Zoonotic Transmission of Avian Influenza Virus (H5N1), Egypt, 2006–2009

A lower case-fatality rate may have been caused by a less virulent virus clade

Electric field distribution of optimized composite insulator profiles under different pollution conditions

This paper presents the simulation results of electric field distribution for optimally designed medium voltage composite insulators under polluted conditions with and without water droplets. Four different profiles of 11 kV composite insulators were used. Simulation was executed for both typical and optimized insulators by using Comsol Multiphysics program. The main objective of this paper was investigating the effect of pollution conditions and water droplets on the electric field distribution of the optimally designed insulators. The effect of pollution layer thickness and conductivity on the electric field distribution was studied. The simulation results showed that the maximum electric field stresses of optimally designed insulators were less than those of typically designed insulators in clean, polluted and wet conditions. The results of this study are able to provide theoretical support to design and select the suitable profile of composite insulators in order to obtain better performance under clean and polluted conditions. Keywords: Electric field distribution, Composite insulators, Pollution, Water droplet

Investigation the dielectric strength and mechanical features of nitrile butadiene rubber enhanced by different nanoparticles

To investigate the dielectric strength and mechanical features of modified nitrile butadiene rubber (NBR), titanium dioxide (TiO2) and magnesium oxide (MgO) nanoparticles have been used. Specimens have been experimentally prepared with loading various concentrations (0.5, 1, 1.5 and 3 parts per hundred part of rubber “Phr”) to NBR base material. The dielectric strength has been evaluated by applying AC high voltage on the prepared samples up to reaching the breakdown state. On the other hand tensile strength, elongation at break and modulus at 100% elongation have been experimented to exploration the mechanical features of the NBR enhanced by nanoparticles. Although all the recorded results of modified NBR samples showed improvement more than the base material at dielectric, tensile strength and modulus at 100% elongation tests. The elongation at break result showed a negative impact; it was caused by forming a new links between NBR and nanoparticles. The dielectric constants of applied nanoparticles are greater than NBR base materials, which can physically explain the improvement in all recorded breakdown results. But the enhancement in the measured mechanical features can be attributed to chemical bonds which were reconstructed and the gaps of NBR base material that had been filled

Partial discharge behavior on solid- air interfaces at AC stress condition

Partial discharge (PD) is one of the major factors that damage dielectric materials in medium and high voltage components. Therefore, partial discharge evaluation is generally used to observe the status of electrical insulation in high and medium voltage components used in the performance appreciation of an insulation system. In this work, partial discharge behavior on solid- air interfaces has been investigated commonly characterized as surface discharge. The investigation was performed by PD measurement as well as by adequate modelling for different insulating materials as the Natural Rubber (NR), Silicone Rubber (SiR), Ethylene Propylene Diene Monomer Rubber (EPDM) and High- Density Polyethylene (HDPE). Through modeling the partial discharge process, a better conception of the phenomenon may be achieved. The model of different homogeneous insulating materials has developed using Finite Element Analysis (COMSOL) software in parallel with MATLAB programming function. The results of the study indicate that the repetition rate and the peak apparent charge increased with the insulating material relative permittivity increase while the inception voltage does not change significantly

Achievement of the best design for unequally spaced grounding grids

The configuration of grounding grids which are used to earth electrical substations could be equally or unequally spaced. Unequally spaced grids were introduced to improve the requirements of the grids such as grounding grid resistance (Rg), ground potential rise (GPR), maximum touch voltage (Et) and maximum step voltage (Es) values. Also, unequal spacing can reduce the cost of the grids and enhance the level of safety for people and equipments. In this paper two different approaches were used to determine the best possible configuration of grounding grid. These approaches based on sequential multiplicative and sequential power techniques

The Effect of Superplasticizers on Eco-friendly Low-Energy One-Part Alkali-Activated Slag

Abstract One-part alkali-activated materials (OP-AAM) have become a promising binder with low carbon and energy requirements associated with superior mechanical and durability characteristics. This study aims to employ commercial superplasticizers (naphthalene-based “Nb-SP” and polycarboxylate-based “PCb-SP”), as well as laboratory-prepared one (phenol–formaldehyde sulfanilate “PFS-SP”) in enhancing the properties of OP-AAM. The main problem of superplasticizers (SPs) in the AAM is their hydrolysis in the alkaline activator (NaOH) used in the activation reactions. Therefore, the thermo-chemical treatment process was utilized to mitigate the high activator alkalinity by impeding the NaOH in the aluminosilicate precursor matrix. The OP-AAM was fabricated from thermo-chemical treatment powder (TCT-P) resulting from sintering blast furnace slag (GGBFS) with 10 wt% NaOH at 300 and 500 °C. The XRD-pattern showed that NaOH was impeded in the GGBFS via sodium aluminum silicate phase formation after sintering at 500 °C. The results showed that the admixed OP-AAM prepared from TCT-P at 500 °C greatly enhanced the workability and mechanical properties. The PFS-SP proved its efficiency in improving the properties of OP-AAM prepared TCT-P at 300 and 500 °C, referring to its high stability in an alkaline medium. While PCb-SP reinforced the properties of OP-AAM prepared from TCT-P at 500 °C only, proving that PCb-SP promotes high capability in TCT-P-500 as well as in Portland cement