• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.390-391
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• 2009

Recently, composite hollow bushings have been increasingly employed mainly from the various characteristics. Composite bushings are superior to porcelain bushings in several respects, including lighter weight, better anti-pollution and anti-explosion properties, and easer manufacturing. This paper deals with the optimal thermal fitting for improved tightness characteristics of composite bushing. Two types of composite bushings were fabricated. For optimal fitting process, it is necessary using adhesive and designed internal structure of flange and FRP tube. In this study, for improved tightness characteristics of composite bushing has prominence and interface tolerance of flange and FRP tube. From FE-SEM analysis the adhesive layers were different with interface tolerance, sample 1 and 2 which have respective about $120{\mu}m$ and $50{\mu}m$.

• Journal of electromagnetic engineering and science
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• 제16권3호
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• pp.150-158
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• 2016

This paper reports on a study of LiNiZn-ferrite composite as a radiation absorbent material (RAM). The electromagnetic (EM) wave absorbers are composed of an EM wave absorbing material and a polymeric binder. The surface morphology, chemical composition, weight percent of the ferrite composite of the toroid sample, magnetic properties, and return loss are investigated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and network analyzer. For preparing the absorbing sheet, chlorinated polyethylene (CPE) is used as a polymeric binder. The EM wave absorption properties of the prepared samples were studied at 4 - 8 GHz. We can confirm the effects of the thickness of the samples for absorption properties. An absorption bandwidth of more than a 10-dB return loss shifts toward a lower frequency range along with an increase in the thickness of the absorber.

• Restorative Dentistry and Endodontics
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• 제25권1호
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• pp.109-115
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• 2000

This study was designed to evaluate the microhardness of restorative composite resin and dual-cured composite resin cement which were light cured through the 1.5mm thickness composite overlay. For restorative materials, Z100 and Tetric Ceram were used. For dual cured composite cements, Variolink II((VL II) of three consistency (low, high, ultra high) were used. To determine the optimal microhardness of Z100, Tetric Ceram and Variolink II, each material was packed into the 1mm thickness teflon mold without composite overlay and light cured for 60 seconds. Then the microhardnesses of each sample were measured, averaged and regarded as optimal hardness of each material. To evaluate the microhardness of restorative composite resin and dual-cured composite resin cement which were light cured through the 1.5mm thickness composite overlay, the composites were packed into 1mm thickness teflon mold, coverd with celluloid strip, and then precured composite overlay which was made of Targis(Ivoclar/Vivadent, Liechtenstein) was positioned. 2 types of visible light curing machine, the power density of one of which was 400$mW/cm^2$ and the other was 900$mW/cm^2$, and one type of argon laser were used to cure the restorative composite and dual cured cement. For each group, 10 sample were assigned. The light curing tip was positioned over the composite overlay and light cured for 1min., 2min. or 3min with visible light curing machine or 15sec, 30 sec, 45sec, and 60 sec with argon laser. The Vickers hardnesses of upper and lower surface of Z100, Tetric Ceram, and 3 types of VL II cement were measured. When the 900 $mW/cm^2$ curing light was used, 2min. was needed for optimal curing of Z100 and Tetric Ceram. Variolink II did not be cured optimally even though the curing time was extended to 3min. When 400$mW/cm^2$ curing light was used, 3min. was necessary for Z100, whereas 3min. was not enough for Tetric Ceram. Variolink II was not cured optimally even though the curing time was extended to 3min. When argon laser was used, Z100, Tetric Ceram and Variolink II were not cured optimally in 60 seconds.

• Journal of applied mathematics & informatics
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• 제12권1_2호
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• pp.107-117
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• 2003

We study the integration problem in which one wants to compute the approximation to the definite integral in the average case setting. We choose the composite Newton- Cotes quadratures as our algorithm and the function values at equally spaced sample points on the given interval［0, 1］as information. We compute the average case error of composite Newton-Cotes quadratures and show that it is minimal (modulo a multi-plicative constant).

• 한국조사연구학회지:조사연구
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• 제10권1호
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• pp.141-154
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• 2009

정보화 사회에서는 목표지향적이고 세분화된 통계의 필요성이 높아지고 있으나 현재 사용되는 조사체계를 이용하면 추정 분산이 커져 생산된 통계의 정확도가 낮아진다. 표본크기를 늘리면 추정분산을 줄일 수 있으나 비용이나 시간 면에서는 비효율적이다. 현재와 비슷한 규모의 표본조사구 조사와 일반 행정통계를 이용하여 일정 신뢰수준을 갖춘 통계를 생산할 수 있는 소지역 추정법에 대한 연구가 진행되어 개발 적용되고 있다. 본 연구에서는 소지역 추정법을 활용하여 대전광역시의 5개 구별 실업자 수를 추정하고 추정치의 CV 값을 계산하여 추정방법의 효율성을 비교하는 사례분석을 실시하였다. 또한 합성추정량과 복합추정량의 MSE를 보다 정확하게 계산하는 방법으로 잭나이프 방법을 제안하고 계산방법을 보였다.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2451-2456
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• 2011

0.5mm 크기의 타원형 무기분말을 충전한 폴리우레탄 폼 복합재료에 대한 가교반응의 특성과 후가교처리에 따른 기계적 물성의 변화에 대하여 생성반응의 온도 측정, TGA, 및 인장시험을 이용하여 연구하였다. 중량비로 20% 정도를 충전하는 $CeO_2$ 무기분말(Ce500)을 충전한 샘플 폼복합재료는 10분 이내에 $100^{\circ}$ 정도의 최고 반응속도점 온도에 도달하였으며, 만들어진 샘플의 열분해반응은 약 $250^{\circ}$ 부근의 저온 열분해와 약 $350^{\circ}$ 부근의 고온 열분해의 이중모드로 일어나는 것이 관찰되었다. Kissinger의 해석방법에 의한 분해활성화에너지는 저온영역에서의 열분해에 대하여서는 117.4kJ/mol이며 고온영역에 대해서는 139.4kJ/mol의 값을 각각 나타내었다. $160^{\circ}C$에서의 샘플의 후가교 처리시간에 따른 기계적 성질은 후가교 시간에 따라서 파단응력이나 경도는 크게 변하지 않는 것으로 나타났으나 파단신율은 최대 1.72배까지 증가하였으며, 본 실험에서 사용된 샘플의 경우 $160^{\circ}C$, 7시간 정도의 후가교 시간이 가장 적절한 후가교 조건으로 생각되었다.

• 한국안전학회지
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• 제23권6호
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• pp.34-37
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• 2008

The composite materials are widely used in the many applications of industry as well as aerospace field because of their high specific stiffness and strength which benefits the material and provides potential energy savings. However, composite materials also have a low property about external applied impact. In this paper, impact tests were conducted on different sample types(glass, carbon and kevlar composite) to obtain information such as absorbed energy and composite deformation using an instrumented impact test machine (DYNATUP 8250). 3 type samples were compared to experimental results. The data from impact test provided valuable information between the different type samples by wet lay up. This paper shows results of that kevlar composite has larger absorption energy and deformation than others.

• Restorative Dentistry and Endodontics
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• 제26권6호
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• pp.485-491
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• 2001

The purpose of this study was to compare the mechanical properties of three condensable composite resins and one hybrid composite resin. The compressive strength, diametral tensile strength, Vicker's microhardness were tested for mechanical properties of condensable composite resins (SureFil, Ariston pHc, Synergy compact), and hybrid composite resin (Z 100). The tested materials were divided into four groups: control group Z 100 (3M Co. USA), experimental group I Ariston pHc, (Vivadent, Co., Liechtenstein) experimental group II SureFil (Dentsply, Co., U.S.A.), experimental group III Synergy Compact (Coltene, Co., Swiss). According to the above classification, we made samples of SureFil, Ariston pHc, Synergy Compact, Z 100 with separable cylindrical metal mold. And then, we measured and compared the value of compressive strength, diametral tensile strength and Vicker's microhardness of each sample. (omitted)

• 응용통계연구
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• 제24권6호
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• pp.1129-1138
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• 2011

지방자치제가 정착되면서 시군구와 같은 소지역 단위의 실업률에 대한 통계는 실업대책이나 고용지원 사업을 위한 예산 편성과 같은 지역 노동시장정책의 수립은 물론 정책 집행 후 그에 대한 사후평가를 하는데 있어서도 중요한 기준을 제공해주기 때문에 지자체 기관장들의 관심의 대상이 되고 있는 실정이다. 그러나 경제적, 시간적으로 많은 제약이 따르는 기초자치단체에서 지속적으로 실업률 통계를 생산하는 데에는 자료의 신뢰성, 연속성및 시의성 면에서 많은 문제를 노정하고 있다. 본 연구에서는 소지역 실업률 추정치에 대한 신뢰성(변동계수 25% 이하)을 확보하면서 통계생산에 소요되는 조사비용을 최소화할 수 있는 효율적인 추정법 및 최소 표본조사구 수를 모의실험을 통하여 제시하고자 한다.

• 한국전기전자재료학회논문지
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• 제24권10호
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• pp.834-838
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• 2011

This research shows the electrical characteristic using excellent epoxy nano-composite of MgO 5.0 wt% and $SiO_2$ 0.4 wt% in mechanical strength test depending on nano-additive. First of all, volume resistance depending on nano-additive and temperature using high resistance meter (HP. 4329A) by increasing 10, 100, 1,000 V of applying voltage was measured. Moreover, temperature range of $25{\sim}120^{\circ}C$ with virgin sample was tested using TO-9B oven by Ando Company. The result showed that virgin and the samples added with MgO and $SiO_2$ had similar value of volume resistance in low temperature and low electric field region and reduced with slow slope. The nano-composite's volume resistance of sample added with MgO and $SiO_2$ had higher value than virgin sample's volume resistance in high temperature region more than $80^{\circ}C$. Moreover, the slope has steeply reduced. The volume resistance of sample added with MgO 5.0 wt% was $8.38{\times}10^{13}\;{\Omega}{\cdot}cm$ and it was 6.8 times more than virgin sample in high temperature at $120^{\circ}C$. The insulation characteristics were constant although filler has changed in low temperature region. But, in high temperature region, the value of volume resistance of sample with MgO 5.0 wt% was 7.6 times more than the virgin sample's volume resistance.