• 한국표면공학회지
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• 제53권6호
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• pp.360-368
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• 2020

Wear resistance of cutting tools is one of the most important requirements in terms of the durability of cutting tool itself as well as the machining accuracy of the workpiece. Generally, tungsten carbide ball end mills have been processed with hard coatings for high durability and wear resistance such as diamond coating and tetrahedral amorphous carbon(ta-C) coating. In this study, we developed multilayer ta-C coatings whose wear resistance is comparable to that of diamond coating. First, we prepared single layer ta-C coatings according to the substrate bias voltage and Ar gas flow, and the surface microstructure, raman characteristics, hardness and wear characteristics were evaluated. Then, considering the hardness and wear resistance of the single layer ta-C, we fabricated multilayer coatings consisting of hard and soft layers. As a result, it was confirmed that the wear resistance of the multilayer ta-C coating with hardness of 51 GPa, and elastic recovery rate of 85% improved to 97% compared to that of the diamond coated ball end mill.

• Structural Engineering and Mechanics
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• 제76권5호
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• pp.561-578
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• 2020

The present work addresses the surface integrity and chip morphology in finish hard turning of AISI D3 steel under nanofluid assisted minimum quantity lubrication (NFMQL) condition. The surface integrity aspects include microhardness, residual stress, white layer formation, machined surface morphology, and surface roughness. This experimental investigation aims to explore the feasibility of low-cost multilayer (TiCN/Al2O3/TiN) coated carbide tool in hard machining applications and to assess the propitious role of minimum quantity lubrication using graphene nanoparticles enriched eco-friendly radiator coolant based nano-cutting fluid for machinability improvement of hardened steel. Combined approach of central composite design (CCD) - analysis of variance (ANOVA), desirability function analysis, and response surface methodology (RSM) have been subsequently employed for experimental investigation, predictive modelling and optimization of surface roughness. With a motivational philosophy of "Go Green-Think Green-Act Green", the work also deals with economic analysis, and sustainability assessment under environmental-friendly NFMQL condition. Results showed that machining with nanofluid-MQL provided an effective cooling-lubrication strategy, safer and cleaner production, environmental friendliness and assisted to improve sustainability.

• 한국재료학회지
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• 제31권11호
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• pp.601-607
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• 2021

Laser cladding a surface treatment process that grants superior characteristics such as toughness, hardness, and corrosion resistance to the surface, and rebuilds cracked molds; as such, it can be a strong tool to prolong service life of mold steel. Furthermore, compared with the other similar coating processes - thermal spray, etc., laser cladding provides superior bonding strength and precision coating on a local area. In this study, surface characteristics are studied after laser cladding of low carbon steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), known for its high hardness and excellent corrosion resistance. A diode laser with wavelength of 900-1070 nm is adopted as laser source under argon atmosphere; electrical power for the laser cladding process is 5, 6, and 10 kW. Fundamental surface characteristics such as crossectional microstructure and hardness profile are observed and measured, and special evaluation, such as a soldering test with molten ALDC12 alloy, is conducted to investigate the corrosion resistance characteristics. As a result of the die-soldering test by immersion of low carbon alloy steel in ALDC12 molten metal, the clad layer's soldering thickness decreases.

• 센서학회지
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• 제32권3호
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• pp.147-153
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• 2023

Metal-organic frameworks (MOFs) of cobalt gallate were synthesized and deposited on gold electrodes using self-assembly monolayers (SAMs) and hydrothermal processing. These MOF films exhibit strong adsorption capabilities for gaseous particulates, and the use of SAMs allows the synthesis and deposition processes to be completed in a single step. When cobalt gallate is mixed with SAMs, a coordination bond is formed between the cobalt ion and the carboxylate or hydroxyl groups of the SAMs, particularly under hydrothermal conditions. Additionally, the quartz crystal microbalance (QCM) gas sensor accurately measures the number of particulates adsorbed on the MOF films in real-time. Thus, the QCM gas sensor is a valuable tool for quantitatively measuring gases, such as SO₂, NO₂, and CO₂. Furthermore, the QCM MOF film gas sensor was more effective for gas adsorption than the MOF particles alone and allowed the accurate modeling of gas adsorption. Moreover, the QCM MOF films accurately detect the adsorption-desorption mechanisms of SO₂ and NO₂, which exist as gaseous particulate matter, at specific gas concentrations.

• 반도체디스플레이기술학회지
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• 제21권4호
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• pp.39-44
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• 2022

Using a CFD (computational fluid dynamics) simulation tool, we have offered a design guideline of a slot-die head having a simple T-shaped cavity through an analysis of the fluid dynamics in terms of cavity pressure and outlet velocity, which affect the uniformity of coated thin films. We have visualized the fluid flow with a transparent slot-die head where poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) is injected. We have shown that the fluid dynamics inside the slot-die head depends sensitively on the cavity depth, cavity length, land length, and channel gap (i.e., shim thickness). Of those, the channel gap is the most critical parameter that determines the uniformity of the pressure and velocity distributions. A pressure drop inside the cavity is shown to be reduced with decreasing shim thickness. To quantify it, we have also calculated the coefficient of variation (CV). In accordance with Hagen-Poiseuille's laws and electron-hydraulic analogy, the CV value is decreased with increasing cavity depth, cavity length, and land length.

• Korean Chemical Engineering Research
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• 제50권1호
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• pp.11-17
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• 2012

졸-겔 방법에 의하여 제조된 $TiO_2$와 $TiO_2-SiO_2$ 광촉매를 이용한 음용수 중의 대장균 살균과 엔도톡신 제거에 관한 연구를 수행하였다. 대장균 살균실험은 대장균이 포함된 물이 순환되는 annular-흐름식 광촉매 코팅 반응기에서 수행되었다. 대장균의 살균능은 $TiO_2$와 $TiO_2-SiO_2$ 광촉매의 아나타제 결정성피크의 세기와 비례하였다. UV-A 조사하에 $TiO_2$가 코팅된 반응기에서 2시간 내에 대장균을 100% 살균시킬 수 있었으며, 대장균 사멸시 생성되는 독성물질인 엔도톡신이 존재하지 않았다. 그러나 UV-C 조사하에서는 30분 이내에 대장균을 100% 살균할 수 있었으나 엔도톡신이 완전히 제게되지 않았다. 따라서 광촉매와 UV-A 조사가 음용수 살균에 유용함을 알 수 있었다.

• Archives of Plastic Surgery
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• 제34권2호
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• pp.169-175
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• 2007

Purpose: $Allevyn^{(R)}$(Smith & Nephew, England) is a type of polyurethane foam material with good wound discharge absorption. $Acticoat^{(R)}$(Smith & Nephew, England) is a silver coated dressing material which is effective in infected wound. The purpose of this study is to compare the effects of dry gauze, $Acticoat^{(R)}$ and $Allevyn^{(R)}$ on infected full-thickness wound healing in rat. Methods: One hundred and twenty rats were divided into 3 groups: group I(dressing with dry gauze, n=40), group II(dressing with $Allevyn^{(R)}$, n=40), group III(dressing with $Acticoat^{(R)}$, n=40). A $15{\times}15mm$ square full-thickness wound was made on the dorsum and left open for 24 hours. The size of wound defects were measured each dressing changes. The histological evaluation was performed on the 3rd day, 7th day, 14th day, 21th day. Results: After the wound was left open for 24 hours, typical findings of bacterial infection was observed. After the 7th day, group III showed larger area of epithelialization, smaller defect size compared to those of two other groups. Complete replacement by fibrotic scar tissue was observed in group III with no signs of inflammation on the 14th day. By day 21, the average defect size in group III was decreased from initial 100% to 3.63%. while in group I and II, it was decreased to 62.66% and 53.62%, respectively. Conclusion: $Acticoat^{(R)}$ is an effective tool in the treatment of infected wound.

• 대한수혈학회지
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• 제23권2호
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• pp.162-168
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• 2012

배경: 세포 내 공간에서 가장 흔한 양이온은 칼륨이며 생리적으로 중요한 역할을 한다. 칼륨 불균형 발생시 생명을 위협할 수 있는 문제가 생길 수 있으며 그 문제들은 전신 쇠약부터 심실 세동에 의한 심장마비까지 있다. 따라서 응급의학과 의사가 짧은 시간 내에 그런 문제를 찾아내야 하는 것은 매우 중요하다. 이 연구에서 우리는 전혈과 혈청의 샘플들을 서로 짝을 지어 비교 분석하여 전혈의 결과가 혈청의 결과만큼 유용하게 쓰일 수 있는지 알아보기로 했다. 방법: 227명의 환자에게서 두 종류의 샘플을 채취하여 비교했다. 하나의 샘플은 요골동맥에서 채취한 전혈을 헤파린 처리된 주사기에 담아 검사했으며 다른 하나는 혈청 샘플을 담아 검사실에서 검사했다. 그 후 샘플들을 정상, 저 칼륨, 고 칼륨의 세 그룹으로 나누어 각각의 그룹에서 혈청과 전혈의 샘플들을 비교하였다. 결과: 혈청과 전혈의 칼륨 수치들의 차이는 통계학적으로 큰 의미를 보이지는 않았으며(P<0.05) 세 그룹 내에서의 칼륨 수치들간의 연관성은 통계학적으로 의미 있게 상관관계를 보였다(P<0.05). 세 그룹 중 고 칼륨 그룹에서 전혈과 혈청의 칼륨 수치가 가장 높은 상관관계를 보였으며 저 칼륨 그룹에서 가장 낮은 상관관계를 보였다. 결론: 전혈을 이용한 응급 검사가 칼륨 이상 소견, 특히 고칼륨혈증이 의심되는 환자의 진단에 선별검사로써 유용하게 사용될 수 있을 것으로 사료된다.

• 한국식생활문화학회지
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• 제25권2호
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• pp.179-188
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• 2010

In order to aide in the design of an improved menu book, which could play an important role as a marketing tool, the current version of the menu books and managers (subjects) of 295 restaurants in the Incheon area were examined. These were managers of Korean (36.3%), Western (25.8%), Japanese (14.6%), cafeteria (12.5%) and Chinese (10.8%) style restaurants. The level of service (self-evaluation, 3-point scale) was average $2.25{\pm}0.45$. The general colorings of the menu books were green (19.0%), brown (18.6%), black (17.6%), yellow (15.9%), red (13.6%) and blue (13.2%). The material of the menu book cover was mainly leather (35.9%), and the internal material was mainly coated paper (59.7%). Physically, the design was two-panel fold (38.3%), two-panel multi-page (35.6%), die style (10.2%), single panel (8.1%) and tent style (7.8%). The type sizes were unchanged in 49.9% of the menu books and in 61.7% photos were not used. 53.9% of menu books did not explain the menus, and 13.2% did not classify the items into groups. Emphasis of profit-making menus was not done in 66.8%. 51.5% of menu books were irreplaceable in parts. The emphasis of profit-making menus was less among the Korean style restaurants (p<0.001). The possibility of partial replacement of menu books was lower in both Korean and Chinese restaurants (p<0.001). The explanation of the items was lower in the Japanese restaurants (p<0.001). The classification of items into groups was lower in cafeteria (p<0.001). In cases in which there were both seasonal and event menus, the possibility of partial replacements of menu books was higher (p<0.001). Restaurants of which service level was less than ordinary were lower in the differentiation of type sizes (p<0.001), the use of photos (p<0.001), the explanation of menus (p<0.001), the classification of menus by groups (p<0.05), the emphasis of profit-making menus (p<0.001) and the possibility of partial replacement of menu books (p<0.001). If these study findings are applied to the designing of menu books, the role of the menu book as an important tool for marketing could be greatly improved.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1996년도 The 9th KACG Technical Annual Meeting and the 3rd Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.5-18
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• 1996

The solid state cesium ion source os alumino-silicate based zeolite which contains cerium. The material is an ionic conductor. Cesiums are stably stored in the material and one can extract the cesiums by applying electric field across the electrolyte. Cesium ion bombardment has the unique property of producing high negative ion yield. This ion source is used as the primary source for the production of a negative ion without any gas discharge or the need for a carrier gas. The deposition of materials as an ionic species in the energy range of 1.0 to 300eV is recently recognized as a very promising new thin film technique. This energetic non-thermal equilibrium deposition process produces films by “Kinetic Bonding / Energetic Condensation" mechansim not governed by the common place thermo-mechanical reaction. Under these highly non-equilibrium conditions meta-stable materials are realized and the negative ion is considered to be an optimum paeticle or tool for the purpose. This process differs fundamentally from the conventional ion beam assisted deposition (IBAD) technique such that the ion beam energy transfer to the deposition process is directly coupled the process. Since cesium ion beam sputter deposition process is forming materials with high kinetic energy of metal ion beams, the process provider following unique advantages:(1) to synthesize non thermal-equilibrium materials, (2) to form materials at lower processing temperature than used for conventional chemical of physical vapor deposition, (3) to deposit very uniform, dense, and good adhesive films (4) to make higher doposition rate, (5) to control the ion flux and ion energy independently. Solid state cesium ion beam sputter deposition system has been developed. This source is capable of producing variety of metal ion beams such as C, Si, W, Ta, Mo, Al, Au, Ag, Cr etc. Using this deposition system, several researches have been performed. (1) To produce superior quality amorphous diamond films (2) to produce carbon nitirde hard coatings(Carbon nitride is a new material whose hardness is comparable to the diamond and also has a very high thermal stability.) (3) to produce cesiated amorphous diamond thin film coated Si surface exhibiting negative electron affinity characteristics. In this presentation, the principles of solid state cesium ion beam sputter deposition and several applications of negative metal ion source will be introduced.