A novel planar omnidirectional dipole antenna for wireless local area network (WLAN) applications is proposed. The antenna consists of a sleeve dipole antenna for the lower band and a cage dipole antenna for the upper band. Employing a unique planar composite structure, good dual‐band impedance matching can be achieved without an external matching circuit. The lower‐band dipole antenna adopts a sleeve structure, which reduces the size by bending in the middle and thickening at the end as inductance and capacitance loading, respectively. The upper‐band dipole antenna is embedded in the lower‐band dipole antenna, and the impedance bandwidth is broadened by adopting a cage structure and coupling with the lower‐band dipole antenna. The proposed antenna occupies an area of 0.38 λ0 × 0.08 λ0 (λ0 represents the wavelength of the lower frequency) on FR4 substrate of thickness 0.8 mm. The measured results show that the impedance bandwidths with a return loss more than 10 dB are 2.27–2.65 GHz and 4.89–6.02 GHz. The antenna has an omnidirectional radiation pattern, and both E‐plane and H‐plane have lower cross‐polarization levels. The average gain reaches 2.4 and 3.3 dBi in the 2.4‐ and 5‐GHz bands, respectively. The antenna is compact and easy to fabricate, and can be used for small omnidirectional WLAN terminal device.
Under “the Belt and Road” initiative, China promoted cooperation between domestic enterprises and international ports vigorously, which brought back fruitful results, while the rational selection of strategic pivots ports and the optimization of the layout of the port network are important guarantees to a further promotion to the economic development of “the Belt and Road” ports and give full play to the driving and radiation role of strategic pivots ports. On the basis of constructing a network of 155 ports in the world, according to the number of ports crossed by the shortest path and betweenness centrality in the network, this paper uses K-Medoids clustering algorithm to train the strategic importance of ports and verifies the reliability of the analysis results. On this basis, the joint coverage analysis of strategically important ports is carried out, 17 ports are identified as strategic pivots ports of the global port network, and, finally, based on the two attributes of “the Belt and Road” and “Chinese enterprise participation” of strategic pivots ports, the leading role of strategic pivots ports in geographical location, path coverage, development potential, cooperation stability, and control is analyzed, and instructive suggestions are put forward.
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