• Korean Chemical Engineering Research
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• 제53권5호
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• pp.584-589
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• 2015

잠수함 및 수중무인체계 등의 산소희박환경에서 연료전지를 통한 효과적인 전력생산을 위해서는 높은 수소저장밀도를 갖는 수소공급원이 필요하다. 디젤연료는 액체연료로서 저장 및 공급이 용이하며, 연료전지의 연료가 되는 수소의 단위질량 및 단위부피당 저장밀도가 높은 장점을 갖고 있다. 이러한 디젤연료의 장점을 기반으로 본 연구에서는 산소희박환경에서 수소생산을 위해 디젤연료의 개질반응을 이용하였으며, 산화제로 단위부피당 산소 저장밀도가 높고 액상으로 보관이 용이한 과산화수소 수용액을 기존의 산화제인 물과 산소의 대체산화제로 이용하는 방법을 제안하였다. 과산화수소 수용액의 디젤개질 산화제로써의 특성을 파악하기 위해 물, 공기 산화제와의 비교실험을 진행하였으며, 기존의 산화제와 디젤 개질반응 시 동일한 특성을 갖는 것을 실험적으로 확인하였다. 또한 상용디젤을 연료로 온도 및 과산화수소 수용액의 농도에 따른 개질성능을 평가하였으며, 49시간의 가속 열화실험을 통하여 디젤, 과산화수소 수용액을 이용한 수소생산의 가능성을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.281-285
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• 2002

The photophysical properties and the singlet oxygen generation efficiencies of meso-tetraphenyl-trithiasapphyrin $(S_3TPS)$ and meso-tetmkis(p-methoxy phenyl)-trithiasapphy rin ((p-MeO)-$S_3TPS$) have been investigated, utilizing steady-state and time-resolved spectroscopic methods to elucidate the possibility of their use as photosensitizers for photodynamic therapy (PDT). The observed photophysical properties were compared with those of other porphyrin-like photosensitizers in geometrical and electronic structural aspects, such as extended ${\pi}$ conjugation, structural distortion, and internal heavy atoms. The steady-state electronic absorption and fluorescence spectra were both red-shifted due to the extended ${\pi}$-conjugation. The fluorescence quantum yields were measured as very small. Even though intersystem crossing rates were expected to increase due to the increment of spin orbital coupling, the triplet quantum yields were measured as less than 0.15. Such characteristics can be ascribed to the more enhanced internal conversion rates compared with the intersystem crossing rates. Furthermore, the triplet state lifetimes were shortened to -1.0 ${\mu}s$ as expected. Therefore, the singlet oxygen quantum yields were estimated to be near zero due to the fast triplet state decay rates and the inefficient energy transfer to the oxygen molecule as well as the low triplet quantum yields. The low efficiencies of energy transfer to the oxygen molecule can be attributed to the lower oxidation potential and/or the energetically low lying triplet state. Such photophysical factors should be carefully evaluated as potential photosensitizers that have extended ${\pi}$-conjugation and heavy core atoms synthesized for red-shifted absorption and high triplet state quantum yields.

• 한국작물학회지
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• 제64권4호
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• pp.287-298
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• 2019

본 연구는 담수직파 초기 입모율 개선을 위해 혐기발아 내성이 우수한 자원들과 국내에서 육성된 직파적응성 품종 간 담수 중 입모관련 특성을 조사하고 담수 환경이 입모 관련 형질에 미치는 영향을 분석하였다. 저온에서 AGT 3자원들의 평균 저온발아율은 92.9%, 평균발아일수 9.1일로 KV품종들의 평균 저온 발아율 62.0%, 평균 발아속도 11.2일에 비해 저온조건에서도 발아율이 높았으며 발아 속도도 빠른 것으로 나타났다. 노지 담수 조건에서 AGT 품종들의 평균 생존율은 53%로 국내 직파 품종의 평균 생존율 22.7%보다 높았으며 온실 담수조건에서도 KV 품종에 비해 입모특성이 우수한 경향이었다. 특히 KHO, PBR, WD3는 저온발아율 및 혐기발아율 등 담수직파 관련형질이 우수하여 담수 직파 전용 벼품종개발을 위한 유용 유전자원으로 활용성이 클 것으로 판단되었다. 모든 공시품종들은 저온(15℃, 18℃)의 담수조건에서 대체적으로 혐기발아율 및 생존율이 낮았으며 초엽 및 유근의 생장도 불량하였으나 21℃ 이상의 조건에서는 생존율과 혐기발아 특성이 크게 개선되었다. 초기입모 관련 형질의 변이에는 온도>용존산소>품종 순으로 영향을 미치는 것으로 나타났으며 발아율 및 유근생장 변이에는 다른 형질에 비해 용존산소 농도의 영향이 다소 크게 작용하는 것으로 나타났다.

• 한국환경과학회지
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• 제4권3호
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• pp.259-267
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• 1995

This study was conducted to evaluate the effects of pressure and dissolved oxygen concentration on the activated slut비e and to determine the optimum depth of deep shaft process. Some results from this study were summarized as follows. 1. It is considered that low sludge product in the activated sludge system maintaining high dissolved oxygen concentration is attributed to the increase of endogeneous respiration rate caused by the increase of aerobic zone in the sludge floe. 2. The increase of dissolved oxygen concentration does not affect to the increase of organic removal efficiency greatly and therefore the limiting factor is the substrate transfer into the inner part of floe. 3. The yield coefficient, Y is decreased in proportion to the increase of oxygen concentration. In this study, Y values arre ranged from 0.70 to 0.41 according to the variation of dissolved oxygen concentration from 18.0mg/$\ell$ to 258 mg/$\ell$. 4. The optimum depth of deep shaft process should be determined within the limits of non-toxicity to the microorganism and it is about loom in this study.

• 한국막학회:학술대회논문집
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• 한국막학회 2002년도 춘계 총회 및 학술발표회
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• pp.35-41
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• 2002

Dense oxygen ionic conducting materials can be used for oxygen separation membranes at high temperatures. However, they show relatively low permeation flux because of their large resistances. To reduce resistances and improve the oxygen permeation flux, thin dense yttria-stabilized-zirconia (YSZ)/Pd composite dual-phase membranes were fabricated by a new approach that combines the reservoir method and chemical vapor deposition (CVD). A thin porous YSZ layer was coated on a porous alumina support by dip-coating the YSZ suspension. A continuous Pd phase was formed inside pores of the YSZ layer by the reservoir method. The residual pores of the YSZ/Pd layer were plugged with yttria/zirconia by CVD to ensure the gas tightness of the membranes. The oxygen permeation fluxes through these composite membrane were 2.0$\times$10$^{-8}$ mol/cm$^2$.s and 4.8$\times$10$^{-8}$ mol/cm$^2$.s at 105$0^{\circ}C$ when air and oxygen were used as the permeate gases, respectively. These oxygen permeation values are about 1 order of magnitude higher than those of pure YSZ membranes prepared under similar conditions.

• 대한기계학회논문집B
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• 제21권12호
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• pp.1690-1700
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• 1997

Entrained coal gasification tests with Datong coal were performed to assess the influence of oxygen/coal ration and pressure. When gasification condition in oxygen/coal ratio has changed from 0.5 to 1.0, optimal gasification condition from low pressure runs was oxygen/coal ratio of approximately 0.9 where CO was produced about 40% and H, about 20%. Under the pressure condition of 12-14 atmospheres, optimal oxygen/coal ratio value was in the region of 0.6 where CO was produced about 55% and H2about 25%. From these results, it was found that the oxygen/ coal ratio for the maximum production of CO and H, was decreasing with the increase in gasifier pressure and also, with increasing oxygen content, carbon conversion was increased. For the Chinese Datong coal, cold gas efficiency was in the range of 40-80%.

• 대한한의학회지
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• 제19권2호
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• pp.100-111
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• 1998

This study is designed to investigate the effects of Saengmaegsan extract on cultured myocardial cell sheets affected by oxygen tension change. The results were as follows : 1. Saengmaegsan meaningfully restored the cellular activity decrease in the cultured myocardial cells affected by high oxygen tension. 2. Saengmaegsan meaningfully lessened the degree of total protein decrease in the myocardial cells caused by high oxygen tension. 3. Saengmaegsan meaningfulJy refrained from syntetic decrease of 4-hydroxyproline in both low oxygen tension group and high oxygen tension group.

• 한국진공학회지
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• 제8권4B호
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• pp.507-513
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• 1999

8mol%-yttria-stabilized zirconia(YSZ) thin films as oxygen ion conductor were deposited by rf-magnetron sputtering, and the oxygen gas sensors with the structure of $SiO_2$ substrate/Ni-NiO mixed reference layer/Pt/YSZ/Pt were fabricated and their oxygen sensing properties were investigated. The steady-state electro-motive force (EMF) values were measured as a function of oxygen partial pressure ($PO_2;form 1.013\times10^3 \textrm{Pa \;to}\; 1.013\times10^5$Pa) and operating temperature ($300^{\circ}C$ to $700^{\circ}C$). The fabricated YSZ oxygen sensor showed the best oxygen sensing properties at 50$0^{\circ}C$. However, oxygen sensing properties were very low at the temperature lower than 30$0^{\circ}C$ due to the lack of oxygen ion mobility and at the temperature higher than $700^{\circ}C$ due 새 intermixing of materials between the layers. Especially, the YSZ sensor operating at $500^{\circ}C$ and oxygen partial pressure above $1.565\times10^4$Pa showed the oxygen sensing properties close to the values predicted by ideal Nernst equation.

• Tuberculosis and Respiratory Diseases
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• 제40권3호
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• pp.283-291
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• 1993

연구배경 : 장기간의 저농도 산소요법은 저산소혈증을 가진 만성폐쇄성폐질환 환자들의 생존율을 향상시킬 뿐만 아니라 삶의 질을 향상시킨다. 저자들은 재택산소요법을 시행하는 환자의 실태를 알아보고 효과적인 개선책을 알아보기 위하여 추적관찰중인 환자 26예에 대한 임상적 관찰을 하였다. 방법 : 대상환자는 경북대학병원 호흡기내과에서 진료를 받고 있는 환자 가운데 가정에서 장기간의 저농도 산소요법을 시행하고 있는 남자 18명 여자 8명 이었으며 재택산소요법을 시행하기전에 신체적 특성과 병력, 폐기능검사, 심전도, 동맥혈가스 및 말초 혈액검사 소견들과 사용중인 산소용기의 종류, 하루에 흡입하는 시간, 투여산소의 농도, 그리고 사용기간 및 문제점 등에 대해서 조사하였다. 결과 : 원인질환은 만성폐쇄성폐질환 14예, 중증폐결핵의 후유증 9예, 기관지확장증 2예 그리고 특발성 폐섬유증 1예였다. 산소치료의 시행동기는 폐성심이 21예, 운동시 호흡곤란 및 심한 환기장애 4예, 그리고 수면중 산소포화도가 90%미만인 경우가 1예였다. 치료시작전의 동맥혈가스소견의 평균치는 $PaO_2$ 57.7 mmHg, $PaCO_2$ 48.2 mmHg 및 $SaO_2$ 87.7% 였으며 폐활량의 평균치는 VC 2.05 L, $FEV_1$ 0.92 L, $FEV_1$/FVC% 51.9%였다. 사용중인 산소용기는 산소탱크를 사용하는 경우가 19예, 산소농축기를 사용하는 경우가 1예, 산소탱크와 액화산소를 함께 사용하는 경우가 2예, 그리고 산소탱크와 휴대용산소를 함께 사용하는 경우 4예였다. 산소사용 기간은 1년 미만이 3예, 1년에서 2년이 15예, 3년에서 5년이 6예 그리고 9년, 10년 동안 산소요법을 시행한 경우도 각각 1예씩 있었다. 산소농도는 전예에서 2.5L/min 이하를 사용하고 있었고 하루 사용시간은 10예 만이 15시간 이상을 사용하였고 대부분이 짧은 시간 동안만 산소를 사용하고 있었다. 결론 : 효과적인 산소투여를 위해서는 환자 및 주위의 사람들에게 장기간의 저농도 산소요법에 대한 교육이 필요하며 편리하게 사용할 수 있는 산소용기의 구입을 위한 제도적 뒷받침이 필요하다.

• 한국기계가공학회지
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• 제15권3호
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• pp.28-35
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• 2016

Forging operations are non-stationary processes occurring because of indirect pressure, generally, under conditions of three-dimensional stress and deformation. Furthermore, due to friction and the constraints of die geometry, deformation is not homogeneous. Material flow and deformation are largely determined by the shape of the tools. It is well known that net-shape forging can improve the mechanical strength of the final product as well as reduce material waste. Oxygen-free copper that is used for electrical and electronic components has excellent electrical and thermal conductivity. Oxygen-free copper parts have a low productivity in cutting process. Thus, the forging process is performed in order to improve the low productivity in cutting process. The forging of oxygen-free copper for electrode body parts was modeled using finite element simulation and forging experiments that were conducted for producing electrode body parts at room temperature. In order to reduce the cost of cutting products, the forging was performed in a closed cavity to obtain near-net or net-shape parts.