• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.93-104
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• 2011

In this paper, a numerical procedure of probabilistic steady seepage analysis that considers the spatial variability of soil permeability is presented. The procedure extends the deterministic analysis based on the finite element method to a probabilistic approach that accounts for the uncertainties and spatial variation of the soil permeability. Two-dimensional random fields are generated based on a Karhunen-Lo$\grave{e}$ve expansion in a fashion consistent with a specified marginal distribution function and an autocorrelation function. A Monte Carlo simulation is then used to determine the statistical response based on the random fields. A series of analyses were performed to verify the application potential of the proposed method and to study the effects of uncertainty due to the spatial heterogeneity on the seepage behavior of soil foundation beneath water retaining structure with a single sheet pile wall. The results showed that the probabilistic framework can be used to efficiently consider the various flow patterns caused by the spatial variability of the soil permeability in seepage assessment for a soil foundation beneath water retaining structures.

• Journal of the Korean Geotechnical Society
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• v.22 no.4
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• pp.73-83
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• 2006

Seepage analysis through unsaturated zone based on the theory of unsaturated flow is commonly performed to evaluate dam safety. However, the concepts of unsaturated soil behavior have not been transferred into the hands of practicing geotechnical engineers since the problems involving unsaturated soils often have the appearances of being extremely complex. There is variability and uncertainty associated with the unsaturated hydraulic properties that in turn will lead to variability in predicting unsaturated soil behavior such as seepage rate and the pore water pressure distribution. In this paper, measurements of the soil-water characteristic curve and saturated hydraulic conductivity for the core material of dam were conducted. Then, finite element stochastic analysis was used to capture the effect of unsaturated hydraulic properties on the seepage behavior of dam. It is observed that the amount of seepage increases, as the values of unsaturated soil parameters a and n increase. The values of m and p showed opposite trend.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.627-632
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• 1997

Recently, the prestressed concrete box girder bridges are increasingly built at various locations in the world. The mechanical and structural behavior of prestressed concrete brides varies because of time-dependent material properties and sequential change of structural system due to stepwise construction. The time-dependent behavior of concrete is of importance in the design and construction of segmentally constructed and cast-in-place prestressed concrete box girder bridges. The structural response is affected b variations in creep, shrinkage properties of concrete. In this study, the example of time-dependent deformations is extended to establish how the variability in concrete properties affects the accuracy of the calculated deformations in such a bridge, and finally the results are discussed.

• Structural Engineering and Mechanics
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• v.37 no.6
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• pp.685-691
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• 2011

Developing accurate prediction models for deterioration behavior represents a challenging but essential task in comprehensive Infrastructure Management Systems. The challenge may be a result of the lack of historical data, impact of unforeseen parameters, and/or the past repair/maintenance practices. These realities contribute heavily to the noticeable variability in deterioration behavior even among similar components. This paper introduces a novel approach to predict the deterioration of any infrastructure component. The approach is general as it fits any component, however the prediction is custom for a specific item to consider the inherent impacts of expected and unexpected parameters that affect its unique deterioration behavior.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.2
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• pp.267-274
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• 2017

Objective: The objective of this study was to investigate the effect of 20-day litter weight on behavior and heart rate variability (HRV) of piglets under stress. Methods: Forty four original litters were categorized as high litter weight (HW) litters (n = 22) and low litter weight (LW) litters (n = 22) by 20-day litter weight. From each original HW litter, three males and three females were randomly selected after weaning and the 12 piglets from two original litters with similar age of days were regrouped into one new high litter weight (NHW) litter (11 NHW litters in total). The original LW litters were treated with a same program, so that there were 11 new low litter weight (NLW) litters as well. The latencies to first fighting, fighting frequencies and duration within three hours were recorded after regrouping and the lesions on body surface within 48 hours were scored. Besides, HR (heart rate, bpm, beats per minute) and activity count (ACT), time domain indexes and frequency domain indexes of the piglets were measured in an isolation trial to analyze the discrepancy in coping with stress between the original HW and LW litters. Results: The results exhibited that piglets from the HW litters launched fighting sooner and got statistically higher skin lesion score than those from the LW litters (p = 0.03 and 0.02, respectively). Regarding the HRV detection, compared with the HW litters, the LW litters exhibited a lower mean HR (p<0.05). In the isolation test, a highly significant higher ACT value was observed between the HW litters, compared to the LW litters (p<0.01). Significant differences were observed in standard deviation of R-R intervals, standard deviation of all normal to normal intervals, and most frequency-domain indicators: very low-frequency, low-frequency, and high frequency between the HW and LW litters as well. The difference in LF:HF was not significant (p = 0.779). Conclusion: This study suggests that compared with litters of low 20-day litter weights, litters with higher 20-day litter weight take more positive strategies to cope with stress and have stronger HRV regulation capacity; HW litters demonstrate better anti-stress and adaptation capacity in the case of regrouping and isolation.

• Architectural research
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• v.7 no.2
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• pp.61-68
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• 2005

A methodology for design of reinforced concrete members for serviceability in general and deflection control in particular is presented based on application of utility theory. The approach is based on minimizing total cost including both initial construction and cost of failure considering variability in structural behavior and various forms of serviceability loss function. The method is demonstrated for the case of a simply supported slab for example.

• Human Ecology Research
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• v.56 no.2
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• pp.157-165
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• 2018

Using data from the Panel Study on Korean Children, this study investigated whether children with high levels of problem behaviors adjusted more poorly on the $1^{st}-grade$ than children with low levels of problem behaviors, and whether there was evidence of intra-individual stability in behavior problems over time. Data were analyzed by use of the Latent Growth Model and group differences analyses. Three findings were noteworthy. First, there was evidence of intra-individual and inter-individual variability in behavior problems between poor- and non-poor household children. Second, children with higher initial levels of internalizing and externalizing behaviors at 4 years had lower school readiness scores at 6 years. Finally, children with lower levels of school readiness at 6 years had lower school adjustment scores in $1^{st}$ grade. The results discuss implications for future research and policies for preschool children. With mediating effect of school readiness, developmental trajectories of child's problem behavior have been found to be predictors of delayed achievements in school. The results show that intervention programs are necessary for children with high levels of problem behavior. This study also showed that children who experienced poverty at home could have more difficulties in school readiness and school adjustment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.27-32
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• 2008

The laminated composite materials have been applied to various mechanical structures due to their high performance to weight ratios. In this study, we suggest a stochastic finite element scheme for the probabilistic analysis of the composite laminated plates. The composite materials consist of two different materials which constitute the matrix and fiber. The material properties in the major and minor directions are determined depending on the volume fraction of these two materials. In this study, the elastic modulus and shear modulus are considered as random and the effect of these random properties on the behavior of the composite plate is investigated. We adopt the weighted integral scheme in the formulation, which has been recognized as the most accurate method in the statistical methodologies. For verification of the proposed scheme, Monte Carlo analysis is also performed for the comparison with the proposed scheme.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.5
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• pp.206-214
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• 1996

Because of the wide variety of the composite materials, inherent variability in properties, and complex temperature and strain rate dependence, large strain behavior of these materials has not been well characterized. Large strain behavior under uniaxial tension is characterized over a range of temperatures and strain rates, and a modified simple linear viscoelastic model is fit to the observed data. Of particular importance is the strain rate and temperature dependence of these composites, and it is the primary focus of this study. The strain rate and temperature dependence is then used to predict limiting tensile strains, based on Marciniak imperfection theory. Excellent correlation was obtained between model and experiment and the results are summarized in maps of forming limit as a function of strain rate and temperature.

• Wind and Structures
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• v.31 no.1
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• pp.1-14
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• 2020

This paper presents a method of estimation of fatigue demands on connection bolts of tubular steel wind turbine towers. The presented method relies on numerical simulation of aerodynamic loads and structural behavior of bolted connections modeled using finite element method. Variability of wind parameters is represented by a set of values derived from their probability densities, which are adjusted based on field measurements. Numerically generated stress time-series show agreement with the measurements from strain gauges inside bolts, in terms of power spectra and the resulting damage. Position of each bolt has a determining effect on its fatigue damage. The proposed framework for fatigue life estimation represents the complexities in loading and local behavior of the structure. On the other hand, the developed procedure is computationally efficient since it requires a limited number of simulations for statistically representing the wind variations.