• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.13-18
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• 1993

The purpose of this study is to analyze the seismic effects of Lead Rubber Bearing base isolators on bridges. Base isolation is the tool to minimize the effect of earthquake before the seismic force is transfered to the structure. Currently, many structures including the buildings, power plants, and bridges, were built and planned with base isolation method. The simple model is developed for bridges with Lead Rubber Bearings. Equations of motion are solved by Newmark ${\beta}$ method. Springs representing the base isolators are assumed as bilinear springs and piers are modeled as nonlinear springs implementing Q-HYST model. Analysis is performed for the selected bridge. El Centro (N-S) earthquake(1940) is used. Deck displacement, pier ductility and pier shear force are calculated for the various Lead Rubber Bearings.

• Journal of Korea Water Resources Association
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• v.51 no.3
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• pp.235-246
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• 2018

The main purpose of this study is to suggest a methodology for identifying vulnerable region in Choyang creek basin susceptible to soil losses based on runoff aggregation structure and energy expenditure pattern of natural river basin within the framework of power law distribution. To this end geomorphologic factors of every point in the basin of interest are extracted by using GIS, which define tractive force and stream power as well as drainage area, and then their complementary cumulative distributions are graphically analyzed through fitting them to power law distribution to identify the sensitive points within the basin susceptible to soil losses with respect to scaling regimes of tractive force and stream power. It is observed that the range of vulnerable region by scaling regime of tractive force is much narrower than by scaling regime of stream power. This result seems to be due to the tractive force is a kind of scale dependent factor which does not follow power law distribution and does not adequately reflect energy expenditure pattern of river basins. Therefore, stream power is preferred to be a more reasonable factor for the evaluation of soil losses. The methodology proposed in this study can be validated by visualizing the path of soil losses, which is generated from hill-slope process characterized by local slope, to the valley through fluvial process characterized by drainage area as well as local slope.

• Journal of Korea Water Resources Association
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• v.54 no.1
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• pp.49-60
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• 2021

This study presents a methodology to estimate two distinct fractal dimensions of natural river basin by using fractal tree concept. To this end, an analysis is performed on fractal features of a complete drainage network which consists of all possible drainage paths within a river basin based on the growth process of fractal tree. The growth process of fractal tree would occur only within the limited drainage paths possessing stream flow features in a river basin. In the case of small river basin, the bifurcation process of network is more sensitive to the growth step of fractal tree than the meandering process of stream segment, so that various bifurcation structures could be generated in a single network. Therefore, fractal dimension of network structure for small river basin should be estimated in the form of a range not a single figure. Furthermore, the network structures with fractal tree from this study might be more useful information than stream networks from a topographic or digital map for analysis of drainage structure on small river basin.

• Proceedings of the Microbiological Society of Korea Conference
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• 2008.05a
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• pp.118-118
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• 2008

The phylogenetic diversity of microbial communities in calcareous mats from Spearfish Creek, a freshwater stream located in the Black Hills of South Dakota, was examined using PCR-based 16S rDNA sequence analysis. In this study, two types of calcareous mats were compared: mature mats formed on the natural substrate of rock surfaces and developing mats on an artificial substrate of glass slides. Among 63 unique isolates from a clone library of 16S rRNA genes from mature mat samples, there were 8 phyla of Bacteria represented. The predominant phylum was Proteobacteria (48%), with the $\beta$ subclass being the largest group. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes from slide samples collected at intervals for four months showed considerable diversity of the microbial community from the earliest stages of community development. Amplicons isolated from DGGE gels and sequenced indicated that community succession has occurred without increasing microbial diversity. However, light microscopic analysis revealed a significant increase in microbial cell density throughout the community development. Scanning electron microscopy of mat samples provides evidence that diatoms are also important members of calcareous mat communities.