• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.23.1-23.1
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• 2008

A space shuttle with a Prototype Synchrotron Radiation Detector (PSRD) was launched in 2001. PSRD was set in the Endeavour payloads and got data for 12 days. The purpose of PSRD is to measure synchrotron photons which are created by high energy charged particles near earth. Synchrotron photons are confused with background photons. We studied how to separate synchrotron photons from backgrounds.

• Korean Journal of Environmental Biology
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• v.35 no.4
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• pp.622-630
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• 2017

The induction of regeneration and the maturation of the free-living gametophytes of Undaria pinnatifida were studied at temperatures(5, 10, 15 and $20^{\circ}C$), irradiance (5, 10, 20 and $40{\mu}mol\;photons\;m^{-2}\;s^{-1}$) and photoperiods (14 : 10, 12 : 12 and 10 : 14 h L: D). Female gametophyte fragments were maintained in active regeneration without them reaching sexual maturity under conditions of $15^{\circ}C$, $20{\mu}mol\;photons\;m^{-2}\;s^{-1}$, 10 : 14 h (L : D); by contrast, the conditions for male gametophytes were slightly different at $15^{\circ}C$, $5{\mu}mol\;photons\;m^{-2}\;s^{-1}$, 14 : 10 h (L: D). The sexual maturation of female and male gametophytes took place under $5^{\circ}C$, $20-40{\mu}mol\;photons\;m^{-2}\;s^{-1}$, 10 : 14 h (L : D) and $15^{\circ}C$, $40{\mu}mol\;photons\;m^{-2}\;s^{-1}$, 10 : 14 h (L : D), respectively. These results provide basic information for controlling the regeneration and maturation of free-living gametophytes for srain improvement as well as the cross breeding of U. pinnatifida.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.576-583
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• 2018

Investigation of optimal temperature, irradiance and photoperiod conditions for free-living gametophytes of Saccharina sculpera for natural resources conservation and mass cultivation of endangered species in the eastern coast of Korea. Induction of regeneration and maturation of the free-living gametophytes of S. sculpera were cultured at temperatures (5, 10, 15, 20 and $25^{\circ}C$), irradiance (10, 20, 40, 60 and $80{\mu}mol\;photons\;m^{-2}\;s^{-1}$ and photoperiods (14:10, 12:12 and 10:14 h L:D). The female gametophyte were actively regenerated without reaching sexual maturity under $10^{\circ}C$, $20{\mu}mol\;photons\;m^{-2}\;s^{-1}$ and 12:12 h (L:D) conditions. In contrast, the conditions for male gametophytes were slightly different at $15^{\circ}C$, $10{\mu}mol\;photons\;m^{-2}\;s^{-1}$ and 12:12 h (L:D). The sexual maturation of female and male gametophytes took place under $15^{\circ}C$, $40{\mu}mol\;photons\;m^{-2}\;s^{-1}$, 14:10 h (L:D) and $10^{\circ}C$, $20{\mu}mol\;photons\;m^{-2}\;s^{-1}$, 10:14 h (L:D), respectively. These results provide basic information for controlling the regeneration and maturation of free-living gametophytes for conservation and utilization of S. sculpera.

• Journal of the Korea Computer Graphics Society
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• v.16 no.3
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• pp.41-48
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• 2010

Photon mapping is a traditional global illumination method using many photons emitted from the light source for photo-realistic rendering. However, this method needs a lot of resources to perform tracing of millions of photons. Progressive photon mapping solves this problem. Typical progressive photon mapping performs ray tracing at first to find the hit points on diffuse surface of objects. Next, light source repeatedly emits a small number of photons in photon tracing pass, and power of photons in each sphere that has a fixed radius with the hit points in the center is accumulated. This method requires less resources than previous photon mapping, but it spends much time for gathering enough photons since each of photons progresses through a random direction and rendering high quality image. To improve the method, we propose photon probing that calculates variance of photons in the sphere and controls radius of sphere. In addition, we apply cone filter in radiance estimation step for reducing aliasing at the edges in result image.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.40.1-40.1
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• 2021

Hydrogen is the most abundant element in the universe, which is, in the cosmological context, attributed to its simplest structure consisting of a proton and an electron. Hydrogen interacts with an electromagnetic wave in astrophysical environments. Rayleigh scattering refers to elastic scattering, where the frequencies of the incident and scattered photons are the same. Rayleigh and resonance scattering is a critical role study Lyman Alpha objects in the early universe. The scattering causes the frequency and spatial diffusion of Lyα. In the case of Raman scattering, the energies of the incident and scattered photons are different. The photons near Lyβ convert to the optical photons near Hα through Raman scattering. The photon scattered by atomic hydrogen can carry both of the properties of the H I region and the emission region. I adopt a Monte Carlo approach to investigate the formation of the various spectral line features through Rayleigh and Raman scattering in highly thick media of atomic hydrogen. In this thesis, I present my works on radiative transfer involving the scattering processes between far UV photon and atomic hydrogen. I introduce scattering processes with atomic hydrogen and the spectral, spatial, and polarized information originating from the scattering.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1633-1637
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• 2019

While considering the photon attenuation coefficient (${\mu}$) and its related parameters for photons shielding, it is necessary to account for its transmitted and reflected photons energy spectra and dose contribution. Monte Carlo simulation was used to study the efficiency of clay ($1.99g\;cm^{-3}$) as a shielding material below 150 keV photon. Am-241 gamma source and an X-ray of 150 kVp were calculated. The calculated value of ${\mu}$ for Am-241 is higher within 5.61% compared to theoretical value for a single-energy photon. The calculated half-value layer (HVL) is 0.9335 cm, which is lower than that of ordinary concrete for X-ray of 150 kVp. A thickness of 2 cm clay was adequate to attenuate 90% and 85% of the incident photons from Am-241 and X-ray of 150 kVp, respectively. The same thickness of 2 cm could shield the gamma source dose rate of Am-241 (1 MBq) down to $0.0528{\mu}Sv/hr$. For X-ray of 150 kVp, photons below 60 keV were significantly decreased with 2 cm clay and a dose rate reduction by ~80%. The contribution of reflected photons and dose from the clay is negligible for both sources.

• Korean Journal of Materials Research
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• v.32 no.10
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• pp.419-424
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• 2022

Halide perovskite solar cells (PSCs) have improved rapidly over the past few years, and research on the optoelectrical properties of halide perovskite thin films has grown as well. Among the characterization techniques, photoluminescence (PL), a method of collecting emitted photons to evaluate the properties of materials, is widely applied to evaluate improvements in the performance of PSCs. However, since only photons emitted from the film in the escape cone are included, the photons collected in PL are a small fraction of the total photons emitted from the film. Unlike PSCs power conversion efficiency, PL measuring methods have not been standardized, and have been evaluated in a variety of ways. Thus, an in-depth study is needed of the methods used to evaluate materials using PL spectra. In this study, we examined the PL spectra of the perovskite light harvesting layer with different measurement protocols and analyzed the features. As the incident angle changed, different spectra were observed, indicating that the PL emission spectrum can depend on the measuring method, not the material. We found the intensity and energy of the PL spectra changes were due to the path of the emitted photons. Also, we found that the PL of halide perovskite thin films generally contains limited information. To solve this problem, the emitted photons should be collected using an integrating sphere. The results of this study suggest that the emission spectrum of halide perovskite films should be carefully interpreted in accordance with PL measuring method, since PL data is mostly affected by the method.

• Journal of Photoscience
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• v.9 no.2
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• pp.170-173
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• 2002

Space is full of energetic events emitting high-energy radiations which may be fatal to all living things unless protected. The present paper briefly describes high-energy photons and particles incident on Earth surface and their common properties toward living things. Role of radiation played in evolution of life and earth environment will be presented.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.2
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• pp.190-197
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• 2016

We examined for differences in the growth and fertility of microscopic stages between Costaria costata and Undaria pinnatifida in crossed temperature×irradiance (12, 17, 22℃×20, 60 μmol photons m^–2s^–1) and daylength×irradiance (8, 12, 16, 24 h×20, 60 μmol photons m^–2s^–1) experimental designs. After 13 days in culture, maximum gametophyte growths of the two species were obtained under the following combinations of factors: 17℃×60 μmol photons m^–2s^–1 and 24 h daylength×60 μmol photons m^–2s^–1. C. costata gametophytes produced sporophytes about 6 days earlier than those of U. pinnatifida. Sporophyte densities were highest in the 12 h daylength×60 μmol photons m^–2s^–1 combination after 20 days in C. costata (9.7 plants mm^–2) and 26 days in U. pinnatifida (9.1 plants mm^–2). However, optimal growth conditions for the microscopic sporophytes differed between species: 17℃×60 μmol photons m^–2 s^–1 for C. costata, 12℃×60 μmol photons m^–2 s^–1 for U. pinnatifida. Thus, C. costata gametophytes grew faster and produced sporophytes earlier than those of U. pinnatifida, even though the haploid gametophytes of the two species responded similarly to environmental conditions. Optimal growth temperatures for the microscopic sporophytes also differed between species.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.17
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• pp.7785-7788
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• 2015

Utilization of high energy photons (>10MV) with an optimal weight using a mixed energy technique is a practical way to generate a homogenous dose distribution while maintaining adequate target coverage in intact breast radiotherapy. This study represents a model for estimation of this optimal weight for day to day clinical usage. For this purpose, treatment planning computed tomography scans of thirty-three consecutive early stage breast cancer patients following breast conservation surgery were analyzed. After delineation of the breast clinical target volume (CTV) and placing opposed wedge paired isocenteric tangential portals, dosimeteric calculations were conducted and dose volume histograms (DVHs) were generated, first with pure 6MV photons and then these calculations were repeated ten times with incorporating 18MV photons (ten percent increase in weight per step) in each individual patient. For each calculation two indexes including maximum dose in the breast CTV ($D_{max}$) and the volume of CTV which covered with 95% Isodose line ($V_{CTV,95%IDL}$) were measured according to the DVH data and then normalized values were plotted in a graph. The optimal weight of 18MV photons was defined as the intersection point of $D_{max}$ and $V_{CTV,95%IDL}$ graphs. For creating a model to predict this optimal weight multiple linear regression analysis was used based on some of the breast and tangential field parameters. The best fitting model for prediction of 18MV photons optimal weight in breast radiotherapy using mixed energy technique, incorporated chest wall separation plus central lung distance (Adjusted R2=0.776). In conclusion, this study represents a model for the estimation of optimal beam weighting in breast radiotherapy using mixed photon energy technique for routine day to day clinical usage.