• Elastomers and Composites
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• 제52권3호
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• pp.167-172
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• 2017

Ultra-high performance (UHP) tires, for which demand has recently surged, are subject to severe strain conditions due to the low aspect ratio of their sidewalls. It is important to ensure sidewall material durability, since a sudden tire sidewall breakage during vehicle operation is likely to cause a major accident. In the automotive application of rubber parts, cracking is defined as a failure because when cracks occur, the mechanical properties of rubber change. According to Mars, Andre et al., strain and strain energy density (SED) are mainly used as a failure parameters and the SED is generally used as a fatigue damage parameter. In this study, the fatigue life curves of sidewall rubber of tires were determined by using the SED as fatigue damage parameter while the effect of aging on fatigue life was evaluated after obtaining the SED-Nf curves according to aging condition.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2245-2250
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• 2003

Particulate matters(PM) have bad effect on the health. We carried out measurements of diesel PM under $10{\mu}m$ diameter from a HSDI diesel engine with a diesel oxidation catalyst(DOC) by using the ELPI. This paper compares the two results of the smoke level and the PM level of masses and numbers. We also investigated the effect of the DOC. Under high speed and load, HSDI diesel engine exhausts much masses of particulate matters over 100nm diameter, and a number of PM from 7 to 100nm diameters at the same condition. DOC could reduce the total mass of the PM. However, the DOC could increase the number of ultra fine PM. Before light-off of the soot, the DOC absorb the PM and the DOC oxidize the PM after light-off temperature. The fine PM could be made during the oxidation. Therefore, the advanced DOC is needed to reduce the number of the fine PM.

• 한국전기전자재료학회논문지
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• 제18권11호
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• pp.996-1000
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• 2005

Experimental results are presented for the degradation of 3 nm-thick gate oxide $(SiO_2)$ under both Negative-bias Temperature Instability (NBTI) and Hot-carrier-induced (HCI) stresses using P and NMOSFETS, The devices are annealed with hydrogen or deuterium gas at high-pressure $(1\~5\;atm.)$ to introduce higher concentration in the gate oxide. Both interface trap and oxide bulk trap are found to dominate the reliability of gate oxide during electrical stress. The degradation mechanism depends on the condition of electrical stress that could change the location of damage area in the gate oxide. It was found the trap generation in the gate oxide film is mainly related to the breakage of Si-H bonds in the interface or the bulk area. We suggest that deuterium bonds in $SiO_2$ film are effective in suppressing the generation of traps related to the energetic hot carriers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 영호남 합동 학술대회 및 춘계학술대회 논문집 센서 박막 기술교육
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• pp.152-155
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• 2006

Carbon nitride ($CN_X$) films were prepared by reactive RF magnetron sputtering system at various deposition conditions and the C-V characteristics of MIS(metal - insulator - semiconductor) capacitors that have the structures of Al/$CN_x$/p-Si/Al and Al/$CN_x$/$Si_3N_4$/p-Si/Al were investigated. The resistivity of carbon nitride was above $2.40{\times}10^8{\Omega}{\cdot}cm$ at room temperature. The C-V plot showed a typical capacitance-voltage characteristics of semiconductor insulating layers, while it showed hysterisis due to interface charges. Amorphous carbon nitride (a-$CN_x$) films, that have relatively high resistivity and low dielectric constant could be useful as interlayer insulator materials of VLSI(very large-scale integration) and ULSI(ultra large-scale integration).

• 운동영양학회지
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• 제25권3호
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• pp.16-22
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• 2021

[Purpose] Exercise-associated hyponatremia (EAH) is a well-known condition among endurance athletes at low altitudes. The incidence of EAH during ultramarathons at high altitudes warrants further investigation. This prospective observational study was conducted on the participants of the Leadville Trail 100 run, a 161-km race held at a high altitude (2,800 m-3,840 m). [Methods] Venous blood samples were collected before and immediately after the race. The participants completed an electronic survey after the race. Our main outcome measure was the post-race serum sodium ([Na⁺]) level. [Results] Of the 672 athletes who started the race, 351 (52%) successfully completed the event within the 30-hour cut-off. Post-race blood samples were collected from 84 runners (66 finishers). Both pre- and post-race blood samples were collected from 37 participants. Twenty percent of the post-race participants had EAH. Only one post-race participant had a [Na⁺] level of <130 mmol/L. All participants with EAH were asymptomatic. One participant had an abnormal pre-race [Na⁺] level (134 mmol/L). Female participants had a significantly higher rate of EAH than male participants (40% vs. 16%; p=0.039). Age, body mass index, weight changes, race completion status, nonsteroidal anti-inflammatory drug use, and urine specific gravity were not associated with the development of EAH. Lower postrace [Na⁺] levels were associated with higher serum creatine kinase values (R²=0.1, p<0.005). [Conclusion] High altitude (3,840 m peak) does not appear to enhance the incidence of EAH after an ultramarathon footrace. This suggests that ambient temperature (low temperatures reduce risk), sex (female predilection), endurance running, and overhydration are more prominent risk factors for EAH than high altitude.

• 대한의용생체공학회:의공학회지
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• 제20권1호
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• pp.99-106
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• 1999

인공관절용 재료의 내마모성 향상을 목적으로 초고분자량 폴리에틸렌(UHMWPE)을 가교시켜 기계적 성질과 내마모성을 조사하였다. 가교제로 dicumyl peroxide(DCP)를 사용하고 가교보조제로 triallyl cyanurate(TAC)를 사용하여 용융상태에서 UHMWPE를 가교시켰다. DCP와 TAC의 함량이 증가할수록 가교된 초고분자량 폴리에틸렌(XUMPE)의 젤 함량은 증가하고 녹는점, 결정화온도, 결정화도, 인장성질은 감소하였다. Pin-on-disk 마모시험과 작은 하중을 가한 ball-on-disk 마모시험에서는 기계적 성질의 감소에도 불구하고 XUMPE의 마모부피가 UHMWPE보다 감소하였다. 이 두 시험에서의 마모는 주로 변형에 의한 것으로 판단되었으며, 마모부피는 Hertz 접촉 이론으로 계산한 최대접촉응력과 XUMPE의 항복강도의 비에 비례함을 보였다. 큰 하중을 가한 ball-on-disk 마모시험에서는 기계적 성질이 낮을수록 더 큰 마모부피를 보였으며, 마모자국의 표면거칠기와 마찰계수도 증가하였다. 이는 인장강도를 넘는 응력이 가해졌을 때 항복강도와 인장강도가 더 낮은 XUMPEDml 변형과 파괴가 촉진되기 때문으로 생각되었다.

• 한국광물학회지
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• 제22권2호
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• pp.107-114
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• 2009

본 연구는 고령토, 유황, 소다회, 규석 그리고 송진을 원료로 군청안료 제조기술 개발을 위하여 환원소성 방법 및 조건, 산화 조건 규명을 위하여 2 kg/회 규모의 회분식 실험을 수행하였다. 환원 소성 및 산화 공정에서 분말 형태로 소성할 경우 열전도율이 낮아 규모가 커짐에 따라 반응물 내 외부 온도차가 커져 소성 시간이 길어지고 반응 생성물이 불균일한 결과를 보였다. 군청의 색상은 원료 중의 성상, 소성 조건에 대단히 민감하며 동일한 원료에 대해서도 재현성이 낮았다. 환원 소성 시 승온율은 군청 생성에 매우 중요한 인자이며 분말 소성 시 소성 규모에 따라 값이 달라진다. 본 연구에서 사용한 3 ${\ell}$, 용량일 경우 승온율 $0.6^{\circ}C/min$, 반응온도 $850^{\circ}C$ 그리고 반응시간은 4시간 이상이 필요하였다. 녹색군청의 산화 공정에서 필요한 공기 양은 녹색군청 kg당 $500{\sim}550\;{\ell}$ 이고 적정한 반응온도는 $500{\sim}550^{\circ}C$에서 청색($-b^{\ast}$) 값이 가장 높았다.

• 환경위생공학
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• 제12권1호
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• pp.25-37
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• 1997

The synthesis of high purity and ultra-fine $BaTiO_{3}$ by precipitation with gaseous $NH_{3}$ as precipitator was investigated to find an alternative process to solve various problems of present wet methods. This study consisted of two parts ; synthesis of $BaTiO_{3}$ precipitation with gaseous $NH_{3}$ and test of electrical property for the $La_{2}O_{3}$ doped $BaTiO_{3}$. The proper condition for the synthesis of $BaTiO_{3}$ by precipitation with gaseous $NH_{3}$ is as follows. The pH was 9.0. $H_{2}O_{2}$ mole ratio to $TiCl_{4}$ was 10. $NH_{3}$ gas follow rate did not influence the synthesis of $BaTiO_{3}$. The calcination temperature of $BaTiO_{3}$ was $300^{\circ}C$. Also, the synthesis of $La_{2}O_{3}$-doped $BaTiO_{3}$ was tested through the wet process. Under these condition, the shape of prepared $BaTiO_{3}$ powder was spherical type and the size of that was about $0.2{\mu}m$. After the powder was pressed, this green body was sintered at the $1300^{\circ}C$. Under these conditions, the water absorptance and the density of the obtained sintered body were below 0.04 %, 5.2 g/$cm^{3}$, respectively. Also the grain size of that was about $10{\mu}m$ and it was similar to commercial product.

• Design & Manufacturing
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• 제17권3호
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• pp.8-14
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• 2023

In this study, basic research was conducted on manufacturing technology of thick-walled light guide a component that controls the light source of automobile lamps. As a preliminary study for manufacturing the final injection molded parts, a model for analyzing the influence of micro patterns on light guides is presented. The optical characteristics of the light guide were analyzed according to the change of the curvature radius of the micro-optical pattern, and the injection molding characteristics of the light guide according to the change of injection molding conditions were analytically evaluated. It was confirmed that the luminance uniformity improves as the R value decreases for changes in the micro-pattern R value, but it was confirmed that there are technical limitations in actual injection mold core processing and high-replication injection molding. Injection molding analysis showed that cooling channel design is very important compared to general injection molding due to thick-wall characteristics and thickness variation. It was also confirmed that the cooling channel has a great influence on the cycle time and birefringence result due to residual stress. As a result of analyzing the influence of filling time, holding condition, and cooling on shrinkage, it was found that the cooling water temperature has a significant effect on the shrinkage of ultra-fine light guide parts, and the holding condition also has a significant effect.

• 한국산학기술학회논문지
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• 제3권2호
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• pp.74-79
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• 2002

80년대 반도체 산업의 급격한 성장으로 오늘날 반도체 산업은 반도체소자의 초고집접화, 웨이퍼의 대구경화로 발전이 거듭났으며, 소자의 성능과 생산 수율의 향상을 위하여 실리콘 웨이퍼의 세정하는 기술 및 연구를 계속 진행하고 있다. 기존의 반도체 세정은 과다한 화학약품의 사용으로 비 환경친화적이며, 이에 본 연구에서는 기존의 세정방법을 대체하기 위한 방법으로 환경친화적인 전리수를 이용한 반도체 세정법을 하였다. 이때 실리콘 웨이퍼 표면의 원자적 상태의 변화가 발생하여 다양한 방법으로 확인할 수 있다. 본 연구에 서는 이러한 분석을 하기 위하여 기존세정의 화학약품과 전리수로 세정한 웨이퍼의 표면을 비교하였으며, 또한 온도 및 시간별 표면상태변화를 분석하였다. 특히 접촉각 변하에 중점을 두어 변화를 관찰하였으며, 음극수의 경우 17.28°, 양극수의 경우 34.1°의 낮은 접촉각을 얻을 수 있었다.