• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.34-34
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• 2018

본 연구는 다목적 유전자 알고리즘 Non-Dominated Sorting Genetic Algorithm II (NSGA-II)를 활용하여 자동 검보정 알고리즘을 개발하고, 이를 준분포형 수문모형인 SWAT (Soil and Water Assessment Tool) 모형에 적용하여 평가하고자 한다. 집중형 모형과 달리, 분포형 모형은 유역 내 다양한 물리적 변수와 공간 이질성(spatial heterogeneity)을 표현하기 위한 많은 매개변수를 포함하고 있고, 최근에는 기후 변화와 장기 가뭄과 같은 이상 기후에 따른 물 부족, 수질 오염 및 녹조 현상 등을 고려하기 위해 매개변수의 시간적인 변동성을 고려하기 위한 연구도 수행되고 있다. 이에 따라 본 연구에서 개발한 다목적 알고리즘은 다양한 매개변수의 시공간적 특성을 고려할 수 있도록 작성되었으며, Python으로 개발하여 타 모형으로의 확장성 및 범용성을 고려하였다. SWAT 모형의 유출 해석은 결정계수(Coefficient of determination, $R^2$), RMSE(Root mean square error), 모형 효율성 계수(Nash-Sutcliffe efficiency, NSE) 및 IOA(Index of agreement) 등을 활용해 기존 연구 결과와 비교분석할 수 있도록 하였으며, 사용자의 선택에 따라 다른 목적함수 또한 활용할 수 있도록 하였다. NSGA-II를 활용한 SWAT 모형의 유출 해석은 다목적 함수를 고려함에 따라 실측값과 높은 상관성을 보여줄 것으로 판단되며, 이상 기후 기간 설정에 따른 유동적인 매개변수 변화를 적용할 수 있을 것으로 기대된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.85-92
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• 2007

In 1980s, a number of bridges with bare concrete deck were constructed on the Korea highway. After 20 years service, many bare concrete decks are still in good condition without special maintenance activity. Therefore, the application of the bare concrete deck is being reestimated from the view of construction and maintenance. As a part of the program, the characteristic of penetration(surface chloride and apparent diffusion coefficient) of de-icing salt into bare concrete bridge deck was analyzed in order to predict the service life of bridge on Korea highway.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.109-116
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• 2006

An incremental approach to predict the time dependent flexural behavior of composite girder is presented in the framework of incremental finite element method. Age dependent nature of creep, shrinkage, and maturing of elastic modulus of concrete is prescribed in the incremental tangent description of constitutive relation derived based on the first order Taylor series expansion applying to the total from of stress-strain relation. The loop phenomenon in which age dependent nature of concrete causes stress redistribution and it causes creep in turn is taken into account in the formulation through the incremental representation of constitutive relation. The developed algorithm predicts the time dependent deflections of 4.8m long two span double composite box girder subjected to shrinkage, maturing of elastic modulus, and creep initially induced by self weight. Comparison shows a good agreement between the predicted and measured results.

• The Journal of the Korea Contents Association
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• v.10 no.7
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• pp.420-428
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• 2010

The advancement of the Science for complex systems enables the analysis of many social networks. We constructed and analyzed a Korean movie star network as one of social networks, based on the 100 Korean movie selection for a main data source. Until now, the research trend has been the structural analysis of network, focused on link numbers, such as degree, betweenness and clustering coefficient. But it is time that the research is not limited by the structural analysis of networks only. Rather, the research goal should be aimed to an information analysis, performed by identifying and analyzing central modules that are regarded as the core of complex networks, using k-core analysis method. In this research, we constructed a network of movie stars who have appeared in 100 Korean movie selection, provided by Korean movie database, also we analyzed its core modules with and without weights, and the trend of seasonal expansion of the network. We expect our findings can be used as the basic data applicable to a model for understanding of the expansion and evolution of networks.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.5
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• pp.577-588
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• 2011

This paper provides a novel extended Moving Least Squares(MLS) difference method for the potential problem with weak and strong discontinuities. The conventional MLS difference method is enhanced with jump functions such as step function, wedge function and scissors function to model discontinuities in the solution and the derivative fields. When discretizing the governing equations, additional unknowns are not yielded because the jump functions are decided from the known interface condition. The Poisson type PDE's are discretized by the difference equations constructed on nodes. The system of equations built up by assembling the difference equations are directly solved, which is very efficient. Numerical examples show the excellence of the proposed numerical method. The method is expected to be applied to various discontinuity related problems such as crack problem, moving boundary problem and interaction problems.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.229-238
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• 2017

This study started to deduce a permeability relationship that can consider the geometric features of various porous media under different flow regimes. With reference to the previous works of Kozeny and Carman, the conventional Darcy-Weisbach relation (Darcy's friction flow equation) was reviewed and expanded for porous flow analysis. Based on the capillary model, this relation was transformed to the friction equivalent permeability (FEP) definition. The validity of the FEP definition was confirmed by means of comparison with the Kozeny-Carman equation. Hereby, it was shown that the FEP definition is the generalized form of the Kozeny-Carman equation, which is confined to laminar flow through a circular capillary. In conclusion, the FEP definition as a new permeability estimation method was successfully developed by expanding the Darcy-Weisbach relation for porous flow analyses.

• Tuberculosis and Respiratory Diseases
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• v.42 no.3
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• pp.332-341
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• 1995

Background: Measurement of bronchodilator response is necessary to establish reversibility of airflow obstruction that was helpful to estimate the diagnosis, treatment, and prognosis in obstructive airway disease. An useful index should be able to detect the bronchodilator response more sensitively not related with degree of airflow obstruction and also be independent of initial $FEV_1$. Method: Sensitivities of bronchodilator response in each group classified by degree of airflow obstruction in $FEV_1$, FVC, $FEF_{25\sim75%}$, Isovolume $FEF_{25\sim75%}$, sGaw were studied and correlation coefficients were calculated between initial $FEV_1$ and reversibilities expressed as absolute, %initial, % predicted, %possible in $FEV_1$. Result: Sensitivities of bronchodilator response were 61.5% in FVC, Isovolume $FEF_{25\sim75%}$ and sGaw, in severe group, and 56.3% in Isovolume $FEF_{25\sim75%}$ and sGaw, in moderate group, and 62.5% in $FEV_1$ and sGaw and 50.0% in FVC and Isovolume $FEF_{25\sim75%}$, in mild group, and 60.0% in sGaw and 58.0% in Isovolume $FEF_{25\sim75%}$ in total patients. Correlation coefficients between initial $FEV_1$(L) and absolute, % initial, % predicted, % possible were 0.15, -0.22(p<0.05), 0.02, 0.24(p<0.05) and correlation coefficients between initial $FEV_1$(% predicted) and absolute, % initial, % predicted, %possible were 0.06, -0.28(p<0.05), 0.08, 0.39(p<0.05). Conclusion: Volume related parameters were more sensitive index not related with degree of airway obstruction and the change in $FEV_1$ expressed as % predicted was the least dependent on initial $FEV_1$ and reversibilities, expressed as % initial or as % possible(predicted minus initial $FEV_1$)were correlated with initial $FEV_1$.

• Journal of Korea Water Resources Association
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• v.47 no.2
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• pp.119-133
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• 2014

The study adopted extended Kalman filter technique in an effort to predict Z-R relationship parameter as a stable value in real-time. Toward this end, a parameter estimation model was established based on extended Kalman filter in consideration of non-linearity of Z-R relationship. A state-space model was established based on a study that was conducted by Adamowski and Muir (1989). Two parameters of Z-R relationship were set as state variables of the state-space model. As a result, a stable model where a divergence of Kalman gain and state variables are not generated was established. It is noteworthy that overestimated or underestimated parameters based on a conventional method were filtered and removed. As application of inappropriate parameters might cause physically unrealistic rain rate estimation, it can be more effective in terms of quantitative precipitation estimation. As a result of estimation on radar rainfall based on parameters predicted with the extended Kalman filter, the mean field bias correction factor turned out to be around 1.0 indicating that there was a minor difference from the gauge rain rate without the mean field bias correction. In addition, it turned out that it was possible to conduct more accurate estimation on radar rainfall compared to the conventional method.

• Journal of Chest Surgery
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• v.32 no.3
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• pp.299-302
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• 1999

Heart transplantation was planned for a 10-year old boy who had dilated cardiomyopathy with severe congestive heart failure and had been on dopamine for 1month. However, partial left ventriculectomy and mitral annuloplasty were performed instead, because there was no donor heart of the adequate size and the symptoms were aggravated. The clinical symptoms were markedly improved after the surgery. Comparing the postoperative echocardiographic results with the preoperative results, there were remarkable changes in the left ventricular ejection fraction(preoperative LV EF 17% to postoperative 3 months 29%, 6 months 35%, 1 year 36%) and the left ventricular end-diastolic dimension(preoperative 72 mm to postoperative 3 months 59 mm, 6 months 61 mm, 1 year 61 mm). Partial left ventriculectomy and mitral annuloplasty reduced the cardiac loading in the dilated cardiomyopathy. Partial left ventriculectomy and mitral annuloplasty may be considered as one of the alternative surgical metho s to carry over until a heart transplantation can be performed, especially for children.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.21-32
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• 2023

Interrill erosion dominates in forest areas, and the erosion rate in surface-disturbed areas is significantly increased by the development and expansion of rill. In this study, soil erosion experiments using simulated rainfall and inflow were performed to understand the development and the micromorphological changes of rill on steep slopes. The characteristic factors of the micromorphology, such as the rill cross section, rill volume, rill density, rill order, and rill sharpness, were analyzed according to steepness and location (upper or lower) of slope. The head-cut of the simultaneous incised rills by rainfall simulation moved rapidly upslope, and the randomly developed rills expanded deeply and widely with their connection. The rill cross section evolved to downslope gradually increased. The rill volume occupied about 78 % of the sediment volume, confirming that the contribution of the sediment from the rill erosion is greater than that of the interrill erosion. Although the rate of increase in rill order slowed as the slope increased, the total length and density of the rill generally increased. As the slope increased from 15° to 20°, the bed incision of rills became larger than the sidewall expansion, and the rill sharpness increased by 1.6 times. The runoff coefficient on the lower slope decreased by 12.3 % than that on the upper slope. It was evaluated that the subsoil exposures and formation changes by the rill expansion increased the infiltration rate. Although the sediment accompanying the rills generally increased with slope increase, it was directly influenced by the hydraulic velocity of enhanced rill with the local convergence and expansion in the process of the rill evolution.