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81.
R. Awad M. Roumié A. I. Abou-Aly S. A. Mahmoud M. M. Barakat 《Journal of Superconductivity and Novel Magnetism》2012,25(2):273-291
Superconducting samples of type Bi1.8Pb0.4Sr2Ca2.1Cu3−x
Ru
x
O10+δ
, (Bi, Pb)-2223, with 0.0≤x≤0.4 and type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ
, (Tl, Pb)/Sr-1212, with 0.0≤x≤0.525 were synthesized using the standard solid-state reaction technique. The lattice parameters and the surface morphology
for these samples were determined using X-ray powder diffraction (XRD) and scanning electron microscope (SEM) measurements,
respectively. All element-contents of the samples prepared were estimated from the electron dispersive X-ray (EDX) technique,
and their results were compared with those obtained from particle-induced X-ray emission (PIXE). In addition, the oxygen-content
was determined using elastic Rutherford backscattering spectroscopy (RBS) technique at 3 MeV proton beam. The superconducting
transition temperature T
c and the hole carrier concentration P were determined from the electrical resistivity measurement. The data of both T
c and P for Bi1.8Pb0.4Sr2Ca2.1Cu3−x
Ru
x
O10+δ
and Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ
phases increased up to x=0.05 and 0.075, respectively and then they decreased as x increased. The superconductivity was completely destroyed around x=0.4 and 0.525 for (Bi, Pb)-2223 and (Tl, Pb)/Sr-1212 phases, respectively. The normal-state electrical resistivity data were
analyzed using the two and three dimensional variable range hopping (2D-VRH and 3D-VRH) and the Coulomb gab (CG). 相似文献
82.
Mahmoud KhazmaAdeline Goullieux Rose-Marie DheillyMichèle Quéneudec 《Cement and Concrete Composites》2012,34(2):223-230
Lignocellulosic lightweight concretes are a potential contributor to sustainable development. However, lignocellulosic aggregates are not always fully compatible with cement matrices leading to setting delays, significant dimensional variations and low mechanical strengths. An aggregate treatment, reducing water absorption and water-soluble molecule release, can avoid or reduce these drawbacks. In this study a coating treatment, using a pectin/polyethylenimin (PP) mixture, was applied to flax shives, which is a lignocellulosic by-product. Before shive coating, a dilution with distilled water or a micro-wave heating were conducted to decrease PP mixture viscosity.The PP treatment involved a decrease in shive water absorption. Compared to standard shive concrete, treated shive concrete exhibited a decrease in setting delay with an increase in cement hydration enthalpy, an increase in mechanical strengths and a significant reduction in dimensional variations. Although a slight increase in thermal conductivity and bulk density was measured, the cement-shive composite obtained still belongs to the insulating concrete category. 相似文献
83.
Transmission pricing has become a major issue in the discussions about the deregulated electricity markets.Conse-quently,open access to the transmission system is one of the basic topics to allow compe... 相似文献
84.
Nitrile butadiene rubber loaded with different concentrations of thin graphite nanosheets have been successfully prepared by using a two‐roll mill. The percolation concentration of the nanocomposites was 0.5 phr. The I–V characteristic curves showed that the nanocomposites exhibited ohmic behaviour at a certain voltage and then non‐linear behaviour. The Richardson–Schottky and Poole–Frenkel models were used to investigate the reason for the space charge. The experimental data fit the Schottky model well. The conductivity as a function of temperature was also studied and the data were fitted by using the Mott relation. The Mott relation showed that as the concentration of graphite nanosheets in the rubber composite increases, the hopping distance between the graphite nanosheet layers decreases, which enhances the conductivity of the nanocomposite at low concentrations. Copyright © 2011 Society of Chemical Industry 相似文献
85.
86.
Normal ultrasonic transducers of 0.5, 1, and 2 MHz are modified using delay lines which are made of Quartz. Such modification is to ameliorate the capability of the transducer to investigate Gd-doped ZnO thin films whose thickness is too thin. The normal transducers cannot test materials that have too thin thickness due to the near fields of these transducers. The near field is considered as blind area of the transducer. Therefore, the specimen under test must have thickness bigger than the near field of the used transducer, or instead delay lines can be used. Samples of Gd-doped ZnO thin films are prepared using sol gel technique. The ultrasonic pulse echo method is used at room temperature. Flaws are found in different prepared specimens. Results show that such delay lines are suitable to ameliorate the ultrasonic transducer to test Gd-doped ZnO thin films. 相似文献
87.
Mahmoud A. Hamad 《Journal of Superconductivity and Novel Magnetism》2014,27(7):1777-1780
Magnetocaloric effect in half-metallic double perovskite Sr0.4Ba1.6?x La x FeMoO6 (x = 0, 0.1, 0.2, 0.3) were investigated. It is shown that Sr0.4Ba1.6?x La x FeMoO6 exhibits the largest magnetic entropy change (ΔS M ) of 0.086 J/kg K upon 0.2 T magnetic field variation. Furthermore, ΔS M distribution of the Sr0.4Ba1.6?x La x FeMoO6 is much more uniform than that of gadolinium. Through these results, polycrystalline samples of Sr0.4Ba1.6?x La x FeMoO6 have some potential applications for magnetic refrigerants in a wide temperature range, including room temperature. 相似文献
88.
In the flooded lead_acid batteries (FLAB), gas bubbles are initially formed on the surface of the electrodes, which are produced by electrochemical reactions, and then released into the electrolyte. In the present investigation, the effect of surface characterization of electrodes of FLAB on the gas bubble dynamic parameters in the electrolyte flow at different charging/discharging rates (C-rates) are studied utilizing particle image velocimetry (PIV) method. The results show that the capacity of FLAB have a linear behav-ior due to changes in each of the two parameters of the surface characterization of electrodes and the C-rate. At all State of charges (SOCs) of FLAB cells in different tests, increasing average roughness (Ra) and average wavelength of the roughness (ka) in the electrode surfaces, results in an increase in average bub-ble diameter and bubble rising velocity. Nevertheless, a sharp decrease in the void fraction of bubbles within the electrolyte was observed due to the increment in ka and Ra. Also, the effect of the rising move-ment of gas bubbles within the electrolyte on the average electrolyte velocity pattern in the gap between the electrodes by changing the surface characterization of electrodes are investigated in detail. 相似文献
89.
Ahmed AbdelMonteleb M. Ali Abdelazim M. Negm Mahmoud F. Bady Mona G. E. Ibrahim Masaaki Suzuki 《Clean Technologies and Environmental Policy》2016,18(4):1053-1068
Egypt in 2015 announced the alteration of the fuels used in cement plants without the least regard to minimizing the environmental burden (EB) excesses. This study conducts a life-cycle assessment (LCA) of Egyptian cement-manufacturing unit, which is considered as the first one on LCA cement analysis to be conducted in Egypt. This study investigates the LCA of the cement industry in Egypt compared to the Swiss industry, using two methodologies. The first one has been done on-site, surveying the most common types of cement used in the construction industry in Egypt. Meanwhile, SimaPro software has been used to assess the environmental impacts, and three different cement plants were selected for this study: an Egyptian cement plant (ECP) which uses electricity, natural gas, and diesel as energy sources; a Swiss cement plant (SCP) which depends mainly on electricity, natural gas, and coal; and an Egyptian hypothetical plant (EHP) in which electricity and coal are assumed to be the main energy feeds, and comparisons of different strategies including midpoint and endpoint methods are outlined. Regarding the midpoint method, ETP recorded higher respiratory inorganics, aquatic acidification, global warming, and nonrenewable energy impacts than ECP, because of using coal, while for SCP, global warming and respiratory inorganics achieved the highest adverse impacts compared to ECP and EHP—due to the different manufacturing technology used. With regard to the endpoint method, the peak possibility of human health deterioration has been recorded due to the use of coal as fuel. This possibility was reduced by 46 % in the case of SCP as a result of the technology applied, which interestingly represents a reasonable reduction in terms of technological application. 相似文献
90.
In this study, various Artificial Neural Networks (ANNs) were developed to estimate the production yield of greenhouse basil in Iran. For this purpose, the data collected by random method from 26 greenhouses in the region during four periods of plant cultivation in 2009–2010. The total input energy and energy ratio for basil production were 14,308,998 MJ ha?1 and 0.02, respectively. The developed ANN was a multilayer perceptron (MLP) with seven neurons in the input layer, one, two and three hidden layer(s) of various numbers of neurons and one neuron (basil yield) in the output layer. The input energies were human labor, diesel fuel, chemical fertilizers, farm yard manure, chemicals, electricity and transportation. Results showed, the ANN model having 7-20-20-1 topology can predict the yield value with higher accuracy. So, this two hidden layer topology was selected as the best model for estimating basil production of regional greenhouses with similar conditions. For the optimal model, the values of the models outputs correlated well with actual outputs, with coefficient of determination (R2) of 0.976. For this configuration, RMSE and MAE values were 0.046 and 0.035, respectively. Sensitivity analysis revealed that chemical fertilizers are the most significant parameter in the basil production. 相似文献