• Journal of the Korean Vacuum Society
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• v.17 no.1
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• pp.73-79
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• 2008

In order to apply for transparent conductive oxide(TCO), we deposited ZnO thin films on the glass at room temperature by RF magnetron sputtering method. Deposition conditions for high transmittance and low resistivity were optimized in our previous studies. Under the deposition condition with the RF power of 200 W, target to substrate distance of 30 mm and working pressure of 5 mTorr, highly conductive($7.4{\times}10^{-3}{\Omega}cm$) and transparent(over 85%) ZnO films were prepared. Highly oriented ZnO film in the [002] direction were obtained with specifically designed ZnO targets. Systematic study on dependence of deposition parameters on electrical and optical properties of the as-grown ZnO films were mainly investigated in this work. And for application tests using these films as transparent conductive oxide anodes, wet chemical etching behaviors of ZnO films were also investigated using various chemicals. Wet-chemical etching behavior of ZnO films were investigated using various acid solutions. The concentrations of these different acid solutions were controlled to study the etching shapes and etching rate. ZnO films were anisotropically etched at various concentrations and wet etching led to crater-like surface structure. Also we firstly found that the etching rate and etching shapes of ZnO films strongly depended on the etchant concentrations (i.e. pH) and the etching rate is exponentially decreased with increasing pH values regardless of the acid etchants.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.589-600
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• 2007

Statement of Problem: Titanium has many advantages of high biocompatibility, physical porperties, low-weight, low price and radiolucency, but it is incompatible with conventional dental porcelain due to titanium's oxidative nature. Many previous studies have shown that they used the method of sandblast surface treatment prior to porcelain application, the researchs are processing about the method of acid etching or surface coating. Purpose: The purpose of this research is to study the effect on bond strength between titanium and porcelain when using macro-surface treatment and micro-surface treatment and macro and micro surface treatment. Material and method: In this study, we evaluated the bond strength by using 3-point bending test based on ISO 9693 after classified 7 groups-group P : polished with #1200 grit SiC paper, group SS : sandblasted with $50{\mu}m$ aluminum oxides, group LS : sandblasted with $250{\mu}m$ alumium oxides, group HC : treated with 10% hydrochloric acid, group NF : treated with 17% solution of fluoric acid and nitric acid, group SHC : treated with 10% hydrochloric aicd after sandblsting with $50{\mu}m$ alumium oxides, group SNF treated with 17% solution of fluoric acid and nitric acid. Results : Within the confines of our research, the following results can be deduced. 1. Group SS which was sandblasted with $50{\mu}m$ aluminum oxides showed the highest bond strength of 61.74 MPa and significant differences(P<0.05). The bond strengths with porcelain in groups treated acid etching after sandblasting decreased more preferable than the group treated with sandblasting only. It gives significant differences(P<0.05). 2. After surface treatments, the group treated with sandblasting showed irregular aspect formed many undercuts, in the SEM photographs. The group treated with hydrochloric acid had the sharp serrated surfaces, the group treated with the solution of fluoric acid and nitric acid had the smooth surfaces, the group with sandblasting and hydrochloric acid had irrigular and porous structure, the group with sandblasting and the solution of fluoric acid and nitric acid had crater-like surfaces. But all of the groups treated with acid etching was not found and undercut. Conclusion: In above results, average surface roughness increase, bond strength also increase, but surface topographs influences more greatly on bond strengths.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.319-334
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• 2006

Mechanical and chemical methods are the two ways to treat the implant surfaces. By using mechanical method, it is difficult to eliminate bacteria and by-products from the rough implant surface and it can also cause the structural change to the implant surface. Therefore, chemical method is widely used in order to preserve and detoxicate the implant surface more effectively. The purpose of this study is to evaluate the effect of tetracylcline-hydrochloride(TC-HCI) on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface, SLA surface and porous surface were used in this study. Implant surface was rubbed with sponge soaked in 50mg/ml TC-HCI solution for $\frac{1}{2}$ min., 1 min., $1\frac{1}{2}$ min., 2 min., and $2\frac{1}{2}$ min. respectively in the test group and with no treatment in the control group. Then, specimens were processed for scanning electron microscopic observation. 1. Both test and control group showed a few shallow grooves and ridges in pure titanium machined surface implants. There were not significant differences between two groups. 2. In the SLA surfaces, the control specimen showed that the macro roughness was achieved by large-grit sandblasting. Subsequently, the acid-etching process created the micro roughness, which thus was superimposed on the macro roughness. Irrespective of the application time of 50mg/ml TC-HCI solution, in general, test specimens were similar to control. 3. In the porous surfaces, the control specimen showed spherical particles of titanium alloy and its surface have a few shallow ridges. The roughness of surfaces conditioned with tetracycline-HCI was lessened and seen crater-like irregular surfaces relative to the application time. In conclusion, pure titanium machined surfaces and SLA surfaces weren't changed irrespective of the application time of tetracycline-HCI solution. But the porous surfaces conditioned with tetracycline-HCI solution began to be slightly changed from 2 min. This results are expected to be applied to the regenerative procedures for peri-implantitis treatment.

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.128-133
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• 2010

ZnO:Al films were deposited by DC-pulsed magnetron sputtering using a two-step process involving the control of the oxygen pressure. The seed layers were prepared with various Ar to oxygen flow ratios and the bulk layers were deposited under pure Ar. As the oxygen pressure during the deposition of the seed layer increased, the crystallinity and degree of (002) texturing increased. The resistivity gradually decreased with increasing crystallinity from $4.7\times10^4\Omega{\cdot}cm$ (no seed) to $3.7\times10^4\Omega{\cdot}cm$ (Ar/$O_2$ = 9/1). The etched surface showed a crater-like structure and an abrupt morphology change appeared as the crystallinity was increased. The sample deposited at an Ar/$O_2$ flow ratio of 9/1 showed a very high haze value of 88% at 500 nm, which was explained by the large feature size of the craters, as shown in the AFM image.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.513-523
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• 2012

The upper sedimentary layer of the Ulleung Basin in the East Sea shows stacked mass-flow deposits such as slide/slump deposits in the upper slope, debris-flow deposits in the middle and lower slope, and turbidites in the basin plain. Shallow gases or gas hydrates are also reported in many area of the Ulleung Basin, which are very important in terms of marine resources, environmental changes, and geohazard. This paper aims at studying acoustic characteristics and distribution pattern of gas-related structures such as acoustic column, enhanced reflector, dome structure, pockmark, and gas seepage in the upper sedimentary layer, by analysing high-resolution chirp profiles. Acoustic column shows a transparent pillar shape in the sedimentary layer and mainly occurs in the basin plain. Enhanced reflector is characterized by an increased amplitude and laterally extended to several tens up kilometers. Dome structure is characterized by an upward convex feature at the seabed, and mainly occurs in the lower slope. The pockmark shows a small crater-like feature and usually occurs in the middle and lower slope. Gas seepage is commonly found in the middle slope of the southern Ulleung Basin. These gas-related structures seem to be mainly caused by gas migration and escape in the sedimentary layer. The distribution pattern of the gas-related structures indicates that formation of these structures in the Ulleung Basin is controlled not only by sedimentary facies in upper sedimentary layer but also by gas-solubility changes depending on water depth. Especially, it is interpreted that the chaotic and discontinuous sedimentary structures of debris-flow deposits cause the facilitation of gas migration, whereas the continuous sedimentary layers of turbidites restrict the vertical migration of gases.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.381-390
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• 2004

The purpose of this in vitro study was to investigate the effects of Nd:YAG laser irradiation and fluorides on acid drink demineralized enamel. The materials were 30 freshly extracted permanent premolars with intact smooth enamel surfaces. They were demineralized with Coca-cola at $37^{\circ}C$ for 12hours and then irradiated by Nd:YAG laser with 6W power, $50mJ/cm^2$ energy density, and 20Hz pulse repetition. After laser irradiation, teeth were treated by three kinds of fluorides; (1)0.05% NaF fluoride solution (2)1.23% APF gel and (3)0.1%F fluoride varnish, microhardness(VHN) and Diagnodent scores were measured and the surfaces of each treated specimens were also observed with SEM under 1500 magnification. The results were as follows: 1. In the change of microhardness(VHN), it decreased to 34.68% from the initial micrhardness, increased to 78.37% after laser irradiation and increased to 82.62% after fluoride treatment, there were significant differences except when it was irradiated and treated with fluoride(P<0.05). 2. In the change of Diagnodent scores, it was decreased to 28.08% from the initial scores after demineralization, and then increased to 59.81% after laser irradiation, and increased to 82.17% after fluoride treatment. Scores were different significantly between the scores of initial, demineralization, laser irradiation and fluoride treatment(P<0.05). All the scores were not different significantly between fluoride types. 3. SEM observation showed that the lased enamel surfaces after demineralization were thermally degenerated and showed molten lava-like appearance and crater with cracks and many microholes.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.675-689
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• 2007

Kilauea volcano's summit area was formed by continuous ind/or sporadic eruption activities for several hundreds years. In this study, we mainly focused on the trace elements characteristics through systematic sample rocks erupted from 1790 to September of 1982. Under the microscope it can be observed some main minerals such as olivine, clinopyroxene. and plagioclase with minor opaque minerals including Cr-spinel and ilmenite. Zr, V, Y, Ti elements show incompatible activities with MgO while Ni, Cr, Co elements show highly compatible properties. Elements like as Ba, Rb, Th, Sr, Nd are highly incompatible to show positive trends with $K_2O$. In the REE diagram LREE is more enriched than HREE suggesting typical Oceanic Island Basalt(OIB) type. It can be suggested that Sr have an effect on the fractionation of plagioclase from the kink in the $K_2O$ variation diagram. Y/Ho ratio diagram shows there was no fluids effect in the historical Kilauea volcano but Zr/Hf ratio diagram shows a significant difference between Kilauea lavas and PuuOo lavas. There are distinctive changes of trace element contents showing in particular abrupt changes of temporal variations between 1924 and 1954. Moreover, PuuOo lavas which had been erupted since 1983 follow these decreasing trends of trace element variation. Therefore, it is strongly suggested that these abrupt changes of trace elements trends result from the huge collapse geological event which formed Halemaumau crater in 1924 causing contamination effects of crustal contents into magma chamber and from the changes of parental magma composition injected into Kilauea volcano's summit magma reservoir.

• Journal of the Korean Institute of Landscape Architecture
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• v.49 no.2
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• pp.128-140
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• 2021

This study applied the theory of Landscape Ecology to representative resources of Jeju Olle-gil, which is a representative subject of walking tourism, to identify ecological characteristics and to establish a technique for landscape ecological analysis of Olle-gil resources. Jeju Olle Trail type based on the biotope type, major land use, vegetation status around Olle Trail and roads were divided into 12 types. Based on the type of ecological tourism resource classification, the Jeju Olle-gil walking tourism resource classification was divided into seven types of natural resources and seven types of humanities resources, and each resource was characterized by Geotope, Biotope, and Anthropopope, just like the landscape ecology system. Geotope resources are strong in landscape characteristics such as coast and beach, rocks, bedrocks, waterfalls, geology and Jusangjeolli Cliff, Oreum and craters, water resources, and landscape viewpoints. The Biotope resources showed strong ecological characteristics due to large tree and protected tree, Gotjawal, forest road and vegetation communities, biological habitat, vegetation landscape view point. Antropotope include Culture of Jeju Haenyeo and traditional culture, potting and lighthouses, experience facilities, temples and churches, military and beacon facilities, other historical and cultural facilities, and cultural landscape views. Jeju Olle Trail The representative resources for each type of Jeju Olle Trail are coastal, Oreum, Gotjawal, field and Stonewall Fencing farming land, Jeju Village and Stone wall of Jeju. In order to learn about the components and various functions of the resources representing the Olle Trail's ecological culture, the landscape ecological technique was interpreted. Looking at the ecological and cultural characteristics of coastal, the coast includes black basalt rocks, coastal vegetation, coastal grasslands, coastal rock vegetation, winter migratory birds and Jeju haenyeo. Oreum is a unique volcanic topography, which includes circular and oval mountain bodies, oreum vegetation, crater wetlands, the origin and legend of the name of Oreum, the legend of the name of Oreum, the culture of grazing horses, the use of military purposes, the object of folk belief, and the view from the summit. Gotjawal features rocky bumps, unique microclimate formation, Gotjawal vegetation, geographical names, the culture of charcoal being baked in the past, and bizarre shapes of trees and vines. Field walls include the structure and shape of field walls, field cultivation crops, field wall habitats, Jeju agricultural culture, and field walls. The village includes a stone wall and roof structure built from basalt, a pavilion at the entrance of the village, a yard and garden inside the house, a view of the lives of local people, and an alleyway view. These resources have slowly changed with the long lives of humans, and are now unique to Jeju Island. By providing contents specialized for each type of Olle Trail, tourists who walk on Olle will be able to experience the Olle Trail in depth as they learn the story of the resources, and will be able to increase the sustainable use and satisfaction of Jeju Olle Trail users.