• Tribology and Lubricants
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• 제34권6호
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• pp.270-278
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• 2018

STS 316L prepared by additive manufacturing (AM) exhibits deterioration of mechanical properties and wear resistance due to the presence of defects such as black-of-fusion defects, internal porosity, residual stress, and anisotropy. In addition, high surface roughness (integrity) of AM products remains an issue. This study aimed to apply ultrasonic nanocrystal surface modification (UNSM) technology to STS 316L prepared by AM to increase the surface hardness, to reduce the surface roughness, and to improve the friction and wear behavior to the level achieved by bulk material manufactured using traditional processes. Herein, the as-received and polished specimens were treated by UNSM technology and their resulting properties were compared and discussed. The results showed that UNSM technology increased the surface hardness and reduced the surface roughness of the as-received and polished specimens. These results can be attributed to grain size refinement and pore elimination from the surface. Moreover, the friction of the as-received and polished specimens after UNSM technology was lower compared to those of the as-received and polished specimens, but no significant differences in wear resistance were found.

• 대한치과보철학회지
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• 제46권1호
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• pp.53-64
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• 2008

임플랜트 주위 변연골의 흡수는 임플랜트의 기능적 및 심미적 성공에 큰 장애가 되는 요인이다. Adell은 임플랜트에 지대주 연결 후 첫 1년간 평균적으로 1.5mm의 변연골 소실을 보이고, 이 후에는 매년 0.1mm이하의 변연골 흡수가 있었다고 하였다(Adell et al.,1981). 이러한 변연골 흡수를 막기위한 많은 노력들이 행해져 왔다. 특히 임플랜트 collar의 특징에 따라서 변연골의 흡수가 달라질 수 있다. 본 연구의 목적은 임플랜트 collar에서의 laser microtexturing(microgroove)이 변연골 흡수에 미치는 영향에 대해 알아보고자 하는 것이다. 4종류의 임플랜트 총 101개를 식립한 환자 53명에서 임플랜트 식립시부터 보철물 장착한 후 평균 6개월 후 정기 검사 시까지의 임플랜트 주위 변연골의 흡수를 측정하여 비교하였다. 생물학적 폭경을 충분히 확보한 임플랜트(ITI standard)와 생물학적 폭경이 부족한 임플랜트 (ITI esthetic plus, Silhouette IC Laser-$Lok^{TM}$, Silhouette IC)에서 변연골 흡수의 차이를 비교하였고, 임플랜트 주위 변연골의 흡수에 대한 laser를 이용한 미세나사산의(Silhouette IC Laser-$Lok^{TM}$) 영향을 알아보았다. 다음의 결과를 얻었다. 1. ITI standard와 Silhouette IC Laser-$Lok^{TM}$ 이 ITI esthetic plus 와 Silhouette IC 보다 임플랜트 주위 변연골의 흡수가 적었고 (p<0.05), ITI standard 와 Silhouette IC Laser-$Lok^{TM}$ 사이에는 변연골의 흡수가 유의차가 없었고(P>0.05), ITI esthetic plus와 Silhouette IC 사이에도 변연골의 흡수가 유의차가 없었다(P>0.05). 2. 사용된 임플랜트 전체에 대한 상하악의 비교에서는 상하악 사이에서 임플랜트 주위 변연골의 흡수는 통계학적으로 유의한 차이가 없었다(p>0.05). 3. 흡수각도에 대한 비교에서도 4종류 임플랜트 그룹 간에 통계학적으로 유의한 차이는 없었다(P>0.05). 본 연구에서 제한이 있긴 하지만, 임플랜트 디자인에서 생물학적 폭경이 부족한 경우(ITI esthetic plus, Silhouette IC)에는 생물학적 폭 경 보상을 위한 임플랜트 주위 변연골의 흡수가 있었음을 보여주고 있으나, laser를 이용한 microgroove 가 부여된 임플랜트에서는 collar의 거칠기와 laser microtexturing 등의 특징에 의해 임플랜트 주위 변연골의 흡수가 적게 일어난 것이 관찰되었다. 심미적인 요구도가 높은 전치부에서 충분한 생물학적 폭경이 확보된 임플랜트를 식립할 경우 변연골의 흡수에 따른 치은퇴축에 의해 metal collar의 노출이 우려되기에 충분한 생물학적 폭경이 부여되지 않은 임플랜트를 선정하게 되는데 이때 collar에서의 laser microtexturing은 변연골의 유지에 도움이 되었다. 이것은 조직의 단단한 부착으로 인한 안정화로 추정해 볼 수 있는데, 이에 대해서는 더 장기간의 연구와 더 많은 수의 임플랜트를 대상으로 한 연구와 조직학적인 연구도 필요할 것으로 사료된다.

• 대한방사선치료학회지
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• 제33권
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• pp.109-116
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• 2021

목 적: 본 연구는 표면유도환자셋업(Surface-Guided Patient Setup, SGPS)을 활용한 Markerless환자(피부에 표시를 시행하지 않은 환자)와 레이저기반환자셋업(Laser-Based Patient Setup, LBPS)을 활용한 Marker환자(피부에 표시를 시행한 환자)를 영상유도방사선치료(Image Guided Radiotherapy, IGRT)로 시행했을 때 환자 위치 정확도를 비교하여 SGPS의 유용성을 평가하는데 목적이 있다. 대상 및 방법: 3개의 카메라를 이용한 광학 표면 스캐닝시스템을 사용하여 SGPS로 초기 셋업한 Markerless 환자와 환자 피부에 그려진 Marker와 레이저를 정렬하는 LBPS로 초기 셋업한 Marker환자의 IGRT시 위치 오차를 비교하였다. SGPS,LBPS 모두 각각 전립선암 환자 20명, 뇌정위적방사선수술(Stereotactic Radiation Surgery, SRS) 환자 10명을 대상으로 시행하였고 SGPS의 경우는 추가로 유방암 환자 60명을 대상으로 시행하였다. 모두 CBCT 또는 OBI를 사용하여 IGRT를 시행하였다. 자동위치교정시스템(Auto-Matching System)을 이용하여 6방향(6 Degree Of Freedom, 6 DoF)의 위치 오차를 획득하였고 치료계획시스템에서 Offline-Review를 이용하여 비교, 분석하였다. 결 과 : 전립선암환자의 SGPS와 LBPS의 RMS(Root Mean Square) 차이는 Vrt -0.02cm, Log -0.02cm, Lat -0.01cm, Pit -0.01°, Rol -0.01°, Rtn -0.01°이였고 SRS 환자는 Vrt 0.02cm, Log -0.05cm, Lat 0.00cm, Pit -0.30°, Rol -0.15°, Rtn -0.33°으로 두 부위 모두 큰 차이가 없었다. 유방암환자의 IGRT기준 RMS는 Vrt 0.26, Log 0.21, Lat 0.15, Pit 0.81, Rol 0.49, Rtn 0.59으로 나타났다. 결 론 : 본 연구의 결과 LBPS 대비 SGPS의 위치 오차 값은 전립선암 환자와 SRS 환자의 경우 큰 차이를 보이지 않았다. 추가로 실시한 SGPS의 유방암 환자의 경우에도 IGRT기준으로 위치 오차 값이 크지 않았다. 따라서 환자 피부 표시를 필요로 하지 않는 큰 장점을 가진 SGPS로 LBPS를 대체하기에 유용할 것으로 사료된다.

• Korean Chemical Engineering Research
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• 제45권6호
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• pp.591-595
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• 2007

기존 마이크론 금속섬유 필터를 지지체로 그 표면 위에 나노입자 증착 후, 열처리를 하여 나노구조 기공층이 표면에 부착 형성된 멤브레인 필터를 제작하였다. 가지상 구조의 나노입자 응집체를 마이크론 금속섬유 필터상에 부착함으로써 기존 금속 멤브레인 필터에 비하여 여과성능이 향상된 나노구조 기공층 멤브레인 필터를 개발하였다. 증착한 나노구조 기공층을 지지체 필터 표면상에 부착시키기 위한 열처리 온도가 증가함에 따라 나노입자 응집체의 수축 현상으로 인하여 나노구조 기공층 멤브레인 필터의 차압은 감소하였지만, 여과효율의 감소는 미미하였다.

• Journal of Ceramic Processing Research
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• 제20권6호
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• pp.589-596
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• 2019

Pigments with minute particle sizes, such as carbon black (CB) and pigment red 48:2 (P.R.48:2), are the most important types of pigment and have been widely used in many industrial applications. However, minute particles have large surface areas, high oil absorption and low surface energy. They therefore tend to be repellent to the vehicle and lose stability, resulting in significant increases in viscosity or reaggregation in the vehicle. Therefore, finding the best way to improve the dispersion properties of minute particle size pigments presents a major technical challenge. In this study, minute particle types of CB and P.R.48:2 were treated with nitrogen gas plasma generated via radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) to increase the dispersion properties of minute particles in deionized (DI) water. The morphologies and particle sizes of untreated and plasma treated particles were evaluated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The average distributions of particle size were measured using a laser particle sizer. Fourier transform infrared spectroscopy was carried out on the samples to identify changes in molecular interactions during plasma processing. The results of our analysis indicate that N2 plasma treatment is an effective method for improving the dispersibility of minute particles of pigment in DI water.

• 한국공작기계학회논문집
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• 제14권2호
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• pp.33-41
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• 2005

ZnO epilayer was synthesized by the pulsed laser deposition(PLD) process on Al$_2$O$_3$ subsorte after irradiating the surface of ZnO sintered pellet by ArF(193nm) excimer laser. The epilayers of ZnO were achieved on sapphire(A1203) substrate at the 境mperature of 400$^{circ}$C. The crystalline structure of epilayer was investigated by the Photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of ZnO epilayer measure with Hall effect by van der Pauw mothod are $8.27\times$1016cm$^{-3}$ and 299 cm$^{2}$/V$\cdot$s at 293 K respectively, The temperature dependence of the energy band gap of the ZnO obtained from the absorption spectra was well described by the Varshni's relation, E$_g$(T)= 3.3973 eV - ($2.69\times$ 10$^{-4}$ eV/K)T$^{2}$/(T + 463K). After the as-grown ZnO epilayer was annealed in Zn atmospheres, oxygen and vaccum the origin of point defects of ZnO atmospheres has been investigated by the photoluminescence(PL) at 10K. The native defects of V$_{Zn}$, V$_{O}$, Zn$_{int}$, and O$_{int}$ obtained by PL measurements were classified as a donor or acceptor type. In addition we concluded that the heat-treatment in the oxygen atmosphere converted ZnO thin films to an optical p-type. Also, we confirmed that vacuum in ZnO/Al$_2$O$_3$ did not firm the native defects because vacuum in ZnO thin films existed in the form of stable bonds.

• The Plant Pathology Journal
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• 제26권3호
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• pp.238-244
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• 2010

Spatial and temporal distribution of Bacillus licheniformis N1 was investigated over time on the leaves, petioles and crowns of the strawberry plants. Bacterial population on the strawberry plants was quantified over time by selective plating. Bacterial population of N1 containing a plasmid pWH43G carrying green fluorescent protein (GFP) declined relatively faster on the plant surface as compared to the Strain N1 itself. However, this result was found to be enough to utilize the strain to visualize bacterial colonization on the plant surface. When B. licheniformis N1 was treated together with Silwet L-77 at 0.03%, the bacterial population on plant surface persisted for up to 7 days. B. licheniformis N1 (pWH43G) containing Silwet L-77 was applied on the strawberry plants and the GFP expressing bacteria were visualized by confocal laser scanning microscopy. Bacterial persistence was also investigated in a growth chamber and in a plastic house after N1 bioformulation treatment on the strawberry plant. The Strain N1 colonized three different tissues well and persisted over 3 to 5 days on the strawberry plants. They formed bacterial aggregates on plant surfaces for at least 3 days, resulting in a biofilm to resist fluctuating plant surface environment. However, the bacterial persistence dramatically declined after 7 days in all tested tissues in a plastic house. This study suggest that B. licheniformis N1 colonizes the strawberry plant surface and persists for a long time in a controlled growth chamber, while it can not persist over 7 days on the plant surface in a plastic house.

• 대한치과보철학회지
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• 제43권3호
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• pp.363-378
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• 2005

Statement of problem. Hydroxyapatite(HA) coated titanium surfaces have not yet showed the reliable osseointegration in various conditions. Purpose. This study was aimed to investigate microstructures, chemical composition, and surface roughness of the surface coated by the hydrothermal method and to evaluate the effect of hydrothermal coating on the cell attachment, as well as cell proliferation. Material and Methods. Commercially pure(c.p.) titanium discs were used as substrates. The HA coating on c.p. titanium discs by hydrothermal method was performed in 0.12M HCl solution mixed with HA(group I) and 0.1M NaOH solution mixed with HA(group II). GroupⅠ was heated at 180 $^{\circ}C$ for 24, 48, and 72 hours. GroupⅡ was heated at 180 $^{\circ}C$ for 12, 24, and 36 hours. And the treated surfaces were evaluated by Scanning electron microscopy(SEM), Energy dispersive X-ray spectroscopy(EDS), X-ray photoelectron spectroscopy(XPS), X-ray diffraction method(XRD), Confocal laser scanning microscopy(CLSM). And SEM of fibroblast and 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) assay were used for cellular responses of the treated surfaces. Results. The color of surface changed in both groups after the hydrothermal process. SEM images showed that coating pattern was homogeneous in group II, while inhomogeneous in group I. H72 had rosette-like precipitates. The crystalline structure grew gradually in group II, according to extending treatment period. The long needle-like crystals were prominent in N36. Calcium(Ca) and phosphorus(P) were not detected in H24 and H48 in EDS. In all specimens of group II and H72, Ca was found. Ca and P were identified in all treated groups through the analysis of XPS, but they were amorphous. Surface roughness did not increase in both groups after hydrothermal treatment. The values of surface roughness were not significantly different between groups I and II. According to the SEM images of fibroblasts, cell attachments were oriented and spread well in both treated groups, while they were not in the control group. However, no substantial amount of difference was found between groups I and II. Conclusions. In this study during the hydrothermal process procedure, coating characteristics, including the HA precipitates, crystal growth, and crystalline phases, were more satisfactory in NaOH treated group than in HCl treated group. Still, the biological responses of the modified surface by this method were not fully understood for the two tested groups did not differ significantly. Therefore, more continuous research on the relationship between the surface features and cellular responses seems to be in need.

• 대한치과보철학회지
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• 제53권1호
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• pp.9-18
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• 2015

목적: 본 연구는 Tricalcium phosphate 입자를 사용한 모재분사 후 양극산화처리를 한 임플란트 표면의 특성을 분석하고, 골모유사세포의 반응을 평가하고자 하였다. 재료 및 방법: 직경 10 mm, 두께 3.0 mm 크기의 Grade IV 타이타늄 디스크를 시편으로 사용하였으며, 양극산화처리(ASD)군, 모재 분사 후 양극산화(RBM/ASD)군, 대조군(machined surface)으로 나누어 표면처리하였다. 표면처리 후 FE-SEM, 에너지분산분광기와 주사전자현미경을 사용하여 표면특성을 평가하였다. 세포의 부착을 평가하기 위해 골모유사세포를 이용해 crystal violet assay를 통해 세포부착을 평가하고, 세포 형태는 공초점 레이저 현미경을 사용하여 관찰하였다. 세포증식을 평가하기 위해 XTT 시험을, 세포분화는 역전사 중합효소연쇄반응을 사용하였으며 침착된 칼슘의 양을 측정하기 위해 Alizarin red S stain 을 이용하였다. 비교분석은 one-way ANOVA (SPSS version 18.0)로 유의수준 5%에서 검정하였다. 결과: ASD군과 RBM/ASD군에서, 분화구 모양의 표면 형상이 나타났으며, 대조군과 비교하여 산소와 인산 이온이 관찰되었다. 단위면적당 거칠기는 대조군에서 $0.08{\pm}0.04{\mu}m$, ASD군에서 $0.52{\pm}0.14{\mu}m$, RBM/ASD군에서 $1.45{\pm}0.25{\mu}m$를 보였다. 세포반응실험에서, ASD군과 RBM/ASD군이 대조군에 비해 세포의 부착정도가 높았으며 대조군이 세포증식에서 가장 높은 값을 보였다(P<.05). RT-PCR 실험에서, RBM/ASD군이 다른 군들보다 높은 ALP를 보였다(P<.05). ASD군과 비교했을 때 RBM/ASD군은 세포부착과 증식 정도에서 큰 값을 보였다(P<.05). 결론: 본 연구의 한계내에서 모재분사 후 양극산화 처리한 티타늄 표면 처리 방식이 단순 양극산화 처리한 군이나 대조군보다 골모유사세포의 반응에 효과적인 방법임을 확인하였다.

• 대한치과보철학회지
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• 제39권1호
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• pp.71-83
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• 2001

The purpose of this study was to compare the effects of various surface treatments by measuring removal torque on bone healing around titanium implants. 40 Screw-shaped cp titanium implants with length of 4mm, outer diameter of 3.75mm, and pitch-height of 0.5mm were used Group 1 was left as machined(control), Group 2 was blasted with $50{\mu}m\;Al_2O_3$, group 3 was blasted and etched in etching solution($NH_4OH : H_2O_2:H_2O= 1 : 1 : 5$) at $90^{\circ}C$ for 1 minute group 4 was blasted and oxidated under pure oxygen at $800^{\circ}C$. The implant surface roughness was analyzed with SEM and CLSM(Confocal Laser Scanning Microscope) and implants were placed in proximal tibial metaphysis of 10 New Zealand White rabbits. After 3 months of healing period, removal torque of each implant was measured to compare bone healing around implant. The results obtained were as follows 1. In SEM view, blasting increased the roughness of the surface, but etching of that rough surface decreased the roughness due to the removal of the tip of the peak. Oxidation also decreased the roughness due to formation of needle-like oxide grains on the implant surface. 2. The Sa value from CLSM was least in the machined group($0.47{\mu}m$), greatest in blasted group($1.25{\mu}m$), and the value decreased after etching($0.91{\mu}m$) and oxidation($0.94{\mu}m$). 3. The removal torque of etched group(24.5Ncm) was greater than that of machined group(16.7Ncm) (P<0.05), and was greatest in the oxidated group(40.3Ncm) and the blasted group(34.7Ncm).