Evolving combinatorial problem instances that are difficult to solve

This paper demonstrates how evolutionary computation can be used to acquire difficult to solve combinatorial problem instances. As a result of this technique, the corresponding algorithms used to solve these instances are stress-tested. The technique is applied in three important domains of combinatorial optimisation, binary constraint satisfaction, Boolean satisfiability, and the travelling salesman problem. The problem instances acquired through this technique are more difficult than the ones found in popular benchmarks. In this paper, these evolved instances are analysed with the aim to explain their difficulty in terms of structural properties, thereby exposing the weaknesses of corresponding algorithms.     

Primary reconstruction of the mandible after resection for oral cancer

Forty-seven patients with cancer of the lower half of the oral cavity underwent primary restoration of mandibular continuity with a threaded wire after "en bloc" resection. The overall 3 years tolerance rate of the wire calculated according to the actuarial method is 0.29. Preoperative radiotherapy and inclusion of the wire into silastic reduced tolerance of the prosthesis. The occurrence of an oral fistula required removal of the wire.     

Inhibition effect of swine wastewater heavy metals and antibiotics on anammox activity

The feasibility of anaerobic ammonium oxidation (anammox) process to treat wastewaters containing antibiotics and heavy metals (such as the liquid fraction of the anaerobically digested swine manure) was studied in this work. The specific anammox activity (SAA) was evaluated by means of manometric batch tests. The effects of oxytetracycline, sulfathiazole, copper and zinc were studied. The experimental data of the short-term assays were fitted with an inhibition model to identify the half maximal inhibitory concentration (IC(50)). After 24 h exposures, IC(50)-values equal to 1.9, 3.9, 650 and 1,100 mg L(-1) were identified for copper, zinc, sulfathiazole and tetracycline respectively. The effect of prolonged exposure (14 days) to oxytetracycline and sulfathiazole was studied by means of repeated batch-assays. Anabolism and catabolism reactions were active during the inhibition tests indicating that anammox bacteria could grow even in the extreme conditions tested. Considering the average concentrations expected in swine wastewaters, the inhibitors studied do not seem to represent a problem for the application of the anammox process. However, in order to verify the effect of these compounds on the growth of anammox bacteria, continuous culture experiments could be conducted.     

Democratic Legitimacy of New Forms of Water Management in the Netherlands

Due to changes in the Dutch flood management paradigm, governance practices have been shifting from technocratic and state-oriented towards more collaborative governance approaches in which many governmental actors, together with private and societal actors, search out integral solutions. This shift has had an impact on how water management is legitimized. This paper evaluates two water governance processes that reflect the new management paradigm in different ways, and analyzes how these changing paradigms influence the democratic legitimacy of water governance. It is concluded that the extent to which the new paradigm is implemented influences the way in which democratic legitimacy is organized. It is also shown that new forms of democratic legitimacy do not replace existing ones but rather contribute to hybrid and contextualized forms of legitimacy.     

An ENO-Based Method for Second-Order Equations and Application to the Control of Dike Levels

This work aims to model the optimal control of dike heights. The control problem leads to so-called Hamilton-Jacobi-Bellman (HJB) variational inequalities, where the dike-increase and reinforcement times act as input quantities to the control problem. The HJB equations are solved numerically with an Essentially Non-Oscillatory (ENO) method. The ENO methodology is originally intended for hyperbolic conservation laws and is extended to deal with diffusion-type problems in this work. The method is applied to the dike optimisation of an island, for both deterministic and stochastic models for the economic growth.     

On behavioural pseudometrics and closure ordinals

A behavioural pseudometric is often defined as the least fixed point of a monotone function F on a complete lattice of 1-bounded pseudometrics. According to Tarski?s fixed point theorem, this least fixed point can be obtained by (possibly transfinite) iteration of F, starting from the least element ⊥ of the lattice. The smallest ordinal α such that $F^{\alpha }(\perp )=F^{\alpha +1}(\perp )$ is known as the closure ordinal of F. We prove that if F is also continuous with respect to the sup-norm, then its closure ordinal is ω. We also show that our result gives rise to simpler and modular proofs that the closure ordinal is ω.     

Intelligent product search with soft-boundary preference relaxation

This paper proposes a novel method for preference relaxation in online product search, which enables consumers to make quality choices without suffering from the commonly experienced information overload. In online shopping scenarios that involve multi-attribute choice tasks, it can be difficult for consumers to process the vast amounts of information available and to make satisfactory buying decisions. In such situations consumers are likely to eliminate potentially good choices early on, using hard-constraint filtering tools. Our approach uses edge sets to identify the alternatives on the soft boundary and the principle of alternative domination to suppress the alternatives on this boundary that are irrelevant. We demonstrate how our approach outperforms existing methods for product search in a set of simulations using two sets of 2650 car advertisements and 1813 digital cameras gathered from a popular online store.