• Journal of the Society of Naval Architects of Korea
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• v.56 no.5
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• pp.383-388
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• 2019

It is essential to reduce the Infra-red signature for increasing ship's survivability in ship design stage. However the ship's IR signature is quite sensitive to the maritime and atmosphere. Therefore, it is very important to select the marine meteorological data to be applied to the signature analysis. In this study, we selected the three meteorological sample sets from the population of the Korea Meteorological Administration's marine environment data in 2017. These samples were selected through the two-dimensional stratified sampling method, taking into account the geopolitical threats of the Korean peninsula and the effective area of the buoy. These sample sets were applied to three naval ships classified by their tonnage, and then the IR signature analysis was performed to derive the Contrast Radiant Intensity (CRI) values. Based on the CRI values, the validity of each sample set was determined by comparing Cumulative Distribution Function (CDF), and Probability Density Function (PDF). Also, we checked the degree of scattering in each sample set and determined the efficiency of analysis time and cost according to marine meteorological sample sets to confirm the possibility of a probabilistic method. Through this process, we selected the standard for optimization of marine meteorological sample for ship IR signature analysis. Based on this optimization sample, by applying probabilistic method to the management of IR signature for naval ships, the robust design is possible.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.48-55
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• 2016

The assessment and prediction of service life of a structure are usually under uncertainty so that rational probabilistic concepts and methods have to be applied. Based on these rational assessment and prediction, optimum maintenance strategies to minimize the life-cycle cost and/or maximize the structural safety can be established. The service life assessment and prediction considering maintenance actions generally includes effects of maintenance types and times of the structural components on the service life extensions of structural system. Existing researches on the service life management have revealed the appropriate system modeling considering the correlation among the components is required for system reliability analysis and probabilistic service life estimation. However, the study on correlation among the maintenance actions is still required. This paper deals with such a study for more effective and efficient service life management. In this paper, both the preventive and essential maintenances are considered for the extended service life estimation and management.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.710-720
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• 2017

In Korea, many nuclear power plants operate at a single site based on geographical characteristics, but the population density near the sites is higher than that in other countries. Thus, multiunit accidents are a more important consideration than in other countries and should be addressed appropriately. Currently, there are many issues related to a multiunit probabilistic safety assessment (PSA). One of them is the quantification of a multiunit PSA model. A traditional PSA uses a Boolean manipulation of the fault tree in terms of the minimal cut set. However, such methods have some limitations when rare event approximations cannot be used effectively or a very small truncation limit should be applied to identify accident sequence combinations for a multiunit site. In particular, it is well known that seismic risk in terms of core damage frequency can be overestimated because there are many events that have a high failure probability. In this study, we propose a quantification method based on a Monte Carlo approach for a multiunit PSA model. This method can consider all possible accident sequence combinations in a multiunit site and calculate a more exact value for events that have a high failure probability. An example model for six identical units at a site was also developed and quantified to confirm the applicability of the proposed method.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.6
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• pp.799-811
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• 2006

As an alternative measure to replace reactive stance with proactive one, a risk based management scheme has been commonly applied to enhance public satisfaction on water service by providing a higher creditable solution to handle a rehabilitation problem of pipe having high potential risk of leaks. This study intended to examine the feasibility of a simulation model to predict a recurrence probability of pipe leaks. As a branch of the data mining technique, probabilistic neural network (PNN) algorithm was applied to infer the extent of leaking recurrence probability of water network. PNN model could classify the leaking level of each unit segment of the pipe network. Pipe material, diameter, C value, road width, pressure, installation age as input variable and 5 classes by pipe leaking probability as output variable were built in PNN model. The study results indicated that it is important to pay higher attention to the pipe segment with the leak record. By increase the hydraulic pipe pressure to meet the required water demand from each node, simulation results indicated that about 6.9% of total number of pipe would additionally be classified into higher class of recurrence risk than present as the reference year. Consequently, it was convinced that the application of PNN model incorporated with a data base management system of pipe network to manage municipal water distribution network could make a promise to enhance the management efficiency by providing the essential knowledge for decision making rehabilitation of network.

• Journal of Korea Water Resources Association
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• v.38 no.6 s.155
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• pp.471-483
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• 2005

A monthly Ensemble Streamflow Prediction (ESP) system was developed by applying a daily rainfall-runoff model known as the Streamflow Synthesis and Reservoir Regulation (SSARR) model to the Han, Nakdong, and Seomjin River basins in Korea. This study first assesses the accuracy of the averaged monthly runoffs simulated by SSARR for the 3 basins and proposes some improvements. The study found that the SSARR modeling of the Han and Nakdong River basins tended to significantly underestimate the actual runoff levels and the modeling of the Seomjin River basinshowed a large error variance. However, by implementing optimal linear correction (OLC), the accuracy of the SSARR model was considerably improved in predicting averaged monthly runoffs of the Han and Nakdong River basins. This improvement was not seen in the modeling of the Seomjin River basin. In addition, the ESP system was applied to forecast probabilistic runoff forecasts one month in advance for the 3 river basins from 1998 to 2003. Considerably improvement was also achieved with OLC in probabilistic forecasting accuracy for the Han and Nakdong River basins, but not in that of the Seomjin River basin.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.685-691
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• 2014

The result of probabilistic maritime risk evaluation is represented by the probability(P=0.0~1.0) These results are shown by an index using Risk Acceptance Criteria(RAC) to base the evaluation generally to know the risk level easily. Current RAC is divided into 3 steps, 5 steps, 7 steps, etc. Despite need to evaluate whether the number of RAC for risk evaluation is reasonable, there is not a related research yet. In this study, It was proposed the evaluation method to determine the optimum index number of RAC using the Sensitivity distribution characteristics and the Sensitivity by the index number of RAC. As application result from the proposed method for probabilistic risk evaluation data obtained from the prior studies, It could be determined the optimum index number of RAC by Sensitivity below 10 times and confirmed that the proposed method is reasonable by this study.

• Tunnel and Underground Space
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• v.31 no.5
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• pp.360-373
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• 2021

Many sources of uncertainty exist in geotechnical analysis ranging from the material parameters to the sampling and testing techniques. The conventional deterministic stability analysis of a plane failure in rock slope produce a safety factor but not a probability of failure or reliability index. In the conventional slope stability analysis by evaluating the ground uncertainty as an overall safety factor, it is difficult to evaluate the stability of the realistic rock slope in detail. This paper reviews some established probabilistic analysis techniques, such as the MCS, FOSM, PEM, Taylor Series as applied to plane failure of rock slopes in detail. While the Monte - Carlo methods leads to the most accurate calculation of the probability of safety, this method is too time consuming. Therefore, the simplified probability methods could be alternatives to the MCS. In this study, using these simple probability methods, the failure probability estimation of a plane failure in rock slope is presented.

• Journal of the Korean School Mathematics Society
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• v.24 no.4
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• pp.349-367
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• 2021

In this study, 85 studies on probability education from 2000 to 2020 were analyzed by publishing year, journals, research subjects, and research topics. Especially, fundamental probabilistic ideas presented by Batanero et al.(2016) were applied to examine which topics were dominant in domestic probability education research. As a result, it was found that there has been a few research in probability education in Korea during the past 20 years, and the number of human subject studies was slightly more than the number of non-human subject studies. In addition, the analysis of research topics according to the fundamental probabilistic ideas showed that two topics, conditional probability and independence and combinatorial enumeration and counting, were dominant in domestic probability education research. However, while both conditional probability and independence and combinatorial enumeration and counting are introduced to young children using intuitive manners in international probability education research, subjects related to these topics were primarily high school students and pre and in-service teachers. Based on the results of this study, the implications for the goal and the direction of future probability education research were discussed.

• Earthquakes and Structures
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• v.22 no.2
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• pp.169-184
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• 2022

The importance of seismicity in developing countries and the strengthening of buildings is a topic of major importance. Therefore, the study of several solutions with the development of new technologies is of great importance to investigate the damage on retrofitted structures by using probabilistic methods. The Federal Emergency Management Agency considers three types of performance levels by considering different scenarios, intensity and duration. The selection and scaling of ground motions mainly depends on the aim of the study. Intensity-based assessments are the most common and compute the response of buildings for a specified seismic intensity. Assessments based on scenarios estimate the response of buildings to different earthquake scenarios. A risk-based assessment is considered as one of the most effective. This research represents a practical method for developing countries where exists many active faults, tall buildings and lack of good implementable approaches. Therefore, to achieve the main goal, two high-rise steel buildings have been modeled and assessed. The contribution of buckling-restrained braces in the elastic design of both buildings is firstly verified. In the nonlinear static range, both buildings presented repairable damage at the central top part and some life safety hinges at the bottom. The nonlinear incremental dynamic analysis was applied by 15 representative/scaled accelerograms to obtain levels of performance and fragility curves. The results shown that by using probabilistic methods, it is possible to estimate the probability of collapse of retrofitted buildings by buckling-restrained braces and tuned mass dampers, which are practical retrofitting options to protect existing structures against earthquakes.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.315-322
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• 1999

The probabilistic keyblock concept which was based upon block theory was applied to the example site by using the observed block moulds data. The more was the block failure likelihood (P(B)) which was defined by the product of the joint combination probability, the shape parameter and the instability parameter, the more were the frequencies of failures observed. If we can acquire these data during a tunnel construction stage, they will be used as a very useful data to construct another tunnel in the neighborhood. Furthermore, a sedimentary rock may have larger P(B) values than a crystalline rock, and for the given P(B) value, the percent block moulds are larger in the former than latter.