• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2019.08a
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• pp.318-319
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• 2019

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.179-179
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• 2015

Citarum River is one of the important river in West Java, Indonesia. During the rainy season, flood happens almost every year in Upper Citarum Watershed, hence, it is necessary to establish the countermeasure in order to prevent and mitigate flood damages. Since the lack of hydrological data for the modelling is common problem in this area, it is difficult to prepare the countermeasures. Therefore, we used Rainfall-Runoff-Inundation (RRI) Model developed by Sayama et al. (2010) as the hydrological and inundation modelling for evaluating the inundation case happened in Upper Citarum Watershed, West Java, Indonesia and the satellite based information such as rainfall (GSMaP), landuse and so on instead of the limited hydrological data. In addition, 3 arc-second HydroSHEDS Digital Elevation Model (DEM) is used. To verify the model, the observed data of Nanjung water stage gauging station and the daily observation data are used. Simulated inundation areas are compared with the flood extent figure from Upper Citarum Basin Flood Management Project (UCBFM).

• Structural Engineering and Mechanics
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• v.6 no.3
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• pp.347-362
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• 1998

In this study an improved design method for the traditional A-type(or V-type) offshore template platform system was proposed to mitigate the vibration induced by the marine environmental loadings and the strong ground motions of earthquakes. A newly developed material model was combined into the structural system and then a nonlinear dynamic analysis in the time domain was carried out. The analysis was focused on the displacement and rotation induced by the input wave forces and ground motions, and the mitigation effect for these responses was evaluated when the viscoelastic damping devices were applied. The wave forces exerted on the offshore structures are based on Stokes fifth-order wave theory and Morison equation for small body. A step by step integration method was modified and used in the nonlinear analysis. It was found that the new design approach enhanced with viscoelastic dampers was efficient on the vibration mitigation for the structural system subjected to both the wave motion and the strong ground motion.

• Structural Engineering and Mechanics
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• v.41 no.6
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• pp.791-803
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• 2012

Significant structural damages due to pounding between adjacent superstructures of multi-span reinforced concrete (RC) highway bridges have been observed in past earthquakes. Different methods have been proposed in the literature to mitigate the adverse seismic pounding effects. This paper presents an analytical investigation on the use of magnetorheological (MR) dampers in reducing seismic pounding effects of base-isolated multi-span RC highway bridges. It has been observed that MR damper can effectively reduce the seismic pounding effect. Three control strategies (passive off, passive on, and bang bang control) of MR damper have been investigated. Although all the control strategies are found to be effective, bang bang control has been observed to be the most effective.

• Computers and Concrete
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• v.13 no.5
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• pp.679-694
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• 2014

The selected carrier systems of reinforced concrete frame buildings are quite important on structural damages. In this study are examined comparatively nonlinear behaviours of reinforced concrete frames which having different stiffening members under a horizontal load. In that respect, the study consists of six parametric models. With this purpose, nonlinear structural analyses of reinforced concrete frames which having different stiffening members were carried out with LUSAS which uses the finite element method. Thus, some conclusions and recommendations to mitigate the damage of reinforced concrete buildings in the future designs are aimed to present. The obtained results revealed that in terms of performance, the x-shaped diagonal elements can be used as an option to shear walls. In addition, it was found that frame-2, frame-3 and frame-4 showed a better performance than traditional frame system (frame-1).

• Journal of the Korea Safety Management & Science
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• v.18 no.4
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• pp.73-80
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• 2016

This study highlights the main effect of job demand, work shift, work environment and stressors on the railway traffic controller's health, and the moderating effect of work0life balance. The result of empirical analysis based on questionnaires received from 328 traffic controllers working at 10 railway operating companies indicates that job demand, work shift, work environment and stressors have significant effect on their health, among which stressors is a major factor. In the respect of moderating effect, WLB showed no significance except for job demand. This result implies that controller's health can not be enhanced through their individual family or leisure life. Therefore, effective countermeasures and policy to mitigate their health problems and heal their symptoms are urgent.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.615-619
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• 2009

There are many increasing demands for efficient high power density of auxiliary power unit(APU) for high speed traction application. Many techniques have been proposed to measure the voltage flicker on the traditional pulse width modulation(PWM) inverter. This paper proposes a novel functionality of the static inverter on the APU to mitigate the voltage flicker and regulate the output voltage. A new control algorithm for the inverter based on the Hilbert transform(HT) is presented. The HT is employed as an effective technique for tracking the voltage flicker levels in APU systems. Simulation results are provided to verify the tracking capabilities of the HT and to evaluate the performance of the proposed DG interface for multi-function operation.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.467-470
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• 2013

We propose a blind feedforward phase noise mitigation method in the time-domain for a coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. By exploiting the redundancy of the cyclic prefix (CP), the proposed scheme acquires the overall phase noise difference information during an OFDM block and attempts to mitigate the phase noise in the time domain using a linear approximation. The proposed algorithm mitigates common phase error (CPE) and inter-carrier-interference (ICI) due to phase noise simultaneously, improving the system performance, especially when decision-directed equalizers are used. The simulation results demonstrate the effectiveness of the proposed feedforward phase noise mitigation approach in time domain.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.471-480
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• 2013

The beating of two or more lasers that have the same or a finite difference in the central frequencies, is the main source of noise in spectral amplitude coding optical code division multiple access (SAC OCDMA) systems. In this paper we adopt a spatial multiplexing (SM) scheme for SAC OCDMA systems to mitigate this beat noise. The results show that for different code weights and different data rates SM SAC can support a larger number of users than the conventional SAC for all different laser source configurations. However, SM SAC requires a more complex system than the conventional SAC, and almost twice as much optical component.

• KDI Journal of Economic Policy
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• v.43 no.2
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• pp.23-51
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• 2021

The persistence of the employment shock by COVID-19 has various policy implications during the pandemic and beyond it. After evaluating the impact of the health crisis at the individual level, this study decomposes employment losses into persistent and transitory components using the observed timing of the three major outbreaks and subsequent lulls. The estimation results show that while face-to-face services were undoubtedly hit hard by the COVID-19 crisis, the sectoral shock was less persistent for temporary jobs and self-employment. Permanent jobs in the hard-hit sector showed increasingly large persistent losses through the recurring crises, indicating gradual changes in employer responses. The persistent job losses were concentrated on young and older workers in career transitions, whose losses are likely to have long-term effects. These results suggest that targeted measures to mitigate the persistent effects of the employment shock should take priority during the recovery process.