Fast Quadratic Local Meta-Models for Evolutionary Optimization of Anguilliform Swimmers

International audienceWe combine second order local regression meta-models with the Covariance Matrix Adaptation Evolution Strategy in order to enhance its efficiency in the optimization of computationally expensive problems. Computationally intensive direct numerical simulations of an anguilliform swimmer provide the testbed for the optimization. We propose two concepts to reduce the computational cost of the meta-model building. The novel versions of the local meta-model assisted Evolution Strategy are tested on benchmark problems and compared to results from literature. The results demonstrate that the use of local meta-models increases significantly the efficiency of already competitive evolution strategies and that the model building cost can be successfully reduced. The meta-model assisted Evolution Strategy is applied to the optimization of the swimming motion of a three-dimensional, self-propelled eel-like body. The motion of the self-propelled body is determined by a set of parameters but the motion is not prescribed apriori. Instead here we introduce the concept of identifying the swimming motion parameters from an evolutionary optimization procedure. The optimization successfully identifies a motion pattern that is 30% more efficient than an existing reference motion pattern. During the efficient swimming motion, the deformation of the body is extended along its length in a controlled fashion

Synergetic Utilization of Renewable and Fossil Fuels: Dual Fluidized Bed Steam Co-gasification of Coal and Wood

AbstractGasification of biomass and coal is an attractive technology for combined heat and power production, as well as for synthesis processes such as the production of liquid and gaseous biofuels. The allothermal steam blown gasification process yields a high calorific product gas, practically free of nitrogen. Originally designed for wood chips, the system can also handle a large number of alternative fuels. To demonstrate the influence on the system performance of fuels that have a different origin, wood pellets, as the designated feedstock, and hard coal as an example fossil fuel were fed into the DFB gasifier with a fuel blend ratio of 20% coal in terms of energy. A fuel power of 78kW and a steam to fuel ratio of 1.0kg/kgdb were achieved. The system was operated at gasification temperatures between 830 and 870°C. This paper points out the influence of the temperature on the system

Boarding and Alighting Time of Passengers of the Berlin Public Transport System

The overall transportation speed is a significant factor influencing the attractiveness as well as the profitability of the transit system. If a vehicle needs less time to complete a tour, it can serve more tours and thus more passengers within the same time. Likewise, the passengers benefit from a decreased in-vehicle travel time. In this paper, the factors affecting the passenger transfer time are discussed for the case of Berlin, Germany. Furthermore, the paper presents the results of a survey that focuses (i) on the average time needed for passengers to board and alight a vehicle, (ii) its deviation, and (iii) the impact of the vehicle’s occupancy and number of boarding/alighting passengers. Such data can also be used to model the boarding and alighting process at stops in transport simulations in a more realistic way. For buses and subways, more passengers standing in the door area of a vehicle are found to slow down the boarding and alighting process. The Berlin specific policy to allow the boarding of a bus only at the first door induces a significantly higher boarding time per passenger

A new algorithm to retrieve the sea ice concentration using weather-corrected 85GHz SSM/I measurements

Sea ice is a very important component of the climate system. While the Arctic sea ice extent has retreated during the past 20 years, it has remained constant in the Antarctic. In order to better understand the role of sea ice in the climate system in the context of global warming currently used coupled Atmosphere-Ocean Global Circulation Models have to be improved. This requires to know the sea ice concentration C for a long period for both hemispheres and at the best possible spatial resolution. Currently used methods to obtain C like the NASA Team (NT) algorithm are based on data acquired by the Special Sensor Microwave/Imager (SSM/I) at 19 and 37GHz. The SEA LION (SL) algorithm presented here allows to infer C from the polarization P at 85GHz taking advantage of the higher spatial resolution at this frequency. However, the decrease of P caused by the weather influence leads to an overestimation of C. Therefore, P is corrected using a radiative transfer model and atmospheric data taken from Numerical Weather Prediction models and/or derived from SSM/I measurements. The various sea ice and snow properties are considered calculating monthly sea ice tie points. The average standard deviation of C derived with the SL algorithm is 12% for C 90%. The SL ice edge agrees within 10km with the one evident in VIS/IR images. The SL ice concentration gradient across the marginal ice zone (MIZ) agrees much better with the one evident in SAR images compared to results of the NT algorithm. Using the higher spatial resolution at 85GHz the SL algorithm allows to detect smaller open water areas than known algorithms. A major limitation of the SL algorithm arises from the quality of atmospheric data needed for the weather correction. A spatial resolution of these data lower than the 85GHz SSM/I channels and/or a time lag larger than half an hour between both data sets can cause relative errors above 100%, particulary in the cloud-covered parts of the MIZ

Kommunaler Klimaschutz in Deutschland : Handlungsoptionen, Entwicklung und Perspektiven

In der vorliegenden Studie werden die Handlungsoptionen deutscher Kommunen als Akteure im Klimaschutz untersucht. Gerade auf lokaler Ebene ist die Durchführung entsprechender Maßnahmen unverzichtbar, sollen die global, europaweit und national angestrebten CO2-Reduktionsziele erreicht werden. Hierbei werden die Handlungsoptionen der Kommunen vor allem durch die ihnen im deutschen Staatsaufbau zukommenden Aufgaben, durch ihre finanzielle Situation und zunehmend durch die Richtlinien der EU bestimmt. Vor diesem Hintergrund werden im zweiten Abschnitt die rechtlichen Grundlagen für kommunale Klimaschutzaktivitäten herausgearbeitet, die verschiedenen Rollen aufgezeigt, die Kommunen in ihrem klimapolitischen Handeln einnehmen können, und die einzelnen Handlungsfelder näher beleuchtet. Darüber hinaus werden vor dem Hintergrund der fortschreitenden Europäisierung die drei transnationalen Städtenetzwerke im Bereich des Klimaschutzes vorgestellt, in denen sich europäische Kommunen zum Austausch ihrer Erfahrungen und zum direkten Lobbying der politischen Institutionen der EU organisieren. Im dritten Abschnitt wird auf Basis einer umfassenden Umfrage mittels leitfadengestützter Telefoninterviews der aktuelle Stand lokaler Klimaschutzmaßnahmen in deutschen Großstädten untersucht. Hier geht es um die Frage, wie die Kommunen ihre Handlungsoptionen nutzen, und welche Rolle die transnationale Vernetzung dabei spielt. Im vierten Abschnitt folgt eine qualitativ-vergleichende Analyse dreier deutscher Erfolgsfälle im Bereich des lokalen Klimaschutzes: Heidelberg, Frankfurt am Main und München. Basis des Vergleichs sind Fallstudien, die vor allem die institutionelle Verankerung, die Kapazitäten, die Schwerpunkte und die Rolle der transnationalen Städtenetzwerke in der lokalen Klimaschutzpolitik eingehend untersuchen. Durch die anschließende vergleichende Analyse werden zum einen generelle Erfolgsbedingungen für lokalen Klimaschutz, zum anderen spezifische Strategien herausgearbeitet, mit denen die Kommunen auf lokale Problemlagen reagieren. Im fünften und letzten Abschnitt werden diese Ergebnisse zusammengefasst, übergreifende Schlussfolgerungen gezogen und die Perspektiven lokaler Klimaschutzpolitik in Deutschland eingeschätzt.This study investigates the available options for German municipalities as active agents in climate change policy. If global goals, Europe-wide goals, and national goals for the reduction of CO2 are to be reached, it is imperative that appropriate measures be taken at local level. The choices for municipalities in this regard are determined primarily by the responsibilities they have within the structure of the German government, by their respective financial situations, and increasingly, by European Union directives. Against this backdrop, section two of the study will elaborate the legal principles underlying municipal climate protection activities, will identify various roles that municipalities can have in climate policy action, and will more closely illuminate individual areas of activity. Moreover, in light of the progressive “Europeanization” of local governments, section two will present all three transnational city networks devoted to climate change policy, in which European municipalities have organized, in order to have a forum for the exchange of ideas and information, and in order to have a vehicle by which to lobby the political institutions of the EU directly. Section three of the study will investigate the present status of local climate protection measures in German cities. This investigation is based upon a comprehensive survey conducted via guideline-supported telephone interviews. The point was to determine how municipalities use their available options and what role transnational networking plays in this. Section four presents a qualitative-comparative analysis of three successful cases in the area of local climate protection, namely, the cities of Heidelberg, Frankfurt am Main, and Munich. Case studies provide the comparative data which, first and foremost, cover in-depth the institutional basis, capacities, main areas of activity, and roles of transnational city networks in local climate change policy. The final comparative analysis permits the elaboration of general conditions for successful local-level policy and presents specific strategies which municipalities have used in reaction to the overall problem situation. The fifth and final section of this study summarizes these results, draws some comprehensive conclusions, and presents some perspectives for local climate change policy in Germany

The Role of Word-Eye-Fixations for Query Term Prediction

Throughout the search process, the user's gaze on inspected SERPs and websites can reveal his or her search interests. Gaze behavior can be captured with eye tracking and described with word-eye-fixations. Word-eye-fixations contain the user's accumulated gaze fixation duration on each individual word of a web page. In this work, we analyze the role of word-eye-fixations for predicting query terms. We investigate the relationship between a range of in-session features, in particular, gaze data, with the query terms and train models for predicting query terms. We use a dataset of 50 search sessions obtained through a lab study in the social sciences domain. Using established machine learning models, we can predict query terms with comparably high accuracy, even with only little training data. Feature analysis shows that the categories Fixation, Query Relevance and Session Topic contain the most effective features for our task

Business Process Modelling with Continuous Validation

In this paper, we demonstrate the prototype of a modelling tool that applies graph-based rules for identifying problems in business process models. The advantages of our approach are twofold. Firstly, it is not necessary to compute the complete state space of the model in order to find errors. Secondly, our technique can even be applied to incomplete business process models. Thus, the modeller can be supported by direct feedback during the model construction. This feedback does not only report problems, but it also identifies their reasons and makes suggestions for improvements