• Journal of Information Technology Services
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• v.12 no.4
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• pp.255-265
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• 2013

This paper proposes a DEA-AR model for the efficiency evaluation of the iron ore brands in an integrated steel mill. The input factor is defined as unit cost of each brand based on CIF and two output factors are chosen as Fe and Al which are the important ingredients of iron ore. The relative importance between two output factors is determined by several experts using AHP model. The efficiency of each brand is determined using DEA and DEA-AR models. The negative correlation between the DEA-AR efficiency and the unit cost (CIF) is shown as significant whereas no significant correlation exist between the efficiency and the output factors. Also, the Kruskal Wallis rank sum test shows that there exist efficiency differences among the iron ore types whereas no difference is shown among the countries. The result could be utilized in selecting good brands of iron ores based on the DEA-AR efficiency in an integrated steel mill.

• Journal of the Korean Mathematical Society
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• v.44 no.1
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• pp.211-235
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• 2007

In this paper, first we introduce the full expression of the curvature tensor of a real hypersurface M in complex two-plane Grass-mannians $G_2(\mathbb{C}^{m+2})$ from the equation of Gauss and derive a new formula for the Ricci tensor of M in $G_2(\mathbb{C}^{m+2})$. Next we prove that there do not exist any Hopf real hypersurfaces in complex two-plane Grassmannians $G_2(\mathbb{C}^{m+2})$ with parallel and commuting Ricci tensor. Finally we show that there do not exist any Einstein Hopf hypersurfaces in $G_2(\mathbb{C}^{m+2})$.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.4
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• pp.719-728
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• 1997

In the AGV routing a vehicle can select the shortest route on which no conflicts are anticipated. The procedure includes time constraint and the node/arc occupation times of vehicles in order to locate the conflicting paths. The slight differences among AGV routing algorithms exist in identifying the conflict regions encountered while reaching out to the destination node. In this paper, a novel approach to the use of the re-routing scheme is presented. It will be used to minimize the travel distance of vehicles in a regular vehicle routing process rather than to cope with emergency situations. The proposed algorithm provides existing active vehicles with the ability of changing their current paths for a new vehicle whenever the equal-distance paths exist, in on attempt to optimize the AGV transportation system. This ability is possible because of the flexibility of on AGV system controlled by a computer system.

• Journal of Environmental Science International
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• v.2 no.3
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• pp.201-206
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• 1993

The concentration of Total Suspended Particulates(T.S.P), size distribution of suspended particulates, and soluble anions of T.S.P in atmosphere of industrial region in Busan were investigated. T.S.P was measured by High-Volume Air Sampler and particle size distribution was measured by Anderson Air Sampler. We analyzed the chemical component of the T.S.P by ion Chromatography and measure4 the shape and size of T.S.P by Scanning Electron Micrography The small size of T.S.P mainly exist in industrial region, but the large size of T.S.P mainly exist in residentail area.

• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.489-497
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• 1995

The DDS((CH3)2SiCl2)＋H2 gas mixture, where C atoms exist in excess in the molecules, was used for chemical vapor deposition of SiC in order to prevent codeposition of free Si in MTS(Ch3SiCl3)＋H2 system. The deposition rate was more rapid than MTS, however differ from that of MTS, it decreased after shwoing a maximum at 140$0^{\circ}C$. The stoichiometry was highly improved by using the DDS as a precursor, although there exist a little pyrolytic C at 150$0^{\circ}C$. The preferred orientation was (220) in MTS, however, it changed to (111) in DDS. The microstructure of the layer deposited at lower temperature were dense, however it grew coarse with the increase in the temperature.

• Research in Mathematical Education
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• v.14 no.3
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• pp.299-308
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• 2010

The gender differences of mathematics achievement exists in many counties in the world. Some Chinese scholars think that the differences also exist in China. The researchers explain the gender differences of mathematics learning mainly from the individual psychology and education. This paper, firstly, introduces an investigation of the gender differences of mathematics achievement in grade 1-9 in three areas (Hefei urban area, Cuozhen area, and Chenji area) of Hefei in China. The investigation found that the gender differences of mathematics achievement exist but are different in these areas. Then, the results are explained from the theory of the gender socialization.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.327-330
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• 2003

In this paper, a viscoelastic structural analysis for the spent pressurized water reactor(PWR) nuclear fuel disposal canister is carried out to predict the collapse of the canister while the canister is stored in a deep repository for long time. There may exist some subterranean heat in a deep repository while the nuclear fuel disposal canister is stored for long time. Then, a time-dependent viscoelastic structural deformation may occur in the canister due to the subterrnean heat Hence, the viscoelastic stress variation according to time should be computed to predict the structural strength of the canister. A viscoelastic material model is adopted. Analysis results show that even though some subterrnean heat may exist for quite a long time, the canister structure still endures stresses below the yield strength of the canister. Hence, some subterranean heat cannot seriously affect the structural strength of the canister.

• Journal of Ocean Engineering and Technology
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• v.34 no.3
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• pp.194-201
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• 2020

In this study, an optical-fiber sensor was used to measure loads that could act in an environment similar to the loading conditions that exist in an actual pipe. The structure and the installation method of the optical-fiber strain sensor were applied considering the actual large pipe and the buried pipe environment. Load tests were performed using a displacement sensor and sandbags to determine the deflection of the pipe according to the external load, and the linear measurement results were verified. Considering the conditions that could exist in the actual pipe, the test method was presented, and the strain of the buried pipe generated at this time was measured.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.71-74
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• 1995

Diamond shaping is one of the machining strategies to make the optical micro-groove molds,and it is especially useful when rhe component is an assembly of the linear micro-groove array. A mirror-like surface and arbitrary crose-sectional curve can be easily made by diamond. Howerver, the cutting speed of shaping is relatively lower than that of the other cutting methods, and there exist an unstable cutting conditions that generate the chatter. This study is focused on the modeling of the simplified self-induced chatter of the diamond shapping. Form the chatter model and experiments, it is found that the unstable cutting conditions exist wwhen the depth of cut is low and cutting speed is high.

• Journal of the Korean Operations Research and Management Science Society
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• v.28 no.1
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• pp.11-23
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• 2003

This study Investigates the short and long-run dynamic relationships between the domestic and U.S. stock markets for the period of declining stock prices. It Is well known that the domestic stock market variations are largely caused by the U.S. stock market movements. Multivariate causal tty test Is utilized to examine the lead-lag relationships among four stock prices of KOSPI and KOSDAQ In the domestic part and DOWJONES and NASDAQ In the U.S. part. When the stock prices tend to decrease In the long run, It Is found that both KOSPI and KOSDAQ have closer relations with NASDAQ than DOWJONES. When both of domestic stock markets are severely fluctuate, bidirectional causal relationships appear to exist between NASDAQ and each of KOSPI and KOSDAQ. On the other hand. when the domestic stock markets are relatively stable, unidirectional causality Is found to exist between NASDAQ and each of KOSPI and KOSDAQ. which is explicitly validated by the analysis of variance decomposition.