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Tunable aryl imidazolium ionic liquids acting as Br&oslash, nsted acid ionic liquids were found to be efficient catalysts for per-O-acetylation and reductive ring opening of benzylidene acetals. This method requires a truly catalytic amount of the least expensive available ionic liquids that are water-stable and reusable and also stable at room temperature. The reactions were obtained in one hour with good to excellent yields. These reactions can form C&minus, O and C&minus, H bonds with a high atom economy. Furthermore, the ionic liquid is an anomeric selective catalyst in per-O-acetylation and reductive ring opening of benzylidene acetals of sugar moieties.

Unique tunable aryl imidazolium ionic liquids successfully catalyzed Friedel&ndash, Crafts acylation and thioesterification in sealed tubes. These reactions can form a C&minus, C bond and a C&minus, S bond with high atom economy. Ionic liquids exhibited high activity and catalyzed essential reactions with good to excellent yields while retaining their catalytic activities for recycling.

The soil microbial community is an important part in soil ecosystem, and it is sensitive to the ecological environment. Phospholipid-derived fatty acids ( PLFA ) analysis was used to examine variations in soil microbial community diversity and its influencing factors. The results showed that: there existed 48 PLFAs that were significant in the soil samples from six altitudes. The PLFAs of six altitudes with the highest contents were i16:0, 10Me17:0, 10Me18:0 TBSA. The citrus forest exhibited richer soil PLFAs distribution both in type and amount than those in masson pine. The microbial activity and functional diversity of masson pine were increased with increasing altitudes, and citrus forest gradually decreased, the PLFA content of different microbial groups in each altitude were significantly different. The richness index, Shannon-Wiener index and Pielou evenness index of masson pine in low elevation were holistically higher than those in high elevation. However, the highest richness index of citrus forest was in low altitude, the highest Shannon-Wiener index and Pielou evenness index were in high altitude. The PLFAs content of different microbial groups were closely correlated to the soil enzyme activities and environmental factors. The PLFAs of bacteria, actinomycetes, G⁻ (Gram- positive), G⁺ (Gram-negative) were positively correlated with Ure(urease) , Ive(invertase) , CAT( catalase activity) and forest type, the PLFAs of fungi was significantly correlated with Ure, Ive, CAT, the PLFAs of bacteria, fungi, actinomycetes, G⁻ , G⁺ were significantly negatively or less correlated with elevation. Ure, Ive, CAT, forest type and elevation are the pivotal factors controlling the soil microbial biomass and activities.

Based on researches in material properties of reinforced concrete under high temperature, and combined with the whole process of fire, the fire-resistance test curve of building components suggested by ISO834 instead of the actual heating-up process. nonlinear transient temperature field simulates and analyses under fire of concrete frame columns based on Abaqus in this study. And temperature field distribution laws of column section are obtained. Conclusions of the paper are helpful to further understand of the mechanical properties of frame column under high temperature, and provide theoretical support for safety evaluation and reinforcement techniques of the structure after fire.

Thin shell structure can show interesting bi-stable behavior. As a novel deployable structure, it shows a broad application prospect in the field of aeronautics and civil engineering, etc. The thesis deduces the general constitutive equations of thin shell structure on the basis of classical laminate theory. If the layup of the composite is anti-symmetric, the results show that there exist tension-bend coupling in the deformation of the shell structure; if the layup is symmetric, there exist bend-twist coupling. For isotropic shell, it has no tension-bend and bend-twist coupling, but if made unstressed from isotropic materials it is only stable in the initial configuration, which coincides with the known conclusion.

Bi-stable structure can be stable in both its extended and coiled forms. As a novel deployable structure, it shows a broad application prospect in the field of aeronautics and civil engineering, etc. Considered two cylindrical shells having the same flattening configurations, they can be closely bound together by applying external forces. And the corresponding double-layered cylindrical shell model is proposed. Expressions for the bending and stretching strain energies of the cylindrical shells are presented. Calculations show that total strain energy has two local minimal values, which reveals that the double-layered cylindrical shell has its bi-stability. The corresponding rolled-up radii are thus determined.

Bi-stable structure can be stable in both its extended and coiled forms. For the elastic isotropic shell, a theoretical model in terms of only two parameters is proposed. Based on the principle of minimum potential energy, the conditions for bi-stability of isotropic shell are derived. The results indicate that, a pre-stressed shell will have its two stable states if the acting pre-stress satisfies some confined conditions. Further, the bi-stable model is improved taking into account boundary effect of the shell. The results show the rolled-up radius for the second stable state becomes larger. Meanwhile, using shell element in ABAQUS code, numerical simulation on bi-stable process is carried out. The numerical results of rolled-up radius characterizing the bi-stability agree well with the predicted results.