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이재형,안현욱,윤영식,조명우,조원승,Lee, Jaehyung,Ahn, Hyun-Wook,Yoon, Young-Sik,Cho, Myeong-Woo,Cho, Won-Seung 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.8
AlN-BN ceramic composites were fabricated and their mechanical properties were investigated. The relative density of hot-pressed composites decreased with increasing BN content, but over $99\%$ could be obtained with 30 $vol\%$ BN in AlN. YAG was formed in the composites and monolithic AlN as a second phase by the reaction between $Y_2O_3$, added as sintering aid, and $Al_2O_3$. As expected, Vickers hardness and Young's modulus decreased with increasing BN content. The three-point flexural strength also showed similar behavior decreasing from 500 MPa of monolith down to 250 MPa by the addition 30 $vol\%$ BN. However, interestingly, the standard deviation of the strength values decreased significantly as BN was added to AlN. As a result, the Weibull modulus of the AlN-30 $vol\% BN composite was 21.3, which was extremely high. Fractography and crack path studies revealed that BN platelets induced grain pull-out and crack bridging in a bigger scale during crack propagation. Consequently, fracture toughness increased as more BN was added, reaching 4.5 $MPa\sqrt{m}$ at 40 $vol\%$ BN.
수동 셀 밸런싱 알고리즘 비교 분석을 통한 밸런싱 최적화에 관한 연구
이재형(Jaehyung Lee),윤재중(Jaejung Yun) 한국자동차공학회 2023 한국자동차공학회 학술대회 및 전시회 Vol.2023 No.11
The passive cell balancing techniques currently commercialized in electric vehicles and railway vehicles include algorithms based on minimum and average voltage values and smart balancing algorithms proposed by TI. The balancing speed and efficiency of these techniques differ depending on the battery type and application, and optimization is required to improve performance and stability depending on the requirements of the system. Therefore, this paper constructed a BMS test bench with a Mater-Slave structure using an LFP battery module to optimize the balancing algorithm. The balancing operation range for experiments of the each algorithm was set between OCV at 80% SOC and full charge voltage. The experimental results of the minimum voltage based algorithm showed that the balancing efficiency was 86.7% and the charging speed was slow. The results of the average voltage based algorithm showed that balancing efficiency was 90% and the charging speed was fast. The smart balancing algorithm had the fastest charging speed but the balancing efficiency was low at 85.3%. Based on the results of each balancing algorithm, we researched to optimize the balancing method to improve the performance and efficiency of a battery system.
지자체 기후변화 취약성 평가와 적응 정책 연계방안 연구 - 건강부문을 중심으로 -
이재형 ( Jaehyung Lee ) 한국환경경제학회·한국자원경제학회(구 한국환경경제학회) 2016 한국환경경제학회 학술발표논문집 Vol.2016 No.경제학 공동
본 연구는 건강부문을 중심으로 하여 기후변화 적응정책과 취약성 평가 및 지자체의 특성과의 상관관계를 살펴보고, 정책 수립에 있어서 적정 예산 규모를 살펴보았다. 분야별로 추정 예산을 비교한 결과 총예산과의 차이는 종합대책이 가장 큰 것으로 나타났다. 이는 기반구축 및 SOC 사업을 적응대책에 포함하여 제시한 지자체의 종합대책 분야의 총예산이 과도하게 책정되어 있음을 의미한다. 본 연구는 광역지자체 기후변화 적응대책과 취약성 평가 및 지자체의 특성과의 상관관계를 처음으로 분석했다는 데 의미가 있다. 본 연구를 다른 6개 부문으로 확장하여 2차 계획기간(‘18~‘22년)의 지자체 기후변화적응 세부시행계획의 적정 예산 수립 기준을 정립하는 데 활용하였으면 한다. In this study, analysis on the relationship among the climate change adaptation policy, vulnerability assessment and local government characteristics have been performed by focusing on health sector. In the comparison study of the estimated gap in the total budget and estimated budget by each sector, the comprehensive policy showed the largest gap. This shows that total budget of the comprehensive policy which includes the budget relevant to SOC projects have been over estimated. This study is significant in terms of that it is the first time to analyze the relationship among the climate change adaptation policy, vulnerability assessment and local government characteristics. By expanding this approach to six other sectors, the results of this study would be used on the setting up of the optimal adaptation budget on detailed implementation plans of 2nd climate change adaptation period in Republic of Korea.
Spurious RTO를 위한 효율적인 혼잡윈도우 회복 기법
이재형 ( Jaehyung Lee ),안수빈 ( Soobeen Ahn ),추현승 ( Hyunseung Choo ) 한국정보처리학회 2008 한국정보처리학회 학술대회논문집 Vol.15 No.1
인터넷상에서 TCP 프로토콜은 사실상 표준으로써 널리 이용되고 있다. 그러나 네트워크 환경이 발전해 감에 따라서 무선 네트워크, CDMA, 3G 네크워크등 다양한 환경이 공존하게 되었고, 이러한 환경에서 TCP의 성능저하가 이슈가 되어 많은 연구가 진행되었으며, 많은 알고리즘들이 발표되었다. 본 논문에서는 무선환경에서 다양한 TCP 성능저하 원인 중에서 spurious RTO에 관한 문제를 해결하고자 한다. 이 전의 연구인 E-RTO는 delay spike문제를 효과적으로 다루고 있다 하지만 delay spike이후 혼잡 윈도우를 회복하는 과정을 효과적으로 다루고 있지 못하다. 우리는 BCR를 제안하여 이러한 문제를 해결하고자 한다. BCR의 성능평가는 NS2를 이용하여 이루어 졌으며 throughput, goodput에서 좋은 성능을 보여주고 있다.