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991.
We give a topological bound on the number of minimal models of a class of three-dimensional log smooth pairs of log general type. 相似文献
992.
993.
994.
A strengthened and generalized version of the standard Virtual Work Principle is shown to imply, in addition to bulk and boundary
balances, a one-to-one correspondence between surface and edge hypertractions and hyperstress fields in second-gradient continua.
When edge hypertractions are constitutively taken null, the hyperstress is shown to take the form it has for a relevant example
of second-gradient fluid-like material, referred to as a Navier–Stokes—α fluid. 相似文献
995.
996.
For a simple complex Lie algebra g we study the space of invariants A=(?g?⊗g?)g, which describes the isotypic component of type g in ?g?, as a module over the algebra of invariants (?g?)g. As main result we prove that A is a free module, of rank twice the rank of g, over the exterior algebra generated by all primitive invariants in (?g?)g, with the exception of the one of highest degree. 相似文献
997.
Paolo Bartolini 《Meccanica》1977,12(4):208-213
Summary It has been experimentally shown that in a uniform laminar free surface flow, the boundary conditions at the free surface cannot be represented by a simple non-shear condition.This statement is in particular supported by some experiments performed by the author on a high viscosity oil flow in a rectangular pipe. A surface shear viscosity may be introduced in order to characterize the behaviour of the free surface (Boussinesq).The velocity profile was measured along the axis of simmetry of the cross section. The results were in agreement with these of some numerical computations based on the above model. Similar agreement was not achieved on comparing the experimental and theoretical values obtained for the shape factor, a global parameter depending on the shape of the cross section.Such a disagreement cannot be due to experimental error and suggests that the above model is unable.
Sommario E' fatto sperimentalmente accertato che in un moto laminare uniforme le condizioni al contorno sulla superficie libera non possono essere rappresentate dalla semplice assenza di tensioni tangenziali superficiali. Una chiara conferma viene dalla attuale serie di misure eseguite su una condotta rettangolare percorsa da olio.Per caratterizzare il comportamento della superficie libera si introduce un coefficiente di viscosità tangenziale superficiale, nell'ipotesi di comportamento newtoniano della superficie stessa (Boussinesq).I confronti fra i nostri risultati sperimentali ed i risultati numerici derivanti da tale ipotesi mostrano una possibile concordanza nella distribuzione di velocità sull'asse di simmetria della condotta ma mettono in evidenza andamenti decisamente discordanti per quanto riguarda il comportamento di un coefficiente globale, variabile con la forma della sezione.Tale discordanza non è attribuibile ad errori di misura ed indica l'inadeguatezza di un modello basato sull'ipotesi di comportamento newtoniano della superficie libera.相似文献
998.
Carla Ciarcià Paolo Falsaperla Andrea Giacobbe Giuseppe Mulone 《Mathematical Methods in the Applied Sciences》2015,38(14):2937-2952
In this paper, we propose a mathematical model to study the dynamics of anorexic and bulimic populations. The model proposed takes into account, among other things, the effects of peers' influence, media influence, and education. We prove the existence of three possible equilibria that without media influences are disease‐free, bulimic‐endemic, and endemic. Neglecting media and education effects, we investigate the stability of such equilibria, and we prove that under the influence of media, only one of such equilibria persists and becomes a global attractor. Which of the three equilibria becomes global attractor depends on the other parameters. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
999.
An operator splitting approach for the interaction between a fluid and a multilayered poroelastic structure
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Martina Bukač Ivan Yotov Paolo Zunino 《Numerical Methods for Partial Differential Equations》2015,31(4):1054-1100
We develop a loosely coupled fluid‐structure interaction finite element solver based on the Lie operator splitting scheme. The scheme is applied to the interaction between an incompressible, viscous, Newtonian fluid, and a multilayered structure, which consists of a thin elastic layer and a thick poroelastic material. The thin layer is modeled using the linearly elastic Koiter membrane model, while the thick poroelastic layer is modeled as a Biot system. We prove a conditional stability of the scheme and derive error estimates. Theoretical results are supported with numerical examples. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 1054–1100, 2015 相似文献
1000.
An identity s = t is linear if each variable occurs at most once in each of the terms s and t. Let T be a tolerance relation of an algebra ${\mathcal{A}}$ in a variety defined by a set of linear identities. We prove that there exist an algebra ${\mathcal{B}}$ in the same variety and a congruence θ of ${\mathcal{B}}$ such that a homomorphism from ${\mathcal{B}}$ onto ${\mathcal{A}}$ maps θ onto T. 相似文献