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1.
Pascal Noble 《Archive for Rational Mechanics and Analysis》2007,186(1):53-76
The phenomenon of roll-waves occurs when shallow water flows down open inclined channels. This flow is described by the Saint
Venant’s equations with a friction term due to Chezy. In the case of a flat bottom, their existence (as entropic and periodic
travelling waves) follows from a classical work due to DRESSLER [6].
The aim of this paper is to prove the existence of roll-waves when the bottom is modulated by a small periodic perturbation.
Following JIN and KATSOULAKIS [15], we first compute a Burgers-type equation which possesses “pulsating” roll-waves (the wave
speed oscillates around an average velocity). We prove, in a mathematically rigorous fashion, the existence of these solutions. 相似文献
2.
Tracy Noble Ricardo Nemirovsky Cara Dimattia Tracey Wright 《International Journal of Computers for Mathematical Learning》2004,9(2):109-167
In this article, we will describe the results of a study of 6th grade students learning about the mathematics of change. The
students in this study worked with software environments for the computer and the graphing calculator that included a simulation
of a moving elevator, linked to a graph of its velocity vs. time. We will describe how the students and their teacher negotiated
the mathematical meanings of these representations, in interaction with the software and other representational tools available
in the classroom. The class developed ways of selectively attending to specific features of stacks of centimeter cubes, hand-drawn
graphs, and graphs (labeled velocity vs. time) on the computer screen. In addition, the class became adept at imagining the
motions that corresponded to various velocity vs. time graphs. In this article, we describe this development as a process
of learning to see mathematical representations of motion. The main question this article addresses is: How do students learn
to see mathematical representations in ways that are consistent with the discipline of mathematics?
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
I.J. Galpin F.E. Hancock B.K. Handa A.G. Jackson G.W. Kenner P. McDowell P. Noble R. Ramage 《Tetrahedron》1981,37(17):3043-3050
The previously synthesised (1–37), (38–75), (76–93), (94–104), (105–117) and (118–129) fragments of the analogue were combined making extensive use of the DCCI/HONSu method. The final coupling involved the (1–75) and (76–129) sub-fragments. Aggregation of the latter fragment caused problems in purification by routine gel filtration methods employing Enzacryl K2 or Sephadex LH60. The fully protected (1–129) product was partially purified by washing, then deprotectcd and purified by gel filtration and ion exchange chromatography. Satisfactory removal of the acetamidomethyl group used for cysteine protection could not be achieved. 相似文献
4.
5.
The Stark splittings and rotational asymmetry splittings of a number of levels of the Ã1A″ excited state of HNO have been measured using the sub-Doppler technique of optical—optical double resonance, μa is found to be 1.08 ± 0.01 D for the 100 vibronic state, and 1.05 ± 0.01 D for the 020 vibronic state. These values are to be compared with a recently determined ground state value of μa = 0.996 D. The asymmetry splittings of some of the levels studied are considerably larger than predicted from the known rotational constants, indicating minor rotational perturbations. 相似文献
6.
Thirty-six listeners localized continuous filtered noise bursts centered on 2.3 or 8.3 kHz under normal listening conditions or while wearing earmuffs. The noise bursts were from any one of 20 loudspeakers, 18 degrees apart, visible to the listeners, and arranged in the horizontal and vertical planes. Listeners were free to move, while remaining seated, throughout all trials. The noise bursts were terminated by the listeners. Measures of accuracy and latency showed that earmuff listening had a significant effect whereas, overall, signal frequency had no significant effect. There was, however, an apparent downward shift of the 2.3-kHz signals presented above the midline in the vertical plane. Analysis of video records of listeners' behavior revealed a strong tendency for initial orientation by head or eye movement to correlate with final response, even when both were inaccurate. The paradigm adopted in this latter aspect of the study illustrates an "ecological" approach to the study of auditory phenomena. 相似文献
7.
Noble PF Cayre OJ Alargova RG Velev OD Paunov VN 《Journal of the American Chemical Society》2004,126(26):8092-8093
Novel colloidosome microcapsules with aqueous gel cores and integral shells of rodlike polymeric particles have been prepared and characterized. The synthesis is based on templating water-in-oil emulsions stabilized by rodlike particles followed by gelling of the aqueous phase, dissolution of the oil phase in ethanol, and redispersion of the obtained colloidosome capsules in water. Such capsules may find applications as vehicles for delivery and controlled release of drugs, cosmetics, and food supplements. 相似文献
8.
9.
Journal of Radioanalytical and Nuclear Chemistry - 相似文献
10.
Radu Vacaronceanu Gheorghe Ilia Ludovic Kurunczi Petria Şoimu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The study of GC separation of 2-chloroethylphosphonic acid di-n-alkyl (1–5 C atoms) esters (synthesised by us) on silicone stationary phases (OV-1, OV-17, OV-225) revealed a deviation from the expected linear dependence of retention indexes (RI) versus the number of C atoms of the alkyl chain: the first member of the series presents stronger retention than one can expect. This anomalous behaviour was observed especially on polar stationary phase (OV-225, see Figure l), and was emphasised with the increase of the column temperature. In an attempt to rationalise the above mentioned facts, we tried to relate the RI values to a global polarity parameter: the dipole moment, μ. The μ values for ClC2H4P(O)(OR)2 were calculated by a method described in [1] (tested by comparing the calculated μ values with experimental ones for alkyl phosphonic acid dialkylesters), using molecular mechanics (COSMIC package) in the search of the conformational space, AM1 method (MOPAC 6.0) for the μ values of the conformers, and Boltzmann distribution for the global value (see Table I). At low temperature, the μ values are not related to the Kovats indexes. Those calculated at 200°C (column temperature range) demonstrate that, indeed, only in the case of the methyl derivative, the temperature rising led to a higher μ (enhanced population of the more polar conformers: ac position for the C-Ethyl group - ac for the Cl, μ ≈ 27 D, or ±ap for one R, μ ≈ 3.8 ÷ 4.3 D). It can be concluded that dipole-dipole forces contribute to the separation process of the first members of the series. 相似文献