• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.582-585
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• 2012

The aluminum extruded panel used for a high speed train shows the largest contribution to sound insulation performance of the train body. However, comparing with the flat panel having the same weight, the transmission loss falls sharply in the local resonance frequency band. Such fall of transmission loss can be improved by increasing the damping of local resonance. This study examines the charging effect of an urethane foam on the aluminum extruded panel of a high speed train. We charged the urethane foam with different mass density and in different way in the core part of the extruded panel. We measure the transmission loss and compare the sound insulation performance according to the density and charging method. Finally, Improvement effect of the transmission loss is compared and analysed in aspect of weight increment.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.27-28
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• 2015

In this paper a high efficiency wireless on-board charger for Electric Vehicle (EV) is proposed and the theoretical analysis based on the two-port network model to come up with suitable design for the battery charge application is presented. The proposed Wireless Power Transfer (WPT) method has adopted four-coil system with air core and its superior performance is proved by comparing it to the conventional two-coil system by the mathematical analysis. In addition, since the proposed WPT converter is able to operate at an almost constant frequency regardless of the load, CC/CV charge of the battery can be simply implemented. A 6.6kW prototype is implemented with 20cm air gap to prove the validity of the proposed method. The experimental results show that the dc to dc conversion efficiency of the proposed system achieves 97.08% at 3.7 kW.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.6
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• pp.255-261
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• 2005

Recently, the RF inductive discharge or inductively coupled plasma continues to attract growing attention as an effective plasma source in many industrial applications, the best known of which are plasma processing and lighting technology. To the point of lighting sources, the ring-shaped electrodeless fluorescent lamps utilizing an inductively coupled plasma have been objects of interest and research during the last decades, mainly because of their potential for extremely long life, high lamp efficacies, rapid power switching response. In this paper, maxwell 3D finite element analysis program (Ansoft) was used to obtain electromagnetic properties associated with the coil and nearby structures. The electromagnetic emitting properties were presented by 3D simulation software operated at 250 kHz and some specific conditions. The electromagnetic field in the ferrite core was shown to be high and symmetric. An LS-100 luminance meter and a Darsa-2000 spectrum analyzer were used in the experiment. According to data on the lamp tested using high magnetic field ferrite, the optical and thermal wave fields were shown to be high around the ring-shaped electrodeless fluorescent lamp. The optical or light field was high at the center of the bulb rather than around the ferrite core. The light conditions of the bulb were assumed to be complex, depending on the condition of the filler gas, the volume of the bulb, and the frequency of the inverter. Our results have shown coupling between the gas plasma and the field of the light emitted to be nonlinear.

• Journal of Science Education
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• v.44 no.2
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• pp.157-166
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• 2020

In this study, we analyzed the reflection degree of science core competencies, which is presented in second grade middle school science textbooks, and the perception of science core competencies of second year middle school students. To do this, we analyzed the frequency of presentation of science core competencies in middle school second grade textbooks, and surveyed 400 students from three schools in Chungnam area to find out their perception of science core competency. The survey consisted of 15 questions consisting of a five-step Likert scale and 5 ranking questions. The survey analyzed the responses of 327 people who responded faithfully and conducted a post-interview survey to interpret the survey results. The main findings are as follows: First, in the second grade middle school science textbook, the proportion of 'scientific thinking', 'scientific inquiry,' and 'scientific communication' is large, and the students are perceived to have a high proportion of 'scientific thinking,' 'scientific inquiry,' and 'scientific problem solving' in the textbook. Second, students recognize that the proportion of 'scientific inquiry' and 'scientific problem solving' in the evaluation conducted in school was high, and the proportion of 'scientific communication' and 'scientific participation and lifelong learning' was very low. Third, the most important competency in science that students perceive is the 'scientific problem solving,' the competency they wanted most from science is the 'scientific inquiry,' and the competency most needed to live in future society is the 'scientific communication.' Fourth, in the case of 'scientific participation and lifelong learning,' it is an important element of science literacy, but the proportion of consisting science textbooks is low, and students are not aware of the importance or necessity in science.

• Journal of the Korea Convergence Society
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• v.12 no.5
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• pp.239-254
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• 2021

The aim of this study is to provide basic data for college life adaptation support measures at the college level by identifying college life adaptation status, the relevance of university life adaptation and the core competencies. In order to ahieve this aim there are three objectives. This study is a research study to understand the relationship between college life adaptation and core competencies of college students before and after the coronavirus. The subject of this study was 171 university students from Seoul, Gyeonggi, and Honam. Data was collected through an untact questionnaire, and data analysis was performed using the SPSSWIN 25.0 program for mean, descriptive statistics, frequency analysis, T-test, correlation, and regression analysis. As a result, first, the difficulty of "emotional adaptation" before the coronavirus was high, and the difficulty of "academic adaptation" was high after the coronavirus. Second, the core competencies of college students were highest in the order of 'interpersonal relationship competency', 'problem solving competency', and 'information communication competency'. Third, as a result of analysis of the relationship between core competency factors and adaptation to university life, difficulties in social adaptation were found both before and after the coronavirus. After the corona, difficulties in adapting to school and learning new skills appeared. In conclusion, in order for university students to adapt to university life in the post-corona era, university-level support is needed to reinforce interpersonal relations competencies in unrect situations, reinforce information and communication competencies to promote academic adaptation, and reinforce new skills acquisition competencies.

• Journal of Power Electronics
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• v.8 no.3
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• pp.217-227
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• 2008

The electric power subsystems (EPS) of most remote sensing satellites consist of a solar array as a source of energy, a storage battery, a power management and control (PMC) unit and a charge equalization unit (CEU) for the storage battery. The PMC and CEU use high frequency transformers in their power modules. This paper presents a design, implementation and testing results of a high frequency transformer for the EPS of satellite applications. Two approaches are used in the design process of the transformer based on the pre-determined transformer specifications. The transformer is designed based on an ETD 29 ferrite core. The implemented transformer consists of one center-tapped primary coil with eleven center-tapped secondary coils. The offline calculation results and measured values of R, L for transformer coils are convergence. A test circuit for measuring the transformer parameters like voltage, current and B-H hysteresis was implemented and applied. The test results confirm that the voltage waveforms of both primary and secondary coils were as desired. No overlapping occurred between the control signal and the transformer, which was not saturated during testing even during a short circuit test of the secondary channels. The dynamic B-H loop characteristics of the used transformer cores were measured. The sample test results are given in this paper.

• Progress in Superconductivity and Cryogenics
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• v.13 no.2
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• pp.9-12
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• 2011

Superconducting motor has a lot of benefits from high power density for ship propulsions, so a number of research project are in progress worldwide. Despite of all the benefits, there is always a difficulty of cryo-moving part for conventional air-core superconducting synchronous motors. In order to get rid of this moving cryogenic part, we propose a homopolar superconducting synchronous motor, which has high temperature superconducting armature and field coils. The rotor is supposed to be made of iron only and excited by the stationary HTS field coils. The stationary field coils make the cooling system simple and easy to realize because there is no cryo-moving part. A design result of a 10 hp homopolar synchronous motor is presented in this paper. The self and mutual inductance of the motor having the size of air gap as variable parameter are calculated by a 3-dimemsional finite element method. The value of design variables such as the dimension of a motor and the number of turns, etc. is decided by performing the coordinate transformation of the calculated inductance. The operating frequency is supposed to be below 5 Hz for low rotating speed which is needed for a purpose of ship propulsion. Low frequency also has the benefit of low AC losses.

• Journal of the Korean Magnetics Society
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• v.21 no.2
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• pp.77-82
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• 2011

The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-to-particle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

• Journal of Oriental Neuropsychiatry
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• v.27 no.2
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• pp.119-130
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• 2016

Objectives The Purpose of this study was to conduct a characteristic study on cancer patients using the Core Seven Emotions Inventory (CSEI) followed by a correlation analysis with STAI, STAXI and BDI.Methods This study was conducted by analyzing the medical records of 21 patients who had visited ○○ University Oriental hospital and completed the Core Seven Emotions Inventory (CSEI), BAI, and BDI. A total of 21 patients diagnosed with Cancer were analyzed using SPSS (Statistical Package for the Social Science, IBM, United States of America, Version 22.0). Frequency Analysis, independent t-test, one-sample t-test, and correlation analysis were conducted.Results 1. The Seven Emotion Characteristics of the Cancer patients showed a fairly stable emotional Distribution. The Gong (恐) and Kyeong (驚) emotions were relatively higher than U (憂), Bi (悲), Sa (思), Hui (喜), No (怒). 2. According to Gender, Female patients exhibited higher Sa (思) and Kyeong (驚) emotions while male patients exhibited higher Bi (悲) Emotion. 3. No (怒), U (憂), Bi (悲), Sa (思), Gong (恐), and Kyeong (驚) emotions showed a high correlation with the BDI and BAI scores of cancer patients.

• Computers and Concrete
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• v.26 no.3
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• pp.213-226
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• 2020

The present study covenants with the static and free vibration behavior of nanocomposite sandwich plates reinforced by carbon nanotubes resting on Pasternak elastic foundation. Uniformly distributed (UD-CNT) and functionally graded (FG-CNT) distributions of aligned carbon nanotube are considered for two types of sandwich plates such as, the face sheet reinforced and homogeneous core and the homogeneous face sheet and reinforced core. Based on the first shear deformation theory (FSDT), the Hamilton's principle is employed to derive the mathematical models. The obtained solutions are numerically validated by comparison with some available cases in the literature. The elastic foundation model is assumed as one parameter Winkler - Pasternak foundation. A parametric study is conducted to study the effects of aspect ratios, foundation parameters, carbon nanotube volume fraction, types of reinforcement, core-to-face sheet thickness ratio and types of loads acting on the bending and free vibration analyses. It is explicitly shown that the (FG-CNT) face sheet reinforced sandwich plate has a high resistance against deflections compared to other types of reinforcement. It is also revealed that the reduction in the dimensionless natural frequency is most pronounced in core reinforced sandwich plate.