• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.1
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• pp.206-216
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• 1997

The purpose of this study was to determine the pore size distributions (PSDs) of polyester woven fabrics by using liquid extraction method. Three types of PSDs-percent PSD, PSD per unit area of sample and PSD per unit weight of sample-were evaluated. Plain, twill and satin polyester fabrics with various fabric counts were used as specimens. Results showed that the interyarn PSDs reflected the fabric characteristics such as the fabric count and the weave type and the intrayarn PSDs reflected the thread characteristics such as the number of fibers, the fiber diameter, the thread diameter and the thread twist. Of three types of PSDs, the PSD per unit area of sample best reflect fabric and thread characteritics. As the fabric count decreased, rc increased and interyarn pore volume increased. The PSDs were skewed to the small pore sizes and the pore volumes decreased in the order of plain> twill> satin. As the number of fibers, the fiber diameter and the thread twist decreased, the intrayarn pore volumes were increased.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.878-887
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• 2020

A neutral extract (NE), that is soluble in cold water and has excellent antioxidant activity, from Pinus radiata pine bark was prepared by sodium bicarbonate treatment, and its chemical characteristics were investigated. NE was prepared by treating P. radiata bark with 0.8% NaHCO₃ aqueous solution with a 5 : 1 liquor-to-bark ratio at boiling temperature for 1 h, resulting in 44% yield and final pH of 6.66. The yield of NE was 11% higher than that of the hot water extract (HWE) due to the increase in the solubility of polyphenols, the main component in the bark, by NaHCO₃ treatment. NE was characterized through FT-IR, NMR, and MALDI TOF MS analyses. The results indicated that NE is mostly composed of proanthocyanidins (PAs) consisting of procyanidin (PC) units. The acetylated neutral extract (Ac-NE) had weight average molecular weight (${\bar{M}}w$) of 5,300 Da. The Ac-NE had wide molecular weight distribution and its polydispersity (${\bar{M}}w/{\bar{M}}n$) was 6 times higher than that of pure PA. The antioxidant activity of NE was determined by 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and showed that NE had comparable antioxidant activity with pure PA.

• Macromolecular Research
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• v.17 no.4
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• pp.240-244
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• 2009

High molecular weight(MW), 3-arm star poly(methyl methacrylate)(PMMA) with a narrow MW distribution($M_n$=570,000 g/mol, PDI=1.36) was successfully synthesized by activators regenerated by electron transfer(ARGET) atom transfer radical polymerization(ATRP). The polymerization was carried out with a trifunctional initiator/$CuBr_2$/N,N,N',N",N"-pentamethyldiethy lenetriamine(PMDETA) initiator/catalyst system in the presence of a tin(II) 2-ethylhexanoate [$Sn(EH)_2$] reducing agent at $90^{\circ}C$. The concentration of the copper catalyst was as low as 30 ppm, and a high initiation efficiency of the initiating sites was obtained. The chain-end functionality of the high MW, 3-arm star PMMA was confirmed by a chain extension experiment with styrene via ARGET ATRP, using the same catalyst system.

• Journal of the Korean Society for Advanced Composite Structures
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• v.4 no.4
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• pp.1-8
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• 2013

Pile foundations constructed by the fiber reinforced polymer plastic piles have been used in coastal and oceanic regions in many countries. Generally, fiber reinforced polymer plastic piles are consisted of filament winding FRP which is used to wrap the outside of concrete pile to increase the axial load carrying capacity or pultruded FRP which is located in the core concrete to resist the bending moment arising due to eccentric loading. In this paper, the analytical procedures of hybrid concrete filled FRP tube flexural members are suggested based on the CFT design method. Moreover, the analytical results are compared with the experimental results to obtained by the previous researches. The results of comparison analyses are performed to estimate the accuracy of the analytical procedure for hybrid FRP-concrete composite compression test, members under eccentrical loading.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.245-250
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• 2002

We study numerically the temporal evolutions of two orthogonally polarized pulses with width less than 100fsec in all-optical phase-shift switches. We analyze the complicated interplay between a soliton pulse and a higher-order soliton pulse, including the self-and the cross-Raman scattering and the walk-off effect. We also investigate the influence of these interactions on switching performance, including pulse-shape, phase-shift distribution, and contrast ratio. In particular we show that an optical fiber with a typical birefringence (Δn : 2.4$\times$10$^{-5}$ ) can be used with good switching performance in such all-optical switches.

• Fibers and Polymers
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• v.5 no.3
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• pp.239-244
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• 2004

Solution-cast films of polymethylmethacrylate (PMMA) and polyurethane (PU) containing polymeric styryl dye up to 5 % by weight were prepared to investigate their acid-sensitivity and mechanical and thermal properties. Original red samples due to styryl dye turned out yellow very rapidly as they were exposed to acid vapor of hydrochloric acid or p-toluenesulfonic acid. According to UV/VIS spectroscopic measurements, characteristic peak intensities near 430 nm and 520 nm increased or decreased relatively with exposed amounts of acid, respectively. Both PMMA and PU samples showed uniform color distribution due to a good miscibility between polymer and dye which can be evidenced by measurements of glass transition temperature. No significant difference in acid-sensitivity was found between PU and PMMA except relative absorbance. However, dependence of their mechanical properties on dye content was somewhat different with PU or PMMA. In case of PMMA, modulus and breaking stress increased up to about 50 % with increasing dye content, whereas those of PU samples showed only slight increase. It was ascribed to whether the matrix polymer was in the glassy or rubbery state.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.1
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• pp.53-61
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• 2011

Edge notched A16061-T6 aluminum was repaired with a GFRP composite patch as a function of the number of stacking, Damage progress of specimen for tension load has been monitored by acoustic emission(AE), AE energy rate, hit rate, amplitude, waveform and 1st peak frequency distribution were analyzed. Fracture processes were classified into Al cracking, Fiber breakage, Resin cracking and Delamination. Displacement of a specimen can be divided into Region I, II and ill according to acoustic emission characteristics. Region II where the patch itself was actually fractured was focused on to clarify the AE characteristics difference for the number of stacking.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.1
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• pp.79-88
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• 2015

In this paper, it is investigated that the limitation due to the asymmetry of optical power and chromatic dispersion with respect to optical phase conjugator (OPC) for compensating optical signal distortion in WDM system is overcomed by using OPC position offset and optimal dispersion coefficients of fiber sections, which depend on OPC position offset. It is confirmed that overall WDM channels are efficiently compensated by applying the optimal parameter values obtained from the proposed method into 24 channels ${\times}40$ Gbps WDM system with non zero - dispersion shifted fiber (NZ-DSF) of 1, 000 km, such as power penalties of inter-channel are reduce to almost 3.5 dB from the infinite value. It is also confirmed that the flexible design of WDM system with OPC is possible by using the optimal parameters, in which OPC is placed at ${\pm}15km$ from 500 km for efficiently compensating overall channels. Thus, the methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which generates a serious problem if it was not made but it is the condition in the case of applying the OPC into multi-channels WDM system.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1619-1629
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• 1995

The Al/Al$_{2}$O$_{3}$ SiC and Al/Al$_{2}$O$_{3}$/C hybrid metal matrix composites (MMCs) were fabricated by squeeze infiltration method. Uniform distribution of reinforcements were found in the microstructure of metal matrix composites. Mechanical tests were carried out under various test conditions to clearly identify mechanical behavior of MMCs, and the wear mechanism of Al/Al$_{2}$O$_{3}$/(SiC or C) hybrid metal matrix composites were investigated. The tensile strength and hardness of hybrid composites was resulted in increasing compared with those of the unreinforced matrix alloy. Wear resistance was strongly dependent upon kinds of fiber, volume fraction and sliding speed. The wear resistance of metal matrix composites was remarkably improved by the addition of reinforcements. Especially, the wear resistance of the hybrid composites of carbon fibers was more effective than in the composites reinforced with alumina and SiC whiskers of reinforcements. This was due to the effect of carbon fiber on the solid lubrication. Wear mechanisms of hybrid composites were suggested from wear surface analyses. The major wear mechanism of hybrid composites was the abrasive wear at low to intermediate sliding speed, and the melting wear at intermediate to high sliding speed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8C
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• pp.689-695
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• 2007

Wireline relay stations(RS's) are connected to cellular base stations(BS's) via radio-over-fiber(RoF) to enhance system capacity and to reduce shadow areas. Unlike wireless multi-hop systems, BS-to-RS signaling is transmitted out-of-band, thus reducing the effect of interference caused by frequency reuse. In this paper, antenna arrays used in addition to the wireline RS's are considered to evaluate the transmission capacity gain and performance variations according to the may structures. In particular, RS locations to maximize the gain, may distribution patterns for a given number of antenna elements, performance enhancement for a varying number of elements are experimentally determined to suggest a proper utilization of antenna ways in conjunction with wireline RS's.