• Journal of Astronomy and Space Sciences
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• 제18권1호
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• pp.1-6
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• 2001

In this paper we investigate the properties of advection-dominated accretion flows (ADAFs) in case that outflows carry away infalling matter with its angular momentum and energy. Positive Bernoulli number in ADAFs allow a fraction of the gas to be expelled in a form of outflows. The ADAFs are also unstable to convection. We present self-similar solutions for advection-dominated accretion flows in the presence of outflows from the accretion flows(ADIOS). The axisymmetric flow is treated in variables integrated over polar sections and the effects of outflows on the accretion flow are parameterized for possible configurations compatible with the one dimensional self-similar ADAF solution. We explicitly derive self-similar solutions of ADAFs in the presence of outflows and show that the strong outflows in the accretion flows result in a flatter density profile, which is similar to that of the convection-dominated accretion flows(CDAFs) in which convection transports the angular momentum inward and the energy outward. There two different versions of the ADAF model should show similar behaviors in X-ray spectrum to some extent. Even though the two models may show similar behaviors, they should be distinguishable due to different physical properties. We suggest that for a central object of which mass is known these two different accretion flow should have different X-ray flux value due to deficient matter in the wind model.

• 대한안전경영과학회지
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• 제8권6호
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• pp.29-39
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• 2006

The effect of parameters on the consequence of the flash fire accident by the release of heavy gas(in this study, xylene vapor) was analyzed. Simulation results showed that the distance with the lower flammable limit($X_{LFL}$) was increased with the increase of the release hole diameter. For the case of the elevated release, $X_{LFL}$ was increased with the increase of the wind speed and the release height, but $X_{LFL}$ was not affected by the wind speed for the release on the ground level. Therefore, the accident in the elevated release was more dangerous than the release on the ground level. In this condition, the release height had more effect on $X_{LFL}$ at the night time than the daytime and in the urban area than the rural area.

• 한국환경농학회지
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• 제31권3호
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• pp.229-234
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• 2012

BACKGROUND: The fruit quality and flowering characteristics of Kiwifruit (A. deliciosa cv. Hayward) in the following year is known to be affected by the extent and timing of defoliation of the current year. In korea, the production of kiwi, which is a perennial, straggling deciduous warm-temperate fruit, is often restricted by wind damage due to typhoons resulting to defoliation at the middle season of its growing period. In this paper, we report the effect of the different timing of defoliation and severities at the current season to the kiwifruit quality. METHODS AND RESULTS: Twenty seven-year-old 'Hayward' trees grown under polyethylene film rain-shelter were defoliated in different days from August to September at seven day-intervals. In each day, 0, 25, 50, 75 and 100% of leaves were removed from the trees. Fruits from each treatment were classified into four floating types (L: lying in bottom, S: standing on bottom, F: floating and SF: floating at the surface of water) by submerging them into tap water. Defoliation of kiwifruit trees in August and September caused air holes in locules of inner pericarp. Increased number of air hole in locules of a fruit was observed in floating types F and SF, and most of the air holes were located in stem end. The defoliation of trees in August significantly reduced the ratio of L-floating type fruits, which have the least number of locule air holes. The extent of defoliation also affected the distribution of the four types, the more leaves removed, the less L-floating type fruits harvested. The weight of fruits from trees defoliated in August was lower than that of fruits from September. Soluble solids content decreased as the number of locule air holes increased. Negative correlations were observed between the extent of defoliation and the weight and soluble solids content of fruits. CONCLUSION: Early defoliation effect on kiwifruit locule air hole occurrence and fruit quality were more severe in August than in September. And also if the defoliation severity is over 25%, severe fruit quality reduction expected to happen due to increase of fruit locule air hole in the inner pericarp.

• 박물관보존과학
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• 제21권
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• pp.53-66
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• 2019

본 연구는 강원도 영월 하송리 유적에서 출토된 금속유물의 보존처리 과정과 표면성분분석 결과를 제시하였다. 금동소형풍탁 1점, 풍설 2점, 호리병 형태 소형 청동병 1점을 대상으로 XRF를 이용한 표면 성분분석을 진행하였고, 호리병 형태 소형청동병은 X-ray를 통한 내부구조관찰을 실시하였다. 금동소형풍탁과 풍설은 같은 위치에서 출토되었으나, 금동소형풍탁은 도금층이 확인되는데 반해, 풍설은 부식층이 표면에 고착되어 가시적으로 확인되지 않았다. 분석결과 금동소형풍탁은 Cu-Sn-Pb 3원계 합금 청동소지에 Au를 수은 아말감으로 도금하여 제작하였음을 확인하였다. 풍설은 소지가 구리이며, 소량의 금성분이 검출되었다, 호리병 형태 소형 청동병은 형태적으로 비슷한 고려시대 화폐인 은병(銀甁)인지 여부를 확인하고자 표면 성분분석과 함께 X-ray 촬영을 실시하였다. X-ray 촬영 결과 저부의 가운데 부분에 작은 구멍을 막았던 것으로 보이는 흔적이 확인되었으며, 전체적인 표면분석 결과에서는 은이 검출되지 않아 은병이 아닌 청동유물임을 알 수 있었다.

• Journal of Astronomy and Space Sciences
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• 제29권1호
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• pp.51-55
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• 2012

A few high-mass X-ray binaries-consisting of an OB star plus compact companion-have been observed by Fermi and ground-based Cerenkov telescopes like High Energy Stereoscopic System (HESS) to be sources of very high energy (VHE; up to 30 TeV) ${\gamma}$-rays. This paper focuses on the prominent ${\gamma}$-ray source, LS 5039, which consists of a massive O6.5V star in a 3.9-day-period, mildly elliptical ($e{\approx}0.24$) orbit with its companion, assumed here to be an unmagnetized compact object (e.g., black hole). Using three dimensional smoothed particle hydrodynamics simulations of the Bondi-Hoyle accretion of the O-star wind onto the companion, we find that the orbital phase variation of the accretion follows very closely the simple Bondi-Hoyle-Lyttleton (BHL) rate for the local radius and wind speed. Moreover, a simple model, wherein intrinsic emission of ${\gamma}$-rays is assumed to track this accretion rate, reproduces quite well Fermi observations of the phase variation of ${\gamma}$-rays in the energy range 0.1-10 GeV. However for the VHE (0.1-30 TeV) radiation observed by the HESS Cerenkov telescope, it is important to account also for photon-photon interactions between the ${\gamma}$-rays and the stellar optical/UV radiation, which effectively attenuates much of the strong emission near periastron. When this is included, we find that this simple BHL accretion model also quite naturally fits the HESS light curve, thus making it a strong alternative to the pulsar-wind-shock models commonly invoked to explain such VHE ${\gamma}$-ray emission in massive-star binaries.

• 생물환경조절학회지
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• 제29권2호
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• pp.120-129
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• 2020

본 연구는 '후지/M.9'와 '홍로/M.9'가 재식된 사과원에 바람이나 우박을 막기 위해 사용되는 망(구멍크기 : 2×2mm)을 수관상부에 색상별로 백색과 청색을 나누어 설치한 후 햇빛의 차광정도 및 생육환경 차이 등에 따른 과실품질 변화를 조사하였다. '후지' 사과의 경우 대기온도 34.8℃인 오후 2~3시경의 과실표면 온도를 측정한 결과, 무처리는 40.0℃로 가장 높았고, 청색 방풍망과 백색 방풍망 처리구는 각각 34.9℃, 36.6℃로 크게 낮았다. '홍로'에서는 무처리구가 44.2℃일 때, 청색 방풍망 처리구는 38.3℃, 백색 방풍망 처리구는 38.5℃를 기록하여 '후지'와 마찬가지로 온도 경감효과를 보였다. '후지'의 과피색차를 조사한 결과, 과피적색도(a^⁎)는 무처리구가 16.5, 청색 방풍망 처리구는 18.0였으나, 백색 방풍망 처리구는 19.3으로 가장 높은 값을 보였다. '홍로'에서도 백색 방풍망 처리구가 적색도가 34.9로 무처리구 28.1에 비해 유의하게 높은 적색도 발현을 보였다. 일소피해 조사결과, '후지'에서 청색 방풍망 처리구 3.8%, 백색 방풍망 처리구 4.2%로 무처리구 9.4%에 비하여 크게 경감되었고, '홍로'의 경우는 청색 방풍망 처리구는 8.8%, 백색 방풍망 처리구는 12.4%로 무처리구 28.8%에 비하여 일소발생이 현저히 감소하였다. 이 같은 결과는 처리별 자외선 수치를 측정하였을 때 무처리 구간의 자외선 값에 비해 청색 방풍망 처리구에서 유의하게 낮아 방풍망 처리에 의한 자외선 차단 효과에 의한 것을 확인할 수 있었다.

• 대한안전경영과학회지
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• 제9권3호
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• pp.21-27
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• 2007

This paper analyses the effect of parameters on the consequences of the unconfined vapor cloud explosion accident (UVCE) by the release of heavy gas (xylene vapor). Simulation results showed that the overpresure was increased with the increase of the release hole diameter and with the decrease of the interested distance and the wind speed. While, the overpresure was not nearly affected by the release height, weather and environmental conditions. From the results of the consequence analysis and analysis of affecting the consequences of UVCE, the emergency plan should be established taking into account these parameters.

• 한국농공학회논문집
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• 제49권6호
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• pp.55-62
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• 2007

Actual states of energy utilizations were investigated and analyzed on three representative rural villages in Chungcheongnam-Do. Rural residents were almost using the ondol boiler as a heating facility and oil(diesel, kerosene) and electricity(night thermal-storage power service) as a heating energy. There were a few households using briquette or firewood in a fuel hole with Korean hypocaust. Most of their cooking facilities were gas ranges using LPG. The most popular hot-water supply system was an oil boiler and the next was an electricity boiler. The amount of energy use in a rural household generally showed 20,000 to 40,000 won/month of the electric power rate, 400 to 800 liter/year of the oil and 60 to 120 kg/year of the LPG. Prompt measures should be taken to promote the spread of new and renewable energy such as solar heat, biomass and wind power, etc.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.240-245
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• 2000

This paper presents the experimental study of drilling for duralumin A2024 with intermittently decelerated feed rate. It is achieved through a programmed periodic increase and decrease in the feed rate using a machining center. The following experimental result were performed with the objective of solving chip to disposal problems. In conventional drilling of aluminum, long continuous chips are produced that wind around the drill causing difficulties in eliminating chips from the cutting zone. In order to acquire the basic data necessary to regulate the chip profile, the relationship between cutting variables and chip shape was investigated. The following conclusions are established from the experimental results. At a suitable feed fluctuation ratio, intermittently decelerated feed drilling proved successful in breaking chips to appropriate lengths while maintaining stable cutting. Thus, it is an effective method for improving chip disposal. The amplitude of the dynamic component of cutting force in intermittent feed frilling is influenced by the feed fluctuation ratio.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.258-263
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• 2007

The performance of louver-finned flat-tube radiators for computer CPU liquid cooling were experimentally investigated. In this study, 5 samples of louver-finned flat-tube radiators with different width size (19mm, 24mm), tube hole (1, 9) and pass number (1, 2, 5) were tested in a wind tunnel. The experiments were conducted under the different air velocity ranging from 1 to 5 m/s. The water flow rate through a pass was 1.7 LPM. Inlet temperatures of air and water were $20^{\circ}C$ and $30^{\circ}C$ respectively. The results showed that the best performance in the 24mm sample considering pressure drop and heat transfer coefficient.