• The Korean Journal of Ceramics
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• 제5권3호
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• pp.235-238
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• 1999

In a ceramic green body, some degree of nonuniformity in density always presents. These differences in green density will appear as nonuniform shrinkage after sintering takes place. For the complex ceramic bodies with various curves and angles, therefore, it is quite difficult to foresee the final dimensions precisely after sintering. This simulation study shows that, considering the sintering process as a thermal shrinkage phenomenon, the use of NASTRAN enables to predict the precise shape of a sintered body. Based on this result, 'the reverse engineering technique' has been developed that can unfold the exact dimensions of a green body to have the desired shape after sintering. This approach will provide a simple and useful tool for ceramic engineers to fabricate complicate bodies with tight dimensional tolerances.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.923-928
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• 1997

An MCP (Microchannel Plate) is a secondary electron multiplier to detect and amplify electrons. An MCP has many rnicrochannels whose diameters range from 10 to 100pm and whose lengths range from 40 to 100times of the diameter. Each microchannel of the MCP amplifies electrons over IOOOtimes by the secondary electron emission. Even though MCPs have high performance for electron amplification, the application of MCPs is limited to high performance electronic equipments because of their high fabricating cost and the limit of increasing their size due to the conventional fabrication process. Therefore, in this work, microchannels of the MCP are manufactured by micro-drilling to reduce the cost of the MCP and to increase their size. Alumina green body with epoxy binder was machined for fabricating microchannels using a high speed air turbine spindle and micro-drills with diamond grinding abrasives. Then alumina MCP was fabricated through the sintering of the machined alumina green body.

• 대한수의학회지
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• 제42권4호
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• pp.475-483
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• 2002

We performed this study to determine the effect of Korean favorite teas (green tea, ginseng tea, coffee and barley tea) on jejunal crypt survival, endogenous spleen colony formation and apoptosis in jejunal crypt cells of mice irradiated with high and low dose of ${\gamma}$-radiation. Jejunal crypts were protected by pretreatment of green tea (P.O.: 1.25% water extract, for 7 days before irradiation., I.P.: 50 mg/kg of body weight, at 12 and 36 hours before irradiation, p<0.01) or ginseng (I.P.: 50 mg/kg of body weight, at 12 and 36 hours before irradiation, p<0.05). Green tea (p<0.05) or ginseng (p<0.05) administration before irradiation (I.P. at 12 and 36 hours before irradiation) resulted in an increase of t formation of endogenous spleen colony. The frequency of radiation-induced apoptosis was also reduced by pretreatment of green tea (P.O.: p<0.005, I.P.: p<0.05), pretreatment of ginseng (P.O.: p<0.005, I.P.: p<0.005) or posttreatment of ginseng (I.P.: 50 mg/kg of body weight, at 30 minutes after irradiation, p<0.05). Treatment with coffee or barley tea showed no significant modifying effects on the radiation-induced damages. These results indicated that green tea and ginseng might be a useful radioprotector, especially since it is a relatively nontoxic natural product. Further studies are needed to characterize better the promotion nature of green tea, ginseng and its components.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.552-558
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• 2011

A 50 kW class rotating body type wave energy converter consisted of two floating bodies and a PTO (Power Takeoff) unit is studied. As an wave energy extractor, the body is designed to have a VLCO (Variable Liquid-Column Oscillator) having a liquid filled U-tube with air chambers. Owing to the oscillation of the liquid in the U-tube caused by the air spring effect of the air chambers, the amplitude of response of the VLCO becomes significantly amplified for a target wave period. The PTO converts the rotational moment introduced from the relative motion of the hinged bodies to an hydraulic power by means of a cylinder. A high pressure accumulator, hydraulic motor and a generator are equipped in the PTO to convert the hydraulic power to electric power. A control law for adjusting the oscillation period of the VLCO is proposed for the efficient operation of the VLCO with various wave conditions. It is found that the effect of the air spring has an important role to play in making the oscillation of the VLCO match with the ocean wave. In this way, the wave energy converter equipped with the VLCO provides the most effective mode for extracting energy from the ocean wave.

• Journal of Nutrition and Health
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• 제32권4호
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• pp.337-352
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• 1999

The effects of dried leaf powders and ethanol extract of persimmon, green tea and pine needle on lipid metabolism, lipid peroxidation and antioxidative activity were investigated in rats. Forty-nine male Spargue-Dawley rats weighing 107.8$\pm$1.8g were blocked into seven groups according to body weight. Rats were raised for four weeks with diets containing either 5%(w/w) dried leaf powders of one of three different Korea traditional teas, persimmon(Diospyros kaki Thunb), green tea(Camellia Sinensis O.Ktzc)or pine needle(pinus Koreansis Sieb. Et Zucc), or ethanol from equal amounts of each dried tea powder. Food intake, weight gain, food efficiency ratio, and weights of liver, kidney and epididymal fat were significantly higher in the green-tea-powder group, and significantly lower in the pine-needle-powder and pine-needle-extract groups. Persimmon-leaf powder was found to decrease plasma total lipid, triglyceride and cholesterol concentration by increasing fecal total lipid triglyceride and cholesterol excretions. Liver cholesterol concentration was significantly lower in the green-tea and pine-needle-extract groups. Red-blood-cell superoxide dismutase(SOD) and glutathione peroxidase(GSH-px) activities were significantly increased in rats fed green-tea extract. Liver SOD activity was increased in rats fed pine-needle powder or extract, and liver GSH-px activity was increased in rats fed greentea powder. Plasma and liver thiobarbituric acid reactive substance(TBARS) concentration were both decreased in rats fed dried leaf posers or extracts of persimmon or green tea. It is believed that high vitamin E levels in persimmon leaf, and high flavonoid, beta-carotene and vitamin C levels in green tea effectively inhibited lipid peroxidation. In conclusion, persimmon and green tea leaves were effective in lowering lipid levels and inhibiting lipid peroxidation in animal tissue, while pine needles were effective and lowering body weight gain. From these results, persimmon and green tea leaves can be recommended in the treatment and prevention of chronic discorders such as cardiovascular disease, cancer and aging. As ethanol extracts from these teas were also effecitive in lowering tissue lipid levels and inhibiting lipid peroxidation, we recommend the use of discarded tea grounds for this.

• 생명과학회지
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• 제16권6호
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• pp.972-977
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• 2006

복합운동과 녹차섭취가 비만 여고생의 체중과 아디포넥틴에 미치는 영향을 구명하기 위하여 U시 U여고생 중 체질량 지수(BMI) $27\;kg/m^2$ 이상인 자를, 운동군 9명, 녹차군 9명, 운동녹차군 9명, 통제군 9명, 총 36명을 대상으로 하였다. 복합운동은 12주간, 주 4회, 1일 $60{\sim}70$분, $55{\sim}75%$HRmax의 걷기운동과 $1\sim}2\;kg$의 덤벨체조를 병행하여 실시하였으며, 녹차는 1스틱 당 0.8 g 든 가루녹차를 1일 4회, 12주 동안 섭취시킨 결과 다음과 같은 결론을 얻었다. 체중은 집단내 변화에서 운동군, 녹차군, 운동녹차군은 유의한 차이를 보였으며, 집단간 변화에서는 운동군과 운동녹차군이 녹차군과 통제군보다 유의한 차이를 나타내었다. 아디포넥틴은 집단내 변화에서, 운동군, 녹차군, 운동녹차군은 유의한 차이가 없었으나, 통제군은 유의하게 감소한 것으로 나타났으며, 집단간 변화에서, 운동군과 운동녹차군은 통제군보다 아디포넥틴이 유의하게 증가한 것으로 나타났다. 이상의 결과를 통해 복합운동과 녹차섭취가 비만 여고생들의 체증 감량에 긍정적인 효과를 보였으나, 비만의 결정인자인 아디포넥틴을 증가시키기 위해서는 다량의 체중감량이 우선되어야 하므로, 향후 비만 예방과 개선을 위해서는 복합운동과 녹차섭취에 대한 보다 효율적이고 맞춤적인 운동처방과 섭취방법의 연구가 요구되어진다.

• 한국식품조리과학회지
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• 제27권6호
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• pp.773-781
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• 2011

Coffee beans are processed from coffee cherries by either natural, pulped natural, or washing. The aim of the present study was to evaluate the physiochemical and sensory characteristics of espresso coffees processed by different methods. The color of the washed coffee sample presented the highest value of lightness while the natural coffee sample presented the highest value of redness and yellowness. The biggest difference in brewed coffee, whether natural, pulped natural, or washed, was in the TDS content, which was higher in natural coffee and lower in washed coffee. Sensory descriptive analysis and acceptance test for espresso coffee using a 15 cm line scale were carried out by 12 trained panelists. Natural coffee had the highest cherry-like flavor and sweetness taste while washed coffee had the highest citrus flavor and acidity taste. An important attribute of espresso coffee is body, and natural coffee presented strong body while washed coffee presented a low body attribute. In conclusion, significant differences were observed among the three processing methods of green coffee. Pulped natural coffees presented intermediate physiochemical and sensory characteristics compared to washed and natural coffee. Natural coffees are appreciated for their increased body, and washed coffees are appreciated for added citrus flavors and acidity espresso coffee blends.

• Journal of Ship and Ocean Technology
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• 제10권1호
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• pp.10-26
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• 2006

The radiation problem for oscillating bodies on the free surface has been formulated by the over-determined Green integral equation, where the boundary condition on the free surface is satisfied by adopting the Kelvin-type Green function and the irregular frequencies are removed by placing additional control points on the free surface surrounded by the body. The B-Spline based higher order panel method is then applied to solve the problem numerically. Because both the body geometry and the potential on the body surface are represented by the B-Splines, that is in polynomials of space parameters, the unknown potential can be determined accurately to the order desired above the constant value. In addition, the potential expressed in B-Spline can be differentiated analytically to get the velocity on the surface without introducing any numerical error. Sample computations are performed for a semispherical body and a rectangular box floating on the free surface for six-degrees of freedom motions. The added mass and damping coefficients are compared with those by the already-validated constant panel method of the same formulation showing strikingly good agreements.

• 한국세라믹학회지
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• 제44권4호
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• pp.235-239
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• 2007

For the pressure compaction process of the ceramic powder, the density distribution is very important for the uniform shrinkages at the sintered body. In this paper, we fabricated alumina green body using compaction process and simulated about same condition. Then comparison of simulation and experimental result confirmed that accuracy of simulation. On the average density of top and lower part was each $2.41g/cm^3,\;2.27g/cm^3$ and deviation at final step was calculated with 0.06 in simulation. Also, experiments show that total density of top and lower part was each $2.59g/cm^3,\;2.36g/cm^3$, and deviation was 0.09. Conclusion, that was not a difference to the simulation and experimental result. The application using the finite element simulation method is possible optimization of the compressing process, predict generated part of cracks and there is a possibility of getting result of more fast, more accurate then existing experience method.

• 한국식품영양과학회지
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• 제21권6호
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• pp.595-600
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• 1992

본 연구는 흰 쥐에 있어서의 식이단백질 수준, 카페인 또는 녹차가 체지방 축적에 미치는 영향을 검토하였다. 실험동물은 체중 90g 전후의 이유기후의 수컷 Wistar rat를 사용하여 식이단백질 수준을 달리하여, 카페인 또는 녹차의 첨가유뮤로 6군으로 나누어 8주동안 실시하였다. 그 결과 요약하면 다음과 같다. 5% PEP 수준에 있어서 카페인 또는 녹차문말을 첨가한 군의 체중 및 사료효율이 유의하게 낮았다(p<0.05). 카페인 또는 녹차분말을 첨가한 5% PEP 수준에서 체중 및 백색지방조직의 중량이 유의하게 감소하였다(p<0.01). 카페인 또는 녹차를 첨가한 5% PEP 수준에서 혈장 및 간장중의 triglyceride 농도가 유의하게 감소하였다(p<0.01). 이와 같은 영향은 녹차첨가군에서 현저하게 나타났다. 5% 및 15% PEP군에 카페인 또는 녹차분말을 첨가한 군에서 혈장 콜레스테롤, 유리 콜레스테롤 및 콜레스테롤 에스테르의 수준이 대조군에 비해 유의하게 높은 것이었다(p<0.01). 반면에 HDL 콜레스테롤 수준은 유의하게 높은 값이었다(p<0.01). 특히 6.1% 녹차분말 첨가군에서의 동맥경화지수가 대조군에 비해 현저하게 낮게 나타났다.