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81.
During experiments simulating the destruction of organic waste or the conversion of biomass with water at supercritical water conditions (SCW, T > 374 °C, p > 22.1 MPa), severe corrosion phenomena were observed. Depending on the experimental conditions applied, scale formation and precipitation of corrosion products occurred. The harsh conditions and the chemical properties of the feed solutions lead to consecutive chemical reactions with the materials involved. To study such hydrothermal reactions on simplified model systems, tubular reactors made of Ni‐based alloys were exposed to feed solutions composed of water, methanol and alkaline salts. After each experiment, the reaction tubes were cut and examined by optical microscopy. Hydrothermally formed corrosion layers were studied by field emission electron microscopy and combined energy dispersive X‐ray spectroscopy. Element line scans and mappings were performed which depicted selective dissolution of alloying elements (dealloying of Ni, Fe, Mo). The formation of the corrosion layers was accompanied by a subsequent reduction of the tube wall diameter. Atomic force microscopy gained additional morphological information; a Monte Carlo programme was applied to simulate X‐ray line scans. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
82.
Georgios D. Samaras Nikolaos F. Matsatsinis Constantin Zopounidis 《European Journal of Operational Research》2008
The paper describes a multicriteria decision support system which aims at presenting an evaluation of the Athens Stock Exchange (ASE) stocks, on the basis of fundamental analysis. The system evaluates the stocks based on the method of fundamental analysis ratios, which is the most appropriate evaluation approach regarding investment decisions within a long term horizon. In addition to quantitative data deriving from fundamental analysis, the system uses qualitative data as well, in order to improve the reliability of the evaluation. The system introduced in this paper, utilises multicriteria analysis methodologies in order to rank the stocks by placing the best stock first and the worst last. Stock evaluation considers the specific characteristics of the potential investor, as well as his attitude towards undertaken risk. The final output of the system is four stock rankings which respond to four different criteria groups, depending on the type of accounting plan each listed company belongs to. The system incorporates a large volume of relevant information and operates in ‘real world conditions’ since its data are constantly updated. Finally, the system is intended for both institutional and private investors. 相似文献
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84.
Sotiria Karagiovanaki Alexandros Koutsioubas Nikolaos Spiliopoulos Dimitris L. Anastassopoulos Alexandros A. Vradis Chris Toprakcioglu Angeliki Elina Siokou 《Journal of polymer science. Part A, Polymer chemistry》2010,48(14):1676-1682
We have studied the adsorption of end-attaching block copolymer chains inside the cylindrical pores of nanoporous alumina. Highly asymmetric PS-PEO block copolymers, with a small PEO anchoring block and a long PS dangling block, were allowed to adsorb onto porous alumina substrates with an average pore diameter of ∼200 nm from toluene solution. The adsorption process was monitored using FTIR spectroscopy, whereas depth profile analysis was performed by means of XPS and Ar+ ion sputtering. It is found that the PS-PEO adsorption kinetics in porous alumina are ∼4 orders of magnitude slower than the corresponding case of a flat alumina substrate. It appears that chains adsorbed near the pore entrance early on tend to form a barrier for chains entering the pore at later times, thereby slowing down the adsorption process significantly. This effect is much more pronounced for large chains whose dimensions are comparable with the pore diameter. The equilibrium adsorbance value is also affected by chain size due to the additional entropic penalty associated with chain confinement, the adsorbance falling substantially when the chain dimensions become comparable with the pore diameter. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1676–1682, 2010 相似文献
85.
Nikolaos Zervos 《Tetrahedron letters》2010,51(18):2453-2456
B3LYP/6-31+G(d,p) calculations predicted the presence of improper hydrogen-bonded C-Hax?Yax contacts of different strength in cyclohexane derivatives;1 it was predicted that the addition of an appropriate bridging fragment Xax between an axial substituent Y1 and a cyclohexane carbon would strengthen the improper hydrogen-bonded contact C-Hax?Y1 when the Xax-Y1 bond vector bisects the cyclohexane ring. To support the theoretical predictions with experimental evidence for this effect, several 2-substituted adamantane analogues with suitable improper H-bonded C-Hax?O contacts of different strength were synthesized, as models of the corresponding cyclohexane derivatives, and their 1H NMR spectra were recorded at 298 K. The 1H NMR signal separation within the cyclohexane ring γ-CH2s is increased when the B3LYP/6-31+G(d,p)-calculated strength of the H-bonded C-Hax?O=Cax contact interaction is increased. 相似文献
86.
In this Note, we study a class of Neumann parametric elliptic equations driven by a nonhomogeneous differential operator and with a reaction that exhibits competing terms (concave–convex nonlinearities). Using the Ambrosetti–Rabinowitz condition and related topological and variational arguments, we prove a bifurcation result for large values of the parameter. 相似文献
87.
88.
This work considers the global optimization of general nonconvex nonlinear and mixed-integer nonlinear programming problems with underlying polynomial substructures. We incorporate linear cutting planes inspired by reformulation-linearization techniques to produce tight subproblem formulations that exploit these underlying structures. These cutting plane strategies simultaneously convexify linear and nonlinear terms from multiple constraints and are highly effective at tightening standard linear programming relaxations generated by sequential factorable programming techniques. Because the number of available cutting planes increases exponentially with the number of variables, we implement cut filtering and selection strategies to prevent an exponential increase in relaxation size. We introduce algorithms for polynomial substructure detection, cutting plane identification, cut filtering, and cut selection and embed the proposed implementation in BARON at every node in the branch-and-bound tree. A computational study including randomly generated problems of varying size and complexity demonstrates that the exploitation of underlying polynomial substructures significantly reduces computational time, branch-and-bound tree size, and required memory. 相似文献
89.
Sergiu Aizicovici Nikolaos S. Papageorgiou Vasile Staicu 《Journal of Differential Equations》2007,243(2):504-535
We consider a nonlinear periodic problem driven by the scalar p-Laplacian with a nonsmooth potential (hemivariational inequality). Using the degree theory for multivalued perturbations of (S)+-operators and the spectrum of a class of weighted eigenvalue problems for the scalar p-Laplacian, we prove the existence of at least three distinct nontrivial solutions, two of which have constant sign. 相似文献