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21.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ... 相似文献
22.
《International Journal of Hydrogen Energy》2021,46(64):32480-32489
Based on that hydrogen energy is widely used in fuel cells, we focus our interests on the design and research of new complexes that catalyze the reaction in both directions, such as hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs). A highly efficient catalyst for both hydrogen evolution and oxidation, based on a nickel(II) complex, [Ni-en-P2](ClO4)2, has been designed and provided by the reaction of Ni(ClO4)2 with N,N′-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en-P2) in our group. Its structure has been determined by X-ray diffraction. [Ni-en-P2](ClO4)2 can electro-catalyze hydrogen evolution both from acetic acid and a neutral buffer (pH 7.0) with a turnover frequency (TOF) of 204 and 1327 mol of hydrogen per mole of catalyst per hour (H2/mol catalyst/h) under an overpotential (OP) of 914.6 mV and 836.6 mV, respectively. [Ni-en-P2](ClO4)2 also can electro-catalyze hydrogen oxidation with a TOF of 111.7 s−1 under an OP of 330 mV. The results can be attributed to that [NiII-en-P2](ClO4)2 has three good reversible redox waves at 1.01 (NiIII/II), −0.79 (NiII/I) and −1.38 V (NiI/0) versus Fc+/0, respectively. We hope these findings can afford a new method for the design of electrocatalysts for both H2 evolution and H2 oxidation. 相似文献
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24.
F. Schröder R. M. Ward A. R. Walpole R. P. Turner M. M. Attallah J.-C. Gebelin 《Materials Science & Technology》2015,31(3):372-384
Linear friction welding of the Ti6Al4V alloy is studied. A new definition of the energy input rate is proposed, based on an integration over time of the in-plane force and velocity; a strong correlation with the upset rate is then found. The effective friction coefficient is estimated to be 0·5±0·1 for varying frequencies and amplitudes, with only a weak dependence on the processing conditions displayed. A model is proposed that accounts for both the conditioning and equilibrium stages of the process, which is shown to be in good agreement with the experimental data. The model is used to study the mechanism by which the flash is formed. A criterion is proposed by which the rippled nature of its morphology can be predicted. 相似文献
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Wenyun Yang Qiwei Hu Guanyi Qiao Liang Zha Shunquan Liu Jingzhi Han Honglin Du Yan Zhang Yingchang Yang Changsheng Wang 《中国稀土学报(英文版)》2019,37(10):1102-1107
In this work, we report the tuning effect of the Si substitution on the magnetic and high frequency electromagnetic properties of R2Fe17 compounds and their paraffin composites. It is found that the introduction of Si can remarkably improve the magnetic and electromagnetic properties of the R2Fe17 compounds, making the R2Fe17–xSix-paraffin composites excellent microwave absorption materials (MAMs). By introducing the Si element, their saturation magnetizations decrease slightly, while much higher Curie temperatures are obtained. Furthermore, better impedance match is reached due to the decrease of the high-frequency permittivity ε′ by about 40%–50%, which finally enhances the performance of the microwave absorption. The peak frequency (fRL) of the reflection loss (RL) curve moves toward high frequency domain and the qualified bandwidth (QB, RL ≤ ?10 dB) increases remarkably. The maximum QB of 3.3 GHz (12.0–15.3 GHz) is obtained for the Sm1.5Y0.5Fe15Si2-paraffin composite (d = 1.0 mm) and the maximum RL of ?53.6 dB is achieved for Nd2Fe15Si2-paraffin composite (d = 2.2 mm), both surpassing most of the reported MAMs. Additionally, a distinguished dielectric microwave absorption peak is observed, which further increases the QB in these composites. 相似文献
27.
This study addresses the problem of choosing the most suitable probabilistic model selection criterion for unsupervised learning
of visual context of a dynamic scene using mixture models. A rectified Bayesian Information Criterion (BICr) and a Completed
Likelihood Akaike’s Information Criterion (CL-AIC) are formulated to estimate the optimal model order (complexity) for a given
visual scene. Both criteria are designed to overcome poor model selection by existing popular criteria when the data sample
size varies from small to large and the true mixture distribution kernel functions differ from the assumed ones. Extensive
experiments on learning visual context for dynamic scene modelling are carried out to demonstrate the effectiveness of BICr
and CL-AIC, compared to that of existing popular model selection criteria including BIC, AIC and Integrated Completed Likelihood
(ICL). Our study suggests that for learning visual context using a mixture model, BICr is the most appropriate criterion given
sparse data, while CL-AIC should be chosen given moderate or large data sample sizes. 相似文献
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29.
Non-standard fault models often require the application of two-pattern testing. A fully-automated approach for generating a multiple scan chain-based architecture is presented so that two-pattern test sets generated for the combinational core can be applied to the sequential circuit. Test time and area overhead constraints are considered. 相似文献
30.