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排序方式: 共有214条查询结果,搜索用时 198 毫秒
21.
Between the most mature interdisciplinary areas, computational fluid dynamics (CFD) comes recently into focus. In the same time, it becomes more and more difficult to contribute fundamental research to it. However, although it remains unpredictable how CFD develops, it is part of what makes it an exciting and attractive discipline.This paper aims to exhibit some part of recent work in CFD. It concerns the qualitative approach of the turbulent behaviour of a mixing flow in an excitable media. Studying a mixing for a flow implies the analysis of successive stretching and folding phenomena for its particles, the influence of parameters and initial conditions. In the previous works, the study of the 3D non-periodic models exhibited a quite complicated behaviour. In agreement with experiments, there were involved some significant events, the so-called “rare events”. The variation of parameters had a great influence on the length and surface deformations. The experiments were realized with a special vortex installation, it was used a well-known aquatic algae as biologic material, and the water as basic fluid.In the paper there are presented some features of a qualitative comparative analysis of the model associated to the vortex flow technology. In the computational analysis there were used the fast analysis tools of MAPLE11 soft, in order to check the “rare events” and to complete the statistical analysis of the behaviour of the model. 相似文献
22.
Adela Capătă 《Journal of Global Optimization》2011,51(4):657-675
In this paper, we present sufficient conditions for the existence of Henig efficient solutions, superefficient solutions and
Henig globally efficient solutions of a vector equilibrium problem in topological vector spaces, using a well-known separation
theorem in infinite dimensional spaces. As an application, using a scalarization technique, existence results for proper efficient
solutions of generalized vector variational inequalities are given. 相似文献
23.
Benjamin Richard Frédéric Ragueneau Lucas Adelaïde Christian Cremona 《European Journal of Mechanics - A/Solids》2011,30(6):950-961
Taking into account the specific behavior of the steel/concrete interface is of primary importance to predict properly the structural response of RC structures. Several constitutive models have been proposed in the literature within the framework of nonlinear finite element method (2D and 3D). Such approaches usually lead to high computational costs due to the large number of degrees of freedom. In the present paper, a multifiber-based model including the steel/concrete interface behavior is proposed. Despite the fact that the kinematics of the multi-fiber approach is based on the theory of beams, this simplified strategy accounts for local phenomena such as the relative sliding between concrete and steel. Furthermore, this steel/concrete interface constitutive model can be extended to model the loss of bond properties due to corrosion. The numerical implementation aspects are described and local responses at the Gauss point level are exposed in the cases of monotonic loadings with and without corrosion. The efficiency and the reliability of the proposed approach are tested on structural case studies which highlight a good agreement between numerical and experimental results. This multifiber-based model provides a pertinent tool for the engineers concerns with the structural assessment of degraded reinforced concrete structures. 相似文献
24.
In this paper, we extend some results of D.Dolzan on finite rings to profinite rings, a complete classification of profinite
commutative rings with a monothetic group of units is given. We also prove the metrizability of commutative profinite rings
with monothetic group of units and without nonzero Boolean ideals. Using a property of Mersenne numbers, we construct a family
of power 2ℵ0 commutative non-isomorphic profinite semiprimitive rings with monothetic group of units. 相似文献
25.
P. Bermejo-Barrera C. Pita-Calvo A. Bermejo-Barrera F. Bermejo-Martinez 《Fresenius' Journal of Analytical Chemistry》1991,340(4):265-268
Summary Various modifiers were investigated for the molybdenum determination in human serum samples by electrothermal atomization atomic absorption spectrometry. Methods with magnesium nitrate, barium difluoride, nitric acid, palladium-magnesium nitrate and palladium-hydroxylamine were studied by introducing the serum samples directly into the graphite furnace with 0.2% triton X-100. The mineralisation and atomization curves, the amount of modifier and the calibration and addition graphs were studied in all instances. The characteristic masses were 18, 22, 17, 12 and 13 pg of molybdenum for magnesium nitrate, barium difluoride, nitric acid, palladium-magnesium nitrate and palladium-hydroxylamine, respectively. The precision, accuracy and interferences of the methods were also investigated. 相似文献
26.
Adela Kotočová 《Monatshefte für Chemie / Chemical Monthly》1992,123(8-9):709-711
Summary The half-wave potentials of the redox system [Co(en)3]3+/[Co(en)3]2+ have been influenced by the tetraalkylamonium cation of the supporting electrolyte used. This was explained with the specific interactions (solvation) of the tetraalkylamonium ion with the nonaqueous solvent.
Einfluß von Tetraalkylammoniumionen auf die Struktur nichtwäßriger Lösungsmittel (Kurze Mitt.)
Zusammenfassung Das Halbwellenpotential des Redoxsystems [Co(en)3]3+/[Co(en)3]2+ wird von Tetraalkylammonium-Ionen des Stützelektrolyten beeinflußt. Dies wird durch die spezifischen Wechselwirkungen (Solvatation) der Ionen mit dem nichtwäßrigen Lösungsmittel erklärt.相似文献
27.
Resonance non-positone and non-isotone problems for first order differential systems subjected to non-local boundary conditions are reduced to the non-resonance positone and isotone case by changes of variables. This allows us to prove the existence of multiple positive solutions. The theory is illustrated by two examples for which three positive numerical solutions are obtained using the Mathematica shooting program. 相似文献
28.
Ultrasound measurements of cavitation bubble radius for femtosecond laser-induced breakdown in water
A recently developed ultrasound technique is evaluated by measuring the behavior of a cavitation bubble that is induced in water by a femtosecond laser pulse. The passive acoustic emission during optical breakdown is used to estimate the location of the cavitation bubble's origin. In turn, the position of the bubble wall is defined based on the active ultrasonic pulse-echo signal. The results suggest that the developed ultrasound technique can be used for quantitative measurements of femtosecond laser-induced microbubbles. 相似文献
29.
Correlations involving bond lengths and bond angles in the molecular structure of the Cu4OCl6(4-Mepy)4 complex (4-Mepy = 4-methylpyridine) with four symmetrically independent molecules present in the unit cell showed that the
donor-acceptor behavior involving the π-back donation into the pyridine rings of the 4-Mepy ligands is most effectively stimulated by a suitable orientation of the
pyridine rings in the trigonal bipyramidal geometry. The pyridine ring planes are almost in parallel orientation with one
of the three Cu-Cl bonds. The bond lengths of these Cu-Cl bonds are in a significant linear correlation with the Cu-N bond
lengths and the bonds lengths of the pyridine rings. The pyridine rings orientation is affected by distortion of the trigonal
bipyramidal geometry to tetragonal pyramidal coordination, by out-of plane pyridine rings deviation and in-plane pyridine
rings tilting, by puckering of the pyridine rings and by the effects of the methyl groups. The pyridine rings in at least
seven of the sixteen trigonal bipyramidal coordinations exhibit an orientation supporting the π-back bonding between the Cu(II) atoms and the pyridine rings. 相似文献