Electrical characteristic changes by setting conditions of Normal-Mode Helical Antenna in a phantom

Normal-Mode Helical Antenna (NMHA) is a promising candidate for medical implantable application due to its ability to achieve high efficiency in very small size, when self-resonant structure of the antenna is achieved. In use of NMHA for implantable application, a human body phantom is employed in antenna development stage. In the case of measurement of NMHA placed in a phantom, antenna setting and feeder cable may influence measured results. In this paper, relations of antenna setting conditions and measured electric characteristics such as antenna input impedance and radiation patterns are clarified through electromagnetic simulations

An experimental study on surface discharge characteristics of different types of polymeric material under AC voltage

Surface discharge is a common electrical discharge that normally occurs on the surface of outdoor insulators and also causes the failure in the electrical insulation system. One of the causes of surface discharge is the presence of high voltage stress. Experimental works had been carried out to examine the surface discharge characteristics on polymeric samples as insulation material. The IEC (b) electrode configuration had been used to investigate the surface discharges phenomena of different types of polymeric materials with controlled of air relative humidity (RH). In these experimental works, three types of polymeric sample were selected, namely high-density polyethylene (HDPE), ethylene-vinyl acetate (EVA), and polystyrene (PS), respectively. The characteristics of the discharge are critically depending on the types of polymer. Surface discharges intensity, number of discharge occurrence, and surface morphology of each polymeric material were also investigated. Comparisons of these electrical characteristics were conducted among the samples. Results from the experiment showed that the EVA samples experienced severe degradation as compared to HDPE and PS samples

Conversion and characterization of bio-coke from abundant biomass waste in Malaysia

Depletion of fossil fuels and the adverse impacts burning these fuels has increased the attention towards utilizing biomass energy sources, thus increasing the focus on Bio-Coke technology, which can fully convert biomass waste into alternative fuels. This study analyzed the characteristics of Bio-Coke conversion from biomass abundantly found in Malaysia, which included rice husk, rubber wood sawdust, coconut husk, sugarcane bagasse, oil palm frond, oil palm trunk and empty fruit bunch (EFB). Results indicated better physical feature characteristics of biomass solid fuel. For example, Bio-Coke produced from EFB showed an apparent density of 1.414 g/cm3, combustion duration of 1664 s, and maximum compressive strength at room temperature (25 °C) and 700 °C of 95.107 and 9.412 MPa, respectively, which were found to be higher than that of wood pellet. This study showed Bio-Cokes can be potentially used as an alternative fuel to reduce the usage of coal coke in the future

The effectiveness of biological pretreatment of oil palm empty fruit bunch on its conversion into bio-coke

The demand for affordable energy will continue to increase. On the other side, the utilization of fossil fuels is causing drastic changes to our climate forcing us to search for more sustainable sources of energy. Lignocellulosic biomass waste from palm oil industry in Malaysia is one of the most abundant and economically attractive sources of renewable energy. This can be utilized as the raw material for solid biofuel, i.e., Bio-Coke. Some efforts have been made to improve the quality of Bio-Coke in recent years. This study aims to determine the influence of biological pretreatment of oil palm empty fruit bunch (EFB) on its subsequent Bio-Coke characteristics. The results show after pretreatment, the fiber structure of EFB could be seen clearly and a looser connection between single fibers is observed. The pretreatment leads to the biologically pretreated Bio-Coke having higher apparent density and longer combustion duration than the Bio-Coke without pretreatment

Wavelet analysis of the onset of vhf and microwave radiation emitted by lightning

Lightning flash is an electrical discharge in air (dielectric breakdown) which emits electromagnetic (EM) fields across very wide spectra from a few Hertz up to visible wavelength. Electrical breakdown process is an important event that initiates lightning. For electrical breakdown process to occur, it must fulfill two conditions which are at least has one free electron and the electric field region is more than 3 MV/m. This process starts with electron avalanche in millimeter scale then grows into streamer in centimeter scale. Lastly, from streamer it will grow into leader in meter scale. It has already established that streamer emits intensely at Very High Frequency (VHF) band as it's already proven both theoretically and experimentally. A study by Cooray, theoretically proved that emission of electron avalanche peaks at microwave band. Air-gap parallel plate antenna which could operate at 1 GHz with remote sensing is designed and simulated to measure the microwave radiation emitted by lightning. Both temporal and wavelet analyses are used to compare the onset of microwave radiation and VHF radiation in both time and frequency domains to determine electron avalanche appears at which electromagnetic band