• Journal of the Ergonomics Society of Korea
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• v.21 no.3
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• pp.13-24
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• 2002

Reduction and prevention of human error is one of the major interests for the enhancement of system safety and availability in Nuclear Power Plants (NPPs). As human beings have become the weak point in the system safety, a systematic evaluation on human performance during emergency situation should be performed in advance to identify the potential vulnerability of human tasks. Though the data gathering and analysis from real field is an important precondition, there were no available data in nuclear field of korea. This paper presents the result of human performance analysis on emergency tasks in NNPs. Firstly, a task analysis was performed to identify the characteristics of operator tasks during emergency condition and to classify them into a set of generic emergency tasks. Secondly, simulation data were collected and analyzed for the emergency tasks using the full scope simulator of Younggwang NPPs. The analyzed human performance information cover the event diagnosis time, the execution time of each procedural step, observation parameters, typer of irrelevant response, pattern of communication among staffs, and so on. These performance data would be used for human reliability analysis and the research of human error as technical bases.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2456-2467
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• 2018

Wireless multimedia sensor networks (WMSNs) require real-time quality-of-service (QoS) guarantees to be provided by the network. The end-to-end delay is very critical metric for QoS guarantees in WMSNs. In WMSNs, due to the transmission errors incurred over wireless channels, it is difficult to obtain reliable delivery of data in conjunction with low end-to-end delay. In order to improve the end-to-end delay performance, the system has to drop few packets during network congestion. In this article, our proposal is based on optimization of end-to end delay for WMSNs. We optimize end-to-end delay constraint by assuming that each packet is allowed fixed number of retransmissions. To optimize the end-to-end delay, first, we compute the performance measures of the system, such as end-to-end delay and reliability for different network topologies (e.g., linear topology, tree topology) and against different choices of system parameters (e.g., data rate, number of nodes, number of retransmissions). Second, we study the impact of the end-to-end delay and packet delivery ratio on indoor and outdoor environments in WMSNs. All scenarios are simulated with multiple run-times by using network simulator-2 (NS-2) and results are evaluated and discussed.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.3
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• pp.117-126
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• 2013

This paper is written for the development and application of boiler furnace pressure control algorithm and distributed control system of coal-fired power plant by the steps of design, coding, simulation test, site installation and site commissioning test. The control algorithms were designed in the shape of cascade control for two parts of furnace pressure control and induced draft fan pitch blade by standard function blocks. This control algorithms were coded to the control programs of distributed control systems. The simulator for coal-fired power plant was used in the test step and automatic control, sequence control and emergency stop tests were performed successfully like the tests of the actual power plant. The reliability was obtained enough to be installed at the actual power plant and all of distributed control systems had been installed at power plant and all signals were connected mutually. Tests for reliability and safety of plant operation were completed successfully and power plant is being operated commercially. It is expected that the project result will contribute to the safe operation of domestic new and retrofit power plants, the self-reliance of coal-fired power plant control technique and overseas business for power plant.

• Journal of Biomedical Engineering Research
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• v.29 no.4
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• pp.295-301
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• 2008

A wireless 3 channel ECG monitoring system was developed so that it could monitor the health and movement state during subject's daily life. The developed system consists of a wireless biomedical signal acquisition device, a personal healthcare server, and a remote medical server. Three experiments were performed to evaluate the accuracy, reliability and operability, applicability during daily life of the developed device. First, ECG signals were measured using the developed device and commercial reference device during sitting and marking time and compared to verify the accuracy of R-R intervals. Second, the reliable data transmission to remote server was verified on two types of simulated emergency event using patient simulator. Third, during five types of motion in daily life, the accuracy of data transmission to remote server using CDMA network was verified on two types of event occurring. By acquiring and comparing subject's biomedical signal and motion signal, the accuracy, reliability and operability, applicability during daily life of the developed device were verified. In addition, PDA-phone based wireless system enabled subject to be monitored without any constraints. Therefore, the developed system is expected to be applicable for monitoring the aged and chronic diseased people and giving first-aid in emergency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.5
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• pp.1929-1950
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• 2020

Reliable and secure data transmission in the application environment assisted by the wireless sensor network is one of the major challenges. Problem like blind forwarding and data inaccessibility affect the efficiency of overall infrastructure performance. This paper proposes routing protocol for forwarding and error recovery during packet loss. The same is achieved by energy and hops distance-based formulation of the routing mechanism. The reachability of the intermediate node to the source node is the major factor that helps in improving the lifetime of the network. On the other hand, intelligent hop selection increases the reliability over continuous data transmission. The number of hop count is factor of hop weight and available energy of the node. The comparison over the previous state of the art using QualNet-7.4 network simulator shows the effectiveness of proposed work in terms of overall energy conservation of network and reliable data delivery. The simulation results also show the elimination of blind forwarding and data inaccessibility.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.63-71
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• 2013

This paper describes the coordinated droop control method for stand-alone type DC micro-grid to improve reliability and utilization of distributed generations and energy storage. The stand-alone type DC micro-grid consists of several distributed generations such as a wind power generation, solar power and micro-turbine, and energy storage. The proposed method which is based on autonomous control method shows high reliability and stability through coordinated droop control of distributed generations and energy storage and also capability of battery management. The operation of stand-alone type DC micro-grid was analyzed using detail simulation model with PSCAD/EMTDC software. Based on simulation results, a hardware simulator was built and tested with commercially available components and performance of system was verified.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.6
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• pp.717-721
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• 2010

In general, wireless MAC uses the ACK for reliability. Meanwhile, in wireless sensor network, data is delivered periodically and redundantly. In these situations, every ACK transmission causes the reliability flexible applications to waste some energy. IEEE 802.15.4 developed for energy efficiency has the option of using ACK or not, but there are no researches exploiting this peculiarity. In this paper, we proposed the selective unacknowledged transmission satisfying some requirements (e.g., end-to-end delivery) by removing the ACK when frames are delivered well and using the ACK when frames are delivered poorly. Also, we performed several evaluations exploiting the NS2 simulator.

• Journal of the Ergonomics Society of Korea
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• v.33 no.1
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• pp.1-14
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• 2014

Objective: The purpose of this study is to select the methodology for SMR HRA which has characteristics that are different from existing nuclear power plants and digital-based plants. Background: We must assure safety to preoccupy export of technology to developing countries or countries interested in nuclear application. And we can be an advanced country in nuclear technology by securing original technology in the field of SMR such as SMART. Method: THERP, which is the most representative HRA methodology among all, and RARA, which is the latest HRA methodology. This study compared and evaluated THERP and RARA. Results: As a result of applying THERP and RARA methodologies which are based on LOCA EOG task analysis result, this research concluded that RARA has higher personal errors than THERP. Conclusion: This study needs validation for LOCA, emergency operations, normal and abnormal scenarios since HRA methodology was only focused on LOCA scenario. Application: The results of this study can apply as base line data when designing MMIS, which is the main control room of SMART, and when building a simulator.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.71-76
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• 2006

With the rapid development of spatial infrastructure in US, Europe, Japan, China and India, there is no doubt that the next generation Global Navigation Satellite System (GNSS) will improve the integrity, accuracy, reliability and availability of the position solution. GNSS is becoming an essential element of personal, commercial and public infrastructure and consequently part of our daily lives. However, the applicability of GPS in supporting a range of location-sensitive applications such as location based services in an urban environment is severely curtailed by the interference of the 3D urban settings. To characterize and gain in-depth understanding of such interferences and to be able to provide location-based optimization alternatives, a high-fidelity 3D urban model of Melbourne CBD built with ArcGIS and large scale high-resolution spatial data sets is used in this study to support a comprehensive simulation of current and future GNSS signal performance, in terms of signal continuity, availability, strength, geometry, positioning accuracy and reliability based on a number of scenarios. The design, structure and major components of the simulator are outlined. Useful time-stamped spatial patterns of the signal performance over the experimental urban area have been revealed which are valuable for supporting location based services applications, such as emergency responses, the optimization of wireless communication infrastructures and vehicle navigation services.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.23-28
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• 2023

This paper demonstrates a novel NAND flash memory structure and annealing configuration including through-silicon via (TSV) inside the silicon substrate to improve annealing efficiency using an electro-thermal annealing (ETA) technique. Compared with the conventional ETA which utilizes WL-to-WL current flow, the proposed annealing method has a higher annealing temperature as well as more uniform heat distribution, because of thermal isolation on the silicon substrate. In addition, it was found that the annealing temperature is related to the electrical and thermal conductivity of the TSV materials. As a result, it is possible to improve the reliability of NAND flash memory. All the results are discussed based on 3-dimensional (3-D) simulations with the aid of the COMSOL simulator.