• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제21권10호
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• pp.901-905
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• 2008

In this study, $0.95(K_{0.5}Na_{0.5})NbO_{3}-0.05Li(Sb_{0.8}Nb_{0.2})O_{3}+0.2\;wt%Ag_{2}O$ were investigated as a variations of sintering times in order to improve dielectric and piezoelectric properties of lead-free piezoelectric ceramics. $Ag_{2}O$ were used as sintering aids and the specimens were sintered during 3, 5, 7, 9 and 11 hours, respectively. At the specimen sintered during 7 hour, Electromechanical coupling factor ($k_p$), density, dielectric constant (${\epsilon}_{\gamma}$), piezoelectric constant ($d_{33}$) and curie temperature ($T_c$) of composition ceramics showed the optimal value of 0.450, 4.274 $[g/cm^3]$, 1007, 257 [pC/N] and $396^{\circ}C$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 방전 플라즈마 유기절연재료 초전도 자성체연구회
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• pp.173-176
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• 2004

The piezoelectric ceramics for AE sensor piezoelectric devices are desirable to possess higher resonance vibrations. The compositions of $0.9Pb(Zr_xTi_{1-x})O_3-0.1Pb(Mn_{1/3}Nb_{1/3}Sb_{1/3})O_3$ (PZT-PMNS) in this work are selected for obtaining especially large electromechanical coupling factor, high mechanical quality factor and high Curie temperature. This ceramic has higher piezoelectric activity and higher electromechanical coupling factor, but the ceramic has lower Curie temperature. The piezoelectric and dielectric characteristics of PZT-PMNS ternary system are investigated as functions of $Ti^{2+}$, $Zi^{2+}$ mol rate. As the results, MPB(morphotropic phase boundary) in this piezoelectric ceramic is x=0.522. Resonance vibrations of PZT ceramics are investigated as ball-bearing drop test. For the use of AE sensor that driving with pre-amplifier, filter circuit after packed this ceramic and an elastic body.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제15권7호
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• pp.597-601
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• 2002

In this study, the structural, dielectric and piezoelectric properties of $Pb[(Ni_{1/3}Nb_{2/3})_x-(Mn_{1/3}Nb_{2/3})_{0.09-x}-(Zn_{0.505}Ti_{0.495)_0.91]O_3$ (x=0, 0.01, 0.02, 0.03, 0.04, 0.05) system ceramics were investigated to develop the composition ceramics for piezoelectric transformer. All the specimens were sintered at $1250^{\circ}C$ and its physical properties were measured, and the results are as follows : With increasing PNN substitution for PMN-PZT system, dielectric constant was increased and electro-mechanical coupling factor($k_p$) was increased to 0.62 at 5 mol% while mechanical quality factor(Qm) was decreased.

• Anxiety and mood
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• 제13권2호
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• pp.86-92
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• 2017

Objective : This study evaluated the factor structure of a Korean version of the Penn State Worry Questionnaire (K-PSWQ) with exploratory factor analysis in healthy adult subjects, and confirmatory factor analysis of subjects who have received psychiatric treatment. Methods : Exploratory principal component analysis was conducted with data from 318 non-psychiatric subjects, and 118 psychiatric patients were subjected to confirmatory factor analysis (maximum likelihood estimation). Participants were voluntary visitors at the booth who agreed to undergo screening for anxiety disorder at 2013 & 2014 Korea Mental Health Exhibitions. Results : Exploratory analysis revealed a two factor structure of the scale with total variance of 56.3%. Factor 1 was considered 'Worry engagement', and factor 2 was considered 'Absence of worry'. However, the results of the confirmatory factor analysis supported that both one factor model with method factor and two factor model are fit to structure of the scale considering fit indices. Internal consistency of total questions was good (Cronbach's ${\alpha}=0.899$). Conclusion : Our results supported the previously suggested factor structure of the PSWQ, and proved factorial validity of the K-PSWQ in both populations.

• Proceedings of the KIEE Conference
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.187-189
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• 2003

Conventional Switched Mode Power Supplies(SMPS) with diode-capacitor rectifier have distorted input current waveform with high harmonic content. Typically, these SMPS have a power factor lower than 0,65. To improve with this problem the power factor correction(PFC) circuit of power supplies has to be introduced. Specially. to the reduce size and manufacture cost of power conversion device, the single-stage PFC converter is increased to demand as necessary of study. in this paper, The comparative analysis of power factor correction circuit using Feedforward control with average current mode flyback converter(single-stage) and boost converter(two-stage). Also, the validity of designed and manufactured high power factor flyback converter and boost converter is confirmed by simulation and experimental results.

• Proceedings of the KIEE Conference
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1244-1246
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• 2003

Conventional Switched Mode Power Supplies(SMPS) with diode-capacitor rectifier have distorted input current waveform with high harmonic content. Typically, these SMPS have a power factor lower than 0.65. To improve with this problem. the power factor correction(PFC) circuit of power supplies has to be introduced. Specially, to reduce size and manufacture cost of power conversion device, the single-stage PFC converter is increased to demand as necessary of study. In this case single-stage PFC converter has been used DC-DC converter with boost converter. However in this paper, it is studied flyback converter of high power factor, high efficiency by feedforward control. Also, the validity of designed and manufactured high power factor flyback converter is confirmed by simulation and experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제37권11호
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• pp.1361-1369
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• 2013

This study performs a computational fluid dynamics (CFD) analysis of the inner flow of a multihole injector nozzle by using ANSYS CFX 13.0. Based on the obtained results, a design of experiment (DOE) was performed and applied to investigate the effects of injector nozzle design parameters on cavitation. To analyze the design sensitivity and signal-to-noise ratio (S/N ratio), the hole diameter, hole length, hole angle, and K-factor of the nozzle hole were selected as design parameters, and the effect of these parameters was investigated at 16 experimental points. Consequently, it was found that the effect of the K-factor on the cavitation and inner flow of the injector nozzle is the greatest. Thus, the selection of a suitable K-factor is important in nozzle design considering cavitation flow.

• Clinical and Experimental Pediatrics
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• 제57권10호
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• pp.440-444
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• 2014

Purpose: Febrile seizures are induced by fever and are the most common type of seizures in children. Although numerous studies have been performed on febrile seizures, their pathophysiology remains unclear. Recent studies have shown that cytokines may play a role in the pathogenesis of febrile seizures. The present study was conducted to identify potential links between serum interleukin-1beta (IL-$1{\beta}$), tumor necrosis factor-alpha (TNF-${\alpha}$), and febrile seizures. Methods: Ninety-two patients with simple or complex febrile seizures (46 patients per seizure type), and 46 controls with comparable age, sex, and severity of temperature were enrolled. Results: The median concentrations of serum IL-$1{\beta}$ in the simple, complex febrile seizure, and control groups were 0.05, 0.1, and 0.67 pg/mL, respectively (P=0.001). Moreover, the median concentrations of TNF-${\alpha}$ in the simple, complex febrile seizure, and control groups were 2.5, 1, and 61.5 pg/mL, respectively (P=0.001). Furthermore, there were significant differences between the case groups in serum IL-$1{\beta}$ and TNF-${\alpha}$ levels (P<0.05). Conclusion: Unlike previous studies, our study does not support the hypothesis that increased IL-$1{\beta}$ and TNF-${\alpha}$ production is involved in the pathogenesis of febrile seizures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.212-213
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• 2005

In this study, in order to develop low temperature sintering piezoelectric actuator, $Pb_{0.985}Bi_{0.01}(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.13}(Zr_{0.50},Ti_{0.50})_{0.84}$ (PMW-PNN-PZT) ceramic systems were fabricated using $CaCO_3-Li_2CO_3$, sintering aid through a post-annealing process. The sinterability of PMW-PNN-PZT ceranics was remarkably enhanced by liquid phase sintering of $CaCO_3$ and $Li_2CO_3$. But, it was confimed form the X-ray diffraction pattern that the secondary phase along grain boundaries, deteriorated the piezoelectric properties. The secondary phase along grain boundaries was significantly removed by annealing after sintering. The 0.2wt% $Li_2CO_3$-0.25wt% $CaCO_3$-added PMW-PNN-PZT ceramics post-annealed at 900$^{\circ}C$ for 90min exhibited the excellent electromechanical coupling factor($k_p$) of 63.3% and piezoelectric constant($d_{33}$) of 452pC/N, respectively, for multilayer piezoelectricactuatorapplication.

• Women's Health Nursing
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• 제8권1호
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• pp.124-137
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• 2002

The purpose of this study was to identify the need for sex education in middle school students Research subjects were 194 students who attended at I seminary in B city. The period of data collection was from July to August, 2001. Research instrument was composed of 61 structured items 17 items related to demographics and sex, 44 items related to the need of sex education. Data were collected through the self-report method by the researcher and one trained assistant. The instrument developed by the researchers was employed to measure the need of sex education and it's Cronbach's $\alpha$ = 0.9349 in this research. Data were analyzed by frequency, percentage factor analysis and t-test using SPSS WIN Program. The findings of this study are summarized as follows : 1. The highest score among characteristics of sex was 'less interest about sex(42.6%)', 39.0% of subjects got information about sex from friends or elders. 52.3% of subjects consulted friends or elders about sex problems. The number of sex education lessons was 1-2 times in school during last semester (61.0%). Education by the school nurse was 35.9% to students. 43.1% of subjects announced moderate satisfaction on sex education. 2. The mean score of the need for sex education was $2.88{\pm}0.47$ (lowest value 1, highest 4). The most wanted sex education factor was 'chastity and sexual responsibility($3.33{\pm}0.67$)' and followed by 'family and marriage ($3.26{\pm}0.62$)' and 'considerations of sex($3.07{\pm}0.69$)'. Meanwhile, the lowest wanted sex education factor is 'physiological characteristics of male ($2.47{\pm}0.72$)', followed by 'sexual behavior ($2.49{\pm}0.75$)'. The most wanted sex education item was 'the meaning of family ($3.54{\pm}0.75$)' and followed by 'the cautions to prevention from sexual abuse ($3.49{\pm}0.78$)' and sexual activity and responsibility($3.43{\pm}0.77$)'. Meanwhile, the lowest wanted sex education item is 'masturbation ($2.16{\pm}0.97$)', followed by 'circumcision($2.32{\pm}0.97$)'. 3. There is no significant difference between boys and girls in mean score about the need for sex education(t=-.715, p=.476). Sex education factor that girl-students wanted was 'physiological characteristics of female'. Sex education factor that boy-students wanted was 'family and marriage'. Sex education items that girl-students wanted were 'cautions during menstruation', the relation of ovulation and pregnancy', caution to prevention from sexual abuse' and sexual behavior and responsibility'. Sex education items that boy-students wanted were 'the meaning of family', 'the importance of marriage', 'male's sex organs', 'a wet dream', 'the method to resolve sexual curiosity', 'sexual intercourse' and 'the connection with the other sex'. In conclusion, the mean score of the need for sex education is medium. The route to attain knowledge about sex and sexual problem is through consulting friends and elders. Therefore, it is necessary to give sex education that is suitable to the subject's needs and methods. Also, it is necessary to give differently strong point about sex education between female and male students.