Free space microwave measurement for detecting corrosion under a thin paint of aluminium panel
This paper presents a free space microwave measurement methods which are non-destructive and noncontact to determine the corrosion under a thin paint on aluminium panel. For free space microwave measurements techniques, the measured parameters are reflection coefficients S11, transmission coefficients S21, dielectric constants, loss factors, and complex permittivity as a function of frequencies. This paper is focusing on metal backed method in order to detect corrosion under thin paint on Aluminium panel. The metal backed method will measure the free space reflection coefficients, S11 only. In order to obtain smaller errors of dielectric constant, it is required that the sample thickness to be close to odd multiples of quarter wavelength. The results of the complex permittivity of the samples were calculated from measured reflection coefficient S11 at frequency range of 8 GHz-12 GHz.
A novel preliminary study on microwave characterization of Siamese Mangoes ripeness at K-Band
This project presents a microwave non-destructive testing (MNDT) method to determine the ripeness of Siamese mangoes at a frequency range of 18 to 26.5 GHz (K-Band) using free space microwave measurement (FSMM) system. The basic components of the FSMM system are spot focusing horn lens antennas, a vector network analyzer (VNA) and a computer. In this method, the free space reflection, S11 and transmission, S21 coefficients are measured for the samples sandwiched between two Teflon plates that are quarter wavelengths at mid-band. The thru, reflect and line (TRL) calibration technique is used to eliminate the effect of undesirable multiple reflections. The extracted S11 and S21 are keyed in a developed algorithm to calculate the complex permittivity of moisture contents within the samples. Results have shown that the dielectric constants for ripe and unripe mangoes are between 26.3 to 29.5 and 26.1 to 29.2 respectively. Other parameters including loss factor and loss tangent are also discussed.
ROOM- AND HIGH-TEMPERATURE MAGNETIC PROPERTIES OF Sm(CobalFexCu0.088Zr0.025)7.5 (x=0.30) SINTERED MAGNETS
The effect of Fe content on room- and high-temperature magnetic properties of Sm(CobalFexCu0.088Zr0.025)7.5 (x=0-0.30) sintered magnets, prepared by the conventional powder metallurgy method, has been systematically studied. With increasing Fe content, the remanences BT and maximum energy products (BH)max at room temperature gradually increase and reach optimal values of 1.055 T with x=0.27 for BT, and 205 kJ/m3 with x=0.21 for (BH)max, respectively, and then drop sharply with further Fe increase. An excessive addition of Fe (x≥0.24) results in rapid deterioration of permanent magnetic properties due to the formation of a considerable amount of FeCo soft magnetic phase. It was found that the effect of Fe content on high temperature stability is huge. The lower the Fe content, the smaller the temperature coefficient of coercivity. When x=0.07, a temperature coefficient of coercivity of -0.14%/K (293-723 K) can be achieved, as compared with -0.23%/K for x=0.21. BT of 0.725 T, bHc of 517 kA/m, iHc of 764 kA/m, and (BH)max of 95 kJ/m3 at 723 K were obtained, and the B-H demagnetization curve remains a straight line.