• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.481-487
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• 2011

This paper provides a comparison between finite element analysis results and test data of rupture disc. Rupture disc is safety device of high pressure equipment. Rupture disc of solid rocket motor is a device to control rupture pressure. Rupture discs were made of AISI 316L. By the elastic-plastic analysis, the stress limit of rupture discs were compared to the test results. The results can be used to control the rupture pressure by the change of the disc size.

• The Journal of the Acoustical Society of Korea
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• v.20 no.3
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• pp.91-97
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• 2001

Since the new field information of target signal is important in the development and verification of active sonar system, experimental method and simulation technique are widely used in order to analyze the detail characteristics of target scattered echoes. Therefore, in this paper, the scale target experiment is performed to develope and Improve the target signal simulation model. Since the experimental results show that the specular reflection is the major component among scattering mechanisms, the target signal simulation model based on the Geometric Optics Theory (GOT) is developed. Complex target is separated into simple shapes, known as canonical shape. The contribution from individual canonical shapes are summed with proper phase and amplitude to produce the target strength of the whole complex body. Simulated target signal is compared with the experimental results and discussed.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.1
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• pp.69-76
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• 2011

PEMFC (polymer electrolyte membrane fuel cell) is device that generates electricity from hydrogen. It is one of the subjects related to renewable energy and various research has been conducted on the PEMFC. PEMFC has low operating temperature and high efficiency among fuel cells, and is given attention as means for automobile and domestic use. Analysis of flow field pattern in supplying hydrogen and oxygen is part of the research to increase PEMFC efficiency. In this study, separation plate currently used in PEMFC is transformed to wave shape and mass transfer characteristics in the channel is examined through numerical and experimental analysis. Wave shape separation plate yielded 18% increase of efficiency compared to separation plate used in normal channel. And improvements in mass transfer characteristics were verified.

• CDE review
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• v.21 no.1
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• pp.7-12
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• 2015

본 글을 통해 학생들과 함께 수행한 다양한 디지털 디자인 모델을 기반으로 5가지의 디지털 패브리케이션 방식을 적용하여 여러 실제 인테리어패널의 제작 과정 및 그 결과물들을 요약적으로 소개하였다. 해당 과정은 기존의 분리된 설계와 제작 및 시공이 아닌, 설계-제작 통합적인 접근방법을 활용함으로써 학생들로 하여금 디지털 디자인과 패브리케이션의 효과를 극대화 할 수 있음을 체득하도록 하였다. 패브리케이션 기기 및 재료 등의 차이점에 따라 실제 구현된 모델과 원래의 디지털 모델과의 형상적인 차이점은 아직까지 한계점으로 남을 수 있지만, 비정형적으로 생성된 디지털 디자인의 형상이 직접적으로 실현이 가능하다는 점에서 의의가 있다고 할 수 있다. 또한 패러매트릭 모델링 기법이나 실제 제작 경험이 거의 없는 학생들을 대상으로 개별적인 교육이 아닌 설계-제작 통합적인 교육을 실시함으로써 각 요소들이 어떻게 유기적으로 관련되어 디지털 디자인 과정이나 패브리케이션과정에서 상호 보완적으로 중요한지 직접 체득할 수 있도록 하였다는데 의의가 있다. 본 글에서 소개한 재료를 깎는 등의 방식인 "마이너스"의 방식이 아닌 3D프린팅과 같이 재료를 이용해 만들어가는 "플러스"적인 방식 또한 해당 사례에서 수행되었으며 마찬가지로 다양한 특성을 지니고 있으나, 본 글에서는 전자의 방식에 대해 주로 논하였다. 본 글에서 다룬 제작기법뿐만 아니라 3D프린팅 기술의 발전과 보급에 따라 디지털 패브리케이션 역시 다양하게 진보하고 있으며, 팹랩 등을 통한 학교에서의 건축설계 교육도 다양하게 진화하고 있다. 본 사례 및 기타 실험적인 교육과 선도적인 여러 시도를 통해서, 디지털 디자인과 패브리케이션 영역을 확장시켜나가고 해당 기술의 발전에 적극적으로 보조할 수 있는 교육과정을 수립하고 이행하는데 일조 할 수 있기를 희망한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.2
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• pp.112-123
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• 1990

This paper presents a vertex-detecting of Hanguel patterns using nested contour shape. Inputed binary character patterns are transformed by distance transformation method and make a new file of transferred data by analysis of charactersitcs. A new vertex-detecting algorithm for recognizing Hanguel patterns using the two data files is proposed. This algorithm is able to reduce the projecting parts of Hanguel pattern, separate the connecting parts between different strokes, set the code number by transformed value of coorked features. It makes the output of results in order to apply the Hanguel recognition.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.862-874
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• 1989

A phase evil method and spectrum analysis were instrument error which is originated from measurement system and the form error of standard specimens. An instrument with a rotating table supported by an air bearing is calibrated using standard specimens. The phase of standard specimens was measured 12 times on the rotating table with rotating 30 in turn and its measurement magnification was set by 100000 times. As a result of data analysis of all the observations, read out at each of 144 orientations(per 2.5) from recorded datafiles, the error of the performance of the instrument and those of the standard specimens are evaluated and a systematic deviation of the instrument is determined. In the particular instrument used in the present experiment, the deviation of the instrument is determined with the accuracy of 15nm and those of standard specimens with the accuracy of 23, 13 n, respectively. The reproducibility of the instrument is investigated, too. If the instrument is calibrated by using the above standard specimens, then the accuracy of the measurement of roundness error can be improved to about 15nm.

• Journal of Energy Engineering
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• v.27 no.4
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• pp.13-19
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• 2018

In this study, the lightweight design of butterfly valve disc component for power plant based on topology optimization was performed. Here, commercial finite element (FE) analysis software was used. The external shape of the basic disc model was not deformed, and the internal element density was removed to make it lightweight. Optimal design was performed each other after the disc plate and two brackets attached on the surface of the disc were separated. Once the optimal shapes were selected, they were assembled to build up the 3-D lightweight valve disc model. After applying pressure to this model, FE analysis was performed to confirm the structural safety.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.433-433
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• 2021

본 연구는 개수로 흐름에서 조류발전단지의 터빈 최적 배열의 거시적 특성에 관한 연구를 수행하였다. 천수방정식을 통해 직사각형 개수로의 흐름장을 해석하였고, 상류와 하류단에 대해 각각 유입경계조건(inlet boundary condition)과 Flather 형식의 개방경계조건(open boundary condition)을 부여하여 일정 유량으로 흐르는 개수로 흐름을 구현하였다. 더불어, Strickler의 법칙을 확장한 반력공식을 연계하여, 개수로 흐름에 대한 조류 터빈의 영향을 반영하였다. 주어진 상류의 흐름 조건에 대해 조류발전량을 최대로 하는 최적 배열을 구하기 위해 터빈 반력모형을 연계한 천수방정식, 터빈간 최소간격, 그리고 발전단지영역을 제한조건으로 하는 발전량 최대화 문제를 구성하였다. 여기서 조류 터빈의 위치를 나타내는 벡터를 설계변수로 두었는데, 설계되는 터빈의 수가 증가함에 따라 최적화 문제의 계산량이 증가하지 않도록 수반법(adjoint method)을 경사도기반법(gradient-based method)에 연계한 방법이 이용되었다. 다수의 터빈초기배치로 상당한 수치실험이 수행되었고, 발전량 최대화를 이루도록 최적화된 터빈의 배치들이 큰 규모에서 고유한 형상으로 수렴함을 확인하였다. 이러한 특성은 발전단지의 너비와 터빈의 최소간격의 함수로 정의된 무차원수 E를 바탕으로 설명되었다. 구체적으로, E가 1보다 작을 때에는 선형배열이 최적배열로 나타났고, E가 1을 넘어 점차 커짐에 따라 하류에 오목한 형상을 보이다가 V-형태로 발전하는 양상을 보였다. 또한, 어느 임계 수 이상의 터빈이 배치되는 경우 일열 배열을 유지하지 못하고 이열 배열로 분리됨이 관찰되었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.375-382
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• 2010

This paper presents the extraction of natural frequencies and mode shapes of a cable-stayed bridge using data acquired from GNSS. The response signals of 6 GNSS measuring points installed at the Seohae cable-stayed bridge are used for analysis of dynamic characteristics. Using normalization process and a third order Butterworth filter for the measured signals, the related pass band's signals have been isolated. Then, the acceleration data by double differentiation for these signals are obtained. Total five natural frequencies have been extracted by the fast Fourier transform and compared to the results of different studies. For the acceleration obtained from GNSS signals, the mode shapes of the bridge have been successfully extracted by TDD technique.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.23-32
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• 2016

A single particle crushing test was carried out for recycled aggregates from waste concrete while demolishing various structures. When the recycled aggregates were used for backfill or road subbase materials, load-displacement and crushing characteristics were analyzed. The recycled aggregates with hydrates and aggregates were sorted into 40 mm size (75-40 mm) and 20 mm size (40-20 mm). At initial loading, their irregular surface was closed to and then crushed by loading plate. Such first crushing stage was called 'Surface crushing'. Further loading, some hydrate was crushed and detached from aggregate, and such process repeated several times. This state is called 'hydrate crushing'. The final state is called 'aggregate crushing' in which aggregate crushed and following load suddenly dropped down. As the load increased, such crushing cycle is repeated several times. The shapes of aggregates are round or square, and triangle or long shaped. Depending on their shapes and surface conditions, they crushed in different ways. The 63% of aggregates showed more than 50% load reduction due to aggregate crushing. The 90% load reduction occurred at 15% of aggregates. The 40 mm aggregate crushed at maximum load between 3.05-4.38 kN and 70% of crushed aggregates were less than 20 mm.