• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.175-184
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• 2011

To take advantage of reduced on-site construction periods and minimize traffic impacts various types of steel grid composite deck have been developed since 1930's. Modular prefabricated unfilled grid decks permit a long-distance transportation and construction under unfavorable condition, for example, in mountainous regions due to its comparatively light-weighter structure than fully filled grid deck. In this study bending tests of unfilled grid decks for the deck member of various kinds of infrastructure are carried out, bending strength and behaviour of composite action are experimentally evaluated. In this bending test, design variables are considered, such as type of shear connection between steel grid and concrete slab, spacing between cross bars and thickness of concrete slab. Through test results bending strength and behaviour of composite action are evaluated, reference data for proper type of shear connection and other details of the deck, such as spacing between cross bars, are obtained.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.34-34
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• 2021

본 연구에서는 격자기반 분포형 수문모델링을 통해 하천갈수량을 추정하고자 한다. 분포형 수문모형은 단방향흐름 알고리즘에 의한 토양 물수지식을 기반으로 개발되었으며 운동파(kinematic wave) 이론을 적용하여 지표 및 지표하 유출을 모의한다. 또한, 격자별로 수문학적 물수지요소인 차단량, 증발산량, 침투 및 침루량, 지하수충전량 등을 계산하며, 댐·보 방류량을 해당 지점 격자의 물수지에 적용할 수 있도록 개발하였다. 본 모형은 2개의 다목적댐과 3개의 다기능보가 위치한 금강유역(9,645.5 km²)에 적용하였으며, 유역 면적과 하천 유속을 고려하여 1 km × 1 km 격자를 구성하고 10분 간격으로 2013년부터 2020년까지 수문모의를 진행하였다. 모형의 입력자료로 유역 인근의 12개 기상관측소로부터 시단위 기상자료를 구축하였으며, 모형의 검보정은 일단위 관측유량(Q), 플럭스 타워 증발산량, 실측 토양수분 및 지하수위 자료를 구축하여 활용하였다. 댐 및 보 지점에 대해 Q와 1/Q로 검보정을 수행한 결과, 평균 결정계수(R²)는 댐 지점에서 0.53~0.65, 보 지점에서 0.46~0.69의 값을 나타냈으며, Nash-Shtcliffe efficiency(NSE)는 댐 지점에서 0.46~0.55, 보 지점에서 0.31~0.65의 값을 나타냈다. 공간 보정을 위해 증발산량, 토양수분, 지하수위에 대한 검보정을 수행할 예정이며, 유황곡선을 활용하여 하천차수, 토양속성 및 토지이용에 따른 하천갈수량을 분석할 예정이다.

• Korean Journal of Remote Sensing
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• v.20 no.2
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• pp.91-102
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• 2004

This paper reflects the estimation of using the EOC(Electro-optical Camera) images supporting GIUH(geomorphological instantaneous unit hydrograph) approach. We have analyzed GIUH in its density and frequency distribution by creating a DEM(digital elevation model) for the sub basin produced from the EOC images and examined topographical and hydrological application possibility of the EOC images. In this process, we have topographical basin characteristic analysis that use the remote sensing technique analyzing the DEM creation process of the EOC stereo images by studying the basic topographical hydrology analysis about abstraction technique since it is flirty complex and is more time-consuming than other method. we executed statistical analysis of a basin size and river length using the frequency function after divided lattice spacing applied have to the sub river basin from the image data and the digital map into 10m intervals ranging from 10m to 100m. After comparing and examining the peak and time to peak of the GIUH, we proceeded with a comparative analysis by lattice concerning the topographical divergence rate, area ratio, length ratio. Accumulating the peak and time to peak of the GIUH is altered to non-linear form in accordance to lattice dimension as well as basin factor. It was proved that the lattice dimension is one of the important factors about the peak and time to peak of the GIUH.

• Journal of the Korean Society of Radiology
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• v.16 no.3
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• pp.217-223
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• 2022

In this study, images taken using a grid and images taken using Air Gap Technique were evaluated in X-ray chest radiography. Subjective Evaluation The ROC (Receiver Operating Characteristic) evaluation was evaluated by 5 radiologists who had worked for more than 10 years in the radiology department of a university hospital. Objective evaluation SNR (Signal to noise ratio) was evaluated. As a result of the analysis, the Cronbach Alpha value was 0.714, which was significantly higher. In the Air Gap Technique, the distance between the phantom and the subject was set at 20 cm, and the image was taken with a tube voltage of 100 kVp, a tube current and a recording time of 8 mAs. In the ROC (Receiver Operating Characteristic) evaluation, the highest score was obtained with 18 score and an objective evaluation SNR (signal to noise ratio) of 6,149 scored. Also, in the imaging method using a grid, when the distance between the phantom and the constant receptor is 15 cm apart, and the tube voltage is 110 kVp, the tube current and the recording time are taken at 8 mAs, the ROC evaluation score is 19 and the objective evaluation SNR (Signal to noise ratio) is the highest with 6.622 scored. Therefore, if the Air Gap Technique imaging method is used, which overcomes the shortcomings such as delay in reading, increase in patient's exposure dose, and shortening of mechanical lifespan, as well as re-radiography due to the cut-off phenomenon of the grid that appears using the grid, the It is thought that it will be very helpful for chest imaging, including the case of using a portable X-ray imaging device.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.1
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• pp.23-32
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• 1999

A new numerical method using solution-adaptive grids (SAG) is developed to solve the Richards' equation (RE) for unsaturated flow in porous media. Using a grid generation technique, the SAG method automatically redistributes a fixed number of grid points during the flow process, so that more grid points are clustered in regions of large solution gradients. The method uses the coordinate transformation technique to employ a new transformed RE, which is solved with the standard finite difference method. The movement of grid points is incorporated into the transformed RE, and therefore all computation is performed on fixed grid points of the transformed domain without using any interpolation techniques. Thus, numerical difficulties arising from the movement of the wetting front during the infiltration process have been substantially overcome by the new method. Numerical experiments for an one-dimensional infiltration problem are presented to compare the SAG method to the modified Picard method using a fixed grid. Results show that accuracy of a SAG solution using 41 nodes is comparable with the solution of the fixed grid method using 201 nodes, while it requires only 50% of the CPU time. The global mass balance and the convergence of SAG solutions are strongly affected by the time step size (Δt) and the weighting parameter (${\gamma}$) used for generating solution-adaptive grids. Thus, the method requires automated readjustment of Δt and ${\gamma}$ to yield mass-conservative and convergent solutions, although it may increase computational costs. The method can be effective especially for simulating unsaturated flow and other transport problems involving the propagation of a sharp-front.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.73-81
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• 2022

Recently, as the service life of structures increased, the load-carrying capacity of deteriorated reinforced concrete, where corrosion of reinforcing bars occurs due to various causes, is frequently decreased. In order to address this problem, many studies on the bond characteristic of FRP (Fiber Reinforced Polymer) bars with corrosion resistance, light weight and high tensile strength have been conducted, however there are not many studies on the bond characteristic of grid-typed CFRP embedded in concrete. Therefore, in order to evaluate the bond characteristics of grid-typed CFRP and its usability as a substitute for steel rebar, a pull-out test is performed using the longitudinal bond length and transverse grid length of the grid-typed CFRP as variables. Through the pull-out test, the bond load-slip curve of the grid-typed CFRP is derived, and the bond behavior is analyzed. The total bond load equation is proposed as the sum of the bond force of the longitudinal bond length and the shear force of the grid in the transverse direction. Also, expressing the area of the bond load-slip curve as total work, the change in dissipated energy with respect to the slip is analyzed to examine the effect of the tranverse grid on the bond force.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1251-1255
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• 2006

도로 조건에 따른 빗물받이 유입구의 설치간격, 적정크기 및 관리 방안을 마련하여야 하며, 빗물받이 설계 시, 빗물받이 유입구의 통수능력을 저하시키는 빗물받이 유입구의 막힘 현상을 고려한 빗물받이 유입구의 합리적인 설계와 관리 방안을 마련하여 빗물 배제 능력을 향상시킴으로써 도시 홍수피해의 경감대책을 수립하여야 한다. 따라서 본 연구에서는 합리식을 이용하여 우수유출량을 계산하고, 빗물받이 차집효율 실험을 통하여 산정된 빗물받이 규격별 차집유입량 경험식을 이용하여 빗물받이의 차집유입량을 산정하였다. 막힘 현상을 고려한 빗물받이 유입구의 찻집효율 분석 실험을 실시하여 제시되어진 막힘 계수를 이용하여 빗물받이 유입구의 막힘 현상을 고려한 도로의 격자형 빗물받이 유입구의 설계 방법을 제시하였으며, Excel을 이용하여 간략하게 프로그램화 하였다. 제시된 설계방법은 실무에서 도로 조건의 변화와 빗물받이의 막힘 현상을 고려한 빗물받이 유입부의 설계에 사용 가능하다고 판단된다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.561-565
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• 1988

In the present study, a new method of generating a nearly orthogonal boundary-fitted coordinate systems with automatic grid spacing control is introduced. Applications of the method to a two dimensional simply-connected region is then demonstrated. The nearly orthogonal boundary-fitted method has the following features, (a) Strong grid control in the .eta.-direction can be made, (b) The generated boundary-fitted coordinates are nearly orthoronal, (c) Both the .xi.-and .eta.-direction control function are mathematically derived. Especially the .eta.-direction control function is derived under the assumption that the .eta.-direction grid spacing is by far smaller than the .xi.-direction grid spacing when the .eta.-direction grid line is strongly clustered. (d) The grid control functions are dynamically adjusted by the metric scale factors imposed on the boundary. The control function is fully automatic and eliminates the need of user manipulation of the control function.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.161-163
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• 2007

본 연구에서는 CFUBMS (Closed Field Unbalanced Magnetron Sputtering) 방법을 사용하여 TiN 박막을 합성하는 과정에서 TiN 박막의 색상을 결정하는 공정변수(질소량, Substrate Bias, Target power, 합성 온도)의 영향에 관하여 연구하였다. 합성된 박막은 UV-vis spectrophotometer, AFM, XRD를 통하여 특성을 분석하였다. 공정변수 가운데 Target power의 변화와 합성온도의 변화는 합성된 박막의 색 변화에 크게 영향을 미치지 않는 것으로 나타났다. 반면에 질소량의 변화와 Substrate bias 변화에 따라서는 색의 변화가 크게 나타났으며, 박막의 격자상수 차이로 인한 격자 간격에 차이가 생겨서 박막의 색이 붉은 갈색으로 변화게 됨을 확인 할 수 있었다. 한편 변수의 크기가 증가함에 따라 RMS가 증가하면서 $L{\ast}(brightness)$이 감소하게 되고 합성된 박막의 색은 노란색에서 붉은색으로 변화되는 결과를 확인할 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.909-913
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• 2012

본 연구는 XP-SWMM 2011 모형의 최적 해석범위설정과 월류에 의한 2차원 지표유출량을 포함한 도시유역의 총 유출량 산정에 대한 방법을 연구한 것이다. 하수 및 우수 관망 해석 모형으로 1차원 관로해석과 2차원 지표면 해석이 가능한 XP-SWMM 2011 모형을 이용하였으며, 연구의 대상지역은 최근 연속적인 침수 피해를 일으켰던 광화문 일대로 선정하였다. 발생가능한 빈도별 지속시간별 확률강우량은 Huff의 4분위법을 이용하여 10분 간격으로 분포시켰으며, 기존의 유역 출구점에 기준한 설계기준의 문제점을 제시하고, 월류에 의한 2차원 지표유출수를 포함한 유역 내에서의 총 유출량 산정에 대한 방법을 제시하였다. 모의 결과분석시 기존의 제한된 격자확장 경계조건으로 인한 문제점 극복을 위해 해석범위 설정 시 적합한 격자경계의 설정이 필요함을 확인하였다. 도시유역의 관로유출량과 본 연구에 제시된 지표유출량을 함께 고려한다면 치수계획규모를 설정하는데 주요 판단기준으로 활용될 수 있을 것이다.