Showing papers in "Journal of Quantitative Spectroscopy & Radiative Transfer in 2005"

The HITRAN 2008 molecular spectroscopic database

Abstract: This paper describes the contents of the 2016 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2012 and its updates during the intervening years. The HITRAN molecular absorption compilation is composed of five major components: the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, collision-induced absorption data, aerosol indices of refraction, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of accuracy, spectral coverage, additional absorption phenomena, added line-shape formalisms, and validity. Moreover, molecules, isotopologues, and perturbing gases have been added that address the issues of atmospheres beyond the Earth. Of considerable note, experimental IR cross-sections for almost 300 additional molecules important in different areas of atmospheric science have been added to the database. The compilation can be accessed through www.hitran.org. Most of the HITRAN data have now been cast into an underlying relational database structure that offers many advantages over the long-standing sequential text-based structure. The new structure empowers the user in many ways. It enables the incorporation of an extended set of fundamental parameters per transition, sophisticated line-shape formalisms, easy user-defined output formats, and very convenient searching, filtering, and plotting of data. A powerful application programming interface making use of structured query language (SQL) features for higher-level applications of HITRAN is also provided.

Atmospheric radiative transfer modeling: a summary of the AER codes

Abstract: The radiative transfer models developed at AER are being used extensively for a wide range of applications in the atmospheric sciences. This communication is intended to provide a coherent summary of the various radiative transfer models and associated databases publicly available from AER ( http://www.rtweb.aer.com ). Among the communities using the models are the remote sensing community (e.g. TES, IASI), the numerical weather prediction community (e.g. ECMWF, NCEP GFS, WRF, MM5), and the climate community (e.g. ECHAM5). Included in this communication is a description of the central features and recent updates for the following models: the line-by-line radiative transfer model (LBLRTM); the line file creation program (LNFL); the longwave and shortwave rapid radiative transfer models, RRTM_LW and RRTM_SW; the Monochromatic Radiative Transfer Model (MonoRTM); the MT_CKD Continuum; and the Kurucz Solar Source Function. LBLRTM and the associated line parameter database (e.g. HITRAN 2000 with 2001 updates) play a central role in the suite of models. The physics adopted for LBLRTM has been extensively analyzed in the context of closure experiments involving the evaluation of the model inputs (e.g. atmospheric state), spectral radiative measurements and the spectral model output. The rapid radiative transfer models are then developed and evaluated using the validated LBLRTM model.

Direct measurement of the Rayleigh scattering cross section in various gases

Abstract: Using the laser-based technique of cavity ring-down spectroscopy extinction measurements have been performed in various gases straightforwardly resulting in cross sections for Rayleigh scattering. For Ar and N 2 measurements are performed in the range 470–490 nm, while for CO 2 cross sections are determined in the wider range 470–570 nm. In addition to these gases also for N 2 O, CH 4 , CO, and SF 6 the scattering cross section is determined at 532 nm, a wavelength of importance for lidar applications and combustion laser diagnostics. In O 2 the cross section at 532 nm is found to depend on pressure due to collision-induced light absorption. The obtained cross sections validate the cross sections for Rayleigh scattering as derived from refractive indices and depolarization ratios through Rayleigh's theory at the few %-level, although somewhat larger discrepancies are found for CO, N 2 O and CH 4 .

ARTS, the atmospheric radiative transfer simulator

Abstract: ARTS is a modular program that simulates atmospheric radiative transfer. The paper describes ARTS version 1.0, which is applicable in the absence of scattering. An overview over all major parts of the model is given: calculation of absorption coefficients, the radiative transfer itself, and the calculation of Jacobians. ARTS can be freely used under a GNU general public license. Unique features of the program are its scalability and modularity, the ability to work with different sources of spectroscopic parameters, the availability of several self-consistent water continuum and line absorption models, and the analytical calculation of Jacobians.

The 2003 edition of the GEISA/IASI spectroscopic database

Abstract: The content of the current 2003 version, GEISA/IASI-03, of the computer-accessible spectroscopic database, GEISA (Gestion et Etude des Informations Spectroscopiques Atmospheriques: Management and Study of Atmospheric Spectroscopic Information)/IASI (Infrared Atmospheric Sounder Interferometer) is described. The GEISA/IASI-03 system comprises three independent spectroscopic archives related with: an individual line transition spectroscopic parameters sub-database which contains 14 molecules, i.e.: H2O, CO2, O3, N2O, CO, CH4, O2, NO, SO2, NO2, HNO3, OCS, C2H2, N2, representing 51 isotopomers and 702,550 entries, in the spectral range 599-3001 cm-1; an absorption cross-sections sub-database which comprehends 6,572,329 entries related to 6 molecules, i.e.: CFC-11, CFC-12, CFC-14, HCFC-22, N2O5, CCl4; a catalog on micro-physical and optical properties of atmospheric aerosols, mainly refractive indices. The modifications and improvements, made since former editions in terms of database content and management, are detailed. GEISA/IASI is elaborated with the purpose of assessing the IASI (Infrared Atmospheric Sounding Interferometer: http://earth-sciences.cnes.fr/IASI/) measurements capabilities, within the ISSWG (IASI Sounding Science Working Group), in the frame of the CNES (Centre National d'Etudes Spatiales, France)/EUMETSAT (EUropean organization for the exploitation of METeorological SATellites) European Polar System (EPS) preparation. All the archived data can be handled though general and user friendly associated management software facilities, which are interfaced on the ARA (Atmospheric Radiation Analysis)/LMD (Laboratoire de Meteorologie Dynamique) group web site at: http://ara.lmd.polytechnique.fr.

Qpack, a general tool for instrument simulation and retrieval work

Abstract: Remote sensing requires a complete observation system, consisting of the instrument, a forward model and a retrieval environment. This paper presents a software tool to complement atmospheric sensors, with focus on passive instruments operating in the mm and sub-mm wavelength regions. The tool is of general character and offers a complete, flexible and fast calculation environment, demonstrated in both preparatory instrument studies and operational inversions. Its features include a rapid approach for modelling of sensor characteristics, several types of data reduction, simple definition of covariance matrices, a large number of retrieval and error quantities, inversion characterisation and random realisation of measurements. The software is freely available for scientific use.

Influence of the vertical profile of Saharan dust on the visible direct radiative forcing

Abstract: The vertical profile of Saharan dust in the atmosphere is generally characterized by a large aerosol concentration in the mid troposphere, differently from the climatological distribution of other types of particles, that show a peak at the surface and a rapid decrease with height. Saharan dust is also characterized by particles of relatively large size of irregular shape, and variable values of the single scattering albedo (the ratio between radiation scattering and extinction). The dust's peculiar vertical distribution is expected to produce an effect on the calculation of the direct aerosol radiative forcing at the surface and at the top of the atmosphere. This effect is investigated by comparing estimates of aerosol direct visible radiative forcing at the surface and at the top of the atmosphere for dust vertical profiles measured in the Mediterranean, and for the climatological profile. The radiative forcing is estimated by means of an accurate radiative transfer model, and for the ocean surface. The sensitivity of the results on the solar zenith angle, aerosol optical depth, and aerosol absorption is also investigated. The aerosol radiative forcing at the surface shows a very small dependency on the aerosol vertical profile. At the top of the atmosphere, the radiative forcing is weakly dependent on the vertical profile (up to 10% variation on the daily average forcing) for low absorbing particles; conversely, it shows a strong dependency (the daily radiative forcing may vary up to 100%) for absorbing particles. The top of the atmosphere visible radiative forcing efficiency produced by dust having single scattering albedo

Study on Z dependence of partial and total mass attenuation coefficients

Abstract: The partial and total mass attenuation coefficients μ / ρ ( cm 2 g - 1 ) of photons at energy of 1 keV–100 GeV have been calculated as a function of atomic number and photon energies using the XCOM program (version 3.1) and data base and the calculated results were compared with the measurement. The results show that the mass attenuation coefficients ( μ / ρ ) depend on incoming photon energies and Z numbers of the target nuclei.

High-accuracy, compact database of narrow-band k-distributions for water vapor and carbon dioxide

Abstract: An accurate and compact narrow-band k-distribution database has been constructed for water vapor and carbon dioxide from the HITEMP and CDSD-1000 spectroscopic databases. The systematic approach of k-distribution data generation and compaction, storage optimization and interpolation is discussed in this paper. The new database enables the user to obtain narrow-band, part-spectrum and full-spectrum k-distributions for inhomogeneous gas mixtures.

Measurements of positions, strengths and self-broadened widths of H2O from 2900 to 8000 cm−1: line strength analysis of the 2nd triad bands

Abstract: High-resolution spectra of H 2 O were recorded with a Fourier-transform spectrometer covering H 2 O transitions from 2900 to 8000 cm −1 . Over 13,000 absorptions were measured to determine line positions, strengths and self-broadened half-width coefficients. The H 2 16 O line strengths of the (0 3 0)–(0 1 0), (1 1 0)–(0 1 0), (0 1 1)–(0 1 0) and (0 3 0)–(0 0 0), (1 1 0)–(0 0 0), (0 1 1)–(0 0 0) bands were fitted to a quantum mechanical model which involves the interactions between the (0 3 0), (1 1 0), and (0 1 1) vibrational states. Also fitted were experimental strengths of the hot bands; (1 2 0)–(0 1 0) and (0 2 1)–(0 1 0). The model includes 14 dipole matrix elements for B- and A-type transitions. The measured line positions were used along with hot water emission measurements (for the (0 3 0), (0 4 0), and (0 5 0) states of H 2 16 O) in an analysis to obtain high-accuracy energy level values in the (0 3 0), (1 1 0), (0 1 1), (0 4 0), (1 2 0), (0 2 1), (2 0 0), (1 0 1), (0 0 2), and (0 5 0) vibrational states of H 2 16 O and the (1 1 0) and (0 1 1) states of H 2 17 O. Also included were measurements and analysis of self-broadened half-widths for over 4700 absorptions between 4405 and 7729 cm −1 . The results from this investigation provide new information for the noted H 2 17 O bands and present a more accurate representation of the measured H 2 16 O bands.

Ray tracing in absorbing media

Abstract: In ray tracing, it is standard practice to consider solely the real part of any medium's refractive index for determining the changes in a ray's direction at the interface between two media. Any absorption is accounted for by reducing the intensity or weight of the ray in accordance with its propagation distance. This practice is adequate at optical wavelengths where absorption is generally very low but in the infrared and other regimes absorption can be significant and refraction angles and reflectances can deviate substantially from lossless cases. We calculate the quantitative consequence of a more rigorous approach to ray tracing for a lossy wedge and explore the potential differences in results from a Monte Carlo simulation of reflection from a rough, lossy surface. Comparisons between the traditional and complex ray tracing approaches are made and show that there can be significant discrepancies.

Empirical line parameters of methane from 1.1 to 2.1 μm

Abstract: To provide line parameters for the near-infrared methane spectrum, 35,306 line positions and intensities at room temperature were retrieved between 6180 and 9200 cm−1, along with 4936 lines between 4800 and 5500 cm−1. For this, laboratory absorption spectra were recorded at 0.010–0.022 cm−1 resolution using the McMath-Pierce Fourier Transform Spectrometer located on Kitt Peak in Arizona. Positions were calibrated using CO transitions at 2.3 and 1.6 μm and H2O lines at 1.9 and 1.3 μm. The minimum line intensity included was 3.7×10−26 cm−1/(molecule cm−2), and the combined sum of the intensities in these two intervals was 7.085×10−20 cm−1/(molecule cm−2) at 296 (±4) K. Quantum assignments from the literature were matched for 1% of the features, and a new methane database was compiled for the near-infrared.

Spectra calculations in central and wing regions of CO2 IR bands. IV: software and database for the computation of atmospheric spectra

Abstract: In the preceding companion papers a model, based on the impact and the Energy-Corrected Sudden approximations, was proposed for the calculation of the absorption shape of CO 2 in both central and wing regions of infrared bands. It was successfully tested using laboratory measurements as well as atmospheric transmission and emission spectra in the 10– 20 μ m interval. In the present paper, this approach is used to generate a set of suitable parameters and FORTRAN software for the calculation of absorption by CO 2 under atmospheric conditions which can be easily included in radiance/transmission computer codes. This package which includes all bands of significant contribution to atmospheric spectra, is an extension, now accounting for all P, Q, and R lines, of the tools proposed previously for Q branches only. Comparisons between balloon-borne limb emission stratospheric spectra and the results of forward calculations confirm the quality of the tools proposed.

Simulation of whispering-gallery-mode resonance shifts for optical miniature biosensors

Abstract: Finite element analyses are made of the shifts of resonance frequencies of whispering-gallery-mode (WGM) for a fiber–microsphere coupling miniature sensor. The time-domain Maxwell's equations were adopted to describe the near-field radiation transport and solved by the in-plane TE waves application mode of the FEMLAB. The electromagnetic fields as well as the radiation energy distributions can be easily obtained by the finite element analysis. The resonance intensity spectrum curves in the frequency range from 213 to 220 THz were studied under different biosensing conditions. Emphasis was put on the analyses of resonance shift sensitivity influenced by changes of the effective size of the sensor resonator (i.e., microsphere) and/or the refractive index of the medium surrounding the resonator. It is estimated that the WGM biosensor can distinguish molecular size change to the level of 0.1 nm and refractive index change in the magnitude of ∼ 10 - 3 even with the use of a general optical spectrum analyzer of one GHz linewidth. Finally, the potential of the WGM miniature biosensor for monitoring peptide growth is investigated and a linear sensor curve is obtained.

Effects of primary particle diameter and aggregate size distribution on the temperature of soot particles heated by pulsed lasers

Abstract: Temperature histories of nanosecond-pulsed laser-heated soot particles of different primary particle diameters and different aggregate sizes were calculated using an aggregate-based heat transfer model. Relatively low laser fluences were considered to ensure maximum particle temperatures were below about 3800 K to avoid soot particle sublimation. After the laser pulse, the temperature of soot particles in larger aggregates decreases more slowly than that of particles in smaller aggregates due to the increased shielding effect. For a given aggregate size, the temperature of particles of smaller diameter decays faster as a result of a larger surface area-to-volume ratio. The effective temperature of soot particles in the laser probe volume was calculated based on the ratio of thermal radiation intensities of soot particles at 400 and 780 nm to simulate the experimentally measured soot particle temperature using two-color optical pyrometry. The effect of aggregate size distribution of soot particles on the effective particle temperature was investigated under different initial temperatures.

Radiative heat transfer in fire safety science

Abstract: In fire safety science literature thermal radiation is commonly acknowledged as the dominant mode of heat transfer for medium or large scale fires, which determines the growth and spread of a number of fires. This paper is an attempt to overview the contribution of radiative heat transfer research to fire safety science over the last decade, and to highlight the needs for further research.

Entropy generation through radiative transfer in participating media: analysis and numerical computation

Abstract: Thermodynamics’ second law analysis is the gateway for optimization in thermal equipments and systems. Through entropy minimization techniques it is possible to increase the efficiency and overall performance of all kinds of thermal systems. This approach is becoming common practice in the analysis and/or design of thermal equipments. However, evaluation of entropy generation due to radiative transfer in participating media seems to be lacking. Since radiation is the dominant mechanism of heat transfer in high-temperature systems, such omission seems quite unjustifiable. Although the subject of entropy production through radiative transfer has been dealt with for quite some time, notably by Max Planck himself, it has not been approached in the perspective of its numerical calculation in a way that is compatible and coherent with the standard heat transfer approach. In the present work, the issue of entropy generation by radiative transfer in participating media is approached from the view-points of its mathematical modeling and numerical calculation using standard radiative heat transfer techniques, namely the discrete ordinates method. Effects from emission, absorption and scattering are isolated and considered independently.

A T-matrix method and computer code for randomly oriented, axially symmetric coated scatterers

Abstract: A computer code is described for the calculation of light-scattering properties of randomly oriented, axially symmetric coated particles, in the framework of the T-matrix theory. The underlying mathematical background is outlined briefly and convergence procedures are discussed. After outlining the input–output interaction between user and code, benchmark results are presented for two distinct shapes: coated, centered spheroids and offset coated spheres.

Numerical developments for short-pulsed Near Infra-Red laser spectroscopy. Part II: inverse treatment

Abstract: Indirect optical spectroscopy or tomography, that is, mapping of optical properties in scattering and absorption inside a medium given a set of measurements at the boundaries, is highly dependent on the radiative transfer model used to track radiative energy propagation in semi-transparent materials. In the first part of this study, a numerical tool adapted for treating radiative transfer in the frame of short-pulsed laser beam interaction with non-homogeneous matter has been presented. In this paper, it is intended to show how such numerical tools can undergo inversion through adjoint treatment or reverse differentiation. Adjoint models, as well as reverse differentiation, are used in order to allow an efficient computation of the gradient, in the unknown optical parameters space, of an objective or cost function estimating the residual between data obtained at the boundary and predictions by numerical simulations. This gradient is a crucial indication as to update, through line minimization, the set of internal optical properties of the medium. First, the theoretical background of the inverse treatments, both reverse differentiation and adjoint model, for the transient radiative transfer equation model introduced in Part I is developed. Second, different reconstruction configurations are presented. Time-dependent sampling and time filtering effects of the measurements are addressed. Image reconstructions from simulated data are achieved for material phantoms of simple geometry.

Fast radiative transfer modeling for infrared imaging radiometry

Abstract: Fast radiative transfer codes have been developed for simulating the outgoing radiance (and corresponding brightness temperature) to be measured by the Infrared Imaging Radiometer (IIR) of the space Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission. Two simple codes (FASRAD and FASAA), for which scattering is neglected, as well as an accurate code (FASDOM), accounting for scattering and absorption with the Discrete Ordinate Method (DOM), are presented. Their accuracy has been estimated with a reference code including a line-by-line model and the DOM. Simulations have shown that the accuracy is generally better than 0.3 K on the brightness temperature for clear or cloudy atmospheres. This accuracy agrees with the expected one of future IIR measurements. In addition, the impact of scattering on the brightness temperature has been evaluated for semi-transparent liquid clouds in the IIR spectral range. Especially, simulations have shown that cloud microphysics retrieval might be possible with the Brightness Temperature Difference (BTD) between two IIR bands, using the couple of wavelengths (8.7– 12 μ m ) or (10.6– 12 μ m ). However, scattering strongly influences the radiation for shorter wavelengths. The error on the BTD with (8.7– 12 μ m ) can reach 4 K when scattering is neglected, leading to large uncertainties in the retrieval of droplet effective radius.

WWW scattering matrix database for small mineral particles at 441.6 and 632.8nm

Abstract: We present a new extensive database containing experimental scattering matrix elements as functions of the scattering angle measured at 441.6 and 632.8 nm for a large collection of micron-sized mineral particles in random orientation. This unique database is accessible through the World-Wide Web. Size distribution tables of the particles are also provided, as well as other characteristics relevant to light scattering. The database provides the light scattering community with easily accessible information that is useful, for a variety of applications such as testing theoretical methods, and the interpretation of measurements of scattered radiation. To illustrate the use of the database, we consider cometary observations and compare them with (I) cometary analog data from the database, and (2) with results of Mie calculations for homogeneous spheres, having the same refractive index and size distribution as those of the analog data. (C) 2004 Elsevier Ltd. All rights reserved.

Application of principal component analysis to high spectral resolution radiative transfer: A case study of the O2 A band

Abstract: Radiative transfer computation is the rate-limiting step in most high spectral resolution remote sensing retrieval applications. While several techniques have been proposed to speed up radiative transfer calculations, they all suffer from accuracy considerations. We propose a new method, based on a principal component analysis of the optical properties of the system, that addresses these concerns. Taking atmospheric transmission in the O_2A band as a test case, we reproduced the reflectance spectrum at the top of the atmosphere (TOA), obtained using the multiple scattering code DISORT, with an accuracy of 0.3%, while achieving an order of magnitude improvement in speed.

Inverse design methods for radiative transfer systems

Abstract: Radiant enclosures used in industrial processes have traditionally been designed by trial-and-error, a technique that usually demands considerable time to find a solution of limited quality. As an alternative, designers have recently adopted optimization and inverse methodologies to solve design problems involving radiative transfer; the optimization methodology solves the inverse problem implicitly by transforming it into a multivariable minimization problem, while the inverse design methodology solves the problem explicitly using regularization. This paper presents the details of both methodologies, and demonstrates them by solving for the optimal heater settings in an industrially relevant radiant enclosure design problem.

A consistent multigroup model for radiative transfer and its underlying mean opacities.

Abstract: In some regimes, such as in plasma physics or in superorbital atmospheric entry of space objects, the effects of radiation are crucial and can tremendously modify the hydrodynamics of the gas. In such cases, it is therefore important to have a good prediction of the radiative variables. However, full transport solutions of these multi-dimensional, time-dependent problems are too expensive to get to be involved in a coupled configuration. It is hence necessary to develop other models for radiation that are cheap, yet accurate enough to give good predictions of the radiative effects. We will herein introduce the multigroup- M 1 model and look at its characteristics and in particular try to separate the angular error from the frequential one since these two approximation play very different roles. The angular behaviour of the model will be tested on a case proposed by Su and Olson and used by Olson et al. to compare various moments and (flux-limited) diffusion models. For the frequency behaviour, we use a simplified flame test-case and show the importance of taking good mean opacities.

Finite element method for radiative heat transfer in absorbing and anisotropic scattering media

Abstract: This article proposes a finite element method (FEM) for simulation of radiative heat transfer in absorbing, emitting and anisotropic scattering media. This simulation is developed on the base of discrete ordinates method and theories of finite element. The finite element formulations of triangle isoparametric element and detailed steps of numerical calculation are given. Unstructured triangular element grids are employed in spatial discretization, azimuthal discretization strategy is used in the angular discretization. Two efficient iterative solvers are employed to solve the sparse equations of FEM. Some typical two-dimensional problems are used to verify the method. Pure absorbing cases and anisotropic scattering cases with four different scattering phase functions are investigated and analyzed. A simple irregular geometry case is also used to verify the method. The results of present research have a good agreement with the Monte-Carlo method or published reference.

Semi-empirical calculation of air-broadened half-widths and air pressure-induced frequency shifts of water-vapor absorption lines

Abstract: This paper describes a semi-empirical calculation of the air-broadened half-widths and the air pressure-induced frequency shifts for the H216O isotopologue. This semi-empirical calculation is based on fits of several recent high-quality measurements and theoretical calculations to the first-order terms in the expansion of the complex Robert–Bonamy (CRB) equations, which yields a second- and first-order polynomial function of the differences in the upper- and lower-state vibrational quantum numbers for the half-width and line shift, respectively. The aim of this work was to obtain a complete set of air-broadened half-widths and air pressure-induced frequency shifts for transitions of H216O present in the HITRAN database from microwave to the visible in order to supplement the observed and calculated values. For around 700 sets of rotational quantum numbers ( J ′ K a ′ K c ′ ← J ″ K a ″ K c ″ ), semi-empirical coefficients describing the vibrational dependence of the air-broadened half-widths and the air pressure-induced frequency shifts have been obtained directly from the fit of experimental and/or theoretical data. The accuracy of the parameters deduced from this calculation is estimated to be between 5% and 10% for the air-broadened half-widths and between 0.001 and 0.01 cm - 1 atm - 1 for the air pressure-induced frequency shifts. For sets of rotational quantum numbers for which either none or insufficient experimental/theoretical data were available to deduce a vibrational dependence, further approximations have been used to obtain a complete set of semi-empirical coefficients.

Collisional parameters of H2O lines: effect of temperature

Abstract: High-resolution Fourier transform spectra of H 2 O –air mixtures have been measured at 296, 742, and 980 K for total pressures of 0.5 and 1.0 atm in the region of the ν 2 band. From these recordings, air-broadening coefficients have been determined for the doublet lines with K c = J . From these data and previous experimental determinations, line-broadening parameters γ ( T ) are obtained at all three temperatures for the doublet lines from J = 0 up to 16. These values are then used to deduce the temperature-dependence exponent n such that γ ( T ) = γ ( 296 ) × ( 296 / T ) n . The values of n obtained using the two elevated temperatures are consistent and show that line widths decrease with T for small J-values ( n ≈ + 0.8 ) , are almost temperature independent on T for J ≈ 10 , and increase with T for high J lines ( n ≈ - 0.3 for J ≈ 15 ). This original result, which confirms theoretical predictions made about 15 years ago with a semi-classical approach (J. Chem. Phys. 86 (1987) 144), is analyzed here using an improved version of the model. Comparisons between measured and computed widths show that calculations cannot correctly reproduce the experimental results at all temperatures simultaneously. This failure is attributed to the use of an inappropriate interaction potential and to the very strong dependence of the broadening γ ( v ) on the relative velocity v for high J lines. This strong variation of γ ( v ) raises the question (which is discussed here) of what calculated quantity is to be compared with measured values (i.e. γ [ v ¯ ( T ) ] , [ γ ( v ) ] ¯ ( T ) , or some other more complex mean to account for the velocity averaging of the spectral profile itself?). Nevertheless, when the temperature exponent n is considered, satisfactory agreement between experiments and predictions is obtained, particularly when the averaging of widths over the relative velocity distribution is made.

Effective atomic numbers for CoCuNi alloys using transmission experiments

Abstract: Effective atomic numbers for CuCoNi alloys against changing Ni contents were measured in the X-ray energy range from 15.746 to 40.930 keV. The gamma rays emitted a 241 Am point source have been send on absorbers to be used transmission arrangement. The X-rays were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. The compositions of the Ni films were determined to be 0.03, 0.47, 0.62, 1.23, 1.22 and 1.6 by a scanning electron microscopy in CuCoNi alloys prepared against changing Ni contents. CoCuNi alloy films were prepared with an electrodeposition technique. Also, the total effective atomic numbers of each alloy were estimated using mixture rule. The measured values were compared with estimated values for alloys.

On radiative transfer in water spray curtains using the Discrete Ordinates Method

Abstract: Radiative transfer through water spray curtains has been presently addressed in conditions similar to devices used in fire protection systems. The radiation propagation from the heat source through the medium is simulated using a 2D Discrete Ordinates Method. The curtain is treated as an absorbing and anisotropically scattering medium, made of droplets injected in a mixing of air, water vapor and carbon dioxide. Such a participating medium requires a careful treatment of its spectral response in order to model the radiative transfer accurately. This particular problem is dealt with using a correlated-K method. Radiative properties for the droplets are calculated applying the Mie theory. Transmissivities under realistic conditions are then simulated after a validation thanks to comparisons with some experimental data available in the literature. Owing to promising results which are already observed in this case of uncoupled radiative problem, next step will be to combine the present study with a companion work dedicated to the careful treatment of the spray dynamics and of the induced heat transfer phenomena.

Reverse Monte Carlo simulations of light pulse propagation in nonhomogeneous media

Abstract: This paper presents a follow-up study of our previous work on the reverse Monte Carlo solution of transient radiation transport in the homogeneous media. In this study, the method is extended to consider nonhomogeneous media, which exist in many practical problems. The transport process of ultra-short light pulse propagation inside the non-emitting, absorbing, and anisotropically scattering multi-layer media is studied. Although only one-dimensional geometry is treated here, the method is applicable and easy to extend to multi-dimensional geometries. In multi-layer media, the time-resolved reflectance exhibits a direct correlation between the signal magnitude and the travel time to the layer interface if the ballistic photons encounter a strongly scattering layer. Furthermore, it is found that even with a symmetric radiative property distribution in a three-layer medium, the reflectance and transmittance signals do not converge at long time when the mid-layer is optically thick. The long time slope of the temporal signal does not provide the specificity required for an inverse analysis parameter as stipulated by earlier studies.