• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.258-270
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• 2020

A new task of using the Jacobian-Free-Newton-Krylov (JFNK) method for the PWR core transient simulations involving neutronics, thermal hydraulics and mechanics is conducted. For the transient scenario of PWR, normally the Picard iteration of the coupled coarse-mesh nodal equations and parallel channel TH equations is performed to get the transient solution. In order to solve the coupled equations faster and more stable, the Newton Krylov (NK) method based on the explicit matrix was studied. However, the NK method is hard to be extended to the cases with more physics phenomenon coupled, thus the JFNK based iteration scheme is developed for the nodal method and parallel-channel TH method. The local gap conductance is sensitive to the gap width and will influence the temperature distribution in the fuel rod significantly. To further consider the local gap conductance during the transient scenario, a 1D mechanics model is coupled into the JFNK scheme to account for the fuel thermal expansion effect. To improve the efficiency, the physics-based precondition and scaling technique are developed for the JFNK iteration. Numerical tests show good convergence behavior of the iterations and demonstrate the influence of the fuel thermal expansion effect during the rod ejection problems.

• Journal of Korea Society of Digital Industry and Information Management
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• v.16 no.2
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• pp.27-33
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• 2020

Backward compatibility is one of the key issues for radio equipment supporting IEEE 802.11, the typical wireless local area networks (WLANs) communication protocol. For a successful packet decoding with the backward compatibility, the frame format detection is a core precondition. This paper presents a novel frame format detection method based on a deep learning procedure for WLANs affiliated with IEEE 802.11. Considering that the detection performance of conventional methods is degraded mainly due to the poor performances in the symbol synchronization and/or channel estimation in low signal-to-noise-ratio environments, we propose a novel detection method based on convolutional neural network (CNN) that replaces the entire conventional detection procedures. The proposed deep learning network provides a robust detection directly from the receive data. Through extensive computer simulations performed in the multipath fading channel environments (modeled by Project IEEE 802.11 Task Group ac), the proposed method exhibits superb improvement in the frame format detection compared to the conventional method.

• The Korean Journal of Health Service Management
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• v.5 no.4
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• pp.53-63
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• 2011

This study focused on 'The Health' which should considered as a precondition for the local residents by reinvestigating the indicators of happiness after Young-Do ward formulate a community social welfare plan. There is purpose of this study as below. I searched an general attribute and the indicators of happiness, then looked how does results from questions about health and factors of the indicators of happiness can affects the health with some kinds of elements. Five hundred people from the inhabitants of Young-Do ward who is living in Young-Do district were separated by using the random sampling method as the subject of the study. The investigation took effect from October to November of 2010 and an investigator visited the inhabitants of a ward with structured questionnaire. An investigator had one-on-one talk with inhabitants of Young-Do ward while the investigation and I also collected the data through self-administered questionnaire as well. I found the physical elements influence in the health much more than the outside factors from the study. Higher satisfaction of their career, relationship between friends and co-workers, work environment and married life reflects the fact that higher self-contentment means high quality health level.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.10
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• pp.939-946
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• 2008

Euler codes or Navier-Stokes codes for compressible flows suffer severe degradation in convergence as Mach number approaches zero. The convergence problem arose from the wide disparity in characteristic speeds can be solved using preconditioning methods without large modifications. In this paper, a preconditioned RANS(Reynolds Averaged Navier-Stokes) solver is developed for analysis of low Mach number flows. In order to validate the method, computational examples are chosen and the results are compared with the experimental data and the existing computed results showing a good accuracy and convergence characteristics for steady inviscid, laminar and turbulent flows at low Mach number.

• Journal of Navigation and Port Research
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• v.39 no.4
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• pp.319-327
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• 2015

This study can be summarized as follows : First, main participant, procedure and method of redevelopment of Inner port shall be additionally reviewed. Demands of stakeholder of Incheon Inner Port are actively accommodated to avoid the disruption in undertaking the project. Second, it must ensure the adequacy and appropriateness of policies regarding the redevelopment of the Inner Port in Incheon. It is necessary to obtain consent of people on this project. Third, appropriate system must be established to undertake the project. For this purpose, the governance system shall be built to collect the opinions of the people. The conclusions of this study are as follows. The national master plan and modify plans of Port redevelopment have been being undertaken based on Port Act. Incheon Inner Port redevelopment has been showing slight discrepancy with that of other ports. It's the essential part to coordinate the opinions and needs between the parties prior to the establishment of a redevelopment plan. This can be settled when it's warranted for dock workers to secure the job, and for port companies to provide replaceable piers as the precondition. In addition, eco-friendly waterfront leisure space shall be planned and alternative policies shall be arranged with accommodating the needs of local residents and merchants.