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        Experimental study on air-water countercurrent flow limitation in a vertical tube based on measurement of film thickness behavior

        Wan, Jie,Sun, Wan,Deng, Jian,Pan, Liang-ming,Ding, Shu-hua Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.6

        The gas-liquid counter-current flow limitation (CCFL) is closely related to efficient and safety operation of many equipment in industrial cycle. Air-water countercurrent flow experiments were performed in a tube with diameter of 25 mm to understand the triggering mechanism of CCFL. A parallel electrode probe was utilized to measure film thickness whereby the time domain and frequency domain characteristics of liquid film was obtained. The amplitude of the interface wave is small at low liquid flow rate while it becomes large at high liquid flow rate after being disturbed by the airflow. The spectral characteristic curve shows a peak-shaped distribution. The crest exists between 0 and 10 Hz and the amplitude decreases with the frequency increase. The analysis of visual observation and characteristic of film thickness indicate that two flooding mechanisms were identified at low and high liquid flow rate, respectively. At low liquid flow rate, the interfacial waves upward propagation is responsible for the formation of CCFL onset. While flooding at high liquid flow rate takes place as a direct consequence of the liquid bridging in tube due to the turbulent flow pattern. Moreover, it is believed that there is a transition region between the low and high liquid flow rate.

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        Fifth Generation Communication Performance of Poly(ether ketone ketone)/Modified Montmorillonite Substrate

        Guang Kui Zhou,Xiao Dong Zhi,Deng Ming Pan,Tim Hsu,Jen-taut Yeh 한국고분자학회 2022 Macromolecular Research Vol.30 No.2

        Quaternary ammonium salt modified montmorillonite (QASMMT) nanoplatelets were well dispersed in poly(ether ketone ketone) (PEKK) polymers to make pleasing fifth generation (5G) substrates. Substantially smaller dielectric properties and linear thermal expansion coefficient (LCTE) were found for each PEKKa xQASMMTy film series filled with small and appropriate QASMMT loadings. The dielectric constant (εr) and dielectric loss (tan δ) values acquired for each PEKKa xQASMMTy film series reduced to a lowest value as QASMMT loadings approached 3wt%. Satisfactory εr (2.59, 2.71, and 2.80 at 1 MHz), tan δ (0.0032, 0.0038, and 0.0042 at 1 MHz) and LCTE (~36.8×10-6/℃, 38.8×10-6/℃ and 40.5×10-6/℃) for 5G communication were acquired for PEKKa 97QASMMT3 films filled with only 3wt% optimum loading of QASMMT nano-platelets. In the meantime, the onset degradation temperatures acquired for each PEKKa xQASMMTy film series increased substantially with increasing QASMMT loadings. All free volume properties, such as, the radius of the free-volume-cavity or free-volume-cavity numbers per unit volume evaluated for every PEKKa xQASMMTy film sequence enlarged to a largest value, as QASMMT loadings approached an appropriate value of 3wt%. Substantial smaller εr and tan δ were acquired for PEKKa and PEKKa xQASMMTy with larger free volume properties. Possible reasons accounting for these substantially diminished dielectric and LCTE properties of PEKKa xQASMMTy films are proposed.

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