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University of Twente Publications (62.565 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 7.397

  1. Influence of retention basins on tidal dynamics in estuaries: application to the Ems estuary

    Li, A.; Schuttelaars, H.M.; Roos, P.C.; Damveld, J.H.; Gong, W.; Hulscher, S.J.M.H.
    We present a quick assessment method using an idealized one-dimensional linear model to explore the influence of multiple retention basins, whose construction is proposed as a measure to reduce tidal amplitudes in estuaries/tidal channels. To this end, we have developed a process-based network model for the cross-sectionally averaged water motion, including width and depth convergence (thus extending earlier studies), bottom friction, radiation damping and allowing for multiple basins at arbitrary locations. For frictionally dominated tidal channels, model results show that construction of a retention basin generally leads to a reduction of the tidal amplitude at the channel head. This reduction is...

  2. A cross-coupled switch-RC mixer-first technique achieving +41dBm out-of-band IIP3

    Westerveld, Hugo; Klumperink, Eric; Nauta, Bram
    Abstract — With the growing amount of wireless devices, interference robustness is a receiver specification of increasing importance. This paper presents a technique that improves both out-of-band compression and weakly non-linear distortion. It mitigates the effect of non-linearity in the baseband amplifier by preceding it by a cross-coupled passive filter. This provides a highly linear passive shunt path for out-of-band currents, while maintaining wideband input matching. The 65nm CMOS prototype chip achieves 41dBm out-of-band IIP3 at 40MHz offset and an 11dBm out-of-band blocker compression point. The chip has an area of 0.8mm2 and consumes 46mW from a 1.2V supply.

  3. Calibration techniques in nyquist A/D converters

    Ploeg, Hendrik van der; Nauta, Bram

  4. In-air Microfluidics for Chip-free Generation of Microdroplets-, Particles, -Fibers, and 3D Hierarchical Prints

    Kamperman, T.; Visser, C.W.; Leijten, J.C.H.; Lohse, D.; Karperien, H.B.J.

  5. Method and apparatus for in-air production of single droplets, compound droplets, and shape-controlled (compound) particles or fibers

    Visser, C.W.; Kamperman, T.; Karperien, H.B.J.; Lohse, D.

  6. Heat transfer augmentation in rectangular micro channel covered with vertically aligned carbon nanotubes

    Taha, T.J.; Lefferts, L.; Meer, T.H. van der

  7. Effect of carbon nanofiber surface morphology on convective heat transfer from cylindrical surface: Synthesis, characterization and heat transfer measurement

    Taha, T.J.; Mojet, B.L.; Lefferts, L.; Meer, T.H. van der

  8. Experimental Techniques for Retrieving Flow Information from within Inkjet Nozzles

    Meulen, M.P. van der; Reinten, H.; Dijksman, J.F.; Lohse, D.; Versluis, M.
    In drop-on-demand (DOD) inkjet printing microdroplets are ejected from the nozzle as a result of the internal acoustics set in motion by a pressure pulse from an expanding bubble or a piezoelement. The acoustic response, both in the frequency domain and in the time domain, and the resulting droplet formation processes are well-modeled and characterized by various experimental techniques. However, the behavior of the liquid meniscus in the nozzle is a critical mediator between these regimes and poorly accessible in experiment. The meniscus shape and motion vary between different print head designs, electrical pulse shapes and wetting conditions. In the...

  9. 3D spherical-cap fitting procedure for (truncated) sessile nano- and micro-droplets & -bubbles

    Tan, H.; Peng, S.; Sun, C.; Zhang, X.; Lohse, D.
    In the study of nanobubbles, nanodroplets or nanolenses immobilised on a substrate, a cross-section of a spherical cap is widely applied to extract geometrical information from atomic force microscopy (AFM) topographic images. In this paper, we have developed a comprehensive 3D spherical-cap fitting procedure (3D-SCFP) to extract morphologic characteristics of complete or truncated spherical caps from AFM images. Our procedure integrates several advanced digital image analysis techniques to construct a 3D spherical-cap model, from which the geometrical parameters of the nanostructures are extracted automatically by a simple algorithm. The procedure takes into account all valid data points in the construction...

  10. Ultrafast imaging method to measure surface tension and viscosity of inkjet-printed droplets in flight

    Staat, H.J.J.; Bos, J.A. van der; Berg, M. van den; Reinten, H.; Wijshoff, H.; Versluis, M.; Lohse, D.
    In modern drop-on-demand inkjet printing, the jetted droplets contain a mixture of solvents, pigments and surfactants. In order to accurately control the droplet formation process, its in-flight dynamics, and deposition characteristics upon impact at the underlying substrate, it is key to quantify the instantaneous liquid properties of the droplets during the entire inkjet-printing process. An analysis of shape oscillation dynamics is known to give direct information of the local liquid properties of millimeter-sized droplets and bubbles. Here, we apply this technique to measure the surface tension and viscosity of micrometer-sized inkjet droplets in flight by recording the droplet shape oscillations...

  11. On the spreading of impacting drops

    Wildeman, S.; Visser, C.W.; Sun, C.; Lohse, D.
    The energy budget and dissipation mechanisms during droplet impact on solid surfaces are studied numerically and theoretically. We find that for high impact velocities and negligible surface friction at the solid surface (i.e. free slip), approximately one-half of the initial kinetic energy is transformed into surface energy, independent of the impact parameters and the detailed energy loss mechanism(s). We argue that this seemingly universal rule is related to the deformation mode of the droplet and is reminiscent of pipe flow undergoing a sudden expansion, for which the head loss can be calculated by multiplying the kinetic energy of the incoming...

  12. Introduction and history

    Reinhoudt, David N.

  13. Supramolecular Technology

    Reinhoudt, D.N.

  14. Rocco Ungaro, 40 years of Calixarene chemistry

    Reinhoudt, D.N.

  15. Carbon nano-fiber based membrane reactor for selective nitrite hydrogenation

    Brunet Espinosa, R.; Rafieian, D.; Lammertink, R.G.H.; Lefferts, L.
    Catalytic hydrogenation of nitrite in drinking water demands control over the selectivity towards nitrogen, minimizing the formation of ammonia. This selectivity is strongly influenced by the H/N ratio of reaction intermediates at the catalyst surface. Therefore, we fabricated a membrane reactor that feeds separately hydrogen gas and a nitrite solution. This allows dosing low but homogeneous hydrogen concentrations along the axial direction of the catalyst bed. As a consequence, low H/N ratios can be achieved, favouring the formation of nitrogen without limiting the nitrite conversion. We demonstrate that this reactor concept offers better nitrogen selectivity than conventional reactor configurations where...

  16. Homogeneous nucleation: Patching the way from themacroscopic to the nanoscopic description

    Lohse, Detlef; Prosperetti, Andrea
    How and when does water ‘‘fracture’’? In other words, how and when does a small cavity, or nucleus, form that does not heal but grows to macroscopic size, thus becoming a bubble? This question is important in various areas of technology and nature, affecting, for example, the ability of tall trees to draw sap to great heights (1, 2). The classical answer, developed by Volmer in the 1930s and described in his monograph (3), implies that, in ideal conditions, it is next to impossible to create a bubble in water because the tension (or negative pressure) required is of the...

  17. Stability of Surface Nanobubbles: A Molecular Dynamics Study

    Maheshwari, Shantanu; Hoef, Martin van der; Zhang, Xuehua; Lohse, Detlef
    The stability and growth or dissolution of a single surface nanobubble on a chemically patterned surface are studied by molecular dynamics simulations of binary mixtures consisting of Lennard-Jones (LJ) particles. Our simulations reveal how pinning of the three-phase contact line on the surface can lead to the stability of the surface nanobubble, provided that the concentration of the dissolved gas is oversaturated. We have performed equilibrium simulations of surface nanobubbles at different gas oversaturation levels ζ > 0. The equilibrium contact angle θe is found to follow the theoretical result of Lohse and Zhang (Phys. Rev. E 2015, 91, 031003(R)),...

  18. Vertically Bounded Double Diffusive Convection in the Finger Regime: Comparing No-Slip versus Free-Slip Boundary Conditions

    Yang, Yantao; Verzicco, R.; Lohse, D.
    Vertically bounded fingering double diffusive convection is numerically investigated, focusing on the influences of different velocity boundary conditions, i.e., the no-slip condition, which is inevitable in the lab-scale experimental researches, and the free-slip condition, which is an approximation for the interfaces in many natural environments, such as the oceans. For both boundary conditions the flow is dominated by fingers and the global responses follow the same scaling laws, with enhanced prefactors for the free-slip cases. Therefore, the laboratory experiments with the no-slip boundaries serve as a good model for the finger layers in the ocean. Moreover, in the free-slip case,...

  19. Laser particle counter validation for sand transport measurements using high speed camera

    Duarte Campos, L.A.; Wijnberg, K.M.; Oyarte Galvez, L.A.; Hulscher, S.J.M.H.

  20. The effectiveness of negotiated agreements and its inspirations for Chinese knowledge mangement

    Shi, Hongwei; Wangyu, .; Bressers, Hans T.A.; Bruijn, Theo J.N.M. de
    Negotiated agreements have become a widely used management model with respective covenants for different social network context in European countries. Negotiated agreements between government and industry in which industry obliges to take 'voluntary' action to help realizing regional management objectives. This paper describes and analyses development of the use of such covenant model in European public administration practice. After an extensive evaluation of the effects of the covenants in the European social network context, the paper conducts a comparable study of the Chinese knowledge management also in social network context, and expose that Chinese knowledge management policy and knowledge management...

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