• 한국광학회지
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• 제15권1호
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• pp.79-85
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• 2004

후면의 석영면에 위상 패턴을 형성하여 투과율 조절을 구현한 포토마스크에 대해 보고한다. 위상 패턴의 크기와 패턴 조밀도에 따른 조명 동공의 형태 변화에 관한 이론적 결과와 투과율 조절 포토마스크를 사용한 웨이퍼 상 CD(critical dimension) 균일도 개선에 관한 실험적 결과에 대해 기술한다. 투과율 조절을 위한 위상 패턴은 패턴이 형성되지 않은 영역에 대해 180$^{\circ}$의 상대적 위상을 갖도록 석영면을 식각한 콘택홀 형태의 패턴을 사용하였다. 콘택홀 패턴의 크기가 작을수록 본래의 조명동공 형태를 유지하게 되며, 동일한 패턴 조밀도에서 더욱 큰 노광 광세기 저하가 일어남을 알 수 있었다. 패턴 조밀도를 위치별로 변화시켜 CD균일도 개선에 적합한 투과율 분포를 포토마스크 후면에 형성하였다. 투과율 조절 포토마스크를 140nm 디자인 롤을 갖고 있는 DRAM(Dynamic Random Access Memory)의 한 주요 레이어에 적용하여 CD 균일도를 3$\sigma$값으로 24.0nm에서 10.7nm 로 개선할 수 있었다.

• 한국콘텐츠학회논문지
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• 제16권12호
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• pp.203-212
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• 2016

본 연구의 목적은 문제중심학습을 적용한 시뮬레이션 실습 교육이 간호학생의 문제해결능력, 비판적 사고성향 및 학습만족도에 영향을 미치는 효과를 파악하고자 시도되었다. 연구 대상자는 K 지역 U 대학교 통합시뮬레이션 실습교과목을 수강한 63명의 간호학생으로 자료는 자가보고식 설문지를 이용하여 시뮬레이션 실습 수업 전 후에 수집되었다. 연구결과 문제해결능력과 학습만족도가 유의하게 향상된 효과가 있는 것으로 나타났으며, 문제해결능력, 비판적 사고성향 및 학습만족도간에는 양의 상관관계가 나타나 문제해결능력이 높아지면 비판적 사고성향과 학습만족도가 향상되는 것으로 나타났다. 따라서 문제중심학습을 적용한 시뮬레이션 실습교육이 문제해결능력과 학습만족도를 향상시키고 비판적 사고성향을 향상시키기 위해서는 충분한 반복 연습이 실습에서 이루어져야 할 것으로 사료된다.

• 융합정보논문지
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• 제9권1호
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• pp.1-11
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• 2019

본 연구는 J지역, H대학교 치위생학과 학생 322명을 대상으로 문제해결능력과 비판적 사고 성향과의 관계를 규명하기 위해 2018년 7월 1일부터 8월 30일까지 조사하였다. 수집된 자료는 SPSS 18.0 프로그램을 사용하여 일원배치분산분석, 피어슨의 상관분석, 회귀분석을 하였다. 기술통계 분석에 따라 비판적 사고 성향은 평균 3.36점 이었고, 문제 해결 능력은 평균 3.41점이었다. 상관분석 결과 비판적 사고 성향과 대상자의 문제해결능력은 통계적로 유의한 차이를 나타내었다(p<0.001). 유의미한 변수들은 전공만족도, 학업성적, 비판적 사고 성향을 포함하였고, 모형의 설명력은 52.2%였다. 치위생학과 학생들의 전공만족도, 학업성적, 비판적 사고 성향과과 문제해결능력을 향상시키는데 있어서는 교수학습방법과 교육과정개발, 교육환경의 변화가 필요하다고 본다.

• Journal of Welding and Joining
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• 제6권4호
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• pp.16-26
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• 1988

The effect of carbon content on hot cracking of welded carbon steel was investigated Eight steel plates whose carbon content range from 0.02 to 0.23 percent were welded by autogeous gas tungsten are process. Constant strain was applied to the hot crack test specimen under the strain rate of 0.15 mm per second during welding. The hot cracking susceptibility ws high in the rnage of 0.02-0.05 and 0.12-0.23 percent carbon contents. The critical carbon content immune to hot cracking is in the range from 0.07 to 0.12 percent carbon. By electron probe microanalyser, amanganese segregation was not seen significantly in the whole carbon range. But segregation of silicon was higher in the region of low carbon contents. However, sulphur was segregated remarkably in the region betwen 0.18 and 0.23 percent carbon by peritectic reaction. Very smal lamount of dnedritic structure was observed in the region from 0.02 to 0.05 percent carbon by peritectic reaction. Very small amount of dendritic structure was observed in the region from 0.02 to 0.05 percent carbon but the predominant solidification structure was smooth by cellular growth. The higher the carbon content is, the more the columnar dendritic structure was observed.

• Journal of Mechanical Science and Technology
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• 제19권5호
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• pp.1169-1181
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• 2005

Experimental and numerical studies on the unsteady wake field behind a square cylinder near a wall were conducted to find out how the vortex shedding mechanism is correlated with gap flow. The computations were performed by solving unsteady 2-D Incompressible Reynolds Averaged Navier-Stokes equations with a newly developed ${\epsilon}-SST$ turbulence model for more accurate prediction of large separated flows. Through spectral analysis and the smoke wire flow visualization, it was discovered that velocity profiles in a gap region have strong influences on the formation of vortex shedding behind a square cylinder near a wall. From these results, Strouhal number distributions could be found, where the transition region of the Strouhal number was at $G/D=0.5{\sim}0.7$ above the critical gap height. The primary and minor shedding frequencies measured in this region were affected by the interaction between the upper and the lower separated shear layer, and minor shedding frequency was due to the separation bubble on the wall. It was also observed that the position (y/G) and the magnitude of maximum average velocity $(u/u_{\infty})$ in the gap region affect the regular vortex shedding as the gap height increases.

• 한국정밀공학회지
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• 제8권2호
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• pp.27-35
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• 1991

We propose the crack growth rate equation which applied over three regions (threshold region, stable region, unstable region) of fatigue crack propagation. Constant stress amplitude fatigue tests are conducted for four materials under three stress ratios of R=0.05, R=0.2 and R=0.4. Materials which have different mechanical properties i.e. stainless steel, low carbon steel, medium carbon steel and aluminum alloy are used. The fatigue crack growth rate equation is given by $da/dN={\beta} (1-R)^{\delta}\({\DELTA}K-{\DELTA}K_t)^{\alpha} / (K_{cf}-K_{max})$${\alpha}, {\beta}$ , and ${\delta}$ are constants, and ${\Delta}K_t$ is stress intensity factor range at low ${\Delta}K$ region. The constants are obtained from nonlinear least square method. $K_{ef}$is critical fatigue stress intensity factor. The relation between half crack length and number of cycles obtained by integrating the crack growth rate equation is in agreement with the experimental data. It is also experimented with constant maximum stress and decreasing stress ratios, and the fatigue growth rate of each material is in accord with the proposed equation.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2785-2796
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• 2023

How to generate the precise broad group cross section is important for the fast reactor design. In this study, a fast reactor multi-group cross-section generation code MGGC2.0 are developed in-house for processing ultrafine group MATXS format library. Validation and verification are performed for MGGC2.0 code by applying the benchmarks of ICSBEP handbook, and the results of MGGC2.0 agree well with that of MCNP. The consistent P_N method with critical buckling search is in good agreement that condensed with TWODANT flux and flux moment for the inner core and outer core region. For the radial blanket and reflector, two region approximation method has been applied in MGGC2.0 by using collision Probability Method neutron flux solver. The RBEC-M benchmark was used to verify the power distribution calculation, and the relative error of power distribution comparison with the reference are less than 0.8% in the fuel region and the maximum relative error is 5.58% in the reflector region. Therefore, the precise broad cross section can be generated by MGGC2.0 for fast reactor.

• 유통과학연구
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• 제14권11호
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• pp.75-82
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• 2016

Purpose - In order for actively pursuing medium and long term policies of Gangwon region to be effectively and efficiently driven, efficacious and practical development strategies are needed. In terms of regional revitalization in most regions that are dependent on the primary industry like Gangwon-do Province, the maintaining of local community becomes difficult and there are limitations on the support from the central government and local governments. Therefore, local communities need to implement measures not only to be financially independent but also maintain and activate themselves. And community business can be adopted to be a proper strategy to cope with this change. This study drew importance of a community business model appropriate for Gangwon-do region to figure out success factors. Research design, data, and methodology - This study aimed to come up with importance of community business model for Gangwon-do region by using AHP Method. AHP Method, which was developed by Professor Saaty in 1970', is a methodology to simplify complex problems for a rational decision making. A survey targeting related public officials and expert group was carried out and a total of 30 questionnaires were collected for the analysis. Results - Analysis model used in this study was to prioritize community business models of Gangwon-do region. The second hierarchy was divided according to local restoration type, local resource utilization type, environment improvement type, and life support type. The third hierarchy consisted of 5 items such as network, the middle structure, program, government support, and human resources to measure each importance. As a result, in the second hierarchy, local resource utilization type had the highest importance. In the third hierarchy, the middle structure had the highest importance, followed by government support, program, network, and human resources. Collectively, the results suggested that important critical factors of community business model of Gangwon-do region was the importance of local resource utilization model and the middle structure. Conclusions - Not only should projects that are already operating in the region but next community business projects that are planning in the Gangwon-do region should be practically operated in view of the importance and the models derived from this study.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3033-3038
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• 2007

In this research, Rayleigh instability of gas-liquid flow in annular pipe is studied in film boiling using viscous potential flow. Viscous potential flow is a kind of approximation of gas-liquid interface considering velocity field as potential including viscosity. A dispersion relation is obtained including the effect of heat and mass transfer and viscosity. New expression for dispersion relation in film boiling and critical wave number is obtained. Viscosity and heat and mass transfer have a stabilizing effect on instability and its effect appears in maximum growth rate and critical wave number. And the existence of marginal stability region is shown.

• Earthquakes and Structures
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• 제5권2호
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• pp.207-223
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• 2013

Practical seismic assessment and design of retrofit for the multitude of small ecclesiastical monuments that abound in the Balkans is the subject of this work. Application of the proposed procedures and methodologies are illustrated in an example case study, a small byzantine church located in Western Greece, which is the region with the highest seismicity in Europe. The church, known as the Fragavilla Monastery, had remained almost undamaged for 800 years, until 1993 when the Pyrgos earthquake caused critical damage mainly in the vaults. Linear elastic analysis to the recorded ground motion, capped by a biaxial failure criterion reproduced the developed damage. The same modelling and analysis procedure was subsequently used for assessment of the intended retrofitting measures. Proposed retrofitting measures included mitigation of the undesirable implications of past interventions along with a combination of strengthening schemes with externally bonded AFRPs strategically placed in the structure. The effectiveness of the proposed solutions is gauged by successful reduction of stress intensity in the critical regions and mitigation of stress localization throughout the structure.