The effect of catalysts on ZnO nanowire growth was investigated by comparing the performances of Au, Pt, and Ag nanoparticles. Additional control of growth was achieved by implementing a substrate temperature of either 800 °C with a ZnO/graphite powder source or 500 °C with a Zn powder source. At 800 °C, the vaporliquid-solid mechanism plays a very important role when the Au and Pt nanoparticles are in the liquid phase. On the other hand, nanowires can also be grown on solid nanoparticles, that is, oxidized Ag at 800 °C and nanoscale cracks, that is, Pt at 500 °C, where, the vapor-solid is the only possible mechanism. At 500 °C, the vapor-liquid mechanism still dominates even though Au and Ag appear to be liquid, which is a result of high Zn vapor pressure.

A virtual multipath (VM) based technique focusing on mitigating both weak and strong short-delay multipath (MP) signals in the global positioning system (GPS) is presented in this letter. Simulations based on the real GPS signal indicate that the proposed technique is able to achieve an absolute range error within 2 m for multipath-to-direct (M/D) ratio of 0.5 and 6.5 m for M/D of 10.

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GPS positioning accuracy in indoor and urban canyons environments is greatly affected by multipaths due to distortions in its autocorrelation function. In this paper, the first sidelobe of Pseudorandom Noise (PN) code autocorrelation is studied and a new multipath mitigation technique based on PN code autocorrelation function is presented. This new technique relies on the detection of the partial autocorrelation function that is affected by multipath signals. The increase in fractional delay of the line-of-sight (LOS) signal is calculated. Simulation results indicate that the proposed technique has superior performance compared with the 0.1-chip-spacing narrow correlator on mitigating multipath signals, especially the short-delay multipath signals.

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