• Journal of Radiation Protection and Research
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• 제26권4호
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• pp.367-374
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• 2001

방사선 조사가 흰쥐 식도에 미치는 영향과 sucralfate의 효과 여부를 알아보고자 하였다. 총 60마리의 흰쥐를 대상으로 정상대조군, sucralfate투여군, 10 Gy 와 20 Gy의 방사선 단독조사군, 10 Gy와 20 Gy의 방사선 조사-sucralfate병용군 등 여섯 군으로 구분하였다. 실험기간동안 흰쥐의 체중 변화의 조사와 함께 바륨-식도 조영술을 시행하였고, 방사선조사 후 3일, 7일, 14일 및 28일째에 얻은 식도에 나타난 병리조직학적 병변을 점수화하여 각 처리군을 비교관찰 하였다. 정상대조군은 10 Gy 와 20 Gy의 방사선 단독 조사군과 10 Gy 와 20 Gy의 방사선조사-sucralfate병용군에 비하여 체중 증가를 보였으나 (p=0.03, p=0.02, p=0.04, p=0.02), 이들 실험군들 사이에는 차이가 없었다. 10 Gy와 20 Gy의 방사선 단독조사군의 식도 조영술 소견은 7일째부터 식도 전장에 걸쳐 식도 내강이 좁아지고 경직성을 보였으며 10 Gy, 방사선조사-sucralfate병용군은 대조군과 유사한 소견을 보였다. 10 Gy와 20 Gy의 방사선 단독조사군에서 식도의 병리조직학적 손상등급은 정상군과 비교하여 매우 유의한 차이를 보였다 (p=0.03, p=0.008). 10 Gy 방사선 단독조사군과 10Gy 방사선조사-sucralfate병용군간의 손상등급은 방사선조사 후 3일 및 7일째까지 유의한 차이를 보였다( p=0.04, p=0.03 ), 본 연구에서 sucralfate는 한계선량이내에서 방사선조사시 흰쥐의 식도점막을 보호하는 데 도움이 됨을 확인하였다.

• Journal of Astronomy and Space Sciences
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• 제36권1호
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• pp.21-33
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• 2019

This paper focuses on the interpretation of radiation fluxes from active galactic nuclei. The advantage of positron annihilation spectroscopy over other methods of spectral diagnostics of active galactic nuclei (therefore AGN) is demonstrated. A relationship between regular and random components in both bolometric and spectral composition of fluxes of quanta and particles generated in AGN is found. We consider their diffuse component separately and also detect radiative feedback after the passage of high-velocity cosmic rays and hard quanta through gas-and-dust aggregates surrounding massive black holes in AGN. The motion of relativistic positrons and electrons in such complex systems produces secondary radiation throughout the whole investigated region of active galactic nuclei in form of cylinder with radius R= 400-1000 pc and height H=200-400 pc, thus causing their visible luminescence across all spectral bands. We obtain radiation and electron energy distribution functions depending on the spatial distribution of the investigated bulk of matter in AGN. Radiation luminescence of the non-central part of AGN is a response to the effects of particles and quanta falling from its center created by atoms, molecules and dust of its diffuse component. The cross-sections for the single-photon annihilation of positrons of different energies with atoms in these active galactic nuclei are determined. For the first time we use the data on the change in chemical composition due to spallation reactions induced by high-energy particles. We establish or define more accurately how the energies of the incident positron, emitted ${\gamma}-quantum$ and recoiling nucleus correlate with the atomic number and weight of the target nucleus. For light elements, we provide detailed tables of all indicated parameters. A new criterion is proposed, based on the use of the ratio of the fluxes of ${\gamma}-quanta$ formed in one- and two-photon annihilation of positrons in a diffuse medium. It is concluded that, as is the case in young supernova remnants, the two-photon annihilation tends to occur in solid-state grains as a result of active loss of kinetic energy of positrons due to ionisation down to thermal energy of free electrons. The single-photon annihilation of positrons manifests itself in the gas component of active galactic nuclei. Such annihilation occurs as interaction between positrons and K-shell electrons; hence, it is suitable for identification of the chemical state of substances comprising the gas component of the investigated media. Specific physical media producing high fluxes of positrons are discussed; it allowed a significant reduction in the number of reaction channels generating positrons. We estimate the brightness distribution in the ${\gamma}-ray$ spectra of the gas-and-dust media through which positron fluxes travel with the energy range similar to that recorded by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) research module. Based on the results of our calculations, we analyse the reasons for such a high power of positrons to penetrate through gas-and-dust aggregates. The energy loss of positrons by ionisation is compared to the production of secondary positrons by high-energy cosmic rays in order to determine the depth of their penetration into gas-and-dust aggregations clustered in active galactic nuclei. The relationship between the energy of ${\gamma}-quanta$ emitted upon the single-photon annihilation and the energy of incident electrons is established. The obtained cross sections for positron interactions with bound electrons of the diffuse component of the non-central, peripheral AGN regions allowed us to obtain new spectroscopic characteristics of the atoms involved in single-photon annihilation.

• The Korean Journal of Ecology
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• 제7권3호
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• pp.99-108
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• 1983

Diurnal acid fluctuation, stomatal resistance, and solar radiation with regard to the cladode orientation were investigated in Opuntia lanceolata Haw. growing at WPeolryeong-ri, Hallim-eup, Chejudo, Korea. Diurnal changes of titratable acidity showed the typical CAM pattern in all investigated cladodes. Water tissue in the cladode had the same pattern of acid fluctuation as mesophyll tissue. Stomatal resistance was low during the night, increased rapidly to be a peak right after sunrise and decreased again thereafter. The southern side of the cladode showed higher stomatal resistance than the northern side during the day time. It suggests that the stomata of the northern side opens under diffuse radiation. The amount of solar radiation varied depending upon the cladode orientation. It is thought that C4 acids move inter and intra mesophyll tissues in the cladode through the unknown pathways. RuBP carboxyulase activity in the cladode was very high at 14:00, but was not significant at 01:00. PEP-carboxylase had high activities both at 14:00 and at 01:00. The results of this study showed the possibility that O. lanceolata Haw. had the C3, C4 and CAM photosynthetic patterns under the environmental conditions at Weolryeong-ri.

• 천문학회지
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• 제25권2호
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• pp.111-128
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• 1992

Infrared emissions from spherical dust, clouds are calculated using quasi-diffusion method. We have employed graphite-silicate mixture with power-law size distribution for the dust model. The grains are assumed to be heated and cooled by radiative processes only. The primary heating source is diffuse interstellar radiation field. hut the cases with an embedded source are also considered. Since graphite grains have higher temperature than silicate grains, the observed IR emission is mainly due to graphite grains, unless the fraction of graphite grains is negligibly small. The color temperature of Bok globules obtained from IRAS 60 and $100{\mu}m$ data are found to be consistent with the dust cloud with graphite-silicate mixture exposed to average interstellar radiation field. The color temperature is sensitive to the external radiation field, but rather insensitive to the size distribution of the grains. We found that the density distribution can be recovered outside the beam size using the inversion technique that assumes negligible optical depth. However, the information within the beam size is lost for if beam convolved intensity distributions are used in deriving density profile.

• 천문학회보
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• 제35권2호
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• pp.73.2-73.2
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• 2010

In order to understand internal dynamics of starless cores, molecular line emissions are usually observed. From profiles of the molecular lines, internal motions of starless cores have been deduced using a simple radiative transfer model such as the two-layer model (Myers et al.1996). This brings complexities arising from the chemical evolution. The motivation of this study is to follow the chemical evolution of a starless core that goes through gravitational contraction. For this purpose, we have performed hydrodynamical simulations with a marginally unstable Bonnor-Ebert sphere as an initial condition. We follow the chemical evolution of this core with changing conditions such as the chemical reaction rate at the dust surface and the strength of radiation field that penetrate into the core. At the core center, the molecules suffer from a higher degree of molecular depletion on the dust covered by ice rather than on the bare silicate dust. The stronger radiation field dissociates more molecules at the core envelope. From analysis on the line profile using the two-layer model, we found that the speed of inward motion deduced from the HCN F = 2-1 line adequately traces the true infall speed, when the dust is covered by ice and the core is exposed to the diffuse interstellar radiation field. Under different conditions, the two-layer model significantly underestimate the infall speed.

• 천문학회보
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• 제42권1호
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• pp.56.1-56.1
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• 2017

When turbulent motions perturb magnetic field lines and produce magnetic fluctuations, the perturbations leave imprints of turbulence statistics on magnetic field. Observation of synchrotron radiation is one of the easiest ways to study turbulent magnetic field. Therefore, we study statistical properties of synchrotron polarization emitted from media with magnetohydrodynamic (MHD) turbulence, using both synthetic and MHD turbulence simulation data. First, we obtain the spatial spectrum and its derivative with respect to wavelength of synchrotron polarization arising from both synchrotron radiation and Faraday rotation. The study of spatial spectrum shows how the spectrum is affected by Faraday rotation and how we can recover the statistics of underlying turbulent magnetic field as well as turbulent density of electrons from interferometric observations that incorporate the effects of noise and finite telescopic beam size. Second, we study quadrupole ratio to quantitatively describe the degree of anisotropy introduced by magnetic field in the presence of MHD turbulence. We consider the case that the synchrotron emission and Faraday rotation are spatially separated, as well as the situation that the sources of the synchrotron radiation and thermal electrons causing Faraday rotation exist in the same region. In this study, we demonstrate that the spectrum and quadrupole ratio of synchrotron polarization can be very informative tools to get detailed information about the statistical properties of MHD turbulence from radio observations of diffuse synchrotron polarization.

• 대한기계학회논문집B
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• 제25권10호
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• pp.1451-1458
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• 2001

The effects of a specularly reflecting surface on the wall heat flux and medium temperature distribution are studied. The system is an infinite square duct enclosing an absorbing and emitting medium. The walls are opaque, and black or gray. The walls emit diffusely but reflect diffusely or speculary. Heat is transferred by the combined effect of conduction and radiation. The radiative heat transfer is analyzed using direct discrete-ordinates method. The parameters under study are conduction, to radiation parameter, optical depth, wall emissivity, and reflection characteristics. The specular reflection and diffuse reflection show sizeable differences when the conduction to radiation parameter is less than around 0.01. The differences appear only either on the side wall heat flux or on the medium temperature profiles for the range of this study. The differences on the side wall heat flux are observed for optical thickness less than around 0.1 However the differences on the medium temperate profiles are found for optical thickness greater than around 1. The difference increase with increasing reflectance. The specular reflection increases the well heat flux gradient along the side wall.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.316-321
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• 2000

In this study, heat collecting performance was study of flat plate solar collector by the angle. A method of study on were made turn out artificial sun by the angle of 0, 15, 30 degrees. The heat performances were measured the tube array surface temperature by thermo-couple. The winter season natural condition for 4 times on the angles of various general and emboss glass at optimum distance(0.68m) calculated of between sun and solar collector. To sum up temperature rise is appear more or less that emboss glass is all the better for general glass. The temperature variable at below of 30 degree was appear very less. The maximum performance of this system at that it is tilt angle of 30 with general glass is appear Q:11.54(kcal/min) and ${\Delta}T=18.9^{\circ}C$.

• Radiation Oncology Journal
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• 제10권1호
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• pp.15-20
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• 1992

1980년부터 1990년까지 연세의료원 암쎈터 치료방사선과에서 방사선 치료를 받은 20예 (남자 : 여자=10:10, 성인 소아=8:12)의 뇌간종양 환자의 치료결과를 분석하여 보았다. 총 20예의 환자 중 13예에서는 보통 분할 방사선치료(분할 당 180%200 cGy, 주 5회, 총 4680\~5400 cGy)를 시행하였고 나머지 7예에서는 과분할 방사선치료(분할 당 100 cGy, 1일 2회, 주 10회 총 7200 cGy)를 시행하였다. 중앙 추적 기간은 보통 분할 방사선 치료군과 과분할 방사선 치료군에서 각각 36개월과 10개월이었다. 20예의 환자중 4예에서는 치료전 병리학적 진단을 얻을 수 있었다. 이중 3예는 저분화 성상 세포종양 이었고 1예는 미분화 성상 세포종양이었다. 전체 대상환자의 실제 2년 생존율은 30%이었다. 예후인자로 나이, 증상 발현기간, 종양 형태 등을 분석해 보았는데, 증상 발현기간이 긴 환자에서 짧은 환자보다 예후가 좋았고, 성인에서 소아보다 예후가 좋았다. 종양 형태간에는 차이가 없었다. 보통 분할 방사선 치료군보다 과분할 방사선 치료군에서 초기 임상적 치료 반응이 좋았다. 보통 분할 방사선 치료군과 과분할 방사선치료군을 비교하는 것은 환자의 숫자가 적고, 과분할 방사선치료군의 추적 기간이 짧아 어려웠다.

• 한국농림기상학회지
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• 제22권3호
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• pp.144-151
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• 2020

작물을 재배하는 동시에 전력 생산도 가능한 영농형 태양광 발전은 농업·농촌 분야와 재생에너지 산업 모두로부터 주목 받고 있다. 하지만, 그 역사가 짧은 만큼 영농형 태양광 하부에서의 미기상 환경 변화에 대한 이해와 관측 방법론이 정립되지 않은 실정이다. 따라서 본고에서는 보성군에 설치된 영농형 태양광에서 2019년 11월 부터 2020년 5월까지의 보리 생육기간 동안 일사광, 광합성유효복사광, 기온, 습도, 토양습도·온도, 풍향·풍속을 5분 간격으로 측정하여 공개했다. 또한, 노지의 일사량 및 광합성유효복사량에 대한 약 13일 간의 자료 결손에 대해서는 가까운 기상청 관측 자료를 활용하거나 영농형 태양광 하부의 자료를 이용한 두 가지 경험적 메우기 방법을 제안하였다. 본고 자료가 영농형 태양광에 대한 농업적 평가에 다양하게 활용되기를 기대한다.