Development of switching principles and phase comparison techniques for distance protective schemes

The paper represents further work on phase comparison techniques by the same author. Two techniques are reported here. The first one describes a new principle of operation employed for the main functions of starting elements for fault detection and selection of phase(s). The principle is based on a process of phase comparison accomplished between comparison quantities derived from the three symmetrical components of line current relative to only one phase of the protected line section. Fault detection and phase selection are achieved by delivering nine distinct orders from the starting element corresponding to the nine cases of asymmetrical faults. The starting element based on this principle reduces the switching time to 3.33 ms.The second technique is concerned with phase comparison techniques to improve the security and reliability of the high-speed comparator described previously by the same author. The modus operandi consists of continuously monitoring the coincidence of compared comparison periods derived from the two relaying signals and simultaneously the non-coincidence of another set of compared comparison periods derived from the same relaying signals. Fault detection is achieved by delivering a trigger output from the comparator corresponding to non-coincidence of the first set and coincidence of the second set of comparison periods.     

BER improvement of PRCPM in mobile radio channels withdiscriminator detection using decision feedback equalization

The authors investigate the bit error rate (BER) improvement of partial-response continuous-phase modulation (PRCPM) signals in mobile radio channels, when decision feedback equalization (DFE) to cancel the effect of intersymbol interference (ISI) of one adjacent bit is added to the limiter discriminator. A closed-form expression for the average probability of error as a function of the Doppler shift is derived for discriminator detection with decision feedback. Numerical results are presented to compare the BER performance of discriminator detection with and without feedback equalization     

Determination of trace metals in cottonseed oil and hydrogenated cottonseed oil

The main vegetable oils used in Egypt are cottonseed oil and hydrogenated cottonseed oil; these are used as salad oil and for cooking. Determination of trace heavy metals in the oils is important. This is because of the association of trace metals with the origin of the oils, metal processing equipment and catalysts used for hydrogenation, and toxicity of edible oils, and because of the effect of trace metals on the characteristics, such as colour and taste, of finished products.Iron, copper, aluminium and magnesium were found in the cottonseed oil. These metals were also found in the hydrogenated cottonseed oil, together with lead, silver and calcium. The amounts of metals were below the limits permitted by public health and safety regulations.     

Fusion-fission hybrid design with analysis of direct enrichment and non-proliferation features (the SOLASE-H study)

The role of a fusion-fission hybrid in the context of a nuclear economy with and without reprocessing is examined. An inertial confinement fusion driver is assumed and a consistent set of reactor parameters are developed. The form of the driver is not critical, however, to the general concepts. The use of the hybrid as a fuel factory within a secured fuel production and reprocessing center is considered. Either the hybrid or a low power fission reactor can be used to mildly irradiate fuel prior to shipment to offsite reactors thereby rendering the fuel resistant to diversion. A simplified economic analysis indicates a hybrid providing fuel to 10 fission reactors of equal thermal power is insensitive to the recirculating power fraction provided reprocessing is permitted. If reprocessing is not allowed, the hybrid can be used to directly enrich light water reactor fuel bundles fabricated initially from fertile fuel (either ThO₂ or ²³⁸UO₂). A detailed neutronic analysis indicates such direct enrichment is feasible but the support ratio for ²³³U or ²³⁹Pu production is only 2, making such an approach highly sensitive to the hybrid cost. The hybrid would have to produce considerable net power for economic feasibility in this case. Inertial confinement fusion performance requirements for hybrid application are also examined and an integrated design, SOLASE-H, is described based upon the direct enrichment concept.     

Navigator echo motion artifact suppression in synthetic aperture ultrasound imaging

We develop a simple yet effective technique for motion artifact suppression in ultrasound images reconstructed from multiple acquisitions. Assuming a rigid-body motion model, a navigator echo is computed for each acquisition and then registered to estimate the motion in between acquisitions. By detecting this motion, it is possible to compensate for it in the reconstruction step to obtain images that are free of lateral motion artifacts. The theory and practical implementation details are described and the performance is analyzed using computer simulations as well as real data. The results indicate the potential of the new method for real-time implementation in lower cost ultrasound imaging systems.     

Desulphurization of petroleum coke by butagas

The work described concerns the desulphurization of Egyptian petroleum coke by butagas in a fixed-bed reactor. Optimum values for reaction temperature and coke particle size were observed; but increased gas flow rate, prolonged reaction time, and decreased coke bed depth all favoured increased sulphur removal throughout the ranges studied. The effects of the different factors could be interpreted satisfactorily in terms of the thermodynamic potential of the desulphurization reaction and the diffusion of gases into and out of the coke particles. While gas/coke ratio governs the former, the latter is mainly influenced by sintering of the coke particles. For comparison, some desulphurization runs were carried out using hydrogen in place of butagas, and Syrian petroleum coke instead of the Egyptian coke. The Syrian coke proved difficult to desulphurize.     

Synthesis of some new disperse anthraquinone dyes

1-Hydroxy and/or 1-aminoanthraquinone was allowed to react with formaldehyde in an alkaline medium to give 1-hydroxy or 1-amino-2-hydroxymethyl-9,10-dihydroxy-anthracenes, which gave on air oxidation, hydroxymethylanthraquinone derivatives (I). Interaction of 1-amino-2-hydroxymethylanthraquinone or its 4-bromo derivative with carbonyl compounds in the presence of an acid catalyst gave (1,3)oxazine derivatives (II). The methylene group in position-2 of the (1,3)oxazine ring was found to be highly reactive and reacted with carbonyl compounds to form the corresponding arylidenes (III). Selective oxidation of dimethyl oxazine derivatives with SeO₂ gave the corresponding dialdehyde (IV), which interacted with aromatic amines to give the corresponding Schiff bases (V). The bromine atom in the 6-position of II was easily replaced by aromatic amines to give blue disperse dyes (VI).     

Implementation of a New Linear Control Technique Based on Experimentally Validated Small-Signal Model of Three-Phase Three-Level Boost-Type Vienna Rectifier

In this paper, the design and implementation of a new multiple-input-multiple-output linear control technique based on a theoretically established and experimentally validated small- signal model for the three-phase three-level boost-type ac/dc Vienna converter are presented. Averaging and local linearization techniques are used to derive the dynamic model expressed in the dqo reference frame. The resulted transfer functions are discretized for the sake of a digital controller design. Multiple-loop control strategy is adopted and consists of inner current feedback loops, which are based on the straightforward looping technique that neglects interactions between the dq components of control inputs and currents, respectively, and of an outer voltage loop, which is designed to ensure dc voltage regulation by adjusting the magnitude of the references for the inner current loops. The output dc voltage unbalance is also controlled in the inner loops. The proposed modeling and control approaches are first simulated and then validated on a 1.5-kW laboratory prototype supported by the DS 1104 digital real-time controller board of dSPACE. The obtained results prove the accuracy of the proposed new small-signal model and, therefore, its reliability for dynamic analysis and control design purposes. It is also proved that a judicious choice of controller parameters, as well as an adequate rating of boost inductors, allows one to meet the IEEE standard requirements in terms of ac line-current total harmonic distortion and power factor. The efficiency of the proposed control technique is maintained in case of disturbances occurring on both source and load sides.