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961.
962.
Pitting of Al and Al-6%Zn and Al-12%Zn alloys in KSCN solutions was studied by means of potentiodynamic anodic polarization, cyclic voltammetry, potentiostatic and impedance techniques. Measurements were conducted under different experimental conditions, complemented by ex situ scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA). The potentiodynamic anodic polarization curves do not exhibit active dissolution region due to spontaneous passivation. The passivity is due to the presence of thin film of Al2O3 on the anode surface (in case of Al) and the formation of ZnO on the Al2O3 matrix, in case of the two Al-Zn alloys (as evidenced from EDXA). The passive region is followed by pitting corrosion as a result of passivity breakdown by the aggressive attack of SCN− anions. SEM images confirmed the existence of pits on the electrode surface. Alloyed Zn was found to enhance pitting attack. The pitting potential (Epit) decreases with an increase in SCN− concentration and temperature, but increases with increasing potential scan rate. The current/time transients show that the incubation time for passivity breakdown decreases with increasing applied positive potential, SCN− concentration, and temperature. Impedance measurements showed that Nyquist plots are characterized by a depressed charge-transfer semicircle, the diameter of which is a function of SCN− concentration, applied potential, solution temperature and sample composition. 相似文献
963.
Jiqing Qiu Kunfeng Lu Peng Shi Magdi S. Mahmoud 《International Journal of Adaptive Control and Signal Processing》2010,24(9):760-785
This paper investigates the problem of global robust exponential stability for discrete‐time interval BAM neural networks with mode‐dependent time delays and Markovian jump parameters, by utilizing the Lyapunov–Krasovskii functional combined with the linear matrix inequality (LMI) approach. A new Markov process as discrete‐time, discrete‐state Markov process is considered. An exponential stability performance analysis result is first established for error systems without ignoring any terms in the derivative of Lyapunov functional by considering the relationship between the time‐varying delay and its upper bound. The delay factor depends on the mode of operation. Three numerical examples are given to demonstrate the merits of the proposed method. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
964.
Green approaches have the potential to significantly reduce the costs and environmental impact of chemical syntheses. Here, the authors used green tea (GT) leaf extract to synthesise and anchor palladium nanoparticles (PdNPs) to silica. The synthesised PdNPs in GT extract were characterised by ultraviolet–visible spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction, and transmission electron microscopy. PdNPs primarily formed as capped NPs dispersed in GT extract before reduction completed after 24 h. This capped phytochemical solution was employed as a green precursor solution to synthesise PdNP‐embedded solid supports. The morphology of PdNPs anchored to silica differed to that of PdNPs in solution. Silica‐embedded PdNPs was employed as a new ligand exchanger to isolate trace polycyclic aromatic sulphur heterocycles from a hydrocarbon matrix. The isolation efficiency of the new, greener ligand exchanger was the same as an efficient chemical ligand exchanger and may, therefore, hold promise for future applications.Inspec keywords: nanofabrication, palladium, visible spectra, transmission electron microscopy, nanoparticles, reduction (chemical), ultraviolet spectra, X‐ray diffraction, Fourier transform infrared spectra, surface morphologyOther keywords: ultraviolet–visible spectroscopy, Fourier‐transform infrared spectroscopy, transmission electron microscopy, phytochemical solution, green precursor solution, PdNP‐embedded solid supports, solid support‐embedded PdNPs, green tea leaf extract, chemical ligand exchanger, anchor palladium nanoparticles, X‐ray diffraction, isolate trace polycyclic aromatic sulphur heterocycles, hydrocarbon matrix, green synthesis, time 24.0 hour, Pd 相似文献
965.
Radwan S. Farag Mostafa M. Farag Amany M. Basuny Rehab F. Mohammed 《International Journal of Food Science & Technology》2008,43(10):1742-1753
Sunflower, jojoba, paraffin oils and binary oil mixtures of sunflower, jojoba and sunflower–paraffin oils were continuously heated at 180 °C for 12 h. Aliquots of potato chips were fried in the aforementioned oil samples. Organoleptic tests were performed on fried chips and safety limits of the oil samples were measured by certain biochemical tests. Histopathological examinations of rat liver and kidney tissues were microscopically done. Organoleptic results for fried potato chips indicate that all types of chips obtained from heated oils were categorised good. Histopathological examinations indicate changes in rat tissues of liver and kidney paralleled the biochemical data. In general, the results suggest that paraffin oil alone and in mixtures with sunflower oil have to ban its use in frying processes. 相似文献
966.
In this article, we propose and evaluate a preemption-based scheme for the concurrent improvement of network throughput and
burst fairness in optical burst switched networks. The scheme uses a preemption weight consisting of two terms: the first
term is a function of the size of the burst and the second term is the product of the hop count times the length of the lightpath
of the burst. The second term is adjusted by a minimum function to prevent the problem of reverse unfairness. Extensive simulation
tests showed that the application of the scheme results in higher throughput and at the same time improves the fairness coefficient.
The scheme is further enhanced by combining it with a fairness-improving scheme previously proposed in the literature. Detailed
performance tests are presented and analyzed. 相似文献
967.
968.
A new category of linear poly(ether-ketone)s IVa–d and copoly(ether-ketone)s Va–f containing diarylidenecycloalkanone moieties in the main chain has been synthesized by solution polycondensation of 4,4′-bis (chloroacetyl)diphenylether I , with different phenoxides of diarylidenecycloalkanones IIa–d . The model compound III was synthesized from the monomer I with sodium phenoxide in DMF and K2CO3, and its structure was confirmed by elemental and spectral analyses. The resulting polyketones and copolyketones were characterized by elemental and spectral analyses, beside solubility and viscometry measurements. The thermal properties of those polymers were evaluated by TGA and DTA measurements and correlated to their structural units. X-ray analysis showed that polymers having some degree of crystallinity in the region 2θ = 5–60°. In addition, the biological screening and morphological properties of selected examples of the polymers were tested. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
969.
Low voltage CMOS fully differential current feedback amplifier with controllable 3-dB bandwidth 总被引:1,自引:0,他引:1
Ahmed H. Madian Soliman A. Mahmoud Ahmed M. Soliman 《Analog Integrated Circuits and Signal Processing》2007,52(3):139-146
This paper presents a CMOS fully differential current feedback operational amplifier with controllable 3-dB bandwidth. The
FDCFOA has the advantage of a wide range controllable 3-dB bandwidth (∼57–500 MHz) without changing the feedback resistance.
The FDCFOA has a standby current of 320 μA. Application of the proposed FDCFOA in realizing second order low-pass filter with
controllable 3-dB bandwidth is given. PSpice simulations of the FDCFOA block and its application are given using 0.25 μm CMOS
technology from MOSIS and dual supply voltages ±0.75 V. 相似文献
970.
Yaqoub Ali Hamam Hasan Moh'd El Ghanem Issam Mahmoud Arafa Moh'd Rida Said Ibrahim Abo aljarayish 《Polymer International》2007,56(3):376-380
FeII, FeIII and mixed‐valence FeII–III chlorides were reacted with poly[N,N′‐bis(dimethylsilyl)ethylenedi‐ amine], [? Si(CH3)2NHCH2CH2NH? ]n, to form the corresponding Fe‐polycarbosilazane macromolecular complexes. The average chain–chain spacing in these materials was estimated from X‐ray diffraction data and found to be 6.94, 7.29, 7.30 and 7.45 Å in metal‐free and FeII? , FeIII? and FeII–III‐containing polycarbosilazanes, respectively. This demonstrates that FeII, FeIII and FeII–III chlorides are encapsulated between the polycarbosilazane chains. The chain–chain expansions in the divalent FeII and trivalent FeIII chloride macromolecular complexes are comparable, but less than that in the FeII–III chloride analog, which suggests that different chain–chain packings exist in the mixed‐valence macromolecular complex. The magnetic properties of the resulting complexes were investigated by measuring the magnetization in magnetic fields up to 8 kOe and in the temperature range from liquid nitrogen temperature to room temperature. Copyright © 2007 Society of Chemical Industry 相似文献