• Journal of The Korean Astronomical Society
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• v.56 no.1
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• pp.59-73
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• 2023

The second generation of stars in the globular clusters (GCs) of the Milky Way (MW) exhibit unusually high N, Na, or Al, compared to typical Galactic halo stars at similar metallicities. The halo field stars enhanced with such elements are believed to have originated in disrupted GCs or escaped from existing GCs. We identify such stars in the metallicity range -3.0 < [Fe/H] < 0.0 from a sample of ~36,800 giant stars observed in the Sloan Digital Sky Survey and Large Sky Area Multi-Object Fiber Spectroscopic Telescope survey, and present their dynamical properties. The N-rich population (NRP) and N-normal population (NNP) among our giant sample do not exhibit similarities in either in their metallicity distribution function (MDF) or dynamical properties. We find that, even though the MDF of the NRP looks similar to that of the MW's GCs in the range of [Fe/H] < -1.0, our analysis of the dynamical properties does not indicate similarities between them in the same metallicity range, implying that the escaped members from existing GCs may account for a small fraction of our N-rich stars, or the orbits of the present GCs have been altered by the dynamical friction of the MW. We also find a significant increase in the fraction of N-rich stars in the halo field in the very metal-poor (VMP; [Fe/H] < -2.0) regime, comprising up to ~20% of the fraction of the N-rich stars below [Fe/H] = -2.5, hinting that partially or fully destroyed VMP GCs may have in some degree contributed to the Galactic halo. A more detailed dynamical analysis of the NRP reveals that our sample of N-rich stars do not share a single common origin. Although a substantial fraction of the N-rich stars seem to originate from the GCs formed in situ, more than 60% of them are not associated with those of typical Galactic populations, but probably have extragalactic origins associated with Gaia Sausage/Enceladus, Sequoia, and Sagittarius dwarf galaxies, as well as with presently unrecognized progenitors.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.56.2-56.2
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• 2016

We present chemical abundances for about 800 red giant stars in Omega Centauri, based on medium-resolution spectra obtained using Hydra multi-fiber spectrograph at the CTIO 4-m telescope. Our sample covers 14.2 < V < 15.0, and is almost unbiased against colors (and therefore metallicity). The metallicity distribution function (MDF) constructed from our data has an overall shape and local peaks that approximately match those for brighter giant stars in Johnson et al.. We also find that more metal-rich cluster members are more concentrated in the cluster center, which is consistent with previous studies. On the other hand, we find no clear evidence for such a spatial dependence with respect to alpha elemental abundance ([${\alpha}/Fe$]).

• Journal of the Korean Wood Science and Technology
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• v.40 no.6
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• pp.406-417
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• 2012

In this study, eco-friendly hybrid composite boards were manufactured from green tea, three kinds of charcoals and wood fiber for developing interior materials to reinforce the functionalities such as the deodorization and the absorbability on the green tea-wood fiber hybrid boards in the previous researches. The effects of kind of raw materials and the component ratio of raw materials on dimensional stability, deodorization and emission of formaldehyde were investigated. Thickness swelling of the hybrid composite boards increased with increasing of component ratio of green tea and charcoals, but the values were markedly lower than that of Korean standard (KS) for commercial medium density fiber board (MDF), except for hybrid composite boards composed of greed tea, activated charcoal and wood fiber. Reduction rate of ammonia gas for the hybrid composite boards composed of green tea, activated charcoal and wood fiber showed a high value of 96% after 30 minute from the beginning of the test, and the other hybrid boards also showed a high value of about 95% after one hour. Emission amount of formaldehyde was similar to that of $E_0$ grade in case of using $E_1$ grade urea resin, and was similar to that of super $E_0$ grade in case of using $E_0$ grade urea resin.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.4
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• pp.1-7
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• 2012

The increase of OCC solid content after wet pressing will save drying energy greatly. We applied spacers, which used to increase draining rate and bulk in fiber furnishes, to increase the OCC solid contents. MDF fibers (fibers for making medium density fiberboard) and diatomaceous earth were used as spacers, and added 10% by weight to the OCC fiber furnish. Application of high wet pressing pressure to the mixed furnish of spacers and refined OCC did not deteriorate bulk and drainage rate, but their solid contents were increased to 0.5-1.5% without loss of compressive strength when compared to those of unrefined OCC, which is the furnish normally used for mill commercial practice. It is believed that the spacers caused the rate of solid content increase faster in the mixed furnish with OCC at high wet pressing pressure area than the unrefined OCC furnish did. Little amount of starch addition (0.5%) to the spacers helped to keep the strength properties.

• Journal of agriculture & life science
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• v.45 no.6
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• pp.41-46
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• 2011

In this study, in addition to the green tea-wood fiber hybrid composite boards of previous researches, to make effective use of saw dust of domestic cypress tree with functionalities and application as interior materials, eco-friendly hybrid composite boards were manufactured from wood fiber, green tea and saw dust of cypress tree. We investigated the effect of the component ratio of saw dust and green tea on static bending strength performances. Static bending MOE (modulus of elasticity) was within 0.956~1.18GPa, and showed the highest value in wood fiber : green tea : saw dust = 50 : 40 : 10 of the component ratio, and had the lowest value in 50 : 30 : 20 of component ratio. These values were 2.0~3.1times lower than those of green tea-wood fiber hybrid composite boards reported in the previous researches. The bending MOR (modulus of rupture) showed 8.99~11.5MPa, the change of the bending MOR with component ratio of the factors was the same as that of bending MOE. These values had 1.9~3.5 times lower value than those of green tea-wood fiber hybrid composite boards, and showed the slightly lower values than the MOR of particle boards (PB) and medium density fiberboards (MDF) prescribed in Korean Industrial Standard. Therefore, it is considered that these hybrid composite boards need to improve strength performances by component ratio change, hybrid composite with other materials and adhesive change etc. in order to industrialize the hybrid composite boards.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.8 no.1
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• pp.23-29
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• 2010

Purpose : This study is to offer clinical primary data that examines the change of imaging structure and the quantitative evaluation of muscle activity on myofascial trigger points. This study examines neuromuscular physiological characteristic by comparing the differences in physical findings, pressure pain threshold, imaging, and electrophysiological characteristics in latent and active myofascial trigger points muscle and normal muscle through the following experimental procedures. Methods : The participants for the study were thirty-three adults in their twenties. We divided three groups into normal, latent and active myofascial trigger points groups by physical findings. We analyzed the results of measured pressure pain, threshold for pain, ultrasound imaging perform for structure characteristic of muscle, surface EMG according to type of muscle contraction for function of muscle contraction. Results : Significant differences were indicated in pressure pain threshold (p<0.05). Significant differences were discovered in the ultrasound imaging analysis. There were increases in muscle Echogenicity white area index (p<0.001). There were significant differences that decrease in %MVIC (p<0.05), increase in MDF (p<0.05). Conclusion : From these results, active rnyotascial trigger points muscle showed quality deterioration on ultrasound imaging and decreased function of muscle contraction, increased motor unit action potential of II type fiber, and electrophysiologically. Imaging structure and neuromuscular physiological characteristic can be diagnostic and quantitative analytical techniques for myofascial pain syndrome and a primary factor that reflected in physical therapy intervention.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.6
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• pp.616-623
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• 2010

Recently, interests in indoor air quality (IAQ) have been increased; however, a number of researchers have mainly focused on anthropogenic volatile organic compounds (AVOC) emitted from building materials. Therefore, the properties of natural VOC (NVOC) and anthropogenic VOC (AVOC) emitted from wood-based panels was investigated in this work. VOCs emitted from these panels were sampled through Tenax TA/Cabotrap and analyzed by GC-MS and GC-FID. Comparisons were made concerning TVOC, NVOC, and composition ratios of NVOC. It was revealed that TVOC emission rates of midium density fiber (MDF) were the highest. Besides, it was found that emissions of NVOC from wood-based panels were much higher than those of anthropogenic AVOC except for plywood of Oceania timber. It was also observed that the composition ratio of NVOC emitted from plywood of Pinus radiata was the highest as 65% of TVOC. Major NVOC components were monoterpene compounds such as $\alpha$-pinene, $\beta$-pinene, d-limonene, camphene and $\alpha$-terpinene. It was concluded that the composition rates of VOCs emitted from building materials were clearly different according to the raw materials and manufacturing methods.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.11
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• pp.1102-1110
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• 2008

This research was performed to analyze the characteristics of wood wastes from origin and to suggest grade-classification for them. Korean proximate analysis was conducted, and heating value, heavy metals and Cl concentrations were analyzed for gradeclassification. Wood wastes were sampled from forest, living, construction and demolition, and industrial areas with origin. Moisture content of most wood wastes was ranged in 5$\sim$10%. VS (volatile solids) and ash contents of them showed > 95% and < 5%, respectively. Most wood wastes except wood for growing mushroom permitted the standard (low heating value $\geq$ 3,500 kcal/kg) for refusederived fuel. CCA (Cr, Cu, As) concentration of wood wastes used in bench, wasted fishing boat, and railroad crosstie was higher than that of the other ones. Cl content showed approximately 1.3% in wood box for fish and $\leq$ 0.2% in the other wood wastes. Cl content of all wood wasted used in this research permitted the standard (Cl $\leq$ 0.2%, dry weight basis) for refuse-derived fuel. If the wood wastes were classified in 3-grade, plywoods would be in 2nd grade, and MDF (medium density fiber), wooden bench, painted electric wire drum, wasted fishing boat, and railroad crosstie be in 3rd grade.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.781-789
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• 2009

The absorption coefficients of the materials used in a 1:50 scale model multipurpose hall were measured based on ISO 354 and related laws. The shape and materials for the scale model were evaluated based on reflective surfaces, variable acoustic elements and sound-absorbing quality (125Hz-1kHz average) of seats. The measured average absorption coefficients of audience seats, audience and orchestra were 0.64, 0.74 and 0,45, respectively, which were simulated with the combination of wood, absorption materials and foam board. Various mounting methods for absorption curtain and banner were considered according to the installation methods. The average absorption coefficient was measured as 0.42, 0.47 and 0.45 in the conditions of Type A mounting, E mounting with 0.9 m backing air cavity, and Type G mounting which is suspended at the ceiling, respectively. It was confirmed that the absorption coefficient was increased at low frequency by backing air gap. The finishing material of stage house was an absorption material covered with thin fabric, which aimed average absorption coefficient of 0.68 by using fiber glass board. Each part of the real materials was compared with those of 1:50 scale model and it was found that the absorption characteristics of both cases were similar.

• 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.