• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.20-20
• /
• 2010

GTA (Gas Tungsten Arc)용접은 불활성 분위기에서 용접이 이루어지기 때문에 타 아크용접법에 비해 용접부 품질이 우수하여 고품질이 요구되는 산업분야에 널리 이용되고 있다. 하지만 스테인리스강으로 pipe를 제조하기 위해 GTA 용접을 적용할 경우, Laser 및 고주파 용접 (HFIW)에 비해 용접부 품질 및 용접속도가 낮기 때문에 pipe를 제조하는 산업에서 적용에 제한을 받고 있다. 하지만, GTA는 laser 혹은 HFIW에 비해 가격이 1/10수준으로 낮고, 용접부 gap tolerance 및 용접면 관리범위가 넓은 장점이 있기 때문에 GTA의 용접속도 및 용접품질을 향상시키기 위한 연구가 꾸준히 진행되고 있다. 일반적으로 스테인리스강 GTA용접 시 용접속도를 향상시키기 위해, 모재의 성분 제어 (합금성분 최적화-Al, S, Se, O등), Flux 도포 기술 (산화물을 용접전에 도포하여 용접속도 향상) 및 혼합보호가스 적용 등이 있다. 스테인리스강 용접 시 보호가스로는 용접부 품질을 확보하기 위해 Ar을 주로 사용하고 있다. 하지만 용입 특성을 향상시키기 위해 아크의 온도를 높일 수 있는 He, 혹은 $H_2$ gas를 단독 혹은 혼합하여 사용하고 있다. 오스테나이트계 스테인리스의 경우 용입특성을 향상시키기 위해 Ar에 $H_2$를 2~10%정도 혼합하여 사용하고 있다. 페라이트계 스테인리스강은 수소에 대한 고용도가 상대적으로 작아 용접부 수소 취화를 일으킬 수 있기 때문에 적용에 제한을 받고 있어 그 대안으로 산소를 극히 소량을 혼합하여 용입성 향상에 대한 연구가 보고 되고 있다. 따라서 본 연구에서는 페라이트계 스테인리스강의 용입특성을 향상시킬 목적으로 Ar에 산소를 미량 첨가 (1%미만) 하여 용접전류 및 산소 함량에 따른 용입특성의 변화에 대해 연구하였다. 또한 기계적인 물성 및 부식특성을 평가하였고, 최종적으로 실용화 가능성을 파악하기 위해 용접전극의 수명 테스트를 실시하였다. 실시한 결과, 산소가 첨가량 증가 할수록 용입특성은 상승하였으며, 기계적인 물성 또한 산소를 첨가하지 않은 경우에 비해 거의 유사한 값을 얻을 수 있었다, 하지만 산소함량이 증가 할수록 전극의 수명은 감소하여 교체주기가 증가함을 알 수 있다. 본 연구를 통해 얻어진 기술을 상용화시키기에는 극복해야할 문제가 있지만, 소재 합금성분 설계 시 용접생산성 향상위한 산소성분 범위를 제시할 수 있으리라 판단된다.

• Science of Emotion and Sensibility
• /
• v.11 no.1
• /
• pp.105-112
• /
• 2008

This study investigated the effect of 40% oxygen administration on the addition task performance in three levels of difficulties and physiological signals. Ten male and female college students were selected as the subjects for this study. The experiment consisted of two runs: one was a addition task, with normal air (21% oxygen) administered and the other was with hyperoxic air (40% oxygen) administered. The experimental sequence in each run consisted of Rest1 (3 min), Task1 (1 min, one digit addition task), Task2 (1 min, two digit addition task), Task3 (1 min, three digit addition task), and Rest2 (4 min). Blood oxygen saturation and heart rate were measured throughout the five phases. The accuracy rates of the addition task were enhanced with 40% oxygen administration compared to 21% oxygen. Difference in the accuracy rates grew higher with the rise of difficulty. When 40% concentration oxygen is supplied, blood oxygen saturation increased and heart rate was decreased comparing to 21%. This study showed that the supply of high concentration oxygen increases blood oxygen saturation, which in turns accelerates brain activation resulting from cognitive process and enhances arithmetic abilities. Particularly when difficulty is high, demand for oxygen increases and, as a result, the effect of high concentration oxygen becomes more significant.

• Journal of Korean Ophthalmic Optics Society
• /
• v.16 no.1
• /
• pp.107-116
• /
• 2011

Purpose: The review article was written to establish an excel program that could calculate minimal Dk of contact lens without $O^2$ deficiency and actual $O^2$ concentration on cornea when contact lens were being fitted by changing lens-related factors. Methods: An excel program was formulated to calculate the thickness of post-lens lacrimal layer, Dk of contact lens and $O^2$ concentration on cornea. Results: With the excel program established, minimal $O^2$ concentration needed on cornea could be calculated when the thickness of post-lens lacrimal layer was changed by varying lens-related factors. A different route in the excel program was needed to choose based on the shape of lacrimal layer. The thickness of lacrimal layer was determined by the shape of meniscus made of tear between lens edge and cornea with flat fit. Thus, the $O^2$ concentration showing negative number in calculation decreased on peripheral cornea with flatter fitting and actual $O^2$ concentration would be zero on cornea. With tight fitting, the thickness of post-lens lacrimal layer is much thicker than lens itself thus negative number in calculation by the excel program is shown indicating zero oxygen on cornea. It can cause $O^2$ deficiency regardless of Dk of contact lens. Conclusions: The calculation of thickness of post-lens lacrimal layer and $O^2$ concentration on cornea by the established excel program is suggested to avoid $O^2$ deficiency when fitting state is varied by changing lens-related factors.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.107-110
• /
• 2009

A basic design for a Technical Development Model (TDM) of liquid oxygen lines from the turbopump exit to the oxidizer valves of the combustion chamber and the gas generator was conducted to develop a turbopump-fed liquid rocket engine. The TDM is composed of straight lines, elbows, bellows, a branch, an orifice, flanges and a heat insulator. Materials were determined by consideration of operation conditions, weight constraint and manufacturing procedures. The size and the location of each component were determined by flow analysis of the required flowrate and the pressure loss. Basic designs of the components were conducted by consideration of the operating temperature and the maximum expectation operating pressure. The safety factors were evaluated by structural analysis of design of each component.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.8
• /
• pp.805-811
• /
• 2009

An oxidizer pump of a turbopump for a 30-ton class gas generator cycle engine was tested in the medium of liquid oxygen. The turbine was driven by cold hydrogen gas in the test. The oxidizer pump was operated stably at both design and off-design conditions, satisfying the performance requirements. The pump head coefficient from the liquid oxygen test was 2~3% lower than that from the water test. The power required to run the oxidizer pump was well balanced with the power produced by the turbine.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.33 no.1
• /
• pp.97-101
• /
• 1988

The objective of this paper was to examine the oxygen requriement of rice seeds when the seeds were germinating under the water. The trial was carried out in the laboratory with the different water temperature (25$^{\circ}C$, 17$^{\circ}C$) in the Crop Experiment Station, Suwon. The tested varieties were 6 in japonica and 6 in indica (I) ${\times}$ japonica (J). In the 25$^{\circ}C$ water temperature rice seeds absorbed more dissolved oxygen (DO) and germinating duration was shorter than in the 17$^{\circ}C$ water temperature. DO uptake of japonica rice seeds was faster than that of indica ${\times}$ japonica rice seeds, and the germinating ratio of japonica rice seeds was higher than that of I${\times}$J rice seeds in the water. DO requirements of germinating rice seeds in the water were average 82.4 ${\mu}$g per seed up to coleoptile appearance and average 123.6 ${\mu}$g per seed up to appearance of radicle in the japonica varieties, but I${\times}$J varieties were 96.9 ${\mu}$g and 145.1 ${\mu}$g respectively. Especially when the rice seeds were germinated in the water, length of coleoptile and radicle of japonica rice were significantly longer than those of I${\times}$J rice varieties.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.15 no.2
• /
• pp.86-96
• /
• 2010

The oxygen utilization rate (OUR) is one of the crucial parameters for ocean carbon cycling and climate models. However, parameterization of OUR in the East Sea (Sea of Japan) is yet to be established. We estimated the basin-specific OURs in the East Sea and fitted them with exponential functions with depth by using pCFC- 12 age and apparent oxygen utilization (AOU) measured in summer 1999. The estimated OURs are higher in the upper water column and decrease with depth, in general. The vertical distributions of the estimated OURs in the Western and Eastern Japan Basins (WJB & EJB) are very similar. The OURs in the Ulleung Basin (UB) varied greatly depending on whether the surface layer (0~200 m) data are included in the OUR estimate or not. Apparently, weaker oxygen consumption occurs in the deep layer of Yamato Basin (YB). The ranges of the OURs between 200 m and 2000 m at WJB, EJB, UB, and YB are 8.15~0.83, 8.11~0.68, 5.29~0.73, and 7.31~0.06 ${\mu}mol$ $kg^{-1}$ $yr^{-1}$, respectively. Consideration of the wintertime surface water oxygen disequilibrium condition in estimating the OUR will be necessary in the future study.

• Food Science and Preservation
• /
• v.5 no.3
• /
• pp.239-246
• /
• 1998

Polyimide membrane system was designed for manufacturing nitrogen-enriched gas, and basic technical data was suggested for appling this system to controlled atmosphere storage. The permeability characteristics of pure oxygen and nitrogen could be explained by dual-mode sorption model. There was substantial decrease in the permeation rates of oxygen, which is the more permeable gas, through the polyimide membrane due to the presence of nitrogen in comparison with pure oxygen. However, the permeation rates of nitrogen was increased by the presence of oxygen. The ideal separation factor was in the range of 5 to 6 in the range of temperature and pressure difference studied, and the separation factor of air was lower than the ideal separation factor. The increase of ideal separation factor with increasing temperature is due to the fact that the activation energy for oxygen is larger than that for nitrogen. Nitrogen concentration decreased rapidly with increasing product recovery, and it was found that this is a major operating factor to obtain nitrogen concentration required for controlled atmosphere storage. A relation equation, by which nitrogen concentration in storehouse can be predicted, was suggested under the establishment of a hypothetical model for controlled atmosphere storage process using polyimide membrane system.

• Journal of the Korea Convergence Society
• /
• v.9 no.1
• /
• pp.393-403
• /
• 2018

Although the use of silicone hydrogel contact lenses which are known to have high oxygen transmissibility is increasing, they are being sold without any product labeling of physical properties such as water content and oxygen transmissibility. To analyze the physical properties such as the water content and oxygen transmissibility of approved silicone hydrogel contact lenses, this study collected and analyzed the approval information published on the KFDA website. Of 68 cases of domestic silicone hydrogel contact lenses analyzed in this study, 61 cases (89.7%) did not meet the international standard for oxygen permeability. This is because lenses that are not different from hydrogel contact lenses were submitted for approval as silicone hydrogel contact lenses because there is no domestic standard for silicone hydrogel contact lenses. In future, besides the information published on the website, analysis of the physical properties of a wide variety of actual silicone hydrogel contact lenses on the market is required.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.3
• /
• pp.25-37
• /
• 2005

For pump-fed rocket propulsion system, the temperature of LOX to be supplied to turbopump inlet should be satisfied with pump inlet temperature requirement during all operating stages, as excessive temperatures can result in cavitation due to reduction in NPSH, thus either damaging the pump or adversely affecting pump performance rise. So exact estimation of LOX temperature rise is absolutely needed for developing reliable propulsion system. This paper presents systematic analysis scheme for estimating inner process of cryogenic propellant tank which is needed for LOX temperature rise. And this paper presents LOX temperature rise and thermal stratification for all rocket operating stages including cooling, filling, waiting, pre-pressurization and firing, with the application of buoyancy driven boundary layer theory.