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산업장 네트워크 환경에서 IEEE 802.15.4e 동적 TSCH 기법
김영준(YoungJun Kim),김기형(Kihyung Kim),유승화(SeungWha Yoo),김영한(Younghan Kim),이상산(Sangsan Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Wireless Sensor Networks(WSN) have begun to take significant roles in various applications but there have been many researches to improve the reliability of data transmission in WSN. The main causes of failure along communication links are external interference and persistent multipath fading. In IEEE 802.15.4e network which is amended version of IEEE 802.15.4 network, the microscopic channel hopping mechanism is used to solve the failure of data communication in WSN. However, the proposed scheme in IEEE 802.15.4e network has a predefined hopping channel pattern. Therefore, sensor node can use the worst channel because the status of channel may be affected several factors (e.g. time, interference, traffic from other device). To solve this problem, we propose a novel channel hopping algorithm which can be operated dynamically based on the real-timely estimated link status.
지방정부 정책의 진화적 합리성에 관한 연구 - 서울역 고가 공원화 사업을 중심으로 -
김지수(Jisu Kim),김기형(Kihyung Kim) 한국지방행정학회 2016 한국지방행정학보 (KLAR) Vol.13 No.3
This case study on the Seoul Station 7017 project, by seeing it through the lens of evolutionary rationality, explores rationality of policy that the (local) government and the related stakeholders should seek for in a complicated, uncertain, and dynamic situation. This research suggested evolutionary rationality as an alternative to substantial rationality and procedural rationality, which consist of the two basic dimensions of policy rationality. The study contrasted between the classical policy rationality dimensions and evolutionary rationality of the case. The mayor’s political consideration expedited the planning of the project that had failed to confirm substantial rationality in the beginning due to conflicting interests in terms of its values and potential effects. Such a politics-led fast process lacking substantial rationality had also not gained its procedural rationality. Nevertheless, the later participatory process (discussion and deliberation) that stakeholders involved successfully fulfilled evolutionary rationality in soothing conflicts and contributed to improving substantial rationality to some extent. This study suggests how local governments can secure the rationality of policy in the introduction of policies that are expected to conflict with existing social and economic values.
A study on wafer surface passivation properties using hydrogenated amorphous silicon thin film
이승직(Lee, Seungjik),김기형(Kim, Kihyung),오동해(Oh, Donghae),안황기(Ahn, Hwanggi) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.11
Surface passivation of crystalline silicon(c-Si) surface with a-Si:H thin films has been investigated by using quasi-steady-state photo conductance(QSSPC) measurements. Analyzing the influence of a-Si:H film thickness, process gas ratio, deposition temperature and post annealing temperature on the passivation properties of c-Si, we optimized the passivation conditions at the substrate temperature of 200-250?C. Best surface passivation has been obtained by post-deposition annealing of a-Si:H film layer. Post annealing around the deposition temperature was sufficient to improve the surface passivation for silicon substrates. We obtained effective carrier lifetimes above 5.5 ms on average.
강원석(Wonseok Kang),김기형(Kihyung Kim) 한국정보과학회 2003 한국정보과학회 학술발표논문집 Vol.30 No.2Ⅱ
DEVS(Discrete Event System Specification) 형식론은 계층적이고 모듈화된 형태로 이산사건 시스템을 기술한다. 본 논문에서는 CORBA를 이용한 Multi-threaded 분산 시뮬레이션 방법을 제시한다. 본 논문에서 제시한 시뮬레이션 방법은 기존에 선행 연구된 DEVSCluster를 기반으로 한다. DEVSCluster는 계층적 DEVS 모델들을 비 계층적 모델로 구성하여 시뮬레이션한다. DEVSCluster는 전통적인 계층적인 시뮬레이션 시 발생하는 overhead를 제거한다. CORBA기반으로 DEVSCluster를 구성함으로써 산업 표준에 맞는 확정을 가지는 분산 시뮬레이션이 가능해졌다. 그리고 CORBA를 이용함으로써 기존에 분산 시뮬레이션 동기화를 위한 새로운 패러다임도 적용이 가능해 졌다. 제시한 시뮬레이션 방법의 효용성을 보이기 위해 Windows 시스템에서 분산 시뮬레이션 엔진을 구현하여 대규모 물류 시스템으로 성능을 측정하였다.