• Journal of the Korean Society for Precision Engineering
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• v.27 no.5
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• pp.36-47
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• 2010

The Korean Railroad Research Institute (KRRI) has developed the rubber tired AGT system (Model: K-AGT) between 1999 and 2005. The K-AGT is a light rail transit system does not require a driver and generally operates on an elevated railroad for transporting passengers. Accidents caused by driverless vehicles can severely affect social confidence, safety and economy therefore, it is very important to minimize the occurrences of such faults, and to accurately perform detailed maintenance tasks and thoroughly investigate the cause of any repeated failures. This research develops the web-based Preventive Maintenance (PM) system for the KAGT train system. The framework of the PM system is based on performing a reliability analysis and a failure mode effects analyses (FMEA) procedure on all the sub-systems in the K-AGT system. Out of the devices that have a low reliability, the high failure ranked devices are included high in the list for performing the overall maintenance plans. Through registration of historical failure data, the reliability indexes can be updated. Such a process is repeated continuously and can achieve very accurate predictions for device operational life times and failure rates. Therefore, this research describes the development of the overall PM system consists of a reliability analysis module, a failure mode effect analysis module, and maintenance request module.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.2
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• pp.125-132
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• 2017

Intermittent pneumatic compression is frequently used for prophylaxis of deep vein thrombosis, however there is a lot of complains by frequent adverse event. In this paper, we analyzed the cause of adverse event and we tried to improve for the cause of machine, nurses, patients, system by diverse strategy. And we could improve the index of each cause, the rate of error was decreased finally. The proactive activity of quality improvement for medical device can contribute to decrease the error, that will improve the quality of medical service and achieve the safe medial culture.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.133-142
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• 2010

P-type fire control panel, currently in use, has a big hazard that can cause the large scaled human death tolls and property damage in the massive fire because it is difficult to identify in real time the location of fire outbreak and whether search-device are broken down or not. In this paper, I suggest that the integrated fire automation system on based p-type fire control panel should be used, which can detect in real time the signal that occur when whether search-device are broken down or not, and can detect the arisen circumstances information of p-type fire control panel on the fire signal in the far away. The devised systems have designed and embodied the analysis of circumstances information and module that can analyze the circumstances information from the p-type fire control panel and the part of internet access installment which can gather and deliver the circumstances information from the fire prevention facility receiver.

• Journal of the Korean Institute of Gas
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• v.23 no.5
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• pp.35-43
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• 2019

The safety of industrial valves, which are the core parts of plant facilities, are managed by manpower and there are difficulties because of side area for inspection and limited accessibility due to the nature of facilities. The industrial valves used in plant facilities cause problems such as interrupted production; a loss of life due to leak or explosion of poisonous material and flammable gases, and difficulty in locating accident positions in the event of leakage or failure. Therefore, safety management and control systems based on IoT technology are needed. This study is about the development of risk factor prediction technique among the safety management of industrial valves through IoT- based wireless communication and the development of actuator control system. We have developed IoT-based industrial valve safety management techniques to prevent accidents caused by main risk factors by conducting an analysis of the structural characteristics of valves and an analysis of the causes of main risk factors through review of failure data and literature and an analysis of accident scenarios.

• Nuclear Engineering and Technology
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• v.21 no.1
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• pp.1-11
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• 1989

Numerous losses of decay heat removal capability have occurred at U during stutodwn while its significance to safety is needless to say. A study is carried out as an attempt to assess what could be done to lower the frequency of these events and to mitigate their consequences in the unlikely event that one occurs. The shutdown risk model is developed and analyzed using Event/Fault Tree for the typical pressurized water reactor. The human cognitive reliability (HCR) model, two-stage bayesian approach and staircase function model are used to estimate human reliability, initiating event frequency and offsite power non-recovery probability given loss of offsite power, respectively. The results of this study indicate that the risk of a Pm at shutdown is not much lower than the risk when the plant is operating. By examining the dominant accident sequences obtained, several design deficiencies are identified and it is found that some proposed changes lead to significant reduction in core damage frequency due to loss of cooling events.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4112-4118
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• 2011

Electrical Railroads provide electric power, which can operate vehicles, via feeder wires. And the supplied current returns to the transformer substation through lines and ground net. The return current, related to signal, power and power line, and track circuit systems, is one of the most important component in the electric railway. Therefore, to prevent system faults and breakdown according to unbalance and overcurrent of the return current, various and detailed analyses for the return current are needed. In the paper, we present measurement and analysis manners in real environment and evaluate its safety. For analysis, we utilize the measured values of return currents measured in track circuits in electric railway. we expect that this research plays a key role to the related fields.

• Journal of the Korea Computer Industry Society
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• v.3 no.1
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• pp.77-84
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• 2002

An cluster system used consist of large number of running servers, one has the problem that does the low availability occured by the high chance of the server failures and it is difficult to provide occuring software aging. In this paper, running cluster web servers consists of n primary servers and k backup servers, based on the operational parameters such as number of running primary servers, number of backup severs, rejuvenation period, rejuvenation time, failure rate of sewers, repair rate of servers, unstable rate of servers. We calculate to evaluate the rejuvenation policy such steady-state probabilities, downtime, availability, and downtime cost. We validate the solutions of mathematical model by experiments based on various operation parameters and find that the software rejuvenation method can be adopted as prventive fault tolerant technique for stability of system. The failure rate and unstable rate of the servers are essential factors for decision making of the rejuvenation policies.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.169-174
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• 2019

This paper propose a system to notify the user that detects failure of malfunction of smart farm ICT devices. As the fourth industrial revolution approaches, agriculture is also fused with ICT technology to improve competitiveness. Smart farming market is rapidly growing every year, but there is still a lack of standardization and certification systems. Especially, smart farm devices that are widely used in Korea are different in product specifications, software and hardware are developed separately, and quality and compatibility are poor. Therefore, a system that can recognize the abnormality of the equipment due to the frequent damage of farmers using low cost smart farm equipment is needed. In this paper, we review smart farm domestic and overseas policy trends and domestic smart agriculture trends, analyze smart farm failure or malfunctions and proactively prevent them, and propose a system to inform users when problems occur.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.5
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• pp.135-140
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• 2024

DC capacitors used in PV inverters have a relatively short lifespan compared to other power semiconductor devices and have a failure rate of 60%, making them the most vulnerable among the elements that make up a power conversion system (PCS). In addition, the lifespan of the capacitor varies depending on environmental factors, greatly affecting the lifespan and operating conditions of PV inverters and PV power generation systems. Therefore, research is needed on the development of inverter deterioration diagnostic sensor technology optimized for building-integrated and general PV power generation systems and the development of bypass compensation capacitor modules that can maintain the efficiency of the inverter in the event of a failure. Based on this research, the DC capacitor deterioration diagnosis module inside the PV inverter measures the capacity of the actual internal components and can check the trend information of the deterioration state in the long term, enabling rapid response to fires. In addition, it seeks to improve the efficiency of power generation facilities and reduce carbon emissions, and prevents electrical fires, allowing the PV power generation system to be maintained in optimal condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8700-8706
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• 2015

The first driving device of the power bogies for the Korean high-speed railway vehicle consists of the traction motor (TM) and the motor reduction gears unit (MRU). Although TM and MRU are the mechanically integrated structures, their time between overhauls (TBO) have two separate intervals due to different technical requirements(i.e. TBO of MRU: $1.8{\times}10^6km$, TBO of TM: $2.5{\times}10^6km$). Therefore, to reduce the unnecessary number of preventive maintenances, it is important to evaluate the optimal TBO with a viewpoint of reliability-center maintenance towards cost-effective solution. In this study, derived from the field data in maintenance, fault tree analysis and failure rate of the subsystem considering criticality of the components are evaluated respectively. To minimize the conventional total maintenance cost, the same optimal TBO of the components is derived from genetic algorithm considering target reliability and improvement factor. In this algorithm, a chromosome which comprised of each individual is the minimum preventive maintenance interval. The fitness function of the individual in generation is acquired through the formulation using an inverse number of the total maintenance cost. Whereas the lowest common multiple method produces only a four percent reduction compared to what the existing method did, the optimal TBO of them using genetic algorithm is $2.25{\times}10^6$km, which is reduced to about 14% comparing the conventional method.