• Particle and aerosol research
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• v.11 no.1
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• pp.1-8
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• 2015

In this study, indoor $PM_{10}$ concentration was measured by different type of real-time instruments in public transport vehicles. Light-scattering method is widely used in measuring the size of particulate matters and there is two types of light-scattering methods; one is the nephelometer type which measures the light-scattering degree by aerosol cloud, the other is the spectrometer type which measures light-scattering degree by individual particle. We observed the variation of $PM_{10}$ in KTX, subway and express bus carriages by 1-minute resolution and found that there is similar tendency in pattern among 4 light-scattering devices but difference in absolute concentrations. By comparing gravimetric result in a subway cabin, the spectrometer type device, C, was chosen as a reference device. The conversion factors of nephelometer device A-1, A-2, and B were 1.666, 1.463 and 2.125 respectively.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.53.2-53.2
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• 2011

A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles indicating the presence of a relativistic accretion disk model. Using a Monte Carlo technique, we compute the linear polarization of a double peaked broad emission line. A Keplerian accretion disk is adopted for the double peak emission line region and the Schwarzschild geometry is assumed in the emission region. Far from the accretion disk where flat Minkowski geometry is appropriate, we place a scattering region in the shape of a spherical shell sliced. We generate a line photon in the accretion disk in an arbitraray direction in the local rest frame and follow the geodesic of the photon until it hits the scattering region. The profile of the polarized flux is mainly determined by the relative location of the scattering region with respect to the emission source. When the scattering region is in the polar direction, the linear degree of polarization also shows a double peak structure. Under a favorable condition we show that up to 1% of linear degree of polarization may be obtained.

• Korean Journal of Optics and Photonics
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• v.3 no.3
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• pp.161-166
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• 1992

The s-polarized laser beam is incident with an angle ~$-30^{\circ}$ to a uniformly rotating rough metal surface and the degree of second order temporal coherence $g_{s}^{(2)}(\tau)$ of the backscattered wave, which has the same polarization with the incident laser beam, is measured. The contribution of shot noise involved in the measurement of $g_{s}^{(2)}(0)$ is subtracted from the photoelectric signal to obtain the accurate value of $g_{s}^{(2)}(0)$.At each scattering angle$\theta_{s}$에서$g_{s}^{(2)}(\tau)$ is almost consistent with the function {1+exp($-\tau^2/\tau_0^2$)}, which is the same result with the case of the laser speckle formed by scattering on the rotating ground glass suface. In addition, a peak in the angular distribution of $\tau_0$ is observed with the maximum at$\theta_s=34^{\circ}$.It is found that the rough metallic scattering with multiple scattering over than 10% has the same function of the degree of second order temporal coherence with that of the ground glass surface scattering where the multiple scattering is ignorably small.

• Korea-Australia Rheology Journal
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• v.12 no.1
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• pp.69-76
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• 2000

We have derived the translation diffusion coefficient and the intrinsic viscosity formula adopting the Kholodenko's theory using 3＋1 dimensional Dirac propagator in the Kirkwood and Riseman scheme. We also performed static light scattering experiments and intrinsic viscosity measurement of dilute solutions of polyimides with different rigidities. In the framework of Kholodenko's theory, we can easily measure the persistence length of polyimide. We prepared five different polyamic acids and polyimides with different degree of imidization by controlling imidization temperatures. From experimental results, we obtained molecular weights and persistence lengths according to the Kholodenko's plot. The molecular weight and the intrinsic viscosity decreased and then increased with the imidization temperature but the persistence length increased monotonically and then leveled off. The persistence lengths calculated from intrinsic viscosities showed very good agreement with those from light scattering experiments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.181-187
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• 1998

The ionization energy and degree of ionization for p-type $Si_{1-x}Ge_x$ with boron doping are calculated taking into account the screening and broadening effects. The drift and Hall mobilities are then calculated using the relaxation time approximation and compared with the previously reported measurement data for relaxed and strained $Si_{1-x}Ge_x$ alloys to estimate the alloy scattering potential. From a fit, the alloy scattering potential is found to be 0.5 eV. The in-plane drift mobility for p-type strained $Si_{1-x}Ge_x$ grown on (001) Si substrate is approximately 1+$10x^2$ times higher than that for bulk Si in the high doping range.

• The Journal of the Acoustical Society of Korea
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• v.22 no.3
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• pp.162-168
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• 2003

The degree of diffusion, characterized by the "scattering coefficient" of surface materials, has been known to be one of the most important factors in determining the acoustical qualities of concert halls. Based on the suggested ISO method, which measures the random-incidence scattering coefficient of surfaces in a diffuse field, the scattering coefficients of different sizes and densities of wooden hemispheres and cubes were measured in model-scale reverberation rooms. As a result, wooden hemispheres with a structural depth of more than 15㎝ have the highest average (500㎐∼4㎑) scattering coefficient. It was also found that the scattering coefficient becomes higher when the diffuser density reaches about 50% for hemispheres and 30% for cubes.

• Journal of Ocean Engineering and Technology
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• v.28 no.4
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• pp.338-344
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• 2014

The purpose of this study was to evaluate the dispersion degree of particles using a nanoindentation test for titanium oxide nanoparticles/epoxy resin nanocomposites. Thus, the effects of the particle size and weight fraction, dispersion agent, and position of the sample on the modulus and degree of particle dispersion in the nanocomposites were investigated. As a result, the dispersion degree of large particles was found to be better than that of smaller particles in composites. It could be found that the aggregation or agglomeration of small particles with large surface energy occurred more easily in nanocomposites because of the large specific surface area. The moduli of the upper side of the film-shaped sample obtained from a nanoindentation test were low scattering, while the values for the bottom side were high scattering. Thus, the dispersion situation of the nanoparticles on the upper side of film-shaped samples could be considered to be better than that for the bottom side. This could be concluded due to the non-uniform nanoparticle dispersion in the same sample. The modulus obtained from nanoindentation test increased slightly with the content of nanoparticles and increased with the indented depth for the same sample. The latter is presumably due to the increase in the accumulated particles facing the indenter with the indented depth. The nanoindentation test was found to be a useful method to evaluate the dispersion status of nanoparticles in nanocomposites.

• Korean Journal of Remote Sensing
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• v.25 no.3
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• pp.255-261
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• 2009

A new polarimetric SAR image classification technique based on the degree of polarization (DoP) and the co-polarized phase-difference (CPD) is presented in this paper. Since the DoP and the CPD of a scattered wave provide information on the randomness of the scattering and the type of scattering mechanisms, at first, the statistics of the DoP and CPD are examined with measured polarimetric SAR image data. Then, a DoP-CPD diagram with appropriate boundaries between six different classes is developed based on the SAR image. The classification technique is verified using the JPL AirSAR and ALOS PALSAR polarimetric data. The technique may have capability to classify an SAR image into six major classes; a bare surface, a village, a crown-layer short vegetation canopy, a trunk-layer short vegetation canopy, a crown-layer forest, and a trunk-dominated forest.

• Journal of The Korean Astronomical Society
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• v.44 no.2
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• pp.59-65
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• 2011

A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles that are well-fitted by a relativistic accretion disk model. We develop a Monte Carlo code to compute the linear polarization of a double peaked broad emission line arising from Thomson scattering. A Keplerian accretion disk is adopted for the double peak emission line region and the geometry is assumed to be Schwarzschild. Far from the accretion disk where flat Minkowski geometry is appropriate, we place an azimuthally symmetric scattering region in the shape of a spherical shell sliced with ${\Delta}{\mu}=0.1$. Adopting a Monte Carlo method we generate line photons in the accretion disk in arbitrary directions in the local rest frame and follow the geodesic paths of the photons until they hit the scattering region. The profile of the polarized flux is mainly determined by the relative location of the scattering region with respect to the emission source. When the scattering region is in the polar direction, the degree of linear polarization also shows a double peak structure. Under favorable conditions we show that up to 0.6% linear polarization may be obtained. We conclude that spectropolarimetry can be a powerful probe to reveal much information regarding the accretion disk geometry of these active galactic nuclei.

• Journal of The Korean Astronomical Society
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• v.40 no.1
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• pp.1-7
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• 2007

About 10 percent of quasars are known to exhibit deep broad absorption troughs blueward of prominent permitted emission lines, which are usually attributed to the existence of outflows slightly above he accretion disk around the supermassive black hole. Typical widths up to 0.2c of these absorption roughs indicate the velocity scales in which special relativistic effects may not be negligible. Under he assumption of the ubiquity of the broad absorption line region in quasars, the broad emission line flux will exhibit Thomson scattered components from these fast outflows. In this paper, we provide our Monte Carlo calculation of linear polarization of singly Thomson scattered line radiation with the careful considerations of special relativistic effects. The scattering region is approximated by a collection of rings that are moving outward with speeds ${\upsilon}=c{\beta}<0.2c$ near the equatorial plane, and the scattered line photons are collected according to its direction and wavelength in the observer's rest frame. We find that the significantly extended red tail appears in the scattered radiation. We also find that the linear degree of polarization of singly Thomson scattered line radiation is wavelength-dependent and hat there are significant differences in the linear degree of polarization from that computed from classical physics in the far red tail. We propose that the semi-forbidden broad emission line C III]1909 may be significantly contributed from Thomson scattering because this line has small resonance scattering optical depth in the broad absorption line region, which leads to distinct and significant polarized flux in this broad emission line.