Forced transport of deformable containers through narrow constrictions

We study, numerically and analytically, the forced transport of deformable containers through a narrow constriction. Our central aim is to quantify the competition between the constriction geometry and the active forcing, regulating whether and at which speed a container may pass through the constriction and under what conditions it gets stuck. We focus, in particular, on the interrelation between the force that propels the container and the radius of the channel, as these are the external variables that may be directly controlled in both artificial and physiological settings. We present Lattice-Boltzmann simulations that elucidate in detail the various phases of translocation, and present simplified analytical models that treat two limiting types of these membrane containers: deformational energy dominated by the bending or stretching contribution. In either case we find excellent agreement with the full simulations, and our results reveal that not only the radius but also the length of the constriction determines whether or not the container will pass.Comment: 9 pages, 4 figure

Eurace@Unibi Model v1.0 User Manual

Dawid H, Gemkow S, Harting P, van der Hoog S, Neugart M. Eurace@Unibi Model v1.0 User Manual. Bielefeld: Universität Bielefeld; 2011

Eurace@Unibi Model v1.0 User Manual

Dawid H, Gemkow S, Harting P, van der Hoog S, Neugart M. Eurace@Unibi Model v1.0 User Manual. Bielefeld: Universität Bielefeld; 2011

3D simulations of gas puff effects on edge plasma and ICRF coupling in JET

Recent JET (ITER-Like Wall) experiments have shown that the fueling gas puffed from different locations of the vessel can result in different scrape-off layer (SOL) density profiles and therefore different radio frequency (RF) coupling. To reproduce the experimental observations, to understand the associated physics and to optimize the gas puff methods, we have carried out three-dimensional (3D) simulations with the EMC3-EIRENE code in JET-ILW including a realistic description of the vessel geometry and the gas injection modules (GIMs) configuration. Various gas puffing methods have been investigated, in which the location of gas fueling is the only variable parameter. The simulation results are in quantitative agreement with the experimental measurements. They confirm that compared to divertor gas fueling, mid-plane gas puffing increases the SOL density most significantly but locally, while top gas puffing increases it uniformly in toroidal direction but to a lower degree. Moreover, the present analysis corroborates the experimental findings that combined gas puff scenarios-based on distributed main chamber gas puffing-can be effective in increasing the RF coupling for multiple antennas simultaneously. The results indicate that the spreading of the gas, the local ionization and the transport of the ionized gas along the magnetic field lines connecting the local gas cloud in front of the GIMs to the antennas are responsible for the enhanced SOL density and thus the larger RF coupling

Eurace@Unibi Model v1.0 Source Code

Gemkow S, Harting P, van der Hoog S. Eurace@Unibi Model v1.0 Source Code. Bielefeld University; 2014.Eurace@Unibi Model v1.0.1 Source Code is compatible with xparser-0.17.1 (GSL-2.4)

The physics of water and wax in the pores of a working Gas-to-Liquids catalyst

The so-called Fischer-Tropsch catalysis allows to convert natural gas into liquid products and is the underlying mechanism of commercially used "Gas-to-Liquids" plants. The actual reaction takes place in millimetre sized porous pellets in which active metallic particles are dispersed as catalysts. Due to the reaction the pores of the pellets will become filled with the reaction products ("wax" and water), but it is uncertain if the fluid in the pores can be understood as a single liquid phase, a liquid-gas mixture, or multiple continuous phases. The answer to this question is important for a thorough understanding of the transport processes inside the reactor and can be utilized to improve its eciency. In this project, a theoretical analysis of the behaviour inside the pores is performed. It is concluded that a liquid water phase might well exist next to the wax phase. However, the analysis is based on very limited experimental data of unknown quality. Therefore, we propose a number of possible experiments to validate the theoretical concepts

Agent-Based Macroeconomic Modeling and Policy Analysis: The Eurace@Unibi Model

Dawid H, Gemkow S, Harting P, van der Hoog S, Neugart M. Agent-Based Macroeconomic Modeling and Policy Analysis: The Eurace@Unibi Model. In: Chen S-H, Kaboudan M, Du Y-R, eds. The Oxford Handbook of Computational Economics and Finance. New York: Oxford University Press; 2018: 490-519.Agent-based simulation models are a relatively new addition to the tool-box of macroeconomists. The aim of this chapter is to review work that has been carried out in recent years. Particularly, we present the Eurace@Unibi model and set it into perspective with other agent-based macroeconomic models. Besides presenting a sketch of the Eurace@Unibi model, we show how agent-based models can be used to identify economic mechanisms, and how we have applied them for spatial policy analysis. Our assessment is that agent-based modelers have passed the stage of a proof-of-concept. It has been shown that new kinds of insights can be obtained using such an approach complementing established modeling approaches. We conclude by pointing towards potentially fruitful areas of agent-based macroeconomic research

A Heterogeneous Agent Macroeconomic Model for Policy Evaluation: Improving Transparency and Reproducibility

Dawid H, Harting P, van der Hoog S, Neugart M. A Heterogeneous Agent Macroeconomic Model for Policy Evaluation: Improving Transparency and Reproducibility. Working Papers in Economics and Management. Vol 06-2016. Bielefeld: Bielefeld University, Department of Business Administration and Economics; 2016.This paper provides a detailed description of the Eurace@Unibi model, which has been developed as a versatile tool for economic policy analysis. The model explicitly incorporates the decentralized interaction of heterogeneous agents across different sectors and regions. The modeling of individual behavior is based on heuristics with empirical microfoundations. Although Eurace@Unibi has been applied successfully to different policy domains, the complexity of the structure of the model, which is similar to other agent-based macroeconomic models, has given rise to concerns about the reproducibility and robustness of the obtained insights. This paper addresses these concerns by describing the exact details of all decision rules, interaction protocols and balance sheets used in the model. Furthermore, we discuss the use of a virtual appliance as a tool allowing third parties to reproduce and verify the simulation results. The paper provides a systematic and extensive sensitivity analysis of the simulation output with respect to a set of key parameters. Particular emphasis is put on the question which parameter constellations give rise to strong economic fluctuations and high frequencies of sudden downturns in economic activity

Steering in computational science: mesoscale modelling and simulation

This paper outlines the benefits of computational steering for high performance computing applications. Lattice-Boltzmann mesoscale fluid simulations of binary and ternary amphiphilic fluids in two and three dimensions are used to illustrate the substantial improvements which computational steering offers in terms of resource efficiency and time to discover new physics. We discuss details of our current steering implementations and describe their future outlook with the advent of computational grids.Comment: 40 pages, 11 figures. Accepted for publication in Contemporary Physic

Agent-Based Macroeconomic Modeling and Policy Analysis: The Eurace@Unibi Model

Dawid H, Gemkow S, Harting P, van der Hoog S, Neugart M. Agent-Based Macroeconomic Modeling and Policy Analysis: The Eurace@Unibi Model. Working Papers in Economics and Management. Vol 01-2014. Bielefeld: Bielefeld University, Department of Business Administration and Economics; 2014.Agent-based simulation models are a relatively new addition to the tool-box of macroe- conomists. In this chapter we introduce the Eurace@Unibi model and the research that has been done within this framework. We show how an agent-based model can be used to identify economic mechanisms and how it can be applied to spatial policy analysis. Our assessment is that agent-based models in economics have passed the proof-of-concept phase and it is now time to move beyond that stage. It has been shown that new kinds of insights can be obtained that complement established modeling approaches. We conclude by pointing towards some potentially fruitful areas of agent-based macroeconomic research