格序群的上下子群和Saturated子群的构造

本文对[1]中关于极大上下对的公开问题给出否定的回答并构造了例子说明[2]中命题2.1证明过程中的错误;研究了saturated子群的构造,得到了任意ι-群的正交子集生成的saturated子群以及投射ι—群的任一子集生成的saturated子群的具体形式.     

阳极支撑型单气室固体氧化物燃料电池的性能

 使用浆料旋涂法制备了致密氧化钇稳定的氧化锆电解质薄膜,进而组装成阳极支撑型单气室固体氧化物燃料电池. 该电池在CH4, N2和O2混合气氛下运行,可产生很高的输出性能. 在700 ℃时开路电压达到1 V, 最大功率密度达到398 mW/cm2. 在开路状态下,电池的欧姆电阻为0.097 Ω·cm2, 仅为电极阻抗的6.4%, 远小于电极极化电阻. 通过优化电极材料,阳极支撑型单气室固体氧化物燃料电池将具有更优异的输出性能和更广阔的应用前景.     

Passive source range estimation with a single receiver in shallow water

An approach for long-range passive impulsive source ranging with a single receiver in shallow water is proposed,which utilizes the frequency spectrum of the warped signal autocorrelation function via warping transform.For an ideal waveguide,there are invariable frequency features both in the frequency spectrum of the warped signal corresponding to modal cut-off frequencies and the warped signal autocorrelation function due to modal interference.These intrinsic frequency features can be used to passive source ranging.So,the approximate relationship between the frequency of warped signal at an unknown source range and the intrinsic frequency extracted by the time warping transform is derived.These rules can be generalized to an actual shallow water waveguide.Employing an acoustic model to offer the invariable frequency spectrum features,the impulsive signal data collected by a single hydrophone in the North Yellow Sea in December 2011 are analyzed to verify the proposed source ranging approach.The estimated ranges are in good agreement with the ranges measured by GPS,and the mean relative error of range estimation is less than 10%.     

Properties of nonstoichiometric Pr0.6−xSr0.4MnO3 as the cathodes of SOFCs

A series of samples Pr_0.6−xSr_0.4MnO₃ (x=0, 0.01, 0.05, 0.1, 0.15, 0.2) were synthesized by a solid state reaction method. Pr deficiency at the A site has a great effect on the properties of Pr_0.6−xSr_0.4MnO₃ as the cathode of SOFCs (solid oxide fuel cells). Compared to the commonly used La_0.6Sr_0.4MnO₃ and La_0.55Sr_0.4MnO₃ cathode, Pr_0.6−xSr_0.4MnO₃ is better in the properties of conductivity, overpotential and impedance. In all the samples, the one with x=0.05, Pr_0.55Sr_0.4MnO₃, revealed the best performance in the measured temperature range.     

一般变系数KdV方程的精确解

By asing the nonclassical method of symmetry reductions, the exact solutions for general variable-coefficient KdV equation with dissipative loss and nonuniformity terms are obtained. When the dissipative loss and nonuniformity terms don‘t exist, the multisoliton solutions are found and the corresponding Painleve II type equation for the variable-coefficient KdV equation is given.     

A novel PdNi/Al2O3 catalyst prepared by galvanic deposition for low temperature methane combustion

Galvanic deposition method was used to prepare the Pd/Ni-Al2O3-GD catalyst for the combustion of methane under lean conditions. The new catalyst and compared catalysts (Pd/Al2O3-IW, Pd-Ni/Al2O3-IW, Pd/Ni-Al2O3-IW) prepared by incipient wetness impregnation were characterized by N2-physisorption, XRD and TEM to clarify particle size and size distribution of palladium species. Combined O2-TPD and XPS results with the catalytic data, it shows that the surface palladium species with low valence exhibits better combustion performance due to their stronger interaction with support. The results indicate that the galvanic deposition method is an effective route to prepare efficient catalyst for methane combustion, and it also provides useful information for improving the present commercial catalyst.     

Effect of gas supply method on the performance of the single-chamber SOFC micro-stack and the single cells

The effect of gas supply method on the performance of a single-chamber solid oxide fuel cell micro-stack and single cells was studied, and a novel gas supply method with separated gas vents in the gas tube was proposed. The traditional gas supply method was also investigated for comparison. Results showed that the single cells could obtain a uniform open-circuit voltage and power output by using the separated gas supply method. For the traditional gas supply method, the cell at the outlet position yielded inferior performance compared to that of the inlet cell. The gas flow rate showed a significant effect on the performance of the cells. Finally, the stack operated with the separated gas supply method produced a higher power output than that operated with the traditional gas supply method.     

Reactions and structural changes during thermal annealing in a semicrystalline,aromatic diacetylene‐containing polyester

Thermally induced solid‐state reactions and microstructure changes in a high molar mass, semicrystalline, aromatic diacetylene‐containing polyester, poly[2,4‐hexadiyn‐1,6‐ylene terephthalate], were investigated with a combination of laser Raman spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction analysis. The study has provided some new insights into the rather complex solid‐state reactions in the semicrystalline diacetylene‐containing polyester. Results suggest that, in addition to the usual desired solid‐state topochemical crosspolymerization in the crystalline region, a certain degree of random crosslinking reaction occurs in the amorphous region, especially when the annealing is carried out above the glass transition. After prolonged annealing or annealing at a higher temperature, a further reaction involving the formed polydiacetylene chains may occur, as evident from the reduction in crystallinity and even complete loss of crystallinity. An attempt has been made to separate the contribution of the topochemical reaction from the overlapping exothermic activities in the differential scanning calorimetry curves via subtraction. This allows the monitoring of the crystalline‐phase solid‐state topochemical crosspolymerization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2354–2363, 2002     

Fabrication and performance test of solid oxide fuel cells with screen-printed yttria-stabilized zirconia electrolyte membranes

Yttria-stabilized zirconia (YSZ) membranes were deposited onto porous NiO?CYSZ anode supports by screen printing. Combined with La_0.7Sr_0.3MnO₃?CYSZ composite cathode, the prepared anode-supported solid oxide fuel cells (SOFCs) were electrochemically tested. A typical SOFC with a 30-??m-thick YSZ electrolyte membrane gave the maximum power densities (MPDs) of 0.26, 0.53, 0.78, and 1.03?W/cm² at 650, 700, 800, and 850?°C, respectively, using hydrogen as fuel and stationary air as oxidant. Replacement of stationary air with pure oxygen flow exerted a significant positive effect on the MPDs of the cell. Using 100- and 200-ml/min oxygen as oxidants, the MPDs of the cell were enhanced 35.3% and 68.6%, respectively. Polarization analysis indicated that, at the MPD points, the electrode polarization resistances accounted for 80% of the cell total resistances.