Synchronous machine parameter identification in frequency and time domain

This paper presents the results of a frequency and time-domain identification procedure to estimate the linear parameters of a salient-pole synchronous machine at standstill. The objective of this study is to use several input signals to identify the model structure and parameters of a salient-pole synchronous machine from standstill test data. The procedure consists to define, to conduct the standstill tests and also to identify the model structure. The signals used for identification are the different excitation voltages at standstill and the flowing current in different windings. We estimate the parameters of operational impedances, or in other words the reactance and the time constants. The tests were carried out on synchronous machine of 1.5 kVA 380V 1500 rpm

Simulation metamodelling with neural networks: An experimental investigation

Artificial neural networks are often proposed as an alternative approach for formalizing various quantitative and qualitative aspects of complex systems. This paper examines the robustness of using neural networks as a simulation metamodel to estimate manufacturing system performances. Simulation models of a job shop system are developed for various configurations to train neural network metamodels. Extensive computational tests are carried out with the proposed models at various factor levels (study horizon, system load, initial system status, stochasticity, system size and error assessment methods) to see the metamodel accuracy. The results indicate that simulation metamodels with neural networks can be effectively used to estimate the system performances

Étude des propriétés structurales, optiques et électriques des couches minces de ZnO dopées Al déposées par Spray Pyrolysis

Les couches minces de ZnO dopées Aluminium (AZO) ont été déposées par la technique spray pyrolysis sur des substrats de verre ordinaire préchauffés à la température de 425°C. Des solutions aqueuses de chlorure de zinc de concentration 0.1M et dopées à partir du nitrate d’aluminium ont été utilisées pour le dépôt. Le pourcentage de l’aluminium dans la solution variait de 0 à 5%. Après dépôt, les couches ont été caractérisées et l’effet de la concentration du dopage de l’aluminium sur leurs propriétés structurale, optique et électrique a été étudié. L’analyse structurale a montré que les films déposés ont cristallisé suivant la direction préférentielle (002) et que le dopage de l’aluminium avait un effet important sur l’intensité et le déplacement des pics. Les spectres de transmission montrent que les films AZnO sont transparents (~ 90%) dans les régions du proche ultraviolet et du visible. Les mesures électriques réalisées par la technique des 4 pointes a donné une conductivité maximale de 1.6 x104 (Ω.cm)-1 pour le film déposé à 2% Al.Mots-clés : ZnO, dopage, spray pyrolysis, propriétés électriques

Effect of Treatment Methods on Used Lubricating Oil for Recycling Purposes

The need to treat used lubricating oil for possible reuse has arisen due to concern for the environment, scarcity, price stability, and increasing dependence on this product for many industrial applications. Various methods, such as distillation/clay, acid/clay, acid, and activated charcoal/clay treatment methods, were employed in this study for the treatment of used Mobil and Total lubricating oil samples with the aim of improving their qualities for reuse. The characteristics of the fresh, used, and treated oil are tested for water content, specific gravity, kinematic viscosity, viscosity index, flash point, pour point, sulphur content, and concentrations of heavy metals (aluminum, iron, and lead). The results obtained showed that the usage of the lubricant oil affects the qualities of oil, for instance the sulphur of both brands of the oil samples was below the detectable limit, while the sulphur contents of the used oil are 0.80 and 0.69% for the used Mobil and Total oil samples, respectively. The results also revealed that treatments employed in this work were able to improve the characteristics of the used oil samples after treatment. The analyses of the results showed that the acid/clay method was the most effective method of treatment that brings the characteristics of the treated oil close to the fresh oil sample, while the distillation/clay and activated/charcoal methods were the best in terms of recovery of the oil after treatment. These two methods also recovered about 80% of the used lube oil samples compared to acid and acid/clay treatment methods, where the oil recovered was about 50% of the charge used oil sample

Multi-epoch Near-Infrared Interferometry of the Spatially Resolved Disk Around the Be Star Zeta Tau

We present interferometric observations of the Be star Zeta Tau obtained using the MIRC beam combiner at the CHARA Array. We resolved the disk during four epochs in 2007-2009. We fit the data with a geometric model to characterize the circumstellar disk as a skewed elliptical Gaussian and the central Be star as a uniform disk. The visibilities reveal a nearly edge-on disk with a FWHM major axis of ~ 1.8 mas in the H-band. The non-zero closure phases indicate an asymmetry within the disk. Interestingly, when combining our results with previously published interferometric observations of Zeta Tau, we find a correlation between the position angle of the disk and the spectroscopic V/R ratio, suggesting that the tilt of the disk is precessing. This work is part of a multi-year monitoring campaign to investigate the development and outward motion of asymmetric structures in the disks of Be stars.Comment: Accepted for publication in the Astronomical Journal. 27 pages, 7 Figure

Effect of Liquid Salt Bath Nitrocarburizing on Mechanical Properties of Low-Alloy Sintered Steels

The purpose of this study is to produce Fe–2Cu–2Ni–0.7Mo–XC steels by means of the powder metallurgy at different sintering temperatures. The mechanical properties of sintered steels have recently reached a level equivalent to that of steels produced by other processes. The static and dynamic mechanical properties of parts made of sintered steel depend on density and microstructure. Many process parameters such as initial composition, alloying elements, atmosphere, time, sintering temperature, and nitrocarburizing influence the microstructure of steel parts. The compacts’ preparation involves powder mixing, cold pressing at 500 MPa, and sintering at 1250°C within the H2 atmosphere for 2 hours and 25 min. The influence of sintering temperature on both hardness and microstructure of the steel is investigated. In this study, sintered Fe–2Cu–2Ni–0.7Mo–XC-type steels are developed. The impact of nitrocarburizing on this structure is evaluated. Microscopy, SEM, and destructive testing are used for characterization of the sintered steels.Метою даної роботи є одержання сталей типу Fe–2Cu–2Ni–0,7Mo–XC методами порошкової металурґії за різних температур спікання. Механічні властивості спечених сталей нещодавно сягнули рівня, аналогічного рівню сталей, що виробляються іншими методами. Статичні та динамічні механічні властивості деталів із спеченої сталі визначаються густиною та мікроструктурою. При цьому велика кількість характеристик процесу, наприклад, вихідний склад, леґувальні елементи, атмосфера, час, температура спікання та нітроцементація впливають на мікроструктуру сталевих деталів. Виготовлення пресованого матеріялу потребує змішування порошку, холодного пресування при 500 МПа та спікання при температурі у 1250°C в атмосфері Н22 протягом 2 годин 25 хв. Було досліджено вплив температури спікання на твердість і мікроструктуру сталі. В даній роботі було розглянуто сталі типу Fe–2Cu–2Ni–0,7Mo–XC. Було проведено оцінку впливу нітроцементації на такі структури. Для характеризації спечених сталей використовувалися мікроскопія, СЕМ та випробування на руйнування.Целью данной работы является получение сталей типа Fe–2Cu–2Ni–0,7Mo–XC методами порошковой металлургии при различных температурах спекания. Механические свойства спечённых сталей недавно достигли уровня, аналогичного уровню сталей, производимых другими методами. Статические и динамические механические свойства деталей из спечённой стали определяются плотностью и микроструктурой. При этом большое количество характеристик процесса, например, исходный состав, легирующие элементы, атмосфера, время, температура спекания и нитроцементация, влияют на микроструктуру стальных деталей. Изготовление прессованного материала требует смешивания порошка, холодного прессования при 500 МПа и спекания при температуре 1250°C в атмосфере Н22 в течение 2 часов 25 мин. Было исследовано влияние температуры спекания на твёрдость и микроструктуру стали. В данной работе были рассмотрены стали типа Fe–2Cu–2Ni–0,7Mo–XC. Была проведена оценка влияния нитроцементации на такие структуры. Для характеризации спечённых сталей использовались микроскопия, СЭМ и испытания на разрушение

Green approach to corrosion inhibition of mild steel in 1 M HCl solutions by Monosaccharides derivatives

Effect of new synthesized monosaccharide derivatives, namely: D-mannose (M1), D-gluconic acid-γ-lactone (M2), D-galactono-γ-lactone (M3), monoacetoneglucose (M4), diacetoneglucose (M5), on mild steel corrosion inhibition in an aerated acidic solution of 1 M HCl was investigated using weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy measurements. The results indicate that the type of inhibition depends on the type of compounds. Impedance measurements showed that the charge transfer resistance increased and double layer capacitance values decreased with inhibitor’s concentration. It is seen that the M2 performed excellently as a corrosion inhibitor which its efficiency reaches 91 % at 10-3 M. Adsorption of M2 molecules on mild steel surface was also studied to examine basic information on the interaction between the inhibitors and the metal surface. It is found that the inhibitor adsorb on the metal surface following the Langmuir isotherm model. The temperature effect on the performance of mild steel in 1 M HCl in the absence and presence of the best compound was studied in the temperature range from 293 to 323 K. Also, some thermodynamic data for the adsorption and dissolution processes are calculated and discussed

Effet de certaines espèces fongiques sur le développement de la ternissure des grains de riz (Oryza sativa L.)

Sept (7) espèces fongiques isolées à partir des lésions foliaires et des semences de riz (Helminthosporium oryzae, Helminthosporium sativum, Helminthosporium spiciferum, Helminthosporium australiensis, Curvularia lunata, Fusarium moniliforme et Epicoccum nigrum) ont été utilisées pour inoculer les grains de riz des variétés Arco et Taibonnet dans le but d’observer les symptômes que ces champignons sont capables de provoquer sur ces semences. Trois mois après inoculation des grains par les différentes espèces fongiques et dans les trois mois qui suivent l’expérience, les indices de ternissure et les pourcentages d’altération des grains ont été notés. Les indices de ternissure les plus importants et les pourcentages d’altération des grains les plus élevés sont induits par Fusarium moniliforme, Curvularia lunata et Helminthosporium oryzae