• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.51-61
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• 2003

This research is a park of a research program to develope a new design method for reinforced concrete bridge columns under axial load and cyclic lateral load. The objectives of this paper are to investigate the relationship between curvature ductility and displacement ductility and to propose a correlation equation for designing of reinforced concrete bridge columns under axial load and cyclic lateral load. Computer program NARCC was used for parametric study, which was proved to provide good and conservative analytical result especially for deformation capacity and ductility factor compared with test result. A total of 7,200 spirally reinforced concrete columns were selected considering the main variables such as section diameter, aspect ratio, concrete strength, yielding strength of longitudinal and confinement steel, longitudinal steel ratio, axial load ratio, and confinement steel ratio. A new equation between curvature ductility factor displacement ductility factor with the aspect ratio was proposed by investigation of 21,600 data produced from the selected column models by applying 3 different definitions of yield displacement.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.10
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• pp.1845-1851
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• 2007

Background noise and room reverberation are two causes of degradation in speech in listening situations. Many algorithms developed to enhance reverberant speech. In this paper we propose a dereverberation method for enhancement of speech using modified the linear prediction(LP) residual in reverberant room condition. The proposed dereberberation method based on the fact that the signification excitation of the vocal tract system takes place at the instant of glottal closure in voiced speech. Our method used delay information form each sensor, and we need reverberant signals from 3 sensors. We obtain a new LP residual signal using modified IP residual combination which derived form weighting of the LP residual and the Hilbert transform of LP residual. The nature of the coherently added Hilbert envelop has several large amplitude spikes because of the effects of noise and reverberation. This residual of the clean speech is used to excite the time-varying all-pole filter to obtain the enhanced speech. We achieved simulation of proposed algorithm for performance analysis in reverberation environment. The proposed algorithm improves substantially the quality of reverberant speech.

• Convergence Security Journal
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• v.18 no.5_1
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• pp.25-32
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• 2018

Cyber hackings are increasing and becoming more intelligent. The government and private companies conduct various information protection activities by investing lots of money and employing security personnel to protect import ant assets and personal information. It is important to evaluate the efficiency of the information protection activities that cost lots of money and manpower. However, the studies on the efficiency of the information protection activities were mainly conducted for government agencies the information of which is more readily available. This study suggests a model that can evaluate the efficiency of the activities of information protection and information security certification of various private companies. Our model evaluates the efficiency of the information protection activities by applying AHP and DEA on the information that are publicly announced by the private companies. Our model identifies the DMUs that are efficiently operated and suggests the improvement policies for the DMU that are non-efficiently operated.

• Journal of Korea Port Economic Association
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• v.32 no.1
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• pp.165-178
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• 2016

Container port nowadays becomes one of the most vital link of the transportation chain, plays an important role in trading with other countries. Therefore, evaluating the operational efficiency of container ports to reflect their status and to reveal their position in this competitive environment is very important for port development. Although there have been lots of methods used to measure efficiency in the past, the DEA (Data Envelopment Analysis) model is still the most commonly applied approach. However, the data used in the model sometimes is complex and uncertain to handle using the basic DEA model. In this paper, we applied an uncertainty theory to create an uncertainty DEA model (UDEA), which can solve the limitation of the traditional one. This study mainly focuses on measuring efficiency of 41 container ports by applying proposed an UDEA model. The results show that among 41 container ports, only six container ports are regarded to have efficient operation through the clustering, meanwhile others have technical and scale inefficiencies. We found out that an UDEA model is better to analysis efficiency than existing DEA model.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.117-131
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• 2015

Conventional data envelopment analysis (DEA) models require that inputs and outputs are given as crisp values. Very often, however, some of inputs and outputs are given as imprecise data where they are only known to lie within bounded intervals. While a typical approach to addressing this situation for optimization models such as DEA is to conduct sensitivity analysis, it provides only a limited ex-post measure against the data imprecision. Robust optimization provides a more effective ex-ante measure where the data imprecision is directly incorporated into the model. This study aims to apply robust optimization approach to DEA models with imprecise data. Based upon a recently developed robust optimization framework which allows a flexible adjustment of the level of conservatism, we propose two robust optimization DEA model formulations with imprecise data; multiplier and envelopment models. We demonstrate that the two models consider different risks regarding imprecise efficiency scores, and that the existing DEA models with imprecise data are special cases of the proposed models. We show that the robust optimization for the multiplier DEA model considers the risk that estimated efficiency scores exceed true values, while the one for the envelopment DEA model deals with the risk that estimated efficiency scores fall short of true values. We also show that efficiency scores stratified in terms of probabilistic bounds of constraint violations can be obtained from the proposed models. We finally illustrate the proposed approach using a sample data set and show how the results can be used for ranking DMUs.

• Journal of the Korea Society of Computer and Information
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• v.19 no.11
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• pp.17-24
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• 2014

This paper proposes a fault detection method for low-speed rolling element bearings of an induction motor using acoustic emission signals and histogram modeling. The proposed method performs envelop modeling of the histogram of normalized fault signals. It then extracts and selects significant features of each fault using partial autocorrelation coefficients and distance evaluation technique, respectively. Finally, using the extracted features as inputs, the support vector regression (SVR) classifies bearing's inner, outer, and roller faults. To obtain optimal classification performance, we evaluate the proposed method with varying an adjustable parameter of the Gaussian radial basis function of SVR from 0.01 to 1.0 and the number of features from 2 to 150. Experimental results show that the proposed fault identification method using 0.64-0.65 of the adjustable parameter and 75 features achieves 91% in classification performance and outperforms conventional fault diagnosis methods as well.

• Journal of Digital Convergence
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• v.19 no.5
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• pp.353-363
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• 2021

This study analyzed to provide information for business improvement by analyzing the management efficiency of start-up investment companies so that startup investment companies can operate efficiently and by presenting information on inefficient factors. From 2014 to 2018, 83 start-up investment companies were analyzed using the DEA model. Input variables were he number of employees, capital, and output variables were selected for start-up investment assets, operating income, and net profit. As a result of the analysis, technical efficiency and pure technical efficiency showed a pattern with an increase in average, but scale efficiency repeatedly increased and decreased. It is believed that the decline in technology efficiency was due to the decrease in pure technology efficiency, and the inefficiency of start-up investment companies seems to have influenced the inefficiency of start-up investment companies rather than the inefficiency of scale. In addition, the size revenue shows that the DRS value is gradually decreasing, and the IRS value is generally increasing. It is believed that efficiency can be improved if operational inefficiency is improved based on the results and efficiency measures are established through scale expansion.

• International Area Studies Review
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• v.15 no.3
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• pp.307-324
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• 2011

The global economic crisis made most of governments to overcome the economic depression as well as the challenging tasks for global warming. It is not easy political vision to harmonize these two rabbits race, and thus it needs to be developed new paradigm for the sustainable development. Unfortunately, the traditional cost-approach based productivity could not resolve this trade-off relation. Therefore, the paper is aimed to develop new approach on the green productivity index with the DEA models in the 1st stage, and then based on these green productivity scores, the paper is analyzed the determinants of these green productivity in the 2nd stage among the G 20 countries. The empirical result shows that the effect of GDP, carbon intensity, and capital and labor intensity toward the green growth is positive on the green productivity, while the level of government efforts is not significant on the green productivity.

• International Area Studies Review
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• v.14 no.1
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• pp.299-319
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• 2010

This thesis analyzed that which countries won the Olympic medals more efficiently at the Olympic Games. Unlike the previous studies, I measured efficiency under the CRS, found implications for investment to improve sports skills through understanding the characteristics of sports race. A methods for research is a DEA-based approach which measures efficiency by using the data only, not assuming the parameters. The inputs are total population and GDP, the output is Olympic medals at 2004 Athens Olympic Games and 2006 Turin Winter Olympic Games. I applied different weights based on the medal colors. The results showed the tendencies that the larger the scales of total population and GDP were, the lower efficient values were. These tendencies imply that sports skills are related with the law of diminishing returns and international convergence. According to these phenomenons, surging investments for sports performance are hard to get proper justification. In the case of limited resources, investing uniformly in various sport entries is more productive than in just one or two sport entries.

• International Area Studies Review
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• v.14 no.3
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• pp.205-219
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• 2010

In general, industrial production involves large amounts of harmful by-product, causing serious pollution and ecological risk. Eco-efficiency, which indicates how efficient the economic activity is by considering both the environmental risks and economic performance, is a new concept for economic sustainability analysis and quantitative ecological risk analysis. Data envelopment analysis (DEA) has been widely used to examine eco-efficiency in recent years. Whereas traditional DEA models such as CCR and BCC model neglect undesirable outputs, this paper adopts a stochastic undesirable-output DEA model to measure the eco-efficiency of each province of China and Korea. The results indicate that whereas the eco-efficiency of the eastern region was the highest, that of the western region was the lowest. The reason may come from the negative external dis-economies of environment. And thus the governmental efforts for outreach on the underdeveloped regions should be promoted.