Improvement in the mechanical properties of Al/SiC nanocomposites fabricated by severe plastic deformation and friction stir processing

Severely deformed aluminum sheets were processed by friction stir processing(FSP) with Si C nanoparticles under different conditions to improve the mechanical properties of both the stir zone and the heat affected zone(HAZ).In the case of using a simple probe and the same rotational direction(RD) of the FSP tool between passes,at least three FSP passes were required to obtain the appropriate distribution of nanoparticles.However,after three FSP passes,fracture occurred outward from the stir zone during transverse tensile tests;thus,the strength of the specimen was significantly lower than that of the severely deformed base material because of the softening phenomenon in the HAZ.To improve the mechanical properties of the HAZ,we investigated the possibility of achieving an appropriate distribution of nanoparticles using fewer FSP passes.The results indicated that using the threaded probe and changing the RD of the FSP tool between the passes effectively shattered the clusters of nanoparticles and led to an acceptable distribution of Si C nanoparticles after two FSP passes.In these cases,fracture occurred at the HAZ with higher strength compared to the specimen processed using three FSP passes with the same RD between the passes and with the simple probe.The fracture behaviors of the processed specimens are discussed in detail.

Observations of Magnetic Reconnection in the Magnetotail Associated With Substorms

Magnetic reconnection is one of the most important,dynamic phenomena in the magnetotail in terms of magnetic field line configuration change and energy release.It is believed to occur in the distant magnetotail mainly during southward interplanetary magnetic field periods and in the near-Earth magnetotail in association with substorms.In the present paper,we discuss several important issues concerning magnetic reconnection in the magnetotail associated with substorms,such as reconnection signatures,location,timing,spatial scale,and behavior,from the macroscopic,observational point of view.

Application of neural networks and ultraviolet spectroscopy to simultaneous determination of multiple vitamins

Multivariate analysis and filtering techniques are widely applied to simultaneous and/or selective determination of multicomponent systems. Many methods among them are based on the principle of linear addition, while this principle does not always hold due to various physical and chemical factors. Using quite a different way, neural network (NN) based on a given learning rule, such as back propagation (BP) model, needs neither knowing nor using any form of input/output relationship. Particularly, NN can resolve various problems such as those with casual relation, those with fuzzy backgrounds, and those with uncertain inferential processes. NN was used by us to investigate quantitative struc-