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排序方式: 共有5638条查询结果,搜索用时 15 毫秒
1.
Zhengcheng Wang Shangyan Zhou Wei Liao Qian Zhou Meida Chen Jin Long Prof. Qingmei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202201987
The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1Fe3@NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt). Furthermore, the CO oxidation initial potential of Pt1Fe3@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1Fe3@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field. 相似文献
2.
Nonlinear Dynamics - In order to solve the constrained-input problem and reduce the computing resources, a novel event-triggered optimal control method is proposed for a class of discrete-time... 相似文献
3.
4.
Double Michael additions of lithium enolaie of 1,4-dioxaspiro[4.5]dec-6-en-8-one to four acrylates afforded bicyclo[2.2.2]octan-2-ones with high regio- and stereoselectivities in moderate yields. 相似文献
5.
Fiber-optic reflex sensor for in-line production measurement 总被引:1,自引:0,他引:1
The paper describes experiments concerning distance measurement with fiber-optic sensor and improvement of the measurement principle. The sensor probe was well-designed with a small structure and multi-function. The novel optical fiber probe arrangement as well as the possibilities of use for complex measurement problems are explained using the measurement of an internal screw thread as an example. The experimental results show that the measurement uncertainty of the thread minor diameter can reach ±10 μm, and the stability of the measurement system is better than 0.07%. 相似文献
6.
Wang Qing-Lun Zhao Bin Liao Dai-Zheng Yan Shi-Ping Cheng Peng Jiang Zong-Hui 《Transition Metal Chemistry》2003,28(3):326-330
The copper(II) complex Na2[Cu(pba)] · 6H2O has been synthesized and its structure determined. It consists of a novel two-dimensional network of [Cu(pba)]2– anions connected to each other through the sodium ion as a bridge. Spectroscopic and magnetic properties have been measured and a spin distribution calculation has been carried out with the GAUSSIAN-94. Theoretical calculations indicate the rather larger spin density on nitrogen atoms should be responsible for the satellite lines appearing beside the main hyperfine coupling signs of copper(II). The antiferromagnetic interaction may be due to the intermolecular interaction and/or different copper(II) ions through the Na+ bridge in the same layer. 相似文献
7.
Liang Liao Yi Pang Liming Ding Frank E. Karasz 《Journal of polymer science. Part A, Polymer chemistry》2003,41(20):3149-3158
A soluble cyano‐substituted poly[(1,3‐phenylene vinylene)‐alt‐(1,4‐phenylene vinylene)] derivative ( 9 ) was synthesized and characterized. Comparison between 9 and its model compound ( 10 ) showed that the chromophore in 9 remained to be well defined as a result of a π‐conjugation interruption at adjacent m‐phenylene units. The attachment of a cyano substituent only at the β position of the vinylene allowed the maximum electronic impact of the cyano group on the optical properties of the poly(p‐phenylene vinylene) material. At a low temperature (?108 or ?198 °C), the vibronic structures of 9 and 10 were partially resolved. The absorption and emission spectra of a film of 9 were less temperature‐dependent than those of a film of 10 , indicating that the former had a lower tendency to aggregate. A light‐emitting diode (LED) based on 9 emitted yellow light (λmax ≈ 578 nm) with an external quantum efficiency of 0.03%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3149–3158, 2003 相似文献
8.
Sufficient conditions are established for the asymptotic behavior of solutionsof nonlinear delay differential equations x′(t)+sum from i=1 to m(pi(t)x(t-т_i))=F(t,x_t),t≥0where 0<т_1<т_2<…<т_m≤r,pi∈C([0,∞)),i=1,2,…,m,F∈C([0,∞)×C_0,R).C_0=C([-r,0],R)equipped with the sup norm ||·|| forsome r>0. A new result is established, some known results are improved. 相似文献
9.
A convergent-barrel (CB) cold spray nozzle was designed through numerical simulation. It was found that the main factors influencing significantly particle velocity and temperature include the length and diameter of the barrel section, the nature of the accelerating gas and its pressure and temperature, and the particle size. Particles can achieve a relatively low velocity but a high temperature under the same gas pressure using a CB nozzle compared to a convergent-divergent (CD) nozzle. The experiment results with Cu powder using the designed CB nozzle confirmed that particle deposition can be realized under a lower gas pressure with a CB nozzle. 相似文献
10.
Sung‐Fu Hsu Tzong‐Ming Wu Chien‐Shiun Liao 《Journal of Polymer Science.Polymer Physics》2006,44(23):3337-3347
Poly(3‐hydroxybutyrate) (PHB)/layered double hydroxides (LDHs) nanocomposites were prepared by mixing PHB and poly(ethylene glycol) phosphonates (PEOPAs)‐modified LDH (PMLDH) in chloroform solution. Both X‐ray diffraction data and TEM micrographs of PHB/PMLDH nanocomposites indicate that the PMLDHs are randomly dispersed and exfoliated into the PHB matrix. In this study, the effect of PMLDH on the isothermal crystallization behavior of PHB was investigated using a differential scanning calorimeter (DSC) and polarized optical microscopy. Isothermal crystallization results of PHB/PMLDH nanocomposites show that the addition of 2 wt % PMLDH into PHB induced more heterogeneous nucleation in the crystallization significantly increasing the crystallization rate and reducing their activation energy. By adding more PMLDH into the PHB probably causes more steric hindrance of the diffusion of PHB, reducing the transportation ability of polymer chains during crystallization, thus increasing the activation energy. The correlation among crystallization kinetics, melting behavior and crystalline structure of PHB/PMLDH nanocomposites can also be discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3337–3347, 2006 相似文献