• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.2
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• pp.230-235
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• 2009

This paper describes an automatic finite element mesh generation for finite element analysis of three-dimensional structures. It is consisting of fuzzy knowledge processing, bubble meshing and solid geometry modeler. This novel mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of bubbles, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid structures. Bubble is generated if its distance from existing bubble points is similar to the bubble spacing function at the point. The bubble spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of finite element for three-dimensional solid structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for 3D geometry.

• The Journal of Korean Society for School & Community Health Education
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• v.21 no.1
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• pp.15-31
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• 2020

Background and objectives: One-person households are the fastest growing family type in Korea. They bring social concerns such as weakened social integration, increasing poverty and social isolation. They are not homogeneous but heterogeneous groups depending on their socio-demographic characteristics including generation. This study compared the life satisfaction level as well as factors affecting it among the three one-person household generations Methods: The 13th wave of the Korea Welfare Panel dataset with 1,187 respondents was utilized. For data analysis Chi-square test, analysis of variance and hierarchical regression analysis were employed. Generations are divided into three, namely young adult (20-39), the middle-aged (40-64) and the elderly (65 and over). Result: The life satisfaction level was highest among the young adult one-person household generation, followed by the middle-aged and the elderly generation. The common factors affecting life satisfaction of the three generations were physical as well as mental health, including self-esteem and depression. However, there were more factors different from generation to generation. As for the young adult, age, religion, and smoking were significant. As for the middle aged and the elderly, gender (male) and income were significant. Additionally, age, home-ownership and drinking were significant to the elderly generation. Conclusions: As there are differences as well as similarities among the three generations, policies for one-person households need to be devised considering these findings. For all generations, both physical and mental health policies are needed. For young adult strengthening social relations, providing decent jobs, and promoting anti-smoking policy are major agenda, and for the middle-aged and the elderly, assisting in social capital accumulation (for male), providing stable jobs and diverse leisure activities, and securing income. Additionally, for the elderly, expanding the social security system and housing support are needed.

• Journal of Power Electronics
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• v.14 no.2
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• pp.249-256
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• 2014

A novel topology generation method for the no dead-time three-phase AC/DC converter is proposed in this study. With this method, a series of no dead time topologies are generated and their operation principles are analyzed. The classic three-phase bridge AC/DC converter can realize a bidirectional operation. However, dead-time should be inserted in the driving signals to avoid the shoot-through problem, which would cause additional harmonics. Compared with the bridge topology, the proposed topologies lack the shoot-through problem. Thus, dead time can be avoided. All of the no dead time three-phase AC/DC converters can realize bidirectional operation. The operating principles of the converters are analyzed in detail, and the corresponding control strategies are discussed. Comparisons of waveform distortion and efficiency among the converters are provided. Finally, 9 KW DSP-based principle prototypes are established and tested. Simulation and experimental results verify the theoretical analysis.

• Journal of the Korean Institute of Rural Architecture
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• v.5 no.3
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• pp.22-33
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• 2003

I recognized necessity of the space planning to three-generation dwelling because of preservation of wholesome society sense of values of the younger generation indicated often to the point at issue by the change to nuclear family of present and by way to hand down thought of respect for the aged which is our traditional public morals. I wish to present basic data for storage space planning that resident's request and consciousness are reflected in such background. I investigated records in general concept, which is utilization pattern of storage space to achieve the function of these culture intermediation. The object of research is three-generation dwelling, such as 3L-K and 3L-DK as national residences that appear most generally in chongju city. The method of research was question investigation method to write utilization actual conditions and requirement of storage space directly. So I proposed suitable planning to resident's life style analyzing frequency, percentage and average distribution. When supply apartment house hereafter, it should be reflected wide selection by resident's characteristic and needed systematic storage space planning in consideration of user mainly. Also continuous and diversified researches that can improve quality of residence are required.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.472-476
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• 2012

In this paper, a sensorless control scheme for a three-phase bi-directional voltage-type PWM rectifier in wind power generation system that operates without the input AC voltage sensors (generator side) is described. The basic principles and classification of the PWM rectifier are analyzed, and then the three-phase mathematical model of the input AC voltage sensorless PWM rectifier control system is established. The proposed scheme has been developed in order to lower the cost of the three-phase PWM rectifier but still achieve excellent output voltage regulation, limited current harmonic content, and unity input power factor.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.4041-4059
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• 2019

Key establishment method based on channel reciprocity for time division duplex (TDD) system has earned a vital consideration in the majority of recent research. While most of the cellular systems rely on frequency division duplex (FDD) systems, especially the 5G network, which is not characterized by the channel reciprocity feature. This paper realizes the generation of a group secret key for multi-terminals communicated through a wireless network in FDD mode, by utilizing the nature of the physical layer for the wireless links between them. I consider a new group key generation approach, which using bitwise XOR with a modified pairwise secret key generation approach not based on the channel reciprocity feature. Precisely, this multi-node secret key agreement technique designed for three wireless network topologies: 1) the triangle topology, 2) the multi-terminal star topology, and 3) the multi-node chain topology. Three multi-node secret key agreement protocols suggest for these wireless communication topologies in FDD mode, respectively. I determine the upper bound for the generation rate of the secret key shared among multi-node, for the three multi-terminals topologies, and give numerical cases to expose the achievement of my offered technique.

• Journal of the Korean Home Economics Association
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• v.37 no.9
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• pp.85-101
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• 1999

The purpose of this study is to investigate how much traditional family ethics exist in morden society. For this goal, I have analyzed norm consciousness of the family among adolescent, middle and old generation. In this research, three kinds of questionnaire were used and the data were obtained from 1,661 samples of three generation groups living in Gyengnam area. The major findings obtained from this study are as follows: First, the filial piety and consciousness for supporting their parents were not changed at all in traditional family ethics. The filial piety and consciousness for supporting their parents are the most important family concepts without showing any difference in generation-gap in modem society. Second, the decreasing traditional norm consciousness of family was familism value. Specialty the familism value becomes weaker from old to younger generation. Third, the filial piety and familism value were shown to be the important factors to support their parents. These concepts showed same trends without showing generation-gap.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.145-153
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• 1995

An algorithm for the automatic generation of quadrilateral shell elements on three-dimensional sculptured surfaces has been developed, which is one of the key issues in the finite element analysis of structures with complex shapes such as automobile structures. Mesh generation on sculptured surfaces is performed in three steps. First a sculptured surface is transformed to a projection plane, on which the loops are subdivided into subloops by using the best split lines, and with the use of 6-node/8-node loop operators and a layer operator, quadrilateral finite elements are constructed on this plane. Finally, the constructed mesh is transformed back to the original sculptured surfaces. The proposed mesh generation scheme is suited for the generation of non-uniform meshes so that it can be effectively used when the desired mesh density is available. Sample meshes are presented to demonstrate the versatility of the algorithm.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2243-2257
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• 2016

This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.549-553
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• 1999

This paper describes a design method of grid-connected photovoltaic power generation systems with three phase inverter. A 3-phase 50kW photovoltaic power generation system including a DC/AC inverter is designed and made in order to investigate the system performance for grid connection. Also the control scheme of a three phase current-controlled PWM inverter is presented by using d-q transformation. The experimental waveforms show that the proposed system has stable behavior with an unit power factor in utility-interactive operation.