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The Luneburg-lens is a prospective candidate for implementing multibeam antennas. However, the size of the conventional configuration is bulky, and most reported works are linearly polarized (LP), leading to some inconvenience in the practical applications. To deal with these problems, a new approach to realize a compact LP Luneburg-lens antenna is proposed first, and then, a method for implementing circular polarization (CP) property is further proposed. An air-coated dielectric cylinder is rotated around the center axis to form different layers of an equivalent cylindrical Luneburg-lens. The corresponding theoretical model to calculate the equivalent permittivity is given. Based on this approach, a Luneburg-lens is constructed using one dielectric cylinder and nine dielectric rings with the same permittivity but different dimensions. The proposed lens can be easily fabricated through the 3-D printing technology with low manufacturing complexity. For validation, an LP and a CP Luneburg-lens antenna operating at the Ka-band were designed, fabricated, and measured. A good consistency between simulated results and measured ones can be found. The LP antenna achieves a wide-scanning range of 174° and a bandwidth of 28.6%. Also, the CP one exhibits a scanning range of 134° and an AR bandwidth of 17.4%.

•A novel method water-enhanced CO2extraction (WECE) treating oily sludge was used.•Compare the oil recovery of WECE, supercritical CO2and liquid CO2from oily sludge at low temperature and middle pressure.•Orthogonal test method and variance analysis were used to obtain the significance of various factors and confirm operating conditions.•The sewage produced by WECE presented cleaner and better for the environment.