• Restorative Dentistry and Endodontics
• /
• 제8권1호
• /
• pp.97-106
• /
• 1982

The purpose of this study was to evaluate the effect of different polishing procedures on the surfaces of composite resins. Two-paste type comosite restorative resin (Hipol) was selected for this study. 70 cavities prepared on the plaster-stone dies, 6mm in diameter and 2mm in depth, was filled with composite resin according to the manufacturer's specifications and by polymerizing against mylar strips. The polymerized composite resin specimens were polished (surface finished) by using 6 polishing devices; white stones, diamond finishing points, 12-fluted carbide finishing burs, green stones, sand paper disks, and Quasite rubber disk after polished with sand paper disks and green stones. A profilometer (Bendix type) was used to record in microinches the surface roughness of each surface finished composite resin specimens. The results were as follows. 1. The best finished surface that can be obtained is a surface formed by the mylar matrix strip 2. The white stones produced the smoothest surface in the experimental group. 3. The green stones produced the roughest surface in the experimental group. 4. It was proved that the gradual use of finishing instruments from a rough one to fine ones reduced the surface roughness.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2002년도 추계학술발표대회 논문집
• /
• pp.1-4
• /
• 2002

The present study aims to design a multiplayer microstrip antenna with composite sandwich construction and to estimate structural behavior of this multiplayer structure for the next generation of structural surface technology. This is termed Surface-Antenna-Structure indicating that structural surface becomes antenna. Constituent materials were selected considering electrical properties as well as mechanical properties. For the antenna performance, antenna elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was $16\times16$ array antenna. From electrical measurements it was shown that antenna performances were in good agreement with design requirements. Structural analysis showed this antenna structure was well designed for the mechanical rigidity. All constituent materials were characterized independently. The SAS concept is the first serious attempt at integration for both antenna and composite engineers and promises innovative future communication technology.

• Restorative Dentistry and Endodontics
• /
• 제21권1호
• /
• pp.360-365
• /
• 1996

The purpose of this study was to evaluate the changes in the degree of conversion on a composite resin surface following heat treatment and mylar strip finishing. The effects of the time interval between the light-curing and heat-curing process were also evaluated. The composite resin surface which had been covered with a coverglass showed a lower conversion rate than the surface from which a layer of $500{\mu}m$ was ground away. The composite resin surface was definitely affected by oxygen during the heat curing process when it had not been insulated. When the composite resins were heat cured after 3 days of storage following the light curing process, the increased in the degree of conversion through heatcuring was limited.

• 대한치과의사협회지
• /
• 제24권7호통권206호
• /
• pp.633-642
• /
• 1986

In order to evaluate the effects of various finishing devices (Sof-Lex disc, diamond point, rubber point, fussure bur) on the surface roughness or two composite resins (Restodent, Enamelite 500), 15 specimens for each composite resin were made in the mold. Composite resin was prepared on the mixing pad by manufacturer's direction and filled in the mold cavity. A sheet of matrix is immediately placed on it and hold for 5 minutes to polymerize the resin. Surface finish was done after 10 minutes from the start of mixing. Scanning electron microscopy and surface profilometer were used to evaluate the surface roughness, porositites and striations of dental composite resins. The following results were observed; 1. The best finished surface was formed by celluloid matrix band. 2. Rubber point was excellent polishing device for Restodent. 3. Sof-Lex disc was the device of choice for polishing Enamelite 500. 4. Different polishing methods were effective for different composite resins. 5. SEMs of variously finished surfaces supported the profilometer measurements.

• Advanced Composite Materials
• /
• 제17권3호
• /
• pp.215-224
• /
• 2008

The present study aims to design a multilayer microstrip antenna with composite sandwich construction and investigate fatigue behavior of this multilayer SAS (surface antenna structure) that was asymmetric sandwich structure for the next generation of structural surface technology. This term, SAS, indicates that the structural surface becomes an antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, antenna elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.2 GHz. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of the SAS was obtained. The experimental results of bending fatigue were compared with single load level fatigue life prediction equations and in good agreement. The SAS concept is can be extended to give a useful guide for manufacturers of structural body panels as well as antenna designers.

• 한국안전학회지
• /
• 제12권2호
• /
• pp.65-69
• /
• 1997

Especially, Fiber glass Reinforced Plastics(FRP) is the best composite insulating material which has been so far. Therefore, it's worthy of notice to investigate on the corona electrified composite insulating material by surface condition. And then some other materials will be focussed on. In this study, charge decay were measured with charging-time and grid voltage on FRP composite material surface in order to analyze the mechanism. As a result we have studied that the way of the composite glass fiber(GF) and Polymer and the condition of the contaminated surface was different. In case of the GF is mixed with vertical, charge decay speed is fast because the charge is easily leaked. On the other hand, the surface charge decay speed is depend on conductive or insulated of the contaminant.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
• /
• pp.243-247
• /
• 2003

The effect of accelerated weathering(UV) on three type of ethylene propylene diene monomer(EPDM) composite used for higher voltage insulator were investigated by weather-emoter. For weatherability of EPDM composite, surface resistance, dielectric breakdown strength, change of contact angle, surface composition were measured according to UV accelerated weathering time. From the resort of the measurement of surface resistivity, contact angle of EPDM composite decreased and showed chalking and cracking phenomenon when UV weathweing time was for 1500 h and 2000 h. The analysis of surface atomic composition indicated that surface aluminiu(Al) content was detected due to chalking phenomenon after 1500 h of UV weathering, Oxygen content of all composite increased due to the oxidation.

• 대한소아치과학회지
• /
• 제33권3호
• /
• pp.469-481
• /
• 2006

법랑질 침식의 병인 중에서 식이습관은 많은 관심을 받아왔고 특히 산성음료의 음용이 많은 주의를 끌어왔다. 산성음료의 급속한 소비량 증가는 치아뿐만 아니라 치아색 수복재료의 표면에도 많은 영향을 미칠 것으로 생각된다. 따라서 본 연구는 어린이들이 비교적 일상적으로 접하는 산성음료 중 가장 보편화된 3종을 선택하여 치아색 수복재료의 노출시간에 따른 표면의 변화를 조사할 목적으로 시행되었다. Resin-modified glass-ionomer, polyacid-modified composite resin, composite resin을 0.9% NaCl, 콜라, 오렌지 쥬스, 스포츠 음료의 각 4개 군으로 나누어 저장하였다. 저장 전과 저장 후 1일, 1-,2-,3-,4-주에 표면강도 및 표면조도를 측정하였고 다음과 같은 결론을 얻었다. 1. 산성음료에 저장했을 경우 composite resin을 제외한 치아색 수복재들은 통계학적으로 유의한 표면강도와 표면조도의 변화를 보였다(p<0.05). 2. 표면강도 및 표면조도의 변화는 resin-modified glass-ionomer, polyacid-modified composite resin composite resin 순으로 크게 나타났다. 3. 콜라나 오렌지 쥬스보다 스포츠 음료에서 표면변화는 더 크게 나타났다. 4. 산성음료에 저장한 군의 SEM 촬영에서 resin-modified glass-ionomer, polyacid-modified composite resin의 경우 충전제의 상실이 관찰되었으며 특히 resin-modified glass-ionomer의 경우 심한 균열이 관찰되었다.

• Composites Research
• /
• 제30권5호
• /
• pp.273-279
• /
• 2017

This paper describes the fabrication techniques and analysis of hybrid composite plates with an active frequency selective surface (FSS). For fabricating hybrid composite plate with active FSS, an active FSS with a resonance frequency located in the C band can obtained using varactor diodes. The hybrid composite plate was first designed and simulated to determine its electromagnetic properties using the commercial software HFSS. After simulation, active FSSs and hybrid composite plates were fabricated by mounting with varactor diodes. After fabrication, free space measurement was used to determine the electromagnetic properties of active FSS and the hybrid composite plates. The simulation and experimental results were in good agreement.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1989년도 춘계학술대회 논문집
• /
• pp.63-65
• /
• 1989

Piezoelectric BaTiO$_3$-polymer composite were investigated for dielectric and piezoelectric properties with the barium titanate active particle size. Under the condition of the same density and ceramic volume ratio of composite, the dielectric and piezoelectric constant of composite are increasing as the ceramic particle size in composite are increasing. The surface layer model was quoted to explain these phenomena in our system and experimentally confirmed. The connectivity parameter of modified cube model of composite was calculated from the dielectric constant variation as their particle size. The connectivity parameter X and Y were 77.8% and 98.9% respectively. It means that the barium titanate particle distribution in composite nearly approach to the parallel mode. It was experimentally confirmed that the surface layer has low dielectric and nonferroelectric properties. Dielectric constant and thickness of surface layer were calculated from the equivalent circuit of composite.