This paper presents the development of a PC-based microwave five-port reflectometer for the determination of moisture content in oil palm fruits. The reflectometer was designed to measure both the magnitude and phase of the reflection coefficient of any passive microwave device. The stand-alone reflectometer consists of a PC, a microwave source, diode detectors and an analog to digital converter. All the measurement and data acquisition were done using Agilent VEE graphical programming software. The relectometer can be used with any reflection based microwave sensor. In this work, the application of the reflectometer as a useful instrument to determine the moisture content in oil palm fruits using monopole and coaxial sensors was demonstrated. Calibration equations between reflection coefficients and moisture content have been established for both sensors. The equation based on phase measurement of monopole sensor was found to be accurate within 5% in predicting moisture content in the fruits when compared to the conventional oven drying method.
A simple procedure was developed to determine complex permittivity of moist materials for known percentage of moisture content at any frequency based using a standard commercial coaxial sensor. Polynomial fitting and Gaussian elimination method were applied to obtain a single equation of complex permittivity as a function of frequency and moisture content. The empirical equation was tested for new samples and was found to have mean error percentage of 5.14 % and 10.22 % for dielectric constant and loss factor, respectively, when compared to a commercial probe.
Superconducting YBa2Cu3O7-δ (YBCO) agglomerated nanoparticle (ANPs) was fabricated by electrospinning technique and sol-gel of a homogeneous precursor of Y-Ba-Cu acetate and Poly (vinyl pyrrolidone) (PVP). The sol-gel solution of YBCO is conducted by adding 4.0 g of (Y-Ba-Cu) metal acetate according to a stoichiometric ratio of 1:2:3 molar mass and 5.0 g of PVP powder in 25.0 ml solution contains propionic acid 10 ml, acetic acid 5 ml and methanol 10 ml. By optimizing electrospinning process, sol-gel parameters and heat treatment, YBCO ANPs were obtained with a transition temperature of Tc ~90 K using the AC susceptibility. YBCO ANPs was found with high surface area 6.8310 m2/g, and not affected by high calcination temperature at 950 oC in comparison with bulk YBCO sample. XRD Characterization of YBCO was demonstrated YBCO has orthorhombic phase, FESEM images of the electrospun YBCO sample showed ANPs of size in the 200 – 400 nm range. A closer examination revealed that agglomerates contain finer particles of size ~50 nm. Electrospinning is an effective technique can produce various morphologies of YBCO superconductor at the nanoscale with unique properties for practical applications.
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