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41.
We give a complete classification of tilting bundles over a weighted projective line of type (2, 3, 3). This yields another realization of the tame concealed algebras of type E6. 相似文献
42.
Daniel Espinoza 《Operations Research Letters》2010,38(6):559-563
Lifting, tilting and fractional programming, though seemingly different, reduce to a common optimization problem. This connection allows us to revisit key properties of these three problems on mixed integer linear sets. We introduce a simple common framework for these problems, and extend known results from each to the other two. 相似文献
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For a Dynkin quiver Γ with r vertices, a subset S of the vertices of Γ, and an r-tuple d = (d(1), d(2),…, d(r)) of positive integers, we define a “torus-restricted” representation (GS, R d (Γ)) in natural way. Here we put GS = G1 × G2 × … ×Gr, where each Gi is either SL(d(i)) or GL(d(i)) according to S containing i or not. In this paper, for a prescribed torus-restriction S, we give a necessary and sufficient condition on d that R d (Γ) has only finitely many GS-orbits. This can be paraphrased as a condition whether or not d is contained in a certain lattice spanned by positive roots of Γ. We also discuss the prehomogeneity of (GS, R d (Γ)). 相似文献
45.
An analytical model of a tilting pad bearing was developed based on the short bearing assumption with the turbulence effect
included. In order to determine its influence on the dynamic behavior of the rotor, this model was compared against one without
the turbulence effect through a simulation of a Jeffcott/Laval rotor supported by a couple of bearings. Both models were also
used to determine the influence of geometric parameters on tilting pad bearing making use of the aforementioned system at
different rotor speeds.
When analyzing the results, the parameters which presented the largest influence were: pad preload, number of segments, radial
clearance, pad position, and pad pivoting angle. As the pad moment of inertia and the pivoting distance have changed the shaft
motion only a few microns, their effects can be neglected. The bearing model with turbulent flow effect has generated higher
hydrodynamic forces when compared to the one without this effect, which remarks the importance of considering such phenomenon
during the analysis of the high speed hydrodynamic bearings. 相似文献
46.
D. Naderi M. Sadeghi-Mehr 《Communications in Nonlinear Science & Numerical Simulation》2012,17(2):1055-1064
Human body uses different strategies to maintain its stability and these strategies vary from fixed-foot strategies to strategies which foot is moved in order to increase the support base. Tilting movement of foot is one type of the perturbations usually is exposed to human body. In the presence of such perturbations human body must employ appropriate reactions to prevent threats like falling. But it is not clear that how human body maintains its stability by central nervous system (CNS). At present study it is tried that by presenting a musculoskeletal model of human lower extremity with four links, three degrees of freedom (DOF) and eight skeletal muscles, the level of muscle activations causes the maintenance of stability, be investigated. Using forward dynamics solution, leads to a more general problem, rather than inverse dynamics. Hence, forward dynamics solution by forward optimization has been used for solving this highly nonlinear problem. To this end, first the system’s equations of motion has been derived using lagrangian dynamics. Eight Hill-type muscles as actuators of the system were modeled. Because determination of muscle forces considering their number is an undetermined problem, optimization of an appropriate goal function should be practiced. For optimization problem, the characteristics of genetic algorithms as a method based on direct search, and the direct collocation method, has been profited. Also by considering requirements of problem, some constraints such as conservation of model stability are entered into optimization procedure. Finally to investigate validation of model, the results from optimization and experimental data are compared and good agreements are obtained. 相似文献
47.
Anton V. Doroshin 《Communications in Nonlinear Science & Numerical Simulation》2012,17(3):1460-1474
Heteroclinic dynamics of a free coaxial bodies system and dual-spin spacecraft is examined. New analytical solutions for heteroclinic orbits, corresponded to the polhodes-separatrices in the space of the angular moment components, are obtained. On the base of these analytical heteroclinic solutions analysis of possibility of the system motion chaotization with the help of Melnikov method is conducted. The analysis shows the polhode-separatrix-orbit splitting at presence of small harmonical perturbation torques between the coaxial bodies. The separatrix splitting generates the chaotic layer near the unperturbed separatrix region. This fact proves possibility of realization of non-regular dynamics and chaotic tilting motion of the dual-spin spacecraft. 相似文献
48.
This note investigates the modules over the endomorphism algebras of maximal rigid objects in 2-Calabi-Yau triangulated categories. We study the possible complements for almost complete tilting modules. Combining with Happel's theorem, we show that the possible exchange sequences for tilting modules over such algebras are induced by the exchange triangles for maximal rigid objects in the corresponding 2-Calabi-Yau triangulated categories. For the modules of infinite projective dimension, we generalize a recent result by Beaudet–Brüstle–Todorov for cluster-tilted algebras. 相似文献
49.
M. Fazeel Anwar 《代数通讯》2013,41(5):1503-1509
Let G be a semisimple, simply connected linear algebraic group over an algebraically closed field k of characteristic p > 0. In a recent article [6], Doty introduces the notion of r-minuscule weight and exhibits a tensor product factorization of a corresponding tilting module under the assumption p ≥ 2h ? 2, where h is the Coxeter number. We remove this restriction and consider some variations involving the more general notion of (p, r)-minuscule weights. 相似文献
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