• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.17-23
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• 2004

The semi-active suspension system is getting widely adopted in passenger vehicles for its ability to improve ride comfort over the passive suspension system while not degrading driving safety. A key to the success is to develop practical controllers that yield performance enhancement over the passive damper under various driving conditions. To this end, several control strategies have been studied and evaluated in this research in consideration of practical aspects such as nonlinearity and dynamics of the damper. From simulation results. it has been observed that, with the proposed control schemes, ride comfort can be significantly upgraded while suppressing degradation of driving safety.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.898-899
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• 2008

본 논문에서는 3상 정류기부하에서 주로 발생하는 5차, 7차등의 저차 고조파를 제거하기 위하여 간단한 구조와 경제성이 있는 Single-tuned Second-order Filter를 설계하였다. 사례연구는 원자력발전소 무정전전원계통(UPS)의 임의의 한 모선을 대상으로 하였으며 계통을 모델링하여 분석한 결과를 토대로 수동필터를 설계하였다. 설계된 필터는 범용 컴퓨터프로그램인 PSIM을 이용하여 시뮬레이션을 수행하였으며 시뮬레이션 결과 해당차수의 고조파를 현저하게 감소시키는 양호한 결과를 얻었다.

• Journal of the Korean Society of Safety
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• v.36 no.5
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• pp.10-17
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• 2021

The controversy over the risk of the human body being affected by electromagnetic fields emitted from 60 Hz power lines continues without end. There are currently no new studies or research progress being made in this direction that is notable, and the number of civil complaints is gradually increasing. The problem is that each study produces different results, among which the effect of exposure to magnetic fields on childhood leukemia is a major one. In Korea, an electrician who was maintaining a 22.9 kV power line died of leukemia, which has recently been recognized as an occupational disease. Methods to reduce magnetic fields from power lines include shielding with wire loops, incorporating split phases and compaction techniques, installing underground power lines, converting to high-voltage direct current (HVDC), and increasing the ground clearance of transmission towers. Depending on whether a separate power supply is needed or not, there are two types of wire loops: passive loop and active loop. Magnetic field reduction is currently done through underground power lines; however, the disadvantage of this process is high construction costs. Installing passive loops, with relatively low construction costs, leads to lower magnetic field reduction rates than installing underground cables and a weakness to not solving the landscape problem. This methodological study aims at designing methods and reducing the effects of 2-wire set loops-the simplest and most practical. Since the method proposed in this study has been designed after analyzing the distribution of complex electromagnetic fields near the expected loop installation location, a practical design can be implemented without the need for any difficult optimization programming.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.109-124
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• 1996

This study was performed to evaluate the performance of three passive samplers made in U.S.A. Three passive samplers selected for this study included products made by 3M, Gilian, and SKC in U.S.A. Three organic solvents, such as toluene, trichloroethylene, and n-hexane which are used frequently in Korean industry were selected for the study. Conclusions obtained from this study are summarized as follows. 1. For toluene and trichloroethylene, the overall accuracy of the results from all of three products was within 25 %, which is the criteria recommended by the U.S. National Institute for Occupational Safety and Health (NIOSH). For n-hexane, the overall accuracy of the results from two products except 3M was exceeding 25 %. Thus 3M product showed the best accuracy among three products. 2. When passive samplers collected organic vapors were exposed to clean air for two hours, there were 12 - 16 % loss of organic vapors due to reverse diffusion in Gilian products. There was no significant loss in results from other two products. 3. Air velocity affected greatly on the performance of passive samplers which did not have permeation membrane. At high velocity, 100 cm/sec, accuracies of results from Gilian and SKC were 57 - 108 and 128 - 164 %, respectively. However, the results from 3M samplers, which contain permeation membrane, indicated accuracy below 25 %. 4. When passive samplers collected organic vapors for eight hours, the accuracy was reduced. Thus, it is recommended that passive samplers be used for less than four hours.

• Journal of the Korean Society of Safety
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• v.28 no.3
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• pp.123-128
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• 2013

The Advanced Power Reactor Plus(APR+), which is a GEN III+ reactor based on the APR1400, is being developed in Korea. In order to enhance the safety of the APR+, a passive auxiliary feedwater system(PAFS) has been adopted in the APR+. The PAFS replaces the conventional active auxiliary feedwater system(AFWS) by introducing a natural driving force mechanism while maintaining the system function of cooling the primary side and removing the decay heat. As the PAFS completely replaces the conventional AFWS, it is required to verify the cooling capacity of PAFS for the core damage frequency(CDF) evaluation. For this reason, this paper discusses the cooling performance of the PAFS during transient accidents. The test case and scenarios were picked from the result of the sensitivity analysis in APR+ Probabilistic Safety Assessment(PSA). The analysis was performed by the best estimate thermal-hydraulic code, RELAP5/.MOD3.3. This study shows that the plant maintains the stable state without the core damages under the given test scenarios. The results of PSA considering this analysis' results shows that the CDF values are decreased. The analysis results can be used for more realistic and accurate performance of a PSA.

• Nuclear Engineering and Technology
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• v.49 no.5
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• pp.953-967
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• 2017

In this paper, a complete station blackout (SBO) or complete loss of electrical power supplies is simulated and analyzed in a downward cooling 5-MW pool-type Material Testing Reactor (MTR). The scenario is traced in the absence of active cooling systems and operators. The code nodalization is successfully benchmarked against experimental data of the reactor's operating parameters. The passive heat removal system includes downward water cooling after pump breakdown by the force of gravity (where the coolant streams down to the unfilled portion of the holdup tank), safety flapper opening, flow reversal from a downward to an upward cooling direction, and then the upward free convection heat removal throughout the flapper safety valve, lower plenum, and fuel assemblies. Both short-term and long-term natural core cooling conditions are simulated and investigated using the RELAP5 code. Short-term analyses focus on the safety flapper valve operation and flow reversal mode. Long-term analyses include simulation of both complete SBO and long-term operation of the free convection mode. Results are promising for pool-type MTRs because this allows operators to investigate RELAP code abilities for MTR thermal-hydraulic simulations without any oscillation; moreover, the Tehran Research Reactor is conservatively safe against the complete SBO and long-term free convection operation.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.949-958
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• 2024

In contrast to all-time flooded small modular reactor (SMR) systems, an in-kind flooding safety system (FSS) has been proposed as a passive safety system applicable to small modular reactors (SMRs) that adopt a metal containment vessel (MCV). Under transient conditions, the FSS can provide emergency cooling to dry reactor cavities and sustain long-term coolability using re-acquired evaporated steam in the reactor building on demand. When designing an FSS, the effect of the flooding flow area is vital as it affects the overall accident sequence and safety. Therefore, in this study, a MELCOR model of a reference SMR is developed and numerical analysis is performed under postulated accident scenarios. Without flooding, the MCV pressure of the reactor module exceeds the design pressure before core damage. To prevent core damage, an emergency flooding strategy is devised using various flow path parameters and requirements to ensure an adequate emergency coolant supply before the core damage is investigated. The results indicate that a flow area exceeding 0.02 m2 is required in the FSS to prevent MCV overpressure and core damage. This study is the first to report a strategic analysis for appropriately sizing an FSS flooding valve applicable to innovative SMRs.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.623-628
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• 1998

A new advanced integral reactor of 330 MWt thermal capacity named SMART (System-Integrated Modular Advanced Reactor) is currently under development in Korea Atomic Energy Research Institute (KAERI) for multi-purpose applications. Modular once-through steam generator (SG) and self-pressurizing pressurizer equipped with wet thermal insulator and cooler are essential components of the SMART. The SMART Provides safety systems such as Passive Residual Heat Removal System (PRHRS). In this study, a computer code for performance analysis of the PRHRS is developed by modeling relevant components and systems of the SMART. Using this computer code, a performance analysis of the PRHRS is performed in order to check whether the passive cooling concept using the PRHRS is feasible. The results of the analysis show that PRHRDS of the SMART has excellent passive heat removal characteristics.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2517-2526
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• 2011

As technologies are developed and systems are complicated, hazards embedded in the system are also increasing. proving safety and managing the safety is more scientific and organizational domain so that safety management system is pursuing to be active formation detecting the factors of hazard and managing them beyond passive-way. In the future, in order to establish and manage national safety management system, it is important to have effective system and manage it and also more important that all the people related to target system has to change their recognition and to play roles in it.

• Corrosion Science and Technology
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• v.14 no.6
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• pp.261-266
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• 2015

The capacity of passive metal to repassivate after film damage determines the development of local corrosion and the resistance to corrosion failures. In this work, the repassivation kinetics of 316L stainless steel (316L SS) was investigated in borate buffer solution (pH 9.1) using a novel abrading electrode technique. The repassivation kinetics was analyzed in terms of the current density flowing from freshly bare 316L SS surface as measured by a potentiostatic method. During the early phase of decay (t < 2 s), according to the Avrami kinetics-based film growth model, the transient current was separated into anodic dissolution ($i_{diss}$) and film formation ($i_{film}$) components and analyzed individually. The film reformation rate and thickness were compared according to applied potential. Anodic dissolution initially dominated the repassivation for a short time, and the amount of dissolution increased with increasing applied potential in the passive region. Film growth at higher potentials occurred more rapidly compared to at lower potentials. Increasing the applied potential from 0 $V_{SCE}$ to 0.8 $V_{SCE}$ resulted in a thicker passive film (0.12 to 0.52 nm). If the oxide monolayer covered the entire bare surface (${\theta}=1$), the electric field strength through the thin passive film reached $1.6{\times}10^7V/cm$.