High-Power 30-Element Helical Antenna Array

A new radial-line helical array (RLHA) using dual-branch helical antennas has been designed for improving the power capacity of RLHAs. The helical element is cavity-backed to lower the mutual coupling and its power capacity is higher than the conventional ones. The components of the proposed array are discussed and the power capacity is obtained by simulation. Compared with the typical RLHAs, the proposed sub-array has not only higher power capacity but also uses fewer elements. Experimentally, the measured results of an array prototype indicate that high gain as well as circular polarization has been successfully achieved.

Assessing environmental impacts of urban growth using remote sensing

This paper provides a study of the changes in land use in urban environments in two cities,Wuhan,China and western Sydney in Australia.Since mixed pixels are a characteristic of medium resolution images such as Landsat,when used for the classification of urban areas,due to changes in urban ground cover within a pixel,Multiple Endmember Spectral Mixture Analysis(MESMA)together with Super-Resolution Mapping(SRM)are employed to derive class fractions to generate classification maps at a higher spatial resolution using an Artificial Neural Network(ANN)predicted Wavelet method.Landsat images over the two cities for a 30-year period,are classified in terms of vegetation,buildings,soil and water.The classifications are then processed using Indifrag software to assess the levels of fragmentation caused by changes in the areas of buildings,vegetation,water and soil over the 30 years.The extents of fragmentation of vegetation,buildings,water and soil for the two cities are compared,while the percentages of vegetation are compared with recommended percentages of green space for urban areas for the benefit of health and well-being of inhabitants.Changes in Ecosystem Service Values(ESVs)resulting from the urbanization have been assessed for Wuhan and Sydney.The UN Sustainable Development Goals(SDG)for urban areas are being assessed by researchers to better understand how to achieve the sustainability of cities.

Synthesis of N-Heterocyclic Carbine Silver(Ⅰ)and Palladium(Ⅱ)Complexes with Acylated Piperazine Linker and Catalytic Activity in Three Types of C-C Coupling Reactions

Main observation and conclusion Two bis-imidazolium salts LH_(2)·Cl_(2) and LH_(2)·(PF_(6))_(2) with acylated piperazine linker and two N-heterocyclic carbene(NHC)silver(Ⅰ)and palladium(Ⅱ)complexes[L_(2)Ag_(2)](PF_(6))_(2)(1)and[L_(2)Pd_(2)Cl_(4)](2)were prepared.The crystal structures of LH_(2)·Cl_(2) and 1 were confirmed by X-ray analysis.In 1,one 26-membered macrometallocycle was generated through two silver(Ⅰ)ions and two bidentate ligands L.The catalytic activity of 2 was investigated in Sonogashira,Heck-Mizoroki and Suzuki-Miyaura reactions.The results displayed that these C-C coupling reactions can be smoothly carried out under the catalysis of 2.