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Vibration and Dynamic Stability of Pipes Conveying Fluid on Elastic Foundations
Bong-Jo Ryu,Si-Ung Ryu,Geon-Hee Kim,Kyung-Bin Yim 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.12
The paper deals with the vibration and dynamic stability of cantilevered pipes conveying fluid on elastic foundations. The relationship between the eigenvalue branches and corresponding unstable modes associated with the flutter of the pipe is thoroughly investigated. Governing equations of motion are derived from the extended Hamilton's principle, and a numerical scheme using finite element methods is applied to obtain the discretized equations. The critical flow velocity and stability maps of the pipe are obtained for various elastic foundation para-meters, mass ratios of the pipe, and structural damping coefficients. Especially critical mass ratios, at which the transference of the eigenvalue branches related to flutter takes place, are precisely determined. Finally, the flutter configuration of the pipe at the critical flow velocities is drawn graphically at every twelfth period to define the order of the quasi-mode of flutter configuration.<br/>
김건웅(Geon-Ung Kim),최조천(Jo-Cheon Choi),양진호(Jin-Ho Yang),최상길(Sang-Gil Choi),추종윤(Jong-Yun Choo) 한국통신학회 2013 한국통신학회 학술대회논문집 Vol.2013 No.11
Demand for spectrum resources, especially in low frequency bands is ever increasing with the development of mobile telecommunications and so is their economic value as other national resources. As a way to enhance the economic efficiency of use of spectrum resources, many countries. Recently focused on the management of public and broadcasting spectrums which have traditionally been undercharged compared to their economic values. This study discusses economic value valuation for the usage of low frequencies, which has analysed economic effects of the Fishery info-communications using spectrum in this band. That is the spectrum demand valuation which has based of mobile telecommunications and so is their economic value. This will help establish a policy direction for spectrum in low frequency bands.
地下排水가 土地生産性 및 土壤의 生理的 性質에 미치는 影響에 關한 硏究
李錫健,金熙雄 慶北大學校 1979 論文集 Vol.28 No.-
There are considerable area of wet paddy field in Korea, that must be improved its drainage system. And, it is well known that the improving method of drainage system is subsurface drainage in the wet paddy field. This experiment was performed to show a basic information about drainage by culvert, and was analyzed about physical characteristics of soil, weather data, consumptive water depth, cracks, moisture content, bearing capacity of soil, possibility for use of farm machinery, growth of rice, and crop yields. The obtained results were summarized as follows: 1. It was possible to maintain of optimum consumptive water depth by controlling of the relief well. The estimated values of consumptive water depth were 22.0mm/day in the A plot, 21.14mm/day in the B plot, and 12.34mm/day in the Ord. plot respectively. 2. The amount of cracks in the A and B plot was larger than that in the Ord. plot. 3. In the values of moisture content, the A and B plot showed much less than the Ord. plot. Comparing with the different soil depth, the variation of moisture content for the harvest drainage season were estimated larger than that of intermediate drainage season. 4. The A and B plot showed for much than the Ord. Plot in its soil bearing capacity. It was possible to use farm machinery for the harvest season in the A and B plot while impossible in the Ord. plot. 5. The yield of rice increased to the value of 21.1% in the A plot, and 13.4% in the B plot in comparison with the Ord. plot.
Vibration and Dynamic Stability of Pipes Conveying Fluid on Elastic Foundations
Ryu, Bong-Jo,Ryu, Si-Ung,Kim, Geon-Hee,Yim, Kyung-Bin The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.12
The paper deals with the vibration and dynamic stability of cantilevered pipes conveying fluid on elastic foundations. The relationship between the eigenvalue branches and corresponding unstable modes associated with the flutter of the pipe is thoroughly investigated. Governing equations of motion are derived from the extended Hamilton's principle, and a numerical scheme using finite element methods is applied to obtain the discretized equations. The critical flow velocity and stability maps of the pipe are obtained for various elastic foundation parameters, mass ratios of the pipe, and structural damping coefficients. Especially critical mass ratios, at which the transference of the eigenvalue branches related to flutter takes place, are precisely determined. Finally, the flutter configuration of the pipe at the critical flow velocities is drawn graphically at every twelfth period to define the order of the quasi-mode of flutter configuration.