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This study aims to understand the influence of chlorophyll fluorescence parameters on the yield of winter wheat in some areas of China. Nitrogen (N) application is believed to improve photosynthesis in flag leaf, which ultimately increases the final yield. The experiment was conducted in the wheat experimental base of Shanxi Agricultural University in Taigu, Shanxi Province, China; before sowing, four N application rates were set—N0, N120, N150, and N210 kg ha–1 of the Yunhan-20410 variety from 2019 to 2022. The results from different parameters of research showed that the organic manure partial substitution for chemical fertilizer increased post-anthesis N uptake by 16.4 and 81.4%, thus increasing the post-anthesis photosynthetic capacity and delaying leaf senescence. N150 treatment can improve dry matter (DM) accumulation, thus promoting the increase of the yield. The maximum net photosynthesis PN value of the booting stage and flowering stage indicated that nitrogen application could significantly improve the photosynthetic rate of wheat leaves, among which medium nitrogen treatment had the most significant promoting effect. The single-photon avalanche diode (SPAD) value of the leaf of wheat in each treatment increased rapidly in a small range from the jointing stage to the booting stage, respectively. The grain yield under N fertilizer partial substitution for N fertilizer treatment increased by 23%. According to the different significance test, the effects of nitrogen application rate on net photosynthesis PN of winter wheat were extremely significant at all growth stages, indicating that changing the population distribution mode and nitrogen level could effectively improve leaf photosynthetic performance and that N150 level was the best.

The current study was designed to investigate the best sowing method that encourages dry matter accumulation to increase dryland wheat yield, grain quality, and protein content. Three different seeding methods were applied: (I) wide-space sowing (WSS), (II) furrow sowing, and (III) drill sowing. Two nitrogen levels, namely low nitrogen (N1) and high nitrogen (N2), were also applied, and the pure nitrogen was 150 kg ha−1 and 210 kg ha−1, respectively. Wide-space sowing significantly increased the ears and yield production, the maximum, and average grain-filling rate while furrow sowing delayed the disappearance of the population after anthesis, increased the duration of grain filling, and then significantly increased the number of spikes and the 1000-grain weight increased, respectively. Drill sowing compared to wide-space sowing significantly increased the content of nitrogen in the grain of the nitrogen harvest index, and it increased the content of protein and the yield of protein, respectively. In addition, the grain yield and protein yield of wide-precision sowing were significantly higher than that of trench sowing. Our findings suggest that wide-space sowing was beneficial for increasing water consumption during the growth period, increasing the tiller dynamics, improving the plant dry matter quality, and increasing the grain protein.

A designed cryogenic upper stage adopted liquid hydrogen and liquid oxygen (LH2/LO2) as an aerospace propellant. During a zero-gravity coast period in space, the wall heat leakage into the delivery tube could induce liquid propellant evaporation and two-phase flow phenomenon, so that a bubble discharge operation must be employed prior to engine restart. In this study, a CFD approach was utilized to numerically study the bubble discharge behaviors inside the LH2 delivery tube of the upper stage. The bubble motion properties under two different schemes, including positive acceleration effect and circulation flow operation, were analyzed and discussed. The results showed that the boiled hydrogen bubbles could increase to the size of the tube inner diameter and distribute randomly within the entire tube volume, and that, in order for the bubble to spill upward under the acceleration effect, a higher acceleration level than the needed value of acquiring liquid–vapor separation inside the propellant tank should be provided. When creating an acceleration level of 10−3 g0, most of the bubbles could spill upward within 700 s. Significantly, the bubbles could not be completely expelled in the created acceleration condition since a number of small bubbles always stagnate in the bulk liquid region. In the circulation flow operation, the gas volume reduction was mainly attributed to two mechanisms: the vapor condensation effect; and bubble discharge effect. For the case with a circulation flow rate of 0.2 kg/s, a complete bubble discharge purpose was reached within 820 s, while a large bubble stagnation in the spherical distributor occupied a remarkable proportion of the total time. In addition, both the liquid flow rate and liquid subcooling exert important effects on bubble performance. When applying a high circulation flow, the gas volume reduction is mainly due to the inertial effect of liquid flow, but the bubble stagnation in the spherical distributor still affects the total discharge time. The liquid subcooling influence on the gas volume reduction is more significant in smaller circulation flow cases. Generally, the present study provides valuable conclusions on bubble motions inside a LH2 delivery tube in microgravity, and the results could be beneficial to the sequence design of engine restart for the cryogenic upper stage.