Conventional HF geolocation method based on ray tracing relies on strict requirement on ionosphere information while line-of-bearing based geolocation method and time difference of arrival (TDOA) based method require fine angular resolution and large aperture array. In practical applications, these methods will be subject to practical constraints, especially when operated in land-limited environment. This paper investigates a new approach of HF geolocation based on TDOA and direction of arrival (DOA) of multipaths, which can alleviate the strict requirements on ionosphere information and large aperture array. A nonlinear optimization problem is formulated based on the virtual path propagation model and solved by numerical optimization methods. Simulation studies are provided to illustrate the potential of the proposed method.

This paper presents a continuous atmospheric heavy metals monitoring system (AMMS-100) for heavy metals analysis based on X-ray fluorescence (XRF) technology. The AMMS-100 is used to collect the sample automatically with filters and then measure the concentrations of heavy metals by XRF. The accuracy of AMMS-100 for heavy metals analysis has been verified by the standard method. The relative errors, such as Pb and Fe, are lower than 10%. Moreover, the AMMS-100 can be used for long-term continuous monitoring the atmospheric heavy metals under different weather condition. The AMMS-100 described herein presents a continuous system for accurate analysis of atmospheric heavy metals with long-term stability.

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