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Fe3O4 nanospheres, MoS2 nanospheres and Fe3O4@MoS2 nanocomposites were used as lubricating oil additives for steel/steel contact and dispersed in PAO4 base oil. Tribological behavior and wear mechanisms of the steel/steel contacts were investigated. The results indicate that the friction coefficient increased with the addition of Fe3O4 nanospheres and decreased with the addition of MoS2 nanospheres. Their wear types belonged to abrasive wear and furrow wear respectively. In addition, Fe3O4@MoS2 nanocomposites as lubricating additive had excellent lubricating performance and energy-saving potential due to the formation of a stable adsorbed film and a robust tribo-film on the rubbing surfaces which resulted in a mild furrow wear for steel/steel contact.

(Gd 1− x ,Eu x ) 2 O 2 SO 4 nano-phosphors were synthesized by a novel co-precipitation method from commercially available Gd 2 O 3 , Eu 2 O 3 , H 2 SO 4 and NaOH starting materials. Composition of the precursor is greatly influenced by the molar ratio of NaOH to (Gd 1− x ,Eu x ) 2 (SO 4 ) 3 (the m value), and the optimal m value was found to be 4. Fourier transform infrared spectrum (FT-IR) and thermal analysis show that the precursor ( m = 4) can be transformed into pure (Gd 1− x ,Eu x ) 2 O 2 SO 4 nano-phosphor by calcining at 900 °C for 2 h in air. Transmission electron microscope (TEM) observation shows that the Gd 2 O 2 SO 4 phosphor particles ( m = 4) are quasi-spherical in shape and well dispersed, with a mean particle size of about 30–50 nm. Photoluminescence (PL) spectroscopy reveals that the strongest emission peak is located at 617 nm under 271 nm light excitation, which corresponds to the 5 D 0 → 7 F 2 transition of Eu 3+ ions. The quenching concentration of Eu 3+ ions is 10 mol% and the concentration quenching mechanism is exchange interaction among the Eu 3+ ions. Decay study reveals that the 5 D 0 → 7 F 2 transition of Eu 3+ ions has a single exponential decay behavior.

A nonautonomous predator–prey dispersion–delay model with Beddington–DeAngelis functional response is investigated. It is proved that the general nonautonomous system is permanent and globally asymptotically stable under appropriate conditions. Furthermore, if the system is a(n) (almost) periodic one, a set of easily verifiable sufficient conditions are established, which guarantee the existence, uniqueness and global asymptotic stability of a positive (almost) periodic solution of the system.

A flexible structure consisting of a Euler–Bernoulli beam with a tip mass is considered. To stabilize this system we use a boundary control laws: −uxxx(1, t) + mutt(1, t) = −αut(1, t) + βuxxxt(1, t) and uxx(1, t) = −γuxt(1, t). A sensitivity asymptotic analysis of the system's eigenvalues and eigenfunctions is set up. We prove that all of the generalized eigenfunctions of (2.9) form a Riesz basis of H . By a new method, we prove that the operator A generates a C0 contraction semigroup T(t), t ≥ 0. Furthermore T(t), t ≥ 0, is uniformly exponentially stable and the optimal exponential decay rate can be obtained from the spectrum of the system.

First, based on analyzing the process of parity population development, this paper develops a dynamic population model of parity progression in age structure and defines a population development operator of parity progression, while the properties of this operator and the existence and uniqueness of the solution to this model are discussed using operator theory. This model supplies the theoretical basis for further research on parity population dynamics. Then, this paper reveals the quantitative relation between two types of control parameters in population development systems (total fertility rate at macro-level and age-specific parity progressive ratios at micro-level) via developing and discussing a development model of parity women's density ratios. The expression of this relation puts forward a theoretical reference for making population control policy which is based on parity progressive parameters. Finally, this paper introduces a parity-specific model of parity progression with age integration, dicusses the Liapunov's stability of this model, and a criterion of stability is obtained. This result can be used to further the analysis of parity population structure.