• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1060-1062
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• 1996

This paper presents a discrete adaptive observer for MIMO system of an IM model in DQ reference model. The IM model in the stationary frame is discretized and it is transformed into the canonical observer form. The unknown parameter is choosen as rotor speed. The adaptive law for parameter adjustment is obtained as a set of recursive equations which are derived by utilizing an exponentially weighted normalized least-square method. The proposed adaptive observer converges rapidly and is also shown to track time-varying plant parameter quickly. Its effectiveness has been demonstrated by computer simulation.

• Journal of Korean Institute of Industrial Engineers
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• v.37 no.3
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• pp.163-170
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• 2011

This paper proposes a modified version of Particle Swarm Optimization (PSO) called Information Diffusion PSO (ID-PSO). In PSO algorithms, premature convergence of particles could be prevented by defining proper population topology. In this paper, we propose a variant of PSO algorithm using a new population topology. We draw inspiration from the theory of information diffusion which models the transmission of information or a rumor as one-to-one interactions between people. In ID-PSO, a particle interacts with only one particle at each iteration and they share their personal best solutions and recognized best solutions. Each particle recognizes the best solution that it has experienced or has learned from another particle as the recognized best. Computational experiments on the benchmark functions show the effectiveness of the proposed algorithm compared with the existing methods which use different population topologies.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.149-150
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• 2015

압전 마이크로머신 초음파 트랜스듀서(Piezoelectric micro-machined ultrasonic transducers)는 DC 바이어스 전압을 인가해야 구동되는 특성을 가지고 있다. 따라서 초음파 트랜스 듀서를 구동하기 위한 전력증폭기는 DC 바이어스 전압이 요구되므로 기존의 전력증폭기에 비해 효율이 매우 낮아지게 된다. 이를 해결하기 위해 본 논문에서는 압전 마이크로머신 초음파 트랜스듀서를 구동하기 위한 고효율 전력증폭기를 제안한다. 전력증폭기는 AMP부와 전원부로 나뉘며, AMP부는 Class B Amp를 사용하여 높은 증폭 선형성을 갖는다. 전원부는 Amp를 구동하기위한 DC-DC converter가 에너지 회수 동작을 하므로 전력증폭기의 효율을 높일 수 있다. 본 연구에서는 압전 마이크로머신 초음파 트랜스듀서를 구동하기 위한 전력증폭기 회로를 제시하고 시뮬레이션과 실험을 통해 동작 특성을 검증한다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.101-102
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• 2012

수중에서는 대기와 달리 매질의 차이로 인하여 통신의 제약이 따르므로 초음파를 이용하여 정보를 송 수신한다. 수중통신을 하기 위해서는 신호를 증폭시키는 전력증폭기와 증폭된 전기 신호를 초음파로 변환시키는 트랜스듀서가 필요하다. 전력증폭기는 선형적인 출력이 보장되어야 하며, 수중에서의 발열과 연료문제로 인하여 높은 효율로 동작하여야 한다. 하지만 기존의 전력증폭기는 인가되는 고정전압과 출력전압의 차이로 인해 손실이 발생하여 효율이 저하된다. 본 논문에서는 수중 통신에 적합한 특성을 가진 APEX사의 Class B push-pull 타입의 MP108A증폭기를 사용하여 선형적인 출력 특성을 보장하며 넓은 대역폭을 갖는 전력증폭기를 구현하고, 실험을 통해 특성을 확인하였다.

• Communications for Statistical Applications and Methods
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• v.17 no.3
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• pp.319-326
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• 2010

In this paper, a new group sampling plan for the lot acceptance is proposed for the time truncated life test, which can be utilized when multi-item testers are implemented. The design parameters are found using the two-point approach such that the producer's and consumer's risks are satisfied simultaneously at the acceptable reliability level and the lot tolerance reliability level, respectively. The case of Weibull distribution is described to illustrate the procedure that can be used when the quality level is expressed by a multiple of the specified life. The advantage of the proposed plan is demonstrated by comparing with the existing plan in terms of the sample size required. The tables are constructed and some examples are given to illustrate the procedure developed here.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.142.1-142.1
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• 2013

The patterning and doping technique enables graphene to replace the metal electrode as a charge injection layer in the pentacene based thin film transistor. However, it is known that pentacene molecules form lying-down coordination on the graphene surface. Pentacene thin film showed that the highly occupied molecular orbital is 0.2~0.4 eV lower in the standing up coordination than in the lying down coordination. Here, we report the formation of standing-up coordination and lowered HOMO level of the pentacene layer grown on the graphene layer doped with CYTOP.

• Journal for History of Mathematics
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• v.30 no.1
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• pp.1-15
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• 2017

The original proof-argument of Riemann in 1851 for the Riemann mapping theorem, one of the most central theorems in Complex analysis, was found faulty and essentially buried underneath the proof by $Carath{\acute{e}}odory$ of 1929, now accepted as the "textbook" proof. On the other hand, the original Riemann's "proof" was rediscovered and made correct by R.E. Greene and the author of this article in 2016. In this article, we try to shed lights onto the history related to the Riemann mapping theorem and the surrounding developments of 1850-1930 by reflecting upon the main flow of ideas and methods of the proof by R. E. Greene and K.-T. Kim.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.598-600
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• 2001

DNA chip technology enables us to monitor thousands of gene expressions per sample simultaneously. Typically, DNA microarray data has at least several thousands of variables (genes) wish relatively smal1 number of samples. Thus feature (gene) selection by dimensionality reduction is necessary for efficient data analysis. In this paper we employ the partial least squares (PLS) method for gene selection and the principal component analysis (PCA) method for classification. The useful behavior of the PLS is verified by computer simulations.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.161-162
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• 2015

본 논문은 수중음향센서용 전력증폭기를 위한 멀티레벨 가변 출력전압 AC/DC 컨버터를 제안한다. 제안하는 AC/DC 컨버터는 멀티레벨 가변출력전압을 얻기 위해 2개의 flying-capacitor 3-level converters와 하나의 다이오드 브리지 회로로 구성되어 있다. 또한 본 논문에서는 제안하는 AC/DC 컨버터의 상세 회로도와 설계 가이드라인을 제시하였다.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.116-121
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• 2012

Equilibria between Mn-Si melts and $MnO-SiO_2$ slags were studied at 1673 K and 1773 K in MnO crucibles to accurately determine the thermodynamic property of the Mn-Si melts. The Unified Interaction Parameter Formalism (UIPF) was used to describe the thermodynamic property of the Mn-Si liquid. Using the UIPF, the experimental results obtained in the present study were thermodynamically analyzed to determine the activity coefficient of Si at infinite dilution and the 1st- and 2nd-order self-interaction parameters of Si in the Mn-Si melts.