• 전력전자학회논문지
• /
• 제22권1호
• /
• pp.75-81
• /
• 2017

This paper presents a design and parallel control strategy of 1.8 kW low-voltage DC-DC converter (LDC) for mild hybrid electric vehicles to improve their power density, system efficiency, and operation stability. Topology and control scheme are important on the LDC for mild hybrid electric vehicles to achieve high system efficiency and power density because of their very low voltage and large current in input and output terminals. Therefore, the optimal topological structure and control algorithm are examined, and a detailed design methodology for the power and control stages is presented. A working sample of 1.8 kW LDC is designed and implemented by applying the adopted topology and control strategy. Experimental results indicate 92.45% of the maximum efficiency and 560 W/l of power density.

• 한국생물정보학회:학술대회논문집
• /
• 한국생물정보시스템생물학회 2004년도 The 3rd Annual Conference for The Korean Society for Bioinformatics Association of Asian Societies for Bioinformatics 2004 Symposium
• /
• pp.265-271
• /
• 2004

The interaction network of protein -protein plays an important role to understand the various biological functions of cells. Currently, the high -throughput experimental techniques (two -dimensional gel electrophoresis, mass spectroscopy, yeast two -hybrid assay) provide us with the vast amount of data for protein-protein interaction at the proteome scale. In order to recognize the role of each protein in their network, the efficient bioinformatical and computational analysis methods are required. We propose a systematic and mathematical method which can analyze the protein -protein interaction network rigorously and enable us to capture the biological and physical essence of a topological character and stability of protein -protein network, and sensitivity of each protein along the biological pathway of their network. We set up a Laplacian matrix of spectral graph theory based on the protein-protein network of yeast proteome, and perform an eigenvalue analysis and apply a perturbation method on a Laplacian matrix, which result in recognizing the center of protein cluster, the identity of hub proteins around it and their relative sensitivities. Identifying the topology of protein -protein network via a Laplacian matrix, we can recognize the important relation between the biological pathway of yeast proteome and the formalism of master equation. The results of our systematic and mathematical analysis agree well with the experimental findings of yeast proteome. The biological function and meaning of each protein cluster can be explained easily. Our rigorous analysis method is robust for understanding various kinds of networks whether they are biological, social, economical...etc

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.285-285
• /
• 2013

Recently, hexagonal boron nitride (h-BN), which is III-V compound of boron and nitride by strong covalent sp2 bonds has gained great interests as a 2 dimensional insulating material since it has honeycomb structure with like graphene with very small lattice mismatch (1.7%). Unlike graphene that is semi-metallic, h-BN has large band gap up to 6 eV while providing outstanding properties such as high thermal conductivity, mechanical strength, and good chemical stability. Because of these excellent properties, hBN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Low pressure and atmospheric pressure chemical vapor deposition (LPCVD and APCVD) methods have been investigated to synthesize h-BN by using ammonia borane as a precursor. Ammonia borane decomposes to polyiminoborane (BHNH), hydrogen, and borazine. The produced borazine gas is a key material that is a used for the synthesis of h-BN, therefore controlling the condition of decomposed products from ammonia borane is very important. In this paper, we optimize the decomposition of ammonia borane by investigating temperature, amount of precursor, and other parameters to fabricate high quality monolayer h-BN. Synthesized h-BN is characterized by Raman spectroscopy and its absorbance is measured with UV spectrophotometer. Topological variations of the samples are analyzed by atomic force microscopy. Scanning electron microscopy and Scanning transmission Electron microscopy are used for imaging and analysis of structures and surface morphologies.

• 한국자기학회지
• /
• 제26권2호
• /
• pp.39-44
• /
• 2016

대표적 열전물질인 비스무스 텔루라이드에 자성원자를 도핑한 합금에 대한 구조 및 전자적 그리고 자기적 성질에 관한 연구는 고효율 열전물질의 개발이라는 목적뿐만 아니라 특이한 자기적 상호작용 규명 및 위상절연체 분야에서도 큰 관심을 끌고 있다. 본 연구에서는 희토류 원자로서 매우 국소화된 f 전자를 갖는 Gd이 Bi을 치환하여 도핑된 비스무스 텔루라이드 합금의 자성 안정성을 밀도범함수(Density Functional Theory)에 입각하여 제일원리적으로 연구하기 위하여 모든 전자(all-electron) FLAPW(full-potential linearized augmented plane-wave) 방법을 이용하여 전자구조 계산을 수행하였다. 전자간 교환-상관 상호작용은 일반기울기 근사법(Generalized Gradient Approximation)을 도입하여 계산하였으며, 국소화된 f 전자를 기술하는 데 필요한 Hubbard+U 보정과 스핀-궤도 각운동량 상호작용은 제2 변분법적 방법을 이용하여 고려하였다. 계산 결과, 강자성 안정성을 보이는 Gd 덩치계와 다르게 이 합금은 강자성과 반강자성의 총에너지 차이가 ~1 meV/Gd 정도의 아주 작은 값으로 얻어져서, 그 자성 안정성은 결함이나 strain 등에 의한 구조변화에 민감하게 의존하여 변할 수 있음을 알 수 있었다. 특히 Gd 스핀자기모멘트는 덩치에서의 값에 비해 감소하였고, Gd에 가장 가까운 Te에 유도 자기모멘트가 형성되는 것으로 미루어 Te를 매개로 한 자성상호작용이 자성 안정성을 결정하는 데에 중요한 역할을 하는 것으로 예측할 수 있었다.