In this work, Sr0.3Ba0.4Pb0.3Fe12O19/(CuFe2O4)x (x = 2, 3, 4, and 5) as strongly exchange-coupled nanosized ferrites were fabricated using a one-pot sol–gel combustion method (citrate sol-gel method). The X-ray diffraction (XRD) powder patterns of the products confirmed the occurrence of pure, exchange-coupled ferrites. Frequency dependencies of the microwave characteristics (MW) were investigated using a co-axial method. The non-linear behavior of the MW with the composition transformation may be due to different degrees of Fe ion oxidation on the spinel/hexaferrite grain boundaries and strong exchange coupling during the hard and soft phases.
This article proposes a multiband metamaterial microwave absorber based on a split ring‐slot structure. Both simulation and experimental measurements are carried out to obtain the scattering parameters which are used to retrieve the absorption coefficient, relative permittivity, and relative permeability. The influences on the absorption produced by geometrical dimensions, incidence angles and polarisation angles are investigated from 1.5 to 18.0 GHz. The results show that the absorber possesses three resonance peaks with absorption greater than 70% measured experimentally at 3.0, 5.8, and 11.0 GHz. The absorption performance is insensitive to the angle of incidence, θ up to 60°.The absorption mechanisms are studied based on the surface current distribution, electric field distribution, and constitutive parameters (μ
r and ε
r). Furthermore, a mechanical mean using dielectric material to tune the absorption frequencies (up to 1.0 GHz of tuning range) and enhance the absorption bandwidth (up to 50%) is demonstrated.
Physicochemical parameters analysis was used in the identification of varietal honey from different botanical origin. Botanical origin is one of the important parameter to be known as a quality control to meet the legislated mandatory requirement during commercialization. This study assessed the influence of the botanical origin on the physicochemical properties of stingless bee honey or known as kelulut honey in state of Johor, Malaysia. The honey samples were collected in six different botanical origins namely acacia,coconut, mangrove, starfruit, multifruits and multiflowers produced by bee species of Heterotrigona itama. Tualang honey from bee species of Apis dorsata was included as a positive control. The physicochemical properties in terms of pH, moisture, ash content, electrical conductivity (EC) and colour intensity were measured. The result obtained revealed an average pH (3.40 ± 0.15), moisture (28.9 ± 2.69 g/100g), ash (0.37 ± 0.27 g/100g), electrical conductivity (0.11 ± 0.07) mS/cm, and colour intensity (692 ± 187) mAU. In general, the raw honey from state of Johor presented satisfactory quality according to the result obtained help in honey identification and authenticity as well as to sustain meliponiculture industry in Malaysia.
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