• 한국재료학회지
• /
• 제18권11호
• /
• pp.597-603
• /
• 2008

Oxide effects experiments on massive hydriding reactions of Zr alloy with hydrogen gas were carried out at $400^{\circ}C$ under 1 atm in a $H_2$ environment with a thermo-gravimetric apparatus (TGA). Experimental results for oxide effects on massive hydriding kinetics show that incubation time is not proportional to oxide thickness. The results also show that the massive hydriding kinetics of pre-filmed Zr alloys follows linear kinetic law and that the hydriding rates are similar to that of oxide-free Zr alloys once massive hydriding is initiated. Unlikely microstructure of the oxide during incubation time, physical defects such as micro-cracks and pores were observed in the oxide after incubation time. Therefore, it seems that the massive hydriding of Zr alloys can be ascribed to short circuit paths and mechanical or physical defects, such as micro-cracks and pores in the oxide, rather than to hydrogen diffusion through the oxide resulting from the increase of oxygen vacancies in the hypo-stoichiometric oxide.

• 한국해양공학회지
• /
• 제24권5호
• /
• pp.16-21
• /
• 2010

During the loading/offloading operation of a liquefied natural gas carrier (LNGC) that is moored in a side-by-side configuration with an offshore plant, sloshing that occurs due to the partially filled LNG tank and the interactive effect between the two floating bodies are important factors that affect safety and operability. Therefore, a time-domain software program, called CHARM3D, was developed to consider the interactions between sloshing and the motion of a floating body, as well as the interactions between multiple bodies using the potential-viscous hybrid method. For the simulation of a floating body in the time domain, hydrodynamic coefficients and wave forces were calculated in the frequency domain using the 3D radiation/diffraction panel program based on potential theory. The calculated values were used for the simulation of a floating body in the time domain by convolution integrals. The liquid sloshing in the inner tanks is solved by the 3D-FDM Navier-Stokes solver that includes the consideration of free-surface non-linearity through the SURF scheme. The computed sloshing forces and moments were fed into the time integration of the ship's motion, and the updated motion was, in turn, used as the excitation force for liquid sloshing, which is repeated for the ensuing time steps. For comparison, a sloshing motion coupled analysis program based on linear potential theory in the frequency domain was developed. The computer programs that were developed were applied to the side-by-side offloading operation between the offshore plant and the LNGC. The frequency-domain results reproduced the coupling effects qualitatively, but, in general, the peaks were over-predicted compared to experimental and time-domain results. The interactive effects between the sloshing liquid and the motion of the vessel can be intensified further in the case of multiple floating bodies.

• Journal of Chest Surgery
• /
• 제28권11호
• /
• pp.963-966
• /
• 1995

Ischemia reperfusion injury occurs in various diseases. The role of oxygen free radicals in IR injury of the lung has been spotlighted and many studies have been performed. In this study, we tried to prepare a stable rat lung model for IR injury, focusing on surrounding conditions as hilar stripped left lung, clamped left pulmonary artery and bronchus,and declamped after determined period was passed, and right main pulmonary aretery was clamped. Arterial blood gas analyes were performed at 1, 10, 20, 30, minutes after reperfusion. Before clamping, PaO2 was 95 to 120 mmHg in all animals. There were six groups; Group I : temperature 15o C, and 120 minutes clamping, Group II: 20 oC, and 120 minutes clamping, Group III : 25 oC, and 120 minutes clamping, Group IV : 15oC, 90 minutes clamping, Group V : 20 oC, 90 minutes clamping,Group VI: 20 oC, 75 minutes clamping. Each groups contained 10 Sprague Dayley rats. The humidity was maintained 100 % as circulation imerged isotonic Hartmann`s solution of the pleural cavity. In group IV, V, and VI, PaO2 decreased significantly in all animals immediately after reperfusion, but 43 % survived till 10 minutes after reperfusion, it was 74.0$\pm$5.7, 73.3$\pm$10.8,and 88.2$\pm$17.7 mmHg. Pulmonary edema was observed histologically in 2/10 animals in group IV, 6/10 in group V , 3/10 in group VI, 9/10 in group I, and the other lungs showed all edema. We established a stable model by setting ischemic time,and temperature, between 75 to 90 minutes,15 to 20o C, and isotemperature Hartmann`s solution immersion of the pleural cavity.

• 자원리싸이클링
• /
• 제12권5호
• /
• pp.50-56
• /
• 2003

전기로에서 발생하는 분진과 압연스케일의 재활용을 위하여 전기로의 철원과 열원을 동시에 사용할 수 있는 탄화철 제조가 필요하다. 이를 위한 기초 자료를 확보하기 위하여 전기로 분진과 압연스케일의 환원거동과 탄화 거동을 조사하였다. $650^{\circ}C$ 이하의 온도에서 일산화탄소 100%로 탄화를 시키면 유리탄소는 생성되지 않으면서 세멘타이트보다 탄소함량이 더 높은 탄화철(약 9wt% C)을 생성할 수 있었다. 전기로 분진의 환원에 필요한 탄재의 양은 이론 탄재양의 약 1.2배, 그리고 환원온도는 $900^{\circ}C$가 가장 적당하였다. 압연 스케일의 환원온도는 $1000^{\circ}C$가 가장 적당하였다. 전기로 분진 및 압연 스케일의 탄화속도는 압연 스케일의 경우가 모두 빠르게 나타났다. 그리고 슈퍼탄화철의 성분은 대부분 $Fe_2$C이었다.

• 자원리싸이클링
• /
• 제15권1호
• /
• pp.3-11
• /
• 2006

유동층 열분해로에서 상수리나무의 급속열분해를 수행하고 생성된 바이오오일의 물리화학적 특성을 GC/MS를 이용하여 분석하였다. 유동층 열분해로에서 얻어진 상수리나무와 낙엽송의 바이오오일 수율은 각각 $350^{\circ}C,\;400^{\circ}C$에서 최대치를 보였으며 이는 두 수종간의 셀룰로오스 함량차이에 기인하는 것으로 추정된다. 최적온도 이상에서는 반응온도가 증가할수록 프리보드에서의 2차 열분해에 의하여 촤와 오일의 수율이 감소하였고 가스상 성분과 수분의 함량이 증가하였다. 유등층 열분해로에서 시료의 투입량은 생성물의 수율과 조성에는 큰 영향을 주지 않았으며 이는 충분한 혼합이 이루어지기 때문으로 판단되었다.

• 한국산학기술학회논문지
• /
• 제9권1호
• /
• pp.47-52
• /
• 2008

소자가 점점 고집적화 됨에 따라, MOS 소자 제조에 있어서 $SiO_2$의 두께가 ${\sim}1nm$로 낮아질 경우 발생하는 터널링전류와 문틱전압 천이를 방지할 수 있는 새로운 게이트용 유전물질을 개발하여 소자의 크기를 줄이는데 주력하고 있다. 본 실험에서는 원자층증착(ALD: atomic layer deposition) 방법으로 증착된 $ZrO_2$ 박막의 물리적, 전기적 특성에 대하여 연구하였다. ALD $ZrO_2$ 박막을 증착한 후 Ar 가스 분위기에서 $800^{\circ}C$, 1 시간동안 열처리한 다음 XRD, TEM, 그리고 C-V plots을 이용하여 $Pt/ZrO_2/Si$ 소자의 형태, 결정화 동역학, 그리고 경계층 특성을 평가한 결과 열처리에 의해 소자의 특성이 크게 향상됨을 알 수 있었다.

• Toxicological Research
• /
• 제17권
• /
• pp.271-280
• /
• 2001

We report on the applicability oj a method recently developed in our laboratory for measuring the antioxidant potential of isolated chemicals and extracts derived from natural products. Peroxyl radicals generated by thermal homolysis of 2,2'-azobis-amidinopropane (ABAP) oxidize $\alpha$-keto-${\gamma}$-methiolbutyric acid (KMBA) to ethylene, which is monitored by gas chromatography. Inhibition of ethylene formation in the presence of antioxidants that compete with KMBA for peroxyl radicals is the basis of the Total Oxyradical Scavenging Capacity Assay (TOSCA; Winston et al., 1998). Antioxidative activities of water-soluble extracts of American green tea, the anti-hepatotoxic flavonolignan from milk thistle (Silybum marianum) silybin, Ginkgo biloba extract EGb 761, and a series of naturally occuring sesquiterpene lactones (all ger-macranolides found in in fungi, liverworts, and plants) were studied. The specific TOSC value per $\mu$M silybin was 5.2, which is essentially comparable to that of Trolo $x^{ⓡ}$, a water-soluble vitamine E analog. Tea and Ginkgo extracts exhibited potent peroxyl radical scavenging capacity with values, respectively of =1700 and 1000 $\mu$mols Trolo $x^{ⓡ}$ equivalent per gram dry matter. The known anti-inflammatory activity of some germacranolides prompted study of their antioxidant capacity. None of the lactones exhibited antioxidant capacity toward peroxyl radicals comparable to Trolo $x^{ⓡ}$; costunilide, the most lipophilic, had a TOSC value = to glutathione. The potential role of peroxyl radicals in lipidperoxidation, other cellular damage, and var-ious disease states suggest a possible preventive role for silybin, green tea and Ginkgo biloba in oxidative stress caused by these free radical species.ecies.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.576-576
• /
• 2013

Recently, diagnostics of plasma becomes more important due to requirement of precise control of plasma processing based on measurement of plasma characteristics. The Langmuir probe has been used for the diagnostics but it has an inevitable uncertainty and error sources such as incorrect tip length and RF noise. Instead of the Langmuir probe, various diagnostic methods have been developed and researched. The cutoff probe is promising one for plasma density using microwaves and resonance phenomenon at the plasma frequency. The cutoff probe has various advantages as follows; (i) it is simple and robust, (ii) it uses few assumptions, and (iii) it is free from deposition by reactive gas. However, the cutoff probe also has uncertainty and error sources such as gap between tips, tip length, direction of tip plane, and RF noise. In this study, the uncertainty and error sources in manufacturing both probes and in diagnostics process were analyzed via comparative experiment at various discharge conditions. Furthermore, to reveal the user dependence of both probes, three well trained Ph. D students made the Langmuir probe and the cutoff probe, respectively, and it were analyzed. Thought this study, it is established that reliability and validity of the Langmuir probe and the cutoff probe related with not only the intrinsic characteristics of probes but also probe user.

• 한국식품과학회지
• /
• 제47권5호
• /
• pp.652-657
• /
• 2015

다량의 ${\gamma}$-aminobutric acid (GABA)를 함유한 뽕잎차를 제조하기 위해 뽕잎을 채취하여 진공 및 질소가스 치환의 방법으로 12시간 무산소 처리를 하였다. 이후 차를 제조하고 GABA 및 그밖의 주요 성분의 함량 변화를 측정한 결과 뽕잎에 질소 가스 치환처리 및 진공처리를 한 실험군 모두 GABA의 함량이 현저하게 증가하였고(436-472%) 글루탐산은 감소하였다. 일반성분 및 수용성고형물은 거의 변화가 없었으며, 유리당, 카테킨 및 총페놀 함량이 다소 감소한 것으로 나타났다. 뽕잎을 무산소 처리하는 두가지의 방법 즉 질소 가스 치환처리와 진공처리를 비교했을 때 GABA와 주요성분의 함량은 거의 차이가 없었다. 관능평가에서 무처리군과 질소가스, 진공처리군 간에 차이가 없어 무산소 처리를 해도 기호성이 저하되지 않았다. 채잎후 무산소 가공 처리를 하고 뽕잎차를 제조하는 것은 관능적인 품질을 유지하면서도 뽕잎차의 기능을 향상시킬 수 있는 효과적인 방법이라 판단된다.

• 한국자동차공학회논문집
• /
• 제16권4호
• /
• pp.47-55
• /
• 2008

Turbocharger has a main purpose on recycling of the exhaust gas from the engine cylinder. On the basis of the facility characteristics, the turbocharger supported on floating ring bearings has some problems such as the large volume, oil supplement for lubrication and high power loss due to high operating torque. The air foil bearing has been studied as the bearing element to be able to alternate the floating ring bearing without the problems of the floating ring bearing. In this study, the air foil bearing has 2 parts; journal and thrust bearings, and the test facility consists of the engine, exhaust and intake parts. In addiction, the specification of the turbocharger follows a small turbocharger for SUV engine. The engine speed is varied from 750 (idle rpm) to 2,500 rpm and then, the rotating speed of the turbocharger rotor is accelerated from 0 to 100,000 rpm. From those experiments, the comparison between the performances of the air foil bearing and floating ring bearing is conducted and the results show that the air foil bearing has less power loss, maximum 770 watt, than the floating ring bearing, maximum 5,110 watt. This result verifies that the air foil bearing is more efficient and able to output more power under the same condition of the input power.