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231.
St. R. Benedict A. E. Taylor V. Henriques und S. H. Gammeltoft 《Fresenius' Journal of Analytical Chemistry》1912,51(5):338-339
Ohne Zusammenfassung 相似文献
232.
233.
The problem of rerostering service schedules is very common in organizations that work shifts around the clock every day of the year with a set number of employees. Whenever one or more workers announce that they will not be able to attend to tasks previously assigned in their schedule, those tasks must be performed at the expense of alterations in the schedules of other workers. These changes should not conflict with the rules laid down by the administration and employment contracts and should affect the previous schedules as little as possible. This is a difficult real problem calling for a computational tool to cope with it easily. In the paper the issue is described in detail in the context of nurse scheduling and formulated as an integer multicommodity flow problem with additional constraints, in a multi-level acyclical network. A heuristic was implemented as a first approach to solving the problem. Subsequently the integer linear programming formulation of the multicommodity flow model and two linear relaxations were tested using CPLEX [2] optimizers. The computational results reported regard real instances from a Lisbon state hospital. Satisfactory rosters were obtained within acceptable computational times in all instances tested, either with the integer optimizer, or with the heuristic. This being so, refinements will be undertaken to embed these methodologies in a decision support system that may assist the head nurse in her daily rerostering activities. 相似文献
234.
To the memory of our colleague and friend Mario Raimondo
Received 7 July 1994; in final form 6 June 1995 相似文献
235.
Y. Zhang I. Matos M. A. N. D. A. Lemos Filipe Freire Teresa G. Nunes A. M. Botelho do Rego R. T. Henriques I. F. Fonseca M. M. Marques F. Lemos 《Journal of polymer science. Part A, Polymer chemistry》2003,41(23):3768-3780
Cr catalysts supported on silica, zeolite NaY, and charcoal were prepared with two different methods. They were characterized and examined in the polymerization of ethene. Cyclic voltammetry, electron spin resonance, X‐ray photoelectron spectroscopy and silicon‐29 magic‐angle spinning nuclear magnetic resonance spectroscopy were used to characterize them, demonstrating that Cr is not in a single oxidation state, that the distribution among the various oxidation states depends on the history of the sample, and that even for a single oxidation state a variety of different environments can occur. In the polymerization of ethene, the supported Cr catalysts exhibited activity values varying from 103 to 105 gPE · molCr?1 · [M]?1 · h?1, depending on the choice of the support and on the method by which the Cr is placed on it. Silica seemed to be the most efficient support for Cr for this reaction. However, the zeolite‐supported catalysts also showed reasonable activity values (Ap ? 104 units) and presented the advantage of having a strong interaction between the Cr and the support, which may prevent leaching of the cation into the surrounding environment. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3768–3780, 2003 相似文献
236.
Knowing what students bring to the classroom can and should influence how we teach them. This study is a review of the literature associated with secondary and postsecondary students' ideas about acids and bases. It was found that there are six types of alternate ideas about acids and bases that students hold. These are: macroscopic properties of acids and bases, microscopic properties of acids and bases, neutralization, acid strength, pH, and titration. 相似文献
237.
Dr. Luiz Fernando Lepre Prof. Margarida Costa Gomes Prof. Rômulo Augusto Ando 《Chemphyschem》2020,21(12):1230-1234
The sorption of CO2 is often used to modify the macroscopic properties of liquids and solids. In the particular case of ionic liquids, different from molecular liquids, the sorption of CO2 may not induce volume expansions due to the strong Coulombic interactions between the ions of the fluid. However, a considerable viscosity decrease has been systematically observed. In order to understand the mechanisms of properties modifications in ionic fluids, herein we used Raman spectroscopy to probe the effect of CO2 on the structure of ionic liquids. It is shown that CO2 perturbs the electrostatic interactions between cations and anions, thus inducing a change in the polar domain of ionic liquids. It is observed that ionic liquids having bulkier ions are more prone to be perturbed by CO2 in comparison to ionic liquids having smaller ions. These results reveal new means of controlling the electrostatic forces between the ions and contributes to the mechanistic understanding of the modification of the macroscopic properties of ionic liquids by CO2 sorption. 相似文献
238.
Pedro G. Henriques José Natário 《Journal of Optimization Theory and Applications》2012,154(2):500-524
We derive the covariant optimality conditions for rocket trajectories in general relativity, with and without a bound on the magnitude of the proper acceleration. The resulting theory is then applied to solve two specific problems: the minimum fuel consumption transfer between two galaxies in a FLRW model, and between two stable circular orbits in the Schwarzschild spacetime. 相似文献
239.
An abrupt transition from sinus rhythm to atrial fibrillation (AF) is common in patients with chronic heart failure (CHF). We propose a conceptual framework for viewing this malignant transition in terms of a type of sublimation marked by the switch from highly periodic sinus interbeat interval dynamics characteristic of CHF to a state of random disorganization with AF. Sublimation of physical substances involves an increase in entropy via heat transfer. In contrast, the disease‐related sublimation‐like behavior involves a loss of information content, associated decreases in cardiac bioenergetic capacity and in multiscale entropy. © 2016 Wiley Periodicals, Inc. Complexity 21: 24–32, 2016 相似文献
240.
Margarida Brito Ana Cristina Moreira Freitas 《Statistics & probability letters》2010,80(23-24):1835-1843
We consider the estimation of the tail-index for dependent random variables. We establish the consistency of the geometric-type estimator (Brito and Freitas, 2003) for stationary sequences satisfying general mixing conditions and derive a simplified condition, specially adapted for applications. 相似文献