• Journal of Surface Science and Engineering
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• v.49 no.2
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• pp.135-140
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• 2016

In this study, we prepared magnesium ion containing oxide films formed on the Ti-6Al-4V using plasma electrolytic oxidation (PEO) treatment. Ti-6Al-4V surface was treated using PEO in Mg containing electrolytes at 270V for 5 min. The phase, composition and morphology of the Mg ion containing oxide films were evaluated with X-ray diffraction (XRD), Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and filed-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectrometer (EDS). The biocompatibility of Mg ion containing oxide films was evaluated by immersing in simulated body fluid (SBF). According to surface properties of PEO films, the optimum condition was formed when the applied was 270 V. The PEO films formed in the condition contained the properties of porosity, anatase phase, and near 1.7 Ca(Mg)/P ratio in the oxide film. Our experimental results demonstrate that Mg ion containing oxide promotes bone like apatite nucleation and growth from SBF. The phase and morphologies of bone like apatite were influenced by the Mg ion concentration.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.910-915
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• 2011

The microstructures and mechanical properties of roll-bonded STS439/Al1050/STS304 clad materials were investigated after an annealing process at various temperatures. Interfacial layer was developed at the STS439/Al1050 and Al1050/STS304 interfaces at $550^{\circ}C$. STS439/Al1050/STS304 clad metals fractured suddenly in a single step and the fracture decreased with increasing annealing temperatures at $450^{\circ}C$. After annealing at $550^{\circ}C$, samples fractured in three steps with each layer fracturing independently. Interfacial layers formed at $550^{\circ}C$ with a high Vickers microhardness were found to be brittle. During tensile testing, periodic parallel cracks were observed at the interfacial reaction layer. Observed micro-void between Al1050 and the interfacial layer was found to weaken the Al1050/reaction layer interface, leading to the total separation between Al1050 and the reaction layer.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.116-121
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• 2010

The Mg-Zn-RE alloy cladded with the thin Al1050 sheet was fabricated by means of a roll bonding process at $280^{\circ}C$.Microstructures and mechanical properties of the clad sheets were investigated. After heat treatment at $230^{\circ}C$ for 30 min, an Mg-rich diffusion layer with about $2{\mu}m$ in thickness was developed at the Mg and Al interface. Tensile tests were carried out in a temperature range up to $300^{\circ}C$. The clad sheet exhibits superior elongation to failure not only at room temperature but also at elevated temperatures compared with those of the Mg alloy sheet. For the deformed specimens, interface debonding does not occur and the diffusion layer shows only a few cracks.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.1
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• pp.73-77
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• 2021

Inorganic-organic hybrid perovskite solar cells have demonstrated considerable improvements, reaching 25.5% of certified power conversion efficiency in 2020 from 3.8% in 2009. In normal structured perovskite solar cells, TiO2 electron-transporting materials require heat treatment process at a high temperature over 450℃ to induce crystallinity. Inverted perovskite solar cells have also been studied to exclude the additional thermal process by using [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as a non-oxide electron-transporting layer. However, the drawback of the PCBM layer is a charge accumulation at the interface between PCBM and a metal electrode. The impact of bathocuproin (BCP) buffer layer on photovoltaic performance has been investigated herein to solve the problem of PCBM. 2-mM BCP-modified perovskite solar cells were observed to exhibit a maximum efficiency of 12.03% compared with BCP-free counterparts (5.82%) due to the suppression of the charge accumulation at the PCBM-Au interface and the resulting reduction of the charge recombination between perovskite and the PCBM layer.

• Journal of Environmental Impact Assessment
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• v.17 no.4
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• pp.235-242
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• 2008

To develop a watershed management plan for protection of the lake water quality, the linkages among land use activities, stream water quality, and lake water quality must be understood. This study conducted to develop a Decision Support System(DSS) for the reservoir water quality managers and a comprehensive watershed management plan. This DSS has three main components; database, interactive decision model, and data delivery interface system. Graphic User Interface(GUI) was developed as the interface medium to deliver the data and modeling results to the end users. Water quality management scenarios in Yongdam reservoir consist of two parts. One is the watershed management, and the other is water quality management in the reservoir. The watershed management scenarios that were evaluated include as follows : a removal of point sources, control of waste water treatment plant, reductions in nonpoint sources, and the management of developed land. Water quality management scenarios in the reservoir include to install a curtain wall and to operate an algae removal system. The results from the scenario analysis indicate that the strategy of the reservoir water quality management can promise the best effectiveness to conserve the quality of reservoir water. It is expected that many local agencies can use this DSS to analyze the impact of landuse changes and activities on the reservoir watershed and can benefit from making watershed management decisions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.1839-1846
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• 2012

With increasing chronic patients due to population aging, many needs for pro-active health and medical treatment services are rising and desire for health care service is also rising due to national standard of living Especially population aging of Korea is faster than America, France and many other advanced nations, and a study states that arrival time of elderly population rates; 14%(aged society) to 20%(transcendental aged society)l only takes 8 years. In these reasons, health care industry for the next engine industry is reinforced. Many health care terminals are coming out and Continua Health Alliance is founded and working steadily based on Philips in 2006. In this paper, we suggest Gateway interface system for Continua accreditation to control vary communication by designing intelligent health care interface suitable for Continua international accreditation because there are many types of terminals and communication protocols.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.152-163
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• 1995

This experiment was performed to observe the adhesion pattern and microleakage in the gingival margin according to variation in the resin cement thickness which results from thickness of Die spacer. which is considered to effect the adaptability of the composite resin inlays. Clearfil CR inlays were fabricated on stone models with CR Sep applicated once and Nice fit twice, 4 times, and 6 times each. After 2nd curing within the CRC-100 oven, CR inlays were cemented with CR inlay cement. Dye(2% methylene blue) penetration and adhesion pattern were evaluated after sectioning of gingival margin into :3 pieces. The results were as follows ; 1. The thickness of resin cement showed unevenchanging pattern with that of die spacer, namely, it was increased until 4 times' application of Nice-Fit but was decreased with 6 times' application of that. 2. The degree of dye penetration wasn't affected by cement thickness within a limited value. 3. Most of dye penetration was shown through the interface between cement and enamel rather than the interface between cement and CR inlay. This shows that the affinity of resin cement for CR inlay was superior to the adhesive strength with tooth structure. 4. No gap was found at the interface between enamel and cement but some showed separation between dentin and cement. It is concidered that the contraction force of cement was less than the bond strength with the enamel. 5. Lots of voids were found in the CR inlay and resin cement. There was a pooling tendency of bonding agent and cement in the axiogingival line angle portion. 6. In some specimens, cracks were shown in enamel margin. From this it could be considered that cavity preparation and surface treatment weakened the tooth structure.

• Journal of Surface Science and Engineering
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• v.41 no.4
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• pp.147-155
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• 2008

The dental orthodontic wire provides a good combination of strength, corrosion resistance and moderate cost. The purpose of this study was to investigate the effects of TiN and ZrN coating on corrosion resistance and physical property of orthodontic wire using various instruments. Wires(round type and rectangular type) were used, respectively, for experiment. Ion plating was carried out for wire using Ti and Zr coating materials with nitrogen gas. Ion plated surface of each specimen was observed with field emission scanning electron microscopy(FE-SEM), energy dispersive X-ray spectroscopy(EDS), atomic force microscopy(AFM), vickers hardness tester, and electrochemical tester. The surface of TiN and ZrN coated wire was more smooth than that of other kinds of non-coated wire. TiN and ZrN coated surface showed higher hardness than that of non-coated surface. The corrosion potential of the TiN coated wire was comparatively high. The current density of TiN coated wire was smaller than that of non-coated wire in 0.9% NaCl solution. Pit nucleated at scratch of wire. The pitting corrosion resistance $|E_{pit}-E_{rep}|$ increased in the order of ZrN coated(300 mV), TiN coated(120 mV) and non-coated wire(0 mV).

• Journal of Surface Science and Engineering
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• v.36 no.5
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• pp.373-378
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• 2003

With increasing environmental concerns, application of lead-free solder and fluxless soldering process have been taken attention from the electronic packaging industry. Plasma treatment is one of the soldering methods for the fluxless soldering, and it can prevent environmental pollution cased by flux. On this study fluxless soldering process under $Ar-H_2$plasma using lead free solders such as Sn-3.5 wt%Ag, Sn-3.5 wt%Ag-0.7 wt%Cu and Sn-37%Pb for a reference was investigated. As the plasma reflow has higher soldering temperature than normal air reflow, the effects of UBM(Under Bump Metallization) thickness on the interfacial reaction and bonding strength can be critical. Experimental results showed in case of the thin UBM, Au(20 nm)/Cu(0.3 $\mu\textrm{m}$)/Ni(0.4 $\mu\textrm{m}$)/Al(0.4 $\mu\textrm{m}$), shear strength of the soldered joint was relatively low as 19-27㎫, and it's caused by the crack observed along the bonded interface. The crack was believed to be produced by the exhaustion of the thin UBM-layer due to the excessive reaction with solder under plasma. However, in case of thick UBM, Au(20 nm)/Cu(4 $\mu\textrm{m}$)/Ni(4 $\mu\textrm{m}$)/Al(0.4 $\mu\textrm{m}$), the bonded interface was sound without any crack and shear strength gives 32∼42㎫. Thus, by increasing UBM thickness in this study the shear strength can be improved to 50∼70%. Fluxed reflow soldering under hot air was also carried out for a reference, and the shear strength was 48∼52㎫. Consequently the fluxless soldering with plasma showed around 65∼80% as those of fluxed air reflow, and the possibility of the $Ar-H_2$ plasma reflow was evaluated.

• The korean journal of orthodontics
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• v.24 no.2
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• pp.433-445
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• 1994

Bonding of brackets is one of the essential factors for successful orthodontic treatment' so bond strength of orthodontic adhesives are very important. The purposes of this research were to compare shear bond strength of various orthodontic adhesives and to evaluate failure sites. One-hundred twenty extracted human first premolars were prepared for bonding and premolar brackets were bonded to prepared enamel surfaces with Super C Ortho, Mono-$Lok^2$, Transbond, and Super C Ortho after applying Fluorobond. After bonding of brackets, teeth specimens were divided into 3 groups. In group 1 specimens were stored at humidor $37^{\circ}C$ in 1 hour, in group 2 specimens were stored at humidor $37^{\circ}C$ in 24 hours, thermocycled 10 times and in group 3 specimens were stored at humidor $37^{\circ}C$ in 24 hours, thermocycled 1800 times. Then the universal testing machine Instron 6022, Instron Co., U.S.A. was used to test the shear bond strength of brackets to enamel. After debonding, brackets and enamel surfaces were examined under stereoscopic microscope to determine the failure sites The results were as follows : 1. Shear bond strength was significantly highest of using Super C Ortho after applying Fluorobond and Super C Ortho In group 1, was highest of using Super C Ortho in group 2, and was highest of using Mono-$Lok^2$ in group 3. 2. According to time and temperature change, in using Super C Ortho the group 2 had significantly highest strength and group 3 had lowest strength, in using Mono-$Lok^2$ the group 2 and had higher strength than group 1 and in using Super C Ortho after applying Fluorobond shear bond strength decreased constantly, 3. The failure sites were tooth-resin interface in Super C Ortho after applying Fluorobond, Mono $Lok^2$ and Transbond and were at almost same ratio bracket base-resin interface and tooth-resin interface in Super C Orth.