Heterocyclic Synthesis with Nitriles: Synthesis of some novel pyrrolo [2,1-b]thiadiazoline,pyrrolo[2,1-b]thiadiazolo[3,2-a]pyrimidine and pyridine derivatives

α-(Bromothiocyanatomethyl)benzylidenemalononitrile ( 1 ) reacts with the hydrazides 2a – c , cyanoacethoydrazide ( 2d ,) cyanoacetamide ( 3a ) and cyanoacetanilides 3b – d to afford pyrrolo[2,1-b]thiadiazolines 5a – c , pyrrolo[2,1-b]thia-diazolo[3,2-a]pyrimidine ( 8 ) and the pyridone derivatives 11a – d . Structures and conceivable mechanisms are discussed.     

Bis(methylthio)methylene malononitrile in the synthesis of heterocyclic compounds with bridgehead nitrogen

The condensation of bis(methylthio)methylene-malononitrile with some aminoazoles, namely 2-aminobenzimidazole, 2-aminobenzothiazole, 5-aminotetrazole monohydrate, 2-amino-5-ethylthiadiazole, 2-aminothiazole, 2-phenyl-4-aminothiazole and/or creatinine resulted in the formation of bridgehead nitrogen compounds. The structures of these compounds were established by analytical and spectral data.     

Performance analysis of photovoltaic pumping systems using switched reluctance motor drives

A photovoltaic (PV) pumping system using a switched reluctance motor (SRM) is investigated in this work. the motor is supplied by a DC voltage through a simple switching circuit. This drive circuit is much simpler than the normal DC/AC inverter required to supply an induction motor. the efficiency of the SRM is considerably higher than that of equivalent DC or induction motors. In addition, because of its simple construction, the SRM is cheaper than these conventional drives. These advantages give the proposed system higher efficiency and lower cost compared with other systems. In this paper, which has a substantial tutorial content, a design example is studied in detail to explore the advantages of PV pumping systems based on the new drive. Study of the performance of the proposed system showed that the operating efficiency of the motor is about 85% during most of its working time. the matching efficiency between the PV array and the proposed system approaches 95%. the major part of the losses takes place in the pump and the riser pipes; this loss represents one-third of the total available energy.     

Design and allocation of power system stabilizers using the particle swarm optimization technique for an interconnected power system

In this paper, three particle swarm optimization (PSO) based power system stabilizers (PSSs) are developed for three power systems. The system under study here is a power pool consisting of 3 power systems. System I represents the Egyptian power system, system II represents the Jordan and Syrian power systems, and system III for the Libyan power system, which are originally self standing and completely independent systems. As a matter of fact each of them should equipped with its own PSS. For this reason this work is started by designing an optimum power stabilizer for each of them standing alone. After which, the developed PSSs are firstly installed one at a time. Then the three PSSs are installed together in the interconnected power system and their effect on its dynamic performance is studied.As a test for stabilization efficiency, the detailed power system model is subjected to a forced outage of a 600-MW generator, which is the biggest unit in the pool, when it is fully loaded. This outage results in loosing of about 3% of the spinning capacity of system I and about 2% of the spinning capacity of the whole interconnected system. The obtained results show an improvement in the power pool performance accompanied with an improvement in the inter-area oscillation.     

Improvement of the lightning shielding performance of overhead transmission lines by passive shield wires

This paper addresses a numerical electromagnetic analysis of the influence of installing passive shield wires "extra ground wires" (EGW) underneath the bottom phase conductor on the lightning shielding performance of 765-kV, 3-phase, double-circuit transmission lines. The method of moment (MOM) is employed to model the whole structure in three dimensions except the lightning channel. The lightning channel is simulated by the well-known transmission-line model (TLM), where the influence of the lightning-channel-generated electric and magnetic fields (EMF) are taken into account. The lightning shielding performance with and without EGW is introduced and discussed, without ac energization and due to three distinct lightning strokes, namely, the negative first, the negative subsequent and the positive strokes. The produced voltages and currents in the phase conductors and ground wires as well as the voltage across the insulators are computed, with and without the EGW, due to different lightning current waveforms, locations and inclination of the lightning channel, and return-stroke velocities. The introduction of such EGW results in a significant improvement of the shielding effectiveness by reducing the lightning-produced voltages and currents in the phase conductors as well as the voltage across the insulators. Accordingly, much lower transient overvoltages can be expected with less inadvertent outages of the lines, where the probabilities of flashover and back-flashover decrease, and the reliability enhances.     

Corrosion Behavior and Surface Modification of Mg-Zn Implant Alloys

In this study, Mg-Zn alloys (1-4 wt.% Zn) were fabricated with high-purity raw materials using a clean melting process (fluxless method) and a protective atmosphere of CO₂ + 0.4 SF₆. The as-cast microstructures of the investigated alloys were characterized by optical and scanning electron microscopes, EDS and XRD. Corrosion properties of the prepared alloys were examined in simulated body fluid by electrochemical techniques and immersion test (hydrogen evolution method). Surface modification of the prepared alloys was performed using micro-arc oxidation (MAO) treatment and hydroxyapatite (HA) coating. Microstructure observation revealed that Zn was completely dissolved in the α-Mg matrix up to 2 wt.%. Higher Zn content led to a reduction in the grain size and the development of a second phase (MgZn₂). Corrosion testing results revealed that Mg-1,2,3 wt.% Zn have almost the same degradation rate, whereas Mg-4Zn has the highest degradation rate. HA coating on MAO-treated magnesium alloys formed a dense and compact layer on the alloy surface, which had largely improved surface properties and enhanced corrosion resistance of the prepared alloys.     

Generation of asphalt performance grading map for Egypt based on the SUPERPAVE™ program

This work aims to generate an asphalt performance grading map for Egypt based on the SUPERPAVE and LTTP programs. To achieve this aim, 60 weather stations data and air temperatures (maximum and minimum) recorded by Egyptian Meteorological Authority (EMA) collected covered of minimum 30 years of continuous temperature recording. The collected data and the calculated standard deviation were used to obtain surface and pavement temperatures for 21 representative stations for various climatic regions of Egypt. It revealed that four types of asphalt binder performance grades (at 98% reliability) are recommended for use in Egypt. The grades are PG 70-10, 76-10, 76-16 & 76-28.     

Performance analysis of PV pumping systems using switched reluctance motor drives

A PV pumping system using switched reluctance motor (SRM) is thoroughly investigated in this work. This motor is supplied by a d.c. voltage through a simple switching circuit. This drive circuit is much simpler than the normal d.c./a.c. inverter required to supply the induction motor. The efficiency of this motor is considerably higher than that of the equivalent d.c. or induction motors. In addition, because of the simple construction, SRM is cheaper than these conventional drives. Because of the above advantages of the SRM, the proposed system has higher efficiency and lower cost as compared with other systems.A design example is studied in detail to explore the advantages of PV pumping systems based on this new drive. The study of the performance of the proposed system showed that the operating efficiency of the motor is about 85% during most of its working time. The matching efficiency between the PV array and the proposed system approaches 95%. The major part of the losses takes place in the pump and the riser pipes, this loss represents one-third of the total available energy.     

Error analysis of image representations for sources near to a dissipative earth

Various image representations for sources above a dissipative earth are introduced. A criterion for assessing their accuracy is given. Some of these image representations comprise purely discrete images, a purely continuous image or a mixture of both types. It is shown that the error in any representation is a function of the height of the field point from the earth's surface. A mixture of a discrete image and a simple continuous image can lead to a negligibly small error for field calculations over a wide range of the height of the field point. This means that the image theory can offer simplicity and accuracy in many application such as geophysical prospecting of the earth.