• The Journal of Advanced Prosthodontics
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• v.12 no.1
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• pp.1-8
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• 2020

PURPOSE. To investigate the influence of crown material (lithium-disilicate, 3Y-TZP zirconia) and abutment type (rigid implant, resin tooth with artificial periodontium) on wear performance of their antagonist teeth and adjacent teeth. MATERIALS AND METHODS. A mandibular left first molar (#36) with adjacent human teeth (mandibular left second premolar: #35, mandibular left second molar: #37) and antagonistic human teeth (maxillary left second premolar: #25, maxillary left first molar: #26, maxillary left second molar: #27) was prepared simulating a section of the jaw. Samples were made with extracted human molars (Reference), crowned implants (Implant), or crowned resin tooth analogues (Tooth). Crowns (tooth #36; n = 16/material) were milled from lithium-disilicate (Li, IPS e.max CAD) or 3Y-TZP zirconia (Zr, IPS e.max ZirCAD, both Ivoclar Vivadent). Thermal cycling and mechanical loading (TCML) in the chewing simulator were applied simulating 15 years of clinical service. Wear traces were analyzed (frequency [n], depth [㎛]) and evaluated using scanning electron pictures. Wear results were compared by one-way-ANOVA and post-hoc-Bonferroni (α = 0.05). RESULTS. After TCML, no visible wear traces were found on Zr. Li showed more wear traces (n = 30-31) than the reference (n = 21). Antagonistic teeth #26 showed more wear traces in contact to both ceramics (n = 27-29) than to the reference (n = 21). Strong wear traces (> 350 ㎛) on antagonists and their adjacent teeth were found only in crowned groups. Abutment type influenced number and depth of wear facets on the antagonistic and adjacent teeth. CONCLUSION. The clinically relevant model with human antagonistic and adjacent teeth allowed for a limited comparison of the wear situation. The total number of wear traces and strong wear on crowns, antagonistic and adjacent teeth were influenced by crown material.

• Korean Medical Education Review
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• v.16 no.2
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• pp.92-98
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• 2014

Medical education departments or offices are established in response to public expectations relating to health care, societal trends towards increased accountability, educational developments, increased interest in what to teach and how to educate doctors. However, heavy workloads and mixed feelings towards medical education departments or offices by the other members of a medical school can threaten job satisfaction and increase burnout. The authors investigated the prevalence of burnout among medical education specialists and related issues. Individual in-depth interviews with four medical education specialists were conducted to develop a questionnaire. After content analysis of the interview, the authors generated a survey form with 28 items including 6 categories: motivation to choose medical education as a career, job satisfaction, intention to leave their current position in medical education, the frequency and causes of burnout, and demographics. In September 2013, an email survey was administered to 43 faculty including non-tenure staff who were working in the department/office of medical education in 41 medical colleges in Korea. Of 43 medical education specialists, 25 (60%) returned surveys. Forty three-point-three percent of them felt encouraged when their endeavors generated a visible educational improvement in the medical school. A majority (87%) reported feeling burned out. Fifty percent of them experienced the feeling once or twice a year. The extent of burnout tended to be greater in women, those in their forties, those with non-medical doctor degrees, and in non-tenured staff. To reduce and prevent burnout among medical education specialists, the participants suggested that leadership of medical schools and a systematic approach to medical education should be established. A majority of the medical education specialists reported experiencing burnout, although they were satisfied with their jobs. To reduce their burnout and allow them to focus on their own work in medical education, the following factors are needed: perceptual changes of other members of the college about medical education; more systematic institutional strategies; networking among medical education specialists; and personal efforts for professional development.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.423-427
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• 2017

The IMO approved e-navigation strategy implementation plan made e-navigation adoption visible. In addition, the schedule for the modernization of GMDSS by the ITU was confirmed at the 4th NCSR meeting. Accordingly, we will complement the existing communication system and provide the requirements for the new communication system to be introduced in the future, reflecting all the requirements for the communication system capable of supporting the e-navigation service. Although the communication method for supporting e-navigation service should be capable of providing IP-based data communication basically, it is impossible to provide internet service because of the narrow-band characteristic in the MF/HF frequency bands. In addition, as the existing GMDSS satellite communication service organization expands and new services are introduced, IP based data communication service will be possible, but service restriction resulting from expensive communication cost can be solved by introducing VSAT service.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.313-318
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• 1998

Electro-Optical Camera(EOC) is the main payload of Korea Multi-Purpose SATellite(KOMPSAT) with the mission of cartography to build up a digital map of Korean territory including Digital Terrain Elevation Map(DTEM). This instrument which comprises EOC Sensor Assembly and EOC Electronics Assembly produces the panchromatic images of 6.6 m GSD with a swath wider than 17 km by push-broom scanning and spacecraft body pointing in a visible range of wavelength, 510 ~ 730 nm. The high resolution panchromatic image is to be collected for 2 minutes during 98 minutes of orbit cycle covering about 800 km along ground track, over the mission lifetime of 3 years with the functions of programmable rain/offset and on-board image data storage. The image of 8 bit digitization, which is collected by a full reflective type F8.3 triplet without obscuration, is to be transmitted to Ground Station at a rate less than 25 Mbps. EOC was elaborated to have the performance which meets or surpasses its requirements of design phase. The spectral response the modulation transfer function, and the uniformity of all the 2592 pixel of CCD of EOC are illustrated as they were measured for the convenience of end-user. The spectral response was measured with respect to each gain setup of EOC and this is expected to give the capability of generating more accurate panchromatic image to the EOC data users. The modulation transfer function of EOC was measured as greater than 16% at Nyquist frequency over the entire field of view which exceeds its requirement of larger than 10%, The uniformity that shows the relative response of each pixel of CCD was measured at every pixel of the Focal Plane Array of EOC and is illustrated for the data processing.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.346-346
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• 2012

We investigated electrical and optical properties and chemical states of amorphous In-Ga-Zn-O (a-IGZO) thin films deposited at different substrate temperatures (from room temperature to $300^{\circ}C$). a-IGZO thin films were fabricated by radio frequency magnetron sputtering using $In_2O_3$ : $Ga_2O_3$ : ZnO = 1 : 1 : 1 target, and their electrical and optical properties and chemical states were investigated by Hall-measurement, UV-visible spectroscopy and x-ray photoelectron spectroscopy (XPS), respectively. The data showed that as substrate temperature increased, carrier concentration increased, but mobility, conductivity, transmittance in the shorter wavelength region (>350 nm), and the Tauc-plot-estimated optical bandgap decreased. XPS data indicated that the intensity of In 3d peak compared to Ga 3d peak increased but the intensity of Zn 3d peak compared to Ga 3d decreased, and that, from the deconvoluted O 1s peak, defects or oxygen vacancies and non-quaternary contents increased as the temperature increased. The relative intensity changes of the In, Zn, and O 1s sub-component are suggested to explain the changes in electrical and optical properties.

• Korean Journal of Materials Research
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• v.30 no.9
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• pp.489-494
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• 2020

SiC is a material with excellent strength, heat resistance, and corrosion resistance. It is generally used as a material for SiC invertors, semiconductor susceptors, edge rings, MOCVD susceptors, and mechanical bearings. Recently, SiC single crystals for LED are expected to be a new market application. In addition, SiC is also used as a heating element applied directly to electrical energy. Research in this study has focused on the manufacture of heating elements that can raise the temperature in a short time by irradiating SiC-I₂ with microwaves with polarization difference, instead of applying electric energy directly to increase the convenience and efficiency. In this experiment, Polydimethylsilane (PDMS) with 1,2 wt% of iodine is synthesized under high temperature and pressure using an autoclave. The synthesized Polycarbosilane (PCS) is heat treated in an argon gas atmosphere after curing process. The experimental results obtain resonance peaks using FT-IR and UV-Visible, and the crystal structure is measured by XRD. Also, the heat-generating characteristics are determined in the frequency band of 2.45 GHz after heat treatment in an air atmosphere furnace.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.474-482
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• 2000

Currently frequency-dependent type electronic apex locators have been widely used to determine the working length in endodontic treatment. But, accuracy of electronic apex locators is controversial. The purpose of this study was to evaluate the accuracy of Root-ZX(Morita Co., Japan) at different kinds of conditions of root canals compared with the radiographic working length. The 40 extracted human anterior teeth with fully formed apices and without any caries were used. The radiographs were taken for working length with the 0.5mm short of #15 K-file tip just visible at the foramen under the surgical microscope(Carl Zeiss Co. Germany) at 25X. Then the electronic working lengths were determined with Root-ZX at the different kinds of conditions of root canals according to the presence of electrolyte and Crown-down pressureless technique. The results were as follows ; 1. There was no significant statistical difference in working length between radiograph and Root-ZX. 2. There was no significant statistical difference in electronic working length between the canal with electrolyte and without electrolyte. 3. There was no significant statistical difference in electronic working length between the canal without any instrumentation and after Crown-dow pressureless technique. 4. Of the total 40 root canals, 85% in Group I, 92.5% in Group II, 95% in Group III and 95% in Group IV using Root-ZX showed coincidence within 0.5mm accuracy compaing with the radiographic working length. The results showed that the Root-ZX can be use effectively for measuring the working length of root canal after instrumentation with Crown-down pressureless technique regardless of the presence of electrolyte in root canal.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.43.2-43.2
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• 2013

The local environmental effects on the triggering of active galactic nucleus(AGN) activity has been studied with many authors, but there still be controversy. We perform statistical analysis for nearby(0.01 < z < 0.05) volume limited(Mr < -19) samples with visual inspection based on Sloan Digital Sky Survey Data Release7. We inspect ~60,000 galaxy images visually to find peculiar objects which show not only ongoing merging features and tidal features, but also post merging features like ring or shell structures. We found that these peculiar features were shown at least 2 times more frequently among AGN host galaxies than non AGN galaxies, and this trend was still visible when galaxy properties such as color or stellar mass are fixed. Furthermore, L[OIII] and L(Ha) of peculiar galaxies are found to be more increased than those of normal galaxies. In order to ensure this results, we also checked it for a smaller subsample with ~2mag deeper monochromatic images provided from SDSS Stripe82 database, and found consistent results. At last, we perform the same work for pair(r_p<80kpc/h, delta_v<200km/s) systems. Because of some pair systems which do not interact gravitationally in actuality but fulfill the criteria for identification of pair system, the trends are found to be slightly weaker. We also found that line luminosities are increased consistently as projected distance between central and companion galaxy decreased, and as companion color gets bluer. Overall, the results of this study tell us that the local environment of galaxies affect the frequency as well as the strength of AGN activity. Local environmental effects, however, may not be the dominant triggering mechanism for AGN activity since the majority of peculiar galaxies are non AGN galaxies.

• Industrial Engineering and Management Systems
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• v.9 no.3
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• pp.285-293
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• 2010

To obtain visible and traceable information from the supply chain, HW/SW standards for the EPC global network, which process electronic product code (EPC) data read from Radio frequency identification (RFID) tags, are regarded as the de facto industry standard. Supply chain participants install information service systems and provide logistics information to partners by following the EPCglobal architecture framework. Although quality of service (QoS) is essential for providing dependable and scalable services as pointed out by Auto-ID Lab, only a few models for the performance analysis of QoS-related work have been developed in the context of EPC information service systems. Specifically, doing so allows alternative design choices to be tested in an easy and cost-effective manner and can highlight potential performance problems in designs long before any construction costs are incurred. Thus, in this study we construct a model of an EPC information service system for the purposes of performance analysis and designing a dependable system. We also develop a set of building blocks for analytical performance models. To illustrate how the model works, we determine the characteristics of an EPC information service system and then select a combination of these proven modeling concepts. We construct a performance model that considers the response time and shows how to derive meaningful performance values. Finally, we compare the analytical results to measurements of the EPC information service system.

• Transactions on Electrical and Electronic Materials
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• v.10 no.6
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• pp.203-207
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• 2009

We have investigated the effect of ambient gases on the structural, electrical, and optical characteristics of ITO thin films intended for use as anode contacts in OLED (organic light emitting diodes) devices. These ITO thin films are deposited by radio frequency (RF) magnetron sputtering under different ambient gases (Ar, Ar+$O_2$, and Ar+$H_2$) at $300{^{\circ}C}$. In order to investigate the influences of the oxygen and hydrogen, the flow rate of oxygen and hydrogen in argon mixing gas has been changed from 0.5 sccm to 5 sccm and from 0.01 sccm to 0.25 sccm, respectively. The intensity of the (400) peak in the ITO thin films increased with increasing $O_2$, flow rate whilst the (400) peak was nearly invisible in an atmosphere of Ar+$H_2$. The electrical resistivity of the ITO thin films increased with increasing $O_2$ flow rate, whereas the electrical resistivity decreased sharply under an Ar+$H_2$ atmosphere and was nearly similar regardless of the $H_2$ flow rate. The change of electrical resistivity with changes in the ambient gas composition was mainly interpreted in terms of the charge carrier mobility rather than the charge carrier concentration. All the films showed an average transmittance of over 80% in the visible range. The OLED device was fabricated with different ITO substrates made with the configuration of ITO/$\alpha$-NPD/DPVB/$Alq_3$/LiF/Al in order to elucidate the performance of the ITO substrate. Current density and luminance of OLED devices with ITO thin films deposited in Ar+$H_2$ ambient gas is the highest among all the ITO thin films.