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221.
Gianni Di Pillo Stefano Lucidi Laura Palagi 《Computational Optimization and Applications》1999,12(1-3):157-188
In this paper we describe a Newton-type algorithm model for solving smooth constrained optimization problems with nonlinear objective function, general linear constraints and bounded variables. The algorithm model is based on the definition of a continuously differentiable exact merit function that follows an exact penalty approach for the box constraints and an exact augmented Lagrangian approach for the general linear constraints. Under very mild assumptions and without requiring the strict complementarity assumption, the algorithm model produces a sequence of pairs
converging quadratically to a pair
where
satisfies the first order necessary conditions and
is a KKT multipliers vector associated to the linear constraints. As regards the behaviour of the sequence x
k alone, it is guaranteed that it converges at least superlinearly. At each iteration, the algorithm requires only the solution of a linear system that can be performed by means of conjugate gradient methods. Numerical experiments and comparison are reported. 相似文献
222.
In this paper we study the relationship between Constraint Programming (CP) and Shortest Path (SP) problems. In particular, we show that classical, multicriteria, partially ordered, and modality-based SP problems can be naturally modeled and solved within the Soft Constraint Logic Programming (SCLP) framework, where logic programming is coupled with soft constraints. In this way we provide this large class of SP problems with a high-level and declarative linguistic support whose semantics takes care of both finding the cost of the shortest path(s) and also of actually finding the path(s). On the other hand, some efficient algorithms for certain classes of SP problems can be exploited to provide some classes of SCLP programs with an efficient way to compute their semantics. 相似文献
223.
Alfredo De Rossi Gaetano Assanto Stefano Trillo William E. Torruellas 《Optics Communications》1998,150(1-6):390-398
We have identified a family of (2+1)D spatial solitary waves which can stably propagate in bulk media in the presence of coexisting diffraction, self-focusing Kerr and quadratic nonlinearities. In a conspicuous range of excitation conditions close to the stationary solutions, the emerging wavepackets are immune to the detrimental occurrence of filamentation and collapse, typical of pure Kerr media. The presence of a second-order contribution to the cubic nonlinear response is, therefore, able to prevent optical damage in applications relying on self-guidance. We show that the cross-phase modulation plays an important effect on stability. Our estimate shows that the effects of the cubic susceptibility cannot be neglected below a certain beam size in realistic crystals (e.g. KTP or similar). 相似文献
224.
D. Castiello G. Cimino S. De Rosa S. De Stefano G. Sodano 《Tetrahedron letters》1980,21(52):5047-5050
Two series of high molecular weight straight chain polyacetylenes (C46, C49 and C49, C52, C55) have been isolated from two marine invertebrates and partially characterized. 相似文献
225.
226.
G. Cimino S. De Stefano L. Minale R. Riccio K. Hirtosu J. Clardy 《Tetrahedron letters》1979,20(38):3619-3622
The structures of two unique sesterpenes, toxislylide A and B, have been deduced by chemical, spectral, and x-ray crystallographic studies. They are components of the sponge . 相似文献
227.
Francesco Paolo Di Stefano 《Annali dell'Universita di Ferrara》1978,24(1):25-35
Summary In this paper we define a new kind of blowing-up, as a functor from the category of real analytic spaces to the category of
real semianalytic spaces, in such a way that orientability is preserved. Then we prove an existence theorem for ?oriented
blowing-ups? of real analytic spaces.
Riassunto In questo articolo si definisce un nuovo tipo blowing-up, come un funtore dalla categoria degli spazi analitici reali alla categoria degli spazi semianalitici reali, in modo tale che l'orientabilità sia preservata. Si dimostra quindi un teorema di esistenza per blowing-ups orientati di spazi analitici reali.相似文献
228.
G. Cimino S. De Rosa S. De Stefano G. Scognamiglio G. Sodano 《Tetrahedron letters》1981,22(31):3013-3016
The title compound has been isolated from the Mediterranean gorgonian ; upon acetylation it affords a dehydration product and an androstane derivative. 相似文献
229.
The Pd-catalysed Suzuki homocoupling of boronic acids was successfully carried out in water under high-intensity ultrasound (HIU). Heterogeneous catalysis with Pd/C, facilitating work up and purification, could be used without adding phosphine ligands. Reaction rates and yields were strongly influenced by the oxidant employed; excellent results were obtained using either molecular oxygen or 3-bromo-4-hydroxycoumarin. 3-Arylation of the latter with the Suzuki procedure had failed, exclusively affording the homocoupling products, symmetric biaryls. Besides offering a number of operational advantages, the use of HIU broadens the field of application for the Suzuki reaction. 相似文献
230.
Besada P Mamedova L Thomas CJ Costanzi S Jacobson KA 《Organic & biomolecular chemistry》2005,3(10):2016-2025
Diketopiperazines (DKPs) are a common motif in various biologically active natural products, and hence they may be useful scaffolds for the rational design of receptor probes and therapeutic agents. We constructed a new bicyclic scaffold that combines a DKP bridged with a 10-membered ring. In this way we obtained a three-dimensional molecular skeleton, with several amendable sites that provide a starting point to design a new combinatorial library having diverse substituent groups. Structural variation is based upon the flexibility of alkylation of the nitrogen atoms of the DKP and on the side-chain olefin. We obtained a 10-membered secondary ring through a ring-closure metathesis reaction using the second generation Grubbs catalyst. Rings containing both O-ethers and S-ethers were compared. N-Alkyl or arylalkyl groups were introduced optionally at the two Nalpha-atoms. This is a general scheme that will allow us to test rings of varying sizes, linkages, and stereochemical parameters. The DKP derivatives were tested for activity in astrocytoma cells expressing receptors coupled to phospholipase C. Inhibitory effects were observed for signaling elicited by activation of human nucleotide P2Y receptors but not m3 muscarinic receptors. Compound 20 selectively inhibited calcium mobilization (IC50 value of 486 +/- 16 nM) and phosphoinositide turnover elicited by a selective P2Y1 receptor agonist, but this compound did not compete for binding of a radiolabeled nucleotide-competitive receptor antagonist. Therefore, the new class of DKP derivatives shows utility as pharmacological tools for P2Y receptors. 相似文献