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University of Twente Publications (46,625 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 21,328

1. European Universities as Complete Organizations? Understanding Identity, Hierarchy and Rationality in Public Organizations - Seeber, Marco; Lepori, Benedetto; Montauti, Martina; Enders, Jürgen; Boer, Harry de; Weyer, Elke; Bleiklie, Ivar; Hope, Kristin; Michelsen, Svein; Nyhagen Mathisen, Gigliola; Frølich, Nicoline; Scordato, Lisa; Stensaker, Bjorn; Waagene, Erica; Dragsic, Zarko; Kretek, Peter; Krücken, Georg; Magalhaes, Antonio; Ribeiro, Filipa M.; Sousa, Sofia; Veiga, Amelia; Santiago, Rui; Marini, Giulio; Reale, Emanuela
This article investigates the form of European universities to determine the extent to which they resemble the characteristics of complete organizations and whether the forms are associated with modernization policy pressure, national institutional frames and organizational characteristics. An original data set of twenty-six universities from eight countries was used. Specialist universities have a stronger identity, whereas the level of hierarchy and rationality is clearly associated with the intensity of modernization policies. At the same time, evidence suggests limitations for universities to become complete, as mechanisms allowing the development of some dimensions seemingly constrain the capability to develop others

2. Suïcides onder jongeren in de periode 1996-2012 - Bijker, L.; Boere-Boonekamp, M.M.; Duijst, W.L.J.M.; Ghoncheh, R.; Sijperda, O.; Kerkhof, A.J.F.M.
Preventie van suïcide begint bij weten. Een gedegen registratieprocedure is de basis voor analyse in wetenschappelijk onderzoek. Wij voerden een dossieronderzoek uit bij 20 van de 25 GGD-regio’s en de FARR. Van het op basis van gegevens van het CBS geschatte aantal van 1442 jongeren tot en met 23 jaar overleden als gevolg van suïcide konden 607 lijkschouwdossiers (43%) en 129 hiermee corresponderende JGZ-dossiers (21%) worden bestudeerd. De beschikbare dossiers bleken niet gestandaardiseerd en incompleet ingevuld en soms vanwege het handschrift onleesbaar. De registraties waren niet toereikend om relevante kenmerken en omstandigheden te analyseren en daarop preventieve maatregelen te baseren....

3. Effects of adaptive cruise control and highly automated driving on workload and situation awareness: A review of the empirical evidence. - Winter, Joost C.F.; Happee, Riender; Martens, Marieke H.; Stanton, Neville A.
Adaptive cruise control (ACC), a driver assistance system that controls longitudinal motion, has been introduced in consumer cars in 1995. A next milestone is highly automated driving (HAD), a system that automates both longitudinal and lateral motion. We investigated the effects of ACC and HAD on drivers’ workload and situation awareness through a meta-analysis and narrative review of simulator and on-road studies. Based on a total of 32 studies, the unweighted mean self-reported workload was 43.5% for manual driving, 38.6% for ACC driving, and 22.7% for HAD (0% = minimum, 100 = maximum on the NASA Task Load Index or...

4. Generators with a closure relation - Schwenninger, Felix L.; Zwart, Hans

5. Affective Brain-Computer Interfaces: Special Issue Editorial - Mühl, Christian; Allison, Brandan; Nijholt, Anton; Chanel, Guillaume
Over the last several years, brain-computer interface (BCI) research has grown well beyond initial efforts to provide basic communication for people with severe disabilities that prevent them from communicating otherwise. Since BCIs rely on direct measures of brain activity, users do not have to move in any way to convey information. During the early years of BCI research, BCI systems had little to offer healthy users. Since most users can communicate quickly and easily by speaking or typing, why would healthy people use a BCI? Several different answers to this question have been presented. For example, when healthy users’ hands and/or...

6. Using Critical State Theory for Modelling of Asphalt Mix Compaction - Huerne, Henny ter; Maarseveen, Martin F.A.M. van; Molenaar, Andre A.A.; Ven, Martin F.C. van de
This paper focuses on modeling of Hot Mix Asphalt (HMA) material behavior during compaction. During compaction the particle configuration inside the HMA is changing from a relatively loose into a denser one while the bitumen is fluid. Initially particle reorientation is easily possible due to the HMA's loose configuration. The material behavior predominantly falls in the elastic-plastic domain. Critical state theory from soil mechanics is proposed as a basis for modeling this behavior. An extensive laboratory testing program was undertaken using a modified Hveem stabilometer as a tool for parameterization. The program included: different mixtures, different stages of mixture density...

7. DNSSEC meets real world: dealing with unreachability caused by fragmentation - Broek, Gijs van den; Rijswijk-Deij, Roland van; Sperotto, Anna; Pras, Aiko
The Domain Name System (DNS) provides a critical service on the Internet: translating host names into IP addresses. Traditional DNS does not provide guarantees about authenticity and origin integrity. DNSSEC, an extension to DNS, improves this by using cryptographic signatures, at the expense of larger response messages. Some of these larger response messages experience fragmentation, and may, as a result of that, be blocked by firewalls. As a consequence, resolvers behind such firewalls will no longer receive complete responses from name servers, leading to certain Internet zones becoming unreachable because no translation into IP addresses can be performed. Our research shows...

8. Adapting the Complexity Level of a Serious Game to the Proficiency of Players - Oostendorp, Herre van; Spek, Erik D van der; Linssen, Jeroen
As games are continuously assessing the player, this assessment can be used to adapt the complexity of a game to the proficiency of the player in real time. We performed an experiment to examine the role of dynamic adaptation. In one condition, participants played a version of our serious game for triage training that automatically adapted the complexity level of the presented cases to how well the participant scored previously. Participants in the control condition played a version of the game with no adaptation. The adapted version was significantly more efficient and resulted in higher learning gains per instructional case,...

9. Implementation of WirelessHART in the NS-2 Simulator and Validation of Its Correctness - Zand, Pouria; Mathews, Emi; Havinga, Paul; Stojanovski, Spase; Sisinni, Emiliano; Ferrari, Paolo
One of the first standards in the wireless sensor networks domain,WirelessHART (HART (Highway Addressable Remote Transducer)), was introduced to address industrial process automation and control requirements. This standard can be used as a reference point to evaluate other wireless protocols in the domain of industrial monitoring and control. This makes it worthwhile to set up a reliable WirelessHART simulator in order to achieve that reference point in a relatively easy manner. Moreover, it offers an alternative to expensive testbeds for testing and evaluating the performance of WirelessHART. This paper explains our implementation of WirelessHART in the NS-2 network simulator. According...

10. A survey of affective brain computer interfaces: principles, state-of-the-art, and challenges - Mühl, Christian; Allison, Brandan; Nijholt, Anton; Chanel, Guillaume
Affective states, moods and emotions, are an integral part of the human nature: they shape our thoughts, govern the behavior of the individual, and influence our interpersonal relationships. The last decades have seen a growing interest in the automatic detection of such states from voice, facial expression and physiological signals, primarily with the goal of enhancing human-computer interaction with an affective component. With the advent of brain-computer interface research, the idea of affective brain-computer interfaces (aBCI), enabling affect detection from brain signals, arose. In this article, we set out to survey the field of neurophysiology-based affect detection. We outline possible...

11. Editorial for special section of grid computing journal on "Cloud Computing and Services Science" - Sinderen, Marten J. van; Ivanov, Ivan I.
This editorial briefly discusses characteristics, technology developments and challenges of cloud computing. It then introduces the papers included in the special issue on "Cloud Computing and Services Science" and positions the work reported in these papers with respect to the previously mentioned challenges.

12. Change impact analysis for requirements: A metamodeling approach - Göknil, Arda; Kurtev, Ivan; Berg, Klaas van den; Spijkerman, Wietze
Context: Following the evolution of the business needs, the requirements of software systems change continuously and new requirements emerge frequently. Requirements documents are often textual artifacts with structure not explicitly given. When a change in a requirements document is introduced, the requirements engineer may have to manually analyze all the requirements for a single change. This may result in neglecting the actual impact of a change. Consequently, the cost of implementing a change may become several times higher than expected. Objective: In this paper, we aim at improving change impact analysis in requirements by using formal semantics of requirements relations and requirements change...

13. Characterization of bio-inspired hair flow sensors for oscillatory airflows: techniques to measure the response for both flow and pressure - Droogendijk, H.; Dagamseh, A.M.K.; Sanders, R.G.P.; Yntema, D.R.; Krijnen, G.J.M.
Hair sensors for oscillatory airflow, operating in the regime of bulk flow, particle velocity or both, can be characterized by several methods. In this work, we discuss harmonic measurements on MEMS hair flow sensors. To characterize this type of flow sensor the use of three different types of oscillatory airflow source is investigated. A loudspeaker, a vibrating sphere and a standing wave tube all have specific characteristics regarding their acoustic field, frequency range, maximum velocity amplitude and the possibility to chose the ratio between pressure and flow velocity. They are compared and an overview is given with respect to which...

14. Thulium channel waveguide laser with 1.6 W of output power and ~80% slope efficiency - Dalfsen, K. van; Aravazhi, S.; Grivas, C.; García-Blanco, S.M.; Pollnau, M.
Laser experiments were performed on buried, ridge-type channel waveguides in 8 at.% thulium-doped, yttrium– gadolinium–lutetium co-doped potassium double tungstate. By pumping with a Ti:sapphire laser at 794 nm, 1.6 W of output power at 1.84 μm with a maximum slope efficiency of ∼80% was obtained in a laser resonator with a high output-coupling degree of 89%. To the best of our knowledge, this result represents the most efficient 2-μm channel waveguide laser to date.

15. Design and analysis of a high-efficiencyv high-voltage class-D power output stage - Ma, Haifeng; Zee, Ronan van der; Nauta, Bram
The analysis and design of a highly-efficient 80 V class-D power stage design in a 0.14 μm SOI-based BCD process is described. It features immunity to the on-chip supply bounce, realized by internally regulated floating supplies, variable driving strength for the gate driver, and an efficient 2-step level shifter design. Fast switching transition and low switching loss are achieved with 94% peak efficiency for the complete class-D power stage in the realized chip.

16. CRIT-Alternative narrow-passband waveguide filter for microwave photonic signal processors - Zhuang, L.; Hoekman, M.; Oldenbeuving, R.M.; Roeloffzen, C.G.H.; Boller, K.J.
This letter presents a novel use of a waveguide circuit consisting of a two-ring resonator-assisted asymmetrical Mach-Zehnder interferometer, which realizes a narrow-passband filter in the context of microwave photonics (MWP). The filter principle is an alternative to the coupled resonator induced transparency and features easy implementation and robust performance. In the experimental demonstration, such a circuit fabricated in SiO2/Si3N4 waveguide technology exhibits a narrow transmission window surrounded by a region of significant suppression. The transmission window features a -3-dB bandwidth of 1 GHz and a -20-dB bandwidth of 3.5 GHz, equivalently a 20-dB roll-off enhancement of three times as compared...

17. On-chip microwave photonic beamformer circuits operating with phase modulation and direct detection - Zhuang, Leimeng; Hoekman, Marcel; Taddei, Caterina; Leinse, Arne; Heideman, René G.; Hulzinga, Adriaan; Verpoorte, Jaco; Oldenbeuving, Ruud M.; Dijk, P.W.L. van; Boller, Klaus J.; Roeloffzen, Chris G.H.
We propose and experimentally demonstrate the working principles of two novel microwave photonic (MWP) beamformer circuits operating with phase modulation (PM) and direct detection (DD). The proposed circuits incorporate two major signal processing functionalities, namely a broadband beamforming network employing ring resonator-based delay lines and an optical sideband manipulator that renders the circuit outputs equivalent to those of intensity-modulated MWP beamformers. These functionalities allow the system to employ low-circuit-complexity modulators and detectors, which brings significant benefits on the system construction cost and operation stability. The functionalities of the proposed MWP beamformer circuits were verified in experimental demonstrations performed on two...

18. Effects of embryo culture media do not persist after implantation: a histological study in mice - Hemkemeyer, Sandra A.; Schwarzer, Caroline; Boiani, Michele; Ehmcke, Jens; Le Gac, Séverine; Schlatt, Stefan; Nordhoff, Verena
Is post-implantation embryonic development after blastocyst transfer affected by exposure to different assisted reproduction technology (ART) culture media? Fetal development and placental histology of ART embryos cultured in vitro in different ART media was not impaired compared with embryos grown in vivo. The application of different in vitro culture (IVC) media for human ART has an effect on birthweight of newborns. In the mouse model, differences in blastocyst formation were reported after culture in different ART media. Moreover, abnormalities in the liver and heart have been detected as a result of suboptimal IVC conditions. Fertilized oocytes from inbred and outbred...

19. Coaxial stub resonator for online monitoring early stages of corrosion - Hoog, Natalia A.; Mayer, Mateo J.J.; Miedema, Henk; Olthuis, Wouter; Berg, Albert van den
Here we demonstrate the proof-of-principle of a new type of flow-through sensor to assess the corrosion rate of metal surfaces. The method can be applied to all situations where metals are exposed to a corrosive (fluidic) environment, including, for instance, the interior of pipes and tubes. Our sensing device is based on the operating principle of a quarter wave length open-ended coaxial stub resonator. The method described here can be applied for on-line monitoring corrosion.

20. Surface-enhanced Raman Spectroscopy of self-assembled monolayer conformation and spatial uniformity on silver surfaces - Wiedemair, Justyna; Le Thi Ngoc, Loan; Berg, Albert van den; Carlen, Edwin T.
We apply well-characterized silver nanowire grating (Ag-NWG) plasmonic surfaces as a Raman surface spectroscopy tool, which is based on surface-enhanced Raman scattering (SERS), to study the surface conformation characteristics of amine terminated alkanethiol self-assembled monolayers (SAMs). The surface conformation has implications for amine group availability, which is important when SAMs are used as linking layers for the binding of secondary molecules. Two different alkanethiols with different alkane chain lengths, namely 2-aminoethanethiol (cysteamine, CEA) and 11-aminoundecanethiol (AUT), are investigated. It is shown that both alkanethiols bind to Ag surfaces forming corresponding Ag-thiolates, however surface conformations, which are related to the ordering...

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