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排序方式: 共有52条查询结果,搜索用时 31 毫秒
31.
We have employed an ambient, template-based technique that is simple, efficient, and surfactantless to generate a series of bimetallic Pd(1-x)Au(x) and Pd(1-x)Pt(x) nanowires with control over composition and size. Our as-prepared nanowires maintain significantly enhanced activity toward oxygen reduction as compared with commercial Pt nanoparticles and other 1D nanostructures, as a result of their homogeneous alloyed structure. Specifically, Pd(9)Au and Pd(4)Pt nanowires possess oxygen reduction reaction (ORR) activities of 0.49 and 0.79 mA/cm(2), respectively, which are larger than the analogous value for commercial Pt nanoparticles (0.21 mA/cm(2)). In addition, core-shell Pt~Pd(9)Au nanowires have been prepared by electrodepositing a Pt monolayer shell and the corresponding specific, platinum mass, and platinum group metal mass activities were found to be 0.95 mA/cm(2), 2.08 A/mg(Pt), and 0.16 A/mg(PGM), respectively. The increased activity and catalytic performance is accompanied by improved durability toward ORR. 相似文献
32.
Rimmele Ulrike; Davachi Lila; Petrov Radoslav; Dougal Sonya; Phelps Elizabeth A. 《Canadian Metallurgical Quarterly》2011,11(3):553
Emotion strengthens the subjective experience of recollection. However, these vivid and confidently remembered emotional memories may not necessarily be more accurate. We investigated whether the subjective sense of recollection for negative stimuli is coupled with enhanced memory accuracy for contextual details using the remember/know paradigm. Our results indicate a double-dissociation between the subjective feeling of remembering, and the objective memory accuracy for details of negative and neutral scenes. “Remember” judgments were boosted for negative relative to neutral scenes. In contrast, memory for contextual details and associative binding was worse for negative compared to neutral scenes given a “remember” response. These findings show that the enhanced subjective recollective experience for negative stimuli does not reliably indicate greater objective recollection, at least of the details tested, and thus may be driven by a different mechanism than the subjective recollective experience for neutral stimuli. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
33.
Twist drill flute profile design is necessary in order to determine the required grinding wheel profile for a flute production. An accurate drill flute profile design is generated for two-flute conical twist drills using analytical equations to generate a drill flute profile design needed for the production of twist drills with straight lips. The required grinding wheel profile for a flute production was expressed in digitized form as well as in terms of two curve-fitted circular arcs. The drill flute profile geometry can never be precisely generated when required grinding wheel profile is represented by two circular arcs and the generated flute profile is just a very good approximation of the design flute profile. A CAD (computer aided design) software has been developed using MATLAB to determine the required grinding wheel profile for generating a given drill flute profile design. 相似文献
34.
35.
Liang Zhixiu Song Liang Elnabawy Ahmed O. Marinkovic Nebojsa Mavrikakis Manos Adzic Radoslav R. 《Topics in Catalysis》2020,63(7-8):742-749
Topics in Catalysis - The direct formic acid fuel cell holds great promise as a next generation portable power source. Here we report an experimental study on Pt and Pd monolayer (Pt* and Pd*) atop... 相似文献
36.
Radoslav Selecký Daniela Šmogrovičová Pavol Sulo 《Journal of the Institute of Brewing》2008,114(2):97-101
A collection of Saccharomyces cerevisiae strains deficient in the tricarboxylic acid cycle enzymes activities has been examined for the production of beer with reduced ethanol content. Strains deficient in fumarase and α‐ketoglutarate dehydrogenase encoded by the genes FUM1 (0.48%), KGD1 (0.42%) and KGD2 (0.48%) made non‐alcoholic beers with an alcohol content lower than 0.5% (v/v). The rest of the yeast mutants also gave rise to low‐alcoholic beers but with a slightly elevated ethanol concentration (mostly in the range of 0.57‐0.84% and 1.64% for the lip5 mutant). Low ethanol content was compensated by the considerable increase of organic acids (citrate succinate, fumarate, and malate). In addition, some of the mutants released high levels of lactic acid (144 fum1), 622 (kgd1) and 495 (kgd2) mg/L). Lactic acid protects beers against contamination and masks an unacceptable worty off‐flavour. 相似文献
37.
Thomas E. Wood Zhongshu Tan Alison K. Schmoeckel David O’Neill Radoslav Atanasoski 《Journal of power sources》2008
The cost of platinum is one of the major obstacles in the commercialization of proton exchange membrane fuel cells. Non-precious metal catalysts (NPMC) as an inexpensive substitute for platinum have been viewed as the only long-term solution to the problem. In this paper, we introduce new precursors used to synthesize NPMC active sites through metal-assisted polymerization of nitrogen-containing, aromatic molecules. Results of electrochemical characterization, which was performed in a real fuel cell environment, with emphasis on the activity of the catalyst are presented. Catalytic activity among the highest in the NPMC area was obtained when using 4-nitroaniline as a precursor. 相似文献
38.
Radoslav Tomovic Aleksandar Miltenovic 《International Journal of Mechanical Sciences》2010,52(9):1176-1185
Rolling element bearings appear in nearly 90% of all rotating machinery. Their dynamic performance is often the limiting factor in the performance of the machines that use them. The specific construction of a bearing has a decisive influence on its dynamic behaviour. The paper defines a new vibration model of a rigid rotor supported by rolling element bearings. By application of the defined model, the parametric analysis of the influence of internal radial clearance value and number of rolling elements influence on rigid rotor vibrations in unloaded rolling element bearing was performed. The defined vibration model and parametric analysis were verified experimentally. The results of experimental analysis are also presented in this paper. 相似文献
39.
YongMan Choi Kurian A. Kuttiyiel Joselito P. Labis Kotaro Sasaki Gu-Gon Park Tae-Hyun Yang Radoslav R. Adzic 《Topics in Catalysis》2013,56(12):1059-1064
Designing novel cathode materials for a proton exchange membrane fuel cell with high activity for the oxygen reduction reaction, low Pt loading, and enhanced long-term stability is imperative for its sustainability. To date, Pt monolayer based electrocatalysts deposited on a metallic core substrate have shown promising possibilities. In this study, we synthesized bimetallic IrCu nanoparticles and used them as a core for Pt monolayer electrocatalysts. It was found that the de-alloyed IrCu nanoparticle surfaces increased both the mass and specific activities of the resulting Pt monolayer catalyst. In addition, we demonstrated that Pt monolayer electrocatalysts with a de-alloyed IrCu core have a better stability than those using a non-dealloyed core based on a 5,000 potential cycling test. These data describe a new simple synthesis of a high-performance catalyst suitable for practical applications. 相似文献
40.
Wei-Ping Zhou Meng Li Christopher Koenigsmann Chao Ma Stanislaus S. Wong Radoslav R. Adzic 《Electrochimica acta》2011,(27):9824
The morphology of nanostructured Pt catalysts is known to affect significantly the kinetics of various reactions. Herein, we report on a pronounced morphology effect in the electrooxidation of ethanol and carbon monoxide (CO) on Pt nanowires and nanoparticles in an acidic solution. The high resolution transmission electron microscopy analysis showed the inherent morphology difference between these two nanostructured catalysts. Voltammetric and chronoamperometric studies of the ethanol electrooxidation revealed that these nanowires had a higher catalytic activity by a factor of two relative to these nanoparticles. The rate for CO monolayer oxidation exhibits similar morphology-dependent behavior with a markedly enhanced rate on the Pt nanowires. In situ infrared reflection–absorption spectroscopy measurements revealed a different trend for chemisorbed CO formation and CO2-to-acetic acid reaction product ratios on these two nanostructures. The morphology-induced change in catalytic activity and selectivity in ethanol electrocatalysis is discussed in detail. 相似文献