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81.
We generalize Frobenius singular theorem due to Malgrange, for a large class of codimension one holomorphic foliations on
singular analytic subsets of ℂ
N
.
This research was partially supported by Pronex. 相似文献
82.
Petr Ya. Ekel Marden Menezes Fernando H. Schuffner Neto 《Nonlinear Analysis: Hybrid Systems》2007,1(4):527-536
This paper presents results of research into the use of the Bellman–Zadeh approach to decision making in a fuzzy environment for solving multicriteria optimization problems. Its application conforms to the principle of guaranteed result and provides constructive lines in obtaining harmonious solutions on the basis of analyzing associated maxmin problems. The use of the Bellman–Zadeh approach has served as a basis for solving a problem of multicriteria allocation of resources (or their shortages) and developing a corresponding adaptive interactive decision making system (AIDMS1). AIDMS1 includes procedures for considering linguistic variables to reflect conditions that are difficult to formalize as well as procedures for constructing and correcting vectors of importance factors for goals. The use of these procedures permits one to realize an adaptive approach to processing information of a decision maker to provide successive improvment in solution quality. The results of the paper are universally applicable and are already being used to solve power engineering problems. It is illustrated by considering problems of multicriteria power and energy shortage allocation and multicriteria power system operation. 相似文献
83.
M.A. da Nbrega J.M. S F.H.R. Bezerra J.C. Hadler Neto P.J. Iunes S. Guedes C.A. Tello Saenz P.C. Hackspacher F.P. Lima-Filho 《Radiation measurements》2005,39(6):627-633
An apatite fission track study of crystalline rocks underlying sedimentary basins in northeastern Brazil indicate that crustal blocks that occur on opposite sides of a geological fault experienced different thermal histories. Samples collected on the West block yielded corrected fission-track ages from 140 to 375 Ma, whereas samples collected on the East block yielded ages between 90 and 125 Ma. The thermal models suggest that each block experienced two cooling events separated by a heating event at different times. We concluded that the West block moved downward relative to the East block ca. 140 Ma ago, when sediments eroded from the East side were deposited on the West side. This process represents the early stage of sedimentary basin formation and the opening of the South Atlantic Ocean in the region. Downward and upward movements related to heating and cooling events of these crustal blocks at different periods until recent times are proposed. 相似文献
84.
F. Guinea A. H. Castro Neto N. M.R. Peres 《The European physical journal. Special topics》2007,148(1):117-125
We discuss the excitation spectrum, electronic susceptibilities,
and possible electronic instabilities in graphene and graphene stacks. The
corrections due interactions of Landau levels in graphene are analyzed. At
low dopings, and for
sufficiently low couplings, single layer graphene is stable against
ferromagnetism. On the other hand, a graphene bilayer, and
infinite graphite, are unstable towards ferromagnetism and
antiferromagnetism. 相似文献
85.
In order to solve linear programs with a large number of constraints, constraint generation techniques are often used. In
these algorithms, a relaxation of the formulation containing only a subset of the constraints is first solved. Then a separation
procedure is called which adds to the relaxation any inequality of the formulation that is violated by the current solution.
The process is iterated until no violated inequality can be found. In this paper, we present a separation procedure that uses
several points to generate violated constraints. The complexity of this separation procedure and of some related problems
is studied. Also, preliminary computational results about the advantages of using multiple-points separation procedures over
traditional separation procedures are given for random linear programs and survivable network design. They illustrate that,
for some specific families of linear programs, multiple-points separation can be computationally effective. 相似文献
86.
Castro EV Novoselov KS Morozov SV Peres NM dos Santos JM Nilsson J Guinea F Geim AK Neto AH 《Physical review letters》2007,99(21):216802
We demonstrate that the electronic gap of a graphene bilayer can be controlled externally by applying a gate bias. From the magnetotransport data (Shubnikov-de Haas measurements of the cyclotron mass), and using a tight-binding model, we extract the value of the gap as a function of the electronic density. We show that the gap can be changed from zero to midinfrared energies by using fields of less, approximately < 1 V/nm, below the electric breakdown of SiO2. The opening of a gap is clearly seen in the quantum Hall regime. 相似文献
87.
We present a form of the Mean Value Theorem (MVT) for a continuous function f between metric spaces, connecting it with the possibility to choose the relation of f in a homeomorphic way. We also compare our formulation of the MVT with the classic one when the metric spaces are open subsets of Banach spaces. As a consequence, we derive a version of the Mean Value Propriety for measure spaces that also possesses a compatible metric structure. 相似文献
88.
F.G.M. Cunha A.W.M. Pinto P.R. Oliveira J.X. da Cruz Neto 《Applied mathematics and computation》2011,218(8):4523-4532
We obtain a class of primal affine scaling algorithms which generalize some known algorithms. This class, depending on a r-parameter, is constructed through a family of metrics generated by −r power, r ? 1, of the diagonal iterate vector matrix. We prove the so-called weak convergence of the primal class for nondegenerate linearly constrained convex programming. We observe the computational performance of the class of primal affine scaling algorithms, accomplishing tests with linear programs from the NETLIB library and with some quadratic programming problems described in the Maros and Mészáros repository. 相似文献
89.
Sardela VF Sardela PD Pereira HM Aquino Neto FR 《Journal of chromatography. A》2011,1218(9):1266-1272
The compound 3,4-dimethyl-5-phenyl-1,3-oxazolidine can appear as an artifact during the gas chromatographic analysis of ephedrines. Its presence is a risk for doping control and forensic analyses. An evaluation about the consequences of its formation showed the possibility of a false positive for ephedrine, a false negative for pseudophedrine and increased uncertainty in the quantitative approach. Misinterpretations can be avoided with the observation of fragments m/z 56 and 71 in the ephedrine mass spectrum during GC-MS analysis and also by the formation of N-TFA-O-TBDMS derivatives prior to GC analysis. These N-TFA-O-TBDMS derivatives lead to an increase in the number and mass of diagnostic ions, meet the identification criteria, and provide an improvement in chromatographic resolution, allowing the separation of the ephedrines. 相似文献
90.
Machado AE Gomes WR Araújo DM Miglio HS Ueno LT De Paula R Cavaleiro JA Barbosa Neto NM 《Molecules (Basel, Switzerland)》2011,16(7):5807-5821
An imidazolium tetrasubstituted cationic porphyrin derivative (the free base and its Zn(II) complex) with five-membered heterocyclic groups in the meso-positions were synthesized using microwave irradiation, and the compounds obtained characterized by (1)H-NMR and mass spectrometry. We observed that under microwave irradiation the yield is similar to when the synthesis is performed under conventional heating, however, the time required to prepare the porphyrins decreases enormously. In order to investigate the electronic state of these compounds, we employed UV-Vis and fluorescence spectroscopy combined with quantum chemical calculations. The results reveal the presence, in both compounds, of a large number of electronic states involving the association between the Soret and a blue-shifted band. The Soret band in both compounds also shows a considerable solvent dependence. As for emission, these compounds present low quantum yield at room temperature and no solvent influence on the fluorescence spectra was observed. 相似文献