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A mathematical model to describe the detailed three-dimensional transient heat transfer process in friction stir welding (FSW) is presented. This work is both theoretical and experimental. An explicit central diVerential scheme is used in solving the control equations, the heat transfer phenomena during the tool penetrating, the welding and the tool-removing periods that are studied dynamically. The heat input from the tool shoulder is modelled as a frictional heat and the heat from the tool pin is modelled as a uniform volumetric heat generated by the plastic deformation near the pin. The temperature variation during the welding is also measured to validate the calculated results. The calculated results are in good agreement with the experimental data.

We investigated the probiotic properties of Lactobacillus acidophilus NS1, such as acid resistance, bile tolerance, adherence to HT-29 cells, and cholesterol assimilation activity. In an animal study, 7-wk-old male C57BL/6 mice were fed a normal diet, a high-fat diet (HFD), or an HFD with L. acidophilus NS1 (ca. 1.0×10(8) cfu/mL) for 10 wk. Total cholesterol and low-density lipoprotein (LDL) cholesterol levels were significantly lower in mice fed an HFD with L. acidophilus NS1 than in those fed an HFD only, whereas high-density lipoprotein cholesterol levels were similar between these 2 groups. To understand the mechanism of the cholesterol-lowering effect of L. acidophilus NS1 on the HFD-mediated increase in plasma cholesterol levels, we determined mRNA levels of genes involved in cholesterol homeostasis in the liver. Expression of sterol regulatory element-binding protein 2 (Srebp2) and LDL receptor (Ldlr) in the liver was dramatically reduced in mice fed a HFD compared with those fed a normal diet. When L. acidophilus NS1 was administered orally to HFD-fed mice, an HFD-induced suppression of Srebp2 and Ldlr expression in the liver was abolished. These results suggest that the oral administration of L. acidophilus NS1 to mice fed an HFD increased the expression of Srebp2 and Ldlr in the liver, which was inhibited by high fat intake, thus leading to a decrease in plasma cholesterol levels. Lactobacillus acidophilus NS1 could be a useful probiotic microorganism for cholesterol-lowering dairy products and the improvement of hyperlipidemia and hepatic lipid metabolism.

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In this paper, a three-dimensional transient-heat transfer model for both the tool and the workpiece in friction stir welding (FSW) has been presented. A moving coordinate is introduced to reduce the di culty of modelling the heat generation due to the movement of the tool pin. The heat transfer process of the tool and workpiece are coupled at the workpiece/tool interface. The ®nite di erence method was used in solving the energy equations. In order to improve the temperature resolution near the tool in the calculation, a non-uniform grid mesh is generated for the calculation. FSW experiments have been done to validate the modelling results. The calculated results are in good agreement with the experimental ones.