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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Magnetic interactions in 2D and 3D arrays - Alink, Laurens
Magnetostatic interactions manifest themselves via the fields and forces between and within magnetized bodies. This thesis topics magnetostatic interactions in arrays at the nano- and millimeter scale. These arrays may find application in magnetic data storage and in future 3D electronics fabricated by self-assembly.
On the nanoscale, interactions are investigated that are involved in reading and writing 2D patterned arrays of magnetic ~100 nm Co/Pt multilayered islands with perpendicular anisotropy, by magnetic force microscopy (MFM), and by modeling and simulations. Such 2D arrays are prototypes for future hard disk drive media, i.e. bit patterned media.
Concerning reading, a new model for...
Towards smart "lining" for microfluidic channels with stimulus responsive polymers - Dos Ramos, Lionel
In this Thesis, the development and the characterization of polymeric films with the ultimate goal of switching the properties of functionalized microchannel surfaces is presented. The coatings were mainly based on two types of stimulus responsive polymers, temperature responsive poly(N-isopropylacrylamide)(PNIPAM) and redox-responsive poly(ferrocenylsilane) (PFS). These polymers allow one to control wettability, adhesion force, and friction which are important variables for preparing designer microchannels. Surface switching was primarily studied by colloid probe AFM. The motivation for the choice of PNIPAM and PFS is rationalized by their responsiveness and by the opportunities for anchoring these polymers to solid substrates, allowing one to...
Oscillatory flows in jet pumps: towards design guidelines for thermoacoustic applications - Oosterhuis, Joris Pieter
Thermoacoustic engines are an interesting alternative to conventional heat engines (such as Stirling engines) due to the absence of moving parts in the hot region and the small temperature difference required to operate. These engines can provide a durable solution in, for example, waste heat recovery applications. Using a traveling wave based configuration, consisting of a toroidal geometry, thermal-to-acoustic efficiencies of up to 30% have been obtained. However, the traveling wave configuration has a major disadvantage: due to the closed looped geometry a time-averaged mass flow, known as "Gedeon streaming", can occur. This type of acoustic streaming can lead to...
Particles in polymer-functionalized microchannels: electrochemical experiments and molecular dynamics simulations - Kieviet, Bernard Dingeman
The aim of this thesis has been to provide the ground work for the electrochemical sensing of analytes in polymer-functionalized microchannels via gold-coated microfabricated microchannel electrodes and for the in-situ study of the adsorption of particles in polymer brushes through molecular dynamics simulations. Both these objectives encompass polymer systems that are out of equilibrium and reveal how particles interact with these polymers. The aim was accomplished via the successful fabrication of in-channel gold-coated electrodes within a microfluidic device. To these gold-coated electrodes a redox-active polymer, poly(ferrocenylsilane) (PFS), was attached, via which sodium ascorbate could be sensed. To further understand the...
Numerical study of extreme-ultra-violet generated plasmas in hydrogen - Astakhov, Dmitry
In this thesis, we present the development and study a numerical model of EUV-induced plasma. Understanding of behavior of low pressure low density plasmas is of industrial relevance, because of their potential use for on-line removal of different forms of contaminations from multilayer mirrors, which will help increase the throughput of EUV lithography.
The model is 2D axially symmetric particle-in-cell code, hence it allows the full geometry of an axially symmetric chamber to be taken into account. Therefore, a quantitative connection between different experimental data, such as discharge characteristic measurements, and plasma parameters could be established. In order to ensure that...
Divide, combine and conquer: on the effect of individual properties of biomaterials for bone regeneration - Danoux, Charlène Bénédictine Saint Servais
The increase of life expectancy in the developed countries has resulted in a growing demand for replacement of damaged and degraded bone. To overcome the limitations of autologous bone grafts, research efforts have focused for decades on developing synthetic substitutes that can be produced in large quantities, are readily available and relatively inexpensive. Among various synthetic bone graft substitutes, calcium phosphate (CaP)-based ones have been extensively used in bone repair and regeneration because of their close resemblance with natural bone mineral. CaP bone graft substitutes are biocompatible, osteogenic and osteoconductive, and some have shown osteoinductive properties, which are believed to...
System merits or failures? Policies for transition to sustainable P and N systems in the Netherlands and Finland - Hoppe, Thomas; Kuokkanen, Anna; Mikkilä, Mirja; Kahiluoto, Helena; Kuisma, Miia; Arentsen, Maarten; Linnanen, Lassi
Nitrogen (N) and phosphorus (P) cycles are absolutely vital in maintaining sustainable food systems. Human activities disturb the natural balance of these cycles by creating enormous additional nutrient fluxes, causing eutrophication of waterways and pollution in land systems. To tackle this problem, sustainable nutrient management is required. This paper addresses sustainable nutrient management in two countries: The Netherlands and Finland. We adopt a critical perspective on resource politics, especially towards opportunistic policy strategies for the pollutant management of N and P. Two research questions are considered. First, what are the key systemic and policy failures that occurred in the N...
Steering an actuated-tip needle in biological tissue: fusing FBG-sensor data and ultrasound images - Shahriari, Navid; Roesthuis, Roy J.; Berg, Nick J. van de; Dobbelsteen, John J. van den; Misra, Sarthak
Needle insertion procedures are commonly performed in current clinical practice for diagnostic and therapeutic purposes. Although prevailing technology allows accurate localization of lesions, they cannot yet be precisely targeted. Needle steering is a promising technique to overcome this challenge. In this paper, we describe the development of a novel steering system for an actuated-tip flexible needle. Strain measurements from an array of Fiber Bragg Grating (FBG) sensors are used for online reconstruction of the needle shape in 3D-space. FBG-sensor data is then fused with ultrasound images obtained from a clinically-approved Automated Breast Volume Scanner (ABVS) using an unscented Kalman filter....
Feasibility of external rhythmic cueing with the Google Glass for improving gait in people with Parkinson’s disease - Zhao, Yan; Nonnekes, Jorik; Storcken, Erik J.M.; Janssen, Sabine; Wegen, Erwin E.H. van; Bloem, Bastiaan R.; Dorresteijn, Lucille D.A.; Vugt, Jeroen P.P. van; Heida, Tjitske; Wezel, Richard J.A. van
New mobile technologies like smartglasses can deliver external cues that may improve gait in people with Parkinson’s disease in their natural environment. However, the potential of these devices must first be assessed in controlled experiments. Therefore, we evaluated rhythmic visual and auditory cueing in a laboratory setting with a custom-made application for the Google Glass. Twelve participants (mean age = 66.8; mean disease duration = 13.6 years) were tested at end of dose. We compared several key gait parameters (walking speed, cadence, stride length, and stride length variability) and freezing of gait for three types of external cues (metronome, flashing...
Implementing a low-latency parallel graphic equalizer with heterogeneous computing - Norilo, Vesa; Verstraelen, Math; Valimaki, Vesa
This paper describes the implementation of a recently introduced parallel graphic equalizer (PGE) in a heterogeneous way. The control and audio signal processing parts of the PGE are distributed to a PC and to a signal processor, of WaveCore architecture, respectively. This arrangement is particularly suited to the algorithm in question, benefiting from the low-latency characteristics of the audio signal processor as well as general purpose computing power for the more demanding filter coefficient computation. The design is achieved cleanly in a high-level language called Kronos, which we have adapted for the purposes of heterogeneous code generation from a uniform...
Product evolution: how new (types of) products come about & develop over time into families of advanced versions - Ehlhardt, Huub
This thesis presents a Theory of Product Evolution which builds on the work of many scholars who have described evolutionary patterns in innovation processes. It challenges the popular notion that we owe the availability of products solely to genius inventors. Instead arguments are presented to show that a process of variation, selection and retention driving the accumulation of ‘know-how’ (to make) and ‘know-what’ (function to realize) provide an explanation for the emergence of products and their subsequent development into families of advanced versions. This theory employs the Product Evolution Diagram as an analytical framework to reconstruct the development history of...
Why Does Positive Mental Health Buffer Against Psychopathology? An Exploratory Study on Self-Compassion as a Resilience Mechanism and Adaptive Emotion Regulation Strategy - Trompetter, Hester R.; Kleine, Elian de; Bohlmeijer, Ernst T.
Growing evidence suggests that positive mental health or wellbeing protects against psychopathology. How and why those who flourish derive these resilient outcomes is, however, unknown. This exploratory study investigated if self-compassion, as it continuously provides a friendly, accepting and situational context for negative experiences, functions as a resilience mechanism and adaptive emotion regulation strategy that protects against psychopathology for those with high levels of positive mental health. Participants from the general population (n = 349) provided measures at one time-point on positive mental health (MHC-SF), self-compassion (SCS-SF), psychopathology (HADS) and negative affect (mDES). Self-compassion significantly mediated the negative relationship between...
The efficacy of the Internet and Social Media as Medical Marketing Tools - Constantinides, Efthymios; Karantinou, Kalipso; Alexiou, Maria; Vlachaki, Athanasia
The role and efficacy of online marketing in healthcare remains underexplored. The present study, focusing on one medical specialty, investigates the perceived role of the Internet and social media as marketing tools from the perspectives of both healthcare providers and patients. It assesses their role as communication and customer acquisition channels and identifies differences in perceptions between providers and patients. The findings suggest that the role of the Internet and social media as patient acquisition channels is limited but presence of healthcare providers in these channels is considered as important for reassuring customers. The results indicate that the online presence...
Impact of online product reviews on purchasing decisions - Holleschovsky, Nina Isabel; Constantinides, Efthymios
Online consumer reviews, product and services recommendations and peer opinions play an increasingly growing role in the customer’s decision making process. The various online product review and recommendation platforms differ in their objectives, function and characteristics. The literature has so far paid little attention on function characteristics of these platforms as an element of customer adoption and preference. Given the importance of this form of customer generated content on business sales and profitability the monitoring and often responding to customer reviews by business organizations has become a major managerial challenge and an important reputation management issue. In order to respond...
Het 'Oekraïne-referendum' in de ogen van de kiezers - Rosema, Martin; Kanne, Peter; Klein Kranenburg, Laurens
Het tweede landelijke referendum in Nederland sinds de invoering van het algemeen kiesrecht zal gaan over het associatieverdrag tussen de Europese Unie en Oekraïne. Hoe de bevolking tegen dit referendum aankijkt hebben we onderzocht op basis van een enquête onder ongeveer 3.500 kiezers. Zij zijn verdeeld over de vragen of dit referendum wenselijk is en of de politici in Den Haag de uitslag moeten volgen. Veel kiezers hadden enkele maanden voor de stemming al een stemintentie, zonder veel te weten van de inhoud van het verdrag, en een meerderheid was van plan om ‘tegen’ te stemmen. De stemvoorkeur is primair...
Evaluation of the tip-bending response in clinically used endoscopes - Rozeboom, Esther D.; Reilink, Rob; Schwartz, Matthijs P.; Fockens, Paul; Broeders, Ivo A.M.J.
Background and study aims: Endoscopic interventions require accurate and precise control of the endoscope tip. The endoscope tip response depends on a cable pulling system, which is known to deliver a significantly nonlinear response that eventually reduces control. It is unknown whether the current technique of endoscope tip control is adequate for a future of high precision procedures, steerable accessories, and add-on robotics. The aim of this study was to determine the status of the tip response of endoscopes used in clinical practice.
Materials and methods: We evaluated 20 flexible colonoscopes and five gastroscopes, used in the endoscopy departments of a...
Governance across regional borders: which models are best suited to Central and Eastern Europe? - Groenendijk, Nico
The need for efficient and effective cross-border cooperation is apparent in many policy fields. Increasingly, regional local and local authorities in Europe have become involved in cross-border cooperation schemes. Apart from political advantages, the main rationale for such cooperation is better policy delivery. However, the more diverse regions and their policies are, the more challenging it is to establish adequate governance systems across borders that ensure this outcome. This paper puts forward a typology of governance models for cross-border cooperation, largely based on multi-level governance literature. This typology is tentatively applied to Central and Eastern Europe.
Verbeterde afsprakenplanning voor patiënt en gipsverbandmeester - Vrugt, Maartje van de; Matel, Petra; Boucherie, Richard J.; Engelen, Peter van; Beukman, Tiny; Laat, John de
De gipsverbandmeesters van het Jeroen Bosch Ziekenhuis (JBZ) ervaren een sterk wisselende werkdruk en moeten geregeld overwerken. Doordat er verschillende poli’s afhankelijk zijn van de dienstverlening van de gipskamer, hebben lange wachttijden bij de gipskamer ook negatieve gevolgen elders in huis. Met behulp van een computersimulatiemodel zijn verschillende scenario’s geanalyseerd en zijn de aankomstmomenten van patiënten geoptimaliseerd. De gipsverbandmeesters onderzoeken momenteel de implementatie van de resultaten.
A Review on the Mechanical Modeling of Composite Manufacturing Processes - Baran, Ismet; Cinar, Kenan; Ersoy, Nuri; Akkerman, Remko; Hattel, Jesper H.
The increased usage of fiber reinforced polymer composites in load bearing applications requires a detailed understanding of the process induced residual stresses and their effect on the shape distortions. This is utmost necessary in order to have more reliable composite manufacturing since the residual stresses alter the internal stress level of the composite part during the service life and the residual shape distortions may lead to not meeting the desired geometrical tolerances. The occurrence of residual stresses during the manufacturing process inherently contains diverse interactions between the involved physical phenomena mainly related to material flow, heat transfer and polymerization or...