A geneal vaiable neighbohood seach fo solving the uncapacitated $$$$-allocation $$p$$p-hub median poblem

The \(p\)-hub median problem consists of choosing \(p\) hub locations from a set of nodes with pairwise traffic demands in order to route the traffic between the origin-destination pairs at minimum cost. We accept general assumption that transportation between non-hub nodes is possible only via \(r\)-hub nodes, to which non-hub nodes are assigned. In this paper we propose a general variable neighborhood search heuristic to solve the problem in an efficient and effective way. Moreover, for the first time full nested variable neighborhood descent is applied as a local search within Variable neighborhood search. Computational results outperform the current state-of-the-art results obtained by GRASP based heuristic.     

Solving the clique partitioning problem as a maximally diverse grouping problem

In this paper we show that the clique partitioning problem can be reformulated in an equivalent form as the maximally diverse grouping problem (MDGP). We then modify a skewed general variable neighborhood search (SGVNS) heuristic that was first developed to solve the MDGP. Similarly as with the MDGP, significant improvements over the state of the art are obtained when SGVNS is tested on large scale instances. This further confirms the usefulness of a combined approach of diversification afforded with skewed VNS and intensification afforded with the local search in general VNS.     

Excitation volumetric effects (EVE) in metal-enhanced fluorescence

Metal-Enhanced Fluorescence (MEF) effects from different density silver island films (SiFs) and the effects of far-field excitation irradiance on the observed enhancement of fluorescence were studied. It is shown that MEF non-linearly depends on silver nanoparticle (NP) size/density, reaching a maximum value for SiFs made at a deposition time (DT) of ～5 minutes, i.e. just before SiFs become continuous. Numerical simulations of the silver-islands growing on glass revealed that the near-field magnitude depends non-linearly on size and interparticle distance exhibiting dramatic enhancement at ～10 nm distance between the NPs. In addition, a remarkable effect of modulation in MEF efficiency by far-field excitation irradiance has been observed, which can be correlated well with numerical simulations that show an excitation power volume dependence. The near-field volume changes non-linearly with far-field power. This unique observation has profound implications in MEF, which has rapidly emerged as a powerful tool in the biosciences and ultimately allows for tunable fluorescence enhancement factors.     

Sol–gel technology for functional finishing of PES fabric by stimuli-responsive microgel

The possibility of incorporating a stimuli-responsive microgel into a silica matrix by the sol–gel method was studied. This method allows the preparation of a novel class of functional finishes for textile material modification, which is aimed at the creation of simultaneous stimulus-responsive behaviour and functional protective properties. Using a pad-dry-cure method, a thermo- and pH-responsive microgel (PNCS) based on poly-(N-isopropylacrylamide) (poly-NiPAAm) and chitosan was embedded into a silica matrix on a previously activated polyester (PES) fabric. The matrix was composed of a model sol–gel precursor, vinyltrimethoxysilane (VTMS), in combination with hydrophilic fumed silica nanoparticles (SiO₂). Functionalized PES fabric samples were characterised by determining the morphological and chemical properties using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The stimuli (temperature and pH) responsiveness of the functionalized PES fabric was established by measuring its porosity, wicking ability, moisture content, drying rate, water vapour transmission rate and water uptake. In order to assess the washing fastness of the surface modifying systems, the tests were done before and after five consecutive washings. The results showed that sol–gel technology is an appropriate method for the incorporation of PNCS microgel on PES fibre surface. Because of the elasticity of the sol–gel matrix, the VTMS/SiO₂ polysiloxane film had no adverse influence on the swelling/deswelling effect of the PNCS microgel, thus retaining and even enhancing its stimulus response.     

Rheological Behavior of Some Cationic Polyelectrolytes

The rheological behavior of some cationic polyelectrolytes in aqueous solution is presented. The polyelectrolytes under study consist of polycations that have positive charges (N,N-dimethyl-2-hydroxypropylenammonium chloride) located along the main chain with or without nonpolar side chains (PCA₅D₁ and PCA₅, respectively). This investigation mainly considers the influence of oscillation frequency and temperature on their rheological behavior in salt-free aqueous solution at three polymer concentrations (c_p = 2%, 4%, and 6%) as well as in the presence of low molar mass salt (NaCl). The results indicate the main effect of these parameters was to modify the hydrophobic interactions between the side nonpolar groups of the modified polyelectrolyte. The comparison between the complex viscosity values, at the same polymer concentration, c_p = 4%, for PCA₅D₁ and PCA₅ shows higher values in the whole interval of temperatures under study and a pseudoplastic behavior at temperatures greater than 50°C for the former system.     

Density of states in a cylindrical GaAs/AlxGa1−xAs quantum well wire under tilted laser field

Within the effective-mass approximation the subband electronic levels and density of states in a semiconductor quantum well wire under tilted laser field are investigated. The energies and wave functions are obtained using a finite element method, which accurately takes into account the laser-dressed confinement potential. The density of states obtained in a Green's function formalism is uniformly blueshifted under the laser's axial field whereas the transverse component induces an additional non-uniform increase of the subband levels. Our results confirm that the tilted laser field destroys the cylindrical symmetry of the quantum confinement potential and breaks down the electronic states' degeneracy. Axial and transversal effects of the non-resonant laser field on the density of states compete, bringing the attention to a supplementary degree of freedom for controlling the optoelectronic properties: the angle between the polarization direction of the laser and the quantum well wire axis.