• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.104.2-104.2
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• 2012

이종 재료의 접합에 대한 연구는 단일 재료에서 얻을 수 없는 물리적/기계적 특성과 이종 재료의 우수한 특성을 얻을 수 있다는 장점이 있어 국내외 적으로 연구가 활발히 진행되고 있다. 이러한 이종 접합 기술은 구조재료와 에너지 변환분야에 가장 많이 사용되고 있으며, 그 외 광촉매와 Thin film, 경량구조재료 등에도 사용되고 있다. 그 중 FGM(Functional Graded Materials)는 조성의 점진적인 변화를 통하여 접합하는 방법으로 이종 재료 접합 시 발생하는 내부 응력을 해소해줌으로써 적합한 방법이라고 할 수 있다. FGM 제작에 사용되는 방법으로 널리 알려진 것들로는 plasma spraying, 원심주조, 분말 야금법, PVD, CVD 그리고 EPD(electrophoretic deposition) 등이 있다. 이중에서 EPD는 수용액이나 유기용매와 같은 분산매체 중에 콜로이드 입자의 표면에 대전되는 전하를 이용하여, 외부에서 전장을 걸어서 입자의 움직임을 제어하는 기술이다 EPD는 코팅 속도가 상대적으로 빠르고 두꺼운 코팅 층 제작이 가능하다. 또한 바인더, 윤활제 또는 가소제를 사용하지 않고 다양한 종류와 모양의 기판 위에 균일한 코팅이 가능하다는 장점이 있다. 본 연구에서는 Ni substrate를 이용하여 그 위에 Ni과 $Al_2O_3$의 조성을 점진적으로 변화시켜 FGM을 EPD 방법으로 코팅하였다. 여기서 사용된 Ni은 높은 녹는점과 좋은 연성으로 인해 성형이 용이하여 구조재료로 적합하며, $Al_2O_3$는 고내열성과 내부식성을 가지며 경도가 높다는 장점이 있다. 본 연구에서는 EPD 방식을 이용하여 Ni/$Al_2O_3$ FGM을 코팅하였으며, 코팅 후 발생하는 substrate와의 접착력 문제를 해결하기 위해서 건조 방식과 substrate의 표면 상태를 최적화하여 다층의 Ni/$Al_2O_3$ FGM을 코팅 및 소결하였다. Zeta-potential 측정을 통해 electrophoretic mobility와 suspension의 분산 안정도를 평가 할 수 있었으며, X-ray 회절 분석(XRD)을 통하여 Ni 의 환원 여부를 확인하였다. 또한 Scanning electron microscopy(SEM) 분석을 통하여 미세구조 분석을 하였고, 최종적으로 Electron Probe Micro Analyzer (EPMA) 를 이용하여 다층 구조의 조성변화를 확인함으로 Ni/$Al_2O_3$의 FGM 코팅이 이루어졌음을 확인하였다.

• 한국치위생학회지
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• 제20권4호
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• pp.535-543
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• 2020

Objectives: The aim of this study was to investigated the surface roughness and change in the amount of adhesion of Streptococcus mutans to the commercial pit and fissure sealant containing cerium oxide nano particles(CNPs). Methods: The CNPs was incorporated into a commercial pit and fissure sealant at 0-4.0 wt%. Disk Specimens (ϕ 10 mm × 2 mm) were prepared by light polymerization the front and back for 40s. Average surface roughness was measured and Streptococcus mutans adhesion was observed under confocal laser scanning microscopy (CLSM) after 24 hour. Data were statistically analyzed by one-way ANOVA and Tukey HSD^a post-hoc test. Results: Difference of the surface roughness(Ra) between groups was not statistically significant in both non CNPs group and CNPs group(p>0.05). In CNPs group, the amount of S. mutans adhesion was significantly different between control group and decreased in order of CNPs 4.0, CNPs 0.5, CNPs 1.0 and CNPs 2.0(p<0.05). Conclusions: Within the limitation of this study, these aspects of oral bacteria performances suggest potential usefulness of the CNPs incorporation, especially CNPs 1% and 2%, in pit and fissure sealant for inducing antibacterial effect.

• 대한약침학회지
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• 제20권1호
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• pp.36-44
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• 2017

Objectives: The goal of this study was to characterize Suvarna Bhasma Parada Marit by using the Ayurvedic test parameters, physico-chemical tests, and various instrumentation techniques. Methods: Suvarna Bhasma, an Ayurvedic formulation manufactured as per Bharat Bhaishajya Ratnakar 5/8357 (BBR), has been studied using various instrumentation techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), laser particle size distribution (PSD) analysis, fourier transform infrared spectroscopy (FT-IR), and atomic absorption spectroscopy (AAS), and physico-chemical parameters, such as the loss on drying (LOD), loss on ignition (LOI), and acid insoluble Ash (AIA) were determined. In addition, Ayurvedic tests, such as Rekhapurnatva (enterable in the furrows of the fingers), Varitaratwa (floatable over water), Nirdhoomta (smokeless), Dantagre Kach-Kach (gritty particle feeling between the teeth), were performed. Results: The XRD study showed Suvarna Bhasma to be crystalline in nature and to contain more than 98% gold. The mean size of the gold crystallites was less than 10 microns, and the morphology was globular and irregular. Suvarna Bhasma contains gold as its single and major element, with EDAX and FT-IR spectra showing that it is more than 98% pure gold. The moisture content (LOD) is less than 0.5%, the LOI is less than 2%, and the AIA is not less than 95%. The Ayurvedic tests, as specified above, helped to confirm the quality of Suvarna bhasma prepared as per the text reference (BBR). Conclusion: This chemical characterization of Suvarna Bhasma performed in this study by using modern instrumentation techniques will be helpful in understanding its pharmacological actions and will help in establishing quality protocols and specifications to substantiate the safety, efficacy & quality of Suvarna Bhasma.

• 한국주조공학회지
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• 제23권5호
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• pp.276-285
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• 2003

In the undercooled melt of $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy, the solidification behavior including nucleation and growth of crystals at the micrometer level has been observed in-situ by use of a confocal scanning laser microscope combined with an infrared image furnace. The $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy specimens were cooled from the liquid state to glass transition temperature. 575 K, at various cooling late under a helium gas flow. According to the cooling rate, the morphologies of the solidification front are changed among various types, irregular jog like front, columnar dendritic front, cellular grain, star like shape jog and fine grain, etc. The velocities of the solid-liquid interface are measured to be $10^{-5}{\sim}10^{-8}$ m/s which are at least two orders higher than the theoretical crystal growth rates. Combining the morphologies observed in terms of cooling rates and their solidification behaviors, we conclude that phase separation takes place in the undercooled molten $Pd_{40}Cu_{30}Ni_{10}P_{20}$ alloy. The continuous cooling transformation (CCT) diagram was constructed from solidification onset time at various linear cooling conditions with different rate. The CCT diagram suggests that the critical cooling rate for glassy solidification is about 1.5 K/s, which is in agreement with the previous calorimetric findings.

• 대한공간정보학회지
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• 제19권1호
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• pp.79-86
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• 2011

최근 수치표고모델(DEM : Digital Elevation Model)을 구축하기 위한 목적으로 항공레이저측량(LiDAR : Light Detection And Ranging) 기술이 주목받고 있다. DEM은 항공레이저측량으로부터 획득된 라이다 데이터에서 지면점만 추출한 수치지면자료(DTD : Digital Terrain Data)의 정확성에 의해 그 품질이 좌우된다. 하지만 원시자료에서 수치지면자료를 추출하기 위한 자동 필터링 작업은 필터링 알고리즘의 한계 및 라이다 데이터의 고유한 특성으로 인하여 항상 오분류 영역이 발생한다. 따라서 이를 보완하기 위해서는 작업자에 의한 수동분류 작업이 반드시 필요하다. 본 연구에서는 수동 작업이 원활하게 이루어 질 수 있도록 자동 필터링 작업에서 얻어진 수치지면자료에서 오분류 될 가능성이 있는 영역을 자동으로 탐지하는 알고리즘을 제안한다. 제안된 알고리즘은 2D 격자 구조를 적용하였으며 'Slope Angle', 'Slope DeltaH', 'NNMaxDH(Nearest Neighbor Max Delta Height)'로 명명한 매개변수를 사용하였다. 실험 결과, 제안된 알고리즘은 지형형태나 라이다 데이터 평균 점밀도에 제한받지 않는 안정적인 결과를 보여주었다.

• 대한치과기공학회지
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• 제38권3호
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• pp.157-163
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• 2016

Purpose: It is to compare and evaluate the change of the wear rate and phase variation of the Zirconia before and after the sintering after the grinding by a high speed equipment manufactured for the Zirconia. Methods: The specimen of the sintered Zirconia was manufactured as size of $15mm{\times}15mm{\times}2mm$. The grinding has been applied to each of all pieces of each test groups for a minute fit for each condition at same speed of 50,000 rpm by a diamond bur at high speed handpiece with injection of the air and water. For the observation of the surface before and after the sintering of the each test piece, the cross section of it was observed as 100 magnification by a scanning electron microscope after it was coated by PT, and the diffraction analysis was performed by XDR to compare the crystal phase of the Zirconia. The average surface roughness value of all specimens were evaluated. The wear test was performed at room temperature by applying a load of 1kg for 120,000 cycles for the chewing period 6 months. Wear was analyzed for the enamel cusps by measurement of the vertical substance loss with a laser scanner. Conclusion: The phase variation from the tetragonal phase to the monoclinic phase was confirmed in the test group of the pre-sintered Zirconia after the grinding, and the value of the surface roughness and the wear rate was increased in experimental group.

• 대한치과기공학회지
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• 제40권2호
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• pp.63-69
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• 2018

Purpose: The purpose of this study is to investigate the non-precious metal core materials used in the dental laboratory to fabricate the implant superstructure by CAD / CAM method. And to observe and compare the morphology and distribution of the osteoblasts in relation to implant osseointegration. Methods: In this study, the mandibular right first molar tooth model was selected as an international standard to produce a single core. Using this model, the impression was made with the silicone rubber, the tooth model was scanned, and a single core was designed and 5-axis milling was performed. The materials used were Cobalt-Chromium and Nickel-Chromium, and the cores for dental implant top structures were fabricated according to the procedures of the dental labs. After the fabrication, the marginal area of the core was separated and cell culture experiment was performed. The osteoblast cells used MC3T3-E1, which is currently widely used. For morphological analysis of osteoblasts, cells were posttreated and observed using CLSM (Confocal Laser Scanning Microscope) and compared. Results: The cell adhesion behavior of the specimen surface measured by CLSM was uniformly distributed in specimen A (Cobalt-Chromium) than in specimen B (Nickel-Chromium). The distribution and changes of the cells were different in the two specimens. Conclusion : It is possible to confirm that specimen A (Cobalt-Chromium) is suitable for the living body through adhesion and proliferation of osteoblasts related to implant osseointegration in the non-precious metal superstructure used after implantation. It is considered that it is preferable to use Co-Cr when fabricating the superstructure.

• 한국태양에너지학회 논문집
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• 제32권4호
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• pp.1-8
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• 2012

A Fiber Bragg Grating (FBG) sensor imbedded small wind turbine blade was manufactured to experimentally investigate the feasibility to embed FBG sensors between layers of glass fiber to monitor dynamic strains of the wind turbine blade. The blade which is similar to a commercial 300 W wind turbine blade was manufactured with glass fiber as a reinforcement and epoxy resin as base material. A total of five FBG sensors including one temperature sensor were imbedded in the blade to sense mechanical strain and temperature. While manufacturing the blade, residual strain and temperature that occurred in the small wind turbine blade were monitored using the imbedded FBG sensor array. To examine the sensor performance, an impact test was carried out. The experimental results from the FBG sensors were close to those from electrical strain gages mounted on the blade root surface. The mode shapes of the blade were analyzed also using a commercial Ansys simulation with a model obtained from a three dimensional laser scanning of the blade.

• 사상체질의학회지
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• 제20권1호
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• pp.42-47
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• 2008

1. Objectives The Body Shape and Feature is one of the important standard for classification of Sasang Constitutions. In order to evaluate one's Body Shape and Feature objectively we have been developing the Body Measuring Machine. Now we develop the 3D Automatic Body Measuring Machine(3D-ABMM). So we make an analysis of the 3D-ABMM's Accuracy. 2. Methods By using the 3D-ABMM and Vivid 9i(3D laser scanner, Konica Minolta) we have a surface scan of the three objects which are the upper body of the female and male Manikin and a male model. We overlap each scan data using the RapidForm2006 (3D scan data solution, INUS Technology) and calculate the average distance and standard deviation between the same point of each scan data. 3. Results and Conclusions In the female Manikin, the average distance is 0.84mm and the standard deviation is 1.16mm and the maximum distance is 10.68mm. In the male Manikin, the average distance is 1.12mm and the standard deviation is 1.19mm and the maximum distance is 12.00mm. In the male model, the average distance is 3.26mm and the standard deviation is 2.59mm and the maximum distance is 12.75mm. From the results, 3D-ABMM has good accuracy for scanning body and will be a usable hardware of the 3D Automatic Body Analysis Machine.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.99.1-99.1
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• 2012

The thin-film photovoltaic absorbers (CdTe and $Cu(In,Ga)Se_2$) can achieve solar conversion efficiencies of up to 20% and are now commercially available, but the presence of toxic (Cd,Se) and expensive elemental components (In, Te) is a real issue as the demand for photovoltaics rapidly increases. To overcome these limitations, there has been substantial interest in developing viable alternative materials, such as $Cu_2ZnSnS_4$ (CZTS) is an emerging solar absorber that is structurally similar to CIGS, but contains only earth abundant, non-toxic elements and has a near optimal direct band gap energy of 1.4 - 1.6 eV and a large absorption coefficient of ~104 $cm^{-1}$. The CZTS absorber layers are grown and investigated by various fabrication methods, such as thermal evaporation, e-beam evaporation with a post sulfurization, sputtering, non-vacuum sol-gel, pulsed laser, spray-pyrolysis method and electrodeposition technique. In the present work, we report an alternative aqueous chemical approach based on chemical bath deposition (CBD) method for large area deposition of CZTS thin films. Samples produced by our method were analyzed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, absorbance and photoluminescence. The results show that this inexpensive and relatively benign process produces thin films of CZTS exhibiting uniform composition, kesterite crystal structure, and some factors like triethanolamine, ammonia, temperature which strongly affect on the morphology of CZTS film.