• Journal of Korea Water Resources Association
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• v.40 no.9
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• pp.735-742
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• 2007

In this study, a methodology which is based on segments and minimum outsets to estimate the reliability of a real water distribution system efficiently and accurately is suggested. The current reliability assessment models based on minimum cutset consider a pipe as only area impacted by a pipe failure which incurs underestimation of pipe failure impact. In contrary, the suggested methodology adopts "segment" and "unintended isolation" with the hydraulic pressure failure area to define the actual service interruption area in a water distribution system due to a pipe failure, which is different from the Previous reliability estimating methodologies. In addition, a minimum cutset is defined as a single segment incurring abnormal operating conditions and the success mode approach is used to account for the probability of multiple failure combinations of minimum outsets. The model considers numbers and locations of on-off valves when the service interruption area is defined. Once the methodology is applied to a real water distribution system, it is possible to define actual service interruption areas and using the defined areas, the reliability of the water distribution system is estimated reliably, compared with the previous reliability assessment methodologies.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.8
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• pp.462-469
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• 2017

Eutrophication and shortage of phosphate ore raise the necessity of phosphate removal and recovery from wastewater treatment plants. Especially, a sludge treatment system containing highly concentrated phosphate should be targeted for phosphate removal and recovery. This study thus aimed to evaluate the capability of the struvite crystallization process for phosphate removal and recovery from a sludge treatment system of a wastewater treatment plant. Analysis on phosphate concentrations and masses in the sludge treatment system revealed that digested sludge and centrate have phosphate concentrations and masses, high enough to adopt the struvite crystallization process. Chemical equilibrium modeling indicated that the struvite crystallization reaction substantially occurred with pH higher than 8 and $Mg^{2+}$ concentration 1.2 times higher than its theoretical requirement. A series of batch tests with digested sludge and centrate indicated that the phosphate removal reaction by struvite crystallization followed a first-order kinetics and reached over 80% removal efficiency at equilibrium. Aeration in the batch tests was found to purge $CO_2$ in sludge or centrate and increase pH up to 8.7, without adding NaOH. Thus, we concluded that the struvite crystallization process could be an efficient and economical process for phosphate removal and recovery from a wastewater treatment plant.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.1
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• pp.1-22
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• 2012

This paper tried to verify whether the fixed fire fighting system (FFFS) that is installed in road tunnel improves evacuation performance or not. Verification was performed according to the Disaster Prevention Facilities Installation and Management Guide at Road Tunnel. Twenty seven different fire scenarios were set up for the verification and the cases that FFFS was installed were compared with the cases that FFFS was not installed. The result of the comparison showed that the average equivalent death was reduced in 26 cases out of 27 cases when water spray extinguishing system was installed. It was confirmed that the risk when was not installed was unacceptable in Hong Kong and the Netherlands. On the other hand, it was confirmed that the risk was reduced to as low as reasonably practicable (ALARP) when was installed. The cumulative frequency of average death in case with FFFS was compared against the frequency of death without FFFS: death of one or more is about 50 times less; 10 or more is about 100 times less; and the death of more than 100 is four times less. It was verified that FFFS makes improved conditions to escape from the fires in road tunnel.

• Journal of Korea Water Resources Association
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• v.47 no.10
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• pp.891-906
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• 2014

This study suggests the hedging rule of MIP (Mixed Integer Programing) in counting the risk evaluation criteria of the objective function and constraints in order to provide the optimum operating rule in reservoir system as constraining water shortage as much as possible which may happen in the downstream control point of water supply in the aspect of water system management. The proposed model is applied to the Han-river reservoir system for two testing periods (Case I: Jan. 1993~Dec. 1997, Case II: Jan. 1999~Dec. 2003). The model based on the hedging rule with trigger volume, estimated in this study shows that in Case I, the monthly minimum discharge was $310.6{\times}10^6m^3$ in the single operation, $56.3{\times}10^6m^3$ in the joint operation, and $317.5{\times}10^6m^3$ in the hedging rule and also, in Case II, the monthly minimum discharge was found to be $204.2{\times}10^6m^3$ in the single operation, $111.2{\times}10^6m^3$ in the joint operation, and $243.7{\times}10^6m^3$ in the hedging rule. In conclusion, the hedging rule, proposed in this study can decrease vulnerability while guarantees reliability and resiliency.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.537-546
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• 2009

Determination of optimal pressure monitoring location is essential to manage water distribution system efficiently and safely. In this study, entropy theory is applied to overcome defects of previous researches about determining the optimal sensor location. The previous studies required the calibration using historical data, therefore, it was difficult to apply the proposed method in the place where the enough data were not available. Also, most researches have focused on the locations to minimize cost and maximize accuracy of the model, which is not appropriate for the purpose of maintenance of the water distribution system. The proposed method in this study quantify the entropy which is defined as the amount of information calculated from the pressure change due to the variation of discharge. When abnormal condition is occurred in a node, the effect on the entire network is presented by the entropy, and the emitter is used to reproduce actual pressure change pattern in EPANET. The optimal location to install pressure sensors in water distribution system is the nodes having the maximum information from other nodes. The looped and branched networks are evaluated using the proposed model. As a result, entropy theory provides general guideline to select the locations to install pressure sensors and the results can be used to help decision makers.

• Fire Science and Engineering
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• v.31 no.6
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• pp.67-73
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• 2017

An aircraft maintenance hangar is a building that stores, maintains, and inspects expensive aircraft. The frequency of fire occurrence is low, but the resulting human and material damage can be very serious. Therefore, in this study, we conducted a qualitative analysis of the fire safety of the currently operating fire suppression systems for aircraft maintenance hangars using the Fault Tree method, and then performed a quantitative analysis using the failure rate data for the derived basic events and analyzed the importance of the minimal cut sets. As a result of the qualitative analysis by the minimal cut set, it was found that there were 14 accident paths that could be expanded to a large fire, due to the fire control failure of the aircraft hangar fire suppression system. The quantitative analysis revealed that, the probability of the fire expanding into a large one is $2.08{\times}E-05/day$. The analysis of the importance of the minimal cut set shows that four minimal cut sets, namely the fire detector and foam head action according to the zone and blocking of the foam by the aircraft wing and the fire plume, had the same likelihood of causing the fire to develop into a large one, viz. 24.95% each, which together forms the majority of the likelihood. It was confirmed for the first time by fault tree method that the fire suppression system of aircraft maintenance hangars is not suitable for fires under the aircraft wings and needs to be improved.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.131-138
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• 2010

Due to the increased water demand and severe drought as an effect of the global warming, the effluent from wastewater treatment plants becomes considered as an alternative water source to supply agricultural, industrial, and public (gardening) water demand. The effluent from the wastewater treatment plant is a sustainable water source because of its good quality and stable amount of water discharge. In this study, the water reuse system was developed to minimize total construction cost to cope with the uncertain water demand in future using two-stage stochastic linear programming with binary variables. The pipes in the water reuse network were constructed in two stages of which in the first stage, the water demands of users are assumed to be known, while the water demands in the second stage have uncertainty in the predicted value. However, the water reuse system has to be designed now when the future water demands are not known precisely. Therefore, the construction of a pipe parallel with the existing one was allowed to meet the increased water demands in the second stage. As a result, the trade-off of construction costs between a pipe with large diameter and two pipes having small diameters was evaluated and the optimal solution was found. Three scenarios for the future water demand were selected and a hypothetical water reuse network considering the uncertainties was optimized. The results provide the information about the economies of scale in the water reuse network and the long range water supply plan.

• The Journal of the Convergence on Culture Technology
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• v.6 no.1
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• pp.135-145
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• 2020

This research is mainly aimed at finding out about the effects of the safety and health management system on corporate performance through systematic operation by efficiently allocating material and human resources within the company by participating all employees and stakeholders in order to prevent and maintain industrial accidents and the optimal working environment, and how to maintain and activate the safety and health management system at the center of electric contractors.The analysis results are as follows. First, management, organizational management and resource preparation will have a positive impact on the management capability of the electric power corporation. It was assessed that the more well-transmitted and understood within the organization, the better the construction plan, the better the equipment management status, the more positively the management capability of electric works was to be achieved. Second, management, organizational management and resource preparation will have a positive impact on corporate management performance.This seems to have a positive effect on a company's business performance when the standards of OHSAS are met with construction plan and construction equipment management are high as related information such as industrial safety and health laws are strengthened and companies' safety and health activities, advanced safety and culture are released to facilitate organizational management.Third, the management ability of the electric power corporation will have a mediated effect on the effect of management, organization management and resource preparation on the performance of the enterprise. This means that the direct effect of the independent variable management organization on corporate management performance is .401 The indirect effect is .168.658 shows that the direct effect of resource preparation on corporate management performance is .423, the indirect effect is .178 and the total effect.It was analyzed at 643.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.5
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• pp.417-425
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• 2018

This paper proposes a safety management method that extracts ETA (event tree analysis) based scenario and combines ICT technology to reduce serious disasters occurring workplace for shipbuilding and offshore plant. The statistics of Safety and Health Agency and (previous)Ministry of Public Safety and Security show that the most frequent accident among the serious disasters related to shipbuilding and offshore plant is falling. The main cause of accidents is absence of a safety belt and safety belt ring. To solve these problems, we create ETA based scenarios to derive results based on safety considerations. Based on these results, we propose a solution by applying ICT technology for accident prevention. Deriving ETA based scenarios and ICT technology, the proposed solutions include a system for detecting the wearing of safety belts and safety helmets, a system for detecting whether or not the safety belts are connected, and a hook system for measuring safety distances. These safety related systems can reduce the probability of death of workers. By preventing accidents using the proposed method, we can reduce serious disasters in shipbuilding and offshore plant and establish systematic safety management.

• The Korean Society of Law and Medicine
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• v.23 no.4
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• pp.29-74
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• 2022

As social disasters occur under the Disaster Management Act, which can damage the people's "life, body, and property" due to the rapid spread and spread of unexpected COVID-19 infectious diseases in 2020, information collected through inspection and reporting of infectious disease pathogens (Article 11), epidemiological investigation (Article 18), epidemiological investigation for vaccination (Article 29), artificial technology, and prevention policy Decision), (3) It was used as an important basis for decision-making in the context of an infectious disease crisis, such as promoting vaccination and understanding the current status of damage. In addition, medical policy decisions using infectious disease data contribute to quarantine policy decisions, information provision, drug development, and research technology development, and interest in the legal scope and limitations of using infectious disease data has increased worldwide. The use of infectious disease data can be classified for the purpose of spreading and blocking infectious diseases, prevention, management, and treatment of infectious diseases, and the use of information will be more widely made in the context of an infectious disease crisis. In particular, as the serious stage of the Disaster Management Act continues, the processing of personal identification information and sensitive information becomes an important issue. Information on "medical records, vaccination drugs, vaccination, underlying diseases, health rankings, long-term care recognition grades, pregnancy, etc." needs to be interpreted. In the case of "prevention, management, and treatment of infectious diseases", it is difficult to clearly define the concept of medical practicesThe types of actions are judged based on "legislative purposes, academic principles, expertise, and social norms," but the balance of legal interests should be based on the need for data use in quarantine policies and urgent judgment in public health crises. Specifically, the speed and degree of transmission of infectious diseases in a crisis, whether the purpose can be achieved without processing sensitive information, whether it unfairly violates the interests of third parties or information subjects, and the effectiveness of introducing quarantine policies through processing sensitive information can be used as major evaluation factors. On the other hand, the collection, provision, and use of infectious disease data for research purposes will be used through pseudonym processing under the Personal Information Protection Act, consent under the Bioethics Act and deliberation by the Institutional Bioethics Committee, and data provision deliberation committee. Therefore, the use of research purposes is recognized as long as procedural validity is secured as it is reviewed by the pseudonym processing and data review committee, the consent of the information subject, and the institutional bioethics review committee. However, the burden on research managers should be reduced by clarifying the pseudonymization or anonymization procedures, the introduction or consent procedures of the comprehensive consent system and the opt-out system should be clearly prepared, and the procedure for re-identifying or securing security that may arise from technological development should be clearly defined.