• 한국농공학회논문집
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• 제61권1호
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• pp.31-44
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• 2019

The main objective of this research is to develop a hydroclimate drought index (HCDI) using the gridded climate data inputs in a Variable Infiltration Capacity (VIC) modeling platform. Typical drought indices, including, Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), and Self-calibrated Palmer Drought Severity Index (SC-PDSI) in South Korea are also used and compared. Inverse Distance Weighting (IDW) method is applied to create the gridded climate data from 56 ground weather stations using topographic information between weather stations and the respective grid cell ($12km{\times}12km$). R statistical software packages are used to visualize HCDI in Google Earth. Skill score (SS) are computed to evaluate the drought predictability based on water information derived from the observed reservoir storage and the ground weather stations. The study indicates that the proposed HCDI with the gridded climate data input is promising in the sense that it can help us to predict potential drought extents and to mitigate its impacts in a changing climate. The longer term drought prediction (e.g., 9 and 12 month) capability, in particular, shows higher SS so that it can be used for climate-driven future droughts.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.131-143
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• 2023

Constitutive equations in a nuclear reactor safety analysis code are mostly empirical correlations developed from experiments, which always accompany uncertainties. The accuracy of the code can be improved by modifying the constitutive equations fitting wider range of data with less uncertainty. Thus, the sensitivity of the code with respect to the constitutive equations is evaluated quantitatively in the paper to understand the room for improvement of the code. A new methodology is proposed which first starts by dividing the thermal hydraulic conditions into multiple sub-regimes using self-organizing map (SOM) clustering method. The sensitivity analysis is then conducted by multiplying an arbitrary set of coefficients to the constitutive equations for each sub-divided thermal-hydraulic regime with SOM to observe how the code accuracy varies. The randomly chosen multiplier coefficient represents the uncertainty of the constitutive equations. Furthermore, the set with the smallest error with the selected experimental data can be obtained and can provide insight which direction should the constitutive equations be modified to improve the code accuracy. The newly proposed method is applied to a steady-state experiment and a transient experiment to illustrate how the method can provide insight to the code developer.

• 지구물리와물리탐사
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• 제23권3호
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• pp.168-177
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• 2020

해저면 탄성파 겹반사는 발파점 모음자료와 겹쌓기 단면에서 모두 일차 반사파의 해석에 잘못된 결과를 초래할 수 있다. 따라서, 해저면 겹반사는 자료처리를 통해 제거해야 한다. 전통적인 자료처리 과정에서 겹반사 제거는 예측오차 곱풀기와 라돈 필터링 등과 같은 모델-기반 기법과 지표관련-겹반사제거와 같은 데이터-기반 기법에 의해 이루어져 왔다. 그러나 대다수의 자료처리 과정들은 방대한 컴퓨터 자원과 전문적인 자료처리 기법뿐만 아니라 자료처리 변수들을 테스트하고 선택하는데 많은 시간을 필요로 한다. 이 논문에서는 머신러닝 시스템을 활용한 해저면 겹반사의 제거효과를 살펴보기 위해 Marmousi2 속도모델에 대한 수치모델링으로 겹반사가 포함된 입력데이터와 겹반사가 포함되지 않은 레이블데이터를 생성하였다. 수직시간차가 보정된 공통중간점 모음자료로 훈련데이터를 구성하였으며 인공신경망은 U-Net 모델을 적용하였다. 해저면 겹반사를 제거하기 위해 훈련된 모델은 레이블데이터에 거의 근접하는 예측 결과를 만들어내며, 현장자료에 대한 예측 테스트에서 해저면 겹반사를 효과적으로 제거하는 것으로 나타났다.

• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.295-301
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• 2013

Long-term global energy-demand growth is expected to increase driven by strong energy-demand growth from developing countries. Fusion power offers the prospect of an almost inexhaustible source of energy for future generations, even though it also presents so far insurmountable scientific and engineering challenges. One of the challenges is safe handling of hydrogen isotopes. Metal hydrides such as depleted uranium hydride or ZrCo hydride are used as a storage medium for hydrogen isotopes reversibly. The metal hydrides bind with hydrogen very strongly. In this paper, we carried out a modeling and simulation work for absorption/desorption of hydrogen by ZrCo in a horizontal annulus cylinder bed. A comprehensive mathematical description of a metal hydride hydrogen storage vessel was developed. This model was calibrated against experimental data obtained from our experimental system containing ZrCo metal hydride. The model was capable of predicting the performance of the bed for not only both the storage and delivery processes but also heat transfer operations. This model should thus be very useful for the design and development of the next generation of metal hydride hydrogen isotope storage systems.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.507-512
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• 2011

최근 하천의 유동 및 하상 자료를 광범위한 영역에서 신속하게 계측할 수 있는 전자기파 기반의 수리계측기기들이 등장하여 하천의 특성을 이해하는 방식을 전통적인 수치모델링을 통한 방식으로부터 자료만을 활용하는 방식으로 전환되고 있다. 본 논문은 최신 관측기기로 초음파유속계(ADCP), 이미지 유속계(LSPIV), 복수빔 음파수심계(MBES), 공중 전파수심계(ABL) 의 관측 방식과 적용 사례를 보여준다. 그리고 관측된 2차원 혹은 3차원의 유동 및 하상 자료를 GIS에 기반하여 상호 연계하고 저장하여 하천의 시공간적인 변화를 추적할 수 있게 하는 하천정보화시스템의 구축방안을 제시한다.

• 한국지능시스템학회논문지
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• 제11권7호
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• pp.603-610
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• 2001

Industrial processes are normally operated by skilled humans who have the cumulative and logical information about the system. Fuzzy control has been investigated for many application. Intelligent control approaches based on fuzzy logic have a chance to include human thinking. This paper represents modeling approach based upon operators knowledge without mathematical model of the system and optimize the controller. The experimented system is constructed for sending a ball to the goal position using wind of two DC motors in the predefined path. A vision camera to mimic human eyes detects the ball position. The system used in this experiment could be hardly modeled by mathematical methods and ould not be easily controlled by conventional manners. The controller is designed based on the input-output data and experimental knowledge obtained by trials, and optimized under the predefined performance criterion. And this paper shows the data adaptation for changeable operating condition. When the system is driven in the abnormal condition with unconsidered noise, the new optimal operating parameters could be defined by adjusting membership functions. Thus, this technique could be applied in industrial fields.

• Nuclear Engineering and Technology
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• 제50권1호
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• pp.151-158
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• 2018

The neutron powder diffractometer (NPD) is used to study a variety of technologically important and scientifically driven materials such as superconductors, multiferroics, catalysts, alloys, ceramics, cements, colossal magnetoresistance perovskites, magnets, thermoelectrics, zeolites, pharmaceuticals, etc. Monte Carlo-based codes are powerful tools to evaluate the neutronic behavior of the NPD. In the present study, MCNPX 2.6.0 and Vitess 3.3a codes were applied to simulate NPD facilities, which could be equipped with different optic devices such as pyrolytic graphite or neutron chopper. So, the Monte Carlo-based codes were used to simulate the NPD facility of the 5 MW Tehran Research Reactor. The simulation results were compared to the experimental data. The theoretical results showed good conformity to experimental data, which indicates acceptable performance of the Vitess 3.3a code in the neutron optic section of calculations. Another extracted result of this work shows that application of neutron chopper instead of monochromator could be efficient to keep neutron flux intensity higher than $10^6n/s/cm^2$ at sample position.

• 한국보육지원학회지
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• 제15권3호
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• pp.21-38
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• 2019

Objective: The goal of this study was to investigate the effects of early childhood teachers' current working conditions such as welfare and wages, working hours, ECEC center's environmental characteristics, and parental involvement and community engagement on the professionalism of teachers. Method: A total of 988 respondents participated in the nationwide online survey. The data were analyzed by correlation analysis and structual equation modeling. Results: First, there were no statistically significant direct effects of ECEC teachers' working conditions on teacher professionalism. Second, there were significant direct effects of teacher efficacy and well-being on teacher professionalism. Third, there were significant indirect effects of teachers' working conditions on their professionalism, via efficacy and well-being, linking the impact of working conditions and the professionalism of teachers. Conclusion/Implication: The results of this structural model imply that policy input for teacher welfare, wage increases, and the enhancement of teachers' well-being and efficacy are valid and significant for the professional development of ECEC teachers. These results provide the data-driven evidence for the importance of welfare and socio-cognitive approaches for teachers.

• The Journal of Asian Finance, Economics and Business
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• 제8권3호
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• pp.237-249
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• 2021

Indonesia has successfully increased its ranking to 40th place in the 2019 Travel & Tourism Competitiveness Index. While tourism has become the country's second largest foreign exchange contributor, there is no existing competitive advantage model for Indonesian tourist destinations. The purpose and novelty of this study is to develop and formulate a competitive advantage model for Indonesia's tourism industry. The model will be based on the supply-side perception analysis of competitiveness indicators from Bali and five designated super-priority destinations in Indonesia. This model is expected to become a guideline for policymakers to design an effective and focused strategy. Data were obtained from in-depth interviews with, and questionnaires given to, 62 qualified industry players from the public and private sectors. This data-driven approach builds a relationship between competitiveness indicators and competitive advantages using a combination of importance-performance analysis and confirmatory factor analysis, thereby leveraging these advantages to generate a strategic model to compete in the international tourism industry. This would also be the first study to use this method in defining the competitive advantage of a destination. Using structural equation modeling, the study found that there are 54 indicators representing twelve dimensions of competitive advantages with good fit criteria.

• 스마트미디어저널
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• 제12권10호
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• pp.38-46
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• 2023

Farming activities are transforming from traditional skill-based agriculture into knowledge-based and technology-driven digital agriculture. The use of intelligent information and communication technology introduces the idea of smart farming that enables farmers to collect weather data, monitor crop growth remotely and detect crop diseases easily. The introduction of Plantix, a pest and disease management tool in the form of a mobile application has allowed farmers to identify pests and diseases of the crop using their mobile devices. Hence, this study collected the reviews of Plantix to explore the response of the users on the Google Play Store towards the application through Latent Dirichlet Allocation (LDA) topic modeling. Results indicate four latent topics in the reviews: two positive evaluations (compliments, appreciation) and two suggestions (plant options, recommendations). We found the users suggested the application to additional plant options and additional features that might help the farmers with their difficulties. In addition, the application is expected to benefit the farmer more by having an early alert of diseases to farmers and providing various substitutes and a list of components for the remedial measures.