• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.32-38
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• 2021

We developed an inductively coupled plasma (ICP) etcher for GaN etching using a parallel plasma electrode source with a multifunctional chuck matched to it in order for the low power consumption and low process cost in comparison with the conventional ICP system with a helical-type plasma electrode source. The optimization process condition using it for the micro light-emitting diode (µ-LED) chip fabrication was established, which is an ICP RF power of 300 W, a chuck power of 200 W, a BCl₃/Cl₂ gas ratio of 3:2. Under this condition, the mesa structure with the etch depth over 1 ㎛ and the etch angle over 75° and also with no etching residue was obtained for the µ-LED chip. The developed ICP showed the improved values on the process pressure, the etch selectivity, the etch depth uniformity, the etch angle profile and the substrate temperature uniformity in comparison with the commercial ICP. The µ-LED chip fabricated using the developed ICP showed the similar or improved characteristics in the L-I-V measurements compared with the one fabricated using the conventional ICP method

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.42.4-43
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• 2020

The hydrogen-rich envelope mass of a dying massive star is the key factor that determines the type and properties of the resulting supernova. Emulating wind-driven mass loss of single stars with the MESA(Modules for Experiments in Stellar Astrophysics) stellar evolution code, we made a grid of models for a large parameter space of initial mass (12 M⊙ to 30M⊙), metallicity (solar, LMC and SMC), hydrogen envelope mass (0.01M⊙ to 10M⊙) for progenitor stars in their final step of evolution. Our results suggest the final luminosity of the progenitor is largely determined by the initial mass, which means there is luminosity degeneracy for stars with the same initial mass but with different hydrogen-rich envelope masses. Since we can break this degeneracy by correcting luminosity with surface gravity (spectroscopic HR diagram), we can infer the exact mass property of an observed progenitor. The surface temperature drastically varies near the envelope mass of ~0.1M⊙ and surface temperature of ~10000 K, where the demarcation between the hydrogen-rich envelope and the helium core lies, which explains the rarity of 'white' supergiants. There also exists a discontinuity in the chemical composition of the progenitor envelope around this critical hydrogen-rich envelope mass of ~0.1 M⊙, which can be tested in future observations of "flash spectroscopy" of supernovae.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.70.4-71
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• 2020

One of the distinctive characteristics of the evolution of binary systems would be mass transfer. Close binary systems experience so-called Case A mass transfer during the main-sequence. We have performed calculations of the evolution of massive Case A (with the initial period 1.5 ~ 4.5 days) binary systems with the initial mass of 10 ~ 20 solar masses and mass ratio 0.5 ~ 0.95 using the MESA code. We find that in some systems, after the first mass transfer, the secondary stars evolve faster than the primary stars and undergo so-called 'reverse' mass transfer. Such phenomena tend to occur in relatively low-mass (initial mass < 16 solar masses) and close (initial period < 3 day) systems. Unless a system enters the common-envelope phase, the primary star would become a single helium star after the secondary star ends its life if the system were unbound by the neutron star kick. We find the various evolutionary implications of the remaining primary stars. In addition to the evolution into the compact single helium star progenitor, there is a possibility that the remaining primary star could evolve into a helium giant star, which could be a promising candidate for Type Ibn supernova progenitor, depending on the core mass. Further, we find that some primary stars satisfy the conditions for the formation of electron-capture supernova progenitor.

• Journal of the Korean association of regional geographers
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• v.16 no.3
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• pp.216-223
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• 2010

The study deals with classification of drought-flood intensity using Z index based on the precipitation data in Hyesan of the past 50 years(1957~2006). The frequencies of years and four seasons of flood drought and their change features have also been analyzed based on tendency analysis and MESA and wavelet methods. Results show that the annual and seasonal frequencies of flood-drought exceed 24% in Hyesan and flood-drought disasters have been high frequency. Inter-decadal variability seems to be clear in autumn but those of inter-annual variability are obvious in other three seasons and years. Recently the probability of drought disaster become higher in autumn. The flood disaster in other three seasons and years are estimated to become higher in the future.

• Journal of Periodontal and Implant Science
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• v.45 no.6
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• pp.252-256
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• 2015

Purpose: The purpose of this report was to describe the clinical and microbiological characteristics of two rare cases of necrotizing stomatitis, and the outcomes of a non-invasive treatment protocol applied in both cases. Methods: We report two cases of necrotizing stomatitis in a rare location in the hard palate of a 40-year-old woman and a 28-year-old man. Neither had a relevant medical history and both presented with highly painful ulceration in the palate and gingival margin that was accompanied by suppuration and necrosis. 3% hydrogen peroxide was applied to the lesions using sterile swabs, and antibiotic and anti-inflammatory treatment was prescribed to both patients in addition to two daily oral rinses of 0.2% chlorhexidine. Results: In both cases, radiological examination ruled out bone involvement, and exfoliative cytology revealed a large inflammatory component and the presence of forms compatible with fusobacteria and spirochetes. There was a rapid response to treatment and a major improvement was observed after 48 hours, with almost complete resolution of the ulcerated lesions and detachment of necrotic areas with partial decapitation of gingival papillae. Conclusions: Necrotizing periodontal lesions can hinder periodontal probing and the mechanical removal of plaque in some cases due to the extreme pain suffered by the patients. We present a non-invasive treatment approach that can manage these situations effectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.6
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• pp.539-545
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• 2014

Contact resistivity between silver electrodes and the emitter layer of a silicon solar cell wafer has been measured using either the circular transmission line method or the linear transmission line method. The circular transmission line method has an advantage over the linear transmission line method, in that it does not require an additional process for mesa etching to eliminate the leakage current. In contrast, the linear transmission line method has the advantage that its specimen can be acquired directly from a silicon solar cell. In this study, measured resistance data for the calculation of contact resistivity is compared for these two methods, and the mechanism by which the linear transmission line method can more realistically reflect the impact of the width and thickness of a silver electrode on contact resistivity is investigated.

• Clean Technology
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• v.11 no.2
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• pp.69-74
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• 2005

A metal ion detector with a submicron size electrode was fabricated by field-induced AFM oxidation. The square frame of the mesa pattern was functionalized by APTES for the metal ion detection, and the remaining portion was used as an electrode by the self-assembly of MPTMS for Au metal deposition. The conductance changed with the quantity of adsorbed copper ions, due to electron tunneling between the mobile and surface electrodes. The smaller electrode has a lower limit of detection due to the enhancement in electron tunneling through metal ions that are adsorbed between the conductive-tip (mobile) and the surface (fixed) electrode. This two-electrode system immobilized with different functional groups was successfully used in the selective adsorption and detection of target materials.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.12
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• pp.27-34
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• 2005

We have investigated the correlation between the active-layer uniformity and reliability of InGaN/GaN blue LEDs. According to initial characteristics, the devices are classified into two groups: group I devices of uniform light-emission and group II devices of non-uniform light-emission. The group II devices are more dependent on temperature and we have found two degradation mechanisms through reliability test. One is bulk degradation in which the degradation occurred over the entire chip and another one is edge degradation in which the degradation occurred from the edge of the chip. Bulk degradation caused by the nonradiative defects is found to be faster in group II devices while there is no difference in the rate of the much faster edge degradation, where darkening starts from the n-Ohmic contact edge. Therefore, more uniform active layer, more uniform current spreading, and the passivation of the dry-etched side-wall are essential for the high reliability of InGaN/GaN LEDs.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.2
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• pp.28-35
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• 2003

This study was conducted to identify the characteristics of social carrying capacity at mega-events, especially the 2000 Kwangju Biennale in Korea. In particular, this paper has proposed some management policies for mega events taking into account the relations between social carrying capacity, satisfaction and crowding. The research method was to look into the general characteristics and distributive forms of the location, and then to confirm the possibility of sampling the factors involved in satisfaction degree; last, A factor analysis for causal analysis of perceived crowding was performed. The study needed correlation analysis in order to compare expected crowding and perceived crowding, and performed regression to examine the causality of perceived crowding and satisfaction. The research results were as follows: the correlation of expected crowding, perceived crowding, and the total satisfaction was very low or meaningless. The relation between satisfaction and elements for factor analysis such as convenient facilities and value experience showed partial meaningfulness. The factors of convenient facilities, entrance fee, parking lot use, toilet convenience, and exhibit room use had meaningful results; on the other hand, the factors of value experience showed a meaningful result in the guide service of an event place. In conclusion when those holding an event make a basic project, they should consider management measures for convenience of facilities, proper education for guide service, and systematic guidance. Also, as a method for perceived crowding lower than expected crowding, the study has proposed that it is possible to lower expected crowding by providing appropriate information on the number of tourists expected on the weekends and weekdays. Future research should control variables such as personal characteristics, seasons proper for vacation and holidays, and carefully consider their investigation and design. Moreover, it is necessary to study variables involved in expected crowding of more various space-intensive sightseeing places (mesa-events).

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.327-332
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• 1997

We fabricated the high speed 1.55${\mu}{\textrm}{m}$ distributed feedback laser diodes (DFB-LD) using both two-step mesa etching process and semi-insulating InP current blocking layers. The devices characteristics were threshold current of ~15mA, slope efficiency of ~0.13mW/mA, and dynamic resistance of ~6.0Ω, with as-cleaved facets. The fabricated DFB-LD showed the single longitudinal mode with more than 40dB up to 6 $I_{th}$(CW condition), emitting at the wavelength of 0.546${\mu}{\textrm}{m}$. The -3dB bandwidth was >10㎓ at the driving current of 27mA, and the maximum -3dB bandwidth was ~18㎓ at 90 mA current, showing the superior frequency response of SI-PBH DFB-LD. In the 10Gb/s transmission experiment for 1.55${\mu}{\textrm}{m}$ DFB-LD module, maximum 10 km of single mode fiber(SMF) or 80 km of dispersion shifted fiber (DSF) could be transmitted with error free.