RESUMEN
A dual-band four-element MIMO antenna was designed and fabricated with enhanced isolation. The introduced antenna was fed by a coplanar waveguide (CPW) and consisted of four identical monopole antenna elements placed perpendicular to each other. A cross-shaped stub and orthogonal placement of four elements were introduced for high isolation. Modified ground structure was used for extending bandwidths. The measured results demonstrate that the introduced antenna has double bands (S11 < -10 dB) covering 3.28-4.15 GHz and 4.69-6.01 GHz, with fractional bandwidths of 23.4% and 24.7% and a high isolation S21, S31 better than 19 dB. The curves of the envelope correlation coefficient (ECC) and diversity gain (DG) were less than 0.0025 and higher than 9.999, respectively, indicating a low correlation between antenna elements. Furthermore, gain, efficiency, channel capacity loss (CCL), total active reflection coefficient (TARC) and mean effective gain (MEG) have all been investigated over the operating band to determine the antenna's diversity performance. In accordance with the simulated and measured results, it confirms that the proposed antenna is appropriate for 5G applications.
RESUMEN
A 2 × 2 ultra-wideband MIMO flexible antenna with a low profile and good isolation was designed for Internet of Things (IoT) realms and wearable devices. The antenna elements were placed on a novel flexible substrate of liquid crystal polymer (LCP) with compact dimensions fed by a coplanar waveguide (CPW). In order to ameliorate isolation, the cross-shaped decoupling branches were placed among the antenna elements. The proposed UWB antenna can operate from 2.9 GHz to 10.86 GHz with a good reflection coefficient of S11 < −10 dB as well as a high isolation better than 22 dB. Its operating bands include 5G, WiFi, X-band, etc. Moreover, the parameters of diversity performance were also tested. These parameters included an average gain of approximately 4 dB, a low ECC of less than 0.01, and good diversity gain of 9.999. The flexible MIMO antenna performs well in bending and on-body conditions. To sum up, the antenna has good prospects in IoT applications and wearable fields.
RESUMEN
Mercury is harmful to the environment, which has gradually become one of the research hotspots. Sediments, as a main repository of pollutants, have an important impact on water quality and the internal organisms, which deserves our research. In this paper, we focused on Hefei landscape water sediment and tried to investigate the status of inorganic mercury and methylmercury pollutions in the sediment. To study the conversion process from inorganic mercury to methylmercury and their enrichment levels and mechanism, we established the ecological chain of "sediment-water-grass-fish" through analog microcosm examination. The results were as follows: from ten water and sediment samples in Hefei landscape water sediment, we found that the contents of inorganic mercury and methylmercury ranged 11.74-13.12 µg · kg⻹ and 0.37-2.23 µg · kg⻹, respectively. The microcosm examination showed that: with increasing culture time, inorganic mercury in sediments gradually decreased. There was a phenomenon that the content of methylmercury increased at first and then decreased to reach the balance later. Both the inorganic mercury and methylmercury in water change showed an increasing trend. The enrichment contents of inorganic mercury in Egeria densa Planch, and golden mandarin fish (Siniperca scherzeri Steindachner) were low while their enrichment of methylmercury could he great. In addition, we found that both the bioaccumulation ability and the enrichment coefficient of methylmercury in the body of golden mandarin fish were the maximum during the same period.