• 한방재활의학과학회지
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• 제21권4호
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• pp.219-226
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• 2011

Objectives: The aim of this pilot study is to investigate qigong as a trailing method to treat diseases and improve the quality of life. Methods: We used a controlled clinical study in this research qigong group(n=34) practiced the zhan zhuang gong for 2 minutes. Control group(n=33) did low intensity walking for 2 minutes. Changes of grip strength, heat rate and rating of perceieved exertion were measured before and after treatment. Paired t-tests and independent t-tests were applied for statistical analysis. Results: Qigong group showed significant improvement in grip strength(p<0.05), whereas the control group showed insignificant changes(p<0.05). Both groups demonstrate significant changes in heart rate(p<0.05). In rating of perceieved exertion, significant difference showed between groups(p<0.05). Conclusions: The zhan zhuang gong, a kind of qigong improved grip strength by 2 minutes of practice. We may conclude that zhan zhuang gong could be a method of improving physical strength.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.474-478
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• 2010

순수 파라핀에 10 wt%의 LDPE를 첨가한 용융성 혼합 연료로 제작한 다이아프램을 장착한 연료를 사용하여 하이브리드 로켓 연소 실험을 수행하였고 다이아프램이 없는 파라핀 연료의 결과와 비교하였다. 용융성 다이아프램을 설치한 경우 강화된 난류와 열전달로 인해 다이어프램 후방의 연료 후퇴율이 크게 증가하였으며 특성속도와 비추력이 증가하였다. 연소 불안정 해석에서는 심각한 연소 불안정이 관찰되지 않았다. 이를 통해 용융성 다이어프램이 용융성 연료를 사용하는 하이브리드 로켓의 낮은 연소 효율 개선에 효과적임을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.400-405
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• 2004

In this study, the optimal welding condition of the input power was selected experimentally through the ERW simulator, which is equal to welding status of ERW part in pipe. This condition is the input power 250kW in the heat treatment of the $900^{\circ}C$ normalizing derived from the nondestructive technique and impact energy. In order to evaluate the variation of the fatigue life in the pipe, fatigue surface crack growth test of base and optimal welded metal were performed statistically. As stress intensity factor range (${\Delta}K_s$) increases, the fatigue crack propagation rate (da/aN) of the base metal is faster than that of the welded joint. The variation of the fatigue life in the ERW pipe was estimated statistically using Monte-Carlo simulation with the standard deviation of material constants (C and m) of the paris law in the specimen.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.416-422
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• 2007

The application analysis of bubble pump on the domestic solar water heater system is presented. The system investigated in this study is a passive device, self pumping and self regulating. It was test to use the bubble pump on solar water heater system. The test experiment has been taken on the existed vacuum tube about the efficiency, working fluid temperature and pressure and circulated power. In order to check the working temperature and working pressure effectively, the bubble pump was test separated from the solar water heater. The equipment consists of the bubble pump, heater and heat exchanger. The main structure of bubble pump was design depend on the character of two phase flow. The complete system was instrumented to measure pressures, temperatures and their relationship with the solar radiation intensity. The theory analysis of design bubble pump has been given and the experiment result analysis has been included in the paper.

• 한국결정성장학회지
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• 제6권1호
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• pp.19-31
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• 1996

갈륨 비소 반도체 결정을 성장시키는 데 많이 사용되는 수평브렷지만법에 의하여 성장된 갈륨비소 단결정 내에셔 불순물 분포를 알아보기 위하여 액상에서 열전달, 물질전달, 유 체흐름과 고상에서 열전달을 묘사하는 과도기 모탤을 수립하였고 유한요소법과 음함수 척분법 에 의하여 수치모사를 행하였다. 그 결과 Gr이 작은 경우에는 확산조절성장의 특성을 보였으며 G Gr이 1,700 정도만 되어도 농도의 최소값이 계면 근처로 이동하였다. 응고가 진행됨에 따라 계 면의 곡률이 증가하였고, 흐름에 의한 혼합이 안정될 때까지 수직편석이 증가하였다. 수펑편석 은 응고가 진행됨에 따라 증가하였지만 흐름의 강도가 강한 경우에는 곧 일정하게 유지되였다. G Gr이 아주 작거나 큰 경우에는 Smith식과 Scheil식의 경우와 잘 일치하였다.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3723-3729
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• 2010

We investigated the high-excitation voltage cathodoluminescence (CL) performance of blue light-emitting (ZnS:Ag,Al,Cl) and green light-emitting (ZnS:Cu,Al) phosphors coated with metal oxides ($SiO_2$, $Al_2O_3$, and MgO). Hydrolysis of the metal oxide precursors tetraethoxysilane, aluminum isopropoxide, and magnesium nitrate, with subsequent heat annealing at $400^{\circ}C$, produced $SiO_2$ nanoparticles, an $Al_2O_3$ thin film, and MgO scale-type film, respectively, on the surface of the phosphors. Effects of the phosphor surface coatings on CL intensities and aging behavior of the phosphors were assessed using an accelerating voltage of 12 kV. The MgO thick film coverage exhibited less reduction in initial CL intensity and was most effective in improving aging degradation. Phosphors treated with a low concentration of magnesium nitrate maintained their initial CL intensities without aging degradation for 2000 s. In contrast, the $SiO_2$ and the $Al_2O_3$ coverages were ineffective in improving aging degradation.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2006년도 학술발표대회 논문집
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• pp.48-54
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• 2006

In this thesis, accelerated life test (ALT) method and procedure for rubber O-ring are applied to assure specified reliability of the products at guaranteeing the life of the products. Rubber O-ring is parts that keep intensity or make machine operation smoothly on attrition portion of machine and is used to prevent that oil is leaked. Usually. Rubber O-ring used NBR that is copolymer of acrylonitrile and butadiene. this are superior oil resistance, heat resistance, durability of abrasion, cold resistance, chemical resistance etc. The accelerated life test model for rubber O-ring are developed using the relationship between stresses and life characteristics of products. Using the accelerated life test method and the acceleration life test equipment which is developed, we performed life test, collected life data and analyzed the results of tests. The proposed accelerated life test method and procedure may be extended and applied to testing similar kinds of products to reduce test times and costs of the tests remarkably.

• 한국자동차공학회논문집
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• 제11권5호
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• pp.140-146
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• 2003

Metal matrix composites had generated a lot of interest in recent time because of their high specific strength and stiffness in specific properties. It was also highlighted as the material of frontier industry because strength, heat-resistance, corrosion-resistance and wear-resistance were superiored. In this study, the strength properties of $Al_{18}B_{4}O_{33}$/AC4CH composites were represented mixing the binder of $SiO_2$. It was also fabricated by squeeze casting. $Al_{18}B_{4}O_{33}$/AC4CH was fabricated at the melt temperature of $760^{\circ}C$, the perform temperature of $700^{\circ}C$ and mold temperature of $200^{\circ}C$ under the pressure of 83.4MPa. Consequently, fatigue life was observed roughly in the order of AC4CH> nobiner> $SiO_2$, independently on crack propagation direction and stress ratio.

• Carbon letters
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• 제15권4호
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• pp.262-267
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• 2014

Pyrolized fuel oil (PFO) was reformed by novel electron beam (E-beam) radiation, and the elemental composition, chemical bonds, average molecular weight, solubility, softening point, yields, and density of the modified patches were characterized. These properties of modified pitch were dependent on the reforming method (heat or E-beam radiation treatment) and absorbed dose. Aromaticity ($F_a$), average molecular weight, solubility, softening point, and density increased in proportion to the absorbed dose of E-beam radiation, with the exception of the highest absorbed dose, due to modification by free radical polymerization and the powerful energy intensity of E-beam treatment. The H/C ratio and yield exhibited the opposite trend for the same reason. These results indicate that novel E-beam radiation reforming is suitable for the preparation of aromatic pitch with a high ${\beta}$-resin content.

• 조명전기설비학회논문지
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• 제17권1호
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• pp.80-85
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• 2003

본 논문에서는 유도가열조리기의 효과적인 설계를 위하여 입력주파수 변화에 따른 유도가열조리기의 자계와 열계 해석 방법을 제시하였다. 유도가열조리기의 내부자계는 3차원 축대칭 유한요소법을 사용하여 해석하였으며, 열원은 유도가열조리기의 내부에서 유도된 와전류에 의하여 발생되고, 열은 열원과 열방정식을 사용하여 계산되어진다. 또한, 유도가열조리기의 온도특성을 스테인레스와 알루미늄 각각에 대하여 주파수와 투자율에 따라 제시하였다.