University of Twente Publications
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.
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International academic mobility: towards a concentration of the minds in Europe - Wende, Marijk van der
International mobility of academics has risen over the last few decades, especially among PhD students and post-docs. This may be the result of deliberate policies to stimulate such mobility on the one hand and of growing imbalances in academic career opportunities on the other. The general belief that attracting international talents helps to ensure that a country plays a leading role in research and innovation, stimulates countries to develop initiatives to attract international students to doctoral programmes or to attract researchers who emigrated back to the country of origin. More traditional intercontinental mobility patterns from the south to the north...
Editorial - Weerd-Nederhof, Petra de; Visscher, Klaasjan
Lean startup for materials ventures and other science-based ventures: under what conditions is it useful? - Harms, Rainer; Marinakis, Yorgos D.; Walsh, Steven T.
Materials-based ventures face a high degree of technology uncertainty and market uncertainty when engaging in the technology entrepreneurial process. Recently, the lean startup methodology (LSM) has been introduced to practice and education as an integrated approach on how entrepreneurs can resolve these uncertainties when starting up a business. While the literature provides examples of LSM's successful application in a range of application areas, its focus application tends to be on consumer software. The purpose of this article is to discuss the degree to which LSM can be applied to the context of technology entrepreneurship. We find that LSM has strengths...
The stuff that motor chunks are made of: Spatial instead of motor representations? - Verwey, Willem B.; Groen, Eduard C.; Wright, David L.
In order to determine how participants represent practiced, discrete keying sequences in the discrete sequence production task, we had 24 participants practice two six-key sequences on the basis of two pre-learned six-digit numbers. These sequences were carried out by fingers of the left (L) and right (R) hand with between-hand transitions always occurring between the second and third, and the fifth and sixth responses. This yielded the so-called LLRRRL and RRLLLR sequences. Early and late in practice, the keypad used for the right hand was briefly relocated from the front of the participants to 90° at their right side. The...
Effect of temporal stimulus properties on the nociceptive detection probability using intra‑epidermal electrical stimulation - Doll, Robert J.; Maten, Annefloor C.A.; Spaan, Sjoerd P.G.; Veltink, Peter H.; Buitenweg, Jan R.
Chronic pain disorders can be initiated and maintained by malfunctioning of one or several mechanisms underlying the nociceptive function. Although several quantitative sensory testing methods exist to characterize the nociceptive function, it remains difficult to distinguish the contributions of individual mechanisms. Intra-epidermal electrical stimulation of nociceptive fibers allows defining stimuli with temporal properties within the timescale of these mechanisms. Here, we studied the effect of stimulus properties on the psychophysical detection probability. A psychophysical detection experiment was conducted including 30 healthy human participants. Participants were presented with electrical stimuli having various temporal properties. The pulse-width was varied for single pulse...
Probing atmospheric electric fields in thunderstorms through radio emission from cosmic-ray induced air showers - Schellart, P.; Trinh, T.N.G.; Buitink, S.; Corstanje, A.; Enriquez, J.E; Falcke, H.; Bentum, M.J.
We present measurements of radio emission from cosmic ray air showers that took place during thunder storms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields.
Mobile health systems and emergence - Jones, Valerie M.
Changes in the age distribution of the population and increased prevalence of chronic illnesses, together with a shortage of health professionals and other resources, will increasingly challenge the ability of national healthcare systems to meet rising demand for services. Large-scale use of eHealth and mHealth services enabled by advances in ICT are frequently cited as providing part of the solution to this crisis in future provision. As part of this picture, self-monitoring and remote monitoring of patients, for example by means of smartphone apps and body-worn sensors, is on the way to becoming mainstream. In future, each individual’s personal health...
Numerical modelling of granular flows: a reality check - Windows-Yule, C.R.; Tunuguntla, D.R.; Parker, D.J.
Discrete particle simulations provide a powerful tool for the advancement of our understanding of granular media, and the development and refinement of the multitudinous techniques used to handle and process these ubiquitous materials. However, in order to ensure that this tool can be successfully utilised in a meaningful and reliable manner, it is of paramount importance that we fully understand the degree to which numerical models can be trusted to accurately and quantitatively recreate and predict the behaviours of the real-world systems they are designed to emulate. Due to the complexity and diverse variety of physical states and dynamical behaviours...
Competition between geometrically induced and density-driven segregation mechanisms in vibrofluidized granular systems - Windows-Yule, C.R.; Douglas, G.J.M.; Parker, D.J.
The behaviors of granular systems are sensitive to a wide variety of particle properties, including size, density, elasticity, and shape. Differences in any of these properties between particles in a granular mixture may lead to segregation, or “demixing,” a process of great industrial relevance. Despite the known influence of particle geometry in granular systems, a considerable fraction of research into these systems concerns only uniformly spherical particles. We address, for the case of vertically vibrated granular systems, the important question of whether the introduction of differing particle geometries entirely invalidates our existing knowledge based on purely spherical granulates, or whether...
Tapped granular column dynamics: simulations, experiments and modeling - Rosato, A.D.; Zuo, L.; Blackmore, D.; Wu, H.; Horntrop, D.J.; Parker, D.J.; Windows-Yule, C.R.
This paper communicates the results of a synergistic investigation that initiates our long term research goal of developing a continuum model capable of predicting a variety of granular flows. We consider an ostensibly simple system consisting of a column of inelastic spheres subjected to discrete taps in the form of half sine wave pulses of amplitude a/d and frequency f. A three-pronged approach is used, consisting of discrete element simulations based on linear loading-unloading contacts, experimental validation, and preliminary comparisons with our continuum model in the form of an integro-partial differential equation.
Tapped Granular Column Dynamics: Simulations, Experiments and Modeling....
Editorial: Modelling and computational challenges in granular - Weinhart, T.; Thornton, A.R.; Einav, Itai
This is the editorial for the special issue on “Modelling and computational challenges in granular materials” in the journal on Computational Particle Mechanics (CPM).
The issue aims to provide an opportunity for physicists, engineers, applied mathematicians and computational scientists to discuss the current progress and latest advancements in the field of advanced numerical methods and modelling of granular materials. The focus will be on computational methods, improved algorithms and the modelling of interesting industrial and academic problems.
Resonance effects on the dynamics of dense granular beds: achieving optimal energy transfer in vibrated granular systems - Windows-Yule, C.R.; Rosato, A.D.; Thornton, A.R.; Parker, D.J.
Using a combination of experimental techniques and discrete particle method simulations, we investigate the resonant behaviour of a dense, vibrated granular system. We demonstrate that a bed of particles driven by a vibrating plate may exhibit marked differences in its internal energy dependent on the specific frequency at which it is driven, even if the energy corresponding to the oscillations driving the system is held constant and the acceleration provided by the base remains consistently significantly higher than the gravitational acceleration, g. We show that these differences in the efficiency of energy transfer to the granular system can be explained...
Combining situated Cognitive Engineering with a novel testing method in a case study comparing two infusion pump interfaces - Schnittker, R.; Schmettow, M.; Verhoeven, F.; Schraagen, J.M.C.
We validated the usability of a new infusion pump interface designed with a situated Cognitive Engineering approach by comparing it to a reference interface using a novel testing method employing repeated measurements and process measures, in addition to traditional outcome measures. The sample consisted of 25 nurses who performed eight critical tasks three times. Performance measures consisted of number and type of errors, deviations from a pre-established normative path solution, task completion times, number of keystrokes, mental effort and preferences in use. Results showed that interaction with the new interface resulted in 18% fewer errors, 90% fewer normative path deviations,...
Predicting turnaround time reductions of the diagnostic track in the histopathology laboratory using mathematical modelling - Leeftink, A.G.; Boucherie, R.J.; Hans, E.W.; Verdaasdonk, M.A.M.; Vliegen, I.H.M.; Diest, P.J. van
Background Pathology departments face a growing volume of more and more complex testing in an era where healthcare costs tend to explode and short turnaround times (TATs) are expected. In contrast, the histopathology workforce tends to shrink, so histopathology employees experience high workload during their shifts. This points to the need for efficient planning of activities in the histopathology laboratory, to ensure an equal division of workload and low TATs, at minimum costs.
Methods The histopathology laboratory of a large academic hospital in The Netherlands was analysed using mathematical modelling. Data were collected from the Laboratory Management System to determine...
A new reduced model for the moments of droplet size distribution in condensing flow - Ku, X.; Hagmeijer, R.
Purpose - The purpose of this paper is to create a computationally efficient reduced model (RM) for the moments of droplet size distribution (DSD) in condensing flow. Design/methodology/approach - The kinetic equation (KE) exactly describes the time dependence of the DSD and can be regarded as the most rigorous representation of a system with condensation. Because of the typical wide range in droplet size, the KE requires excessive computational time and is not attractive for most practical applications. To reduce the overall computational efforts, a novel set of moment equations, derived from the KE has been proposed. Findings - To...