• Journal of Korea Society of Industrial Information Systems
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• v.28 no.6
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• pp.1-10
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• 2023

The nuclear power plant(NPP)'s Instrumentation and Control(I&C) system periodically conducts integrity checks for the maintenance of self-diagnostic function during normal operation. Additionally, it performs functionality and performance checks during planned preventive maintenance periods. However, there is a need for technological development to diagnose failures and prevent accidents in advance. In this paper, we studied methods for estimating the reliability function by utilizing environmental data and self-diagnostic data of the I&C equipment. To obtain failure data, we assumed probability distributions for component features of the I&C equipment and generated virtual failure data. Using this failure data, we estimated the reliability function using representative artificial intelligence(AI) models used in survival analysis(DeepSurve, DeepHit). And we also estimated the reliability function through the Cox regression model of the traditional semi-parametric method. We confirmed the feasibility through the residual lifetime calculations based on environmental and diagnostic data.

• Tunnel and Underground Space
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• v.14 no.4
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• pp.248-260
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• 2004

Damage in brittle rock due to stress increase starts from initiation of microcracks, and then results in failure by forming macro failure planes due to propagation and coalescence of these discrete cracks. Conventionally, continuum approaches using macro-failure criteria or a number of elasto-plastic models have been major solution to implement rock damage and failure. However, actual brittle failure processes can be better described in phenomenological approach if initiation and propagation of discrete fractures are explicitly considered. This study presents damage and failure process of rock using a boundary element code, FRACOD, which has been developed to model fracturing process of rocks. Through a series of numerical uniaxial compressive tests, the feasibility of the developed model was verified, and realistic rock failure process was reproduced considering scale effects in rocks. In addition, the fracturing process and the corresponding rock damage in the vicinity of deep shaft in rock mass were presented as an application of this approach. This approach will be expected to contribute to finding better engineering solutions for the analysis of stability problems in brittle rock masses.

• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.294-299
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• 2008

The present study investigates the ventilation effects on smoke spreading with the rescue stations. Experiments for tunnel fires were carried out for n-heptane pool em at different fire locations, and the heat release rates (HRR) were obtained by addition, using the commercial code (FLUENT), the present article presents numerical results for smoke behavior in railway tunnels with rescue station, and it uses the MVHS (Modified Volumetric Heat Source) model for estimation of combustion products resulting from the fire source determined from the HRR measurement. As a result, it is found that smoke propagation is prevented successfully by the fire doors located inside the cross-passages and especially, the smoke behavior in the accident tunnel can be controlled through the ventilation system because of substantial change in smoke flow direction in the cross-passages.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.1
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• pp.25-38
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• 1993

Numerical models of directional wave spectra for the analysis of offshore structural cable responses are verified. Alternative spreading models are used to predict wave-induced flows in water and for mooring systems. Hydrodynamic wave forces upon cable are estimated. using a Morison formula encompassing considerations for drag and for inertial forces both parallel and tangential to the slope of the cable. Numerical analysis for directional random waves. including consideration of displacement and velocity, trajectory, phase plane response. and tension are shown for mooring system cable responses at both the tether point for a buoy and at the anchor point. The effects of wave forces far different drag coefficients, various significant wave heights, and selected wave parameters are considered in the analysis. For the specific systems considered in the examples, it is demonstrated that wave period and height as well as wave spreading function parameters and drag coefficients, have an important effect upon the dynamic responses of the cable-buoy systems.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.367-373
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• 2016

Many of plastic powders handled in industry are combustible and have the hazard of dust fire and explosion accidents. However poor information about the safe handling has been presented in the production works. The aim of this research is investigated experimentally on explosive characteristics of various plastic powders used in industry and to provide additional data with safety informations. The explosibility parameters investigated using standard dust explosibility test equipment of Siwek 20-L explosion chamber. As the results, the dust explosion index ($K_{st}$) of ABS ($209.8{\mu}m$), PE ($81.8{\mu}m$), PBT ($21.3{\mu}m$), MBS ($26.7{\mu}m$) and PMMA ($14.3{\mu}m$) are 62.4, 59.4, 70.3, 303 and 203.6[$bar{\cdot}m/s$], respectively. And flame propagation velocity during plastic dust explosions for prediction of explosive damage was estimated using a flame propagation model based on the time to peak pressure and flame arrival time in dust explosion pressure assuming the constant burning velocity.

• The KIPS Transactions:PartB
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• v.12B no.3 s.99
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• pp.349-356
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• 2005

Artificial Organism-used application areas are expanding at a break-neck speed with a view to getting things done in a dynamic and Informal environment. A use of general programming or traditional hi methods as the representation of Artificial Organism behavior knowledge in these areas can cause problems related to frequent modifications and bad response in an unpredictable situation. Strategies aimed at solving these problems in a machine-learning fashion includes Genetic Programming and Evolving Neural Networks. But the learning method of Artificial-Organism is not good yet, and can't represent life in the environment. With this in mind, this research is designed to come up with a new behavior evolution model. The model represents behavior knowledge with Classification Rules and Enhanced Backpropation Neural Networks and discriminate the denomination. To evaluate the model, the researcher applied it to problems with the competition of Artificial-Organism in the Simulator and compared with other system. The survey shows that the model prevails in terms of the speed and Qualify of learning. The model is characterized by the simultaneous learning of classification rules and neural networks represented on chromosomes with the help of Genetic Algorithm and the consolidation of learning ability caused by the hybrid processing of the classification rules and Enhanced Backpropagation Neural Network.

• The Journal of the Acoustical Society of Korea
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• v.31 no.6
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• pp.391-398
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• 2012

In this paper, prediction of centrifugal fan was conducted through combination the hybrid CAA method which was used to predict the fan noise with the FRPM technique which was used to generate the broadband noise source. Firstly, flow field surround the centrifugal fan was computed using the RANS equations and noise source region was deducted from the computed flow field. Then the FRPM technique was applied to the source region for generation of turbulence which satisfies the stochastic features. The noise source of the centrifugal fan was modeled by applying the acoustic analogy to the synthesized flow field from the computed and generated flow fields. Finally, the broadband noise of the centrifugal fan was predicted through combination the modeled noise source with the linear propagation which was realized using the boundary element method. It was confirmed that the proposed technique is efficient to predict the tonal and broadband noises of centrifugal fan through comparison with the measured data.

• Journal of the Korean earth science society
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• v.37 no.4
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• pp.200-210
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• 2016

Geoacoustic modeling is used to predict sound transmission through submarine bottom layers of sedimentary strata and acoustic basement. This study reconstructed four geoacoustic models for sediments of 50 m thick at the Jeongdongjin area in the western continental margin of the East Sea. Bottom models were based on the data of the highresolution air-gun seismic and subbottom profiles (SBP) with sediment cores. P-wave speed was measured by the pulse transmission technique, and the resonance frequency of piezoelectric transducers was maintained at 1MHz. Measurements of 42 P-wave speeds and 41 attenuations were fulfilled in three core sediments. For actual modeling, the P-wave speeds of the models were compensated to in situ depth below the sea floor using the Hamilton method. These geoacoustic models of coastal bottom strata will be used for geoacoustic and underwater acoustic experiments reflecting vertical and lateral variability of geoacoustic properties in the Jeongdongjin area of the East Sea.

• The Journal of the Acoustical Society of Korea
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• v.31 no.8
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• pp.551-560
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• 2012

Target detection by acoustic barrier method includes active and passive sonar technique and time reversal process whose theoretical background is already well defined. In this paper, the concept and theory of underwater detection by passive ocean time reversal is established. Also, the reason that this study was conducted was to investigate feasibility of complex mathematical modeling to provide some predictive capability for underwater acoustic barrier with passive time reversal. It may eventually lead to a useful predictive tool when designing underwater acoustic barrier detection system using the passive time reversal concept.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.2
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• pp.69-83
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• 2018

The South China Sea (SCS) is a typical marginal sea characterized with the deep basin, shelf break, shallow shelf, many straits, and complex bathymetry. This study investigated the tidal characteristics and propagation, and reproduced typhoon-induced storm surge in this region using the regional real-time tide-surge model, which was based on the unstructured grid, resolving in detail the region of interest and forced by tide at the open boundary and by wind and air pressure at the surface. Typhoon Haiyan, which occurred in 2013 and caused great damage in the Philippines, was chosen as a case study to simulate typhoon's impact. Amplitudes and phases of four major constituents were reproduced reasonably in general, and the tidal distributions of four constituents were similar to the previous studies. The modelled tide seemed to be within the acceptable levels, considering it was difficult to reproduce the tide in this region based on the previous studies. The free oscillation experiment results described well the feature of tide that the diurnal tide is prevailing in the SCS. The tidal residual current and total energy dissipation were discussed to understand the tidal and sedimentary environments. The storm-surge caused by typhoon Haiyan was reasonably simulated using this modeling system. This study established the regional real-time barotropic tide/water level prediction system for the South China Sea including the seas around the Philippines through the validation of the model and the understanding of tidal characteristics.