• Journal of Astronomy and Space Sciences
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• 제33권1호
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• pp.21-28
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• 2016

Caves can serve as major outposts for future human exploration of the Moon and Mars. In addition, caves can protect people and electronic equipment from external hazards such as cosmic ray radiation and meteorites impacts and serve as a shelter. Numerous pit craters have been discovered on the Moon and Mars and are potential entrances to caves; the principal topographic features of pit craters are their visible internal floors and pits with vertical walls. We have devised two topographical models for investigating the relationship between the topographical characteristics and the inner void of pit craters. One of our models is a concave floor void model and the other is a convex floor tube model. For each model, optical photographs have been obtained under conditions similar to those in which optical photographs have been acquired for craters on the Moon and Mars. Brightness profiles were analyzed for determining the profile patterns of the void pit craters. The profile patterns were compared to the brightness profiles of Martian pit craters, because no good-quality images of lunar pit craters were available. In future studies, the model profile patterns will be compared to those of lunar pit craters, and the proposed method will likely become useful for finding lunar caves and consequently for planning lunar bases for manned lunar expeditions.

• Journal of Astronomy and Space Sciences
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• 제31권4호
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• pp.325-333
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• 2014

We are motivated by both the accumulating evidence for the connection of solar variability to the chemistry of nitrogen oxide in the atmosphere and recent finding that the Galactic cosmic-ray (GCR) influx is associated with the solar north-south asymmetry. We have analyzed the measured pH in precipitation over the 109 stations distributed in the United States. We have found that data of pH in precipitation as a whole appear to be marginally anti-correlated with the solar asymmetry. That is, rain seems to become less acidic when the southern hemisphere of the Sun is more active. The acidity of rain is also found to be correlated with the atmospheric temperature, while not to be correlated with solar activity itself. We have carried on the analysis with two subsamples in which stations located in the east and in the west. We find that the pH data derived from the eastern stations which are possibly polluted by sulfur oxides and nitrogen oxides are not correlated with the solar asymmetry, but with the temperature. On the contrary, the pH data obtained from the western stations are found to be marginally anti-correlated with the solar asymmetry. In addition, the pH data obtained from the western stations are found to be correlated with the solar UV radiation. We conclude by briefly pointing out that a role of the solar asymmetry in the process of acidification of rain is to be further examined particularly when the level of pollution by sulfur oxides and nitrogen oxides is low.

• Journal of Radiation Protection and Research
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• 제36권1호
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• pp.35-43
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• 2011

The PHENIX Experiment is the largest of the four experiments that have taken data at the Relativistic Heavy Ion Collider. PHENIX, the Pioneering High Energy Nuclear Interaction eXperiment, is designed specifically to measure direct probes of the collisions such as electrons, muons, and photons. The primary goal of PHENIX is to discover and study a new state of matter called the Quark-Gluon Plasma. Among many particles, muons coming from W-boson decay gives us key information to analyze the spin of proton. Resistive plate chambers are proposed as a suitable solution as a muon trigger because of their fast response and good time resolution, flexibility in signal readout, robustness and the relatively low cost of production. The RPC detectors for upgrade were assembled and their performances were evaluated. The procedure to make the detectors better was optimized and described in detail in this thesis. The code based on ROOT was written and by using this the performance of the detectors made was evaluated, and all of the modules for north muon arm met the criteria and installation at PHENIX completed in November 2009. As RPC detectors that we made showed fast response, capacity of covering wide area with a resonable price and good spatial resolution, this will give the opportunity for applications, such as diagnosis and customs inspection system.

• Journal of Astronomy and Space Sciences
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• 제22권4호
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• pp.537-558
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• 2005

본 논문에서는 HAUSAT-2위성이 운용될 케도의 우주 방사능 환경 및 총 피폭효과(Total Ionizing Dose), 단일사건 효과(Single Event Effects) 등에 대해 분석하였다. 총 피폭효과에 영향을 미치는 우주 방사능은 포획된 양성자, 전자, 태양 양성자 및 우주선이다. 총 피폭효과는 선량 심도선 분석을 통해 해석을 수행하였으며, DMBP(Design Margin Breakpoint) 방법과 3-D 구분구적법을 이용하여 HAVSAT-2의 부품의 총 피폭량에 대한 내성을 검증하였다. 단일사건 효과에 대하여 위성체 외부와 내부 방사능 환경으로 양성자와 중이온에 대하여 선형에너지 전달량(LET) 스펙트럼을 분석하였으며, HAUSAT-2의 전자소자로 사용예정인 MPC860T2B 마이크로프로세서와 메모리 K6X8008T2B에 대한 SEU(Single Event Upset) 및 SEL(Single Event Latch-up) 발생률을 추정하였다. 분석 결과 SEU는 운용 중에 수차례 발생하며 SEL 발생은 임무기간동안 일어나지 않을 것으로 추정되었다. HAUSAT-2는 소프트웨어 해밍코드 EDAC을 이용하여 SEU 발생에 대처할 수 있는 시스템 레벨의 설계를 반영하였다. 이 연구에서 수행된 방사능 해석은 ESA의 SPENVIS소프트웨어를 이용하였다.

• Journal of Astronomy and Space Sciences
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• 제29권4호
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• pp.343-349
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• 2012

The solar proton telescope (SPT) is considered as one of the scientific instruments to be installed in instruments for the study of space storm (ISSS) which is determined for next generation small satellite-1 (NEXTSat-1). The SPT is the instrument that acquires the information on energetic particles, especially the energy and flux of proton, according to the solar activity in the space radiation environment. We performed the simulation to determine the specification of the SPT using geometry and tracking 4 (GEANT4). The simulation was performed in the range of 0.6-1,000 MeV considering that the proton, which is to be detected, corresponds to the high energy region according to the solar activity in the space radiation environment. By using aluminum as a blocking material and adjusting the energy detection range, we determined total 7 channels (0.6~5, 5~10, 10~20, 20~35, 35~52, 52~72, and >72 MeV) for the energy range of SPT. In the SPT, the proton energy was distinguished using linear energy transfer to compare with or discriminate from relativistic electron for the channels P1-P3 which are the range of less than 20 MeV, and above those channels, the energy was determined on the basis of whether silicon semiconductor detector (SSD) signal can pass or not. To determine the optimal channel, we performed the conceptual design of payload which uses the SSD. The designed SPT will improve the understanding on the capture and decline of solar energetic particles at the radiation belt by measuring the energetic proton.

• 천문학회보
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• 제37권2호
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• pp.104.2-104.2
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• 2012

미국, 중국, 일본, 인도 등과 같은 세계 여러 국가들이 달 및 화성 탐사를 수행하고 있는 현시점에서 우리나라도 2025년에 달 탐사를 계획하고 있다. 인간에게 있어서 우주공간은 고에너지 환경의 영향을 많이 받는 곳이다. 향후 달, 화성과 같은 다른 행성으로의 이주를 생각하고 있는 현 시점에서 우리는 고에너지우주방사선 환경의 영향을 고려해야 한다. 지구에서의 인간은 지구 자기장과 대기에 의해 고에너지 우주선 환경으로부터의 영향을 덜 받는다. 그러나 달과 화성의 경우는 다르다. 달의 대기는 거의 없고 자기장도 무시할 정도로 매우 작으며, 화성 또한 자기장이 거의 없으며 대기 또한 얇아서 Galactic Cosmic Ray (GCR)나 Solar Energetic Proton (SEP) 등으로부터 인간은 많은 영향을 받을 수 있다. 이러한 위험으로부터 인간이 보호받을 수 있는 곳은 달과 화성의 지표 아래나 동굴이라고 볼 수 있다. 그래서 달 및 화성의 표면과 지하 영역에 대한 고에너지 우주선 환경의 깊이에 따른 영향을 분석하여 어느 정도로 두터운 천장을 가진 동굴이어야 우주인들이 상주하는 지하공간을 지구표면에서의 방사선 환경과 같은 수준으로 유지할 수 있는지를 추정해 보려고 한다. 달 표면 토양의 화학적 구성성분은 Maria와 Highlands로 구분되어 약간의 차이가 있다. 달의 Maria 토양은 $SiO_2$ - 45.4%, $Al_2O_3$ - 14.9%, CaO - 11.8%, FeO - 14.1%, MgO - 9.2%, $TiO_2$ - 3.9%, $Na_2O$ - 0.6%이고 Highlands의 토양은 $SiO_2$ - 45.5%, $Al_2O_3$ - 24.0%, CaO - 15.9%, FeO - 5.9%, MgO - 7.5%, $TiO_2$ - 0.6%, $Na_2O$ - 0.6%의 화학적인 구성비를 가진다. 또한 화성표면은 $SiO_2$ - 43.9%, $Al_2O_3$ - 8.1%, CaO - 6.0%, FeO - 18.1%, MgO - 7.1%, $Na_2O$ - 1.4%의 토양의 화학적인 구성비를 가지고 있다. 본 연구에서는 이러한 구성비를 가지고 있는 달과 화성 표면에 대한 우주방사선의 영향을 분석하기 위해서 GEANT4를 사용하여 수행한 전산 모사의 결과를 발표할 것이다.

• 천문학회보
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• 제43권2호
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• pp.42.2-43
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• 2018

When galaxy clusters interact, the intergalactic gas collides, forming shocks that are characterized by a low sonic Mach number (~3) but a comparatively high Alfvenic Mach number (~30). Such shocks behave differently from the more common astrophysical shocks, which tend to have higher sonic Mach numbers. We wish to determine whether these shocks, despite their low sonic Mach number, are capable of accelerating particles and thereby contributing to the cosmic ray spectrum. Using the PIC-MHD method, which separates the gas into a thermal and a non-thermal component to increase computational efficiency, and relying on existing PIC simulations to determine the rate at which non-thermal particles are injected in the shock, we investigate the evolution of galaxy cluster shocks and their ability to accelerate particles. Depending on the chosen injection fraction of non-thermal particles into the shock, we find that even low-Mach shocks are capable of accelerating particles. However, the interaction between supra-thermal particles and the local magnetic field triggers instabilities and turbulence in the magnetic field. This causes the shock to weaken, which in turn reduces the effectiveness of the supra-thermal particle injection. We investigate how this influences the shock evolution by reducing the particle injection rate and energy and find that a reduction of the particle injection fraction at this stage causes an immediate reduction of both upstream and downstream instabilities. This inhibits particle acceleration. Over time, as the instabilities fade, the shock surface straightens, allowing the shock to recover. Eventually, we would expect this to increase the efficiency of the particle injection and acceleration to previous levels, starting the same series of events in an ongoing cycle of increasing and decreasing particle acceleration.

• 한국지반공학회논문집
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• 제38권11호
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• pp.137-147
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• 2022

지하시설물의 정확한 매설위치를 파악하기 위해 다양한 지구물리탐사방법이 사용되고 있고, 정확도를 개선하기 위해 다수의 연구가 진행되고 있다. 본 연구에서는 우주선 뮤온이라는 입자를 활용하여 새로운 개념의 탐사 방법을 통해 지하매설물 탐사 가능성을 분석하였다. 신틸레이터(scintillator)와 광증배관(silicon photomultiplier)을 조합하여 소형 뮤온 검출기 시작품을 제작하고, 뮤온 입자 계수에 대한 보정 작업을 수행하였다. 시작품을 활용하여 모형 토조의 지반두께를 측정하였으며, 실측값과 약 3%의 오차로 실측값에 가까운 값을 추정할 수 있었다. 또한 뮤온 검출기를 지하매설물 탐사용으로 활용하기 위해 토모그래피 해석기술에 대한 이론적 기반을 분석하고, 천정각(zenith angle) 보정 방법을 제시하였다. 연구 결과 뮤온 입자에 의한 탐사는 밀도 그 자체를 고해상도로 해석하는 것이 가능한 기술로써 지하매설물 탐사를 위해 활용 가능할 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1021-1030
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• 2023

We propose an overall procedure for measuring and unfolding fast neutron spectra using a trans-stilbene scintillation detector. Detector characterization was described, including the information on energy calibration, detector resolution, and nonproportionality response. The digital charge comparison method was used for the investigation of neutron-gamma Pulse Shape Discrimination (PSD). A pair of values of 600 ns pulse width and 24 ns delay time was found as the optimized conditions for PSD. A fitting technique was introduced to increase the trans-stilbene Proton Response Function (PRF) by 28% based on comparison of the simulated and experimental electron-equivalent distributions by the Cf-252 source. The detector response matrix was constructed by Monte-Carlo simulation and the spectrum unfolding was implemented using the iterative Bayesian method. The unfolding of simulated and measured spectra of Cf-252 and AmBe neutron sources indicates reliable, stable and no-bias results. The unfolding technique was also validated by the measured cosmic-ray induced neutron flux. Our approach is promising for fast neutron detection and spectroscopy.

• 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.