A Knudsen pump operates under the thermal transpiration effect or the thermal edge effect on the micro-scale. Due to the uneven temperature distribution of the walls in the channel axis direction or the constant temperature of the tips on the walls, directional thermally-induced flow is generated. In this paper the Direct Simulation Monte Carlo (DSMC) method is applied for N2–O2 gas mixtures in the ratios of 4:1, 1:1, and 1:4 with different Knudsen numbers in a classic rectangular Knudsen pump to study the flow characteristics of the gas mixtures in the pump. The results show that the changing in the gas physical properties does not affect the distribution of the velocity field, temperature fields, or other fields in the Knudsen pump. The thermal creep effect is related to the molecular mass of the gas. Even in N2 and O2 gas mixtures with similar molecular masses, N2 can be also found to have a stronger thermal creep effect. Moreover, the lighter molecular weight gas (N2) can effectively promote the motion of the heavier gas (O2).
Longju temple, located in Guanghan County, Sichuan province of China, is a Buddhist temple with great cultural significance. It has preserved polychrome relics since 1466 of the Ming dynasty. The deterioration of these ancient colored paintings is posing an extremely serious issue, it is exceptionally critical to propose an appropriate protection plan. In this paper, pigments and binding media were analyzed from ten polychrome samples collected from the central hall of Longju temple. A series of analysis methods were adopted, including the Raman spectrum, scanning electron microscopy-energy disperse spectrometer (EDS-SEM), and enzyme-linked immunosorbent assay (ELISA). Results demonstrate the existence of atacamite, azurite, carbon black, cinnabar, and gold in the color layer of the samples. Egg white, animal glue, and casein were found to be used as binders in the colored paintings. This study not only offered essential data for the follow-up protection and repair projects but also provided a reference to further explore the polychrome relics of other Buddhist temples in the Ming dynasty of China.
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