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바나듐 산화물 필름의 온도에 따른 중적외선 영역 반사율 측정
서준용(Junyong Seo),채지연(Ji-Yeon Chae),백태종(Taejong Paik),이정철(Jungchul Lee),이봉재(Bong Jae Lee) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Temperature-based phase change material, such as vanadium dioxide (VO₂), has variable optical property depending on its temperature. Specifically, VO₂ can be utilized for an adaptive radiative cooling application because the phase of VO₂ switches between non-metallic and metallic phase. That is, when the temperature is higher than the phase transition temperature, VO₂ has metallic phase and well reflects solar irradiation as well as can be used for photonic radiative cooling structure, otherwise it behaves as photonic insulator so that no cooling effect is induced. To develop adaptive radiative cooling system with VO₂, it is important to measure optical property according to various temperatures. In this work, we measure the temperature-dependent reflectivity of VO₂ film using reflectometry setup coupled with Fourier-transform infrared spectrometer. The temperature-based optical property of VO₂ are going to be investigated. Furthermore, we also analyze applicability of VO₂ for adaptive radiative cooling system using measured result.
구매종속성이 존재하는 상황에서 주문충족율을 계산하는 근사법에 관한 연구
박창규(Changkyu Park),서준용(Junyong Seo) 한국경영과학회 2016 韓國經營科學會誌 Vol.41 No.2
This paper proposes a new approximate approach to calculate the order fill rate and the probability of filling an entire customer order immediately from the shelf in a business environment under purchase dependence characterized by customer purchase patterns observed in such areas as marketing, manufacturing systems, and distribution systems. The new approximate approach divides customer orders into item orders and calculates fill rates of all order types to approximate the order fill rate. We develop a greed iterative search algorithm (GISA) based on the Gauss-Seidel method to avoid dimensionality and prevent the solution divergence for larger instances. Through the computational analysis that compares the GISA with the simulation, we demonstrate that the GISA is a dependable algorithm for deriving the stationary joint distribution of on-hand inventories in the type-K pure system. We also present some managerial insights.
박창규(Changkyu Park),서준용(Junyong Seo) 한국경영과학회 2013 經營 科學 Vol.30 No.3
The purpose of this paper is to illustrate the importance of identifying and considering ‘purchase dependence’ when purchase of an item is dependent on availability of other items demanded in the same order. This paper is the first study to develop an inventory model for purchase?dependent inventory systems. Through simulation experiments, we demonstrate that the developed inventory model incurs less inventory operations cost than other inventory models that ignore purchase dependence. For empirical validation of the developed inventory model, the actual inventory data at the Hyundai Engine Europe Service Center is used. We explain the process of identifying purchase dependencies among items through a data mining technique. The empirical study results in similar results to the simulation experiment, demonstrating that the developed inventory model is applicable to real situations.
박창규(Changkyu Park),서준용(Junyong Seo),홍윤숙(Yunsook Hong) 한국경영과학회 2013 經營 科學 Vol.30 No.1
We conduct the future studies suggested by Park and Seo [3]. They considered a seat inventory control problem in which flights depart sequentially during a similar time-interval and passengers purchase available seats depending on individual customer choice behavior. Customer choice behavior can lead to one among a horizontal shift, a diversion-up, and a booking loss when a desired fare class is unavailable. We investigate how seat availability calculation method, booking limit control mechanism, seat inventory capacity, number of booking class, type of seat demand influence on revenues in an airline industry through thorough computer simulation experiments.