• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.3
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• pp.105-117
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• 2001

This paper models supply uncertainty in the dynamic Newsboy problem context. The system consists of one supplier and one retailer who places an order to the supplier every period to meet stochastic demand. Supply uncertainty is modeled as the uncertainty in quantities delivered by the supplier. That is, the supplier delivers exactly the amount ordered by the retailer with probability of $\beta$ and the amount minus K with probability of (1-$\beta$). We formulate the problem as a dynamic programming problem and prove that retailer’s optimal replenishment policy is a stationary base-stock policy. Through a numerical study, we found that the cost increase due to supply uncertainty is significant and that the costs increase more rapidly as supply uncertainty increases. We also identified the effects of various system parameters. One of the interesting results is that as retailer’s demand uncertainty, the other uncertainty in our model, increases, the cost increase due to supply uncertainty becomes less significant.

• Journal of the Korean Institute of Intelligent Systems
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• v.4 no.1
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• pp.64-80
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• 1994

본 연구에서는 장기전원구성의 수립에 있어서 가정한 시나리오에서 최적해를 찾는 기존의 방법을 탈피하여 건설단가나 연료단가의 변동과 같은 경제성의 변동 및 최대부하의 예측의 불확실성에 대한 외부충격등에 견딜 수 있는 유연성을 정량적으로 고려할 수 있는 새로운 방법을 제안한다.그 수법으로 Fuzzy 동적계획법을 이용하여 각 대표년도별로 최적전원구성안을 결정하므로써 년도별 전원 구성의 추이를 쉽게 알 수 있고 비선형 멤버쉽함수도 용이하게 고려할 수 있도록 하였다. 여기서는 경제성, 신뢰성, 부하불확실성 및 유연성에 대한 멤버쉽 함수치를 각상태별로 계산하고 Bellman-Zadeh의 최대화 결전과정에 따라 처리하므로서 그 안을 결정하도록 하였다. 본 수법을 우리나라 KEPCO 계통에 적용하여 그 유용성을 검토하였다.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.236-241
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• 1999

산업이 발전해 가며 공장 자동화를 하는 회사는 나날이 늘어가고 있으며 현재 산업 전반에 걸쳐 자동화 시스템을 채택하지 않는 곳을 찾아보기 어렵고 이 시스템의 시험 및 운영자 교육용으로 시뮬레이터에 대한 관심은 높아 가고 있는 실정이다. 여기에서는 한국전력에서 사용하고 있는 터빈 제어 삼중화 시스템이 어떠한 보팅 기법들을 적용하여 설계되었으며 그 기능이 어떻게 구현되었는지를 실제 제품의 사례분석을 통해 검토해 보고자 한다. 검토 대상은 삼중화 제어기에 대해서만 시행할 예정이다. 이는 실제 현장이 경제성을 수반한 제어기의 신뢰, 이용, 안정, 수행, 지속, 시험, 확실성 등을 원하고 있으며 또한 시뮬레이터를 설계하는 사람들에게 삼중화 주제어기에 대한 비교(MARK-V, Triconex-TMR, GE-Fanuc, Woodward-Micronet) 소개함으로서 더욱더 현장과 가까운 시뮬레이터를 설계할 수 있도록 하기 위함이다.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.285-288
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• 2013

의료영상에서의 노이즈는 환자 진단에 있어서 막대한 영향을 미치는 영상의 화질을 떨어트림으로써, 진단에 대한 유효성을 낮추게 된다. 특히, 현재 이슈화 되고 있는 저선량 의료영상은 기존의 고선량 의료영상보다 노이즈 레벨이 높으며, 이에 따라서 의료영상에서의 노이즈 제거 기술은 매우 중요한 사안으로 부각되고 있다. 본 논문에서 제시하는 노이즈 제거 기술은 각각의 투영 영상을 여러개의 부대역(sub-band)으로 분해하는 것으로부터 시작한다. 분해된 각각의 부대역 영상은 엣지 검출기를 통하여 엣지 부분과 평탄한 영역으로 구별되어 진다. 검출된 엣지는 0 ~ 1 사이의 값으로 정규화 되며, 퍼지기반의 연산을 통하여 엣지의 확실성을 나타내는 엣지맵으로 변환하게 된다. 이 엣지맵을 통하여 각 부대역 영상의 필터링 정도를 제어하고, 분해된 각 부대역을 결합하는 방식을 취함으로써 영상의 엣지 부분을 최대한 보존하면서 노이즈는 효과적으로 제거하도록 하였다.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.3
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• pp.123-131
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• 2022

출산율이 낮아지면서 대학에 진학하는 학령인구도 점차 줄어들고 있다. 본 연구는 항공서비스를 전공하는 대학생의 학업지속의향에 영향을 미치는 요인을 살펴봄으로써 전공만족, 진로성숙도, 학업지속의향의 관계를 규명하는 것을 목적으로 한다. 본 연구의 목적을 달성하기 위한 자료 수집은 전국의 4년제 항공서비스학을 전공하는 학생들을 대상으로 설문을 받았으며, 이를 통해 결과를 분석하였다. SPSS 21.0 프로그램을 통하여 전산 처리하였다. 본 연구의 가설검증 결과를 요약하면 다음과 같다. 첫째, 주요만족은 진로성숙도의 하위변수인 결정성, 목적성, 확실성, 준비성, 독립성에 유의한 영향을 미치는 것으로 확인되었다. 둘째, 전공만족이 학업지속의향에 유의한 영향을 미치는 것으로 나타났다. 셋째, 진로성숙도는 학업지속의향에 영향을 미치는 것으로 확인되었으며, 하위변수별 결정성, 준비도, 독립성에 유의한 영향을 미치는 것으로 나타났다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.4
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• pp.409-415
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• 2015

For the design of Concrete-Filled Steel Tube(CFST) columns, the outside diameter D to the steel tube thickness t ratio(D/t ratio) is limited to prevent the local buckling of steel tubes. Each design code proposes the respective model to compute the maximum D/t ratio using the yield strength of steel $f_y$ or $f_y$ and the elastic modulus of steel E. Considering the uncertainty in $f_y$ and E, the reliability index ${beta}$ for the local buckling of a CFST section can be calculated by formulating the limit state function including the maximum D/t models. The resulted ${beta}$ depends on the maximum D/t model used for the reliability analysis. This variability in reliability analysis is due to ambiguity in choosing computational models and it is called as "modelling uncertainty." This uncertainty can be considered as "non-specificity" of an epistemic uncertainty and modelled by constructing possibility distribution functions. In this study, three different computation models for the maximum D/t ratio are used to conduct reliability analyses for the local buckling of a CFST section and the reliability index ${beta}$ will be computed respectively. The "non-specific ${beta}s$" will be modelled by possibility distribution function and a metric, degree of confirmation, is measured from the possibility distribution function. It is shown that the degree of confirmation increases when ${beta}$ decreases. Conclusively, a new set of reliability indices associated with a degree of confirmation is determined and it is allowed to decide reliability index for the local buckling of a CFST section with an acceptable confirmation level.

• Journal of Korean Philosophical Society
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• v.148
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• pp.239-267
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• 2018

In the matter of ethical and moral practice, Thomas Aquinas's thought is called "intellectualism". It does not mean only that intelligence is more important than will in moral practice, but that it has epistemological, metaphysical, and psycho-psychological implications significance. The first means affirming "the first principles of knowing" as the problem of certainty of knowing. In Thomism, there are surely above suspicion notions in the domain of practice as well as in the domain of reason, which are obviously self-evident, and because of that certainty, they become the basis of certainty of all other knowings that follow. The principle to know these knowings is the first principle of knowing, reason and Synderesis(conscience). Therefore, the "intellectualism" of Tomism is the basis for providing the ground of metaphysics. In the case of reason, it is classified into superior reason and inferior reason according to whether it is object. The object of higher reason is "metaphysical object" which human natural reason can not deal with. This affirmation of superior reason provides a basis for human "autonomy" in the moral and religious domain. This is because even in areas beyond the object of natural reason, it is possible to derive certain knowledge through self-reasoning, and thus to be able to carry out the act through their own choosing. Likewise, for Thomas Aquinas, "Synderesi" as the first principle of good and evil judgment can be applied to both the superior reason and the inferior reason, and thus, except for the truth by the direct divine revelation, precedes any authority of the world, scrupulous Act always guarantees truth and good. This means "subjectivity" that virtually in the act of moral practice, it can become the master of one's act. Furthermore, "consciousness(conscientia)", which means the ability to comprehend everything in a holistic and simultaneous manner, is based on conscience(synderesis). So, at least in principle, correct behavior or moral behavior in Tomism is given firstly in correct knowledge. Therefore, it can be said that true awareness (conscious awareness) in Thomas Aquinas's thought coincide with practical practice, or at least knowledge can be said to be a decisive 'driver' for practice. This will be the best explanation of the definition of "intellectualism" by Thomism.

• Journal of Educational Research in Mathematics
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• v.26 no.1
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• pp.47-62
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• 2016

Cultivating mathematical creativity is one of the aims in the recently revised mathematics curricular. However, there have been lack of researches on how to nurture mathematical creativity for ordinary students. Perspective of Realistic Mathematics Education(RME), which pursues education of creative person as the ultimate goal of mathematics education, could be useful for developing principles and methods for cultivating mathematical creativity. This study reanalyzes RME from the points of view in mathematical creativity education. Major findings are followed. First, students should have opportunities for mathematical creation through mathematization, while seeking and creating certainty. Second, it is vital to begin with realistic contexts to guarantee mathematical creation by students, in which students can imagine or think. Third, students can create mathematics in realistic contexts by modelling. Fourth, students create the meaning of 'model of(MO)', which models the given context, the meaning of 'model for(MF)', which models formal mathematics. Then, students create MOs and MFs that are equivalent to the intial MO and MF given by textbook or teacher. Flexibility, fluency, and novelty could be employed to evaluate the MOs and the MFs created by students. Fifth, cultivation of mathematical creativity can be supported from development of local instructional theories by thought experiment, its application, and reflection. In conclusion, to employ the education model of cultivating mathematical creativity by RME drawn in this study could be reasonable when design mathematics lessons as well as mathematics curriculum to include mathematical creativity as one of goals.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.12 no.1
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• pp.73-85
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• 2017

The purpose of this study is to investigate the effect of career uncertainty and career education on entrepreneurship and entrepreneurial intention of potential entrepreneur in Korea. A total number of 381 potential entrepreneurs responded to the questionnaire. The collected data were analyzed by SPSS Statistics 22. The results of the empirical analysis are as follows: First, career uncertainty did not have a significant effect on entrepreneurial intention. Second, career uncertainty had a negative(-) effect on entrepreneurship. Third, career education had a negative(-) effect on entrepreneurial intention. Fourth, career education did not have a significant effect on entrepreneurship. Fifth, career uncertainty had a negative(-) effect on self-determination. Sixth, self-determinism was found to fully mediate the relationship between career uncertainty and entrepreneurial intention. Seventh, self-determination was found to fully mediate the relationship between career uncertainty and entrepreneurship. Based on these results, it is necessary to expand and strengthen the scope of career education of students by lowering the uncertainty of career and reinforcement of intrinsic motivation through self-determination in order to improve student's entrepreneurship and entrepreneurial intention. At the same time, institutional efforts to include entrepreneurship education in career education should be concurrently accompanied by efforts to improve self-determination of potential entrepreneurs.

• The Korean Journal of Financial Management
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• v.26 no.1
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• pp.165-188
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• 2009

This paper has suggested the methodology for the frontier portfolios and the optimal portfolio under the mean-VaR framework, not assuming the normal distribution and considering the investor's preferences for the higher moments of return distributions. It suggested the grid and rank approach which did not need an assumption about return distributions to find the frontier portfolios. And the optimal portfolio was selected using the utility function that considered the 3rd and the 4th moments. For the application of the methodology, weekly returns of the developed countries index, the emerging market index and the KOSPI index were used. After the frontier portfolios of the mean-variance framework and the mean-VaR framework were selected, the optimal portfolios of each framework were compared. This application compared not only the difference of the standard deviation but also the difference of the utility level and the certainty equivalent expressed by weekly expected returns. In order to verify statistical significances about the differences between the mean-VaR and the mean-variance, this paper presented the statistics which were obtained by the historical simulation method using the bootstrapping. The results showed that an investor under the mean-VaR framework had a tendency to select the optimal portfolio which has bigger standard deviation, comparing to an investor under the mean-variance framework. In addition, the more risk averse an investor is, the bigger utility level and certainty equivalent he achieves under the mean-VaR framework. However, the difference between the two frameworks were not significant in statistical as well as economic criterion.