• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.804-813
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• 2020

This paper finds that Korean zero-leverage firms are not homogeneous. By conducting both univariate and multivariate logit regression analysis, this paper finds that Korean zero-leverage firms have zero leverage as either a consequence of financial constraints or because of a strategic decision to mitigate under-investment incentives and preserve financial flexibility. There are two distinct groups of unlevered firms with different levels of constraints as measured by their dividend policy, namely dividend payers and non-payers. Importantly, this paper finds new evidence that these two groups have different motives for selecting a zero leverage policy. Firms in the first group (non-payers) have zero leverage, mainly due to financial constraints. They rely heavily on their internal funds and consequently invest in fewer growth opportunities than their levered counterparts. Firms in the second group (payers) deliberately avoid debts and preserve financial flexibility to mitigate investment distortions, as predicted by the under-investment and financial flexibility hypotheses.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.15-19
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• 2013

The auxiliary feedwater is an important to remove the heat from the reactor core when the main feedwater system is unavailable. In most initiating events in Probabilistic Safety Assessment(PSA), the operaton of this system is required to mitigate the accidents. For one of domestic nuclear power plants, a design change of a turbine-driven auxiliary feedwater pump(TD-AFWP), pipe, and valves in the auxiliary system is implemented due to the aging related deterioration by long time operation. This change includes the replacement of the TD-AFWP, the relocation of some valves for improving the system availability, a new cross-tie line, and the installation of manual valves for maintenance. The design modification affects the PSA because the system is critical to mitigate the accidents. In this paper, the safety effect of the change of the auxiliary feedwater system is assessed with regard to the PSA view point. The results demonstrate that this change can supply the auxiliary feedwater from the TD-AFWP in the accident with the motor-driven auxiliary feedwater pump(MD-AFWP) unavailable due to test or maintenance. In addition, the change of MOV's normal position from "close" to "open" can deliver the water to steam generator in the loss of offsite power(LOOP) event. Therefore, it is confirmed that the design change of the auxiliary feedwater system reduces the total core damage frequency(CDF).

• Journal of Distribution Science
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• v.18 no.2
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• pp.99-108
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• 2020

Purpose: This paper investigated the relationship between market competition and firm valuation error. Furthermore, Additional analyses were made according to the quality of financial reports and the listed market. Through the process we confirm to the impact of competition on the capital market. The purpose of this study is to analyze the impact of competition on valuation errors. The preceding studies did not provide a consistent results of the effects of competing functions on the capital market. One view is that the competition could mitigate the information asymmetry, and the other is that monopolistic lessens the manager's involvement in financial reporting. This study is intended to expand the prior study by analyzing the impact of competition on the capital market and on the valuation of investors. Research design, data, and methodology: The analysis was conducted on 12,031 samples over 11 years from 2008 to 2018 using data from market in Korea. Here the valuation error was measured by the research methodology of Rhodes-Kropf, Robinson and Viswanathan (2005), and competition measured by Herfindahl-Hirschman Index multiplied by (-1), and Concentration Ratio by (-1). Results: We confirm that the positive relationship between competition and the valuation error. In addition, we also found that the positive relation between competition and valuation error was in cases of low discretionary accruals and the KOSDAQ market. This means that the net function of competition does not mitigate valuation errors. Conclusions. This study has the following contributions when compared to prior research. First, the relevance between the level of competition and the valuation of the entity was confirmed. The study by Haw, Hu and Lee (2015) suggested that monopolistic industry of analysts' forecast is more accurate due to lower the variability in earnings. This study magnified it to confirm that monopolistic lessen information uncertainty in valuation. Second, the study on valuation errors was expanded. While the study on the effect of valuation errors on the capital market is generally relatively active, it is different that competition degree has analyzed the effect on valuation errors amid the lack of research on the effect on valuation errors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.681-686
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• 2017

Degradation is commonly observed in field-aged PV modules due to corrosion of the photovoltaic ribbon. The reduced performance is caused by a loss of fill factor due to the high series resistance in the PV ribbon. This study aimed to mitigate the degradation by corrosion using five sacrificial anodes - Al, Zn and their alloys - to identify the most effective material to mitigate the corrosion of the PV ribbon. The corrosion behavior of the five sacrificial anode materials were examined by open circuit potential measurements, potentiodynamic polarization tests, and galvanic current density and potential measurements using a zero resistance ammeter. Immersion tests for 120 hours were also conducted using materials and damp heat test tests were performed for 1500 hours using 4 cell mini modules. The Al-3Mg and Al-3Zn-1Mg sacrificial anodes had a low corrosion rate and reduced drop in power, making then suitable for long-term use.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.4
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• pp.138-149
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• 2018

In this paper, we propose a system model which effectively mitigates impulsive noise that degrades the performance of power line communication. Recently, deep learning have shown effective performance improvement in various fields. In order to mitigate effective impulsive noise, we applied a convolution neural network which is one of deep learning algorithm to conventional system. Also, we used a successive interference cancellation scheme to mitigate impulsive noise generated from multi-users. We simulate the proposed model which can be applied to the power line communication in the Section V. The performance of the proposed system model is verified through bit error probability versus SNR graph. In addition, we compare ZF and MMSE successive interference cancellation scheme, successive interference cancellation with optimal ordering, and successive interference cancellation without optimal ordering. Then we confirm which schemes have better performance.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.319-319
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• 2017

Methane is the main greenhouse gas released from rice paddy field. Methane from paddy fields accounts for 11 % of the global total methane emission. The global warming potential (GWP) of methane is 25 times more than that of carbon dioxide on a mass basis. It is well known that most effective practice to mitigate methane in paddy is related to the water management during rice growing season and the use of organic matters. This study was conducted to investigate the effects of tillage and cultivation method on methane emission in paddy. Tillage (tillage and no-tillage) and cultivation methods (transplanting and direct seeding) were combined tillage-transplanting (T-T), tillage-wet hill seeding (T-W), tillage-dry seeding (T-D) and no-till dry seeding (NT-D) to evaluate methane mitigation efficiency. Daily methane emission was decreased on seeding treatments (T-W, T-D, NT-D) than transplanting treatment (T-T). Amount of methane emission during rice growing season is highest in T-T ($411.7CH_4\;kg\;ha^{-1}y^{-1}$) and lowest in NT-D treatment (89.7). In T-W and T-D treatments, methane emissions were significantly decreased by 36 and 51 % respectively compared with T-T. Methane emissions were highly correlated with the dry weight of whole rice plant ($R^2=0.62{\sim}0.93$). T-T treatment showed highest $R^2$ (0.93) among the four treatments. Rice grain yields did not significantly differ with the tillage and cultivation methods used. These results suggest that direct seeding practice in rice production could mitigate the methane emissions without loss in grain yield.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.10
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• pp.1180-1187
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• 2012

In this paper, joint transmission space division multiple access(JT-SDMA) scheme is proposed to mitigate inter-cell interference(ICI) in cooperative wireless communications system with limited feedback. We propose a systematic design method for a codebook consisting of a finite number of unitary matrices suitable for network multiple-input multiple-output( MIMO) channel characteristics. A centralized cluster scheduling scheme is proposed to both mitigate ICI and maximizes multiuser diversity gain with limited feedback. It is shown that the proposed JT-SDMA scheme outperforms a existing coordinated SDMA scheme even in wireless network environments where sufficient multiuser diversity order can not be provided through efficient ICI mitigation.

• Smart Structures and Systems
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• v.26 no.4
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• pp.435-449
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• 2020

To effectively extract the vast wind resource, offshore wind turbines are designed with large rotor and slender tower, which makes them vulnerable to external vibration sources such as wind and wave loads. Substantial research efforts have been devoted to mitigate the unwanted vibrations of offshore wind turbines to ensure their serviceability and safety in the normal working condition. However, most previous studies investigated the vibration control of wind turbines in one direction only, i.e., either the out-of-plane or in-plane direction. In reality, wind turbines inevitably vibrate in both directions when they are subjected to the external excitations. The studies on both the in-plane and out-of-plane vibration control of wind turbines are, however, scarce. In the present study, the NREL 5 MW wind turbine is taken as an example, a detailed three-dimensional (3D) Finite Element (FE) model of the wind turbine is developed in ABAQUS. To simultaneously control the in-plane and out-of-plane vibrations induced by the combined wind and wave loads, another carefully designed (i.e., tuned) spring and dashpot are added to the perpendicular direction of each Tuned Mass Damper (TMD) system that is used to control the vibrations of the tower and blades in one particular direction. With this simple modification, a bi-directional TMD system is formed and the vibrations in both the out-of-plane and in-plane directions are simultaneously suppressed. To examine the control effectiveness, the responses of the wind turbine without control, with separate TMD system and the proposed bi-directional TMD system are calculated and compared. Numerical results show that the bi-directional TMD system can simultaneously control the out-of-plane and in-plane vibrations of the wind turbine without changing too much of the conventional design of the control system. The bi-directional control system therefore could be a cost-effective solution to mitigate the bi-directional vibrations of offshore wind turbines.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.82-93
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• 2006

In this paper, filters are designed to reduce transients overvoltage in inverter fed high-voltage large-capacity induction motor drive system. Design issues for a LCR filter at the inverter output terminals to reduce the dv/dt of the inverter output pulse and a RC filter at the induction motor input terminals to match the characteristic impedance between cable and induction motor are examined in detail. These filters are modeled to be suitable to high-voltage large-capacity induction motor. The performance of the filter is evaluated through simulation using EMTP(ElectroMagnetic Transients Program). We presented filters that used high voltage large-capacity induction Motor on the basis of this. Effect of the filter is analyzed for variation of the cable length. Characteristics of filters are analyzed to reduce harmonic in voltage waveform of induction motor input terminal. The switching surge voltage became the major cause to occur the insulation failure by serious voltage stress in the stator winding of induction motor. Filter for to mitigate transients overvoltage presents a required component in drive system of high-voltage large-capacity induction motor. Also, proposed filters are proved through simulation using EMTP.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2008.04a
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• pp.235-240
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• 2008

The environment has played a key role to improve the living condition and develop the industry. In building industries, we should consider the environment and mitigate the environmental affect. For mitigating the its affect, various areas of building technology have been developed and applied into filed work. In addition, the process in applying into field requires to conduct the assessment of the environmental affect and improve its applied technology. A lot of assessment methods are proposed in evaluate the building condition such as post-occupancy evaluation, life cycle management and life cycle assessment. Among these assessment methods, life cycle assessment is effectively utilized the environmental affect in building life cycle. Therefore, this paper aimed at analyzing the energy consumption and $CO_2$ emission in building life cycle, using the life cycle assessment and application of the example in apartment housing. This study shows that the maintenance and the production of building materials stage shares most of the amount of energy consumption and $CO_2$ emission and therefore plays an important role to planning the building in terms of the life cycle. Second, the other stages brings about a very small amount. It is important to decide the building shape and contents to mitigate the environmental affect in terms of material, volume, the pattern of the energy use and others.