• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.566-574
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• 2015

We report for the first time highly efficient trans-reflective color filters capable of demonstrating coloration in both transmission and reflection modes by taking advantage of a multilayer stack consisting of MgF₂ and TiO₂ used respectively as the low and high index materials. In order to enable such trans-reflective performance, securing an optimal stop band assuming an appropriate bandwidth within the visible regime is pivotal, which was realized by tailoring the thicknesses and the numbers of TiO₂-MgF₂ bi-layers. Three devices were designed through rigorous simulations and developed via e-beam evaporation to demonstrate vivid blue, green, and red colors in the reflection mode, and yellow, magenta, and cyan colors in the transmission mode, featuring an enhanced efficiency exceeding 90% under normal incidence. The color performance of the filters was examined by referring to the chromaticity coordinates of the transmission and reflection spectra, alongside photographed color images. The dependence of the performance on the angle of incidence was explored with respect to incident polarization, indicating that a transmission surpassing 60% could be stably maintained up to an angle of 75°. Polarization independent transfer characteristics were especially achieved for the normal incidence. The proposed devices may be readily extended to other spectral regimes by adjusting the thicknesses of the films.

• Journal of the Optical Society of Korea
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• v.14 no.3
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• pp.260-265
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• 2010

This paper proposes a transflective configuration of the dual operating mode liquid crystal display, which has transmissive dynamic and reflective memory parts in its pixel. By employing a wideband structure and optimizing the cell-gap of the liquid crystal layer, the reflective memory part shows a very low reflectance in the dark state, good dispersion properties for the entire visible range, as well as high reflectance in the bright state. The transmissive dynamic part is designed to have the same cell-gap and rubbing direction as those of the reflective part. The driving voltage of the dynamic part and transmittance of the bright state can also be controlled by using compensation film with a positive a-plate, which can compensate the reflective part. Experimental results in the memory part operation demonstrate that the contrast ratio is over 50:1 and the reflectance in the dark state is reduced to 56% on average of that of the conventional dual mode configuration for the entire visible range. The contrast ratio of the dynamic part is 300:1.

• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.24-29
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• 2009

The SiOC film as inter layer insulator was researched the reason of the decreasing the dielectric constant by the ionic polarization and electronic polarization, respectively. The dielectric constant was measured using the conventional C-V measurement system, and the reflective index owing to the electronic polarization. Two kinds of dielectric constants were compared and then induced the origin of low-k materials. The chemical properties of the SiOC film were analyzed by the FTIR spectra, and the carbon content was obtained by the deconvoluted data of FTIR spectra. The variation of the carbon content tended to similar to the trend of reflective index, but was in inverse proportion to the dielectric constant. The effect of the electronic polarization did not affect the decreasing the dielectric constant, however the ionic polarization decreased effectively the dielectric constant of the SiOC film.

• Korean Medical Education Review
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• v.23 no.3
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• pp.194-203
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• 2021

Learning communities in medical education have demonstrated favorable outcomes in terms of students' learning, professional development, and wellness. Despite these strengths and the widespread adoption of learning communities in US medical schools, there has been little interest in medical learning communities in Korea. In this context, the present study examined the development and implementation of the Yonsei Medical Learning Community (YMLC) and analyzed its outcomes and areas of improvement. The Yonsei University College of Medicine has operated a learning community as part of the undergraduate medical education curriculum since 2014. The YMLC is the first program of its type in Korea. The overall structure of the YMLC consists of four distinct communities (pillars), which are named after four distinguished alumni, and each pillar is organized into five learning community classes. Each class is vertically integrated across students in different medical school years, and one faculty advisor is matched to about 30 students. As the YMLC focuses on fostering reflective practice in students and providing them with opportunities to build teamwork and experience social relatedness, two educational approaches have been adopted: reflective writing and mentoring and community activities. In this study, we obtained and analyzed second-year students' feedback on the YMLC curriculum and identified its achievements, merits, and areas that need improvement. The results have shown that over 75% and 60% of respondents reported satisfaction with reflective writing and mentoring and community activities, respectively. The educational activities of the learning community helped students regularly reflect on their learning and progress and establish close relationships with faculty advisors. However, several areas of improvement regarding content, format, and logistical issues were also identified. The present findings may provide valuable information for other institutions to develop learning communities relevant to their own context.

• Asia Marketing Journal
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• v.18 no.2
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• pp.63-93
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• 2016

As one of the most popular forms of electronic commerce, cross-border e-commerce provides numerous consumer benefits, such as broad and deep product assortments at low prices. However, consumers tend to exhibit high involvement in cross-border e-commerce purchases due to high risks associated with such purchases. The paper focuses on identifying causal relationships between e-commerce website traits (i.e., website trustworthiness, interactivity and convenience) and consumer satisfaction and along with loyalty. We proposed a reflective-reflective hierarchical model (first-order reflective and second-order reflective model) and used the Partial Least Square Analysis Statistical method to test the hypotheses. The results demonstrated that website trustworthiness, convenience and interactivity were all positively related to consumer satisfaction. Also, higher satisfaction led to stronger customer loyalty, which may well increase revisit intentions. We also compared the strength of each path from a website trait to satisfaction. Results illustrated that the path from website convenience to satisfaction is the strongest among the three website traits. In addition, we separately examined differences within Korean group and Chinese group. No statistically significant difference among website traits was found within Korean group. However, within Chinese group, we found that website convenience is the most important predictor of satisfaction. This indicates that Chinese consumers are more concerned about the website convenience than interactivity and trustworthiness when they make cross-border e-commerce purchases. Moreover, this study investigated possible differences between Korean and Chinese group. We used multi-group analysis of Smart PLS 3.0 to test the results. It was shown that the two groups do not display statistically significant difference in trustworthiness, interactivity, or convenience in influencing customer satisfaction. Finally, we presented further implications which are useful for understanding of the proposed model. Limitations and improvements of this research were presented, too.

• Journal of Information Display
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• v.2 no.3
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• pp.39-43
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• 2001

The glass compositions of $PbO-SiO_2-B_2O_3$ system and $P_2O_5-PbO-ZnO$ system for the transparent dielectric materials for front panel and $P_2O_5$-ZnO-BaO and $SiO_2-ZnO-B_2O_3$ for the reflective dielectric materials for back panel of PDP (Plasma Display Panel) were investigated. As a result, transparent dielectric materials for front panel showed good dielectric properties, high transparency, and proper thermal expansion matching to soda lime glass substrate. And the reflective dielectric layers for back panel were prepared from two series of parent glass and oxide filler. It was found that these glassceramics are useful materials for dielectric layers in PDP device, as they have similar thermal expansion to soda-lime glass plate, high reflectance, and low sintering temperature. In particular, the addition of $BPO_4$ and $TiO_2$ as fillers to $SiO_2-ZnO-B_2O_3$ system is considered to be the most effective for acquiring good properties of lower dielectric layer for PDP device.

• Journal of the Korean School Mathematics Society
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• v.8 no.1
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• pp.77-87
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• 2005

Smith(2001) calls for practice-based professional development for teachers of mathematics. This paper discusses laboratory class as a model for conducting professional development program for a group f elementary school mathematics teachers. The laboratory class seeks to promote teachers' generative growth (Carpenter & Levi, 1999) and all the core and structural features (Garet, Porter, Desimone, Birman & Kwang, 2001) of a professional development are also engaged in this program and the ultimate goal is for teachers to be reflective in their practices to be generative (Carpenter & Leher, 1999) in their teaching and learning. This paper also discusses the design of the laboratory class based on the principles of reflective thinking and psychological observation by Dewey to connect theory with practice.

• Journal of the Optical Society of Korea
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• v.17 no.2
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• pp.142-147
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• 2013

In order to deduce the difficulty of fixing the Ritchey-Chretien (R-C) dual reflective optical system and enhance the stability of the secondary mirror, a compact integral structure is presented here composed of two transmitting and two reflective aspheric surfaces. The four surfaces were manufactured from a single germanium lens and integrated together. The two reflective surfaces formed by coating the inner reflecting films were assembled in one lens. It makes the installation of the two mirrors easier and the structure of the secondary mirror more stable. A design of mid-wave infrared (MWIR) compact imaging system is presented with a spectral range chosen as $3.7-4.8{\mu}m$. The effective focal length is f=90 mm. The field of view (FOV) for the lens is $4.88^{\circ}$. It has good imaging capability with Modulation Transfer Function (MTF) of all field of view more than 0.55 close to the diffraction limitation. Outdoor experiments were carried out and it is shown that the integral catadioptric optical system performs well on imaging.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.160-166
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• 2012

We performed the development and performance evaluation of reflective type heart rate measurement system for PAPS. We used chip LED and chip photo TR. for low power driving. The measured PPG signal is preprocessed using high pass filter and low pass filter, and the preprocessed signal is displayed by LabVIEW. Also LabVIEW include the algorithm that extract effective signal and calculate the heart rate. We made sure that it will be able to apply to measurement equipment with high accuracy and repetition from exercising subject using this system and algorithm.

• Transactions on Electrical and Electronic Materials
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• v.13 no.5
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• pp.233-236
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• 2012

The driving properties of a particle-insertion method that filters non-moving particles are analyzed, by measuring its optical and electrical properties. An area that is occupied by the moved particles is proposed, as a desirable evaluation method for a reflective display. To compare the driving property of the particle-moving method with that of the reported simple particle-loading method, two panels are fabricated, according to the different particle-insertion methods, in the same panel condition, of which the width of ribs is $30{\mu}m$, the cell size is $220{\mu}m{\times}220{\mu}m$, the cell gap is $116-120{\mu}m$, the q/m value of the black particles is $+1.8{\mu}C/g$ and that for the white particles is $-4.3{\mu}C/g$. The particle-moving method has a filtering effect which excludes the non-moving particles, inserting only movable particles into the respective cell, so that a panel fabricated by the particle-moving method can drive most of the particles in a cell. Also, most of the particles move at the threshold voltage of 40 V, with enhanced reflectivity. The driving property is also verified by measurement of the occupation rate of the moved particles.