• 한국산학기술학회논문지
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• 제7권5호
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• pp.817-822
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• 2006

다이아몬드는 산업적으로도 보석으로서도 경제적으로 매우 유용한 소재이다. 최근의 소형 고압고온 처리기의 발달로 저급한 갈색의 보석용 천연다이아몬드를 쉽게 고부가가치의 보석인 무색 또는 팬시칼라의 다이아몬드로 향상시키는 처리기술이 가능하게 되었다. 이러한 처리 다이아몬드는 천연의 무색, 팬시칼라 다이아몬드와 물성이 동일하여 기존의 보석감정 방안으로는 구별이 어려워서, 처리 다이아몬드를 경제적이고, 신속하고, 비파괴적으로 천연다이아몬드로부터 감별해 낼 필요성이 생겼다 기존의 광학적인 확대분석으로는 천연석과 처리석의 감별이 불가능하였다. 마이크로 라만 분석기를 이용하여 다이아몬드의 고유피크가 고압고온 처리시의 잔류응력에 의해 이동되는 현상으로 처리석의 감별 가능성을 확인하였다. Type I 다이아몬드는 처리에 의해 $10^4$ 정도의 압축스트레인이, Type II는 인장 잔류 스트레인이 존재하였다. 따라서 적절한 처리전의 기준시료가 있다면 이러한 잔류응력을 확인하는 것이 가능하였다.

• 패션비즈니스
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• 제7권5호
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• pp.108-118
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• 2003

Surface properties, including the texture and the luster, of cotton fibers and yarns thereof play an important role in textile technology. The convolutions and the cross-sectional shape of the cotton fiber affect the fabric texture and the luster accordingly. Mercerization of the cotton fabric affects the luster, strength, and other properties of the fabric. In this study, the effect of mercerization was examined on the luster of the cotton fabric, together with the effect of polishing treatment. One of the traditional methods determining the fabric luster is the use of glossmeter or goniometric glossmeter. The use of glossmeter gives successful results in determining the gloss of rather flat and continuous surface such as plastic sheet, painted surface, or paper products. Since the textile fabrics have diverse surface structures and textures, these could be regarded as having three-dimensional surface. Such complexity imposes some difficulties for differentiating subtle surface luster properties of diverse textile fabrics. The advancement in the area of imaging technologies has enabled the micro-scale analysis of the surface textures and the fabric luster recently. Using a CCD camera, the surface luster images were taken at various incident illumination conditions. Microscale analysis, including the blob analysis, of the images could differentiate the subtle luster properties present in a group of cotton fabric samples comprising mercerized cotton fabric, non-mercerized cotton fabric, polished cotton fabric, and a 'standard' cotton fabric. The glossmeter measurement gave satisfactory but limited differentiation among the samples, whose luster differences are easily recognizable with visual observation, except for the mercerized cotton fabric sample and the non-mercerized cotton fabric. The microscale analysis of the fabric luster could, therefore, help understand the nature of diverse textile fabric luster.

• 한국표면공학회지
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• 제37권5호
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• pp.249-252
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• 2004

Effects of HA and TiN coating on the electrochemical characteristics of Ti-6AI-4V alloys for bone plates were investigated using various test methods. Ti-6AI-4V alloys were fabricated by using a vacuum induction furnace and bone plates were made by laser cutting and polishing. HA was made of extracted tooth sintered and then tooth ash was used as HA coating target. The TiN and HA film coating on the surface were carried on using electron-beam physical vapor deposition (EB-PVD) method. The corrosion behaviors of the samples were examined through potentiodynamic method in 0.9% NaCI solutions at $36.5\pm$$1^{\circ}C$ and corrosion surface was observed using SEM and XPS. The surface roughness of TiN coated bone plates was lower than that of tooth ash coated plates. The structure of TiN coated layer showed the columnar structure and tooth ash coated layer showed equiaxed and anisotrophic structure. The corrosion potential of the TiN coated specimen is comparatively high. The active current density of TiN and tooth ash coated alloy showed the range of about $1.0xl0^{-5}$ $A\textrm{cm}^2$, whereas that of the non-coated alloy was$ 1.0xl0^{-4}$ $A\textrm{cm}^2$. The active current densities of HA and TiN coated bone plates were smaller than that of non-coated bone plates in 0.9% NaCl solution. The pitting potential of TiN and HA coated alloy is more drastically increased than that of the non-coated alloy. The pit number and pit size of TiN and HA coated alloy decreased in compared with those of non-coated alloy. For the coated samples, corrosion resistance increased in the order of TiN coated, tooth ash coated, and non-coated alloy.

• The Journal of Advanced Prosthodontics
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• 제13권1호
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• pp.1-11
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• 2021

PURPOSE. The study compared the color change, lightness, and translucency of hybrid resin ceramics exposed to toothbrush abrasion and surface treatment. MATERIALS AND METHODS. Four hybrid ceramics [Lava Ultimate (LU), Vita Enamic (EN), Shofu HC (SH), and Crystal Ultra (CU)] were compared with a glass-ceramic (Vita Mark II) control. One hundred and twenty specimen blocks were prepared using a precision saw machine. Specimens in each material were divided into four subgroups based on the surface treatment (polishing or staining) and a storage medium (water or citric acid). Simulated tooth brushing with a mixture of 100 RDA (radioactive abrasives) with 0.3 ml distilled water was used for 3650 cycles (7300 strokes) for each specimen. Measurements for the color change, lightness, and translucency were measured after toothbrushing using a spectrophotometer. Statistical analysis compared outcomes using paired t-test, ANOVA, and Tukey post hoc test. RESULTS. The maximum color change was identified in SH (stained acid) [1.44 (0.40)], whereas the lowest was identified in EN (polished water) [0.66 (0.16)] material. The maximum and minimum loss of surface translucency was observed in SH (polished water) [12.3 (0.52)] and EN (stained acid) [6.5 (0.55)] specimens, respectively. Lastly, loss of lightness was the highest in VM (polished acid) [69 (0.95)], whereas the lowest was observed in CU (stained water) [56.7 (0.86)]. CONCLUSION. The comparison presented a significant effect of toothbrush abrasion on translucency and lightness of the hybrid resin ceramics. Color change was not significantly influenced irrespective of the storage medium employed. Surface staining demonstrated the preservation and stability of color and optical properties under the influence of toothbrush abrasion and chemical trauma.

• 대한치과기공학회지
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• 제43권2호
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• pp.56-61
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• 2021

Purpose: This study aimed to produce resin prosthetics using a dental automatic barrel finishing. Surface roughness and surface topography of resins were observed according to the grinding time of the dental automatic barrel finishing. Methods: This study was performed with thermopolymer, autopolymer, and photopolymer resins. The dimensions of the specimen were 10×10×2 mm. Each specimen was polymerized according to the manufacturer's instructions. The polymerized resin was honed for 30 minutes at 5-min intervals in a dental automatic barrel finishing. The specimen was observed using a three-dimensional (3D) optical microscope, and the surface roughness was measured. Results: After the polishing with the dental automatic barrel finishing, the heat-cured (HC) specimen showed the highest and lowest values of Ra after 10 and 15 minutes, respectively. The self-cured (SC) specimen showed the highest and lowest values of Ra after 10 and 25 minutes, respectively. Finally, the 3D specimen showed the highest and lowest values of Ra after 5 and 20 minutes, respectively. Conclusion: After measuring the surface roughness of the three types of resins according to the grinding time of the dental automatic barrel finishing, the lowest Ra values for the HC, SC, and 3D specimens were measured after 15, 25, and 20 minutes, respectively. Therefore, we concluded that a limit on the grinding time of the resin using a dental automatic barrel finishing is needed.

• Safety and Health at Work
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• 제15권1호
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• pp.96-101
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• 2024

Background: Silicosis among workers who fabricate engineered stone products in micro or small-sized enterprises (MSEs) was reported from several countries. Workplace exposure data of these workers at high risk of exposure to respirable crystalline silica (RCS) dust are limited. Methods: We surveyed workers performing cutting, shaping and polishing tasks at 6 engineered stone fabricating MSEs in Sydney, Australia prior to regulatory intervention. Personal exposure to airborne RCS dust in 34 workers was measured, work practices were observed using a checklist and worker demography recorded. Results: Personal respirable dust measurements showed exposures above the Australian workplace exposure standard (WES) of 0.1 mg/m³ TWA-8 hours for RCS in 85% of workers who performed dry tasks and amongst 71% using water-fed tools. Dust exposure controls were inadequate with ineffective ventilation and inappropriate respiratory protection. All 34 workers sampled were identified as overseas-born migrants, mostly from three linguistic groups. Conclusions: Workplace exposure data from this survey showed that workers in engineered stone fabricating MSEs were exposed to RCS dust levels which may be associated with a high risk of developing silicosis. The survey findings were useful to inform a comprehensive regulatory intervention program involving diverse hazard communication tools and enforcing improved exposure controls. We conclude that modest occupational hygiene surveys in MSEs, with attention to workers' demographic factors can influence the effectiveness of intervention programs. Occupational health practitioners should address these potential determinants of hazardous exposures in their workplace surveys to prevent illness such as silicosis in vulnerable workers.

• Restorative Dentistry and Endodontics
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• 제24권2호
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• pp.381-391
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• 1999

A new 5th generation adhesive system(ONE-STEP) has been supplied which operators can apply to conditioned tooth surfaces by one simplified step. The purpose of this study was to determine whether different methods of adhesive application and various air drying duration after applying adhesive affect the shear bond strength of composite resin to dentin, and to evaluate the adhesive pattern of composite resin and dentin under SEM. Seventy-seven extracted human molar teeth were cleaned and mounted in palstic test tubes. The occlusal dentin surfaces were exposed with Diamond Wheel Saw and smoothed with Lapping and Polishing Machine (South Bay Technology Co., U.S.A.). Teeth were randomly divided into 7 groups (n=11), In experimental A group, adhesive was applied to dentin with agitation for 20 sec. In experimental N-A group, adhesive were continuously applied to dentin for 20 sec. Also control and experimental 1, 2, 3, 4 groups were dried for 10, 0, 5, 20, 30 seconds after applying adhesive, respectively, Adhesives were light cured for 10 sec. A gelatin capsule 5mm in diameter was filled with Aelitefil$^{TM}$ composite resin, placed on the treated dentin surface and light cured for 40 see, from three sides, All specimens were stored in distilled water at room temperature for 24 hours. The shear bond strengths were measured using a universal testing machine(AGS-1000 4D, Japan) at a crosshead speed of 5mm/min. An one-way ANOVA and LSD test were used for statistical analysis of the data. For SEM evaluation, seven specimens were made and sectioned. Representive postfracture and seven specimens were mounted on brass stubs, sputter-coated with gold and observed under SEM. The results were as follows : 1. The shear bond strength of experimental A group which adhesive were applied to dentin with agitation was higher than that of experimental N-A group (continuous application), and there was significant difference between two groups (p<0.01). 2. The interface between composite and dentin according to different application methods showed close adaptation in experimental A group and showed tinny gap in experimental N-A group. 3. The shear bond strength accoding to various air drying duration was the lowest value(7.57${\pm}$2.60 MPa) in experimental 1 group, so there was significant difference between experimental 1 group and other four groups (p<0.05). But there was no significant difference of shear bond strength between four groups (p>0.05). 4. The interface between composite and dentin according to various air drying duration showed close adaptation in control group and tinny gap in experimental 3 and 4 groups. But experimental 1 and 2 groups showed $30{\mu}$ and 6 - $10{\mu}m$ thick gaps, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.375-375
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• 2010

CdTe as an absorber material is widely used in thin film solar cells with the heterostructure due to its almost ideal band gap energy of 1.45 eV, high photovoltaic conversion efficiency, low cost and stable performance. The deposition methods and preparation conditions for the fabrication of CdTe are very important for the achievement of high solar cell conversion efficiency. There are some rearranged reports about the deposition methods available for the preparation of CdTe thin films such as close spaced sublimation (CSS), physical vapor deposition (PVD), vacuum evaporation, vapor transport deposition (VTD), closed space vapor transport, electrodeposition, screen printing, spray pyrolysis, metalorganic chemical vapor deposition (MOCVD), and RF sputtering. The RF sputtering method for the preparation of CdTe thin films has important advantages in that the thin films can be prepared at low growth temperatures with large-area deposition suitable for mass-production. The authors reported that the optical and electrical properties of CdTe thin film were closely connected by the thickness-uniformity of the film in the previous study [1], which means that the better optical absorbance and the higher carrier concentration could be obtained in the better condition of thickness-uniformity for CdTe thin film. The thickness-uniformity could be controlled and improved by the some process parameters such as vacuum level and RF power in the sputtering process of CdTe thin films. However, there is a limitation to improve the thickness-uniformity only in the preparation process [1]. So it is necessary to introduce the external or additional method for improving the thickness-uniformity of CdTe thin film because the cell size of thin film solar cell will be enlarged. Therefore, the authors firstly applied the chemical mechanical polishing (CMP) process to improving the thickness-uniformity of CdTe thin films with a G&P POLI-450 CMP polisher [2]. CMP process is the most important process in semiconductor manufacturing processes in order to planarize the surface of the wafer even over 300 mm and to form the copper interconnects with damascene process. Some important CMP characteristics for CdTe were obtained including removal rate (RR), WIWNU%, RMS roughness, and peak-to-valley roughness [2]. With these important results, the CMP process for CdTe thin films was performed to improve the thickness-uniformity of the sputtering-deposited CdTe thin film which had the worst two thickness-uniformities of them. Some optical properties including optical transmittance and absorbance of the CdTe thin films were measured by using a UV-Visible spectrophotometer (Varian Techtron, Cary500scan) in the range of 400 - 800 nm. After CMP process, the thickness-uniformities became better than that of the best condition in the previous sputtering process of CdTe thin films. Consequently, the optical properties were directly affected by the thickness-uniformity of CdTe thin film. The absorbance of CdTe thin films was improved although the thickness of CdTe thin film was not changed.

• 구강회복응용과학지
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• 제34권1호
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• pp.39-45
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• 2018

목적: 치석제거 및 치근면활택술(scaling and root planing, SRP)은 만성 치주염 환자에서 대표적인 비외과적 치주치료법이나 술자가 잔존치석을 시각적으로 확인하지 못하는 한계가 있다. 본 연구는 중등도 만성 치주염 환자에서 비외과적 치주치료 시 SRP에 부가적으로 erythritol 공기분말 연마기구를 사용하는 것의 임상적 효과를 평가해 보고자 한다. 연구 재료 및 방법: 중등도 만성 치주염을 가지는 21명의 환자에서 비외과적 치주치료를 위해 SRP로만 치료받은 21부위(대조군)와 SRP에 부가적으로 erythritol 공기분말 연마기구를 사용하여 치료한 21부위(실험군)에서 4 - 6 mm의 치주낭을 가지는 치아를 선택하여 평가하였다. 치료 전, 치료 완료 1개월, 3개월 후에 치주낭 깊이, 치은퇴축, 임상부착수준, 치태지수, 탐침시 출혈이 임상지표로 측정되었다. 결과: 실험군과 대조군 모두에서 치료 전에 비해 치료 1개월 후, 3개월 후 치주낭 깊이, 치태지수, 탐침시 출혈의 유의한 감소와 치은 퇴축의 증가 및 임상부착수준의 유의한 획득이 관찰되었다. 그러나 실험군과 대조군 간에 임상지표들의 변화에는 유의한 차이가 관찰되지 않았다. 치료 3개월 후 모든 임상지표들은 치료 전에 비해서는 개선되었으나 치료 1개월 후에 비해서는 악화되었다. 결론: 중등도 만성 치주염 환자의 비외과적 치주치료 시 erythritol 공기분말 연마기구는 부가적으로 적용될 수 있으나 SRP 단독과 비교하였을 때 임상적으로 더 효과적이라고 제안할 수는 없다. 또한 최소 3개월 간격의 주기적인 유지관리치료가 필요함을 알 수 있다.

• 대한치과보철학회지
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• 제62권2호
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• pp.95-103
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• 2024

목적: 디지털 기술이 발전함에 따라 3D 프린팅 기술이 의치상 제작에 활용되고 있으나 적층 제조의 특성상 의치상 표면에 미생물 부착이 증가한다는 단점이 있다. 본 연구는 3D 프린팅 의치상 레진의 항진균성을 개선하기 위하여, 이산화티타늄 나노입자를 각기 다른 중량비로 첨가하였을 때 균사 형태의 Candida albicans에 대한 의치상 레진의 항진균성과 그에 따른 굽힘 강도의 변화에 대해 알아보고자 하였다. 재료 및 방법: 항진균성을 평가하기 위해 3D 프린팅 레진에 이산화티타늄 나노입자를 0.5, 1, 1.5, 2 wt%의 중량비로 혼합하고, 이산화티타늄 나노입자를 포함하지 않은 대조군을 포함해 5개 군을 직경 20 mm 높이 3 mm의 원기둥 형태의 형태로 각각 20개씩 출력하였다. Autogrinder를 이용하여 10개는 연마를 시행하였고, 나머지 10개는 연마를 시행하지 않았다. 각 시편에 균사 형태의 C.albicans를 접종하고, 흡광도와 집락수를 분석하였고, 시편의 표면을 주사전자현미경으로 관찰하였다. 또한, 굽힘 강도 비교를 위해 의치상 레진에 이산화티타늄 나노입자를 0.5, 1, 1.5, 2 wt%의 중량비로 혼합하고, 길이 64 mm, 높이 10 mm, 폭 3 mm 형태(ISO 20795-1)의 시편을 각 군당 20개씩 출력하였고, 만능시험기로 3점 굽힘 강도 시험을 시행하였다. 결과: C.albicans의 집락수와 배양액의 흡광도는 연마를 시행하지 않은 군에서 차이가 없었으나, 연마를 시행한 군에서는 대조군에 비해 감소하였다. 굽힘 강도는 이산화티타늄 나노입자 농도 0, 1, 1.5 wt%에서 증가하였으나 2 wt%에서 1.5 wt%에 비해 감소하였다. 결론: 3D 프린팅 의치상 레진에 이산화티타늄 나노입자를 1.5 wt% 첨가하였을 때, 의치상 레진의 항진균성과 굽힘 강도가 증가하였다.