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81.
Mihai Mihăilescu Gheorghe Moroşanu 《Nonlinear Analysis: Real World Applications》2013,14(3):1466-1476
This paper investigates a nonlinear and non-homogeneous system of partial differential equations. The motivation comes from the fact that in a particular case the problem discussed here can be used in modeling the behavior of nonlinear Hencky-type materials. The main result of the paper establishes the existence of a nontrivial solution in an adequate functional space of Orlicz–Sobolev type by using Schauder’s fixed point theorem combined with adequate variational techniques. 相似文献
82.
83.
Miles Lubin J. A. Julian Hall Cosmin G. Petra Mihai Anitescu 《Computational Optimization and Applications》2013,55(3):571-596
We present a parallelization of the revised simplex method for large extensive forms of two-stage stochastic linear programming (LP) problems. These problems have been considered too large to solve with the simplex method; instead, decomposition approaches based on Benders decomposition or, more recently, interior-point methods are generally used. However, these approaches do not provide optimal basic solutions, which allow for efficient hot-starts (e.g., in a branch-and-bound context) and can provide important sensitivity information. Our approach exploits the dual block-angular structure of these problems inside the linear algebra of the revised simplex method in a manner suitable for high-performance distributed-memory clusters or supercomputers. While this paper focuses on stochastic LPs, the work is applicable to all problems with a dual block-angular structure. Our implementation is competitive in serial with highly efficient sparsity-exploiting simplex codes and achieves significant relative speed-ups when run in parallel. Additionally, very large problems with hundreds of millions of variables have been successfully solved to optimality. This is the largest-scale parallel sparsity-exploiting revised simplex implementation that has been developed to date and the first truly distributed solver. It is built on novel analysis of the linear algebra for dual block-angular LP problems when solved by using the revised simplex method and a novel parallel scheme for applying product-form updates. 相似文献
84.
Mihai Todica Traian Stefan Diana Trandafir Simion Simon 《Central European Journal of Physics》2013,11(7):928-935
The effects of gamma radiation on the local structure of PVA membranes containing TiO2 were investigated by ESR and XRD methods. An intense ESR signal is observed after irradiation at 16 KGy dose. This signal appears only for irradiated samples and it is associated with the breaking of the polymeric chain, followed by local reorganization of the polymeric segments and the apparition of the unpaired electrons and free radicals. The intensity of the signal decreases with the concentration of TiO2, indicating a shielding effect of the dopand. That the modification of local order of the polymeric chains has been modified after irradiation is confirmed by XRD method. 相似文献
85.
Anantaram Balakrishnan Mihai Banciu Karolina Glowacka Prakash Mirchandani 《European Journal of Operational Research》2013
A central design challenge facing network planners is how to select a cost-effective network configuration that can provide uninterrupted service despite edge failures. In this paper, we study the Survivable Network Design (SND) problem, a core model underlying the design of such resilient networks that incorporates complex cost and connectivity trade-offs. Given an undirected graph with specified edge costs and (integer) connectivity requirements between pairs of nodes, the SND problem seeks the minimum cost set of edges that interconnects each node pair with at least as many edge-disjoint paths as the connectivity requirement of the nodes. We develop a hierarchical approach for solving the problem that integrates ideas from decomposition, tabu search, randomization, and optimization. The approach decomposes the SND problem into two subproblems, Backbone design and Access design, and uses an iterative multi-stage method for solving the SND problem in a hierarchical fashion. Since both subproblems are NP-hard, we develop effective optimization-based tabu search strategies that balance intensification and diversification to identify near-optimal solutions. To initiate this method, we develop two heuristic procedures that can yield good starting points. We test the combined approach on large-scale SND instances, and empirically assess the quality of the solutions vis-à-vis optimal values or lower bounds. On average, our hierarchical solution approach generates solutions within 2.7% of optimality even for very large problems (that cannot be solved using exact methods), and our results demonstrate that the performance of the method is robust for a variety of problems with different size and connectivity characteristics. 相似文献
86.
Mihai Răducă Cristian D. Ene Sorana Ionescu Mihaela Florea 《Journal of Coordination Chemistry》2019,72(8):1222-1237
Abstract1-D coordination polymers, 1∞[Zn(fl)2]·2EtOH and 1∞[Zn(fl)2]·2MeOH, and a dinuclear complex, [{Zn(fl)2}2(dienpip)]·4H2O·4EtOH (dienpip?= N,N′-bis(2-aminoethyl)piperazine), were obtained using Zn(II) ions and fluorescein anions (fl). Thermal analysis shows stability of the polymers after solvent removal up to more than 400?°C. Crystallization solvent molecules were removed under reduced pressure with the preservation of the polymeric structure, 1∞[Zn(fl)2]. Desolvated crystals were exposed to I2 vapors and the crystal structure determination by X-ray diffraction confirmed the presence of I2 molecules in the channels generated in crystals by the metal-organic framework. The iodine content, evaluated by X-ray diffraction, corresponds to the overall formula 1∞[Zn(fl)2]·0.3I2. The optical properties of the coordination polymers and the dinuclear complex have been investigated. 相似文献
87.
Gheorghe Daniela Neacsu Ana Contineanu Iulia Anghel Elena Maria Teodorescu Florina Chican Irina Elena Perisanu Stefan Tanasescu Speranta 《Journal of Thermal Analysis and Calorimetry》2019,138(2):1233-1242
Journal of Thermal Analysis and Calorimetry - A systematic thermodynamic study has been performed for a series of nitrates having cations derived from the α-amino acids glycine (Gly),... 相似文献
88.
Stan Stelian Chisamera Mihai Riposan Iulian Stefan Eduard Neacsu Loredana Cojocaru Ana Maria Stan Iuliana 《Journal of Thermal Analysis and Calorimetry》2019,138(4):2529-2540
Journal of Thermal Analysis and Calorimetry - Simultaneous thermal and contraction/expansion analysis of hypoeutectic grey (lamellar graphite) and ductile (nodular graphite) cast irons... 相似文献
89.
Stefan Eduard Riposan Iulian Chisamera Mihai 《Journal of Thermal Analysis and Calorimetry》2019,138(4):2491-2503
Journal of Thermal Analysis and Calorimetry - The new generation of acid-lined medium-frequency coreless induction furnaces revolutionized the iron foundries, resulting higher overheating and lower... 相似文献
90.
Eigenvalue problems involving the p-Laplacian and rapidly growing operators in divergence form are studied in an Orlicz–Sobolev setting. An asymptotic analysis of these problems leads to a full characterization of the spectrum of an exponential type perturbation of the Laplace operator. 相似文献