• International Journal of Aeronautical and Space Sciences
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• v.15 no.1
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• pp.32-43
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• 2014

Automatic fiber placement (AFP) has become a popular processing technique for composites in the aerospace industry, due to its ability to place prepregs or tapes precisely in the exact position when complex parts are being manufactured. This paper presents the design, analysis, and manufacture of an AFP mandrel for composite aircraft fuselage skin fabrication. According to the design requirements, an AFP mandrel was developed and a numerical study was performed through the finite element method. Linear static load analyses were performed considering the mandrel structure self-weight and a 2940 N load from the AFP machine head. Modal analysis was also performed to determine the mandrel's natural frequencies. These analyses confirmed that the proposed mandrel meets the design requirements. A prototype mandrel was then manufactured and used to fabricate a composite fuselage skin. Material load tests were conducted on the AFP fuselage skin curved laminates, equivalent flat AFP, and hand layup laminates. The flat AFP and hand layup laminates showed almost identical strength results in tension and compression. Compared to hand layup, the flat AFP laminate modulus was 5.2% higher in tension and 12.6% lower in compression. The AFP curved laminates had an ultimate compressive strength of 1.6% to 8.7% higher than flat laminates. The FEM simulation predicted strengths were 4% higher in tension and 11% higher in compression than the flat laminate test results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.841-850
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• 2008

Strength and failure of composite-to-aluminum rivetted, bonded, and rivet/bonding hybrid single-lap joints were investigated by experiment. A total of 82 joint specimens were tested with 3 different overlap lengths and 2 types of stacking sequence. FM73m adhesive film and NAS9308-4-03 rivet were used for hybrid joints. While failure loads of the bonded and hybrid joints increased as the overlap length increased, failure loads of the rivetted joints were not affected by the overlap length. Effect of the stacking sequence was not remarkable in the simple bonded or rivetted joints. Failure loads of the hybrid joints, however, showed the maximum of 30% difference depending on the stacking sequence. Major failure mode of the bonded and hybrid joints was the delamination of the composite adherend and failure mode of riveted joints was the rivet failure with local bearing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.119-128
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• 2010

The hygrothermal effect on the strength of composite single-lap bonded joints were investigated. The specimens were manufactured in four different manufacturing methods and tested in three different environmental conditions. An interesting result is that the strengths of the joints in the elevated temperature and wet (ETW) conditions were found to be 11 ~ 23% higher than those in the room temperature and dry (RTD) environment. In contrast, the strengths of the joints in the cold temperature and dry (CTD) condition decrease by 8 ~ 21% compared to those in the RTD environment except for cobonded joint. The difference in the strength by testing environments is mainly attributed to the change of the material properties of adhesive by temperature and moisture.

• Nutrition Research and Practice
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• v.4 no.1
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• pp.16-22
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• 2010

Flavonoids are known to be effective scavengers of free radicals. In particular, proanthocyanidins are flavonoids that possess cardiovascular protection, antioxidative activities, and immunomodulatory activities. Here, we evaluated proanthocyanidin contents in the total polyphenolic compounds of pine needle extracts prepared by hot water, ethanol, hexane, hot water-hexane (HWH), and hot water-ethanol (HWE). Analysis of each extract indicated that the ethanol extract contained the highest proanthocyanidin concentration. The HWH and hexane extracts also contained relatively high concentrations of proanthocyanidin. On the other hand, proanthocyanidin content analyses out of the total polyphenolic compounds indicated that the HWH extract contained the highest content. These results suggest that HWH extraction is a suitable method to obtain an extract with a high level of pure proanthocyanidins and a relatively high yield. The HWH extract possessed superior activity in diverse antioxidative analyses such as 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferrous ion chelating (FIC), and ferric-ion reducing power (FRAP) assays. In addition, upon assessing the effects of the pine needle extracts on macrophages (Raw 264.7 cell), the HWH extract exhibited the highest activity. In this study, we discerned an efficient extraction method to achieve relatively pure proanthocyanidins from pine needles and evaluated the biological functions of the resulting extract, which could potentially be used for its efficacious components in functional food products.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.1
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• pp.449-452
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• 2013

Polymorphisms in DNA repair genes have been shown to influence DNA repair processes and to modify cancer susceptibility. Here we conducted a case-control study to assess the role of potential SNPs of DNA repair genes on the risk of glioma and meningioma. We included 297 cases and 458 cancer-free controls. Genotyping of XRCC1 Gln399Arg, XRCC1 Arg194Trp, XRCC2 Arg188His, XRCC3 Thr241Met, XRCC4 Ala247Ser, ERCC1 Asn118Asp, ERCC2 Lys751Gln and ERCC5 Asp1558His were performed in a 384-well plate format on the Sequenom MassARRAY platform. XRCC1 Arg194Trp (rs1799782) and ERCC2 Asp312Asn rs1799793 did not follow the HWE in control group, and genotype distributions of XRCC1 Gln399Arg rs25487, XRCC2 Arg188His rs3218536 and ERCC2 Asp312Asn rs1799793 were significantly different between cases and controls (P<0.05). We found XRCC1 399G/G, XRCC1 194 T/T and XRCC3 241T/T were associated with a higher risk when compared with the wild-type genotype. For ERCC5 Asp1558His, we found G/G genotype was associated with elevated susceptibility. In conclusion, our study has shown that XRCC1 Gln399Arg, XRCC1 Arg194Trp, XRCC3 Thr241Met and ERCC5 Asp1558His are associated with risk of gliomas and meningiomas. This finding could be useful in identifying the susceptibility genes for these cancers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.266-272
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• 2002

The stochiometric mixture of evaporating materials for the ZnIn$_2$S$_4$ single crystal thin film was prepared from horizontal furnace. To obtain the ZnIn$_2$S$_4$ single crystal thin film, ZnIn$_2$S$_4$ mixed crystal was deposited on throughly etched semi-insulating GaAs(100) in the Hot Wall Epitaxy(HWE) system. The source and substrate temperature were 610 $^{\circ}C$ and 450 $^{\circ}C$, respectively and the growth rate of the ZnIn$_2$S$_4$ single crystal thin film was about 0.5 $\mu\textrm{m}$/hr. The crystalline structure of ZnIn$_2$S$_4$ single crystal thin film was investigated by photo1uminescence and double crystal X-ray diffraction(DCXD) measurement. The carrier density and mobility of ZnIn$_2$S$_4$ single crystal thin film measured from Hall effect by van der Pauw method are 8.51${\times}$10$\^$17/ cm$\^$-3/, 291 $\textrm{cm}^2$/V$.$s at 293 $^{\circ}$K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the ZnIn$_2$S$_4$ single crystal thin film, we have found that the values of spin orbit splitting ΔSo and the crystal field splitting ΔCr were 0.0148 eV and 0.1678 eV at 10 $^{\circ}$K, respectively. From the photoluminescence measurement of ZnIn$_2$S$_4$ single crystal thin film, we observed free excition (E$\_$X/) typically observed only in high quality crystal and neutral donor bound exciton (D$^{\circ}$,X) having very strong peak intensity. The full width at half maximum and binding energy of neutral donor bound excition were 9 meV and 26 meV, respectively. The activation energy of impurity measured by Haynes rule was 130 meV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.281-287
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• 2002

The stochiometric composition of AgGaS$_2$ polycrystal source materials for the AgGaS$_2$/GaAs epilayer was prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns it was found that the polycrystal AgGaS$_2$ has tetragonal structure of which lattice constant a$\sub$0/ and c$\sub$0/ were 5.756 ${\AA}$ and 10.305 ${\AA}$, respectively. AgGaS$_2$/GaAs epilayer was deposited on throughly etched GaAs(100) substrate from mixed crystal AgGaS$_2$ by the Hot Wall Epitaxy (100) system. The source and substrate temperature were 590$^{\circ}C$ and 440$^{\circ}C$ respectively. The crystallinity of the grown AgGaS$_2$/GaAs epilayer was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for AgGaS$_2$/GaAs epilayer at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by ${\alpha}$ : 8.695${\times}$10$\^$-4/ eV/K, and ${\beta}$ = 332 K. From the photocurrent spectra by illumination of polarized light of the AgGaS$_2$/GaAs epilayer, we have found that crystal field splitting ΔCr was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pain are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.257-265
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• 2002

A stoichiometric mixture of evaporating materials for AgInS$_2$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, AgInS$_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy(HWE) system. The source and substrate temperatures were 680 $^{\circ}C$ and 410 $^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of AgInS$_2$ single crystal thin films measured from Hall effect by van der Pauw method are 9.35${\times}$10$\^$16/ cm$\^$-3/ and 294 $\textrm{cm}^2$/V$.$s at 293 K, respectively. From the optical absorption measurement, the temperature dependence of the energy band gap on AgInS$_2$ single crystal thin films was found to be E$\_$g/(T) : 2.1365 eV - (9.89 ${\times}$ 10$\^$-3/ eV) T$^2$/(2930 + T). After the as-grown AgInS$_2$ single crystal thin films was annealed in Ag-, S-, and In-atmospheres, the origin of point defects of AgInS$_2$ single crystal thin films has been investigated by using the photoluminescence(PL) at 10 K. The native defects of V$\_$AG/, V$\_$S/, Ag$\_$int/, and S$\_$int/ obtained from PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the S-atmosphere converted AgInS$_2$ single crystal thin films to an optical p-type. Also, we confirmed that In in AgInS$_2$/GaAs did not form the native defects because In in AgInS$_2$ single crystal thin films did exist in the form of stable bonds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.171-174
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• 2004

The stochiometric $AgGaSe_2$ polycrystalline mixture of evaporating materials for the $AgGaSe_2$ single crystal thin film was prepared from horizontal furnace. To obtain the single crystal thin films, $AgGaSe_2$ mixed crystal and semi-insulating GaAs(100) wafer were used as source material and substrate for the Hot Wall Epitaxy (HWE) system, respectively. The source and substrate temperature were fixed at $630^{\circ}C$ and $420^{\circ}C$, respectively. The thickness of grown single crystal thin films is $2.1{\mu}m$. The single crystal thin films were investigated by photoluminescence and double crystal X-ray diffraction(DCXD) measurement. The carrier density and mobility of $AgGaSe_2$ single crystal thin films measured from Hall effect by van der Pauw method are $4.89{\times}10^{17}\;cm^{-3},\;129cm^2/V{\cdot}s$ at 293K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the $AgGaSe_2$ single crystal thin film, we have found that the values of spin orbit splitting ${\Delta}S_o$ and the crystal field splitting ${\Delta}C_r$ were 0.1762 eV and 0.2494 eV at 10 K, respectively. From the photoluminescence measurement of $AgGaSe_2$ single crystal thin film, we observed free excition $(E_X)$ observable only in high quality crystal and neutral bound exciton $(D^o,X)$ having very strong peak intensity And, the full width at half maximum and binding energy of neutral donor bound excition were 8 meV and 14.1 meV, respectively. By Haynes rule, an activation energy of impurity was 141 meV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.226-229
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• 2004

A stoichiometric mixture of evaporating materials for $CuAlSe_2$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $CuAlSe_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $680^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuAlSe_2$ single crystal thin films measured with Hall effect by van der Pauw method are $9.24{\times}10^{16}\;cm^{-3}$ and $295\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CuAlSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)\;=\;2.8382\;eV\;-\;(8.68{\times}10^{-4}\;eV/K)T^2/(T+155K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $CuAlSe_2$ have been estimated to be 0.2026 eV and 0.2165 eV at 10K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $CuAlSe_2$. The three photocurrent peaks observed at 10K are ascribed to the $A_1-$, $B_1-$, and $C_1$-exciton peaks for n = 1.