• Journal of Korean Elementary Science Education
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• v.28 no.4
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• pp.440-449
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• 2009

The purpose of this study is to make a preference and result analysis on the free inquiry method of pre-service elementary school teachers. Also, this study investigates how free inquiry activities effect the science-related attitudes and the self-directed learning characteristics of pre-service elementary school teachers. For this study 76, second year, science education pre-service elementary school teachers from Busan National University of education were selected. The inquiry examined the effectiveness of each of the following teaching methods: the IIM method, the PBL method, the PROJECT method, and the small group inquiry method. The students were divided into groups in which they incorporated the respective methods into their practice. In conclusion, the IIM free inquiry activities proved to be much more effective than the PBL method, the PROJECT method, and the small group inquire method in terms of developing self-directed learning characteristics and science related attitudes at the significant difference of p=0.05.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.215-218
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• 2005

We have investigated on the development of 2-2 piezocomposites that have better piezoelectric activity and lower acoustic impedance than those of conventional piezoceramics. In this study, we have investigated the piezoelectric and acoustic properties of 2-2 piezocomposites sensor which were fabricated using dice-and-fill technique for the different volume fraction of PZT. The resonance characteristics measured by an impedance analyzer were similar to the analysis of finite element method. The resonance characteristics and the electromechanical coupling factor were the best when the volume fraction PZT was 0.6. It also showed the highest result from the standpoint of sensitivity, bandwidth and ring-down property and so on at the same condition. The specific characteristics shows that the 2-2 piezocomposites turned out to be superior to the ultrasonic sensor composed by single phase PZT.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1624-1626
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• 1997

In this paper, a new PD measurement technique of pulse superposition method was proposed in order to investigate both PD mechanism and phase related PD patterns. From the experimental results, we could find that the polarity and the phase angle of the superposed pulse take great effects on PD characteristics and these method make it possible to get the physical information which statistical approach can not give. We could conclude that the changes of PD characteristics in the void surrounded by polymers may be attributed to the injection of charge carriers thereby formation of space charge in the surface and/or the bulk of the polymer.

• International Journal of Fluid Machinery and Systems
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• v.5 no.3
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• pp.126-133
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• 2012

The transfer matrix and unsteady cavitation characteristics, cavitation compliance and mass flow gain factor, of cavitating inducer were evaluated by CFD using commercial software. Quasi-steady values of cavitation compliance and mass flow gain factor were obtained first by using steady calculations at various flow rate and inlet cavitation number. Then unsteady calculations were made to determine the transfer matrix and the cavitation characteristics. The results are compared with experiments to show the validity of calculations.

• International Journal of Fluid Machinery and Systems
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• v.7 no.1
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• pp.7-15
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• 2014

In the present study, a computational analysis of the flow in a centrifugal blower is carried out to predict a performance and to explain noise characteristics of the blower. Unsteady, 3D Navier-Stokes equations were solved with k-${\varepsilon}$ turbulence model using CFX software. CFD results were compared with the experimental data that is acquired from an experiment conducted with the same blower. The pressure fluctuation in the blower was transformed into the frequency domain by Fourier decomposition to find the relationship between flow behaviors and noise characteristics. Sound pressure level (SPL) which is obtained from wall pressure fluctuation at impeller outlet represents relative overall sound level of the blower well. Sound spectra show that there are some specific peak frequencies at each mass flow rate and it can be explained by flow pattern.

• Journal of the Korean Home Economics Association
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• v.39 no.7
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• pp.37-58
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• 2001

The Purpose of this study was to examine the direct or indirect effects of psychological family environment self-control, and friends characteristics of middle school students on their problem behaviors. Data were corrected from 520 senior students of middle school (266 boys and 254 girls) who reside in Inchon. The level of problem behaviors was directly influenced positively by closeness with friends and negatively by self-control and open communication with mothers. And the level of problem behaviors was indirectly influenced positively by intrafamily conflicts and negatively by self-control, parental monitoring and open communication with parents. Self-control was the most powerful predicator of problem behaviors of middle school students. Self-control was directly influenced positively by open communication with fathers and negatively by intrafamily conflicts. Closeness with friends was directly influenced positively by parental monitoring and negatively by self-control and open communication with mothers.

• The Mathematical Education
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• v.52 no.3
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• pp.423-442
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• 2013

The purpose of the study was to examine the effects of the reciprocal peer tutoring in high school students' affective characteristics with respect to mathematics. The study was conducted with 111 first graders in one high school located in Gyeonggi-do, and the study lasted for 1 year in regular mathematics classrooms. According to the results, reciprocal peer tutoring was very effective in improving students' interest and self-efficacy toward mathematics and reducing mathematics anxiety. Especially, in high and low performing student groups, there were statistically significant improvements in affective factors such as interest, self-efficacy toward mathematics, and mathematics anxiety after reciprocal peer tutoring. However, average performing student group showed statistically significant improvements in affective factors of interest and self-efficacy toward mathematics.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.44-47
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• 2005

This paper presents the efficient plan for the EMI improvement from of TFT-LCD Module. It investigates the frequency characteristics of Power/Ground Plane of TFT-LCD drive circuit PCB concretely. After the frequency characteristics is reviewed, EMI improvement is tried to insert to RC termination between Power/Ground Plane and to shift resonance frequency. It is confirmed by a simulation result and RC Termination which is inserted the point where the resonance characteristics change is necessary. It applied in 19 "SXGA TFT-LCD drive circuits and the EMI improvement verification is described.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.4
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• pp.253-258
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• 2017

This paper presents a numerical study on the thermal characteristics of a milling process of titanium alloy with nanofluid minimum-quantity lubrication (MQL). The computational fluid dynamics (CFD) approach is introduced for establishing the numerical model for the nanofluid MQL milling process, and estimated temperatures for pure MQL and for nanofluid MQL using both hexagonal boron nitride (hBN) and nanodiamond particles are compared with the temperatures measured by thermocouples in the titanium alloy workpiece. The estimated workpiece temperatures are similar to experimental ones, and the model is validated.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.121-122
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• 2000

The understanding of reset scheme is essential for the driving of AC PDP (Plasma Display Panel). The characteristics of reset period of AC PDP was examined with the variation of pulse time and voltage in the ADS (Address Display Separated) driving method presented by Fujitsu,. The addressing characteristics showed drastic change as a function of the erasing time and addressing pulse width. In this paper, these results were explained by the change of wall charge variation, and it was estimated with the currents through each electrode.