• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.235.2-235.2
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• 2014

Plasma hardly grows in low pressure because of lack of collision. Especially, in extremely low pressure like 1 mTorr, the experiment scale is far larger than mean free path therefore plasma is hardly generated in such low pressure. But low pressure plasma has useful properties like low damage or fine sputtering process because it has typically low electron density. In here, thermal electron is used to make breakdown in low pressure easily and cylindrical geometry is used to help discharge easily. And we changed magnetic field strength to control electron density or temperature. In low pressure, density and temperature behavior is very interesting so its characteristics are examined here.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.605-609
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• 2001

Low density ceramic supporter was prepared by using fly ash as a starting material for the application to the biological aerated filter (BAF) system, and the effect of additives and sintering atmosphere on the apparent and bulk density of the carrier was examined. Borax, Na$_2$O and glass powders were added to produce liquid phase. The density of the supporter decreased as the amount of borax increased. The bulk density of 0.79 g/㎤ and the apparent density of 1.10 g/㎤ were obtained when the fly ash with 15% of borax was sintered at 116$0^{\circ}C$ for 15 minutes. The density also decreased as the plate glass powders past through 22${\mu}{\textrm}{m}$ size were mixed. When the fly ash with 12% of grass powder was sintered at 128$0^{\circ}C$ for 10 minutes, the bulk and apparent density were 0.90g/㎤ and 1.00 g/㎤, respectively. Apparent density of 1.6~1.8g/㎤ was obtained when the fly ash was sintered at 120$0^{\circ}C$ in a weak reducing atmosphere. By maintaining the reducing atmosphere and sintering at a high heating rate, the liquid phase was farmed from the reduced composition of fly ash. This resulted in the formation of closed pores that enabled the low apparent density.

• 한국초전도ㆍ저온공학회논문지
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• 제21권3호
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• pp.6-12
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• 2019

Extended Drude model has been used to obtain information of correlations from measured optical spectra of strongly correlated electron systems. The optical self-energy can be defined by the extended Drude model formalism. One can extract the optical self-energy and the electron-boson spectral density function from measured reflectance spectra using a well-developed usual process, which is consistent with several steps including the extended Drude model and generalized Allen's formulas. Here we used a reverse process of the usual process to investigate the extended Drude analysis when an additional low-energy interband transition is included. We considered two typical electron-boson spectral density model functions for two different (normal and d-wave superconducting) material states. Our results show that the low-energy interband transition might give significant effects on the electron-boson spectral density function obtained using the usual process. However, we expect that the low-energy interband transition can be removed from measured spectra in a proper way if the transition is well-defined or well-known.

• 한국축산식품학회지
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• 제24권3호
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• pp.209-215
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• 2004

본 시험은 고에너지 수준의 사료를 급여한 돼지의 사양성적, 돈육의 도체 특성, 일반성분, 이화학적 특성 및 지방산 조성에 미치는 영향을 조사하기 위해 실시하였다. 80$\pm$3 kg의 삼원교잡종 120두를 공시하여 비육돈 사료 변화의 영양소 수준에 따라 저에너지 DE 3,290 kcal/kg, CP 14.5%, Lysine 0.70%, Ca 0.78로 배합한 사료를 38일간 급여하였고, 고에너지 DE 3,350 kcal/kg, CP 15.0%, Lysine 0.10%, Ca 0.78%로 배합한 사료를 27일간 급여하였다. 저에너지와 고에너지 사료를 급여한 돼지의 종료체중이 101 kg내외에 도달했을 때 도축하여 시험에 공시하였다. 고에너지 사료를 급여한 돼지가 일당 증체량이 높았고, 사료섭취량과 사료요구율은 낮았다(p<0.05). 도체특성과 일반성분은 차이를 보이지 않았다 이화학적 특성 중 고에너지 사료를 급여한 돈육의 가열 감량과 황색도는 저에너지 사료를 급여한 돈육에 비해 현저히 높게 나타내었다(p<0.05). 지방산 조성에서는 저에너지와 고예너지 사료를 급여한 돈육에서 차이를 보이지 않았다. 이상에서 고에너지 사료를 27일간 급여한 돼지는 저에너지 사료를 38일간 급여한 돼지에 비해 성장률이 향상되었고, 돼지의 도체 특성, 물리적 특성 및 지방산 조성에는 미치지 않았지만 돈육의 가열 감량과 황색도가 높았다.

• 대한기계학회논문집B
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• 제29권10호
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• pp.1111-1118
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• 2005

In this study, a unified numerical investigation has been performed on the evolution of weld pool and key-hole geometry during low-power and high-power density laser welding. Unsteady phase-change heat transfer and fluid flow with the surface tension are examined. The one-dimensional vaporization model is introduced to model the overheated surface temperature and recoil pressure during high-power density laser welding. It is shown that Marangoni convection in the weld pool is dominant at low-power density laser welding, and the keyhole with thin liquid layer and the hump are visible at high-power density laser welding. It is also shown that the transition from conduction welding to penetration welding fur iron plate exists when the laser power density is about $10^6W/Cm^2$.

• 천문학회보
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• 제39권1호
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• pp.47.1-47.1
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• 2014

We examine the effect of environment on star formation activity of a sample of galaxy group catalogue given in Tempel et al.(2012) constructed from the Sloan Digital Sky Survey Data Release 8. In order to compare galaxies in different environment, we classify galaxies into two groups: galaxies in low density environment and galaxies in high density environment. After matching colors and apparent magnitudes of the galaxies, we are left with 5912 galaxies in each of the environment category. The fraction of star-forming galaxies in low-density environment is ~34%, higher than ~15% in high-density environment. Star-forming galaxies in low density environment have a higher average SFR value than those in high density environment. The bulge-to-disk ratio for galaxies in two different environment shows bimodal distribution. Regardless of the environment, we find galaxies with high star formation rate despite their red (g-r) color, for which the origin enhancing their star formation rate is investigated.

• 한국화재소방학회논문지
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• 제29권4호
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• pp.81-88
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• 2015

본 연구에서는 다양한 화재실험에서 광학 연기밀도 측정을 위하여 광소멸법을 이용한 저가형 장치가 개발되었다. 저가형 장치의 상대적 측정 정확도는 He-Ne 레이저, 포토디텍터 및 다양한 광학부품을 이용한 고가의 표준장치에 의해 측정된 연기밀도의 비교를 통해 평가되었다. 저가형 장치는 레이저 모듈, 포토셀 그리고 아크릴 보드로 구성되었다. 연기농도의 조절이 용이한 연기 발생장치 실험을 통해, 저가형 장치는 표준장치에 비해 ${\pm}10%$의 범위 내에서 연기밀도를 측정할 수 있음을 확인하였다. 저가 장치의 신뢰성은 또한 폴리에틸렌 화염을 이용한 실험에서도 확인되었다. 결론적으로 개발된 저가형 장치는 연기밀도 측정을 위한 간편한 설치 및 실시간 측정과 함께 고가의 표준장치를 대신하여 사용될 것으로 기대된다.

• 대한물리치료과학회지
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• 제8권2호
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• pp.1015-1021
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• 2001

Objectives: The objective of this study was to investigate analysis of women with low back pain and osteoporosis were measured for 40 normal in the women from July 20, 2000 to October 20, 2000. Methods: Bone mineral density(BMD) of lumbar spine was measured using energy absorptiometry and were correlated with age, calcium. alkaline phosphatase. bone mineral density standard T scores(p<0.05). Results: The bone mineral density of the lumbar spine decreased with aging, The bone mineral density of the lumbar spine decreased with the serum calcium and phosphate increased. The mean bone mineral density of the lumbar spine of healthy women in age($50\sim59$) was $0.83g/cm^2$, the lumbar spine of women low back pain in age($50\sim59$) was 0.75 glad. Conclusion: In the multiple regression of risk factors to bone mineral density(BMD) of lumbar spine were correlated with age, of abortion, calcium, bone mineral density standard T scores(p<0,05). In the prevention and early diagnosis and treatment of osteoporosis, the physician should consider the risk factors.

• 한국항공우주학회지
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• 제49권10호
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• pp.841-847
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• 2021

본 논문에서는 저밀도 표면필름 구리망에 대한 비행체 적용 가능성을 분석하였다. 최근 기존 표면 필름 구리망에서 중량 및 비용을 절감할 수 있도록 표면 필름의 두께를 낮춘 저밀도 표면 필름 구리망이 개발되었다. 이러한 저밀도 표면필름 구리망을 비행체에 적용하기 위해서는 샌드위치 구조에서의 핀 홀 방지 효과와 같은 제작성 확인과 함께 적용 시 전자기 영향성에 대한 분석이 필요하다. 따라서 본 연구에서는 저밀도 필름 구리망 2종과 기존 비행체 적용 구리망 1종에 대해 제작성 및 전자기 영향성을 분석하였다. 표면 구리망에 대한 제작성은 샌드위치 복합재와 표면 구리망을 결합하여 핀 홀 방지효과를 확인하였다. 전자기 영향성 분석은 3D 전자기파 시뮬레이션을 통해 각 샘플에 대한 주기구조를 이용하여 해석하였으며, 자유공간 측정방법을 이용한 저밀도 필름 구리망의 전자기파 투과특성 측정결과를 통해 시뮬레이션 결과가 유효함을 확인하였다. 위 결과로 비행체 적용이 필요한 저밀도 표면필름 구리망에 대한 해석 및 비행체 적용 가능성을 판단할 수 있다.

• Journal of Forest and Environmental Science
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• 제34권1호
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• pp.61-65
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• 2018

To know if small changes in rearing water temperature and density affect the number of bacterial and fungal colonies in metamorphosed frogs, Dybowski's frog tadpoles were reared from Gosner 25-26 stages at either low ($1^{\circ}C$ low to ambient water temperature), ambient, or high ($1^{\circ}C$ high) water temperature (each 15 tadpoles in 20 L water) condition and at either low (10 tadpoles/20 L water), medium (20 tadpoles), or high (30 tadpoles) density condition. Immediately after metamorphosis, we sampled bacteria and fungi from skin, liver, and heart of six metamorphosed frogs, randomly selected for each treatment group. After separate incubation of bacteria and fungi on 3M Petrifilm plates, we counted the number of bacterial and fungal colonies appeared on the plates and compared the numbers among the temperature and density treatment groups. For temperature treatment, high-temperature group had fewer bacterial colonies, while low-temperature group had more fungal colonies than the other two groups. For density treatment, low-density group had fewer bacterial colonies than the other two groups, but the number of fungal colonies were not different among the groups. Our results suggest that small increased rearing water temperature and lowered rearing density could potentially reduce pathogens in farming frogs.