• Journal of applied mathematics & informatics
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• 제13권1_2호
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• pp.393-404
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• 2003

In general, a differential operator can be used as a tool of treating the local properties of given function. However, when the given function is varied with high frequency and has irregular form with non-stationary evolution it may not act its role sufficiently as in case of nowhere differentiable curves. In this paper we introduce a multi-scale derivative as a form of weakened global derivative so that it may explain its semi global diffusion properties as well as local ones for the various irregular diffusion phenomena.

• Animal Systematics, Evolution and Diversity
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• 제24권2호
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• pp.215-218
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• 2008

Two new marine sponges in genus Suberites, S. hataedoensis n. sp and S. waedoensis n. sp have been collected from Hataedo Island and Waedo Island, Korea during 2005-2006. S. hataedoensis n. sp. is similar to S. durissimus in the spicule composition and texture. However, they differ in growth form, skeleton and surface. S. waedoensis n. sp. is similar to S. japonicus in spicule composition and skeleton. However, they differ in growth form, surface and texture.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1887-1892
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• 2005

In the future, a machine-tool will be more improved in the form of a knowledge evolution based device. In order to develop the knowledge evolution based machine-tool, this paper proposes the structure of standard M2M(Machine To Machine) and the scheme of agent communication in environment. The communication agent such as dialogue agent has a role of interfacing with another machine for cooperation. To design of the communication agent module in M2M environment, FIPA(Foundation of Intelligent Physical Agent) and ping agent based on JADE(Java Agent Development Framework) or FIPA-OS(Open Source) are analyzed in this study. Through this, it is expected that the agent communication can be more efficiently designed and the knowledge evolution based machine-tool can be hereafter more easily implemented.

• 천문학회보
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• 제43권1호
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• pp.46.1-46.1
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• 2018

In order to investigate the origin of multiple stellar populations in the halo and bulge of the Milky Way, we have constructed chemical evolution models for the low-mass proto-Galactic subsystems such as globular clusters. Unlike previous studies, we assume that supernova blast waves undergo blowout without expelling the pre-enriched gas, while relatively slow winds of massive stars, together with the winds and ejecta from low and intermediate mass asymptotic-giant-branch stars, are all locally retained in these less massive systems. We find that the observed Na-O anti-correlations in metal-poor GCs can be reproduced when multiple episodes of starbursts are allowed to continue in these subsystems. A specific form of star formation history with decreasing time intervals between the stellar generations, however, is required to obtain this result, which is in good agreement with the parameters obtained from our stellar evolution models for the horizontal-branch. The "mass budget problem" is also much alleviated by our models without ad-hoc assumptions on star formation efficiency and initial mass function. We also applied these models to investigate the origin of super helium-rich red clump stars in the metal-rich bulge as recently suggested by Lee et al. (2015). We find that chemical enrichments by the winds of massive stars can naturally reproduce the required helium enhancement (dY/dZ = 6) for the second-generation stars. Disruption of proto-globular clusters in a hierarchical merging paradigm would have provided helium enhanced stars to the bulge field.

• Korean Journal of Mathematics
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• 제23권3호
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• pp.479-489
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• 2015

We study the GMGHS spacetime to analyze anisotropic cosmology model which represents homogeneous but anisotropically expanding(contracting)cosmology. In this paper we investigate the solution of GMGHS spacetime in form of doubly warped products possessing warping functions and find the Ricci curvature associated with three phases in the evolution of the universe.

• 천문학회지
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• 제53권6호
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• pp.117-123
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• 2020

We investigate the plausibility of mass return, from stellar mass loss processes within the central ~100 pc region of the Milky Way (the inner nuclear bulge), as a mass supply mechanism for the Circumnuclear Disk (CND). Gas in the Galactic disk migrates inward to the Galactic centre due to the asymmetric potential caused by the Galactic bar. The inward migration of gas stops and accumulates to form the central molecular zone (CMZ), at 100-200 pc from the Galactic center. It is commonly assumed that stars have formed in the CMZ throughout the lifetime of the Galaxy and have diffused inward to form a 'r-2 stellar cusp' within the inner nuclear bulge. We propose that the stars migrating inward from the CMZ supply gas to the inner nuclear bulge via stellar mass loss, resulting in the formation of a gas disk along the Galactic plane and subsequent inward migration down to the central 10 pc region (CND). We simulate the evolution of a gas distribution that initially follows the stellar distribution of the aforementioned stellar cusp, and illustrate the potential gas supply toward the CND.

• 소성∙가공
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• 제28권6호
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• pp.361-367
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• 2019

Microstructure evolution and tensile properties of Al-8mass%Mg alloy casting billet by biaxial alternative forging were investigated in this study. An alternative forging system tailored in this study was used to allow continuous strain accumulations on the alloy workpiece. A finite element (FE) simulation results revealed that the strain was mainly concentrated in the core and that the shear bands developed into a form with an X shape in the cross-section of workpiece after the alternative forging using octangular rod shaped dies. With increasing the forging passes, it was observed that the Al-8mass%Mg alloy workpieces were significantly deformed, and cracks began to form and propagate on the both ends of the forged workpieces after five passes at room temperature. In as-forged microstructures taken by microscopes, twins, clustering of dislocations, and fine subgrains were found. Tensile strengths of the forged specimens showed significant increases depending on the number of forging passes, and a trade-off relationship was observed between the elongation and strength. At room temperature and 100℃ the workpieces showed similar behaviors in microstructural evolution and tensile properties depending on forging passes, while the increase range in strength was reduced at 200℃.

• Animal Systematics, Evolution and Diversity
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• 제14권4호
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• pp.327-334
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• 1998

북한산 등줄쥐의 분류학적 위치를 결정하기 위해, 극동아시아(한국, 북한, 북동 중국, 극동 러시아)의 15개 지역에서 채집한 등줄쥐(Apodemus agrarius) 3아종의 31개 형태 형질들을 다변량방법으로 분석하였다. 분석 결과 세 군으로 나누어졌는데, 한국의 2개 지역(제주도, 완도)의 큰형, 한국과 북한의 8개 지역(진도, 군산, 지리산, 청주, 월악산, 태백산 : 해주, 신의주)의 중간형과 북한, 중국, 러시아의 5개 지역(금강산, 모향산; 길림, 이춘; 블라디보스톡)의 작은형이었다. 큰형, 중간형, 그리고 작은형은 고 등(1991, 1997)이 밝힌대로 각각 A. a. chejuensis. A.a.coreae, A. a. manchuricus임이 확인되었다. 북한의 서부지역(해주, 신의주)의 등줄쥐 (중간형)는 Thomas(1908)가 언급한 대로 A. a. coreae로 분류된다고 밝혀졌지만, 북한의 동부지역(금강산, 묘향산)의 등줄쥐(작은형)는 A.a manchuricus이었다.

• Animal Systematics, Evolution and Diversity
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• 제30권2호
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• pp.95-102
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• 2014

The four species of the suborder Holaxonia, Anthogorgia japonica Studer, 1889 of family Acanthogorgiidae, Astrogorgia rubra (Thomson & Henderson, 1906), Euplexaura attenuata (Nutting, 1910), and E. erecta (Kukenthal, 1908) of family Plexauridae have been newly recorded in Korea. They were collected from intertidal and sublittoral zones in the western and southern coasts and Jeju-do Island of Korea by SCUBA diving and fishing nets from 1969 to 2010. This study approaches holaxonians by focusing on external and internal morphologies including size, form, and color of colonies, branches, polyps, coenenchyme, axis, and spicules. Anthogorgia japonica is characterized by its planar growth form, dichotomously branched form, non-retractile polyps, and Astrogorgia rubra by arrangement of calyxes being situated in lateral side at stems and alternately in all sides at branches. Euplexaura attenuata is sparsely and laterally branched colony, and has straight wand-like stems. Euplexaura erecta has branches which run parallel to the main stem.

• 영어어문교육
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• 제3호
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• pp.123-139
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• 1997

This paper describes the evolution of the infinitive in terms of its progressive formal and semantic grammaticization, using the German infinitive as an example. It is shown that the infinitive has its diachronic origin in a nominal purposive form and that the grammaticization of a purposive form to an infinitive is a widespread phenomenon in the languages of the world. This original function of the infinitive is important for understanding its nature, and the most interesting syntactic property of infinitive, the absence of an explicit subject, can be shown to follow from it. Finally, this paper shows that the diachronic process of the grammaticization of a purposive form is even more general, occurring also in the case of purposive markers in finite clauses.