Strategies to suppress grain growth of nanocrystalline aluminum

The grain growth behaviors of nanocrystalline aluminum, alloy and composite are compared. First, nanocrystalline aluminum is fabricated by consolidation of ball-milled powder. Second, nanocrystalline aluminum alloy is designed to have elements such as Mn, Zr, and Misch metals, which can form thermally stable second phases at grain boundaries and also drag the movement of grain boundaries. Third, nanocrystalline aluminum-based composites containing multi-walled carbon nanotubes(MWCNTs) are also prepared because MWCNTs are expected to be located at grain boundaries and to suppress the grain growth of nanocrystalline aluminum. These three types of samples are annealed at 550 °C for up to 5 d and the effect of annealing time on Vickers hardness of the samples is compared. As a result, MWCNTs are found to be most effective to impede grain growth of nanocrystalline aluminum.

Performance comparison of leg detection methods using laser range finder

Human interaction becomes an important issue in the field of mobile robotics. To achieve humanfriendly naviga tion, the robot needs to recognize human on cluttered backgrounds, and this can be fulfilled by the detection of human legs. The detection of human legs is advantageous because it enables detecting environmental obstacles at such heights. In this pa per, we compared the performance of an algorithm using a single laser range finder（LRF） proposed in Ref. L 1 ] with that of wellknown feature extraction approaches bounding box and circle fitting proposed in Ref. [ 2 ] by using the same laser scanned image.