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In this paper, chitooligosaccharide was prepared via the enzymatic hydrolysis of papain with chitosan as a raw material. The effects of pH, reaction time, temperature, and mass ratio of chitosan and enzyme on the product yield were analyzed. Single-factor and orthogonal experiments were used to determine the main factors affecting the reaction, and response surface methodology was used to optimize chitooligosaccharide preparation conditions. Optimum conditions were achieved at pH 4.50, with an enzymolysis time of 77.4 min, an enzymolysis temperature of 45 °C, a substrate concentration of 1.75% and an enzyme to chitosan weight ratio of 8.85. Under these conditions, the chitooligosaccharide yield reached 37.78%.

A magneto-elastic-optical coupling model for Terfenol-D based single-mode optical fibers is proposed, in which the nonlinear magneto-elastic coupling characteristics of Terfenol-D is taken into consideration. The field-dependent material constants for magnetic coating is predicted and in good agreement with experimental results. The coupling effects of external stimuli (e.g. magnetic field and stress) on magneto-optic (MO) coupling coefficient of optical fibers are investigated for the first time. The results show that the relative phase change is enhanced by changing the thickness or Poisson's ratio of constituent materials. More importantly, appropriate applied tensile/compressive stress can control the value of optimal bias field as well as enhance MO coupling coefficient of optical fibers under different magnetic fields. This research provides a method to evaluate and improve magnetic performance of the optical fiber magnetic field sensors consisting of giant magnetostrictive materials.

Six kinds of 2D T700/E44 composites with pressure-free curing times of 40 min, 60 min, 80 min, 100 min, 120 min and 140 min are prepared by improved compression molding process (ICM). The macroscopic morphology of the composites is satisfactory. The microstructure observation and bending performance tests show that composites have poor infiltration effect. When the pressure-free curing time is less than 80 min, defects are easy to occur such as insufficient infiltration and voids. Bad infiltration and void defects will lead to poor continuity of carbon fiber and resin, and their bending fracture will also be unreasonable, so the bending strength of composite at 40 min is 275 MPa. The infiltration effect is gradually improved with the increase of pressure-free heating curing time. However, when the pressure-free heating curing time reaches 120 min or more, the infiltration effect of the composites is deteriorated, and this is due to excessive infiltration time and extrusion force in subsequent heating extrusion infiltration process. Defects such as fiber aggregation and uneven infiltration are prone to occur, and bending strength of composites reduces to 380 MPa. When the pressure-free curing time is 100 min, the infiltration effect of the prepared composite is satisfactory, and the imbalanced infiltration and hole defects are effectively eliminated. The bending fracture of composite material is uneven, carbon fibers and resin play the roles of reinforcement and transferring loads effectively respectively, so the bending strength of the prepared 2D T700/E44 composite reaches 730 MPa.