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Dielectric properties of natural rubber Hevea brasiliensis latex were measured at frequencies 0.2 to 20 GHz, at temperatures of 2, 15, 25, 35, and 50°C and around 30-98% moisture content. Measurements were done using open-ended coaxial line sensor and automated network analyzer. As expected, results showed that dielectric constant increased with increasing moisture. From 0.2 to 2.6 GHz, the losses were governed by conductive losses but for frequencies greater than 2.6 GHz, these were mainly due to dipolar losses. The former is due to conducting phases in hevea latex, while the latter is mainly governed by the orientation of water molecules. The results were analyzed at 2.6, 10, and 18 GHz, respectively. These were then compared with the values predicted by the dielectric mixture equations recommended by Weiner, Bruggeman and Kraszewski. All the measured values were found to be within the Weiner's boundaries and close to the upper limit of Weiner's model. It is also close to the predicted values of Bruggeman's model with a/b = 0.1. All the models including Kraszewski are suitable for predicting the dielectric properties of hevea latex for frequencies 2.6 to 18 GHz, moisture content 30 to 98% and temperatures 2 to 50°C.

Some geometrical aspects of Bianchi type III space‐time are investigated. This is followed by the study of Bianchi type III string cosmological models with perfect fluid distribution of matter.

This research was designed to form better dielectric composite material using one steady state dielectric (mullite) with a good dielectric material (strontium titanate). Distinct dielectric composites were successfully produced using locally sourced kaolinite clay. The samples were made using mullite as the base matrix and strontium titanate (ST) added at varying ratios. Strontium titanate was synthesized via solid-state reaction using strontium carbonate and rutile titanium (IV) oxide sintered at 1300°C. Local white kaolinite was used to fuse the strontium titanate material at varying weight ratios. The powders were dry-mixed and made into pellets for calcination at 1000°C. XRD and SEM characterizations were made. The dielectric measurements were carried out using the HP 4192A LF Impedance Analyzer dielectric setup in the frequency range of 10 Hz to 1 MHz. Three samples were prepared, namely ST 60%, ST 70% and ST 80%. The dielectric measurements were carried out in a controlled LT furnace at 30°C - 400°C. Measurements showed distinct varying interfacial encapsulation and dipolar relaxation for all composite samples.

Strontium Titanate, SrTiO3 samples were prepared using the conventional solid state reaction method. SrTiO3 samples were sintered at 1100°C, 1200°C, and 1300°C. XRD was used to determine the crystalline structure of the samples. The AFM showed the grain size was significantly increased with an increase in sintering temperatures. The dielectric properties of the sample were measured using Agilent 4291B Impedance/material Analyzer in the sub-microwave region in the frequency range 1 MHz to 1.5 GHz at room temperature. The dielectric constant and the average grain size were found to be the highest for the SrTiO3 sample sintered at 1200°C. Hence, greatest dielectric polarization occurred in the sample with the largest grain size.

CaCu3Ti4O12 (CCTO) was prepared by a conventional solid state reaction method. CCTO sample was pre-sintered at 900°C for 10 hours and sintered at 1075°C for 12 hours. The dielectric properties of the sample were measured using HP 4192A LF Impedance Analyzer. The complex permittivity was measured within the frequency range from 10 Hz to 106 Hz and the temperature ranging from 30°C to 400°C. The results showed that the dielectric constant and dielectric loss factor of the sample are frequency dependent and temperature dependent. CCTO sample exhibits a high dielectric constant which is around 105. Dielectric constant increases with decreasing frequency due to interfacial polarization. This could be explained by the Maxwell- Wagner effect.

This research was designed to form better dielectric composite material using one steady state dielectric with a good dielectric material. Distinct dielectric composites were successfully produced using locally sourced kaolinite clay. The samples were made using kaolinite as the base matrix and Barium Titanate (BT) added at varying ratios. Barium Titanate was synthesized via solid-state reaction using Barium Carbonate and rutile Titanium (IV) Oxide sintered at 1300°C. Local white kaolinite was used as the matrix at varying weight ratios. The powders were dry-mixed and made into pellets for calcination at 1000°C. The dielectric measurements were carried out using HP 4291B Impedance Analyzer dielectric setup. Three samples were prepared, namely 50%BT, 60%BT, and 70%BT. The dielectric measurements were carried out in an LT furnace at temperatures 30°C - 400°C with frequencies ranging from 10 Hz to 1 MHz. Measurements showed varying ionic relaxation for all samples.

This paper presents a new technique of predicting the reflection coefficient of a microwave sensor for oil palm fruits using finite element method (FEM). Comparison results between measured and calculated reflection coefficient were found to be in good agreement with magnitude and phase errors of less than 0.05 and 0.2 radian.

The dielectric properties of Thermoplastic Natural Rubber (TPNR)/Strontium Titanate (SrTiO3) composites was determined at room temperature, 27oC using the Impedance Analyzer at frequencies 10 Hz to 1 MHz. TPNR is formed as the matrix while SrTiO3 acts as the filler. Six samples were prepared at percentages of fillers from 0 to 50% at 10% intervals. The results indicate that the dielectric constant is almost independent of frequency from 100 Hz to 1 MHz, but the dielectric loss factor decreased with increasing frequency. This could probably be due to interfacial polarization and ionic losses. The dielectric properties are also affected by the composition of the filler, SrTiO3.

This research was designed to form better dielectric composite material using one steady state dielectric with a good dielectric material. Distinct dielectric composite was successfully produced using locally sourced kaolinite clay. The samples were made using kaolinite as the base matrix and Strontium Titanate (ST) added in varying ratios. Strontium Titanate were synthesized via solid‐state reaction using Strontium Carbonate and rutile Titanium (IV) Oxide with sintering at 1300 °C. Local white kaolinite was used to fuse the barium titanate material in varying weight ratios. The powders were dry‐mixed and made into pellets for calcination at 1000 °C. The dielectric measurements were carried out using the HP 4291B Impedance Analyzer dielectric setup. Three samples were prepared, namely 10%ST, 20%ST and 30%ST. The dielectric measurements were carried out at room temperature. Microwave region measurements showed steady state and linear dielectric relaxation ranging from 7 in the control sample and dropping down to 5 in 30%ST. The responses indicate linear relation between ST addition and microwave region dielectric permittivity.

Ceramic matrix composites (CMC) combine reinforcing ceramic phases, CaCu3Ti4O12 (CCTO) with a ceramic matrix, kaolinite to create materials with new and superior properties. 10% and 20% CCTO were prepared by using a conventional solid state reaction method. CMC samples were pre‐sintered at 800 °C and sintered at 1000 °C. The dielectric properties of samples were measured using HP 4192A LF Impedance Analyzer. Microstructures of the samples were observed using an optical microscope. XRD was used to determine the crystalline structure of the samples. The AFM showed the morphology of the samples. The results showed that the dielectric constant and dielectric loss factor of both samples are frequency dependent. At 10 Hz, the dielectric constant is 1011 for both samples. The CMC samples were independent with temperature with low dielectric constant in the frequency range of 104–106 Hz. Since the CMC samples consist of different amount of kaolinite, so each sample exhibit different defect mechanism. Different reaction may occur for different composition of material. The effects of processing conditions on the microstructure and electrical properties of CMC are also discussed.

The average cross-link density, number of the network bonds per unit volume, average stretching force constant, atomic ring size and the ratio Kbc/Ke have been calculated and discussed according to bond compression model for borotellurite glass. The result showed that the connectivity and rigidity of the borotellurite glasses increases with TeO2 content due to the transformation of BO3 units to BO4 and TeO3 units to TeO4. Comparison between theoretical calculated and experimental elastic moduli and Poisson's ratio has been carried out. The results showed good agreement between experimental and theoretical calculated elastic moduli.

In this review, we would like to highlight the three known no-go theorems in quantum physics in relation to the process of quantization that maps classical observables to quantum ones. The quantization approach considered is a mixture of Isham’s group-theoretic quantization and geometric quantization with special emphasis on underlying compact phase space geometry of spheres. The first is Groenewold-van Hove theorem that states the obstruction of quantizing the full algebra of observables and in the sphere case, only limited to the spin observables plus the constant functions. The other two are theorems of Bell and Kochen-Specker stating that the only hidden variable theories allowed by quantum physics are nonlocal and contextual ones. We give simple examples of these no-go theorems and indicate some interesting problems arising from them for the field of quantization

In the standard photopyroelectric technique, a precise control of thermal coupling fluid between the solid sample and the sensor is sometimes difficult, and yet an important factor in sample characterization. In this paper, we propose a non-contact photopyroelectric configuration for thermal diffusivity measurement of solids by considering the phenomena of thermal wave interference. We adopted the thermal wave interferometry, which was extensively discussed by Bennett and Patty in the photoacoustic signal generation, to our photopyroelectric signal generation in a thermally thick condition for a nondestructive testing. A normalization procedure has been used to eliminate a number of media parameters of photopyroelectric cell that otherwise needed to be known before one can determine thermal diffusivity of the sample. The thermal diffusivities obtained for Al, Cu, and Ni samples were close to literature values and thus justified the proposed model.

Measuring moisture content is a very important process to produce good quality materials and products. The standard technique of measuring moisture content is oven-drying method. Knowing the moisture level of grain is important for harvest, transport, safety storage, selling price and etc. In this study, a microstrip sensor is developed to determine the optimum moisture content of grains based on microwave attenuation. It is a four layered semi-infinite microstrip structure: consists of RT-Duroid substrate, protective layer, wet medium, and air. It is a functional relation between the transmission characteristics and the wet media which is affected by the configuration and dimension of the sensor and the electric properties of the dielectric layers have been developed. Characteristic impedance and phase constant are two important transmission parameters which involved in this interaction. The propagation of the electromagnetic wave in the microstrip is based on Quasi-transverse electromagnetic mode. Computational Analysis is used to obtain these two parameters and mostly numerical method is applied to analyze the multilayer microstrip structure. The characteristic impedance and the effective dielectric constant are drastically affected by the thickness of the protective layer. Based on this planner structure it is suitable to determine moisture content of grain inside sack more efficiently with a greater accuracy.

An open-ended coaxial sensor for the determination of complex permittivity and moisture content of oil palm fruits is presented in this paper. The measurement system consisting of the sensor and a PC-controlled vector network analyzer have been tested successfully on a range of oil palm fruits of various degrees of ripeness. The initial values of the complex permittivity were estimated using the admittance model of the sensor. The amount of moisture content was found by matching the values of permittivity from the quasistatic model with the permittivity of a dielectric mixture model using the moisture content values obtained from the standard oven drying method. © 2005 IEEE.

Close relationship between oil content and moisture content [Ariffin et al., 1990, Khalid & Abbas, 1992] suggests the possibility of using moisture content as a parameter to gauge fruit ripeness. It is found [Khalid & Abbas, 1992] that the amount of moisture content is higher at early stage of fruit development. Excess water is reduced in the ripe fruit as the oil accumulates in the mesocarp.

The dielectric properties of Hevea Rubber Latex have not been thoroughly investigated and are, therefore, not well understood. It is a biological product with a complex composition. A typical composition of freshly tapped natural rubber is made up of 50-80% water, 18-45% rubber hydrocarbon and 2-5% non-rubber constituents. The basic components of non-rubber constituent are proteins, lipids, quebrachitol and inorganic salts. Measurements of the dielectric properties at various moisture contents and temperature s -20 to -60°C in the lowfrequency region of 10⁻² to 10⁶ Hz were done using the Dielectric Spectrometer. The results of the measurement in the low-frequency region are expressed using the dielectric response model. For Hevea rubber latex, three distinct responses have been indicated. These are the real relative permittivity at high frequency ɛ(∞), the loss peak response ɛip and the conductance G. The total losses are conductive losses which arise due to the conducting phases found in latex, and dipolar losses which appear as loss peak responses due to the relaxation of the water molecules. The relaxation peak is shifted to a higher frequency as water content in the latex decreases and as temperature increases. This phenomenon could be due to the difference in the mechanism of polarisation relating to ion and the polarisation relating to ice. The activation energy for latex concentrate is l.66 eV while for fresh latex 2.34 eV. Ice has a non-constant activation process. This is due to the existence of two activation processes. The first activation process gives an activation energy of 0.51 eV whilst the second activation process results in a much lower activation energy. The high activation energy for fresh latex as compared to ice could be due to latex particles being bonded by the water molecules which needs more energy to dissociate. In the microwave region of 0.2 to 20 GHz, dielectric measurements were done using an open-ended coaxial sensor and an automated

The dielectric properties of hevea rubber latex were measured at selected microwave frequencies over the temperature range of -30°C to 50°C. The measurements were made on latex concentrate, fresh latex and diluted fresh latex by using an open-ended coaxial-line probe and an automated network analyser. There is a steep increase in the dielectric constant of about one order and dielectric loss factor of about two orders as the phase of latex changes from solid to liquid. The effect of temperature on the ionic conductivity at 0.2 GHz and dipole orientation at 2.6 GHz and above can be clearly seen in these studies. It was found that, the frequency around 10 GHz is a suitable operating frequency for microwave latexometer as dielectric properties are fairly independent of the temperature.