• 융복합기술연구소 논문집
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• 제1권1호
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• pp.24-28
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• 2011

The purposes of this study are predictions of the changes in the section geometry and determination of the initial cross section so that opposite side in height direction is exactly parallel after coiling process. Finite element analysis is carried out for the calculation of the sectional changes for mold spring item. Analysis results reveal that the slope of the top and bottom sides varies in the range of 5 to 8 degrees and the amount depends on the dimension of the outer diameter. The slopes of the sides should be defined first among design variables.

• 천문학회보
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• 제43권2호
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• pp.51.2-51.2
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• 2018

Star clusters are important in understanding star formation. In star-forming regions, the number of stars with mass forms with an initial mass function (IMF), i.e. Chabrier, Salpeter, Kroupa, etc. In our simulations, initially sub-virial fractal star clusters evolve to become surviving sub-regions in strong tidal fields. We investigate the slope of the mass function (MF) of these sub-regions with time near the Galactic centre (GC). These sub-regions would appear to have a top-heavy IMF at ~ 2 Myr. Therefore, although our star-forming region near the GC has a normal IMF, stars in surviving 'clusters' can have a top-heavy 'IMF' due to the violent environment.

• 한국전기전자재료학회논문지
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• 제20권1호
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• pp.1-7
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• 2007

In this paper, two kinds of initial oxidation methods i.e., SLTO(Slow Low Temperature Oxidation: $700^{\circ}C$) and RTO(Rapid Thermal Oxidation: $850^{\circ}C$) are applied prior to the plasma nitridation for ultra thin oxide of RPNO (Remote Plasma Nitrided Oxide). It is observed that SLTO has superior characteristics to RTO such as lower SS(Sub-threshold Slope) and improved Ion-Ioff characteristics. Low frequency noise characteristics of SLTO also showed better than RTO both in linear and saturation regime. It is shown that flicker noise is dominated by carrier number fluctuation in the channel region. Therefore, SLTO is promising for nano-scale CMOS technology with ultra thin gate oxide.

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.63-68
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• 2005

Optimum design of the big brackets is performed through iterated 3-D FE analyses to meet the permissible limits of stress, which consumes an excessive amount of calculation time. Therefore, this study has been prepared to determine rapidly and accurately an optimum size and scantling of the big brackets at the initial design stage. The generalized slope deflection method (GSDM) based on the span point concept is applied to enhance the efficiency of iterated structural analyses. The accuracy and applicability of the present method is verified by comparing with a detail 3-D FE analysis of web frame structures. As an optimization technique, evolution strategies (ES) are applied using discrete design variables for practical design.

• 한국터널지하공간학회 논문집
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• 제20권1호
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• pp.11-22
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• 2018

철도터널의 방재시설 계획 시 터널의 안전성을 정량적 위험도 평가에 의해서 정량화하여 방재시설의 적정성 여부를 판단하도록 하고 있다. 이에 본 연구에서는 터널화재에 대한 정량적 위험도 평가 시 결과에 크게 영향을 미치는 화재열차의 터널 내 정차확률을 예측하는 방법을 제시하였다. 이를 위해서 열차의 주행저항계수를 고려하여 타력운전거리를 계산하기 위한 모델을 개발하였으며, 타력운전특성과 비상제동거리를 고려하여 몬테카를로 시뮬레이션 기법에 의해 터널연장 및 경사도, 초기주행속도를 변수로 하여 화재열차가 터널에 정차할 확률을 예측하였다. 타력운전거리의 예측을 위한 운동방정식은 KTX II의 주행저항계수를 반영하여 분석하였다. KTX II 열차의 경우, 타력운전거리는 상향경사의 터널에서는 경사도가 증가할수록 감소하나 하향경사구간에서는 정지하지 않고 계속하여 주행이 가능하다. 화재열차의 터널 내 정차확률은 열차의 주행속도가 증가할수록, 경사도가 낮을수록 감소하며, 고속열차(주행속도 250 km/h 이상)는 인적오류를 고려하지 않는 경우, 경사도 0.5% 이하의 터널에서는 화재 시 열차가 터널에 정차할 확률은 0%이고, 경사도가 증가하고 터널연장이 증가하면 정차확률은 급격하게 증가하는 것으로 나타났다.

• 조명전기설비학회논문지
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• 제16권2호
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• pp.113-120
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• 2002

본 논문은 인체에 의해 발생하는 정전기 방전과도전압 파형의 특성에 관한 것으로 정전기 방전전압의 피크 크기와 초기상승부분의 특성에 대한 통계를 분석하기 위해서 여러 가지 실험조건에서 정전기 방전전압을 측정하였다. 정전기 방전전압의 측정에는 주파수대역이 DC∼400[MHz]인 전압측정계를 사용하였으며, 정전기 방전전압의 파형은 전류 파형과 거의 동일하였다. 또한 본 연구에서 제안한 등가회로를 적용한 시뮬레이션결과는 측정결과와 거의 일치하였다. 정전기 방전전압 파형은 접촉 물체의 재질과 접근속도에 크게 영향을 받으며, 빠른 접근일 때가 느린 접근일 때보다 초기상승시간이 짧은 파형으로 나타났다. 손에 의한 정전기 방전전압의 상승시간은 10∼30[ns]로 비교적 길었으나, 크기는 작았다. 반면에 절연손잡이를 갖는 드라이버를 통한 정전기 방전전압 파형은 1[ns]이하의 매우 짧은 상승시간과 매우 큰 피크값을 나타내었다. 본 연구결과는 저전압 소전류인 전자기기의 정전기 장해에 대한 대책의 마련에 응용될 것이다.

• 한국토양비료학회지
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• 제47권1호
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• pp.16-22
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• 2014

This study was conducted to determine the changes in soil chemical properties and the growth of seedling according to the different dredged soil improving methods at slope of Saemangeum sea dike. Undersea dredged soil was improved by five different methods. Seedlings of Ulmus davidiana var. japonica, Chionanthus retusa, Celtis sinensis, and Pinus thunbergii were planted after 9 month of experience site installation, then soil pH, NaCl concentration in soil, soil organic matter (SOM), and survival rate and height of seedling was measured. Initial soil pH was highest in the control plot but it decreased to the similar level with other soil improving plots after 35 months. There were no differences in NaCl concentration between the control and soil improving plots, and it showed decreasing tendency during the study period. In the control plot, initial SOM was lowest among that of other plots during the study period. The survival rate of 36 months after planting of P. thunbergii was highest among the species. The gap of the tree growth of P. thunbergii between the control plot and the soil improving plots was small, however, other species showed relatively higher tree height in the soil improving plots than the control plots. Creation forest with P. thunbergii might be a cost effective afforestation in coastal reclaimed land since it rarely needs additional improvement of dredged soil.

• 대한기계학회논문집A
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• 제32권2호
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• pp.105-118
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• 2008

The newly developed analysis method for nanoindentation load-displacement curves are focused on not only obtaining elastic modulus and hardness values but also other mechanical properties, such as yield strength and strain hardening properties. Dao et al. developed a forward and reverse algorithm to extract the elasto-plastic properties of materials from the load-displacement curves obtained in nanoindentation test. These algorithms were only applicable for engineering metals (Poisson#s ratio 0.3) using the equivalent conical indenter of the Berkovich. However, the applicable metals are substantially limited because range of used in the finite element analysis is narrow. This study is designed to expand range of the applicable metals in the reverse algorithms established by Dao et al. and to improve the accuracy of that for extracting the elasto-plastic properties of materials. In this study, a representative strain was assumed to vary according to specific range of $E^*/{\sigma}_r$ and was defined as function of $E^*/{\sigma}_r$. Also, an initial unloading slope in reverse algorithms improved in this study was not considered as independent parameters of the load-displacement curves. The mechanical properties of materials for finite element analysis were modeled with the elastic modulus, E, the yield strength, ${\sigma}_y$, and the strain hardening exponents, n. We showed that the representative strain (0.033) suggested by Dao et al. was no longer applicable above the $E^*/{\sigma}_r$ of 400 and depended on values of $E^*/{\sigma}_r$. From these results, we constructed the dimensionless functions, in where the initial unloading slope was not included, for engineering metals up to $E^*/{\sigma}_r$ of 1500. These functions allow us to determine the mechanical properties with greater accuracy than Dao#s study.

• Journal of Nutrition and Health
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• 제46권4호
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• pp.324-331
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• 2013

We investigated dietary effects of green tea powder (GTP) on plasma lipids, platelet aggregation, hemolysis, plasma TBARS, and liver enzymes. Thirty one volunteer diving women living on Jeju island consumed 4 g green tea powder daily for a period of four weeks and data for the study subjects were analyzed on the basis of diagnostic criteria for blood pressure (BP)(${\geq}$ 140/90 mmHg), plasma total cholesterol (TC)(${\geq}$ 200 mg/dL), and triglyceride (TG)(${\geq}$ 150mg/dL). Subjects with high BP had significantly higher TC and TG than those with normal BP. Subjects with higher TC had higher TG, and those with higher TG had lower HDL cholesterol. Platelet aggregation in the initial slope was significantly higher in subjects with normal BP, normal TC, or normal TG than their counterparts in high BP, TC, and TG. HDL cholesterol after GTP intake increased only in subject groups with normal BP, normal TC, or normal TG, and plasma TG after GTP intake decreased only in groups with higher BP, higher TG, or higher TC. Plasma TC and TG in subjects with normal BP increased after GTP intake. GTP intake caused a decrease in the initial slope of platelet aggregation in all subject groups with little effect on maximum aggregation. Total bilirubin showed a significant increase and GOT increased in all subject groups after GTP intake. Beneficial effects of short term intake of green tea powder might differ depending on the subject conditions in terms of blood pressure, plasma lipids, and other cardiovascular conditions. However, with the hypolipidemic, antithrombotic, and antioxidant actions of its bioactive flavonoids, long term usage of GTP or brewed green tea may provide preventive effects against cardiovascular disease.

• 한국식품과학회지
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• 제19권2호
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• pp.171-175
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• 1987

삶은 국수의 식미 평가를 위한 객관적 측정 방법으로 레오메타에 특수하게 고안한 test cell을 사용하는 층밀림 압출 시험법을 개발하였다. 층밀립 압출 시험에서 얻어지는 힘-거리 곡선을 분석하여 최초 압출력, 최고 압출력, 압출일, 경사도 등의 파라메타를 구하였다. 17종류의 호주밀로부터 만든 밀국수(건면)에 대한 실험 결과, 최초 압출력 압출일은 삶은 국수의 기호도를 가장 크게 영향하는 단단하고 무른 성질과 쫄깃쫄깃한 성질의 정도를 나타낼 수 있었다. 한편, 경사도는 삶은 국수의 저장중에 일어나는 조직감 변화를 감지할 수 있었다. 이들 파라메타들은 원료 밀가루의 단백질 함량, 수분흡수력, 발전시간(D.T.), 인장도와 높은 삼관관계를 나타내었으나 비스코그램의 최고 점도와는 상관관계를 나타내지 않았다. 비스코스램의 최고 점도와 층밀림 압출 시험의 최고 압출력을 두 독립변수로 한 다중회귀분석 결과 관능적 조직감 기호도와의 상관계수는 최고 압출력만을 사용한 단순회귀분석상관계수보다 크게 증가하지 않았다.