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991.
The hydrogen evolution reaction on the electrodeposited Ni–Mo alloy coatings, as well as their electrochemical properties in the NaOH solutions, have been investigated by the polarization measurements, cyclic voltammetry and EIS technique. It was shown that the Ni–Mo alloy coatings electrodeposited from the pyrophosphate-sodium bicarbonate bath possess high catalytic activity for hydrogen evolution in the NaOH solutions. Their stability in the 1 M NaOH at 25 °C under the condition of the reverse polarization was shown to be very good, while in the 33% NaOH at 85 °C (conditions of the industrial electrolysis) the electrodeposited Ni–Mo alloy coatings exhibited also high catalytic activity, but low stability, as a consequence of a deterioration of the alloy coatings.  相似文献   
992.
 A useful straightforward controller order reduction procedure for multivariable robust control is presented. Reduced controllers regarding robust stability criterion and robust performance criterion are developed. Weighted Balanced Truncation is used as the concept for the real reduction work. The procedure is applied to Loop Shaping Design Procedure, Internal Model Control and Decentralized robust controllers of parallel operating dc/dc converters. Uncertainty robustness and performance of the closed-loop systems with reduced controllers are investigated. The reduction procedure efficiently decreases high controller orders, from which robust theory suffers, preserving at the same time closed-loop robust stability and robust performance at a desired level.  相似文献   
993.
The influence of the initial reactant concentrations on the composition of the solid phases formed in the precipitation system MgCl(2)-NH(4)H(2)PO(4)-NaOH-H(2)O was investigated. The precipitation diagram constructed shows the approximate concentration regions within which struvite, newberyite, and their mixtures exist at 25 degrees C and an aging time of 60 min. It was found that immediately after mixing the reactant solutions, struvite (MgNH(4)PO(4).6H(2)O) precipitated in nearly the whole concentration area, while newberyite (MgHPO(4).3H(2)O) appeared mostly within the region of the excess of magnesium concentration. It was also found that after aging time of 60 min the precipitation domain of struvite alone is much broader than that of newberyite or the domain of their coexistence, and shows that struvite is more abundant in the systems in which the initial concentration of ammonium phosphate is higher than that of magnesium. The kinetics of struvite to newberyite transformation (conversion) was systematically studied under the conditions of different initial reactant concentrations and different initial pH in the systems in which a mixture of both phases precipitated spontaneously. The struvite to newberyite conversion period was found to be strongly related to the ratio of initial supersaturations, S(N)/S(S), rather than to the any particular physical quantity that can describe and predict the behavior of the precipitation system. Experimental data suggest a solution-mediated process as a most possible transformation mechanism. Along with a continuous monitoring of the changes in the liquid phase, the content of struvite in the solid phase was estimated by means of a Fourier transform infrared (FT-IR) method, developed for this particular precipitation system.  相似文献   
994.
This study investigates distribution of three micronutrients in milling streams of three common wheat cultivars to estimate nutritive value of white and brown flours. Among the analysed wheat cultivars, the majority of flour streams of NS Todorka showed a higher content of soluble micronutrients than the other two investigated wheat cultivars. It is necessary to improve bioavailability of Fe and Zn in flours since these micronutrients were mostly in insoluble form. In contrast, considering average Serbian portion sizes for bread, bread made from flour Type ‘110’ could supply almost 75% of the recommended daily intake for Mn.  相似文献   
995.
996.
Owing to their ability to adsorb at interfaces, polysorbates have an important role in pharmaceutical formulations. Because surfactant mixtures can have improved properties, it was hypothesized in this work that introduction of poloxamer 407 to aqueous solutions of polysorbates (polysorbate 60, polysorbate 80 and polysorbate 85) might improve their surface properties. Nonideal behavior of surfactant mixtures at the air/water interface was investigated using Rosen's model and recently introduced method for the determination and quantification of nonideal behavior regarding surface tension reduction and adsorption effectiveness. Although nonideal behavior was noticed in all mixed monolayers, it was shown that the structure of the hydrophobic domain of the polysorbates and the conformation of poloxamer 407 at the interface have strong influence on the nonideality.  相似文献   
997.
998.
The cobaltite Ca3Co4O9+δ has shown large thermopower and is considered to be a good candidate for use as a thermoelectric material. The composition of Ca3Co4O9+δ is better expressed as [Ca2CoO3][CoO2] b1/b2 with the misfit-layered structure featuring different periodicities along the b axis, with b 1 referring to the b-axis length of the NaCl-type [Ca2CoO3] sublattice and b 2 referring to the b-axis length of the [CoO2] sublattice. The crystal structure of Ca3Co4O9+δ can be viewed as being of two subsystems, i.e., the distorted NaCl-type [Ca2CoO3] sublattice and the CdI2-type [CoO2] sublattice, alternately stacked along the c-axis. In this paper, we report measurements of the electrical resistivity and Seebeck coefficient for a series of misfit-layered oxides Ca3Co4−x Si x O9+δ prepared by solid-state reaction. Structural parameters are refined with the superspace group X2/m(0β0)s0 using powder x-ray diffraction data. With partial substitution of Si4+ for Co3+, the resistivity decreases, while the thermopower increases simultaneously. These results indicate that partial substitution of Si4+ improves the thermoelectric characteristics of Ca3Co4O9+δ .  相似文献   
999.
It is well known that medium-voltage (MV) paper-insulated cables essentially reduce the potentials appearing during a ground fault in substations located in urban surroundings. This is explained by the fact that these cables usually (normally) have an uncoated metallic sheath. Due to this, MV cable lines leaving a high-voltage/middle-voltage (HV/MV) substation act as long external grounding electrodes and spontaneously form one very large and complex grounding system around this substation. Cables with an insulated metallic sheath however, are progressively being more applied in contemporary power distribution practice. Consequently, the following quite logical question arises: how will a cable with such constructive characteristic influence the general conditions for solving the grounding problem of distribution substations, especially of those working in high-voltage (HV) networks with directly grounded neutral(s)? The analysis performed in this paper shows that, when applied these cables spontaneously form a grounding system which also exhibits excellent grounding performances.  相似文献   
1000.
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