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University of Twente Publications (63.031 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 13.533

  1. Strongly Enhanced Piezoelectric Response in Lead Zirconate Titanate Films with Vertically-Aligned Columnar Grains

    Nguyen, M.D.; Houwman, E.P.; Dekkers, J.M.; Rijnders, A.J.H.M.
    Pb(Zr0.52Ti0.48)O3 (PZT) films with (001) orientation were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using pulsed laser deposition. Variation of the laser pulse rate during the deposition of the PZT films was found to play a key role in the control of the microstructure and to change strongly the piezoelectric response of the thin film. The film deposited at low pulse rate has a denser columnar microstructure, which improves the transverse piezoelectric coefficient (d31f) and ferroelectric remanent polarization (Pr), whereas the less densely packed columnar grains in the film deposited at high pulse rates give rise to a significantly higher longitudinal piezoelectric coefficient...

  2. Porous titanium particles for acetabular reconstruction in total hip replacement show extensive bony armoring after 15 weeks

    Walschot, L.H.B.; Aquarius, R.; Verdonschot, N.J.J.; Buma, P.; Schreurs, B.W.

  3. De letter en de geest : Vakspecifieke regels bij de centrale examens natuurkunde

    Pol, Henk; Wooning, Jacqueline; Smeets, Pieter; Thurlings, Anneke

  4. Homogeneous cooling state of frictionless rod particles

    Rubio-Largo, S.M.; Alonso-Marroquin, F.; Weinhart, T.; Luding, S.; Hidalgo, R.C.
    In this work, we report some theoretical results on granular gases consisting of frictionless 3D rods with low energy dissipation. We performed simulations on the temporal evolution of soft spherocylinders, using a molecular dynamics algorithm implemented on GPU architecture. A homogeneous cooling state for rods, where the time dependence of the system’s intensive variables occurs only through a global granular temperature, has been identified. We have found a homogeneous cooling process, which is in excellent agreement with Haff’s law, when using an adequate rescaling time τ(ξ)τ(ξ), the value of which depends on the particle elongation ξξ and the restitution coefficient....

  5. Micro–macro transition and simplified contact models for wet granular materials

    Roy, S.; Singh, A.; Luding, S.; Weinhart, T.
    Wet granular materials in a quasistatic steady-state shear flow have been studied with discrete particle simulations. Macroscopic quantities, consistent with the conservation laws of continuum theory, are obtained by time averaging and spatial coarse graining. Initial studies involve understanding the effect of liquid content and liquid properties like the surface tension on the macroscopic quantities. Two parameters of the liquid bridge contact model have been identified as the constitutive parameters that influence the macroscopic rheology (i) the rupture distance of the liquid bridge model, which is proportional to the liquid content, and (ii) the maximum adhesive force, as controlled by...

  6. The effect of microscopic friction and size distributions on conditional probability distributions in soft particle packings

    Saitoh, K.; Magnanimo, V.; Luding, S.
    Employing two-dimensional molecular dynamics (MD) simulations of soft particles, we study their non-affine responses to quasi-static isotropic compression where the effects of microscopic friction between the particles in contact and particle size distributions are examined. To quantify complicated restructuring of force-chain networks under isotropic compression, we introduce the conditional probability distributions (CPDs) of particle overlaps such that a master equation for distribution of overlaps in the soft particle packings can be constructed. From our MD simulations, we observe that the CPDs are well described by q-Gaussian distributions, where we find that the correlation for the evolution of particle overlaps is...

  7. Merging fluid and solid granular behavior

    Vescovi, D.; Luding, S.
    Simple homogeneous shear flows of frictionless, deformable particles are studied by particle simulations at large shear rates and for differently soft, deformable particles. Particle stiffness sets a time-scale that can be used to scale the physical quantities; thus the dimensionless shear rate, i.e. the inertial number I (inversely proportional to pressure), can alternatively be expressed as inversely proportional to the square root of particle stiffness. Asymptotic scaling relations for the field variables pressure, shear stress and granular temperature are inferred from simulations in both fluid and solid regimes, corresponding to unjammed and jammed conditions. Then the limit cases are merged...

  8. Numerical study on stress states and fabric anisotropies in soilbags using the DEM

    Cheng, H.; Yamamoto, H.; Thoeni, K.
    Wrapping granular soils in geosynthetic containers, such as soilbags, results in a considerable increase in the bearing capacity due to the effective restraint on the dilatancy of the soil. This paper numerically investigates the stress states and fabric anisotropies in the wrapped soil using the discrete element method, providing a novel perspective for new insights into the reinforcement mechanisms and the development of constitutive relations for soilbags. The two most anticipated loading conditions, namely, unconfined compression and simple shear, are considered, and numerical predictions are compared to experimental results. During unconfined compression, both global and local p–q stress paths evolve...

  9. Keep IT Real: On Tools, Emotion, Cognition and Intentionality in Design

    Wendrich, R.E.; Kruiper, E.
    Keep IT real, create, build, and develop design tools that support designers during the early phases of design processing. This paper investigates how, and whether, current technology can afford real-time interaction and affective computing in a HDT(E) design tool that integrates and blends realities through physical and virtual interaction. Interaction design (IxD) is crucial to the usability (UX) and engagement (UE), concepts and terminology are introduced, after which an interaction framework is set up that takes into account the multi-modal Human Computer Interaction (HCI) with a HDT(E).

  10. Integrated Creativity and Play Environments in Design and Engineering Processes

    Wendrich, R.E.
    The umpire whispers: “Please Play”. We sort of play. But it’s all hypothetical, somehow. Even the ‘we’ is theory: I never get quite to see the distant opponent, for all the apparatus of the game [1]. We find no reason to abandon the notion of play as a distinct and highly important factor in the world’s life and doings. All play means something. If we call the active principle that makes up the essence of play, ‘instinct’, we explain nothing; if we call it ‘mind’ or ‘will’ we say too much. However we may regard it, the very fact that...

  11. HCI/HMI Pleasure: Push Your Buttons

    Wendrich, R.E.
    The four pleasures; a feeling of happy satisfaction, enjoyment, entertainment and sensorial gratification. "What's your pleasure?", asked Mr. Einstein. "Push my buttons, bleeped the machine." "With pleasure...here we go...!" cried Albert and pushed some buttons on the machine interface. The machine riposted; "Creativity is the residue of time wasted, design for life is to learn how to use creativity in our daily lives to fulfill our dreams and passions. Our tools dictate the nature of our work, whereby our hands are the instruments of our mind. Often software interfaces define the boundaries of our work, but only exploration into the...

  12. Lossless microwave photonic delay line using a ring resonator with an integrated semiconductor optical amplifer

    Xie, Yiwei; Zhuang, Leimeng; Boller, K-J.; Lowery, Arthur J.

  13. Multimodal interaction, collaboration, and sysnthesis in design and engineering processing

    Wendrich, R.E.

  14. Onderhoud: van conservatief naar hightech

    Tinga, T.

  15. Identifying the 'right' supplier for module developments-a cross-industrial case analysis

    Eggers, Justus Erich; Hofman, Erwin; Schiele, Holger; Holschbach, Elmar
    Relational view argues that buying companies should integrate supplier resources in new product development (NPD) projects to realise competitive advantages. Due to decoupling of modules and the associated opportunity to allocate development activities to upstream suppliers, modular product architectures are considered to be a driving factor for the integration of supplier resources. Module developments are associated with substantial investments, long-term orientation and risks across product families for the buying firm. Therefore, supplier integration for module development is highly critical. Regardless of the relevance, research has not yet analysed, which supplier competence are considered as antecedents for successful module developments with...

  16. Monolayer functionalization of silicon micro and nanowires: towards solar-to-fuel and sensing devices

    Veerbeek, Janneke
    Silicon is an attractive semiconductor material for wide-ranging applications, especially when taking advantage of the larger surface area of silicon micro and nanowires. Surface functionalization with self-assembled monolayers of (in)organic molecules can be employed to tune the functionality of a substrate towards a desired application. Specifically, solar-to-fuel and sensing devices highly benefit from the use of oxide-free monolayers, since any silicon oxide layer functions as an insulating layer and retards electrical contact with the substrate. For this purpose, hydrosilylation can be used to couple terminal unsaturated carbon-carbon bonds, i.e., 1-alkenes or 1-alkynes, onto H-terminated Si which leads to direct Si-C...

  17. Aspects of flow and viscoelasticity in a model elastohydrodynamically lubricated contact

    Emden, Ellen van
    In order to extend the service life of rolling bearings and other heavily loaded lubricated contacts, the need of lubricant film thickness control significantly increases under more extreme conditions of mechanical and thermal loading and with reduced lubricant supply. To ensure maximum service life, all lubricated contacts should be designed such that under all circumstances a sufficiently large protective layer of lubricant is present to prevent direct contact between the moving parts. Pressures in the order of several gigapascals can be encountered in the contact zone between the moving parts. The field of Elasto-Hydrodynamic Lubrication (EHL) studies cases for which the...

  18. Samenwerken

    Geelkerken, R.H.

  19. Overheidssteun voor luchtvaartsector?

    Heerkens, J.M.G.

  20. Technologische superioriteit VS bedreigd? Deel 2

    Heerkens, J.M.G.

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