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전기자동차 충전기 쿨링시스템에 적용할 상변화물질의 열적 특성 및 융해 거동에 관한 실험적 연구
최두한(Doo-Han Choi),김태우(Tae-Woo Kim),김명준(Myoung-Jun Kim),유직수(Jik-Su Yu),홍대선(Dae-Sun Hong) 한국산학기술학회 2024 한국산학기술학회논문지 Vol.25 No.1
Phase change materials (PCMs) are used widely for various applications because of their ability to absorb or release thermal energy during the phase change process. Phase change materials store thermal energy in the form of latent heat. Hence, they can absorb and release more thermal energy than sensible heat. The phase change temperature varies depending on the material selected, so it is possible to store thermal energy at various temperatures depending on the material. In this study, some suitable PCMs were selected and manufactured to apply them as a heat absorption device targeting the cooling system of an electric vehicle fast charger. The PCMs selected in this study were fatty acids: lauric acid (LA), palmitic acid (PA), and stearic acid (SA). LA-SA mixtures and PA-SA mixtures were produced and applied to a thermal absorption device. The thermal properties of these PCMs were analyzed by measuring the melting peak temperature and latent heat and conducting a melting experiment to identify the melting behavior. Through a series of experiments, the melting peak temperature of the mixture was lowered, and the temperature gradient of the PCMs during melting was identified. In addition, the LA-SA and PA-SA mixture were suitable as thermal absorption devices.
Choi Doo Il(최두일) 한국통신학회 2009 한국통신학회 학술대회논문집 Vol.2009 No.6
Traffics are classified into two types, real-time traffic such as voice and video and nonreal-time traffic such as data. By properties of burstiness and correlation between interarrival, it is assumed the arrival of real-time traffic to be a Markovian Arrival Process ( MAP ). The nonreal-time traffic follows a Poisson Process. We compare performance of diverse scheduling schemes to support real-time and nonreal-time traffic. Concretely, Head of Line priority scheme, Shortest Job First scheme, Longest Job First scheme, Bernoulli scheme, QLT scheme and QLT scheme with Bernoulli, are investigated, and their performance measures, loss and delay, are compared. Finally, this investigation helps the system designer to select optimal scheduling scheme, while satisfying the Quality of Service(QoS) of each traffics.
열화상/적외선 카메라와 레이더를 이용한 딥러닝기반 야생 멧돼지 인식에 대한 연구
최두한(Doohan Choi),옥승현(Seunghyeon Oak),이철희(Cherl-Hee Lee) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
매년 야생 멧돼지의 개체수 증가로 인하여 농가의 피해도 급격이 증가하고 있는 상황이다. 이를 해결하기 위해 본 논문에서는 멧돼지의 움직임을 감지할 수 있는 레이더 및 야간에도 동물이나 사람을 인식 할 수 있는 열화상 카메라와 적외선 카메라를 이용하여 야생 멧돼지를 탐지하고 인식할 수 있는 딥러닝 알고리즘을 제안하였다.
최두일 ( Choi Doo Il ),임대은 ( Lim Dae-eun ) 한국경영공학회 2016 한국경영공학회지 Vol.21 No.4
In this study, we analyze a manufacturing system with a variable production rate. The system produces an item upon a request. If an arriving request finds the system occupied, the request waits in the queue. The production (or service) time distribution of requests (or customers) upon production initiation is changed if the number of requests in the system reaches a predefined threshold L₂. Then, the changed production time distribution continues until the number of requests in the system is reduced to another threshold L₁(≤ L₂), and this process is repeated. We model this system as an MMPP/G/1/K queue with a modified state-dependent service rate and analyze the system using an embedded Markov chain and a supplementary variable method. The performance measures of the queue-length distributions at a customer`s departure epochs and at an arbitrary time are derived. Numerical examples are also presented.