• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.232-238
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• 2001

Experimentally it is well known that the magnetic properties significantly deteriorate when nanocomposite bonded magnet are made from nanocomposite ribbon. A decrease in maximum energy product of F $e_3$B+N $d_2$F $e_{14}$B nanocomposite from 14 MGOe in nanocomposite ribbon to 6.5 MGOe in powder compact was fecund to be general. Thus, the present study is focused on finding out the root of exchange decoupling of N $d_4$F $e_{73.5}$ $Co_3$H $f_{0.5}$G $a_{0.5}$ $B_{18.5}$ nanocomposite powder compacts. The exchange decoupling behavior of the powder compact of F $e_3$B+N $d_2$F $e_{14}$B composition was studied by measuring DC demagnetization and isothermal remanent demagnetization curves, which are essential for plotting produced $\delta$M curve. From the $\delta$M plot the deterioration in the magnetic properties resulted from the fact that the magnetostatic interaction became dominant rather thanthe exchange interaction in powder compact. It is concluded that the demagnetization behavior governed by the dominant magnetostatic interaction reduced the remanence magnetization, which caused the reduction of maximum energy Product of the powder compact. We also found that the elimination of residual stress which is unavoidably accumulated during grinding process enhanced the magnetic properties considerably.bly.bly.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.4
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• pp.294-297
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• 2021

A grid voltage estimation method for modular plug-in active power decoupling (APD) circuits is proposed in this study as direct replacements of electrolytic capacitors. Since modular plug-in APD circuits cannot have additional grid voltage sensors and should be operated independently without information exchange with the front-end converter, it is impossible to obtain the phase information of the grid directly. Therefore, the proposed method uses the second-order harmonic component of the DC-link voltage to estimate the grid voltage necessary to control the APD circuit. By employing the proposed method, the concept of modular plug-in APD circuits can be realized and implemented without direct detection of the grid voltage. The experimental results based on hardware-in-the-loop simulation (HILS) validate the effectiveness of the proposed control method.

• The Southeast Asian review
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• v.23 no.1
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• pp.313-362
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• 2013

중국의 위안화 국제화(지역화)는 중국경제의 성장 및 중국정부의 전략적, 정책적 지원에 따라 가속화되고 있다. 특히 최근 ASEAN과 중국 간 경제통합이 빠르게 진행됨에 따라 동남아시아 지역에서 중국 위안화의 유통이 확대되고 있다. 본 논문은 이러한 위안화 유통의 확대와 관련하여 위안화 국제화(지역화)가 동남아시아 국가들의 환율정책에 미치는 영향을 분석하고자 한다. 동 지역에서 위안화의 유통의 확대(위안화 국제화)가 유의미하다면 달러화 대비 위안화 환율과 달러화 대비 동남아시아 개별국가통화 환율 간에 인과적 관계를 보일 것이다. 왜냐하면 환율정책의 중요한 목적 중 하나는 환율의 안정적 운영인데 환율결정에 있어 위안화의 비중이 크다면 그 만큼 달러화 대비 개별국가통화 간 환율의 영향도 커지기 때문이다. 본 논문은 이러한 가설을 바탕으로 두 환율변수 간 공적분 분석 등 계량분석을 통해 가설검정을 실시하였다. 분석 결과 2008년 글로벌 금융위기 이전(2005.8~2008.6)에는 두 환율변수 간 동조화 현상이 나타나는데 비해 그 이후(2010.7~2012.6)는 비동조화 현상이 나타나는 것으로 나타났다. 이는 2010년 이후 유럽의 재정 위기 등 글로벌 경기침체로 인해 동남아시아 국가들의 환율 정책 우선순위가 환율의 안정적 운영에서 경기회복을 위한 수출증가 및 이를 위한 개별국가 통화의 환율절하로 전환하였음을 의미한다고 할 수 있다. 또한 중국과의 국경무역 등 경제적 영향이 상대적으로 큰 GMS(라오스, 미얀마, 베트남)국가들의 경우 그 외 아세안 7개국들에 비해 두 환율변수 간 동조화 현상이 강하게 나타나는 것으로 분석되었다. 이는 이들 국가들이 상대적으로 기타 국가들에 비해 위안화 국제화에 대한 민감도가 높다는 것을 의미한다. 향후 동남아시아 국가들의 경기가 회복되고 위안화의 국제화가 가속되면 두 환율 간 동조화 기조는 강화될 것으로 예상된다.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.113.1-113.1
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.200-201
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• 2004

The $H_{EB}$ was investigated for exchange coupling $20\;{\AA}\;Fe/x\;{\AA}\;NiO\;(type-I samples)$, $20\;{\AA}\;Fe/x\;{\AA}$ nonmagnetic layer $(MgO, Ag, Cu)/(500-x{\AA})$ NiO (type-II smaples). In type-I samples, the $H_{EB}$ is long-range coupling when looking from the point of view of the AFM. The $H_{EB}$ consistent with a generalized Meiklejohn-Bean approach. The critical thickness, which $H_{EB}$ is observed, is $130\;{\AA}$. In type-II samples, MgO layer more decouples the thin interfacial NiO from bottom NiO than other nonmagnetic layer. Nd the decoupling of Ag smallest. This means that the Ag layer has strong coupling the thin interfacial NiO with bottom NiO.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.405-412
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• 1992

The problem we consider in this paper is more demanding than the problem of input-output linearization with state equivalence recently solved by Cheng, Isidori, Respondek, and Tarn. We request that the MIMO nonlinear system, for which the problem of input-output linearization with state-equivalence is solvable, can be decoupled. In exchange for further requirement like this, our problem produces more usable and informative results than the problem of input-output linearization with state-equivalence. We present the necessary and sufficient conditions for our problem to be solvable. We characterize each of the nonlinear systems satisfying these conditions by a set of parameters which are invariant under the group action of state feedback and transformation. Using this set of parameters, we can determine directly the unique one, among the canonical forms of decouplable and controllable linear systems, to which a nonlinear system can be transformed via appropriate state feedback and transformation. Finally, we present the necessary and sufficient conditions for our problem to be solvable with internal stability, that is, for stable decoupling.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.4
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• pp.233-246
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• 2009

The partitioning of evapotranspiration (ET) into evaporation (E) and transpiration (T) is critical in understanding the water cycle and the couplings between the cycles of energy, water, and carbon. In forests, the total ET measured above the canopy consists of T from both overstory and understory vegetation, and E from soil and the intercepted precipitation. To quantify their relative contributions, we have measured ET from the floors of deciduous and coniferous forests in Gwangneung using eddy covariance technique from 1 June 2008 to 31 May 2009. Due to smaller eddies that contribute to turbulent transfer near the ground, we performed a spectrum analysis and found that the errors associated with sensor separation were <10%. The annual sum of the understory ET was 59 mm (16% of total ET) in the deciduous forest and 43 mm (~7%) in the coniferous forest. Overall, the understory ET was not negligible except during the summer season when the plant area index was near its maximum. In both forest canopies, the decoupling factor ($\Omega$) was about ~0.15, indicating that the understory ET was controlled mainly by vapor pressure deficit and soil moisture content. The differences in the understory ET between the two forest canopies were due to different environmental conditions within the canopies, particularly the contrasting air humidity and soil water content. The non-negligible understory ET in the Gwangneung forests suggests that the dual source or multi-level models are required for the interpretation and modeling of surface exchange of mass and energy in these forests.