Journal articles: 'Mass absorption coefficients'

1

Buse, Ben, and Stuart Kearns. "Quantification of Olivine Using Fe Lα in Electron Probe Microanalysis (EPMA)." Microscopy and Microanalysis 24, no. 1 (February 2018): 1–7. http://dx.doi.org/10.1017/s1431927618000041.

Full text

Abstract:

AbstractQuantification of first series transition metal Lα X-rays is hampered by absorption and in some cases transition probabilities (fluorescence yields) varying with chemical bonding. Compound mass absorption coefficients for Fe Lα were measured in the olivine solid solution series [Forsterite (Mg2SiO4) to Fayalite (Fe2SiO4)] and the mass absorption coefficients for Fe Lα absorbed by Fe were calculated. The mass absorption coefficients vary systematically between Fo83 and Fo0. Using the measured mass absorption coefficients for both standard and unknown and by correcting for a systematic discrepancy, consistent with varying partial fluorescence yields, a good agreement between calculated k-ratios and measured k-ratios is achieved. The systematic variations allow quantification of unknown k-ratios. The described method of quantification requires modification of matrix correction routines to allow standards and unknowns to have different mass absorption coefficients, and to incorporate solid solution mass absorption coefficients and partial fluorescence yield corrections derived from regression of experimental data.

APA, Harvard, Vancouver, ISO, and other styles

2

Bairlein, Katharina, and Oliver Hupe. "INFLUENCE OF NEW MASS ENERGY-ABSORPTION COEFFICIENTS FROM ICRU REPORT NO. 90 ON AIR KERMA TO DOSE EQUIVALENT CONVERSION COEFFICIENTS." Radiation Protection Dosimetry 185, no. 1 (December 6, 2018): 27–33. http://dx.doi.org/10.1093/rpd/ncy213.

Full text

Abstract:

Abstract In Report No. 90 of the International Commission on Radiation Units and Measurements (ICRU), new mass energy-absorption coefficients are listed which are based on renormalized Scofield photoeffect cross-sections. The mass energy-absorption coefficients are the basis for the conversion coefficients from air kerma to the operational quantities listed in ISO 4037-3. Although ICRU does not give a recommendation if these new mass energy-absorption coefficients should be applied instead of the values used so far, an examination of the possible consequences for radiation protection quantities is necessary. We calculated the conversion coefficients for the X-ray qualities specified in ISO 4037-1 with the new mass energy-absorption coefficients and with the mass energy-absorption coefficients used so far to determine the deviations. Our calculations show that the change of the conversion coefficients due to the new values from ICRU Report No. 90 is negligible.

APA, Harvard, Vancouver, ISO, and other styles

3

Hitzenberger, Regina. "Absorption and mass absorption coefficients measured with the integrating plate method." Journal of Aerosol Science 20, no. 8 (January 1989): 1205–8. http://dx.doi.org/10.1016/0021-8502(89)90798-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Rickerby, David G., and Norbert Wächter. "Effective L-Series Mass Absorption Coefficients for EDS." Microchimica Acta 132, no. 2-4 (April 2000): 157–61. http://dx.doi.org/10.1007/s006040050057.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Seltzer, Stephen M. "Calculation of Photon Mass Energy-Transfer and Mass Energy-Absorption Coefficients." Radiation Research 136, no. 2 (November 1993): 147. http://dx.doi.org/10.2307/3578607.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Mahmoud Aboelkheir, Ibrahim Mohamed. "Trends in an Absorption Column through Mass Transfer Coefficients." Cognizance Journal of Multidisciplinary Studies 2, no. 1 (January 30, 2022): 38–57. http://dx.doi.org/10.47760/cognizance.2022.v02i01.003.

Full text

Abstract:

A study was conducted to measure the values of m.t.c and N of an absorption column. Values of N were in the range of 10-5, while those of m.t.c were in the range of 10-7. The trends with variables were confirmed with the previous studies. However, they were not with m.t.c. Pressure variance was suggested as the reason. Error was assessed at a percentage of 15% for m.t.c, and under 2% for pressure. Using other methods than only measuring concentration of solute with the Hempl apparatus was recommended.

APA, Harvard, Vancouver, ISO, and other styles

7

Babikian, D. S., D. K. Edwards, S. E. Karam, C. P. Wood, and G. S. Samuelsen. "Experimental mass absorption coefficients of soot in spray combustorflames." Journal of Thermophysics and Heat Transfer 4, no. 1 (January 1990): 8–15. http://dx.doi.org/10.2514/3.29157.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Chipera, Steve J., and David L. Bish. "Measurement of Mass Absorption Coefficients Using Compton-Scattered Cu Radiation in X-ray Diffraction Analysis." Advances in X-ray Analysis 34 (1990): 325–35. http://dx.doi.org/10.1154/s0376030800014634.

Full text

Abstract:

AbstractThe mass absorption coefficient is a useful parameter for quantitative characterization of materials. If the chemical composition of a sample is known, the mass absorption coefficient can be calculated directly. However, the mass absorption coefficient must be determined empirically if the chemical composition is unknown. Traditional methods for determining the mass absorption coefficient involve measuring the transmission of monochromatic X-rays through a sample of known thickness and density. Reynolds (1963,1967), however, proposed a method for determining the mass absorption coefficient by measuring the Compton or inelastic X-ray scattering from a sample using Mo radiation on an X-ray fluorescence spectrometer (XRF). With the recent advances in solid-state detectors/electronics for use with conventional powder diffractometers, it is now possible to readily determine mass absorption coefficients during routine X-ray diffraction (XRD) analyses.Using Cu Kα radiation and Reynolds’ method on a Siemens D-500 diffractometer fitted with a Kevex Si(Li) solid-state detector, we have measured the mass absorption coefficients of a suite of minerals and pure chemical compounds ranging in μ/ρ from graphite to Fe-metal (μ/ρ = 4.6-308 using Cu Kα radiation) to ±4.0% (lσ). The relationship between the known mass absorption coefficient and the inverse count rate is linear with a correlation coefficient of 0.997. Using mass absorption coefficients, phase abundances can be determined during quantitative XRD analysis without requiring the use of an internal standard, even when an amorphous component is present.

APA, Harvard, Vancouver, ISO, and other styles

9

Alkire, R. W. "Approximating the near-edge mass absorption coefficients for Ni using an ultra-thin bimetal foil." Journal of Applied Crystallography 50, no. 1 (February 1, 2017): 1–13. http://dx.doi.org/10.1107/s1600576716017544.

Full text

Abstract:

In an effort to improve the characteristics of a fluorescing metal-foil-based beam position monitor, a new bimetal ultra-thin (0.98/0.67 µm) Ti–Ni foil was introduced to replace an existing single-element ultra-thin 0.5 µm thick Cr foil. During characterization it was determined that absorption measurements on the bimetal foil could be used to fit the Ni mass absorption coefficients accurately in the vicinity of the Ni K edge. Comparison with experimental results from the literature demonstrated that the fitting procedure produced coefficients with uncertainties of the order of ±1%. Once determined, these fit coefficients allowed the thickness of an independently mounted 8 µm thick Ni foil to be computed from absorption measurements instead of relying on a tool-based measurement of the foil thickness. Using the 8 µm thick foil, a continuous map of Ni mass absorption coefficients was produced at 1 eV resolution throughout the near-edge region. This high-resolution map marks a significant improvement over the existing NIST XCOM or FFAST database mass absorption coefficients, which have estimated errors of 10–20% for the near-edge region.

APA, Harvard, Vancouver, ISO, and other styles

10

Gabitto, Jorge, and Costas Tsouris. "Determination of reactive mass transfer coefficients for CO2 absorption predictions." Separation Science and Technology 54, no. 13 (April 13, 2019): 2026–33. http://dx.doi.org/10.1080/01496395.2019.1603240.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Cordey, J. "Quantitative computed tomography: From linear absorption coefficients to bone mass." Injury 23 (January 1992): S47—S53. http://dx.doi.org/10.1016/s0020-1383(10)80005-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Fujita, Isamu, and Eiji Hihara. "Heat and mass transfer coefficients of falling-film absorption process." International Journal of Heat and Mass Transfer 48, no. 13 (June 2005): 2779–86. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2004.11.028.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Willis, J. P. "Mass Absorption Coefficient Determination Using Compton Scattered Tube Radiation: Applications, Limitations and Pitfalls." Advances in X-ray Analysis 34 (1990): 243–61. http://dx.doi.org/10.1154/s0376030800014543.

Full text

Abstract:

Trace element determination by X-ray fluorescence spectrometry is subject, like almost all instrumental analytical techniques, to systematic errors, also known as matrix effects. This paper deals with the determination of mass absorption coefficients (MACs), using Compton peak intensities, for the correction of matrix effects arising only from elemental absorption in the sample.When absorption effects are significant the relationship between net analyte peak intensity and concentration will no longer be constant, and corrections will be necessary for accurate analyses.

APA, Harvard, Vancouver, ISO, and other styles

14

Ristić, Goran S., Stefan D. Ilić, Sandra Veljković, Aleksandar S. Jevtić, Strahinja Dimitrijević, Alberto J. Palma, Srboljub Stanković, and Marko S. Andjelković. "Commercial P-Channel Power VDMOSFET as X-ray Dosimeter." Electronics 11, no. 6 (March 16, 2022): 918. http://dx.doi.org/10.3390/electronics11060918.

Full text

Abstract:

The possibility of using commercial p-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors (VDMOSFETs) as X-ray sensors is investigated in this case study. In this aspect, the dependence of sensitivity on both the gate voltage and the mean energy for three X-ray beams is examined. The eight gate voltages from 0 to 21 V are applied, and the dependence of the sensitivity on the gate voltage is well fitted using the proposed equation. Regarding X-ray energy, the sensitivity first increases and then decreases as a consequence of the behavior of the mass energy-absorption coefficients and is the largest for RQR8 beam. As the mass energy-absorption coefficients of SiO2 are not found in the literature, the mass energy-absorption coefficients of silicon are used. The behavior of irradiated transistors during annealing at room temperature without gate polarization is also considered.

APA, Harvard, Vancouver, ISO, and other styles

15

Sobieszuk, Paweł, Filip Ilnicki, and Ryszard Pohorecki. "Contribution of Liquid- and Gas-Side Mass Transfer Coefficients to Overall Mass Transfer Coefficient in Taylor Flow in a Microreactor." Chemical and Process Engineering 35, no. 1 (March 1, 2014): 35–45. http://dx.doi.org/10.2478/cpe-2014-0003.

Full text

Abstract:

Abstract Gas-liquid microreactors find an increasing range of applications both in production, and for chemical analysis. The most often employed flow regime in these microreactors is Taylor flow. The rate of absorption of gases in liquids depends on gas-side and liquid-side resistances. There are several publications about liquid-side mass transfer coefficients in Taylor flow, but the data about gas-side mass transfer coefficients are practically non existent. We analysed the problem of gas-side mass transfer resistance in Taylor flow and determined conditions, in which it may influence the overall mass transfer rate. Investigations were performed using numerical simulations. The influence of the gas diffusivity, gas viscosity, channel diameter, bubble length and gas bubble velocity has been determined. It was found that in some case the mass transfer resistances in both phases are comparable and the gas-side resistance may be significant. In such cases, neglecting the gas-side coefficient may lead to errors in the experimental data interpretation.

APA, Harvard, Vancouver, ISO, and other styles

16

Utry, N., T. Ajtai, M. Pintér, E. Tombácz, E. Illés, Z. Bozóki, and G. Szabó. "Mass-specific optical absorption coefficients and imaginary part of the complex refractive indices of mineral dust components measured by a multi-wavelength photoacoustic spectrometer." Atmospheric Measurement Techniques 8, no. 1 (January 22, 2015): 401–10. http://dx.doi.org/10.5194/amt-8-401-2015.

Full text

Abstract:

Abstract. Mass-specific optical absorption coefficients (MACs) and the imaginary part (κ) of the refractive indices of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at the wavelengths of 1064, 532, 355 and 266 nm. The MAC values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. Values of κ were calculated from the measured and particle-loss-corrected data by using a Mie-theory-based retrieval algorithm. The determined values could be used for comparisons with calculated wavelength-dependent κ values typically deduced from bulk-phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk-phase measurements.

APA, Harvard, Vancouver, ISO, and other styles

17

Beavers, A. H., and Ken R. Olson. "Use of Rayleigh Scatter for Determining X-ray Mass Absorption Coefficients." Soil Science Society of America Journal 50, no. 4 (July 1986): 1088–91. http://dx.doi.org/10.2136/sssaj1986.03615995005000040051x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Ladhaf, Bibifatima M., and Pravina P. Pawar. "Studies on mass energy-absorption coefficients and effective atomic energy-absorption cross sections for carbohydrates." Radiation Physics and Chemistry 109 (April 2015): 89–94. http://dx.doi.org/10.1016/j.radphyschem.2014.12.015.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Hu, Meilin, Kangxian Guo, Zhongmin Zhang, Xiancong Jiang, Keyin Li, and Dongfeng Liu. "The effect of position-dependent mass on nonlinear optical absorption coefficients and refractive index changes in a quantum well." International Journal of Modern Physics B 31, no. 03 (January 23, 2017): 1750009. http://dx.doi.org/10.1142/s0217979217500096.

Full text

Abstract:

The influence of position-dependent mass (PDM) on nonlinear optical absorption (OA) coefficients and refractive index changes (RICs) is theoretically studied, within the framework of the iterative method and the compact-density-matrix approach. Through solving Schrödinger equation, the eigenfunctions and energy eigenvalues are obtained. The analytic expressions of the optical absorption coefficients and the refraction index changes are derived theoretically. The results reveal that the OA coefficients and the RICs are strongly affected by PDM, and both the peaks of them increase when considering PDM.

APA, Harvard, Vancouver, ISO, and other styles

20

Kouhi, Mohammad. "Nonlinear optical absorption in the core shell nanowire." International Journal of Modern Physics B 31, no. 23 (September 14, 2017): 1750164. http://dx.doi.org/10.1142/s0217979217501648.

Full text

Abstract:

In this paper, the effect of incident light intensity, relaxation time, core radius and shell thickness on linear, nonlinear, total optical absorption coefficients and refractive index changes in [Formula: see text] core–shell nanowire are theoretically investigated. The presented nanostructure is a cylindrical quantum wire including a shell around the cylinder core. By numerical solution of Schrödinger equation in the cylindrical coordinates with effective mass approximation, the optical absorption coefficients are calculated. The results show that the magnitude of optical absorption coefficients can be adjusted by varying the relaxation time. The positions of resonant peaks of optical absorption coefficients are redshifted by increase of core radius due to decrease of the energy difference between two energy levels. With increase of shell thickness initially, the resonance wavelength of absorption coefficient increases (redshift) and magnitude of absorption coefficient decreases. Then with more increases of the shell thickness, redshifting of resonance wavelength is stopped and magnitude of absorption coefficient is increased. There is a significant increase in the refractive index change with increase of relaxation time.

APA, Harvard, Vancouver, ISO, and other styles

21

Yong and, Li, and K. Sumathy. "Experimental Study on Forced Convection Heat Transfer Inside Horizontal Tubes in an Absorption/Compression Heat Pump." Journal of Heat Transfer 124, no. 5 (September 11, 2002): 975–78. http://dx.doi.org/10.1115/1.1473142.

Full text

Abstract:

Quasi-local absorption heat transfer coefficients and pressure drop inside a horizontal tube absorber have been investigated experimentally, with R-22/DMA as the working pair. The absorber is a counterflow coaxial tube-in-tube heat-exchanger with the working fluid flowing in the inner tube while the water moves through the annulus. A large temperature gliding has been experienced during the absorption process. Experimental results show that the heat transfer coefficient of the forced convective vapor absorption process is higher compared to the vertical falling film absorption. A qualitative study is made to analyze the effect of mass flux, vapor quality and solution concentration on pressure drop and heat transfer coefficients. On the basis of the experimental results, a new correlation is proposed whereby the two-phase heat transfer is taken as a product of the forced convection of the absorption and the combined effect of heat and mass transfer at the interface. The correlation is found to predict the experimental data almost within 30 percent.

APA, Harvard, Vancouver, ISO, and other styles

22

Mahmoud A. Elawi. "Mass Attenuation Coefficient Measurements of Photoelectric Absorption of Gamma-Rays in Copper Using Coincidence Technique." Tikrit Journal of Pure Science 25, no. 4 (August 2, 2020): 80–85. http://dx.doi.org/10.25130/tjps.v25i4.275.

Full text

Abstract:

The photoelectric absorption mass attenuation coefficients (m.a.c.) of ɤ- rays in Cu are measured using a two 3"x3" NaI(Tl) detector coincidence spectrometer at 511, 1173 and 1332keV energy gates using Na-22 and Co-60 point sources. The m.a.c. (in cm²/g) measured by coincidence method were lower than those obtained from direct measurement. Coincidence measurements revealed the coefficients 0.0429, 0.0212 and 0.0205 and direct measurements the coefficients 0.0561, 0.0239 and 0.0220 for the studied energies respectively. The μm (co) /μm (dir) ratios were 0.763, 0.8900 and 0.9345at the three energies mentioned respectively. The coincidence coefficients also behave as those of direct spectra as with change in energy.

APA, Harvard, Vancouver, ISO, and other styles

23

Toraya, Hideo. "Quantitative Phase Analysis Using the Whole–Powder– Pattern Decomposition Method: II. Solution Using External Standard Materials." Advances in X-ray Analysis 38 (1994): 69–73. http://dx.doi.org/10.1154/s0376030800017651.

Full text

Abstract:

Abstract A new procedure for the quantitative phase analysis using the whole–powder–pattern decomposition method has been proposed (Toraya and Tsusaka, 1995). The procedure is based on the determination of the scale factor for the profile intensity of each phase in a mixture, which is identical to the ratio of integrated intensity in a mixture to that of the corresponding reflection in a single component sample. Weight fractious were obtained by solving the simultaneous equations, of which coefficients include the scale factors and the mass absorption coefficients. In a previous study, the mass absorption coefficients were calculated from chemical compositions and u,/p data of respective phases. In the present study, an alternative way of deriving the weight fraction without using the knowledge of chemical composition is proposed.

APA, Harvard, Vancouver, ISO, and other styles

24

Danilov, Valery A., and Il Moon. "A Method for Estimating Mass Transfer Coefficients in a Packed Column Using Reactive Absorption Data." Collection of Czechoslovak Chemical Communications 70, no. 3 (2005): 383–402. http://dx.doi.org/10.1135/cccc20050383.

Full text

Abstract:

This paper is devoted to the development of a new method for estimating mass transfer coefficients and effective area in packed columns in the case of reactive absorption. The method is based on a plug-flow model of reactive absorption of carbon dioxide with sodium hydroxide solution. The parameter estimation problem is solved using an optimization technique. Some mass transfer parameters are found to be correlated. Global sensitivity analysis by Sobol's technique showed that the unit model with the defined objective function is sensitive to the estimated parameter. Case studies of reactive absorption with different packings illustrate application of the proposed method for estimating mass transfer coefficients and effective area from column operation data. The model calculations are compared with experimental data obtained by other authors. The concentration profiles calculated by the unit model with the estimated parameters are shown to match well with experimental profiles from literature. A good agreement between estimated values and experimental data from literature confirms the applicability of this method.

APA, Harvard, Vancouver, ISO, and other styles

25

Zhang, Ting An, Yan Liu, Qiang Wang, Ji Cheng He, and Sano Masamichi. "Enhancement of Absorption of Injected Gas in New Type Mechanical Stirring Injection Refine Equipment." Advanced Materials Research 455-456 (January 2012): 97–102. http://dx.doi.org/10.4028/www.scientific.net/amr.455-456.97.

Full text

Abstract:

The bubble disintegration is of great scientific importance in metal refining, In order for further improvement, Research on bubble disintegration and dispersion becomes necessary, The intensification of bubble disintegration experiment that we have done in cold water model by study absorption rate ,The purpose is to research bubble disintegration under difference experimental condition . In this paper, we use mass transfer coefficients stand for absorption rate, we also study utilization rate, we want to research the best experimental condition which can enhance mass transfer coefficients and utilization rate. On the basis of experimental result, Provided a scientific and experimental basis to high-temperature experiment of bubble dispersion and disintegration .Experimental results show:the rate of absorption of CO2 injected in aqueous NaOH solution can be increased greatly by mechanical stirring when the positive-reverse rotation mode is adopted. Dispersion of small bubbles in the liquid is very effective for increasing the absorption rate.

APA, Harvard, Vancouver, ISO, and other styles

26

Sayyed, Mohammed I., Ferdi Akman, Veysel Turan, and Aslı Araz. "Evaluation of radiation absorption capacity of some soil samples." Radiochimica Acta 107, no. 1 (December 19, 2018): 83–93. http://dx.doi.org/10.1515/ract-2018-2996.

Full text

Abstract:

Abstract The aim of the present work is to investigate the radiation absorption capacity of different soil samples in Turkey. For this purpose, we used a γ ray transmission geometry to measure the mass attenuation coefficients of eight soil samples collected between Bingöl city and Solhan district, Turkey at different γ-ray energies in the range of 13.94–88.04 keV. The radioactive sources utilized in the experiment were 241Am, 109Cd and 133Ba. FFAST and WinXCOM programs were used to evaluate the theoretical mass attenuation coefficients values of the selected soil samples. There is a good agreement between experimental and theoretical results. Additionally, the mass attenuation coefficients values used to evaluate different radiation shielding parameters such as effective atomic number, half value layer and mean free path. The variation of shielding parameters was examined for soil composition and photon energy. The obtained results revealed that S6 soil sample is the best soil in terms of shielding effectiveness among all the collected soils due to lower values for half value layer and mean free path. The effective removal cross-section (ΣR) of fast neutrons for the collected soils was also computed to examine neutrons shielding properties of the soil samples. It is found that the ΣR values for the soil samples are almost constant and lie within the range (0.04286–0.04949 cm−1).

APA, Harvard, Vancouver, ISO, and other styles

27

Dumont, E., G. Darracq, A. Couvert, C. Couriol, A. Amrane, D. Thomas, Y. Andrès, and P. Le Cloirec. "Volumetric mass transfer coefficients characterising VOC absorption in water/silicone oil mixtures." Chemical Engineering Journal 221 (April 2013): 308–14. http://dx.doi.org/10.1016/j.cej.2013.01.102.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Vrebos, B. A. R., and P. A. Pella. "Uncertainties in mass absorption coefficients in fundamental parameter X-ray fluorescence analysis." X-Ray Spectrometry 17, no. 1 (February 1988): 3–12. http://dx.doi.org/10.1002/xrs.1300170103.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Umadevi, B., Dinesh P.A., Indira R. Rao, and Vinay C.V. "The Effect of Particle Drag and Wall Absorption on Mass Transfer in Concentric Annulus Flows." Mapana - Journal of Sciences 10, no. 1 (June 30, 2011): 1–13. http://dx.doi.org/10.12723/mjs.18.1.

Full text

Abstract:

The effects of the irreversible boundary reaction and the particle drag on mass transfer are studied analytically in concentric annulus flows. The solution of mathematical model, based on the generalized dispersion model brings out the mass transport following by the insertion of catheter on an artery in terms of the three effective transport coefficients, viz., the exchange, convection and diffusion coefficient. A general expression is derived which shows clearly the time dependent nature of the coefficients in the dispersive model. The complete time dependent expression for the exchange coefficient is obtained explicitly and independent of velocity distribution in the flow; however it does depend on the initial solute distribution. Because of the complexity of the problem only asymptotic large time evaluations are made for the convective and diffusion coefficients, but these are sufficient to give the physical insight into the nature of the problem of the effects of drag and absorption parameters. It is found that as absorption parameter increases exchange and convection coefficients will be enhanced, but diffusion coefficient will be reduced. After certain period of time exchange coefficient will be constant for different values annular gap. As the drag parameter increases convection and diffusion coefficients will be reduced. With the enhancement of catheter radius i.e., the annular gap will be reduced then the convection and diffusion coefficients will be decreased.

APA, Harvard, Vancouver, ISO, and other styles

30

Xu, X., W. Zhao, Q. Zhang, S. Wang, B. Fang, W. Chen, D. S. Venables, et al. "Optical properties of atmospheric fine particles near Beijing during the HOPE-J<sup>3</sup>A Campaign." Atmospheric Chemistry and Physics Discussions 15, no. 22 (November 27, 2015): 33675–730. http://dx.doi.org/10.5194/acpd-15-33675-2015.

Full text

Abstract:

Abstract. The optical properties and chemical composition of PM1.0 (particulate with an aerodynamic diameter of less than 1.0 μm) particles in a suburban environment (Huairou) near the mega-city Beijing were measured during the HOPE-J3A (Haze Observation Project Especially for Jing-Jin-Ji Area) field campaign. The campaign covered the period November 2014 to January 2015 during the winter coal heating season. The average and standard deviations for the extinction, scattering, absorption coefficients, and the aerosol single scattering albedo (SSA) at λ = 470 nm during the measurement period were 201 ± 240, 164 ± 202, 37 ± 43 Mm-1, and 0.80 ± 0.08, respectively. The mean mass scattering (MSE) and absorption (MAE) efficiencies were 4.77 ± 0.01 and 0.87 ± 0.03 m2g-1, respectively. Highly time-resolved air pollution episodes clearly show the dramatic evolution of the PM1.0 size distribution, extensive optical properties (extinction, scattering, and absorption coefficients) and intensive optical properties (single scattering albedo and complex refractive index) during haze formation, development and decline. Time periods were classified into three different pollution levels (clear, slightly polluted, and polluted) for further analysis. It was found that: (1) The diurnal patterns of the aerosol extinction, scattering, absorption coefficients, and SSA differed for the three pollution classes. (2) The real and imaginary part of complex refractive index (CRI) increased, while the SSA decreased from clear to polluted days. (3) The relative contributions of organic and inorganic species to observed aerosol composition changed significantly from clear to polluted days: the organic mass fraction decreased (50 to 43 %) while the proportion of sulfates, nitrates, and ammonium increased strongly (34 to 44 %). (4) The fractional contribution of chemical components to extinction coefficients was calculated by using the modified IMPROVE algorithm. Organic mass was the largest contributor (58 %) to the total extinction of PM1.0. When the air quality deteriorated, the change of the relative contribution of sulfate aerosol to the total extinction was small, but the contribution of nitrate aerosol increased significantly (from 17 % on clear days to 23 % on polluted days). (5) The observed mass scattering efficiencies increased consistently with the pollution extent, however, the observed mass absorption efficiencies increased consistently with increasing mass concentration in slightly pollution conditions, but decreased under polluted conditions.

APA, Harvard, Vancouver, ISO, and other styles

31

Elser, Miriam, Benjamin Tobias Brem, Lukas Durdina, David Schönenberger, Frithjof Siegerist, Andrea Fischer, and Jing Wang. "Chemical composition and radiative properties of nascent particulate matter emitted by an aircraft turbofan burning conventional and alternative fuels." Atmospheric Chemistry and Physics 19, no. 10 (May 21, 2019): 6809–20. http://dx.doi.org/10.5194/acp-19-6809-2019.

Full text

Abstract:

Abstract. Aircraft engines are a unique source of carbonaceous aerosols in the upper troposphere. There, these particles can more efficiently interact with solar radiation than at ground. Due to the lack of measurement data, the radiative forcing from aircraft exhaust aerosol remains uncertain. To better estimate the global radiative effects of aircraft exhaust aerosol, its optical properties need to be comprehensively characterized. In this work we present the link between the chemical composition and the optical properties of the particulate matter (PM) measured at the engine exit plane of a CFM56-7B turbofan. The measurements covered a wide range of power settings (thrust), ranging from ground idle to take-off, using four different fuel blends of conventional Jet A-1 and hydro-processed ester and fatty acids (HEFA) biofuel. At the two measurement wavelengths (532 and 870 nm) and for all tested fuels, the absorption and scattering coefficients increased with thrust, as did the PM mass. The analysis of elemental carbon (EC) and organic carbon (OC) revealed a significant mass fraction of OC (up to 90 %) at low thrust levels, while EC mass dominated at medium and high thrust. The use of HEFA blends induced a significant decrease in the PM mass and the optical coefficients at all thrust levels. The HEFA effect was highest at low thrust levels, where the EC mass was reduced by up to 50 %–60 %. The variability in the chemical composition of the particles was the main reason for the strong thrust dependency of the single scattering albedo (SSA), which followed the same trend as the fraction of OC to total carbon (TC). Mass absorption coefficients (MACs) were determined from the correlations between aerosol light absorption and EC mass concentration. The obtained MAC values (MAC532=7.5±0.3 m2 g−1 and MAC870=5.2±0.9 m2 g−1) are in excellent agreement with previous literature values of absorption cross section for freshly generated soot. While the MAC values were found to be independent of the thrust level and fuel type, the mass scattering coefficients (MSCs) significantly varied with thrust. For cruise conditions we obtained MSC532=4.5±0.4 m2 g−1 and MSC870=0.54±0.04 m2 g−1, which fall within the higher end of MSCs measured for fresh biomass smoke. However, the latter comparison is limited by the strong dependency of MSC on the particles' size, morphology and chemical composition. The use of the HEFA fuel blends significantly decreased PM emissions, but no changes were observed in terms of EC∕OC composition and radiative properties.

APA, Harvard, Vancouver, ISO, and other styles

32

Maughan, Richard L., Paul Chuba, Arthur T. Porter, Edgar Ben-Josef, David R. Lucas, and Bengt E. Bjarngard. "Mass energy-absorption coefficients and mass collision stopping powers for electrons in tumors of various histologies." Medical Physics 26, no. 3 (March 1999): 472–77. http://dx.doi.org/10.1118/1.598544.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Ekanayake, Ruwini S. K., Christopher T. Chantler, Daniel Sier, Martin J. Schalken, Alexis J. Illig, Martin D. de Jonge, Bernt Johannessen, Peter Kappen, and Chanh Q. Tran. "High-accuracy measurement of mass attenuation coefficients and the imaginary component of the atomic form factor of zinc from 8.51 keV to 11.59 keV, and X-ray absorption fine structure with investigation of zinc theory and nanostructure." Journal of Synchrotron Radiation 28, no. 5 (July 19, 2021): 1492–503. http://dx.doi.org/10.1107/s1600577521005981.

Full text

Abstract:

High-accuracy X-ray mass attenuation coefficients were measured from the first X-ray Extended Range Technique (XERT)-like experiment at the Australian Synchrotron. Experimentally measured mass attenuation coefficients deviate by ∼50% from the theoretical values near the zinc absorption edge, suggesting that improvements in theoretical tabulations of mass attenuation coefficients are required to bring them into better agreement with experiment. Using these values the imaginary component of the atomic form factor of zinc was determined for all the measured photon energies. The zinc K-edge jump ratio and jump factor are determined and results raise significant questions regarding the definitions of quantities used and best practice for background subtraction prior to X-ray absorption fine-structure (XAFS) analysis. The XAFS analysis shows excellent agreement between the measured and tabulated values and yields bond lengths and nanostructure of zinc with uncertainties of from 0.1% to 0.3% or 0.003 Å to 0.008 Å. Significant variation from the reported crystal structure was observed, suggesting local dynamic motion of the standard crystal lattice. XAFS is sensitive to dynamic correlated motion and in principle is capable of observing local dynamic motion beyond the reach of conventional crystallography. These results for the zinc absorption coefficient, XAFS and structure are the most accurate structural refinements of zinc at room temperature.

APA, Harvard, Vancouver, ISO, and other styles

34

Mužíková, Barbora, Tereza Otcovská, and Pavel Padevět. "WATER ABSORPTION CAPACITY COEFFICIENT AND MASS MOISTURE OF RAMMED EARTH MATERIAL." Acta Polytechnica CTU Proceedings 13 (November 13, 2017): 85. http://dx.doi.org/10.14311/app.2017.13.0085.

Full text

Abstract:

This article presents the development of mass moisture of rammed earth material and determines the water absorption capacity coefficient for rammed earth with illite-kaoline clay. Specimens of two prescriptions were rammed in the moulds. They were settled in the box with soft foam that was moistened. The level of moistening was kept constant. The specimens were regularly measured and weighted. Two measuerements were carried out – one of montmorillonite clay during 13 days and one of illite-kaoline clay during three hours. The development of moisture increase was captured and the water absorption capacity coefficient for illite-kaoline clay was determined and compared to coefficients of common building materials.

APA, Harvard, Vancouver, ISO, and other styles

35

Amaris, Carlos, Maria E. Alvarez, Manel Vallès, and Mahmoud Bourouis. "Performance Assessment of an NH3/LiNO3 Bubble Plate Absorber Applying a Semi-Empirical Model and Artificial Neural Networks." Energies 13, no. 17 (August 20, 2020): 4313. http://dx.doi.org/10.3390/en13174313.

Full text

Abstract:

In this study, ammonia vapor absorption with NH3/LiNO3 was assessed using correlations derived from a semi-empirical model, and artificial neural networks (ANNs). The absorption process was studied in an H-type corrugated plate absorber working in bubble mode under the conditions of an absorption chiller machine driven by low-temperature heat sources. The semi-empirical model is based on discretized heat and mass balances, and heat and mass transfer correlations, proposed and developed from experimental data. The ANN model consists of five trained artificial neurons, six inputs (inlet flows and temperatures, solution pressure, and concentration), and three outputs (absorption mass flux, and solution heat and mass transfer coefficients). The semi-empirical model allows estimation of temperatures and concentration along the absorber, in addition to overall heat and mass transfer. Furthermore, the ANN design estimates overall heat and mass transfer without the need for internal details of the absorption phenomenon and thermophysical properties. Results show that the semi-empirical model predicts the absorption mass flux and heat flow with maximum errors of 15.8% and 12.5%, respectively. Maximum errors of the ANN model are 10.8% and 11.3% for the mass flux and thermal load, respectively.

APA, Harvard, Vancouver, ISO, and other styles

36

Utry, N., T. Ajtai, M. Pintér, E. Tombácz, E. Illés, Z. Bozóki, and G. Szabó. "Mass specific optical absorption coefficients of mineral dust components measured by a multi wavelength photoacoustic spectrometer." Atmospheric Measurement Techniques Discussions 7, no. 9 (September 8, 2014): 9025–46. http://dx.doi.org/10.5194/amtd-7-9025-2014.

Full text

Abstract:

Abstract. Mass specific optical absorption coefficients of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at wavelengths of 1064, 532, 355 and 266 nm. These values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. These results are expected to have considerable importance in global radiative forcing calculations. They can also serve as reference for validating calculated wavelength dependent imaginary parts (κ) of complex refractive indices which up to now have been typically deduced from bulk phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk phase measurements.

APA, Harvard, Vancouver, ISO, and other styles

37

Horvath, Isabelle R., and Siddharth G. Chatterjee. "A surface renewal model for unsteady-state mass transfer using the generalized Danckwerts age distribution function." Royal Society Open Science 5, no. 5 (May 2018): 172423. http://dx.doi.org/10.1098/rsos.172423.

Full text

Abstract:

The recently derived steady-state generalized Danckwerts age distribution is extended to unsteady-state conditions. For three different wind speeds used by researchers on air–water heat exchange on the Heidelberg Aeolotron, calculations reveal that the distribution has a sharp peak during the initial moments, but flattens out and acquires a bell-shaped character with process time, with the time taken to attain a steady-state profile being a strong and inverse function of wind speed. With increasing wind speed, the age distribution narrows significantly, its skewness decreases and its peak becomes larger. The mean eddy renewal time increases linearly with process time initially but approaches a final steady-state value asymptotically, which decreases dramatically with increased wind speed. Using the distribution to analyse the transient absorption of a gas into a large body of liquid, assuming negligible gas-side mass-transfer resistance, estimates are made of the gas-absorption and dissolved-gas transfer coefficients for oxygen absorption in water at 25°C for the three different wind speeds. Under unsteady-state conditions, these two coefficients show an inverse behaviour, indicating a heightened accumulation of dissolved gas in the surface elements, especially during the initial moments of absorption. However, the two mass-transfer coefficients start merging together as the steady state is approached. Theoretical predictions of the steady-state mass-transfer coefficient or transfer velocity are in fair agreement (average absolute error of prediction = 18.1%) with some experimental measurements of the same for the nitrous oxide–water system at 20°C that were made in the Heidelberg Aeolotron.

APA, Harvard, Vancouver, ISO, and other styles

38

Linke, C., O. Möhler, A. Veres, Á. Mohácsi, Z. Bozóki, G. Szabó, and M. Schnaiter. "Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study." Atmospheric Chemistry and Physics Discussions 6, no. 2 (April 11, 2006): 2897–922. http://dx.doi.org/10.5194/acpd-6-2897-2006.

Full text

Abstract:

Abstract. In aerosol chamber experiments optical properties of airborne mineral dust samples of defined size distribution were measured. Extinction coefficients (bext) and mass specific extinction cross sections (σext) were determined for Saharan dust samples from different locations. The results for σext were not very sensitive to the type of dust and varied at λ=550 nm between 3.3±0.4 m2 g−1 and 3.7±0.4 m2 g−1. The absorption coefficients (babs) and mass specific absorption cross sections (σabs) were determined with a novel multi-wavelength photo-acoustic absorption spectrometer (PAS). Between λ=266 nm and λ=1064 nm the derived single scattering albedos (SSA) ranged from 0.63±0.04 to 0.99±0.01. Additionally the chemical and mineralogical composition of the dust samples was analysed with special regard to the iron oxide phases hematite and goethite. At λ=266 nm the mineral dust sample without any detectable iron oxides showed a significantly higher SSA compared to the sample with a hematite content of 0.6 wt-%.

APA, Harvard, Vancouver, ISO, and other styles

39

Prieto, Cristina, Harry Alvarez-Ospina, Dara Salcedo, Telma Castro, and Oscar Peralta. "Mass Absorption Efficiency of PM1 in Mexico City during ACU15." Atmosphere 14, no. 1 (January 3, 2023): 100. http://dx.doi.org/10.3390/atmos14010100.

Full text

Abstract:

From January to March 2015, an atmospheric aerosol measurement campaign, “Aerosoles en Ciudad Universitaria 2015” (ACU15), was carried out in Mexico City to determine the particles’ optical properties and chemical composition. Two photoacoustic spectrometers measured the scattering and absorption coefficient at two different wavelengths. The average absorption coefficient at 532 nm was 12.71 ± 9.48 Mm−1 and at 870 nm was 10.35 ± 7.36 Mm−1. The average scattering coefficient was 65.63 ± 47.12 Mm−1 (532 nm) and 21.12 ± 14.24 Mm−1 (870 nm). The chemical composition was determined via an aerosol chemical speciation monitor. The organic aerosol fraction represented 53% of the total PM1 and was made up of 63% low volatile (4.64 µg m−3), 22% hydrogenated (1.90 µg m−3), and 15% semi-volatile organics (1.54 µg m−3). The correlation coefficient of chemical species (NO3−, NH4+, SO42−, low-volatile, and semi-volatile organics) and optical properties was 0.92. The multilinear regression showed a good agreement among chemical species and optical properties (r > 0.7). The mass absorption coefficient calculated for the measuring site at 870 nm was MAE870 = 5.8 m2 g−1, instead of the default 4.74 m2 g−1. Furthermore, based on the median AAE, the 532 nm MAE532 resulting from the multiple linear regression (MLR) showed the following coefficients: 7.70 m2 g−1 (eBC), 0.22 m2 g−1 (HOA), and 0.16 m2 g−1 (LV–OOA). The coefficients of MLR were: 7.08 m2 g−1 (eBC), 5.83 m2 g−1 (NO3−), 5.69 m2 g−1 (low volatile organic aerosol), 2.78 m2 g−1 (SO42−), 2.40 m2 g−1 (hydrocarbon-like organic aerosol), and 1.04 m2 g−1 (semi volatile organic aerosol).

APA, Harvard, Vancouver, ISO, and other styles

40

Rudinsky, Samantha, Nicholas C. Wilson, Colin M. MacRae, Yu Yuan, Hendrix Demers, Mark A. Gibson, and Raynald Gauvin. "The Impact of Chemical Bonding on Mass Absorption Coefficients of Soft X-rays." Microscopy and Microanalysis 26, no. 4 (May 14, 2020): 741–49. http://dx.doi.org/10.1017/s1431927620001579.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Ovejero, G., R. Van Grieken, L. Rodriguez, and J. L. Valverde. "The use of gas absorption correlations for mass transfer coefficients in distillation processes." International Journal of Heat and Mass Transfer 35, no. 11 (November 1992): 2963–68. http://dx.doi.org/10.1016/0017-9310(92)90316-k.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Sobieszuk, Paweł, and Karolina Napieralska. "Investigations of mass transfer in annular gas-liquid flow in a microreactor." Chemical and Process Engineering 37, no. 1 (March 1, 2016): 55–64. http://dx.doi.org/10.1515/cpe-2016-0006.

Full text

Abstract:

Abstract The paper presents an investigation of mass transfer in gas-liquid annular flow in a microreactor. The microreactor had a meandered shape with a square cross-section of the channel (292×292 μm, hydraulic diameter 292 μm) and 250 mm in length. The rate of CO2 absorption from the CO2/N2 mixture in NaOH (0.1 M, 0.2 M, 0.7 M, 1.0 M and 1.5 M) water solutions was measured. Two velocities of gas flow and two velocities of liquid flow were used. In two cases a fully developed annular flow at the beginning of the channel was observed, whilst in two cases annular flow was formed only in about 2/3 of the microchannel length. Based on the measurements of CO2 absorption rate, the values of volumetric liquid - side mass transfer coefficients with the chemical reaction were determined. Then physical values of coefficients were found. Obtained results were discussed and their values were compared with the values predicted by literature correlations.

APA, Harvard, Vancouver, ISO, and other styles

43

Gurler, O., H. Oz, S. Yalcin, and O. Gundogdu. "Mass absorption and mass energy transfer coefficients for 0.4–10MeV gamma rays in elemental solids and gases." Applied Radiation and Isotopes 67, no. 1 (January 2009): 201–5. http://dx.doi.org/10.1016/j.apradiso.2008.10.001.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Meler, Justyna, Dagmara Litwicka, and Monika Zabłocka. "Variability of light absorption coefficients by different size fractions of suspensions in the southern Baltic Sea." Biogeosciences 20, no. 12 (June 30, 2023): 2525–51. http://dx.doi.org/10.5194/bg-20-2525-2023.

Full text

Abstract:

Abstract. Measurements of light absorption coefficients by particles suspended in seawater (ap(λ)), by phytoplankton (aph(λ)) and detritus (ad(λ)) were carried out in the southern Baltic Sea for the original seawater samples and four size fractions: pico-particles (0.2–2 µm), ultra-particles (2–5 µm), nano-particles (5–20 µm) and micro-particles (20–200 µm). Chlorophyll a (Chl a) and suspended particulate matter (SPM) concentrations were determined. The proportions of particles from the size classes in the ap(443), aph(443) and ad(443) were determined. Pico- and ultra-particles had the largest contribution to the total particle absorption – an average of 38 % and 31 %. Particles of 5–20 µm accounted for approximately 20 % of ap(443) and aph(443) and 29 % of ad(443). The contribution of particles > 20 µm averaged 5 %–10 %. In total SPM contribution of micro-particles averaged 17 %; nano-, ultra- and pico-particles averaged 29 %, 26 % and 27 %, respectively. In total Chl a, the proportions of pico- and ultra-particles averaged 35 % each, nano-particles 16 % and micro-particles 15 %. Temporal and spatial variability of particles contributions in size classes were observed. The average chlorophyll-specific and mass-specific light absorption coefficients, i.e., light absorption coefficients normalized to Chl a or SPM, were determined for all size fractions. The chlorophyll-specific coefficients ap(Chla)(λ), ad(Chla)(λ) and aph(Chla)(λ), ± standard deviations, do not allow clear separation of the individual fractions. For mass-specific coefficients, ap(SPM)(λ), ad(SPM)(λ) and aph(SPM)(λ), it is possible to distinguish between large particles (20–200 µm) and small and medium particles (0.2–20 µm). These results will allow monitoring of suspended matter in size classes in optically complex waters of southern Baltic Sea.

APA, Harvard, Vancouver, ISO, and other styles

45

Roy, Ashis Kumar, Apu Kumar Saha, and Sudip Debnath. "Unsteady Convective Diffusion with Interphase Mass Transfer in Casson Liquid." Periodica Polytechnica Chemical Engineering 62, no. 2 (August 9, 2017): 215. http://dx.doi.org/10.3311/ppch.10328.

Full text

Abstract:

This study aims to examine the dispersion of a passive contaminant of solute released in Casson liquid flow through a tube. The wall of the tube is taken to be chemically active where the flow is driven by the constant pressure gradient. To evaluate the transport coefficients, Aris-Barton’s Moment technique is considered, a finite difference implicit scheme is adopted to handle the differential equation arises in moment methodology. Also to confirm the results obtained by Aris-Barton’s method, the generalized dispersion model has been applied. Unlike the previous studies on dispersion in Casson liquid, the time-dependent behavior of the transport coefficients has been established. Some significant observations have been founded, e.g. exchange coefficient is independent of yield stress while the convection coefficient and dispersion coefficient are inversely proportional to yield stress. Results reveal that transport coefficients are enormously affected by wall absorption.

APA, Harvard, Vancouver, ISO, and other styles

46

Pejanovic, Srdjan, Radmila Garic-Grulovic, and Predrag Bozalo. "Absorption in a three-phase fluidized bed II: Mass transfer investigations." Chemical Industry 57, no. 7-8 (2003): 330–34. http://dx.doi.org/10.2298/hemind0308330p.

Full text

Abstract:

The absorption of carbon dioxide in aqueous diethanolamine solutions was carried out in a three-phase fluidized bed with inert spherical packing. The rate of absorption was calculated on the basis of measuring the concentration change in the liquid phase on-line by a conductivity probe. It was shown that the Danckwerts plot method might be successfully used to simultaneously determine the effective interfacial area and both the gas and liquid-side mass transfer coefficients. While the gas-side mass transfer coefficient is independent of the liquid flow rate, the effective interfacial area and liquid-side mass transfer coefficient increase with increasing liquid flow rate.

APA, Harvard, Vancouver, ISO, and other styles

47

Maceiras, Rocío, Xosé R. Nóvoa, Angeles Cancela, and Estrella Álvarez. "Electrochemical Mass Transfer Measurements of CO₂ in MDEA Solutions." Defect and Diffusion Forum 312-315 (April 2011): 87–92. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.87.

Full text

Abstract:

The mass transfer coefficients at different axial positions in a bubble column have been measured using a conductivity method. Measurements of CO2 absorption in methyldiethanolamine solutions were carried out in a prismatic column 0.06 m side and 1.03 m height. Five electrode pairs were placed at various axial positions in the column. Measurements were conducted at different gas flow rates and amine concentration. It was found that the local mass transfer varied in the axial direction. An experimental model was developed to obtain the absorption rate values using the electrochemical method data. The model agrees quite well with the experimental obtained data.

APA, Harvard, Vancouver, ISO, and other styles

48

Linke, C., O. Möhler, A. Veres, Á. Mohácsi, Z. Bozóki, G. Szabó, and M. Schnaiter. "Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study." Atmospheric Chemistry and Physics 6, no. 11 (August 10, 2006): 3315–23. http://dx.doi.org/10.5194/acp-6-3315-2006.

Full text

Abstract:

Abstract. In aerosol chamber experiments optical properties of resuspended mineral dust samples of defined size distributions were measured. Extinction coefficients (bext) and mass specific extinction cross sections (σext) were determined for Saharan dust samples from different locations. The results for σext were not very sensitive to the type of dust and varied at λ=550 nm between 3.3±0.4 m2 g−1 and 3.7±0.4 m2 g−1. The absorption coefficients (babs) and mass specific absorption cross sections (σabs) were determined with a novel multi-wavelength photo-acoustic absorption spectrometer (PAS). The single scattering albedo was close to 1 (0.98 to 0.99) at 532 nm and 1064 nm, but significantly lower (0.63 to 0.76) at 266 nm. Additionally the chemical and mineralogical composition of the dust samples were analysed with special regard to the iron oxide phases hematite and goethite. At λ=266 nm the mineral dust sample without any detectable iron oxides showed a significantly higher SSA compared to the sample with a hematite content of 0.6 wt-%.

APA, Harvard, Vancouver, ISO, and other styles

49

Xu, Xuezhe, Weixiong Zhao, Qilei Zhang, Shuo Wang, Bo Fang, Weidong Chen, Dean S. Venables, et al. "Optical properties of atmospheric fine particles near Beijing during the HOPE-J<sup>3</sup>A campaign." Atmospheric Chemistry and Physics 16, no. 10 (May 26, 2016): 6421–39. http://dx.doi.org/10.5194/acp-16-6421-2016.

Full text

Abstract:

Abstract. The optical properties and chemical composition of PM1.0 particles in a suburban environment (Huairou) near the megacity of Beijing were measured during the HOPE-J3A (Haze Observation Project Especially for Jing–Jin–Ji Area) field campaign. The campaign covered the period November 2014 to January 2015 during the winter coal heating season. The average values and standard deviations of the extinction, scattering, absorption coefficients, and the aerosol single scattering albedo (SSA) at λ = 470 nm during the measurement period were 201 ± 240, 164 ± 202, 37 ± 43 Mm−1, and 0.80 ± 0.08, respectively. The average values for the real and imaginary components of the effective complex refractive index (CRI) over the campaign were 1.40 ± 0.06 and 0.03 ± 0.02, while the average mass scattering and absorption efficiencies (MSEs and MAEs) of PM1.0 were 3.6 and 0.7 m2 g−1, respectively. Highly time-resolved air pollution episodes clearly show the dramatic evolution of the PM1.0 size distribution, extensive optical properties (extinction, scattering, and absorption coefficients), and intensive optical properties (SSA and CRI) during haze formation, development, and decline. Time periods were classified into three different pollution levels (clear, slightly polluted, and polluted) for further analysis. It was found that (1) the relative contributions of organic and inorganic species to observed aerosol composition changed significantly from clear to polluted days: the organic mass fraction decreased from 50 to 43 % while the proportion of sulfates, nitrates, and ammonium increased strongly from 34 to 44 %. (2) Chemical apportionment of extinction, calculated using the IMPROVE algorithm, tended to underestimate the extinction compared to measurements. Agreement with measurements was improved by modifying the parameters to account for enhanced absorption by elemental carbon (EC). Organic mass was the largest contributor (52 %) to the total extinction of PM1.0, while EC, despite its low mass concentration of ∼ 4 %, contributed about 17 % to extinction. When the air quality deteriorated, the contribution of nitrate aerosol increased significantly (from 15 % on clear days to 22 % on polluted days). (3) Under polluted conditions, the average MAEs of EC were up to 4 times as large as the reference MAE value for freshly generated black carbon (BC). The temporal pattern of MAE values was similar to that of the OC / EC ratio, suggesting that non-BC absorption from secondary organic aerosol also contributes to particle absorption.

APA, Harvard, Vancouver, ISO, and other styles

50

Chan, T. W., L. Huang, W. R. Leaitch, S. Sharma, J. R. Brook, J. G. Slowik, J. P. D. Abbatt, et al. "Observations of OM/OC and specific attenuation coefficients (SAC) in ambient fine PM at a rural site in central Ontario, Canada." Atmospheric Chemistry and Physics 10, no. 5 (March 9, 2010): 2393–411. http://dx.doi.org/10.5194/acp-10-2393-2010.

Full text

Abstract:

Abstract. Ambient particulate matter (PM) samples were collected on quartz filters at a rural site in central Ontario during an intensive study in 2007. The concentrations of organic carbon (OC), pyrolysis organic carbon (POC), and elemental carbon (EC) were determined by thermal analysis. The concentrations are compared to the organic aerosol mass concentration (OM) measured with an Aerodyne C-ToF Aerosol Mass Spectrometer (AMS) and to the particle absorption coefficient (basp) obtained from a Radiance Research Particle Soot Absorption Photometer (PSAP). The total organic mass to organic carbon ratios (OM/OC) and specific attenuation coefficients (SAC=basp/EC) are derived. Proportionality of the POC mass with the oxygen mass in the aerosols estimated from the AMS offers a potential means to estimate OM/OC from thermal measurements only. The mean SAC for the study is 3.8±0.3 m2 g−1. It is found that the SAC is independent of or decrease with increasing particle mass loading, depending on whether or not the data are separated between aerosols dominated by more recent anthropogenic input and aerosols dominated by longer residence time or biogenic components. There is no evidence to support an enhancement of light absorption by the condensation of secondary material to particles, suggesting that present model simulations built on such an assumption may overestimate atmospheric warming by BC.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Mass absorption coefficients'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles