Engineering, Technology & Applied Science Research

532-539

Authors: G. A. Gamal, F. A. Al-Mufadi, A. H. Said

In this article, some Fe (III) doped hydroxyapatite samples (FeHAp) were prepared using the wet chemical method. The prepared samples were characterized via the use of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Detailed structural analysis were done by Scherrer and Williamson–Hall plot methods to detect the effect of iron on the structure of hydroxyapatite (HAp). XRD patterns showed that all samples were single phased HAp. Relations between the Fe content and the deformation of the lattice parameters, dislocation density, grain size, microstrain, crystallinity were investigated. The presence of iron in the HAp lattice is found to decrease both the crystal size and the dislocation density. Further results are presented and discussed.

544-548

Authors: D. Pylarinos, K. Theofilatos, K. Siderakis, E. Thalassinakis

A number of 387 discharge portraying waveforms recorded on 18 different 150 kV post insulators installed at two different Substations in Crete, Greece are considered in this paper. Twenty different features are extracted from each waveform and two feature selection algorithms (t-test and mRMR) are employed. Genetic algorithms are used to classify waveforms in two different classes related to the portrayed discharges. Five different data sets are employed (1. the original feature vector, 2. time domain features, 3. frequency domain features, 4. t-test selected features 5. mRMR selected features). Results are discussed and compared with previous classification implementations on this particular data group.

552-561

Authors: B. L. Dokic

Autonomy of power supply used in portable devices directly depends on energy efficiency of digital logic. This means that digital systems, beside high processing power and very complex functionality, must also have very low power consumption. Power consumption depends on many factors: system architecture, technology, basic cells topology-speed, and accuracy of assigned tasks. In this paper, a review and comparison of CMOS topologies techniques and operating modes is given, as CMOS technology is expected to be the optimum choice in the near future. It is shown that there is a full analogy in the behavior of digital circuits in sub-threshold and strong inversion. Therefore, synthesis of digital circuits is the same for both strong and weak operating modes. Analysis of the influence of the technology, MOS transistor threshold voltage (Vt) and power supply voltage (Vdd) on digital circuit power consumption and speed for both operating modes is given. It is shown that optimal power consumption (minimum power consumption for given speed) depends on optimal choice of threshold, and power supply voltage. Multi Vdd /Vt techniques are analyzed as well. A review and analysis of alternative logical circuit's topologies – pass logic (PL), complementary pass logic (CPL), push-pull pass logic (PPL) and adiabatic logic – is also given. As shown, adiabatic logic is the optimum choice regarding energy efficiency.