• 핵의학기술
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• 제13권3호
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• pp.147-151
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• 2009

Purpose: 2-[$^{18}F$]Fluoro-2-deoxy-D-glucose ([$^{18}F$]FDG) particularly plays as a important role in Positron Emission Tomography (PET) imaging in nuclear medicine. Domestic [$^{18}F$]FDG auto synthesizers are installed in Seoul National University Bundang Hospital (SNUBH) at June 2008, these modules were known that it's synthetic yields were guaranteed in average $45{\pm}5%$ so far. To improve yields and convenience of domestic [$^{18}F$]FDG auto synthesizer, numerous trials in reaction time, base concentration, pressure and temperature were performed to increase [$^{18}F$]FDG yields. Materials and Methods: Several synthetic factors (temperature, time and pressure) and shortcoming were corrected based on many evaporation test. Syringe dispensing of tetra-butylammonium bicarbonate (TBAB) was replaced with micro pipette to prepare tetrabutyl ammonium fluoride salt ([$^{18}F$]TBAF). Troublesome refill of liquid nitrogen every 2 hours which was used to protect vacuum system was changed to charcoal cartridge, base guard filter. To monitor the volume of delivered $[^{18}O]OH_2$ from cyclotron by surveillance camera, we set up the volumetric vial on the cover of the module. In addition to, the recovery vial was added in [$^{18}F$]FDG production system to recover [$^{18}F$]FDG loss due to the leak of valve ($V_{13,14}$) in [$^{18}F$]FDG purification process. Results: When we used micro pipette for adding TBAB ($30\;{\mu}L$ in 12% $H_2O$ in acetonitrile), this quantitative dispensation has enabled to improve $5.5{\pm}1.7%$ residual fluorine-18 activity in fluorine separation cartridge compared to syringe adding. Besides, the synthetic yields of [$^{18}F$]FDG has increased $58{\pm}2.6%$ (n=19), $58{\pm}2.9%$ (n=14), $60%{\pm}2.5%$ (n=17) for 3 months. The life cycle of charcoal cartridge and base vacuum was 3 months prior to filling liquid nitrogen every 2 hours and additional side separator can prevent pump corrosion by organic solvent. After setting of volumetric indicator vial, the operator can easily monitor the total volume of irradiated $[^{18}O]OH_2$ from cyclotron. The recovery vial can be used for the stabilizer when an irregular [$^{18}F$]FDG loss was generated by the leak of valves ($V_{13,14}$). Conclusions: We has optimized appropriate synthetic conditions (temperature, time, pressure) in domestic [$^{18}F$]FDG auto synthesizer. In addition to, the remodeling with several accessories improve yields of domestic [$^{18}F$]FDG auto synthesizer with reliable reproducibility.

• Journal of Nutrition and Health
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• 제36권6호
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• pp.603-612
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• 2003

Postmenopausal women are at an increased risk of developing coronary artery disease. This is due to primarily dyslipidemia accompanying the loss of estrogen secretion. Soy isoflavones are known to have weak estrogenic effects. The purpose of this study is to investigate whether isoflavone supplement improves the risk of cardiovascular disease in hypercholesterolemic postmenopausal women. Subjects consisted of 39 Korean postmenopausal women with hypercholesterolemia (total cholesterol $\geq$ 200 mg/㎗ or LDL cholesterol $\geq$ 130 mg/㎗). Subjects were divided into 2 groups; placebo group (PG), isoflavone supplement group (IG). During 12 weeks, subjects were given placebo and 80mg isoflavone daily. Anthropometric measurement, blood sample analysis and dietary intake measurement were taken at baseline and after 12 weeks. After 12 weeks, systolic blood pressure was decreased significantly (p ＜ 0.01) and plasma HDL cholesterol level was increased significantly (p ＜ 0.05) in IG. But there were no significant changes in plasma total cholesterol, LDL cholesterol and triglyceride levels after isoflavone supplementation. There was a negative correlation between initial plasma HDL cholesterol level and the extent of plasma HDL cholesterol reduction in IG (r＝-0.572, p＝0.012). Atherogenic index (AI), total-/LDL- cholesterol ratio and LDL/HDL cholesterol ratio were improved significantly after isoflavone supplementation. In subjects whose initial plasma LDL cholesterol level were above 160 mg/㎗, plasma malondialdehyde (MDA) level were decreased and total antioxidant status (TAS) were increased significantly after isoflavone supplement (p ＜ 0.05). However there were no significant changes in flow-mediated dilator (FMD), the marker of endothelium-dependent vasodilation and nitroglycerine-mediated dilator (NMD), the marker of endothelium-independent vasodilation and the extent of DNA damage after isoflavone supplement. In conclusion, these results indicate that isoflavone supplement may decrease the risk of cardiovascular disease via improving blood pressure, HDL cholesterol level and AI in hypercholesterolemic postmenopausal women. Futhermore, in case of subjects with elevated LDL cholesterol level, isoflavone supplementation may have more antiatherogenic effects via improving antioxidant status.

• 분석과학
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• 제14권5호
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• pp.451-457
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• 2001

절삭유(Metalworking Fludis, MWF) 노출로 인한 건강상의 장애는 암, 호흡기질환, 피부질환이다. MWF는 20여가지 이상의 화학물질이 혼합된 고분자의 화합물로서 상온에서 쉽게 증발되지 않는다. 이러한 특성으로 공기 중 MWF미스트의 측정과 분석은 PVC필터를 이용한 중량법이 국제적으로 공인되어 이용되고 있다. 그러나 사업장에서 MWF는 사용과정에서 분산되면 표면적이 커지고 증발하기 쉬운 상태로 된다. 본 연구는 실험실에서 MWF미스트 발생장치를 제작하여 MWF미스트가 필터에 채취되고 분석되는 과정에서 손실되는 양과 원인을 정량적으로 분석하였다. 즉 챔버에서 MWF가 채취된 PVC필터를 깨끗한 공기로 일정시간동안(10 ~ 240 분) 접촉하고 건조하여 각각의 과정(공기접촉, 건조기간)에서의 손실을 평가하였다. 공기와의 접촉 10분 후에 손실된 MWF양은 원래양의 12.4% - 21.8%였다. 전과정에서 손실된 양의 53.3%가 공기의 접촉초기에 일어나는 것을 확인하였다. PVC필터에 채취된 MWF의 손실은 건조과정에서 일어난 것을 확인하였다. PVC필터에 채취된 MWF의 손실에 영향을 미치는 요인을 분석하기 위한 다중회귀분석에서 MWF의 특성(사용중인 것과 사용하지 않는 것)이 유의한 예측변수였다. 이 연구 결과에 따르면, 국제적으로 공인된 증량법에 의한 공기중 MWF측정은 과소평가되는 것으로 판단된다.

• 대기
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• 제23권1호
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• pp.1-11
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• 2013

The angular momentum transport of an idealized axisymmetric vortex in the developing stage was investigated using the Weather Research and Forecast (WRF) model. The balanced axisymmetric vortex was constructed based on an empirical function for tangential wind, and the temperature, geopotential, and surface pressure were obtained from the balanced equation. The numerical simulation was carried out for 6 days on the f-plane with the Sea Surface Temperature (SST) set as constant. The weak vortex at initial time was intensified with time, and reached the strength of tropical cyclone in a couple of days. The Absolute Angular Momentum (AAM) was transported along with the secondary circulation of the vortex. Total AAM integrated over a cylinder of radius of 2000 km decreased with simulation time, but total kinetic energy increased rapidly. From the budget analysis, it was found that the surface friction is mainly responsible for the decrease of total AAM. Also, contribution of the surface friction to the AAM loss was about 90% while that of horizontal advection was as small as 8%. The trajectory of neutral numerical tracers following the secondary circulation was presented for the Lagrangian viewpoint of the transports of absolute angular momentum. From the analysis using the trajectory of tracers it was found that the air parcel was under the influence of the surface friction continuously until it leaves the boundary layer near the core. Then the air parcel with reduced amount of angular momentum compared to its original amount was transported from boundary layer to upper level of the vortex and contributed to form the anti-cyclone. These results suggest that the tropical cyclone loses angular momentum as it develops, which is due to the dissipation of angular momentum by the surface friction.

• 구강회복응용과학지
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• 제19권2호
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• pp.57-67
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• 2003

Suppose that dental occlusion is related to body posture. We want to find out that improving occlusal balance may affect vibration and distribution of C.O.P. in which way, by measuring change of posture and center of gravity (center of pressure, C.O.P.) which plays important role in measuring balance sensation. Total 11 students at Kyung Hee dental college students, 4 females and 9 males (age: 23-30) participated in this test, who have normal occlusion (Angle's classification I), no TMJ problems. All of the participants have no tooth loss except 3rd molar, no prosthesis over single tooth restoration, no orthopedic problems which affect balance sensation, and no otorhinolaryngological problems. First, we registrated bite by centric relation, and then fabricated stabilization splint that is increased 3.5mm vertical dimension around premolar region. By F-scan (Tekscan Inc., Boston, Mass), we measured discrepancy of average contact pressure of left and right foot. And we also measured discrepancy of vibration of C.O.P(center of pressure). before setting stabilization splint and after wearing stabilization splint at intervals of 1 week, 2 weeks, 3 weeks after. In normal human beings, improved occlusal balance by stabilization splint leads to decrease of vibration of C.O.P. (P<0.05). One week after wearing stabilization splint, vibration of C.O.P. decreased reliably (P<0.05), two weeks after wearing stabilization splint, vibration of C.O.P. decreased similarly comparing to before wearing and one week after wearing. (P<0.05) After two weeks and three weeks, however, it was hard to find reliability. (P>0.05) Difference between average contact pressure of right and left foot also decreased. (P<0.05) We could find decrease after one week of wearing stabilization splint (P<0.05) and two weeks after, the decrease was more reliable than one week after. (P<0.05) After two weeks and three weeks, however, it was hard to find reliability. Improvement of occlusal balance leads to decrease of vibration of C.O.P. and decrease of difference between right and left average contact pressure.

• 한국추진공학회지
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• 제18권1호
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• pp.33-41
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• 2014

초음속 터빈에서는 동익 유로에서의 질식 가능성을 줄이며, 설계 압력비를 구현할 수 있도록 한다. 하지만 동익 오버랩을 적용하면, 펌핑손실, 확산손실 등의 추가적인 손실이 동반된다. 따라서 터빈성능을 극대화하기 위한 최적 오버랩 형상을 찾기 위해 근사최적화 기법을 적용하였다. 설계변수는 동익 오버랩의 형상변수이다. 최적설계 결과, 기준모델 대비 팁 누설유량은 약 50% 감소하였으며, 정효율은 약 4% 증가하였다. 팁 오버랩 크기가 성능에 미치는 영향이 크게 나타난 반면, 허브 오버랩 크기가 성능에 미치는 영향은 작게 나타났다.

• 한국정밀공학회지
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• 제29권1호
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• pp.121-125
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• 2012

This paper presents the friction and anti-wear characteristics of nano-oil with a mixture of a refrigerant oil and carbon nano-particles in the thrust slide-bearing of scroll compressors. Frictional loss in the thrust slide-bearing occupies a large part of total mechanical loss in scroll compressors. The characteristics of friction and anti-wear using nano-oil is evaluated using the thrust bearing experimental apparatus for measuring friction surface temperature and the coefficient of friction at the thrust slide-bearing as a function of normal loads up to 4,000 N and rotating speed up to 3,200 rpm. It is found that the coefficient of friction increases with decreasing rotating speed and normal force. The friction coefficient of carbon nano-oil is 0.023, while that of pure oil is 0.03 under the conditions of refrigerant gas R-22 at the pressure of 5 bars. It is believed that carbon nano-particles can be coated on the friction surfaces and the interaction of nano-particles between surfaces can be improved the lubrication in the friction surfaces. Carbon nano-oil enhances the characteristics of the anti-wear and friction at the thrust slide-bearing of scroll compressors.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.34-39
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• 2005

본 논문에서는 3차원 초음속 노즐 형상 변수에 따른 부분입사형 터빈의 유동 및 성능 특성을 알아보기 위하여 3차원 노즐 형상 변수를 노즐 모양 및 노즐 출구 단면 형상으로 설정하여 전산해석을 실시하였다. 먼저 노즐 모양에 따른 유동 및 성능 특성을 비교해 본 결과, 사각형 노즐이 원형 노즐보다 축방향 간극내에서 발생하는 전압력 손실이 적었으며, 이로 인하여 파워가 약 1.5% 증가하였다. 다음으로 사각형 노즐출구단면의 면적에 따른 유동 및 성능 특성을 비교해 본 결과, 노즐 출구 단면과 로터의 hub/tip 사이의 간극과 노즐간의 간격이 터빈 성능에 크게 영향을 줌을 확인할 수 있었다.

• Nuclear Engineering and Technology
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• 제32권4호
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• pp.395-409
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• 2000

Parametric studies were performed to assess the sensitivity in determining the maximum in-vessel heat removal capability from the core material relocated into the lower plenum of the reactor pressure vessel (RPV）during a core melt accident. A fraction of the sensible heat can be removed during the molten jet delivery from the core to the lower plenum, while the remaining sensible heat and the decay heat can be transported by rather complex mechanisms of the counter-current flow limitation (CCFL) and the critical heat flux (CHF）through the irregular, hemispherical gap that may be formed between the freezing oxidic debris and the overheated metallic RPV wall. It is shown that under the pressurized condition of 10MPa with the sensible heat loss being 50% for the reactors considered in this study, i.e. TMI-2, KORI-2 like, YGN-3&4 like and KNGR like reactors, the heat removal through the gap cooling mechanism was capable of ensuring the RPV integrity as much as 30% to 40% of the total core mass was relocated to the lower plenum. The sensitivity analysis indicated that the cooling rate of debris coupled with the sensible heat loss was a significant factor The newly proposed heat removal capability map (HRCM) clearly displays the critical factors in estimating the maximum heat removal from the debris in the lower plenum. This map can be used as a first-principle engineering tool to assess the RPV thermal integrity during a core melt accident. The predictive model also provided ith a reasonable explanation for the non-failure of the test vessel in the LAVA experiments performed at the Korea Atomic Energy Research Institute (KAERI), which apparently indicated a cooling effect of water ingression through the debris-to-vessel gap and the intra-debris pores and crevices.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1219-1224
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• 2006

This paper presents the friction and anti-wear characteristics of nano-oil with n mixture of a refrigerant oil and carbon nano-particles in the thrust slide-bearing of scroll compressors. Frictional loss in the thrust slide-bearing occupies a large part of total mechanical loss in scroll compressors. The characteristics of friction and anti-wear Lising nano-oil is evaluated using the thrust bearing tester for measuring friction surface temperature and the coefficient of friction at the thrust slide-bearing as a function of normal loads up to 4,000 N and orbiting speed up to 3,200 rpm. It is found that the coefficient of friction increases with decreasing orbiting speed and normal force. The friction coefficient of carbon nano-oil is 0.015, while that of pure oil is 0.023 under the conditions of refrigerant gas R-22 at the pressure of 5 bars. It is believed that carbon nano-particles can be coated on the friction surfaces and the interaction of nano-particles between surfaces can be improved the lubrication in the friction surfaces. Carbon nano-oilenhances the characteristics of the anti-wear and friction at the thrust slide-bearing of scroll compressors.