Journal articles on the topic 'Vapor mole fraction'
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1
Li, Xiao, and Yun Ren Qiu. "Vapor-Liquid Equilibrium for Binary Systems of Methyl Ethyl Ketone and Methyl Isobutyl Ketone." Advanced Materials Research 550-553 (July 2012): 2616–20. http://dx.doi.org/10.4028/www.scientific.net/amr.550-553.2616.
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Atmospheric vapor-liquid equilibrium data of methyl ethyl ketone (MEK) - methyl isobutyl ketone (MIBK) were measured using an improved Rose still and were used to recover the parameters of NRTL and UNIQUAC models. The results show that the simulated results agree well with the experimental data. The mean temperature variation is 0.14 °C and the mean mole fraction variation is 0.0023 using UNIQUAC model while the mean temperature variation is 0.17 °C and the mean mole fraction variation is 0.0025 using NRTL model. Both models can be used to calculate the atmospheric vapor-liquid equilibrium data of MEK - MIBK.
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Okajima, Idzumi, Kaichi Ito, Yusuke Aoki, Chang Yi Kong, and Takeshi Sako. "Extraction of Rice Bran Oil Using CO2-Expanded Hexane in the Two-Phase Region." Energies 15, no. 7 (April 2, 2022): 2594. http://dx.doi.org/10.3390/en15072594.
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The performance of CO2-expanded hexane in the vapor-liquid two-phase region was examined to extract phosphorus-free bio-oil from rice bran. Previously, it was found that in the uniform liquid phase region, it is difficult to maintain the phosphorus concentration at a stable and low level when the CO2 mole fraction changed slightly. To overcome this issue, the dependences of the phosphorus and free fatty acid concentrations, the oil solubility, and the oil yield on the CO2 mole fraction in the CO2-expanded hexane were measured at 25 °C, 5.1–5.2 MPa, and at a CO2 mole fraction of 0.88–0.94 in the two-phase region. Thus, a relatively constant phosphorus concentration of <10 ppm was maintained in the extracted oil, which was ~1/50 of that in the oil extracted by hexane, thereby satisfying the European unified standard for biodiesel fuel. Furthermore, a high oil yield exceeding that of hexane extraction was maintained over all CO2 mole fractions. Moreover, the oil solubility in the CO2-expanded hexane decreased linearly with the CO2 mole fraction, and so this factor represented the oil-dissolving power of the extractant more accurately than the oil yield used previously. The free fatty acid concentration was 83% of that extracted by hexane.
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Zhao, Weilong, Hao Wu, Jing Wen, Xin Guo, Yongsheng Zhang, and Ruirui Wang. "Simulation Study on the Influence of Gas Mole Fraction and Aqueous Activity under Phase Equilibrium." Processes 7, no. 2 (January 22, 2019): 58. http://dx.doi.org/10.3390/pr7020058.
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This work explored the influence of gas mole fraction and activity in aqueous phase while predicting phase equilibrium conditions. In pure gas systems, such as CH4, CO2, N2 and O2, the gas mole fraction in aqueous phase as one of phase equilibrium conditions was proposed, and a simplified correlation of the gas mole fraction was established. The gas mole fraction threshold maintaining three-phase equilibrium was obtained by phase equilibrium data regression. The UNIFAC model, the predictive Soave-Redlich-Kwong equation and the Chen-Guo model were used to calculate aqueous phase activity, the fugacity of gas and hydrate phase, respectively. It showed that the predicted phase equilibrium pressures are in good agreement with published phase equilibrium experiment data, and the percentage of Absolute Average Deviation Pressures are given. The water activity, gas mole fraction in aqueous phase and the fugacity coefficient in vapor phase are discussed.
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Boylan, P., D. Helmig, and J. H. Park. "Characterization and mitigation of water vapor effects in the measurement of ozone by chemiluminescence with nitric oxide." Atmospheric Measurement Techniques Discussions 6, no. 5 (October 29, 2013): 9263–95. http://dx.doi.org/10.5194/amtd-6-9263-2013.
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Abstract. Laboratory experiments were conducted to investigate the effects of water vapor on the reaction of nitric oxide with ozone in a chemiluminescence instrument used for fast response and high sensitivity detection of atmospheric ozone. Water vapor was introduced into a constant level ozone standard and both ozone and water vapor signals were recorded at 10 Hz. The presence of water vapor was found to reduce, i.e. quench the ozone signal. A correction factor was determined to be 4.15 ± 0.14 × 10−3, which corresponds to a 4.15% increase in the measured ozone signal per 10 mmol mol−1 co-sampled water vapor. An ozone-inert water vapor permeable membrane (Nafion dryer) was installed in the sampling line and was shown to remove the bulk of the water vapor mole fraction in the sample air. At water vapor mole fractions above 25 mmol mol−1, the Nafion dryer removed over 75% of the water vapor in the sample. This reduced the ozone signal correction from over 11% to less than 2.5%. The Nafion dryer was highly effective at reducing the fast fluctuations of the water vapor signal (more than 97%) while leaving the ozone signal unaffected, which is a crucial improvement for minimizing the interference of water vapor fluxes on the ozone flux determination by the eddy covariance technique.
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Rivera, Abdiel, Anas Mazady, and Mehdi Anwar. "ZnMgO/ZnO Core-Shell Structures for Gas Sensing." International Journal of High Speed Electronics and Systems 24, no. 03n04 (September 2015): 1550010. http://dx.doi.org/10.1142/s012915641550010x.
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Co-axial Zn1−xMgxO core, ZnO shell structures were grown using metal organic chemical vapor deposition (MOCVD), with Mg mole fractions of 2, 5 and 10%. The co-axial core shell structure, with the respective Mg concentration is verified using scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS). The response times (ṟise time and fall time) of the devices, after being exposed to methanol, varied with Mg mole fraction at the core, r-0.17s and, f-0.37s & f-0.48s for 2% Mg, r-0.81s and, f-5.98s & f-0.89s for 5% Mg and r-0.33s and f-0.13s for 10% Mg. The sensitivity of the devices at room temperature increased with the increment of Mg mole fraction at the core, 25%, 48% and 50% with Mg concentration of 0.02, 0.05 and 0.1, respectively, under high concentration of methanol. The estimated activation energy, corresponds to doubly charged oxygen vacancy (Vo2+).
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Fan, Q. H., H. Y. Li, L. X. Jia, Q. H. Fan, Yi Min Shao, and X. H. Zhan. "Selection of Mixed Refrigerant for CBM Liquefaction System and its Optimization Analysis." Advanced Materials Research 443-444 (January 2012): 193–97. http://dx.doi.org/10.4028/www.scientific.net/amr.443-444.193.
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In the mixed refrigerant cycle, the key technology is the choosing of the mixed refrigerant and its optimization mixture ratio. Based on a small-scale CBM liquefaction system LNG5, which the capacity is 5 cube meters LNG per day, the numerical simulation and optimization for the LNG5 are carried out. It provides the composition of the mixed refrigerant. It analyzes the effects of mixed refrigerant components on the temperature difference of the heat exchangers and the vapor fraction of the key nodes. The analysis results show that a reasonable mixture ratio of mixed refrigerant is given, such as CH4 mole fraction being 41.8% ～ 44.3%, C2H6 mole fraction being 40.8% ～ 42.2%, C5H12 molar fraction being 14.3% ～ 16%, and N2 mole fraction being 1.5% ～ 3.3%. The results provide guidelines for the design of the small-scale CBM liquefaction device, and for the application and commissioning of CBM liquefaction plant in China.
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Buchholz, Bernhard, and Volker Ebert. "Absolute, pressure-dependent validation of a calibration-free, airborne laser hygrometer transfer standard (SEALDH-II) from 5 to 1200 ppmv using a metrological humidity generator." Atmospheric Measurement Techniques 11, no. 1 (January 23, 2018): 459–71. http://dx.doi.org/10.5194/amt-11-459-2018.
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Abstract. Highly accurate water vapor measurements are indispensable for understanding a variety of scientific questions as well as industrial processes. While in metrology water vapor concentrations can be defined, generated, and measured with relative uncertainties in the single percentage range, field-deployable airborne instruments deviate even under quasistatic laboratory conditions up to 10–20 %. The novel SEALDH-II hygrometer, a calibration-free, tuneable diode laser spectrometer, bridges this gap by implementing a new holistic concept to achieve higher accuracy levels in the field. We present in this paper the absolute validation of SEALDH-II at a traceable humidity generator during 23 days of permanent operation at 15 different H2O mole fraction levels between 5 and 1200 ppmv. At each mole fraction level, we studied the pressure dependence at six different gas pressures between 65 and 950 hPa. Further, we describe the setup for this metrological validation, the challenges to overcome when assessing water vapor measurements on a high accuracy level, and the comparison results. With this validation, SEALDH-II is the first airborne, metrologically validated humidity transfer standard which links several scientific airborne and laboratory measurement campaigns to the international metrological water vapor scale.
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Shi, Xiu Min, and Min Wang. "Isobaric Vapor-Liquid Equilibrium for Ethyl Acetate-Isopropanol-1-Octyl-3-Methylimidazolium Tetrafluoroborate." Advanced Materials Research 641-642 (January 2013): 160–64. http://dx.doi.org/10.4028/www.scientific.net/amr.641-642.160.
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Abstract: In order to study the possibility of separating ethyl acetate and isopropanol by extractive distillation with ILs as an entrainer. Isobaric vapor-liquid equilibrium data for ethyl acetate + isopropanol+1-octyl-3-methylimidazolium tetrafluoroborate ([OMIM]BF4) ternary system at 101.32 kPa were determined using a recirculating still. The results showed that the ionic liquid (IL) studied produced a notable salting-out effect, which enhanced the relative volatility of ethyl acetate to isopropanol and eliminated the azeotrope when the mole fraction of IL in the liquid phase was greater than 0.10. Therefore, [OMIM]BF4 can be used as the extraction agent of extractive distillation for ethyl acetate + isopropanol systerm, the suitable mole fraction of [OMIM]BF4 is about 20%. The experimental data were correlated with the NRTL model, the correlated results agreed well with the experimental data.
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Zhao, Chen Lu, Wei Qiu Huang, Ying Xia Wang, and Li Shi. "Experimental Study on Adsorption of Gasoline Vapor on Activated Carbon at High Concentration." Advanced Materials Research 807-809 (September 2013): 549–52. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.549.
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Dynamic and thermodynamic characteristics of gasoline vapor adsorption at 0.3 mol/mol on different activated carbons (ACs) were investigated. The adsorption capacities of AC1 and AC3 were 0.295 g/g and 0.189 g/g at 20 oC, and 0.284 g/g and 0.165 g/g at 30 °C, respectively. Bed temperature rise was up to 50°C to 60°C in the adsorption of gasoline vapor at 0.3 mol/mol.The heat effect formula for high concentration vapor adsorption was deduced to evaluate the relationship of the adsorption capacity of the activated carbons, the mole fraction of the inlet gasoline vapor, the recovery efficiency of the gasoline vapor with the temperature rise.
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Chu, C. Judith, Mark P. D'Evelyn, Robert H. Hauge, and John L. Margrave. "Mechanism of diamond film growth by hot-filament CVD: Carbon-13 studies." Journal of Materials Research 5, no. 11 (November 1990): 2405–13. http://dx.doi.org/10.1557/jmr.1990.2405.
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Mixed carbon-12/carbon-13 diamond films were synthesized by hot-filament chemical vapor deposition, using mixtures of 13CH4 and 12CH4 or 12C2H2 in H2. The first-order Raman peak at 1332 cm−1 for 12C-diamond was found to shift by 50 cm−1 to 1282 cm−1 for pure 13C-diamond. For mixed-isotope films, the Raman peak frequency shifts linearly between these values as a function of the 13C mole fraction. The mechanism of diamond film growth by hot-filament CVD has been investigated by growth from mixtures of 13CH4 and 12C2H2, using the shifted Raman frequency to determine the relative incorporation rates of 13C and 12C into the film. The 13C mole fraction in the film agrees closely with the 13C mole fraction inferred for the methyl radical but differs substantially from that of acetylene, indicating that the methyl radical is the dominant growth precursor under the conditions studied.
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Shi, Xiu Min, and Min Wang. "Vapor-Liquid Equilibria for the Ternary System Ethyl Acetate-Acetonitrile-1-Octyl-3-Methylimidazolium Tetrafluoroborate." Advanced Materials Research 791-793 (September 2013): 141–44. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.141.
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In order to research the possibility of separating the azeotrope of ethyl acetate + acetonitrile with ionic liquid as the extractant. Isobaric vapor-liquid equilibria for the ternary system ethyl acetate + acetonitrile + 1-octyl-3-methylimidazolium tetrafluoroborate ([OMIBF4) were measured at 101.32 kPa using a recirculation still. The results showed that the VLE of the ternary system was different from that of the binary system. The ionic liquid (IL) studied showed a slight crossover salt effect, which changed the relative volatility of ethyl acetate to acetonitrile and eliminated the azeotropic point when the mole fraction of IL in the liquid phase was greater than 0.05. Therefore, [OMIBF4 can be used as the extractant of extractive distillation for ethyl acetate + acetonitrile system, the suitable mole fraction of [OMIBF4 is about 10%.
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An, Lisha, Zhe Yang, Yingwen Liu, and Gao Bo. "Numerical simulation of polysilicon deposition characteristics in chemical vapor deposition process." Thermal Science 22, Suppl. 2 (2018): 719–27. http://dx.doi.org/10.2298/tsci171009057a.
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This paper addresses the complex component evolution and silicon dynamic deposition characteristics in the traditional Siemens reactor. A two-dimensional heat and mass transfer model coupled with a detailed chemical reaction mechanism was developed. The distributions of temperature, velocity, and concentration are presented in detail. The influencing factors (such as feeding mole ratio, inlet velocity, base temperature and reactor pressure) on the molar concentration evolutions of ten major components and silicon growth rate were obtained and analyzed. Results show that base temperature is main influence of HCl mole fraction. In order to get more growth rate of silicon and better silicon quality, the complex operating parameters need to be reasonably designed on collaborative optimization.
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Pophristic, M., S. P. Guo, and B. Peres. "High-conductivityn-AlGaN with high Al mole fraction grown by metalorganic vapor phase deposition." Applied Physics Letters 82, no. 24 (June 16, 2003): 4289–91. http://dx.doi.org/10.1063/1.1582377.
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Biquard, M., P. Letellier, and M. Fromon. "Pressions de vapeur des mélanges eau – nitrate d'éthylammonium à 298,15 K. Propriétés thermodynamiques des milieux eau – sel fondu." Canadian Journal of Chemistry 63, no. 12 (December 1, 1985): 3587–92. http://dx.doi.org/10.1139/v85-589.
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The activity and activity coefficient of water in water and ethylammonium nitrate (EAN) mixtures were determined by vapor pressure measurements between pure water and pure fused salt at 298.15 K. For a wide range of mole fractions of salt, (0.3 < X ≤ 1) the behaviour of water can be described very accurately by a "one parameter" empirical equation which involves activity coefficient, γE, mole fraction of EAN, and limiting Gibbs energy of the dilution of water in pure fused salt, [Formula: see text]:[Formula: see text]Interpretation of experimental results was also attempted by use of the B.E.T. equation. It appears that the energy, ΔEd = E − EL, in those solutions is very low. Partial molar volumes of water and salt are also discussed in relation to empirical and B.E.T. equations. It can be shown that the two equations lead to similar results.
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Rella, C. W., H. Chen, A. E. Andrews, A. Filges, C. Gerbig, J. Hatakka, A. Karion, et al. "High accuracy measurements of dry mole fractions of carbon dioxide and methane in humid air." Atmospheric Measurement Techniques Discussions 5, no. 4 (August 21, 2012): 5823–88. http://dx.doi.org/10.5194/amtd-5-5823-2012.
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Abstract. Traditional techniques for measuring the mole fractions of greenhouse gas in the well-mixed atmosphere have required extremely dry sample gas streams (dew point < −25 °C) to achieve the inter-laboratory compatibility goals set forth by the Global Atmospheric Watch program of the World Meteorological Organization (WMO/GAW) for carbon dioxide (±0.1 ppm) and methane (±2 ppb). Drying the sample gas to low levels of water vapor can be expensive, time-consuming, and/or problematic, especially at remote sites where access is difficult. Recent advances in optical measurement techniques, in particular Cavity Ring Down Spectroscopy (CRDS), have led to the development of highly stable and precise greenhouse gas analyzers capable of highly accurate measurements of carbon dioxide, methane, and water vapor. Unlike many older technologies, which can suffer from significant uncorrected interference from water vapor, these instruments permit for the first time accurate and precise greenhouse gas measurements that can meet the WMO/GAW inter-laboratory compatibility goals without drying the sample gas. In this paper, we present laboratory methodology for empirically deriving the water vapor correction factors, and we summarize a series of in-situ validation experiments comparing the measurements in humid gas streams to well-characterized dry-gas measurements. By using the manufacturer-supplied correction factors, the dry-mole fraction measurements have been demonstrated to be well within the GAW compatibility goals up to at least 1% water vapor. By determining the correction factors for individual instruments once at the start of life, this range can be extended to at least 2% over the life of the instrument, and if the correction factors are determined periodically over time, the evidence suggests that this range can be extended above 4%.
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Delval, C., B. Fluckiger, and M. J. Rossi. "The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles." Atmospheric Chemistry and Physics 3, no. 4 (August 1, 2003): 1131–45. http://dx.doi.org/10.5194/acp-3-1131-2003.
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Abstract. Using a multidiagnostic approach the rate Rev [ molec cm-3 s-1] or flux Jev [ molec cm-2 s-1] of evaporation of H2O and its corresponding rate constant for condensation, kcond [s-1 ], on a 1 µm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions for pure ice are Jev = 1.6 · 10 28 ± 1 · exp (- 10.3 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 1.7 · 10 - 2 ± 1 · exp (+ 1.6 ± 1.5/ RT ) [s -1], in the presence of a HCl mole fraction in the range 3.2 · 10 - 5 - 6.4 · 10 - 3 : Jev = 6.4 · 10 26 ± 1 · exp (- 9.7 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 2.8 · 10 - 2 ± 1 · exp ( + 1.5 ± 1.6 /RT) [s -1], and a HBr mole fraction smaller than 6.4 · 10 - 3 : Jev = 7.4 · 10 25 ± 1 · exp ( - 9.1 ± 1.2 /RT) [ molec cm-2 s-1] , kcond = 7.1 · 10 - 5 ± 1 · exp (+ 2.6 ± 1.5/ RT) [s -1]. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl = Eev - Econd = 11.9 ± 2.7 kcal mol-1 , DHsubl = 11.2 ± 2.8 kcal mol-1, and DHsubl = 11.7 ± 2.8 kcal mol-1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol-1 . Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3–6 and 10–20, respectively, for submonolayer coverages of HX once the fraction of the ice not contaminated by HX has evaporated.
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JONGLEARTTRAKULL, Panus, Kazuyoshi FUSHINOBU, and Masami KADONAGA. "Refractive index and mole fraction field of the vapor evaporated from ethanol-water mixture droplet." Journal of Thermal Science and Technology 17, no. 3 (2022): 22–00284. http://dx.doi.org/10.1299/jtst.22-00284.
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Bluhme, Anders B., Jonas L. Ingemar, Carl Meusinger, and Matthew S. Johnson. "Water vapor inhibits hydrogen sulfide detection in pulsed fluorescence sulfur monitors." Atmospheric Measurement Techniques 9, no. 6 (June 24, 2016): 2669–73. http://dx.doi.org/10.5194/amt-9-2669-2016.
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Abstract. The Thermo Scientific 450 Hydrogen Sulfide–Sulfur Dioxide Analyzer measures both hydrogen sulfide (H2S) and sulfur dioxide (SO2). Sulfur dioxide is measured by pulsed fluorescence, while H2S is converted to SO2 with a molybdenum catalyst prior to detection. The 450 is widely used to measure ambient concentrations, e.g., for emissions monitoring and pollution control. An air stream with a constant H2S concentration was generated and the output of the analyzer recorded as a function of relative humidity (RH). The analyzer underreported H2S as soon as the relative humidity was increased. The fraction of undetected H2S increased from 8.3 at 5.3 % RH (294 K) to over 34 % at RH > 80 %. Hydrogen sulfide mole fractions of 573, 1142, and 5145 ppb were tested. The findings indicate that previous results obtained with instruments using similar catalysts should be re-evaluated to correct for interference from water vapor. It is suspected that water decreases the efficiency of the converter unit and thereby reduces the measured H2S concentration.
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Kangawa, Yoshihiro, Norihito Kawaguchi, Ken-nosuke Hida, Yoshinao Kumagai, and Akinori Koukitu. "Study of Pulse Laser Assisted Metalorganic Vapor Phase Epitaxy of InGaN with Large Indium Mole Fraction." Japanese Journal of Applied Physics 43, No. 8A (July 16, 2004): L1026—L1028. http://dx.doi.org/10.1143/jjap.43.l1026.
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Porter, J. M., J. B. Jeffries, and R. K. Hanson. "Mid-infrared laser-absorption diagnostic for vapor-phase fuel mole fraction and liquid fuel film thickness." Applied Physics B 102, no. 2 (March 6, 2010): 345–55. http://dx.doi.org/10.1007/s00340-010-3942-9.
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Filges, Annette, Christoph Gerbig, Chris W. Rella, John Hoffnagle, Herman Smit, Martina Krämer, Nicole Spelten, et al. "Evaluation of the IAGOS-Core GHG package H<sub>2</sub>O measurements during the DENCHAR airborne inter-comparison campaign in 2011." Atmospheric Measurement Techniques 11, no. 9 (September 19, 2018): 5279–97. http://dx.doi.org/10.5194/amt-11-5279-2018.
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Abstract. As part of the DENCHAR (Development and Evaluation of Novel Compact Hygrometer for Airborne Research) inter-comparison campaign in northern Germany in 2011, a commercial cavity ring-down spectroscopy (CRDS) based gas analyzer (G2401-m, Picarro Inc., US) was installed on a Learjet to measure atmospheric water vapor, CO2, CH4, and CO. The CRDS components were identical to those chosen for integration aboard commercial airliners within the IAGOS (In-service Aircraft for a Global Observing System) project. Since the quantitative capabilities of the CRDS water vapor measurements were never evaluated and reviewed in detail in a publication before, the campaign allowed for an initial assessment of the long-term IAGOS water vapor measurements by CRDS against reference instruments with a long performance record (Fast In-situ Stratospheric Hygrometer (FISH) and CR-2 frost point hygrometer (Buck Research Instruments L.L.C., US), both operated by Research Centre Jülich). For the initial water calibration of the instrument it was compared against a dew point mirror (Dewmet TDH, Michell Instruments Ltd., UK) in the range from 70 000 to 25 000 ppm water vapor mole fraction. During the inter-comparison campaign the analyzer was compared on the ground over the range from 2 to 600 ppm against the dew point hygrometer used for calibration of the FISH reference instrument. A new, independent calibration method based on the dilution effect of water vapor on CO2 was evaluated. Comparison of the in-flight data against the reference instruments showed that the analyzer is reliable and has a good long-term stability. The flight data suggest a conservative precision estimate for measurements made at 0.4 Hz (2.5 s measurement interval) of 4 ppm for H2O < 10 ppm, 20 % or 10 ppm (whichever is smaller) for 10 ppm < H2O < 100 ppm, and 5 % or 30 ppm (whichever is smaller) for H2O > 100 ppm. Accuracy of the CRDS instrument was estimated, based on laboratory calibrations, as 1 % for the water vapor range from 25 000 ppm down to 7000 ppm, increasing to 5 % at 50 ppm water vapor. Accuracy at water vapor mole fractions below 50 ppm was difficult to assess, as the reference systems suffered from lack of data availability.
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LI, ZIHAN, JIANWEN XIN, XUEMING HUA, DONGSHENG WU, SHINICHI TASHIRO, MANABU TANAKA, and HUAN WANG. "Influence Mechanism of Metal Vapor in Plasma Arc Lap Welding." Welding Journal 101, no. 6 (June 1, 2022): 161–71. http://dx.doi.org/10.29391/2022.101.012.
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A three-dimensional coupled tungsten electrode–plasma arc–metal vapor– weld pool model was developed to investigate plasma arc and metal vapor characteristics, weld pool convection, and energy transfer in conduction plasma arc lap welding. The arc energy efficiency was also calculated. The numerical results showed that in conduction plasma arc lap welding, the constraint effects of the plasma arc by a small constricting nozzle, plasma gas, and electromagnetic force were strong, and no keyhole was formed inside the weld pool, so the heat flux on the weld pool surface was high as well as the weld pool temperature and mole fraction of Fe vapor above the weld pool surface. The high concentration of Fe vapor in the arc decreased the conduction energy from the plasma arc to the weld pool along with the arc energy efficiency. The calculated arc energy efficiency was only 50.2%. Without considering Fe vapor, the calculated weld pool had complete joint penetration. When considering Fe vapor, the calculated weld geometry agreed well with the experimental result.
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Delval, C., B. Fluckiger, and M. J. Rossi. "The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: Implications for the lifetime of atmospheric ice particles." Atmospheric Chemistry and Physics Discussions 3, no. 3 (May 8, 2003): 2179–218. http://dx.doi.org/10.5194/acpd-3-2179-2003.
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Abstract. Using a multidiagnostic approach the rate Rev or flux Jevof evaporation of H2O and its condensation, kcond, on a 1mm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions with RT in kcal mol-1 for pure ice are Jev=1.6×1028+/−1·exp({−10.3+\\−1.2}/{RT}) [molec cm−2 s−1], kcond=1.7×10−2+\\-1×exp({+1.6+\\−1.5}/{RT}) [s−1], in the presence of an HCl mole fraction in the range 3.2×10−5-6.4×10−3: Jev=6.4×1026+/−1×exp({−9.7+/−1.2}/{RT}) [molec cm−2 s−1], kcond=2.8×10−2+/-1×exp({+1.5+/−1.6}/{RT}) [s−1], and an HBr mole fraction smaller than 6.4×10−3:Jev=7.4×1025+/−1×exp({−9.1+/−1.2}/{RT}) [molec cm−2 s−1], kcond=7.1×10−5+\\−1×exp({+2.6+/−1.5}/{RT}) [s−1]}. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl=Eev-Econd=11.9+/−2.7 kcal mol−1, DHsubl=11.2+/−2.8 kcal mol−1, and DHsubl=11.7+/−2.8 kcal mol−1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol−1. Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3–6 and 10–20, respectively, for submonolayer coverages of HX.
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Maitlo, Ghulamullah, Imran Nazir Unar, Rasool Bux Mahar, and Khan Mohammad Brohi. "Numerical simulation of lignocellulosic biomass gasification in concentric tube entrained flow gasifier through computational fluid dynamics." Energy Exploration & Exploitation 37, no. 3 (April 2, 2019): 1073–97. http://dx.doi.org/10.1177/0144598719839760.
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Thermochemical conversion of biomass is an encouraging way for the production of syngas. In the present research, four different biomass materials were used for gasification which includes rice husk, cotton stalks, sugarcane bagasse, and sawdust. These biomass sources were selected because they are common Pakistani feedstocks. Gasification of selected biomasses was performed using concentric tube entrained flow gasifier. Three-dimensional computational fluid dynamics model was used to investigate the impacts of kinetic rate and diffusion rate on the gasification performance. The Euler–Lagrange method was used for the development of entrained flow biomass gasifier using commercial computational fluid dynamics code ANSYS FLUENT®14. Discrete phase model was used to predict the movement of particles, whereas the gas phase was treated as the continuous phase with a standard k–ε turbulent model to predict the behavior of gas phase flow. Finite rate/Eddy dissipation model was applied for the calculation of homogenous and heterogeneous reaction rates. Oxygen was used as a gasifying agent. Cotton stalks and sugarcane bagasse produced higher mole fractions of hydrogen (H2) and carbon monoxide (CO) than sawdust and rice husk. Regarding carbon conversion efficiency, cold gas efficiency, and higher heating value cotton stalks and sugarcane bagasse produced better syngas quality as compared to sawdust and rice husk. The oxygen/fuel (O/F) ratio is a key operating parameter in the field of gasification and combustion. The O/F ratio above 0.42 favored combustion reactions and increased mole fraction of water vapor (H2O) and carbon dioxide (CO2) in syngas composition, whereas gasification reactions dominated below 0.42 O/F ratio, resulting increased mole fraction of H2 and CO in syngas composition.
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Pan, Changzhao, Haiyang Zhang, Gérard Rouillé, Bo Gao, and Laurent Pitre. "Helmholtz Free Energy Equation of State for 3He–4He Mixtures at Temperatures Above 2.17 K." Journal of Physical and Chemical Reference Data 50, no. 4 (December 1, 2021): 043102. http://dx.doi.org/10.1063/5.0056087.
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The work presents the first wide-range equation of state (EOS) for 3He–4He mixtures based on the reduced Helmholtz free energy multi-fluid approximation model. It covers the temperature range from 2.17 to 300 K and the pressure from the vapor pressure up to 3 MPa for any given mixture 3He mole fraction. In this model, the 4He and 3He reduced Helmholtz free energy equations and departure functions from the literature are employed and only five unknown mixture parameters are needed for each given departure function. The parameters and the best model for the concerned binary mixture were determined by the Levenberg–Marquardt optimization method. With the best developed model, the liquid, gaseous, and saturated thermophysical properties of the mixture can be mostly described with an accuracy better than 5%. Furthermore, a database for the thermophysical properties of 3He–4He mixtures is generated and provided for interpolation in temperature, pressure, and 3He mole fraction. The current EOS and database can be applied to the design and optimization of ultra-low temperature refrigerators.
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Nurmawati, Ardika, Rizky Tetrisyanda, and Gede Wibawa. "Isothermal Vapor-Liquid Equilibrium Measurement of Isobutanol + Isooctane/N-Heptane Binary Mixtures at Temperatures Range of 303.15-323.15 K." Key Engineering Materials 840 (April 2020): 501–6. http://dx.doi.org/10.4028/www.scientific.net/kem.840.501.
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The addition of alcohol as an oxygenated compound in gasoline blends may increase the vapor pressure of gasoline mixture. As a result, the study of vapor-liquid equilibrium for gasoline component and alcohol is necessary. In this study, the vapor-liquid equilibrium of isobutanol – isooctane/n-heptane blends were obtained experimentally at temperatures in the range 303.15 to 323.15 K using modified simple quasi-static ebulliometer. The apparatus was validated by comparing the vapor pressure of pure isobutanol, isooctane, and n-heptane with the published data and giving average absolute deviation (AAD) between experimental and calculated ones with magnitude less than 1.0%. The addition of isobutanol with the mole fraction range from 0.2 to 0.6 would increase the vapor pressure of the isooctane and n-heptane up to 12% and 14% respectively. The vapor pressure of binary mixtures was correlated with the Wilson, Non-random two-liquid (NRTL), and Universal quasi-chemical (UNIQUAC) equations with AAD 1.6%, 1.5%, and 1.7%, respectively for isobutanol + isooctane system and 1.8%, 1.7%, and 2.0%, respectively for isobutanol + n-heptane system. The systems studied show positive deviation from Raoult’s Law.
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Hung, Hui-Ming, and Scot T. Martin. "Infrared Spectroscopic Evidence for the Ice Formation Mechanisms Active in Aerosol Flow Tubes." Applied Spectroscopy 56, no. 8 (August 2002): 1067–81. http://dx.doi.org/10.1366/000370202321274980.
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Interest in quantifying processes of ice formation in the atmosphere has led to the recent development of new laboratory techniques, including an aerosol flow tube (AFT) reactor employed for the study of the ice nucleation kinetics of suspended submicrometer aqueous particles. The AFT technique employs an infrared (IR) beam along the flow tube axis. Spectral changes between 700 and 6000 cm−1 indicate the formation of ice at sufficiently cool temperatures. Apparent freezing temperatures are determined as a function of condensed-phase mole fraction composition. A typical aqueous chemical system is (NH4)2SO4/H2O. The mole fraction composition of the condensed-phase of this aerosol is determined by the ratio of the integrated spectroscopic bands for H2O and SO42–. A key uncertainty in the AFT-IR technique is the freezing mechanism, and knowledge of the mechanism is essential to estimate homogeneous nucleation rates ( J, cm−3 s−1) from observed apparent freezing temperatures. The current work provides observational and modeling spectral evidence, based upon changes in the scattering component of the recorded IR extinction spectra with temperature, that observed ice freezing events at warmer temperatures arise from the following mechanism: relatively few particles in the aerosol freeze (e.g., 1 in 106) and this primary event is followed by rapid scavenging of water vapor to grow the few ice particles into large ice particles observed in the IR spectra. Correspondingly, the remaining aqueous particles partially evaporate. In contrast, the spectral evidence provides support that a modified mechanism is operative at cooler temperatures: the ice freezing event consists of the freezing of a much larger fraction of the particles (e.g., 1 in 10) accompanied by a much less important vapor-phase mass transfer event.
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Morell, José I., Demetre J. Economou, and Neal R. Amundson. "Pulsed-power volume-heating chemical vapor infiltration." Journal of Materials Research 7, no. 9 (September 1992): 2447–57. http://dx.doi.org/10.1557/jmr.1992.2447.
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The dynamic behavior of a novel chemical vapor infiltration (CVI) technique called pulsed-power volume-heating CVI is investigated using a diffusion-reaction model. In this technique, a volume-heating source (e.g., RF or microwave) is used to heat the preform. The source power is modulated in time (e.g., square-wave modulation) with a specific period and duty cycle. During the low-power part of the cycle, the temperature of the composite drops, reducing the reaction rate and thus allowing the precursor gas to diffuse into the composite, essentially “refilling” the composite. This alleviates reactant concentration gradients within the composite minimizing density nonuniformities. The high-power part of the cycle is used to achieve rapid reaction rates, thereby minimizing processing time. CVI of a carbon fiber preform with carbon resulting from methane decomposition is taken as an example to illustrate the technique. The results reveal the dependence of density uniformity and processing time on relevant variables such as pulse period, duty cycle, power density level, and methane mole fraction. It is shown that pulsed-power volume-heating CVI can provide a window of operating conditions leading to rapid and complete densification.
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Gherasimova, M., B. Gaffey, P. Mitev, L. J. Guido, K. L. Chang, K. C. Hsieh, S. Mitha, and J. Spear. "Synthesis of Nitrogen-Rich GaNAs Semiconductor Alloys and Arsenic-Doped GaN by Metalorganic Chemical Vapor Deposition." MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 299–304. http://dx.doi.org/10.1557/s1092578300002623.
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Arsenic-doped GaN films and GaNAs films have been synthesized by MOCVD. Samples were grown on sapphire, GaN-coated sapphire, and GaAs substrates. Composition, structure, and phase distribution were characterized by EPMA, SIMS, XRD, and TEM. The arsenic content increases demonstrably as the growth temperature descreases from 1030 to 700 °C. In the high temperature limit, high quality arsenic-doped GaN forms on GaN-coated sapphire. In the low temperature regime, nitrogen-rich GaNAs forms under some growth conditions, with a maximum arsenic mole fraction of 3%, and phase segregation in the form of GaAs precipitates occurs with an increase in arsine pressure. Preferential formation of the nitrogen-rich phase on GaN-coated sapphire suggests the presence of substrate-induced “composition pulling”.
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Suto, Hiroshi, and Gen Inoue. "A New Portable Instrument for In Situ Measurement of Atmospheric Methane Mole Fraction by Applying an Improved Tin Dioxide–Based Gas Sensor." Journal of Atmospheric and Oceanic Technology 27, no. 7 (July 1, 2010): 1175–84. http://dx.doi.org/10.1175/2010jtecha1400.1.
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Abstract A new portable instrument based on a tin dioxide natural gas leak detector was developed to monitor the atmospheric methane mixing ratio in areas lacking sufficient infrastructure to sustain a conventional measurement system, such as a large power source, carrier gas supply, and temperature-stabilized laboratory. The effect of water vapor, the dominant factor influencing the stable measurement of methane, was examined. Reducing water vapor to less than 10 ppm in the sample air enabled stable and sensitive detection of atmospheric methane. The selectivity of the sensor to other flammable gases was also examined and improved, without additional power consumption, by applying an additional catalytic layer made of platinum-black powder suspended in quartz wool. The developed system is small (W × D × H = 300 mm × 250 mm × 200 mm) and lightweight (4 kg). The normal power consumption of the detector unit, consisting of a detector, a heater for controlling temperature, and an electronic circuit for each device, is less than 10 W. The precision of the tin dioxide–based sensor system for methane measurement in ambient air was compared with that of a conventional system, a gas chromatograph equipped with a flame ionization detector. Diurnal variations were clearly detected, and an excellent linear relationship was found between the two systems, with a standard deviation of 4 ppb (1σ).
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Hasan, Md Soyaeb, Apurba Kumar Saha, Md Rafiqul Islam, and Nowshad Amin. "Mathematical Modeling of Growth Conditions and Interpretation of Phase Diagram for InxGa1-xN Epitaxial Layer." Applied Mechanics and Materials 372 (August 2013): 70–74. http://dx.doi.org/10.4028/www.scientific.net/amm.372.70.
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It is imperative to determine the dependence of the quality and characteristics of the epitaxial film on different growth parameters. A mathematical model has been developed showing the effect of different growth parameters e.g. temperature, TMI and TEG flow rate, molar ratio on epitaxial film. This model is considered for InGaN film on GaN template with an Indium mole fraction up to 0.4 by Metal Organic Vapor Phase Epitaxy (MOVPE). The results obtained from this model has been compared and fitted with experimentally obtained data through XRD, RSM, PL, SEM etc. Finally, a phase diagram has been proposed to interpret the phase separation and Indium content evolution under the influence of growth temperature and precursor gas flow.
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Gao, Qinglin, Zongchang Zhao, Peng Jia, and Xiaodong Zhang. "Effect of Ionic Liquids on the Isobaric Vapor-Liquid Equilibrium Behavior of Acetone-Chloroform." Applied Sciences 8, no. 9 (September 1, 2018): 1519. http://dx.doi.org/10.3390/app8091519.
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Isobaric vapor-liquid equilibrium (VLE) data of the ternary system acetone + chloroform + 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]) or 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]) were obtained at 101.3 kPa. Results indicated that the addition of [MMIM][DMP] or [EMIM][DEP] could eliminate the azeotropic point of the binary system of acetone + chloroform when the mole fraction of ionic liquids (ILs) was above 0.15. Besides, the experimental data could be well correlated by the nonrandom two-liquid (NRTL) model. The structures as well as interactions between molecular solvents (acetone, chloroform) and the ion pairs ([MMIM][DMP], [EMIM][DEP]) were studied by quantum chemical calculations. The result indicated that the interaction energies (ΔE) follow the order of ΔE(acetone + [EMIM][DEP]) > ΔE(acetone + [MMIM][DMP]) > ΔE(chloroform + [EMIM][DEP]) ≈ ΔE(chloroform + [MMIM][DMP]), and chloroform had stronger affinity to ionic liquids than acetone.
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Wolden, C. A., R. F. Davis, Z. Sitar, and J. T. Prater. "In situ mass spectrometry during diamond chemical vapor deposition using a low pressure flat flame." Journal of Materials Research 12, no. 10 (October 1997): 2733–42. http://dx.doi.org/10.1557/jmr.1997.0364.
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A combination of experiments and detailed kinetic modeling was used to investigate diamond deposition chemistry in low pressure combustion synthesis. Microprobe sampling was employed to provide in situ, quantitative measurements of the stable gas-phase species impinging the growth surface. The reactant gas ratio was found to be the most critical experimental variable. A detailed kinetic model was developed for the stagnation flow system. Comparison of experimental measurements showed very good agreement with model predictions. The model was then used to predict the concentration of radical species and analyze the sensitivity of predictions to γH, the probability of atomic hydrogen recombination on the surface. It was shown that γH dramatically affects the distribution of radical species near the diamond surface. The analysis also indicates that atomic carbon may be an important gas-phase precursor in this system. Comparison of mole fraction measurements and observations of film morphology were used to draw conclusions on the growth mechanism.
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Lang, Benjamin, Wolfgang Breitfuss, Simon Schweighart, Philipp Breitegger, Hugo Pervier, Andreas Tramposch, Andreas Klug, Wolfgang Hassler, and Alexander Bergmann. "Photoacoustic hygrometer for icing wind tunnel water content measurement: design, analysis, and intercomparison." Atmospheric Measurement Techniques 14, no. 3 (March 31, 2021): 2477–500. http://dx.doi.org/10.5194/amt-14-2477-2021.
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Abstract. This work describes the latest design, calibration and application of a near-infrared laser diode-based photoacoustic (PA) hygrometer developed for total water content measurement in simulated atmospheric freezing precipitation and high ice water content conditions with relevance in fundamental icing research, aviation testing, and certification. The single-wavelength and single-pass PA absorption cell is calibrated for molar water vapor fractions with a two-pressure humidity generator integrated into the instrument. Laboratory calibration showed an estimated measurement accuracy better than 3.3 % in the water vapor mole fraction range of 510–12 360 ppm (5 % from 250–21 200 ppm) with a theoretical limit of detection (3σ) of 3.2 ppm. The hygrometer is examined in combination with a basic isokinetic evaporator probe (IKP) and sampling system designed for icing wind tunnel applications, for which a general description of total condensed water content (CWC) measurements and uncertainties are presented. Despite the current limitation of the IKP to a hydrometeor mass flux below 90 gm-2s-1, a CWC measurement accuracy better than 20 % is achieved by the instrument above a CWC of 0.14 g m−3 in cold air (−30 ∘C) with suitable background humidity measurement. Results of a comparison to the Cranfield University IKP instrument in freezing drizzle and rain show a CWC agreement of the two instruments within 20 %, which demonstrates the potential of PA hygrometers for water content measurement in atmospheric icing conditions.
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Paul, Dipayan, Hubertus A. Scheeren, Henk G. Jansen, Bert A. M. Kers, John B. Miller, Andrew M. Crotwell, Sylvia E. Michel, et al. "Evaluation of a field-deployable Nafion™-based air-drying system for collecting whole air samples and its application to stable isotope measurements of CO<sub>2</sub>." Atmospheric Measurement Techniques 13, no. 7 (July 28, 2020): 4051–64. http://dx.doi.org/10.5194/amt-13-4051-2020.
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Abstract. Atmospheric flask samples are either collected at atmospheric pressure by opening a valve of a pre-evacuated flask or pressurized with the help of a pump to a few bar above ambient pressure. Under humid conditions, there is a risk that water vapor in the sample leads to condensation on the walls of the flask, notably at higher than ambient sampling pressures. Liquid water in sample flasks is known to affect the CO2 mixing ratios and also alters the isotopic composition of oxygen (17O and 18O) in CO2 via isotopic equilibration. Hence, for accurate determination of CO2 mole fractions and its stable isotopic composition, it is vital to dry the air samples to a sufficiently low dew point before they are pressurized in flasks to avoid condensation. Moreover, the drying system itself should not influence the mixing ratio and the isotopic composition of CO2 or that of the other constituents under study. For the Airborne Stable Isotopes of Carbon from the Amazon (ASICA) project focusing on accurate measurements of CO2 and its singly substituted stable isotopologues over the Amazon, an air-drying system capable of removing water vapor from air sampled at a dew point lower than −2 ∘C, flow rates up to 12 L min−1 and without the need for electrical power was needed. Since to date no commercial air-drying device that meets these requirements has been available, we designed and built our own consumable-free, power-free and portable drying system based on multitube Nafion™ gas sample driers (Perma Pure, Lakewood, USA). The required dry purge air is provided by feeding the exhaust flow of the flask sampling system through a dry molecular sieve (type 3A) cartridge. In this study we describe the systematic evaluation of our Nafion™-based air sample dryer with emphasis on its performance concerning the measurements of atmospheric CO2 mole fractions and the three singly substituted isotopologues of CO2 (16O13C16O, 16O12C17O and 16O12C18O), as well as the trace gas species CH4, CO, N2O and SF6. Experimental results simulating extreme tropical conditions (saturated air at 33 ∘C) indicated that the response of the air dryer is almost instantaneous and that approximately 85 L of air, containing up to 4 % water vapor, can be processed staying below a −2 ∘C dew point temperature (at 275 kPa). We estimated that at least eight flasks can be sampled (at an overpressure of 275 kPa) with a water vapor content below −2 ∘C dew point temperature during a typical flight sampling up to 5 km altitude over the Amazon, whereas the remaining samples would stay well below 5 ∘C dew point temperature (at 275 kPa). The performance of the air dryer on measurements of CO2, CH4, CO, N2O, and SF6 and the CO2 isotopologues 16O13C16O and 16O12C18O was tested in the laboratory simulating real sampling conditions by compressing humidified air from a calibrated cylinder, after being dried by the air dryer, into sample flasks. We found that the mole fraction and the isotopic composition difference between the different test conditions (including the dryer) and the base condition (dry air, without dryer) remained well within or very close to, in the case of N2O, the World Meteorological Organization recommended compatibility goals for independent measurement programs, proving that the test condition induced no significant bias on the sample measurements.
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TAN, GUIYING, and YONGBO SU. "DEPENDENCE OF CAPACITANCE–VOLTAGE CHARACTERISTICS OF NOMINALLY UNDOPED AlGaN/GaN HETEROSTRUCTURES ON SEVERAL KEY PARAMETERS OF THE MATERIALS." Modern Physics Letters B 25, no. 15 (June 20, 2011): 1293–302. http://dx.doi.org/10.1142/s0217984911026267.
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Nominally undoped AlGaN / GaN heterostructure samples were grown on c-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition, and their material properties, such as crystal quality, roughness of heterointerface, thickness and Al mole fraction of AlGaN barrier layer, were identified by high resolution X-ray diffraction (HRXRD). Mercury-probe capacitance–voltage (C–V) measurements were carried out to investigate the carrier distribution in the heterostructures and accurately evaluate the sheet carrier concentration of two-dimensional electron gas (2DEG) formed at AlGaN / GaN heterointerface. The dependence of C–V characteristics of these samples on some key material parameters were clearly revealed. The Al -content effect, barrier-thickness effect in AlGaN layer, and their synergy effect were specifically studied. It demonstrated that the C–V characteristics of AlGaN / GaN heterostructure could be improved by perfecting the crystal epitaxial process, and adjusting the Al -content or thickness of AlGaN barrier layer.
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Феофанова, Мариана Александровна, Юлия Ивановна Софронова, Андрей Николаевич Евдокимов, and Александр Вячеславович Курзин. "APPLICATION OF IMIDAZOLINES BASED ON TALL OIL FATTY ACIDS AND THEIR QUATERNARY SALTS FOR THE SEPARATION OF THE BINARY NON-AQUEOUS AZEOTROPE SYSTEMS." Вестник Тверского государственного университета. Серия: Химия, no. 4(42) (December 21, 2020): 63–69. http://dx.doi.org/10.26456/vtchem2020.4.7.
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Методом экстрактивной (в том числе солевой) ректификации с использованием имидазолинов и четвертичных солей на их основе разделены на компоненты неводные двойные азеотропные системы. В качестве разделяющих агентов выбраны: промышленный продукт 1-гидроксиэтил-2-алкенил-2-имидазолин на основе жирных кислот таллового масла, а также его четвертичные соли - хлорид и тетрафторборат 1-гидроксиэтил-2-алкенил-3-бензил-2-имидазолиния. Для разделения были использованы неводные азеотропные системы: ацетон-метанол, метилацетат-метанол, этилацетат-этанол и хлороформ-метанол. Равновесие жидкость-пар в соответствующих тройных системах исследовано в модифицированном приборе Отмера при 101,3 кПа, состав жидкой и паровой фаз определен газохроматографическим методом анализа. Минимальные концентрации (в мольных долях) имидазолина и имидазолиниевых солей для разрушения азеотропов составили 0,156-0,264. Для корреляции экспериментальных данных о парожидкостном равновесии в системах, содержащих имидазолиниевые соли использована электролитная модель NRTL. Средние абсолютные отклонения расчетных данных от экспериментальных значений мольного содержания растворителей в паровой фазе и температуры в системах составили 0,007-0,008 и 0,25-0,35 К, соответственно. The non-aqueous binary azeotrope systems have been separated into components by the method of extractive rectification (and salt rectification) using imidazolines and their quaternary salts. The following were selected as separating agents: industrial product 1-hydroxyethyl-2-alkenyl-2-imidazoline based on tall oil fatty acids, as well as its quaternary salts - chloride and tetrafluoroborate 1-hydroxyethyl-2-alkenyl-3-benzyl-2-imidazolinium. Non-aqueous azeotrope acetone - methanol, methyl acetate - methanol, ethyl acetate - ethanol, and chloroform - methanol systems were used for separation. The vapor-liquid equilibrium in the corresponding ternary systems was investigated in a modified Othmer still at 101.3 kPa, the composition of the liquid and vapor phases was determined by gas chromatographic analysis. The minimum concentrations (in molar fractions) of imidazoline and imidazolinium salts for the azeotrope breaking were 0.156-0.264. The mean absolute deviations between experimental and calculated data for the solvent mole fraction in the vapor phase and temperature in the imidazolinium salt containing systems were 0,007-0,008 and 0,25-0,35 К respectively.
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Hall, Bradley D., Andrew M. Crotwell, Benjamin R. Miller, Michael Schibig, and James W. Elkins. "Gravimetrically prepared carbon dioxide standards in support of atmospheric research." Atmospheric Measurement Techniques 12, no. 1 (January 28, 2019): 517–24. http://dx.doi.org/10.5194/amt-12-517-2019.
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Abstract. We have explored a one-step method for gravimetric preparation of CO2-in-air standards in aluminum cylinders. We consider both adsorption to stainless steel surfaces used in the transfer of highly pure CO2 and adsorption of CO2 to cylinder walls. We demonstrate that CO2-in-air standards can be prepared with relatively low uncertainty (∼ 0.04 %, ∼95 % confidence level) by introducing aliquots whose masses are known to high precision and by using well-characterized cylinders. Five gravimetric standards, prepared over the nominal range of 350 to 490 µmol mol−1 (parts per million, ppm), showed excellent internal consistency, with residuals from a linear fit equal to 0.05 ppm. This work compliments efforts to maintain the World Meteorological Organization, Global Atmosphere Watch, mole fraction scale for carbon dioxide in air, widely used for atmospheric monitoring. This gravimetric technique could be extended to other atmospheric trace gases, depending on the vapor pressure of the gas.
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Nara, H., H. Tanimoto, Y. Tohjima, H. Mukai, Y. Nojiri, K. Katsumata, and C. Rella. "Evaluation of factors affecting accurate measurements of atmospheric CO<sub>2</sub> and CH<sub>4</sub> by wavelength-scanned cavity ring-down spectroscopy." Atmospheric Measurement Techniques Discussions 5, no. 4 (July 20, 2012): 5009–41. http://dx.doi.org/10.5194/amtd-5-5009-2012.
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Abstract. We examined potential interferences from water vapor and atmospheric background gases (N2, O2, and Ar), and biases by isotopologues of target species, on accurate measurement of atmospheric CO2 and CH4 by means of wavelength-scanned cavity ring-down spectroscopy (WS-CRDS). Variations in the composition of the background gas substantially impacted the CO2 and CH4 measurements: the measured amounts of CO2 and CH4 decreased with increasing N2 mole fraction, but increased with increasing O2 and Ar, suggesting that the pressure-broadening effects (PBEs) increased as Ar < O2 < N2. Using these experimental results, we inferred PBEs for the measurement of synthetic standard gases. The PBEs were negligible (up to 0.05 ppm for CO2 and 0.01 ppb for CH4) for gas standards balanced with purified air, although the PBEs were substantial (up to 0.87 ppm for CO2 and 1.4 ppb for CH4) for standards balanced with synthetic air. For isotopic biases on CO2 measurements, we compared experimental results and theoretical calculations, which showed excellent agreement within their uncertainty. We derived empirical correction functions for water vapor for three WS-CRDS instruments (Picarro EnviroSense 3000i, G-1301, and G-2301). Although the transferability of the functions was not clear, no significant difference was found in the water vapor correction values among these instruments within the typical analytical precision at sufficiently low water concentrations (< 0.3%V for CO2 and < 0.4%V for CH4). For accurate measurements of CO2 and CH4 in ambient air, we concluded that WS-CRDS measurements should be performed under complete dehumidification of air samples, or moderate dehumidification followed by application of a water vapor correction function, along with calibration by natural air-based standard gases or purified air-balanced synthetic standard gases with isotopic correction.
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Tasi, Chi-Tsung, Wei-Kai Wang, Sin-Liang Ou, Shih-Yung Huang, Ray-Hua Horng, and Dong-Sing Wuu. "Structural and Stress Properties of AlGaN Epilayers Grown on AlN-Nanopatterned Sapphire Templates by Hydride Vapor Phase Epitaxy." Nanomaterials 8, no. 9 (September 10, 2018): 704. http://dx.doi.org/10.3390/nano8090704.
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In this paper, we report the epitaxial growth and material characteristics of AlGaN (Al mole fraction of 10%) on an AlN/nanopatterned sapphire substrate (NPSS) template by hydride vapor phase epitaxy (HVPE). The crystalline quality, surface morphology, microstructure, and stress state of the AlGaN/AlN/NPSS epilayers were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The results indicate that the crystal quality of the AlGaN film could be improved when grown on the AlN/NPSS template. The screw threading dislocation (TD) density was reduced to 1.4 × 109 cm−2 for the AlGaN epilayer grown on the AlN/NPSS template, which was lower than that of the sample grown on a flat c-plane sapphire substrate (6.3 × 109 cm−2). As examined by XRD measurements, the biaxial tensile stress of the AlGaN film was significantly reduced from 1,187 MPa (on AlN/NPSS) to 38.41 MPa (on flat c-plane sapphire). In particular, an increase of the Al content in the overgrown AlGaN layer was confirmed by the TEM observation. This could be due to the relaxation of the in-plane stress through the AlGaN and AlN/NPSS template interface.
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Xi, Y. A., K. X. Chen, F. W. Mont, J. K. Kim, W. Lee, E. F. Schubert, W. Liu, X. Li, and J. A. Smart. "Kinetic study of Al-mole fraction in AlxGa1−xN grown on c-plane sapphire and AlN bulk substrates by metal-organic vapor-phase epitaxy." Applied Physics Letters 90, no. 5 (January 29, 2007): 051104. http://dx.doi.org/10.1063/1.2437681.
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Helmig, Detlev, Alex Guenther, Jacques Hueber, Ryan Daly, Wei Wang, Jeong-Hoo Park, Anssi Liikanen, and Arnaud P. Praplan. "Ozone reactivity measurement of biogenic volatile organic compound emissions." Atmospheric Measurement Techniques 15, no. 18 (September 26, 2022): 5439–54. http://dx.doi.org/10.5194/amt-15-5439-2022.
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Abstract. Previous research on atmospheric chemistry in the forest environment has shown that the total reactivity from biogenic volatile organic compound (BVOC) emissions is not well considered in forest chemistry models. One possible explanation for this discrepancy is the unawareness and neglect of reactive biogenic emissions that have eluded common monitoring methods. This question motivated the development of a total ozone reactivity monitor (TORM) for the direct determination of the reactivity of foliage emissions. Emission samples drawn from a vegetation branch enclosure experiment are mixed with a known and controlled amount of ozone (resulting in, e.g., 100 ppb of ozone) and directed through a temperature-controlled glass flow reactor to allow reactive biogenic emissions to react with ozone during the approximately 2 min residence time in the reactor. The ozone reactivity is determined from the difference in the ozone mole fraction before and after the reaction vessel. An inherent challenge of the experiment is the influence of changing water vapor in the sample air on the ozone signal. Sample air was drawn through Nafion dryers to mitigate the water vapor interference, and a commercial UV absorption ozone monitor was modified to directly determine the ozone differential with one instrument. These two modifications significantly reduced interferences from water vapor and errors associated with the determination of the reacted ozone as the difference from two individual measurements, resulting in a much improved and sensitive determination of the ozone reactivity. This paper provides a detailed description of the measurement design, the instrument apparatus, and its characterization. Examples and results from field deployments demonstrate the applicability and usefulness of the TORM.
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Kuai, Le, John R. Worden, King-Fai Li, Glynn C. Hulley, Francesca M. Hopkins, Charles E. Miller, Simon J. Hook, Riley M. Duren, and Andrew D. Aubrey. "Characterization of anthropogenic methane plumes with the Hyperspectral Thermal Emission Spectrometer (HyTES): a retrieval method and error analysis." Atmospheric Measurement Techniques 9, no. 7 (July 21, 2016): 3165–73. http://dx.doi.org/10.5194/amt-9-3165-2016.
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Abstract. We introduce a retrieval algorithm to estimate lower tropospheric methane (CH4) concentrations from the surface to 1 km with uncertainty estimates using Hyperspectral Thermal Emission Spectrometer (HyTES) airborne radiance measurements. After resampling, retrievals have a spatial resolution of 6 × 6 m2. The total error from a single retrieval is approximately 20 %, with the uncertainties determined primarily by noise and spectral interferences from air temperature, surface emissivity, and atmospheric water vapor. We demonstrate retrievals for a HyTES flight line over storage tanks near Kern River Oil Field (KROF), Kern County, California, and find an extended plume structure in the set of observations with elevated methane concentrations (3.0 ± 0.6 to 6.0 ± 1.2 ppm), well above mean concentrations (1.8 ± 0.4 ppm) observed for this scene. With typically a 20 % estimated uncertainty, plume enhancements with more than 1 ppm are distinguishable from the background values with its uncertainty. HyTES retrievals are consistent with simultaneous airborne and ground-based in situ CH4 mole fraction measurements within the reported accuracy of approximately 0.2 ppm (or ∼ 8 %), due to retrieval interferences related to air temperature, emissivity, and H2O.
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Menningen, K. L., M. A. Childs, H. Toyoda, L. W. Anderson, and J. E. Lawler. "Evaluation of a substrate pretreatment for hot filament CVD of diamond." Journal of Materials Research 9, no. 4 (April 1994): 915–20. http://dx.doi.org/10.1557/jmr.1994.0915.
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The absolute concentration of methyl radicals (CH3) and the mole fraction of acetylene (C2H2) are measured in a hot filament chemical vapor deposition (CVD) system both during and after an initial pretreatment that has been used successfully in microwave plasma and oxyacetylene torch CVD systems to produce more uniform and higher density crystal nucleation. The pretreatment technique, which consists of deposition for a relatively short time with a high input concentration of hydrocarbon in the feed gas, was studied for both methane (CH4) and C2H2 as the input hydrocarbon diluted in H2. Scanning electron micrographs of diamond films deposited under the conditions studied indicate that the pretreatment using CH4 is not effective in increasing the crystal nucleation density, but is moderately effective in increasing the crystal size. The C2H2 pretreatment has no apparent effect upon either the crystal size or nucleation density. The spectroscopie measurements suggest that the surface condition of the filament is the prominent factor affecting the gas phase chemistry both during and after the pretreatment stage.
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Fiedler, V., F. Arnold, H. Schlager, A. Dörnbrack, L. Pirjola, and A. Stohl. "East Asian SO<sub>2</sub> pollution plume over Europe – Part 2: Evolution and potential impact." Atmospheric Chemistry and Physics 9, no. 14 (July 20, 2009): 4729–45. http://dx.doi.org/10.5194/acp-9-4729-2009.
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Abstract. We report on the first observation-based case study of an aged East Asian anthropogenic SO2 pollution plume over Europe. Our airborne measurements in that plume detected highly elevated SO2 mole fractions (up to 900 pmol/mol) between about 5000 and 7000 m altitude. Here, we focus on investigations of the origin, dispersion, evolution, conversion, and potential impact of the observed excess SO2. In particular, we investigate SO2 conversion to gas-phase sulfuric acid and sulfuric acid aerosols. Our FLEXPART and LAGRANTO model simulations, along with additional trace gas measurements, suggest that the plume originated from East Asian fossil fuel combustion sources and, 8–7 days prior to its arrival over Europe, ascended over the coast region of central East Asia to 9000 m altitude, probably in a cyclonic system with an associated warm conveyor belt. During this initial plume ascent a substantial fraction of the initially available SO2 must have escaped from removal by cloud processes. Hereafter, while mostly descending slowly, the plume experienced advection across the North Pacific, North America and the North Atlantic. During its upper troposphere travel, clouds were absent in and above the plume and OH-induced gas-phase conversion of SO2 to gas-phase sulfuric acid (GSA) was operative, followed by GSA nucleation and condensation leading to sulfuric acid aerosol formation and growth. Our AEROFOR model simulations indicate that numerous large sulfuric acid aerosol particles were formed, which at least temporarily, caused substantial horizontal visibility degradation, and which have the potential to act as water vapor condensation nuclei in liquid water cloud formation, already at water vapor supersaturations as low as about 0.1%. Our AEROFOR model simulations also indicate that those fossil fuel combustion generated soot particles, which have survived cloud induced removal during the initial plume ascent, have experienced extensive H2SO4/H2O-coating, during upper troposphere plume travel. This coating may have dramatically altered the morphology and markedly increased the light absorption efficiency of soot particles.
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Malyshev, V. P., and A. M. Makasheva. "Description of dynamic viscosity depending on the alloys composition and temperature using state diagrams." Izvestiya Visshikh Uchebnykh Zavedenii. Chernaya Metallurgiya = Izvestiya. Ferrous Metallurgy 61, no. 9 (October 21, 2018): 743–49. http://dx.doi.org/10.17073/0368-0797-2019-9-743-749.
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The equilibrium nature of viscosity and fluidity is discovered on the basis of the Boltzmann distribution within the framework of the concept of randomized particles as a result of the virtual presence of crystal-mobile, liquid-mobile and vapor-mobile particles. It allows one to consider the viscosity and fluidity of solutions, in particular, melts of metal alloys, from the point of view of the equilibrium partial contributions of each component in the total viscosity and fluidity, despite the kinetic interpretation of natural expressions for these properties of the liquid. A linearly additive partial expression of viscosity is possible only for perfect solutions, in this case, for alloys with unrestricted mutual solubility of the components. Alloys with eutectics, chemical compounds and other features of the state diagram are characterized by viscosity dependencies that repeat the shape of liquidus curve over entire range of the alloy composition at different temperatures, with an increase in smoothness and convergence of these curves at increasing temperature. It was established that these features of viscosity temperature dependence are completely revealed within the framework of the concept of randomized particles and the virtual cluster model of viscosity in calculating the fraction of clusters determining the viscosity of the alloy. That viscosity of the alloy is found by the formula in which thermal energy RTcr at liquidus temperature is the thermal barrier of chaotization, characterizing the crystallization temperature of the melt Tcr, as well as the melting point of pure substances. On this basis, a method is proposed for calculating the alloys viscosity by phase diagrams using the temperature dependences of pure components viscosity to change the alloy’s viscosity in proportion to ratio of the clusters fractions at any temperature above liquidus line and for the pure component, taking into account the mole fraction of each component. As a result, a three-factor model of the liquid alloy viscosity has been obtained in which the thermal barrier of chaotization RTcr is used as variable for the first time. It determines the fraction of clusters for both pure substances (at RTcr = RTm ) and for alloys. This thermal barrier reflects the essence of the virtual cluster theory of liquid and adequacy of the concept of randomized particles.
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Welp, L. R., R. F. Keeling, R. F. Weiss, W. Paplawsky, and S. Heckman. "Design and performance of a Nafion dryer for continuous operation at CO<sub>2</sub> and CH<sub>4</sub> air monitoring sites." Atmospheric Measurement Techniques Discussions 5, no. 4 (August 7, 2012): 5449–68. http://dx.doi.org/10.5194/amtd-5-5449-2012.
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Abstract. In preparation for the routine deployment of the Earth Networks greenhouse gas monitoring network, we have designed and tested a simple method for drying ambient air to below 0.2% mole fraction H2O using a Nafion dryer. The inlet was designed for use with a Picarro model G2301 cavity ring down spectrometer (CRDS) CO2/CH4/H2O analyzer. The analyzer measures water vapor mixing ratio at the same frequency as CO2 and CH4 and then corrects for the dilution and peak broadening effects of H2O on the CO2 and CH4 mixing ratios. This analyzer is remarkably stable and performs well on water vapor correction tests, but there is potentially an added benefit of reducing the dependence on the H2O correction for long term field measurement programs. Substantially lowering the amount of H2O in the sample can reduce uncertainties in the applied H2O corrections by an order of magnitude or more, and eliminate the need to determine an instrument-specific H2O correction factor and to verify its stability over time. Our Nafion drying inlet system takes advantage of the extra capacity of the analyzer pump to redirect 30% of the dry gas exiting the Nafion to the outer shell side of the dryer and has no consumables. We tested the Nafion dryer against a cryotrap (−95 °C) method for removing H2O and found that it does not significantly alter the CO2 and CH4 dry mixing ratios of the sample gas. Systematic differences between the drying methods were at the level of 0.05 ppm in CO2 and 0.1 ppb in CH4 for the wet-air tests, well within the WMO compatibility guidelines.
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Trieu, Tran Thi Ngoc, Isamu Morino, Hirofumi Ohyama, Osamu Uchino, Ralf Sussmann, Thorsten Warneke, Christof Petri, et al. "Evaluation of Bias Correction Methods for GOSAT SWIR XH2O Using TCCON data." Remote Sensing 11, no. 3 (February 1, 2019): 290. http://dx.doi.org/10.3390/rs11030290.
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This study evaluated three bias correction methods of systematic biases in column-averaged dry-air mole fraction of water vapor (XH2O) data retrieved from Greenhouse Gases Observing Satellite (GOSAT) Short-Wavelength Infrared (SWIR) observations compared with ground-based data from the Total Carbon Column Observing Network (TCCON). They included an empirically multilinear regression method, altitude bias correction method, and combination of altitude and empirical correction for three cases defined by the temporal and spatial collocation around TCCON site. The results showed that large altitude differences between GOSAT observation points and TCCON instruments are the main cause of bias, and the altitude bias correction method is the most effective bias correction method. The lowest biases result from GOSAT SWIR XH2O data within a 0.5° 0.5° latitude longitude box centered at each TCCON site matched with TCCON XH2O data averaged over ±15 min of the GOSAT overpass time. Considering land data, the global bias changed from −1.3 ± 9.3% to −2.2 ± 8.5%, and station bias from −2.3 ± 9.0% to −1.7 ± 8.4%. In mixed land and ocean data, global bias and station bias changed from −0.3 ± 7.6% and −1.9 ± 7.1% to −0.8 ± 7.2% and −2.3 ± 6.8%, respectively, after bias correction. The results also confirmed that the fine spatial and temporal collocation criteria are necessary in bias correction methods.
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Delval, Christophe, and Michel J. Rossi. "The influence of HCl on the evaporation rates of H<sub>2</sub>O over water ice in the range 188 to 210 K at small average concentrations." Atmospheric Chemistry and Physics 18, no. 21 (November 7, 2018): 15903–19. http://dx.doi.org/10.5194/acp-18-15903-2018.
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Abstract. The evaporation flux Jev(H2O) of H2O from HCl-doped typically 1.5 µm or so thick vapor-deposited ice films has been measured in a combined quartz crystal microbalance (QCMB)–residual gas mass spectrometry (MS) experiment. Jev(H2O) has been found to show complex behavior and to be a function of the average mole fraction χHCl of HCl in the ice film ranging from 6×1014 to 3×1017 molecule cm−2 s−1 at 174–210 K for initial values χHCl0 ranging from 5×10-5 to 3×10-3 at the start of the evaporation. The dose of HCl on ice was in the range of 1 to 40 formal monolayers and the H2O vapor pressure was independent of χHCl within the measured range and equal to that of pure ice down to 80 nm thickness. The dependence of Jev(H2O) with increasing average χHCl was correlated with (a) the evaporation range rb∕e parameter, that is, the ratio of Jev(H2O) just before HCl doping of the pure ice film and Jev(H2O) after observable HCl desorption towards the end of film evaporation, and (b) the remaining thickness dD below which Jev(H2O) decreases to less than 85 % of pure ice. The dependence of Jev(H2O) with increasing average χHCl from HCl-doped ice films suggests two limiting data sets, one associated with the occurrence of a two-phase pure ice/crystalline HCl hydrate binary phase (set A) and the other with a single-phase amorphous HCl∕H2O binary mixture (set B). The measured values of Jev(H2O) may lead to significant evaporative lifetime extensions of HCl-contaminated ice cloud particles under atmospheric conditions, regardless of whether the structure corresponds to an amorphous or crystalline state of the HCl∕H2O aggregate.
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Welp, L. R., R. F. Keeling, R. F. Weiss, W. Paplawsky, and S. Heckman. "Design and performance of a Nafion dryer for continuous operation at CO<sub>2</sub> and CH<sub>4</sub> air monitoring sites." Atmospheric Measurement Techniques 6, no. 5 (May 14, 2013): 1217–26. http://dx.doi.org/10.5194/amt-6-1217-2013.
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Abstract. In preparation for routine deployment in a network of greenhouse gas monitoring stations, we have designed and tested a simple method for drying ambient air to near or below 0.2% (2000 ppm) mole fraction H2O using a Nafion dryer. The inlet system was designed for use with cavity ring-down spectrometer (CRDS) analyzers such as the Picarro model G2301 that measure H2O in addition to their principal analytes, in this case CO2 and CH4. These analyzers report dry-gas mixing ratios without drying the sample by measuring H2O mixing ratio at the same frequency as the main analytes, and then correcting for the dilution and peak broadening effects of H2O on the mixing ratios of the other analytes measured in moist air. However, it is difficult to accurately validate the water vapor correction in the field. By substantially lowering the amount of H2O in the sample, uncertainties in the applied water vapor corrections can be reduced by an order of magnitude or more, thus eliminating the need to determine instrument-specific water vapor correction coefficients and to verify the stability over time. Our Nafion drying inlet system takes advantage of the extra capacity of the analyzer pump to redirect 30% of the dry gas exiting the Nafion to the outer shell side of the dryer and has no consumables. We tested the Nafion dryer against a cryotrap (−97 °C) method for removing H2O and found that in wet-air tests, the Nafion reduces the CO2 dry-gas mixing ratios of the sample gas by as much as 0.1 ± 0.01 ppm due to leakage across the membrane. The effect on CH4 was smaller and varied within ± 0.2 ppb, with an approximate uncertainty of 0.1 ppb. The Nafion-induced CO2 bias is partially offset by sending the dry reference gases through the Nafion dryer as well. The residual bias due to the impact of moisture differences between sample and reference gas on the permeation through the Nafion was approximately −0.05 ppm for CO2 and varied within ± 0.2 ppb for CH4. The uncertainty of this partial drying method is within the WMO compatibility guidelines for the Northern Hemisphere, 0.1 ppm for CO2 and 2 ppb for CH4, and is comparable to experimentally determining water vapor corrections for each instrument but less subject to concerns of possible drift in these corrections.