• Journal of the Korean earth science society
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• v.32 no.5
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• pp.461-473
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• 2011

In this paper, trends of the widely used stability indices (SIs) and environmental parameters (EPs) were examined by using the 30-year routine rawinsonde data observed in three upper air observatories (Osan, Gwangju and Pohang) over South Korea. To take into account of the contribution of water vapor to a parcel density, we applied the virtual temperature correction in calculating the SIs and EPs. The trends of SIs and EPs indicated significant increases of temperature and moisture contents, especially at the low-to-mid troposphere during the last 10 years. The warming trend in the lower troposphere shows about 3 times greater than that of the global average (+0.10- $+0.20^{\circ}C$/10 years), whereas the cooling trend of lower stratosphere demonstrates a similar trend with the global average (-0.33- $-0.60^{\circ}C$/10 years). The vertical stability is clearly reduced due to the unsymmetrical change of atmospheric elements. The unstabilizing trend with the increased moisture contents gradually changed the atmospheric environment in South Korea into the conditions favorable for the occurrence of severe weather or intensifications of such events. These trends are consistent with the recent observations, which showed clear increase in the intensity and frequency of heavy rainfalls.

• Journal of Ocean Engineering and Technology
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• v.13 no.1 s.31
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• pp.121-129
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• 1999

Double-diffusive convection with verical temperature and concentration gradients in thermally stratified fluids has been investigated experimentally using an electrochemical technique. Cupric sulfuric-sulffuric acid solution confined between two horizontal copper electrodes was used. The change of thermal and solutal buoyance has no influence on the range of voltage for the limiting current. Due to Soret effect, the onset time of natural convection is delayed as the stabilizing thermal buoyancy decreases. Also it is found that the shrinkage of the unstabilizing solutal buoyancy makes the onset of natural convection retard. Multi-layered convective phenomena do not appear because cupric sulfate-sulfuric acid solution is thermally stratified, and heat diffuses faster than cupric sulfate solfate solution.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.77-82
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• 2004

This paper presents polar converting logic(PCL) of BTT missiles against slowly moving or stationary targets. A guidance commands expressed in rectangular coordinates must be converted in the form of polar coordinates for BTT control. Since conventional PCL has nonlinear and discontinuous function, the missiles may lose controllability when pitch acceleration command equals to zero. Further, roll coupling may have a serious unstabilizing influence on homing guidance with two gimbals seeker. In this paper, a linear homotopy equation is introduced to improve the controllability and a command following performance at midcourse phase. We also design a PCL which is less sensitive to pitch acceleration command so that it may improve the stability of the homing loop. To substantiate our conclusion, results of the computer simulation have been illustrated.