• The KSFM Journal of Fluid Machinery
• /
• v.9 no.5 s.38
• /
• pp.22-27
• /
• 2006

Sedimentation phenomenon of suspended solids occurs by the gravitational force. Pollution particles are separated from slowly flowing waste water in clarifier. Recently, the sludge suction collector is Preferred rather than the scraper type sludge collector due to the enhancement of the clarifier efficiency. The sludge suction collector is usually operated by the user's experiences without any scientific and/or technical consideration. To evaluate the performance of sludge suction collector, the three dimensional numerical simulation was conducted by the finite volume method. To analyze the performance, the velocity vectors and the suction flow rates of the orifices were investigated. The result showed that each suction flow rate through out the collector was equivalent in the sludge suction collector and the efficiency of suction collector was good to remove high concentrated sludge in clarifier.

• Proceedings of the KIPE Conference
• /
• 2018.07a
• /
• pp.42-44
• /
• 2018

본 논문에서는 Bridgeless 정류기가 적용된 무선전력전송(Inductive Power System, IPT) 시스템의 성능 향상을 위한 스위칭 주파수의 변조 기법에 대해 제안한다. Bridgeless 정류기의 기존 제어 방식과 제안하는 제어 방식의 동작을 비교하고 3.3kW급 무선전력전송 시스템에 대한 시뮬레이션을 통해 제안하는 제어 방식에 대한 동작을 검증한다. 제안하는 제어 방식의 성능을 검증하기 위해 기존 제어 방식과의 손실을 비교 분석한다.

• Proceedings of the KIPE Conference
• /
• 2019.11a
• /
• pp.158-159
• /
• 2019

본 논문은 전기자동차용 inductive power tranasfer (IPT) 방식의 양방향 무선전력전송에 활용 가능한 공진 네트워크를 선정한다. 각 공진 네트워크별 수식 분석을 통해 패드의 인덕턴스를 설계하고, 공진 네트워크 종류에 따라 달라지는 출력 특성을 분석한다. 분석 결과를 바탕으로 IPT 방식의 양방향 무선전력전송을 위한 공진 네트워크를 선정하고 시뮬레이션을 통하여 선정한 네트워크의 적합성을 검증한다.

• Proceedings of the KIPE Conference
• /
• 2019.11a
• /
• pp.55-57
• /
• 2019

본 논문에서는 3.3[kW] on board charger(OBC)의 고전력 밀도 달성을 위한 LLC 공진형 컨버터의 최적 스위칭 주파수를 설계한다. 스위칭 주파수에 따라 달라지는 손실 양상 및 전력 밀도를 분석하기 위해 각 스위칭 주파수 별 반도체 소자 손실을 계산하고, 각 주파수에 적합한 변압기를 설계하여 주파수 변화에 따른 시스템 손실과 부피를 비교한다. 비교 결과를 바탕으로 최적 스위칭 주파수를 설계한다.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.25 no.5
• /
• pp.404-411
• /
• 2020

Inductive power transfer (IPT) systems for electric vehicles generally require zero phase angle (ZPA) frequency tracking control to achieve high efficiency. Current sensors are used for ZPA frequency tracking control. However, the use of current sensors causes several problems, such as switching noise, degrading control performance, and control complexity. To solve these problems, this study proposes ZPA frequency tracking control without current sensors. Such control enables ZPA frequency tracking without real-time control and achieves stable zero voltage switching operation closed to ZPA frequency within all coupling coefficient and load ranges. The validity of the proposed control algorithm is verified on LCCL-S topology with a 3.3 kW rating IPT experimental test bed. Simulation verification is also performed.

• Korean Journal of Environment and Ecology
• /
• v.15 no.4
• /
• pp.319-329
• /
• 2002

The vascular plants in the region of Guryongsan and Cheongoksan. Bonghwa-gun, Kyeongsangbuk-do, were consisted of 405 taxa; 96 families, 268 genus. 349 species. 51 varieties, 5 forms. From the floristic point of view, Guryoungsan and Cheongoksan belongs to the middle province in Korea. The rare and endangered plants appeared to 6 taxa were Dryopteris crassirhizoma, Iris ensata var. spontanea, Gastrodia elata, Rodgersia podophylla, Rhododendron micranthum and Scrophularia buergeriana investigated these area.

• Korean Journal of Environment and Ecology
• /
• v.3 no.1
• /
• pp.16-27
• /
• 1989

The flora of Kayasan National Park which was located at the southern part of Korea was investigated between April 30-31. August 10-14, and October 9-10. 1989. The number of vascular plants investigated in the present study was summarized as 96 families, 292 genera, 465 species, 72 varities, and 4 forms. The middle and Southern types of distribution pattern were the largest as of 9 families and 12 species. It was very interesting that the warm temperate types of species, as well as southern coast and island types of plant were introduced to this region.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1851-1856
• /
• 2004

Sedimentation phenomenon of suspended solids occurs by the gravitational force. Pollution particles are separated from slowly flowing wastewater in clarifier. Recently, the sludge suction collector is preferred rather than the scraper type sludge collector due to enhancement of the clarifier efficiency. The sludge suction collector is usually operated by the user's experiences without any scientific and/or technical consideration. To evaluate the performance of sludge suction collector, the three dimensional computer simulation was conducted by the finite volume method. To analyze the performance, the velocity vectors and the suction flow rates of the orifices were investigated. The result showed that each suction flow rate through out the collector was equivalent in the sludge suction collector and the efficiency of suction collector was good to remove high concentrated sludge in clarifier.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.5 no.3
• /
• pp.52-59
• /
• 2001

In this study, a technique has been developed to analyze the performance of the launching system using a gas generator of solid propellant. The physical model which described the thermodynamic behaviors of all launching devices from gas generator to canister and the dynamic behavior of missile was established, applying the empirical coefficients in the heat loss model. The processes of combustion, flow, and heat transfer inside the chamber of gas generator and the launching system were simulated by numerical method. The theoretical analysis guided the optimal design of gas generator and system, which made the launching system satisfy the requirements of good performance and high reliability.

• Journal of Plant Biology
• /
• v.24 no.1
• /
• pp.27-30
• /
• 1981

This paper is proposed to describe three new species, two varieties and one forma of flowering plants from central Korea and the Island of Cheju in southern Korea. The taxa of new plants are as follows: Astragalus koraiensis Y. Lee, sp. nov.; Astragalus nakaianus Y. Lee, sp. nov.; Commelina minor Y. Lee & Oh Y., sp. nov.; Cirsium rhinoceros Nakai var. albiflorum Y. Lee, var. nov.; Tripterospermum japonicum (Sieb. & Zucc.) Max. var. albiflorum Y. Lee, var. nov.; Adenophora remotiflora (Sieb. & Zucc.) Miq. form. albiflora Y. Lee, form. nov.