In recent years, gas shielded arc welding processes with flux cored wire have been widely used in many industrial sectors because of various advantages in fabrication: weldability, productivity, etc. In this study, MAG welding phenomena with titania-based flux cored wire were experimentally investigated in comparison with those with solid wire. In the vertical upward position, feasible operation range of welding current and welding speed was examined for both wires of flux cored wire and solid wire. Through the observation of high speed photography, dynamic behaviors of droplet transfer and molten pool were clarified and discussed in MAG welding with titania-based flux cored wire. Melting temperature of the titania-based slag was confirmed to be higher than that of mild steel by using differential thermal analysis (DTA). It is found that the molten metal at the wire tip is transferred along the flux pillar to weld pool in flux cored wire welding. The slag of higher melting temperature solidifies ahead of metal and supports liquid metal in the weld pool in the vertical upward position.
Internal structures of the inner wall of the left ventricle (LV), such as trabeculae carneae (TC) and papillary muscles, may reduce the blood flow velocity, resulting in thrombus formation in the LV of a healthy heart or a heart with atrial fibrillation. The purpose of the present study was to numerically clarify the effects of simplified TC models around the LV wall and atrial fibrillation on the blood flow field as a fundamental study. The LV model was constructed from magnetic resonance images, and the model considering atrial fibrillation was constructed based on the volume change data of a healthy subject from which volume increase with atrial contraction was removed. Numerical analysis was performed considering eight simplified TC models around the LV wall. The numerical results revealed that the oscillatory shear index and relative residence time (RRT) at the apex in the LV model with internal structures were larger than those in the LV model without internal structures, which indicates that the blood flow tends to stagnate. On the other hand, as a result of the LV model considering the atrial fibrillation, the time-averaged wall shear stress decreases and the RRT increases at valley points of the internal structures.
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