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11.
A method is presented for obtaining periodic solutions to forced oscillations of non-linear systems governed by equations of the form uss?uyy?εf(u,u,y,uyy…,s) = 0. The method is presented by application to the equation uss?uyy?εu2yuyy= 0 which governs the vibrations of a soil layer that is free on the top surface and is forced harmonically at the bedrock. It is shown that unlike the ODE case (Duffing equation), the PDE requires an infinite number of periodicity conditions to correctly characterize the resonant region and these conditions lead to an infinite number of branches in the dispersion spectrum. Calculations indicate that these branches tend to an envelope curve. The uniform approach presented by Millmann and Keller is discussed in order to determine in what sense it can be viewed as an effective approximation for the fundamental mode. 相似文献
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T. Gamze Ulusoy Ghobadi Amir Ghobadi Merve Demirtas Muhammed Buyuktemiz Kubra N. Ozvural Elif Akhuseyin Yildiz Prof. Emre Erdem Prof. H. Gul Yaglioglu Prof. Engin Durgun Prof. Yavuz Dede Prof. Ekmel Ozbay Prof. Ferdi Karadas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(35):8966-8976
The replacement of traditional ruthenium-based photosensitizers with low-cost and abundant iron analogs is a key step for the advancement of scalable and sustainable dye-sensitized water splitting cells. In this proof-of-concept study, a pyridinium ligand coordinated pentacyanoferrate(II) chromophore is used to construct a cyanide-based CoFe extended bulk framework, in which the iron photosensitizer units are connected to cobalt water oxidation catalytic sites through cyanide linkers. The iron-sensitized photoanode exhibits exceptional stability for at least 5 h at pH 7 and features its photosensitizing ability with an incident photon-to-current conversion capacity up to 500 nm with nanosecond scale excited state lifetime. Ultrafast transient absorption and computational studies reveal that iron and cobalt sites mutually support each other for charge separation via short bridging cyanide groups and for injection to the semiconductor in our proof-of-concept photoelectrochemical device. The reorganization of the excited states due to the mixing of electronic states of metal-based orbitals subsequently tailor the electron transfer cascade during the photoelectrochemical process. This breakthrough in chromophore-catalyst assemblies will spark interest in dye-sensitization with robust bulk systems for photoconversion applications. 相似文献
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The electrical, magnetic and structural properties of synthetic chalcopyrite, CuFeS2, have been studied up to 873 K using DC resistance measurements performed in-situ during neutron powder diffraction experiments. Under ambient conditions the material adopts the accepted structural model for CuFeS2 in the space group I4?2d, with the magnetic moment of the Fe3+ cations aligned along [001]. The electrical resistivity is around 0.3 Ω cm under ambient conditions, consistent with semiconductor character, and decreases slightly with increase in temperature until a more abrupt fall occurs in the region 750-800 K. This abrupt change in resistivity is accompanied by a structural transition to a cubic zinc blende structured phase (space group F4?3m) in which Cu+ and Fe3+ cations are disordered over the same tetrahedral crystallographic sites and by a simultaneous loss of long-range magnetic order. The implications of these results are discussed in the context of previous studies of the chalcopyrite system. 相似文献
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Cationic diimine Ru(II) complexes were synthesized and tested as catalysts for the formation of cyclic organic carbonates from CO2 and liquid epoxides (propylene oxide, epichlorohydrine, 1,2‐epoxybutane and styrene oxide) which served as both reactant and solvent. The reaction rates not only depended on the type of ligand, but also on reaction conditions such as temperature, pressure, base, the epoxide substrates and the use of an additional solvent. Reaction rates in terms of turnover frequencies up to 4050 molproduct molcat.?1 h?1 at 99% selectivity were achieved by optimizing the diimine ligand as well as the reaction temperature and CO2 pressure. Consistent with CV measurements, the electron donating group on the p‐position of the aryl ring accelerated the reaction rate. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Tufan Kumbasar Ibrahim Eksin Mujde Guzelkaya Engin Yesil 《International Journal of Approximate Reasoning》2013,54(2):253-272
It has been demonstrated that type-2 fuzzy logic systems are much more powerful tools than ordinary (type-1) fuzzy logic systems to represent highly nonlinear and/or uncertain systems. As a consequence, type-2 fuzzy logic systems have been applied in various areas especially in control system design and modelling. In this study, an exact inversion methodology is developed for decomposable interval type-2 fuzzy logic system. In this context, the decomposition property is extended and generalized to interval type-2 fuzzy logic sets. Based on this property, the interval type-2 fuzzy logic system is decomposed into several interval type-2 fuzzy logic subsystems under a certain condition on the input space of the fuzzy logic system. Then, the analytical formulation of the inverse interval type-2 fuzzy logic subsystem output is explicitly driven for certain switching points of the Karnik–Mendel type reduction method. The proposed exact inversion methodology driven for the interval type-2 fuzzy logic subsystem is generalized to the overall interval type-2 fuzzy logic system via the decomposition property. In order to demonstrate the feasibility of the proposed methodology, a simulation study is given where the beneficial sides of the proposed exact inversion methodology are shown clearly. 相似文献
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Jin Li Dr. Lei Wang Jinrong Li Yujie Shao Ziang Liu Dr. Guangzhe Li Prof. Dr. Engin U. Akkaya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(34):e202200506
Naphthalene endoperoxides are known as convenient sources of singlet oxygen (O2, 1Δg), which is the major product of endoperoxide cycloreversion reaction. However, their potential as carriers of ground-state molecular oxygen (O2, 3Σg) similar to artificial oxygen carriers remains largely unexplored. This is due to the extreme reactivity and cytotoxic effects of the released singlet oxygen. We now report that a compound with a bimodular design, which incorporates an endoperoxide and an efficient physical quencher of singlet oxygen, 1,4-diazabicyclo[2.2.2]octane (DABCO), produces exclusively ground-state molecular oxygen. This result, coupled with the fact that oxygen release rates from endoperoxides are highly amenable to fine-tuning in a very broad range, and open to targeting by ligand attachment, raises the potential of these compounds far above any comparable chemical, or even biochemical sources. In cell culture experiments, we showed that the addition of the endoperoxide-quencher conjugate can enhance and sustain cell proliferation. 相似文献
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