http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
나노유체 : 비정상열선법 나노유체 열전도도 측정 시 자연대류효과 제거법
구준모 ( June Mo Koo ),한기수 ( Ki Soo Han ),( Clement Kleinstreuer ) 한국액체미립화학회 2012 한국액체미립화학회 학술강연회 논문집 Vol.2012 No.-
Significant deviations between published results have been reported when measuring the effective thermal conductivity of nanofluids with the transient hot-wire method (THWM). This may be attributed to a poor selection of the temperature data range, which should meet the following conditions. The start time should be chosen after the conductive heat flux delay time, while the end time should be selected before a crossover point when natural convection becomes significant. Furthermore, the data range should be large enough not to be affected by the local oscillation of the data estimates. Proper selection of the temperature data range depends also on both the fluid type, e.g., water or EG, and the base temperature. As the most suitable temperature data range cannot be predetermined before taking measurements, it is recommended that temperature history data are carefully investigated for each data acquisition cycle. Although the nanofluid viscosity increases slightly and the thermal expansion coefficient decreases significantly, natural convection has a significant impact on THWM-accuracy when measuring thermal mixture properties. This may be the result of local motion of nanoparticles invoking natural convection early on. Considering an EG-based 1.06 vol.% ZnO nanofluid, he thermal conductivity was measured to increase by 5.4%.
Frequency-domain elastic full waveform inversion for VTI media
Lee, Ho-Yong,Koo, June Mo,Min, Dong-Joo,Kwon, Byung-Doo,Yoo, Hai Soo Blackwell Publishing Ltd 2010 Geophysical journal international Vol.183 No.2
<P>SUMMARY</P><P>To describe subsurface structures in anisotropic media properly, particularly in transversely isotropic media with a vertical symmetry axis (VTI), which frequently appear in sedimentary basin environments, we develop a frequency-domain elastic full waveform inversion algorithm for 2-D VTI media. The inversion algorithm is based on the cell-based finite-difference modelling method and the adjoint state of the wave equation.</P><P>Because the anisotropic inversion for VTI media deals with more elastic constants than the isotropic inversion, it is more prone to obtain local minimum solutions. For this reason, we may not succeed in properly describing the elastic constants of subsurface media if we only apply the standard inversion techniques to anisotropic waveform inversion. To compensate for the ill-posedness of the anisotropic waveform inversion, we couple elastic constants C<SUB>11</SUB> and C<SUB>33</SUB> based on Thomsen's relationship, which is also supported by the sensitivity analysis with respect to the parameters. To enhance the inversion results, we apply the frequency-selection strategy, moving from lower to higher frequencies and we carry out the inversion process over two stages. In both stages, all of the elastic constants are simultaneously optimized, as is done in the conventional waveform inversion. However, we only accept the inversion results for C<SUB>11</SUB>, C<SUB>33</SUB> and C<SUB>44</SUB> at the first stage, which will be used as the starting models for the second stage and C<SUB>13</SUB> is reinitialized as a linearly increasing model. We apply our waveform inversion algorithm to a simple 3-layered model and a part of the overthrust model. For the 3-layered model, the first inversion stage is enough to yield reasonable inversion results for all of the elastic constants. For the overthrust model, the second stage is needed to enhance the inversion results for C<SUB>13</SUB>.</P>