• Smart Structures and Systems
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• v.21 no.5
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• pp.591-600
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• 2018

The probabilistic characterization of wind field characteristics is a significant task for fatigue reliability assessment of long-span railway bridges in wind-prone regions. In consideration of the effect of wind direction, the stochastic properties of wind field should be represented by a bivariate statistical model of wind speed and direction. This paper presents the construction of the bivariate model of wind speed and direction at the site of a railway arch bridge by use of the long-term structural health monitoring (SHM) data. The wind characteristics are derived by analyzing the real-time wind monitoring data, such as the mean wind speed and direction, turbulence intensity, turbulence integral scale, and power spectral density. A sequential quadratic programming (SQP) algorithm-based finite mixture modeling method is proposed to formulate the joint distribution model of wind speed and direction. For the probability density function (PDF) of wind speed, a double-parameter Weibull distribution function is utilized, and a von Mises distribution function is applied to represent the PDF of wind direction. The SQP algorithm with multi-start points is used to estimate the parameters in the bivariate model, namely Weibull-von Mises mixture model. One-year wind monitoring data are selected to validate the effectiveness of the proposed modeling method. The optimal model is jointly evaluated by the Bayesian information criterion (BIC) and coefficient of determination, $R^2$. The obtained results indicate that the proposed SQP algorithm-based finite mixture modeling method can effectively establish the bivariate model of wind speed and direction. The established bivariate model of wind speed and direction will facilitate the wind-induced fatigue reliability assessment of long-span bridges.

• The Journal of the Korea Contents Association
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• v.12 no.1
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• pp.176-184
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• 2012

People are exposed to various media. After the Digital Revolution, quantitative expansion of the media is at a rapid pace. Because of the expansion of the media, advertising needs efforts that induce the audiences' reaction. Rhetorical devices are used as the efforts. This study noted the visual paradox of rhetorical devices because it is an effective representation device that induced audiences' reaction by deliberate contradiction and ambiguity. This study has defined the visual paradox based on define and classification of paradox in logic. This study also tried to reveal the relationship between images and text for signification by metalanguage because it is important to the visual paradox in advertising. And analyzed cases of Volkswagen ads to prove the research process. Finally identified that images and text interact to create a new meaning.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.375-382
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• 2000

The surface hydrology of large watershed is susceptible to several preferred stable states with transitions between stable states induced by stochastic fluctuations. This comes about due to the close coupling of land surface and atmospheric interaction. An interesting and important issue is the duration of residence in each mode. In this study, mean transition tunes between the stable modes are analyzed for the Han River Basin. On the basis of historical data, the nonlinear water balance model is calibrated for the Han River Basin. The transition times between the stable modes in the model are studied based on the stochastic representation of the physical processes and on the calibrated model parameters. This study has implications for prediction of the transition time between stable modes or residence times, that is, the time the system spends in a given stable modes, since this would be equivalent to predicting the duration of drought or wet conditions.

• School Mathematics
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• v.12 no.4
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• pp.585-604
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• 2010

This study aims to investigate understanding of meanings of division, quotitive division and partitive division, by the third graders and preservice elementary teachers. To do this, we analysed and compared mathematics textbooks according to 9 mathematics curricula, gathered information about their understanding by questionnaire method targeting 5 third graders and 36 preservice elementary teachers, and analysed their responses in relation to recognition of division-based situations, solution using visual representations, and awareness of quotitive division and partitive division. In Korea, meanings of division have been taught in grade 2 or 3 in various ways according to curricula. In particular, the mathematics textbook of present curriculum shows a couple of radical changes in relation to introduction of division. We raised the necessity of reexamination of these changes, based on our results from questionnaire analysis that show lack of understanding about two meanings of division by the preservice elementary teachers as well as the third graders. And we also induced several didactical implications for teaching meanings of division.

• The Journal of the Korea Contents Association
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• v.13 no.7
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• pp.9-15
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• 2013

In the VnR (Virtual and Real Worlds) of recent virtual reality convergence, the modelling of realistic human face is focused on the facial appearance such as the shape of facial parts and muscle movement. However, the facial changing parameters caused by environmental factors beyond the facial appearance factors can be regarded as important ones in terms of effectively representing virtual avatar. Therefore, this study evaluates user's visual feeling response according to the opacity variation of eye reflection of virtual avatar which is considered as a new parameter for reprenting realistic avatar. Experimental result showed that more clear eye reflection induced more realistic visual feeling of subjects. This result can be regarded as a basis for designing realistic virtual avatar by supporting a new visual realistic representing factor (eye reflection) and its degree of representation (reflectance ratio).

• Journal of Physiology & Pathology in Korean Medicine
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• v.20 no.1
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• pp.202-208
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• 2006

The goal of this study is to develop knowledge representation method for the construction and evaluation of ontology for diagnosis in oriental medicine. To develop the expert system for decision making on diagnosis and treatment, the systematic and structural knowledge which can be processible in EMR(Electronic Medical Record) must be precedent, and the Computational Process which control the system as well. This study set up an ontology as a trial model to represent the oriental medical knowledge into the machine processible one. Protege 2.1 has been used to build the ontology, and the serialization format of our ontology is the XML document based on OWL. The components of oriental medical diagnosis was arranged with the combination of symptoms which belong to the certain symptom patterns. Then natural language which expresses the oriental medical diagnosis components were converted into the logical sentence, and individual characteristic symptoms into each values of specific properties. In addition to the study, the diagnosis software for oriental medicine was developed and it used the ontology which we developed. Sequently, we tested the software to confirm the appropriateness of ontology. The result of the test shows that diagnostic questions are automatically formulated according to the diagnosis components of this ontology and that as such diagnostic results are induced. Therefore, the ontology system in this study will be efficient to develop the diagnosis program and useful as a tool for doctors to make decision. But, it is not recommendable to apply the system to the clinical environment until the clear diagnosis standards are introduced, and the more reliable diagnosis program can be developed based on the more appropriate ontology mentioned above.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.4
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• pp.343-352
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• 2018

In this study, a motion control problem for the vessels towed by tugboats or towing ships on the sea is considered. The towed vessel looks like the barge ship, which is used for many purposes. In these vessels, basically, the power propulsion system is not installed but just towed by a towing vessel such as tugboats with ropes and wires. It means that the motions of towed vessel are basically dependent on the tracking route of towing boat. Therefore, in some cases, undesirable and unpredictable motions may be made by environmental factors such as wave, wind attack and so on. As a result, a collision accident with others may occur during maneuvering situation. Based on these facts, the authors try to encourage the steering performance of the towed vessel by using controllable rudders without any propulsion system. In this study, especially, a controllable vessel with three rudders is considered, and a mathematical model is induced for the future study. The model is described as surge, sway motion and inertia moment by following the general representation method for the surface ship.

• Smart Structures and Systems
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• v.23 no.6
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• pp.565-577
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• 2019

One of the most effective countermeasures for mitigating cable vibration is to install mechanical dampers near the anchorage of the cable. Most of the dampers used in the field are so-called passive dampers where their parameters cannot be changed once designed. The parameters of passive dampers are usually determined based on the optimal damper force obtained from the universal design curve for linear dampers, which will provide a maximum additional damping for the cable. As the optimal damper force is chosen based on a predetermined principal vibration mode, passive dampers will be most effective if cable undergoes single-mode vibration where the vibration mode is the same as the principal mode used in the design. However, in the actual engineering practice, multi-mode vibrations are often observed for cables. Therefore, it is desirable to have dampers that can suppress different modes of cable vibrations simultaneously. In this paper, MR dampers are proposed for controlling multi-mode cable vibrations, because of its ability to change parameters and its adaptability of active control without inquiring large power resources. Although the highly nonlinear feature of the MR material leads to a relatively complex representation of its mathematical model, effective control strategies can still be derived for suppressing multi-mode cable vibrations based on nonlinear modelling, as proposed in this paper. Firstly, the nonlinear Bouc-wen model is employed to accurately portray the salient characteristics of the MR damper. Then, the desired optimal damper force is determined from the universal design curve of friction dampers. Finally, the input voltage (current) of MR damper corresponding to the desired optimal damper force is calculated from the nonlinear Bouc-wen model of the damper using a piecewise linear interpolation scheme. Numerical simulations are carried out to validate the effectiveness of the proposed control algorithm for mitigating multi-mode cable vibrations induced by different external excitations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.5
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• pp.267-275
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• 2022

Using a nonconforming mesh in enrichment methods results in several numerical issues induced by discontinuities and singularities found within the solution spaces, including the computational overhead during integration. In this study, we present a novel enrichment technique based on the selective expansion technique of moment fitting (Düster and Allix, 2020). In particular, two modifications are proposed to address the inefficiency during the integration process. First, a feedforward artificial neural network is introduced to correlate the implicit functions and integration moments. Through numerical examples, it is shown that the efficiency of the method is greatly improved when compared with existing expansion techniques, whereas the solution accuracy is maintained. Additionally, the finite element and domain representation grids are separated, which in turn improves the solution accuracy even for coarse mesh conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.657-664
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• 2008

Rain-wind induced cable vibration can cause the damages in the cable-stayed bridge due to very little inherent damping characteristics and low fundamental frequency. External Dampers attached to stay cables near anchorages have been shown to be effective means at short stay-cables. However, installation locations of external dampers are limited to a particular range due to aesthetic and practical reasons for very long stay-cables. A recent study by the authors showed that the stay-cable vibration system can perform better than the optimal passive viscous damper, thereby demonstrating its applicability in large cable-stayed bridges. This paper extends the previous study on the taut string representation of the cable by adding cable sag and inclination. The response of the proposed system compared to those of the cable with and without an external damper, and the movable anchorage system provides very effective mitigation of cable vibration. Cable damping ratio is seen to be remarkably reduced by movable anchorage system for a wide range of cable sag. This result shows that the sag effects of the proposed system should be considered.