A hybrid method for solving multi-objective global optimization problems

Real optimization problems often involve not one, but multiple objectives, usually in conflict. In single-objective optimization there exists a global optimum, while in the multi-objective case no optimal solution is clearly defined but rather a set of optimums, which constitute the so called Pareto-optimal front. Thus, the goal of multi-objective strategies is to generate a set of non-dominated solutions as an approximation to this front. However, most problems of this kind cannot be solved exactly because they have very large and highly complex search spaces. The objective of this work is to compare the performance of a new hybrid method here proposed, with several well-known multi-objective evolutionary algorithms (MOEA). The main attraction of these methods is the integration of selection and diversity maintenance. Since it is very difficult to describe exactly what a good approximation is in terms of a number of criteria, the performance is quantified with adequate metrics that evaluate the proximity to the global Pareto-front. In addition, this work is also one of the few empirical studies that solves three-objective optimization problems using the concept of global Pareto-optimality.     

Proteases screening for the kinetic resolution of amines with N-acyl α-amino acid trifluoromethyl esters: automated docking approach of binding energies using Subtilisin Novo as a prototype for serine proteases

The screening of a panel of 17 proteases resulted in the selection of 4 serine proteases for the resolution of 3-amino-1-phenylbutane. The latter were used to determine the best acyl donor from a series of N-acyl α-amino acid trifluoroethyl esters selected as peptide mimetics (E factor up to 99). The results were correlated to an automated docking determination of their binding affinities for Subtilisin Novo.     

Action of a pulsed electron beam on Cu-Ni foils and accompanying phenomena

Influence of the action of a pulsed electron beam in the millisecond range on the composition of surface layers, structure, topography, and mechanical properties of Cu₅₀Ni₅₀ and Cu₈₀Ni₂₀ foils depending on the energy’s and pulse’s current density is studied. The formation of concentration inhomogeneities in ultrathin near-surface layers is found as well as variations in the structure, mechanical properties, and topography of the foils depending on the alloy composition and irradiation parameters.     

Modification of properties of polymer membranes by low-temperature plasma treatment

The results of investigations into the use of low-temperature plasma for modification of porous polymer membranes are summarized. The basic lines of research in this area are considered. It is shown that plasma treatment is a quite effective tool for both improving the properties of existing polymer membranes and manufacturing new composite membranes with unique characteristics.     

The effect of direct-current discharge treatment on the surface properties of a poly(1-(trimethylsilyl)-1-propyne) membrane

The effect of treatment in low-pressure direct-current discharge on the surface properties of poly(1-trimethylsilyl)-1-propyne) membranes was investigated by the goniometric technique. It was shown that the treatment of the membranes at the anode makes it possible to significantly improve their contact properties (to increase the hydrophilicity of the surface). The structure of the membranes before and after plasma treatment was examined by means of Fourier-transform IR reflection spectroscopy. In addition, the sorption of ethanol onto the plasma-treated and untreated membranes was studied with the use of this technique in the transmission mode and it was assumed that it proceeds via different mechanisms, a behavior that can be due to a change in the free volume of the polymer or the formation of a surface charge on the membrane as a result of plasma treatment.     

Synthesis of high glass transition temperature copolymers based on poly(vinyl chloride) via single electron transfer—Degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of vinyl chloride in water

α,ω‐di(iodo) poly(isobornyl acrylate) macroiniators (α,ω‐di(iodo)PIA) with number average molecular weight from M _n,TriSEC = 11,456 to M _n,TriSEC = 94,361 were synthesized by single electron transfer‐degenerative chain transfer mediated living radical polymerization (SET‐DTLRP) of isobornyl acrylate (IA) initiated with iodoform (CHI₃) and catalyzed by sodium dithionite (Na₂S₂O₄) in water at 35 °C. The plots of number average molecular weight vs conversion and ln{[M]₀/[M]} vs time are linear, indicating a controlled polymerization. α,ω‐di(iodo) poly(isobornyl acrylate) have been used as a macroinitiator for the SET‐DTLRP of vinyl chloride (VCM) leading to high T_g block copolymers PVC‐b‐PIA‐b‐PVC. The dynamic mechanical thermal analysis of the block copolymers suggests just one phase indicating that copolymer behaves as a single material. This technology provides the possibility of synthesizing materials based on PVC with higher T_g in aqueous medium. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Rheological and mechanical properties of epoxy/polyurethane blends initiated by N‐benzylpyrazinium hexafluoroantimonate salt

In this work the cure behavior and rheological and mechanical interfacial properties of the diglycidylether of bisphenol A (DGEBA)/polyurethane (PU) blend system, initiated by 1 wt % N‐benzylpyrazinium hexafluoroantimonate as a latent thermal catalyst, were investigated. To characterize the mechanical interfacial properties of the system, the critical stress intensity factor (K_IC) was calculated with a single‐edge‐notched beam (SEN) beam fracture toughness test. And an impact test was performed at room and cryogenic temperatures to determine the performance of PU at room and low‐temperatures, respectively. As a result, the E_c of the blend system was increased with increasing PU content, showing a maximum value at 30 wt % PU, which was in good agreement with the mechanical properties of the blend system. Consequently, these results could be explained by the improvement that occurred in intermolecular hydrogen bonding between the hydroxyl group in EP and the isocyanate group in PU, resulting in increased compatibility of the components within the interpenetrating polymer networks. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3841–3848, 2004     

Resolvents of operators inverse to Schatten–von Neumann ones

The paper deals with linear operators in a Hilbert space, whose inverse ones belong to the Schatten–von Neumann ideal of compact operators, and whose imaginary Hermitian components are bounded. A sharp norm estimate for the resolvents of the considered operators is derived. That estimate enables us to investigate spectrum perturbations and to establish bounds for the norms of the semigroups and Hirsch operator functions. The operator logarithm and fractional powers are examples of the Hirsch functions.