• Journal of Power Electronics
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• v.17 no.3
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• pp.725-732
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• 2017

This paper proposed a real-time, low-cost, fast transistor open-circuit fault diagnosis method for voltage-source inverter fed induction motors. A transistor open-circuit changes the symmetry of the inverter topology, leading to different similarities among three phase load currents. In this paper, dynamic time warping is proposed to describe the similarities among load currents. The proposed diagnosis is independent of the system model and needs no extra sensors or electrical circuits. Both simulation and experimental results show the high efficiency of the proposed fault diagnosis method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.9
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• pp.3782-3796
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• 2020

A three-dimensional (3D) reconstruction is an important research area in computer vision. The ability to detect and match features across multiple views of a scene is a critical initial step. The tracking matrix W obtained from a 3D reconstruction can be applied to structure from motion (SFM) algorithms for 3D modeling. We often fail to generate an acceptable number of features when processing face or medical images because such images typically contain large homogeneous regions with minimal variation in intensity. In this study, we seek to locate sufficient matching points not only in general images but also in face and medical images, where it is difficult to determine the feature points. The algorithm is implemented on an adaptive threshold value, a scale invariant feature transform (SIFT), affine SIFT, speeded up robust features (SURF), and affine SURF. By applying the algorithm to face and general images and studying the geometric errors, we can achieve quasi-dense matching points that satisfy well-functioning geometric constraints. We also demonstrate a 3D reconstruction with a respectable performance by applying a column space fitting algorithm, which is an SFM algorithm.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.354-360
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• 2002

The piezoelectric composites had many advantages in comparison with conventional piezoelectric ceramics and piezopolymers for ultrasonic transducers used in NDT and in medical ultrasionic imaging. The electromechanical coupling coefficient should be high and the acoustic impedance should be low in these applications. However, the cross-coupling with spurious oscillations caused by laterally running plate waves exhibited complex motions in the surface of piezoelectric composites with coarse lateral spatial scale. The thickness mode electromechanical coupling coefficient of 1-3type of piezoelectric compoistes were 0.36 to 0.64, and the acoustic impedance of them were 9.8 to 22.7 MRayl. The lateral resonance frequency of 1-3 type piezoelectric composites shifted to high frequency region with decreasing lateral spatial scale.

• Journal of Engineering Education Research
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• v.13 no.6
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• pp.143-151
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• 2010

This paper presents a case study on the assessment of program outcomes using the capstone design course based on 16-year management experience and improvements of the school of mechanical design and automation engineering in the seoul national university of science and technology. First, the program outcomes related with the capstone design course are introduced, and the assessment methods and items are described. Based on them, the assessment results in 2008 were obtained and a strategy to improve the results were built after analyzation. As for the strategy, we revealed the assessment items and good examples in an internet web site in advance. As a result, we were able to obtain about 3.3% improved assessment results in 2009. Finally, the validity, efficiency, internal stability, and sustainability of the assessment of the program outcomes using the capstone design course are addressed in terms of a notion of the course-embedded assessment.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1505-1514
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• 2019

The permanent magnet synchronous motor (PMSM) is widely used in various fields and the proportional-integral (PI) controller is popular in PMSM control systems. However, the motor parameters are usually unknown, which can lead to a complicated PI controller design and poor performance. In order to design a PI controller with good performance when the motor parameters are unknown, a control algorithm based on stability margin is proposed in this paper. First of all, based on the mathematical model of the PMSM and the least squares (LS) method, motor parameters are estimated offline. Then based on the estimation values of the motor parameters, natural angular frequency and phase margin, a PI controller is designed. Performance indices including the natural angular frequency and the phase margin are used directly to design the PI controller in this paper. Scalar functions of the d-loop and the q-loop are selected. It can be seen that the designed controller parameters satisfy Lyapunov large scale asymptotic stability theory if the natural angular frequencies of the d-loop and the q-loop are large than 0. Experimental results show that the parameter estimation method has good accuracy and the designed PI controller proposed in this paper has good static and dynamic performances.

• Korean Journal of Construction Engineering and Management
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• v.23 no.4
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• pp.57-64
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• 2022

A plant factory is a facility that creates an artificial environment in a controlled space and produces plants systematically through automated facilities. However, automation in the cultivation process is insufficient compared to the internal environment control technology in plant factories. This causes the problem of an increase in operating costs due to the input of a large number of workers. Therefore, this study aims to evaluate economic feasibility by comparing before and after introducing automation in the cultivation process of plant factories. The target plant factory to be analyzed was selected, and the break-even point analysis method was used by comparing the cost required compared to the operating period. As a result, the break-even point was analyzed to be 3.4 years when automation was introduced into six processes for plant cultivation. Therefore, it can be judged that the introduction of automation is excellent in terms of economic feasibility when the target plant factory has been operated for more than 3.4 years. This study is expected to be used as basic data to analyze the economic feasibility of introducing automation in domestic and foreign plant factories.

• Transactions on Electrical and Electronic Materials
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• v.17 no.6
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• pp.335-340
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• 2016

The vibrational energy is prevalent in the natural environment, which is studied by energy researchers as a new energy resource in recent years. Vibration generation utilizes electromagnetic induction technology, piezoelectric technology and certain characteristics of smart materials to convert mechanical energy into electrical energy. In this paper, a new method of using MSMA (magnetic shape memory alloy) to generate electricity is proposed and the principle of generating electricity is demonstrated. Martensitic variants and magnetic domain characteristics of MSMA are analyzed. Combining with Gibbs free energy function thermal theory, the mathematics model of MSMA vibration generator is established. The basic structure of MSMA vibration generator is designed and simulation is done to analyze that the effects of generator output voltage when the input amplitude and frequency of vibration stress change. The simulation experiments verify the feasibility of using MSMA to make the micro vibration generators and the correctness of the mathematical model, which lays a good foundation for the further research and application of MSMA vibration generator.

• Journal of Information Management
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• v.26 no.4
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• pp.64-99
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• 1995

As advanced information technology has been developing rapidly, libraries are moving from an ownership-centered information service toward information access service. Consequently, integrated automation systems of information centers that give not only cataloging information of their own collections but also various electronic information have appeared. In this study, a model of integrated automation system of an information center is suggested in terms of information types and cost, by taking case studies of some domestic and foreign libraries. Furthermore, the MIPOS Information & Resource Center System of POSCO Group is introduced as a good example of integrated automation systems in Korea.

• Journal of the Korean housing association
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• v.16 no.6
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• pp.139-147
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• 2005

The purpose of this study was to determine the factors which affect older people's innovativeness toward technologies and factors which affect their demand of home automation system. The study collected data from 289 persons who are 50 years and older with experience living in an apartment currently or past. Innovativeness toward technologies of respondents were low level and the significant factors which affected their innovativeness were age, education, employment, marital status, current housing types, health status of self and spouse, consideration of home automation system for a newly-moved house. Education, employment types, consideration of home automation system for a newly-moved house, and plan for moving were the major factors which affect demand of home automation system. Also, older people's innovativeness toward technologies was the most important factor which affected demand of home automation system. Th results of this study explained that high technologies which are adopted in residential environment should be considered target consumers' abilities and attitudes for acceptance toward new ideas. Especially, for older consumers, various ideas to expand their understanding of new technologies should be developed and the positive effect of technologies to increase the quality of their later life should be educated.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2005.11a
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• pp.67-72
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• 2005

The purpose of this study was to determine the factors which affect older people's innovativeness toward technologies and factors which affect their demand of home automation system. The study collected data from 289 persons who are 50 years and older with experience living in an apartment currently or past. Innovativeness toward technologies of respondents were low level and the significant factors which affect their innovativeness were age, education, employment, marital status, current housing types, health status of self and spouse, consideration of home automation system for a newly-moved house. Education, employment types, consideration of home automation system for a newly-moved house, and plan for moving were the major factors which affect demand of home automation system. Also, older people's innovativeness toward technologies was the most important factors which affect demand of home automation system. Th results of this study explained that high technologies which are adopted in residential environment should be considered target consumers' abilities and attitudes for acceptance toward new ideas. Especially, for older consumers, various ideas to expand their understanding of new technologies should be developed and the positive effect of technologies to increase the qualify of their later life should be educated.