaction mechanisms.

Samuel, E.A.; Gal, E.; Mengel, M.; Arnold, M.

1990-03-01

233

Influence of Obstacles on Flame Propagation of Multi-Composition Mixture Gas  

NASA Astrophysics Data System (ADS)

In this paper, we experiment with city coal gas/air mixture in enclosed duct to investigate the acceleration mechanism of orifice plate obstacles on flame and its influence on explosion overpressure. Experimental results indicate that obstacle-induced turbulence can continually accelerate flame during its propagation and enhance explosion overpressure, and that flame acceleration is due to the unburned mixture heated by leading compression wave in front of flame front and the positive feedback of obstacle-induced turbulent zone to combustion process. Based on multi-material cell program, we adopt two-step chemical reaction model to simulate explosion process of city coal gas-air mixture in the duct, and the results agree well with the experimental ones.

Ning, Jianguo; Wang, Cheng; Lu, Jie

234

Ignition of a combustible gas mixture by a laser spark excited in the reactor volume  

SciTech Connect

Ignition of a stoichiometric CH{sub 4}: O{sub 2} mixture by a laser spark excited in the reactor volume is studied experimentally. It is found that the spark initiates a feebly radiating incomplete-combustion wave, which is much faster than the combustion wave, but is substantially slower than the detonation wave. With a time delay of 500-700 {mu}s, a bright optical flash occupying the entire chamber volume is observed, which indicates fast (involving branching chain reactions) ignition of the gas mixture. A conclusion is drawn regarding the common nature of the process of ignition of a combustible gas mixture by a laser spark excited in the reactor volume and the previously investigated initiation of combustion by laser sparks excited at solid targets, high-power microwave discharges, and high-current gliding discharges.

Kazantsev, S. Yu.; Kononov, I. G.; Kossyi, I. A.; Tarasova, N. M.; Firsov, K. N. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation)

2009-03-15

235

Hydrocracking of vacuum gas oil-vegetable oil mixtures for biofuels production.  

PubMed

Hydrocracking of vacuum gas oil (VGO)--vegetable oil mixtures is a prominent process for the production of biofuels. In this work both pre-hydrotreated and non-hydrotreated VGO are assessed whether they are suitable fossil components in a VGO-vegetable oil mixture as feed-stocks to a hydrocracking process. This assessment indicates the necessity of a VGO pre-hydrotreated step prior to hydrocracking the VGO-vegetable oil mixture. Moreover, the comparison of two different mixing ratios suggests that higher vegetable oil content favors hydrocracking product yields and qualities. Three commercial catalysts of different activity are utilized in order to identify a range of products that can be produced via a hydrocracking route. Finally, the effect of temperature on hydrocracking VGO-vegetable oil mixtures is studied in terms of conversion and selectivity to diesel, jet/kerosene and naphtha. PMID:19231171

Bezergianni, Stella; Kalogianni, Aggeliki; Vasalos, Iacovos A

2009-06-01

236

Transient refractive index measurements in XeF laser gas mixtures  

SciTech Connect

Transient refractive index (TRI) measurements have been made in e-beam-pumped, XeF laser gas mixtures as a function of energy loading. Both NF/sub 3/ and F/sub 2/ were used as halogen donors in a neon base. TRI due to halogen donor burnup and to plasma dispersion was measured at 578.4 nm in typical laser mixtures containing Xe and at 353.2 nm in mixtures without Xe. The net index of refraction of the mixtures decreased with increasing energy loading, resulting in a difference of about 50 x 10/sup -9/ to 100 x 10/sup -9/ between a pumped and unpumped region at a typical loading of 150 J/I.

Fulghum, S.F.; Trainor, D.; Appel, C.

1989-05-01

237

Modeling of dense gas–solid reactive mixtures applied to biomass pyrolysis in a fluidized bed  

Microsoft Academic Search

A model is presented for mathematically describing the thermofluid dynamics of dense, reactive, gas–solid mixtures. The model distinguishes among multiple particle classes, either on the basis of their physical properties (diameter, density) or through their thermochemistry (reactive versus inert particles). A multifluid approach is followed where macroscopic equations are derived from the kinetic theory of granular flows using inelastic rigid-sphere

D. Lathouwers; J. Bellan

2001-01-01

238

BRIEF COMMUNICATIONS: Possibility of spontaneous circulation of a gas mixture in a pulse-periodic laser  

Microsoft Academic Search

An analysis is made of gasdynamic processes in an electrically pumped gasdynamic CO2 laser. It is shown that, in principle, it is possible to use the energy of shock waves resulting from pulsed evolution of energy in a discharged gap to drive a gas mixture along a closed duct. This is done by placing a nonreturn valve at the entry

A. V. Gubarev; S. V. Drobyazko; A. A. Yakushev

1978-01-01

239

BRIEF COMMUNICATIONS: Thermal diffusion separation of gas mixtures with the aid of laser radiation  

Microsoft Academic Search

An analysis is made of thermal diffusion processes in gas mixtures stimulated by laser radiation. It is shown that these processes may be characterized by high values of the separation coefficient. Complex dynamic regimes of thermal diffusion in a laser radiation field are revealed by the calculations. The results of an experimental study are also given.

F. V. Bunkin; N. A. Kirichenko; B. S. Luk'yanchuk; Georgii A. Shafeev

1982-01-01

240

BRIEF COMMUNICATIONS: Automatic replenishment of the gas mixture in excimer lasers  

Microsoft Academic Search

The possibility of automatic circulation of a gas mixture in cells subjected to pulse-periodic pumping was demonstrated experimentally. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints

N. G. Zubrilin; P. I. Korenyuk; O. N. Tkachenko; M. P. Chernomorets

1990-01-01

241

Approximation of flammability region for natural gas-air-diluent mixture.  

PubMed

The growing implementation of exhaust gas recirculation (EGR) in reducing NO(x) emissions of engine is of paramount motivation to perform a fundamental research on the flammability characteristics of fuel-air-diluent mixtures. In this work, the influences of EGR on the flammability region of natural gas-air-diluent flames were experimentally studied in a constant volume bomb. An assumption of critical burning velocity at flammability limit is proposed to approximately determine the flammability region of these mixtures. Based on this assumption, an estimation of the flammability map for natural gas-air-diluent mixtures was obtained by using the empirical formula of burning velocity data. The flammability regions of natural gas-air mixtures with EGR are plotted versus the EGR rate. From the comparison of estimated results and experimental measurements, it is suggested that the accuracy of prediction is largely dependent upon the formula of burning velocity used. Meanwhile, the influence of pressure on the critical burning velocity at flammability limit is also investigated. On the basis of the pressure dependence criterion, the estimation was performed for the circumstance of high temperature and pressure, and the prediction results still agree well with those of experiments. PMID:15990227

Liao, S Y; Jiang, D M; Huang, Z H; Cheng, Q; Gao, J; Hu, Y

2005-10-17

242

THE EXACT PENETRATION MODEL OF DIFFUSION IN MULTICOMPONENT IDEAL GAS MIXTURES. ANALYTICAL AND NUMERICAL SOLUTIONS  

Microsoft Academic Search

An exact analytical solution is derived for the penetration model of diffusion in multicomponent ideal gas mixtures at constant pressure and temperature. It takes the form of a matrizant solution to the continuity and Maxwell-Stefan equations transformed by introduction of a similarity variable, and includes as special cases the corresponding binary and linearized theory solutionsDirect numerical implementation of the analytical

CLAUDIO OLIVERA-FUENTES; JOAQUÍN PASQUEL-GUERRA

1987-01-01

243

High pressure autoignition of natural gas\\/air mixtures and the problem of engine knock  

Microsoft Academic Search

A detailed chemical kinetic reaction mechanism is used in a numerical model to examine the rate of autoignition in mixtures of natural gas and air under conditions which occur in internal combustion engines. The effects of variations in typical engine operating parameters on this autoignition rate are assessed, and the rate of ignition is related to the onset of engine

C. K. Westbrook; W. J. Pitz

1987-01-01

244

Concentration measurement systems with stable solutions for binary gas mixtures using two flowmeters  

NASA Astrophysics Data System (ADS)

The previously proposed gas concentration measurement system (Yamazaki et al 2007 Meas. Sci. Technol. 18 2762-8) shows a considerable error for some combinations of gases. The error increases when the system of equations determining mole fractions becomes a mathematically ill-conditioned system. Because the parameters of the equations reflect the material properties of the gases, the current paper considers flowmeters whose flow rate indication does not involve any gas property. This paper firstly illustrates the ill condition for the combination of venturi meter and laminar flowmeters. The paper then discusses the simultaneous measurement of flow rate and mole fractions by flowmeter combinations: an ultrasonic flowmeter and a venturi meter, an ultrasonic flowmeter and a laminar flowmeter. Experiments are conducted for a mixture of argon and air. When a venturi meter and a laminar flowmeter are used, the equations to evaluate the gas mixture ratio become an ill-conditioned system, and hence the evaluated mixture ratio shows a considerable error. On the other hand, the combination of an ultrasonic flowmeter and a laminar flowmeter detects the gas mixture ratio with proper accuracy.

Youn, Chongho; Kawashima, Kenji; Kagawa, Toshiharu

2011-06-01

245

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)...

246

Bose-Einstein condensation temperature of a trapped interacting Bose-Fermi gas mixture  

Microsoft Academic Search

We calculate the critical temperature of a trapped interacting Bose-Fermi gas mixture by means of a first-order perturbation method in a local-density approximation. An explicit analytical expression is derived for the dependence of the critical temperature on the numbers of bosons and fermions, the strengths of boson-boson and boson-fermion interactions, and the trapping frequencies.

Yong-Li Ma; Siu-Tat Chui

2002-01-01

247

Program computes equilibrium normal shock and stagnation point solutions for arbitrary gas mixtures  

NASA Technical Reports Server (NTRS)

Program computes solutions for flow parameters in arbitrary gas mixtures behind a normal and a reflected normal shock, for in-flight and shock-tube stagnation conditions. Equilibrium flow calculations are made by a free-energy minimization technique coupled with the steady-flow conservation equations and a modified Newton-Raphson iterative scheme.

Callis, L. B.; Kemper, J. T.

1967-01-01

248

Membrane system design for multicomponent gas mixtures via mixed-integer nonlinear programming  

Microsoft Academic Search

An optimal design strategy for membrane networks separating multicomponent gas mixtures based on an approximate permeator model and mixed-integer nonlinear programming (MINLP) is proposed. A permeator system superstructure is used to embed a very large number of possible network configurations and allows the permeator feed-side pressure to be fixed or a design variable. A MINLP design model is developed to

Runhong Qi; Michael A. Henson

2000-01-01

249

Energy distribution of heavy particles generated in the cathode fall of a gas mixture glow discharge  

Microsoft Academic Search

An analytical model based on the solution of the Boltzmann equation and the theory of ion avalanches has been developed for the energy distributions of ions and neutrals created in the cathode fall of a gas mixture glow discharge. The model allows the determination of the energy distributions and flux densities of all possible species, including multiply charged ions. The

Z. Wronski; J. L. Sullivan; C. G. Pearce

1994-01-01

250

10 CFR 503.38 - Permanent exemption for certain fuel mixtures containing natural gas or petroleum.  

Code of Federal Regulations, 2010 CFR

...Btu heat input of the primary energy sources needed to maintain operational...the use of a mixture of solar energy (including wind, tide, and other intermittent sources...natural gas, where: (1) Solar energy will account for at least 20...

2009-01-01

251

A lattice fluid approach to complex mixtures: natural gas and crude oil  

Microsoft Academic Search

Densities and vapor-liquid compositions for twelve complex mixtures (crude oil and natural gas) are calculated using a lattice fluid model equation of state. Fractions of the heavy ends are approximated as pseudocomponents defined in terms of their ‘equivalent normal alkane’. The lattice fluid model equation of state of Sanchez-Lacombe is used, three parameters are required for each pure component and

R. von Bergen; Y. von Bergen; E. Rogel

1997-01-01

252

Growth Kinetics and Modeling of Direct Oxynitride Growth with NO-O2 Gas Mixtures.  

National Technical Information Service (NTIS)

We have modeled growth kinetics of oxynitrides grown in NO-O2 gas mixtures from first principles using modified Deal-Grove equations. Retardation of oxygen diffusion through the nitrided dielectric was assumed to be the dominant gr...

S. Everist J. Nelson R. Sharangpani P. M. Smith S. P. Tay

1999-01-01

253

Hyperpolarized xenon-129 production and applications  

NASA Astrophysics Data System (ADS)

Hyperpolarized 3He and 129Xe were initially developed and used in the nuclear physics community. Lately they are primarily used in Medical Resonance Imaging (MRI). Although first MRI polarized gas images were acquired using 129Xe, the research community has focused mostly on 3He, due to the well-known polarizing methods and higher polarization numbers achieved. The main purpose of this thesis is to present a novel design of a large-scale SEOP polarizer for producing large quantities of highly polarized 129Xe. High Rb-Xe spin-exchange rates through long-lived van de Waals molecules at low total pressure, implemented in a novel counterflow polarizer design, resulted in xenon polarization as high as 50% for 1.2 liters/hour, with a maximum of 64% for 0.3 l/h. We characterized and improved the polarization process by finding the optimum operating parameters of the polarizer. Two new methods to efficiently use high-power diode lasers are described: a new optical arrangement for a better beam shaping of fiber coupled lasers and the first external-cavity spectrum narrowing of a stack of laser diode arrays. A new accumulation technique for the hyperpolarized xenon was developed and full recovery of polarization after a freeze-thaw cycle was demonstrated for the first time. Two approaches for xenon delivery, frozen and gas states, were developed. Hyperpolarized xenon transportation to Brigham and Women's Hospital was successfully accomplished for collaborative research. First MRI images using hyperpolarized xenon acquired at BWH are presented. Final chapter is focused on describing a low field human MRI scanner using hyperpolarized 3He. We built a human scale imager with open access for orientational studies of the lung functionality. Horizontal and vertical human lung images were acquired as a first stage of this project.

Ruset, Iulian C.

254

Xenon diffusion studies with prompt gamma activation analysis  

Microsoft Academic Search

Developing a better understanding of xenon transport through porous systems is critical to predicting how this gas will enter\\u000a the atmosphere after a below ground nuclear weapons test. Radioxenon monitoring is a vital part of the Comprehensive Nuclear-Test-Ban\\u000a Treaty (CTBT) International Monitoring System. This work details the development of prompt gamma activation analysis for measuring\\u000a the diffusion rates of xenon

Carlos A. Rios Perez; Justin D. Lowrey; Steven Biegalski; Mark R. Deinert

255

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

256

Ignition of a combustible gas mixture by a high-current electric discharge in a closed volume  

SciTech Connect

Results are presented from experimental studies and numerical calculations of the ignition of a stoichiometric CH{sub 4}: O{sub 2} gas mixture by a high-current gliding discharge. It is shown that this type of discharge generates an axially propagating thermal wave (precursor) that penetrates into the gas medium and leads to fast gas heating. This process is followed by an almost simultaneous ignition of the gas mixture over the entire reactor volume.

Berezhetskaya, N. K.; Gritsinin, S. I.; Kop'ev, V. A.; Kossyi, I. A. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation); Kuleshov, P. S. [Baranov Central Institute of Aviation Motors (Russian Federation); Popov, N. A. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation); Starik, A. M. [Baranov Central Institute of Aviation Motors (Russian Federation); Tarasova, N. M. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation)

2009-06-15

257

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.

2010-01-01

258

PIXeY - Liquid Xenon R&D at Yale  

NASA Astrophysics Data System (ADS)

In recent years xenon has risen as a medium for particle detection, exhibiting a number of desirable qualities that make it well-suited for applications such as medical imaging, imaging of nuclear materials, and fundamental physics research. Xenon is a bright scintillator, with a fast (˜45 ns) response time, a large charge yield and high electron mobility. The high density (3 g/mL) and high atomic number (Z = 54) of liquid xenon make it ideal for detecting gamma rays with high efficiency over large energy ranges. PIXeY (Particle Identification in Xenon at Yale) is a compact, liquid-xenon-based TPC that operates in either single or two-phase (liquid/gas) mode and detects both charge and light signals produced by particle interactions within the detector. The initial goal of the experiment is to study xenon physics with implications for the operation and design for future large scale experiments (for dark matter or double beta decay), including energy resolution and event discrimination. This presentation will provide an overview of the experiment and discuss the xenon physics studies planned, the results so far and a brief overview of future plans.

Edwards, Blair; Bernard, Ethan; Cahn, Sidney; Larsen, Nicole; Lyashenko, Alexey; McKinsey, Daniel; Nikkel, James; Shin, Yunchang; Tennyson, Brian; Wahl, Christopher; Destefano, Nicholas; Gai, Moshe

2013-04-01

259

Biofiltration of mixtures of gas-phase styrene and acetone with the fungus Sporothrix variecibatus  

Microsoft Academic Search

The biodegradation performance of a biofilter, inoculated with the fungus Sporothrix variecibatus, to treat gas-phase styrene and acetone mixtures under steady-state and transient conditions was evaluated. Experiments were carried out by varying the gas-flow rates (0.05–0.4m3h?1), leading to empty bed residence times as low as 17.1s, and by changing the concentrations of gas-phase styrene (0.01–6.3gm?3) and acetone (0.01–8.9gm?3). The total

Eldon R. Rene; Radka Špa?ková; María C. Veiga; Christian Kennes

2010-01-01

260

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.

1990-06-26

261

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

262

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

Code of Federal Regulations, 2013 CFR

...of cylinders with a mixture of compressed gas and other material. 173.305 Section...REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.305...of cylinders with a mixture of compressed gas and other material. (a) Detailed...

2013-10-01

263

Investigation of the dielectric barrier discharge properties in different gas mixtures  

NASA Astrophysics Data System (ADS)

Experimental investigations of the dielectric barrier discharge (DBD), aimed at the study of the discharge properties at different gas mixtures, are presented. They are devoted to the time- and space-resolved measurements of the DBD radiation. Radiation of the molecular bands over the period of the applied voltage was investigated. The experimental setup allowed to collect radiation from the region near one electrode. The measurements revealed the dependence of the band intensities on the gas mixture and the polarity of the electrode. A range of gases in binarycombinations of helium, argon and oxy gen with nitrogen were explored. With the help of the well known method of Lissajous figure acquisition, the discharge was characterized electrically. The conditions chosen were typical for this kind of discharges: pressure 1 bar, room temperature, the frequency of the applied voltage 1 kHz. The power dissipated in the discharge was within limits of 10 watts. For some gas mixtures, measurements in the presence of a gas flow were performed. The results have shown that under given conditions, DBD exists in a filamentaryform and onlyin few cases, one can obtain a homogeneous appearance. The change in the appearance corresponds to the changes of the emission intensities in the near-electrode region according to the polarity of the electrode. Also, it was found that the presence of the gas flow has no influence on the discharge properties examined here.

Kozakov, R.; Sonnenfeld, A.; Behnke, J. F.; Lebedev, V.

2000-03-01

264

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

265

The synthesis of NiS, ZnS and SrS through solid-gas reaction of sulfidizing gas mixture  

Microsoft Academic Search

In this study, the sulfidizations of NiO, ZnO, SrNO3 and SrCO3 were investigated by using solid-gas reactions under sulfidizing gas mixture, which contains the gas mixture of carbonyl sulfide (COS), carbon disulfide (CS2) and sulfur (S2).The powder crystalline forms of nickel sulfide (NiS), zinc sulfide (ZnS) and strontium sulfide (SrS) were prepared purely by solid-gas reaction technique. The product crystalline

H. Güler; F. Kurtulu?

2006-01-01

266

An experimental setup with ultrasonic gas analyzers and real time analysis of the composition of a binary gas mixture  

NASA Astrophysics Data System (ADS)

This paper describes an automated measuring apparatus with an ultrasonic gas analyzer and realtime analysis of the composition of the gas. The apparatus is designed for preparing binary gas mixtures and making measurements in a wide range of pressures (from 0.8 bara to 15 bara) and temperatures (between -15°C and 80°C). The apparatus was developed to determine the thermophysical properties of fluorocarbon mixtures for potential use in the cooling circuits of several Large Hadron Collider projects at CERN. The design of its control system took into account the safety and reliability o the gas analyzer, and the need to limit the presence of laboratory personnel. The control system was implemented in PVSS-II, the Supervisory, Control and Data Acquisition standard chosen for LHC and its experiments at CERN. The second part of the paper describes the implementation and verification of the algorithm for continuous real-time determination of the composition of the refrigerant mixture. The algorithm is based on minimizing the quadratic norm fromthe measured data and from the pre-generated look-up tables acquired from the NIST REFPROP software package.

Vacek, V.; Vítek, M.; Doubek, M.

2013-04-01

267

Methane Replacement in Natural Gas Hydrate Sediments with CO2 and a CO2/N2 Gas Mixture  

NASA Astrophysics Data System (ADS)

The direct recovery of methane from massive methane hydrates, artificial MH-bearing clays, and natural MH-bearing sediments is demonstrated, using either CO2 or a CO2/N2 gas mixture (20 mol% of CO2 and 80 mol% of N2, reproducing flue gas from a power plant) for methane replacement in complex marine systems. Natural gas hydrates (NGHs) can be converted into CO2 hydrate by a swapping mechanism. The overall process provides a dual purpose of sustainable energy-source exploitation and greenhouse-gas sequestration. Thus far, scant attention has been paid to the clay portion in deep-sea gas hydrate sediment, despite the fact that these materials are capable of storing a tremendous amount of NGHs. The clay particles have a peculiar structure that makes the behavior of NGHs very different from that of pure MHs. In this study, we pull out methane from intercalated methane hydrates in a clay interlayer using CO2 and a CO2/N2 gas mixture. The results of this study can contribute to the understanding of physicochemical background required for large-scale NGH production under the seabed.

Park, S.; Koh, D.; Kang, H.; Lee, J.; Kim, S.; Lee, H.

2012-12-01

268

XENON in medical area: emphasis on neuroprotection in hypoxia and anesthesia.  

PubMed

Xenon is a medical gas capable of establishing neuroprotection, inducing anesthesia as well as serving in modern laser technology and nuclear medicine as a contrast agent. In spite of its high cost, its lack of side effects, safe cardiovascular and organoprotective profile and effective neuroprotective role after hypoxic-ischemic injury (HI) favor its applications in clinics. Xenon performs its anesthetic and neuroprotective functions through binding to glycine site of glutamatergic N-methyl-D-aspartate (NMDA) receptor competitively and blocking it. This blockage inhibits the overstimulation of NMDA receptors, thus preventing their following downstream calcium accumulating cascades. Xenon is also used in combination therapies together with hypothermia or sevoflurane. The neuroprotective effects of xenon and hypothermia cooperate synergistically whether they are applied synchronously or asynchronously. Distinguishing properties of Xenon promise for innovations in medical gas field once further studies are fulfilled and Xenon's high cost is overcome. PMID:23369273

Esencan, Ecem; Yuksel, Simge; Tosun, Yusuf Berk; Robinot, Alexander; Solaroglu, Ihsan; Zhang, John H

2013-01-01

269

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

270

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

271

Calculation of the thermodynamic properties of gas and liquid solutions - Mixtures of complex substances  

NASA Astrophysics Data System (ADS)

Reference is made to a previous study (Kessel'man et al., 1986) in which a method has been proposed for calculating the thermodynamic properties of gas and liquid solutions in the one- and two-phase regions on the basis of a unified equation of state. Here, by using an effective intermolecular potential with temperature-dependent parameters, this method is extended to the calculation of the thermodynamic parameters of mixtures with complex components. Results are presented for a number of mixtures, including Ar+CO2, Ar+N2, N2+CH4, N2C2C6, CH4+CO2, and CH4+C4H10.

Kessel'Man, P. M.; Tkachenko, V. V.; Ugol'Nikov, A. P.

1987-12-01

272

Reactive sputtering of titanium in Ar/CH4 gas mixture: Target poisoning and film characteristics  

SciTech Connect

Reactive sputtering of titanium target in the presence of Ar/CH{sub 4} gas mixture has been investigated. With the addition of methane gas to above 1.5% of the process gas a transition from the metallic sputtering mode to the poison mode was observed as indicated by the change in cathode current. As the methane gas flow concentration increased up to 10%, the target was gradually poisoned. The hysteresis in the cathode current could be plotted by first increasing and then subsequently decreasing the methane concentration. X-ray diffraction and X-ray photoelectron spectroscopy analyses of the deposited films confirmed the formation of carbide phases and the transition of the process from the metallic to compound sputtering mode as the methane concentration in the sputtering gas is increased. The paper discusses a sputtering model that gives a rational explanation of the target poisoning phenomenon and shows an agreement between the experimental observations and calculated results.

Fouad, O.A.; Rumaiz, A.; Shah, S.

2009-03-01

273

Cosmic ray tests of a GEM-based TPC prototype operated in Ar-CF 4-isobutane gas mixtures  

NASA Astrophysics Data System (ADS)

Argon with an admixture of CF 4 is expected to be a good candidate for the gas mixture to be used for a time projection chamber (TPC) in the future linear collider experiment because of its small transverse diffusion of drift electrons especially under a strong magnetic field. In order to confirm the superiority of this gas mixture over conventional TPC gases we carried out cosmic ray tests using a GEM-based TPC operated mostly in Ar-CF 4-isobutane mixtures under 0-1 T axial magnetic fields. The measured gas properties such as gas gain and transverse diffusion constant as well as the observed spatial resolution are presented.

Kobayashi, M.; Yonamine, R.; Tomioka, T.; Aoza, A.; Bito, H.; Fujii, K.; Higashi, T.; Hiramatsu, K.; Ikematsu, K.; Ishikawa, A.; Kato, Y.; Kuroiwa, H.; Matsuda, T.; Nitoh, O.; Ohta, H.; Sakai, K.; Settles, R. D.; Sugiyama, A.; Tsuji, H.; Watanabe, T.; Yamaoka, H.; Yazu, T.

2011-06-01

274

Gamma detectors based on high-pressure xenon: their development and application  

NASA Astrophysics Data System (ADS)

Various modifications of xenon detectors and their parameters in comparison with gamma-detectors of other types are considered. Prospects of xenon detectors' applicatins in gamma-spectroscopy based on experimental results are discussed including detection and control of radioactive and fissile materials displacement, definition of uranium enrichment rate, and measurements of nuclear reactor radioactive gas waste concentration. Possibilities for xenon detector use for environmental control and measurement of cosmic gamma radiation on orbital stations are considered.

Ulin, Sergey E.; Dmitrenko, Valery V.; Grachev, V. M.; Uteshev, Z. M.; Vlasik, K. F.; Chernysheva, I. V.; Dukhvalov, A. G.; Kotler, F. G.; Pushkin, K. N.

2004-10-01

275

Gamma detectors based on high pressure xenon: their development and application  

NASA Astrophysics Data System (ADS)

Various modifications of xenon detectors and their parameters in comparison with gamma-detectors of other types are considered. Prospects of xenon detectors' applications in gamma-spectroscopy based on experimental results are discussed including detection and control of radioactive and fissile materials displacement, definition of uranium enrichment rate, and measurements of nuclear reactor radioactive gas waste concentration. Possibilities for xenon detector use for environmental control and measurement of cosmic gamma radiation on orbital stations are considered.

Ulin, Sergey E.; Dmitrenko, Valery V.; Grachev, V. M.; Uteshev, Z. M.; Vlasic, K. F.; Chernysheva, I. V.; Duhvalov, A. G.; Kotler, F. G.; Pushkin, K. N.

2004-01-01

276

Implementation of ultrasonic sensing for high resolution measurement of binary gas mixture fractions.  

PubMed

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

277

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.

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

278

Radon removal from gaseous xenon with activated charcoal  

NASA Astrophysics Data System (ADS)

Many low background experiments using xenon need to remove radioactive radon to improve their sensitivities. However, no method of continually removing radon from xenon has been described in the literature. We studied a method to remove radon from xenon gas through an activated charcoal trap. From our measurements we infer a linear relationship between the mean propagation velocity vRn of radon and vXe of xenon in the trap with vRn/vXe=(0.96±0.10)×10-3 at -85 °C. As the mechanism for radon removal in this charcoal trap is its decay, knowledge of this parameter allows us to design an efficient radon removal system for the XMASS experiment. The verification of this system found that it reduces radon by a factor of 0.07, which is in line with its expected average retention time of 14.8 days for radon.

Abe, K.; Hieda, K.; Hiraide, K.; Hirano, S.; Kishimoto, Y.; Kobayashi, K.; Koshio, Y.; Liu, J.; Martens, K.; Moriyama, S.; Nakahata, M.; Nishiie, H.; Ogawa, H.; Sekiya, H.; Shinozaki, A.; Suzuki, Y.; Takachio, O.; Takeda, A.; Ueshima, K.; Umemoto, D.; Yamashita, M.; Hosokawa, K.; Murata, A.; Otsuka, K.; Takeuchi, Y.; Kusaba, F.; Motoki, D.; Nishijima, K.; Tasaka, S.; Fujii, K.; Murayama, I.; Nakamura, S.; Fukuda, Y.; Itow, Y.; Masuda, K.; Nishitani, Y.; Takiya, H.; Uchida, H.; Kim, Y. D.; Kim, Y. H.; Lee, K. B.; Lee, M. K.; Lee, J. S.; Xmass Collaboration

279

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

280

Quantitative comparison of combined gas chromatographic/mass spectrometric profiles of complex mixtures  

NASA Technical Reports Server (NTRS)

The paper describes a method called HISLIB for automatic quantitative comparison of gas chromatographic/mass spectrometric (GC/MS) results obtained on complex mixtures of organic compounds. The method is based on comparing new mixtures to 'historical' libraries of previous results. Co-occurrence of components is determined by matching relative retention indices (RRIs) and mass spectra after background removal and resolution of overlapping GC components. Internal standards are used to quantify the relative concentrations of components. Applications of HISLIB include validation of analytical procedures to isolate complex mixtures; development of historical libraries which might include complete summaries of all past observations, compilations of controls, or any other selected subset of results; improvement of the quality of existing libraries of mass spectral data; and detection of differences in kind and/or amounts of individual components. Limitations of the method are mentioned along with causes of their occurrence.

Smith, D. H.; Achenbach, M.; Yeager, W. J.; Anderson, P. J.; Fitch, W. L.; Rindflelsch, T. C.

1977-01-01

281

Experimental study and kinetics modeling of gas hydrate formation of methane-ethane mixture  

NASA Astrophysics Data System (ADS)

In this study, gas hydrate formation kinetics of methane and ethane binary mixtures has been studied and data of mixed methane-ethane hydrate formation at 0.1, 0.2, 0.3, 0.5, 0.68, 0.8, and 0.9 mole fractions of methane and at a temperature of 277.15 K and an initial pressure of approximately 3.6 MPa were collected. The thermodynamic natural path was used for modeling the hydrate formation rate in a constant volume process. The results show that there is good agreement between model prediction and experimental data, with an average error of 0.9%. It was observed that the values of these parameters are dependent on the concentration of components in the mixtures. The results indicate that this model can predict constant volume experimental data of binary mixture hydrate.

Naeiji, Parisa; Varaminian, Farshad

2013-09-01

282

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

283

Primary scintillation characteristics of Ar+CF4 gas mixtures excited by proton and alpha particles  

NASA Astrophysics Data System (ADS)

In this paper, we report how the concentration of carbon-tetrafluoride (CF4) affects the primary scintillation from Ar+CF4 gas mixtures excited by proton and alpha particles. The single photon counting method was used to measure the time spectra of the primary scintillation from Ar, CF4 and their mixtures at atmospheric pressure. Pure Ar exhibits a fast decay time constant, which is approximately 6 ns, and a slow decay time tail. Initially, increases in the concentration of CF4 increase the decay time of the Ar+CF4 gas mixture. However, when the concentration of CF4 exceeds a certain threshold, the decay time decreases to that of pure CF4, approximately 8-9 ns. We also report the photon emission spectra of Ar+CF4 mixtures excited by protons. The emission spectrum of the primary scintillation from Ar is improved by CF4 in both the ultraviolet region and the visible to near-infrared region.

Liu, Jinliang; Ouyang, Xiaoping; Chen, Liang; Zhang, Xianpeng; Liu, Jun; Zhang, Zhongbing; Ruan, Jinlu

2012-12-01

284

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

285

Kinetic solution of the structure of a shock wave in a nonreactive gas mixture  

NASA Astrophysics Data System (ADS)

The multispecies Boltzmann equation is numerically integrated to characterize the internal structure of a Mach 3 shock wave in a hard sphere gas. The collision integral is evaluated by the conservative discrete ordinate method [F. G. Tcheremissine, Comput. Math. Math. Phys. 46, 315 (2006)]. There was excellent agreement of macroscopic variables [Kosuge et al.., Eur. J. Mech. B/Fluids 20, 87 (2001)]. The effect of species concentration and mass ratio on the behavior of macroscopic variables and distribution functions in the structure of the shock wave is considered for both two- and three-species gas mixtures. In a binary mixture of gases with different masses and varying concentrations, the temperature overshoot of the parallel component of temperature near the center of the shock wave is highest for the heavy component when the concentration of the heavy component is the smallest. The rise in the parallel component of temperature is revealed by the behavior of the distribution function.

Josyula, Eswar; Vedula, Prakash; Bailey, William F.; Suchyta, Casimir J.

2011-01-01

286

Kinetic Solution of the Structure of a Shock Wave in a Non-Reactive Gas Mixture  

NASA Astrophysics Data System (ADS)

The multi-species Boltzmann equation is numerically integrated to characterize the internal structure of a Mach 3 shock wave in a hard sphere gas. The collision integral is evaluated by the conservative discrete ordinate method of Tcheremissine [1]. There was excellent agreement of macroscopic variables with those of Kosuge, Aoki, and Takata. [2] The effect of species concentration and mass ratio on the behavior of macroscopic variables and distribution functions in the structure of the shock wave is considered for both two and three-species gas mixtures. In a binary mixture of gases with different masses and varying concentrations, the temperature overshoot of the parallel component of temperature near the center of the shock wave is highest for the heavy component when the concentration of the heavy component is the smallest. A physical basis for the temperature overshoot is put forth.

Josyula, Eswar; Vedula, Prakash; Bailey, William F.; Suchyta, Casimir J.

2011-05-01

287

Cryotrapping assisted mass spectrometry for the analysis of complex gas mixtures  

SciTech Connect

A simple method is described for the unambiguous identification of the individual components in a gas mixture showing strong overlapping of their mass spectrometric cracking patterns. The method, herein referred to as cryotrapping assisted mass spectrometry, takes advantage of the different vapor pressure values of the individual components at low temperature (78 K for liquid nitrogen traps), and thus of the different depletion efficiencies and outgassing patterns during the fast cooling and slow warming up of the trap, respectively. Examples of the use of this technique for gas mixtures with application to plasma enhanced chemical vapor deposition of carbon and carbon-nitrogen hard films are shown. Detection of traces of specific C{sub 3} hydrocarbons (<50 ppm of initial methane) in methane/hydrogen plasmas and the possible trapping of thermally unstable C-N compounds in N{sub 2} containing deposition plasmas are addressed as representative examples of specific applications of the technique.

Ferreira, Jose A.; Tabares, Francisco L. [Laboratorio Nacional de Fusion por Confinamiento Magnetico, CIEMAT, Avda Complutense 22, Madrid 28040 (Spain)

2007-03-15

288

Noble gas mixture CW hollow cathode laser with internal anode system  

Microsoft Academic Search

A hollow cathode discharge tube with internal anodes was found to operate at significantly higher discharge voltages than a conventional HCD. A laser tube having internal anodes was constructed and laser operation was investigated in He-Kr, He-Ar and He-Ne-Xe gas mixtures. Due to the increased voltage low threshold currents and increased output power were obtained at the 4694 A Kr

K. Rozsa; M. Janossy; J. Bergou; L. Csillag

1977-01-01

289

Brief communication A suitable mixture fraction for diffusion flames of wood pyrolysis gas  

Microsoft Academic Search

Gaseous fuel released from pyrolysis of wood is a complex and highly variable mixture that includes four main gases (H2, CO, CH4 and CO2) (1). Since wood pyrolysis and combustion processes are very complex, most current approaches to modeling spread of wildland fire ignore the details of the gas- eous combustion (2-3). Instead, global reaction rate and thermodynamical parameters are

Xiangyang Zhou; Shankar Mahalingam

290

Life cycle greenhouse emissions of compressed natural gas–hydrogen mixtures for transportation in Argentina  

Microsoft Academic Search

We have developed a model to assess the life cycle greenhouse emissions of compressed natural gas–hydrogen (CNG–H2) mixtures used for transportation in Argentina. The overall fuel life cycle is assessed through a well-to-wheel (WTW) analysis for different hydrogen generation and distribution options. The combustion stage in road vehicles is modeled using the COPERT IV model. Hydrogen generation options include classical

P. Martínez; L. Dawidowski; D. Gómez; D. Pasquevich

2010-01-01

291

Emission analysis of a compressed natural gas directinjection engine with a homogenous mixture  

Microsoft Academic Search

In an era in which environmental pollution and depletion of world oil reserves are of major concern, emissions produced by\\u000a automotive vehicles need to be controlled and reduced. An ideal solution is to switch to a cleaner fuel such as natural gas,\\u000a which generates cleaner emissions. In addition, control over the in-cylinder air-fuel mixture can be best achieved through\\u000a a

S. Abdullah; W. H. Kurniawan; M. Khamas; Y. Ali

2011-01-01

292

Hot gas ignition temperatures of hydrocarbon fuel vapor-air mixtures  

Microsoft Academic Search

Laminar hot air jets of ¹\\/â to ³\\/â-inch diameter were employed to determine the hot gas ignition temperatures of various combustible vapor-air mixtures. The combustibles were n-hexane, n-octane, n-decane, a hydrocarbon jet fuel (JP-6) and an adipate ester aircraft engine oil (MIL-L-7808). Minimum ignition temperatures occurred at a fuel-air weight ratio of about 0.5 and were not greatly sensitive to

R. J. Cato; J. M. Kuchta

1965-01-01

293

Shock and detonation wave diffraction at a sudden expansion in gas–particle mixtures  

Microsoft Academic Search

Numerical modeling of the propagation of shock and detonation waves is carried out in a duct with an abrupt expansion for\\u000a a heterogeneous mixture of fine particles of aluminum and oxygen. A considerable difference from corresponding flows in pure\\u000a gas is found. The influence of the size and mass loading of particles on the flow and shock wave structure behind

A. V. Fedorov; T. A. Khmel; Yu. V. Kratova

2008-01-01

294

Flow rate measurements of binary gas mixtures through long trapezoidal microchannels  

Microsoft Academic Search

The flow rate of two noble gas mixtures, namely He\\/Ar and He\\/Kr, is measured through a microsystem containing 400 long trapezoidal microchannels placed in parallel configuration. Each microchannel has a trapezoidal cross section with long base 5.38 micrometers and height 1.90 micrometers, while its length is 5000 micrometers. The experiment is based on the constant volume method. The flow is

Lajos Szalmas; Stéphane Colin; Dimitris Valougeorgis

2012-01-01

295

Rapid plasma etching of cubic SiC using NF 3\\/O 2 gas mixtures  

Microsoft Academic Search

SiC is known as a chemically inert material. Therefore structuring of SiC by dry chemical processes is difficult and the reported etch rates are usually low. For sensor and micro-machining applications, however, three-dimensional structuring processes of bulk SiC with high etch rates are needed. We made a systematic study of plasma etching processes with NF3\\/O2 gas mixtures. Silicon substrates with

Christoph Richter; Klaus Espertshuber; Christoph Wagner; Martin Eickhoff; Gerhard Krötz

1997-01-01

296

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

297

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

298

Quantum scattering theory of rotational relaxation and spectral line shapes in H2He gas mixtures  

Microsoft Academic Search

A systematic study is presented of the rotational relaxation and spectral line shape properties of dilute gas mixtures of H2 in He, in an effort to determine the radial and angular dependence of the H2&sngbnd;He intermolecular potential. The quantum mechanical theory of relaxation in gases is reviewed, and we express the results in terms of a matrix of cross sections

Richard Shafer; Roy G. Gordon

1973-01-01

299

Classical Theory of Collision-Induced Absorption in Rare-Gas Mixtures  

Microsoft Academic Search

Collision-induced far-infrared absorption has been observed experimentally in several rare-gas mixtures. A theoretical calculation of these spectra is carried out using classical radiation theory to determine the emission spectrum and converting to absorption via Kirchhoff's law. Using a simple empirical form to describe the variation of the collision-induced dipole moment with internuclear separation, and assuming straight-line collision paths, an analytic

Howard B. Levine; George Birnbaum

1967-01-01

300

MECHANISMS OF THE REDUCTION OF ZINC FERRITES IN H2\\/N2 GAS MIXTURES  

Microsoft Academic Search

The rates of reduction of dense pure zinc ferrite and zinc ferrite containing 1 wt% of CaO, MgO, MnO, and Al2O3 in solid solution reduced with H2\\/N2 gas mixtures have been investigated at temperatures between 500 and 1100°C. The rate measurements obtained in these studies were complemented with the structural characterization of the partially reduced zinc ferrite samples. The presence of

Lee Fui Tong; Peter Hayes

2006-01-01

301

Numerical Simulation of Shock Wave Propagation n a Mixture of a Gas and Solid Particles  

Microsoft Academic Search

A numerical method based on the cubic interpolated polynomial (CIP) approach is applied for simulation of two-velocity two-temperature\\u000a two-phase flow dynamics. Validation of the results is provided by numerical tests. A problem of shock wave propagation in\\u000a a mixture of a viscous heat-conducting gas and solid particles of essential volume fractions is investigated as an application\\u000a case. The influence of

A. V. Fedorov; I. A. Fedorchenko

2010-01-01

302

Artificial neural networks to correlate in-tube turbulent forced convection of binary gas mixtures  

Microsoft Academic Search

Turbulent forced convection correlations are documented in the literature for air, gases and vapors (Pr?0.7), for common liquids (Pr>1) and for liquid metals (Pr0.03). In spite of this, there is a small gap in the Pr sub-interval between 0.1 and 1.0, which is occupied by binary gas mixtures. In this paper, data for turbulent forced convection for the in-tube flow

Gerardo Diaz; Antonio Campo

2009-01-01

303

Sound speed in liquid-gas mixtures: Water-air and water-steam  

Microsoft Academic Search

The sound speed of a two-phase fluid, such as a magma-gas, water-air, or water-steam mixture, is dramatically different from the sound speed of either pure component. In numerous geologic situations the sound speed of such two-phase systems may be of interest: in the search for magma reservoirs, in seismic exploration of geothermal areas, in prediction of P wave velocity decreases

Susan Werner Kieffer

1977-01-01

304

On the Possible of Gas Detonation Explosion of BaO2/Zr Powder Mixture  

NASA Astrophysics Data System (ADS)

According to common criteria of thermodynamic possibility of detonation the most of pyrotechnic mixtures can't provide the unsupported detonation regime. Then, the possible hazards can be caused only by the simple combustion of such systems. Nevertheless, we have observed the unexpected accidents of explosion in pressing of BaO2 and Zr powders mixture. The thermodynamic calculation of possible intermediate states of reacting substance showed, that the pressures needed to provide the observed explosion of hard steel pressforms are beyond the region of pressures, attained in simple combustion of the mixture. Thus, the possibility of detonation in the reacting mixture must be introduced to explain the effects observed. The unsupported detonation in the BaO2/Zr mixture can be realised according to the Raileigh line tangent to the Hugoniots of some intermediate state. This state contains some amount of free oxygen, expansion of which provides the mechanical work needed for detonation. Thus, we have a gas detonation in nongasproducing pyrotechnic system, which provides the explosions observed.

Dobler, E. A.; Gryadunov, A. N.; Shteinberg, A. S.

1997-07-01

305

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

306

Xenon-Ion Drilling of Tungsten Films  

NASA Technical Reports Server (NTRS)

High-velocity xenon ions used to drill holes of controlled size and distribution through tungsten layer that sheaths surface of controlled-porosity dispenser cathode of traveling wave-tube electron emitter. Controlled-porosity dispenser cathode employs barium/calcium/ aluminum oxide mixture that migrates through pores in cathode surface, thus coating it and reducing its work function. Rapid, precise drilling technique applied to films of other metals and used in other applications where micron-scale holes required. Method requires only few hours, as opposed to tens of hours by prior methods.

Garner, C. E.

1986-01-01

307

High-power atomic xenon laser  

NASA Astrophysics Data System (ADS)

The high pressure atomic xenon laser is becoming the most promising light source in the wavelength region of a few microns. The merits are high efficiency (so far up to 8 percent), high output energies (15 J/liter at 9 bar), high continuous output power (more than 200 W/liter), no gas dissociation and thermal heating of the lower laser level. Compared with the well-known low pressure xenon laser the power performance is now roughly a factor thousand higher. The operation of the system, based on three-body-collisions, uses the metastable state of the xenon atom as the ground state so that in the recirculation of energy a high quantum efficiency is obtained. Furthermore the homogeneous line broadening caused by the high collision frequency has also a strong beneficial effect on the efficiency. However, the required intense homogeneous excitation of the gas medium at high density is from a technical point of view a great challenge. From our experimental and theoretical work we found that at optimum performance the input power must be 1 to 2.5 [KW cm-3 atm-2]. We describe our results obtained with e-beam sustained and x-ray preionized systems delivering pulsed energies in the range of joules per liter. Furthermore we describe our recent results on continuous RF excited wave guide systems of about 37 cm length with output powers in the range of watts.

Witteman, Wilhelmus J.; Peters, Peter J.; Botma, Hako; Tskhai, S. N.; Udalov, Yu. B.; Mei, Qi-Chu; Ochkin, V. N.

1995-03-01

308

Extremely low flow tracheal gas insufflation of helium-oxygen mixture improves gas exchange in a rabbit model of piston-type high-frequency oscillatory ventilation.  

PubMed

OBJECTIVE: The purpose of this study was to show the effects of the tra gas insufflation (TGI) technique on gas exchange using helium-oxygen mixtures during high-frequency oscillatory ventilation (HFOV). We hypothesized that a helium-oxygen mixture delivered into the trachea using the TGI technique (0.3 L/min) would enhance gas exchange during HFOV. METHOD: Three rabbits were prepared and ventilated by HFOV with carrier 70% helium/oxygen or 70% nitrogen/oxygen gas mixture with TGI in a crossover study. Changing the gas mixture from nitrogen70% to helium70% and back was performed three times per animal with constant ventilation parameters. RESULTS: Compared with the nitrogen-oxygen mixture, the helium-oxygen mixture of TGI reduced PaCO2 by 7.6 mmHg (p < 0.01) and improved PaO2 by 14 mmHg (p < 0.01). Amplitude during TGI was significantly lower with the helium-oxygen mixture than with the nitrogen-oxygen mixture (p < 0.01) and did not significantly affect mean airway pressure. CONCLUSION: This study demonstrated that a helium-oxygen mixture delivered into the trachea using the TGI technique would enhance CO2 elimination and improve oxygenation during HFOV. PMID:23566050

Baba, Atsushi; Nakamura, Tomohiko; Aikawa, Tetsuya; Koike, Kenichi

2013-04-01

309

A general stagnation-point convective heating equation for arbitrary gas mixtures  

NASA Technical Reports Server (NTRS)

The stagnation-point convective heat transfer to an axisymmetric blunt body for arbitrary gases in chemical equilibrium was investigated. The gases considered were base gases of nitrogen, oxygen, hydrogen, helium, neon, argon, carbon dioxide, ammonia, and methane and 22 gas mixtures composed of the base gases. Enthalpies ranged from 2.3 to 116.2 MJ/kg, pressures ranged from 0.001 to 100 atmospheres, and the wall temperatures were 300 and 1111 K. A general equation for the stagnation-point convective heat transfer in base gases and gas mixtures was derived and is a function of the mass fraction, the molecular weight, and a transport parameter of the base gases. The relation compares well with present boundary-layer computer results and with other analytical and experimental results. In addition, the analysis verified that the convective heat transfer in gas mixtures can be determined from a summation relation involving the heat transfer coefficients of the base gases. The basic technique developed for the prediction of stagnation-point convective heating to an axisymmetric blunt body could be applied to other heat transfer problems.

Sutton, K.; Graves, R. A., Jr.

1971-01-01

310

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

311

Tin oxide gas sensing: comparison among different measurement techniques for gas mixture classification  

Microsoft Academic Search

In this paper, a study is presented aimed at the selection of the most appropriate measurement technique for wine classification. In particular, the problem of detecting typical wine aroma components in mixtures where ethanol is present is taken into account. The literature proposes different solutions in order to enhance metal-oxide sensor selectivity. An interesting approach concerns the application of different

Ada Fort; Nicola Machetti; Santina Rocchi; M. B. Serrano Santos; L. Tondi; N. Ulivieri; V. Vignoli; G. Sberveglieri

2003-01-01

312

Pressure measurements at the combustion front of gas-free pyrotechnic mixtures with low gas permeability  

Microsoft Academic Search

It is shown that the method of continuous measurement of pressure at the combustion front using an axial-force gauge is applicable\\u000a to gas-free pyrotechnic systems producing solid reaction products and characterized by low gas permeability of specimens in\\u000a the initial state. Small inclusions of a high-energy material producing gas combustion products are placed in the specimens\\u000a to check the reliability

V. F. Proskudin; V. A. Golubev; P. G. Berezhko

1997-01-01

313

Carbon ion pump for removal of carbon dioxide from combustion gas and other gas mixtures  

DOEpatents

A novel method and system of separating carbon dioxide from flue gas is introduced. Instead of relying on large temperature or pressure changes to remove carbon dioxide from a solvent used to absorb it from flue gas, the ion pump method, as disclosed herein, dramatically increases the concentration of dissolved carbonate ion in solution. This increases the overlying vapor pressure of carbon dioxide gas, permitting carbon dioxide to be removed from the downstream side of the ion pump as a pure gas. The ion pumping may be obtained from reverse osmosis, electrodialysis, thermal desalination methods, or an ion pump system having an oscillating flow in synchronization with an induced electric field.

Aines, Roger D. (Livermore, CA) [Livermore, CA; Bourcier, William L. (Livermore, CA) [Livermore, CA

2010-11-09

314

Shear Thinning in Xenon  

NASA Technical Reports Server (NTRS)

We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.

Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.

2009-01-01

315

Bonding of xenon hydrides.  

PubMed

We have computed the structure and stability of the xenon hydrides HXeY (with Y = F, Cl, Br, I, CCH, CN, NC) using relativistic density functional theory (DFT) at ZORA-BP86/TZ2P level. All model systems HXeY studied here are bound equilibrium structures, but they are also significantly destabilized with respect to Xe and HY. We have analyzed the bonding in HXeY in order to arrive at a simple picture that explains the main trends in stability. PMID:19658392

Pérez-Peralta, Nancy; Juárez, Rosalba; Cerpa, Erick; Bickelhaupt, F Matthias; Merino, Gabriel

2009-09-01

316

Bonding of Xenon Hydrides  

NASA Astrophysics Data System (ADS)

We have computed the structure and stability of the xenon hydrides HXeY (with Y = F, Cl, Br, I, CCH, CN, NC) using relativistic density functional theory (DFT) at ZORA-BP86/TZ2P level. All model systems HXeY studied here are bound equilibrium structures, but they are also significantly destabilized with respect to Xe and HY. We have analyzed the bonding in HXeY in order to arrive at a simple picture that explains the main trends in stability.

Pérez-Peralta, Nancy; Juárez, Rosalba; Cerpa, Erick; Bickelhaupt, F. Matthias; Merino, Gabriel

2009-08-01

317

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

318

Gas-jet synthesis of diamond-like films from an H2 + CH4 gas mixture glow  

NASA Astrophysics Data System (ADS)

Synthesis of diamond-like coatings from a high-velocity flow of gas mixtures in flow regimes from free-molecular to continuum with flow velocities from hundreds to thousands meters per second at different specific flow rates and temperatures in the case of activation of gases on hot surfaces is studied experimentally. Deposition of carbon films at low (less than 0.15 Pa) and high (2600 Pa) pressures from a mixture of hydrogen and methane is considered. The hydrogen flow is computed by the Direct Simulation Monte Carlo (DSMC) method in accordance with test conditions with given surface temperatures and chemical transformations on the surfaces. It is found that coatings obtained at the high pressure contain particles typical for diamonds and unusual inclusions shaped as prisms with a hexagonal cross section.

Emel'yanov, A. A.; Rebrov, A. K.; Yudin, I. B.

2014-03-01

319

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

320

Using an 80% CF4+20% CO2 gas mixture to recover aged anode wires in proportional chambers  

NASA Astrophysics Data System (ADS)

A technique to recover a gas proportional counter with 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 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 restores the gas gain and the signal amplitude in the damaged zone of the wire. SEM/XEM analysis confirmed that the tungsten oxide deposits have been removed.

Gavrilov, G. E.; Aksenov, D. A.; Conti, R.; Fetisov, A. A.; Krivchitch, A. G.; Maysuzenko, D. A.; Shvecova, N. Yu.; Vakhtel, V. M.

2012-12-01

321

Wide-band exciplex halogen lamps operating on inert gas mixtures with chlorine and Freon-12 molecules  

NASA Astrophysics Data System (ADS)

The results of analysis of the spectral characteristics of short-wave radiation sources operating on transitions in argon, krypton, and xenon monohalogenides, as well as chlorine molecules, excited by a longitudinal low-pressure glow discharge are considered. Radiation emitted by ArCl*, KrCl*, XeCl*, Cl{2/**}, and Cl{2/*} molecules in a spectral range of 170-350 nm is optimized using complex working mixtures of Ar-Kr-(Xe)-Cl2 in the lamps. The average radiation power of the lamps ranges from 1 to 10 W for an efficiency of ?25%. Optimization of wide-band lamps on transitions in chlorine molecules and the decay products of Freon-12 molecules (CF2Cl2) is carried out on mixtures of helium with chlorine and Freon-12 molecules. This makes it possible to develop lamps emitting in a spectral range of 140-270 nm and containing no costly inert gases (Xe or Kr) in their working mixtures. Exciplex halogen lamps with a wide-band emission spectrum in the VUV-UV range can be used in spectrometers as radiation sources in experiments with absorption and in high-energy chemistry, ecology, and medicine.

Shuaibov, A. K.; Shevera, I. V.

2007-09-01

322

Intradiscal injection of oxygen-ozone gas mixture for the treatment of cervical disc herniations.  

PubMed

For disc herniations the use of open surgical approaches is reduced since new percutaneous methods allowing shrinkage of the disc and improvement of the radicular function are gaining interest. Studies on the spontaneous disappearance of disc fragments have demonstrated autoimmune responses with a chronic inflammatory reaction. Also radicular pain has been shown to be mostly due to biochemical mechanisms. Researchers in different fields surprisingly noticed that a brief, calculated, oxidative stress by ozone administration may correct a persistent imbalance due to excessive, chronic oxidative injury. Oxygen-ozone gas injection in painful patients has a dramatic effect on clinical symptoms. On these bases the intradiscal injection of oxygen-ozone gas has been conceived. We report the treatment on a series of patients affected by cervical disc pathology, treated by intradiscal injection of oxygen-ozone gas mixture. The effects both on pain and on radicular dysfunction are impressive. The morphological effect of the treatment was also evaluated by pathological examination. PMID:15830973

Alexandre, A; Corò, L; Azuelos, A; Buric, J; Salgado, H; Murga, M; Marin, F; Giocoli, H

2005-01-01

323

Additional development of large diameter carbon monofilament. [from boron, hydrogen, and methane gas mixture  

NASA Technical Reports Server (NTRS)

The chemical vapor process for preparing a large diameter carbon-base monofilament from a BCl3, Ch4 and H2 gas mixture with a carbon substrate fiber was studied. The effect of reactor geometry, total gas flows and deposition temperature on the tensile strength of the monofilament were investigated. It was noted that consistent results could only be obtained when the carbon substrate fiber was cleaned. The strength of the monofilament was found to depend on the highest temperature and the temperature profile of the monofilament in the reactor. The strength of monofilament produced in the dc and RF reactors were found to be similar and similar alloy compositions in the monofilament were attained when the same gas ratios were used. The tensile strength of the monofilament at 500 C was found to be 60 to 70% of the room temperature tensile strength. No degradation was noted after exposure to molten aluminum.

Jacob, B. A.; Veltri, R. D.

1974-01-01

324

SF 6 quenched gas mixtures for streamer mode operation of RPCs at very low voltages  

NASA Astrophysics Data System (ADS)

In the present paper we describe a search for gases that allow to reduce the energy of the electrical discharge produced in Resistive Plate Chambers (RPCs) operated in streamer mode, by reducing both the operating voltage and the released charge. This can be achieved, with current gas mixtures of argon, tetrafluoroethane (TFE) and isobutane, by reducing the total amount of quenching components (TFE+isobutane) down to 10-15% and compensating for the lower gas quenching power with the addition of small amounts of SF 6. We show here that SF 6, even for concentrations as low as 1% or less, has a strong effect in reducing the delivered charge in low quenched gases and allows to achieve a proper working mode of the RPC even at voltages as low as 4- 5 kV over a 2 mm gas gap.

Aielli, G.; Camarri, P.; Cardarelli, R.; Di Ciaccio, A.; Di Stante, L.; Liberti, B.; Paoloni, A.; Pastori, E.; Santonico, R.

2002-11-01

325

Thermodynamic stability, spectroscopic identification, and gas storage capacity of CO2-CH4-N2 mixture gas hydrates: implications for landfill gas hydrates.  

PubMed

Landfill gas (LFG), which is primarily composed of CH(4), CO(2), and N(2), is produced from the anaerobic digestion of organic materials. To investigate the feasibility of the storage and transportation of LFG via the formation of hydrate, we observed the phase equilibrium behavior of CO(2)-CH(4)-N(2) mixture hydrates. When the specific molar ratio of CO(2)/CH(4) was 40/55, the equilibrium dissociation pressures were gradually shifted to higher pressures and lower temperatures as the mole fraction of N(2) increased. X-ray diffraction revealed that the CO(2)-CH(4)-N(2) mixture hydrate prepared from the CO(2)/CH(4)/N(2) (40/55/5) gas mixture formed a structure I clathrate hydrate. A combination of Raman and solid-state (13)C NMR measurements provided detailed information regarding the cage occupancy of gas molecules trapped in the hydrate frameworks. The gas storage capacity of LFG hydrates was estimated from the experimental results for the hydrate formations under two-phase equilibrium conditions. We also confirmed that trace amounts of nonmethane organic compounds do not affect the cage occupancy of gas molecules or the thermodynamic stability of LFG hydrates. PMID:22380606

Lee, Hyeong-Hoon; Ahn, Sook-Hyun; Nam, Byong-Uk; Kim, Byeong-Soo; Lee, Gang-Woo; Moon, Donghyun; Shin, Hyung Joon; Han, Kyu Won; Yoon, Ji-Ho

2012-04-01

326

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

PubMed Central

Ion mobility spectrometry (IMS) has been explored for decades, and its versatility in separation and identification of gas-phase ions 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. Implementation of FAIMS/IMS and IMS/MS interfaces using electrodynamic ion funnels greatly improves sensitivity. Evaluation of FAIMS/IMS/TOF performance for 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 peak capacities in analyses of tryptic peptides are ~500 for FAIMS/IMS separations and ~106 for 3-D FAIMS/IMS/MS, providing a potential platform for ultrahigh-throughput analyses of complex mixtures.

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

2007-01-01

327

Separation of Fischer-Tropsch catalyst/wax mixtures using dense gas extraction  

SciTech Connect

The separation of a Fischer-Tropsch catalyst from wax products is an important issue when the synthesis is conducted in a slurry bubble column reactor. This paper describes a new technique based on dense gas extraction of the soluble hydrocarbon components from the insoluble catalyst particles using light hydrocarbons as propane, butane, and pentane an the solvent. The extractions were conducted in a continuous unit operated near the critical point of the extraction gas on a catalyst/wax mixture containing about 4.91 wt% catalyst. The catalyst-free wax was collected in the second stage collector while the catalyst and some insoluble wax components were collected in the first stage collector. The yield of catalyst-free wax was about 60 wt% of the food mixture. The catalyst content of the catalyst/wax mixture in the first stage was about 14.8 wt%. The catalyst content in the second stage collector was less than 1 part in 100,000.

Eyring, M.W.; Rohar, P.C.; Hickey, R.F.; White, C.M. [PETC, Pittsburgh, PA (United States); Quiring, M.S. [Kerr-McGee Technical Center, Oklahoma City, OK (United States)

1995-12-31

328

Kinetic model for the vibrational energy exchange in flowing molecular gas mixtures. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

The present study is concerned with the development of a computational model for the description of the vibrational energy exchange in flowing gas mixtures, taking into account a given number of energy levels for each vibrational degree of freedom. It is possible to select an arbitrary number of energy levels. The presented model uses values in the range from 10 to approximately 40. The distribution of energy with respect to these levels can differ from the equilibrium distribution. The kinetic model developed can be employed for arbitrary gaseous mixtures with an arbitrary number of vibrational degrees of freedom for each type of gas. The application of the model to CO2-H2ON2-O2-He mixtures is discussed. The obtained relations can be utilized in a study of the suitability of radiation-related transitional processes, involving the CO2 molecule, for laser applications. It is found that the computational results provided by the model agree very well with experimental data obtained for a CO2 laser. Possibilities for the activation of a 16-micron and 14-micron laser are considered.

Offenhaeuser, F.

1987-01-01

329

BRIEF COMMUNICATIONS: Experimental investigation of a gasdynamic laser utilizing mixtures of carbon monoxide and an inert gas  

Microsoft Academic Search

Stimulated emission was obtained from mixtures of CO molecules with inert gases (He, Ne, Ar, Kr) expanding supersonically in a planar nozzle 4 cm long (the expansion ratio at the edge of the nozzle was 100). The influence of the nature of the inert gas and of the initial pressure of the mixture on the output power of the stimulated

V. F. Gavrikov; A. P. Dronov; V. K. Orlov; A. K. Piskunov

1975-01-01

330

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

331

Experiments on mass transfer in a natural convection of high temperature gas mixture with graphite corrosion due to air ingress.  

National Technical Information Service (NTIS)

Experiments on mass transfer in a natural convection of gas mixture with graphite corrosion at high temperature due to air ingress have been performed to predict the thermohydraulic characteristics with high accuracy at the pipe rupture in a high temperat...

Han Bing M. Ogawa K. Emori M. Hishida

1992-01-01

332

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

333

Environmental Considerations for Xenon Electric Propulsion  

Microsoft Academic Search

In the present study, the focus is on potential environmental effects associated with electric thrusters that use xenon propellant. The study is broad in scope, providing background on electric propulsion systems, structure of the atmosphere, xenon production and applications, xenon chemistry, etc. Few measurement data exist concerning the atmospheric distribution of xenon, therefore this distribution has been calculated. Although the

Mark W. Crofton; Toby D. Hain

334

Investigation of hypersonic flow of a detonable gas mixture ahead of a forward facing step  

NASA Astrophysics Data System (ADS)

The hypersonic flow of a detonable gas mixture, which includes the establishment of shock and detonation waves, over a forward facing step is investigated. The positions and shapes of the shock and detonation waves are calculated for a hydrogen-oxygen mixture for initial pressures of 1 atm to 50 atm and for hypersonic Mach numbers. The detonation wave is seen to approach the shock wave as the Mach number and/or initial pressure increase. It is found that these wave practically unite as the Mach number is increased beyond 10 and when the initial pressure is increased to above 10-20 atm. This shock-detonation wave is seen to become an oblique wave as it emerges from the face of the step into the flow above the step.

Tivanov, Genadi; Rom, Josef

1993-01-01

335

Transport coefficients in nonequilibrium gas-mixture flows with electronic excitation.  

PubMed

In the present paper, a one-temperature model of transport properties in chemically nonequilibrium neutral gas-mixture flows with electronic excitation is developed. The closed set of governing equations for the macroscopic parameters taking into account electronic degrees of freedom of both molecules and atoms is derived using the generalized Chapman-Enskog method. The transport algorithms for the calculation of the thermal-conductivity, diffusion, and viscosity coefficients are proposed. The developed theoretical model is applied for the calculation of the transport coefficients in the electronically excited N/N(2) mixture. The specific heats and transport coefficients are calculated in the temperature range 50-50,000 K. Two sets of data for the collision integrals are applied for the calculations. An important contribution of the excited electronic states to the heat transfer is shown. The Prandtl number of atomic species is found to be substantially nonconstant. PMID:19905461

Kustova, E V; Puzyreva, L A

2009-10-01

336

Rigorous solution to the extended kinetic equations for homogeneous gas mixtures  

NASA Astrophysics Data System (ADS)

The paper deals with a recently introduced extended kinetic theory for gas mixtures. Such a generalization is aimed at accounting for effects of removal, generation and source, as well as for the presence of a background medium. These physical effects are modeled by suitable gain and loss terms into the set of Boltzmann equations governing the gas distribution functions. The outstanding work done for the search of exact or rigorous analytical solutions to the standard Boltzmann equation in the space homogeneous case and for Maxwell scattering models is reviewed. It is then shown how the previous results can be generalized to treat also gas mixtures in the extended version. In particular, in spite of the nonlinearities, a Fourier transform technique, with suitably defined generating functions, leads to a hierarchy of moment equations solvable in cascade, and a series reconstruction of the distribution functions, converging in an appropriate Hilbert space, follows then by resorting to a Bobylev transformation. Finally, the role played by the theory of dynamical systems in extended kinetic theory is discussed, and some examples of application are presented and commented on.

Spiga, Giampiero

337

Evaluation of the age of landfill gas methane in landfill gas-natural gas mixtures using co-occurring constituents.  

PubMed

At a municipal solid waste landfill in southern California (USA) overlying a natural gas reservoir, methane was detected at concentrations of up to 40% (by volume) in perimeter soil gas probes. Stable isotope and (14)C values of methane together with gas composition (major components and volatile organic compounds) data were evaluated to assess the relative contributions of landfill gas and natural gas to the measured methane concentrations. The data was further used to estimate the residence time of the landfill gas in the probes. Results showed that up to 37% of the measured methane was derived from landfill gas. In addition, the landfill gas in the probe samples has undergone extensive alteration due to dissolution of carbon dioxide in pore water. Data further indicates that the measured methane was released from the waste approximately 1.2 to 9.4 years ago, rather than representing evidence of an ongoing release. PMID:23660592

Kerfoot, Henry B; Hagedorn, Benjamin; Verwiel, Mark

2013-06-01

338

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

339

Prediction of dew points of semicontinuous natural gas and petroleum mixtures. 2. Nonideal solution calculations  

SciTech Connect

A simple method was previously developed based on ideal solution theory for the calculation of dew points of semicontinuous natural gas condensates. The method employed a gamma distribution function with the effective carbon number as the continuous distribution variable. The simple method is extended in this paper to account for nonidealities of the vapor and liquid phases. The new modified approach employs extensions of the viral equation and regular solution theory to continuous mixtures. No adjustable parameters are required, and the predictions are comparable to those of an equation of state method.

Willman, B.; Teja, A.S.

1987-05-01

340

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

341

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

342

Asymptotic modeling of the flow of a binary gas mixture in a microchannel  

NASA Astrophysics Data System (ADS)

The micrometric devices are present in various industrial manufacturing processes (such as microfilters), medical tools (micro pumps for instance) and in measuring instruments. In order to describe the gas flows in microchannels involved in these systems, the DSMC methods are very well adapted but they are expensive in computation time [1, 2]. Consequently, it is of main interest to develop asymptotic models describing these flows. In this contribution, our purpose is to model the flow of a mixture of two compressible gases in microchannels. We are interested in flows at low Mach numbers and with low to moderate Knudsen numbers so that the flow is in the slip regime.

Mashhadi, M. Reyhanian; Croizet, C.; Gatignol, R.

2012-11-01

343

Dendritic solidification of xenon  

NASA Astrophysics Data System (ADS)

Experiments on xenon dendrites growing in a three-dimensional volume of pure, supercooled melt have been performed. The shapes of the dendrites have been determined with high lateral resolution. The dendrites grow in a stable mode and do not show oscillations in the growth velocity nor in the curvature of the dendrite tip. The dendrites do not have the shape of a paraboloid of revolution. Surface anisotropies determine the shape of the dendrites. Four fins grow along a dendrite. The contour of these fins can be described by a power law z ˜ | x| ? with ? ? 1.67. These experimental results are in agreement with the analytical work of E. Brener [Phys. Rev. Lett. 71 (1993) 3653]. Both experiments and analytical work are compatible with the assumption that thermal fluctuations initiate side branching. Tip oscillations can be excluded.

Bisang, U.; Bilgram, J. H.

1996-09-01

344

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

345

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

346

Transport Properties of He-N2 Binary Gas Mixtures for CBC Space Applications  

NASA Astrophysics Data System (ADS)

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 N2 and the binary mixtures of He-N2. 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.

2008-01-01

347

Pressure and temperature dependence of gas amplification gains in R134a-isobutane-SF6 mixtures for RPCs  

NASA Astrophysics Data System (ADS)

The PHENIX first level muon trigger upgrade will include dedicated muon tracking spectrometers based on resistive plate chamber (RPC) technology. We have studied the pressure and temperature dependence of gas amplificiation in typical gas mixtures expected for the RPC application in PHENIX.

Wood, John

2007-10-01

348

A shock-tube investigation of the dynamics of gas-particle mixtures: Implications for explosive volcanic eruptions  

Microsoft Academic Search

Reynolds numbers reach 104 and impulsive accelerations reach 150 g. The experiments suggest that particles hinder gas motion via an interphase drag force, reducing shock strength and velocity. Gas-particle mixture velocities decrease with increasing particle diameter for a given initial pressure ratio and are less than those predicted by pseudogas approximations and existing interphase drag relationships due to imperfect phase

K. Chojnicki; A. B. Clarke; J. C. Phillips

2006-01-01

349

Optical absorption method for the real-time component analysis of natural gas: Part 1. Analysis of mixtures enriched with ethane and propane  

NASA Astrophysics Data System (ADS)

An optical method is developed for the real-time component analysis of natural gas mixtures. The method is based on the measurement of the absorption coefficients of the gas mixture at several wavelengths in the IR spectral range (7-14 ?m). The resulting accuracy of the measurements of the methane, ethane, and propane contents in gas mixtures is sufficient for the monitoring of the component composition of natural gas in pipelines.

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

2011-01-01

350

Simulation of plasma parameters in He-Xe gas mixtures and comparison with experiment  

NASA Astrophysics Data System (ADS)

Breakdown (Paschen) and current-voltage(I-V) curves for discharge in He/Xe mixtures are calculated for a simple 1D-space geometry. The necessary for the calculation values of secondary emission coefficients, gamma, for excited and ionized atoms of He and Xe were obtained through the best fit of the breakdown curves acquired in the simulation to the experimental discharge curves for pure He and Xe [Postel and Cappelli, Appl. Phys. Lett. 76, 544]. The values of gammas are within the range of similar experimental data available in the literature [Y. Raizer, Gas Discharge Physics (Springer-Verlag, 1991) p. 74]. Using these secondary emission coefficients and assuming their applicability to gas mixtures Paschen and I-V curves are calculated and compared with the experimental ones. Our results indicate that higher values of the discharge voltage, compared to those obtained through the Townsend's equation, ? (e^? d - 1) = 1, could be explained by the reactions that effectively transfer positive charge from He ions and ionized molecules to neutral Xe atoms (i.e. Xe + He^+ arrow Xe^+ + He and He_2^+ + Xe arrow Xe^+ + 2He). Values of the charge transfer reaction constants are estimated through a best fit of the simulations to the experimental curves.

Sosov, Yuriy; Theodosiou, Constantine

2003-10-01

351

Electron beam excitation of rare-gas alkali ionic excimers  

SciTech Connect

The observation of fluorescence from ionic rare-gas alkali molecules excited by an electron beam is reported. Gas mixtures of argon and xenon with hot vapors of either rubidium or cesium were excited to obtain emission from (XeRb){sup +} at 164 nm and (XeCs){sup +} at 160 nm. The spectral features observed in (XeRb){sup +} are assigned to three upper electronic states.

Millar, P.S.; Warwar, G.; Wisoff, P.J.; Sauerbrey, R. (Department of Electrical and Computer Engineering and Rice Quantum Institute, Rice University, Houston, Texas 77251-1892 (USA)); Balasubramanian, K. (Chemistry Department, Arizona State University, Tempe, Arizona 85287-1604 (USA))

1989-11-20

352

Gas energy meter for inferential determination of thermophysical properties of a gas mixture at multiple states of the gas  

DOEpatents

A gas energy meter that acquires the data and performs the processing for an inferential determination of one or more gas properties, such as heating value, molecular weight, or density. The meter has a sensor module that acquires temperature, pressure, CO2, and speed of sound data. Data is acquired at two different states of the gas, which eliminates the need to determine the concentration of nitrogen in the gas. A processing module receives this data and uses it to perform a "two-state" inferential algorithm.

Morrow, Thomas B. (San Antonio, TX) [San Antonio, TX; Kelner, Eric (San Antonio, TX) [San Antonio, TX; Owen, Thomas E. (Helotes, TX) [Helotes, TX

2008-07-08

353

Study of quantification and distribution of explosive mixture in a confined space as a result of natural gas leak  

NASA Astrophysics Data System (ADS)

The contribution deals with quantification of natural gas leak from a domestic low pressure pipe to a confined space in relation to formation of explosive concentration. Within the experiments, amount of leak gas was determined considering the character of pipe damage. Leakage coefficients, natural gas expansion and time before reaching the lower explosive limit of a gas-air mixture were taken. Conducted experiments were then modelled using CFD software and the results were verified. In numerical model, several models of flow were used and afterwards following issues were analysed: leakage velocity, spatial distribution of the mixture in a confined space, formation of concentration at the lower explosive limit etc. This work should contribute to better understanding of propagation and distribution of gaseous fuel mixtures in confined spaces and thereby significantly reduce the risk of fires or explosions or prevent them.

Tulach, Aleš; Mynarz, Miroslav; Kozubková, Milada

2014-03-01

354

Study of DC Circuit Breaker of H2-N2 Mixture Gas for High Voltage  

NASA Astrophysics Data System (ADS)

Global warming caused by CO2 etc. is a field where the concern is very high. Especially, automobile emissions are problem for it. Therefore, the hybrid car is widely development and used recently. Hybrid car used electric power and gasoline. So, the car reduces CO2. Hybrid car has engine and motor. To rotate the motor, hybrid car has battery. This battery is large capacity. Therefore, the relay should interrupt high DC current for the switch of the motor and the engine. So, hybrid car used hydrogen gas filling relay We studied interruption test for the research of a basic characteristic of hydrogen gas. DC current has not current zero point. So, it is necessary to make the current zero by high arc voltage and forcible current zero point. The loss coefficient and arc voltage of hydrogen is high. Therefore, we studied interruption test for used high arc voltage. We studied interruption test and dielectric breakdown test of air, pure Hydrogen, and Hydrogen- nitrogen mixture gas. As a result, we realized H2-N2(80%-20%) is the best gas.

Shiba, Yuji; Morishita, Yukinaga; Kaneko, Shuhei; Okabe, Shigemitsu; Mizoguchi, Hitoshi; Yanabu, Satoru

355

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

356

Gas Energy Meter for Inferential Determination of Thermophysical Properties of a Gas Mixture at Multiple States of the Gas.  

National Technical Information Service (NTIS)

A gas energy meter that acquires the data and performs the processing for an inferential determination of one or more gas properties, such as heating value, molecular weight, or density. The meter has a sensor module that acquires temperature, pressure, C...

E. Kelner T. B. Morrow T. E. Owen

2005-01-01

357

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

358

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

359

Development of a xenon detector for treaty verification. Final report  

SciTech Connect

The project objective was to determine the feasibility of the gas proportional scintillator detector (GPSD) technology to sensitively and selectively detect the decay products of the metastable xenon isotopes as a means of treaty verification for the CTBT. During the course of the project, the investigation involved both computer simulations and laboratory measurements with a GPSD. During the fourth quarter the authors have further investigated the dedicated GPSD response to x-rays and conversion electrons from {sup 109}Cd and {sup 57}Co radioactive sources, comparing simulated and experimental results. The response of a customized high pressure GPSC was also simulated to the higher energy conversion electrons from xenon radioisotopes. An alternative hybrid detector system is proposed showing excellent prospects for xenon radioisotope detection.

NONE

1998-07-21

360

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

361

Effect of mixture ratios and nitrogen carrier gas flow rates on the morphology of carbon nanotube structures grown by CVD  

Microsoft Academic Search

We report on the growth of carbon nanotubes (CNTs) by thermal Chemical Vapor Deposition (CVD) and investigate the effects\\u000a of nitrogen carrier gas flow rates and mixture ratios on the morphology of CNTs on a silicon substrate by vaporizing the camphor\\/ferrocene\\u000a mixture at 750 °C in a nitrogen atmosphere. Carbon layers obtained after each CVD growth run of 15 min are characterized

Gerald Franky Malgas; Christopher J. Arendse; Nonhlanhla P. Cele; Franscious R. Cummings

2008-01-01

362

Electron drift velocities in gas mixtures of He, N/sub 2/, and CO/sub 2/  

SciTech Connect

An electron swarm experiment has been used to obtain electron drift velocities in the He:CO/sub 2/:N/sub 2/ mixtures 0:1:1, 3:1:2, and 3:1:1. The E/N range of 3 to 57 Td was studied with total gas pressure varied from 50 to 200 Torr. These particular mixtures have not been previously studied experimentally. Good agreement is observed between theoretical calculations and experimental data.

Cornell, M.C.; Littlewood, I.M.; Brooks, H.L.; Nygaard, K.J.

1983-04-01

363

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

364

Biofiltration of mixtures of gas-phase styrene and acetone with the fungus Sporothrix variecibatus.  

PubMed

The biodegradation performance of a biofilter, inoculated with the fungus Sporothrix variecibatus, to treat gas-phase styrene and acetone mixtures under steady-state and transient conditions was evaluated. Experiments were carried out by varying the gas-flow rates (0.05-0.4m(3)h(-1)), leading to empty bed residence times as low as 17.1s, and by changing the concentrations of gas-phase styrene (0.01-6.3 g m(-3)) and acetone (0.01-8.9 g m(-3)). The total elimination capacities were as high as 360 g m(-3)h(-1), with nearly 97.5% removal of styrene and 75.6% for acetone. The biodegradation of acetone was inhibited by the presence of styrene, while styrene removal was affected only slightly by the presence of acetone. During transient-state experiments, increasing the overall pollutant load by almost 3-fold, i.e., from 220 to 600 g m(-3)h(-1), resulted in a sudden drop of removal efficiency (>90-70%), but still high elimination capacities were maintained. Periodic microscopic observations revealed that the originally inoculated Sporothrix sp. remained present in the reactor and actively dominant in the biofilm. PMID:20869172

Rene, Eldon R; Spa?ková, Radka; Veiga, María C; Kennes, Christian

2010-12-15

365

Effect Of Gas Mixture Composition On Tar Removal Process In A Pulsed Corona Discharge Reactor  

NASA Astrophysics Data System (ADS)

The simulation of naphthalene (C10H8) removal from several gas mixtures (pure nitrogen, mixtures containing N2 with CO2, CO, H2, H2O, and biogas - the product of biomass gasification), has been investigated. The modeling is based on the experimental data obtained in the reactor with a pulsed positive corona discharge. The problem of simulation of the cleaning process includes description of two stages. The first, fast stage is generation of primary active species during streamer propagation. The second, slow stage is the chain of chemical transformations triggered by these species. The input parameters for the modeling of the second stage are G-values for generation of primary active species, obtained under consideration of streamer dynamics. Simulation of the second stage of the removal process takes into account the processes of chemical kinetics and diffusion outside and inside of streamer traces during multi-pulsed treatment. Besides neutral active species, streamer discharges produce electrons and ions. Primary positive ions (N2+, CO+, CO2+, H2+, H2O+) in a chain of fast ion-molecule reactions transform into more stable positive ions. The ions recombine with electrons. Both ion-molecule reactions and electron-ion recombination process are additional (to dissociation of gas molecules by electron impact in the streamer head) sources of neutral active species. The relative contribution of these sources to the G-values for H, OH and O is rather large. In our modeling two approaches have been used. At the first approach the contribution of ion-molecule reactions is estimated approximately assuming that the dominating stable ion is N4+ (in pure N2 and its mixtures with H2) or CO2+ (in mixtures including CO2). Other way is the calculations with kinetic scheme including the molecular ions, aquated ions such as H3O(H2O)m+, NO2(H2O)-, NO2(H2O)+ and other. The comparison of results of two approaches is presented. Only full kinetic scheme allowed describing the experimental results for 82.5%N2+17.5%H2O mixture on C10H8 removal. Obtained dependencies of the remaining naphthalene fraction versus the specific energy input have been compared with the experimental data. The results agree rather well for considered mixtures. The best decomposition has been obtained in nitrogen with water vapor, a little better than that in pure nitrogen, both in experiments and in the simulation. It has been found that the reaction of naphthalene with excited nitrogen molecules N2(A3S) plays a key role in the removal process. Addition to N2 of such gases as CO, CO2 and H2 reduces the removal efficiency noticeably.

Filimonova E.; Naidis, G.

2010-07-01

366

Global atmospheric change: potential health effects of acid aerosol and oxidant gas mixtures.  

PubMed Central

Inhalation toxicology experiments in whole animals have demonstrated a remarkable lack of toxicity of sulfuric acid in the form of respirable aerosols, especially in rats and nonhuman primates. Thus, much of the current experimental emphasis has shifted to the evaluation of the potential health effects of acid aerosols as components of mixtures. Rats have been concurrently exposed to mixtures of ozone or nitrogen dioxide with respirable-sized aerosols of sulfuric acid, ammonium sulfate, or sodium chloride, or to each pollutant individually. Their responses to such exposures have been evaluated by various quantitative biochemical analysis of lung tissue or wash fluids ("lavage fluid") or by quantitative morphological methods ("morphometry"). Such studies have mainly been performed in the acute time frame due to the inherent limitations of the most sensitive assays available and have generally involved exposures for 1 to 9 days, depending on the assays used. Good correlations were found between the most sensitive biochemical indicators of lung damage (protein content of lung lavage fluid or whole lung tissue and lung collagen synthesis rate) and the exposure concentration of oxidant gas present alone or in mixtures with acidic aerosols showing interactive effects. Synergistic interaction between ozone and sulfuric acid aerosol was demonstrated to occur at environmentally relevant concentrations of both pollutants by several of the analytical methods used in this study. Such interactions were demonstrated at concentrations of ozone as low as 0.12 ppm and of sulfuric acid aerosol at concentrations as low as 5 to 20 micrograms/m3.(ABSTRACT TRUNCATED AT 250 WORDS)

Last, J A

1991-01-01

367

Performance of a fungal biofilter treating gas-phase solvent mixtures during intermittent loading.  

PubMed

Biological treatment processes used to remove and degrade volatile organic compounds (VOCs) from contaminated gases emitted by industrial operations or waste treatment processes are almost always subjected to transient loading conditions because of the inherently unsteady-state nature of contaminant generating processes. In the study presented here, a laboratory-scale biofilter populated by a mixed culture of fungi was used to study the transient response to various periods of no contaminant loading in a system treating a model waste gas stream containing a mixture of commonly used solvents. The biofilter, packed with cubed polyurethane foam media and operated with an empty bed residence time of 15s, was supplied with a four-component mixture of n-butyl acetate, methyl ethyl ketone, methyl propyl ketone, and toluene at target influent concentrations of 124, 50.5, 174, and 44.6 mg/m(3), respectively. This corresponds to a total VOC loading rate of 94.3g/(m(3)h). Biofilter performance was evaluated over a 94-day period for three loading conditions intended to simulate processes generating contaminated gases only during daytime operation, daytime operation with weekend shutdown periods, and with long term (9-day) shutdown. Results indicate that fungal biofilters can be an effective alternative to conventional abatement technologies for treating solvent contaminated off-gases even under discontinuous loading conditions. PMID:15142786

Moe, William M; Qi, Bing

2004-05-01

368

Methodology for Predicting Flammable Gas Mixtures in Double Contained Receiver Tanks [SEC 1 THRU SEC 3  

SciTech Connect

This methodology document provides an estimate of the maximum concentrations of flammable gases (ammonia, hydrogen, and methane) which could exist in the vapor space of a double-contained receiver tank (DCRT) from the simultaneous saltwell pumping of one or more single-shell tanks (SSTs). This document expands Calculation Note 118 (Hedengren et a1 1997) and removes some of the conservatism from it, especially in vapor phase ammonia predictions. The methodologies of Calculation Note 118 (Hedengren et a1 1997) are essentially identical for predicting flammable gas mixtures in DCRTs from saltwell pumping for low DCRT ventilation rates, 1e, < 1 cfm. The hydrogen generation model has also been updated in the methodology of this document.

HEDENGREN, D.C.

2000-01-31

369

Filament-induced amplified spontaneous emission in air-hydrocarbons gas mixture  

NASA Astrophysics Data System (ADS)

Filament-induced amplified spontaneous emission, ASE, in air-hydrocarbons (~2%) gas mixture, CH4, C2H2, and C2H4, was investigated by detecting fluorescence emitted from CH fragments prepared in the electronically excited A2? state in the filament. The fluorescence signal recorded from the side direction of the filament was linearly proportional to the length of the filament, while the fluorescence signal emitted in the backward direction of the laser propagation increased nonlinearly with the filament length. This difference showing that the filament acted as a gain medium in which the spontaneous emission from CH was amplified (ASE). This process realized by a small amount of hydrocarbon molecular species in air can be applied to remote sensing of pollutants in air.

Hosseini, Sima; Azarm, Ali; Daigle, Jean-François; Kamali, Yousef; Chin, See Leang

2014-04-01

370

Universality of temperature distribution in granular gas mixtures with a steep particle size distribution  

NASA Astrophysics Data System (ADS)

The distribution of granular temperatures in granular gas mixtures is investigated analytically and numerically. We analyze space uniform systems in a homogeneous cooling state (HCS) and under a uniform heating with a mass-dependent heating rate \\Gamma_k\\sim m_k^{\\gamma} . We demonstrate that for steep size distributions of particles the granular temperatures obey a universal power-law distribution, T_k \\sim m_k^{\\alpha} , where the exponent ? does not depend on a particular form of the size distribution, the number of species and inelasticity of the grains. Moreover, ? is a universal constant for a HCS and depends piecewise linearly on ? for heated gases. The predictions of our scaling theory agree well with the numerical results.

Bodrova, Anna; Levchenko, Denis; Brilliantov, Nikolay

2014-04-01

371

Early treatment with xenon protects against the cold ischemia associated with chronic allograft nephropathy in rats.  

PubMed

Chronic allograft nephropathy (CAN) is a common finding in kidney grafts with functional impairment. Prolonged hypothermic storage-induced ischemia-reperfusion injury is associated with the early onset of CAN. As the noble gas xenon is clinically used as an anesthetic and has renoprotective properties in a rodent model of ischemia-reperfusion injury, we studied whether early treatment with xenon could attenuate CAN associated with prolonged hypothermic storage. Exposure to xenon enhanced the expression of insulin growth factor-1 (IGF-1) and its receptor in human proximal tubular (HK-2) cells, which, in turn, increased cell proliferation. Xenon treatment before or after hypothermia-hypoxia decreased cell apoptosis and cell inflammation after reoxygenation. The xenon-induced HK-2 cell proliferation was abolished by blocking the IGF-1 receptor, mTOR, and HIF-1? individually. In the Fischer-to-Lewis rat allogeneic renal transplantation model, xenon exposure of donors before graft retrieval or recipients after engraftment enhanced tubular cell proliferation and decreased tubular cell death and cell inflammation associated with ischemia-reperfusion injury. Compared with control allografts, xenon treatment significantly suppressed T-cell infiltration and fibrosis, prevented the development of CAN, and improved renal function. Thus, xenon treatment promoted recovery from ischemia-reperfusion injury and reduced susceptibility to the subsequent development of CAN in allografts. PMID:24025645

Zhao, Hailin; Luo, Xianghong; Zhou, Zhaowei; Liu, Juying; Tralau-Stewart, Catherine; George, Andrew J T; Ma, Daqing

2014-01-01

372

Oxidation of Fe-V Melts Under CO2-O2 Gas Mixtures  

NASA Astrophysics Data System (ADS)

The oxidation mechanism of liquid Fe-V alloys with V content from 5 to 20 mass pct under different oxygen partial pressures using CO2-O2 mixtures with CO2 varying from 80 pct to 100 pct was investigated by thermogravimetric analysis between 1823 K and 1923 K (1550 °C and 1650 °C). The products after oxidation were identified by scanning electron microscopy energy-dispersive spectrograph and X-ray diffraction. The results indicate that the oxidation process can be divided into the following steps: an apparent incubation period, followed by a chemical reaction step with a transition step before the reaction, and diffusion as the last stage. At the initial stage, a period of slow mass increase was observed that could be attributed to possible oxygen dissolution in the liquid iron-vanadium coupled with the vaporization of V2O. The length of this period increased with increasing temperature as well as vanadium content in the melt and decreased with increasing oxygen partial pressure of the oxidant gas. This analysis was followed by a region of chemical oxidation. The oxidation rate increased with the increase of the O2 ratio in the CO2-O2 gas mixtures. During the final stage, the oxidation seemed to proceed with the diffusion of oxygen through the product layer to the reaction front. The Arrhenius activation energies for chemical reaction and diffusion were calculated, and kinetic equations for various steps were setup to describe the experimental results. The transition from one reaction mechanism to the next was described mathematically as mixed-control equations. Thus, uniform kinetic equations have been setup that could simulate the experimental results with good precision.

Wang, Haijuan; Teng, Lidong; Zhang, Jiayun; Seetharaman, Seshadri

2010-10-01

373

Obtaining the cumulative k-distribution of a gas mixture from those of its components. [radiative transfer in stratosphere  

NASA Technical Reports Server (NTRS)

A review of the convolution theorem for obtaining the cumulative k-distribution of a gas mixture proven in Goody et al. (1989) and a discussion of its application to natural spectra are presented. Computational optimizations for use in analyzing high-altitude gas mixtures are introduced. Comparisons of the results of the optimizations, and criteria for deciding what altitudes are 'high' in this context are given. A few relevant features of the testing support software are examined. Some spectrally integrated results, and the circumstances the might permit substituting the method of principal absorbers are examined.

Gerstell, M. F.

1993-01-01

374

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

375

Gas mixtures for spark gap closing switches with emphasis on efficiency of operation  

SciTech Connect

The efficient operation of a spark gap closing switch requires a gaseous medium with large breakdown strength, low conduction voltage, and a short formative time lag. Gas properties necessary to achieve these requirements are identified and discussed. Based on available knowledge of such properties, a number of binary (e.g., c-C/sub 4/F/sub 8/, or l-C/sub 3/F/sub 6/, or n-C/sub 4/F/sub 10/, or C/sub 3/F/sub 8/, or C/sub 6/F/sub 6/ in Ar or He or H/sub 2/) and ternary gas mixtures (e.g., c-C/sub 4/F/sub 8/, or n-C/sub 4/F/sub 10/, or C/sub 3/F/sub 8/ in Ar or He + C/sub 2/H/sub 2/ or another low ionization onset additive) have been identified which may be suitable for use in spark gap closing switches.

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

1987-01-01

376

On-line analysis of complex hydrocarbon mixtures using comprehensive two-dimensional gas chromatography.  

PubMed

This paper discusses the first setup for on-line qualitative and quantitative comprehensive two-dimensional gas chromatography (GC × GC) of complex hydrocarbon mixtures. A built-in 4-port 2-way valve allows switching between flame ionization detection (FID) and time-of-flight mass spectrometry (TOF-MS) between runs, without the need to cool down and vent the MS. Proper selection of GC carrier gas flow rates enables maximal agreement between the obtained chromatograms in both configurations. For on-line analysis of reactor effluents, a dedicated sampling system allows automatic sampling of the hot reactor effluent gases and immediate injection of the sample on the GC × GC. To determine a complete effluent composition in a single run of the GC × GC, a subzero oven starting temperature was employed. Modulation is started when the oven temperature reaches 40°C, thus dividing the chromatogram in a conventional 1D and a comprehensive 2D part. This work illustrates the mature and robust character of GC × GC, extending its capabilities from mere laboratory use to on-line routine analysis for industrial processes in the (petro-)chemical industry. PMID:20444456

Van Geem, Kevin M; Pyl, Steven P; Reyniers, Marie-Françoise; Vercammen, Joeri; Beens, Jan; Marin, Guy B

2010-10-22

377

Using Point Reactor Models and Genetic Algorithms for On-Line Global Xenon Estimation in Nuclear Reactors  

Microsoft Academic Search

Estimation of xenon concentration at a given time instant is usually a difficult problem since the initial conditions are often unknown as well as a number of the model parameters. The feasibility of obtaining the model parameters of a point reactor xenon evolution model with genetic algorithms (GAs) has been investigated earlier using data obtained from a point reactor model

Tunc Aldemir; Giancarlo Torri; Marzio Marseguerra; Enrico Zio; Jeffrey A. Borkowski

2003-01-01

378

Radioactive Plume from the Three Mile Island Accident: Xenon133 in Air at a Distance of 375 Kilometers  

Microsoft Academic Search

The transit of an air mass containing radioactive gas released from the Three Mile Island reactor was recorded in Albany, New York, by measuring xenon-133. These measurements provide an evaluation of Three Mile Island effluents to distances greater than 100 kilometers. Two independent techniques identified xenon-133 in ambient air at concentrations as high as 3900 picocuries per cubic meter. The

Martin Wahlen; Charles O. Kunz; John M. Matuszek; William E. Mahoney; Roger C. Thompson

1980-01-01

379

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

PubMed

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

Dong, Ki-Young; Choi, Jinnil; Lee, Yang Doo; Kang, Byung Hyun; Yu, Youn-Yeol; Choi, Hyang Hee; Ju, Byeong-Kwon

2013-01-01

380

Development of a Binary Mixture Gas Composition Instrument for Use in a Confined High Temperature Environment  

NASA Astrophysics Data System (ADS)

With recent advancements in material science, industrial operations are being conducted at higher and higher temperatures. This is apparent in the nuclear industry where a division of the field is working to develop the High Temperature Gas Reactor and the Very High Temperature Gas Reactor concurrently. Both of these facilities will have outlet gas temperatures that are at significantly higher temperatures than the typical water cooled reactor. These increased temperatures provide improved efficiency for the production of hydrogen, provide direct heating for oil refineries, or more efficient electricity generation. As high temperature operations are being developed, instruments capable of measuring the operating parameters must be developed concurrently. Within the gas reactor community there is a need to measure the impurities within the primary coolant. Current devices will not survive the temperature and radiation environments of a nuclear reactor. An instrument is needed to measure the impurities within the coolant while living inside the reactor, where this instrument would measure the amount of the impurity within the coolant. There are many industrial applications that need to measure the ratio of two components, whether it be the amount of particulate in air that is typical to pneumatic pumping, or the liquid to gas ratio in natural gas as it flows through a pipeline. All of the measurements in these applications can be met using a capacitance sensor. Current capacitance sensors are built to operate at ambient temperatures with only one company producing a product that will handle a temperature of up to 400 °C. This maximum operating temperature is much too low to measure the gas characteristics in the High Temperature Gas Reactor. If this measurement technique were to be improved to operate at the expected temperatures, the coolant within the primary loop could be monitored for water leaks in the steam generator, carbon dust buildup entrained in the flow, or used to measure the purity of the coolant itself. This work details the efforts conducted to develop such an instrument. While the concept of designing a capacitance sensor to measure a gas mixture is not unique, the application of using a capacitance sensor within a nuclear reactor is a new application. This application requires the development of an instrument that will survive a high temperature nuclear reactor environment and operate at a sensitivity not found in current applications. To prove this technique, instrument prototypes were built and tested in confined environments and at high temperatures. This work discusses the proof of concept testing and outlines an application in the High Temperature Test Facility to increase the operational understanding of the instrument. This work is the first step toward the ultimate outcome of this work, which is to provide a new tool to the gas reactor community allowing real-time measurements of coolant properties within the core.

Cadell, Seth R.

381

Impulse partial discharge characteristics and their mechanisms under non-uniform electric field in N2\\/SF6 gas mixtures  

Microsoft Academic Search

We have investigated impulse partial discharge (PD) and breakdown (BD) characteristics of a needle-plane gap in N2\\/SF6 gas mixtures under positive lightning impulse voltage application, and discussed their physical mechanisms. The 50% probability PD inception voltage (PDIV50), leader discharge onset voltage (LOV) and BD voltage (BDV50) were measured and analyzed as a function of gas pressure and SF6 content. Experimental

Naoki Hayakawa; Yuichiro Yoshitake; Naoto Koshino; Toshiaki Ueda; Hitoshi Okubo

2005-01-01

382

In-situ formation of SiC-reinforced Al-Si alloy composites using methane gas mixtures  

Microsoft Academic Search

Theoretical and experimental studies on the in-situ formation of an Al-Si alloy composite using a methane gas mixture were carried out. An Al-Si alloy composite with in-situ formed SiC as a reinforced phase was produced by bubbling methane gas at temperatures from 1223 to 1423 K. An optical microscope,\\u000a scanning electron microscope (SEM), and electron microprobe were used for the

Banqiu Wu; Ramana G. Reddy

2002-01-01

383

Measurement of Gas Composition Ratio of H-He Mixture Plasmas in Divertor Simulator MAP-II  

NASA Astrophysics Data System (ADS)

The gas composition ratio inthe divertor region of a fusion reactor must be measured in order to evaluate its atomic-molecular processes precisely. In this research we propose a method to measure the gas composition ratio of He, H and H2 of the H-He mixture plasmas in divertor simulator MAP-II by using passive spectroscopy of the Balmer series of hydrogen atoms, the Fulcher-? band of hydrogen molecules and the He I emissions.

Kuwahara, Yosuke; Kado, Shinichiro; Okamoto, Atsushi; Shikama, Taiichi; Iida, Yohei; Kurihara, Kiminori; Scotti, Filippo; Tanaka, Satoru

384

High kinetic energy ion mobility spectrometer: quantitative analysis of gas mixtures with ion mobility spectrometry.  

PubMed

We present a high kinetic energy ion mobility spectrometer (HiKE-IMS) for quantitative gas analysis. Drift tube and reaction tube can be operated at reduced fields up to 110 Td. At such conditions the distribution of reactant ion water clusters is shifted toward smaller clusters. Due to the resulting presence of bare reactant ions (e.g., H3O(+)) and the kinetic control of the ionization process with decreasing reaction time, unlike conventional IMS, a quantitative detection with ppbv detection limits of low proton affine analytes even in humid gas mixtures containing high proton affine compounds is possible using a direct sample gas inlet. A significantly improved dynamic range compared to conventional IMS is achieved. An incremental change in reduced fields enables the observation of parameters like field dependent ion mobilites or analyte fragmentation. Also, the characteristic of the analyte signal with respect to the reduced reaction field gives insight into the ionization process of the analyte. Thus, HiKE-IMS enables substance identification by ion mobility and additional analytical information that are not observed with conventional IMS. The instrumental effort is similar to conventional desktop IMS with overall dimensions of the drift and reaction tube of 4 cm × 4 cm × 28.5 cm. However, the mobility resolution is limited and between 30 and 40. Because of the moisture independent ionization and the decrease in competing ion-molecule reactions, no preseparation or membrane inlet is necessary when the compounds of interest are distinguishable either by a significant difference in ion mobility or the additional analytical information. PMID:24937741

Langejuergen, Jens; Allers, Maria; Oermann, Jens; Kirk, Ansgar; Zimmermann, Stefan

2014-07-15

385

Pressure-dependent electron attachment and breakdown strengths of unitary gases, and synergism of binary gas mixtures: a relationship  

SciTech Connect

The relationship between the pressure-dependent electron attachment rate constants (k/sub a/) which have been observed in 1-C/sub 3/F/sub 6/ and in several perfluoroalkanes, and the uniform field breakdown strengths (E/N)/sub lim/ in these gases is discussed. Measurements of the pressure dependence of k/sub a/ of OCS in a buffer gas of Ar are presented and the possible pressure dependence of (E/N)/sub lim/ in OCS is discussed. Uniform field breakdown measurements have been performed in C/sub 3/F/sub 8/, n-C/sub 4/F/sub 10/, and SO/sub 2/ over a range of gas pressures (3 less than or equal to P/sub T/ less than or equal to 290 kPa) and are reported. All three molecules have been found to possess pressure-dependent (E/N)/sub lim/ values. The various types of synergistic behavior which have been observed in binary gas dielectric mixtures are summarized and discussed. A new mechanism is outlined which can explain the synergism observed in several gas mixtures where the (E/N)/sub lim/ values of the mixutres are greater than those of the individual gas constituents. Model calculations are presented which support this mechanism, and can be used to explain the pressure-dependent synergistic effects which have been reported in 1-C/sub 3/F/sub 6//SF/sub 6/ gas mixture.

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

1984-04-01

386

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

387

Prevention of fog in the condensation of vapour from mixtures with inert gas, by a regenerative thermal process  

Microsoft Academic Search

In processing, vapours often have to be separated from mixtures mainly containing inert gas, as for example in the cleaning of exhaust air and the recovery of pollutant solvent vapours (volatile organic compounds, VOC). Whenever possible, condensation is applied for this task, since it is thermodynamically the most energy-efficient process. It can be carried out successfully, provided that the vapour

Stephan Kaufmann; Karl Hilfiker

1999-01-01

388

Hydrate formation of a synthetic natural gas mixture in aqueous solutions containing electrolyte, methanol, and (electrolyte + methanol)  

Microsoft Academic Search

Hydrate formation has been studied for a synthetic natural gas mixture in pure water and in aqueous solutions containing electrolyte(s), methanol, and a combination of (electrolyte + methanol). Special attention has been given to (electrolyte + methanol) systems, as such data are extremely scarce in the open literature yet are of industrial significance. Sixteen experiments (a total of 107 data

Dong-Hai Mei; Jian Liao; Ji-Tao Yang; Tian-Min Guo

1998-01-01

389

Reactive-ion Etching of Tungsten Silicide Using NF3 Gas Mixtures. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

We report in this paper the reactive-ion etching of WSix films using gas mixtures containing NF 3. A combination of NF3/H3 or NF3 /He was used to anisotropically etch WSix films as thick as 4000 A with photoresist masks. They yielded satisfactorily high e...

R. L. Lee F. L. Terry

1991-01-01

390

Production of H3O(+).NH2O From No(+) Precursor in No-H2O Gas Mixtures.  

National Technical Information Service (NTIS)

Stationary afterglow techniques were employed to determine reaction rate constants for ions reacting in NO-H2O gas mixtures. Krypton resonance radiation at 123.6 and 116.5 nm is used to ionize only the NO molecules. The NO(+) ion is the precursor to a cha...

L. J. Puckett M. W. Teague

1970-01-01

391

Study of gas mixtures and ageing of the multigap resistive plate chamber used for the Alice TOF  

Microsoft Academic Search

We present in this paper a study of the Alice-TOF Multigap Resistive Plate Chamber (MRPC) performance by using several gas mixtures. We also present a search for possible ageing effects, by studying two MRPCs irradiated at the CERN Gamma Irradiation Facility.

A. V. Akindinov; A. Alici; F. Anselmo; P. Antonioli; M. Basile; G. Cara Romeo; L. Cifarelli; F. Cindolo; F. Cosenza; I. D' Antone; A. De Caro; S. De Pasquale; A. Di Bartolomeo; M. Fusco Girard; V. Golovine; M. Guerzoni; M. Guida; D. Hatzifotiadou; A. B. Kaidalov; D. H. Kim; D. W. Kim; S. M. Kisselev; G. Laurenti; E. Lioublev; K. Lee; S. C. Lee; M. L. Luvisetto; A. Margotti; A. N. Martemiyanov; F. Massera; S. Meneghini; R. Michinelli; R. Nania; P. Otiougova; G. Pancaldi; A. Pesci; R. Pilastrini; O. Pinazza; P. A. Polozov; M. Rizzi; E. Scapparone; G. Scioli; S. B. Sellitto; F. Semeria; S. Serra; A. V. Smirnitski; M. M. Tchoumakov; E. Ugolini; E. Usenko; G. Valenti; K. G. Voloshin; M. C. S. Williams; B. V. Zagreev; C. Zampolli; A. Zichichi; A. Zucchini; M. Zuffa

2004-01-01

392

Study of gas mixtures and ageing of the multigap resistive plate chamber used for the Alice TOF  

NASA Astrophysics Data System (ADS)

We present in this paper a study of the Alice-TOF Multigap Resistive Plate Chamber (MRPC) performance by using several gas mixtures. We also present a search for possible ageing effects, by studying two MRPCs irradiated at the CERN Gamma Irradiation Facility.

Akindinov, A. V.; Alici, A.; Anselmo, F.; Antonioli, P.; Basile, M.; Cara Romeo, G.; Cifarelli, L.; Cindolo, F.; Cosenza, F.; D'Antone, I.; De Caro, A.; De Pasquale, S.; Di Bartolomeo, A.; Fusco Girard, M.; Golovine, V.; Guerzoni, M.; Guida, M.; Hatzifotiadou, D.; Kaidalov, A. B.; Kim, D. H.; Kim, D. W.; Kisselev, S. M.; Laurenti, G.; Lioublev, E.; Lee, K.; Lee, S. C.; Luvisetto, M. L.; Margotti, A.; Martemiyanov, A. N.; Massera, F.; Meneghini, S.; Michinelli, R.; Nania, R.; Otiougova, P.; Pancaldi, G.; Pesci, A.; Pilastrini, R.; Pinazza, O.; Polozov, P. A.; Rizzi, M.; Scapparone, E.; Scioli, G.; Sellitto, S. B.; Semeria, F.; Serra, S.; Smirnitski, A. V.; Tchoumakov, M. M.; Ugolini, E.; Usenko, E.; Valenti, G.; Voloshin, K. G.; Williams, M. C. S.; Zagreev, B. V.; Zampolli, C.; Zichichi, A.; Zucchini, A.; Zuffa, M.

2004-11-01

393

Optimizing the parameters of the gas mixture for the proportional counters in the SAGE gallium-germanium neutrino experiment  

Microsoft Academic Search

The parameters of the gas mixture for the proportional counters have been optimized using calibrations with 55Fe and Cd-Se sources. As a result, the accuracy in determining the energy region of 71Ge decays detected in the SAGE experiment with the aim of measuring the solar neutrino flux has been improved.

J. N. Abdurashitov; V. N. Gavrin; V. V. Gorbachev; T. V. Ibragimova; I. N. Mirmov; A. A. Shikhin; V. E. Yants; B. T. Cleveland

2011-01-01

394

Radioisotopic method development for express determination of working mixtures proppant concentration used with the hydraulic break of gas and oil production beds  

Microsoft Academic Search

This paper describes the RIPC-01 radioisotopic meter for the determination of the working mixture proppant concentration used in the hydraulic break to increase oil and gas bore output. The method involves simultaneously measuring the helium density at the input into the unit for the working mixture preparation and the working mixture at the output from the unit for the working

O. T. Nurgaliev; V. K. Kuleshov; Yu. A. Volchenko; M. S. Suhkanov

2003-01-01

395

A study of the feasibility of using a gas-filled proportional counter as an in-core high energy gamma-ray spectrometer. Final report  

Microsoft Academic Search

The feasibility of using a gas-filled proportional counter as an in-core gamma-ray spectrometer was examined. The detector fill gas was matched to the stainless steel detector wall using general cavity theory considerations. The gas consisted of a mixture of argon, xenon, and methane, with 14C added for calibration purposes, and at a fill pressure of 10 atmospheres. The maximum energy

R. S. Reynolds; R. L. Thomas

1978-01-01

396

Analysis of a mixture of linear and cyclic siloxanes by cryo-gas chromatography-Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry  

Microsoft Academic Search

A mixture of linear and cyclic methylsiloxanes was analysed to characterize the different types of siloxane structures using gas chromatography (GC), mass spectrometry (MS) and Fourier transform infrared (FT-IR) spectroscopy. Siloxane structures are formed by hydrolysis of dimethyldichlorosilane under controlled conditions in technical applications. In the presence of methyltrichlorosilane or even trimethylchlorosilane, linear polydimethylsiloxanes and mono-, bi- or polycyclic methylsiloxanes

S. Wachholz; F. Keidel; U. Just; H. Geissler; K. Käppler

1995-01-01

397

Joule-Thomson inversion curves of mixtures by molecular simulation in comparison to advanced equations of state: natural gas as an example  

Microsoft Academic Search

Molecular modelling and simulation as well as four equations of state (EOS) are applied to natural gas mixtures regarding Joule-Thomson (JT) inversion. JT inversion curves are determined by molecular simulation for six different natural gas mixtures consisting of methane, nitrogen, carbon dioxide and ethane. These components are also regarded as pure fluids, leading to a total of ten studied systems.

J. Vrabec; A. Kumar; H. Hasse

2009-01-01

398

Joule–Thomson inversion curves of mixtures by molecular simulation in comparison to advanced equations of state: Natural gas as an example  

Microsoft Academic Search

Molecular modelling and simulation as well as four equations of state (EOS) are applied to natural gas mixtures regarding Joule–Thomson (JT) inversion. JT inversion curves are determined by molecular simulation for six different natural gas mixtures consisting of methane, nitrogen, carbon dioxide and ethane. These components are also regarded as pure fluids, leading to a total of 10 studied systems.

Jadran Vrabec; Ashish Kumar; Hans Hasse

2007-01-01

399

Similarity solutions of a strong shock wave propagation in a mixture of a gas and dusty particles  

NASA Technical Reports Server (NTRS)

The similarity solutions of a strong shock wave propagation in a mixture of a gas and small solid particles have been investigated. Similarity solution exists only when the shock is very strong and the surrounding medium is of a constant density and at rest and with negligible counterpressure. The non-dimensional fundamental equations are derived and studied. The results depend on three non-dimensional parameters; i.e. (1) the ratio of the specific heats of the gas, (2) the mass concentration of the solid particles in the mixture and (3) the ratio of the density of the solid to that of initial density of the gas. Numerical solutions for various values of these parameters are presented and discussed. The speeds of the shock wave front and its location with various energy releases are given.

Pai, S. I.; Menon, S.; Fan, Z. Q.

1980-01-01

400

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

401

A logarithmic multi-parameter model using gas sensor main and cross sensitivities to estimate gas concentrations in a gas mixture for SnO 2 gas sensors  

Microsoft Academic Search

In a metal-oxide semiconductor gas sensor, the sensitivity of the metal-oxide resistance to concentrations of reducing gases in the surrounding atmosphere is known to be related to adsorption and desorption of gas on the redox reactions between the gas and oxygen. Changes in the electric conductance due to these reactions were measured for tin dioxide semiconductor gas sensors. In this

A. Chaiyboun; R. Traute; T. Haas; O. Kiesewetter; T. Doll

2007-01-01

402

Direct Prediction of Cricondentherm and Cricondenbar Coordinates of Natural Gas Mixtures using Cubic Equation of State  

NASA Astrophysics Data System (ADS)

A numerical algorithm is presented for direct calculation of the cricondenbar and cricondentherm coordinates of natural gas mixtures of known composition based on the Michelsen method. In the course of determination of these coordinates, the equilibrium mole fractions at these points are also calculated. In this algorithm, the property of the distance from the free energy surfaces to a tangent plane in equilibrium condition is added to saturation calculation as an additional criterion. An equation of state (EoS) was needed to calculate all required properties. Therefore, the algorithm was tested with Soave-Redlich-Kwong (SRK), Peng-Robinson (PR), and modified Nasrifar-Moshfeghian (MNM) equations of state. For different EoSs, the impact of the binary interaction coefficient ( k ij) was studied. The impact of initial guesses for temperature and pressure was also studied. The convergence speed and the accuracy of the results of this new algorithm were compared with experimental data and the results obtained from other methods and simulation softwares such as Hysys, Aspen Plus, and EzThermo.

Taraf, R.; Behbahani, R.; Moshfeghian, Mahmood

2008-12-01

403

Effect of focal size on the laser ignition of compressed natural gas–air mixture  

NASA Astrophysics Data System (ADS)

Laser ignition of compressed natural gas–air mixtures was investigated in a constant volume combustion chamber (CVCC) as well as in a single cylinder engine. Laser ignition has several potential advantages over conventional spark ignition system. Laser ignition relies on the fact that optical breakdown (plasma generation) in gases occurs at high intensities of ?1011 W/cm2. Such high intensities can be achieved by focusing a pulsed laser beam to small focal sizes. The focal spot size depends on several parameters such as laser wavelength, beam diameter at the converging lens, beam quality and focal length. In this investigation, the focal length of the converging lens and the beam quality were varied and the corresponding effects on minimum ignition energy as well as pressure rise were recorded. The flame kernel was visualized and correlated with the rate of pressure rise inside the combustion chamber. This investigation will be helpful in the optimization of laser and optics parameters in laser ignition. It was found that beam quality factor and focal length of focusing lens have a strong impact on the minimum ignition energy required for combustion. Combustion duration depends on the energy density at the focal spot and size of the flame kernel.

Srivastava, Dhananjay Kumar; Wintner, Ernst; Agarwal, Avinash Kumar

2014-07-01

404

Flow rate measurements of binary gas mixtures through long trapezoidal microchannels  

NASA Astrophysics Data System (ADS)

The flow rate of two noble gas mixtures, namely He/Ar and He/Kr, is measured through a microsystem containing 400 long trapezoidal microchannels placed in parallel configuration. Each microchannel has a trapezoidal cross section with long base 5.38 micrometers and height 1.90 micrometers, while its length is 5000 micrometers. The experiment is based on the constant volume method. The flow is driven by pressure gradient. The flow rate measurements refer to downstream pressures of 15.1 kPa and 8.05 kPa. The pressure ratio is in the range of 3-7 and 4-7 for the larger and smaller downstream pressures, respectively. The investigated rarefaction range is in the slip and early transition regions. The concentration of He varies from zero to one. The measured flow rates are compared to the corresponding computational ones obtained by the numerical solution of the McCormack kinetic model. Very good agreement between the experimental and computational results is reached. The difference between the corresponding results is less than the experimental uncertainty. Typical pressure and concentration profiles along the axis and the velocity profiles in the center of the channel obtained from the numerical solution are also presented.

Szalmas, Lajos; Colin, Stéphane; Valougeorgis, Dimitris

2012-05-01

405

Moment method and non-equilibrium thermodynamics of rarefied gas mixture  

NASA Astrophysics Data System (ADS)

The problem of the kinetic justification of the extended irreversible thermodynamics on the basis of Grad's moment method for multicomponent rarefied gas mixture is discussed. The examination is carried out of linearized kinetic Boltzmann equation which is used to obtain an infinite chain of linked equations (moment equations) for the coefficients of expansion of the distribution function in a system of tensor polynomials. Using these equations generalized expressions are obtained for the entropy density, entropy flux density and entropy production as functions of an arbitrary number of state variables, which allow different variants of the relations between fluxes and thermodynamic forces to be considered. For spatially homogeneous systems these relations correspond to the Onsager version of the linear non-equilibrium thermodynamics. In a more general case thermodynamic forces involved in the transport equations are significantly redefined to include, besides the usual gradients of the initial macroscopic parameters, derivatives of the dissipative fluxes with respect to time and coordinates. Some consequence and physical effects, following from the obtained equations are analyzed.

Zhdanov, Vladimir M.; Roldughin, Vjacheslav I.

2012-11-01

406

Explosion-driven Rayleigh-Taylor instability in gas-particle mixtures  

NASA Astrophysics Data System (ADS)

The structure and growth of an explosion-driven Rayleigh-Taylor instability in gas-particle mixtures is investigated using two-dimensional numerical simulations. Particle concentration and diameter are varied and the growth of the ensuing mixing layer and its dependence on these parameters is investigated. The hydrodynamic structures are subdued and lose their coherence with increase in solid particle concentrations. When the solid particle concentration is fixed but particle diameter varied, a non-monotic behavior is observed. It is found that an intermediate particle size results in the widest mixing zone and degree of mixing. This is due to the differences in the spatial accumulation of the particles as they disperse. Small particles accumulate in the bubbles and around the spikes of the Rayleigh-Taylor structures; intermediate-sized particles in the tips of the spikes and as roots into the driver fluid; large particles accumulate primarily in the spikes and as thin, elongated roots into the driver fluid. Such differences are attributed to the response time or Stokes number of the particles. Finally, future directions for extending the current research are summarized.

Balakrishnan, Kaushik

2014-04-01

407

Shell Perturbations of an Acoustic Thermometer Determined from Speed of Sound in Gas Mixtures  

NASA Astrophysics Data System (ADS)

With the goal of achieving a better understanding of gas-shell coupling perturbations in the acoustic resonators used at INRiM for the determination of the Boltzmann constant, we measured the variation of their acoustic and microwave resonances induced by changing the composition of a binary He-Ar mixture which filled the cavity at constant temperature and pressure. As a consequence of the progressive dilution of a sample of initially pure He with Ar, the radial acoustic modes of the resonator spanned decreasing frequency intervals, partially overlapping, for several modes. In addition to the expected breathing mode of the shell, the results evidenced the presence of several other shell resonances at lower and higher frequencies, confirming that the elastic response of the assembled resonator significantly differs from that of a simple spherical shell. Experimental results are reported for two resonators which differ in design, dimensions, and constructing material. In spite of their being preliminary and susceptible of significant improvement, these results favor the interpretation of acoustic thermometry measurements with pure gases.

Gavioso, R. M.; Madonna Ripa, D.; Guianvarc'h, C.; Benedetto, G.; Giuliano Albo, P. A.; Cuccaro, R.; Pitre, L.; Truong, D.

2010-09-01

408

Xenon hydrate dissociation measurements with model protein systems.  

PubMed

Effective long-term storage remains a significant challenge to the use and development of protein pharmaceuticals. We have investigated the interactions between clathrate hydrates and model protein solutions to determine the effects on hydrate formation. Here, the dissociation curve and equilibrium conditions for xenon clathrate hydrate with model lysozyme and lactate dehydrogenase (LDH) protein solutions have been studied using calorimetry measurements at pressures ranging from 3 to 20 bar. Sucrose in solution was shown to exhibit small inhibition effects on xenon hydrate formation, shifting the dissociation curve and decreasing the conversion of water to hydrate by 15-26%. The addition of l-histidine buffer and lysozyme at low concentrations did not substantially inhibit hydrate formation. However, small shifts in the dissociation curve were demonstrated for solutions containing LDH. The presence of lysozyme and LDH in solution did not significantly alter the conversion of water to hydrate, indicating that these and similar proteins do not substantially affect the extent of xenon gas hydrate formation. Preliminary experiments were performed for LDH solutions to assess the impact of xenon hydrate formation and dissociation on enzymatic activity, with samples stored in hydrate systems showing small decreases in activity. PMID:21790193

Booker, Ryan D; Koh, Carolyn A; Sloan, E Dendy; Sum, Amadeu K; Shalaev, Evgenyi; Singh, Satish K

2011-09-01

409

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

PubMed

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. PMID:24880347

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

2014-05-01

410

Reduced xenon diffusion for quantitative lung study--the role of SF(6)  

NASA Technical Reports Server (NTRS)

The large diffusion coefficients of gases result in significant spin motion during the application of gradient pulses that typically last a few milliseconds in most NMR experiments. In restricted environments, such as the lung, this rapid gas diffusion can lead to violations of the narrow pulse approximation, a basic assumption of the standard Stejskal-Tanner NMR method of diffusion measurement. We therefore investigated the effect of a common, biologically inert buffer gas, sulfur hexafluoride (SF(6)), on (129)Xe NMR and diffusion. We found that the contribution of SF(6) to (129)Xe T(1) relaxation in a 1:1 xenon/oxygen mixture is negligible up to 2 bar of SF(6) at standard temperature. We also measured the contribution of SF(6) gas to (129)Xe T(2) relaxation, and found it to scale inversely with pressure, with this contribution approximately equal to 1 s for 1 bar SF(6) pressure and standard temperature. Finally, we found the coefficient of (129)Xe diffusion through SF(6) to be approximately 4.6 x 10(-6) m(2)s(-1) for 1 bar pressure of SF(6) and standard temperature, which is only 1.2 times smaller than the (129)Xe self diffusion coefficient for 1 bar (129)Xe pressure and standard temperature. From these measurements we conclude that SF(6) will not sufficiently reduce (129)Xe diffusion to allow accurate surface-area/volume ratio measurements in human alveoli using time-dependent gas diffusion NMR.

Mair, R. W.; Hoffmann, D.; Sheth, S. A.; Wong, G. P.; Butler, J. P.; Patz, S.; Topulos, G. P.; Walsworth, R. L.

2000-01-01

411

Temperature and density dependence of ?-catalysis cycling rate in dense D\\/T and H\\/D\\/T gas mixtures  

Microsoft Academic Search

Muon catalyzed dt fusion in dense D\\/T and H\\/D\\/T gas mixtures of hydrogen isotopes is studied by the MCF collaboration at JINR.\\u000a The measurements were carried out with a high pressure target at the JINR phasotron in the temperature range 300-800 K at\\u000a mixture densities \\u000a $$ \\\\simeq 0.4{\\\\text{ and }} \\\\simeq {\\\\text{0}}{\\\\text{.8 LHD}}$$\\u000a . Tentative experimental results obtained by several

V. R. Bom; J. N. Bradbury; J. D. Davies; A. M. Demin; D. L. Demin; A. E. Drebushko; V. P. Dzhelepov; C. W. E. van Eijk; V. V. Filchenkov; A. N. Golubkov; N. N. Grafov; V. G. Grebinnik; S. K. Grishechkin; V. G. Klevtsov; A. D. Konin; A. A. Kukolkin; S. V. Medved; V. A. Nazarov; V. V. Perevozchikov; V. I. Pryanichnikov; V. Ya. Rozhkov; A. I. Rudenko; S. M. Sadetsky; G. G. Semenchuk; V. T. Sidorov; Yu. V. Smirenin; I. I. Sukhoi; N. I. Voropaev; A. A. Yukhimchuk; V. G. Zinov; S. V. Zlatoustovskii

1999-01-01

412

Xenon emission accompanying fracture of xenon-implanted cubic zirconia  

SciTech Connect

The emission of xenon following the fracture of xenon-implanted cubic zirconia has been studied using mass spectrometry. All samples showed intense Xe bursts at failure. Order of magnitude estimates of the amount of Xe released suggest that micrometer-scale regions of the tensile surface on either side of the fracture surface of these samples do not show sufficient damage to account for this emission. However, SEM micrographs of the fracture surface show evidence for extensive microcracking immediately adjacent to the tensile surface. It is believed that these microcracks are formed when the advancing crack encounters the tensile stresses immediately below the Xe-implanted surface layer and disrupts the Xe inclusions produced by implantation. Some samples also show Xe bursts prior to failure; SEM observations of these samples show shallow conchoidal cracks on the tensile surface, which apparently form during loading and would account for the release of Xe prior to failure.

Norton, M.G.; Jiang, Wenbiao (Washington State Univ., Pullman, WA (United States). Dept. of Mechanical and Materials Engineering); Dickinson, J.T.; Jensen, L.C.; Langford, S.C. (Washington State Univ., Pullman, WA (United States). Dept. of Physics); Fleischer, E.L.; Mayer, J.W. (Cornell Univ., Ithaca, NY (United States). Dept. of Materials Science and Engineering)

1993-08-01

413

First operation of bulk micromegas in low pressure negative ion drift gas mixtures for dark matter searches  

NASA Astrophysics Data System (ADS)

A bulk micromegas micropattern charge readout device has, for the first time, been operated at room temperature in low pressure carbon disulphide vapour. This is a key step opening prospects for use of micromegas readout for large volume negative ion time projection chambers (TPCs) without magnets, such as proposed for directional dark matter detectors and other rare event applications. The dependence of the gain on the amplification field, pressure and drift field has been evaluated. For the available gap size of 75 ?m a maximum gain of 1300 ± 120 was achieved in 40 torr vapour with an energy resolution of 22% for 5.9 keV 55Fe X-rays. From a fit to the data, the Townsend coefficient gas parameters A and B have been derived. Operation has also been successfully achieved in xenon:carbon disulphide blends over a range of partial and total pressures. A gain of 890 ± 130 at an energy resolution of 35% has been recorded for a 1:1 blend at a total pressure of 80 torr. Possible improvements are discussed in the context of operation in directional dark matter TPCs as a replacement for multi-wire proportional counters.

Lightfoot, P. K.; Spooner, N. J. C.; Lawson, T. B.; Aune, S.; Giomataris, I.

2007-07-01

414

Modeling pulse characteristics in Xenon with NEST  

NASA Astrophysics Data System (ADS)

A comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, the effects of the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, the ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. This modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors.

Mock, J.; Barry, N.; Kazkaz, K.; Stolp, D.; Szydagis, M.; Tripathi, M.; Uvarov, S.; Woods, M.; Walsh, N.

2014-04-01

415

Fission Xenon on Mars  

NASA Technical Reports Server (NTRS)

Fission Xe components due to Pu-244 decay in the early history of Mars have been identified in nakhlites; as in the case of ALH84001 and Chassigny the fission gas was assimilated into indigenous solar-type Xe. Additional information is contained in the original extended abstract.

Mathew, K. J.; Marti, K.; Marty, B.

2002-01-01

416

Modeling high-pressure adsorption of gas mixtures on activated carbon and coal using a simplified local-density model  

SciTech Connect

The simplified local-density (SLD) theory was investigated regarding its ability to provide accurate representations and predictions of high-pressure supercritical adsorption isotherms encountered in coalbed methane (CBM) recovery and CO{sub 2} sequestration. Attention was focused on the ability of the SLD theory to predict mixed-gas adsorption solely on the basis of information from pure gas isotherms using a modified Peng-Robinson (PR) equation of state (EOS). An extensive set of high-pressure adsorption measurements was used in this evaluation. These measurements included pure and binary mixture adsorption measurements for several gas compositions up to 14 MPa for Calgon F-400 activated carbon and three water-moistened coals. Also included were ternary measurements for the activated carbon and one coal. For the adsorption of methane, nitrogen, and CO{sub 2} on dry activated carbon, the SLD-PR can predict the component mixture adsorption within about 2.2 times the experimental uncertainty on average solely on the basis of pure-component adsorption isotherms. For the adsorption of methane, nitrogen, and CO{sub 2} on two of the three wet coals, the SLD-PR model can predict the component adsorption within the experimental uncertainties on average for all feed fractions (nominally molar compositions of 20/80, 40/60, 60/40, and 80/20) of the three binary gas mixture combinations, although predictions for some specific feed fractions are outside of their experimental uncertainties.

Fitzgerald, J.E.; Robinson, R.L.; Gasem, K.A.M. [Oklahoma State University, Stillwater, OK (United States). School of Chemical Engineering

2006-11-07

417

Modeling high-pressure adsorption of gas mixtures on activated carbon and coal using a simplified local-density model.  

PubMed

The simplified local-density (SLD) theory was investigated regarding its ability to provide accurate representations and predictions of high-pressure supercritical adsorption isotherms encountered in coalbed methane (CBM) recovery and CO2 sequestration. Attention was focused on the ability of the SLD theory to predict mixed-gas adsorption solely on the basis of information from pure gas isotherms using a modified Peng-Robinson (PR) equation of state (EOS). An extensive set of high-pressure adsorption measurements was used in this evaluation. These measurements included pure and binary mixture adsorption measurements for several gas compositions up to 14 MPa for Calgon F-400 activated carbon and three water-moistened coals. Also included were ternary measurements for the activated carbon and one coal. For the adsorption of methane, nitrogen, and CO2 on dry activated carbon, the SLD-PR can predict the component mixture adsorption within about 2.2 times the experimental uncertainty on average solely on the basis of pure-component adsorption isotherms. For the adsorption of methane, nitrogen, and CO2 on two of the three wet coals, the SLD-PR model can predict the component adsorption within the experimental uncertainties on average for all feed fractions (nominally molar compositions of 20/80, 40/60, 60/40, and 80/20) of the three binary gas mixture combinations, although predictions for some specific feed fractions are outside of their experimental uncertainties. PMID:17073487

Fitzgerald, James E; Robinson, Robert L; Gasem, Khaled A M

2006-11-01

418

Exploring the Behavior of Solid/Gas Mixtures via Shock-Tube Experiments With Relevance to Vulcanian Eruptions  

NASA Astrophysics Data System (ADS)

Scaled 1-D shock-tube experiments were conducted to understand the behavior of rapidly-decompressed solid-gas mixtures, with relevance to the initial phase of Vulcanian explosions. Using experimental apparatus and methods similar to Cagnoli et al. (2002; J. Volcanol.Geotherm. Res., 101-113), a bed of very-well-sorted glass spheres and interstitial air was suddenly decompressed from atmospheric to vacuum pressures in a vertical glass shock tube. Decompression was achieved by nearly instantaneous rupture of a diaphragm separating the high-pressure mixture from the low-pressure region. Pressure ratios across the diaphragm and particle size were varied systematically. Velocities were determined by photogrammetric analysis of high-speed video footage. Pressure evolution was recorded at 0.30, 0.90 and 1.20 m above the diaphragm by high frequency (100,000 Hz sampling rate) PCB pressure sensors, revealing pressure wave velocity and relative strength. Pressure waveforms recorded in the experiments resemble those recorded by microbarographs of Vulcanian explosions. Mixture and pressure wave velocities are lower than typically observed in eruptions, likely due to lower pressure ratios across the diaphragm. Results show particle size plays an important role in overall behavior. As expected, mixture velocity increases with increasing pressure ratio across the diaphragm and decreases with increasing particle size. Several existing formulations intended to predict behavior of solid-gas mixtures were tested against the data. Pseudo-gas approximations of fluid properties are sufficient to allow 1-D shock-tube theory to mimic behavior of the finest (4-45 microns) mixtures, whereas inertial effects become important for larger-particle experiments causing deviation from theory. Pressure wave velocity and strength are reduced from those predicted for an ideal gas, suggesting momentum loss from the gas phase due to frictional interaction with the particle beds. The well-accepted theory of Ergun (1952) and other standard drag relationships used to parameterize interactions between gas phases and high concentrations of solids in numerical models of explosive eruptions are also tested.

Chojnicki, K. N.; Clarke, A. B.; Phillips, J. C.

2005-12-01

419

Recovery of methane from gas hydrates intercalated within natural sediments using CO(2) and a CO(2)/N(2) gas mixture.  

PubMed

The direct recovery of methane from massive methane hydrates (MHs), artificial MH-bearing clays, and natural MH-bearing sediments is demonstrated, using either CO(2) or a CO(2)/N(2) gas mixture (20 mol % of CO(2) and 80 mol % of N(2), reproducing flue gas from a power plant) for methane replacement in complex marine systems. Natural gas hydrates (NGHs) can be converted into CO(2) hydrate by a swapping mechanism. The overall process serves a dual purpose: it is a means of sustainable energy-source exploitation and greenhouse-gas sequestration. In particular, scant attention has been paid to the natural sediment clay portion in deep-sea gas hydrates, which is capable of storing a tremendous amount of NGH. The clay interlayer provides a unique chemical-physical environment for gas hydrates. Herein, for the first time, we pull out methane from intercalated methane hydrates in a clay interlayer using CO(2) and a CO(2)/N(2) gas mixture. The results of this study are expected to provide an essential physicochemical background required for large-scale NGH production under the seabed. PMID:22730158

Koh, Dong-Yeun; Kang, Hyery; Kim, Dae-Ok; Park, Juwoon; Cha, Minjun; Lee, Huen

2012-08-01

420

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

421

Gamma-ray spectrometer utilizing xenon at high pressure  

Microsoft Academic Search

A prototype gamma-ray spectrometer utilizing xenon gas near the critical point (166°C, 58 atm) is under development. The spectrometer will function as a room-temperature ionization chamber detecting gamma rays in the energy range 100 keV2 MeV, with an energy resolution intermediate between semiconductor (Ge) and scintillation (NaI) spectrometers. The energy resolution is superior to that of a NaI scintillation spectrometer

G. C. Smith; G. J. Mahler; B. Yu; W. R. Kane; J. K. Markey

1994-01-01

422

Supercritical xenon-filled hollow-core photonic bandgap fiber.  

PubMed

We demonstrate that filling a hollow-core photonic-bandgap fiber with supercritical xenon creates a medium with a controllable density up to several hundred times that at STP, while working at room temperature. The high compressibility of the supercritical fluid allows rapid tuning of the spectral guidance window by making small changes of gas pressure near the critical point. We discuss potential applications of this system in linear and nonlinear optics. PMID:23736625

Lynch-Klarup, K E; Mondloch, E D; Raymer, M G; Arrestier, D; Gerome, F; Benabid, F

2013-06-01

423

Adsorption behavior of ternary mixtures of noble gases inside single-walled carbon nanotube bundles  

NASA Astrophysics Data System (ADS)

In order to study the gas-storage and gas-filtering capability of carbon nanotube (CNT) bundles simultaneously, we considered the adsorption behavior of a ternary mixture of noble gases, including Argon (Ar), Krypton (Kr), and Xenon (Xe), i.e., Ar-Kr-Xe mixture, on (10, 10) single-walled carbon nanotube (SWCNT) bundles. Molecular dynamics (MD) simulations at different temperatures of (75, 100, 150, 200, 250, and 300) K were performed, and adsorption energies, self-diffusion coefficients, activation energies, and radial distribution functions (RDFs) were computed to analyze the thermodynamics, transport and structural properties of the adsorption systems. It is observed that the SWCNT bundles have larger contents of heavier noble gases compared to the lighter ones. This interesting behavior of SWCNT bundles makes them proper candidates for gas-storage and gas molecular-sieving processes.

Foroutan, Masumeh; Nasrabadi, Amir Taghavi

2010-09-01

424

Ar-Xe mixtures and their use in curved grid gas proportional scintillation counters for X-rays  

NASA Astrophysics Data System (ADS)

An experimental study of the scintillation properties of Ar-Xe mixtures has been carried out with a gas proportional scintillation counter instrumented with a photomultiplier tube. Energy resolutions of 7.7, 7.8, 7.8, 8.3, 8.5, 9.1 and 11.5% were obtained for 5.9 keV X-rays respectively for the 100% Xe, 60%Ar-40%Xe, 80%Ar-20%Xe, 90%Ar-10%Xe, 95%Ar-5%Xe, 97%Ar-3%Xe and 99%Ar-1%Xe mixtures at 800 Torr. Thresholds for scintillation and ionization were also determined. The performance of Ar-Xe mixtures as detection media in large detection area applications has been studied for a 52 mm diameter photomultiplier and a 38 mm diameter radiation window. The curved grid technique was used to minimize spectra distortion due to solid angle effects.

do Carmo, S. J. C.; Trindade, A. M. F.; Borges, F. I. G. M.

2009-03-01

425

A comparison of solar wind and estimated solar system xenon abundances - A test for solid/gas fractionation in the solar nebula  

NASA Technical Reports Server (NTRS)

The solar Xe elemental abundance is determined here using solar wind measurements from lunar ilmenites which are normalized to Si by spacecraft data. The results are compared with estimated abundances assuming no fractionation. When corrected for solar wind/photospheric fractionation, the Xe-130 abundance given by surface layer oxidation of ilmenite from solid 71501 exposed within the last 200 m.y. is 0.24 +/- 0.09 normalized to Si = 10 exp 6. This is indistinguishable from estimates made assuming no solid/gas fractionation. Results from breccia 79035 ilmenite exposed at least 1 Gyr ago indicate that the solar wind Xe flux may have been significantly higher relative to other noble gases, perhaps due to more efficient Xe ionization. If this is true, fluxes of C and S, which have first ionization potentials similar to Xe, should also be higher in the ancient solar wind from the same time period.

Wiens, Roger C.; Burnett, D. S.; Neugebauer, M.; Pepin, R. O.

1992-01-01

426

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

NASA Astrophysics Data System (ADS)

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 carbon monoxide or hydrogen, the electric stability of the discharge increases, specific input energy per molecular component being higher more than order of magnitude and coming up to 6.5 kJ/(l atm). Theoretical calculations demonstrated that for the experimental conditions the singlet delta oxygen yield may reach ~20% exceeding its threshold value needed for oxygen-iodine laser operation at room temperature. The results of experiments on spectroscopy of the singlet delta and singlet sigma oxygen states in the EBSD are presented.

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

2004-05-01

427

Electronically driven transport of oxygen from liquid iron to CO + CO2 gas mixtures through stabilized zirconia  

NASA Astrophysics Data System (ADS)

Transport of oxygen in the following electrochemical system was investigated; O (liquid iron) Oin2- (in ZrO22-CaO) O2 (CO + CO2) An alumina crucible was charged with liquid iron containing 580 ± 10 ppm oxygen. A calcia-stabilized zirconia tube (closed at one end) was immersed in the liquid iron. The inside of the zirconia tube was flushed with a stream of CO + CO2 gas mixture. Oxygen was removed from liquid iron to the CO + COO2 gas mixture without application of an external current. Kinetics of oxygen transport in this system are discussed in terms of mixed ionic and electronic conduction of the zirconia, and also diffusion of oxygen in liquid iron. The rate controlling step for this oxygen removal process was found to be transport of oxygen across a boundary layer in the melt at the melt/electrolyte interface.

Iwase, M.; Tanida, M.; McLean, A.; Mori, T.

1981-09-01

428

High Precision Xenon Measurements Reveal the Presence of Solar Xenon in the Mantle Source of Mid Ocean Ridge Basalts  

NASA Astrophysics Data System (ADS)

Xenon isotopes provide unique insights into the sources of volatile material for planet Earth, the degassing of the mantle, and the chemical evolution of the mantle. Whether the Earth's mantle has solar or planetary heavy noble gases has remained a fundamental and outstanding question. Resolving this issue is crucial for planet accretion models and understanding how volatiles were incorporated into the solid Earth. Here we report the detection of solar, or possibly chondritic (Q), xenon in a gas-rich basalt glass. The sample was collected from the Hotu Matua seamount chain, located south of the Sojourn Ridge, during the 2001 Cook16MV expedition. Xenon was extracted by step crushing fresh basalt glass in vacuum, and xenon isotopes were measured using the Nu multicollector noble gas mass spectrometer at Harvard. Based on reproducibility of standards run over a period of 3 days, which were similar in size (3.5 x 10^{-14}cc of ^{130}Xe) to the sample, external precision for ^{124,126}Xe/^{130}Xe ratios are better than 2%, for ^{128}Xe/^{130}Xe is 7‰, and for ^{129}Xe/^{130}Xe and ^{136}Xe/^{130}Xe ratios are 4‰. These uncertainties are only marginally larger than predicted from counting statistics. A clear excess in ^{124,126,128}Xe was observed. The anomalies in non-radiogenic isotopes of xenon cannot result from instrumental mass fractionation or other experimental artifacts since excesses in ^{128}Xe are correlated with excesses in ^{129}Xe. In addition, the ^{129}Xe/^{130}Xe and ^{136}Xe/^{130}Xe ratios fall on the MORB line. Thus, we conclude that the anomalies in the non-radiogenic isotopes of xenon are a real feature of the mantle source of MORBs. Excesses in ^{124,126,128}Xe/^{130}Xe ratios plot on the air solar mixing line and indicate the presence of a solar xenon component in the MORB source. Since the non-radiogenic isotopic composition of solar and Q xenon are similar, a chondritic xenon component cannot be ruled out. Krypton isotopes can potentially distinguish between a solar and a Q component and additional high-precision Kr isotopic measurements are currently underway. The correlation between ^{128}Xe and ^{129}Xe excesses in our sample defines a steeper trajectory than the correlation seen in CO2 well gases, although given the small number of data points such a conclusion is tentative. Nevertheless, a steeper trend implies a significantly larger solar component than previously determined values of 20% (e.g., Holland and Ballentine, 2006). While we are in the process of making additional Xe measurements, a major implication of the current data is that subduction zones must form a significant barrier to the transport of atmospheric Xe into the mantle in order to preserve the solar signature. Alternatively, mantle domains that have been largely isolated from the convective mantle must exist. Leakage of xenon from such a reservoir would then provide the excess ^{129}Xe associated with the solar signature seen in the MORB source. [Ref:Holland and Ballentine, Nature 441, 186, 2006].

Mukhopadhyay, S.; Langmuir, C. H.

2006-12-01

429

NMR Study of Dilute Molecular Hydrogen in Liquid Xenon  

NASA Astrophysics Data System (ADS)

Pulsed NMR measurements have been made at 20.00 MHz of the diffusion coefficient D, the spin-lattice relaxation time T(,1), and the spin-spin relaxation time T(,2) of ortho-hydrogen as a dilute impurity (< 1%) in liquid xenon. The measurements were obtained as a function of temperature (T) near the saturated vapor pressure curve from the triple point to the critical point, and represent the behavior of an isolated hydrogen molecule in the otherwise pure liquid. Samples were prepared by condensing xenon gas into a liquid near the triple point and circulating gaseous hydrogen through the sample with a closed cycle pump until the desired concentration was attained. Diffusion coefficients were determined using the spin-echo technique in a calibrated field gradient. Near the triple point they are found to have an activated temperature dependence similar to that of self-diffusion in liquid xenon but deviate upward at higher temperatures. The principle of corresponding states is used to compare D to similar data taken by Conradi for ortho-hydrogen in other rare gas liquids. This comparison is found to successful when the xenon potential parameters along with the reduced mass an H(,2)-Xe gas pair are used. Self-diffusion in liquid xenon is well described using the empirical expression (rho)D = cT('(beta)) with (beta) = 2.87 and (rho) the density. This expression is also found to describe the temperature dependence of D near the triple point. A hard sphere molecular dynamics calculation for the ratio of impurity to self-diffusion is found to describe qualitatively the behavior of the experimental ratio. T(,1) is found to be larger than the corresponding times in the other rare gas liquids. Consequently (tau)(,1), the molecular relaxation time, is smaller, but still in the weak collision limit, and therefore Bloom-Oppenheim theory is still appropriate. (T(,1))(,liquid) < (T(,1))(,gas) below 230K, and Deutch and Oppenheim's extension of Bloom -Oppenheim theory to multiple particle collisions is used to explain this fact. Above 230K (T(,1))(,liquid) (DBLTURN) (T(,1))(,gas) which is interpreted to mean that binary collisions are primarily responsible for relaxation.

Edwards, Carl Monroe

430

Development of a computer program describing the real gas isentropic expansion of an ammonia-water vapor mixture  

Microsoft Academic Search

A special computer program has been developed, using QBASIC, to calculate numerically the thermodynamic changes of an ammonia-water vapor mixture along an isentropic expansion. The thermodynamic relations used were obtained in terms of the Gibbs' free energy equation for the gas phase of pure components and the entropy was held constant with an accuracy better than 0·000001 kJ\\/kg K. Results

D. A. Kouremenos; X. K. Kakatsios; O. E. Floratos

1996-01-01

431

Determination of mixtures in vegetable oils and milk fat by analysis of sterol fraction by gas chromatography  

Microsoft Academic Search

A rapid gas-chromatographic (GC) procedure was developed for the analysis of the total sterol fraction of vegetable oils,\\u000a milk fat or mixtures, to detect possible admixtures of sunflower with olive oil and the addition of vegetable oils to milk\\u000a fat. The method, which employs alkali-catalyzed transesterification with KOH\\/methanol, was compared with saponification procedures\\u000a with and without transformation of sterols into

L. Alonso; J. Fontecha; L. Lozada; M. Juárez

1997-01-01

432

Calculation of steady-state three-dimensional flows of viscous gases and chemically reacting gas mixtures  

NASA Astrophysics Data System (ADS)

In an earlier study (Strelets and Shur, 1988), a method, referred to as the compressibility scaling method, has been developed for the numerical modeling of two-dimensional steady-state compressible flows for arbitrary freestream Mach numbers. Here, the method is extended to the case of three-dimensional steady-state flows of viscous gases and multicomponent gas mixtures in the presence of chemical reactions. The capabilities of the finite difference algorithm proposed here are illustrated by two examples.

Kuznetsov, A. E.; Strelets, M. Kh.; Shur, M. L.

1991-02-01

433

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

434

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

435

Lifetime improvement of nitrided carbon stripper foils by ion-beam sputtering with a binary gas mixture  

Microsoft Academic Search

The lifetimes of our carbon stripper foils (10–25?g\\/cm2) prepared by reactive nitrogen ion-beam sputtering were distributed in a wide range. Expressed in units of integrated beam current received, lifetimes of 750±400mC\\/cm2 were usual for a 3.2MeV Ne+ beam. This wide distribution of lifetimes have been improved by applying a binary gas mixture (N2+Ne) for sputtering of carbon. With high reproducibility,

I. Sugai; Y. Takeda; M. Oyaizu; H. Kawakami; Y. Hattori; K. Kawasaki; K. Yoshida; A. Itoh

2004-01-01

436

A Redetermination of the Relative Abundances of the Isotopes of Neon, Krypton, Rubidium, Xenon, and Mercury  

Microsoft Academic Search

A careful redetermination of isotopic abundance ratios in neon, krypton, rubidium, xenon, and mercury has been made. The mass spectrometer employed was calibrated for mass discriminative effects with a synthetic argon isotope mixture made from essentially pure samples of A36 and A40. The present results together with those obtained from an earlier study on carbon, nitrogen, oxygen, argon, and potassium

Alfred O. Nier

1950-01-01

437

NEW COMPOUNDS OF NOBLE GASES: THE FLUORIDES OF XENON AND RADON  

Microsoft Academic Search

Synthesis of xenon di-, tetra-, and hexafluoride and radon difluoride is ; described and properties of the compounds are discussed. Radon difiuoride was ; prepared by heating a radon--fluorine mixture to 400 deg for 30 min. It is much ; less volatiie than its Xe analog, and has resistance to reduction by H, which ; occurs only above 200 deg

Bartlett

1963-01-01

438

Response of electrochemical oxygen sensors to inert gas-air and carbon dioxide-air mixtures: measurements and mathematical modelling.  

PubMed

Electrochemical oxygen gas sensors are widely used for monitoring the state of inertisation of flammable atmospheres and to warn of asphyxiation risks. It is well established but not widely known by users of such oxygen sensors that the response of the sensor is affected by the nature of the diluent gas responsible for the decrease in ambient oxygen concentration. The present work investigates the response of electrochemical sensors, with either acid or alkaline electrolytes, to gas mixtures comprising air with enhanced levels of nitrogen, carbon dioxide, argon or helium. The measurements indicate that both types of sensors over-read the oxygen concentrations when atmospheres contain high levels of helium. Sensors with alkaline electrolytes are also shown to underestimate the severity of the hazard in atmospheres containing high levels of carbon dioxide. This deviation is greater for alkaline electrolyte sensors compared to acid electrolyte sensors. A Computational Fluid Dynamics (CFD) model is developed to predict the response of an alkaline electrolyte, electrochemical gas sensor. Differences between predicted and measured sensor responses are less than 10% in relative terms for nearly all of the gas mixtures tested, and in many cases less than 5%. Extending the model to simulate responses of sensors with acid electrolytes would be straightforward. PMID:21112151

Walsh, P T; Gant, S E; Dowker, K P; Batt, R

2011-02-15

439

Electron ranaway and ion-ion plasma formation in afterglow low-pressure plasma of oxygen-containing gas mixtures  

NASA Astrophysics Data System (ADS)

Experimental investigation of temporal evolution of charged plasma species in afterglow plasma of oxygen-containing mixtures have been investigated. The probe VAC and the time dependence of the saturation positive and negative particles currents to a probe in a fixed bias voltage were performed. The decay of afterglow low-pressure electronegative gas plasmas take place in two distinct stages (the electron-ion stage, and the ion-ion stage) as it was shown in [1] for pure oxygen. In the first stage, the negative ions are locked within a discharge volume and plasma is depleted of electrons and positive ions. The electron density decay is faster, than exponential, and practically all electrons leave plasma volume during finite time followed by the ion--ion (electron-free) plasma formation. The decay of the ion-ion plasma depends on the presence of detachment. With a large content of electronegative gas (oxygen) in a mixture, when there is a ``detachment particles,'' a small fraction of the electrons appearing as a result of the detachment continue to hold all negative ions in the discharge volume. In this case, the densities of all charged plasma components decay according to the same exponential law with a characteristic detachment time. At a low oxygen content in the gas mixture there is no detachment and plasma decays by an ion--ion ambipolar diffusion mechanism.[4pt][1]. S.A.Gutsev, A.A.Kudryavtsev, V.A.Romanenko. Tech.Phys. 40, 1131, (1995).

Kudryavtsev, Anatoly; Bogdanov, Eugene; Kosykh, Nikolay; Gutsev, Sergey

2012-10-01

440

Oxidation of Minor Elements from an Iron–Nickel–Chromium–Cobalt–Phosphorus Alloy in 17.3% CO 2 –H 2 Gas Mixtures at 700–1000 °C  

Microsoft Academic Search

Fe–Ni–Cr–Co–P alloys were exposed to 17.3% CO2–H2 gas mixtures to investigate the oxidation of minor elements in metallic alloys in the early solar system. Reaction temperatures\\u000a varied between 700 and 1000 °C. Gas-phase equilibrium was attained at 800, 900, and 1000 °C, yielding H2–H2O–CO–CO2 gas mixtures. Experiments at 700 and 750 °C did not achieve gas-phase equilibrium and were performed in H2–CO2 gas

Dante S. Lauretta; Britney E. Schmidt

2009-01-01

441

Use of a solid mixture containing diethylenetriamine\\/nitric oxide (DETANO) to liberate nitric oxide gas in the presence of horticultural produce to extend postharvest life  

Microsoft Academic Search

Postharvest treatment of fruit and vegetables with a low concentration of nitric oxide gas can extend postharvest life but application of nitric oxide by release from a gas cylinder is not feasible for many horticultural situations. This paper reports on development of a solid mixture to generate nitric oxide gas in the presence of horticultural produce. The solid NO-donor compound,

R. B. H. Wills; L. Soegiarto; M. C. Bowyer

2007-01-01

442

Analytical Method for Measuring Total Protium and Total Deuterium in a Gas Mixture Containing H2, D2, and HD Via Gas Chromatography  

SciTech Connect

A new analytical technique has been developed that measures both total protium (H) and deuterium (D) in a gas mixture containing H2, D2, and HD. This new analytical technique uses a micro gas chromatograph (GC) with two molecular sieve columns. One column uses D2 as the carrier gas and the other uses H2 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 sensitivity of less than 20 ppm. This new analytical technique was developed as a result of a request to provide instrumentation to measure the protium and deuterium concentrations at several process points during initial testing of the new hydrogen tritium thermal cycling absorption process columns.

SESSIONS, HENRY

2004-03-24

443

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

444

K-distribution models for gas mixtures in hypersonic nonequilibrium flows  

NASA Astrophysics Data System (ADS)

Calculation of nonequilibrium radiation field in plasmas around a spacecraft entering into an atmosphere at hypersonic velocities is a very complicated and computationally expensive task. The objective of this Dissertation is to collect state-of-the art spectroscopic data for the evaluation of spectral absorption and emission coefficients of atomic and molecular gases, develop efficient and accurate spectral models and databases, and study the effect of radiation on wall heat loads and flowfield around the spacecraft. The most accurate simulation of radiative transport in the shock layer requires calculating the gas properties at a large number of wavelengths and solving the Radiative Transfer Equation (RTE) in a line-by-line (LBL) fashion, which is prohibitively expensive for coupled simulations. A number of k-distribution based spectral models are developed for atomic lines, continuum and molecular bands that allow efficient evaluation of radiative properties and heat loads in hypersonic shock layer plasma. Molecular radiation poses very different challenges than atomic radiation. A molecular spectrum is governed by simultaneous electronic, vibrational and rotational transitions, making the spectrum very strongly dependent on wavelength. In contrast to an atomic spectrum, where line wings play a major role in heat transfer, most of the heat transfer in molecular spectra occurs near line centers. As the first step, k-distribution models are developed separately for atomic and molecular species, taking advantage of the fact that in the Earth's atmosphere the radiative field is dominated by atomic species (N and O) and in Titan's and Mars' atmospheres molecular bands of CN and CO are dominant. There are a number of practical applications where both atomic and molecular species are present, for example, the vacuum-ultra-violet spectrum during Earth's reentry conditions is marked by emission from atomic bound-bound lines and continuum and simultaneous absorption by strong bands of N2. For such cases, a new model is developed for the treatment of gas mixtures containing atomic lines, continuum and molecular bands. Full-spectrum k-distribution (FSK) method provides very accurate results compared to those obtained from the exact line-by-line method. For cases involving more extreme gradients in species concentrations and temperature, full-spectrum k-distribution model is relatively less accurate, and the method is refined by dividing the spectrum into a number of groups or scales, leading to the development of multi-scale models. The detailed methodology of splitting the gas mixture into scales is presented. To utilize the full potential of the k-distribution methods, pre-calculated values of k-distributions are stored in databases, which can later be interpolated at local flow conditions. Accurate and compact part-spectrum k-distribution databases are developed for atomic species and molecular bands. These databases allow users to calculate desired full-spectrum k-distributions through look-up and interpolation. Application of the new spectral models and databases to shock layer plasma radiation is demonstrated by solving the radiative transfer equation along typical one-dimensional flowfields in Earth's, Titan's and Mars' atmospheres. The k-distribution methods are vastly more efficient than the line-by-line method. The efficiency of the method is compared with the line-by-line method by measuring computational times for a number of test problems, showing typical reduction in computational time by a factor of more than 500 for property evaluation and a factor of about 32,000 for the solution of the RTE. A large percentage of radiative energy emitted in the shock-layer is likely to escape the region, resulting in cooling of the shock layer. This may change the flow parameters in the flowfield and, in turn, can affect radiative as well as convective heat loads. A new flow solver is constructed to simulate coupled hypersonic flow-radiation over a reentry vehicle. The flow solver employs a number of existing schemes and tools av

Bansal, Ankit

445

Analytical Modeling of Weld Bead Shape in Dry Hyperbaric GMAW Using Ar-He Chamber Gas Mixtures  

NASA Astrophysics Data System (ADS)

Hyperbaric arc welding is a special application of joining the pipeline steels under seawater. In order to analyze the behavior of the arc under ambient pressure, a model is required to estimate the arc efficiency. A distributed point heat source model was employed. The simulated isotherms were calibrated iteratively to fit the actual bead cross section. Basic gas mixture rules and models were used to calculate the thermal properties of the low-temperature shielding gas under the ambient pressure of 10 bar. Nine bead-on-plate welds were deposited each of which under different Ar-He chamber gas compositions. The well-known correlation between arc efficiency (delivered heat) and the thermal conductivity was established for different gas mixtures. The arc efficiency was considered separately for the transverse and perpendicular heat sources. It was found that assigning single heat efficiency factor for the entire arc, which is usually below unity, causes a noticeable underestimation for the heat transfer in the perpendicular direction and a little overestimation in the transverse direction.

Azar, Amin S.; Ås, Sigmund K.; Akselsen, Odd M.

2013-03-01

446

Dc breakdown strengths of some multicomponent gas mixtures in concentric cylinder geometries  

Microsoft Academic Search

The results are reported of dc breakdown tests performed on mixtures of electron attaching gases from the group SFâ, c-CâFâ, and 2-CâFâ, and electron moderating gases from the group Nâ, CHFâ, 1,1,1-CâFâHâ, in cylindrical-electrode geometries with different degrees of surface roughness, at total pressures of 0.1 and 0.44 MPa. Better electron moderating gases were sought. The binary mixture (c-CâFâ and

C. C. Chan; M. O. Pace; L. G. Christophorou

1980-01-01

447

Conditions of detonation initiation by focusing shock waves in a combustible gas mixture  

Microsoft Academic Search

Based on experiments on focusing shock waves in hydrogen-air mixtures and available publications, the critical shock-wave\\u000a Mach number at which detonation is initiated near the apex of a concave reflector is analyzed as a function of the reflector\\u000a size and reactivity of the mixture. The effect of the reflector shape and size on the value of this Mach number is

S. V. Khomik; S. P. Medvedev; A. N. Polenov; B. E. Gelfand

2007-01-01

448

Gas--liquid equilibrium in binary mixtures of methane with n-decane, benzene, and toluene  

Microsoft Academic Search

Compositions of saturated equilibrium liquid and vapor phases are determined in a flow apparatus for mixtures of methane and n-decane at 150, 240, 270, 290, and 310°C, for methane and benzene at 150, 190, and 230°C, and for methane and toluene at 150, 190, 230, and 270°C. Pressures extend to near the criticals of the mixtures starting from 20 atm

Ho-Mu Lin; Herbert M. Sebastian; James J. Simnick; Kwang-Chu Chao

1979-01-01

449

On the Possible of Gas Detonation Explosion of BaO2\\/Zr Powder Mixture  

Microsoft Academic Search

According to common criteria of thermodynamic possibility of detonation the most of pyrotechnic mixtures can't provide the unsupported detonation regime. Then, the possible hazards can be caused only by the simple combustion of such systems. Nevertheless, we have observed the unexpected acc