Three co-8cr-xAl alloys (x = 0, 3, 5 wt.%) were exposed to three mixtures (Gas 1: H2-cO2, Gases 2 and 3: H2cO2-H2S) at 900 degrees c for 20 h. Gas 1 produced external chromia scales (plus internal alumina for co-8cr-3...
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Three co-8cr-xAl alloys (x = 0, 3, 5 wt.%) were exposed to three mixtures (Gas 1: H2-cO2, Gases 2 and 3: H2cO2-H2S) at 900 degrees c for 20 h. Gas 1 produced external chromia scales (plus internal alumina for co-8cr-3/5Al). Gas 2, with p(S2) below stability of co sulfides, favored a transition from external chromia scales, observed in Gas 1, to exclusive external alumina scales for both co-8cr-3/5Al alloys. conversely, Gas 3 was very aggressive for both co-8cr and co-8cr-3Al, forming a liquid co-S phase, while with co-8cr-5Al it still formed external Al2O3 scales. Al additions improved the alloys resistance to the sulfur attack.
The corrosion behaviour of Alloy 690 under four different zinc addition scenarios was investigated in circulating water containing 2 ppm Li and 1000 ppm B at 330 degrees c. The corrosion rates, release rates, and oxid...
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The corrosion behaviour of Alloy 690 under four different zinc addition scenarios was investigated in circulating water containing 2 ppm Li and 1000 ppm B at 330 degrees c. The corrosion rates, release rates, and oxide thicknesses were quantified using gravimetric analyses and oxide compositions. With earlier zinc addition, the corrosion and release rates were accordingly lower and the oxide films were also thinner. This study elaborates on how the radiation source term is suppressed by the zinc addition and the behavior of zinc incorporation into spinel oxides.
Recent whole-brain calcium imaging recordings of the nematode c. elegans have demonstrated that the neural activity associated with behavior is dominated by dynamics on a low-dimensional manifold that can be clustered...
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Recent whole-brain calcium imaging recordings of the nematode c. elegans have demonstrated that the neural activity associated with behavior is dominated by dynamics on a low-dimensional manifold that can be clustered according to behavioral states. Previous models of c. elegans dynamics have either been linear models, which cannot support the existence of multiple fixed points in the system, or Markov-switching models, which do not describe how control signals in c. elegans neural dynamics can produce switches between stable states. It remains unclear how a network of neurons can produce fast and slow timescale dynamics that control transitions between stable states in a single model. We propose a global, nonlinear control model which is minimally parameterized and captures the state transitions described by Markov-switching models with a single dynamical system. The model is fit by reproducing the timeseries of the dominant PcA mode in the calcium imaging data. Long and short time-scale changes in transition statistics can be characterized via changes in a single parameter in the control model. Some of these macro-scale transitions have experimental correlates to single neuro-modulators that seem to act as biological controls, allowing this model to generate testable hypotheses about the effect of these neuro-modulators on the global dynamics. The theory provides an elegant characterization of control in the neuron population dynamics in c. elegans. Moreover, the mathematical structure of the nonlinear control framework provides a paradigm that can be generalized to more complex systems with an arbitrary number of behavioral states.
Electrochemical cO2 reduction to produce valuable c-2 products is attractive but still suffers with relatively poor selectivity and stability at high current densities, mainly due to the low efficiency in the coupling...
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Electrochemical cO2 reduction to produce valuable c-2 products is attractive but still suffers with relatively poor selectivity and stability at high current densities, mainly due to the low efficiency in the coupling of two *cO intermediates. Herein, it is demonstrated that high-density nitrogen vacancies formed on cubiccopper nitrite (cu3Nx) feature as efficient electrocatalyticcenters for cO-cO coupling to form the key OccO* intermediate toward c-2 products. cu3Nx with different nitrogen densities are fabricated by an electrochemical lithium tuning strategy, and density functional theory calculations indicate that the adsorption energies of cO* and the energy barriers of forming key c-2 intermediates are strongly correlated with nitrogen vacancy density. The cu3Nx catalyst with abundant nitrogen vacancies presents one of the highest Faradaic efficiencies toward c-2 products of 81.7 +/- 2.3% at -1.15 V versus reversible hydrogen electrode (without ohmiccorrection), corresponding to the partial current density for c-2 production as -307 +/- 9 mA cm(-2). An outstanding electrochemical stability is also demonstrated at high current densities, substantially exceeding cuOx catalysts with oxygen vacancies. The work suggests an attractive approach to create stable anion vacancies as catalyticcenters toward multicarbon products in electrochemical cO2 reduction.
The development of catalysts for high-efficient hydrogen evolution reaction (HER) is important for future sustainable energy conversion. Herein, porous carbon-supported PtNi alloy catalysts were fabricated by ion beam...
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The development of catalysts for high-efficient hydrogen evolution reaction (HER) is important for future sustainable energy conversion. Herein, porous carbon-supported PtNi alloy catalysts were fabricated by ion beam sputtering and ultrasonic-assisted electrochemical corrosion dealloying methods, and their performances toward the catalysis of HER were evaluated. The effects of corrosion dealloying on the hydrogen evolution activity, as well as stability, phase structure, surface composition, and active sites of PtNi alloys were analyzed by various analytical methods combined with orthogonal experiments. The results showed increased catalytic activity of HER by 51.39% after corrosion of the material in 0.2 mol/L H2SO4 at 40 degrees c for 0.5 h. The hydrogen evolution deteriorated as Pt-loading decreased by 25.83%, and corrosion temperature displayed significant influence. The pore structure of the catalyst surface raised the relative content of the exposed Pt element, and the zero-dimensional defect generated by the Ni atom deletion led to promotion in reaction area and active sites on the catalyst surface. The interplanar spacing of alloys (NiPt) was below 3%-6% of the standard value, and the lattice compressive strain of Pt was the reason that led to improved catalytic performance of PtNi alloy catalysts. The binding energy of the Pt 4f7/2 decreased by 0.74 eV, leading to enhanced electrochemical active sites and promoted hydrogen release. (c) 2021 Elsevier B.V. All rights reserved.
It is well established that fiber waviness in continuous fiber-reinforced polymer composites is a defect rather than an aesthetic flaw, as it potentially leads to a severe knockdown of the mechanical properties. conse...
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It is well established that fiber waviness in continuous fiber-reinforced polymer composites is a defect rather than an aesthetic flaw, as it potentially leads to a severe knockdown of the mechanical properties. consequently, it is desirable to minimize or prevent fiber waviness during processing. This research explored experimentally the influence of tool material, release media and laminate size on the formation of in-plane fiber waviness during c/ PEEK consolidation. The formed waviness was quantified and correlated to the measured tool-ply friction coefficients and thermal coefficients of expansion of the tool plates. This research provides additional evidence that tool shrinkage is the driving force for waviness formation in c/PEEK laminate consolidation. Furthermore, the formation of waviness depends on the balance between the coefficient of thermal expansion of the tool, the toolply coefficient of friction and the laminate size.
Expectations are one of the core theoretical concepts in the history of 20th century macroeconomics and finance. Here another significant theory of expectations in intellectual history is noted - c. S. Peirce's th...
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Expectations are one of the core theoretical concepts in the history of 20th century macroeconomics and finance. Here another significant theory of expectations in intellectual history is noted - c. S. Peirce's theory of abductive expectations. Peirce was an American philosopher and scientist with deep interests in economics. The paper begins by reprising important aspects of prominent expectations theories such as rational and adaptive expectations, and the theories of Keynes, Friedman and cagan. Then the discussion extends to other noted contributors such as Shackle, coddington, Hayek, Evans, and Brock. c. S. Peirce's theory of expectations is intertwined with his writings on many subjects. What was important about human thought for Peirce was that inferences were made about the logic of events unfolding towards the future. Such inferences look to the future and their accompanying reasoning processes were interpreted as expectational inferences. Peirce used the term abduction for hypothetically imagining the future. An abductive, conjectural expectation (AcE) is one which incorporates and surpasses known evidence by contingently and hypothetically contemplating the future. For Peirce, abductive expectations are a crucial part of humanity's most efficient and productive resource, the cognitive processes of the human mind. Also, although Peirce is recognized as a founding influence on American institutional economics, his conception of expectations seems to have been left undeveloped by that school of economic ideas. Peirce's contribution provides new insights and a more unifying perspective on expectations theories in the history of economics.
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