• Title/Summary/Keyword: scattering effect

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Asymmetric Absorption Profile of Damped Lyman Alpha and Beta Systems

  • Lee, Hee-Won
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.79.1-79.1
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    • 2012
  • Due to the quantum interference of many atomic levels, the exact scattering cross section around a given resonance transition deviates from the Lorentz function when the frequency of the incident radiation is quite far from the resonance frequency. This atomic effect is quite significant in the case of damped Ly alpha systems, where HI column density is in excess of 10^20 cm^-2. In this poster, we present the deviation quantitatively taking into consideration of the Rayleigh and Raman scattering around Lyman alpha and Lyman beta.

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Development of New Ultrasonic Transducer for Coarse-Grained Materials (Coarse Grain 소재용 초음파 변환기 개발)

  • Kim, B.G.;Lee, J.O.;Lee, S.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.10 no.1
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    • pp.18-23
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    • 1990
  • In materials with the large grain size, ultrasonic waves are highly attenuated by the grain boundary acting as scattering centers due to discontinuity of elastic constant. In this study, the improved probes were developed so that they minimized the effect of grain scattering in order to detect deep flaws in coarse grained materials. As the result, the developed ultrasonic transducers showed the better sensitivity and signal to noise ratio when compared with the commercial probes in testing the interior of coarse grained material.

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Analysis of Complex Forced Raleigh Scattering Decay Profiles for the Diffusion of Methyl Yellow in Binary Solution

  • 박하선;성정문;이현정;장태현;Daniel R. Spiegal
    • Bulletin of the Korean Chemical Society
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    • v.18 no.9
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    • pp.1006-1010
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    • 1997
  • The nature and analysis methods of complicated decay profiles found in forced Rayleigh scattering (FRS) have been investigated for the probe diffusion of methyl yellow in 2-propanol. The complementary shifted and ground state grating effect, which is known to be the origin of non-single exponential decays, was analyzed by non-linear regression fitting to a double exponential model function. We confirmed that the parameters were highly correlated so that it was difficult to extract a unique set of parameters in the presence of experimental noise. Nevertheless, a reasonable range of decay time constants could be estimated from the grating spacing dependence.

A Spectral Inverse Scattering Technique with Series-Expanded Field in Dirlectric Object (유전체 내의 전계를 급수전개로 표시한 모멘트 방법을 적용한 파수영역의 역산란 방법)

  • 최현철
    • Proceedings of the Optical Society of Korea Conference
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    • 1989.02a
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    • pp.147-151
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    • 1989
  • A spectral inversion scheme, based on the moment-method procudure with series-expanded field within each cell by dividing the dielectric object into a small number os rectangular cells with large area, is developed to regularize the ill-posedness inherent in inverse scattering problems. One of the interesting features on the presented scheme is that the relative dielectric constant may be obtained by averaging over each cell. This averaging is expected to play an important role in regularizing the high-frequency effect due to noise.

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The Effect of the Intake Flow on the Spray Structure of a High Pressure 11-Hole Fuel Injector in a DISI Engine (직접분사식 가솔린 기관에서 흡입유동이 고압 11공 연료분사기의 분무형상에 미치는 영향)

  • Kim, Seong-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.9
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    • pp.722-727
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    • 2009
  • The effect of the intake flow on the spray structure of a high pressure 11-hole fuel injector were examined in a single cylinder optical direct injection spark ignition (DISI) engine. The effects of injection timing and in-cylinder charge motion were investigated using the 2-dimensional Mie scattering technique. It was confirmed that in the homogeneous charge mode, the in-cylinder swirl charge motion played a major role in the fuel spray distribution during the induction stroke rather than the tumble flow. But, in the stratified charge mode, the effect of the in-cylinder charge was not so large that the injected spray pattern was nearly maintained and the increase of in-cylinder pressure by the upward moving piston reduced the fuel spray penetration.

Chemical Composition of Fine Aerosol Associated with Visibility Degradation in Seoul Metropolitan Area in 1994 (1994년 수도권 지역에서의 시정과 미세 입자상물질 화학조성과의 관계해석)

  • 한진석;김병곤;김신도
    • Journal of Korean Society for Atmospheric Environment
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    • v.12 no.4
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    • pp.377-387
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    • 1996
  • This study was carried out to monitor the visibility including measurement and analysis of the various parameters such as particle size distribution, chemical composition, and meteorotical conditions to understand the characteristics and causes of this phenomenon. According to the analysis of intensive sampling, $SO_4^{2-}, NO-3^-, Cl^-, NH_4^+$ ion concentration increased together with the mass concentration around 1 $\mu$m in the case of low visibility. $(NH_4)_2SO_4, NH_4NO_3$, and $NH_4Cl$ were thought to be the major components of fine particles. The statistical analysis showed that the scattering effect of particle was 81.2%, the absorption effect was 14.9%. Therefore, these effects were the major factors to reduce the visibility. In conclusion, the visibility was reduced by the fine particle of sulfate (18.6%), nitrate (14.2%), organic carbon (10.8%), element carbon (25.8%), and residual (24.8%) during this study.

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Image Enhancement Algorithm and its Application in Image Defogging

  • Jun Cao
    • Journal of Information Processing Systems
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    • v.19 no.4
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    • pp.465-473
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    • 2023
  • An image enhancement algorithm and image defogging method are studied in this paper. The formation of fog and the characteristics of fog image are analyzed, and the fog image is preprocessed by histogram equalization method; then the additive white noise is removed by foggy image attenuation model, the atmospheric scattering physical model is constructed, the image detail characteristics are enhanced by image enhancement method, and the visual effect of defogging image is enhanced by guided filtering method. The proposed method has a good defogging effect on the image. When the number of training iterations is 3,000, the peak signal-to-noise ratio of the proposed method is 43.29 dB and the image structure similarity is 0.9616, indicating excellent image defogging effect.

An Experimental Study of Silica Particle Growth in a Coflow Diffusion Flame Utilizing Light Scattering and Local Sampling Technique (II) - Effects of Diffusion - (광산란과 입자포집을 이용한 동축류 확산화염 내의 실리카 입자의 성장 측정(II) - 확산의 영향 -)

  • Cho, Jaegeol;Lee, Jeonghoon;Kim, Hyun Woo;Choi, Mansoo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.9
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    • pp.1151-1162
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    • 1999
  • The effects of radial heat and $H_2O$ diffusion on the evolution of silica particles in coflow diffusion flames have been studied experimentally. The evolution of silica aggregate particles in coflow diffusion flames has been measured experimentally using light scattering and thermophoretic sampling techniques. The measurements of scattering cross section from $90^{\circ}$ light scattering have been utilized to calculate the aggregate number density and volume fraction using with combination of measuring the particle size and morphology through the localized sampling and a TEM image analysis. Aggregate or particle number densities and volume fractions were calculated using Rayleigh-Debye-Gans and Mie theory for fractal aggregates and spherical particles, respectively. Flame temperatures and volumetric differential scattering cross sections have been measured for different flame conditions such as inert gas species, $H_2$ flow rates, and burner injection configurations to examine the relation between the formation of particles and radial $H_2O$ diffusion. The comparisons of oxidation and flame hydrolysis have also been made for various $H_2$ flow rates using $N_2$ or $O_2$ as a carrier gas. Results indicate that the role of oxidation becomes dominant as both carrier gas($O_2$) and $H_2$ flow rates increases since the radial heat diffusion precedes $H_2O$ diffusion in coflow flames used in this study. The effect of carrier gas flow rates on the evolution of silica particles have also been studied. When using $N_2$ as a carrier gas, the particle volume fraction has a maximum at a certain carrier gas flow rate and as the flow rate is further increased, the hydrolysis reaction Is delayed and the spherical particles finally evolves into fractal aggregates due to decreased flame temperature and residence time.

Studies on the Wave Propagation and Fluctuation in Randomly Ditribution Media of L-Aspartic Acid (L-Aspartic Acid의 무질서하게 분포된 매질에서 파동전개와 변동에 관한 연구)

  • Kim, Ki-Jun;Lee, Joo-Youb
    • Journal of the Korean Applied Science and Technology
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    • v.29 no.1
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    • pp.122-128
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    • 2012
  • The influences of fluorescence, scattering, and flocculation in turbid material by light scattering of L-aspartic acid, preservative and emulsifier were interpreted for the scattered fluorescence intensity and wavelength. They have been studied the molecular properties by the spectroscopy of laser induced fluorescence (LIF) and flocculation. The effects of optical properties in scattering media have been found by the optical parameters(${\mu}_s$, ${\mu}_a$, ${\mu}_t$). Flocculation is an important step in many solid-liquid separation processes and is widely used. When two particles approach each other, interactions of several colloid particles can come into play which may have major effect on the flocculation and LIF process. The values of scattering coefficient ${\mu}_s$ are large by means of the increasing scattering of scatterer, The values have been found that the slope decays exponentially as a function of concentration from laser source to detector by our experimental result. It may also aid in designing the best model for oil chemistry, bio-pharmaceutical products, laser medicine and application of medical engineering on LIF and coagulation in particle transport mode.

A Study on the Measurements of Beam Wave Propagation and Fluorescence Spectroscopy in Particles Media (입자매질에서 빔파동전파와 형광분광 측정에 관한 연구)

  • Kim, Ki-Jun;Lee, Jou-Youb;Sung, Wan-Mo
    • Journal of the Korean Applied Science and Technology
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    • v.31 no.2
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    • pp.167-175
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    • 2014
  • The influences of fluorescence, scattering, and flocculation in turbid material were interpreted for the scattered fluorescence intensity and wavelength, it has been studied the molecular properties by the spectroscopy of laser induced fluorescence(LIF). The effects of optical properties in scattering media have been found by the optical parameters(${\mu}_s$, ${\mu}_a$, ${\mu}_t$). Flocculation is an important step in many solid-liquid separation processes and is widely used in Photodynamic therapy. The interactions of several colloid particles can come into play which have major effect on the flocculation and LIF process. We measured scattering and fluorescence spectra of the sample for in vitro as function of concentration from lase source to detector. The value of scattering coefficient ${\mu}_s$ is large by means of the increasing particles of scatterer. Therefore, Phorphyrin A is larger than Phorphyrin C in scattering intensity ${\mu}_s$, but Phorphyrin A is smaller than Phorphyrin C in penetration depth ${\delta}$.