A new hyper-heuristic as a general problem solver: an implementation in HyFlex

This study provides a new hyper-heuristic design using a learning-based heuristic selection mechanism together with an adaptive move acceptance criterion. The selection process was supported by an online heuristic subset selection strategy. In addition, a pairwise heuristic hybridization method was designed. The motivation behind building an intelligent selection hyper-heuristic using these adaptive hyper-heuristic sub-mechanisms is to facilitate generality. Therefore, the designed hyper-heuristic was tested on a number of problem domains defined in a high-level framework, i.e., HyFlex. The framework provides a set of problems with a number of instances as well as a group of low-level heuristics. Thus, it can be considered a good environment to measure the generality level of selection hyper-heuristics. The computational results demonstrated the generic performance of the proposed strategy in comparison with other tested hyper-heuristics composed of the sub-mechanisms from the literature. Moreover, the performance and behavior analysis conducted for the hyper-heuristic clearly showed its adaptive characteristics under different search conditions. The principles comprising the here presented algorithm were at the heart of the algorithm that won the first international cross-domain heuristic search competition.     

Multifractal properties of pore-size distribution in apple tissue using X-ray imaging

The pore-size distribution (PSD) has an important influence on the complex gas transport phenomena (O₂ and CO₂) that occur in apple tissue during storage under controlled atmosphere conditions. It defines the apple tissue microstructure that is correlated to many other apple properties. In this article multifractal analysis (MFA) has been used to study the multiscale structure of the PSD using generalized dimensions in three varieties of apples (Jonagold, Greenstar, and Kanzi) based on X-ray imaging technology (8.5 μm resolution). Tomographic images of apple samples were taken at two positions within the parenchyma tissue: close to the peel and near to the core. The images showed suitable scaling properties. The generalized dimensions were determined with an R² greater than 0.98 in the range of moment orders between −1 and +10. The variation of D_q with respect to q and the shape of the multifractal generalized spectrum revealed that the PSD structure of apple tissue has properties close to multifractal self-similarity measures. Comparisons among cultivars showed that, in spite of the complexity and variability of the pore space of these apple samples, the extracted generalized dimensions from PSD were significantly different (p < 0.05). The generalized dimensions D₀, D₁, D₂, and the quantity D₀–D₂ could be used to discriminate tissue samples from different positions or cultivars. Also, high correlations were found between these parameters and the porosity (R² ? 0.935). These results demonstrate that MFA is an appropriate tool for characterizing the internal pore-size distribution of apple tissue and thus may be used as a quantitative measure to understand how tissue microstructure affects important physical properties of apple.     

New amoxicillin–poly(lactic acid)‐based conjugates: synthesis and in vitro release of amoxicillin

Long‐term antibiotic treatments are required to cure many diseases. Coupling a bioactive compound to a biocompatible polymer offers, in general, many advantages such as better stabilization of drug and controlled release. The work reported deals with the synthesis of new conjugates based on amoxicillin and oligomers of biocompatible and biodegradable poly(lactic acid), as well as release studies of amoxicillin. These new conjugates were obtained via a Curtius rearrangement or acyl chloride activation, leading to substituted urea or amide bonds between amoxicillin and polymer, respectively. Structures of the conjugates were assessed using Fourier transform infrared and ¹H NMR spectroscopy, double‐detection size exclusion chromatography and electrospray ionization mass spectrometry. In vitro release profiles of amoxicillin in phosphate buffered saline were determined using high‐performance liquid chromatography, and the release rates of amoxicillin from the two conjugates were compared. Copyright © 2010 Society of Chemical Industry     

Strategies for size reduction of microreactors by heat transfer enhancement effects

One of the likely aims of reactor miniaturization in the field of chemical production and energy generation is to increase the conversion to the desired product and the selectivity of the process through better control of heat and mass transfer. In addition to the effects related to miniaturization, a further increase of the transfer coefficients is achieved by applying microstructuring techniques. In this context, three different approaches for heat transfer enhancement in miniaturized reaction systems are presented. The ideas put forward rely on entrance flow effects, inertial flows in meandering channels, and suppression of axial heat conduction. Among these ideas the entrance flow effect, realized by an arrangement of microfins with a typical dimension of a few hundred micrometers, provides the most efficient heat transfer. It is found that a heat transfer enhancement of at least one order of magnitude can be achieved compared to unstructured channels. On this basis, a miniaturized heat-exchanger reaction system is investigated, where a kinetic model of an endothermic, heterogeneously catalyzed gas-phase reaction is used. The miniaturized heat-exchanger reactor, both with and without heat transfer enhancement, is subsequently benchmarked against conventional fixed-bed technology. It is shown that, for the reaction system under study, a substantial reduction of the required amount of catalyst can be achieved in microsystems.     

Spectrophotometric titration of bimetallic metal cation binding in polyamido(amine) dendrimer templates

Spectrophotometric titration and a binding isotherm were used to accurately assess the loading capacity of generation four polyamido(amine) (PAMAM) dendrimer templates with terminal alcohol groups (G4-OH). Preparation of bimetallic G4-OH dendrimer-encapsulated metal nanoclusters (DENs) necessitates knowledge of the precise metal-ion binding capacity. The binding of metal ions such as Pt(2+) and Pd(2+) has proven difficult to assess via UV-vis spectroscopy because the absorbance shifts associated with metal-ion binding within the dendrimer template are masked by the absorbance of the PAMAM dendrimer itself. In contrast, the binding of Cu(2+) to G4-OH PAMAM dendrimer results in a strong, distinct absorption band at 300 nm, making UV-vis spectrophotometric titration with copper straightforward. Here we use copper binding as a means to assess the number of binding sites remaining within the PAMAM G4-OH dendrimer after the complexation of a specified molar excess of Pd(2+) or Pt(2+). In addition, we use a binding isotherm to mathematically estimate the loading capacity of the dendrimer in each case. The loading capacities for M(2+) in the G4-OH dendrimer were found to be ～16 for copper alone, ～21 for copper combined with palladium, and ～25 for copper combined with platinum.     

Food-related personality traits, food choice motives and food intake: Mediator and moderator relationships

We investigated the relationship between food-related personality traits, specific food choice motives and food intake. Typically, it is assumed that motives mediate the effect of traits on food intake. Motives may also have different effects on food intake, depending on trait level (moderation). Undergraduate students (N = 324) completed the Food Involvement Scale and the Food Neophobia Scale measuring traits, and the Food Choice Questionnaire measuring specific motives. Daily food intake was assessed with a food frequency questionnaire two weeks later. General dietary healthfulness was based on its concordance with official recommendations. Regression analyses tested mediator and moderator relationships for each trait separately. The results partially support the mediation hypothesis: motives, such as Sensory Appeal and Health, mediated the effect of food involvement on intake of specific food categories. In addition, the relation of motives with both food intake and dietary healthfulness appeared to vary with level of food involvement or food neophobia (moderation). Implications to promote eating healthy food are discussed.     

Surface Modification of Ti6Al4V Open Porous Structures Produced by Additive Manufacturing

Additive manufacturing techniques can be used to produce micro‐porous structures with global morphological properties that are highly controlled through robust computer design. Despite these advantages, most of these techniques still hold several functional constraints, resulting from present technical device limits and consequently the inability to control surface morphology at a microscale level. In this study, a novel protocol for surface modification of 3D titanium alloy‐based open porous structures is developed, which applies a combination of chemical etching (CHE) and electrochemical polishing (ECP) using HF‐based solutions. This protocol achieves significant and controllable roughness reduction of additive manufactured 3D Ti6Al4V open porous structures. Chemical etching mainly removes the attached powder grains, while ECP further decreases the roughness. In this way the heterogeneity of the strut surface roughness throughout the full 3D structure is effectively removed.     

MamMoeT: An intelligent agent-based communication support platform for multimodal transport

In this paper, an intelligent agent-based communication support platform for multimodal transport is developed. The rationale for doing so is found in the potential of such a system to increase cost efficiency, service and safety for different transport-related actors. Although, at present several comparable systems exist, their current implementation is far from successful because of technological and economic obstacles. The new expert communication platform put forward here (called MamMoeT) addresses these two issues by using a software agent-based approach. Software agents are pieces of software representing a single user. They are autonomous, communicative and intelligent. The MamMoeT system developed can be described as a real-time decision support system in which intelligent software agents handle communicative tasks, exchange desired amounts of information among different users using common exchange protocols which act as translators between different systems.     

A Memetic Approach to the Nurse Rostering Problem

Constructing timetables of work for personnel in healthcare institutions is known to be a highly constrained and difficult problem to solve. In this paper, we discuss a commercial system, together with the model it uses, for this rostering problem. We show that tabu search heuristics can be made effective, particularly for obtaining reasonably good solutions quickly for smaller rostering problems. We discuss the robustness issues, which arise in practice, for tabu search heuristics. This paper introduces a range of new memetic approaches for the problem, which use a steepest descent improvement heuristic within a genetic algorithm framework. We provide empirical evidence to demonstrate the best features of a memetic algorithm for the rostering problem, particularly the nature of an effective recombination operator, and show that these memetic approaches can handle initialisation parameters and a range of instances more robustly than tabu search algorithms, at the expense of longer solution times. Having presented tabu search and memetic approaches (both with benefits and drawbacks) we finally present an algorithm that is a hybrid of both approaches. This technique produces better solutions than either of the earlier approaches and it is relatively unaffected by initialisation and parameter changes, combining some of the best features of each approach to create a hybrid which is greater than the sum of its component algorithms.