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Viscosity dependence of the fluorescence lifetimes of cryptocyanine, pinacyanol and I, I'-diethyl-2,2'-dicarbocyanine iodide (DDI) has been studied by making relative quantum yield measurements in five solvents. It has also been established. by means of flash kinetic spectroscopy, that, in rigid solvents, φoF+φoIC ≈ 1 for all three dyes, where φoF and φoIC stand for the intrinsic quantum yields of fluorescence emission and internal conversion, respectively. Values of the intrisic rate constant of internal conversion are also presented. 相似文献
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We define mutation on coloured quivers associated to tilting objects in higher cluster categories. We show that this operation is compatible with the mutation operation on the tilting objects. This gives a combinatorial approach to tilting in higher cluster categories and especially an algorithm to determine the Gabriel quivers of tilting objects in such categories. 相似文献
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Kent‐Andre Mardal Bjørn Fredrik Nielsen Xing Cai Aslak Tveito 《Numerical Linear Algebra with Applications》2007,14(2):83-98
The electrical activity in the heart is governed by the bidomain equations. In this paper, we analyse an order optimal method for the algebraic equations arising from the discretization of this model. Our scheme is defined in terms of block Jacobi or block symmetric Gauss–Seidel preconditioners. Furthermore, each block in these methods is based on standard preconditioners for scalar elliptic or parabolic partial differential equations (PDEs). Such preconditioners can be realized in terms of multigrid or domain decomposition schemes, and are thus readily available by applying ‘off‐the‐shelves’ software. Finally, our theoretical findings are illuminated by a series of numerical experiments. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Aslak Bakke?Buan Yu?ZhouEmail authorView authors OrcID profile 《Algebras and Representation Theory》2018,21(1):181-194
We study possible values of the global dimension of endomorphism algebras of 2-term silting complexes. We show that for any algebra A whose global dimension gl.dim A ≤ 2 and any 2-term silting complex P in the bounded derived category D b (A) of A, the global dimension of \(\text {End}_{{D^b(A)}}(\mathbf {P})\) is at most 7. We also show that for each n > 2, there is an algebra A with gl.dim A = n such that D b (A) admits a 2-term silting complex P with \(\mathrm {gl. dim~}\text {End}_{{D^b(A)}}(\mathbf {P})\) infinite. 相似文献
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We generalise the notion of cluster structures from the work of Buan–Iyama–Reiten–Scott to include situations where the endomorphism rings of the clusters may have loops.
We show that in a Hom-finite 2-Calabi–Yau category, the set of maximal rigid objects satisfies these axioms whenever there
are no 2-cycles in the quivers of their endomorphism rings. We apply this result to the cluster category of a tube, and show
that this category forms a good model for the combinatorics of a type B cluster algebra. 相似文献
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Aslak Bakke Buan 《Advances in Mathematics》2006,204(2):572-618
We introduce a new category C, which we call the cluster category, obtained as a quotient of the bounded derived category D of the module category of a finite-dimensional hereditary algebra H over a field. We show that, in the simply laced Dynkin case, C can be regarded as a natural model for the combinatorics of the corresponding Fomin-Zelevinsky cluster algebra. In this model, the tilting objects correspond to the clusters of Fomin-Zelevinsky. Using approximation theory, we investigate the tilting theory of C, showing that it is more regular than that of the module category itself, and demonstrating an interesting link with the classification of self-injective algebras of finite representation type. This investigation also enables us to conjecture a generalisation of APR-tilting. 相似文献
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Bjørn Fredrik Nielsen Ola Skavhaug Aslak Tveito 《Journal of Computational and Applied Mathematics》2008
We derive and analyze a penalty method for solving American multi-asset option problems. A small, non-linear penalty term is added to the Black–Scholes equation. This approach gives a fixed solution domain, removing the free and moving boundary imposed by the early exercise feature of the contract. Explicit, implicit and semi-implicit finite difference schemes are derived, and in the case of independent assets, we prove that the approximate option prices satisfy some basic properties of the American option problem. Several numerical experiments are carried out in order to investigate the performance of the schemes. We give examples indicating that our results are sharp. Finally, the experiments indicate that in the case of correlated underlying assets, the same properties are valid as in the independent case. 相似文献
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Nielsen Bjorn Fredrik; Tveito Aslak; Hackbusch Wolfgang 《IMA Journal of Numerical Analysis》2009,29(1):24-42
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Aslak S. Hellestø Maryam Ghaffari Alex C. Hoffmann 《Journal of Dispersion Science and Technology》2017,38(5):611-620
In this study, we investigate numerically the shear-induced agglomeration of cohesive inertial particles in a simple shear flow. We conduct a series of numerical simulations by implementing a soft-sphere collision model. Post-processing tools are developed in-house to analyze the results of the simulations in terms of transient and terminal numbers of primary particles and agglomerates, magnitudes and distributions of agglomerate size, and fractal dimension as functions of the salient physical parameters. The obtained numerical results compared with existing transient models suggest that, as the system transitions from formation of duplets to larger agglomerates, in most cases the number of agglomerates in the system reveals clear maxima. The results also show evidence of agglomerate densification, as weaker agglomerates with lower fractal dimensions are broken up and stronger ones with higher fractal dimensions are formed. Furthermore, we found that a simple theoretical model proposed by, among others, Chimmili et al. is able to predict the temporal development of the agglomerate size properly. 相似文献