• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.255-258
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• 2000

In this study, the structural, dielectric and piezoelectric properties of Pb[(Sb$\sub$1/2/Nb$\sub$1/2/)$\sub$x/- (Ni$\sub$1/3/Nb$\sub$2/3/)$\sub$0.15-x/- (Zr,Ti)$\sub$0.85/]O$_3$(x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) ceramics is investigated as a function of Pb(Sb$\sub$1/2/Nb$\sub$1/2/)O$_3$ (abbreviated PSN) substitution. With the increase of PSN substitution, the crystal structure is transO$_3$formed from the tetragonal phase to the rhombohedral phase and the grain size is decreased abruptly. The curie temperature is decreased with the PSN substitution. The dielectric constant is increased with the PSN substitution and maximum value of 2290 is obtained at 4mol% PSN. With the PSN substitution, the coercive field is increased and the remnant polarization is decreased. The Electromechanical coupling factor(k$\sub$p/) Is showed the highest value of 0.622 at lmol% PSN and the mechanical quality factor(Q$\sub$m/) is decreased abruptly with the PSN substitution.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.391-395
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• 2000

In this study, the temperature coefficient of resonant frequency(TC $F_{r}$), dielectric and piezoelectric properties of Pb[(S $b_{1}$2/N $b_{1}$2/)$_{0.0035}$-(M $n_{1}$3/N $b_{2}$3/)$_{0.0065}$-(Z $r_{x}$ $Ti_{1-x}$ )$_{0.90}$] $O_3$ceramics is investigated with Zr/Ti ratio. The dielectric constant and electromechanical coupling factor( $k_{p}$) showed the highest values of 1257, 0.562 respectively when the Zr/Ti ratio is 49.5/50.5. The mechanical quality factor( $Q_{m}$) is the lowest value of 713 when the Zr/Ti ratio is 49.5/50.5, and increased with the decrease of the Zr/Ti ratio. The temperature coefficient of resonant frequency(TC $F_{r}$) change abruptly at the morphotropic phase boundary(MPB), which is between the rhombohedral phase with highly negative TC $F_{r}$ of -106ppm/$^{\circ}C$ and the tetragonal phase with highly positive TC $F_{r}$ of +64pp $m^{\circ}C$ as Zr/Ti ratio changes from 50/50 to 49.5/50.5.50.5..5.50.5.5.

• Progress in Medical Physics
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• v.22 no.3
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• pp.148-154
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• 2011

The quality factors ($k_{Q,Q_0}$) were evaluated by appling the results recently studied for the effect of central electrode in TRS-398 protocol. The PTW-31010 and IBA-CC13 chambers were used in this study. The quality factors were calculated as a function of beam quality for high energy electron and photon beams and compared with data currently used in TRS-398 protocol. In the PTW-31010 chamber using aluminium electrode, appling the new central electrode collections, the quality factors were 0.4% and 0.9% higher than current TRS-398 data for high energy photon and electron beams respectively. In the IBA-CC13 chamber using C-552 electrode, there are no variations in quality factors compared to TRS-398 data currently used.

• Korean Journal of Materials Research
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• v.19 no.10
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• pp.550-554
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• 2009

Unreported dielectrics based on the binary system of MgO-SiO$_2$ were investigated as potential candidates for microwave dielectric applications, particularly those demanding a high fired density and high quality factors. Extensive dielectric compositions having different molar ratios of MgO to SiO$_2$, such as 2:1, 3:1, 4:1, and 5:1, were prepared by conventional solid state reactions between MgO and SiO$_2$. 1 mol% of V$_2$O$_5$ was added to aid sintering for improved densification. The dielectric compositions were found to consist of two distinguishable phases of Mg$_2$SiO$_4$ and MgO beyond the 2:1 compositional ratio, which determined the final physical and dielectric properties of the corresponding composite samples. The increase of the ratio of MgO to SiO$_2$ tended to improve fired density and quality factor (Q) without increasing grain size. As a promising composition, the 5MgO.SiO$_2$ sample sintered at 1400 $^{\circ}C$ exhibited a low dielectric constant of 7.9 and a high Q $\times$ f (frequency) value of $\sim$99,600 at 13.7 GHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.403-406
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• 2000

The piezoelectric properties and the doping effect of N $b_2$ $O_{5}$ and Mn $O_2$for 0.95PbZ $r_{x}$ $Ti_{x}$ $O_3$+0.05Pb(M $n_{0.42}$ $W_{0.26}$S $b_{0.32}$) $O_3$ compositions have been investigated. In the composition of 0.95PbZ $r_{0.54}$ $Ti_{0.46}$ $O_3$+0.05Pb(M $n_{0.42}$ $W_{0.26}$S $b_{0.32}$) $O_3$the Values Of $k_{p}$ find and $\varepsilon$$_{33}$ $^{T}$ are maximized, but $Q_{m}$ Was minimized ( $k_{p}$ =0.51, $Q_{m}$ =1750). The grain size was suppressed and the uniformity of grain was improved with doping concentration of N $b_2$ $O_{5}$ for 0.95PbZ $r_{0.54}$ $Ti_{0.46}$ $O_3$+0.005Pb(M $n_{0.42}$ $W_{0.26}$S $b_{0.32}$) $O_3$sample. The values of $k_{p}$ increased and the values of $Q_{m}$ slightly decreased when 0.5 wt% of N $b_2$ $O_{5}$ is doped. And the values of $k_{p}$ was the same formation of the N $b_2$ $O_{5}$ dopant when 0.5 wt% of M $n_2$ $O_{5}$ is doped. But the values of $Q_{m}$ was deeply decreased when 0.5 wt% of Mn $O_2$is doped. As a experiment results under high electric field driving, this piezoelectric ceramics are very stable. Conclusively, piezoelectric ceramic compsiton investigated at this paper is suitable for application to high power piezoelectric devices.. devices..ices.. devices..

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.03a
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• pp.1-11
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• 2002

As the competition among the ports is extreme, the purpose of this study which intendsto keep sustainable competitive advantage in Busan Container Terminals through the quality management of port service is shown as the followings. First, the common factor of quality management activities In the part of domestic container port is to be analysed. secondly, the efforts for enhancing the standard of quality management is to be confirmed lastly the relationship of cause-effect among the source of quality management, quality management activities and quality management is to be clarified. An empirical study was carried out to examine how Busan Container Terminals view quality management activities by the provision of statistical evidence showing the efforts to enhance the standard of quality management, common factors of quality management activities and causal relationship among these factors. The data investigating the quality management for Busan Container Terminals were collected from 170 persons in charge of quality management for port services in Busan Container Terminals the use of questionnaire method and personal interviews. The Cronbach's $\alpha$ coefficient and factor analysis were used to analyze the reliability and the propriety of measured variables. Furthermore SEM method using AMOS 4.0 was used to analyze the cause-effect relationship among the source. activities and accomplishments of quality management representing the core concept of quality management system. The importance of this study is placed in the description of the theoretical and general system on the quality management when the domestic container terminals have activated to promote the quality management, and in suggesting the actual problem and settlement method which are directly helpful to the field, and It can be indicated as having its meaning on future research obect.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.10
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• pp.17-23
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• 2003

In this study, microscale, high-performance, solenoid-type RF chip inductors were investigated. The size of the RF chip inductors fabricated in this work was 1.0${\times}$0.5${\times}$0.5㎣. The materials (96% Al2O3) and shape (I-type) of the core were determined by a Maxwell three-dimensional field simulator to maximize the performance of the inductors. The copper (Cu) wire with 40${\mu}{\textrm}{m}$ diameter was used as the coils. High frequency characteristics of the inductance (L), quality-factor (Q), and capacitance (C) of developed inductors were measured using an RF Impedance/Material Analyzer (HP4291B with HP16193A test fixture). The inductors developed have inductances of 11 to 39 nH and quality factors of 28 to 50 over the frequency ranges of 250MHz to 1 GHz, and show results comparable to those measured for the inductors prepared by CoilCraf $t^{Tm}$ that is one of the best chip inductor company in the world. The simulated data predicted the high-frequency data of the L, Q, and C of the inductors developed well.l.

• The Journal of Korean Academic Society of Nursing Education
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• v.29 no.3
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• pp.247-262
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• 2023

Purpose: This study aimed to identify the types of perception toward non-face-to-face clinical practice and to characterize the types of students who experienced online clinical practice during the coronavirus disease 2019 (COVID-19) pandemic. Methods: Q-methodology was used in this study, and 270 Q populations were formed based on in-depth interviews with 10 nursing students who had experienced non-face-to-face clinical practice, as well as related literature. Interviews were performed from August 1 to 31, 2022. A total of 42 Q samples were extracted, and Q sorting was performed on 33 nursing students who had experienced non-face-to-face clinical practice. A Q factor analysis was performed using the PC-QUANL program. Results: The nursing students' perceptions of non-face-to-face clinical practice were classified into the following five types: "future professional competency-focused type," "realistic convenience priority type," "task burden awareness type," "negative critic type," and "limited experience dissatisfaction type." Conclusion: This study revealed non-face-to-face clinical practice's positive and negative aspects in nursing education. Moreover, it identified the aspects of clinical practice that cannot be replaced by non-face-to-face clinical practice and the elements of non-face-to-face practice that can complement clinical practice. These findings can be used as fundamental data to establish a stable and efficient system for improving the quality of clinical practice in the post-COVID-19 era and to implement effective non-face-to-face clinical practice according to student types.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.6
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• pp.553-561
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• 2011

A theoretical approach is carried out to predict the quality factors of flexible modes of a microcantilever on a squeeze-film. The frequency response function of an inertially-excited microcantilever beam is derived using an Euler-Bernoulli beam theory. The external force due to squeeze-film phenomenon is developed from the Reynolds equation. Slip boundary conditions are employed at the interfaces between the fluid and the structure to consider the gas rarefaction effect, and pressure boundary condition at both ends of fluid analysis region is enhanced to increase the exactness of predicted quality factors. To the end, an approximate equation is derived for the first bending mode of the microcantilever. Using the approximate equation, the quality factors of the second and third bending modes are calculated and compared with experimental results of previously reported work. The comparison shows the feasibility of the current approach.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.22 no.4
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• pp.341-349
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• 2019

Background: A self-assessment questionnaire, the GERD-Questionnaire (GERD-Q) was used to determine the prevalence of GERD in adolescents, describe the related factors, and determine the impact on quality of life (QoL). Methods: The incidence of GERD was evaluated using the GERD-Q in adolescents aged 12-18 years. The Pediatric Gastroesophageal Reflux Disease Symptom Questionnaire and Quality of Life Questionnaire (PGSQ-A) for adolescents were additionally administered. Some factors considered related to GERD were also evaluated. Results: The 520 adolescents were included. The prevalence of suspected GERD, according to a GERD-Q cutoff score of ${\geq}7$ was 32.9%, and those drinking soda were 1.7 times more likely to have GERD (95% confidence interval, 1.3-2.2; p<0.001). However, soda consumption was not a risk factor for development of GERD symptoms. Applying a cutoff score of ${\geq}8$, only 10.9% of the participants had a positive GERD score, but the association with soda consumption persisted. The median PGSQ-A score in subjects suspected of GERD was 8 (range 0-37) on weekends and 1 (range 0-17) during weekdays (p<0.001) compared to those not suspected of GERD, with a median of 2 (range 0-27) during weekends and 0 (range 0-10) during weekdays. Heartburn, regurgitation, and extraesophageal symptoms correlated significantly with QoL (p<0.001). Conclusion: The prevalence of suspected GERD in adolescents was 32.9% or 10.9%, depending on the cutoff score used. There was a statistically significant difference in PGSQ-A scores between the subjects suspected or not of GERD, indicating an impaired QoL.