ABSTRACT
A specially designed dumbbell type polarization conversion metasurface (PCM) is proposed. The designed PCM achieves line-to-line polarization conversion in ultra-wideband (UWB) from 7.63â GHz to 18.80â GHz. A low-profile metasurface antenna composed of PCM and slot feed is proposed based on characteristic mode analysis (CMA), which realizes the integrated design of radiation and scattering. Because of the checkerboard scattering properties, low-radar cross section (RCS) low-profile multiple-input-multiple-output (MIMO) antenna and array antenna are designed with PCM. The low-RCS high-isolation low-profile MIMO antenna with size of 1.27×1.27×0.07λ 0 3 (λ0: the free-space wavelength corresponding to the center frequency point) operating at 5.8â GHz consists of four orthogonal arranged metasurface antennas. The isolation is greater than 26â dB with impedance bandwidth from 5.51â GHz to 6.06â GHz. In addition, the low-RCS high-gain low-profile array antenna with size of 2.55×2.55×0.07λ 0 3 is also designed. The operating band covers from 5.63â GHz to 6.12â GHz with the gain of 12-15.6 dBi. The RCS reduction of the two antennas for normal incidence is between 6â dB and 23â dB in both X- and Ku-bands. The measured results of the antennas agree with the simulated results, which shows that they have potential application value in 5.8â GHz WLAN wireless communication.
ABSTRACT
Purification, characterization and antioxidant activities of polysaccharides from thinned-young apple (TYA) were investigated in the study. A water-soluble polysaccharide (TYAP) was obtained with hot water extraction, which was further purified by chromatography of Cellulose DEAE-52 and Sephadex G-150 to get three purified fractions of TYAP-1, TYAP-2 and TYAP-3. HPLC analysis showed that the three fractions were mainly composed of galactose and arabinose with the average molecular weights of 115 kDa, 479 kDa and 403 kDa, respectively and the monosaccharide compositions of TYAP-2 and TYAP-3 were more complicated than that of TYAP-1. Moreover, TYAP fractions of three had no absorptions at 260 nm and 280 nm in the UV spectrum, indicating the absence of protein and nucleic acid. Their structure properties were further confirmed by FT-IR. In vitro antioxidant activities of three fractions were characterized by DPPH(â¢), HO(â¢), O2(â¢-) and ferric-reducing antioxidant power systems. The results indicated that TYAP-1, TYAP-2 and TYAP-3 possessed significant antioxidant effects in a concentration-dependant manner in the tested concentration range of 0.25-5.0mg/mL. Among the fractions tested, TYAP-3 showed significantly higher antioxidant activity than that of TYAP-1 and TYAP-2. All of these findings provide a scientific basis for the further use of polysaccharides from thinned-young apple.