Andreas Ernst

Ecological knowledge: Acquisition and use in problem solving and in decision making

Abstract Ecological knowledge is analyzed under psychological and educational aspects. In empirical studies three experimental settings were used to investigate this type of knowledge: (1) a computer simulation of an ecological system, (2) an environmental game as a new variant of the Commons Dilemma, and (3) a computerized text base on various aspects of an actual environmental problem. The subjects had to acquire and to apply this knowledge in making predictions, planning intervention, deciding about environmental measures etc. The results show which conditions impair the acquisition and correct utilization of ecological knowledge and how it is possible to provide well-structured learning environments for this content domain.

A Low-Cost, Normally Closed, Solenoid Valve for Non-Contact Dispensing in the Sub-µL Range

We present a disposable, normally closed, non-contact dispensing valve for the sub-µL range. The miniaturized solenoid valve (diameter: 8 mm, height: 27.25 mm) is compatible to standard Luer-Lock interfaces. A highly dynamic actuation principle enables opening times down to 1 ms. The dispensing performance was evaluated for water (η = 1.03 mPas) and a 66% (w/w) glycerol/water solution (η = 16.98 mPas), at pressures varying from 200 to 800 mbar. The experimentally determined minimal dispensing volume was 163 nL (CV 1.6%) for water and 123 nL (CV 4.5%) for 66% (w/w) glycerol/water. The low-cost polymer valve enables high precision dispensing of liquid volumes down to the lower end of the sub-µL range comparable to high-end non-disposable micro-dispensing valves.

Considering baseline homophily when generating spatial social networks for agent-based modelling

Social networks have become an important part of agent-based models, and their structure may have remarkable impact on simulation results. We propose a simple and efficient but empirically based approach for spatial agent-based models which explicitly takes into account restrictions and opportunities imposed by effects of baseline homophily, i.e. the influence of local socio-demography on the composition of one’s social network. Furthermore, the algorithm considers the probability of links that depends on geographical distance between potential partners.The resulting network reflects social settings and furthermore allows the modeller to influence network properties by adjusting agent type specific parameters. Especially the parameter for distance dependence and the probability of distant links allow for control of clustering and agent type distribution of personal networks.

Using Spatially Explicit Marketing Data to Build Social Simulations

To construct a population of artificial agents, modellers either can use available large-scale e.g. demographic orland-use data of built-up areas. Or they rely on detailed data on cognitive and behavioural variables e.g. gathered through a domain-specific survey to craftspecific behavioural agent rules.However, both scales cannot easilybe connected. This chapter describes a method of using data stemming from geo-marketing research to support this scaling-up process with lifestyles and their localisation that are used as an empirical bridge between the micro and the macro levels.

Quantitative volume determination of dispensed nanoliter droplets on the fly

In this paper we present a sensor for non-contact monitoring of dispensed micro-droplets on the fly. In extension to our previous work [1], the sensor now allows for a direct, quantitative volume determination of single liquid droplets in the volume range from 20 to 100 nl. The improved electronic transducer enables to measure the droplet volume with an accuracy of ΔV ± 3 nl. The sensor signal provides a variety of information about the monitored droplet like for examples droplet velocity. This paper considers in particular the influence of the droplet velocity on the volume measurement. It turned out that the velocity effect can be fully compensated, if the signals are interpreted correctly.

Social Simulation: A Method to Investigate Environmental Change from a Social Science Perspective

This chapter discusses six challenges that are posed by the complexity and dynamics in the field of environmental behavior. These challenges are to explicitly represent (1) behavior as a process, (2) decision making, (3) social interaction, (4) interactions of humans with the bio-geo-physical world, (5) space-related interactions, and (6) to connect to the natural sciences, e.g., to climate models. Social simulation is proposed as a method being able to meet all of these challenges. By modeling individual decisions and their interactions as the basis of behavior, macro phenomena at the society level emerge. The method generates observable behavior at runtime, which can be scrutinized and compared to empirical data. It is presented how social simulation deals with each of the challenges, together with corresponding examples. A critical discussion concludes the chapter and relates to the fundamental advantages, but also to the practical costs of simulation.

RApid prototyping of 3D microstructures by direct printing of liquid metal at temperatures up to 500°C using the starjet technology

We present a novel approach for 3D-prototyping of porous metal structures by direct non-contact liquid metal printing, based on the StarJet technology [1]. In contrast to our previous work, the presented droplet generator features an improved nozzle chip design and actuator housing that allows operation at temperatures up to Tmax = 500°C (formerly Tmax = 250°C). This enables the ejection of single droplets of metals with higher melting points like for example magnesium or zinc alloys like ZAMAK. The droplet generation frequency could be increased by a factor of 10 to fmax = 4 kHz. Furthermore, deviations of the droplet trajectory from the symmetry axis of the nozzle are reduced to Δdeg = 0.28° by the new design. This paper reports on experimental results obtained with the improved device and presents 3D metal structures with various porosities.

On the evolution of social groups during coffee breaks

This paper focuses on the analysis of group evolution events in networks of face-to-face proximity. First, we analyze statistical properties of group evolution, e.g., individual activity and typical group sizes. Furthermore, we define a set of specific group evolution events. We analyze these using real-world data collected at the LWA 2010 conference using the Conferator system, and discuss patterns according to different phases of the conference.

Dynamics of Task Oriented Agent Behaviour in Multiple Layer Social Networks

In numerous real-world situations, people are confronted with tasks that they are unable to fulfil alone. Often, such tasks are characterised by the necessity to include a number of different expertises to their accomplishment. Consequently, people organise themselves into networks aimed at the completion of some specific task. Examples of such situations are to be found in virtually any domain, such as science, economy, or in the context of managing and maintaining natural resources.

A Disposable Dispensing Valve for Non-Contact Microliter Applications in a 96-Well Plate Format †

We present a miniaturized, disposable, normally-closed electromagnetic dispensing valve for the microliter range to process 96-well plates. The novel injection-molded valve is designed to fit into a 9 mm grid to realize an eight channel dispensing head, enabling the serial processing of well plates row-by-row. The presented dispensing valve design originates from a miniaturization study of a previously developed functional model. The outer diameter of the valve, including all actuating components, was reduced by 8 mm to an overall diameter of 8.5 mm without compromising the performance. Additionally, the actuation current of the valve could be reduced to 5 A. The valve is characterized for a volume range between 840 nL and 5.3 μL. The performance of the injection molded valve is competitive to commercially available dispensing valves, featuring the advantages of low fabrication costs, disposability, low mounting size, easy handling, and super silent actuation.