• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.458.2-458.2
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• 2014

We have demonstrated that simple brush-painted Ti-doped $In_2O_3$(TIO) films can be used as a cost effective transparent anodes for organic solar cells (OSCs). We examined the RTA effects on the electrical, optical, and structural properties of the brush painted TIO electrodes. By the direct brushing of TIO nanoparticle ink and rapid thermal annealing (RTA), we can simply obtain TIO electrodes with a low sheet resistance of 28.25 Ohm/square and a high optical transmittance of 85.48% under atmospheric ambient conditions. Furthermore, improvements in the connectivity of the TIO nano-particles in the top region during the RTA process play an important role in reducing the resistivity of the brush-painted TIO anode. In particular, the brush painted TIO films showed a much higher mobility ($33.4cm^2/V-s$) than that of previously reported solution-process transparent oxide films ($1{\sim}5cm^2/V-s$) due to the effects of the Ti dopant with higher Lewis acid strength (3.06) and the reduced contact resistance of TIO nanoparticles. The OSCs fabricated on the brush-painted TIO films exhibited cell-performance with an open circuit voltage (Voc) of 0.61 V, shot circuit current (Jsc) of $7.90mA/cm^2$, fill factor (FF) of 61%, and power conversion efficiency (PCE) of 2.94%. This indicates that brush-painted TIO film is a promising cost-effective transparent electrode for printing-based OSCs with its simple process and high performance.

• 폴리머
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• 제29권4호
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• pp.408-412
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• 2005

생체재료로 이용하기 위하여 키토산을 기질로 하여 Bembyx mori로부터 추출한 견 피브로인을 블렌드한 필름에 대한 구조와 특성을 X선 회절분석, 열분석, 적외선 분광분석, 전자현미경 관찰, 접촉각 측정, 흡수율 측정으로 조사하였다. $-\~30wt\%$ 피브로인을 포함하는 블렌드 필름은 리튬이온을 포함하는 초산수용액으로 제조되었다. 키토산/피브로인 블렌드 필름은 키토산의 아미노기와 피브로인의 아미드 카보닐기 사이의 수소결합과 같은 분자간 상호작용의 형성에 의해 결정성이 감소되었다. 피브로인의 비율이 증가할수록 키토산의 무수혈 견정상은 소실되었고, 수화형 결정상은 감소되었으며, 퍼브로인의 P형 결정이 형성되어 혼재된 결정구조를 이루었다. 표면 친수성과 수분 흡수성은 피브로인의 비율이 클수록 증가되었으며, 20 $wt\%$, 이상에서 수화젤 상의 필름을 형성하였다. 전자현미경에 의한 블렌드 필름의 표면과 단면은 균일한 상을 나타내었다.

• Environmental Analysis Health and Toxicology
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• 제20권3호
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• pp.215-221
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• 2005

Environmental polycyclic aromatic hydrocarbones (PAHs), which are formed during incomplete combustion of fossil fuels, are widely distributed in our environment. Human exposure to PAHs may occur through smoking, polluted air, food consumption and occupational contact. Urinary naphthols, 1-and 2-naphthol, have been suggested as route -specific biomarkers for exposure to airborne PAHs. Cytochrome p450 2E1 (CYP2E1) is known to be a great importance for the metabolism of organic solvents, which is a precacinogens with small molecular weight. This study describes the metabolic differences between PstI and RsaI polymorphisms (c1 allele: PstI-. RsaI+ ; c2 allele: PstI+, RsaI-) of CYP2E1 5-flanking region by genetically modified HepG2 cells, which overexpress the polymorphic regions. The results of CAT assay and western blot in the c2 allele overexpressed cells have higher activities than the cl allele over-expressing cells. However, the metabolism of naphthalene to 2-naphthol has no difference due to the two genotypes. In this study, we established the CYP2E1 polymorphic allele transduced HepG2 cells to screen susceptibility -differences in PAH exposure. In conclusion, the CYP2E1 polymorphism may hardly induce susceptibility differences in PAH exposure monitoring with urinary naphthols.

• 대한의용생체공학회:의공학회지
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• 제34권2호
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• pp.80-90
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• 2013

Recently, functional insoles of wedge-type it is for the young to raise their height inserted between insole and heel cause foot pain and disease. Additionally, these have a problem with stability and excessively load-bearing during gait like high-heel shoes. In this study, we compared the changes in biomechanical characteristics of foot with different insole thickness then we will utilize for the development of the insole with the purpose of relieving the pain and disease. Subjects(male, n = 6) measured COP(center of pressure) and PCP(peak contact pressure) on the treadmill(140cm/s) using F-scan system and different insole thickness(0~50 mm) between sole and plantar surface during gait. Also, we computed changes of stresses at the foot using finite element model with various insole thickness during toe-off phase. COP moved anterior and medial direction and, PCP was increased at medial forefoot surface, $1^{st}$ and $2^{nd}$ metatarsophalangeal, ($9%{\uparrow}$) with thicker insoles and it was show sensitive increment as the insole thickness was increased from 40 mm to 50 mm. Change of the stress at the soft-tissue of plantar surface, $1^{st}$ metatarsal head represents rapid growth($36%{\uparrow}$). Also, lateral moments were increased over the 100% near the $1^{st}$ metatarsal as the insole thickness was increased from 0 mm to 30 mm. And it is show sensitive increment as the insole thickness changed 10 mm to 20 mm. As a result, it was expected that use of excessively thick insoles might cause unwanted foot pain at the forefoot region. Therefore, insole thickness under 30 mm was selected.

• Tribology and Lubricants
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• 제30권2호
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• pp.108-115
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• 2014

The friction behaviors of bulk amorphous thermal spray coating (BAC) and second phase-reinforced composite coatings using a high velocity oxy-fuel spraying process were investigated using a ball-on-disk test rig that slides against a ceramic ball in an atmospheric environment. The surface temperatures were measured using an infrared thermometer installed 50 mm from the contact surface. The crystallinities of the coating layers were determined using X-ray diffraction. The morphologies of the coating layers and worn surfaces were observed using a scanning electron microscope and energy-dispersive spectroscopy. The results show that the friction behavior of the monolithic amorphous coating was sensitive to the testing conditions. Under lower than normal loads, a low and stable friction coefficient of about 0.1 was observed, whereas under a higher relative load, a high and unstable friction coefficient of greater than 0.3 was obtained with an instant temperature increase. For the composite coatings, a sudden increase in friction coefficient did not occur, i.e., the transition region did not exist and during the friction test, a gradual increase occurred only after a significant delay. The BAC morphology observations indicate that viscous plastic flow was generated with low loads, but severe surface damage (i.e., tearing) occurred at high loads. For composite coatings, a relatively smooth surface was observed on the worn surface for all applied loads.

• 대한기계학회논문집A
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• 제38권4호
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• pp.379-384
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• 2014

가스터빈엔진의 가장 핵심 부품인 디스크와 블레이드는 고온, 고압축비, 고속 회전이라는 가혹한 환경에서 지속적으로 운용된다. 이러한 가혹한 환경과 디스크와 블레이드가 가지는 큰 회전 에너지로 인해 디스크 및 블레이드에 의해 유발되는 파손은 항공기 손상 혹은 탑승자의 피해로 이어지는 재해적 고장 혹은 한계 고장으로 이어진다. 그러므로 디스크와 블레이드의 구조적 건전성의 마진을 충분히 확보하기 위해서 본 연구에서는 디스크의 취약 부위인 도브테일의 형상을 최적화하고, 그 해의 강건성을 확인하기 위해 치수 공차와 피로 수명의 산포와 같은 불확실성에 대하여 신뢰도 해석을 수행하고자 한다. 이 결과를 통해 결정론적 방법인 최적설계의 필요성과 함께 한계를 확인하고, 향후 신뢰도 기반 최적설계의 필요성을 인지하고자 한다. 이를 위해 비선형 열-구조 연성해석과 접촉 해석을 포함한 유한요소해석을 수행하였다.

• Tribology and Lubricants
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• 제31권4호
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• pp.148-156
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• 2015

In the study, a design process for ensuring optimal clearance in a fuel injection pump(FIP) is suggested. Structure analysis and hydrodynamic lubrication analysis are performed to determine the optimal clearance. The FIP is simulated using Hypermesh, Abaqus 6.12 to evaluate the reduction of clearance when the maximum supply pressure is applied. The reduction in clearance is caused by the difference in the deformations between the barrel and plunger. When the deformation of the plunger is larger than that of the barrel, a reduction in clearance at the head part occurs. On the other hand, the maximum clearance reduction equals the maximum deformation in the stem part, because the deformation of barrel does not occur in this region. The clearance of FIP should be designed to be larger than maximum reduction of clearance in order to avoid contact between the plunger and barrel. In addition, the two-dimensional Reynolds equation is used to evaluate lubrication characteristics with variations of viscosity, clearance and nozzle for a laminar, incompressible, unsteady state flow. The equation is discretized using the finite difference method. The lubrication characteristics of FIP are investigated by comparing film parameter, which is the ratio of the minimum film thickness and surface roughness. The optimal clearance of FIP is to be designed by considering the maximum reduction in clearance, lubrication characteristics, machining limits and tolerance of clearance.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.1033-1036
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• 2002

Wafer bonding methods such as fusion and anodic bonding suffer from high temperature treatment, long processing time, and possible damage to the micro-scale sensor or actuators. In the localized bonding process, beating was conducted locally while the whole wafer is maintained at a relatively low temperature. But previous research of localized heating has some problems, such as non-uniform soldering due to non-uniform heating and micro crack formation on the glass capsule by thermal stress effect. To address this non-uniformity problem, a new heater configuration is being proposed. By keeping several points on the heater strip at calculated and constant potential, more uniform heating, hence more reliable wafer bonding could be achieved. The proposed scheme has been successfully demonstrated, and the result shows that it will be very useful in hermetic packaging. Less than 0.2 ㎫ contact Pressure were used for bonding with 150 ㎃ current input for 50${\mu}{\textrm}{m}$ width, 2${\mu}{\textrm}{m}$ height and 8mm $\times$ 8mm, 5mm$\times$5mm, 3mm $\times$ 3mm sized phosphorus-doped poly-silicon micro heater. The temperature can be raised at the bonding region to 80$0^{\circ}C$, and it was enough to achieve a strong and reliable bonding in 3minutes. The IR camera test results show improved uniformity in heat distribution compared with conventional micro heaters. For gross leak check, IPA (Isopropanol Alcohol) was used. Since IPA has better wetability than water, it can easily penetrate small openings, and is more suitable for gross leak check. The pass ratio of bonded dies was 70%, for conventional localized heating, and 85% for newly developed FP scheme. The bonding strength was more than 30㎫ for FP scheme packaging, which shows that FP scheme can be a good candidate for micro scale hermetic packaging.

• Journal of the Korean Wood Science and Technology
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• 제37권1호
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• pp.1-11
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• 2009

외장용 기둥재는 년중 사용환경에서 액상수와 직접 접촉할 수가 있으나, 이에 대한 연구는 그다지 많지 않다. 목재의 섬유방향에서 결합수와 자유수 확산계수를 포함한 수분확산계수를 측정하기 위해 상온에서 흡수실험을 실시하였다. 흡수성은 느릅나무, 까치박달나무, 헴록, 가문비나무, 라디에타 소나무, 고로쇠나무 순으로 크게 나타났다. Boltzmann 변환법으로 구한 확산계수는 저함수율에서 섬유포화점 부근까지 감소하다가 최대함수율 부근에서 급격히 증가하는 경향을 나타내었다. 함수율 변화에 따른 확산계수는 $10^{-10}{\sim}10^{-7}m^2/s$ 정도의 값을 나타내었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.110-110
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• 2011

The nanomechanical properties of fully lithiated and unlithiated silicon nanowire deposited on silicon substrate have been studied with atomic force microscopy. Silicon nanowires were synthesized using the vapor-liquid-solid process on stainless steel substrates using Au catalyst. Fully lithiated silicon nanowires were obtained by using the electrochemical method, followed by drop-casting on the silicon substrate. The roughness, derived from a line profile of the surface measured in contact mode atomic force microscopy, has a smaller value for lithiated silicon nanowire and a higher value for unlithiated silicon nanowire. Force spectroscopy was utilitzed to study the influence of lithiation on the tip-surface adhesion force. Lithiated silicon nanowire revealed a smaller value than that of the Si nanowire substrate by a factor of two, while the adhesion force of the silicon nanowire is similar to that of the silicon substrate. The Young's modulus obtained from the force-distance curve, also shows that the unlithiated silicon nanowire has a relatively higher value than lithiated silicon nanowire due to the elastically soft amorphous structures. The frictional forces acting on the tip sliding on the surface of lithiated and unlithiated silicon nanowire were obtained within the range of 0.5-4.0 Hz and 0.01-200 nN for velocity and load dependency, respectively. We explain the trend of adhesion and modulus in light of the materials properties of silicon and lithiated silicon. The results suggest a useful method for chemical identification of the lithiated region during the charging and discharging process.