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솔-젤법을 이용한 aminoalkoxysilane 산소차단필름의 제조
김현준,Kim, Hyun-Joon 한국반도체디스플레이기술학회 2006 반도체디스플레이기술학회지 Vol.5 No.3
The oxygen barrier films were formed on poly(ethylene terephthalate) (PET) substrate by a sol-gel process using aminoalkoxysilanes. The coating layers were characterized by FT-IR and SEM. The oxygen permeability coefficients of coating films were measured by variable volume method, and then the influences of solvent ratio in sol and film drying temperature on the oxygen barrier properties were investigated. The aminoalkoxysilane coating films exhibited much higher oxygen barrier properties than PET film. The oxygen permeability coefficient of the film coated with each of APTEOS and APTMOS was measured to be $2.96{\times}10^{-6}$ and $3.05{\times}10^{-5}\;GPU$, respectively, while that of PET film was $1.16{\times}10^{-4}\;GPU$.
물 분자막의 두께와 윤활특성의 상관관계에 대한 분자시뮬레이션 연구
김현준,허세곤,Kim, Hyun-Joon,Heo, Segon 한국트라이볼로지학회 2022 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.38 No.5
This paper presents a numerical investigation of the influence of water molecule thickness on frictional behavior at the nanoscale using molecular dynamics simulation. Three different models, comprising water thin films of various thicknesses, were built, and indentation and sliding simulations were performed using the models. Various normal loads were applied by indenting the Si tip on the water film for the sliding simulation to evaluate the interplay between the water thin film thickness and the normal load. The results of the simulations showed that the friction force generally increased with respect to the normal load and thickness of the water thin film. The friction coefficient varied with respect to the normal load and the water film thickness. The friction coefficient was the smallest under a moderate normal force and increased with decreasing or increasing normal loads. As the water film became thicker, the contact area between the tip and water film became larger. Under well-lubricated conditions, the friction force was proportional to the contact area regardless of the water film thickness. As the normal force increased above a critical condition, the water molecules beneath the Si tip spread out; thus, the film could not provide lubrication. Consequently, the substrate was permanently deformed by direct contact with the Si tip, while the friction force and friction coefficient significantly increased. The results suggest that a thin water film can effectively reduce friction under relatively low normal load and contact pressure conditions. In addition, the contact area between the contacting surfaces dominates the friction force.
셀롤로오스 분리막을 통한 순수 이산화탄소 메탄 및 혼합기체의 투과 특성 연구
김현준,김홍일,강용수,홍석인 ( Hyun Joon Kim,Hong Il Kim,Yong Soo Kang,Suk In Hong ) 한국공업화학회 1996 공업화학 Vol.7 No.4
Cellulose acetate(CA) 비대칭막, CA 복합막 그리고 cellulose triacetate(CTA) 비대칭막을 통한 순수 이산화탄소 및 메탄의 투과 특성을 측정하여, 투과성능의 운전압력에 대한 영향을 조사하였다. 그리고 이산화탄소와 메탄의 혼합기체(CO ₂/CH₄=57.6/42.4)에 대한 투과 특성을 조사하여, 이를 순수 기체의 투과 특성으로부터 얻어진 결과와 비교하였다. 실험은 25∼125 psig의 분압과 상온에서 실험하였다. CA 복합막과 CTA 막을 통한 기체의 투과거동은 CA 막의 투과거동과 비슷하였다. CA 막, CA 복합막 그리고 CTA 막을 통한 순수 이산화탄소의 투과속도는 상부분압이 증가함에 따라 약간 증가하였으며, 반면에 메탄의 경우에는 상부분압에 의존하지 않고 일정하였다. 그러나 혼합기체의 경우 이산화탄소에 의한 가소화 효과와 각 기체의 경쟁효과에 의해 순수 기체와는 다른 투과거동을 보였다. 각각의 분리막의 투과성능을 비교할 때, CTA 막의 분리인자와 투과속도가 CA 막의 값들보다 높은 값을 나타내었으며, CA 복합막의 투과속도가 CA 막의 값보다 높은 값을 가졌다. 그러나 CTA 막의 경우 기계적 강도가 매우 낮았다. 결국 본 연구에 사용된 CA 복합막이 투과플럭스가 크므로 이산화탄소와 메탄의 분리용 막으로 적합하다고 생각된다. The permeation characteristics were investigated for pure carbon dioxide and methane through asymmetric cellulose acetate(CA) membrane, composite cellulose acetate membrane and asymmetric cellulose triacelate(CTA) membrane. In particular, the effect of operating pressure on the permeation performance was examined. And the permeation behavior for a mixture of carbon dioxide and methane (CO₂/CH₄=57.6/42.4) was also investigated and compared to the characteristics obtained from pure gases. The experiments were run at the range of partial pressure from 25 to 125 psig, and room temperature. The permeation behaviors of the CA composite and CTA membrane were similiar to those of the CA membrane. The permeation rates of pure carbon dioxide for CA, CA composite and CTA membrane were increased slightly with an increase in upstream partial pressure, while in the case of pure methane they were independent of upstream partial pressure. For a binary mixture of carbon dioxide and methane, abnormal permeation behaviors were observed due to the plasticization of carbon dioxide and the competition effect of each gas. The separation factor and permeation rate for CTA membrane were found to be higher than those for CA membrane, but the mechanical strength of CTA membrane was very poor. and the permeation rate for CA composite membrane was higher than that for CA membrane. Consequently, it can be said that the CA composite membrane is a strong candidate for the separation of CH₄and CO₂
김현준,이준호,채제욱,이성배,김인우,Kim, Hyun-Jun,Lee, Joon-Ho,Chae, Je-Wook,Lee, Sung-Bae,Kim, In-Woo 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.6
This paper includes that there are results of designing the flash hider and analyzing fluid dynamics of a front area of the barrel to shorten the length of small arms. Generally, the muzzle flash can be generated out of the barrel by the reaction between the oxygen in the air and unburned gunpowder contained in the propellant gas if a barrel is not long enough to burn gunpowder fully inside of the barrel. Though, the hugh muzzle flash, which is a characteristic of small arms with short barrel length, caused a soldier to aim at the target at night by making the soldier blind for a while and endangers his life by revealing firing position to enemies. Besides, the heat of muzzle flash can weaken the performance of thermal sights, which are attached to small arms for night battlefield. In this paper, flash hiders with several different shapes were designed for a newly developed 5.56mm caliber rifle with short barrel length. The performance of each flash hider to reduce the muzzle flash was compared theoretically and experimentally. Through the authorized test procedure, a highly efficient design of flash hider for reducing the muzzle flash was identified. The result of the paper can be helpful when designing flash hiders for small arms with short barrel length.
김현준 ( Hyun Joon Kim ),정석준 ( Suck Joon Jung ),박은주 ( Eun Joo Park ),김철우 ( Chul Woo Kim ),조희진 ( Hee Jin Jo ),김광호 ( Kwang Ho Kim ),김광중 ( Kwang Joong Kim ) 대한피부과학회 2007 대한피부과학회지 Vol.45 No.1
Papular elastorrhexis is a rare disorder in which children or adolescents present with asymptomatic, non-follicular, 1~5 mm firm white papules on the trunk and extremities. Histologically, there are focal areas of collagen homogenization with decreased and fragmented elastic fibers. Most reported cases are sporadic, but familial occurrence has been described. We report an uncommon and interesting case of papular elastorrhexis in both a brother and sister. (Korean J Dermatol 2007;45(1):82~86)
[Review] 트라이볼로지 관점에서의 그래핀 분자시뮬레이션 연구동향
김현준(Hyun-Joon Kim),정구현(Koo-Hyun Chung) 한국트라이볼로지학회 2020 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.36 No.2
Recently, graphene has attracted considerable attention owing to its unique electrical, optical, thermal, and mechanical properties. The broad spectrum of applications from optics, sensors, and electronics to biodevice have been proposed based on these properties. In particular, graphene has been proposed as a protective coating layer and solid lubricant for microdevices and nanodevices because of its high mechanical strength, chemical inertness, and low friction characteristics. During the past decade, extensive efforts have been made to explore the tribological characteristics of graphene under various conditions and to expand its applicability. In addition to the experimental approaches, the molecular simulations performed provide fundamental insights into the friction and wear characteristics of graphene resulting from molecular interactions. This work is a review of the studies conducted over the past decade on the tribological characteristics of graphene using molecular simulation. These studies demonstrate the principal mechanisms of the superlubricity of graphene and help clarify the influences of surface conditions on tribological behavior. In particular, the investigation of the effects of the number of layers, strength of adhesion to the substrate, surface roughness, and commensurability provides deeper insights into the tribological characteristics of graphene. These fundamental understandings can help elucidate the feasibility of graphene as a protective coating layer and solid lubricant for microdevices and nanodevices.