• Composites Research
• /
• 제36권6호
• /
• pp.441-447
• /
• 2023

최근 경량 소재에 대한 수요 증가로 기존 금속과 복합재간 접합 관심이 지대하다. 리벳팅과 같은 볼트 체결인 기계적 결합의 경우 응력 집중, 균열 및 박리가 발생함에 따라 접착제를 사용한 화학적 결합이 주목받고 있다. 본 논문에서는 접착제의 접합강도 향상을 위해 레이저 및 플라즈마 표면처리를 진행하였으며, 이에 대한 접착특성을 평가하고자 한다. 접합강도 실험을 위해 흔히 자동차용 소재로 사용되는 탄소섬유강화플라스틱(CFRP), CR340(Steel)과 Al6061(Aluminum)을 실험 소재로 선정해 레이저 및 플라즈마 표면처리를 진행 후 단축전단강도를 측정하였다. 플라즈마 표면처리 후 CFRP-CR340 및 CFRP-Al6061 이종소재 시편에서 각각 접합강도가 7.3% 및 39.2% 향상되었다. CR340-Al6061 시편은 레이저 표면처리에서 기준 시편대비 56.2% 증가하였다. 플라즈마 표면처리 후 표면자유에너지(SFE)가 향상되었는데 이는 화학반응 메커니즘을 통해 손상을 최소화해 접합강도 향상을 나타낸 것으로 사료된다. 레이저 표면처리는 물리적 표면처리로 거친 접합 표면 생성으로 인해 mechanical interlocking 효과로 인해 접착 강도가 향상된 것으로 사료된다. 본 연구를 토대로 실제 구조물 파손의 대표적인 원인인 피로파손을 예방하기 위해 장기 피로시험을 진행 할 예정이다.

• Current Research on Agriculture and Life Sciences
• /
• 제15권
• /
• pp.115-122
• /
• 1997

과채류의 재배에 있어서 접목은 작물의 안정적인 생산과 품질 향상을 위해 없어서는 안되는 기술이다. 그러나 지속적인 숙련 노동력의 감소와 농촌 인구 노령화 등으로 나타나는 노동력 부족 현상은 집목묘의 대량생산 공급에 어려움이 되고 있다. 본 연구에서는 기계접목에 있어서 접목법이 간단하며 접합부자재가 불필요한 삽접법을 이용하는 기계접목 메카니즘 개발의 기초연구를 수행하였다. 트레이상의 육묘상태에서 자동으로 접목하기 위한 기계접목의 기초연구로써 1본씩 수동 공급하는 반자동 기계삽접의 메카니즘 개발에 관한 연구로서 얻어진 결과를 요약하면 다음과 같다. 1. 접합부자재를 사용하지 않고 대부분 과채류에 적용가능한 삽접 기계접목장치의 메카니즘을 구성하였다. 2. 오이를 접수로 하고 신토좌와 흑종을 대목으로 하는 기계접목시험에서 모두 98%의 접목성공율을 나타냈다. 3. 1본 수동 공급에 의한 기계접목 시스템은 10초 정도로 접목 성능은 저조하지만 기계접목 메카니즘의 가능성을 확인하였다.

• Genomics & Informatics
• /
• 제14권3호
• /
• pp.112-124
• /
• 2016

Solid tumor is generally observed in tissues of epithelial or endothelial cells of lung, breast, prostate, pancreases, colorectal, stomach, and bladder, where several genes transcription is regulated by the microRNAs (miRNAs). Argonaute (AGO) protein is a family of protein which assists in miRNAs to bind with mRNAs of the target genes. Hence, study of the binding mechanism between AGO protein and miRNAs, and also with miRNAs-mRNAs duplex is crucial for understanding the RNA silencing mechanism. In the current work, 64 genes and 23 miRNAs have been selected from literatures, whose deregulation is well established in seven types of solid cancer like lung, breast, prostate, pancreases, colorectal, stomach, and bladder cancer. In silico study reveals, miRNAs namely, miR-106a, miR-21, and miR-29b-2 have a strong binding affinity towards PTEN, TGFBR2, and VEGFA genes, respectively, suggested as important factors in RNA silencing mechanism. Furthermore, interaction between AGO protein (PDB ID-3F73, chain A) with selected miRNAs and with miRNAs-mRNAs duplex were studied computationally to understand their binding at molecular level. The residual interaction and hydrogen bonding are inspected in Discovery Studio 3.5 suites. The current investigation throws light on understanding miRNAs based gene silencing mechanism in solid cancer.

• 한국정밀공학회지
• /
• 제33권7호
• /
• pp.579-586
• /
• 2016

This paper describes kinematic analysis of a 6-degrees-of-freedom (DOF) ultra-precision positioning stage based on a flexure hinge. The stage is designed for processes which require ultra-precision and high load capacities, e.g. wafer-level precision bonding/assembly. During the initial design process, inverse and forward kinematic analyses were performed to actuate the precision positioning stage and to calculate workspace. A two-step procedure was used for inverse kinematic analysis. The first step involved calculating the amount of actuation of the horizontal actuation units. The second step involved calculating the amount of actuation of the vertical actuation unit, given the the results of the first step, by including a lever hinge mechanism adopted for motion amplification. Forward kinematic analysis was performed by defining six distance relationships between hinge positions for in-plane and out-of-plane motion. Finally, the result of a circular path actuation test with respect to the x-y, y-z, and x-z planes is presented.

• 대한기계학회논문집A
• /
• 제21권3호
• /
• pp.439-446
• /
• 1997

A traditional notion of composites has been composed as a uniform dispersoid, but now it is proposed without regard to such rule with process development. Functionally Graded Material(FGM) consists of a new material design that is to make intentionally irregular dispersion state. In this study, thermal stress analysis of plasma spraying PSZ/NiCrAlY gradient material was conducted theoretically using a finite-element program. A formations of the model are direct bonding material(NFGM) and FGM with PSZ and NiCrAlY component element. The temperature conditions were $700^{\circ}C$ to 1100.deg. C assuming a cooling-down precess up to room temperature. Fracture damage mechanism was analyzed by the parameters of residual stress.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제6권2호
• /
• pp.95-100
• /
• 2006

The GaAs-on-insulator (GOI) wafer fabrication technique has been developed by using ion-cut process, based on hydrogen ion implantation and wafer direct bonding techniques. The hydrogen ion implantation condition for the ion-cut process in GaAs and the associated implantation mechanism have been investigated in this paper. Depth distribution of hydrogen atoms and the corresponding lattice disorder in (100) GaAs wafers produced by 40 keV hydrogen ion implantation were studied by SIMS and RBS/channeling analysis, respectively. In addition, the formation of platelets in the as-implanted GaAs and their microscopic evolution with annealing in the damaged layer was also studied by cross-sectional TEM analysis. The influence of the ion fluence, the implantation temperature and subsequent annealing on blistering and/or flaking was studied, and the optimum conditions for achieving blistering/splitting only after post-implantation annealing were determined. It was found that the new optimum implant temperature window for the GaAs ion-cut lie in $120{\sim}160^{\circ}C$, which is markedly lower than the previously reported window probably due to the inaccuracy in temperature measurement in most of the other implanters.

• 한국전기전자재료학회논문지
• /
• 제18권5호
• /
• pp.407-413
• /
• 2005

Ion implantation provides a unique way to modify the mechanical, optical and electrical properties of polymer by depositing the energy of ions in the material on the atomic scale. Implantation of ions into the polymers generally leads to a radiation damage, which, in many cases, modifies the properties of the surface and bulk of the material. These modifications result from the changes of the chemical structure caused in their turn by changing the chemical bonding when the incident ions cut the polymer chains, breaks covalent bonds, promotes cross-linking, and liberates certain volatile species. We studied the relation among the linear energy transfer (LET) and changes of surface microstructure and surface resistivity on PPS material using the high current ion implantation technology The surface resistivity of nitrogen implanted PPS decreased to $10^{7}{\Omega}/cm^{2}$ due to the chain scission, cross linking, ${\pi}$ electron creation and mobility increase. In this case, the surface conductivity depend on the 1-dimensional hopping mechanism.

• 한국주조공학회지
• /
• 제17권4호
• /
• pp.371-378
• /
• 1997

The study for direct synthesis of TaC carbide which was a reaction product of tantalum and carbon in the cast iron was performed. Cast iron which has hypo-eutectic composition was cast bonded in the metal mold with tantalum thin sheet of thickness of $100{\mu}m$. The contents of carbon and silicon of cast iron matrix was controlled to have constant carbon equivalent of 3.6. The chracteristics of microstructure and the formation mechanism of TaC carbide in the interfacial reaction layer in the cast iron/tantalum thin sheet heat treated isothermally at $950^{\circ}C$ for various time were examined. TaC carbide reaction layer was grown to the dendritic morphology in the cast iron/tantalum thin sheet interface by the isothermal heat treatment. The composition of TaC carbide was 48.5 at.% $Ti{\sim}48.6$ at.% C-2.8 at.% Fe. The hardness of reaction layer was MHV $1100{\sim}1200$. The thickness of reaction layer linearly increased with increasing the total content of carbon in the cast iron matrix and isothermal heat treating time. The growth constant for TaC reaction layer was proportional to the log[C] of the matrix. The formation mechanism of TaC reaction layer at the interface of cast iron/tantalum thin sheet was proved to be the interfacial reaction.

• 한국전기전자재료학회논문지
• /
• 제35권4호
• /
• pp.342-347
• /
• 2022

In-situ analyzation and detection of real-time chemical reactions can be a significant part in interpreting the underlying mechanism in very reactive chemical reactions. To do this, first we have designed a microfluidic device (MFD) pattern for observation of synthesis of hierarchical nanostructures based on graphene oxide (GO), conjugating the well-known coupling reaction by which the solution of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-mediated coupling is enhanced in the presence of n-hydroxysuccinimide (NHS) to make amide bonding, hereafter called as the EDC coupling. Then, we have manufactured microfluidic devices with multiple tens of micrometer-sized channels that can circulate those nanomaterials to be chemically reacted in the channels. These microfluidic devices were made by negative photo lithography and soft lithography. We showed the possibility of using Raman spectroscopy to reveal the basic mechanism of the energy storage applications.

• 마이크로전자및패키징학회지
• /
• 제14권1호
• /
• pp.39-47
• /
• 2007

폴리이미드 표면에 대한 습식 개질 전처리 조건에 따른 폴리이미드와 무전해 도금 Ni 박막사이의 계면파괴에너지를 $180^{\circ}$ 필 테스트를 통해 정량적으로 구하였다. KOH 처리시간이 1분인 경우 계면파괴에너지는 24.5 g/mm에서 5분 처리 시 33.3g/mm로 증가하였고, EDA처리 시간이 1분인 경우 31.6 g/mm에서, 5분 처리 시 22.3g/mm로 저하되었다. 이러한 습식 개질전처리 조건에 따른 폴리이미드 표면 거칠기 변화는 매우 작아서, 기계적 고착 효과는 계면파괴에너지 변화에 기여하지 못했음을 알 수 있다. KOH는 carboxyl기, EDA는 amine기를 폴리이미드 표면에 형성시켜 Ni과 강한 화학적 결합을 이루어, 폴리이미드 내부의 cohesive 박리거동을 보였다. 습식 개질전처리 조건에 따른 계면파괴에너지의 거동은 파면 부근에 형성된 O=C-O 결합과 매우 밀접한 연관성이 있는 것으로 판단된다.