• The Journal of Advanced Prosthodontics
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• 제15권4호
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• pp.189-201
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• 2023

PURPOSE. The aim of this study was to investigate the mechanical properties of three-dimensional (3D) printed denture base resin incorporating microcapsules containing plant essential oils. MATERIALS AND METHODS. Denture base specimens containing up to 3% w/v essential oil microcapsule powders (MCPs), i.e., eucalyptus, geranium, lavender, menthol, and tea tree, in two resins (Detax and NextDent 3D+) were 3D printed using two printers (Asiga and NextDent 5100). The dispersion and interaction of the MCPs in the resin were assessed by SEM while the mechanical properties of the incorporated denture base including flexural strength (MPa), flexural modulus (MPa), Vickers hardness (VHN), and surface roughness (Ra) were also subsequently evaluated. Statistical analysis of any differences in mean values was determined using a two-way ANOVA with Tukey's post hoc testing (α = .05). RESULTS. The spherical shape of the MCPs was maintained during the mixing and polymerization/printing process. However, the Detax-Asiga group showed significant agglomeration of the MCPs even at the lowest MCP concentration levels (0.5% w/v). Overall, as the microcapsule concentration increased, the mean flexural strength decreased, though the menthol MCP groups remained compliant with the ISO standard. The flexural modulus and harness remained relatively unchanged, and the flexural modulus complied with the ISO standard regardless of the MCP concentration. Surface roughness increased with the addition of the MCPs but also remained below that required for clinical acceptance. CONCLUSION. Incorporation of microencapsulated plant essential oils into 3D printed denture base resin was successfully achieved. While incorporation negatively influenced flexural strength and surface roughness, little effect on flexural modulus and Vickers hardness was demonstrated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.65-71
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• 2001

Absorbers such as porous materials and panels have limited absorption characteristics to some frequency bands. There is a need for absorbers with high absorption coefficients in a wide frequency ranges to make good response of room acoustics. This is almost impossible for a single absorption material. Composite absorption structure with cover, porous material. and air gap is known to have those wide frequency characteristics. In this basis. various composite absorption structures are measured and investigated as wide range absorption structures. Measurements are performed according to an international standard, ISO 354. Various surface types such as wooden slits, wood/steel perforated panels are selected as surface covers, and also various porous materials such as polyurethanes, polyesters, and glasswools are used inside the covers. Result shows that the area of void parts of surface materials is critical to high frequency absorptions, and thickness of air gaps are critical factor of the peak absorptions of low frequency bands.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.763-770
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• 1998

This paper deals with evaluation of bending fatigue strength in SCM415 carburized spur gears. The constant stress amplitude fatigue test is performed by using an electrohydraulic servo-controlled pulsating tester. The S-N curves are obtained and the enhanvement of fatigue strength due to carburized treatment is clarified. In this study the improvement of fatigue strength is assumed to be caused by an increase of both hardness and residual stress and experimental formula has been proposed for the estimation of bending fatigue strength of carburized gears. The effect of surface conditions on the fatigue strength is evaluated quantitatively and it is close to the relative surface condition factor used in the ISO strength rating formula.

• Journal of Biosystems Engineering
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• 제31권5호
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• pp.395-402
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• 2006

Mixed heat transfer in an indirected NIR (Near Infrared Ray) dry chamber was investigated numerical analysis. It is Important that the miked heat transfer effects on double parameters which the Reynolds number and the position of emit lamp. Reynolds number are based on the outer diameter of the cylinder range from 103 to $30{\times}105$. Four difference heat transfer regimes of behavior are apparent: forced convection and radiation on the outer surface of the cylinder, pure conduction, pure natural convection and radiation between lamp surface and inner surface of the cylinder. The temperature and flow patterns are illustrated by iso-contour lines for the double parameters. Also presented are results on the convective heat transfer flux and the radiative heat transfer flux as increased with Reynolds number.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2004년도 수소연료전지공동심포지움 2004논문집
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• pp.287-292
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• 2004

In order to understand the relationship between molecular structure of Metal-Organic Framework(MOF) and capacity of hydrogen absorption, quantum mechanical calculations and grand canonical Monte Carlo simulations have been carried out on a series of MOF-5 having various organic linkers. The calculation results about specific surface area and electron density for various frameworks indicated that the capacity of the hydrogen storage is largely dependent on effective surface area rather than the free volume. Based on the iso-electrostatic potential surface from density functional calculation and the amount of adsorbed hydrogens from grand canonical Monte Carlo calculation, it was also found that the electron localization ground organic linker plays an important role in hydrogen capacity of MOFs.

• 청정기술
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• 제27권1호
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• pp.39-46
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• 2021

4 HP, 80 LPM 급 초미세기포수 발생장치를 탑재한 도로 구조물 세척차량을 이용하여 도시 내 아파트 단지 주변 차량 통행이 많은 터널 내 콘크리트 표면과 타일 벽면을 세척하였다. 초미세기포 생성은 대기 중 공기를 2 ~ 3 LPM 으로 기액혼합 자흡펌프로 가압된 공기를 임펠러 회전력을 이용하여 마이크로 크기의 미세기포(fine-bubble)를 생성한다. 생성된 기포를 다단충돌판과 회전 노즐을 통과하면서 평균 직경 크기는 164.5 nm, 6.81 × 107 particles mL-1의 초미세기포(ultrafine bubble)를 생산하였다. 생산된 초미세기포를 함유한 세척수는 압력 150 bar, 토출량 30 LPM 으로 도로 구조물 표면에 흡착된 분진을 고압세척 분사하여 제거하였다. 분석실험은 세척 전과 후로 구분하여 표면에 흡착한 분진을 ISO 8502-3의 표면 오염 측정방법을 적용하였으며, 테이프 흡착으로 분진 입자를 채취하였다. 수집된 테이프는 중량법과 소프트웨어 ImageJ를 적용하여 분진의 무게와 입자 개수에 대한 제거율을 산정하였다. 실험 결과, 타일 벽면 표면에 흡착된 분진 입자 개수는 세척 전과 후로 각각 3,063 ± 218 particles mL-1, 20 ± 5 particles mL-1, 중량은 580 ± 82 mg, 13 ± 4 mg 으로 나타났다. 콘크리트 구조물 표면에서의 입자개수는 세척 전과 후로 각각 8,105 ± 1,738 particles mL-1, 39 ± 6 particles mL-1이었으며, 중량은 1,448 ± 190 mg, 118 ± 32 mg으로 나타났다.

• 한국농공학회논문집
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• 제46권3호
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• pp.73-81
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• 2004

FRP reinforcing bars(rebars) are produced through a variety of manufacturing process includes pultrusion, and filament winding and braiding etc. Each manufacturing method produces a different surface condition of FRP rebar. The surface properties of FRP rebar is an important property for mechanical bond with concrete. Current methods of providing surface deformation to FRP rebars include helical wrapping, surfaces and coating and rib molding. The problem with the helical wrapping method is that it can not provide enough surface deformation for good bond and it can be easily sheard off from the FRP rebars. Sand coating and rib molding provide surface deformation only to the outer FRP skins. Therefore, FRP rebar has about 60% of bond strength of steel rebar. The main objective was to evaluate the bond properties of FRP rebar after environmental exposure. Five types of FRP rebar includes CFRP ISO, GFRP Aslan, AFRP Technora CFRP(Korea), and GFRP(Korea) rebars performed direct bond tests. Also, FRP rebar bond specimens were subjected to exposure conditions including alkaline solution, acid solution, salt solution and deionized water etc. According to bond test results, CFRP(Korea) and CFRP(Korea) rebars were found to have better bond strength with concrete than previous FRP rebars. Also, FRP(Korea) rebar had more than about 70% in bond strength of steel rebar.

• 한국인쇄학회지
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• 제4권1호
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• pp.37-42
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• 1986

This study was made to determine the furctions of I.P.A(iso-Prophyl alchohl)an it is used in lithographic fountais solution. Alcohol acts as a wetting agent, an evaporant, a dilutent, a lubricant and reduces Surface tension and emulsification of link/water mixture/ From many studies, the function of the I.P.A appeurs to be that of a surfactant Cowbined with evaporative and diluent ProPerties.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.371-378
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• 1999

A prototype computer program was developed which visualizes various kinds of geotechnical information using 3D object graphics techniques. The program integrates various kinds of geotechnical data such as surface geology map, boreholes data, geophysical data as well as man made subsurface structures. It also reads NGIS DXF map and generates digital elevation model from iso-elevation line layer of the DXF map. All the data are put into a 3D model as 3D objects. The created 3D model can be viewed and analysed in a interactive 3D way.

• 보존과학회지
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• 제25권4호
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• pp.373-381
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• 2009

야외 전시되는 철제문화재 보존을 위해서 유물 표면을 피복처리 하는 것은 부식방지의 대표적인 방법이다. 근대문화유산 제78호 경의선장단역증기기관차는 보존조치 후 노천에서 전시될 예정이라서 기관차의 재부식 예방에 효과적인 표면 피복재를 내후성 실험을 통해 선별하였다. 실험재료는 기관차 표면 피복에 주로 사용되는 미정질 왁스 2종과 봉밀왁스를 기반으로 제조한 혼합왁스를 선별하였다. 실험방법은 3종의 왁스를 기관차 시편에 각각 피복하고 ISO 4892-1981 기준에 따라 제논아크촉진내후성시험기 속에서 1000시간 내후성 시험을 한 후 그 변화상을 비교 조사하였다. 실험결과 봉밀 왁스는 400시간 이후부터 표면에 백화현상이 발생하면서 노화하였고 미정질 왁스 2종은 800시간 이후부터 변화를 보였다. 시험전과 후 수분접촉각의 변화 역시 봉밀 왁스 보다 미정질 왁스가 적게 나타났다. 따라서 미정질 왁스 중 특히 고온형이 내후성과 수분 차단력이 가장 뛰어난 것으로 확인되어서 이것으로 증기기관차의 표면을 피복하게 되었다.