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At present, in order to improve the performance of spiral groove mechanical seals, the structural parameters of seals are mostly adjusted based on the experience of designers. The integration degree of existing mechanical seal performance research examples is low, and the whole performance optimization process lacks of scientific theoretical framework to guide. In order to solve this problem, combining the axiomatic design theory with the existing mechanical seal performance research, a structural optimization method of spiral groove mechanical seal based on axiomatic design theory was put forward. This method defines the mapping relationship between the three-level functional requirement domain and the design parameter domain of the spiral groove mechanical seal, and thus develops 14×14 diagonal optimization matrix. The research results show that the introduction of axiomatic design provides a basic theoretical framework for the performance optimization of spiral groove mechanical seals and decomposes the optimization process into several design modules, which improves the efficiency and accuracy of the optimization design of spiral groove mechanical seals and has good application value.

Morphing aircraft can flexibly change its aerodynamic shape to adapt to the varying flight conditions during a flight. Compared with the traditional fixed shape aircraft, it has a very obvious advantage. This paper proposed a solution flow based on the multi-fidelity model for the morphing aircraft with morphing wings, and the optimal trajectory and morphing rules are studied. The angle of attack, Mach number, sweep angle and axial position of the morphing wing are defined as variables for generating training data for building the multi-fidelity Kriging model, which is used to predict the aerodynamic performance of the aircraft. Based on the hp-adaptive pseudospectral method, the model is used as aerodynamic input to establish the optimization process of morphing rules, and the trajectory optimization is carried out for the contrast fixed wing aircraft and morphing aircraft with the goal of minimum fuel consumption, respectively. The control parameters such as morphing parameters, angle of attack and engine control parameters are optimized simultaneously while meeting the flight mission requirements. The results show that the morphing aircraft has higher climbing and descending efficiency, and the optimal trajectory has obvious advantages. Moreover, the research flow proposed in this paper is universal, which can effectively reduce the CFD calculation cost and improve the efficiency of trajectory optimization of the variable shape vehicle.

Site preparation is a common practice before afforestation that can increase soil carbon (C) release by changing the soil microbial community. This study examined changes in soil microbial communities at two different times (the 7th and 98th days) after site clearing (brush clearing vs. controlled burning), followed by soil preparation (overall soil preparation (OP), spot soil preparation (SP), and no soil preparation (NP)). Results showed that total, bacterial, fungal, and actinomycetic phospholipid fatty acids (PLFAs) increased in controlled burning plots compared with brush clearing plots at the two sampling times. Within brush clearing plots, OP significantly reduced the total, bacterial, fungal, and actinomycetic PLFAs, whereas SP showed a significant increase in these groups compared with NP. In addition, soil microbial community showed obvious seasonal variation in brush clearing plots. Within controlled burning plots, OP significantly decreased the total, bacterial, fungal, and actinomycetic PLFAs. The variations in microbial community composition significantly correlated with soil organic C, total nitrogen (N), dissolved organic C, and C-N ratios. Our results suggest that controlled burning and spot soil preparation can create some soil conditions more conducive to soil microbial communities in the short term, but the long-term effects merit further investigation. Key words: brush clearing, controlled burning, overall soil preparation, spot soil preparation, subtropical China. La preparation du terrain est une pratique courante avant de reboiser, ce qui peut augmenter la liberation du carbone (C) du sol en modifiant la communaute microbienne dans le sol. Cette etude s'interesse aux changements dans les communautes microbiennes du sol a deux moments differents (les 7e et 98e jours) apres le nettoyage du terrain (debroussaillage vs brulage dirige) suivi de la preparation du sol (preparation generalisee (PG), preparation localisee (PL) et aucune preparation (NP)). Les resultats ont montre que les acides gras phospholipidiques (AGPL) actinomycetiques, fongiques, bacteriens et totaux ont augmente a chaque periode d'echantillonnage dans les placettes soumises au brulage dirige comparativement aux placettes debroussaillees. Dans les placettes debroussaillees, le traitement PG a significativement reduit les AGPL actinomycetiques, fongiques, bacteriens et totaux tandis que ces groupes ont significativement augmente dans le traitement PL comparativement au traitement NP. De plus, la communaute microbienne du sol connaissait une variation saisonniere evidente dans les placettes debroussaillees. Dans les placettes soumises au brulage dirige, le traitement PG a significativement reduit les AGPL actinomycetiques, fongiques, bacteriens et totaux. Les variations dans la composition des communautes microbiennes etaient significativement correlees avec le C organique, l'azote (N) total, le C organique dissout et le rapport C-N dans le sol. Nos resultats indiquent que le brulage dirige et la preparation localisee du sol peuvent creer des conditions plus propices aux communautes microbiennes du sol a court terme mais les effets a long terme meritent qu'on poursuive les etudes. [Traduit par la Redaction] Mots-cles: debroussaillage, brulage dirige, preparation generalisee du sol, preparation localisee du sol, Chine subtropicale., 1. Introduction China has the largest forest plantation area in the world, approximately 69.33 million ha, based on the most recent (8th) national forest inventory. The plantations play an increasingly [...]