Dynamic analysis of motion of spherical metallic particles in non-uniform electric field

This paper presents a theoretical analysis of the dynamics of motion of spherical metallic particles under non-uniform fields for direct-current gas-insulated switchgear (dc GIS) and for electrostatic separators/sizers (ESS). The particle equations of motion between a pair of diverging conducting plates are numerically solved in three dimensions using a computational algorithm. The upper plate is energized by HV dc or HV ac of variable frequency, while the lower one is grounded. In the case of ESS, the lower electrode is also mounted horizontally on a vibratory conveyor. The results reveal that the particle exhibits several phenomena during motion depending on its initial position, radius and density, angle between the diverging plates, tilt angle of the electrode system, and frequency and amplitude of the applied voltage. The influence of vibratory-conveyor variables on the separation/sizing process is studied in the light of the particle trajectory in the third dimension. Moreover, the results are interpreted using dimensional analysis. The use of HV ac causes the separation/sizing process to be imprecise; the higher the applied-voltage frequency and the larger the particle radius, the higher is the risk of breakdown. Depending on the tilt angle and orientation of the earthed electrode relative to the divergent angle between the electrodes, particle trapping can be helped or hindered. Therefore, several factors should be taken into consideration in the design and installation of the particle drivers and traps in GIS. Finally, the effects of dielectric coating on the electrode and of gas pressure on the particle trajectory are also studied.     

Experimental and mathematical modeling of Cr(VI) removal using nano-magnetic Fe3O4-coated perlite from the liquid phase

Modification of perlite using nano-magnetic iron oxide was implemented to produce nano-magneticFe₃O₄-coated perlite composite (Fe₃O₄/Perlite). The prepared composite was characterized using Scanning Electron Microscopy, Fourier-Transform Infrared spectroscopy and Powder X-ray Fluorescence. The potentiality of both perlite and Fe₃O₄/Perlite composite to eliminate Cr(VI) from the environmentally relevant water was investigated. The influence of main factors which could affect the adsorption was studied including; pH of medium, shaking time and Cr(VI) ions concentration. The experimental outcome demonstrated that the modification of perlite by nano-magnetic Fe₃O₄ showed a significantly enhanced Cr(VI) removal efficiency relative to that of unmodified perlite. From the kinetic studies, the experimental data fitted well with the pseudo-second-order model. Moreover, it proposes that Langmuir isotherm is more adequate than the Freundlich isotherm for both perlite and modified perlite. The results recommended that Fe₃O₄/Perlite composite had a great potential as an economic and efficient adsorbent of Cr(VI) from contaminated water, which has huge application potential.     

A study on Claisen Condensation with Diethyl Anilinodiacetate

Sodium hydride prompted reactions of diethyl anilinodiacetate 1 with acetophenone, p-nitroacetophenone, p-fluoroacetophenone and acetylthiophene result in the formation of tetraketones 3a–d . Evidence is presented to support the formation of 3a–d , via a sequence of reactions involving condensation with hydrazine, their acetyl derivatives, and cyclization with polyphosphoric acid. The structures of the hitherto unknown ring systems have been confirmed by i.r., p.m.r. and mass spectral data.     

Effect of cimetidine, bicarbonate and glucose on the bioavailability of different formulations of praziquantel

The effects of cimetidine, bicarbonate and glucose on the bioavailability of the two brands of praziquantel (CAS 55268-74-1) available in Egypt were studied in normal healthy volunteers. Brand 1 when coadministered with cimetidine showed elevated concentration of the drug at all time intervals. The difference was statistically significant at 3, 4, 6 and 8 h following treatment. On the other hand coadministration of cimetidine with brand 2 (Distocide) showed elevated concentration of the drug 1 h post treatment. Analysis of the pharmacokinetic parameters revealed insignificant difference comparing brand 1 versus brand 1 plus cimetidine. Significant differences were observed between the elimination rate constant Ke (h-1) for brand 2 (0.017 +/- 0.004) alone versus brand 2 plus cimetidine (0.006 +/- 0.001). Coadministration of bicarbonate or glucose with either brand 2 or brand 1 tended to depress the serum concentration of praziquantel. Possible explanations of these findings are discussed.     

Three-phase queueing servicing system with renewable servers

A three-phase queueing servicing system is considered in this paper. The servers can fail during their occupation time. A failed server is sent to be repaired immediately. The stationary probabilities of the different states of the system are studied under the assumption that the arrival time, service time, failure time and repair time of the servers all have a Poisson distribution with diferent parameters. Also the mathematical expectation of the number of customers in each phase is obtained. Finally, the results in Mokaddis et al., Ninth International Congress for Statistics, Computer Science, Social and Demographic Research, Ain Shams University, 31 March–10 April, 1984, are obtained as special cases from the results in this paper.     

Spiperone: influence of spiro ring substituents on 5-HT2A serotonin receptor binding

Spiperone (1) is a widely used pharmacological tool that acts as a potent dopamine D2, serotonin 5-HT1A, and serotonin 5-HT2A antagonist. Although spiperone also binds at 5-HT2C receptors, it is one of the very few agents that display some (ca. 1000-fold) binding selectivity for 5-HT2A versus 5-HT2C receptors and, hence, might serve as a useful template for the development of novel 5-HT2A antagonists if the impact of its various substituent groups on binding was known. In the present investigation we focused on the 1, 3,8-triazaspiro[4.5]decanone portion of spiperone and found that replacement of the N1-phenyl group with a methyl group only slightly decreased affinity for cloned rat 5-HT2A receptors. However, N1-methyl derivatives displayed significantly reduced affinity for 5-HT1A, 5-HT2C, and dopamine D2 receptors. Several representative examples were shown to behave as 5-HT2 antagonists. As such, N1-alkyl analogues of spiperone may afford entry into a novel series of 5-HT2A-selective antagonists.     

A kinetic investigation of the reforming of natural gas for the production of hydrogen

An analysis of the thermal uncatalyzed reaction of a homogeneous mixture of steam and methane for the production of hydrogen on the basis of detailed chemical kinetics is presented. A reaction scheme comprising 14 chemical species and 32 elementary reaction steps has been employed.The kinetic behaviour of a homogeneous mixture of steam/methane is investigated over a temperature range of 1400–3000 K, pressure range of 0.5–10 atm, and steam/methane ratio range of 1.0–5.0. The reaction is attractive for high temperatures above 1800 K, and it has been shown that near equilibrium conditions can be achieved within a residence time of about 10.0 s. Moreover, the calculations have shown that the reaction is not sensitive to pressure changes, but is sensitive to variations in the steam/methane ratio. The addition of O₂ to the reacting mixture of methane and steam is also investigated, and it has been found that the addition of a small amount of O₂, about 5%, has only a small effect on the composition of the products. However, such addition tends to reduce the amount of heat required for completing the reaction significantly.     

A simple green synthesis of (Z)-5-arylmethylene-4- thioxothiazolidines and thiopyrano[2,3-d]thiazolidine-2-thiones in PEG-400 under catalyst-free conditions

An improved Knoevenagel condensation of various aromatic aldehydes with thiazolidine-2,4-dithione and with 4-thioxothiazolidin-4-one can be achieved at room temperature in polyethylene glycol-400 without catalyst to afford (Z)-5-arylmethylene-4-thioxothiazolidine derivatives 3a–3o. Also, the [4+2] cyloaddition reaction of 3a–3g with N-phenylmaleimide 4 gave the cycloadducts 5a–5g under the same reactions conditions. The structure of all the newly synthesized compounds was established on the basis of the elemental analysis and spectral data. This process is a simple, efficient, economical, and environmentally benign compared to classical reactions.     

Performance of distribution-class surge arresters under dry and artificial pollution conditions

This paper presents an experimental investigation of distribution-class surge arrester (SA) performance under dry, clean-fog and salt-fog conditions. Two SA rated 11 kV and three SA rated 33 kV were tested inside a salt-fog chamber to investigate how the internal active material (either zinc oxide/metal oxide “ZnO” or silicon carbide “SiC”) and the arrester housing material affect the overall performance under different pollution severities. Tests were conducted on SiC porcelain-, ZnO polymeric- and ZnO silicone rubber- (SiR) housed SA. Both the internal and the external currents were measured for each SA up to its maximum continuous operating voltage (MCOV). Results reveal that new ZnO SiR-housed SA shows its superior performance under salt-fog condition over the other two types tested. On the other hand, aged ZnO SiR-housed SA can have high external current close to that of SiC porcelain-housed SA. New ZnO polymeric-housed SA gives the highest rms external and internal currents under salt-fog condition as its housing material is hydrophobic in nature and has the shortest creepage distance.     

Four-switch Three-phase Inverter Performance Fed Sensorless Speed Control Induction Motor Drives Using Model Reference Adaptive System

Abstract—This article presents an investigation of four-switch inverter performance fed three-phase induction motor drives. Speed estimation is based on fundamental wave models using a model reference adaptive system as a speed estimator technique. The motor is fed from a four-switch three-phase inverter. A comparative study for sensorless speed estimation using a four-switch three-phase inverter, and a six-switch inverter is simulated and experimentally investigated at different operating conditions. Also, a comparison of system performance based on the four-switch inverter and conventional six-switch inverter in terms of speed response and total harmonic distortion of stator currents is presented. Experimental and simulation results at different points of operation are presented, verifying the robustness of sensorless speed estimation at different load levels. Sensorless speed estimation based on the four-switch three-phase inverter is quite acceptable considering its speed response.