A new technique of filling friction stir welding (FFSW) relying on a semiconsumable joining tool has been developed to repair the keyhole left at the end of friction stir welding (FSW) seam. The conventional nonconsumable tool of FSW was transformed, and a semiconsumable joining tool consisting of alloy steel shoulder and aluminium alloy joining bit was designed to create a solid state joint. Using the combined plastic deformation and flow of the consumable joining bit and the wall of the keyhole, the FFSW process is able to repair the keyhole with both metallurgical and mechanical bonding characteristics, and the FSW seam can be achieved without keyhole or other defects. The relative tensile strength and elongation of the FFSW joint are 84?3 and 98?9% of the base weld without defects respectively.

Cardiac tissue engineering holds great promise for the treatment of myocardial infarction. However, insufficient cell migration into the scaffolds used and inflammatory reactions due to scaffold biodegradation remain as issues to be addressed. Engineered heart tissue (EHT) grafts fabricated by means of a cell encapsulation technique provide cells with a tissue-like environment, thereby potentially enhancing cellular processes such as migration, proliferation, and differentiation, and tissue regeneration. This paper presents a study on the fabrication and characterization of EHT grafts from novel alginate/collagen composite microbeads by means of cell encapsulation. Specifically, the microbeads were fabricated from alginate and collagen by barium ion cross-linking, with neonatal rat cardiomyocytes encapsulated in the composite microbeads during the fabrication of the EHT grafts. To evaluate the suitablity of these EHT grafts for heart muscle repair, the growth of cardiac cells in the microbeads was examined by means of confocal microscopy and staining with DAPI and F-actin. The EHT grafts were analyzed by scanning electron microscopy and transmission electron microscopy, and the contractile function of the EHT grafts monitored using a digital video camera at different time points. The results show the proliferation of cardiac cells in the microbeads and formation of interconnected multilayer heart-like tissues, the presence of well-organized and dense cell structures, the presence of intercalated discs and spaced Z lines, and the spontaneous synchronized contractility of EHT grafts (at a rate of 20-30 beats min(-1) after two weeks in culture). Taken together, these observations demonstrate that the novel alginate/collagen composite microbeads can provide a tissue-like microenvironment for cardiomyocytes that is suitable for fabricating native heart-like tissues.

In the present work, 7?8 mm thick AA 2219 rolled plates were successfully joined without keyholes using semiconsumable tools by filling friction stir welding (FFSW). The shoulder further effect was performed to enhance mechanical stir, and mechanical properties were enhanced effectively. The results showed that the bonding interface of AA 2219 bit and keyhole is defect free. The softened region on the advanced side is the weakest part of FFSW joint rather than the bonding interface of the keyhole. The average ultimate tensile strength and elongation are 172 MPa and 11?2%, equal to 90 and 82% of the base weld without defects respectively. Excellent bonding interface and mechanical properties of FFSW joints have been exhibited.

The application of Coanda effect to turbine was first studied in this article through two-dimensional numerical simulation of circulation control turbine cascades. The influence of the aerodynamic and geometric parameters, such as the supply pressure of jet, the slot height, the shape, and curvature of the Coanda surface, on the performance of the circulation control turbine cascade was investigated in detail. The results show that the circulation control turbine cascade can achieve and exceed the performance level of the original turbine cascade (the baseline) at the cost of an acceptable jet supply pressure. The aerodynamic performance of circulation control turbine cascades is largely determined by two critical factors: the velocity of jet and the curvature of the Coanda surface. Low magnitude of jet velocity and large curvature of Coanda surface near the jet exit would lead to a serious jet detachment that is generally responsible for less flow turning and high energy loss. The jet attachment to the Coanda surface with a large curvature can be obtained only when the jet speed is high enough. Also, at this time, circulation control turbine cascade can bring a large flow turning but also a high energy loss based on a modified definition of the energy loss coefficient.