• Journal of Korea Water Resources Association
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• v.45 no.4
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• pp.383-391
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• 2012

This study aims to present the sensitivity analysis approach for multi-criteria decision making (MCDM) method to reduce the uncertainty of weighting and performance values. This study focuses on two major problems of the uncertainty for MCDM method. The first major problem is how to determine the most critical criterion and the second is how to determine the most critical measure of performance. This study used the application of weighted sum method for water resources planning. The criticality degrees and the sensitivity coefficients of criterion and alternative are used. This results of sensitivity analysis can be applied to the general water resources planning in real.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.227-227
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• 2012

본 연구는 수자원계획 문제에서 다기준 의사결정기법을 적용할 때 발생할 수 있는 두 가지 문제에 대해 분석하였다. 첫 번째는 다기준 의사결정기법 선택의 차이가 결과에 어느 정도 영향을 미칠 수 있는지를 제시하였고 두 번째는 평가기준에 대한 가중치와 대안들의 평가치에 대한 불확실성을 최소화하기 위해 민감도 분석을 수행하는 절차를 제시하였다. 첫 번째 문제를 위해 가중합계법, Compromise Programming, 계층화분석과정, 수정된 계층화 분석과정, 가중곱방법, TOPSIS, ELECTRE-2, Regime 방법을 사용하였다. 또한 최근 사용빈도가 높은 삼각형 Fuzzy 숫자와 다기준 의사결정기법을 결합한 기법에 대해서도 분석하였는데 Fuzzy WSM, Fuzzy 계층화분석과정, Fuzzy 수정 계층화분석과정, Fuzzy TOPSIS, Fuzzy Compromise Programming을 검토하였다. 분석결과 평가기준에 대한 가중치 조건과 표준화 방법이 동일한 상황에도 불구하고 조금씩 다른 순위를 제시하는 것으로 나타났다. 또한 다양한 MCDM 기법들을 적용해도 동일한 순위로 나타나는 대안들이 있었다. 따라서 다기준 의사결정기법을 사용한 수자원 관리계획을 수립할 때에는 다양한 분석기법을 활용해서 기법의 선택으로 인한 불확실성을 최소화해야 한다. 두 번째 문제는 평가기준에 대한 가중치와 대안의 효과 정량화 자료의 불확실성을 극복하기 위해 각각에 대한 민감도 분석을 수행하였다. 본 연구는 유량확보와 수질개선을 위한 수자원 계획 수립을 위해 가중합계법을 이용한 문제에 두 경우의 민감도 분석을 모두 수행하였다. 이 과정에서 결정계수와 민감도 계수를 산정하여 이용하였다. 본 연구는 향후 수자원 관리 및 계획 분야에서 다기준 의사결정기법을 적용할 때 사용될 수 있는 기초 가이드라인이 될 것이다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.2
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• pp.89-96
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• 2011

A three dimensional ecological model(EMT-3D) was applied to Ulsan Bay for the simulation of Dioxins. The simulated results of dissolved Dioxins were in agreement with the observed values, with a correlation coefficient(R) of 0.7951 and a coefficient of determination($R^2$) of 0.6265. The results of sensitivity analysis showed that partition rate, adsorption rate and bioconcentration factor were important factors. Therefore, the parameters must be carefully considered in the modeling. In the case of 50% and 80% total loads reduction, concentration of dissolved Dioxins was shown to be lower than 0.150 and 0.250 pg WHD-TEQ/L, respectively.

• The Korean Journal of Applied Statistics
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• v.35 no.1
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• pp.77-91
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• 2022

The optimal threshold estimation is considered in order to discriminate the mixture distribution in the fields of Biostatistics and credit evaluation. There exists well-known various accuracy measures that examine the discriminant power. Recently, Matthews correlation coefficient and the F1 statistic were studied to estimate optimal thresholds. In this study, we explore whether these accuracy measures are appropriate for the optimal threshold to discriminate the mixture distribution. It is found that some accuracy measures that depend on the sample size are not appropriate when two sample sizes are much different. Moreover, an alternative method for finding the optimal threshold is proposed using the correlation coefficient that defines the ratio of the confusion matrix, and the usefulness and utility of this method are also discusses.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.3
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• pp.173-181
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• 2007

A three-dimensional ecological model (EMT-3D) was applied to Tokyo Bay for the simulation of PFOA. EMT-3D was calibrated with seawater analysis data obtained from the study area in 2004. The simulated results of dissolved PFOA were in good agreement with the observed values, with a correlation coefficient(R) of 0.7115${\sim}$0.8759 and a coefficient of determination $(R^2)$ of 0.5062${\sim}$0.7672. The results of sensitivity analysis showed that partition rate, adsorption rate and settling rate were important factors for PFOA in particulate organic matter. In the case of PFOA in phytoplankton, bioconcentration factor, uptake rate and partition rate were important factors. Therefore, the parameters must be carefully considered in the modeling. In the case of 50% and 80% total loads reduction, concentration of dissolved PFOA was shown to be lower than 20ng/L and 10ng/L, respectively. In the case of reduction of loads from rivers in each prefecture, Tokyo prefecture was found to have the most influence on the change of dissolved PFOA in surface water while Chiba prefecture was found to have the most influnce on the change of dissolved PFOA in bottom water.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.649-656
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• 2008

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchic void element based on the integrals of Legendre polynomials is used to characterize the fracture behaviour of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of zero stiffness element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem. It is noted that the proposed hierarchical void element can be one of alternatives to analyze the patched crack problems.

• Journal of the Korean association of regional geographers
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• v.14 no.6
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• pp.736-751
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• 2008

Although a growing number of studies have commonly used a simple areal weighting interpolation method to quantify demographic characteristics of impacted areas in environmental equity analysis, the results obtained are inevitably imprecise because of the method's unrealistic assumption that population is evenly distributed within a census enumeration unit. Two alternative areal interpolation methods such as intelligent areal weighting and regression methods can account for the distributional biases in the estimation of impacted populations by making use of additional information about the geographic distribution of population. This research explores five areal interpolation methods for estimating the population characteristics of impacted areas in environmental equity analysis and evaluates the sensitivity of the outcomes of environmental equity analysis to areal interpolation methods. This study used GIS techniques to allow areal interpolation to be informed by the distribution of land cover types, as inferred from a satellite image. in both the source and target units. Independent samples t-test statistics were measured to verify the environmental equity hypothesis while coefficients of variation were calculated to compare the relative variability and consistency in the socioeconomic characteristics of populations at risk over different areal interpolation methods. Results show that the outcomes of environmental equity analysis in the study area are not sensitive to the areal interpolation methods used in estimating affected populations, but the population estimates within the impacted areas are largely variable as different areal interpolation methods are used. This implies that the use of different areal interpolation methods may to some degree alter the statistical results of environmental equity analysis.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.55-66
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• 2012

The practical way to minimize the greenhouse gas is to reduce the emission of carbon dioxide. For this reason, CCS(Carbon Capture and Storage) technology, which could reduce carbon dioxide emission, has risen as a realistic alternative in recent years. In addition, the researcher is recently working into ways of applying CCS technologies with deep saline aquifer. In this study, the evaluation model on the feasibility of $CO_2$ sequestration in the deep saline aquifer using ANN(Artificial Neural Network) was developed. In order to develop the efficiency-evaluation model, basic model was created in the deep saline aquifer and sensitivity analysis was performed for the aquifer characteristics by utilizing the commercial simulator of GEM. Based on the sensitivity analysis, the factors and ranges affecting $CO_2$ sequestration in the deep saline aquifer were chosen. The result from ANN training scenario were confirmed $CO_2$ sequestration by solubility trapping and residual trapping mechanism. The result from ANN model evaluation indicated there is the increase of correlation coefficient up to 0.99. It has been confirmed that the developed model can be utilized in feasibility of $CO_2$ sequestration at deep saline aquifer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.735-747
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• 2023

In recent times, the sharp increase in extreme flood damages due to climate change has posed a challenge to effectively address flood-related issues solely relying on conventional flood management infrastructure. In response to this problem, this study aims to consider the effectiveness of nature-based flood management approaches, specifically levee retreat and relocation. To achieve this, we utilized a 1D numerical model, HEC-RAS, to analyze the flood reduction effects concerning floodwater levels, flow velocities, and time-dependent responses to a 100-year frequency flood event. The analysis results revealed that the effect of creating a flood buffer zone of the nature-based solution extends from upstream to downstream, reducing flood water levels by up to 30 cm. The selection of the flow roughness coefficient in consideration of the nature-based flood buffer space creation characteristics should be based on precise criteria and scientific evidence because it is sensitive to the flood control effect analysis results. Notably, floodwater levels increased in some expanded floodplain sections, and the reduction in flow velocities varied depending on the ratio of the expanded cross-sectional area. In conclusion, levee retreat and floodplain expansion are viable nature-based alternatives for effective flood management. However, a comprehensive design approach is essential considering flood control effects, flow velocity reduction, and the timing of peak water levels. This study offers insights into addressing the challenges of climate-induced extreme flooding and advancing flood management strategies.

• Journal of Animal Environmental Science
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• v.17 no.sup
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• pp.61-68
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• 2011

To assess the total cost with all stages of facilities, the feasibility of Life Cycle Cost (LCC) analysis was examined in this study to estimate the livestock manure treatment system and optimal decision making process. For the economic evaluation, the plant/equipment investment and annual operation cost of four Public Livestock Recycling Facilities, whose treatment capacity is 100 ton piggery manure per day, was compared. The initial cost was in the range of 2,699 million won to 3,202 million won, where T and E methods were highest and lowest, respectively. The annual operation cost was in the level of 378 million to 498 million won, which decreased in the following order : T method > J method > E method > B method. For the LCC analysis, 4.7% of interest rate, 3.13% of inflation rate, and 1.52% of net discount rate was considered by the data received from Bank of Korea and Statics Korea in the period of 2000 to 2009. Also, for the calculation of present value factor, the durable years of civil engineering & construction, machinery and electric instrument was 30 years, 10 years and 15 years, respectively. Based on these consideration, operation cost was in the range of 17,570 won/ton to 20,661 won/ton, and E method (17,570 won/ton) was economical and B method (20,661 won/ton) was non-economical. Though initial cost of T method was higher than that of B method, LCC analysis of T method was lower than that of T method due to the lower operation cost. Therefore, LCC analysis, which considers both initial cost and operation cost, is more reasonable evaluation method than either initial cost or annual operation cost. For the change of LCC analysis according to the uncertainty, the sensitivity analysis was carried out using fluctuation magnitude of discount rate in the period of 2000 to 2009. As a result, LCC analysis evaluated by discount rate was stable for the uncertain factors since the cost leadership did not change even though the sensitivity analysis varied. In summary, the economic evaluation using LCC analysis could be an efficient reference to choose the suitable livestock manure treatment plants. Furthermore, standardization of statement calculation for the actual cost analysis should be conducted and more detailed study is necessary to validate this summary. Therefore, the application of comprehensive technology evaluation, which considers LCC analysis, should contribute in obtaining objectivity and enhancing reliability for the 'Evaluation of Livestock Manure Treatment System and its Technology'.