• 대한설비공학회지:설비저널
• /
• 제17권5호
• /
• pp.598-606
• /
• 1988

The radiation heat-transfer coefficient is generally used to calculate radiant heat exchange of heating space. The coefficient is evenly adopted in most cases, but it is not correct in actual cases. The purpose of this paper is to grasp the changing aspect of radiation heat-transfer coefficient needed for heating load calculation of radiant heating space. Surface temperatures are measured in an Ondol space, and the coefficients are derived and examined. Gebhart's Absorption Factor Method is used for the calculations of the rates of instantaneous radiant exchange in the room. As the result, it is confirmed that the coefficients are variant according to surface temperatures, and proper coefficients are needed for each of conditions.

• Journal of Semiconductor Engineering
• /
• 제2권1호
• /
• pp.119-124
• /
• 2021

Along with the needs for feasibility in the field of space applications, interests in radiation-hardened electronics is growing rapidly. Gallium nitride (GaN)-based devices have been widely researched so far owing to superb radiation resistance. Among them, research on the most abundant protons in low earth orbit (LEO) is essential. In this paper, proton irradiation effects on parameter changes, degradation mechanism, and correlation with reliability of GaN-based devices are summarized.

• Journal of Radiation Protection and Research
• /
• 제30권1호
• /
• pp.17-25
• /
• 2005

원자력 발전의 안정성이 사회적 문제로 제기된 이후 작업종사자에 대한 작업 중 방사선 피폭량에 대한 관심이 높아지고 있다. 현재의 방법에 의하면 방사선 작업 계획의 수립 시 작업 공간 내 선량률이 일정하다는 가정 하에 피폭선량을 예측하므로 작업 경로에 따른 피폭선량의 변화에 대한 고려가 이루어지지 않고 있다. 본 연구에서는 작업자와 선원과의 거리가 고려되 수정된 방사선 피폭량 계산식을 이용하여 방사성 폐기물 저장시설에서의 작업 중 작업경로 변화에 따른 방사선 피폭량을 계산하였다. 이 계산식을 이용하여 주어진 작업 공간과 선원 조건하에서 작업 중 방사선 피폭량을 최소로 하는 최적 작업경로를 탐색할 수 있는 수치해석 알고리즘을 제안하였다. 이를 위하여 2차원 작업공간에서 무한개의 작업경로를 유한개의 경로로 근사화하고 근사화된 모든 작업경로 중 피폭선량이 최소가 되는 작업경로를 탐색하였다. 또한, 3차원 그래픽 기술과 Java 프로그래밍을 이용한 가상작업 시뮬레이션 프로그램을 개발하고 작업 공간의 선량률 가시화 및 가상 작업 시뮬레이션을 수행하여 방사선 작업 계획의 수립을 위한 도구로서의 가능성을 검토하였다. 수치해석 계산과 시뮬레이션 과정을 통하여 최적 작업경로는 작업자와 선원과의 거리를 증가시키고 작업 시간을 단축시킬 수 있는 경로로 제시되었고, 이를 바탕으로 방사선 피폭량은 작업시간뿐만 아니라 작업자와 선원간의 거리에 영향을 받음과 최적화된 방사선 방호를 위해 작업경로가 고려되어야 함을 확인하였다.

• International Journal of Aeronautical and Space Sciences
• /
• 제3권1호
• /
• pp.95-104
• /
• 2002

Numerical solution of the full Navier-Stokes equation as well as the energy equation has been obtained for the unsteady natural convection in a rectangular enclosure. One side wall was maintained at very high temperature simulating fires. Especially the effect of surface radiation was taken into account. While the enclosed air was assumed to be transparent, the internal walls directly interacted one another through the surface radiation. Due to a significant temperature difference in the flow field, the equation of state was used instead of the Boussinesq approximation. It was found that the rapid heating of the adiabatic ceiling and floor by the incoming radiation from the hot wall made the evolution at thermo-fluid field highly unstable in the initial period. Therefore, the secondary cells brought about at the floor region greatly affected the heat transfer mechanism inside the enclosure. The heat transfer rate was augmented by the radiation, resulting in requiring less time for the flow to reach the steady state. At the steady state neglecting radiation two internal hydraulic jumps were clearly observed in upper/left as well as in lower/right comer. However, the hydraulic jump in the lower/right comer could not be observed for the case including radiation due to its high momentum flow over the bottom wall. Radiation resulted in a faster establishment of the steady state phenomena.

• 방사선산업학회지
• /
• 제4권1호
• /
• pp.59-64
• /
• 2010

This study was conducted to evaluate the microbial (Total aerobic count, Coliform, Coagulase positive Staphylococci, Salmonella, Yeast/Mold, Escherichia coli, Bacillus cereus), Hunter'color values ($L^*$, $a^*$, $b^*$) and organoleptic quality of freeze-dried Miyeokguk, Korean seaweed soup in space food. Bacillus cereus was 1 log level while not detected in the sample irradiated at 10 kGy. Hunter's color values of the samples irradiated less than 10 kGy was not significantly different (p>0.05). The sensory evaluation result showed that the preference scores in all the sensory properties decreased when it was irradiated over 10 kGy, but sensory score of less than 10 kGy samples was similar in all terms. Therefore, it was considered that gamma irradiation at 10 kGy was enough to sterilize the freeze-dried Miyeokguk without deterioration of sensory quality.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2009년도 한국우주과학회보 제18권1호
• /
• pp.30.3-30.3
• /
• 2009

• 천문학회보
• /
• 제38권2호
• /
• pp.95.1-95.1
• /
• 2013

The RBSPICE (Radiation Belt Storm Probes Ion Composition Experiment) is one of five instrument suites onboard the twin Van Allan Probes (or Radiation Belt Storm Probes; RBSP), launched August 30, 2012 by NASA. One of science targets of RBSPICE instrument is to determine "how changes in that ring current affect the creation, acceleration, and loss of radiation belt particles?". For that purpose, it measures ions and electrons simultaneously. Ion's energy range is from ~20 keV to ~1 MeV and electron's energy channel is from ~35 keV to 1 MeV in order to provide supplementary information about the radiation belts. In this paper, we investigate a reliability of the electron flux measured from the RBSPICE by comparing with ECT (The Energetic Particle, Composition and Thermal Plasma Suite) data. We found there is a critical proton contamination problem in the electron channels of ~ 1MeV of RBSPICE observations during one moderate storm event of Sym H ~ -76 nT on March 1, 2013.

• 우주기술과 응용
• /
• 제3권4호
• /
• pp.333-341
• /
• 2023

본 연구는 국내 100 MeV 양성자가속기와 우주부품시험센터 우주전문시험시설기반을 활용하여 우주부품의 우주 방사선환경 시험검증 기술을 개발하고자 한다. 우주개발의 진전에 따라 고도화된 위성의 임무는 위성의 핵심부품인 메모리 등에 고집적 회로를 필수적으로 사용하고, 태양전지, 광학센서 및 opto-electronics 등 부수 장치에 반도체 소자의 활용이 증가하고 있다. 특히, 전자부품을 우주에 적용하기 위해서는 우주환경 시험을 반드시 거쳐야 하며, 그 중 가장 중요한 것이 고 에너지 방사선환경에서의 우주부품시험이다. 따라서 이에 필요한 우주 방사선 환경 구현 시설을 갖추어 체계적인 시험절차를 수립할 필요가 있다. 한국산업기술시험원 우주부품시험센터는 메모리 부품에 대한 방사선 시험 장치를 제작하고 이를 이용한 메모리 방사선 영향 평가 시험을 수행하였다. 경주양성자가속기에서 100 MeV 양성자를 활용하여 한국에서 활용가능한 수준의 방사선 시험을 진행하였다. 이러한 시험을 통해 메모리 반도체에서 나타나는 single event upset을 관찰할 수 있었다. 향후 해당 시험을 체계화하여 우주산업화에 기반을 마련하고자 한다.

• 천문학논총
• /
• 제14권2호
• /
• pp.83-89
• /
• 1999

The Earth is exposed to constant outflow of the solar wind from the outer layers of the Sun, and violent transient events taking place from active regions increase the energy flux of both radiation and particles leaving the Sun. Thus the space surrounding the Earth is a highly dynamic environment that responds sensitively to changes in radiation, particles and magnetic field arriving from the Sun. Nowadays, it becomes increasingly important to understand how the physical system of Earth-space works and how the space around the Earth connects to interplanetary space. In the present paper we describe how explosive solar events, such as CME(Coronal Mass Ejection) and flares affect the Earth-space environment and how the space weather reacts to them. Practical consequences are presented to demonstrate why a broader view of Earth's environment is greatly needed to cope with modern day's inhabitation problem in a rapidly developing space age.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
• /
• pp.301-304
• /
• 2006

For the purpose of investigating the contributions of various gases to climate change, the thermal radiation associated with greenhouse gases are extracted from AIRS (Atmospheric Infrared Sounder) infrared radiances over the tropical pacific region. AIRS instrument which was launched on the EOS-Aqua satellite in May 2002 covers the spectral range from 650 cm-1 to 2700 cm-1 with a spectral resolution of between 0.4 cm-1 and 1 cm-1. In order to extract the thermal radiation absorbed by individual gases, the interfering background radiances at the top of the atmosphere are simulated using the radiative transfer code MODTRAN (MODerate spectral resolution atmospheric TRANsmittance). The simulations incorporated the temperature and water vapor profiles taken from NCEP (National Centers for Environmental Prediction) reanalyses. The differences between the simulated background radiance and AIRS-measured radiance result in the absorption of upward longwave radiation by atmospheric gases (i.e. greenhouse effect). The extracted absorption bands of individual gases will allow us to quantify the radiative forcing of individual greenhouse gases and thus those data will be useful for climate change studies and for the validation of radiative transfer codes used in general circulation models.