Neural networks to analyze surface tracking on solid insulators

Surface tracking on solid insulators is one of the most severe breakdown mechanisms associated with polymeric materials under long term service conditions. A wide range of relays can detect failure in a transmission line and prevent a total breakdown in the systems, but due to the non-healing characteristics of solid insulators, in most cases it might be too late to save the insulator after tracking initiation and growth. The method described here is employed mainly in detecting several conditions, such as discharges, leakage current, dry conditions, severe damage and tracking initiation. Initially a BPN (back propagation network) type NN (neural network) is trained with different signal types. Due to the nature of NN, which always require similar values of input nodes, the system uses the FFT (fast Fourier transform) of the input signal, which might have high amplitude frequency components other than the fundamental frequency depending an the condition of the surface. The system works on a real time basis and warns the user with the first indication of severe damage on the surface and can protect the insulator from excessive damage     

Multi-objective Genetic Algorithms for grouping problems

Linear Linkage Encoding (LLE) is a convenient representational scheme for Genetic Algorithms (GAs). LLE can be used when a GA is applied to a grouping problem and this representation does not suffer from the redundancy problem that exists in classical encoding schemes. LLE has been mainly used in data clustering. One-point crossover has been utilized in these applications. In fact, the standard recombination operators are not suitable to be used with LLE. These operators can easily disturb the building blocks and cannot fully exploit the power of the representation. In this study, a new crossover operator is introduced for LLE. The operator which is named as group-crossover is tested on the data clustering problem and a very significant performance increase is obtained compared to classical one-point and uniform crossover operations. Graph coloring is the second domain where the proposed framework is tested. This is a challenging combinatorial optimization problem for search methods and no significant success has been obtained on the problem with pure GA. The experimental results denote that GAs powered with LLE can provide satisfactory outcomes in this domain, too.     

Detection of object boundary from point cloud by using multi-population based differential evolution algorithm

Neural Computing and Applications - The problem-solving success of an Evolutionary Computing algorithm is too sensitive to the structures of mutation and crossover operators it uses. The mutation...     

Chemical vapor deposition of B12As2 thin films on 6H-SiC

Icosahedral boron arsenide (B₁₂As₂) thin films were deposited on 6H-SiC substrates by chemical vapor deposition using B₂H₆ and AsH₃ sources. X-ray diffraction analysis of the thin films showed them to have the rhombohedral crystal structure and lattice parameters of B₁₂As₂. Transmission electron microscopy showed that the films were polycrystalline with oriented crystal grains. The preferential orientation of the film with respect to the SiC substrate was determined to be: [0001]_B12_{As 2}//[0001]_6H-SiC and [ ]_B12_{As 2}//[ ]_6H-SiC to within 3°. Electron diffraction also revealed the extremely small lattice mismatch (<0.5%) between the B₁₂As₂ basal-plane lattice parameter and twice the SiC basal-plane lattice parameter.     

Simulation studies to improve design for midlife 275-kV cable refurbishment

Simulation studies to reduce the number of link positions on an existing 275-kV cable route due for refurbishment are presented. This reduction in the number of link positions will effectively reduce the overall cost of maintenance and will also improve reliability. It is shown that the proposed layout and bonding arrangement can produce sheath voltages of up to 200 V during load conditions, 3 kV during external faults, and 6.4 kV during internal faults. Transient sheath to ground voltages of up to 100 kVp during lightning and up to 95 kVp during faults can be experienced. These voltages will be acceptable in normal service. The capital efficiency of the refurbishment, which reduces the number of link positions, should also reduce the risks of subsequent failure and the cost of maintenance.     

Comparative studies on the solvent extraction of transition metal cations by calixarene, phenol and ester derivatives

The ionophore solvent extraction of various alkali metal and transition metal cations from the aqueous phase to the organic phase was carried out by using diazo-coupling calix[n]arenes [p-(4-phenylazophenylazo)calix[4]arene (L1) and p-phenylazocalix[6]arene (L2)], phenol derivatives [2,6-dimethyl-3-phenylazophenol (L3), 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol (L4), 2-chloro-4-nitro(phenylazo)-5-sec-butyl-2-phenol (L5) and 2-chloro-4-nitro(phenylazo)-5-tert-butyl-2-phenol (L6)], and ester derivatives [quinoline-8-benzoate (L7), phenyl-1,4-dibenzoate (L8), p-tolyltiobenzoate (L9)]. It was found that, all the compounds (L1-L9) examined showed selectivity for transition metal cations such as Ag+, Hg+ Hg2+, and poor efficiency for alkali metal cations (Na+ and K+). The best extraction efficiency was obtained with L1 and L4.