• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.952-964
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• 1992

The interaction of natural convection and radiation heat transfer in a two dimensional square enclosure containing absorbing, emitting and linear anisotropically scattering gray medium is numerically analyzed. P-1 and P-3 approximation is introduced to calculate radiation heat transfer. The effects of scattering albedo, wall emissivity, scattering anisotropy, and optical thickness on the characteristics of the flow and temperature field and heat transfer are investigated. Temperature and velocity profiles depend a great deal on the scattering albedo, and the importance of this effect increases with decrease in albelo. Planck number is another important parameter in radiation heat transfer. The increase in scattering albedo increases convection heat transfer and decreases radiation heat transfer at hot wall. However, the increase in scattering albedo decreases both convection and radiation heat transfer at cold wall. The increase in optical thickness decreases radiation heat transfer. The scattering anisotropy has important effects on the radiation heat transfer only. The highly forward scattering leads to an increase of radiation heat transfer whereas the highly backward scattering leads to an decrease of radiation heat transfer. The effect of scattering anisotropy decreases when reducing the wall emissivity.

• Ocean and Polar Research
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• v.26 no.2
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• pp.133-143
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• 2004

For the purpose of understanding the cloud scattering effect of UV radiation at King Sejong station In West Antarctica, we analyzed the data measured by UV-Biometer at surface and compared its result with solar radiation model. The parameterization of UV radiation by cloud ice crystal was applied to solar radiation model and the sensitivity of this model for the variation of ice crystal was tested. The cloud optical thickness was calculated by using this solar radiation model. It was compared the result from calculation with CERES satellite data. In solar radiation model, the UV radiation was less scattered with increase of ice crystal size in cloud and this scattering effect was more important to UV-A radiation than Erythemal UV-B radiation. But scattering effects by altitude of cloud was not serious. The calculated cloud optical thicknesses in Erythemal UV-B and UV-A region were compared with CERES satellite data and the result by UV-A was more accurate than Erythemal UV-B region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.8
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• pp.2681-2692
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• 1996

The finite-volume method for radiation in a three-dimensional non-orthogonal gas turbine combustion chamber with absorbing, emitting and anisotropically scattering medium is presented. The governing radiative transfer equation and its discretization equation using the step scheme are examined, while geometric relations which transform the Cartesian coordinate to a general body-fitted coordinate are provided to close the finite-volume formulation. The scattering phase function is modeled by a Legendre polynomial series. After a benchmark solution for three-dimensional rectangular combustor is obtained to validate the present formulation, a problem in three-dimensional non-orthogonal gas turbine combustor is investigated by changing such parameters as scattering albedo, scattering phase function and optical thickness. Heat flux in case of isotropic scattering is the same as that of non-scattering with specified heat generation in the medium. Forward scattering is found to produce higher radiative heat flux at hot and cold wall than backward scattering and optical thickness is also shown to play an important role in the problem. Results show that finite-volume method for radiation works well in orthogonal and non-orthogonal systems.

• Journal of radiological science and technology
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• v.44 no.6
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• pp.629-633
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• 2021

This article is designed to look into the radiation exposure dose to each body part and the shielding effect for workers using an additional shielding to reduce their radiation exposured by scattering radiation which is generated in a space between the operating table and lead curtain during interventional radiology(IR) procedures. After placing a human phantom on the table of SIEMENS' angiography machine, the following measurements were taken, depending on the presence of an additional shield of lead equivalent of 0.25 mmPb, manufactured for this purpose: dose to gonad, dose to an area where the personal dosimeter is placed, and dose to an area of eye lens is located. An ion chamber(chamber volume 1,800 cc) was utilized to measure scattering radiation. The two imaging tests were carried out as follows: fluoroscopy of the abdomen (66 kV, 100 mA, 60 seconds) and of the head (70 kV, 65 mA, 60 seconds); and digital subtraction angiography(DSA) of the abdomen (67 kV, 264 mA, 20 seconds) and of the head (79 kV, 300 mA, 20 seconds). In all the experiments, the shielding efficiency of the gonad position was the largest at 59.8%. In case an additional shielding was used as protection against scattering radiation that came through the operating table and the lead curtain during an IR, the radiation shielding efficiency was estimated to be up to 59.8%, leading to a conclusion that its presence may effectively reduce the radiation exposure dose of medical staffs.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1297-1303
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• 2021

Most thickness measurement techniques using X-ray radiation are unsuitable in field processes involving fast-moving organic films. Herein, we propose a Compton scattering X-ray radiation method, which probes the light elements in organic materials, and a new simple, non-destructive, and non-contact calibration-free real-time film thickness measurement technique by setting up a bench-top X-ray thickness measurement system simulating a field process dealing with thin flexible organic films. The use of X-ray fluorescence and Compton scattering X-ray radiation reflectance signals from films in close contact with a roller produced accurate thickness measurements. In a high-thickness range, the contribution of X-ray fluorescence is negligible, whereas that of Compton scattering is negligible in a low-thickness range. X-ray fluorescence and Compton scattering show good correlations with the organic film thickness (R² = 0.997 and 0.999 for X-ray fluorescence and Compton scattering, respectively, in the thickness range 0-0.5 mm). Although the sensitivity of X-ray fluorescence is approximately 4.6 times higher than that of Compton scattering, Compton scattering signals are useful for thick films (e.g., thicker than ca. 1-5 mm under our present experiment conditions). Thus, successful calibration-free thickness monitoring is possible for fast-moving films, as demonstrated in our experiments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.826-830
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• 2010

This study examined the effect of the scattering dose on the thyroid during a mammography examination. One hundred subjects for a mammography examination were enrolled in this study. The average glandular dose (AGD) and thyroid scattering dose (TSD) were measured. Statistical analysis was carried out using the percentage, t-test and co-variance. The mean radiation exposure to the breast and thyroid was $1.08{\pm}0.16$ and $0.14{\pm}0.04$ mGy, respectively. The percentage TSD to the AGD was 31.19%. There was no difference between the Rt. and Lt., and CC to MLO, and radiation dose to the TSD was 13.78% of the breast. Therefore, the volume of radiation exposure to the thyroid was 54.12% in a single routine mammography examination. These results suggest that the TSD was increased by increasing radiation dose to the breast. A thyroid protector is considered necessary to decrease the level of radiation exposure.

• Publications of The Korean Astronomical Society
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• v.25 no.4
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• pp.113-118
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• 2010

The Henyey-Greenstein (H-G) phase function, which is characterized by a single parameter, has been generally used to approximate the realistic dust-scattering phase function in investigating scattering properties of the interstellar dust. Draine (2003) proposed a new analytic phase function with two parameters and showed that the realistic phase function is better represented by his phase function. If the H-G and Draine's phase functions are significantly different, using the H-G phase function in radiative transfer models may lead to wrong conclusions about the dust-scattering properties. Here, we investigate whether the H-G and Draine's phase functions would indeed produce significant differences in radiative transfer calculations for two simple configurations. For the uniformly distributed dust with an illuminating star at the center, no significant difference is found. However, up to ~ 20% of difference is found when the central star is surrounded by a spherical-shell dust medium and the radiation of $\lambda$ < $2000\;{\AA}$ is considered. It would mean that the investigation of dust-scattering properties using the H-G phase function may produce errors of up to ~ 20% depending on the geometry of dust medium and the radiation wavelength. This amount of uncertainty would be, however, unavoidable since the configurations of dust density and radiation sources are only approximately available.

• Atmosphere
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• v.23 no.1
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• pp.39-45
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• 2013

A parameterization for the scattering of longwave radiation by ice clouds has been developed based on spectral scattering property calculations with shapes and sizes of ice crystals. For this parameterization, the size distribution data by Fu (1996) and by Michell and Arnott (1994) are used. The shapes of ice crystal considered in this study are plate, solid column, hollow column, bullet-rosette, droxtal, aggregate, and spheroid. The properties of longwave scattering by ice crystals are presented as a function of the extinction coefficient, single-scattering albedo, and asymmetry factor. The heating rate and flux by the radiative parameterization model are calculated for wide range of ice crystal sizes, shapes, and optical thickness. The results are compared with the calculated results using a six-stream discrete ordinate scattering algorithm and Chou's method. The new method (with various habits and size distributions) provides a good simulation of the scattering properties and cooling rate in optically thin clouds (optical thickness < 5). Depending on the inclusion of scattering by ice clouds, the errors in the calculation of the cooling rates are significantly different.

• Journal of radiological science and technology
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• v.5 no.1
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• pp.21-34
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• 1982

When unattenuated x-ray radiation passes through the object it is transmitted and scattered from objectes and impinging on the film. During this process certain radiation is absorbed within the object and others transmitted in reduced scattering. The scattering radiation influence upon radiation image quality, confining x-ray beam which means scattering radiation produce increased fog on x-ray film image and as a consequence decrease contrast and less detail of the film there for the elimination of fog and for absorbing scattered radiation, the grid has been used between the object and the film in order to rid of scattering rays. Using grid is good method for the qualification of the better image as well as in using air gap technique. The grid is easy to manipulate and promote good efficiency which is defined by ICRU and JIS. It is the purpose to study for eliminating scattered radiation from the tissue equivalent acryl phantom using grid, we have studied and evaluated the grid permeability about the x-ray exposure, the selection of grid ratio according to phantom thickness, on x-ray exposure are performed as follows. 1. The penetrating ratio of primary x-ray is remarkably decreased by increasing of the grid ratio, but it is almost not influenced in KVP difference and phantom thickness. 2. The scattered radiation is proportionaly increased by thickness of the phantom, having nothing to do with grid ratios. 3. The relative between the penetration rate of primary and secondary x-ray is improved by increasing grid ratio, and decreased by phantom thickness, and slightly decreased by high tube voltage. 4. The grid of 5:1 and 10:1 ratio are adequate to the phantom of 10cm and 15cm thickness, respectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.6
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• pp.658-662
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• 2001

The classification of surface flaw types was performed on the basis of angular dependence of backscattered ultrasound. The copper line adhered on the surface, cower line filled in groove, pure groove and the normal edge were adopted as various surface flaw patterns of glass specimen. A backward longitudinal profile was formed probably by the longitudinal wane scattering at and near 1st critical angle. The wave trains at the peak angles of the backward radiation profiles showed different shapes according to the superposition ratio of scattered and leaky waves. The asymmetry of the backward radiation profile arose due to the scattering effect of flaw. The additive resonance effect of copper line appeared in the left side of the profile. The peak angles of both the longitudinal and radiation profiles were shifted toward small angle by the scattering effect.