• 대한토목학회논문집
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• 제37권5호
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• pp.905-914
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• 2017

본 연구는 공동주택의 부산광역시 554개 국가기초구역과 1832세대의 개별세대주택을 대상으로, 기존의 건축 단지특성과 보행친화특성이 공동주택가격에 끼치는 영향에 대하여 분석하였다. 개별세대주택과 국가기초구역의 다양한 공간구역 특성을 바탕으로 보다 정확한 다층적인 분석을 위해, multi-level models 을 이용하였다. 분석 결과, Level-2의 국가기초구역별 보행친화특성은 전체분산의 약 77%를 잠재적으로 설명하였으며, 그 중 범죄안전특성에서 가장 많은 영향을 미치는 것으로 나타났다. 이것은 이전연구에서 많이 다뤄졌던 개별세대 공동주택별 분석보다, 한국에서 새롭게 제정된 국가기초구역에 따른 공간별 분석이 더욱 전체적으로 의미가 있다는 것을 의미한다. 이 연구결과는 요동치는 한국의 주택가격을 건강하고 안정적으로 유지할 수 있는 보행친화적인 도시설계 및 주택정책에 기여할 수 있을 것이라 생각한다.

• 한국군사과학기술학회지
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• 제13권4호
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• pp.586-593
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• 2010

In this paper, I have proposed that the 1st and 2nd AC-DC transformation methods using multi-level pulsating currents and selection switches. Through making the rectified voltage of the proposed AC-DC translation which is similar to reference voltage by selecting from multi-level pulsating currents, the proposed translation has dramatically reduced the ripple voltage. I have compared the performance of the DC voltage, the ripple voltage and the peak to peak voltage of the proposed method with the conventional method. The simulation results show that the proposed 2nd method has the better performance than the 1st method in the point of average DC voltage drop and peak to peak voltage increase.

• Journal of Power Electronics
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• 제9권4호
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• pp.593-603
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• 2009

This paper proposes and describes the design and operational principles of a three-phase three-level nine switch voltage source inverter. The proposed topology consists of three bi-directional switches inserted between the source and the full-bridge power switches of the classical three-phase inverter. As a result, a three-level output voltage waveform and a significant suppression of load harmonics contents are obtained at the inverter output. The harmonics content of the proposed multilevel inverter can be reduced by half compared with two-level inverters. A Fourier analysis of the output waveform is performed and the design is optimized to obtain the minimum total harmonic distortion. The full-bridge power switches of the classical three-phase inverter operate at the line frequency of 50Hz, while the auxiliary circuit switches operate at twice the line frequency. To validate the proposed topology, both simulation and analysis have been performed. In addition, a prototype has been designed, implemented and tested. Selected simulation and experimental results have been provided.

• 보건행정학회지
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• 제30권3호
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• pp.355-365
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• 2020

Background: This study is aimed to verify individual and regional-level factors affecting the depression of Koreans and to develop social programs for improving the depressive status. Methods: This study used individual-level variables from the Korean Community Health Survey (2018) and used the e-regional index of the Korean Statistical Information Service as the regional-level variable. A multi-level logistic regression was executed to identify individual and regional-level variables that were expected to affect the extent of depressive symptoms and to draw the receiver operating characteristic curve to compare the volume of impact between variables from both levels. Results: The results of the multi-level logistic regression analysis in regards to individual-level factors showed that older age, female gender, a lower income level, a lower education level, not having a spouse, the practice of walking, the consumption of breakfast higher levels of stress, and having high blood pressure or diabetes were associated with a greater increase in depressive symptoms. In terms of regional factors, areas with fewer cultural facilities and fewer car registration had higher levels of depressive symptoms. The comparison of area under the curve showed that individual factors had a greater influence than regional factors. Conclusion: This study showed that while both, individual and regional-level factors affect depression, the influence of the latter was relatively weaker as compared to the first. In this sense, it is necessary to develop programs focused on the individual, such as social prescribing at the local or community-level, rather than the city and nation-level approach that are currently prevalent.

• 벤처창업연구
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• 제14권6호
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• pp.143-153
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• 2019

본 연구는 2017년도 인적자본패널(Human Capital Corporate Panel; HCCP) 자료를 사용하여 사내기업가정신의 효과성을 분석하였다. 사내기업가정신이 기업의 성과로 연결되는 과정에서 주요한 연결고리인 근로자들의 태도는 그동안 자료수집 및 분석방법의 한계로 인하여 대부분 개인 및 조직수준에서 단일수준으로 연구되어 왔다. 사내기업가정신과 구성원의 태도 사이의 관계를 위계적 선형모형(hierarchical linear modeling)을 활용한 다수준분석(multi-level analysis)을 실시하여 변수 간의 관계성 추정에 정확성을 높였다. 또한, 사내기업가정신이 구성원의 태도에 이어지는 과정에서 조직수준의 조절효과에 대해 살펴보았다. 연구결과, 사내기업가정신은 근로자의 조직에 대한 태도인 직무만족 및 이직의도에 긍정적인 영향을 미쳤고, 이 과정에서 조직신뢰는 사내기업가정신과 직무만족의 관계에서 조절역할을 수행하는 것으로 나타났고, 사내기업가정신과 이직의도의 관계에서는 조절역할을 수행하지 않았다. 즉 조직차원의 사내기업가정신은 구성원의 태도에 미치는 중요한 영향변수임을 확인하였다. 이러한 결과를 바탕으로 연구의 시사점, 한계 및 향후 연구과제 등에 관하여 논하고자 한다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.259-260
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• 2011

Using modern techniques from scientific computing and numerical analysis, natural phenomena or scientific experiment can be simulated effectively with a computer and used for computer graphics, for example as special effects for the film industry, manufacturing the thin film, multi-phase simulation and image processing. The Level Set method can make those things happen without a lot of difficulties. This method was devised by Osher and Sethian(1988) to represent dynamically moving interfaces as the zero level set of a scalar function that evolves in time. Since then, many researchers have worked on many applications using a Level Set Method. I will give a talk about the applications of the Level Set Method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.489-493
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• 2007

Mmulti-domain noise analysis method using Power Flow Boundary Element Method(PFBEM) has been developed successfully. Some applications are introduced. several examples. PFBEM is a numerical analysis method formulated by applying Boundary Element Method(BEM) to Power Flow Analysis(PFA). PFBEM is very powerful in predicting noise level in medium-to-high frequency ranges. However there are restrictions in analyzing the coupled structures and multi-media. In this paper, an analysis method for multi-domain acoustic problems in the diverse acoustic fields is suggested. And the developed method is applied to the car interior and exterior multi-domain noise analysis.

• 컴퓨터교육학회논문지
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• 제16권1호
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• pp.51-61
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• 2013

본 연구는 ICT 활용능력과 학습목적 컴퓨터 사용영향 요인을 파악하기 위해 PISA 2009 한국자료 141개 학교의 학생 4,298명을 대상으로 다층분석을 실시하였다. 연구의 결과로 첫째, ICT 활용능력은 여학생, 사회경제문화적지위, 온라인 자료읽기, 컴퓨터 태도 하위항목의 중요성과 관심은 정적으로 유의하였고, 재미 및 시간왜곡은 부적으로 유의하였다. 학교수준에서는 사회경제문화적지위만이 유의하였다. 둘째, 가정에서 학습목적의 컴퓨터 사용은 ICT 활용능력의 학생수준 영향변인들의 결과와 같았으나 컴퓨터 태도 하위항목의 중요성은 유의하지 않았다. 학교수준에서는 사회경제문화적지위가 정적 영향, 지역규모는 부적 영향을 나타내었다. 셋째, 학교에서 학습목적 컴퓨터 사용은 성별 차이가 없었고, 온라인자료읽기는 정적 영향, 재미와 시간왜곡은 부적인 영향을 주었다. 학교수준에서는 사회경제문화적지위와 컴퓨터 비율은 정적 영향, 지역규모와 학생-교사비율은 부적 영향을 주었다. 연구결과는 다층적 접근을 통해 개인차와 학교 간 차이를 고려한 정보교육 정책이 이뤄져야 함을 시사한다.

• Structural Engineering and Mechanics
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• 제64권2호
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• pp.195-204
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• 2017

Analytical and experimental studies of the innovative pipe in pipe damper have been recently investigated by the authors. In this paper, by adding lead or zinc infill or slit diaphragm inside the inner pipe, it is tried to increase the equivalent viscous damping ratio improving the cyclic performance of the recently proposed multi-level control system. The damper consists of three main parts including the outer pipe, inner pipe and added complementary damping part. At first plastic deformations of the external pipe, then the internal pipe and particularly the added core and friction between them make the excellent multi-level damper act as an improved energy dissipation system. Several kinds of added lead or zinc infill and also different shapes of slit diaphragms are modeled inside the inner pipe and their effectiveness on hysteresis curves are investigated with nonlinear static analyses using finite element method by ABAQUS software. Results show that adding lead infill has no major effect on the damper stiffness while zinc infill and slit diaphragm increase damper stiffness sharply up to more than 10 times depending on the plate thickness and pipe diameter. Besides, metal infill increases the viscous damping ratio of dual damper ranging 6-9%. In addition, obtained hysteresis curves show that the multi-level control system as expected can reliably dissipate energy in different imposed energy levels.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.574-582
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• 1999

This paper discusses the multi-level optimization method in dynamic optimization problems through stiffened plate of ship structures. In structural optimization the computational cost increases rapidly as the number of design variables increases. And we need a great amount of cal-culation and time on problems of modified dynamic characteristics of large and complicated struc-tures. In this paper the multi-level optimization is proposed which decreases computational time and cost. the dynamic optimum designs of stiffened plate that control the natural frequency and minimize weight subjected to constraints condition are derived. The way to apply the multi-level optimization methods in this study follow: In the first step the dynamic characteristics is controlled for the two-dimensional model of stiffened plate by sensitivity analysis and quasi-least squares methods. In the second step the cross-section of the stiffener is decided so that the weight is minimized under needed constraints by the steepest descent or ascent method. In the third the three-dimensional model is made based on the results of the first step and the second step confirmation and finer tuning of the objective function are carried out. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate.