• 한국공작기계학회논문집
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• 제10권1호
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• pp.88-93
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• 2001

Carbon fiber epoxy composite are widely used in airframe structures, space vehicles, sports equipment, and high speed reciprocating parts for industrial machinery. In this paper, the groove processing characteristics of carbon fiber epoxy com-posite was experimentally investigated in order to study the endmill operation of fiber reinforce epoxy composites. Followings are main finding from the experimental results. First, the cutting and bending force in groove processing of the carbon fiber epoxy composite increased as the spindle speed deceased. They also deceased as the table feed increased. Second, the good cutting status obtained at the entrance of groove while delamination occurred at the exit of groove, Third, the regular high speed steel endmill was not efficient, thus the new endmill such as coated carbide rooter endmill or dia-mode endmill should be used for the effective endmll operation of carbon filber epoxy composites.

• Composites Research
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• 제17권2호
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• pp.15-20
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• 2004

나사산을 가지는 구조재료는 높은 전단 응력을 한 방향으로 전달해 주는 용도로 많이 사용되며, 이를 응용하여 고속의 충격에너지나 전단하중에 견별 수 있는 기어 모양의 부품 등 항공 및 군수용 재료에 적용되어왔다. 최근에는 재료를 보다 경량화 하려는 노력의 일환으로 기존의 금속재료를 섬유강화 고분자 수지계 복합재료로 대체하기 위한 연구가 활발히 진행되고 있다. 본 연구에서는 탄소섬유/열경화성 수지계 복합재를 사용하여 나사산(groove)을 가지는 시편을 제작한 뒤 역탄도 기법으로 고속변형 특성 평가를 실시하였고, 이를 통하여 군수용 부품 재료로의 적용 가능성을 타진해 보았다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.99-102
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• 2003

Carbon/Epoxy composite specimens formed with buttress groves are fabricated. The buttress form of groove is useful in any application where high shear loads are transferred in one direction between structural components. It is a primary object of the present study to test and evaluate the shear load carrying capability of a carbon/epoxy composite structure with buttress grooves for military applications

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.167-170
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• 2000

Recently the sub-micron structured substrates of 0.74 ${mu}ell$ track pitch and 800 $\AA$groove depth are required for DVD-RAM and the track pitch is expected to be narrower as the need for the information storage density is getting higher. For the accurate replication of the land-groove structure in the stamper to the plastic substrates it is important to control the injection -compression molding process such that the integrity of the replication for the land-groove structure is maximized. in the present study polycarbonate substrates were fabricated by injection comression molding and the land-groove structure regarded as one of mold temperature and the compression pressure on the integrity of the replication were examined experimentally. An efficient design methodology using the response surface method (RSM) the central composite design(CCD) technique and the analysis-of-variance (ANOVA) was developed to obtain the optimum processing conditions which maximize the integrity of the replication with a limited number of experiments.

• 열처리공학회지
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• 제28권6호
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• pp.315-321
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• 2015

Friction stir processing (FSP) was applied to fabricate AZ31/CNT (Carbon Nano Tube) surface composite for improvement of surface hardness of AZ31 Mg-based alloy. The effects of traverse speed of rotating tool and volume fraction of CNT (i.e., groove depth of 3 mm and 4 mm) on the soundness and hardness of the composite layer were investigated. Multi-walled CNTs were fully filled in a machined groove and stirring tool was rotated at the speed of 1400 rpm. Only under the tool traverse speed of 25 mm/min for the specimen with a groove depth of 3 mm, surface composite layer with no defect was successfully produced. Increased hardness of about 35% was observed in the composite layer.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.180-184
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• 2004

The tribological behavior of carbon epoxy composites whose surfaces have many small grooves of $100\mu m$ width was experimentally investigated with respect to the sliding direction against groove orientation, surface pressure (P) and velocity (V). The wear mechanism of the composites was observed to calculate the wear volume with respect to the friction coefficient using scanning electron microscopic (SEM). Experimental results show that the abrasive wear is dominant wear mechanism for the grooved composite surface and the friction and wear are greatly reduced when the sliding direction is parallel to the axis of groove because abrasive particles are removed through the grooves effectively.

• Restorative Dentistry and Endodontics
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• 제23권2호
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• pp.639-646
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• 1998

To evaluate the effect of interface conditions and retention grooves in the Class V composite resin restoration of the maxillary first premolar, the distribution of the values of stress and displacement was analyzed with the two-dimensional finite element method. The results were obtained as follows : 1. Boundary elements and Stiffness values could be used as the interface parameters in the, finite element method. 2. The amount of restriction of the displacement at the cervical margin by placing a retention groove at the cervical wall was about three times as high as that by placing a retention groove at the occlusal wall. 3. Because of the relative amount of tensile components of the stress values in the bucco-lingual direction, the possibility of dislocation of the restoration was much higher at the cervical margin than at the occlusal margin. 4. It might be recommended that both occlusal and cervical retention grooves be used routinely, but if one, it be placed at the cervical wall.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.101-106
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• 2012

In this study, we investigated the effect of groove pattern and gap-fill with lossy materials at 15 GHz frequency of Ku-band. We used Epoxy/MWCNT composite materials as gap-fill materials. Although epoxy does not have an absorbance capability, epoxy added conductive fillers, which are multi-walled carbon nanotubes (MWCNT), can function as radar absorbing material. Specimens were fabricated with different MWCNT mass fractions (0, 0.5, 1.0, 2.0 wt%) and their permittivity in the Ku-band was measured using the waveguide technique. We investigated the effect of gap-fill on monostatic RCS by calculating RCS with and without gap-fill. For arbitrarily chosen thickness and experimentally obtained relative permittivity, we chose the relative permittivity of MWCNT at 2 wt% (${\varepsilon}_r$=8.8-j2.4), which was the lowest reflection coefficient for given thickness of 3.3 mm at V-pol. and $80^{\circ}$ incident angle. We also checked the monostatic RCS and the field intensity inside the groove channel. In the case of H-pol, gap-fill was not affected by the monostatic RCS and magnitude was similar with or without gap-fill. However, in the case of V-pol, gap-fill effectively reduced the monostatic RCS. The field intensity inside the groove channel reveals that different RCS behaviors depend on the wave polarizations.

• Journal of Welding and Joining
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• 제26권2호
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• pp.85-91
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• 2008

In general, the quality of a welding process tends to vary with depending on the work environment or external disturbances. Hence, in order to achieve the desirable quality of welding, we should have the optimal welding condition that is not significantly affected by these changes in the environment or external disturbances. In this study, we used a dual response surface method in consideration of both the mean output variables and the standard deviation in order to optimize the V-groove arc welding process. The input variables for GMA welding process with the dual response surface are welding voltage, welding current and welding speed. The output variables are the welding quality function using the shape factor of bead geometry. First, we performed welding experiment on the interested area according to the central composite design. From the results obtained, we derived the regression model on the mean and standard deviation between the input and output variables of the welding process and then obtained the dual response surface. Finally, using the grid search method, we obtained the input variables that minimize the object function which led to the optimal V-groove arc welding process.

• Restorative Dentistry and Endodontics
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• 제36권3호
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• pp.238-242
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• 2011

구개치은발육구는 상악 전치에 나타나는 이상 치근 형태의 하나로 구개측 결절부에서 구개치은발육구를 관찰하였으며, 이 구는 치근단을 향하여 여러 깊이와 길이로 연장될 수 있다. 구개치은발육구는 세정되기 어렵고 청결이 불가능하여, 치태와 치석 등이 축적되어 접합상피의 파괴를 일으키고 빠르게 골연하 결손부가 발생할 수 있다. 또한 이차적으로 치수 조직을 이환시켜 근관-치주 병소가 발생할 수 있다. 본 증례 보고는 구개치은발육구로인해 근관 문제까지 야기된 임상증례를 보고하고 근관치료와 함께 여러가지 재료를 이용한 구개치은발육구의 치료결과를 관찰함으로써 이러한 치료방법의 효용성을 평가하고자 하였다.