• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.135-136
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• 2012

Carbon atoms near the surface of W(110) induce reconstructions such as $R(15{\times}12)$ -C/W(110) which consists of two characteristic parts, one square shaped and bright protrusion and two smaller ones. In the atomic resolution STM image, the bigger protrusion shows the periodicities of clean W(110), indicating that it is almost carbon poor region. The smaller protrusion contains hexagonal carbide surface layer of ${\alpha}$-W2C on W(110). Employing this carburized W(110) as templates, we grow Co and Fe clusters of less than ten atoms. Due to the selectivity of bonding sites, growth of larger cluster is highly unfavorable for Co and the size of clusters is very uniform. Since Co atoms prefer to sit on the bigger protrusion rather than smaller one, Co cluster can be arranged one-dimensionally in $R(15{\times}12)$-C/W(110) with quite uniform size distribution. However, Fe clusters sit on both sites without favored site, but still with uniform size distribution. On the other hand, Fe clusters can be grown with quasi one-dimensional order in $R(15{\times}3)$-C/W(110), which consists of only smaller protrusions. We investigate the magnetic properties of the ordered nano-sized clusters. Experiments using XMCD reveals little magnetic moment of Co cluster on $R(15{\times}12)$-C/W(110). This observation is consistent with the predictions of our first principles calculations that small Co clusters can be nonmagnetic or antiferromagnetic with low mean magnetic moment per atom.

• Korean Journal of Head & Neck Oncology
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• v.29 no.2
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• pp.48-50
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• 2013

Angiomyoma is a rare, benign smooth muscle cell tumor. These tumors may be found anywhere in the body. They frequently occur in the lower extremities except venous type. Angiomyoma in the head and neck area is very rare, and only a few cases have been reported. A 63 year-old male patient visited to outpatient clinic due to size-growing nodule-like lesion in the Lt. alar area. Excisional biopsy was done for diagnosis. The lesion was totally excised with 2 mm safety margin. Frozen biopsy of the lesion was requested, and all resection margins were proved negative. To cover the raw surface, full thickness skin grafting was performed. The graft was harvested from Rt. posterior auricular area. Tie over dressing was applyed on Lt. alar area. The graft was well taken and healed without any complication in both short term and long term follow up periods of 2 weeks, 1 month, 2 months, and 6 months. Donor site completed healed without any complications. The leiomyoma is benign tumor originated from smooth muscle, and it can be classified into solid leiomyoma, angiomyoma, and epithelioid leiomyoma. Especially, the angiomyoma consists of smooth muscle cell and blood vessel, and it is originated from the tunica media of blood vessel. Angiomyoma alone frequently occurs in the lower extremities as solitary painless subcutaneous tumor. Venous type of angiomyoma in the oral cavity was reported in other references, but on the facial surface it may be the first case reported as paper. So this report can be very meaningful.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.264-265
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• 2014

This Paper reports the photocatalytic activity of $g-C_3N_4/NaTaO_3$ hybrid composite photocatalysts synthesized by ball-mill method. The $g-C_3N_4$ and $NaTaO_3$ were individually prepared by Solid state reaction and microwave hydrothermal process, respectively. The $g-C_3N_4/NaTaO_3$ composite showed the enhanced photocatalytic activity for degradation of rhodamine B dye (Rh. B) under simulated solar light irradiation. The results revealed that the band-gap energy absorption edge of hybrid composite samples was shifted to a longer wavelength as compared to $NaTaO_3$ and the 50 wt% $g-C_3N_4/NaTaO_3$ hybrid composite exhibited the highest percentage (99.6 %) of degradation of Rh. B and the highest reaction rate constant ($0.013min^{-1}$) in 4 h which could be attributed to the enhanced absorption of the hybrid composite photocatalyst in the UV-Vis region. Hence, these results suggest that the $g-C_3N_4/NaTaO_3$ hybrid composite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation in comparison to the commercial $NaTaO_3$.

• Journal of Korea Foundry Society
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• v.21 no.4
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• pp.253-259
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• 2001

There are many methods to produce metal foams, which can be classified into three groups according to the state of the starting metal i.e. liquid or powder or solid. Three types of defects such as cell closing, cell deformation or breakdown and cell misrun are thought to be occurred when we make the open cell aluminum foams by precision casting. Filling ability of the mold slurry between preform is related with cell closing, mold collapsibility is related with cell deformation or breakdown, mold temperature and pouring pressure are related with cell misrun. These factors can be evaluated by measuring slurry fluidity, burnout strength and permeability of the mold. Properties of the plaster mold were evaluated to find optimum mold conditions for high quality open cell aluminum foam in this study. Permeability was almost zero independent of burnout conditions, however, crack initiation was found on the surface of all specimens one or two minutes after taking out from the furnace. Crack has grown and disappeared with time. This crack may facilitate the mold filling when molten metal is poured, because of the improved mold permeability. It was considered that crack initiation and disappearance was closely related with temperature difference between the surface and inner part. Knocking-out the mold is a difficult problem due to the small cell size, because continuous mesh structure of the metal foam is not strong. It is not easy to remove molding material after pouring. We can expect that water quenching can facilitate the knocking-out the mold after solidification without damaging cell structures. Collapsed particles after water quenching became bigger with the increase in time.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.6
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• pp.528-533
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• 2012

Flexible composite propellers are subject to large deformation under heavy loading, and hence the hydrodynamic performance of deformed propeller might deviate from that of the metallic propeller under negligible deformation. To design the flexible propeller, it is therefore necessary to be able to evaluate the structural response of the blades to the hydrodynamic loadings, and then the influence of the blade deformation upon the hydrodynamic loadings. We use the lifting-surface-theory-based propeller analysis and design codes in solving the hydrodynamic problem, and the finite-element-method program formulated with 20-node iso-parametric solid elements for the analysis of the structural response. The two different hydrodynamic and structural programs are arranged to communicate through the carefully-designed interface scheme which leads to the derivation of the geometric parameters such as the pitch, the rake and the skew distributions common to both programs. The design of flexible propellers, suitable for manufacturing, is shown to perform the required thrust performance when deformed in operation. Sample design shows the fast iteration scheme and the robustness of the design procedure of the flexible propellers.

• Food Science and Preservation
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• v.9 no.2
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• pp.184-188
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• 2002

This study was conducted to optimize hot water extraction process of cordyceps militaris for development beverage. Optimal condition for hot water extraction was investigated with changes in extraction concentration and temperature by response surface methodology. The content of soluble solid was effected with concentration. The efficiency of extraction for turbidity, total sugar, reducing sugar and protein increased with low concentration. The response variables had significant with concentration and the established polynomial model was suitable (p>0.05) model by lack-of-fit analysis. Optimal extraction conditions as the limited renditions of 2.0∼2.4% extractable solids, 1.5∼2.0% brix, l14∼120 $\mu\textrm{g}$/g total sugar, 10.5∼11.0 $\mu\textrm{g}$/ｇ reducing sugar and 110∼l15 $\mu\textrm{g}$/g protein were 95∼100$\^{C}$ and 4.0∼4.1% of concentration.

• Ocean and Polar Research
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• v.32 no.3
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• pp.299-307
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• 2010

In conjunction with geochemical characteristics, rate of sulfate reduction was investigated at two sediment sites in the continental slope and rise (basin) of the Ulleung Basin in the East Sea. Geochemical sediment analysis revealed that the surface sediments of the basin site (D2) were enriched with manganese oxides (348 ${\mu}mol$ $cm^{-3}$) and iron oxides (133 ${\mu}mol$ $cm^{-3}$), whereas total reduced sulfur (TRS) in the solid phase was nearly depleted. Sulfate reduction rates (SRRs) ranged from 20.96 to 92.87 nmol $cm^{-3}$ $d^{-1}$ at the slope site (M1) and from 0.65 to 22.32 nmol $cm^{-3}$ $d^{-1}$ at the basin site (D2). Depth integrated SRR within the top 10 cm depth of the slope site (M1; 5.25 mmol $m^{-2}$ $d^{-1}$) was approximately 6 times higher than that at the basin site (D2; 0.94 mmol $m^{-2}$ $d^{-1}$) despite high organic content (>2.0% dry wt.) in the sediment of both sites. The results indicate that the spatial variations of sulfate reduction are affected by the distribution of manganese oxide and iron oxide-enriched surface sediment of the Ulleung Basin.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.96-96
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• 2016

나노섬유(nanofiber), 나노선(nanowire), 그리고 나노튜브(nanotube)와 같은 1차원 구조의(one-dimensional structure) 나노재료는 벌크(bulk) 및 박막(film) 재료와는 다르게 물리적, 화학적으로 특이한 성질을 가지고 있으며, 이러한 성질은 나노재료의 구조, 형상, 크기 등에 큰 영향을 받는다. 첫 째, 전기방사(electrospinning) 공정을 이용한 나노섬유의 합성; 용액의 특성, 전기장 세기, 방사시간 등의 변수를 조절하게 되면 방출되는 재료의 형상을 입자 혹은 섬유상의 형태로 얻을 수 있으며, 전기방사를 통해 합성된 나노재료의 소결 온도 및 시간을 달리함으로써 나노입자의 크기를 조절할 수 있다. 또한, 템플레이트 합성법(template synthesis) 및 이중노즐(coaxial nozzle)을 이용해 속이 빈 형태인 중공(hollow) 구조의 나노섬유를 얻을 수 있으며, 전기방사에 사용되는 전구물질에 원하는 금속 및 산화물을 첨가함으로써 복합체(composite) 나노섬유를 얻을 수 있다. 둘 째, VLS(Vapor-Liquid-Solid) 공정을 이용한 나노선의 성장; 온도, 압력, 전구물질의 양, 그리고 시간 등의 변수를 조절하게 되면 원하는 직경 및 길이를 갖는 나노선을 성장시킬 수 있다. 그리고 ALD(Atomic Layer Deposition)를 이용해 나노선에 추가적인 층을 형성함으로써 코어-셀 구조를 형성할 수 있으며, 감마선, UV와 같은 공정을 이용해 귀금속 촉매를 나노선에 기능화 시킬 수도 있다. 코어-셀 구조를 갖는 나노선/나노섬유는 코어 혹은 셀 층의 전자나 홀의 이동을 유발하여 전자공핍층(electron depletion layer) 또는 정공축적층(hole accumulation layer)을 확대 및 축소시켜 센서의 초기저항을 증가시키거나 감소시키는 역할로써 이용되고 있으며, 특히, 셀 층의 두께가 셀 층 재료의 Debye length와 유사한 크기를 갖게 되면, 셀 층은 완전공핍층(fully depleted layer)을 형성해 최대의 감도를 나타낼 수 있다. 본 연구에서는 다양한 제조 공정을 통해 제작될 수 있는 1차원 나노-구조물을 가스센서에 적용하는 사례들을 소개하고, 이러한 가스센서의 감응성능을 향상시키기 위한 방법의 한 가지로 원자층증착법으로 나노선/나노섬유의 표면에 셀층을 형성하여 감응성 향상 메커니즘 및 관련 주요 변수들을 조사하고자 한다.

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.1989-1996
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• 2006

The $NiSO_4/CeO_2-ZrO_2 $catalysts containing different nickel sulfate and $CeO_2$ contents were prepared by the impregnation method, where support, $CeO_2-ZrO_2$was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of $CeO_2-ZrO_2$. The addition of nickel sulfate (or $CeO_2$) to $ZrO_2$ shifted the phase transition of $ZrO_2$ from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or $CeO_2$) and $ZrO_2$. A catalyst (10-$NiSO_4/1-CeO_2-ZrO_2$) containing 10 wt % $NiSO_4$ and 1 mole % $CeO_2$, and calcined at $600{^{\circ}C}$ exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of $CeO_2$was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.

• Journal of Ecology and Environment
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• v.30 no.3
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• pp.209-223
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• 2007

Twenty-four wetlands located in Higashi-Hiroshima City in West Japan were selected for this study in order to investigate both the relationship between aquatic plant composition and environmental conditions; and the relationship between changing land use patterns in the catchments and the concentration of different forms of nitrogen in the wetlands. The dominant and subdominant species which comprised the principal vegetation were determined based on a vegetation census conducted in each wetland during the growing season from June to August, 2006. The seasonal variations of water quality factors (pH, electrical conductivity, turbidity, dissolved oxygen, total dissolved solid, and temperature) and different forms of nitrogen such as nitrite, nitrate, ammonium, total nitrogen, dissolved organic nitrogen and dissolved inorganic nitrogen concentrations were analyzed as important indicators of water quality for the surface water of the wetlands. The surveyed wetlands were classified into three types (non-disturbed wetlands, moderately-disturbed wetlands and highly-disturbed wetlands), based on the degree of human disturbance to their catchment areas. An analysis of variance indicated that there was a significant difference among the wetland groups in the annual mean values of electrical conductivity, total dissolved solids, total nitrogen, nitrite, dissolved inorganic nitrogen and dissolved organic nitrogen. Classification of the wetlands into three groups has revealed a pattern of changes in the composition of plant species in the wetlands and a pattern of changes in nitrogen concentrations. A majority of the non-disturbed wetlands were characterized by Brasenia schrebi and Trapa bispinosa as dominant; with Potamogeton fryeri and Iris pesudacorus as sub-dominant species. For most of the moderately-disturbed wetlands, Brasenia schrebi were shown to be a dominant species; Elocheriss kuriguwai and Phragmites australis were observed as sub-dominant species. For a majority of the highly-disturbed wetlands, Typha latifolia and T. angustifolia were observed as dominant species, and Nymphea tetragona as the sub-dominant species in the study area. An analysis of land use and water quality factors indicated that forest area played a considerable role in reducing the concentration of nutrients, and can act as a sink for surface/subsurface nutrient inputs flowing into wetland water, anchor the soil, and lower erosion rates into wetlands.