No abstract

No abstract

A broadband dual-polarized omnidirectional antenna based on magnetic dipoles is presented. The proposed antenna consists of a cone radiator for vertical polarization (VP) and eight magnetic dipole elements for horizontal polarization (HP). The dipole elements are arranged around the ground plane to greatly reduce the volume of the proposed antenna. The overall volume of the antenna is only π × 75.5 mm × 75.5 mm × 35 mm (about π × 0.25 λ 0 × 0.25 λ 0 × 0.12 λ 0 at 1 GHz). The dipole elements are carefully designed to achieve the bandwidth about 28.7% from 2.03 GHz to 2.71 GHz. The bandwidth of the cone radiator is about 92% covering from 1 GHz to 2.7 GHz with band reject from 1.63 GHz to 1.7 GHz. The port isolation is more than 30 dB at the whole operation band. A good agreement between the simulated and measured results evidently validates this proposed antenna.

No abstract

As a frequently occurring natural disaster, drought will cause great damage to agricultural production and the sustainable development of a social economy, and it is vital to reasonably evaluate the comprehensive risk level of drought for constructing regional drought-resistant strategies. Therefore, to objectively expound the uncertainty of a drought risk system, the precondition cloud and maximum entropy principle coupling model (PCMEP) for drought risk assessment is proposed, which utilizes the principle of maximum entropy to estimate the probability distribution of cloud drops, and the two-dimensional precondition cloud algorithm to determine the certainty degree of drought risk. Moreover, the established PCMEP model is further applied in a drought risk assessment study in Kunming city covering 1956–2011, and the results indicate that (1) the probability of drought events for different levels exhibits a slight increasing trend among the 56 historical years; and (2) both the integrated certainty degree and its component of drought risk are more evident, which will be more beneficial to determine the drought risk level. In general, the proposed PCMEP model provides a new reliable idea to evaluate the comprehensive risk level of drought from a more objective and systematic perspective.