Mathias Versichele

Loading rate and external resistance control the electricity generation of microbial fuel cells with different three-dimensional anodes

The electricity generation, electrochemical and microbial characteristics of five microbial fuel cells (MFCs) with different three-dimensional electrodes (graphite and carbon felt, 2mm and 5mm graphite granules and graphite wool) was examined in relation to the applied loading rate and the external resistance. The graphite felt electrode yielded the highest maximum power output amounting up to 386Wm(-3) total anode compartment (TAC). However, based on the continuous current generation, limited differences between the materials were registered. Doubling the loading rate to 3.3gCODL(-1)TACd(-1) resulted only in an increased current generation when the external resistance was low (10.5-25 Omega) or during polarization. Conversely, lowering the external resistance resulted in a steady increase of both the kinetic capacities of the biocatalyst and the continuous current generation from 77 (50 Omega) up to 253 (10.5 Omega)Am(-3)TAC. Operating a MFC at an external resistance close to its internal resistance, allows to increase the current generation from enhanced loading rates while maximizing the power generation.

Mobile mapping of sporting event spectators using bluetooth sensors: Tour of Flanders 2011

Accurate spatiotemporal information on crowds is a necessity for a better management in general and for the mitigation of potential security risks. The large numbers of individuals involved and their mobility, however, make generation of this information non-trivial. This paper proposes a novel methodology to estimate and map crowd sizes using mobile Bluetooth sensors and examines to what extent this methodology represents a valuable alternative to existing traditional crowd density estimation methods. The proposed methodology is applied in a unique case study that uses Bluetooth technology for the mobile mapping of spectators of the Tour of Flanders 2011 road cycling race. The locations of nearly 16,000 cell phones of spectators along the race course were registered and detailed views of the spatiotemporal distribution of the crowd were generated. Comparison with visual head counts from camera footage delivered a detection ratio of 13.0 ± 2.3%, making it possible to estimate the crowd size. To our knowledge, this is the first study that uses mobile Bluetooth sensors to count and map a crowd over space and time.

Interactive analysis of time intervals in a two-dimensional space

Time intervals are conventionally represented as linear segments in a one-dimensional space. An alternative representation of time intervals is the triangular model (TM), which represents time intervals as points in a two-dimensional space. In this paper, the use of TM in visualising and analysing time intervals is investigated. Not only does this model offer a compact visualisation of the distribution of intervals, it also supports an innovative temporal query mechanism that relies on geometries in the two-dimensional space. This query mechanism has the potential to simplify queries that are difficult to specify using traditional linear temporal query devices. Moreover, a software prototype that implements TM in a geographical information system (GIS) is introduced. This prototype has been applied in a real scenario to analyse time intervals that were detected by a Bluetooth tracking system. This application shows that TM has the potential to support a traditional GIS to analyse interval-based geographical data.

The continuous spatio-temporal model CSTM as an exhaustive framework for multi-scale spatio-temporal analysis

When studying geographical phenomena, different levels of spatial and temporal granularity often have to be considered. While various approaches have been proposed to analyse geographical data in a multi-scale perspective, they have all focused on either spatial or temporal attributes rather than on the integration of space and time over multiple scales. This study introduces the continuous spatio-temporal model (CSTM), a conceptual model that seeks to address this shortcoming. The presented model is based on (1) the continuous temporal model (CTM), a multi-scale model for temporal information, and (2) the continuous spatial model (CSM), an extension of CTM for multi-scale spatial raster data. At the core of the presented conceptual model is a spatio-temporal evolution element or, in short, stevel, which is described by four variables: (1) pixel location, (2) spatial resolution, (3) temporal interval, and (4) temporal resolution. By varying one or more of these variables, a CSTM-tree consisting of (sets of) stevel arrays is created, forming the basis of an exhaustive CSTM-typology. These arrays can then be used to systematically cluster spatio-temporal information. The value of our approach is illustrated by means of a simplified example of mean temperature evolution. Various suggestions are made for modifications to be developed in future research.

Time-geographic Derivation of Feasible Co-presence Opportunities from Network-constrained Episodic Movement Data

Certain datasets on moving objects are episodic in nature - that is, the data is characterized by time gaps during which the position of the object is unknown. In this article, a model is developed to study the sparsely sampled network-constrained movement of several objects by calculating both potential and feasible (i.e. more likely) co-presence opportunities over time. The approach is applied to the context of a static sensor network, where the location of an object is only registered when passing a sensor location along a road network. Feasibility is incorporated based on the deviation from the shortest path. As an illustration, the model is applied to a large Bluetooth tracking dataset gathered at a mass event. The model output consists of maps showing the temporal evolution of the distribution of feasible co-presence opportunities of tracked visitors over the network (i.e. the number of visitors that could have been present together). We demonstrate the models usefulness in studying the movement and distribution of a crowd over a study area with relatively few sampling locations. Finally, we discuss the results with a special emphasis on the distinction between feasible and actual presence, the need for further validation and calibration, and the performance of the implementation.

Zone-it before IT zones you: a location-based digital notice board to build community while preserving privacy

The current success of ephemeral communication apps such as Snapchat points to the growing awareness among users about online ‘biographic mining’ through information technology by advertisers, companies and government agencies. Based on the literature, we argue that location-based services (LBS) can be the answer to preserving privacy, on the condition that they target trusted communities of anonymous users and that the communication is transient. The paper describes in three steps the development of an app fulfilling these conditions. From the interdisciplinary exchange between digital anthropologists, GIScientists and ICT engineers resulted Zone-it, a virtual notice board for self-zoning, permitting the user to start location-based interactions under certain categories. We present the results of a user survey that determined the apps functionalities. The functionalities offer a way for LBS to invert the purpose of social media such as Facebook by shifting attention from person-based to goal-oriented communication. The paper discusses why this move away from ‘faces’ to ‘places’ meets the purpose of community-building, rather than jeopardising it.

Intelligent Event Management with Bluetooth Sensor Networks

This paper outlines the potential use of Bluetooth tracking of mobile devices in an urban environment for an intelligent and adaptive management of large-scale events. The used methodology is explained in detail, and its information potential is demonstrated through results that were gathered and processed offline. Additionally, a near-future project where the methodology will also generate real-time information is outlined, together with the system architecture necessary for this aim.

A comparative simulation of opportunistic routing protocols using realistic mobility data obtained from mass events

Large crowds at music festivals or other mass events create challenging environments for traditional infrastructure based wireless networks. Mobile devices carried by the attendees produce large amounts of network traffic that can result in network outage or serious delays. Opportunistic networks may offer solutions to enable communication between attendees and/or organizers through direct communication between devices, without requiring a fixed infrastructure. In previous work, researchers have developed numerous opportunistic routing protocols designed to enable communication in such ad hoc networks. In this paper, several of these protocols are evaluated for the specific use case of a music festival by running simulations that make use of realistic mobility data collected during an international music festival. This analysis allows for identification of candidate routing protocols that exhibit properties that make them suitable for the envisaged scenario. The goal is to narrow down the set of candidate protocols and to eventually fine tune them to optimize their working. Based on the simulations, we propose two candidate routing protocols that are most suited for use at mass events.

Towards an Integrated Crowd Management Platform

To date, numerous tracking technologies are being used in order to get insight in various situations where movements of objects are of major importance. Moving objects might be cars moving along the road network, animals running in the forest, people visiting mass events. Our research focuses on this last specific domain. Our aim is to build an integrated centralized system capable of acquiring, analyzing, and modeling the complex movement interactions occurring at mass-events in order to fully support the organizers in crowd management, security and possible evacuation. The integrated system will focus on two systems developed over the past years and successfully deployed at several mass events. The first system (BlueMAP) focuses on visitors, the second system (Terra 3D Incident Management Platform) focuses on the emergency services.