• 대한치과교정학회지
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• 제44권5호
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• pp.229-235
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• 2014

Objective: The aim of this study was to assess artifacts induced by metallic restorations in three-dimensional (3D) dental surface models derived by cone-beam computed tomography (CBCT). Methods: Fifteen specimens, each with four extracted human premolars and molars embedded in a plaster block, were scanned by CBCT before and after the cavitated second premolars were restored with dental amalgam. Five consecutive surface models of each specimen were created according to increasing restoration size: no restoration (control) and small occlusal, large occlusal, disto-occlusal, and mesio-occluso-distal restorations. After registering each restored model with the control model, maximum linear discrepancy, area, and intensity of the artifacts were measured and compared. Results: Artifacts developed mostly on the buccal and lingual surfaces. They occurred not only on the second premolar but also on the first premolar and first molar. The parametric values increased significantly with increasing restoration size. Conclusions: Metallic restorations induce considerable artifacts in 3D dental surface models. Artifact reduction should be taken into consideration for a proper diagnosis and treatment planning when using 3D surface model derived by CBCT in dentofacial deformity patients.

• 한국표면공학회지
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• 제50권4호
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• pp.266-271
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• 2017

In this study, the corrosion resistance of Zn-3wt.%Mg coating was enhanced by controlling the density of coating. During the deposition the substrate temperature was controlled via an intermittent deposition process, resulting in the improvement of coating density. The maximum substrate temperature during this intermittent deposition process could be controlled from $200^{\circ}C$ to $80^{\circ}C$, depending upon the number of coating layer. The density of Zn-3 wt.%Mg coating increased from 76.1 % to 95.8 % as the substrate temperature was controlled. The salt spray test results revealed that the corrosion resistance of Zn-Mg coated steel could increase 3 times by increasing the density in coatings, while adhesion strength of coating was not changed significantly during 0-T bending test.

• 한국표면공학회지
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• 제37권3호
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• pp.152-157
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• 2004

Ti-Al-N ($Ti_{75}$ $Al_{25}$ N) and Ti-Al-Si-N ($Ti_{69}$ $Al_{23}$ $Si_{8}$N) coatings synthesized by a DC magnetron sputtering technique were studied comparatively with respect to phase characterization and high-temperature oxidation behavior. $Ti_{69}$ $Al_{23}$ $Si_{ 8}$N coating had a nanocomposite microstructure consisting of nanosized(Ti,Al,Si)N crystallites and amorphous $Si_3$$N_4$, with smooth surface morphology. Ti-Al-N coating of which surface $Al_2$$O_3$ layer formed during oxidation suppressed further oxidation. It was sufficiently stable against oxidation up to about $700^{\circ}C$. Ti-Al-Si-N coating showed better oxidation resistance because both surface Ab03 and near-surface $SiO_2$ layers suppressed further oxidation. XRD, GDOES, XPS, and scratch tests were performed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
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• pp.87-89
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• 1998

The Y2O3 films on Si(111) was grown by ionized cluster beam depposition (ICBD) in ultrahigh-vacuum (UHV). The acceleration voltage and oxygen ppartial ppressure were fixed at 5 kV and 2$\times$10-5 Torr resppectively. The substrate tempperature was varied from 10$0^{\circ}C$ to $600^{\circ}C$ in order to find the deppendence of crystallinity of Y2O3 films on the substrate tempperature. The crystallinity of the films with the substrate tempperature studied using x-ray diffraction (XRD) and Rutherford backscattering sppectroscoppy (RES). Surface crystallinity and surface morpphology of the films were also investigated using the reflection high-energy electron diffraction (RHEED) and atomic force microscoppe (AFM) resppectively. The films grown at the substrate tempperature below 50$0^{\circ}C$showed the ppoly-crystalline structure of oxygen deficiency. On the contrary the single-crystalline structure was obtained at the substrate tempperature over 50$0^{\circ}C$ and the stochimetry was gradually matched as increasing the substrate tempperature. The surface morpphology showed the increase of the surface roughness as the substrate tempperature was increased upp to 50$0^{\circ}C$ The crystallinity of the film was not good and the minimum channeling yield $\chi$min was measured at 0.91 The stochiometric and high crystallinine film (surface $\chi$min=0.25) was obtained as the substrate tempperature increased upp to 60 $0^{\circ}C$ which indicate the tempperature was sufficient to migrate the depposited atom.

• 대한수학회논문집
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• 제11권3호
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• pp.825-829
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• 1996

We prove that if G is the fundamental group of a closed surface or a Seifert fibered space and K is a finitely generated subgroup of G, and if for any element g in G there exists an integer $n_g$ such that $g^{n_g}$ belongs to K, then K is of finite index in G.

• 호남수학학술지
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• 제30권4호
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• pp.637-644
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• 2008

In this paper, we study some properties about the parallel surfaces of ruled surfaces in a Euclidean 3-space. Furthermore, we classify the parallel surfaces of ruled surfaces in a Euclidean 3-space satisfying a linear type and a quadric type with respect to the Gaussian curvature and the mean curvature.

• Tribology and Lubricants
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• 제28권6호
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• pp.297-302
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• 2012

We conducted 3D elastic contact analysis of a sharkskin surface pattern for the characteristic assessment of biomimetic shark skin structure pattern for engineering applications. Rough sharkskin surfaces of similar size with real shark skin scales are generated numerically. Under the assumption of the contact of a plate on the generated sharkskin surface, contact performances such as contact pressure, real contact area, and surface separation are evaluated.

• 접착 및 계면
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• 제7권2호
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• pp.19-25
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• 2006

미생물 합성 고분자인 poly(hydroxylalkanoate)s (PHAs)의 초기효소분해는 표면침식의 메커니즘으로 진행하므로 이들의 분해거동은 표면특성을 개질로서 조절할 수 있다. 본 연구에서는 효소분해속도를 조절하기 위하여 플라즈마 기법을 PHAs 표면특성의 개질에 적용하였다. $CF_3H$와 $O_2$ 플라즈마를 사용하여 재료 표면에 각각 소수성 및 친수성을 부여하였다. 효소분해 실험은 pH 7.4의 0.1 M potassium phosphate 완충용액에서 Alcaligenes facalis T1에서 정제된 poly(hydroxybutyrate) 분해효소를 첨가하여 행하였다. $CF_3H$ 플라즈마 처리된 시편의 경우 표면 층의 불소화에 따른 소수성의 증가와 분해 효소에 대한 비활성으로 초기분해 속도가 상당히 지연됨을 관찰하였으나 $O_2$ 플라즈마 처리에 의한 표면 친수성은 분해속도의 촉진 등에 큰 영향을 미치지 않았다.

• The Journal of Advanced Prosthodontics
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• 제12권5호
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• pp.291-298
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• 2020

PURPOSE. The aim of this study is to evaluate the influence of repeated surface treatments on wettability and surface roughness for zirconia surface and bond strength of zirconia-based ceramics to resin cement. MATERIALS AND METHODS. Seventy blocks (10 × 10 × 3 mm) of zirconia-based ceramics were fabricated and divided into two groups according to the surface treatments: (A) 110 ㎛ Al₂O₃ airborne-particle abrasion and (R) 110 ㎛ silica modified Al₂O₃ airborne-particle abrasion. At stage 2, each group was subdivided into 5 groups according to the surface retreatments: (a) 110 ㎛ Al₂O₃ airborne-particle abrasion, (r) 110 ㎛ silica modified Al₂O₃ airborne-particle abrasion, (D) diamond bur, (Da) diamond bur + 110 ㎛ Al₂O₃ airborne-particle abrasion, and (Dr) diamond bur + 110 ㎛ silica modified Al₂O₃ airborne-particle abrasion. Cylinders of self-adhesive resin cement were cemented onto each treated ceramic surface and subjected to micro-shear bond strength test. Additional specimens were prepared for roughness and wettability analyses. The data were subjected to t-test and One-way ANOVA followed by Tukey's post hoc test (α=.05). RESULTS. At stage 1, group R presented higher bond strength values than group A (P=.000). There was a statistically significant increase of bond strength at stage 2 for group A (P=.003). The diamond bur influenced the surface roughness, increasing the values (P=.023). Group R provided better wettability. Regardless of the applied surface treatment, most of failures were adhesive. CONCLUSION. The combination of application and reapplication of Rocatec Plus showed the best results of bond strength. Surface retreatment and recementation might be an indicated clinical strategy.

• 한국세라믹학회지
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• 제39권3호
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• pp.315-320
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• 2002

저농도로 희석된 HF 수용액(6 wt%)을 사용하여 $Al(OH)_3$의 표면을 F/Al의 몰비 0.15에서 처리하고, 처리 전후 표면특성을 관찰하였다. 반응계의 온도 및 pH 변화로부터 $Al(OH)_3$에 대한 HF의 표면반응은 HF와 접촉한 $Al(OH)_3$ 표면부에서 metastable한 ${\alpha}$형의 불화알루미늄$({\alpha}-AlF_3{\cdot}3H_2O)$이 안정한 ${\beta}$형의 불화알루미늄$({\beta}-AlF_3{\cdot}3H_2O)$으로 전이되는 과정으로 진행되며, 다량의 발열을 수반하면서 반응계의 온도상승을 유발하였다. 이러한 ${\beta}-AlF_3{\cdot}3H_2O$의 생성은 표면처리된 분말의 FT-IR 및 X-선 회절분석결과를 통해 확인되었다. ${\beta}-AlF_3{\cdot}3H_2O$의 morphology와 분포상태를 SEM을 통해 관찰한 결과 $Al(OH)_3$ 표면에 $1{\mu}m$ 이하의 미세분말 형태로 피복층을 형성하며 균일하게 분포된 것으로 확인되었다. HF로 처리된 시료의 표면 백색도는 미처리에 비해 약 6.6% 증가되었으며, 이는 $Al(OH)_3$보다 높은 백색도를 지닌 ${\beta}-AlF_3{\cdot}3H_2O$ 피복 효과 때문인 것으로 나타났다.