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991.
992.
993.
This paper studies the control for synchronization of a four-dimensional system via a single variable, and a linear feedback
controller and an adaptive controller are proposed. Based on the Lyapunov stability theory, the correctness of the proposed
methods is strictly demonstrated. The numerical simulations further show their effectiveness. 相似文献
994.
Konrad Eichhorn Colombo Vladislav V. Kharton Alexandre P. Viskup Andrei V. Kovalevsky Aliaksandr L. Shaula Olav Bolland 《Journal of Solid State Electrochemistry》2011,15(2):329-347
A gas turbine power plant for CO2 capture, based on oxygen-permeable membranes with mixed ionic-electronic conductivity, was analysed with respect to long-term
stability by means of numerical simulation. Due to the attractive transport and physicochemical properties of mixed-conducting
La2NiO4+δ, this nickelate was selected as a prototype membrane material for this application. Experiments showed very slow degradation
of La2NiO4+δ membranes at oxygen chemical potentials close to atmospheric conditions, which are associated with kinetic demixing and other
microstructure-related factors. Interaction with CO2 in the intermediate temperature range also leads to lower oxygen permeation, whilst increasing oxygen pressure may cause
partial phase decomposition and microstructural changes, thus again limiting the range of possible operation conditions. The
relevant operational constraints were included in a detailed membrane-based gas turbine power plant model. The membrane performance
degradation with time was approximated by a linear function with average rate of 3.3% per 1,000 operation hours. Furthermore,
performance deterioration of the gas turbine compressor and turbine were also considered. Simulations revealed that the power
plant is substantially affected by degradation of the ceramic membranes and turbomachinery components. The already rather
small operating window was further narrowed when compared with a conventional gas turbine power plant. Two different designs
of the membrane-based power plant were analysed: (1) with and (2) without additional combustors (afterburners) between the
membrane reactor and the gas turbine. Afterburners increase thermal efficiency as well as power output, but also lead to non-negligible
CO2 emissions. In order to have a frame of comparison, results for a conventional gas turbine power plant with degradation of
turbomachinery components are also presented. Simulations representing changes in ambient temperature and fuel composition
as well as failure incidents were executed to analyse the susceptibility of the gas turbine power plant to external and internal
changes. 相似文献
995.
996.
Mereology is the logic of part—whole concepts as they are used in many different contexts. The old chemical metaphysics of
atoms and molecules seems to fit classical mereology very well. However, when functional attributes are added to part specifications
and quantum mechanical considerations are also added, the rules of classical mereology are breached in chemical discourses.
A set theoretical alternative mereology is also found wanting. Molecular orbital theory requires a metaphysics of affordances
that also stands outside classical mereology. 相似文献
997.
On general sum-connectivity index 总被引:1,自引:0,他引:1
We report some properties of the reverse degree distance of a connected (molecular) graph, and, in particular, its relationship
with the first Zagreb index and Wiener index. We also show that the reverse degree distance satisfies the basic requirement
for a branching index. 相似文献
998.
Data for optimization problems often comes from (deterministic) forecasts, but it is naïve to consider a forecast as the only future possibility. A more sophisticated approach uses data to generate alternative future scenarios, each with an attached probability. The basic idea is to estimate the distribution of forecast errors and use that to construct the scenarios. Although sampling from the distribution of errors comes immediately to mind, we propose instead to approximate rather than sample. Benchmark studies show that the method we propose works well. 相似文献
999.
以高等数学课堂教学为例,通过科学试验的方法分析数学建模思想渗入大学数学课堂教学对学生学习的影响力。通过精心设计教学试验,采集大量试验数据进行建模分析,结果表明,数学建模思想渗入高等数学课堂教学会对学生的学习产生积极影响,值得推广并长期坚持。 相似文献
1000.
Peter Bouwknegt Jarah Evslin Varghese Mathai 《Communications in Mathematical Physics》2015,337(2):909-954
We introduce spherical T-duality, which relates pairs of the form (P, H) consisting of a principal SU(2)-bundle \({P \rightarrow M}\) and a 7-cocycle H on P. Intuitively spherical T-duality exchanges H with the second Chern class c 2(P). Unless \({dim(M) \leq 4}\), not all pairs admit spherical T-duals and the spherical T-duals are not always unique. Nonetheless, we prove that all spherical T-dualities induce a degree-shifting isomorphism on the 7-twisted cohomologies of the bundles and, when \({dim(M) \leq 7}\), also their integral twisted cohomologies and, when \({dim(M) \leq 4}\), even their 7-twisted K-theories. While spherical T-duality does not appear to relate equivalent string theories, it does provide an identification between conserved charges in certain distinct IIB supergravity and string compactifications. 相似文献