• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.454-457
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• 2009

관이음부는 다양한 장점을 가지고 있어 여러 분야에 널리 이용되며, 관이음부의 구조강도를 증가시키기 위해 내부에 환보강재를 설치하는 방법이 대형 강관구조물에서 사용되고 있다. 그러나 환보강 관이음부의 해석 및 설계 자료에 관한 연구는 미흡한 실정이므로, 보강재의 기하학적 특성과 정적강도와의 관계를 규명하고자 한다. 환보강 K형 관이음부의 정적강도에 대하여 수치적으로 검토하기 위해 원형 중공단면의 관이음부를 유한요소 모델링하였고, 각 부재의 직경, 두께 및 폭의 상관관계를 이용한 무차원 계수를 통해 보강재의 위치와 기하학적 형상에 따른 보강효과를 수치적으로 검토하였다.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.13-21
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• 2007

This paper presents characteristics of steady flow by variation of a combustion chamber and an intake port. Gas flow field inside a combustion chamber is the important factor in improving combustion stability and reduction of emission level. The flow characteristics such as flow coefficient, tumble ratio and swirl ratio are measured by the steady flow rig test with an impulse meter in this study. In the measuring, the valve lifts are varied between 1mm to 10mm. The three combustion chambers and two intake ports were applied to the steady flow apparatus in order to investigate the effect of swirl and tumble on the in-cylinder flow. As a result, tumble ratio were found to be different by variation of the combustion chambers and the intake ports. The data from the present study can be applied to design of a similar engine as basic data.

• Journal of Korea Water Resources Association
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• v.48 no.4
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• pp.299-308
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• 2015

The aim of this study is that a theoretical formula for estimating the one-dimensional longitudinal dispersion coefficient is derived based on a transverse distribution equation for the depth averaged stream-wise velocity in open channel. In "Part I. Theoretical equation for stream-wise velocity" which is the former volume of this article, the velocity distribution equation is derived analytically based on the Shiono-Knight Method (SKM). And then incorporating the velocity distribution equation into a triple integral formula which was proposed by Fischer (1968), the one-dimensional longitudinal dispersion coefficient can be derived theoretically in "Part II. Longitudinal dispersion coefficient" which is the latter volume of this article. The proposed equations for the velocity distribution and the longitudinal dispersion coefficient are verified by using observed data set. As a result, the non-dimensional longitudinal dispersion coefficient is inversely proportional to square of the Manning's roughness coefficient and the non-dimensional transverse dispersion coefficient, and is directly proportional to square of the aspect ratio (channel width to depth).

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.29-41
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• 1999

This Paper applied a simple strength parameter averaging method to double layered systems consisting of the strong sand layer overlying the soft clay deposit. This study derived a formula which defines a critical depth as the strength parameters, and used the correction parameter, $\alpha$ to reduce an error of the strength parameter averaging method. The results of the method were presented in the form of dimensionless charts and were compared with the results of several solutions proposed by Satyanarayana & Grag, Sreenivasulu, and Meyerhof & Hanna. The results of the proposed method coincided with the method of Meyerhof & Hanna and the results obtained from FLAC. But the Satyanarayana & Grag method and the Sreenivasulu method overestimated the bearing capacity. Consequently, the bearing capacity of foundation on sand layer overlying soft clay layer can be approximately estimated by using the proposed dimensionless charts.

• Journal of Soil and Groundwater Environment
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• v.12 no.4
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• pp.1-7
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• 2007

Slug/bail tests were conducted in sand layer (sbt-1 well), silty sand layer (sbt-2 well), and mixed sand and silty sand layer (sbt-3 well). Hydraulic conductivity and specific storage coefficient were estimated through slug/bail tests. Pore volumes of groundwater level drawdown zone for bail test were estimated by using hydraulic conductivity and specific storage coefficient. KGS model was most suitable interpretation method of slug/bail tests. Average hydraulic conductivity for slug/bail tests were estimated to be $6.65{\times}10^{-5}$ m/sec in sbt-1 well, $6.33{\times}10^{-6}$ m/sec in sbt-2 well, and $3.72{\times}10^{-5}$ m/sec in sbt-3 well. Average specific storage coefficient for slug/bail tests were estimated to be 0.0225 in sbt-1 well, 0.0177 in sbt-2 well, and 0.0259 in sbt-3 well. Dimensionless time and dimensionless wellbore storage were estimated by use of transmissivity, storativity, test time, and specification of test wells. And, dimensionless drawdown were selected by parameter ${\alpha}\;and\;{\beta}$ parameter from Cooper et al. (1967). Radius of influence were estimated by estimated dimensionless time, dimensionless wellbore storage, and dimensionless drawdown. The average radius of influnce for slug/bail tests were estimated to be 1.377 m in sbt-1 well, 1.253 m in sbt-2 well, and 1.558 m in sbt-3 well. Pore volume at groundwater level drawdown zone by dummy withdrawal for bail tests were estimated to be $145,636cm^3$ in sbt-1 well, $71,561cm^3$ in sbt-2 well, and $100,418cm^3$ in sbt-3 well. Pore volume excepted well volume at groundwater level drawdown zone by dummy withdrawal for bail tests were estimated to be $145,410cm^3$ in sbt-1 well, $71,353cm^3$ in sbt-2 well, and $100,192cm^3$ in sbt-3 well.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.275-281
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• 2018

It is known that he pollutant emitted from the combustion process of marine fuel oil causes air pollution and harmful effects to the human body. Accordingly, IMO regulates pollutants emitted from ships. However, the regulation of Particulate Matter (PM) is still in the process of debate, so preemptive action is needed. Fundamental research on PM is essential. In this study, the Dimensionless Light Extinction Constant ($K_e$) of fuel oil used in marine diesel engines was measured and analyzed to construct the basic data of the PM generated from marine-based fuel oil. The fuel oil used in the land diesel engine was measured in the same way for character comparison. Both fuel oils differ in sulfur content and density. The $K_e$ was measured via the optical method using a 633 nm laser and was determined by using the volume fraction of PM collected by the gravimetric filter method. The $K_e$ of the PM discharged from marine fuel oil is 8.28, and the land fuel oil is 8.44. The $K_e$ of two fuel oils was similar within the measurement uncertainty range. However, it was found by comparison with the value obtained by the Rayleigh-Limit solution that the light scattering portion could be large. Also, it was found that light extinction characteristics could be different due to the relationship between light transmittance and collected mass.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.149-155
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• 2000

응답변위법에서 이용되는 동지반강성계수의 적절한 평가법에 대한 제안을 하였다. 현재까지의 지진피해조사 및 장기간의 지진관측사례는 지반이 공진할 때의 변형모드가 지중구조물의 피해에 가장 직접적으로 관련이 있는 것으로 알려져 있다. 따라서, 지중구조물의 축방향의 지반의 변형모드와 그 타월 진동수를 특정하여 동지반강성계수를 평가했다. 동지반강성계수는 지반의 공진상태를 상정하고 있기 때문에 결과로써 지진파의 축방행 파장의 영향을 받지 않고, 관상구주물의 반경과 표층두께의 비, 표층두께에 대한 구조물의 매설위치, 표층지반과 기반의 임피단스비 라고 하는 3개의 무차원 변수에 의해 표현된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.137-137
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• 2019

돌출줄눈은 산지하천의 만곡부의 빠른 유속을 감소시키기 위하여 활용된다. 본 연구에서는 친환경 디자인의 나무줄기 돌출줄눈(Tree Trunk Rip, TTR)과 사다리꼴 돌출줄눈(Trapezoid Rip, TR)의 흐름저항을 비교 분석하기 위하여 개수로 수리실험을 수행하였다. 실험은 길이 9m, 폭이 0.6m이며 경사가 0.0035로 고정된 개수로의 한쪽 측벽에 돌출줄눈을 설치하여 진행하였다. 사다리 꼴 돌출줄눈의 형상은 밑변 각이 $63^{\circ}$이며 무차원 설치간격 ${\lambda}_{nv}$가 6, 9, 12인 경우이다. 나무줄기 돌출줄눈의 기본 형상은 사다리꼴이고 표면은 나무껍질 무늬이며 ${\lambda}_{nv}$가 약 10이다. 나무줄기 돌출줄눈의 간격은 사다리꼴 돌출줄눈의 최적 설치 간격 9~12배 범위에 해당되고 평균 마찰계수는 사다리꼴 돌출줄눈의 9~12배의 평균 마찰계수 범위에 포함되었다. 사다리꼴 돌출줄눈의 ${\lambda}_{nv}$가 9, 12일 때의 전체 저항에 대한 형상저항의 비는 평균 $69.4{\pm}5.8%$였으며 나무줄기 돌출줄눈은 $70.2{\pm}2.1%$로 사다리꼴 돌출줄눈과 유사하다. 산지하천 흐름저항을 위한 돌출줄눈 설치에 있어 친환경적 디자인을 고려한 나무줄기가 사다리꼴 돌출줄눈보다 활용도가 클 것으로 기대된다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.820-823
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• 2017

This study experimentally investigate how the Reynolds number affect cavitation performance in a turbopump inducer using water. Cavitation performance has been determined by the static pressure measured at the inlet of the inducer. Reynolds number has been varied by varying water temperature and inducer rotational speed to maintain constant non-dimensional thermal parameter. At low non-dimensional thermal parameter, the critical cavitation number is insensitive to Reynolds number. However, at high non-dimensional thermal parameter, the critical cavitation number increased as Reynolds number increases. Thus, cavitation performance is deteriorated as Reynolds number increases when thermal effect exists.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.9-9
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• 2008

일반적으로 섬광법으로 열전도율을 구하기 위해서는 섬광법으로 열확산계수를 측정하고, 시차주사열량계(Differential Scanning Calorimetry, DSC)로 비열측정을 하며 아르키메데스의 원리를 이용한 용적밀도를 구하여 이들 각각의 값을 사용하여 열전도율을 얻는다. 따라서 열전도율을 정밀하게 측정하기 위해서는 이 세 가지 물성치를 측정할 때 수반되는 오차요인을 종합적으로 검토하여 개선하는 것이 매우 중요하다. 섬광법으로 열확산계수를 측정할 때 시료의 전면에 조사되는 빛의 흡수율을 향상시키고 배면에서의 온도상승의 감지를 증대할 목적으로 시료 양면에 흑연코팅을 하게 된다. 이때 코팅된 흑연이 시료에 부가적으로 열저항을 증가시켜서 열확산계수를 측정하는데 가장 큰 오차요인이 되고 있다. 한편 비열은 대부분 DSC로 측정하는데, 시료와 용기의 열접촉 정도에 따라 큰 오차요인이 되기도 한다. 본 연구에서는 열확산계수를 정밀하게 측정하기 위해서 시료에 부가적인 열저항으로 작용하는 흑연코팅의 두께와 시료배면에서의 온도상승곡선 간의 상관관계를 실험식으로 도출하였으며 이방법은 열확산계수를 정밀하게 측정하는데 매우 유효한 방법임이 입증되었다. 또한 DSC의 접촉에서의 문제점을 해결하기 위해서 시료배면에서의 무차원 시간축(t/$t_{max}$)을 도입하였으며. 무차원 시간축에 따른 온도상승 곡선에서 표준시료와 측정시료의 half time($t_{1/2}$)의 0.5 배와 1.5배 사이 구간을 적분한 뒤 비교하여 열량계산으로부터 비열을 구하는 방법을 새롭게 개발하였으며 기존의 DSC에 비하여 정밀도를 향상시킬 수 있었다. 결론적으로 새롭게 제안된 측정기법들은 열확산계수 및 비열 혹정 시의 근본적인 오차요인을 혁신적으로 해결함으로써 정밀하고 신뢰성 있는 열전도율을 측정할 수 있음을 입증할 수 있었다.