• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.372-375
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• 2007

750kW gearless type wind turbine, named U50, is developed by UNISON in Korea. The newly developed wind turbine should be evaluated the power curve and the estimated annual energy production by following international standard to verify the power performance characteristics. This paper shows the test and evaluation procedure according to IEC 61400-12-1 which specifies a procedure of measuring the power performance characteristics of a single wind turbine and applies to the testing of wind turbines of all types and sized connected to the electrical power network. And this paper also shows the power performance characteristics for U50 wind turbine which is determined in accordance with IEC regulation.

• 대한기계학회논문집B
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• 제25권12호
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• pp.1711-1720
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• 2001

In this study, the heat transfer characteristics of a U-shape heat pipes were investigated. Heat is supplied to the U heat pipe through its middle zone(evaporator), and is released to the environment through its both arms(condensers). Both heat transfer coefficients and heat transport limitations were measured and compared with correlations previously developed for straight type heat pipes. Special concerns were focused to the cases, when each of condensers were submitted to a different cooling conditions, relatively. As a result. the heat transfer limitation of a U-shape heat pipe was found out to be 10∼15% less than the value for a straight heat pipe with an equivalent size.

• 대한치과보철학회지
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• 제35권1호
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• pp.144-164
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• 1997

The purpose of this study were to investigate the chemical composition, mean particle size, linear thermal expansion coefficient and metal-bonding strength of the regular opaque powder and core powder. In this study, 4 types of ceramic powders, namely Duceram Jacket Opaque powder, Duceram Opaque powder, Vita Hi-Ceram powder, Vita VMK Paint On-88 powder were used. Chemical composition was evaluated by EDS(Energy Dispersive X-ray Spectrophotometer, Oxford QX-2000, England), particle size was measured by MALVERN Instruments(MALVERN Instruments SB. OC., U.S.A.. ad linear thermal expansion coefficient was measured by dilatometer(Motoyama, Japan). Bond strength was measured by the Universal tsting machine(Istron Co., Ltd., U.S.A.). The Results were as follows : 1. Through recognition of the relative difference in chemical composition between the core powder and the regular opaque powder, the difference in the proportion of $Al_2O_3$ in each type of material is demonstrated ; Duceram Jaket Opaque powder : 30.16%, Duceram Opaque powder : 16.60%, Vita Hi-Ceram : 63.64%, Vita VMK Paint-On 88 : 16.16%. 2. There was no significant difference in the proportion of metal-bonding materials between the core powder and the regular opaque powder. 3. In the regular opaque powder, alkaline materials were incoporated in order to increase the coefficient of thermal expansion. 4. In the particle size analysis, there was no significant difference in mean particle size or in the particle size distribution between the core powder and the regular opaque powder. 5. In the thermal expansion test for temperature range of $25-600^{\circ}C$, the regular opaque powder had higher coefficient of thermal expansion than that of core powder. 6. In the 4 point flexural bending test, there was no statistically significant difference in the mean bond strength between the core powder and the opaque powder among the Duceram products.

• 한국통신학회논문지
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• 제36권4A호
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• pp.407-413
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• 2011

본 논문은 평행결합 선로의 구조를 갖는 크기가 작아진 광대역 대역통과 필터로서 커플링 계수에 따라 협대역에서 광대역까지 자유롭게 조절이 가능하도록 제안하였다. 기존의 필터는 구조의 특성상 협대역으로만 동작이 가능한데, 만일 그 이상의 대역폭을 요구하게 된다면 급전선로와 공진기 사이의 커플링 양으로 인해 실제의 구현이 어렵다는 단점을 갖게 된다. 이러한 단점을 극복하고 새로운 방법을 도입했을 때 제안한 필터는 SIR 구조와 헤어핀(hair-pin)의 U-형태 개방형 스터브 그리고 세로 형태의 구조를 적용하여 기존의 필터 보다 크기가 작아짐은 물론 커플링 계수에 따라 대역폭의 조절이 자유롭다는 특징을 갖게 된다. 본 논문에서 최종 제시한 필터는 광대역 필터의 결과로서 중성 주파수 5.8 GHz에서 대역폭 60 %, 그리고 삽입손실과 반사손실은 각각 0.42 dB 및 24.5 dB의 결과 값들을 얻었다.

• Smart Structures and Systems
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• 제25권1호
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• pp.23-35
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• 2020

It is important to take into account the thermal behavior in assessing the structural condition of bridges. An effective method of studying the temperature effect of long-span bridges is numerical simulation based on the solar radiation models. This study aims to develop a time-varying solar radiation model which can consider the real-time weather changes, such as a cloud cover. A statistical analysis of the long-term monitoring data is first performed, especially on the temperature data between the south and north anchors of the bridge, to confirm that temperature difference can be used to describe real-time weather changes. Second, a defect in the traditional solar radiation model is detected in the temperature field simulation, whereby the value of the turbidity coefficient t_u is subjective and cannot be used to describe the weather changes in real-time. Therefore, a new solar radiation model with modified turbidity coefficient γ is first established on the temperature difference between the south and north anchors. Third, the temperature data of several days are selected for model validation, with the results showing that the simulated temperature distribution is in good agreement with the measured temperature, while the calculated results by the traditional model had minor errors because the turbidity coefficient t_u is uncertainty. In addition, the vertical and transverse temperature gradient of a typical cross-section and the temperature distribution of the tower are also studied.

• 한국지반공학회논문집
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• 제26권11호
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• pp.99-110
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• 2010

연구에서는 부주면마찰력이 발생하는 3개 지역 총 16본 말뚝의 현장 계측 자료들을 바탕으로 국내 지반 특성에 맞는 주면마찰계수($\alpha$, $\beta$ 계수)의 분포범위를 압밀도(U)와 역청재(S.L) 도포 유무에 따라 역산정하였다. 역청재 도포 말뚝의 부주면마찰력 저감효과는 50~90% 정도인 것으로 나타났으며, 기존 설계에 사용되던 제안 값과의 비교를 통해, 본 연구에서 산정된 $\alpha$와 $\beta$계수가 적정 범위에 있으며, 그 결과 국내지반조건을 반영한 말뚝의 장, 단기 주면마찰력을 예측할 수 있는 기본자료를 제시하였다.

• Ocean Systems Engineering
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• 제11권1호
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• pp.83-97
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• 2021

The submerged U-shape breakwater interaction with the solitary wave is simulated by the Boussinesq equations using the finite-difference scheme. The wave reflection, transmission, and dissipation (RTD) coefficients are used to investigate the U-shape breakwater's performance for different crest width, Lc1, and indent breakwater height, du. The results show that the submerged breakwater performance for a set of U-shape breakwater with the same cross-section area is related to the length of submerged breakwater crest, Lc1, and the distance between the crests, Lc2 (or the height of du). The breakwater has the maximum performance when the crest length is larger, and at the same time, the distance between them increases. Changing the Lc1 and du of the U-shape breakwaters result in a significant change in the RTD coefficients. Comparison of the U-shape breakwater, having the best performance, with the averaged RTD values shows that the transmission coefficients, Kt, has a better performance of up to 4% in comparison to other breakwaters. Also, the reflection coefficients KR and the diffusion coefficients, Kd shows a better performance of about 30% and 55% on average, respectively. However, the model governing equations are non-dissipative. The non-energy conserving of the transmission and reflection coefficients due to wave and breakwater interaction results in dissipation type contribution. The U-shape breakwater with the best performance is compared with the rectangular breakwater with the same cross-section area to investigate the economic advantages of the U-shape breakwater. The transmission coefficients, Kt, of the U-shape breakwater shows a better performance of 5% higher than the rectangular one. The reflection coefficient, KR, is 60% lower for U-shape in comparison to rectangular one; however, the diffusion coefficients, Kd, of U-shape breakwater is 35% higher than the rectangular breakwater. Therefore, we could say that the U-shape breakwater has a better performance than the rectangular one.

• 한국콘텐츠학회논문지
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• 제15권4호
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• pp.263-276
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• 2015

본 연구는 청소년의 초기기억에 나타난 개인심리학의 생활양식과 교류분석의 인생태도와의 관계를 탐색하는데 목적이 있다. 이를 위해 남녀 중학생 409명(남 201, 여 208)을 대상으로 자료를 수집하였다. 연구결과는 첫째, 생활양식변인과 인생태도 변인간의 Pearson 적률상관분석을 실시한 결과 생활양식, 인생태도하위 변인들 간에 대체로 유의미한 상관이 있는 것으로 나타났다. 특히 소속하기/사회적 관심, 인정받기의 생활양식은 자타긍정의 인생태도와 정적 상관이 있는 반면에 잘지내기, 조심하기의 생활양식은 자타부정의 인생태도와 정적상관이 있었다. 둘째, 성별에 따른 생활양식과 인생태도 변인의 차이를 다변량분산분석을 실시하여 살펴본 결과, 특히 여학생이 남학생보다 인정받기 생활양식을 더 유지하고 있었으며, 인생태도의 경우도 모든 하위요인들이 남학생보다 유의하게 높았다. 셋째, 생활양식과 인생태도변인의 관계 탐색을 위하여 중다회귀분석을 실시한 결과 타인부정은 잘지내기, 타인긍정과 자기긍정은 인정받기, 자기부정은 조심하기 생활양식이 가장 높은 유의미한 영향력을 미치는 것으로 예측되었다. 마지막으로 본 연구결과의 함의와 추후연구를 위한 제언을 논의하였다.

• Structural Engineering and Mechanics
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• 제13권6호
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• pp.671-694
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• 2002

This paper presents theoretical investigation on the cross correlation between torsional vibration ($u_{\theta}$) and translation vibration ($u_x$) of asymmetrical structure under white noise excitation. The formula reveals that the cross correlation coefficient (${\rho}$) is a function of uncoupled frequency ratio (${\Omega}={\omega}_{\theta}/{\omega}_x$), eccentricity, and damping ratio (${\xi}$). Simulations involving acceleration records from fifteen different earthquakes show correlation coefficients results similar to the theoretical correlation coefficients. The uncoupled frequency ratio is the dominating parameter to ${\rho}$; generally, ${\rho}$ is positive for ${\omega}_{\theta}/{\omega}_x$ > 1.0, negative for ${\omega}_{\theta}/{\omega}_x$ < 1.0, and close to zero for ${\omega}_{\theta}/{\omega}_x$ = 1.0. When the eccentricity or damping ratio increases, ${\rho}$ increases moderately for small ${\Omega}$ (< 1.0) only. The relation among $u_x$, $u_{\theta}$ and corner displacement are best presented by ${\rho}$; a simple way to hand-calculate the theoretical dynamic corner displacements from $u_x$, $u_{\theta}$ and ${\rho}$ is proposed as an alternative to dynamic analysis.

• 한국농공학회논문집
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• 제48권4호
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• pp.41-49
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• 2006

Since particle size distribution curves are useful to estimate permeability of soil, many formulae for permeability coefficient (k) have been published using the parameter from the curves and factors, such as grain size, particle shape and void ratio of soils. However, the parameters such as $C_c,\;C_u$ and $D_n$ derived from only some discrete points on the curve are insufficient to represent the whole gradation. In this paper fractal dimension which is quite new concept and known to be able to represent the entire curve of particle size distribution is employed for the parameters. An empirical formula of permeability coefficient has been developed with fractal dimension and percent of finer than 0.075 mm. The formula developed from this study has confirmed its effectiveness by a series of laboratory tests and comparison to other published formulae. It is found that permeability coefficient is proportional to fractal dimension and inversely proportional to percent of fines.