• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1208-1211
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• 2008

We study the amorphous In-Ga-Zn-O thin-film transistors (TFTs) properties under monochromatic illumination ($\lambda=420nm$) with different intensity. TFT off-state drain current ($I_{DS_off}$) was found to increase with the light intensity while field effect mobility ($\mu_{eff}$) is almost unchanged; only small change was observed for sub-threshold swing (S). Due to photo-generated charge trapping, a negative threshold voltage ($V_{th}$) shift is also observed. The photofield-effect analysis suggests a highly efficient UV photocurrent conversion in a-IGZO TFT. Finally, a-IGZO mid-gap density-of-states (DOS) was extracted and is more than an order lower than reported value for a-Si:H, which can explain a good switching properties of the a-IGZO TFTs.

• Journal of applied mathematics & informatics
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• v.28 no.3_4
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• pp.863-875
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• 2010

In this paper we apply the martingale approach, which has been widely used in mathematical finance, to investigate the optimal investment problem for an insurer under the criterion of mean-variance. When the risk and security assets are described by the L$\acute{e}$vy processes, the closed form solutions to the maximization problem are obtained. The mean-variance efficient strategies and frontier are also given.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.1
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• pp.111-121
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• 2020

The study measures the resource use efficiency of diesel based power generation in the Maldives and analyses factors which influence efficiency levels. Stochastic frontier analysis (SFA) technique is applied to data on 30 plants over two year period from 2016 to 2017. The study finds that technical efficiency scores varies from 0.44 to 0.98 across power plants. About 33 percent of the plants have scores below the mean technical efficiency score of 0.87. Empirical results indicate ownership and use of solar photovoltaic (PV) have an influence on improving efficiency levels. Privately owned power plants in resort islands obtained higher technical efficiency scores compared to public and community owned power plants. This is a significant finding as the first study that used power plants in tourist sector in a comparative study. Size of the power plants was not found significant, but relatively small installed capacities can also be efficient. This finding is important because in many inhabited islands installed capacities remain oversized compared to the load. The benchmarking exercise offers model power plants that are relatively efficient, for other power plants and policy makers in small islands to learn from.

• Journal of Navigation and Port Research
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• v.29 no.1 s.97
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• pp.105-111
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• 2005

Recently, global terminal operotors are struggling to attract more cargoes into their ports through enlarging facilities and trying to be more efficient operotion Many researches on container terminal efficiency have been conducted, but most of the traditional studies are focused on the partial efficiency of the container terminal using quantitative questionnaires and basic statistical data In this paper, the Stochastic Frontier Model of the interaction among the variables was employed to execute numerical analysis on the efficiency of terminal. The objective of this paper is to measure the level of efficiency in the container terminals every year and to assess the influence in container terminal's efficiency on domestic and foreign terminals by changing the terminal scales and the level of input factors.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2001.10a
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• pp.213-217
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• 2001

This paper deals with the estimation of efficiency of Telecommunication Operators(TOs) using DEA (Data Envelopment Analysis). The measure of efficiency using DEA accomplishes next two steps. First, the efficient frontier is derived using the data of input and output. And then the efficiency of the decision making units are measured by the distances from this frontier To measure efficiency, we consider a one-output, three-input production function. We use the tangible assets, investment cost, the number of employees for input data and measure the output by the revenue. After measuring the efficiency, We can compare the domestic TOs with the international TOs and the wire TOs with wireless ones by average efficiency. After accomplishing the analysis of efficiency, the internal/external efficiency is measured simultaneously through correlation between efficiency and profitability, quality level.

• The Journal of Korea Robotics Society
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• v.2 no.2
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• pp.191-195
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• 2007

Abstract MOCIE(Ministry of Commerce, Industry and Energy) handles 6 Projects for Intelligent Robot, whose budget is around 40 Million dollars per year. In this paper we have tried to analyze the state of robot technology of the projects. Each sub-projects has been divided according to the technological classification. Two major projects of Next Generation Growth Engine and 21C Frontier show different state each other. The former is focused on the product while the latter on the technology. Output of 21C Frontier should be linked to the Next Generation Growth Engine, otherwise, it will fail to advance. The project management handles only the quantitative performance such as business results, number of prototype, and number of patents and papers. Technological Capability is essential and it should be managed. This paper proposes efficient classification of robot technology and technology index.

• Journal of computational fluids engineering
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• v.14 no.4
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• pp.31-40
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• 2009

Although optimization by sequentially refining metamodels is known to be computationally very efficient, the metamodel that can be used for this purpose is limited to Kriging method due to the difficulties related with sample points selections. The present study suggests a novel method for sequentially refining metamodels using Pareto Frontiers, which can be used independent of the type of metamodels. It is shown from the examples that the present method yields more accurate metamodels compared with full-factorial optimization and also guarantees global optimum irrespective of the initial conditions. Finally, in order to prove the generality of the present method, it is applied to a 2D transonic airfoil optimization problem, and the successful design results are obtained.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.3
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• pp.143-149
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• 2021

This paper proposes length rate measurement for relative efficiency that is a core of data envelopment analysis(DEA). It has been said that the linear programming(LP) is a unique method to get the relative efficiency. This method has drawback that applies fractional LP focusing on each DMU in turn. This paper draws bi-dimensional input-output relational graph and distinguishes between efficient and inefficient DMU. The relative efficiency of inefficient DUM is solve using length rate measurement. As a result of various experimental data, the LP shows mistake of application, but this method gets the correct relative efficiency at all times. Also, this method only gets the relative efficiency for only inefficient DMUs without efficient DUMs that already achieved 100% efficiency. This method solves the relative efficiency of inefficient DUM draws the line to efficient frontier and decides the reference set easily.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.5
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• pp.179-186
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• 2014

Current networks such as social network, web page link, traffic network are big data which have the large numbers of nodes and edges. Many applications such as social network services and navigation systems use these networks. Since big networks are not fit into the memory, existing in-memory based analysis techniques cannot provide high performance. Frontier-Expansion-Merge (FEM) framework for graph search operations using three corresponding operators in the relational database (RDB) context. FEM exploits an index table that stores pre-computed partial paths for efficient shortest path discovery. However, the index table of FEM has low hit ratio because the indices are determined by distances of indices rather than the possibility of containing a shortest path. In this paper, we propose an method that construct index table using high degree nodes having high hit ratio for efficient shortest path discovery. We experimentally verify that our index technique can support shortest path discovery efficiently in real-world datasets.

• Journal of Korean Society of Transportation
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• v.27 no.4
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• pp.63-76
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• 2009

On the basis of a Stochastic Frontier Approach (SFA), this paper analyses revenue efficiencies for the same sample of Korean and Japanese railways in the papers which analyze cost efficiencies using a generalized translog functional form. The paper also compares the results of revenue efficiencies with cost efficiencies and evaluates the effects of managerial autonomy and privatization on the firm-specific efficiencies. The results show that the average estimate of revenue inefficiency is 7.02% when the term of inefficiency is assumed to be distributed as a half-normal and 6.98% as a exponential for the total sample. Also, standardized inefficiencies in revenues (7.5%) are greater than those in costs (2.1%). JR East and JR West are found to be most efficient on the revenue side and on the cost side respectively while JNR and JR Kyushu are worst efficient on the both sides. Finally, the correlations between efficiencies in revenues and costs also between efficiencies and privatization are positively correlated. The results suggest that the most independent companies, with increased managerial autonomy via privatization, are the most efficient in both revenues and costs.