• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.3
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• pp.205-217
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• 2006

Rock and discontinuities are main factors consisting of a rock mass and the physical properties of each factor have direct effects on the mechanical stability of artificial structures in the rock mass. Because physical properties of the rock and discontinuities change a lot according to the size of test materials, a close attention is needed when the physical properties, obtained from laboratory tests, are used for the design of field structures. In this study, change of physical properties of intact materials due to the change of their size are studied. Six kinds of artificial materials including crystal, instead of an intact rock, are adopted for the study to guarantee the homogeneity of specimen materials even with relatively large size. Uniaxial strength and Young's modulus of each artificial material are checked out for a size effect and compared with the predicted values by Buckingham's theorem - dimensional analysis. A numerical analysis using PFC (Particle Flow Code) is also applied and primary factors influencing on the size effect are investigated.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2006.09a
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• pp.268-279
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• 2006

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.118-118
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• 2003

전력반도체 소자로 사용되는 p$^{-}$-n$^{-}$ 접합 다이오드의 스위칭 속도를 향상시키고 그에 따른 에너지 손실을 감소시키기 위해 전자 조사를 실시하였다. Reverse recovery time이 현저히 감소한 반면, 전자 조사에 의한 누설전류와 on-state 전압 강하와 같은 그 외의 전기적 특성 저하는 무시할 수 있는 정도였다. 그밖에 시료의 deep level transient spectroscpy(DLTS) 분석 결과와 secondary ion mass spectrometry(SIMS) depth profile을 근거로 결함 분포와 전자조사 유도결함의 유형을 논하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.7-12
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• 2012

Chemical mechanical polishing(CMP) technology is faced with the challenge of processing new electronic materials. This paper focuses on the balance between chemical and mechanical reactions in the CMP process that is required to cope with a variety of electronic materials. The material properties were classified into the following categories: easy to abrade(ETA), difficult to abrade(DTA), easy to react(ETR) and difficult to react(DTR). The chemical and mechanical balance for the representative ETA-ETR, DTA-ETR, ETA-DTR and DTA-DTR materials was considered for defect-free surfaces. This paper suggests the suitable polishing methods and examples for each electronic material.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.792-799
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• 2007

A newly developed cellular metal based on kagome lattice is an ideal candidate for multifunctional materials achieving various optimal properties. Intensive efforts have been devoted to develop efficient techniques for mass production due to its wide potential applications. Since a variety of imperfections would be inevitably included in the realistic fabrication processes, it is highly important to examine the correlation between the imperfections and material strengths. Previous performance tests were mostly done by numerical simulations such as finite element method (FEM), but only for perfect structures without any imperfection. In this paper, we developed an efficient numerical framework using nonlinear random network analysis (RNA) to verify how the statistical imperfections (geometrical and material property) contribute to the performance of general truss structures. The numerical results for kagome truss structures are compared with experimental measurements on 3-layerd WBK (wire-woven bulk kagome). The mechanical strength of the kagome structures is shown relatively stable with the Gaussian types of imperfections.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.78-83
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• 2007

A newly developed cellular metal based on kagome lattice is an ideal candidate for multifunctional materials achieving various optimal properties. Intensive efforts have been devoted to develop efficient techniques for mass production due to its wide potential applications. Since a variety of imperfections would be inevitably included in the realistic fabrication processes, it is highly important to examine the correlation between the imperfections and material strengths. Previous performance tests were mostly done by numerical simulations such as finite element method (FEM), but only for perfect structures without any imperfection. In this paper, we developed an efficient numerical framework using nonlinear random network analysis (RNA) to verify how the statistical imperfections (geometrical and material property) contribute to the performance of general truss structures. The numerical results for kagome truss structures are compared with experimental measurements on 3-layerd WBK (wire-woven bulk kagome). The mechanical strength of the kagome structures is shown relatively stable with the Gaussian types of imperfections.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.1-6
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• 2008

Block copolymers spontaneously assemble into various nanoscale structures such as spheres, cylinders, and lamellar structures according to the relative volumn ratio of each macromolecular block and their overall molecular weights. The self-assembled structures of block copolymer have been extensively investigated for the applications such as nanocomposites, photonic crystals, nanowires, magnetic-storage media, flash memory devices. However, the naturally formed nanostructures of block copolymers contain a high density of defects such that the practical applications for nanoscale devices have been limited. For the practical application of block copolymer nanostructures, a robust process to direct the assembly of block copolymers in thin film geometry is required to be established. To exploit self-assembly of block copolymer for the nanotechnology, it is indispensible to fabricate defect-free self-assembled nanostructure over an arbitrarily large area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.1
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• pp.42-46
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• 2003

Liquid PVC, which is used widely as fiber coating, has brilliant non-luster effect, but it decreases flexibility of coated fiber surface. We used liquid silicone rubber in elastomer series as a coating material to alleviate this problem. We have conducted the former liquid PVC processing and used pressure of roller and preliminary hardening of processing. In this experiment, We measured 70 degree of hardness, 10.3 MPa of tensile strength and 200fs of tensile elongation of Liquid PVC-coated plastic fiber. We measured 40 degree of hardness, 5.1 MPa of tensile strength and 460% of tensile elongation of Liquid silicone PVC-coated plastic fiber. Therefore, Without the second process, Liquid silicone rubber coating increased non-luster effect and flexibility of plastic fiber surface more than Liquid PVC coating.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.503-508
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• 1998

연구용원자로인 하나로(HANARO)에서 중성자 조사된 캡슐 및 핵연료다발을 절단 및 해체하기 위한 장비인 캡슐절단기를 개발하여 조사재시험시설(IMEF)의 M2 핫셀(hot cell)에 설치하였다. 재료 및 핵연료의 개발을 위해 하나로에서 조사되는 캡슐 및 핵연료다발의 절단 및 해체는 핵연료봉 및 캡슐내부에 내장되어 있는 시편에 손상 및 결함이 발생하지 않도록 하는 것이 매우 중요하며, 이러한 장비는 핫셀의 작업구역에서 원격조작기를 사용하여 원격으로 조작이 용이하도록 설계 및 제작되어야 한다. 이에 조사재시험시설에서 개발한 캡슐절단기는 가공물이 회전 및 좌우이송, 절단용 철이 회전 및 전후이송이 각각 되도록 하였고, 핫셀내에 설치하기 전에 가공에 필요한 최적의 조건을 설정하였다. 그리고 핫셀내 설치후 중성자에 조사되지 않은 하나로용 핵연료다발과 조사된 무계장캡슐을 건식상태로 절단 및 해체하여 장비 성능을 확인하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.183-189
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• 2007

Ultra precise processed parts are required together with the development of optoelectronics industry. As important parts of optoelectronics industry, there are ferrule of optical connector and lens for optical devices. In particular, the lens requires high reliability with high precision without including flaws. These optical modules need ultra precise processing in order to reduce the loss of light sources and various nondestructive inspections are carried out in the finishing stage to separate good and bad quality products. Therefore, it was analyzed through the characteristics of response of amplitude and resonant frequency according to the mass variations of aspheric lens that is used currently in laser printers.