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University of Twente Publications (58.244 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 25.151

  1. Hip joint contact forces calculated using different muscle optimization techniques

    Wesseling, M.; Derikx, L.C.; Groote, F. de; Bartels, W.; Meyer, C.; Verdonschot, N.J.J.; Jonkers, I.
    The goal of this study was to calculate muscle forces using different optimization techniques and investigate their effect on hip joint contact forces in gait and sit to stand. These contact forces were compared to measured hip contact forces [3]. The results showed that contact forces were overestimated, especially when muscle forces were calculated using computed muscle control. For static optimization, results were closest to measured contact forces. Also, differences between measured and calculated contact forces were dependent on the movement analyzed.

  2. Reistijd is een slechte indicator voor bereikbaarheid

    Geurs, Karst
    Vaak baseert de overheid zich bij infrastructuurinvesteringen en verkeer- en vervoersbeleid op reistijden. Reistijd is echter slechts één van de vier componenten om bereikbaarheid uit te drukken, stelt professor Karst Geurs van de Universiteit Twente. Bereikbaarheid zou moeten gaan over de mogelijkheden die mensen hebben om bepaalde bestemmingen te bereiken.

  3. Persona's helpen bij klantgerichte ontwerpmethode voor nom-renovaties

    Hovenier, L.; Entrop, A.G.; Jonge, B.

  4. Phantom jam avoidance through in-car speed advice

    Suijs, L.C.W.; Wismans, L.J.J.; Krol, L.; Berkum, E.C. van
    The existence of phantom jams can be explained following the definition of Kerner & Konhäuser (1993) who state that a phantom jam occurs without the existence of a physical bottleneck and is caused by the imperfect driving style of road users under metastable traffic conditions. In order to prevent a phantom jams to occur, one can either focus on the cause of the perturbation, or on the metastability of the traffic flow. Previous studies have shown that the use of dynamic speed limits, displayed by road-side equipment, is a successful instrument to stabilize traffic flow and to dissolve formed phantom...

  5. Short term evaluation of an anatomically shaped polycarbonate urethane total meniscus replacement in a goat model

    Vrancken, A.C.T.; Madej, W.; Hannink, G.; Verdonschot, N.J.J.; Tienen, T.G. van; Buma, P.
    Purpose: Since the treatment options for symptomatic total meniscectomy patients are still limited, an anatomically shaped, polycarbonate urethane (PCU), total meniscus replacement was developed. This study evaluates the in vivo performance of the implant in a goat model, with a specific focus on the implant location in the joint, geometrical integrity of the implant and the effect of the implant on synovial membrane and articular cartilage histopathological condition. Methods: The right medial meniscus of seven Saanen goats was replaced by the implant. Sham surgery (transection of the MCL, arthrotomy and MCL suturing) was performed in six animals. The contralateral knee joints of both...

  6. Quantifying postural control during exergaming using multivariate whole-body movement data: A self-organizing maps approach

    Diest, M. van; Stegenga, J.; Wörtche, H.J.; Postema, K.; Verkerke, G.J.; Lamoth, C.J.C.
    Background: Exergames are becoming an increasingly popular tool for training balance ability, thereby preventing falls in older adults. Automatic, real time, assessment of the user’s balance control offers opportunities in terms of providing targeted feedback and dynamically adjusting the gameplay to the individual user, yet algorithms for quantification of balance control remain to be developed. The aim of the present study was to identify movement patterns, and variability therein, of young and older adults playing a custom-made weight-shifting (ice-skating) exergame. Methods: Twenty older adults and twenty young adults played a weight-shifting exergame under five conditions of varying complexity, while multi-segmental whole-body movement data...

  7. The potential for snow to supply human water demand in the present and future

    Mankin, Justin S.; Viviroli, Daniel; Singh, Deepti; Hoekstra, Arjen Y.; Diffenbaugh, Noah S.
    Runoff from snowmelt is regarded as a vital water source for people and ecosystems throughout the Northern Hemisphere (NH). Numerous studies point to the threat global warming poses to the timing and magnitude of snow accumulation and melt. But analyses focused on snow supply do not show where changes to snowmelt runoff are likely to present the most pressing adaptation challenges, given sub-annual patterns of human water consumption and water availability from rainfall. We identify the NH basins where present spring and summer snowmelt has the greatest potential to supply the human water demand that would otherwise be unmet by...

  8. Ranking water transparency of Dutch stock-listed companies

    Linneman, Marissa H.; Hoekstra, Arjen Y.; Berkhout, Wouter
    A growing world population, changing consumption patterns and climate change are affecting water demands, water scarcity and water quality worldwide, while at present, few companies are incorporating good water stewardship. In order to create awareness on this issue and provide an incentive for companies to improve the water performance in their operations and supply chain, a method for ranking companies based on their water transparency has been developed. The method consists of a checklist that can be completed on the basis of information from annual reports, sustainability reports and websites of companies. This is the first time a ranking of...

  9. The water footprint of food aid

    Jackson, Nicole; Konar, Megan; Hoekstra, A.Y.
    Food aid is a critical component of the global food system, particularly when emergency situations arise. For the first time, we evaluate the water footprint of food aid. To do this, we draw on food aid data from theWorld Food Programme and virtual water content estimates from WaterStat. We find that the total water footprint of food aid was 10 km3 in 2005, which represents approximately 0.5% of the water footprint of food trade and 2.0% of the water footprint of land grabbing (i.e., water appropriation associated with large agricultural land deals). The United States is by far the largest...

  10. Review and classification of indicators of green water availability and scarcity

    Schyns, J.F.; Hoekstra, A.Y.; Booij, M.J.
    Research on water scarcity has mainly focussed on blue water (ground- and surface water), but green water (soil moisture returning to the atmosphere through evaporation) is also scarce, because its availability is limited and there are competing demands for green water. Crop production, grazing lands, forestry and terrestrial ecosystems are all sustained by green water. The implicit distribution or explicit allocation of limited green water resources over competitive demands determines which economic and environmental goods and services will be produced and may affect food security and nature conservation. We need to better understand green water scarcity to be able to...

  11. Neurocontrol of movement: system identification approach for clinical benefit

    Meskers, C.G.M.; Groot, J.H. de; Vlugt, E. de; Schouten, A.C.
    Progress in diagnosis and treatment of movement disorders after neurological diseases like stroke, cerebral palsy (CP), dystonia and at old age requires understanding of the altered capacity to adequately respond to physical obstacles in the environment. With posture and movement disorders, the control of muscles is hampered, resulting in aberrant force generation and improper impedance regulation. Understanding of this improper regulation not only requires the understanding of the role of the neural controller, but also attention for: (1) the interaction between the neural controller and the “plant”, comprising the biomechanical properties of the musculaskeletal system including the viscoelastic properties of...

  12. Oog in oog met Rottumeroog

    Entrop, Bram

  13. Dissertaties

    Hoppe, Thomas

  14. Efficiëntie en verzelfstandiging: economische en politieke efficiëntie als verklaring voor verzelfstandigingen

    Gazendam, H.W.M.; Homburg, V.M.F.
    Welke verklaring kunnen we geven voor het verschijnsel verzelfstandiging? Het door de door de neo-institutionele economie aangedragen motief van grotere economische efficiëntie blijkt niet door empirisch onderzoek te worden ondersteund. Dit rechtvaardigt een beschouwing van theorieën die de neoinstitutionele basis verbreden. De eigendomsrechtentheorie, de theorie van afhankelijkheid van hulpbronnen en de theorieën van Puviani en Pierson over het minder zichtbaar maken van verantwoordelijkheid voor negatieve effecten van beleid kunnen bijdragen aan een betere verklaring van het verschijnsel verzelfstandiging. Een combinatie van deze theorieën leidt tot de conclusie dat niet alleen economische efficiëntie een rol speelt als motief om tot verzelfstandiging te komen, maar dat ook politieke efficiëntie een aanleiding vormt...

  15. Interne besluitvormingsstructuur en het ontwerpen van beleid : Een verkenning

    Heffen, O. van
    Over de wijze waarop het proces van beleid ontwerpen en het proces van besluitvorming elkaar beïnvloeden is relatief weinig bekend. In dit artikel wordt in theoretische zin de relatie verkend tussen de besluitvormingsstructuur van een organisatie en het proces van beleid ontwerpen. Deze verkenning leidt tot de voorlopige conclusie dat slechts bepaalde ontwerpstrategieën geschikt zijn voor de aanpak van bepaalde typen van problemen en dat deze ontwerpstrategieën niet zonder meer in elke organisatie kunnen worden toegepast. Het is dus voorstelbaar dat de aard van een probleem om een bepaalde wijze van het ontwerpen van beleid vraagt, terwijl de besluitvormingsstructuur van...

  16. Op zoek naar harmonie tussen politiek en bestuur : 'Politics and administration' van Frank Goodnow

    Reussing, G.H.
    De start van de Amerikaanse bestuurskunde wordt meestal gelegd in 1887. In dat jaar verscheen in Political Science Quarterly het artikel 'The study of administration' van Woodrow Wilson. Wilson wordt gezien als de wegbereider van de bestuurskunde, de man die de aanzet gaf. Frank Goodnow verdient de titel van de grondlegger van de bestuurskunde, omdat hij Wilsons ideeën heeft uitgewerkt (Caiden, 1971: 33-34). Goodnow was, voor hij rector werd van de John Hopkins University te Baltimore, hoogleraar bestuursrecht aan de Columbia University. Hij was niet alleen betrokken bij het opzetten van bestuurskundige vakken aan deze universiteiten, maar was ook een vooraanstaand lid...

  17. Existence of a Tribo-Modified Surface Layer on SBR Elastomers: Balance between Formation and Wear of the Modified Layer

    Mokhtari, M.; Schipper, D.J.; Vleugels, N.; Noordermeer, J.W.M.
    In most of the tribological contacts, the composition and tribological properties of the original interface will change during use. The tribo-films, with modified properties compared to the bulk, are dynamic structures that play a significant role in friction. The existence of a tribo-modified surface layer and its importance on the overall friction of elastomers has been shown both theoretically and experimentally before. The characteristics of the modified surface layer deserve specific attention since the tribological properties of elastomers in contact with a rough counter-surface are determined by these modified surfaces together with the properties of bulk of the material. Both...

  18. Exploring an alternative aqueous lubrication concept for biomedical applications: Hydration lubrication based on O/W emulsions combined with graphene oxide

    Yan, J.; Zeng, X.; Ren, Tianhui; Heide, E. van der
    Water-based lubrication concepts are of high interest for applications that require friction and wear control in a bio-medical environment. In this work, a concept of aqueous lubrication is presented based on hydration of surface active polymers combined with graphene oxide. Three different kinds of surface-active polymers with or without graphene oxide were coated on a CoCrMo alloy surface, and the samples were characterized by ATR and XPS. Hydration lubrication was created from a tailored oil-in-water (O/W) emulsion. Enhanced friction reducing capability was found for the polymeric coatings in combination with graphene oxide. The tribological behaviour of a PEG-lactide coating in...

  19. Experimental Study on Dry Torrefaction of Beech Wood

    Gucho, E.M.; Shahzad, K.; Bramer, E.A.; Akhtar, N.A.; Brem, G.
    Torrefaction is a thermochemical pre-treatment process for upgrading the properties of biomass to resemble those of fossil fuels such as coal. Biomass properties of particular interest are chemical composition, physical property and combustion characteristics. In this work, torrefaction of beech wood and miscanthus (sinensis) was carried out to study the influence of torrefaction temperature (240–300 °C) and residence time (15–150 min) on the aforementioned properties of the biomass. Results of the study revealed that torrefaction temperature has a significant influence on mass and energy yields, whereas the influence of the residence time becomes more apparent for the higher torrefaction temperatures...

  20. Energietechnieken en -maatregelen voor leegstaande panden

    Colijn, M.; Entrop, A.G.; Platteel, R.
    Leegstaande panden vormen een steeds groter probleem. Er moet naar oplossingen worden gezocht om ongewenste gevolgen te voorkomen. Op financiële lasten kan worden bespaard door energietechnieken en -maatregelen (ETM’s) toe te passen. Panden worden hierdoor aantrekkelijker voor potentiële huurders en/of kopers. Om dit te kunnen bereiken is een instrument ontworpen om ETM’s te koppelen aan specifieke panden.

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