• Transactions on Electrical and Electronic Materials
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• 제6권5호
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• pp.233-237
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• 2005

In the device structure of ITO/hole injection layer/N, N'-biphenyl-N, N'-bis-(1-naphenyl)-[1,1'-biphenyl]4,4'-diamine(NPB)/tris(8-hydroxyquinoline) aluminum$(Alq_3)/Al$, we investigated an effect of hole-injection materials (PTFE, PVK) on the electrical characteristics and efficiency of organic light-emitting diodes. A thermal evaporation was performed to make a thickness of NPB layer with a evaporation rate of $0.5\~1.0\;\AA/s$ in a base pressure of $5\times10^{-6}$ Torr. We measured current-voltage characteristics and efficiency with a thickness variation of hole-injection layer. The PTFE and PVK hole-injection layer improve a performance of the device in several aspects, such as good mechanical junction, reducing the operating voltage and energy band adjustment. Compared with the devices without a hole-injection layer, we have obtained that an optimal thickness of NPB was 20 nm in the device structure of $ITO/NPB/Alq_3/Al$. And using the PTFE or PVK hole-injection layer, the external quantum efficiencies of the devices were improved by $24.5\%\;and\;51.3\%$, respectively.

• 문화기술의 융합
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• 제9권5호
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• pp.557-562
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• 2023

본 연구는 순환자원을 대량 활용한 지반안정재를 터널공사 시 보조공법으로 이용하는 강관다단공법의 주입재로 활용을 검토하기 위해 다양한 주입재 배합비에 따른 겔타임, 호모겔 강도를 비교하였다. 강관다단공법은 터널의 보조공법으로써 시공 후 초기강도의 발현이 중요한 요인으로, 초기에 강도발현이 우수할수록 강관다단공법에 적합한 주입재로 활용이 가능하다. 실내시험 결과, 순환자원을 활용하는 주입재의 호모겔타임은 시멘트를 주입재로 활용하는 배합비에 비해 많은 시간이 필요한 것으로 나타났으며, 2.0MPa를 만족하는 초기강도 양생시간은 24시간 이상이 필요한 것으로 확인되었다. 따라서 순환자원 활용 주입재는 동일 배합비의 시멘트에 비해 긴 초기경화 시간이 필요한 것으로 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1206-1209
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• 2005

In recent, injection molding process for features in sub-micron scale is under active development as patterning nano-scale features, which can provide the master or stamp for molding, and becomes available around the world. Injection molding has been one of the most efficient processes for mass production of the plastic product, and this process is already applied to nano-technology products successfully such as optical storage media like DVD or BD which is a large area plastic thin substrate with nano-scale features on its surface. Bio chip for like DNA sequencing may be another application of this plastic substrate. The DNA can be sequenced using order of 100 nm pore structure when making the DNA flow through the pore structure. Agarose gel and silicon based chip have been used to sequence the DNA, but injection molded plastic chip may have benefit in terms of cost. This plastic DNA sequencing chip has plenty of pillars in order of 100 nm in diameter on the substrate. When the usual features in case of DVD or BD have very low aspect ratio, even less than 0.5, but the DNA chip will have relatively high aspect ratio of about 2. It is not easy to injection mold the large area thin substrate with sub-micron features on its surface due to the characteristics of the molding process and it becomes much more difficult when the aspect ratio of the features becomes high. We investigated the effect of the molding parameters for injection molding with high aspect ratio nano-scale features and injection molded some plastic DNA sequencing chips. We also fabricated PR masters and Ni stamps of the DNA chip to be used for molding

• 대한기계학회논문집B
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• 제37권6호
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• pp.607-614
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• 2013

오늘날 전 세계의 자동차 회사들은 연비를 향상시키고 배기가스를 저감시키기 위해 다양한 기술을 개발하고 있다. 그 중 직접분사식 초희박 연소기술은 연료제어의 정확도를 향상시켜 연소 효율을 극대화하고 초희박 연소를 통해 연비를 향상 시킬 수 있는 차세대 기술로 평가받고 있다. 따라서 기존 가스엔진에 초희박 직접분사 기술을 적용한 초희박 LPG 직접분사 엔진을 개발하기 위해 $2{\ell}$ 급 MPI 엔진을 베이스 엔진으로 실린더 헤드를 재설계하였다. 재설계된 헤드는 초희박 연소를 구현하기 위해 인젝터와 점화플러그가 헤드 중앙에 장착되는 분무유도방식 연소시스템을 적용하였다. 연료 분사 압력별 연료 분사 시기와 점화 시기의 변경을 통해 연료 소비율과 연소 안정성을 측정하였으며 이를 통해 최적연료 분사시기와 점화시기를 선정하였다.

• Fibers and Polymers
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• 제4권2호
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• pp.89-96
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• 2003

A vertebral cage is a hollow medical device which is used in spine forgery. By implanting the cage into the spine column, it is possible to restore disc and relieve pressure on the nerve roots. Most cages have been made of titanium alloys but they detract the biocompatibility. Currently PEEK (polyether ether ketone) if applied to various implants because it has good properties like heat resistance, chemical resistance, strength, and especially biocompatibility. A new shape of vertebral cage is designed and injection molding of PEEK is considered for production. Before injection molding of the cage, it is needed to evaluate process conditions and properties of the final product. Variables affecting the shrinkage of the cage are considered, e.g., injection time, packing pressure, mold temperature, and melt temperature. By using the numerical simula-tion program, MOLDFLOW, several cases are studied. Data files obtained by MOLDFLOW analysis are used for stress anal-ysis with ABAQUS, and shrinkage and residual stress fields are predicted. With these results, optimum process conditions are determined.

• 소성∙가공
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• 제32권3호
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• pp.129-135
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• 2023

The use of engineering plastic products in internal combustion engine and electric cars to improve stiffness and reduce weight is increasing significantly. Among various lightweight materials, engineering plastics have significant advantages such as cost reduction, improved productivity, and weight reduction. In particular, engineering plastics containing glass fibers are used to enhance stiffness. However, the stiffness of glass fibers can increase or decrease depending on their orientation. Before developing plastic products, optimal designs are determined through injection molding and structural analysis to enhance product reliability. However, reliable analysis of products with variable stiffnesses caused by anisotropy cannot be achieved via the conventional isotropic structural analysis, which does not consider anisotropy. Therefore, based on the previously reported study "the Effect of Impacted Fracture in Glass Fiber Orientation with Injection Molding & Structural Coupled Analysis," this study aims to investigate the structural analysis and degradation mechanisms of various polymers. In particular, this study elucidates the actual mechanism of plastic fracture by analyzing various fracture conditions and their corresponding simulations. Furthermore, the objective of this study is to apply the injection molding and structural coupled analysis mechanism to develop engineering plastic products containing glass fibers. In addition, the study aims to apply and improve the plastic fracture mechanism in actual products by exploring anisotropy and stiffness reduction owing to the unfilled polymer weld line.

• 소성∙가공
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• 제11권4호
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• pp.312-322
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• 2002

In this study, an innovative semi-solid die casting technology to replace heavier cast iron compressor parts with lightweight aluminum castings was proposed, and the application possibility for home-appliance component was investigated. The most important factors regarding the semi-solid die casting process are the reheating process of the raw materials to the semi-solid state, specifications of the forming machine, the optimal injection conditions and die design. Materials used in this study were A3S7 and hSn alloys fabricated by the electromagnetic stirring process. The optimal injection conditions for semi-solid die casting process were Presented with the reheating conditions of the semi-solid materials. To investigate the effect of plunger tip shape on the formability and mechanical properties in semi-solid die casting process for complicated shape part, two kinds of plunger tip shape with long and short plunger tip taper are proposed.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.501-502
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• 2006

The present investigation has been performed on full densification behavior and mechanical property of the powder injection molded Fe-8wt%Ni nanoalloy powder. The net shaping process of the nanopowder was conducted by powder injection molding (PIM) process. The key-process for fabricating fully densified net-shaped nanopowder by pressureless sintering is an optimal control of agglomerate size of nanopowder. Enhanced mechanical property of PIMed Fe-Ni nanopowder is explained by grain refinement and microstructural uniformity.

• 소성∙가공
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• 제18권2호
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• pp.160-165
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• 2009

A Study on Effects of the Runner and the Gate of double shot injection molded Parts using CAE Double shot injection molding can inject two different materials or two different colors in the same mold in a injection molding process. Double shot injection molded parts can be characterized that the base part maintains strength and specified part can inject soft-material. It can reduce the production cost by single automatic operations. In this paper, we designed double shot injection mold for automobile emote control To inject secondary part, this part is used as an insert after external appearance of product is injected. CAE analysis was progressed gate location and runner size as variables. The analysis result is reflected in mold design process. As a result, it could solve problems which are generated in the conventional mold. Additionally, cost can be downed by reducing runner weight. As well as it could omit painting process because the surface of finished product is improved through new mold.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1507-1514
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• 2011

플라스틱 재료를 사용한 가공법 중에서 가장 보편적인 가공법이 사출성형이다. 오늘날에는 플라스틱 재료의 활용도는 지속적으로 증가하고 있으며, 신소재 등의 개발로 그 적용범위 또한 확대되고 있다. 인라인 스케이트는 4 가지 구성품으로 이루어진다. 그 4 가지 구성품은 부츠, 프레임, 휠, 브레이크로써 프레임이 가장 중요한 부품이다. 사출 재질에 변화에 따른 사출 성형성을 알아보았다. 런너와 게이트의 치수 변화에 따른 제품의 사출 성형성을 알아보았다. 본 연구에서는 Moldflow를 이용해서 사출성형 해석을 수행하였다. ANSYS를 이용해서 구조해석을 수행하였다.