A study is made of the material dispersion in a‐SiO2 optical fiber material over the infrared region. A model of two series of independent oscillators is proposed to describe phonon and electron contributions to material dispersion, and linear response theory is used to analyze the interactions of light with matter. Expressions and curves are obtained for the dispersion of a‐SiO2 including the zero dispersion wavelength, which is proved to be related to the intrinsic structures of both, phonons and electrons. The important physical content of empirical formulae most in use for the dispersion is also given.

A novel boron‐containing hyperbranched benzoxazine (HB‐B) was synthesized from the reaction of triethanolamine borate (BAE), bisphenol‐A, and paraformaldehyde via Mannich condensation. The chemical structures of BAE and HB‐B were characterized by Fourier transform infrared (FT‐IR) and hydrogen nuclear magnetic resonance (1H NMR). Afterward, the boron‐containing hyperbranched benzoxazine/epoxy resin copolymers (E51/HB‐B) were prepared. The curing behavior of ‐B and E51/HB‐B was studied by FT‐IR and differential scanning calorimeter (DSC). The thermal stability and flame retardancy properties of the cured HB‐B and E51/HB‐B were evaluated by thermogravimetric analyzer (TGA), limited oxygen index (LOI), UL94 rating test, and microscale combustibility calorimeter experiments (MCC). The initial thermal decomposition temperature and glass transition temperature steadily dropped with increasing HB‐B content, while the char yield kept rising. The LOI value of the E51/HB‐B‐12 wt% was 31.8%, meeting the UL94 V‐0 specification. The result of heat release capacity (HRC) decreased by 20.4%. Moreover, the mechanical properties were also improved, and the tensile strength of E51/HB‐B copolymer was increased by 88.5%. Finally, the fracture morphology of E51/HB‐B was characterized by SEM.

In high frequency (HF) hybrid sky-surface wave radar, the first-order sea clutter broadening is severe under the action of ionospheric phase disturbance and bistatic angles. In this study, a spread sea clutter suppression method based on prior knowledge and joint domain localised (JDL) algorithm is proposed. Firstly, the first-order sea clutter broadening mechanisms and model under the action of ionospheric phase disturbance and bistatic angles are introduced. Secondly, the space-time coupling characteristics of the first-order sea clutter is analysed. Then in order to better suppress clutter or avoid target information loss, the spread sea clutter suppression method based on space time adaptive processing is proposed. In the proposed method, the space-time distribution characteristics and simulation model of the first-order sea clutter is used as the prior knowledge into JDL algorithm to improve the sea clutter suppression performance. Finally, the performance of sea clutter suppression based on JDL algorithm is simulated and analysed. And the proposed spread sea clutter suppression method based on prior knowledge and JDL algorithm is proved by measured data.