• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.359-366
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• 2020

In this study, a simulation-based damage estimation method for helidecks is proposed using an artificial neural network. The structural members that share a connecting node in the helideck are regarded as a damage group, and a total of 37,400 damage scenarios are numerically generated by applying randomly assigned damage to up to three damage groups. Modal analysis is then performed for all the damage scenarios, which are selectively used as either training or validation or verification sets based on the purpose of use. An artificial neural network with three hidden layers is constructed using a PyTorch program to recognize the patterns of the modal responses of the helideck model under both damaged and undamaged states, and the network is successively trained to minimize the loss function. Finally, the estimated damage rate from the proposed artificial neural network is compared to the actual assigned damage rate using 400 verification scenarios to show that the neural network is able to estimate the location and amount of structural damage precisely.

• Journal of the Korean Geotechnical Society
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• v.26 no.8
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• pp.59-66
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• 2010

In this study, an applicability by using the FEM was investigated for the prediction of both the depth of improvement and the vibration effect when dynamic compaction method is applied. The region was modelled by the field conditions applying dynamic compaction method and the rigid body force was applied to the dynamic load model. Predicted depth of improvement calculated by the vertical peak particle acceleration was compared and analyzed with an existing empirical equation, and the effect of groundwave by deducing the peak particle velocity from vibration sources was compared and analyzed with the results of another existing empirical equation. The results showed that the prediction of the depth of improvement has similar tendency to practice, and the vibration effect has some differences in a particular section from existing equation, but it could predict the safety distance to some degree. The analyzed results are expected to be basic data for the development of reliability of dynamic compaction design with existing empirical method.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.5
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• pp.11-21
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• 2009

Considering that the weight of a biaxial hollow slab system is not increased with an incremental increase in its thickness, and that the flexural stiffness of a biaxial hollow slab is not significantly lower than that of a general solid slab, there has been a growing need for biaxial hollow slab systems, because long span structures are in great demand. In a long span structure, the problem of vibration of floor slabs frequently occurs, and the dynamic characteristics of a biaxial hollow slab system are quite different from the conventional floor systems. Therefore, in this study, the floor vibration of a biaxial hollow slab system subjected to walking load is investigated in comparison with a conventional floor slab system. For the efficiency of time history analysis, an equivalent plate slab model that can precisely represent the dynamic behavior of a biaxial hollow slab system is used. From the analytical results, it was determined that vibration of a biaxial hollow slab system subjected to walking load is evaluated as "office-level vibration," according to the classifications of the architectural institute of Japan and ANSI.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.5
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• pp.47-56
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• 2008

This study was performed to evaluate the effect of Response modification factors (R-factor) in 3-, 9- and 20- story steel Moment Resisting Frame (MRF) buildings. Each structure was designed using a R-factor of 8, as tabulated in the 2000 International Building Code provision (IBC 2000) and Korea Building Code (KBC) 2008. In order to evaluate the maximum and minimum performance expected for such structures, an upper bound and lower bound design were adopted for each model. Next, each analytical model was designed using different R-factors (8, 9, 10, 11, 12) and four different structural periods with the original fundamental period. For a detailed case study, a total of 150 analytical models were subjected to 20 ground motions representing a hazard level with a 2% probability of being exceeded in 50 years. In order to evaluate the performance of the structures, static push-over and non-linear time history analysis (NTHA) were performed, and displacement ductility demand was investigated to consider the ductility capacity of the structures. The results show that the dynamic behaviors for the 3- and 9-story buildings are relatively stable and conservative, while the 20-story buildings show a large displacement ductility demand due to dynamic instability factors. (e.g. P-delta effect and high mode effect)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.7
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• pp.524-531
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• 2013

This work aims at developing a RTB (Rotor Track and Balance) system to alleviate imbalances originating from various sources encountered during blade manufacturing process and environmental factors. The analytical RTB model is determined based on the linear regression analysis to relate the RTB adjustment parameters and their track and vibration results. The model is validated using the flight test data of a full helicopter. It is demonstrated that the linearized model has been correlated well with the test data. A hybrid optimization problem is formulated to find the best solution of the RTB adjustment parameters using the genetic algorithm combined with the PSO (Particle Swarm Optimization) algorithm. The optimization results reveal that both track deviations and vibration levels under various flight conditions become decreased within the allowable tolerances.

• Journal of Radiation Protection and Research
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• v.14 no.2
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• pp.1-9
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• 1989

An analytic method for quantitative comparisions between the alternatives for radiation protection optimization is required to aid the decision making process. This paper introduces the dynamic Markov model to evaluate the effect of inservice inspection, testing, and repair activities of the plant on radiation protection. In the example to put the Markov model into practice, the steam generator inspection intervals which minimize expected cost and total exposure dose were determined using the data for Kori-2 unit and foreign plants. The results show that the effect of the radiation exposure on the steam generator inspection interval is determined by the cost rather than the radiation exposure. The Markov model used in the example can be applied easily to the domestic NPPs by replenishing the data and also can be used in evaluating the comparative priority between various alternatives for radiation protection optimization.

• Smart Media Journal
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• v.1 no.2
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• pp.12-22
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• 2012

Today we are witnessing an increasingly widespread use of cameras in our lives for video surveillance, robot vision, and mobile phones. This has led to a renewed interest in computer vision in general and an on-going boom in human activity recognition in particular. Although not particularly fancy per se, human gait is inarguably the most common and frequent action. Early on this decade there has been a passing interest in human gait recognition, but it soon declined before we came up with a systematic analysis and understanding of walking motion. This paper presents a set of DBN-based models for the analysis of human gait in sequence of increasing complexity and modeling power. The discussion centers around HMM-based statistical methods capable of modeling the variability and incompleteness of input video signals. Finally a novel idea of extending the discrete state Markov chain with a continuous density function is proposed in order to better characterize the gait direction. The proposed modeling framework allows us to recognize pedestrian up to 91.67% and to elegantly decode out two independent gait components of direction and posture through a sequence of experiments.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.5
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• pp.33-47
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• 2007

In a practical engineering, the equivalent static analysis (E.S.A) and the response spectrum analysis (R.S.A) are generally used for the seismic analysis. The base shears obtained from the E.S.A are invariable no matter how the principal axes of building structures are specified on an analysis program while those from the R.S.A are variable. Accordingly, the designed member size may be changed by how an engineer specify the principal axes of a structure when the R.S.A is used. Moreover, the base shears in the normal direction to the excitation axis are sometimes produced even when an engineer performs a response spectrum analysis in only one direction. This tendency makes the base shear, which is used to calculate the scale-up factor, relatively small. Therefore the scale-up factor becomes larger and it results in uneconomical member sizes. To overcome these disadvantages of the R.S.A, an alternative has been proposed in this study. Three types of example structures were adapted in this study, i.e. bi-direction symmetric structure, one-direction antisymmetric structure and bi-direction antisymmetric structure. The seismic analyses were performed by rotating the principal axes of the example structures with respect to the global coordinate system. The design member forces calculated with the scale-up factor used in the practice were compared with those obtained by using the scale-up factor proposed in this study. It can be seen from this study that the proposed method for the scale-up factor can provide reliable and economical results regardless of the orientation of the principal axes of the structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.373-381
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• 2017

Kyeonggi Provincial Government is considering double decker bus service to solve the problem of heavy rush hour traffic. However, the height-to-width ratio is more than 1.16 times larger than that of a general high-speed single decker bus, and the center of gravity is higher. This could cause driving stability problems, such as turnover and breakaway from the lane, especially under strong side-wind conditions at high speed. In this numerical study, the driving characteristics of a model double decker bus were reviewed under side-wind and superelevation conditions at high driving speed. The rolling, pitching, and yawing moment of the model bus were calculated with CFD numerical simulation, and the results were compared to the recovery angular moments of the model bus to evaluate the dynamic stability under given driving conditions. As the model vehicle moves on a straight level road, it is stable under any side-wind conditions. However, on a curved road under side-wind conditions, it could reach unstable conditions dynamically. There is a chance that the bus will turn over when it moves on a curved road with a radius of gyration less than 100 m under side-wind (15 m/s). However, there is a very small chance of breakaway from the lane under any driving conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2739-2746
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• 2011

This paper proposes the method for more effectively calculating X/R which is the ratio of equivalent reactance(X) and resistance(R) of the bulk power system and analyses the characteristic of X/R values by applying the proposed method to the real bulk power systems. X/R is used to determine the rating of the relay in the bulk power systems and its value has been accepted to be big enough to ignore the equivalent resistance of the bulk power systems. However, X/R is calculated as a big number when only the upper transformer and transmission line are considered. The correct approach to calculating X/R needs to consider all the parameters including generators, transformers, lines and loads. This paper calculates X/R of the bulk power systems using dynamic models which have been used to analyse the power system stability. The effectiveness of the proposed method is verified by applying it to the test system and X/R values of the real bulk power systems are analyzed. In addition, the dependence of X/R on the closeness of its calculating locations to the generator is verified by using the marginal loss factor which has been used in the electricity market.