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81.
82.
Giacomo Bonanno 《Mathematical Logic Quarterly》1996,42(1):305-311
We investigate an axiomatization of the notion of common belief (knowledge) that makes use of no rules of inference (apart from Modus Ponens and Necessitation) and highlight the property of the set of accessibility relations that characterizes each axiom. Mathematics Subject Classification: 03B45, 68T25. 相似文献
83.
The representations of the Riemann and the Weyl tensors of a four-dimensional Riemannian manifold through covariant derivatives of third-order potentials are examined in detail. The Weyl tensor always admits a completely general representation whereas the Riemann tensor does not. Nevertheless there exists a class of Riemannian manifolds whose Riemann tensors may be calculated in terms of potentials; in this connection, specific examples are exhibited explicitly. The possibility of introducing gauges on the potentials is reexamined in connection with the previous result. New properties of the representations are also discussed. 相似文献
84.
One-magnon Raman scattering has been observed in the metamagnets CoCl2 and FeCl2. The k = 0 magnon energies are 16 ± 1 cm-1 at 21 K and 16.4 ± 0.4 cm-1 at 12 K, respectively and these values are in good agreement with previous AFMR and neutron scattering results. A search for two-magnon scattering in both compounds was unsuccessful, largely because of masking from nearby first-order phonons and a weak temperature dependent broad band at 140 cm-1 in CoCl2, which is assigned to two-phonon scattering from acoustic phonons. 相似文献
85.
86.
A.R. Fert P. Carrara M.C. Lanusse G. Mischler J.P. Redoules 《Journal of Physics and Chemistry of Solids》1973,34(2):223-230
In a magnetic field parallel to the magnetization axis of an antiferromagnetic Fe Br2 single crystal, a caracteristic metamagnetic behaviour is observed. The transition from an antiferromagnetic phase to a paramagnetic phase is studied by help of magnetization measurements in a steady field (H < 60 kOe). The measurement precision has allowed a detailed study of the magnetization isotherms, caracteristic of a first order magnetization phase transition (T < Tc = 4, 7 K) and of a second order phase transition (Tc < T < TN = 14, 2 K).We have observed an original phase diagram. In a certain temperature and field range, the ordered phase is stable on the high temperature side of the transition point. Some theoretical studies in an Ising model, or in the hypothesis of a strong magnetoelastic coupling forecast the existence of such a magnetic phase diagram.At present, we proceed to a theoretical study, in a molecular field approximation, of the magnetic phase diagram of compounds similar to Fe Br2 where we take into account the relative values of parameters J1, J2 and D associated with ferromagnetic and antiferromagnetic interactions and crystalline anisotropy. 相似文献
87.
88.
Bianchi I Forlani R Minetto G Peretto I Regalia N Taddei M Raveglia LF 《Journal of combinatorial chemistry》2006,8(4):491-499
An efficient strategy for the solution-phase parallel synthesis of a library of pyrrole-amides is described. Key reactions include functional homologation of beta-ketoesters with a set of aldehydes followed by oxidation to produce a series of differently substituted 1,4-dicarbonyl compounds. Rapid cyclization using a microwave-assisted Paal-Knorr reaction provided a set of 24 pyrrole esters that were further functionalized through a trimethylaluminum-mediated aminolysis to obtain a larger library of 288 diverse pyrrole-3-amides. The tetrasubstitution allows a good exploration of the chemical space around the central pyrrole core. The last step was entirely automated with a Bohdan Myriad personal synthesizer. 相似文献
89.
De Giacomo A Dell'Aglio M Casavola A Colonna G De Pascale O Capitelli M 《Analytical and bioanalytical chemistry》2006,385(2):303-311
Double-pulse laser-induced plasma spectroscopy (DP-LIPS) is applied to submerged targets to investigate its feasibility for
elemental analysis. The role of experimental parameters, such as inter-pulse delay and detection time, has been discussed
in terms of the dynamics of the laser-induced bubble produced by the first pulse and its confinement effect on the plasma
produced by the second laser pulse. The analytical performance of this technique applied to targets in a water environment
are discussed. The elemental analysis of submerged copper alloys by DP-LIPS has been compared with conventional (single-pulse)
LIBS in air. Theoretical investigation of the plasma dynamics in water bubbles and open air has been performed. 相似文献
90.
We consider the problem of optimizing an unknown function given as an oracle over a mixed-integer box-constrained set. We assume that the oracle is expensive to evaluate, so that estimating partial derivatives by finite differences is impractical. In the literature, this is typically called a black-box optimization problem with costly evaluation. This paper describes the solution methodology implemented in the open-source library RBFOpt, available on COIN-OR. The algorithm is based on the Radial Basis Function method originally proposed by Gutmann (J Glob Optim 19:201–227, 2001. https://doi.org/10.1023/A:1011255519438), which builds and iteratively refines a surrogate model of the unknown objective function. The two main methodological contributions of this paper are an approach to exploit a noisy but less expensive oracle to accelerate convergence to the optimum of the exact oracle, and the introduction of an automatic model selection phase during the optimization process. Numerical experiments show that RBFOpt is highly competitive on a test set of continuous and mixed-integer nonlinear unconstrained problems taken from the literature: it outperforms the open-source solvers included in our comparison by a large amount, and performs slightly better than a commercial solver. Our empirical evaluation provides insight on which parameterizations of the algorithm are the most effective in practice. The software reviewed as part of this submission was given the Digital Object Identifier (DOI) https://doi.org/10.5281/zenodo.597767. 相似文献