• 대한기계학회논문집A
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• 제33권11호
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• pp.1187-1194
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• 2009

During the last decade, possibility of flaw occurrences has been rapidly increased world-widely as the increase of operating times of petro-chemical facilities. For instance, from a recent in-service inspection, three different sized surface cracks were detected in welding parts of a spherical oxygen holder in Korea. While API579 code provides corresponding engineering assessment procedures to determine crack driving forces, in the present work, numerical analyses are carried out for the cracked oxygen holder to investigate effects of complex geometry, analysis model and residual stress. With regard to the detailed finite element analysis, stress intensity factors are determined from both the full three-dimensional model and equivalent plate model. Also, as an alternative, stress intensity factors are calculated for equivalent plate model by employing the noted influence stress function technique. Finally, parametric structural integrity evaluation of the cracked oxygen holder is conducted in use of failure assessment diagram method, J/T method and DPFAD method. Effects of the geometry and so forth are examined and key findings from the simulations are fully discussed, which enables to determine practical safety margins of spherical components containing a defect.

• 한국재료학회지
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• 제27권5호
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• pp.237-241
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• 2017

As a basic study for the removal of oxygen in solid Nd metal by metal Ca vapour, by using the thermodynamic data such as ${\Delta}G-T$ diagrams and Nd-O and Nd-Ca equilibrium diagrams, the amount of residual oxygen in solid Nd metal formed based on deoxidation reaction by Ca vapour, instead of by direct contact of solid Nd metal and Ca solution, was determined. Deoxidation experiments were carried out for solid Nd metal in a temperature range of $890{\sim}970^{\circ}C$ for 1h to 4h and content of addition Ca of 0.6~1.8 g (5~15 wt% of solid Nd metal). As a result, it was found that as deoxidation temperature increased, dissolved oxygen decreased. Especially, it was observed that a small amount of Nd-Ca alloy liquid was formed on the surface of the solid Nd metal sample deoxidized at $970^{\circ}C$ for approximately 1 hour. Also, it was found that if the content of addition Ca was 1.8 g (15 wt% of solid Nd metal) the amount of produced Nd-Ca alloy increased slightly. However, for the Nd sample with which the deoxidation reaction was performed at $930^{\circ}C$ for 4h with content of addition of Ca of 1.5 g (13 wt% of Nd metal), the residual oxygen was found to decreased to 12.00 ppm.

• KSBB Journal
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• 제13권6호
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• pp.675-680
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• 1998

In both 7L and 20L fermentor experiments the level of dissolved oxygen (D.O) strongly affected growth and PHBV production of Azotobacter vinelandii UWD. A higher D.O. increased carbon substrate consumption rate and cell growth rate with a similar residual biomass production. However, a lower D.O. was a much better condition for PHBV production. In a 20L fermentor experiments controlled at 5% D.O. cell growth rate was about twice faster(0.555 hr-1 and 0.260 hr-1 at the acid and the glucose phase, respectively) with an equal amount(4.5 g/L) of residual biomass production. However, PHBV content in the cell(62.3 wt%) increased 17.3 times at 1% D.O.

• 전자공학회논문지D
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• 제36D권4호
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• pp.48-56
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• 1999

본 논문에서는 초기 산소 농도가 고에너지 이온 주입시 결정 격자 손상에 의해 발생하는 산소 축적(pileup) 현상 및 주입된 불순물의 확산에 미치는 영향을 실험적으로 고찰하였다. 초기 산소 농도가 11.5, 15.5 ppma인 p-type (100)실리콘 웨이퍼에 \sup 11\B\sup +\ \sup 31\P\sup +\ 이온을 각각 1.2 MeV, 2.2 MeV 의 에너지로 1×10\sup 15\cm\sup 2\ 주입하고, 700℃(20시간)+1000℃(10시간)의 2단계 열처리를 거치 후 주입된 불순물 및 산소 농도의 분포를 이차이온질량분석기 (Secondary Ion Mass Spectrometry, SIMS)로 관찰하였으며 잔류 2차 결함의 분포는 투과전자현미경(Transmission Electron Microscopy, TEM)으로 관찰하였다. SIMS 측정 결과 산소의 축적이 {{{{ { R}_{ } }}}}\sub p\(projected range) 부근에서 관찰되었으며 열처리 후에도 상당한 양의 2차 결합 띠가 {{{{ { R}_{ } }}}}\sub p\부근에서 관찰되는 것으로 보아 2차 결함에 의해 산소가 포획되었음을 알 수 있다. 또한 붕소와 인의 확산은 웨이퍼의 초기 산소 농도가 클수록 벌크 방향으로의 확산이 증대되는 현상을 볼 수 있었다.

• 한국포장학회지
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• 제15권2호
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• pp.49-54
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• 2009

레토르트 삼계탕은 장기간 저장되는 제품이므로 포장 불량률을 가능한 한 최소화하는 것이 품질 안전과 소비자 식중독 문제를 방지하기 위해서 중요한 사안이다. 따라서 업계에서는 현행 사용되는 삼계탕용 포장재를 이용하여 저장 시험을 병행하되 기존 포장재의 물성을 표준화하고, 아울러 포장작업시 가능한 한 포장내 잔존산소량이 낮게 유지되는 포장방법을 동원하고, 봉함부위가 오염되지 않도록 유의하며 멸균 후 열봉함강도가 낮아지는 것을 감안하여 포장재 스펙을 결정하는 방안이 강구되어져야 할 것이다. 이를 위해서는 가능한 한 포장내 잔존산소량을 줄이기 위하여 포장내 headspace를 줄이거나 질소 등 비활성기체를 주입 후 포장하는 것이 바람직하겠다. 그러나 현행 업계에서 삼계탕을 질소치환포장하는 것이 공정의 속도와 운용비용 등을 고려할 때 쉽지 않을 것으로 판단된다. 따라서 삼계탕 포장시 육수의 충진온도는 최소한 85이상 가열된 상태로 주입하고, 주입시 열봉함부위가 오염되지 않도록 유의하며, 필요하면 guide bar등과 같은 보조 장치를 설치하거나 파우치 밀봉 전 headspace를 압착하는 기술, 그리고 파우치 하부의 유사핀홀 현상을 방지하기 위한 보호대를 설치하여 육수를 충진하는 기술 등을 적용하는 것이 바람직할 것으로 사료된다. 그리고 멸균 처리 후 봉함강도가 감소하는 만큼 이를 감안하여 포장재의 선택과 포장작업이 이루어져야 할 것으로 판단된다.

• 한국주조공학회지
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• 제15권2호
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• pp.175-183
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• 1995

It is difficult to remove such interstitial impurities as sulfur, oxygen, hydrogen and carbon in Fe-Ni alloys. Thermodynamic and kinetic studies were carried out on the behavior of hydrogen gas, oxygen gas, Si, Al and slag, and the reaction time by the $Ar/Ar-H_2$ plasma and electron beam melting. After the addition of Al, Si, they were melted by Ar plasma with reaction time changed. 80%Ni-Fe alloys showed a better deoxidation than 36%Ni-Fe alloys. At $Ar-H_2$ plasma melting, the deoxidation was significant. In the case of the electron beam melting, the residual oxygen was higher than in Ar plasma melting because electron beam melting temperature was lower than that of Ar plasma. For the decaburization, it was melted by $Ar-O_2$ plasma melting, which could remove effectively carbon by activated oxygen in plasma. We added slag to Fe-Ni alloys for the desulfurization. As the result of this experiments, the amount of residual sulfur was not changed according to the slag ratio and reaction time.

• 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.

• 펄프종이기술
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• 제37권3호
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• pp.74-80
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• 2005

The compositions of residual extractives in woodmeal, unbleached and oxygen-delignified aspen kraft pulps were investigated with gas chromatography(GC) and gas chromatography-mass spectrometry (GC-MS) with focus on fate of extractives in kraft pulping and oxygen delignification. Steryl esters and shorter retention time (shorter than palmitic acid) extractives were main extractives in aspen woodmeal. Shorter retention time extractives were well removed in kraft pulping. Sterol esters were hydrolyzed to sterols and fatty acids. Sterols and fatty acids were two major extractives classes in unbleached kraft pulps. Linoleic acid was main fatty acids in unbleached pulps compared with palmitic acid which is generally found in aspen woodmeal. Sterolsand fatty acids were also two major extractives classes in oxygen-delignified kraft pulps. However, linoleic acid was well removed in oxygen delignification.

• 한국식품영양학회지
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• 제11권6호
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• pp.635-639
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• 1998

The thermal degradation pattern of $\alpha$-, ${\gamma}$-and $\delta$-tocopherols in glycerol was investigated during heating at 100~25$0^{\circ}C$ for 5-60 min in the absence of oxyge. The tocopherols and thermally decomposed products were separated by HPLC with a reversed phase $\mu$-Bondapak C18-column. The degradation pattern of $\alpha$-tocopherol during the heating in the absence of oxygen was different from those of ${\gamma}$-and $\delta$-tocopherols. But the degradation patterns of ${\gamma}$-and $\delta$-tocopherols were similar to each other. The residual content of $\alpha$-tocopherol during the heating in the absence of oxygen decreased to the range 12~65% and those of ${\gamma}$-and $\delta$-tocopherols decreased to the range 4~96%. The thermal degradation of tocopherols in the absence of oxygen was less than that in the presence of oxygen.

• 한국환경보건학회지
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• 제39권3호
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• pp.289-299
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• 2013

Objectives: For the field application of the dielectric barrier discharge plasma reactor, scale-up of the plasma reactor is needed. This study investigated the possibility of inactivation of microorganisms in sewage using pilot multi-plasma reactor. We also considered the possibility of degradation of total organic carbon (TOC) and nonbiodegradable matter ($UV_{254}$) in sewage. Methods: The pilot plasma reactor consists of plasma reactor with three plasma modules (discharge electrode and quartz dielectric tube), liquid-gas mixer, high voltage transformers, gas supply equipment and a liquid circulation system. In order to determine the operating conditions of the pilot plasma reactor, we performed experiments on the operation parameters such as gas and liquid flow rate and electric discharge voltage. Results: The experimental results showed that optimum operation conditions for the pilot plasma reactor in batch experiments were 1 L/min air flow rate), 4 L/min liquid circulation rate, and 13 kV electric discharge voltage, respectively. The main operation factor of the pilot plasma process was the high voltage. In continuous operation of the air plasma process, residual microorganisms, $UV_{254}$ absorbance and TOC removal rate at optimal condition of 13 kV were $10^{2.24}$ CFU/mL, 56.5% and 8.6%, respectively, while in oxygen plasma process at 10 kV, residual microorganisms, $UV_{254}$ absorbance and TOC removal rate at optimal conditions were $10^{1.0}$ CFU/mL, 73.3% and 24.4%, respectively. Electric power was increased exponentially with the increase in high voltage ($R^2$ = 0.9964). Electric power = $0.0492{\times}\exp^{(0.6027{\times}lectric\;discharge\;voltage)}$ Conclusions: Inactivation of microorganisms in sewage effluent using the pilot plasma process was done. The performance of oxygen plasma process was superior to air plasma process. The power consumption of oxygen plasma process was less than that of air plasma process. However, it was considered that the final evaluation of air and oxygen plasma must be evaluated by considering low power consumption, high process performance, operating costs and facility expenses of an oxygen generator.