• Journal of the Korean Institute of Gas
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• v.16 no.1
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• pp.26-32
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• 2012

The autoignition temperature is one of the most important physical properties used to determine the flammability characteristics of chemical substances. Despite the needs of the experimental autoignition temperature data for the design of chemical plants, it is not easy to get the data. This study have built and compared partial least squares (PLS) and support vector machine (SVM) models to predict the autoignition temperatures of 503 organic compounds out of DIPPR 801. As the independent variables of the models, 59 functional groups were chosen based on the group contribution method. The prediction errors calculated from cross-validation were employed to determine the optimal parameters of two models. And, particle swarm optimization was used to get three parameters of SVM model. The PLS and SVM results of the average absolute errors for the whole data range from 58.59K and 29.11K, respectively, indicating that the predictive ability of the SVM is much superior than PLS.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.154-165
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• 2006

In the present study, a numerical model using Boussinesq equation is set up to predict the interacted equilibrium between waves and their induced currents in the occurrence of breaking waves over an underwater shoal, and the numerical results are compared with results of existing hydraulic experiments. A sensitivity analysis has been done to find out appropriate values of breaking wave parameters with the result (regular wave case) of Vincent and Briggs (1989)’ experiment. Then the numerical model is applied to the irregular wave cases of the experiment and the hydraulic model test of Ieodo which is a natural undersea shoal. The results show that a strong current forms in the wave direction at the downstream side of the shoals, causing the attenuation of wave heights there. The calculated wave heights generally show a similar pattern with the measured data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.29-39
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• 2012

The main objective is to predict the future degradation and maintenance budget for a suspension bridge system. Bayesian inference is applied to find the posterior probability density function of the source parameters (damage indices and serviceability), given ten years of maintenance data. The posterior distribution of the parameters is sampled using a Markov chain Monte Carlo method. The simulated risk prediction for decreased serviceability conditions are posterior distributions based on prior distribution and likelihood of data updated from annual maintenance tasks. Compared with conventional linear prediction model, the proposed quadratic model provides highly improved convergence and closeness to measured data in terms of serviceability, risky factors, and maintenance budget for bridge components, which allows forecasting a future performance and financial management of complex infrastructures based on the proposed quadratic stochastic regression model.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.2
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• pp.51-56
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• 2021

The brachial systolic blood pressure and pulse pressure are the predictors of cardiovascular disease in individuals over 50 years of age. As the stiffness increases, the reflex amplitude and pressure in the late systole increase, resulting in an increase in left ventricular load and myocardial oxygen demand. Therefore, it is necessary to study how stiffness affects blood pressure. In this study, the blood pressure pulse waves were measured before and after taking the drug, and the blood pressure pulse wave was measured before and after myocardial heart transplantation in patients with heart failure. The correlation between R, L, and C components of the Windkessel model was estimated by increasing blood pressure. As a result of modeling the parameters of the Windkessel model using the curve fitting method, the increase in blood pressure and decrease in systolic rise time were due to the increase in the L component in the RLC Windkessel model. Among the various mechanical characteristics of blood vessels, the most important parameter affecting high BP waveform is the inertance.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.82-82
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• 2022

최근 지구온난화로 인한 전 세계적 기후변화가 일어나고 있으며, 이러한 지구온난화 방지 대책으로 탄소의 중요성과 탄소중립을 선언하는 국가가 증가하고 있다. 탄소의 중요성이 증가함에 따라 유역 내의 탄소 중립이 중요 이슈로 떠오르고 있다. 유역 내 탄소 저장원으로는 숲, 하천, 토양 등이 존재하나 하천의 경우 탄소의 저장이 곧 수질 오염과 연결이 되기에 바람직한 방안이 될 수 없다. 그러나 토양의 경우 방대한 양의 탄소를 저장하기에 적합한 기능을 하기에 다른 저장원들에 비해 중요한 저장원으로 대두되고 있다. 토양탄소의 경우 일반적으로 유기물과 무기물의 형태로 토양에 저장된다. 이중 토양유기탄소는 장기간 토양 속에서 대기와의 탄소 조절 역할을 하기에 중요 요인으로 대두되고 있다. 하지만 기후변화로 인한 국지성 호우 및 무분별한 개발 등이 증가함에 따라 유역 내 토양 생태계의 변화가 일어나고 있으며, 이에 따른 유역 내 토양유기탄소 또한 손실이 일어나고 있다. 따라서 본 연구에서는 토양의 특성과 모델을 활용하여 유역단위 토양유기탄소량의 변화량을 산정하여 비교 및 분석을 하고자 한다. 이를 위해서 토양유기탄소의 모의가 가능한 APEX 모델을 활용하였으며, 선정된 연구 대상 지역의 토양 특성 자료를 활용하여 입력자료 전처리를 진행 후 모의를 진행하였다. 이후 선행연구 및 보고서를 통한 실측자료를 기반으로 모델 매개변수 보정을 진행하였으며, 보정된 결과를 통해 유역에 대한 토양유기탄소를 산정을 진행하였고 기간별 변화의 차이를 분석하였다. 해당 연구를 통해 유역 내 잠재되어있는 토양유기탄소량 정량화 등의 연구에 활용될 수 있을 것으로 기대한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1417-1431
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• 1994

In this study, shear strength characteristics of the Nak-Dong river sand in Taegu area are investigated by triaxial compression test, considering shear strain control velocity, relative density, and confining pressure. The results from Lade model and Modified Lade model are compared with the measured value in the laboratory test. The results by the change of shear strain control velocity, relative density, and confining pressure are as follows; 1) The stress limit, which can be Coulomb's law about the Nak-Dong river sand, have ranged 120~200 kpa at 0.08%/min and 120~150 kpa at 0.5%/min. These limits are smaller than that of the calcareous sand and the well-graded, quartz sand. 2) The parameters needed to Lade model and Modified Lade model are much affected by the strain control velocity and the relative density. Consequently, in the field, it is important to use parameters aptly after accurately understanding both the loading condition and subsoil condition. 3) Overall, the principal stress ratio obtained from constitutive model equations is not affected by the control velocity, but both the relative density and confining pressure affect the result of constitutive model equations. Consequently, the study on the various conditions about the relative density and confining pressure is needed to accurately predict the stress-strain behavior on the Nak-Dong river sand. 4) For the range of the used confining pressure in the study, the Lade model shows better agreements with the measured value than the Modified Lade model, comparing the measured value with the principal stress ratio at failure and the internal friction angle of failure envelope obtained from the Lade model and Modified Lade model.

• Journal of Korean Society of Forest Science
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• v.90 no.5
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• pp.650-662
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• 2001

The growth and yield models for five different kinds of natural forest types were systemically developed in the natural Broadleaved-Korean pine Forests in Northeast China. The data were collected from 359 temporary plots and 58 permanent plots with area ranged from 0.06 ha to 1.0 ha, ranging in stand age from 43 to 364 years. The Site Class Index (SCI) was introduced to evaluate site quality and the Crown Competition Factor (CCF) was selected as a measure of stand density for the mixed natural forest. The Chapman-Richards function was adopted to develop SCI equation and height-diameter curve. The Schumacher growth function was selected as base model to develop the DBH, basal area, and stand volume growth models by using re-parameterized method. In modeling mean DBH and basal area growth, it was found that the asymptotic parameter A of Schumacher function was exponentially related to site quality (SCI) and stand density (CCF). The rate parameter k was related to stand density and it was independent of SCI. Several validation measures for predicted stand variables were evaluated in the growth and yield models using independent data sets. The results indicated that relative mean errors (RME) in predicted stand attributes were less than ${\pm}5%$ and the estimated precision values of the stand variables were all greater than 95%.

• Proceedings of the Korea Water Resources Association Conference
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• 1994.02a
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• pp.449-456
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• 1994

넓은 지역(Arkansas River Basin)에 대하여 토양 수분을 기본으로한 물 수지 모델이 계절별 년별 시간단위로 연구되었다. 지표면과 대기 수분사이의 상호 작용과 재순환 효과에 대한 연구가 유역의 매개 변수화 과정에서 수행되었으며 대규모의 지표면과 대기사이의 상호 작용에 의하여 넓은 지역의 지표 수문은 장기간의 확률분포함수에 있어서 두가지 즉 건조와 습한 안정상태의 영향을 받는다. 토양수분 균형 방정식에서 추계학적 변동은 주위환경 변동에 의하여 야기되는 안정상태 사이의 변이와 함께 분리된 선호하는 통계학적 안정상태를 초래한다. 과거의 자료를 바탕으로 비선형 물수지 모델이 Arkansas강 유역에 대하여 검정되었다. 모델에서 안정상태 사이의 평균 변이시간이 물리과정의 추계학적 표현과 검정된 모델변수들로부터 계산되었다. 본 연구는 안정상태 사이의 변이시간 혹은 거주시간, 즉 시스템이 주어진 안정상태에 머무는 시간(가뭄이나 홍수상태의 지속기간)의 예측과 밀접한 관계가 있다.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2003.04a
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• pp.176-181
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• 2003

이 논문은 나대지에서 획득한 polarimetric SAR 자료의 후방 산란 계수(backscattering coefficient) 분석을 위한 surface parameters 추출 및 forward mapping에 대하여 서술하였다. Surface parameter는 토양의 거칠기(ks), 수분 함량(m/sub v/), 유전 상수(ε/sub m/) 등이 포함되어 있고, 유전 상수의 추정을 위하여 0.3-1.3GHz 구간의 자료를 기반으로 제안된 N. R. Peplinski의 경험상의 모델(Empirical Model) 알고리즘을 사용하였다. 추정된 surface parameter는 polarimetric SAR 자료의 산란 현상을 특징짓기 위한 forward mapping의 입력 값으로 이용되었으며, scattering model로 Oh의 경험상의 모델을 사용하였다. 각각의 surface parameter ks, θ, m/sub v/는 Oh 모델을 이용한 시뮬레이션을 통하여 레이더 후방 산란 계수에 미치는 영향에 대하여 조사되었다.

• The KIPS Transactions:PartD
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• v.16D no.5
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• pp.729-736
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• 2009

The accurate estimation of software development cost is important to a successful development in software engineering. Until recent days, the model using regression analysis based on statistical algorithm and machine learning method have been used. However, this paper estimates the software cost using support vector regression, a sort of machine learning technique. Also, it finds the best set of optimized parameters applying genetic algorithm. The proposed GA-SVR model outperform some recent results reported in the literature.