• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.3
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• pp.9-22
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• 2018

Korea meteorological administration(KMA) has started to levy air meteorological service charge on both national and foreign carriers since 2005. The charge has grown on 2010 and 2014 twice. However, KMA has still kept asking airlines to agree with another increase in the charge due to the low cost of goods recovery ratio of 7%. The air meteorological charge has changed from 2,210 KRW at the beginning to 11,400 KRW as of June 2018. According to ARIMA intervention time series analysis, it was proven national carriers would make a payment of 831 million KRW 2018 and 1,024 million KRW 2019, showing 186.2% and 123.2% increase compared to last year respectively. The total amount of charge for both national LCC and foreign airlines was aggregated up to 1,952 million KRW 2019, 227% bigger than the charge paid at 2017. Considering the 50% increase of consumer price index last decade, the increased charge would impair the global competitiveness of national carriers. It could be suggested that current air meteorological charge scheme be improved to apply overseas trend and for national carriers to have a competitive advantage in global aviation market.

• Quality Improvement in Health Care
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• v.4 no.2
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• pp.242-259
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• 1997

This study describes associated factors of readmission of 213 inpatients from an university hospital in Seoul. This retrospective study reviewed medical records of patients who discharged from a hospital stay for general diseases between 1 August 1995 and 31 October 1995, Cases were 68 discharge patients with an unplanned readmission within 30 days of discharge from an index stay. And the other cases are 145 patients who had more than two discharges and didn't have an unplanned readmission within 30 days. Logistic regression model was analyzed and the results were as follows; 1. duration of readmission, rate of unpayed, room, path, and risk of disease were more likely to be readmitted unexpectedly than the expected readmission patients. 2. early readmission, low risk condition group, and inadquateness of discharge plann for patients had unplanned radmissions rather than planned readmissions. Therefore, discharge planning education to health care provider is required and assessement of discharge planning should be evaluated. Readmissions are usually for related problems that arose during the original hopitaliztion and caused cost problems. Especially the unplanned readmissions are frequently preventable. Ultimately, models for readmissions can serve as a valuable clinical tool for target high-risk patients and older patients and with this kind of tools we can reduce hospital readmissions and maintain high-quality of inpatient care.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1729-1742
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• 2017

In designing System Protection Schemes (SPSs) in power systems, protecting transmission network against extreme undesired conditions becomes a significant challenge in mitigating the transmission line overloading. This paper presents an intelligent Special Protection and Control Scheme (SPCS) using of Differential Evolution with Adaptive Mutation (DEAM) approach to obtain the optimum generation rescheduling to solve the transmission line overloading problem in system contingency conditions. DEAM algorithm employs the attraction-repulsion idea that is applied in the electromagnetism-like algorithm to support the mutation process of the conventional Differential Evolution (DE) algorithm. Different N-1 contingency conditions under base and increase load demand are considered in this paper. Simulation results have been compared with those acquired from Genetic Algorithm (GA) application. Minimum severity index has been considered as the objective function. The final results show that the presented DEAM method offers better performance than GA in terms of faster convergence and less generation fuel cost. IEEE 30-bus test system has been used to prove the effectiveness and robustness of the proposed algorithm.

• Structural Engineering and Mechanics
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• v.65 no.6
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• pp.751-760
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• 2018

Damages in concrete structures due to aging and other factors could be a serious and immense matter. Making the best selection of the most viable and practical repairing and strengthening techniques are relatively difficult tasks using traditional methods of structural analyses. This is due to the fact that the traditional methods used for assessing aging structure are not fully capable when considering the randomness in strength, loads and cost. This paper presents a reliability-based methodology for assessing reinforced concrete members. The methodology of this study is based on probabilistic analysis, using statistics of the random variables in the performance function equations. Principles of reliability updating are used in the assessment process, as new information is taken into account and combined with prior probabilistic models. The methodology can result in a reliability index ${\beta}$ that can be used to assess the structural component by comparing its value with a standard value. In addition, these methods result in partial safety factor values that can be used for the purpose of strengthening the R/C elements of the existing structure. Calculations and computations of the reliability indices and the partial safety factors values are conducted using the First-order Reliability Method and Monte Carlo simulation.

• Journal of Applied Reliability
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• v.16 no.2
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• pp.78-89
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• 2016

Purpose: In this paper, we investigate whether the endeavors for Six Sigma quality management by a firm have positive effects on its financial performance and the length of Six Sigma implemented period affects its financial status. We find a relationship between Six Sigma implemented period and several financial performance index using a smoothing spline function. Methods: A smoothing spline function is used in order to analyze the relationship between efforts for quality management and financial performance. Specifically, the return on assets, return on equity, sales cost and business fee are investigated as dependent variables and the efforts for quality management as independent variable. Results: As a result of the analysis, the indication is that companies that put effects into the Six Sigma quality management have a positive result in its financial status. In detail, the efforts for Six Sigma quality management have positive effects on total asset turnover ratio and Six Sigma implemented period on net income to net sales ratio. Additionally, companies with longer (shorter) period of Six Sigma program have more (less) improvement in its financial status. Conclusion: It can be concluded that the company's efforts for quality management positively influence financial performance.

• Environmental and Resource Economics Review
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• v.11 no.3
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• pp.345-375
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• 2002

The purpose of this paper is to measure the change of the production efficiency which may happen when environmental regulation incurs technological constraint in the process of production, and to compute the opportunity cost of pollution reduction with the lost products based on the change of efficiency. The patterns of production technoloy in the paper are divided into the technologies of strong disposability and weak disposabilty to grasp the effect of the technological constraint due to the environmental regulation. The endowment of the technolgical constraints in the process of production is considered to bring the greatest restriction on firm's production. When the environmental efficiencies of Korean regional manufactures were measured with linear programming model, the lost products related with the constraint of production technology that environmental regulation incurred, was average 148.1 billion dollar per year(5.87% of one year overall products) for total manufactures in 1991~1998. The ratio of the lost products for total products was spread from 0.78% to 1l.08%. The average lost products of 15 regions were changed from 4.66% to 18.35% of total products. Generally the environmental efficiency index of regional manufactures being decreased continuously since 1991, it is estimated that the environmental performance of Korean manufactures has been more and more deteriorating.

• The Journal of Asian Finance, Economics and Business
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• v.6 no.4
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• pp.27-35
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• 2019

The paper examines the level of disclosure on Islamic banks' performance in the United Arab Emirates (UAE). The data was collected through content analysis of annual reports and financial statements of all fully-fledged Islamic banks working in the UAE over the period 2009 to 2013. Return on Assets is used as a proxy for the performance of Islamic banks while disclosure index is used as a proxy for Islamic banks' disclosure. Also, predetermined variables are used in the study like Size, Deposits, Non-Performing Investments and Capital to Risk Weighted Assets Ratio. Two-Stage Least-Square regression method is used to check the interdependence relationships between disclosure and performance of Islamic banks in the UAE. The results show a significant relationship between performance and disclosure in the UAE Islamic banks. Our regression results show that Islamic banks with higher levels of disclosure lead to higher operating performance. Furthermore, the performance has a great impact on the level of disclosure which means Islamic banks with high performance measures will disclose more information for investors and other institutions in order to reduce the cost of equity and increase their values in the market. This study is considered as a battery for further studies in the relationship between disclosure and financial performance of Islamic banks at a global level.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1119-1129
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• 2014

This study proposes a novel five-level three-phase hybrid-clamped converter composed of only six switches and one flying capacitor (FC) per phase. The capacitor-voltage-drift phenomenon of the converter under the classical sinusoidal pulse width modulation (SPWM) strategy is comprehensively analyzed. The average current, which flows into the FC, is a function of power factor and modulation index and does not remain at zero. Thus, a specific modulation strategy based on space vector modulation (SVM) is developed to balance the voltage of DC-link and FCs by injecting a common-mode voltage. This strategy applies the five-segment method to synthesize the voltage vector, such that switching losses are reduced while optional vector sequences are increased. The best vector sequence is then selected on the basis of the minimized cost function to suppress the divergence of the capacitor voltage. This study further proposes a startup method that charges the DC-link and FCs without any additional circuits. Simulation and experimental results verify the validity of the proposed converter, modulation strategy, and precharge method.

• Journal of Power Electronics
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• v.18 no.2
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• pp.445-455
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• 2018

A novel algorithm is proposed to regulate the neutral point potential in neutral point clamped three-level inverters. Oscillations of the neutral point potential and an unbalanced dc-link voltage cause distortions of the output voltage. Large capacitors, which make the application costly and bulky, are needed to eliminate oscillations. Thus, the algorithm proposed in this paper utilizes the finite-control-set model predictive control and the multistage medium vector to solve these issues. The proposed strategy consists of a two-step prediction and a cost function to evaluate the selected multistage medium vector. Unlike the virtual vector method, the multistage medium vector is a mixture of the virtual vector and the original vector. In addition, its amplitude is variable. The neutral point current generated by it can be used to adjust the neutral point potential. When compared with the virtual vector method, the multistage medium vector contributes to decreasing the regulation time when the modulation index is high. The vectors are rearranged to cope with the variable switching frequency of the model predictive control. Simulation and experimental results verify the validity of the proposed strategy.

• Proceedings of the KSRS Conference
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• v.1
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• pp.94-97
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• 2006

Timber stand age information of timber in industrialized plantation forest is generally collected by field surveying which is labor-intensive, time-consuming, and very costly. It is also inconsistent in analyses perspective. As an alternative, The objective of this research is to present a practical solution for estimating timber age of loblolly pine plantation using Landsat thematic mapper (TM) images, shuttle radar topography mission (SRTM), and national elevation dataset (NED). A multivariate regression model was developed based upon satellite image-based information (i.e.normalized difference vegetation index (NDVI), tasseled cap (TC) transformation, and derived tree heights). A residual studentized technique was applied to remove potential outliers. After that, a refined age estimation model with a correlation coefficient R-square of 84.6% was obtained. Finally, the feasibility test of estimated model was performed by comparing estimated and measured stand ages of timber plantations using test datasets of plantation stands (2,032 stands). The result shows that the proposed method of this study can estimate loblolly pine stand age within an error of $2{\sim}3$ years in an effective and consistent way in terms of time and cost.