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21.
Monika Wolfmayr 《Numerical Methods for Partial Differential Equations》2017,33(2):403-424
In this work, new results on functional type a posteriori estimates for elliptic optimal control problems with control constraints are presented. More precisely, we derive new, sharp, guaranteed, and fully computable lower bounds for the cost functional in addition to the already existing upper bounds. Using both, the lower and the upper bounds, we arrive at two‐sided estimates for the cost functional. We prove that these bounds finally lead to sharp, guaranteed and fully computable upper estimates for the discretization error in the state and the control of the optimal control problem. First numerical tests are presented confirming the efficiency of the a posteriori estimates derived. © 2016 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 403–424, 2017 相似文献
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本文针对工件间具有链状优先约束和relocation资源约束的极小化加权总完工时间调度优化问题展开研究.针对这一NP难问题,利用relocation约束的性质和贪婪算法的思想,设计了一个多项式近似算法,并证明了当链不可中断,每个链具有相同工件数和工件间具有相同加工时间时,2为该算法的紧界. 相似文献
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Adrian Falkowski Leszek Słomiński 《Stochastic Processes and their Applications》2017,127(11):3536-3557
We study the existence, uniqueness and stability of solutions of general stochastic differential equations with constraints driven by semimartingales and processes with bounded -variation. Applications to SDEs with constraints driven by fractional Brownian motion and standard Brownian motion are given. 相似文献
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In this paper, we propose a Bayesian semiparametric mean-covariance regression model with known covariance structures. A mixture model is used to describe the potential non-normal distribution of the regression errors. Moreover, an empirical likelihood adjusted mixture of Dirichlet process model is constructed to produce distributions with given mean and variance constraints. We illustrate through simulation studies that the proposed method provides better estimations in some non-normal cases. We also demonstrate the implementation of our method by analyzing the data set from a sleep deprivation study. 相似文献
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In this paper, we consider an optimal control problem of switched systems with input and state constraints. Since the complexity of such constraint and switching laws, it is difficult to solve the problem using standard optimization techniques. In addition, although conjugate gradient algorithms are very useful for solving nonlinear optimization problem, in practical implementations, the existing Wolfe condition may never be satisfied due to the existence of numerical errors. And the mode insertion technique only leads to suboptimal solutions, due to only certain mode insertions being considered. Thus, based on an improved conjugate gradient algorithm and a discrete filled function method, an improved bi-level algorithm is proposed to solve this optimization problem. Convergence results indicate that the proposed algorithm is globally convergent. Three numerical examples are solved to illustrate the proposed algorithm converges faster and yields a better cost function value than existing bi-level algorithms. 相似文献
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选用脱碱木质素作为原料,以热裂解气质联用技术(Py-GC/MS)研究木质素在350~600℃下热解产物成分和含量,并利用Joback法、 Lijie法和Tahami法3种基团贡献法计算了生物油各组成成分的临界参数和动力学直径,对木质素热解油产物的分子动力学直径分布特性进行计算.结果显示,愈创木基结构、紫丁香基结构、苯酚类、邻苯二酚类和芳烃类等5种芳香族化合物是350~600℃下木质素热解生物油的主要组成成分,其中愈创木基结构化合物的平均峰面积百分比达到70.7%.随着反应温度从350提高到600℃,分子动力学直径在0.560~0.610 nm区间内的木质素热解油组分含量从14.6%增加至31.3%.木质素热解生物油主要产物的动力学直径在0.560~0.710nm,表明一些孔径尺寸在此范围内的分子筛如SSZ-20、 ZSM-5和Beta可作为木质素裂解制备高品质芳烃燃料的催化剂. 相似文献
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Effectively improving the mechanical properties and thermal resistance of epoxy shape‐memory polymers (ESMPs) without affecting their shape‐memory performance is necessary to expand these polymers in practical applications. In this article, modified multi‐walled carbon nanotubes (MWCNTs) were prepared and used as efficient reinforcement for enhancing the comprehensive properties of ESMPs. Increases of nearly 289% to 444% for impact strength and 112% to 184% for tensile force were obtained by adding only 0.1 to 1 wt% epoxy‐modified MWCNTs. The addition of unmodified and carboxyl‐modified MWCNTs was also investigated but showed less impact on the mechanical properties of the ESMPs than epoxy‐modified MWCNTs. Thermogravimetry analysis (TGA) and dynamic mechanical analyses (DMA) showed that less than 1 wt% modified MWCNTs can enhance the heat resistance of ESMPs greatly. Although the shape recovery time for composite materials increased upon adding the MWCNTs, the entire recovery time was still less than 1 minute, and the shape recovery rate was relatively high, nearly 100%. 相似文献