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University of Twente Publications (47,497 recursos)
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.

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Mostrando recursos 1 - 20 de 21,248

1. Decentralized vs. centralized scheduling in wireless sensor networks for data fusion - Mitici, Mihaela; Goseling, Jasper; Graaf, Maurits de; Boucherie, Richard J.
We consider the problem of data estimation in a sensor wireless network where sensors transmit their observations according to decentralized and centralized transmission schedules. A data collector is interested in achieving a data estimation using several sensor observations such that the variance of the estimation is below a targeted threshold. We analyze the waiting time for a collector to receive sufficient sensor observations. We show that, for sufficiently large sensor sets, the decentralized schedule results in a waiting time that is a constant factor approximation of the waiting time under the optimal centralized scheme.

2. Optimal deployment of caches in the plane - Mitici, Mihaela; Goseling, Jasper; Graaf, Maurits de; Boucherie, Richard J.
We consider wireless caches placed in the plane according to a homogeneous Poisson process. A data file is stored at the caches, which have limited storage capabilities. Clients can contact the caches to retrieve the data. The caches store the data according to one of the two data allocation strategies: partitioning & coding. We consider the Pareto front of the expected deployment cost of the caches and the expected cost of a client retrieving the data from the caches. We show that there is a strong trade-off between the expected retrieval and the expected deployment cost under the partitioning and...

3. Application of a conceptual framework for the modelling and execution of clinical guidelines as networks of concurrent processes - Fung, Nick Lik San; Widya, Ing; Broens, Tom; Larburu, Nekane; Bults, Richard; Shalom, Erez; Jones, Val; Hermens, Hermie
We present a conceptual framework for modelling clinical guidelines as networks of concurrent processes. This enables the guideline to be partitioned and distributed at run-time across a knowledge-based telemedicine system, which is distributed by definition but whose exact physical configuration can only be determined after design-time by considering, amongst other factors, the individual patient's needs. The framework was applied to model a clinical guideline for gestational diabetes mellitus and to derive a prototype that executes the guideline on a smartphone. The framework is shown to support the full development trajectory of a decision support system, including analysis, design and implementation.

4. Sub-base-pair resolution during DNA separation in an optofluidic chip - Pollnau, M.; Hammer, M.; Dongre, C.; Hoekstra, H.J.W.M.
DNA sequencing in a lab-on-a-chip aims at providing cheap, high-speed analysis of low reagent volumes to, e.g., identify genomic deletions or insertions associated with genetic illnesses. Detecting single base-pair insertions or deletions from DNA fragments in the diagnostically relevant range of 150-1000 base-pairs requires a sizing accuracy of S < 10^-3, while only S < 10^-2 were reported. Here we demonstrate a sizing accuracy of S = 4 x 10^-4, thereby paving the way for the envisaged applications.

5. Effective coastal boundary conditions for tsunami wave run-up over sloping bathymetry - Kristina, W.; Bokhove, O.; Groesen, E.W.C. van
An effective boundary condition (EBC) is introduced as a novel technique for predicting tsunami wave run-up along the coast, and offshore wave reflections. Numerical modeling of tsunami propagation in the coastal zone has been a daunting task, since high accuracy is needed to capture aspects of wave propagation in the shallower areas. For example, there are complicated interactions between incoming and reflected waves due to the bathymetry and intrinsically nonlinear phenomena of wave propagation. If a fixed wall boundary condition is used at a certain shallow depth contour, the reflection properties can be unrealistic. To alleviate this, we explore a...

6. Using Trusted Execution Environments in Two-factor Authentication: comparing approaches - Rijswijk-Deij, Roland van; Poll, Erik
Classic two-factor authentication has been around for a long time and has enjoyed success in certain markets (such as the corporate and the banking environ- ment). A reason for this success are the strong security properties, particularly where user interaction is concerned. These properties hinge on a security token being a physi- cally separate device. This paper investigates whether Trusted Execution Environments (TEE) can be used to achieve a comparable level of security without the need to have a separate device. To do this, we introduce a model that shows the security properties of user interaction in two-factor authentication. The...

7. Solving the N-Queens Problem with GROOVE - Towards a Compendium of Best Practices - Zambon, Eduardo; Rensink, Arend
We present a detailed solution to the N-queens puzzle using GROOVE, a graph transformation tool especially designed for state space exploration and analysis. While GROOVE has been freely available for more than a decade and has attracted a reasonable number of users, it is safe to say that only a few of these users fully exploit the tool features. To improve this situation, using the N-queens puzzle as a case study, in this paper we provide an in-depth discussion about problem solving with GROOVE, at the same time highlighting some of the tool’s more advanced features. This leads to a...

8. Graph- versus Vector-Based Analysis of a Consensus Protocol - Delzanno, Giorgio; Rensink, Arend; Traverso, Riccardo
The Paxos distributed consensus algorithm is a challenging case-study for standard, vector-based model checking techniques. Due to asynchronous communication, exhaustive analysis may generate very large state spaces already for small model instances. In this paper, we show the advantages of graph transformation as an alternative modelling technique. We model Paxos in a rich declarative transformation language, featuring (among other things) nested quantifiers, and we validate our model using the GROOVE model checker, a graph-based tool that exploits isomorphism as a natural way to prune the state space via symmetry reductions. We compare the results with those obtained by the standard...

9. Optimal relaxed causal sampling from system theoretic viewpoint - Shekhawat, Hanumant Singh; Meinsma, Gjerrit
This paper studies the design of an optimal relaxed causal sampler using sampled data system theory. A lifted frequency domain approach is used to obtain the existence conditions and the optimal sampler. A state space formulation of the results is also provided. The resulting optimal relaxed causal sampler is a cascade of a linear continuous time system followed by a generalized sampler and a discrete system.

10. Generating and Solving Symbolic Parity Games - Kant, Gijs; Pol, Jaco van de
We present a new tool for verification of modal mu-calculus formulae for process specifications, based on symbolic parity games. It enhances an existing method, that first encodes the problem to a Parameterised Boolean Equation System (PBES) and then instantiates the PBES to a parity game. We improved the translation from specification to PBES to preserve the structure of the specification in the PBES, we extended LTSmin to instantiate PBESs to symbolic parity games, and implemented the recursive parity game solving algorithm by Zielonka for symbolic parity games. We use Multi-valued Decision Diagrams (MDDs) to represent sets and relations, thus enabling...

11. Comparison Of Local And Global Undirected Graphical Models - Zhu, Zhemin; Hiemstra, Djoerd; Apers, Peter; Wombacher, Andreas
CRFs are discriminative undirected models which are globally normalized. Global normalization preserves CRFs from the label bias problem which most local models suffer from. Recently proposed co-occurrence rate networks (CRNs) are also discriminative undirected models. In contrast to CRFs, CRNs are locally normalized. It was established that CRNs are immune to the label bias problem even they are local models. In this paper, we further compare ECRNs (using fully empirical relative frequencies, not by support vector Regression) and CRFs. The connection between Co-occurrence Rate, which is the exponential function of pointwise mutual information, and Copulas is built in continuous case. Also...

12. Flow-based approaches in network management: recent advances and future trends - Editorial - Sadre, Ramin; Sperotto, Anna; Hofstede, Rick; Brownlee, Nevil

13. Six-axis force-torque sensor - Brookhuis, Robert Anton; Lammerink, Theodorus Simon Josef; Wiegerink, Remco John
A sensing device for measuring force and/or torque includes a top part with a top electrode structure, a bottom part with a bottom electrode structure, and a support structure. The support structure includes spring elements for supporting the top part on the bottom part with the top electrode structure parallel to and facing the bottom electrode structure. The spring elements provide a gap between the top and bottom electrode structures and allow displacement of the top part relative to the bottom part in three orthogonal directions two parallel and one perpendicular to the bottom plate, and for rotation of the...

14. Device and method for determining the combustion value of a fuel - Lötters, Joost Conrad; Lammerink, Theodorus Simon Josef; Wiegerink, Remco John; Mouris, Albertus Johannes; Pap, Marco Gabor; Boer, Meint Jelle de; Sanders, Remco Gerardus Petrus
The invention relates to a device (1) for determining the combustion value of a fuel. The device (1) comprises a fuel inlet (40) for supplying the fuel to be measured to the device (1). A gas inlet (50) is provided for supplying an oxygen-containing gas to the device (1). The device (1) further comprises a combustion unit connected to the fuel inlet (40) and the gas inlet (50), which combustion unit is provided with a combustion chamber (7) for combusting the fuel to be measured therein. A gas outlet (8) connected to the combustion chamber (7) makes it possible to...

15. APE: Authenticated Permutation-Based Encryption for Lightweight Cryptography - Andreeva, Elena; Bilgin, Begül; Bogdanov, Andrey; Luykx, Atul; Mennink, Bart; Mouha, Nicky; Yasuda, Kan
The domain of lightweight cryptography focuses on cryptographic algorithms for extremely constrained devices. It is very costly to avoid nonce reuse in such environments, because this requires either a hardware source of randomness, or non-volatile memory to store a counter. At the same time, a lot of cryptographic schemes actually require the nonce assumption for their security. In this paper, we propose APE as the first permutation-based authenticated encryption scheme that is resistant against nonce misuse. We formally prove that APE is secure, based on the security of the underlying permutation. To decrypt, APE processes the ciphertext blocks in reverse...

16. A telehealth programme for self-management of COPD exacerbations and promotion of an active lifestyle: a pilot randomized controlled trial - Tabak, Monique; Brusse-Keizer, Marjolein; Valk, Paul van der; Hermens, Hermie; Vollenbroek-Hutten, Miriam
The objective of this pilot study was to investigate the use of and satisfaction with a chronic obstructive pulmonary disease (COPD) telehealth program applied in both primary and secondary care. The program consisted of four modules: 1) activity coach for ambulant activity monitoring and real-time coaching of daily activity behavior, 2) web-based exercise program for home exercising, 3) self-management of COPD exacerbations via a triage diary on the web portal, including self-treatment of exacerbations, and 4) teleconsultation. Twenty-nine COPD patients were randomly assigned to either the intervention group (telehealth program for 9 months) or the control group (usual care). Page...

17. Face identification in videos from mobile cameras - Mu, Meiru; Spreeuwers, Luuk; Veldhuis, Raymond
It is still challenging to recognize faces reliably in videos from mobile camera, although mature automatic face recognition technology for still images has been available for quite some time. Suppose we want to be alerted when suspects appear in the recording of a police Body-Cam, even a good face matcher on still images would give many false alarms due to the uncontrolled conditions. This paper presents an approach to identify faces in videos from mobile cameras. A commercial face matcher FaceVACS is used to process the face recognition frame by frame. On a video of certain length, in order to...

18. Generating and analyzing synthetic finger vein images - Hillerström, Fieke; Kumar, Ajay; Veldhuis, Raymond
Abstract: The finger-vein biometric offers higher degree of security, personal privacy and strong anti-spoofing capabilities than most other biometric modalities employed today. Emerging privacy concerns with the database acquisition and lack of availability of large scale finger-vein database have posed challenges in exploring this technology for large scale applications. This paper details the first such attempt to synthesize finger-vein images and presents analysis of synthesized images for the biometrics authentication. We generate a database of 50,000 finger vein images, corresponding to 5000 different subjects, with 10 different synthesized finger-vein images from each of the subject. We use tractable probability models...

19. Influence of the relative humidity on the morphology of inkjet printed spots of IgG on a non-porous substrate - Mujawar, Liyakat Hamid; Kuerten, J.G.M.; Siregar, D.P.; Amerongen, A. van; Norde, Willem
During the drying of inkjet printed droplets, the solute particles (IgG-Alexa-635 molecules) in the drop may distribute unevenly on the substrate, resulting in a “coffee-stain” spot morphology. In our study, we investigated the influence of the relative humidity on the distribution of inkjet printed fluorophore labeled IgG molecules on a polystyrene substrate. A theoretical model for an evaporating droplet was developed in order to predict the changes in the spot diameter, height and volume of a drying droplet. An experiment was performed where a sessile droplet was monitored using a CCD camera installed on a goniometer and good agreement was...

20. Increasing the competitiveness of e-vehicles in Europe - Figenbaum, Erik; Fearnley, Nils; Pfaffenbichler, Paul; Hjorthol, Randi; Kolbenstvedt, Marika; Emmerling, Bettina; Jellinek, Reinhard; Bonnema, G. Maarten; Ramjerdi, Farideh; Iversen, Lykke Møller
The 2011 EU White Paper on Transport sets ambitious goals for phasing out conventionally fuelled cars in cities. Take-up and expansion of electric vehicles (e-vehicles, or electromobility) are one way to achieve this, as proposed by, i.a., the European Green Cars Initiative, the EU Action Plan on Urban Mobility, European alternative fuels strategy, and so on. This paper discusses incentives for the take-up and use of e-vehicles that are in place in different European countries. Especially, it analyses Norway and Austria, in order to establish and understand factors influencing the competitiveness of e-vehicles and potential market penetration. Norway currently enjoys...

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