• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.471-471
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• 2015

토양내의 수분흐름을 이해하는 것은 토양수분의 시공간적 분포변화와 유출기작을 규명하는데 매우 중요하다. 본 연구에서는 설마천유역의 작은 사면에서의 장력측정 시스템을 구축하여, 3차원의 흐름방향에 대해 잠재적 흐름구배를 평가하고자 하였다. 또한 흐름구배를 평가하기 위한 일반적 산술적 계산방법인 평균적 흐름구배와 측정시스템의 구조적 영향 및 흐름구배의 공간적 평가 기준을 고려한 계산방법론을 개발하여 비교 평하였다. 3차원의 흐름방향은 사면의 지표경사를 기준으로 x, y, z축을 기준으로 하여, 각 축 방향에 해당하는 흐름구배 값과 흐름방향을 각각 계산하였다. 그 결과, 강우사상에 따른 토양내의 장력변화는 매우 민감하게 변화하였으며, 이에 따른 각 흐름구배 값과 흐름방향의 반응이 빠르게 반응을 하였다. 특히, 습윤, 건조기간동안의 흐름구배의 발달 및 방향이 바뀌는 천이되는 상태인 흐름 굽힘 현상(flow Bending)을 확인하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.153-154
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• 2012

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.3
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• pp.223-237
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• 2010

The initial heating rate is well known as one of the most influencing factors on the occurrence of spalling and the loss of strength in concrete after fire initiation. In this study, a series of fire tests were carried out at different initial heating rates to find out its effects on the deterioration of tunnel structural members. Heat transfer analyses combined with an element elimination model were also carried out to verify its applicability in the same conditions as the fire tests. Moreover, the convection heat transfer coefficients compatible with fire test results were derived from parametric studies. In this course, their time-dependent variations were also analyzed at different initial heating rates. Finally, a numerical formula to estimate the heat transfer coefficients at the various initial heating rates was proposed by the interpolation of the results of numerical analyses.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.67.2-67.2
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• 2010

구형 분자운에서의 복사전달문제를 탈출확률방법에 기초하여 non-local method로 풀었다. 매질을 여러 개의 구간으로 나누고 각 구간에서 물리량이 일정하다고 가정하여 복사전달식을 전개하였고 뉴턴방법을 채택하여 수렴속도를 빠르게 하였다. 이번 연구에서는 분자운 내부의 속도구배가 작든 크든 상관없이 복사전달식을 풀 수 있도록 수치코드를 개발하였다. 우리의 계산 결과는 속도구배가 큰 경우에는 LVG방법을 사용한 결과와 일치하고, 분자운이 정적인 경우에도 이전 연구의 결과와 일치한다. 앞으로 이 방법에 line-overlap과 saturation효과를 추가하여 만기형 별에서의 SiO메이저 연구에 활용할 계획이다.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.448-448
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• 2001

담수가 유입되는 하구역에서 저서동물의 공간 분포 특성을 파악하기 위하여 서남해역에 위치한 법성포항 인근의 와탄천 해역을 조사장소로 선정한 다음, 하구역 입구에서 염분 구배에 따라10개 정점을 설정하였다. 저서동물의 채집을 위해 1998년 5월부터 1999년 1월까지 van Veen grab (0.1$m^2$)을 사용하여 각 정점당 3회씩 퇴적물을 채집하였다. 조사 기간 동안 총 114종이 출현하였으며, 이 가운데 다모류가 44종(전체 출현종수의 39%), 갑각류가 34종(30%), 그리고 연체동물이 24종 (21%)을 차지하였다. (중략)

• The Journal of the Acoustical Society of Korea
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• v.34 no.1
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• pp.66-74
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• 2015

Conventional hydrophones can only measure acoustic pressure. To measure both acoustic pressure and incident direction, various types of vector hydrophones have been researched. In this paper, we deal with a ring-type multimode vector hydrophone divided into 4 elements and present a direction-of-arrival (DoA) estimation method based on the pressure gradient-acceleration relationship. The performance of the presented method is analyzed by the simulation based on the sensor modeling and is verified by the water tank experiment. The proposed method could work under the multi-frequency condition and may be utilized in many applications due to its low computation complexity.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.387-393
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• 2012

It is very difficult to determine suitable cutting conditions in order to obtain accurate cutting profiles because machining errors caused by tool deflection depend upon cutting conditions. In this study the relationship between real cutting profiles (inclined shapes and machining errors) and cutting conditions was modeled in order to fabricate draft angle on micro molds. CCD (Central Composite Design) of DOE (Design Of Experiment) and RSM (Response Surface Method) were applied in order to model the relationship between cutting conditions and machining errors. In order to use CCD the range of radial depth of cut was chosen by $10-90{\mu}m$ and the range of feedrate was chosen by 200-300mm/min, and 9 points of cutting conditions were chosen inside determined ranges. Then, actual cutting processes were carried out as respect to 9 points of cutting conditions, draft angles and real cutting profiles were measured on cutting profiles, each response surface function was determined by conducting response surface analysis and the functions were represented by 3-dimensional graphs, contour lines and $101{\times}101$ matrices. Consequently it is possible to determine suitable cutting conditions in order to obtain arbitrary given draft angles and cutting profiles by using modeling. To validate proposed approach in this study suitable cutting conditions were determined by modeling in order to obtain arbitrary given draft angle and cutting profile, and actual cutting processes were carried out. About 95% of good agreement between predicted and measured values was obtained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.565-570
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• 2017

The various techniques proposed previously to obtain a good antireflection(AR) coating induce a scattering of incident light by nanoparticles or control the refractive index by using different materials. This paper compares a suggested graded index profile with the quintic index profile previously suggested for producing an index profile that gives good performance from an AR coating. We assume the structure of the AR coating has three, six, and nine layers with 180 nm total thickness. The wavelength of incident light ranges from 300 nm to 1100 nm. We use the transfer matrix theory for a single layer to obtain the reflectivity of three, six, and nine layers. The reflectivity of two different index profiles with three, six, and nine layers is compared. As a result, the suggested graded index profile shows lower reflectivity than the quintic index profile with three layers, especially in the wavelength range from about 600 nm to 1100 nm. Therefore, we expect that these results can be applied to optical devices and filters in the range from visible(red) to near infrared.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.304-313
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• 1987

The behaviors of layers developed in a solar pond were studied by experimental and analytical methods. An experimental solar pond heated from below was constructed and operated at the net heat fluxes of 110 and 160W/m$^{2}$ and at the initial salt concentration gradients of 18.2, 27.3 and 36.4%/m. The thicknesses, growth rates, temperature and salt concentration in the top and the bottom mixed layers, the diffusive layer and the upper and the lower interfacial boundary layers were measured. The shadowgraph technique was used in order to observe all layer formation and an electroconductivity-temperature probe consisting of four electrodes was fabricated and used in measuring the salt concentration. Based on the experimental results, a model for the solar pond was developed and the governing equation and the assumptions were established. The governing equations were solved by the numerical method. The calculated results obtained from the analysis were compared with the experimental results.

• Journal of Korean Society of Transportation
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• v.16 no.4
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• pp.113-126
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• 1998

본 논문에서는 1992년 KHCM 작성시 이용된 양방향 2차선 도로 및 고속도로의 승용차 환산계수 산정방법론 및 자료를 연구하였다. 대형차가 2차선도로, 고속도로의 교통류에 미치는 영향은 각기 다르므로 1992년 KHCM 작성시 승용차 환산계수를 산정하는데 있어서 각 도로의 특성을 최대한 반영하기 위해 다양한 방법을 적용하였다. 양방향 2차선 도로의 평지의 서비스 수준 A에서는 Walder 방법, 서비스 수준 B, C, D에서는 지체시간 방법, 서비스 수준 E에서는 차두간격 방법, 구릉지, 산지 특정구배에서는 실측 자료 및 TWOPASKI Simulation에 의한 방법을 적용하였고, 고속도로의 평지에서는 차두간격 방법, 그릉지, 산지, 특정구배에서는 실측 자료 및 VEHEQ Simulation에 의한 방법을 적용하였다. 양방향 2차선 도로는 한 방향당 차선이 하나이므로 추월시 대형차의 영향이 고속도로보다 크기 때문에 각 서비스 수준별고 승용차 환산계수를 제시했으며, 고속도로의 승용차 환산계수는 용량에 가까운 상태에서의 승용차환산계수를 제시하였다. 본 논문은 1992년 KHCM의 양방향 2차선 도로 및 고속도로의 승용차 환산계수 산정에 실지로 적용된 방법론 및 자료를 수정없이 그대로 제시하여 독자들이 승용차 환산계수 산정에 이용된 자료의 양 및 연구 수준의 정도를 이해할 수 있게 하고 독자의 평가를 통하여 미비한 부분은 추후 개정 작업에 반영하기 위함이다.