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Valveless piezoelectric pumps have the advantages of simple fabrication, lower cost, and high cleanliness. Valveless piezoelectric pump compared with valved piezoelectric pump, the backflow phenomenon is more serious, which greatly limits the application in reality. In this paper, a valveless piezoelectric pump with an inner triangle structure is proposed to increase to the resistance of reverse flow by the inner concave triangle structure to achieve the purpose of reducing backflow. The factors influencing the efficiency of forward flow were analyzed by theoretical modeling. Then, the flow resistance of this valveless piezoelectric pump is numerically calculated by finite element analysis. Finally, the output performance of the pump was experimentally investigated. The experimental results show that when the number of concave triangles in the flow channel are two, the inclination angle (B) are 45°, and the height are 3 mm, the performance of this valveless piezoelectric pump is optimal, and the flow rate and pressure reach 190.86 ml/min and 673 Pa respectively. This study provides some valuable insights to improve its performance and practice. This piezoelectric micropump could generate large flow rates and output pressures with great advantages in the fields of mechanical lubrication and biomedicine. [ABSTRACT FROM AUTHOR]

A series of novel titanium(IV) complexes combining a phosphine oxide‐bridged bisphenolato ligand TiCl2{2,2′‐OP‐R3 (4‐R2‐6‐R1‐C6H2O)2}(THF) (6a: R1 = tBu, R2 = H, R3 = Ph; 6b: R1 = Ph, R2 = H, R3 = Ph; 6c: R1 = R2 = tBu, R3 = Ph; 6d: R1 = R2 = cumyl, R3 = Ph; 6e: R1 = tBu, R2 = H, R3 = PhF5) were prepared by the reaction of corresponding bisphenolato ligands with TiCl4 in THF. X‐ray analysis reveals that complex 6a adopts distorted octahedral geometry around the titanium center. These catalysts were performed for ethylene polymerization in the presence of modified methyaluminoxane (MMAO). The effects of reaction parameters on ethylene polymerization behaviors, such as cocatalyst concentration, polymerization temperature, and reaction time were studied in detail. In general, these new complexes exhibited high catalytic activity, good temperature tolerance, and long lifetime for ethylene polymerization. The resulting polymers possess high molecular weight, unimodal distribution, and linear structure. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7062–7073, 2008 [ABSTRACT FROM AUTHOR]