• 천문학회보
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• 제44권1호
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• pp.58.2-58.2
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• 2019

Recent observation of the neutron star merger event, GW170817, through both gravitational wave (GW) and electromagnetic wave (EM) observations opened a new way of exploring the universe, namely, multi-messenger astronomy (MMA). One of the keys to the success of MMA is a rapid identification of EM counterpart through optical/NIR observations. We will present the strategy for prioritization of GW source host galaxy candidates to be observed with narrow-field optical telescopes. Our method relies on recent simulation results regarding plausible properties of GW source host galaxies and the low latency localization map from LIGO/Virgo. We will show the test results for both NS merger and BH merger events using previous events and possible future events and describe observing strategy with our facilities for GW events during the ongoing LIGO/Virgo O3 run.

• 천문학회보
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• 제44권2호
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• pp.76.2-76.2
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• 2019

Recent observation of the neutron star merger event, GW170817, through both gravitational wave (GW) and electromagnetic wave (EM) observations opened a new way of exploring the universe, namely, multi-messenger astronomy (MMA). One of the keys to the success of MMA is a rapid identification of EM counterpart. We will introduce the strategy for prioritization of GW source host galaxy candidates. Our method relies on recent simulation results regarding plausible properties of GW source host galaxies and the low latency localization map from LIGO/Virgo. We will show the test results for both NS merger and BH merger events using previous events and describe observing strategy with our facilities for GW events during the ongoing LIGO/Virgo O3 run. Finally, we report the result of follow-up observation on, the first neutron star merger event, S190425z, during LIGO/VIrgo O3 run.

• 소성∙가공
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• 제26권6호
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• pp.365-371
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• 2017

During sling wear of a ferrous metal, a surface layer is formed. Its microstructure, constituting phases, and mechanical property are different from those of the original wearing material. Since wear occurs at the layer, it is important to characterize the layer and understand how wear rate changes with different layers. Various layers are formed depending on external wear conditions such as load, sliding speed, counterpart material, and environmental conditions. In this research, sliding wear tests of pure iron were carried out against two different counterparts (AISI 52100 bearing steel and $Al_2O_3$) in the air and in an inert Ar gas atmosphere. Pure iron was employed to exclude other effects from secondary phases in steel on the wear. Wear tests were performed at room temperature. Worn surfaces, wear debris, and cross-sections were analyzed after the test. It was found that these two different counterparts and environments produced diverse layers, resulting in significant changes in wear rate. Against the bearing steel, pure iron showed higher wear rate in an Ar atmosphere due to severe adhesion than that in the air. On the contrary, the iron showed much higher wear rate in the air against $Al_2O_3$. Different layers and wear rates were analyzed and discussed by oxidation, severe plastic deformation, and adhesion at wearing surfaces.

• 대한음성학회지:말소리
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• 제63호
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• pp.47-66
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• 2007

This study aims at exploring the degree of phonetic similarity between Korean and Japanese vowels in terms of acoustic features by performing the speech production test on Korean speakers and Japanese speakers. For this purpose, the speech of 16 Japanese speakers for Japanese speech data, and the speech of 16 Korean speakers for Korean speech data were utilized. The findings in assessing the degree of the similarity of the 7 nearest equivalents of the Korean and Japanese vowels are as follows: First, Korean /i/ and /e/ turned out to display no significant differences in terms of F1 and F2 with their counterparts, Japanese /i/ and /e/, and the distribution of F1 and F2 of Korean /i/ and /e/ in the distributional map completely overlapped with Japanese /i/ and /e/. Accordingly, Korean /i/ and /e/ were believed to be "identical." Second, Korean /a/, /o/, and /i/ displayed a significant difference in either F1 or F2, but showed a great similarity in distribution of F1 and F2 with Japanese /a/, /o/, and /m/ respectively. Korean /a/ /o/, and /i/, therefore, were categorized as very similar to Japanese vowels. Third, Korean /u/, which has the counterpart /m/ in Japanese, showed a significant difference in both F1 and F2, and only half of the distribution overlapped. Thus, Korean /u/ was analyzed as being a moderately similar vowel to Japanese vowels. Fourth, Korean /${\wedge}$/ did not have a close counterpart in Japanese, and was classified as "the least similar vowel."

• Structural Engineering and Mechanics
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• 제63권3호
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• pp.385-400
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• 2017

This paper presents an experimental study on the behavior of axially-loaded steel RHS (rectangular hollow section) compression members that are partially reinforced along their lengths with welded steel plates. 28 slender column tests were carried out to investigate the effects of the slenderness ratio of the unreinforced member and the ratio of the reinforced length of the member to its entire length. In addition to the slender column tests, 14 stub-column tests were conducted to determine the basic mechanical properties of the test specimens under uniform compression. Test results show that both the compressive strength and stiffness of an RHS member can be increased significantly compared to its unreinforced counterpart even when only the central quarter of the member is reinforced. Based on the limited test data, it can be concluded that partial reinforcement is, in general, more effective in members with larger slenderness ratios. A simple design expression is also proposed to predict the compressive strength of RHS columns partially reinforced along their length with welded steel plates by modifying the provisions of AISC 360-10 to account for the partial reinforcement.

• 대한가정학회지
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• 제38권10호
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• pp.181-197
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• 2000

The purposes of this study were to compare financial status of home-based family business with that of ensile family business, and to analyze the factors effected on financial status of both business groups. The sample consisted of 295 home-based family business and 418 ensile family business among self-employed household of 1998 Korea Household Panel Data, and analyzed into Frequencies, Percentile, t-test, $\chi$$^2$-test and Regression. The findings were as follows: First, in case of financial status of household, there was no significant difference between home-based family business and ensile family business. Second, in case of financial status of business, total sales amount and net profit of home-based family business were lower than those of onsite family business, however net profit to total sales ratio of home-based family business was higher than those of onsite family business. Third, the factors contributing to total expenditure to total income ratio of home-based family business were business owner's present economic perception, future economic expectancy and residence, while business owner's age, the number of children and of tamer, and residence were significant variables contributing to same ratio of onsite family business. The factors contributing to total asset to total debt ratio of home-based family business was only business owner's future economic expectancy, however factors affected on the counterpart were business owler's future economic expectancy and job type of family business. Fourth, the variables of sex, age, educational level of family business owner, job type and family type of family business were associated with net profit to total sales ratio of home-based family business, and sex, educational level of family business owner, job type of family business, and the number of employees were related to same ratio of the counterpart. In addition, educational level of family business owner, job type and residence were related with total sales to the number of employees ratio of home-based family business, and educational level of family business owner and job tape of family business were related to same ratio of ensile family business.

• Computers and Concrete
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• 제31권6호
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• pp.513-525
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• 2023

This research presents the experimental and theoretical evaluations on circular steel-fiber-reinforced-concrete (SFRC) columns reinforced by glass-fiber-reinforced-polymer (GFRP) rebar under the axial compressive loading. Test programs were designed to investigate and compare the effect of different parameters on the structural behavior of columns by performing tests. Theses variables included conventional concrete (CC), fiber concrete (FC), steel/GFRP longitudinal rebars, and transversal rebars configurations. A total of 16 specimens were constructed and categorized into four groups in terms of different rebar-concrete configurations, including GFRP-rebar-reinforced-CC columns (GRCC), GFRP-rebar-reinforced-FC columns (GRFC), steel-rebar-reinforced-CC columns (SRCC) and steel-rebar- reinforced-FC columns (SRFC). Experimental observations displayed that failure modes and cracking patterns of four groups of columns were similar, especially in pre-peak branches of load-deflection curves. Although the average ultimate axial load of columns with longitudinal GFRP rebars was obtained by 17.9% less than the average ultimate axial load of columns with longitudinal steel rebars, the average axial ductility index (DI) of them was gained by 10.2% higher than their counterpart columns. Adding steel fibers (SFs) into concrete led to the increases of 7.7% and 6.7% of the axial peak load and the DI of columns than their counterpart columns with CC. The volumetric ratio had greater efficiency on peak loads and DIs of columns than the type of transversal reinforcement. A simple analytical equation was proposed to predict the axial compressive capacity of columns by considering the axial involvement of longitudinal GFRP rebars, volumetric ratio, and steel spiral/hoop rebar. There was a good correlation between test results and predictions of the proposed equation.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2005년도 학술발표회 논문집
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• pp.203-210
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• 2005

This paper summarizes full-scale test results on CFT column to flat plate connections subjected to gravity loading. CFT construction has gained wide acceptance in a relatively short time in domestic building practice due to its various structural and construction advantages. Constructing the floor as flat plate is often regarded as being essential for both cost savings and rapid construction. However, efficient details for CFT column to flat plate connections have not been proposed yet, and their development is urgently needed. Based on some strategies that include maximizing economical field construction, several connecting schemes were proposed and tested in this study. Test results showed the proposed connection details can exhibit strength and stiffness comparable to or greater than those of R/C flat plate counterpart.

• Steel and Composite Structures
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• 제24권4호
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• pp.455-465
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• 2017

This paper presents a series of ultimate and fatigue experimental investigation on concrete-filled rectangular hollow section (CRHS) X joints with Perfobond Leister rib (PBR) under tension. A total of 15 specimens were fabricated, in which 12 specimens were tested under ultimate tension and 3 specimens were investigated in fatigue test. Different parameters including PBR stiffening, brace-to-chord ratio (${\beta}$) and inclined angle (${\theta}$) were considered in the test. Each joint was tested to failure under tension load. Obtained from test result, PBR was found to improve the tension strength and fatigue durability of CRHS joint substantially. Concrete dowel consisted by PBR and concrete inside the chord stiffened the joint, which leaded to a combination failure mode of punching shear and chord plastification of CRHS joint under tension. Finite element analysis validated the compound failure mode. Stress concentration on typical spot of CRHS joint was mitigated by PBR which was observed from fatigue test. Initial fatigue crack presented in CRHS joint with PBR also differentiated with the counterpart without PBR.

• 대한기계학회논문집A
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• 제37권5호
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• pp.625-630
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• 2013

본 연구는 직경 45 nm인 원통형 나노동공을 가진 산화알루미늄(AAO) 박막에 오일을 함침시켰을때 동점도가 마찰 마멸에 미치는 영향을 규명하고자 실시하였다. 양극산화법으로 제조한 AAO 박막을 직경 1 mm의 440C 스테인리스 강구를 상대재로 하여 왕복동 미끄럼 접촉시험을 실시하였다. 마찰면과 마멸입자는 주사전자현미경과 에닥스(Energy-dispersive X-ray)를 이용해 분석하였다. 높은 동점도 오일의 윤활효과가 저점도 오일에 비해 크게 향상되었다. 동점도가 낮은 경우엔 모든 하중조건에서 심한 마찰흔적과 함께 두꺼운 소성변형층이 넓게 형성되었으며 경계윤활막의 손상으로 접촉면에 물질전이와 화학적 반응 현상이 모두 발생하였다. 오일의 점도가 높은 경우 마찰면에 존재하는 경계윤활막이 파괴되지 않아 마찰흔적과 소성변형층의 형성이 매우 적었으며 물질전이와 화학적 반응이 방지되었다.