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Sub-domain reduction method in non-matched interface problems
Hyungi Kim,조맹효 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.2
A sub-domain scheme combined with a reduced system is proposed for non-matched interface problems. A twolevel condensation scheme (TLCS) is employed for the selection of primary degrees of freedom of each sub-domain. The degrees of freedom of each domain are divided into primary, secondary and interface degrees of freedom. After the reduced system is constructed in subdomain-level, the penalty frame method, which utilizes a conventional FEM solver, is employed for assembling non-matched subdomains. The present method can construct the reduced system of each domain without coupling with adjacent subdomains. Thus it is remarkably efficient in computation time and does not require a full memory of global system. Numerical examples demonstrate that the proposed method saves computational cost effectively and provides a reduced system which predicts the accurate eigenvalues of global system.
A Study on PID Controller system for DC-DC Converter Using Microcontroller
Hyungi Kim,Yonghui Lee 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
This paper shows a method of using microcontroller to perform simple SMPS control functions. Reliable, efficient well regulated DC-DC converter power conversation equipment is critical for mission on most space platforms. As platforms especially manned spacecraft, it becomes more sophisticated, reliable operation of complete power management and distribution systems (PMAD).
Improvement of reduction method combined with sub-domain scheme in large-scale problem
Kim, Hyungi,Cho, Maenghyo John Wiley Sons, Ltd. 2007 International Journal for Numerical Methods in Eng Vol.70 No.2
<P>For a few decades, various approximate techniques have been developed to calculate the eigenvalues in a reduced manner. In order to construct reliable reduced systems it is essential to select the proper primary degrees of freedom (PDOFs). Unless the PDOFs are selected properly, the selection of PDOFs might be localized and the eigenvalue prediction might emphasize excessively the lower modes or lose the important modes. Moreover, sometimes, it takes considerable amount of computing time to construct a reduced system in large-scale problem. These troubles in constructing reduced system can be avoided by applying reduction scheme in sub-domain level. After dividing global system into a number of sub-domains, reduced system which has only the PDOFs is constructed in each sub-domain. This paper presents new algorithms to construct efficient reduction system through three different schemes. They are version 1, version 2 and version 3 systems. The version 3 system is constructed by combining the advantages of the version 1 and the version 2 systems. Numerical examples demonstrate that the proposed version 3 method saves computational cost effectively and provides a reduced system which can predict accurate eigenvalues of global system. Copyright © 2006 John Wiley & Sons, Ltd.</P>
Hyungi Min,Wonjae Hwang,Min-Suk Kim,Jeong-Gyu Kim 한국환경생물학회 2017 환경생물 : 환경생물학회지 Vol.35 No.1
Climate change is the biggest concern of the 21st century. Greenhouse gas (GHG) emissions from various sectors are attracting attention as a cause of climate change. The DeNitrification-DeComposition (DNDC) model simulates GHG emissions from cropland. To study future GHG emissions using this simulation model, various factors that could change in future need to be considered. Because most problems are from the agricultural sector, DNDC would be unable to solve the factor-changing problem itself. Hence, it is necessary to link DNDC with separate models that simulate each element. Climate change is predicted to cause a variety of environmental disasters in the future, having a significant impact on the agricultural environment. In the process of human adaptation to environmental change, the distribution and management methods of farmland will also change greatly. In this study, we introduce some drawbacks of DNDC in considering future changes, and present other existing models that can rectify the same. We further propose some combinations with models and development sub-models.
Fluorescent Fluoride Sensor Based on Indolizine Core Skeleton for Bioimaging
Hyungi Kim,Minchul Shin,Eunha Kim 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.1
Schematic representation of fluoride anion sensing with Silyl-KIz in live cell