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University of Twente Publications (46,519 recursos)
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.

Group = KEUR

Mostrando recursos 1 - 20 de 6,679

1. Quantum oscillations and subband properties of the two-dimensional electron gas at the LaAlO3/SrTiO3 interface - McCollam, A.; Wenderich, S.; Kruize, M.K.; Guduru, V.K.; Molegraaf, H.J.A.; Huijben, M.; Koster, G.J.; Blank, D.H.A.; Rijnders, A.J.H.M.; Brinkman, A.; Hilgenkamp, H.; Zeitler, U.; Maan, J.C.

2. Globalization, Representation, and Attitudes Towards Democracy - Aarts, Kees; Thomassen, Jacques; Ham, Carolien van

3. A Survey of Provably Secure Searchable Encryption - Bösch, Christoph; Hartel, Pieter; Jonker, Willem; Peter, Andreas
We survey the notion of provably secure Searchable Encryption (SE) by giving a complete and comprehensive overview of the two main SE techniques: Searchable Symmetric Encryption (SSE) and Public Key Encryption with Keyword Search (PEKS). Since the pioneering work of Song, Wagner and Perrig (IEEE S&P ’00), the field of provably secure SE has expanded to the point where we felt that taking stock would provide benefit to the community. The survey has been written primarily for the non-specialist who has a basic information security background. Thus, we sacrifice full details and proofs of individual constructions in favor of an overview...

4. Failing Political Representation or a Change in Kind? Models of Representation and Empirical Trends in Europe - Thomassen, J.J.A.; Ham, C.T. van
This article reviews Peter Mair’s argument on the failure of political parties and the subsequent failure of representative democracy in Europe. It develops a conceptual framework to test the validity of Mair’s argument against competing interpretations of the development of representative democracy. It identifies three ideal typical models of representative democracy that seem to have succeeded each other over time: cleavage-based democracy, competitive democracy, and audience democracy. The article proposes specific empirical hypotheses for political parties and voters in each of these periods and provides empirical evidence to test the validity of these hypotheses. It concludes with a discussion of...

5. The Effects on Students’ Conceptual Understanding of Electric Circuits of Introducing Virtual Manipulatives Within a Physical Manipulatives-Oriented Curriculum - Zacharia, Zacharias C.; Jong, Ton de
This study investigates whether Virtual Manipulatives (VM) within a Physical Manipulatives (PM)-oriented curriculum affect conceptual understanding of electric circuits and related experimentation processes. A pre–post comparison study randomly assigned 194 undergraduates in an introductory physics course to one of five conditions: three experimental conditions with different PM and VM sequences and two control conditions with only PM or VM. Conceptual tests assessed students’ understanding. Instructors’ journals, video data, and interviews provided process-related data. Results showed interplay between manipulative and circuit types. For simple circuits, PM and VM use similarly impacted students’ understanding. However, VM better facilitated understanding than PM for...

6. Effective medium approximations for penetrant sorption in glassy polymers accounting for excess free volume - Ogieglo, Wojciech; Wormeester, Herbert; Wessling, Matthias; Benes, Nieck E.
An accurate determination of a penetrant volume fraction in a swollen polymer is of crucial importance in a range of different technologies. Using optical methods, such as in-situ spectroscopic ellipsometry, it is possible to extract the thickness and refractive index of dry and swollen polymer films. The volume fraction of the penetrant can then be calculated from the change in thickness, or from the refractive index using effective medium approximations. For thermodynamically equilibrated and ideal swollen rubbery polymers, these calculations yield accurate results. However, for glassy polymers the influence of the excess free volume trapped within the polymer network during...

7. Estimating aeolian sand supply from the intertidal beach using video imagery - Duarte Campos, L.A.; Wijnberg, K.M.; Reim, E.; Hulscher, S.J.M.H.

8. Electrostatic potential wells for manipulations of drops in microchannels - Ruiter, R. de; Pit, A.M.; Martins de Oliviera, V.; Wijnperle, D.; Duits, M.H.G.; Ende, H.T.M. van den; Mugele, F.

9. Electrostatic potential wells for on-demand drop manipulation in microchannels - Ruiter, R. de; Pit, A.M.; Martins de Oliviera, V.; Duits, M.H.G.; Ende, H.T.M. van den; Mugele, F.G.
Precise control and manipulation of individual drops are crucial in many lab-on-a-chip applications. We present a novel hybrid concept for channel-based discrete microfluidics with integrated electrowetting functionality by incorporating co-planar electrodes (separated by a narrow gap) in one of the microchannel walls. By combining the high throughput of channel-based microfluidics with the individual drop control achieved using electrical actuation, we acquire the strengths of both worlds. The tunable strength of the electrostatic forces enables a wide range of drop manipulations, such as on-demand trapping and release, guiding, and sorting of drops in the microchannel. In each of these scenarios, the...

10. Trapping of drops by wetting defects - Mannetje, D.J.C.M. 't; Ghosh, S.; Lagraauw, R.; Otten, S.; Pit, A.M.; Berendsen, C.; Zeegers, J.; Ende, H.T.M. van den; Mugele, F.G.
Controlling the motion of drops on solid surfaces is crucial in many natural phenomena and technological processes including the collection and removal of rain drops, cleaning technology and heat exchangers. Topographic and chemical heterogeneities on solid surfaces give rise to pinning forces that can capture and steer drops in desired directions. Here we determine general physical conditions required for capturing sliding drops on an inclined plane that is equipped with electrically tunable wetting defects. By mapping the drop dynamics on the one-dimensional motion of a point mass, we demonstrate that the trapping process is controlled by two dimensionless parameters, the...

11. Direct observation of ionic structure of solid-liquid interfaces: a deep look into the Stern Layer - Siretanu, Igor; Ebeling, Daniel; Andersson, Martin P.; Svane Stipp, S.L. Svane; Philipse, Albert; Cohen Stuart, Martin; Ende, Dirk van den; Mugele, Frieder
The distribution of ions and charge at solid-water interfaces plays an essential role in a wide range of processes in biology, geology and technology. While theoretical models of the solid-electrolyte interface date back to the early 20th century, a detailed picture of the structure of the electric double layer has remained elusive, largely because of experimental techniques have not allowed direct observation of the behaviour of ions, i.e. with subnanometer resolution. We have made use of recent advances in high-resolution Atomic Force Microscopy to reveal, with atomic level precision, the ordered adsorption of the mono- and divalent ions that are...

12. Stick-slip to sliding transition of dynamic contact lines under AC electrowetting - Mannetje, D.J.C.M. 't; Mugele, F.G.; Ende, H.T.M. van den

13. Electrostatic potential wells for manipulations of drops flowing through microchannels - Ruiter, Riëlle de; Pit, A.M.; Martins de Oliviera, V.; Duits, M.H.G.; Ende, H.T.M. van den; Mugele, F.G.

14. Encased cantilevers for low-noise force and mass sensing in liquids - Ziegler, D.; Klaassen, A.; Bahri, D.; Chmielewski, D.; Nievergelt, A.; Mugele, F.; Sader, J.; Ashby, P.D.
Viscous damping severely limits the performance of resonator based sensing in liquids. We present encased cantilevers that overcome this limitation with a transparent and hydrophobic encasement built around the resonator. Only a few micrometers of the cantilever probe protrude from the encasement and water does not enter the encasement. This maintains high Q-factors and reduces the thermo-mechanical noise levels by over one order of magnitude and reaches minimal detectable forces of 12 fN/•Hz in liquids. These probes expand the frontiers of cantilever based sensing. We discuss their design and fabrication with special focus on squeeze film damping and demonstrate their...

15. Privacy-Preserving Verification of Clinical Research - Makri, Eleftheria; Everts, Maarten H.; Hoogh, Sebastiaan de; Peter, Andreas; Akker, Harm op den; Hartel, Pieter; Jonker, Willem
We treat the problem of privacy-preserving statistics verification in clinical research. We show that given aggregated results from statistical calculations, we can verify their correctness efficiently, without revealing any of the private inputs used for the calculation. Our construction is based on the primitive of Secure Multi-Party Computation from Shamir's Secret Sharing. Basically, our setting involves three parties: a hospital, which owns the private inputs, a clinical researcher, who lawfully processes the sensitive data to produce an aggregated statistical result, and a third party (usually several verifiers) assigned to verify this result for reliability and transparency reasons. Our solution guarantees...

16. Distributed Searchable Symmetric Encryption - Bösch, Christoph; Peter, Andreas; Leenders, Bram; Lim, Hoon Wei; Tang, Qiang; Wang, Huaxiong; Hartel, Pieter; Jonker, Willem
Searchable Symmetric Encryption (SSE) allows a client to store encrypted data on a storage provider in such a way, that the client is able to search and retrieve the data selectively without the storage provider learning the contents of the data or the words being searched for. Practical SSE schemes usually leak (sensitive) information during or after a query (e.g., the search pattern). Secure schemes on the other hand are not practical, namely they are neither efficient in the computational search complexity, nor scalable with large data sets. To achieve efficiency and security at the same time, we introduce the...

17. SOFIR: Securely Outsourced Forensic Image Recognition - Bösch, Christoph; Peter, Andreas; Hartel, Pieter; Jonker, Willem
Forensic image recognition tools are used by law enforcement agencies all over the world to automatically detect illegal images on confiscated equipment. This detection is commonly done with the help of a strictly confidential database consisting of hash values of known illegal images. To detect and mitigate the distribution of illegal images, for instance in network traffic of companies or Internet service providers, it is desirable to outsource the recognition of illegal images to these companies. However, law enforcement agencies want to keep their hash databases secret at all costs as an unwanted release may result in misuse which could...

18. Cancellation of OpAmp virtual ground imperfections by a negative conductance applied to improve RF receiver linearity - Mahrof, Dlovan H.; Klumperink, Eric A.M.; Ru, Zhiyu; Oude Alink, Mark S.; Nauta, Bram
High linearity CMOS radio receivers often exploit linear V-I conversion at RF, followed by passive down-mixing and an OpAmp-based Transimpedance Amplifier at baseband. Due to nonlinearity and finite gain in the OpAmp, virtual ground is imperfect, inducing distortion currents. This paper proposes a negative conductance concept to cancel such distortion currents. Through a simple intuitive analysis, the basic operation of the technique is explained. By mathematical analysis the optimum negative conductance value is derived and related to feedback theory. In- and out-of-band linearity, stability and Noise Figure are also analyzed. The technique is applied to linearize an RF receiver, and...

19. Study of failure mechanisms of multi-functional flood defenses - Aguilar Lopez, J.P.; Warmink, J.J.; Schielen, R.M.J.; Hulscher, S.J.M.H.

20. Bed and suspended flux distribution along migrating dunes - Naqshband, S.; Ribberink, J.S.; Hurther, D.; Hulscher, S.J.M.H.

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