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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Drying of supercritical carbon dioxide with membrane processes - Lohaus, Theresa; Scholz, Marco; Koziara, Beata T.; Benes, Nieck E.; Wessling, Matthias
In supercritical extraction processes regenerating the supercritical fluid represents the main cost constraint. Membrane technology has potential for cost efficient regeneration of water-loaded supercritical carbon dioxide. In this study we have designed membrane-based processes to dehydrate water-loaded supercritical carbon dioxide and have evaluated the processes economics as compared to those of a benchmark zeolite process. Seven flowsheet configurations have been simulated in Aspen Plus®. In all processes a low-pressure carbon dioxide sweep stream removes water at the permeate side of the membrane, to maintain a sufficiently large driving force for water transport through the membrane. The performance of the single...
When a game supports prevocational math education but integrated reflection does not - Vrugte, J. ter; Jong, T. de; Wouters, P.; Vandercruysse, S.; Elen, J.; Oostendorp, H. van
The present study addressed the effectiveness of an educational math game for improving proportional reasoning in prevocational education, and examined the added value of support in the form of reflection. The study compared four conditions: the game with reflection prompts, the game with reflection prompts plus procedural information, the game with procedural information only and the game without additional support. It was found that students' proportional reasoning skill improved after playing the game. The game managed to target prevocational students with low prior knowledge, a group that has the potential to understand proportional reasoning but has not yet encountered the...
Small Amplitude Atomic Force Spectroscopy - Beer, Sissi de; Ende, Dirk van den; Ebeling, Daniel; Mugele, Frieder
Over the years atomic force microscopy has developed from a pure imaging technique to a tool that can be employed for measuring quantitative tip–sample interaction forces. In this chapter we provide an overview of various techniques to extract quantitative tip–sample forces focusing on both amplitude modulation and frequency modulation atomic force spectroscopy (AM-AFS and FM-AFS) in the small amplitude regime. We discuss different actuation methods, such as sample modulation, magnetic actuation, and by far the most widely used acoustic driving. Also the corresponding force-inversion methodology is discussed for – in particular – ambient liquid.
The fine art of boundary spanning: Making space for water in the east Netherlands - Warner, Jeroen; Lulofs, Kris; Bressers, Hans
The desire to comply with the European Water Framework Directive, which seeks to promote Integrated Water Management, has led to a large number of proposed projects that in turn make huge demands on the financial and administrative capacity of water managers, who need to combine multiple fields of interest and participation such as agricultural interests, regional economic development, natural values, water safety and water quality issues to complete each project. To achieve these goals, water managers will often need to negotiate and strike alliances with actors in other policy areas such as spatial planning and local and regional economic development....
Factors influencing the use of a web-based application for supporting the self-care of patients with type 2 diabetes: a longitudinal study - Nijland, Nicol; Gemert-Pijnen, Julia E.W.C. van; Kelders, Saskia M.; Brandenburg, Bart J.; Seydel, Erwin R.
The take-up of eHealth applications in general is still rather low and user attrition is often high. Only limited information is available about the use of eHealth technologies among specific patient groups.
The aim of this study was to explore the factors that influence the initial and long-term use of a Web-based application (DiabetesCoach) for supporting the self-care of patients with type 2 diabetes.
A mixed-methods research design was used for a process analysis of the actual usage of the Web application over a 2-year period and to identify user profiles. Research instruments included log files, interviews, usability tests, and a survey.
Effectiveness of a web-based intervention aimed at healthy dietary and physical activity behavior: a randomized controlled trial about users and usage - Kelders, Saskia M.; Gemert-Pijnen, Julia E.W.C. van; Werkman, Andrea; Nijland, Nicol; Seydel, Erwin R.
Recent studies have shown the potential of Web-based interventions for changing dietary and physical activity (PA) behavior. However, the pathways of these changes are not clear. In addition, nonusage poses a threat to these interventions. Little is known of characteristics of participants that predict usage.
In this study we investigated the users and effect of the Healthy Weight Assistant (HWA), a Web-based intervention aimed at healthy dietary and PA behavior. We investigated the value of a proposed framework (including social and economic factors, condition-related factors, patient-related factors, reasons for use, and satisfaction) to predict which participants are users and which participants...
A holistic framework to improve the uptake and impact of eHealth technologies - Gemert-Pijnen, Julia E.W.C. van; Nijland, Nicol; Limburg, Maarten van; Ossebaard, Hans C.; Kelders, Saskia M.; Eysenbach, Gunther; Seydel, Erwin R.
Background: Many eHealth technologies are not successful in realizing sustainable innovations in health care practices. One of the reasons for this is that the current development of eHealth technology often disregards the interdependencies between technology, human characteristics, and the socioeconomic environment, resulting in technology that has a low impact in health care practices. To overcome the hurdles with eHealth design and implementation, a new, holistic approach to the development of eHealth technologies is needed, one that takes into account the complexity of health care and the rituals and habits of patients and other stakeholders.
Objective: The aim of this viewpoint paper...
Why business modeling is crucial in the development of eHealth technologies - Limburg, Maarten van; Gemert-Pijnen, Julia E.W.C. van; Nijland, Nicol; Ossebaard, Hans C.; Hendrix, Ron M.G.; Seydel, Erwin R.
The impact and uptake of information and communication technologies that support health care are rather low. Current frameworks for eHealth development suffer from a lack of fitting infrastructures, inability to find funding, complications with scalability, and uncertainties regarding effectiveness and sustainability. These issues can be addressed by defining a better implementation strategy early in the development of eHealth technologies. A business model, and thus business modeling, help to determine such an implementation strategy by involving all important stakeholders in a value-driven dialogue on what the technology should accomplish. This idea also seems promising to eHealth, as it can contribute to...
Use of a genetic algorithm to improve predictions of alternate-bar dynamics - Knaapen, M.A.F.; Hulscher, S.J.M.H.
Alternate bars may form in sandy beds of straight rivers and channels. These bars are characterized by the alternation of crests, all moving downstream at a speed of several meters per day. The aim of this paper is to predict the dynamics of alternate bars. To that end, we tested predictions of measured alternate bars in flume experiments, as derived from an amplitude evolution model. Weakly nonlinear stability analysis underlies this amplitude evolution model, so that it applies to situations in which the width-to-depth ratio is close to the critical ratio, above which alternate bars occur. The experiments have a...
Ion adsorption-induced wetting transition in oil-water-mineralsystems - Mugele, F.; Bera, B.; Cavalli, A.; Siretanu, Igor; Maestro, M.A.; Duits, M.H.G.; Cohen Stuart, M.A.; Ende, H.T.M. van den; Stocker, I.; collins, I
The relative wettability of oil and water on solid surfaces is generally governed by a complex competition of molecular interaction forces acting in such three-phase systems. Herein, we experimentally demonstrate how the adsorption of in nature abundant divalent Ca2+ cations to solid-liquid interfaces induces a macroscopic wetting transition from finite contact angles (≈10°) with to near-zero contact angles without divalent cations. We developed a quantitative model based on DLVO theory to demonstrate that this transition, which is observed on model clay surfaces, mica, but not on silica surfaces nor for monovalent K+ and Na+ cations is driven by charge reversal...
On the shape of a droplet in a wedge: new insight from electrowetting - Baratian, D.; Cavalli, A.; Ende, H.T.M. van den; Mugele, F.
The equilibrium morphology of liquid drops exposed to geometric constraints can be rather complex. Even for simple geometries, analytical solutions are scarce. Here, we investigate the equilibrium shape and position of liquid drops confined in the wedge between two solid surfaces at an angle α. Using electrowetting, we control the contact angle and thereby manipulate the shape and the equilibrium position of aqueous drops in ambient oil. In the absence of contact angle hysteresis and buoyancy, we find that the equilibrium shape is given by a truncated sphere, at a position that is determined by the drop volume and the...
De excimeerlaser - Blank, Dave
Het gebruik van excimeerlasers neemt steeds meer toe. Ook verschijnen er steeds meer artikelen over het gebruik van deze laser, zowel op het gebied van de medische technologie als op het gebied van f?jnmechanische bewerkingen. Wat maakt deze laser zo uniek en wat zijn de toepassingsgebieden nu en in de nabije toekomst? Dit eerste artikel over de excimeerlaser hoopt daar een antwoord op te geven. In een volgend artikel zal meer worden ingegaan op de technische details van de toepassingen van excimeerlasers.
Distribution and thickness of the surface contaminations on STM tungsten tips, studied by AES/SEM and ARXPS - Lisowski, Wojciech F.; Berg, Albert H.J. van den; Hanekamp, Lambertus J.; Silfhout, Arend van
The combination of Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and angle resolved X-ray photoelectron spectroscopy (ARXPS) has been applied to the analysis of the distribution of elements at the surface region of electrochemically etched tungsten tips and the determination of the thickness of a layer with oxygen and carbon contamination. Auger line profiling revealed a homogeneous distribution of oxygen and significant enrichment of carbon on the W tip between 0 and 1.5 μm from the top. The thickness of the contamination layer on various W materials, electrochemically etched, was found to be 1.35±0.15 nm as measured using ARXPS,...
A sensitive method to measure the integral nonlinearity of a digital-to-time converter based on phase modulation - Palattella, Claudia; Klumperink, Eric A.M.; Ru, Jiayun (Zhiyu); Nauta, Bram
A digital-to-time converter (DTC) produces a time delay based on a digital code. Similar to data converters, linearity is a key metric for a DTC and it can be characterized by its integral nonlinearity (INL). However, measuring the INL of a subpicosecond-resolution DTC is problematic, even when using the best available high-speed oscilloscopes. In this brief we propose a new method to measure the INL of a DTC by applying digital phase modulation and measuring the output spectrum with a spectrum analyzer. The frequency selectivity of this method allows for an improved measurement resolution down to a few femtoseconds and...
Turbulent Rayleigh–Bénard convection described by projected dynamics in phase space - Lülff, Johannes; Wilczek, Michael; Stevens, Richard J.A.M.; Friedrich, Rudolf; Lohse, Detlef
Rayleigh–Bénard convection, i.e. the flow of a fluid between two parallel plates that is driven by a temperature gradient, is an idealised set-up to study thermal convection. Of special interest are the statistics of the turbulent temperature field, which we are investigating and comparing for three different geometries, namely convection with periodic horizontal boundary conditions in three and two dimensions as well as convection in a cylindrical vessel, in order to determine the similarities and differences. To this end, we derive an exact evolution equation for the temperature probability density function. Unclosed terms are expressed as conditional averages of velocities...