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1.
Yuri Bozhkov Antonio Carlos Gilli Martins 《Journal of Mathematical Analysis and Applications》2004,294(1):334-344
It is shown that a Lie point symmetry of the Lane-Emden system is a Noether symmetry if and only if its parameters belong to the critical hyperbola. 相似文献
2.
Abstract Archimedian spiral wave instabilities have been discovered in chemical [1] and biological systems [2]. We present here the first example of such an instability pattern, encountered in a physical medium [3]. This instability is directly observed by polarized optical microscopy, on a positive dielectric anisotropy smectic A sample with homeotropic organization between parallel glass slides. The arm of the spiral is probably constituted of a 180° Bloch wall, separating indistinguishable smectic domains, and incorporating progressively the helicity of the cholesteric phase, excluded from the smectic. 相似文献
3.
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5.
Marek L. Główka Zbigniew J. Kamiński Gastone Gilli Valerio Bertolasi 《Journal of chemical crystallography》1986,16(4):569-576
C14H17NO4 crystallizes in the monoclinic space groupP21/n (Z=4) witha=10.208(2),b=10.888(2),c=11.909(2) Å, and=90.89(2)°. The structure was solved by direct methods and refined by full-matrix LSQ to anR factor of 0.036. The 4-oxo-1,3-dioxane ring is in a slightly distorted O(1)-sofa conformation flattened at the C(4) end with the 5-isopropyl substituent in a pseudoaxial position and planar lactone group. The molecules form dimers by means of intermolecular N-HO(4) hydrogen bonds of 3.091(2) Å. The1H NMR spectrum of the title compound shows unusual features. 相似文献
6.
Anna Abatangelo Roberto Gilli Luciano Navarini Roberto Rizzo Stanley F. Osman William F. Fett 《Journal of carbohydrate chemistry》2013,32(4-5):583-598
Abstract The solution properties of the exopolysaccharide marginalan produced by Pseudomonas marginalis HT041B were investigated by means of low-angle laser light-scattering, capillary viscometry, and rheology. Potentiometric and viscosimetric data indicated the absence of a cooperative transition of the disorder-to-order type. The experimental findings obtained in dilute solution (Mark-Houwink coefficients, rigidity coefficient, characteristic ratio) suggested that the polymer behaves like a semiflexible chain which adopts a disordered conformation. The rheological behaviour of more concentrated marginalan solutions, as determined by means of both steady shear and oscillatory measurements, further confirmed the disordered conformational state of the polymer in solution. 相似文献
7.
Grégoire Fourrié Laurent Keirsbulck Larbi Labraga Patrick Gilliéron 《Experiments in fluids》2011,50(2):385-395
A passive flow control on a generic car model was experimentally studied. This control consists of a deflector placed on the
upper edge of the model rear window. The study was carried out in a wind tunnel at Reynolds numbers based on the model height
of 3.1 × 105 and 7.7 × 105. The flow was investigated via standard and stereoscopic particle image velocimetry, Kiel pressure probes and surface flow
visualization. The aerodynamic drag was measured using an external balance and calculated using a wake survey method. Drag
reductions up to 9% were obtained depending on the deflector angle. The deflector increases the separated region on the rear
window. The results show that when this separated region is wide enough, it disrupts the development of the counter-rotating
longitudinal vortices appearing on the lateral edges of the rear window. The current study suggests that flow control on such
geometries should consider all the flow structures that contribute to the model wake flow. 相似文献
8.
A side chain, mesomorphic polymer has been synthesized, starting from a commercial polybutadiene main chain. A preliminary X-ray diffraction study shows the influence of the degree of substitution and the spacer length on the interdigited SA layer thickness, particularly for strongly polar alkoxycyanobiphenyl mesogens. Some hypotheses are deduced about the particular odd-even effect observed with this backbone and on the conformation of the main and side chains. 相似文献
9.
An alleged weakness of heuristic optimisation methods is the stochastic character of their solutions: instead of finding the
truly optimal solution, they only provide a stochastic approximation of this optimum. In this paper we look into a particular
application, portfolio optimisation. We demonstrate that the randomness of the ‘optimal’ solution obtained from the algorithm
can be made so small that for all practical purposes it can be neglected. More importantly, we look at the relevance of the
remaining uncertainty in the out-of-sample period. The relationship between in-sample fit and out-of-sample performance is
not monotonous, but still, we observe that up to a point better solutions in-sample lead to better solutions out-of-sample.
Beyond this point there is no more cause for improving the solution any further: any in-sample improvement leads out-of-sample
only to financially meaningless improvements and unpredictable changes (noise) in performance. 相似文献
10.