• Journal of the Korean Society for Precision Engineering
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• v.29 no.9
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• pp.938-945
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• 2012

To design and estimate material failures of Type III pressure vessels, which have excellent stability and performance, various modeling techniques have been introduced. This paper provided a hybrid modeling technique composed of ply-based modeling for a cylinder part and laminate-base modeling technique for a dome part for enhancing modeling efficiency. The ply-based modeling technique provided accurate ply stresses directly for predicting material failure, on the other hand, additional manipulations in stress calculations, which may cause some errors, were needed for the case of the laminate-based modeling technique. The ply stresses in fiber, transverse and in-plane shear directions were compared with the corresponding material strengths to predict material failure.

• Applied Science and Convergence Technology
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• v.27 no.5
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• pp.79-85
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• 2018

Many studies have been conducted on large-scale graphene synthesis by chemical vapor deposition. Furthermore, numerous researchers have attempted to develop processes that can continuously fabricate uniform and high-quality graphene. To compete with other types of carbon materials (carbon black, carbon fiber, carbon nanotubes, and so on), various factors, such as price, mass manufacturing capability, and quality, are crucial. Thus, in this study, we examine various large-scale graphene production methods focusing on cost competitiveness and productivity improvements for applications in various fields.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.104-105
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• 2003

We have fabricated a side-illuminated p-i-n photodetectors with evanescently-coupled waveguides for surface hybrid integration in low-cost modules. We adopted WGPD of evanescently-coupled type to have high responsivity and coupling tolerance, and to avoid any reliability problem. This proposed photodetectors have a high responsivity of 1.10 A／W at a wavelength of 1.55 ${\mu}{\textrm}{m}$. The 1dB coupling tolerance to cleaved fiber and photodetectors is $\pm$3.5 ${\mu}{\textrm}{m}$ in the vertical direction and $\pm$11 ${\mu}{\textrm}{m}$ in the horizontal direction.

• Structural Engineering and Mechanics
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• v.83 no.1
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• pp.109-121
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• 2022

Twelve push-out test specimens were conducted with various parameters to study the static and fatigue performance of a new through-bolt shear connector transferring the shear forces of interface between prefabricated hybrid fiber reinforced concrete (HFRC) slabs and steel girders. It was found that the fibers could improve the fatigue life, capacity and initial stiffness of through-bolt shear connector. While the bolt-hole clearance reduced, the initial stiffness, capacity and slippage of through-bolt shear connector increased. After the steel-concrete interface properties were improved, the initial stiffness increased, and the capacity and slippage reduced. Base on the test results, the equation of the load-slip curve and capacity of through-bolt shear connector with prefabricated HFRC slab were obtained by the regression of test results, and the allowable range of shear force under fatigue load was recommended, which could provide the reference in the design of through-bolt shear connector with prefabricated HFRC slabs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.497-502
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• 2013

In this study, the interlaminar fracture toughness in mode I of a hybrid composite inserted with different types of non-woven tissues was determined. The interlaminar fracture toughness in mode I is obtained by a double cantilever beam test. The experiment is performed using three types of non-woven tissues: 8 $g/m^2$ of carbon tissue, 10 $g/m^2$ of glass tissue, and 8 $g/m^2$ of polyester tissue. Considering a specimen with no non-woven tissue as a reference, the interlaminar fracture toughness in mode I of specimens inserted with non-woven carbon and glass tissues decreases by as much as 6.3% and 11.4%, respectively. However, the fracture toughness of a hybrid composite specimen inserted with non-woven polyester tissue increases by as much as 69.4%. It is considered that the specimen inserted with non-woven polyester tissue becomes cheaper, and lighter, and the value of the fracture toughness becomes much greater than that of the non-woven carbon tissue.

• Advanced Composite Materials
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• v.17 no.1
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• pp.25-40
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• 2008

The research and development in soundproof materials for preventing noise have attracted great attention due to their social impact. Noise insulation materials are especially important in the field of soundproofing. Since the insulation ability of most materials follows a mass rule, the heavy weight materials like concrete, lead and steel board are mainly used in the current noise insulation materials. To overcome some weak points in these materials, fiber reinforced composite materials with lightweight and other high performance characteristics are now being used. In this paper, innovative insulation sheet materials with carbon and/or glass fabrics and nano-silica hybrid PU resin are developed. The parameters related to sound performance, such as materials and fabric texture in base fabric, hybrid method of resin, size of silica particle and so on, are investigated. At the same time, the wave analysis code (PZFlex) is used to simulate some of experimental results. As a result, it is found that both bundle density and fabric texture in the base fabrics play an important role on the soundproof performance. Compared with the effect of base fabrics, the transmission loss in sheet materials increased more than 10 dB even though the thickness of the sample was only about 0.7 mm. The results show different values of transmission loss factor when the diameters of silica particles in coating materials changed. It is understood that the effect of the soundproof performance is different due to the change of hybrid method and the size of silica particles. Fillers occupying appropriate positions and with optimum size may achieve a better effect in soundproof performance. The effect of the particle content on the soundproof performance is confirmed, but there is a limit for the addition of the fillers. The optimization of silica content for the improvement of the sound insulation effect is important. It is observed that nano-particles will have better effect on the high soundproof performance. The sound insulation effect has been understood through a comparison between the experimental and analytical results. It is confirmed that the time-domain finite wave analysis (PZFlex) is effective for the prediction and design of soundproof performance materials. Both experimental and analytical results indicate that the developed materials have advantages in lightweight, flexibility, other mechanical properties and excellent soundproof performance.

• Korean Journal of Optics and Photonics
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• v.34 no.1
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• pp.1-12
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• 2023

In this study, we propose a hybrid phase-control algorithm for multi-channel coherent beam combining (CBC) system by combining the covariant matrix adaption evolution strategy (CMA-ES) and stochastic parallel gradient descent (SPGD) algorithms and analyze its operational performance. The proposed hybrid CMA-ES/SPGD algorithm is a sequential process which initially runs the CMA-ES algorithm until the combined final output intensity reaches a preset interim value, and then switches to running the SPGD algorithm to the end of the whole process. For ideal 7-channel and 19-channel all-fiber-based CBC systems, we have found that the mean convergence time can be reduced by about 10% in comparison with the case when the SPGD algorithm is implemented alone. Furthermore, we analyzed a more realistic situation in which some additional phase noise was introduced in the same CBC system. As a result, it is shown that the proposed algorithm reduces the mean convergence time by about 17% for a 7-channel CBC system and 16-27% for a 19-channel system compared to the existing SPGD alone algorithm. We expect that for implementing a CBC system in a real outdoor environment where phase noise cannot be ignored, the hybrid CMA-ES/SPGD algorithm proposed in this study will be exploited very usefully.

• Journal of agriculture & life science
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• v.44 no.5
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• pp.1-8
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• 2010

In this study, eco-friendly hybrid composite boards were manufactured from green tea and wood fibers for application as interior materials with various functionalities of green tea and strong strength properties of wood fibers. In this relation, the effect of green tea content on the static bending strength performances of these green tea and wood fibers composite boards were investigated. Static bending strengths of hybrid composite boards were lower than those of control boards and decreased with the increase of green tea content. Also, the strength performances appeared to be somewhat different by resin type used for board manufacture. The hybrid composite boards manufactured from $E_1$ grade urea resin adhesive, which has higher molar ratio of formaldehyde to urea than that of $E_0$ grade one, were 1.08~1.53 times higher in bending modulus of elasticity (MOE) and 1.19~1.82 higher in modulus of rupture (MOR) than that manufactured from $E_0$ grade. And, the differences of MOE and MOR between hybrid composite boards manufactured from $E_0$ grade and $E_0$ grade urea resin adhesive increased with the increase of green tea content. In the case of hybrid composite boards manufactured from $E_1$ grade urea resin adhesive, the MOR was within 0.94~1.03 times the commercial medium density fiberboard. Thus, it was thought that eco-friendly hybrid composite boards with various functionalities and strong strength performances could be manufactured from green tea and wood fibers.

• Journal of The Korean Society of Grassland and Forage Science
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• v.39 no.2
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• pp.53-60
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• 2019

This study was carried out from 2015 to 2016 to identify the suitable sowing and harvesting dates of summer crops in the mountain of Yeongnam, South Korea. The experimental design consisted of the different sowing and harvesting dates as follows: corn hybrid (Z. mays, Kwangpyeongok) of sowing (May 8, 19, and 27) and harvesting (August 10, 20, and 30); sorghum${\times}$sorghum hybrid (Sorghum bicolor ${\times}$ Sorghum bicolor, SS405) of sowing (May 27, June 19 and June 27) and harvesting (August 10, 20, and 30). In corn hybrid, ear rate and dry matter (DM) yield decreased (p<0.05) with the postponement of sowing date. Otherwise, ear rate and DM yield increased (p<0.05) with the postponement of harvesting date. Crude protein content decreased (p<0.05) with the postponement of sowing date, but neutral detergent fiber content increased (p<0.05). In sorghum${\times}$sorghum hybrid, plant length and DM yield with the postponement of harvesting date increased (p<0.05), while crude protein content with the postponement of harvesting date decreased (p<0.05). This study concluded that sowing corn hybrid in early May and sorghum${\times}$sorghum hybrid in early June then harvest in the middle of August was recommend to increase dry matter yield and feed value.

• Journal of The Korean Society of Grassland and Forage Science
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• v.11 no.2
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• pp.121-128
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• 1991

Forage productivity of two sorghum hybrids, Pioneer(P) 931 and P 956 and a sorghum-sudangrass hybrid, P 988, was studied. The 1st-cut of sorghun hybrids was made for silage 6 times from heading stage at a week-interval and regrowth (2nd-cut) was harvested on Oct. 13 although plants were not reached the same growth stage of 1st-cut. However, the 1st- and 2nd-cut of sorghum-sudangrass were made for green fodder 6 times from 4 weeks before heading stage at a week-interval. 1. Percent dry matter(DM) of 1st-cut of sorghum and 1st- and 2nd-cut of sorghum-sudangrass increased as growth stage advanced. Percent DM of 2nd-cut of sorghum decreased as the 1st-cut date delayed due to insufficient growing period on Oct. 13. 2. In the 1st-cut of sorghum the proportion of leaf blade (LB) or culm+leaf sheath (LS) to total DM decreased, but that of panicle increased as growth stage advanced. The panicle proportion of P 956 increased and culm+LS decreased more rapidly compared with those of P 931. IIowever, in sorghum-sudangrass hybrid the proportion of LB decreased and culmf LS increased as growth stage advanced through heading stage. 3. In the 1st-cut of sorghum hybrids crude(C) protein and C. fiber decreased, but nitrogen free extract (NFE) increased as growth stage advanced although C. fat and C. ash were similar among the growth stages. In the 2nd-cut of sorghum C. protein and C. ash increased, but NFE decreased as harvesting date delayed due to plants were younger although C. fat and C. fiber were similar among the harvesting dates. In the sorghum-sudangrass C. protein of 1st-cut decreased, but C. fiber of 1st-cut and NFE of the 1st-and 2nd-cut increased as growth stage advanced. 4. DM yield of 1st-cut of sorghum increased from heading stage to 3 weeks after heading and then levelled off, but total DM including regrowth was similar among the harvesting time. In the sorghum-sudangrass hybrid DM yield of 1st-cut and total DM yield including 2nd-and 3rd-cut increased as the harvestingtime delayed.