• Progress in Superconductivity
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• v.9 no.1
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• pp.1-4
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• 2007

The most common technique to fabricate $MgB_2$ superconducting wire is by powder-in-tube (PIT) technique. Therefore, the starting powder for the processing of $MgB_2$ superconductors is an important factor influencing the superconducting properties and performance of the conductors. In this study, the influence of magnesium precursor powders and annealing temperatures on the transition temperatures ($T_c$) and critical current densities ($J_c$) of $MgB_2/Fe$ wires was investigated. All the $MgB_2/Fe$ wires were fabricated by in situ PIT process. It was found that higher $J_c$ was obtained for $MgB_2$ wires with smaller particle size of magnesium precursor powders. The $J_c$ also increases with decreasing annealing temperatures.

• The Journal of Korean Society for School & Community Health Education
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• v.19 no.1
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• pp.1-11
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• 2018

Objectives: The purpose of this study is to provide basic data on the use of electronic cigarettes by identifying the relationship between smoking and smoking behavior and the use of electronic cigarettes. Methods: This study used data from 8,150 participants of the 'Korea National Health and Nutrition Examination Survey (KNHANES)' s 7th (2016). In this study, 1,051 people currently smoking were analyzed. The number of people using electronic cigarettes was 74 among current smokers. Results: The age of onset of smoking was 20.46 years old in the group not using electronic cigarette, and the age of starting smoking was 18.12 years old in the group using electronic cigarette(p<.001). In the education level, the current use of electronic cigarette was 1.82 times higher in high school graduates than college graduates(p<.005). The reason for using electronic cigarette was 4.32 times higher than other reasons for using electronic cigarette for the purpose of smoking cessation(p<.005). Conclusions: For the smoking cessation society, education for the electronic cigarette is needed from the adolescence and selective management for the people who use the electronic cigarette for the purpose of smoking cessation is needed.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2007.05a
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• pp.67-69
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• 2007

Customary way of thinking may be the most major stumbling block to creative thinking in basic design education in the information and network era. The basic design education was used to be based on personal experience or subjective ideas, but these days, the role of divergent thinking and convergent thinking which provide the basis of creative techniques has been closely examined. Going beyond a divergent thinking and directly starting a convergent thinking means bypassing the design process of the existing basic design education. Though preceding studies considered various creative techniques apart from divergent thinking and convergent thinking, this study presumed that complementing the most typical methods of divergent thinking and convergent thinking may result in the same basic design education effect. So, what approach must be used to the design? The way of thinking needs to change. For that, we try to apply the mapping to basic design education. It must encompass interactive thinking which includes immaterial elements and communication. Divergent thinking can begin with the accurate understanding of current state, and the created current state resolves the design process that needs to be a certain thing. The purpose of this study was to present the method for applying the mapping techniques to basic design education based on divergent and convergent thinking which provides the basis of creative ideas.

• Journal of Family Resource Management and Policy Review
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• v.10 no.1
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• pp.33-51
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• 2006

Today, the Korean society is experiencing an increase in serious problems, such as child abuse, unmarried mothers, single mothers, which cannot be overlooked as simply trivial family matters. The increase in these problems is caused by the rapid change that has taken place within our society, which has emasculated the power of our traditional values and behavior patterns to cope with contemporary life styles. Premarital Preparation Education is starting to gain attention as a preventive measure that can overcome this serious family crisis. Although the importance of the Premarital Preparation Education program cannot be overemphasized, there are only few cases where engaged couples and unmarried men and women are exposed to this type of program and actually experience its benefits. In other words, there is an urgent need to revitalize and increase the effects of the Premarital Preparation Education Program. This research was conducted in order to find a way to revitalize and to increase the effects of the program, so that more and more people can participate and receive benefits from it. First, we have analyzed the program's contents and the current condition on how the program is actually conducted. Then we have compared real case examples of the program and analyzed the current situation and its problems.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.30-36
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• 2020

We demonstrated a successful fabrication of 4" Gallium Nitride (GaN)/Diamond High Electron Mobility Transistors (HEMTs) incorporated with Inner Slot Via Hole process. We made in manufacturing technology of 4" GaN/Diamond HEMT wafers in a compound semiconductor foundry since reported [1]. Wafer thickness uniformity and wafer flatness of starting GaN/Diamond wafers have improved greatly, which contributed to improved processing yield. By optimizing Laser drilling techniques, we successfully demonstrated a through-substrate-via process, which is last hurdle in GaN/Diamond manufacturing technology. To fully exploit Diamond's superior thermal property for GaN HEMT devices, we include Aluminum Nitride (AlN) barrier in epitaxial layer structure, in addition to conventional Aluminum Gallium Nitride (AlGaN) barrier layer. The current collapse revealed very stable up to Vds = 90 V. The trapping behaviors were measured Emission Microscope (EMMI). The traps are located in interface between Silicon Nitride (SiN) passivation layer and GaN cap layer.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.72-77
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• 2015

When connecting 6 lead wires from stator windings to the terminals of 3 phase induction motors for Y or ${\triangle}$ connection, it is feared that the polarities of windings could be reversed each other if the wire tags are lost or erased, resulting in inadmissibly high current to motors in case of starting. To protect motors against such situations, some test procedures are necessary during wire connection which need to be easy ways to electricians without particular tools except a general multi-tester and with less time-consuming in the field. This study focuses on a test measure to satisfy these requirements which is able to provide them a convenient procedure for winding polarity discrimination considering the field condition. Here, the proposed measure utilizes the residual magnetism of the rotor and checks the indication of voltage or current at windings which are induced by the residual flux of rotor when rotating it by hands with 3 stator windings connected in the form of I connection. Principle characteristics and experiment results for this method are analyzed in the view of the effectiveness and applicability for the winding polarity discrimination.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.2
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• pp.179-186
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• 2007

This paper presents new ignition method and ignition recognition logic for a microturbine. New ignition method is designed by constant speed control of a microturbine with pre-determined time during a ignition period. It make more accurate air-fuel ratio as well as give enough time to ignition system to have full performance under cold temperature. And ignition recognition logic is designed by observing output current change of inverter by generating output torque of a microturbine in the instant of ignition. For filtering a output torque current of inverter with high frequency, we applied a moving average method. So far, ignition recognition is usually implemented by measuring of exhausted gas temperature(EGT) of microturbine. The proposed logic can give more accurate judgement of ignition as well as keep a good working of starting system under out of order a temperature measuring system and biased initial value of EGT sensor. Finally, the two proposed logics are proved by field operating a microturbine under various conditions.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.120-126
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• 1996

In the present study, we have studied on the characteristics of BST thin films with various Ba/Sr ratios by using sol-gel method. Barium-acetate, strontium-acetate and titanium isopropoxide are used as starting materials to fabricate BST thin films by sol-gel method. The fabrication conditions are estabilished through the TG-dT analyses and XRD measurements. BST thin films with the Ba/Sr ratios of 90/10, 70/30, 50/50 and 30/70 were deposited on the Pt/Ta/SiO$_{2}$Si substrate with the estabilished sol-gel process, and their characteristics were examined. The relative permittivity and the leakage current density at 5V vary from 287 to 395 and from 2.3 to 220${\mu}$A/cm$^{2}$, respectively, with various Ba/Sr ratio. Among the films investigatd in this research, BST (70/30) thin film shows the best relative permittivity and dielectric loss of BST (70/30) thin film are 395 and 0.045, respectively and the leakage current density at 5V is 2.3${\mu}$A/cm$^{2}$.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.244-249
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• 2008

This paper deals with speed control of DC servo motor using a Fuzzy tuning observer. Speed sensor detect a speed of rotor continuously. But it have a limit as a driving speed to detect speed precisely. So it is problem to improve the performance of the driving system. To solve the problem, it is studied to detect a speed of DC motor without sensor. In particular, study on the method to estimate the speed using the observer is performed a lot. In this parer, the gain of the observer is properly set up using the fuzzy observer. The fuzzy observer has a superior transient characteristic and is easy to implement compared the existing method is designed. It estimate the derivative of the armature current directly using the armature current measured in the DC motor. It estimate the speed of the rotor using the differentiation. It is proposed speed sensorless control method using the estimated speed. Optimal gain of Luenberger observer is set up using the fuzzy observer and adapted speed control of DC servo motor low speed operation. It is proved excellence and feasibility of the presented observer from the comparison tested a case with a speed sensor and a case without a speed sensor which used a highly efficient drive and 200W DC servo motor starting system.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.6
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• pp.411-419
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• 2008

SFC(Static Frequence Converter)system has come to be used as start up drive system for large synchronous motor in many industry applications. Many papers have been presented the control algorithm for pumped storage power generation using SFC system but they did not included about start up algorithm of SFC system for gas turbine. This paper presents the field weakening control algorithm for a large synchronous motor using output signal of anti-windup in PI current regulator and the results of experiment show that the proposed algorithm is proper and effective.