• Journal of the Korean Society for Heat Treatment
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• v.30 no.6
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• pp.279-284
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• 2017

Mechanical properties of titanium alloy can be improved by controlling microstructure through heat treatment. In this study, Ti-3Al-8V-6Cr-4Mo-4Zr metastable beta titanium alloy, was controlled for excellent mechanical property and sound formability through various high temperature heat treatment and aging conditions and the optimum heat treatment conditions were determined. The specimens were heat-treated at $950^{\circ}C$, followed by various aging treatments from $430^{\circ}C$ to $500^{\circ}C$ for 1 to 24 h. As aging temperature and holding time increased, hardness increased by ${\beta}^{\prime}$ phase formation and precipitation of secondary ${\alpha}$ phase in ${\beta}$ matrix. However, the optimum aging temperature and holding time for mechanical properties were at $450{\sim}470^{\circ}C$ for 8~16 hr. Hardness values of the specimen aged at $450^{\circ}C$ for 8 h were found to be the highest. These results can be effectively applied to fabrication of spring with better formability and mechanical property.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.121-121
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• 2011

Thanks to KMTNet's wide field of view, it is time to implement imaging survey of extensive area of clusters of galaxies in the southern sky with modern instrument. As part of potential long-term survey of nearby (D < 50 Mpc) well-known clusters of galaxies, we propose a wide-field and deep survey of Fornax cluster as a first step of the project. By imaging the 400 square deg region (100 fields) enclosed within the five times virial radius of the Fornax cluster, in three SDSSfilters(g', r', i'), we can provide an unprecedented view of structure of Fornax cluster using sample from giant to dwarf galaxies. We will secure galaxies with brightness comparable to the limiting magnitude (r'=23.1 AB mag) of SDSS. Furthermore, we also request extremely deep (limiting surface brightness of ~ 28 mag $arcsec^{-2}$forr'band) survey for the central region (16 square degree, i.e., four fields) of Fornax cluster. This will allow us to detect the diffuse intracluster light (ICL) that permeates clusters as a valuable tool for studying the hierarchical nature of cluster assembly. In order to complete whole survey, about 285 hr observing time (without overhead) is required. By combining data available at other wavelengths, it will offer unique constraints on the formation of large-scale structure and also provide important clues for theories of galaxy formation and evolution. Our proposed survey will be implemented in the close collaboration with researchers in various countries (Germany, Australia, UK, USA) and ongoing project (e.g., SkyMapper).

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.76.1-76.1
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• 2011

We present ultraviolet (UV) photometric properties of galaxies in two clusters, the Fornax and Virgo, with different dynamical conditions. We construct UV color-magnitude relations (CMRs) of galaxies in the Fornax and Virgo clusters using GALEX UV data matching with optical B band data. Elliptical and lenticular galaxies locate on red sequence in UV CMRs and show UV upturn phenomenon in both clusters. While dwarf lenticular galaxies (dS0s) in the Fornax also follow the extension of red sequence of giant early type galaxies, they are redder than dS0s in the Virgo at a given magnitude. We also investigated the effect of neighbor galaxies and cluster environment to the UV properties. In the space of projected clustercentric radius and projected nearest neighbor galaxy distance, we found that red (NUV-B>3) galaxy fraction of the Fornax depends entirely on clustercentric radius. However, in the case of Virgo, galaxy colors are also affected by interactions between galaxies outside the cluster virial radius. We suggest that UV properties of early-type galaxies in the Fornax cluster is likely consistent with its dynamically evolved system compared to the Virgo cluster.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.69.1-69.1
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• 2011

While the Virgo Cluster Catalog (VCC) is well established catalog from deep photographic plate survey, with available survey data recently released (e.g., SDSS), it can be further updated concerning the membership and morphology of galaxies. While membership and morphology of galaxies included in the VCC are based on the single band imaging data, thanks to the multi-color imaging and spectroscopic observations of SDSS, we are able to revise the membership and morphology of sample galaxies in the fields of the Virgo cluster. We present a new catalog of galaxies in the Virgo cluster using SDSS DR7 data, the extended Virgo cluster catalog. Using SDSS imaging and spectroscopic data, we introduce two kinds of galaxy classifications which are complementary each other. In addition to traditional morphological classification by visual inspection of the images ("Primary Classification"), we also attempt to classify galaxies with the spectroscopic features ("Secondary Classification"). The primary classification is basically based on the scheme of galaxy morphological classification of VCC. The secondary classification relies on the SED shape and presence of emission/absorption lines returned from SDSS. Our morphological classifications allow to study the evolution and associated star formation histories of galaxies in the Virgo cluster.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.39-39
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• 2013

We present a study of correlations between the elemental abundances and galaxy morphologies of 91 blue compact galaxies (BCGs) at z=0.20-0.35 with Sloan Digital Sky Survey (SDSS) DR7 data. We classify the morphologies of the galaxies as either 'disturbed' or 'undisturbed', by visual inspection of the SDSS images, and using the Gini coefficient and M20. We derive oxygen and nitrogen abundances using the Te method. We find that a substantial fraction of BCGs with disturbed morphologies, indicative of merger remnants, show relatively high N/O and low O/H abundance ratios. The majority of the disturbed BCGs exhibit higher N/O values at a given O/H value compared to the morphologically undisturbed galaxies, implying more efficient nitrogen enrichment in disturbed BCGs. We detect Wolf-Rayet (WR) features in only a handful of the disturbed BCGs, which appears to contradict the idea that WR stars are responsible for high nitrogen abundance. Combining these results with Galaxy Evolution Explorer (GALEX) GR6 ultraviolet (UV) data, we find that the majority of the disturbed BCGs show systematically lower values of the $H{\alpha}$ to near-UV star formation rate ratio. The equivalent width of the $H{\beta}$ emission line is also systematically lower in the disturbed BCGs. Based on these results, we infer that disturbed BCGs have undergone star formation over relatively longer time scales, resulting in a more continuous enrichment of nitrogen. We suggest that this correlation between morphology and chemical abundances in BCGs is due to a difference in their recent star formation histories.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.8
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• pp.541-550
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• 2022

An effective real time fault diagnosis approach for UAV engine is drawn from IMM filter and GLRT methods. For this purpose based on the linear diagnosis model derived from engine dynamic performance analysis the Kalman filter for residual estimation and each method are applied to the fault diagosis of the actuator for engine control sensors. From the process of the IMM filter application the effective FDI measure is obtained and the state responses due to actuator fault are estimated. Likewise from the GLRT method the fault magnitudes of actuator and sensors are estimated associated with some FDI functionings. The numerical simulations verify the effectiveness of the IMM filter for FDI and the GLRT in estimating the fault magnitudes of each fault mode.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.51-60
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• 2023

This study is to verify the moderating effect of residential selection on the relationship between marriage and childbirth. According to the analysis results, interactions of first marriage with the financial capacity of local governments for public services, residential stability, the scale of the region, and local economic situation have a moderating effect on childbirth. Interactions of remarriage and marriage with foreigners with the financial capacity of local governments for public services, residential stability, and the scale of the region have a moderating effect on childbirth. These results indicate that when married couples choose to reside in small and medium-sized cities or large cities rather than rural areas, it can more positively affect their intention to have children. While there may be a logical argument against advocating for regional integration based on the moderating effect of residential selection on the relationship between marriage and childbirth, the analysis results of this study and the phenomenon of married couples avoiding rural areas can contribute to raising the need for regional integration.

• Journal of Korean Home Economics Education Association
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• v.25 no.2
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• pp.1-19
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• 2013

The purpose of this study was to develope and implement a project teaching learning process plan in order to improve a creativity and character for 'residential space utilization' section of Technology Home Economics in middle school. The teaching learning process plan consisting of 15-session lessons had been developed and implemented according to the ADDIE model mixed with 6 project learning steps. In the development stage, 8 activity materials(7 individual and 1 group activity sheets) and 7 teaching learning materials(2 sets of pictures & photos, 4 moving pictures and 1 space plan resources book) were developed for the 15-session lessons. The plans applied to 5 classes 163 students in the second grade of G middle school in Gwangju during Oct. 17th to 18th of Nov. 2011. The results from the survey and portfolio showed that the 15-session lessons had overall achieved the general goal of the project teaching learning process plan to improve a creativity and character. Students were stimulated by individual and group activities with creativity and character elements in the class. The students evaluated the whole process of 15 lessons were interesting and helpful to improve creativity and consideration and cooperation of aspect of character. The individual and group results of the portfolio were excellently and creatively done with the average of nearly 85% points. The researcher also found the improving process of students in the whole classes. This plan might apply to other parts of housing as well as various other areas of home economics.

• Journal of Life Science
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• v.23 no.5
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• pp.643-649
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• 2013

In this study, we examined the antioxidative activities of ethanol extracts obtained from three plants; Lithospermum erythrorhizon Siebold & Zucc., Xanthium strumarium Linn, and Lonicera japonica, which have traditionally been used as drugs in Eastern medicine in Korea. Their extraction yields were 7.01%, 2.92%, and 7.95% in Lithospermum erythrorhizon Siebold & Zucc., Xanthium strumarium L, and Lonicera japonica, respectively. The contents of the phenolic compounds were $4.3{\pm}0.1{\mu}g/ml$, $5.4{\pm}0.1{\mu}g/ml$, and $4.6{\pm}0.1{\mu}g/ml$ in Lithospermum erythrorhizon Siebold & Zucc., and Xanthium strumarium L, respectively. Furthermore, the radical scavenging activity measured through the DPPH assay appeared highest in the Lonicera japonica's extract, and its $EC_{50}$ was 0.24 mg/ml. Compared to the control, the xanthine oxidase inhibiting activities of all extracts were effective at 0.01 mg/ml concentration. Superoxide radical scavenging activity in Lithospermum erythrorhizon Siebold & Zucc. and Lonicera japonica was more than 80%, with a concentration of 50 mg/ml. OH radical scavenging activity was 40% in the three plants, with a concentration of 50 mg/ml scavenging activity. From our results, we demonstrated that the ethanol extracts of three medicinal plants have antioxidant activities and could be potential candidates for natural antioxidants.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.744-756
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• 2002

The transient acoustic fields formed by a 3.5 ㎒ curved linear array transducer which is commonly used in ultrasonic medical imaging system for diagnosis of abdomen are systematically analyzed to obtain new design parameters for the better acoustic image. In the analysis with an assumption of radiating waveform, element size, radius of curvature, amplitude apodization are considered as parameters giving constitutive relations with the fields. As simulation results, appropriate new parameters with the reduced curvature and elevation aperture and the apodization of Hamming window, which make an improved acoustic beam with lower side lobe levels than a conventional typical transducer, are obtained.