• Journal of dental hygiene science
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• v.14 no.1
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• pp.15-21
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• 2014

The purpose of this study in vitro investigation was to evaluate the dimensional stability of dental digital models made by impression scanning method. Twenty working models were produced. Twenty impressions were made from study models. The dimensional stability of models of two groups (stone and digital models) was examined using six landmark distances. Stone models were measured through digital vernier calipers. Digital models were measured by the computer program. Statistical analyses were performed with Wilcoxon rank sum test (${\alpha}=0.05$). The mean of six landmark distances were significantly larger in the stone models than in the digital models (p<0.05) but digital models showed clinically acceptable accuracy.

• Journal of the Korean Society for information Management
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• v.15 no.1
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• pp.129-148
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• 1998

The objective of this study is to develop a useful relevance feedback retrieval technique that can be applied to the current Boolean retrieval system. A feedback retrieval technique based on user model is recommended here to achieve this objective. To prove the usefulness of this feedback retrieval technique, two enhanced Boolean retrieval models including DNF model and P-norm model were evaluated first through retrieval effectiveness experiments. After selecting DNF model as the retrieval model, two feedback retrieval experiments were performed using initial and extended user models. It is proved that the feedback retrieval based on user model can greatly enhance the effectiveness of a Boolean retrieval system with a small modification.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.35-35
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• 2022

최근에 딥 러닝(Deep learning) 기반의 많은 방법들이 수문학적 모형 및 예측에서 의미있는 결과를 보여주고 있지만 더 많은 연구가 요구되고 있다. 본 연구에서는 수자원의 가장 대표적인 모델링 구조인 강우유출의 관계의 규명에 대한 모형을 Long Short-Term Memory (LSTM) 기반의 변형 된 방법으로 제시하고자 한다. 구체적으로 본 연구에서는 반응변수인 유출량에 대한 직접적인 고려가 아니라 그의 1차 도함수 (First derivative)로 정의되는 Delta기반으로 모형을 구축하였다. 또한, Attention 메카니즘 기반의 모형을 사용함으로써 강우유출의 관계의 규명에 있어 정확성을 향상시키고자 하였다. 마지막으로 확률 기반의 예측를 생성하고 이에 대한 불확실성의 고려를 위하여 Denisty 기반의 모형을 포함시켰고 이를 통하여 Epistemic uncertainty와 Aleatory uncertainty에 대한 상대적 정량화를 수행하였다. 본 연구에서 제시되는 모형의 효용성 및 적용성을 평가하기 위하여 미국 전역에 위치하는 총 507개의 유역의 일별 데이터를 기반으로 모형을 평가하였다. 결과적으로 본 연구에서 제시한 모형이 기존의 대표적인 딥 러닝 기반의 모형인 LSTM 모형과 비교하였을 때 높은 정확성뿐만 아니라 불확실성의 표현과 정량화에 대한 유용한 것으로 확인되었다.

• The Korean Journal of Applied Statistics
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• v.32 no.2
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• pp.291-300
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• 2019

This study investigates the characteristics of evaluation measures for classification models on a binary response variable in order to evaluate their suitability for use. Six measures are considered: Accuracy, Sensitivity, Specificity, Precision, F-measure, and the Heidke's skill score (HSS). Evaluation measures are reformulated using x(ratio of actually 1), y(ratio predicted by 1), z(ratio of both actual and predicted by 1) from the confusion matrix. We suggest two necessary conditions to assess the suitability of the evaluation measures. The first condition is that the measure function is constant for x and y in the case of a random model. The second condition is that the measure function is increasing for z and decreasing for x and y. Since only HSS satisfies the two conditions, that is always appropriate as an evaluation measure for the classification model on the binary response variable, and the other measures should be used within a limited range.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.87-98
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• 2012

The Ministry of Education, Science and Technology has been implementing the government's recognition project regarding the program accrediting organizations in Higher Education. This research is to establish an evaluation model for the government's recognition process of the program accrediting organizations, and develop the evaluation categories, items and indices for the model. The research has set the concept for the government's recognition regarding the program accrediting organizations and designed an evaluation model for such organizations. The evaluation model embraces a preliminary evaluation process, assessing an eligibility of the accrediting organizations for the higher education based on the formalities set forth for the government recognition organization accrediting process. It also includes the main evaluation process, which assess the eligibility based on the evaluation standards stipulated in the associated legislation and regulations. In addition, through in-depth verification processes by experts, this research finalized 2 evaluation domains, 5 evaluation categories, 24 evaluation items and 33 evaluation indices.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.163-166
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• 2007

본 연구에서는 우수 학생을 알아보기 위해 학생들의 학습 성과 및 과외활동을 바탕으로 평가모형을 설계하고 AHP(Analytic Hierarchy Process) 기법을 통해 분석하였다. 대부분의 대학에서 시행되고 있는 장학금 제도는 평가 기준이 해당 학기 평점으로 장학금 혜택을 받는 학생들이 일부 학생으로 제한되는 경우가 생기기도 한다. 실제로 평점뿐 아니라 다른 평가 기준을 가지고 학생들을 평가하여 학생들의 다양한 특성을 키워 줄 필요가 있다 평점만으로 학생을 평가하는 방식이 아닌 다양한 기준의 평가 모형을 가지고 학생들을 평가하는 새로운 방식의 학생평가모델을 제안하고자 한다.

• Journal of Korean Society of Transportation
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• v.26 no.3
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• pp.31-40
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• 2008

There have been a lot of efforts to find more accurate evaluation methods for traffic signal control effectiveness for a long period of time. Nowadays a newly advanced method called HILSS, 'Hardware-in-the-Loop-Simulation System', is used to evaluate the overall traffic control's effectiveness including physical control environments like communication conditions, hardware performance, controller's mechanical operations and so on. In this study, an Online-HILSS model has been developed, which runs on CORSIM(5.0) micro traffic simulation model on-lined to COSMOS. For the verification of the model, three tests are performed as follows; (1) a comparison of TMC's timing plan with the simulated green interval, (2) as a case study, a delay distribution comparison of the online simulation with the CORSIM stand-alone simulation. The result of the first test shows that the model can run the simulation green interval by TMC's timing plan correctly. The result of second test shows that the online simulation of the model brings the same simulation results with the CORSIM offline simulation in case of the same timing plan. These results mean that the online evaluation model could be a reliable tool to measure a real-time signal control effectiveness of a wide area street network with the HILSS method.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.61-72
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• 2011

In order to assess hydrologic and nonpoint source pollutant behaviors in a watershed with Soil and Water Assessment Tool (SWAT) model, the accuracy evaluation of SWAT model should be conducted prior to the application of it to a watershed. When calibrating and validating hydrological components of SWAT model, the Nash-Sutcliffe efficiency coefficient (EI) has been widely used. However, the EI value has been known as it is affected sensitively by big numbers among the range of numbers. In this study, a Web-based flow clustering EI estimation system using K-means clustering algorithm was developed and used for SWAT hydrology evaluation. Even though the EI of total streamflow was high, the EI values of hydrologic components (i.e., direct runoff and baseflow) were not high. Also when the EI values of flow group I and II (i.e., low and high value group) clustered from direct runoff and baseflow were computed, respectively, the EI values of them were much lower with negative EI values for some flow group comparison. The SWAT auto-calibration tool estimated values also showed negative EI values for most flow group I and II of direct runoff and baseflow although EI value of total streamflow was high. The result obtained in this study indicates that the SWAT hydrology component should be calibrated until all four positive EI values for each flow group of direct runoff and baseflow are obtained for better accuracy both in direct runoff and baseflow.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.43-49
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• 2010

This study deals with the traffic accident of the Cheongju arterial link sections. The purpose of the study is to develop the traffic accident model. In pursuing the above, this study gives particular attentions to developing the ZAM(zero-altered model) model using the accident data of arterial roads devided by 322 small link sections. The main results analyzed by ZIP(zero inflated Poisson model) and ZINB(zero inflated negative binomial model) which are the methods of ZAM, are as follows. First, the evaluation of various developed models by the Vuong statistic and t statistic for overdispersion parameter ${\alpha}$ shows that ZINB is analyzed to be optimal among Poisson, NB, ZIP(zero-inflated Poisson) and ZINB regression models. Second, ZINB is evaluated to be statistically significant in view of t, ${\rho}$ and ${\rho}^2$ (0.63) values compared to other models. Finally, the accident factors of ZINB models are developed to be the traffic volume(ADT), number of entry/exit and length of median. The traffic volume(ADT) and the number of entry/exit are evaluated to be the '+' factors and the length of median to be '-' factor of the accident.

• Environmental and Resource Economics Review
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• v.25 no.1
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• pp.27-60
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• 2016

An integrated assessment model of climate and the economy (IAM) has been a standard tool for the economic analysis of climate change and policy recommendations. Since policy measures to address climate change take places at a national level, a regional integrated assessment model of climate and the economy (RIAM) is gaining more importance. A RIAM is a useful tool for the assessment of regional (or national) impacts of climate change. This paper investigates the main features of the currently available RIAMs. The focus is social welfare functions and the regional aspects of climate change. The comparative analysis shows that there is a huge gap between the economics of climate change and its applications to RIAMs. As an application, this paper examines the effect of social welfare functions on optimal solutions of the RICE (Regional Integrated model of Climate and the Economy) model. It is found that optimal climate policy such as carbon tax or emissions control rate is very sensitive to the assumptions on social welfare functions of RIAMs. It is better for each country to have their own RIAM as a basic tool for national climate policy-making and for international bargaining in greenhouse-gas mitigation. This is because a country's own preferences such as efficiency, equity, and sustainable development as well as national circumstances can be reflected in RIAM. The Republic of Korea has not developed its own RIAM yet. The comparative analysis and the numerical model in this paper can be a stepping stone for the development of such a national model.