• Advanced Composite Materials
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• 제16권2호
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• pp.95-113
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• 2007

Experimental investigations of interlaminar mechanical properties for carbon fiber reinforced plastic (CFRP) laminates were carried out using aramid fiber ($Kevlar^{(R)}$-29 1000d) and carbon fiber (TR40-1K 612d, Mitsubishi Rayon) stitching. Various carbon fiber (CF) stitch densities were used to prepare a number of CF stitched CFRP laminates for double cantilever beam (DCB) tests. An insert tongue-type loading fixture, developed by the Japan Aerospace Exploration Agency (formerly the National Aerospace Laboratory of Japan), was also employed in the DCB test. Interlaminar tension tests were carried out under an out-of-plane directional loading using a single CF stitch thread in the CFRP laminates. The DCB test results clarified that the relationship between the volume fractions of the CF stitch thread ($V_{ft}$) and mode I critical energy release rate ($G_{Ic}$) showed a mostly linear function with a higher gradient than that of the $Kevlar^{(R)}$ stitched CFRP laminates. The CF stitched CFRP tension test results indicated that the consumption energy per unit area ($E_i$) was larger than that of $Kevlar^{(R)}$ stitched CFRP laminates.

• 한국철도학회논문집
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• 제8권6호
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• pp.573-580
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• 2005

Model I interlaminar fracture behaviors of the carbon/epoxy composite, one of the candidate composites for a tilting train carbody, were investigate by the use of DCB(Double cantilever beam) specimens. These specimens were made of CF3327 plain woven fabric with epoxy resin, and an artificial starter delamination was fabricated by inserting Teflon film with the thickness of $12.5{\mu}m$ of $25.0{\mu}m$ at the one end of the specimen. Mode I interlaminar fracture toughness was evaluated for the specimens with the different thickness of an inserter. Also delamination propagating behaviors and interlaminar fracture surface were examined through an ooptical travelling scope and a scanning electron microscope. We found that abruptly unstable crack propagation called as stick-slip phenomena was observed. In addition, interlaminar fracture behaviors were affected on the location and the morphology of a crack tip as well as an interface region.

• Current Optics and Photonics
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• 제1권5호
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• pp.525-528
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• 2017

High-energy, high-power, quasi-continuous wave (QCW) operation of double-clad Yb fiber lasers incorporating an incoherent signal combiner is reported. We constructed four efficient, high-power Yb fiber lasers, each of which produced rectangular pulses at 1080 nm with a pulse energy greater than 15 J, and a pulse duration of 10 ms at a repetition rate of 10 Hz, corresponding to an average power of over 150 W and a peak power of over 1.5 kW for ~200 W of incident pump power at 915 nm. These laser outputs were combined by a homemade incoherent fiber signal combiner with low loss, yielding a maximum peak power of ~6.0 kW in a beam with $M^2{\approx}12.5$. The detailed laser characteristics and prospects for further power scaling in QCW operation are discussed.

• 한국결정성장학회지
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• 제6권1호
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• pp.56-61
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• 1996

두 개의 증발료가 설치된 hot wall epitaxy 장치를 제작하고 GaAs 기판위에 undoped ZnSe 박막을 성장하였다. 기판온도 $350^{\circ}C$, 원료부의 온도 $660^{\circ}C$ 근방에서 성장된 경 연박막의 XRD 측정값은 175 $sec^{-1}$의 반치폭을 냐타내 였다. Photoluminescence 측정 결과 neu t tral acceptor bound exciton emission line이 강하게 얻어지는 양질의 박막을 성장하였다.

• Journal of Radiation Protection and Research
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• 제42권1호
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• pp.63-68
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• 2017

Background: The combined effect of the low energy electron (LEE) irradiation and $Cu^{2+}$ ion on DNA damage was investigated. Materials and Methods: Lyophilized pBR322 plasmid DNA films with various concentrations (1-15 mM) of $Cu^{2+}$ ion were independently irradiated by monochromatic LEEs with 5 eV. The types of DNA damage, single strand break (SSB) and double strand break (DSB), were separated and quantified by gel electrophoresis. Results and Discussion: Without electron irradiation, DNA damage was slightly increased with increasing Cu ion concentration via Fenton reaction. LEE-induced DNA damage, with no Cu ion, was only 6.6% via dissociative electron attachment (DEA) process. However, DNA damage was significantly increased through the combined effect of LEE-irradiation and Cu ion, except around 9 mM Cu ion. The possible pathways of DNA damage for each of these different cases were suggested. Conclusion: The combined effect of LEE-irradiation and Cu ion is likely to cause increasing dissociation after elevated transient negative ion state, resulting in the enhanced DNA damage. For the decrease of DNA damage at around 9-mM Cu ion, it is assumed to be related to the structural stabilization due to DNA inter- and intra-crosslinks via Cu ion.

• Transactions on Electrical and Electronic Materials
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• 제1권3호
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• pp.23-28
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• 2000

A block-oxide layer was formed on the surface of Cu-based leadframe by chamical oxidation method in order to enhance the adhesion strength between Cu-based leadframe and epoxy molding compound (EMC) Using sandwiched double cantilever beam (SDCB) specimens, the adesion strength was measured in terms of interfacial fracture toughness, G$\sub$IC//Results showed that the black-oxide layer was composed of two kinds of layers: pebble-like Cu$_2$O layer and acicular CuO layer, At the initial stage of oxidation the Cu$_2$O layer was preferentially formed and thickened up to around 200 nm whithin 1 minute of the oxidation time. Then the CuO layer started to from atop of the Cu$_2$O layer and thickened up to around 1300 nm until 20 minutes. As soon as the CuO layer formed, the thickness of Cu$_2$O layer began to reduce and finally reached to around 150 nm. The pre-cleaned and the Cu$_2$O coated leadframes showed almost no adhesion of EMC, however, as the CuO precipitates appeared and became continuous, G$\sub$IC/ increased up to around 80 J/㎡. Further oxidation raised G$\sub$IC/ up. to around 100 J/㎡.

• 한국표면공학회지
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• 제29권5호
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• pp.563-569
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• 1996

Degradation of $Zn_3N_2$ films is studied by using several analytical techniques. Polycrystalline $Zn_3N_2$ films prepared by reactie rf magnetron sputtering are kept in the air. Electrical and optical properties are measured by using van der Pauw technique and double-beam spectrometry. Structure and chemical bonding states are studied by X-ray diffraction(XRD), Fourier transfer infrared ray spectroscopy(FT-IR) and X-ray photoelectron specroscopy (XPS). Significant differences are observed in optical properties between the degraded film and the ZnO film. XRD analysis reveals that the degraded film contains very small ZnO grains because very weak and broad ZnO peaks are observed. XPS and FT-IR measurements reveal the formation of $Zn(OH)_2$ in the degraded film. The existence of N-H bonds in degraded films is exhibited from the N 1s spectra. $Zn_3N_2$ change into the mixture of ZnO, $Zn(OH)_2$ and an ammonium salt.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.181-182
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• 2007

In this paper, we investigated the diffraction grating efficiency on $Ge_{75}Se_{25}$ and Ag-doped amorphous chalcogenide $Ag/Ge_{75}Se_{25}$ thin film for used to volume hologram. The film thickness was 2 um and diffraction efficiency was obtained from He-Ne (632.8nm) and DPSS(532nm) (P:P) polarized laser beam on $Ge_{75}Se_{25}$ and Ag/$Ge_{75}Se_{25}$ thin films. As a result. for the films, the diffraction efficiency on Ag/$Ge_{75}Se_{25}$ double layer, was better than single $Ge_{75}Se_{25}$ thin films. The recording speed of DPSS laser is higher than that of He-Ne laser.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.490-493
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• 2003

We have carried out two-beam interference experiment to form holographic grating on amorphous $As_{40}Ge_{10}Se_{15}S_{35}/Ag$ double-layer. In this study holographic grating formed using He-Ne laser(632.8nm) under non-polarization state and p-polarization state and we confirm that the diffraction efficiency depend on thickness of Ag. The diffraction efficiency was obtained by first order intensity. We got the maximum diffraction efficiency that thickness of Ag was $600{\AA}$. The maximum diffraction efficiency was 13.5% in (P:P) polarization state.

• 한국표면공학회지
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• 제36권6호
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• pp.491-499
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• 2003

Copper-based leadframe sheets were oxidized in a hot alkaline solution to form brown-oxide layer on the surface and molded with epoxy molding compound (EMC). The brown-oxide-coated leadframe/EMC joints were machined to form sandwiched double-cantilever beam (SDCB) specimens and sandwiched Brazil-nut (SBN) specimens for the purpose of measuring the fracture toughness of leadframe/EMC interfaces. The SDCB and the SBN specimens were designed to measure the fracture toughness of the leadframe/EMC interfaces under nearly mode-I loading and mixed-mode (mode I ＋ mode II) loading conditions, respectively. Fracture surfaces were analyzed by various equipment such as glancing-angle XRD, SEM, AES, EDS and AFM to elucidate failure path. Results showed that failure occurred irregularly in the SDCB specimens, and oxidation time of 2 minutes divided the types of irregular failures into two classes. The failure in the SBN specimens was quite different from that in the SDCB specimens. The failure path in the SBN specimens was not dependent on the phase angle as well as the distance from tips of pre-cracks.