Relaxed correlation clustering (RCC) is a vertex partitioning problem that aims at minimizing the so-called relaxed imbalance in signed graphs. RCC is considered to be an NP-hard unsupervised learning problem with applications in biology, economy, image recognition and social network analysis. In order to solve it, we propose two linear integer programming formulations and a local search-based metaheuristic. The latter relies on auxiliary data structures to efficiently perform move evaluations during the search process. Extensive computational experiments on existing and newly proposed benchmark instances demonstrate the superior performance of the proposed approaches when compared to those available in the literature. While the exact approaches obtained optimal solutions for open problems, the proposed heuristic algorithm was capable of finding high quality solutions within a reasonable CPU time. In addition, we also report improving results for the symmetrical version of the problem. Moreover, we show the benefits of implementing the efficient move evaluation procedure that enables the proposed metaheuristic to be scalable, even for large-size instances.
In this article we obtain a duality result for an n-manifold N with boundary ∂N = N + ⊔N− a disjoint union, where N+ and N− are arbitrarily chosen parts in ∂N and need not be compact. This duality result is used to generalize the Poincaré–Hopf inequalities in a non-compact setting. 相似文献
Two distinct phases of the Fe?Co?Nb and three of the Fe?Co?V systems have been studied by means of X-ray diffraction and Mössbauer spectroscopy. The dependence of the lattice parameter of the alpha phase on the nominal solute content in equiatomic FeCo together with the alterations of the Mössbauer spectra have shown a very limited solubility of niobium in alpha FeCo. There are indications that the solubility of vanadium in alpha FeCo increases with increasing nominal content of solute in the alloy. A mechanism involving the withdrawal of cobalt from the alpha matrix to form a phase rich in Co and V (gamma) is proposed to explain such a varying solubility. The vanadium content of the sigma phase in equiatomic FeCo alloys with 22 wt% V is proposed to be less than 50 at%. 相似文献
The possibility to excite ferromagnetic magnons with very large k is analyzed theoretically. The proposed excitation mechanism is analogous to the first-order Suhl instability and takes place via non-linear processes involving localized modes associated with imputities in ferromagnetic insulators. A rough estimate of the critical power of a far-infrared laser source necessary to attain the instability threshold shows that the processes are experimentally feasible. 相似文献
We give a simple proof of Feynman's formula for the Green's function of the n-dimensional harmonic oscillator valid for every time t with Im t ≤ 0. As a consequence the Schrödinger equation for the anharmonic oscillator is integrated and expressed by the Feynman path integral on Hilbert space. 相似文献
This work reports the evaluation of the combined use of Pd and HF as chemical modifiers for the direct determination of total chromium in waters derived from petroleum exploration employing electrothermal atomic absorption spectrometry (ET AAS). Such waters, usually called as produced waters, have complex composition presenting a number of organic and inorganic substances. When obtained from offshore operations they also present high salinity. In order establish conditions for chromium measurement pyrolysis and atomization curves were built up in different media and employing Pd and HF as chemical modifiers. Also, a detailed study about calibration strategy was performed. At best conditions, pyrolysis and atomization temperatures were 1200 °C and 2600 °C, respectively, and 10 μL of a 500 mg L− 1 Pd solution was added together with 10 μL of a 50% (v/v) HF solution on 20 μL of sample. Obtained results indicate that, in this kind of sample, chromium can be determined by standard addition method or employing external calibration with standard solutions prepared in 0.8 mol L− 1 NaCl medium. In order to evaluate the accuracy of the procedure, a recovery test was performed with seven spiked samples of produced waters. The detection limit, quantification limit and the relative standard deviation in 0.8 mol L− 1 NaCl were also calculated and the values found were 0.45 μg L− 1, 1.5 μg L− 1 and 6.0% (at 2.5 μg L− 1 level), respectively. 相似文献
This paper demonstrates the application of thermal analysis in compatibility and stability studies between an ACE inhibitor
(enalapril maleate) and excipients. The results have helped to elucidate the reason of a stability problem observed during
the storage of enalapril maleate tablets. Incompatibility between enalapril maleate and colloidal silicon dioxide was detected.
Besides, it was confirmed that the reaction between enalapril maleate and NaHCO3 increases the thermal stability of the drug. This study supports the importance of using thermoanalytical methods in the
development of pharmaceuticals. 相似文献
The present work reports the synthesis of four electron-acceptor beta-substituted thiophenes that were studied as monomers for electrochemical polymerization with 3,4-ethylenedioxythiophene (EDOT), an electron-donating monomer, aiming the combination of electron-acceptor and donor monomer thiophene to a simpler and convenient build up of novel donor–acceptor copolymeric materials via electrochemical polymerization. Four novel copolymers poly(EDOT-co-3-thiophene phenylacetate), (PEDOT-co-PPhTAc-2a), poly(EDOT-co-3-thiophene(4-nitrophenyl)acetate) (PEDOT-co-PPhTAc-2b), poly(EDOT-co-3-thiophenephenylcarboxylate) (PEDOT-co-PPhTCb), and poly(EDOT-co-3-(phenoxymethyl)thiophene) (PEDOT-co-PPhOMT) were electrochemically polymerized. The monomers were characterized by spectrometric techniques (FTIR, 1H NMR, and 13C NMR), and the copolymers were identified by electrochemical analyses and FT-IR. Although the corresponding homopolymers could not be obtained, in the presence of EDOT, the copolymers were formed in a quasi-reversible electrochemical kinetics. The infrared spectra of the copolymers as well the electrochemical profile corroborates their obtaining. The mass variation during the electrosynthesis was analyzed using a quartz crystal microbalance. The film’s morphologies were investigated by SEM. Interestingly, the combination of electron-rich monomer thiophene (EDOT) and these electron-deficient carboxy-substituted thiophenes might be a convenient building block couple to increase the performance control of physic-chemical properties of mixed polythiophenes with innovative applications and they also showed a possible applicability as charge storage device. 相似文献
This work reports the reforming of bio-ethanol on chitosan–TiO2 hybrid photocatalysts at ambient temperature. The influence of chitosan composition on the photocatalytic performance of chitosan–TiO2 hybrid was studied. The hybrids were characterized by CHN elemental analysis, nitrogen adsorption–desorption isotherms, thermogravimetric analysis, diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the preparation variables used for the incorporation of chitosan on TiO2 promoted changes in the morphology, superficial area, crystal size and porosity of the photocatalyst, affecting the band gap of this semiconductor and consequently the reactivity of the chitosan–TiO2 hybrids. The catalysts were evaluated for hydrogen production from ethanol under visible light. It was demonstrated that the calcination temperature of 623 K and a chitosan content of 20% were the most appropriate preparation conditions and the resulting product displays a pore size of 1.9 nm, crystal size of 11.3 nm, BET area of 178 m2 g?1 and band gap of 2.92 eV. The calcination temperature of 623 K and incorporation of 20% of chitosan obtained the same results in the conversion rate of hydrogen in comparison to the pure TiO2 P25. 相似文献