Nanostructured thermoelectric generator for energy harvesting

This paper presents the development processes towards a new generation of nanostructured thermoelectric generators for power harvesting from small temperature gradients by using a combination of traditional silicon microfabrication techniques, electroplating and submicron ion-track nanolithography. Polyimide nanotemplates with pore diameters ranging from 30nm to 120 nm were fabricated. Preliminary results for Bi2Te3 nanowires (50 and 120 nm diameter) electroplated into polycarbonate ion-track commercial membranes are presented. Bi2Te3 nanowires of R ̄ 3m structure, with preferential orientation in the (015) and (110) crystallographic plans with nearly stoichiometric composition were electroplated. The fine-grained observed microstructure (6-10 nm) and (110) crystalline orientation appear extremely promising for improving thermoelectric material properties

Statistical Methods for Convergence Detection of Multi-Objective Evolutionary Algorithms

In this paper, two approaches for estimating the generation in which a multi-objective evolutionary algorithm (MOEA) shows statistically significant signs of convergence are introduced. A set-based perspective is taken where convergence is measured by performance indicators. The proposed techniques fulfill the requirements of proper statistical assessment on the one hand and efficient optimisation for real-world problems on the other hand. The first approach accounts for the stochastic nature of the MOEA by repeating the optimisation runs for increasing generation numbers and analysing the performance indicators using statistical tools. This technique results in a very robust offline procedure. Moreover, an online convergence detection method is introduced as well. This method automatically stops the MOEA when either the variance of the performance indicators falls below a specified threshold or a stagnation of their overall trend is detected. Both methods are analysed and compared for two MOEA and on different classes of benchmark functions. It is shown that the methods successfully operate on all stated problems needing less function evaluations while preserving good approximation duality at the same time.Article / Letter to editorLeiden Inst. Advanced Computer Science

Feshbach spectroscopy and analysis of the interaction potentials of ultracold sodium

We have studied magnetic Feshbach resonances in an ultracold sample of Na prepared in the absolute hyperfine ground state. We report on the observation of three s-, eight d-, and three g-wave Feshbach resonances, including a more precise determination of two known s-wave resonances, and one s-wave resonance at a magnetic field exceeding 200mT. Using a coupled-channels calculation we have improved the sodium ground-state potentials by taking into account these new experimental data, and derived values for the scattering lengths. In addition, a description of the molecular states leading to the Feshbach resonances in terms of the asymptotic-bound-state model is presented.Comment: 11 pages, 4 figure

A feature-based comparison of local search and the Christofides algorithm for the travelling salesperson problem

Understanding the behaviour of well-known algorithms for classical NP-hard optimisation problems is still a difficult task. With this paper, we contribute to this research direction and carry out a feature based comparison of local search and the well-known Christofides approximation algorithm for the Traveling Salesperson Problem. We use an evolutionary algorithm approach to construct easy and hard instances for the Christofides algorithm, where we measure hardness in terms of approximation ratio. Our results point out important features and lead to hard and easy instances for this famous algorithm. Furthermore, our cross-comparison gives new insights on the complementary benefits of the different approaches.Samadhi Nallaperuma, Markus Wagner, Frank Neumann, Bernd Bischl, Olaf Mersmann, Heike Trautmannhttp://www.sigevo.org/foga-2013

Further insights into aspects of the EU illicit drugs market: summaries and key findings

This publication presents key findings and summaries of selected reports from the study ‘Further insights into aspects of the EU illicit drugs market’ (Trautmann, Kilmer and Turnbull, forthcoming 2013), which provides an analysis of characteristics and operations of the EU’s illicit drugs market, as called for by the European Commission. This study is a follow-up of the earlier European Commission study, which presented an analysis of the developments of the global illicit drug markets, the drug problems and drug policy responses in the period 1998-2007 (Reuter and Trautmann 2009). The discussions of that study resulted in a number of further research questions. Some of the questions considered most important by the European Commission have been put together in a call for a further analysis of the EU illicit drugs market and responses to it, focusing on a number of aspects in the following four areas: A. An analysis of specific characteristics, mechanisms and factors that govern the EU illicit drugs market, including a conceptual framework for thinking about the structure of drug suppliers in the EU, an assessment whether there have been significant shifts in how drugs are supplied in the EU and an assessment of the extent to which drug suppliers are involved in different drugs and other criminal activities. B. A detailed analysis of the size and share of the EU illicit drug market, providing an estimate of the volume of the ‘EU market’ in illicit drugs (production and trafficking), providing an estimate of the profits generated by this market, analysing whether the EU drugs market is more supply or demand driven and exploring various aspects of drug use: user types, availability and consumption estimates. C. A detailed analysis of a number of potential policy impacts on the EU drug market(s) in recent years, assessing the impact of opioid substitution treatment (OST) on the European heroin market and the impact of policy changes on two EU drug markets. D. Scanning the future – trends in the market and policy responses, exploring expert views on future key trends of the illicit drug markets and policy responses in the EU