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Abstract Sodium alginate was provided with good processibility according to physical and chemical characterization of itself. Alginate scaffold has been used for preparation of soft or hard tissue engineering, but the structure of the scaffold needs to be improved for better performance for skin tissue engineering. In this study, highly porous alginate membrane was formed with ionic crosslinking. High molecular weight (Mw=3.0×105) alginate showed the best film-forming property. Therefore, the appropriate molecular weight should be selected for improving its performance. With freeze-drying technology and pre-freezing at -10°C, we have built the honeycomb materials (porosity=92.06%). Changing the pre-freezing temperature can regulate pore structure to some extent. With the increased dosage of sodium alginate, the porosity and the pore size of the materials were reduced, whereas tensile strength and elongation at break increased. Water absorption performance of the materials was good. The above studies lay a foundation for construction of skin tissue engineering scaffold.

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In this paper, the performance between cylindrical and twisted blades are analyzed for the same centrifugal pump. The three-dimensional steady and unsteady flow fields under 0.7Qd, Qd and 1.3Qd are simulated. The blade inlet and outlet flow and pressure pulsation inside the centrifugal pumps are discussed by using mathematical statistics and frequency domain analysis methods. The research is verified by experiments. The results show that the twisted blade controls blade outlet better than cylindrical blade at small flow and design flow, cylindrical blade controls blade outlet better than twisted blade at large flow. In the blade inlet and outlet, as the flow changes, the instability of cylindrical blade loading is higher than that of twisted blade. The cylindrical blade inlet pressure is affected by the shaft frequency more than that of the twisted blade. At shaft frequency and blade frequency, pressure pulsation coefficient of cylindrical blade outlet is higher than that of twisted blade outlet. The cylindrical and twisted blades effect on the blade inlet and middle gradually accumulates, resulting twisted blade outlet has larger pressure pulsation. The result can guide the optimum design of centrifugal pump to consider the performance balance between twisted and cylindrical blades.

The micro-processing technology has gradually become a hot topic problem, especially in micro-scale milling chatter prevention with the development of the information age. In allusion to the actual case of micro-milling, the dynamic theoretical research is analyzed in-depth about the Fourier method and the average tooth angle method. Compared to two ways, the former is close to the actual processing requirements. The lobes are obtained use the two ways. Micro milling parameters are selected in the stable area and unstable region. Stable and non-stable curve and surface quality of machined parts are obtained after micro-milling test. The chatter points, non-chatter point and uncertain point are obtained in the high spindle speed, which are consistent with theoretical analysis. In contrast, the distribution of chatter points in the low-speed spindle speed. The reason is that the damping effect is produced in the micro-scale milling process. The research of micro-scale milling chatter, which has a certain significance to improve parts of precision machined parts, reduce the wear and tear of the micro-milling blade and extend micro-tool life.