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941.
Ana R. Díaz-Marrero Gina Porras Luís D'Croz Manuel Lorenzo J. Darias 《Tetrahedron》2009,65(31):6029-3319
The cembranoid 1 and the furanocembranolides 2-4 along with the known pukalide were isolated from Leptogorgia sp. and their structures determined spectroscopically. The 1,4-diketo-cembranoid 1 follows an oxidation pattern of C-18 that reinforces the concept of oxidation profile of C-18 as taxonomical marker for octocorals. The co-occurrence within a species of furanocembranolide/1,4-diketo-cembranoid congeners 1/2-4 raises the question about which one is the biogenetic precursor. A biogenetic pathway is proposed. 相似文献
942.
Cristina M. Cirre Manuel Berenguel Loreto Valenzuela Ryszard Klempous 《European Journal of Operational Research》2009
This paper describes the design and implementation of two-layer hierarchical control strategies for a distributed solar collector field, as well as representative experimental results in which the benefits of using this approach compared to current operations are highlighted. The upper layer of the hierarchical strategy was implemented using two different approaches, fuzzy logic and physical model-based optimization. Both calculate the optimal plant operating point automatically, taking operating constraints into account while maximizing profit from selling the electricity generated. The lower layer uses as setpoint the output generated by the upper layer to automatically track the operating point despite any disturbances affecting the plant. 相似文献
943.
Power flow calculations are one of the most important computational tools for planning and operating electric power systems. After the stabilization of the deterministic power flow calculation methods, the need to capture uncertainty in load definition lead first to the development of probabilistic models, and later to fuzzy approaches able to deal with qualitative declarations and other non-probabilistic information about the value of the loads. Present fuzzy power flow (FPF) calculations use typically incremental techniques, in order to obtain a good approximation of the fuzzy state variables. However, these models and procedures are not entirely satisfactory for the evaluation of the adequacy of the electric transmission system, since they are not completely symmetric. In this paper, we show how to perform the detailed calculation of the state variables of the FPF problem in an exact and symmetrical way, by means of solving multiple optimization problems. The procedure is illustrated using the IEEE 118 test system. 相似文献
944.
Stephan Dahlke Massimo Fornasier Miriam Primbs Thorsten Raasch Manuel Werner 《Numerical Methods for Partial Differential Equations》2009,25(6):1366-1401
This article is concerned with adaptive numerical frame methods for elliptic operator equations. We show how specific noncanonical frame expansions on domains can be constructed. Moreover, we study the approximation order of best n‐term frame approximation, which serves as the benchmark for the performance of adaptive schemes. We also discuss numerical experiments for second order elliptic boundary value problems in polygonal domains where the discretization is based on recent constructions of boundary adapted wavelet bases on the interval. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009 相似文献
945.
There is a well-known correspondence between infinite trees and ultrametric spaces which can be interpreted as an equivalence
of categories and comes from considering the end space of the tree. In this equivalence, uniformly continuous maps between
the end spaces are translated to some classes of coarse maps (or even classes of metrically proper Lipschitz maps) between
the trees. 相似文献
946.
Manuel Pinto 《Mathematical and Computer Modelling》2009,49(9-10):1750-1758
We consider nonlinear differential equations with piecewise constant arguments in the general case. This is based in the study of an equivalent integral equation, and in a solution of an integral inequality of Gronwall type. We establish the existence, uniqueness and the asymptotic behavior of the solutions of the equations. Equivalences, including unbounded solutions, with simpler equations are obtained. 相似文献
947.
Exponentiable functors between quantaloid-enriched categories are characterized in elementary terms. The proof goes as follows:
the elementary conditions on a given functor translate into existence statements for certain adjoints that obey some lax commutativity;
this, in turn, is precisely what is needed to prove the existence of partial products with that functor; so that the functor’s
exponentiability follows from the works of Niefield (J. Pure Appl. Algebra 23:147–167, 1982) and Dyckhoff and Tholen (J. Pure Appl. Algebra 49:103–116, 1987).
相似文献
948.
Micael Gallego Abraham Duarte Manuel Laguna Rafael Martí 《Computational Optimization and Applications》2009,44(3):411-426
The maximum diversity problem presents a challenge to solution methods based on heuristic optimization. We undertake the development
of hybrid procedures within the scatter search framework with the goal of uncovering the most effective designs to tackle
this difficult but important problem. Our research revealed the effectiveness of adding simple memory structures (based on
recency and frequency) to key scatter search mechanisms. Our extensive experiments and related statistical tests show that
the most effective scatter search variant outperforms state-of-the-art methods. 相似文献
949.
Manuel Ritoré 《Calculus of Variations and Partial Differential Equations》2009,34(2):179-192
We give new examples of entire area-minimizing t-graphs in the sub-Riemannian Heisenberg group . They are locally Lipschitz in Euclidean sense. Some regular examples have prescribed singular set consisting of either a
horizontal line or a finite number of horizontal halflines extending from a given point. Amongst them, a large family of area-minimizing
cones is obtained.
Research supported by MEC-Feder grant MTM2007-61919. 相似文献
950.
We study when the stable category ${\mathcal A}/\langle{\mathcal T}\rangleWe study when the stable category A/áT?{\mathcal A}/\langle{\mathcal T}\rangle of an abelian category A{\mathcal A} modulo a full additive subcategory T{\mathcal T} is balanced and, in case T{\mathcal T} is functorially finite in A{\mathcal A}, we study a weak version of balance for A/áT?{\mathcal A}/\langle{\mathcal T}\rangle. Precise necessary and sufficient conditions are given in case T{\mathcal T} is either a Serre class or a class consisting of projective objects. The results in this second case apply very neatly to
(generalizations of) hereditary abelian categories. 相似文献