• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.5
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• pp.279-283
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• 2016

In this study, we intended to achieve both antibacterial properties and electromagnetic shielding using the Al-doped ZnO (AZO) films. FTS (Facial Target Sputtering) magnetron sputtering was used for the AZO thin films instead of the conventional RF sputtering because the FTS sputtering could avoid the damage for the plasma as well as fabrication of thin films with a high quality. The 300-nm thick AZO thin films grown on glass substrate showed a resistivity of about $7{\times}10^{-4}{\Omega}-cm$ and a transmittance of about 90% at a wavelength of 550 nm. AZO thin films were investigated for the electromagnetic shielding effectiveness measured by 2-port network method at 1.5 ~ 3 GHz. The AZO (300 nm)/glass films showed an EMI shielding effectiveness of approximately 27 dB. An antibacterial effect was measured by the film attachment method (JIS Z 2801). The percent reductions of bacteria by AZO films were 99.99668% and 99.99999% against Staphylococcus aureus and Escherichia coli, respectively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.113-122
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• 2018

A hydraulic breaker is an attachment of an excavator, and it crushes stones. Recently, research to reduce the impact and noise of breakers are ongoing. In this paper, a method to improve the upper, lower, and side dampers, which act as insulation for the attenuation of vibration during breaker operation, is studied through testing and simulation. To obtain the nonlinear material constants required for the simulation, the biaxial tensile test was performed with urethane, which is a material used for dampers. The existing parts and the improved parts were compared and evaluated using the LS-DYNA program. As a result, 50% of the equivalent stress was reduced in the bracket body of the hydraulic breaker, and the equivalent stress of the side damper was also decreased. We verified that the fatigue conditions were satisfied by performing a fatigue analysis.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.134.1-134.1
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• 2017

In this study, we propose a new scaffold fabrication method, "direct electro-hydrodynamic jet process," using the initial jet of an electrospinning process and ethanol media as a target. The fabricated threedimensional (3D) fibrous structure was configured with multilayered microsized struts consisting of randomly entangled micro/nanofibrous architecture, similar to that of native extracellular matrixes. The fabrication of the structure was highly dependent on various processing parameters, such as the surface tension of the target media, and the flow rate and weight fraction of the polymer solution. As a tissue regenerative material, the 3D fibrous scaffold was cultured with preosteoblasts to observe the initial cellular activities in comparison with a solid-freeform fabricated 3D scaffold sharing a similar structural geometry. The cell-culture results showed that the newly developed scaffold provided outstanding microcellular environmental conditions to the seeded cells (about 3.5-fold better initial cell attachment and 2.1-fold better cell proliferation).

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.95-105
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• 1988

The dynamic characteristics of a tennis racket were identified by experimental modal analysis and the sweet spot due to these was calculated. A tennis racket was selected as a model reference and modal parameters of the racket were estimated from the transfer function measured by experiment. The transfer function was reconstructed by the modified modal parameters on the assumption that the racket was locally modified, for example, a change in the material of the frame and the attachment of a damping material to the grip. The change of the dynamic characteristics, especially natural frequency and magnitude of the second and the third vibrational modes, were evaluated from the reconstructed transfer function. The change of the sweet spot due to the modified modal parameters was estimated and visualized through computer graphic simulation by the criterion of the sweet spot measured before structural modification. The modal parameters for improvement of the dynamic characteristics.

• Environmental Engineering Research
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• v.24 no.1
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• pp.173-179
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• 2019

Prussian blue (PB) is known to be an effective material for radioactive cesium adsorption, but its nano-range size make it difficult to be applied for contaminated water remediation. In this study, a simple and versatile approach to immobilize PB in the supporting matrix via surface functionalization was investigated. The commercially available poly vinyl alcohol (PVA) sponge was functionalized by acrylic acid (AA) to change its major functional group from hydroxyl to carboxylic, which provides a stronger ionic bond with PB. The amount of AA added was optimized by evaluating the weight change rate and iron(III) ion adsorption test. The FTIR results revealed the surface functional group changing to a carboxyl group. The surface functionalization enhanced the attachment of PB, which minimized the leaching out of PB. The $Cs^+$ adsorption capacity significantly increased due to surface functionalization from 1.762 to 5.675 mg/g. These findings showed the excellent potential of the PB-PAA-PVA sponge as a cesium adsorbent as well as a versatile approach for various supporting materials containing the hydroxyl functional group.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.19-24
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• 2022

The purpose of this research is to determine the hardness of guide hole. A guide pin and a guide hole of SSD(Solid State Drive) tester used to mount SSD in a fixed position accurately. The guide pin and guide hole are worn by friction due to repeated operation, and the wear is concentrated on the guide hole made of weak material rather than the guide pin made of relatively strong material. Because of that reason, it is often overdesigned in the design stage because it can lose its function. If the guide hole is made soft, the manufacturing cost will decrease, but the accuracy will decrease due to wear caused by repeated friction. If the guide hole is manufactured excessively, the manufacturing process becomes complicated and the manufacturing cost increases. It is essential to design a guide hole, but since there is no standard or verified data that can be referenced, it is difficult to design. Experimental device which guides in the same way as the SSD tester is used for this research, and three types of anodizing state are experimented for different hardness. Also, weight of COK(Change over Kit) were analyzed by measuring the wear amount and state of the guide hole according to the number of repeated attachment and detachment.

• Journal of Periodontal and Implant Science
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• v.29 no.1
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• pp.153-171
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• 1999

The purpose of this study was to evaluate the effect of modified calcium sulfate paste on periodontal regeneration. l-wall intrabony defect(mesio-distal width: 4mm, depth: 4mm) was surgically created on the distal side of P2 and mesial side of p4 in four dogs. The control group(GFS) was treated with conventional flap operation alone, and the experimental group(CS) was treated with conventional flap operation with modified calcium sulfate paste application. Both control and experimental groups were sacrificed after 8weeks of healing period, The results of histological and histometric observations were as follows. 1. The length of the junctional epithelium was 0.41${\pm}$0.01mm in the control groups, 0.47${\pm}$0.01mm in the experimental group. 2. The connective tissue attachment was 0.28${\pm}$0.02mm(6.15${\pm}$0.28%) in the control group, 0.18${\pm}$0.01mm(3.41${\pm}$0.14%) in the experimental group. The control group showed more connective tissue attachment. 3. The new cementum formation was 3.80${\pm}$0.06mm(84.80${\pm}$0.33%) in the control group, 4.49${\pm}$0.06mm(87.57${\pm}$0.15%) in the experimental group. Both groups showed a lot of new cementum formation. 4. The new bone formation was 1.43${\pm}$0.03mm(32.37%) in the control group, 2.04${\pm}$O.09mm(40.94%) in the experimental group. 5. The inflamatory cells were observed partially around resorbed calcium sulfate in the connective tissue of the experimental group. 6. Partially resorbed calcium sulfate were found within the connective tissue, around alveolar bone, and in the newly formed alveolar bone, On the basis of these results, newly formed calcium sulfate paste enhanced new bone formation and new cementum formation. The resorption rate of calcium sulfate seems to be controlled by the add-in compounds. Thus research about biocompatibility and adequate resorptionrate is required to develop a improved material.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.1
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• pp.112-120
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• 1996

In this study, the porous glass media was utilized as biomass carrier, and the optimum characteristics of this new media in fixed bed biofilm process were investigated. The characteristics of media considered here are a void volume fraction, a specific surface area, and surface characteristics of media. The effect of surface roughness and material could be clearly demonstrated by the fact that the porous glass media showed a good potential for biofilm development. This might results from the fact that biofilm is initially formed in the surface cavities of the media is protect from the shear effect. Therefore, the microcolonies are not readily detached by the fluid shear. In the steady state, biofilm formation along the packing bed depth was different from media to media. The specific area was also an important factor for the attachment of microorganism on the media surface. The specific area was also an important factor for the attachment of microorganism on the media surface. In the case of porous glass media, about $100m^2/m^3$ was enough to obtain a good organic removal efficiency The organic removal efficiency could be improved by increasing the void volume fraction in the reactor, at least 80% was required to obtain a high removal efficiency and prevent clogging. From the analysis of kinetics study, the yield coefficient, Y, was 0.42 mgMLSS/mgSBOD, endogenous respiration coefficient, ke, was $0.12day^{-1}$ and substrate removel coefficient of Mckinney. km, was $16.8hr^{-1}$ for the porous glass media G-2

• Journal of Periodontal and Implant Science
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• v.24 no.1
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• pp.120-130
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• 1994

The purpose of the present investigation was to compare the effectiveness of porous hydroxyapatite (PHA) and coralline based porous calcium carbonate(PCC) as implant materials in human periodontal osseous defects. 10 adult patients having periodontitis and 2 similar angular osseous defects ${\ge}$5mm as verified by radiographic analysis and clinical probing depth ${\ge}$4mm were selected. The measurements were recorded just before surgery and after 6 month. Clinical parameters used in this study included gingival recession, pocket depth, probing attachment level, Sulcus Bleeding Index, Plaque Index, tooth mobility and bone defect depth measurements. After initial therapy, patients were treated with mucoperiosteal flap surgery. The contralateral bony defects in each patient randomly assigned to either bone graft material, one with PHA(Interpore 200) and the other with coralline based calcium carbonate(Biocoral). After 6 month both groups showed statistically significant reduction of pocket depth, Sulcus Bleeding Index, Plaque Index and significant improvement in probing attachment level. No statistically significant differences were found between the groups. There were 3.0mm or 68% of bone repair with PHA and 3.1mm, 61% with PCC. These values were likewise not significantly different. The data and clinical impression strongly suggest that both PHA and PCC are alloplastic implants with clinically apparent acceptance by the soft and hard tissue and that they can be used as bone graft materials successfully.

• Journal of Environmental Health Sciences
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• v.31 no.4 s.85
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• pp.309-315
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• 2005

Volatile organic compounds (VOCs) and odor materials are major sources of air pollution in Ulsan city, where much chemical plants are located. Therefore, it is necessary to develop a new reactor which can remove VOCs and odor materials effectively and be equipped at the end of pipe easily. A modified reactor (bioscrubber trickling filter, BSTF), which have both characteristics of biofilter and bioscrubber, was developed and tested on its reactivity with several VOCs using two types of media, fiber and activated carbon 4- ceramic(A/C). It was observed that the removal efficiencies of several types of VOCs such as acetaldehyde, ethylalcohol, butanol, diethylamine and triethylamine were up to $95\%$ when they had about 100 ppm of initial concentration and 80 seconds of residence time. Good attachment of microorganisms to both media, where it is thought the reaction efficiency can be determined according to the amount of microorganisms attachment, observed with scanning electron microscopy(SEM). Initial pressure drops of the packed bed with both media were 229 $mmH_2O/m$ at A/C column and 670 $mmH_2O/m$, respectively. However, maximum pressure drop of fiber column during the operation was over 1,647 $mmH_2O/m$. Therefore, it was thought that the fiber material would not suitable to use in the local plant as a packed bed media.