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The issue of velocity‐free practical predefined‐time (PPT) attitude coordination control (ACC) for multiple rigid spacecraft under directed topology and subject to bounded external disturbances is investigated in the article. To gain precise estimates of the spacecraft's velocities together with external disturbances, PPT extended‐state observers are presented by virtue of a time‐varying function technique. Next, distributed PPT state observers are designed to estimate the leader's attitude which is accessible to only some of the followers. One advantage of the designed distributed observers is that the information required to transmit among neighbor spacecraft is only the estimated attitudes, which results in a reduction of the communication burden. Then, a distributed velocity‐free PPT ACC law is put forward in terms of the backstepping approach and the PPT observers. The present control protocol can ensure that the settling time is bounded by a predefined time with no reliance on any other controller parameters or initial conditions. Finally, the efficiency of the developed ACC scheme is illustrated by numerical simulation examples, and it is shown that the designed control law possesses one further salient advantage of required reduced magnitudes of control torques to reach accurate ACC performance. [ABSTRACT FROM AUTHOR]

Electron transport layer (ETL) is a crucial part for perovskite solar cells (PSCs). However, leakage current and oxygen vacancies result from little pores grown from sol‐gel method would inevitably deteriorate the performance of ETL. In contrast, thin films prepared by chemical bath deposition (CBD) could significantly restrain the little cracks. Here, SnO2 ETL are prepared by optimized CBD process, sodium citrate (SC) is explored as an auxiliary reagent to disperse ETL, thus enhances the smoothness and conductivity of the ETL, resulting in a pore‐free flat surface morphology and decreased oxygen vacancy, which is favorable for electron transport and deposition of perovskite (PVK). The PVK film fabricated on the oxygen vacancy free substrate demonstrates high quality and decreased defect density, thus effectively prevents the non‐radiative recombination of carriers. As a result, the short‐circuit current (JSC) and open circuit voltage (Voc) of the PSC devices have been obviously improved, leading to increased photoelectric conversion efficiency from 21.03% to 22.04%. Meanwhile, the long‐term and moisture stability have been promoted simultaneously. [ABSTRACT FROM AUTHOR]

[Objective] The Lower Permian Qixia Stage in southwest Sichuan Basin has shown significant exploration potential in recent years, but the views on the sedimentary filling pattern and paleogeographic framework in this area are not unified, which seriously restricts the further oil and gas exploration and well location deployment in the basin. [Methods] This study of the Lower Permian Liangshan Formation and Qixia Formation in southwestern Sichuan Basin was based on the comprehensive use of field profiles, drilling cores and logging data, and analysis of rock types and sedimentary facies. The application of the principles and methods of marine carbonate stratigraphical sequencing led to the identification of third-order sequence interfaces in the Qixia Stage. Single-factor analysis and multi-factor comprehensive mapping were adopted, taking the three-level sequence as the mapping unit. Combining these with the dominant phase, maps of the SQ0 + SQ1 and SQ2 sequence paleogeographic lithofacies were drawn for the Qixia Stage in the study area. [Results] Four third-order sequence interfaces were identified in the Qixia Stage, from bottom to top: lower interface of Liangshan Formation (SB I), inner interface of Qixia Formation Group 1 section (SB II), interface of Qixia Formation Groups 1 and 2 (SB II) and interface of the Qixia Formation and Maokou Formation (SB I). These occurred in three tertiary sequences, each consisting of a transgressive domain and a high-order domain. Comparative analysis of the sequential stratigraphic framework suggested that the SQ0 sequence of the lower Qixia Stage corresponds roughly to the Liangshan Formation. In the lower Qixia Formation Group 1 section, SQ0 is ev-ident only in the paleogeomorphic lowland before the deposition of Qixia Stage in the study area, with a filling sequence overlapping a paleogeomorphic highland. Sequence SQ1 in the middle region and SQ2 sequence in the upper region are found throughout the area. The sequence in the southwestern Sichuan Basin consists of a marine carbonate platform bordering the Kang-Dian ancient land in the west, with obvious differentiation of paleogeomorphology and sedimentary facies. From west to east, the Kang-Dian land and its eastern margin consisted of a tidal flat, intraplatform depression, intraplatform mound-shoal, and an open semi-confined platform. In addition, an intraplatform mound-shoal beach developed along the intraplatform slope break zone, tending to surround the intraplatform depression. [Conclusions] Analysis of the influence of the slope break zone on carbonate reservoir formation highlighted that the SQ2 sequence is the most favorable reservoir facies belt in the study area, with favorable exploration areas around the intraplatform mound-shoal facies belt. A new understanding of the filling pattern and paleogeographic lithofacies characteristics of the Qixia Stage, as determined from the sequence stratigraphy, provides a new framework for future reservoir studies and the prediction of favorable exploration areas in the Qixia Formation. [ABSTRACT FROM AUTHOR]

Due to long-term cultivation in greenhouses, cucumbers are susceptible to root-knot nematode (RKN), resulting in reduced yield and quality. The objective of this study was to investigate the effect of RKN on the rhizosphere microbial community of cucumber. Understanding the composition of rhizosphere bacterial and fungal communities and the possible interaction between microorganisms and RKN is expected to provide a reference for the eco-friendly control of M. incognita in the future. Three different groups were selected for sampling based on the RKN incidence and root galling scale (NHR, 0%, no root galling; NR, 5–15%, root galling scale 1–2; NS, 60–75%, root galling scale 4–5). Soil properties were determined to evaluate the effect of M. incognita on rhizosphere soil. High-throughput sequencing was used to examine the bacterial and fungal communities in rhizosphere soil. The results showed that the contents of soil nutrients and enzyme activities were significantly lower in the NS than in the NHR. The alpha diversity showed that M. incognita had a greater effect on rhizosphere soil bacteria than on fungi. In beta diversity, there were significant differences among the three groups by PCoA (p = 0.001). Furthermore, bacteria and fungi with significant differences in relative abundance were screened at the genus level for a correlation analysis with soil factors, and a correlation analysis between the bacteria and fungi was performed to study their relationships. A redundancy analysis (RDA) of rhizosphere microorganisms and soil properties showed a negative correlation between nematode contamination levels and soil nutrient content. Finally, we predicted the interaction among RKN, soil factors, and the rhizosphere microbial community, which provided evidence for the prevention of RKN via microecological regulation in the future. [ABSTRACT FROM AUTHOR]