We consider semidefinite programming relaxations of the quadratic assignment problem, and show how to exploit group symmetry
in the problem data. Thus we are able to compute the best known lower bounds for several instances of quadratic assignment
problems from the problem library: (Burkard et al. in J Global Optim 10:291–403, 1997). 相似文献
We consider a waveguide modeled by the Laplacian in a straight planar strip. The Dirichlet boundary condition is taken on
the upper boundary, while on the lower boundary we impose periodically alternating Dirichlet and Neumann condition assuming
the period of alternation to be small. We study the case when the homogenization gives the Neumann condition instead of the
alternating ones. We establish the uniform resolvent convergence and the estimates for the rate of convergence. It is shown
that the rate of the convergence can be improved by employing a special boundary corrector. Other results are the uniform
resolvent convergence for the operator on the cell of periodicity obtained by the Floquet–Bloch decomposition, the two terms
asymptotics for the band functions, and the complete asymptotic expansion for the bottom of the spectrum with an exponentially
small error term. 相似文献
We investigate the existence of solutions of the system of anisotropic discrete boundary value problems using critical point theory. We apply direct variational approach, the Ky Fan min–max inequality and the mountain pass lemma. 相似文献
Elastic constants and bulk modulus for the tetragonal, rhombohedral, and cubic phase of Na0.5Bi0.5TiO3 crystal were calculated from the first principles. From the calculated elastic constants, other structural properties such as bulk modulus, shear modulus, Young's modulus, and Poisson's ratio can be derived using respective relationships from Voight–Reuss–Hill approximation; bulk modulus was calculated as an example in this article. It was shown that elastic constants show different behavior for compression and elongation. The different values of elastic constants have been calculated for the direction parallel to the bismuth layer (crystallographic a(b)-axis) and the perpendicular direction (crystallographic c-axis). It seems to be caused by bismuth layer structure oxides of Na0.5Bi0.5TiO3 crystal. 相似文献
The GE81112 tetrapeptides are a small family of unusual nonribosomal peptide congeners with potent inhibitory activity against prokaryotic translation initiation. With the exception of the 3‐hydroxy‐l ‐pipecolic acid unit, little is known about the biosynthetic origins of the non‐proteinogenic amino acid monomers of the natural product family. Here, we elucidate the biogenesis of the 4‐hydroxy‐l ‐citrulline unit and establish the role of an iron‐ and α‐ketoglutarate‐dependent enzyme (Fe/αKG) in the pathway. Homology modelling and sequence alignment analysis further facilitate the rational engineering of this enzyme to become a specific 4‐arginine hydroxylase. We subsequently demonstrate the utility of this engineered enzyme in the synthesis of a dipeptide fragment of the antibiotic enduracidin. This work highlights the value of applying a bioinformatics‐guided approach in the discovery of novel enzymes and engineering of new catalytic activity into existing ones. 相似文献
The use of agricultural wastes for energy conversion has been widely studied as renewable and carbon neutral energy sources. This paper aims to evaluate the energetic potential of six agricultural wastes—sugarcane bagasse, bean pods, corn stover, pineapple crown leaves, white cotton and natural coloured cotton stalks, through their characterization and pyrolysis kinetic study. The energetic potential of biomasses was evaluated by ultimate and proximate analysis, higher heating value (HHV), apparent density, and kinetic parameters of conversion and apparent activation energy (Ea) determined by Model-Free kinetics though thermogravimetric analysis data. The results indicate energetic density for dry basis biomasses, such as moisture content less than 7%, volatiles higher than 77% and moderate ash content. The HHVs were higher for the biomass with low O:C ratio. The Ea values increased with increasing O:C ratio and were also influenced by the biomass ash content. Among the studied biomasses, PCL are less explored for energy application, although the results confirm its potential for application in thermochemical processes such as pyrolysis or combustion.
Journal of Solid State Electrochemistry - The article presents the results of research and an analysis of the possibility of using sinters made of graphite powder as a material dedicated to the... 相似文献
Quantitative nuclear magnetic resonance (qNMR) is an analytical technique that offers numerous advantages in pharmaceutical applications including minimum sample preparation and rapid data collection times with no need for response factor corrections, being a powerful tool for assaying drug content in both drug discovery and early drug development. In the present work, we have applied qNMR, using both the internal standard and the electronic reference to access in vivo concentrations 2 calibration methods, to assess the purity of RI76, a novel antifungal drug candidate. NMR acquisition and processing parameters were optimized in order to obtain spectra with intense, well-resolved signals of completely relaxed nuclei. The analytical method was validated following current guidelines, demonstrating selectivity, linearity, accuracy, precision, and robustness. The calibration approaches were statistically compared, and no significant difference was observed when comparing the obtained results and their dispersion in terms of relative standard deviation. The proposed qNMR method may, therefore, be used for both qualitative and quantitative assessments of RI76 in early drug development and for characterization of this compound. 相似文献
Journal of Radioanalytical and Nuclear Chemistry - This paper presents results of the development process of low-background, digital gamma-rays spectrometer equipped with Broad Energy Germanium... 相似文献