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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Model reduction of flexible multibody systems with application to large-stroke compliant precision mechanisms - Boer, Steven Ewoud
Numerical simulations are essential to determine the characteristics, performance and structural integrity of mechanisms and robots. With increasingly higher demands on the specifications of such devices, the demands on the accuracy of the numerical models increases as well. Increasing the complexity of the models, inherently increases the computational time of the simulations. Model reduction techniques can offer a reduction of the simulation time, while maintaining sufficient accuracy. In this work, the modelling of flexible multibody systems is considered. The starting point is a numerical approach based on non-linear finite elements such as beams, trusses and hinges. In particular the spatial...
Fourier Spectral of PalmCode as Descriptor for Palmprint Recognition - Mu, Meiru; Ruan, QiuQi; Spreeuwers, Luuk; Veldhuis, Raymond
Study on automatic person recognition by palmprint is currently a hot topic. In this paper, we propose a novel palmprint recognition method by transforming the typical palmprint phase code feature into its Fourier frequency domain. The resulting real-valued Fourier spectral features are further processed by horizontal and vertical 2DPCA method, which proves highly efficient in terms of computational complexity, storage requirement and recognition accuracy. This paper also gives a contrast study on palm code and competitive code under the proposed feature extraction framework. Besides, experimental results on the Hongkong PolyU Palmprint database demonstrate that the proposed method outperforms many currently...
Defusing the debugging scandal - dedicated debugging technologies for advanced dispatching languages - Yin, Haihan
To increase program modularity, new languages have been researched in recent years. They allow changing behavior according to various kinds of contexts at the call sites. In our research, we classified them as advanced-dispatching languages. Advanced-dispatching languages are usually implemented as an extension of main-stream languages. After compilation, their programs are transformed to the compiled form of the main-stream language. Due to this compilation mechanism, source-level abstractions cannot be fully restored during debugging. The information loss increases the effort of comprehending advanced-dispatching programs and fixing advanced-dispatching-specific defects. In this thesis, we performed four works to improve the comprehensibility of debugging...
A micro control valve with integrated capacitive sensing for ambulant blood pressure waveform monitoring - Groen, M.S.; Brookhuis, R.A.; Houwelingen, M.J. van; Brouwer, D.M.; Lötters, J.C.; Wiegerink, R.J.
We have designed and fabricated the first single-wafer proportional micro control valve with built-in capacitive displacement sensing. The displacement sensor can facilitate high-speed active proportional control of gas flow through the valve. This is an essential requirement for non-invasive blood pressure waveform monitoring based on following the arte- rial pressure with a counter pressure. We demonstrate a near-linear relation between valve plate displacement and inverse capacitance. The valve shows monotonously increasing flow with decreasing capacitance and increasing pressure.
Deflection of an eccentric tooth of a comb drive in an electrostatic field - Meijaard, J.P.; Krijnen, B.; Brouwer, D.M.
The elastic deflection of a comb drive tooth in an electrostatic field is considered. The tooth can be symmetrically located between two rigid teeth of the matching comb, in which case the problem reduces to a pure bifurcation problem for which the critical voltage can be determined. Alternatively, due to an ap- proximate straight-line mechanism, the tooth can have a uniform initial lateral displacement and a smooth curve of equilibria is found which has a limit point, after which pull-in occurs. An assumed deflection shape and a series expansion of the electrostatic capacity yield the
deflection curves for the case...
Evaluating a Professional Development Programme for Implementation of a Multidisciplinary Science Subject - Visser, Talitha C.; Coenders, Fer G.M.; Terlouw, Cees; Pieters, Jules
This study aims to evaluate a professional development programme that prepares and assists teachers with the implementation of a multidisciplinary science module, basing the evaluation on participants’ reactions, the first level of Guskey’s five-level model for evaluation (2002). Positive evaluations at the higher levels in Guskey's model are thought to depend upon those at the first level, that is, teachers' positive appreciation for the professional development programme. Different instruments (questionnaires, e-mail correspondence, and interviews) were used at various stages in the four-part professional development programme. The data were categorised by the stage in the programme to which they pertained: individual...
Freedom and constraint analysis and optimization - Brouwer, D.M.; Boer, S.E.; Aarts, R.G.K.M.; Meijaard, J.P.; Jonker, J.B.
Many mathematical and intuitive methods for constraint analysis of mechanisms have been proposed. In this article we compare three methods. Method one is based on Grüblers equation. Method two uses an intuitive analysis method based on opening kinematic loops and evaluating the constraints at the intersection. Method three uses a flexible multibody modeling approach which facilitates the analysis of complex systems. We demonstrate a visualization method using generalized von Mises stress to show overconstraint modes. A four bar mechanism and a two-degree-of- freedom (DOF) flexure-based mechanism serve as a case study. Briefly the optimization of the location and orientation of...
Page sample size in web accessibility testing: how many pages is enough? - Velleman, Eric; Geest, Thea van der
Various countries and organizations use a different sampling approach and sample size of web pages in accessibility conformance tests. We are conducting a systematic analysis to determine how many pages is enough for testing whether a website is compliant with standard accessibility guidelines. This poster reports the work-in-progress. Data collection has been completed and we have started the analysis to determine how many pages is enough for specified reliability levels.
Explaining the performance of Chinese equity funds - Huang, Xiaohong; Shi, Qiqiang
This paper examines the determinants of Chinese equity fund performance measured by market benchmark adjusted returns and risk adjusted return (Jensen’s Alpha). The sample covers 193 equity funds from January 2006 to December 2011, including both bear (2008 and 2011) and bull (2006, 2007, 2009, and 2010) market conditions. We use fund characteristics including size, age, and expense ratio and managerial attributes including manager structure and management education to explain fund performance. We found only expense ratios significantly influence the fund performance under all market conditions. In addition the trading cost is positively associated with fund performance under the bear...
Data dissemination in vehicular environments - Schwartz, Ramon de Souza
In the last few decades, Intelligent Transportation Systems (ITS) have been deployed to reduce congestion, enhance mobility, and help save lives. Among the
various technologies incorporated is vehicular communication which consists
in equipping vehicles with inexpensive wireless devices to enable a decentralized network composed by vehicles and infrastructure points. Such a vehicular network allows vehicles to extend their horizon of awareness to events that are beyond those that on-board sensors alone are able to detect.
In this context, one crucial task is the dissemination of data generated by
a wide range of applications. On the one hand, safety applications are mostly
related to hazardous situations....
Micromachined parallel plate structures for Casimir force measurement and optical modulation - Syed Nawazuddin, Mubassira Banu
In microelectromechanical systems (MEMS), parallel plate structures with submicron separation have been of much use in various types of sensors and actuators. In this thesis such parallel plate structures are employed for two applications viz. the Casimir force measurement and to develop a mechanooptical modulator. Both research studies are focused on realizing parallel plate structures with a separation distance in the order of 1 μm or less.
In this thesis, a methodology to measure the Casimir force using parallel plate structures is described, in which MEMS technology is used to improve the parallelism at sub-micrometer separations. The fabrication of these parallel...
Towards real-time intrusion detection for NetFlow and IPFIX - Hofstede, Rick; Bartos, Vaclav; Sperotto, Anna; Pras, Aiko
DDoS attacks bring serious economic and technical damage to networks and enterprises. Timely detection and mitigation are therefore of great importance. However, when flow monitoring systems are used for intrusion detection, as it is often the case in campus, enterprise and backbone networks, timely data analysis is constrained by the architecture of NetFlow and IPFIX. In their current architecture, the analysis is performed after certain timeouts, which generally delays the intrusion detection for several minutes. This paper presents a functional extension for both NetFlow and IPFIX flow exporters, to allow for timely intrusion detection and mitigation of large flooding attacks....
Eulerian method for super-cooled large-droplet ice-accretion on aircraft wings - Hospers, Jacco Matthijs
Many research has been done to provide scientists and aviation engineers with tools to predict ice accretions on in ight aircraft. The ice accretion problem is often sudden, its eects can be dramatic, leading to aircraft accidents with possible loss of lives. Until now this eld has been relatively steady. It has proven to be fairly easy to model ice accretions for clouds with droplets of relatively small droplet diameter (< 50 μm).
However, a recent trend is to investigate supercooled large droplets, with diameters ranging from 50 μm through 1000 μm or larger. These large droplets have been found...
Serial and parallel processes in working memory after practices: Correction to Oberauer and Bialkova (2011). - Oberaer, Klaus; Bialkova, Svetlana
Reports an error in "Serial and parallel processes in working memory after practice" by Klaus Oberauer and Svetlana Bialkova (Journal of Experimental Psychology: Human Perception and Performance, 2011[Apr], Vol 37, 606-614). Figure 3 was repeated in place of Figure 4. The correct version of Figure 4 appears in the erratum. (The following abstract of the original article appeared in record 2011-06411-008.) Six young adults practiced for 36 sessions on a working-memory updating task in which 2 digits and 2 spatial positions were continuously updated. Participants either did 1 updating operation at a time, or attempted 1 numerical and 1 spatial...
Effect of a nurse-coordinated prevention programme on cardiovascular risk after an acute coronary syndrome: main results of the RESPONSE randomised trial - Jorstad, Harald T.; Birgelen, Clemens von; Alings, A. Marco W.; Liem, Anho; Dantzig, Jan Melle van; Jaarsma, Wiebe; Lok, Dirk J.A.; Kragten, Hans J.A.; Vries, Keesjan de; Milliano, Paul A.R.; Withagen, Adrie J.A.M.; Scholte op Reimer, Wilma J.M.; Tijssen, Jan G.P.; Peters, Ron J.G.
Objective To quantify the impact of a practical, hospital-based nurse-coordinated prevention programme on cardiovascular risk, integrated into the routine clinical care of patients discharged after an acute coronary syndrome, as compared with usual care only.
Design RESPONSE (Randomised Evaluation of Secondary Prevention by Outpatient Nurse SpEcialists) was a randomised clinical trial.
Setting Multicentre trial in secondary and tertiary healthcare settings.
Participants 754 patients admitted for acute coronary syndrome.
Intervention A nurse-coordinated prevention programme, consisting of four outpatient nurse clinic visits, focusing on healthy lifestyles, biometric risk factors and medication adherence, in addition to usual care.
Main outcome measures The main...