An ultrathin dual-band eight-element multiple input–multiple output (MIMO) antenna operating in fifth-generation (5G) 3.4–3.6 GHz and 4.8–5 GHz frequency bands for future ultrathin smartphones is proposed in this paper. The size of a single antenna unit is 9 × 4.2 mm2 (0.105 λ × 0.05 λ, λ equals the free-space wavelength of 3.5 GHz). Eight antenna units are structured symmetrically along with two sideboards. Two decoupling branches (DB1 and DB2) are employed to weaken the mutual coupling between Ant. 1 and Ant. 2 and between Ant. 2 and Ant. 3, respectively. The measured −10 dB impedance bands are 3.38–3.82 GHz and 4.75–5.13 GHz, which can entirely contain the desired bands. Measured isolation larger than 14.5 dB and 15 dB is obtained in the first and second resonant modes, respectively. Remarkable consistency between the simulated and measured results can be achieved. Several indicators, such as the envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and multiplexing efficiency (ME), have been presented to assess the MIMO performance of the designed antenna.

A multiple-input-multiple-output (MIMO) antenna array for triple-band 5G metal-frame smartphone applications is proposed in this paper. Each single antenna element consists of an S-shaped feeding strip and an L-shaped radiation strip on the metal frame. The dimension of the antenna element is only 6.5 mm × 7 mm (0.076 λ0 × 0.082 λ0, λ0 is the free-space wavelength at the frequency of 3.5 GHz). The −6 dB impedance bandwidth of the proposed eight-antenna array can cover 3.3–3.8 GHz, 4.8–5 GHz, and 5.15–5.925 GHz. The evolution design and the analysis of the optimal parameters for a single antenna element are derived to investigate the principle of the antenna. The measured total efficiency is larger than 70%. The measured isolation is better than 13 dB. The measurements of the prototype agree well with the simulation results.

A coplanar waveguide- (CPW-) fed dual-band multiple-input multiple-output (MIMO) antenna for 2.45/5.5 GHz wireless local area network (WLAN) applications is presented in this paper. The presented MIMO antenna consists of two identical trapezoidal radiating elements which are perpendicular to each other. The size of the entire MIMO antenna is 50 × 50 × 1.59 mm3, which is printed on a FR4 substrate. The measured impedance bandwidth of the proposed antenna is 2.25–3.15 GHz and 4.89–5.95 GHz, which can cover IEEE 802.11 a/b/g frequency bands. A rectangular microstrip stub is introduced to achieve a good isolation which is less than −15 dB in both operation frequency bands. The measured peak gain is 5.59 dBi at 2.45 GHz and 5.63 dBi at 5.5 GHz. The measured antenna efficiency is 77.8% and 80.4% in the lower and higher frequency bands, respectively. The ECC values at the lower and higher frequencies are lower than 0.003 and 0.01, respectively.

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Microplastics (MPS), as an emerging environmental pollutant, refers to plastic particles with length or width less than 5mm. Due to the small particle size, stable properties and difficult degradation, they are widely present in various environmental media. Plastic pollution has become one of the major threats to the function of the earth system. The greatest attention to date has been on their potential effect in marine ecosystems. However, a growing number of studies are examining their potential impact on soil ecosystems. In this paper, worldwide research progress on the separation, extraction, identification and ecological impacts of MPs in soil is reviewed. Finally, the development direction of future research on the microplastics is suggested. At present, the separation methods of microplastics in soil mainly include screening method, density separation, foam flotation, etc. The common strategy is to first identify obvious/possible microplastics with a microscope and then confirm by spectroscopy and thermodynamic methods such as Fourier Transform infrared spectroscopy (FTIR) or Raman spectroscopies. These methods have some shortcomings, such as time consuming and destroying the structure of microplastics. Appropriate combination and improvement of these methods are expected to make up the deficiency. The ecological impact of microplastics is mainly reflected in the growth, development and reproduction of animals. Furthermore, the presence of microplastics will cause changes in soil physical and chemical parameters, which will change vegetative stage, plant photosynthesis and oxidative stress. In addition, nanoscale microplastics can get across plant's membranes and cell wall barriers and enriched by plants, and poses an additional risk to humans via trophic food chain transfer. The prospects for future research include (1) standardized analytical methods; (2) dose-responds relationship of microplastics in soil; (3) the ecological of combination and interaction of microplastics with contaminants.