• Journal of Periodontal and Implant Science
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• v.34 no.1
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• pp.35-48
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• 2004

Since the occlusal loading is transmitted to the surrounding bone, the success of an implant treatment is closely related to the distribution of the stress on the implant. The finite element analysis method is often used in order to produce a model for dispersion of stress. Assessment of the success of the implant is usually based on the degree of osseointegration which is a bone and implant surface interface. Implant used in this research was designed through the method of shape optimization after the stress on implant was anaylzed by the finite element analysis method. This study was pertinently assessed by a clinical, histologic, histomorphometric analysis after the shape optimized implant was installed on beagle dog tibia. The results are as follows 1. It clinically showed a good result without mobility and imflammatory reaction. 2. Implant was supported by dense bone and bone remodeling showed on the surrounding area of the implant 3. The average percentage of bone-implant contact was 58.1%.The percentage of bone density was 57.6%. Having above results, shape optimized implant showed the pertinence through clinical and histologic aspects. However, to use the shape optimized implant, the further experiment is required for finding problems, improvement.

• The Journal of the Acoustical Society of Korea
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• v.23 no.5
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• pp.362-369
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• 2004

The High-frequency (30 ∼ 120 ㎑) bottom reflection loss at rough water-sediment interface is affected by the gram size distribution of the sediments. The roughness of the bottom surface is represented by "acoustical roughness. g/sub R/" The grain size of sandy sediments is g/sub R/∼O(1) and the dependence as a function of frequency. We suggest the modified bottom reflection loss model (HYBRL model , HanYang university Bottom Reflection Loss model) that include in the deviation of the reflection loss as a function of the grain size distribution and frequency dependence. And bottom reflection loss model of frequency dependence and deviation of bottom properties is verified by water tank and field experiments.

• Korean Journal of Materials Research
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• v.16 no.4
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• pp.257-263
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• 2006

We have investigated the effect of silver added to Cu films on the microstructure evolution, resistivity, surface morphology, stress relaxation temperature, and adhesion properties of Cu(Ag) alloy thin films deposited on Mo glue layer upon annealing. In addition, pure Cu films deposited on Mo has been annealed and compared. The results show that the silver in Cu(Ag) thin films control the grain growth through the coarsening of its precipitates upon annealing at $300^{\circ}C{\sim}600^{\circ}C$ and the grain growth of Cu reveals the activation energy of 0.22 eV, approximately one third of activation energy for diffusion of Ag dopant along the grain boundaries in Cu matrix (0.75 eV). This indicates that the grain growth can be controlled by Ag diffusion along the grain boundaries. In addition, the grain growth can be a major contributor to the decreased resistivity of Cu(Ag) alloy thin films at the temperature of $300^{\circ}C{\sim}500^{\circ}C$, and decreases the resistivity of Cu(Ag) thin films to $1.96{\mu}{\Omega}-cm$ after annealing at $600^{\circ}C$. Furthermore, the addition of Ag increases the stress relaxation temperature of Cu(Ag) thin films, and thus leading to the enhanced resistance to the void formation, which starts at $300^{\circ}C$ in the pure Cu thin films. Moreover, Cu(Ag) thin films shows the increased adhesion properties, possibly resulting from the Ag segregating to the interface. Consequently, the Cu(Ag) thin films can be used as a metallization of advanced TFT-LCDs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.99-99
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• 2008

To grow the large diameter GaN with high structure and optical quality has been obtained by hydride vapor phase epitaxy(HVPE) method. In addition to the nitridation of $Al_2O_3$ substrate, we also developed a "step-growth process" to reduce or to eliminate the bowing of the GaN substrate caused by thermal mismatch during cool down after growth. The as-grown 380um thickness and 75mm diameter GaN layer was separated from the sapphire substrate by laser-induced lift-off process at $600^{\circ}C$. A problem with the free-standing wafer is the typically large bowing of such a wafer, due to the built in the defect concentration near GaN-sapphire interface. A polished G-surface of the GaN substrate were characterized by room temperature Double crystal X-ray diffraction (DCXRD), photoluminescence(PL) measurement, giving rise to the full-width at half maximum(FWHM) of the rocking curve of about 107 arcsec and dislocation density of $6.2\times10^6/cm^2$.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.24-30
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• 2004

Gas hydrate formation process is studied in this paper. Natural gas was introduced into both pure water and water added anionic surfactant(promotor) at 276.65 K and 6 MPa. Gas hydrate nuclei was easily generated by instantaneous agitation. Gas hydrate film was formed on the interface of water and gas. The very thin film which was instantly covered the surface of the water, followed by generation of the clear film layer. Whiskery crystal of gas hydrate was created more actively in the water added naionic surfactant than in the pure water. Whiskery hydrate formed in the pure water looks like short and thick thread colony while the one shoes long and thin thread colony in the water added promoter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.970-977
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• 2018

Chinese mobile games enjoyed big success in Korean game market in 2017. On the surface, such success owes to their effort to strengthen the collaboration with Korean publishers and to relieve Chinese style in the game structure such as user interface. However, there seems to be other reasons for Korean mobile gamers to accept Chinese games more easily than before. In this paper, we analyze the preferences of Korean gamers playing chinese mobile games in 2017 by survey through many community sites. Among 201 subjects of our survey, 79% were males and most of them were under 20's. We found gender difference of game genre they played such that most young males played Moe-fied Fleet games but females played casual fashion collection games. Other than that, regardless of gender, Korean gamers preferred Chinese games' charging policy and management policy as well as the character illustrations that emphasized fantasy-style sexism (autome or ero-kawai).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.8
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• pp.486-490
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• 2014

$Al_2O_3$ films on silicon carbide were fabricated by Aerosol deposition with annealing temperature at $800^{\circ}C$ and $1,000^{\circ}C$. The effect of thermal treatment on physical properties of $Al_2O_3$ thin films has been investigated by XRD (X-ray diffraction), AFM (atomic force microscope), SEM (scanning electron microscope), and AES (auger electron spectroscopy). Also electrical properties have been investigated by Keithley 4,200 semiconductor parameter analyzer to explain the interface trapped charge density ($D_{it}$), flatband voltage ($V_{FB}$) and leakage current ($I_o$). $Al_2O_3$ films become crystallized with increasing temperature by calculating full width at half maximum (FWHM) of diffraction peaks, also surface morphology is observed by topography measurement in non-contact mode AFM. $D_{it}$ was $2.26{\times}10^{-12}eV^{-1}.cm^{-2}$ at $800^{\circ}C$ annealed sample, which is the lowest value in all samples. Also the sample annealed at $800^{\circ}C$ has the lowest leakage current of $4.89{\times}10^{-13}A$.

• Resources Recycling
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• v.25 no.3
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• pp.74-81
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• 2016

Study on chlorination of ilmenite ore were carried out by using PVC(polyvinyl chloride) as the chlorinating agent in a static bed reactor for selective removal of iron. The effect of amount of PVC and reaction temperature were investigated. It was found that the removal ratio of iron increased with amount of PVC and temperature. After reaction with HCl gas generated from PVC, porous surface of the specimens were observed. As a result, HCl gas could react with iron in the central portion of ilmenite particle through these pores. Examination of data using kinetic model suggest that the selective chlorination rate is controlled by chemical reaction at the interface of particles. The activation energy for the selective chlorination of ilmenite using PVC was calculated as 20.47 kJ/mol.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.809-812
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• 2006

This paper describes about the vision system, which was developed for the recognition of material management characters in the slab processing line. The material management characters, which are marked at the surface of a slab, are recognized by real time processing before slab moves to the next hot strip line. The vision system for the character recognition include that CCD camera system which acquire slab image, image transmission system which transmit captured image to the long distance, I/O devices for the interface with peripheral control system. We have installed vision system to the slab processing line and tested. Through the testing, we have checked durability, reliability and recognition rate of our system. In the results, we have confirmed that our system have good performance and higher recognition ability.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.145-145
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• 2018

Small islands rely heavily on groundwater resources in addition to rainwater as the source of freshwater since surface water bodies are often absent. The groundwater resources are vulnerable to sea level rise, coastal flooding, saltwater intrusion, irregular pattern of precipitation resulting in long droughts and flash floods. Increase in population increases the demand for the limited groundwater resources, thus aggravating the problem. In this study, the effects of climate change on Tongatapu Island, Kingdom of Tonga, a small island in Pacific Ocean, are investigated using a sharp interface transient groundwater flow model. Twenty nine downscaled General Circulation Model(GCM) predictions are input to a water balance model to estimate the groundwater recharge. The temporal variation in recharge is predicted over the period of 2010 to 2099. A set of GCM models are selected to represent the ensemble of 29 models based on cumulative recharge at the end of the century. This set of GCM model predictions are then used to simulate a total of six climate scenarios, three each (2010-2039, 2040-2069, and 2070-2099) under RCP 4.5 and RCP 8.5. The impacts of predicted climate change on groundwater resources is evaluated in terms of freshwater volume changes and saltwater ratios in pumping wells compared to present conditions. Though the cumulative recharge at the end of the century indicates a wetter climate compared to the present conditions the large variability in rainfall pattern results in frequent periods of groundwater drought leading to saltwater intrusion in pumping wells. Thus for sustaining the limited groundwater resources in small islands, implementation of timely assessment and management practices are of utmost importance.