• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.451-454
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• 2006

Fiber optic distributed temperature sensing and thermal line sensor are applied in an observation borehole and a loom deep borehole heat exchanger. For the case of permanently installed system fiber optic DTS is very useful. By comparing with TLS, fiber optic DTS shows good accuracy and reliability. Ground water flow can give influences at heat exchange rate of the heat pump system. According to the hydraulic characteristics and temperature-depth profile, we consider that temperature-depth profile do not seem to be dependent on ground water flow. A permanent installation of fiber optic cable is expected as a reliable temperature measurement technique in a borehole heat exchanger system.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.484-497
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• 2021

This paper proposes an extended time uncertainty analysis approach in Level 2 human reliability analysis (HRA) considering severe accident management (SAM) strategies. The method is a time-based model that classifies two time distribution functions-time required and time available-to calculate human failure probabilities from delayed action when implementing SAM strategies. The time required function can be obtained by the combination of four time factors: 1) time for diagnosis and decision by the technical support center (TSC) for a given strategy, 2) time for strategy implementation mainly by the local emergency response organization (ERO), 3) time to verify the effectiveness of the strategy and 4) time for portable equipment transport and installation. This function can vary depending on the given scenario and includes a summation of lognormal distributions and a choice regarding shifting the distribution. The time available function can be obtained via thermal-hydraulic code simulation (MAAP 5.03). The proposed approach was applied to assess SAM strategies that use portable equipment and safety depressurization system valves in a total loss of component cooling water event that could cause reactor vessel failure. The results from the proposed method are more realistic (i.e., not conservative) than other existing methods in evaluating SAM strategies involving the use of portable equipment.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.3
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• pp.293-303
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• 2015

Optimal design of the water supply pipe network aims to minimize construction cost while satisfying the required hydraulic constraints such as the minimum and maximum pressures, and velocity. Since considering one single design factor (i.e., cost) is very vulnerable for including future conditions and cannot satisfy operator's needs, various design factors should be considered. Hence, this study presents three kinds of design factors (i.e., minimizing construction cost, maximizing reliability, and surplus head) to perform multi-objective optimization design. Harmony Search (HS) Algorithm is used as an optimization technique. As well-known benchmark networks, Hanoi network and Gyeonggi-do P city real world network are used to verify the applicability of the proposed model. In addition, the proposed multi-objective model is also applied to a real water distribution networks and the optimization results were statistically analyzed. The results of the optimal design for the benchmark and real networks indicated much better performance compared to those of existing designs and the other approach (i.e., Genetic Algorithm) in terms of cost and reliability, cost, and surplus head. As a result, this study is expected to contribute for the efficient design of water distribution networks.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.32-40
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• 1993

Flow fields in model engine cooling passages are studied numerically by using TURBO-3D program, a finite volume based 3-D turbulent flow program adopting a general body fitted coordinate system. The effects of exit position on mass flow rate at each gasket hole are examined for a model cooling passage in order to understand the flow distribution inside the water jacket. The results of the present study can be applied to the design of high performance, high reliability engine.

• Smart Structures and Systems
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• v.11 no.5
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• pp.453-476
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• 2013

DuraMote is a remote sensing system developed for the "NIST TIP project: next generation SCADA for prevention and mitigation of water system infrastructure disaster". It is designed for supervisory control and data acquisition (SCADA) of ruptures in water pipes. Micro-electro mechanical (MEMS) accelerometers, which record the vibration of the pipe wall, are used detect the ruptures. However, the performance of Duramote cannot be verified directly on a water distribution system because it lacks an acceptable recordable level of ambient vibration. Instead, a long-span cable-stayed bridge is an ideal test-bed to validate the accuracy, the reliability, and the robustness of DuraMote because the bridge has an acceptable level of ambient vibration. The acceleration data recorded on the bridge were used to identify the modal properties of the structure and to verify the performance of DuraMote. During the test period, the bridge was subjected to heavy rain, wind, and a typhoon but the system demonstrates its robustness and durability.

• Structural Monitoring and Maintenance
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• v.3 no.4
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• pp.335-347
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• 2016

One of major errors in flow rate measurement for two-phase flow using an Electrical Capacitance Sensor (ECS) concerns sensor sensitivity under temperature raise. The thermal effect on electrical capacitance sensor (ECS) system for air-water two-phase flow monitoring include sensor sensitivity, capacitance measurements, capacitance change and node potential distribution is reported in this paper. The rules of 12-electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance and sensitivity map the basis of Air-water two-phase flow permittivity distribution and temperature raise are discussed by ANSYS and MATLAB, which are combined to simulate sensor characteristic. The cross-sectional void fraction as a function of temperature is determined from the scripting capabilities in ANSYS simulation. The results show that the temperature raise had a detrimental effect on the electrodes sensitivity and sensitive domain of electrodes. The FE results are in excellent agreement with an experimental result available in the literature, thus validating the accuracy and reliability of the proposed flow rate measurement system.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.31-36
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• 2008

A water distribution system should be constructed reasonably to supply water for the customer with proper quality and pressure as demands at nodes fluctuate with time. Also it should be reliable to minimize undesirable effects on the customer when various accidents happen such as pipe failures. A new method is presented here to reduce damages by pipe failures. For the work, two methods, namely, the method for estimating practical extent of damage by pipe failures and for estimating water distribution reliability, are adopted to analyze a water distribution system and to explore the damage reduction by pipe failures. As the results from the analysis of the model, the damage can be reduced effectively by increasing durability of each pipe in minimum cutsets according to the order of priority. The suggested method was applied to the Cherry-Hill network to verify its applicability.

• Journal of Korean Society of Transportation
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• v.22 no.6
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• pp.7-16
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• 2004

In mode choice decision, travelers consider not only travel time but also reliability of its modes. In this paper, reliability was expressed in terms of standard deviation and maximum delay that were measured based on triangular distribution. In order to estimate value of time and value of reliability, the Multinomial and Nested Logit models were used. The analysis results revealed that reliability is an important factor affecting mode choice decisions. Elasticity is used to estimate the impacts of the different policies and system improvements for water transportation mode. Among these policies, decision maker can assess and select the best alternative by doing the benefit and cost analysis based on a new market share, the value of time, and the value of reliability. Finally, a set of promising policies and system improvement of the water transportation were proposed.

• Nuclear Engineering and Technology
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• v.15 no.1
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• pp.41-49
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• 1983

A computer code, BERD (Bayesian Estimation of Reliability Data), has been developed and tested in order to update the data for the reliability analysis of safety related systems in a specific nuclear power plant. The code has been used to derive the plant-specific data for reliability analysis of the auxiliary feedwater system of a pressurized water reactor. The prior information for components selected was taken from the U.S. Reactor Safety Study, WASH-1400, and the operating experiences from published licensee event reports. The results show that the updated data are well fitted to log-normal distribution curves and the error factors are reduced significantly.

• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1167-1175
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• 2022

In this study, management index method has been developed to estimate the level of deterioration, applied to Cheongju city, and compared with the previous estimation methods of deterioration level of water distribution system. From the results, distribution systems of Yullyang, Naedeok1 and Yongam2 are found to be seriously deteriorated. And it was also found that probability of pipe breakage was estimated as 3.21%, 4.64% which is highest level at the steel pipe of 200 mm and 300 mm diameter. It was found that risk degree was estimated as 0.2609, 0.2644 by using management index method in Naedeok1 which is the most dangerous distribution system in the city. It was also found that results of risk analysis by management index method have been similar with the results of safety analysis by reliability method and indirect estimation method of deterioration level. Therefore, newly developed management index method can be applied and may be useful to the estimation of deterioration level for the future maintenance and management of water distribution system.