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排序方式: 共有106条查询结果,搜索用时 31 毫秒
21.
We study the forward problem of the magnetic Schrödinger operator with potentials that have a strong singularity at the origin. We obtain new resolvent estimates and give some applications on the spectral measure and on the solutions of the associated evolution problem. 相似文献
22.
Ainara Barriola José I. Miranda Miren Ostra Carlos Ubide 《Analytical and bioanalytical chemistry》2010,398(2):1085-1094
The use of proton nuclear magnetic resonance (1H-NMR) for the quantification of additives in an electrolytic Zn bath is reported. A simple and quick method is described
that does not need any prior sample preparation. Contrary to other analytical methods, the three additives in the bath, benzylidene
acetone (BDA), benzoic acid (BA) and poly(ethylene glycol) (PE400), can be quantified. Two calibration methods were tried:
integration of NMR signals with the use of an internal standard and partial least squares (PLS) regression applied to the
characteristic NMR peaks. Both methods are compared and the univariate method was preferred because of simplicity, accuracy
and precision. The following limits of detection were found: 0.30 g L−1 BA, 0.08 g L−1 BDA and 0.7 g L−1 PE400 with dynamic ranges of at least 1.0–6.0, 0.1–0.6 and 3.0–18.0 g L−1 respectively. Those concentration ranges are suitable to follow the concentration of additives in the bath in real time.
1H-NMR spectra provide evidence for the BDA degradation pattern. 相似文献
23.
Mira Petrovic Marinella Farré Miren Lopez de Alda Sandra Perez Cristina Postigo Marianne Köck Jelena Radjenovic Merixell Gros Damia Barcelo 《Journal of chromatography. A》2010,1217(25):4004-4017
An overview of liquid chromatography–mass spectrometry methods used for the determination of trace organic contaminants in environmental samples is presented. Among the organic contaminants the focus is given on five groups of emerging contaminants that raised most concern as environmental contaminants and therefore attracted attention of a research community: pharmaceuticals, drugs of abuse, polar pesticides, perfluorinated compounds and nanoparticles. Various aspects of current LC–MS methodology, using tandem and hybrid MS instruments, including sample preparation, are discussed. 相似文献
24.
Biprobabilistic values for bicooperative games 总被引:1,自引:0,他引:1
The present paper introduces bicooperative games and develops some general values on the vector space of these games. First, we define biprobabilistic values for bicooperative games and observe in detail the axioms that characterize such values. Following the work of Weber [R.J. Weber, Probabilistic values for games, in: A.E. Roth (Ed.), The Shapley Value: Essays in Honor of Lloyd S. Shapley Cambridge University Press, Cambridge, 1988, pp. 101–119], these axioms are sequentially introduced observing the repercussions they have on the value expression. Moreover, compatible-order values are introduced and there is shown the relationship between these values and efficient values such that their components are biprobabilistic values. 相似文献
25.
J. M. Bilbao J. R. Fernández N. Jiménez J. J. López 《Annals of Operations Research》2008,158(1):99-115
The aim of the present paper is to study a one-point solution concept for bicooperative games. For these games introduced
by Bilbao (Cooperative Games on Combinatorial Structures, 2000) , we define a one-point solution called the Shapley value, since this value can be interpreted in a similar way to the classical
Shapley value for cooperative games. The main result of the paper is an axiomatic characterization of this value. 相似文献
26.
Katiuska Alexandrino Ángela Millera Rafael Bilbao María U. Alzueta 《Flow, Turbulence and Combustion》2016,96(2):343-362
2-methylfuran (2-MF) has become of interest as biofuel because of its properties and the improvement in its production method, and also because it is an important intermediate in the conversion of 2,5-dimethylfuran. In this research, an experimental and kinetic modelling study of the oxidation of 2-MF in the absence and presence of NO has been performed in an atmospheric pressure laboratory installation. The experiments were performed in a flow reactor and covered the temperature range from 800 to 1400 K, for mixtures from very fuel-rich to very fuel-lean, highly diluted in nitrogen. The inlet 2-MF concentration was 100 ppm. In the experiments in the presence of NO, the inlet NO concentration was 900 ppm. An interpretation of the experimental results was performed through a gas-phase chemical kinetic model. A reasonable agreement between the experimental trends and the modelling data is obtained. The results of the concentration profile of 2-MF as a function of temperature indicate that, both in the absence and in the presence of NO, the onset of 2-MF consumption is shifted to lower temperatures only under fuel-lean and very fuel-lean conditions. Furthermore, under these conditions the presence of NO also shifts the onset of 2-MF consumption to lower temperatures. The effect of the 2-MF presence on the NO reduction varies with the oxygen concentration. It is seen that under very fuel-rich and stoichiometric conditions NO is reduced basically by reburn reactions, while under fuel-lean and very fuel-lean conditions, the NO-NO2 interconversion appears to be dominant. 相似文献
27.
M Arenas A Bilbao R Caballero T Gómez M V Rodríguez F Ruiz 《The Journal of the Operational Research Society》2002,53(4):387-396
In this paper, a Goal Programming model is developed in order to study the possibility of decreasing the length of stay on the waiting list of a hospital that belongs to the Spanish Health Service. First, a problem is solved to determine the optimal planning for one year, so as to make the maximum waiting time decrease to six months (at present, some operations have a waiting list of more than a year). Afterwards, two other problems are solved in order to determine the impact that a further reduction of the waiting time (four months) would have on the requirements of extra resources for the hospital. The particular problem for the Trauma service is described in detail, but global results are shown and commented. 相似文献
28.
Two‐Dimensional Nanoporous Networks Formed by Liquid‐to‐Solid Transfer of Hydrogen‐Bonded Macrocycles Built from DNA Bases
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Nerea Bilbao Iris Destoop Prof. Steven De Feyter Dr. David González‐Rodríguez 《Angewandte Chemie (International ed. in English)》2016,55(2):659-663
We present an approach that makes use of DNA base pairing to produce hydrogen‐bonded macrocycles whose supramolecular structure can be transferred from solution to a solid substrate. A hierarchical assembly process ultimately leads to two‐dimensional nanostructured porous networks that are able to host size‐complementary guests. 相似文献
29.
Joana Larreta Urdax Bilbao Asier Vallejo Aresatz Usobiaga Gorka Arana Olatz Zuloaga 《Chromatographia》2008,67(1-2):93-99
In this work the simultaneous purge-and-trap (P&;T) preconcentration of volatile fatty acids (acetic acid, propanoic acid, butanoic acid, iso-butanoic acid, pentanoic acid, iso-pentanoic acid, hexanoic acid and heptanoic acid), phenols (phenol, 4-methylphenol and 4-ethylphenol) and indoles (indole and 3-methylindole) from cow slurries was carried out in order to quantify them by gas chromatography flame ionisation detection (GC–FID). The optimisation of the preconcentration was performed using spiked cow slurries and the variables studied were the nature of the trap, the purge and heating time and the amount of inert salt (NaCl) added. Other parameters such as purge flow, sample volume, desorption time and temperature and baking time and temperature were kept constant. The first variable studied was the nature of the preconcentration trap. Four different commercially available traps (Vocarb 4000, Vocarb 3000, BTEXTRAP and Tenax/silica gel/carbon) were studied and Vocarb 3000 gave best results. Once the optimum trap was chosen, appearance of possible memory peaks were studied and significant signals were observed for 4-methylphenol, 4-ethylphenol, indole and 3-methylindole. In order to improve the blanks after each analysis the following actions were taken: (1) the needle sparger was located in the headspace of the sample and (2) all the replaceable parts of the P&;T (sample tube, needle sparger, Teflon ferrules, nuts, etc.) were washed, sonicated in acetone for 15 min and dried in an oven at 350 °C. Once the blank problems were minimised, the remaining variables (purge and heating time and the amount of NaCl) were optimised using the MultiSimplex® program, which enabled the study of several variables and responses simultaneously. Optimum conditions for the simultaneous preconcentration were obtained after 24 experiments and the final optimised preconcentration conditions were as follows: 0.4 g of NaCl were added to 10 mL sample which was heated at 80 °C for 10 min and purged for 20 min while the Vocarb 3000 trap remained at room temperature. Once the purge step was over, the trap was desorbed at 250 °C for 6 min and baked at 260 °C for 10 min. After the optimisation of the P&;T based preconcentration, the precision (within and among days), accuracy and detection limits of the method were studied. 相似文献
30.
Terrado M Kuster M Raldúa D Lopez de Alda M Barceló D Tauler R 《Analytical and bioanalytical chemistry》2007,387(4):1479-1488
Data sets obtained from quantitative analysis of seventeen pesticides in water samples from a network of irrigation and drainage
channels in the Ebro river delta (Catalonia, NE Spain) have been analysed by chemometric and geostatistical methods. Samples
were taken at fourteen locations during the main rice-growing season, from May to August 2005. Principal-component analysis
enabled investigation of the spatial and temporal distribution of the main pollution patterns caused by application of pesticides
in the region under study. A first pesticide-contamination pattern from the Ebro river was differentiated from a second more
specific pattern from the water-drainage channels of the delta, collected from the rice fields. The seasonal peak in this
more specific rice pesticide source was observed in July. Coupling the results from chemometric data analysis with use of
geostatistical methods was shown to be a useful procedure for discovery of the most significant spatial and monthly variations
of the main pesticide-contamination patterns, taking into account the particular geographical structure of the area under
study. 相似文献