High-temperature Daqu, also called Jiang-flavor Daqu, is the saccharifying and fermenting agent for brewing Jiang-flavor Baijiu. During the spontaneous solid-state fermentation of high-temperature Daqu, variations in temperature and moisture lead to microbial diversity and various metabolites, contributing to the different colors of high-temperature Daqu (customarily referred to as white Daqu, black Daqu, yellow Daqu, and red Daqu in production). We aimed to investigate the differences in microbial communities, physicochemical indices, and potential functions among different high-temperature Daqu with different colors (labeled as QW, QB, QY, and QR) by amplicon sequencing. We found that Kroppenstedtia, Bacillus, and Thermoascus were predominant in all samples; Saccharopolyspora and Thermomyces were predominant in QB and QR; and Unclassfied_O_Eurotiales were predominant in QY. The results on the physicochemical characteristics indicated that compared with other Daqu samples, QW exhibited higher protease activity and lower acidity, whereas QB showed the opposite results. QR had the highest esterification yield, and QY exhibited the highest saccharification but lowest esterification yield. Functional prediction demonstrated that the higher abundances of genes encoding bacterial enzymes of QW and QY were related to the considerably higher abundances of Kroppenstedtia in QW (59%) and QY (87%), respectively. The highest abundance of Thermomyces in QB (80%) contributed to the highest abundance of genes encoding fungal enzymes in QB. This study revealed the microbial and functional dissimilarities of color-based high-temperature starters and helped facilitate the liquor fermentation process.

Stick-slip vibration has been a major problem in drilling operations in B basin, Chad, where rocks in basement formation are hard granite. Premature failure of drill bits and string has profoundly undermined the safe and economical drilling operations. Hence, it is urgent to reveal the mechanism of stick-slip vibration and find a way to eliminate or relieve stick-slip problem. Through the numerical and experimental study on the effects of the cutting parameters on cutting performance, root cause on depth of cut (DOC) or cutting depth is revealed as the mechanism of stick-slip vibration, optimized cutting depths for different rock layers are recommended as well. With it, a novel design of auto-response DOC controller is proposed and those structural parameters are modified and via numerical simulation research. After machining and testing, the structure of the auto-response DOC controller is preliminary determined and it has acquired the satisfactory motion performance and met the testing standards as it can slowly retract into the body by resisting the load and quickly extend outward the body. The auto-response DOC controller and the anti-stick-slip PDC bit have profound application potential in developing the ultra-deep and unconventional reservoirs, especially in this era shocked by low oil price and the pandemic.

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