• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.941-948
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• 2017

Recently, hydrogen energy has been in the spotlight as an alternative to diminishing fossil fuels and as a potential solution to environmental pollution. The development of hydrogen-fueled vehicles and the demands for improved fuel efficiencies have resulted in the need to increase the volume of the hydrogen pressure vessels. Pressure vessels having an elliptical bottom, as opposed to one that is hemispherical, allow for a greater capacity. However, there are insufficient studies on the feasibility of the forming process required for an elliptical bottom. In this study, the liner capacity is calculated according to the ratios of the major to the minor axes of the elliptical bottom part in a hydrogen pressure vessel. Structural safety is verified through finite element analyses, and the results are compared to the theoretical results. The feasibility of the proposed elliptical shape of the pressure vessel bottom, while filled to maximum capacity, is validated through forming analysis.

• Korean Journal of Environmental Agriculture
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• v.21 no.4
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• pp.269-273
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• 2002

A 0.19 hectare stream water purification demonstration wetland was constructed and planted with cattails from April 2001 to May 2001. Some portions of its bottom surfaces adjacent to levees have a variety of slope of 1:4 $\sim$ 1:15 and two small open water areas were installed in the wetland. These make its shape closer to a natural wetlant Nitrogen removal was a major objective of the wetlant Waters of Sinyang Stream flowing into Kohung Esturiane Lake located southern coastal region of Korean Peninsula were pumped and funneled into it. Volumes and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Average inflow and outflow were 120 $m^3/d$ and 112 $m^3/d$, respectively. Hydraulic retention time was about 3.1 days. Average nitrate and total nitrogen removal rate for the early stage of the wetlands were 85.8 $mg/m^2/day$, 171.4 $mg/m^2/day$ respectively. Full establishment of cattails within a few years can develope litter-soil substrates and supply available carbon sources beneficial to the denitrification of nitrate. These can lead to increases of the nitrate retention rate. Short circuiting and dead zone areas which might be occurred due to the close-to-nature layout of the wetland were not observed during the monitoring period.