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전자파의 집중도를 이용한 바이모달 트램의 전자파 차폐 성능 분석
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김남경(Nam-Kyung Kim),송명곤(Myung Kon Song),이강원(Kang-Won Lee),목재균(Jai-Kyun Mok),김동훈(Dong-Hun Kim) 대한전기학회 2011 전기학회논문지 Vol.60 No.7
In this paper, the electromagnetic shielding performance of a BiMODAL Tram is investigated by means of an electromagnetic analysis tool, called HFSS. For the purposed of doing this, first, three-dimensional finite element modeling for the tram including electronic devices and engine room is carried out. Then, for quantitatively assessing the electromagnetic shielding performance of the tram’s body, concentration indexes for electric field magnitude and time-average stored electric energy are introduced. From numerical results, it is inferred that the tram’s body can protect the electronic devices and engine room against external electromagnetic waves from 30 ㎒ to 100 ㎒.
샘플링 기반 민감도를 이용한 국부 유도 가열용 코일의 최적 설계
최낙선(Nak-Sun Choi),김동욱(Dong-Wook Kim),김동훈(Dong-Hun Kim) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.3
This paper proposes a sampling-based sensitivity method for dealing with electromagnetic coupled design problems effectively. The black-box modeling technique is basically applied to obtain an optimum regardless of how strong the electromagnetic, thermal and structural analyses are coupled with each other. To achieve this, Kriging surrogate models are produced in a hyper-cubic local window with the center of a current design point. Then design sensitivity values are extracted from the differentiation of basis functions which consist of the models. The proposed method falls under a hybrid optimization method which takes advantages of the sampling-based and the sensitivity-based methods. Owing to the aforementioned feature, the method can be applied even to electromagnetic problems of which the material properties are strongly coupled with thermal or structural outputs. To examine the accuracy and validity of the proposed method, a strongly nonlinear mathematical example and a coil design problem for local induction heating are tested.
주파수 영역에서 연속체 민감도법을 이용한 유전체 저대역 필터 최적 설계
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김남경(Nam-Kyung Kim),변진규(Jin-Kyu Byun),김동훈(Dong-Hun Kim) 대한전기학회 2010 전기학회논문지 Vol.59 No.8
This paper presents a new methodology for designing a dielectric waveguide filter with the cutoff frequency of 2.4 ㎓ based on the continuum design sensitivity analysis. An analytical sensitivity formula is derived in frequency domain and then unified program architecture applicable to the optimal design of high-frequency devices is proposed. A three-dimensional dielectric resonator used in waveguide filters has been tested to illustrate the validity of the proposed method.
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김동욱(Dong-Wook Kim),양창섭(Chang-Seop Yang),정현주(Hyun-Ju Jun),김동훈(Dong-Hun Kim) 대한전기학회 2012 전기학회논문지 Vol.61 No.10
This paper analyzes re-degaussing performances of various breakdown conditions of degaussing coils in a ship to reduce underwater magnetic field anomaly due to the hull magnetization induced under the Earth’s magnetic field. To achieve this, first, it is implemented to optimize degaussing coil currents by a magnetomotive force sensitivity formula combined with the coil effects. The re-degaussing processes are then executed when a breakdown occurs in degaussing coils, one by one. Finally, the re-degaussing performances are examined with the results of normal degaussing and coil breakdown conditions.
무선 센서 네트워크를 위한 자원 적응형 데이터 확산프로토콜
김현태,최낙선,정규수,전영배,나인호,Kim, Hyun-Tae,Choi, Nak-Sun,Jung, Kyu-Su,Jeon, Yeong-Bae,Ra, In-Ho 한국정보통신학회 2006 한국정보통신학회논문지 Vol.10 No.11
본 논문에서는 무선 센서 네트워크를 구성하는 센서 노드들을 위 한 자원 적응형 데이터 확산 프로토콜을 제안하였다. 무선 센서 네트워크의 각 센서 노드들은 배터리 전력에 의존하여 센싱, 연산, 통신 등 협업 작업을 통해 최종 목적지에 요구된 정보를 전달한다. 따라서 센서 노드들이 수집한 정보를 사용자에게 전달하기 위해 사용되는 프로토콜들은 센서 노드의 전력 소비를 최소화 할 수 있어 야 한다. 이를 위해서는 특히 브로드캐스트와 같은 전송 방식 때문에 발생하는 내부 네트워크 내파, 데이터 중칩 전송, 과다한 메시지 전송 등의 문제를 해결하여 전체 전력 소비를 최소화는 것이 매우 중요하다. 각 센서 노드들간의 최단 경로 유지와 네트워크 생존시간의 연장 및 통신비용 절감을 위해 본 논문에서는 이벤트 지 역에서의 협의를 통한 전송 노드 선출, 홉과 에너지정보를 이 한 최적의 전송경로 유지 기법을 제안하였다. 마지막으로, 본 논문에서는 제안된 기법을 기존의 방향성 확산 및 SPIN 프로토콜과 비교하기 위해 이벤트 발생 주변에 이웃한 센서 노드 수의 증가에 따른 에너지 소비율, 네트워크에 유포되는 메시지 비율, 센서 노드 수의 증가에 따른 전체 네트워크 에너지 소비율 측면에 대한성능 평가를 수행하여 이것들의 성능이 향상됨을 보였다. In this paper, it proposes a protocol of resource adaptive data dissemination for sensor nodes in a wireless sensor network. In general, each sensor node used in a wireless sensor network delivers the required information to the final destination by conducting cooperative works such as sensing, processing, and communicating each other using the battery power of a independent sensor node. So, a protocol used for transferring the acquired information to users through the wireless sensor network can minimize the power consumption of energy resource given to a sensor node. Especially, it is very important to minimize the total amount of power consumption with a method for handling the problems on implosion. data delivery overlapping, and excessive message transfer caused by message broadcasting. In this paper, for the maintaining of the shortest path between sensor nodes, maximizing of the life time of a sensor node and minimizing of communication cost, it presents a method for selecting the representative transfer node for an event arising area based on the negotiation scheme and maintaining optimal transfer path using hop and energy information. Finally, for the performance evaluation, we compare the proposed protocol to existing directed diffusion and SPIN protocol. And, with the simulation results, we show that the proposed protocol enhances the performance on the power consumption rate when the number of overall sensor nodes in a sensor network or neighbor sensor nodes in an event area are increased and on the number of messages disseminated from a sensor node.
김동욱(Dong-Wook Kim),최낙선(Nak-Sun Choi),김동훈(Dong-Hun Kim),양창섭(Chang-Seob Yang),정현주(Hyun-Ju Chung) 한국자기학회 2014 韓國磁氣學會誌 Vol.24 No.4
In this paper, a optimum degaussing technique, which can minimize an underwater magnetic field anomaly generated by the ferromagnetic hull, was verified through the mock-up test of a ship. To predict degaussing field signals due to the degaussing coils installed in a ship, individual coil effects were measured. Exploiting the linearity of coil effects and analytical sensitivity formula, optimum degaussing current values fed to individual coils were decided. To identify degaussing performance of the proposed method, the obtained degaussing currents were applied to the coils. Then the field anomaly signals were measured and analyzed before and after degaussing. Experimental results show the magnitude of the field signal after degaussing is reduced up to 95% of that before degaussing.