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- Jemt, Torsten, 1950, et al.
(författare)
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Measurements of bone and frame-work deformations induced by misfit of implant superstructures. A pilot study in rabbits.
- 1998
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Ingår i: Clinical oral implants research. - : Wiley. - 0905-7161. ; 9:4, s. 272-80
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Tidskriftsartikel (refereegranskat)abstract
- This in vivo study used a 3-D photogrammetric technique to measure distortion of 3 unit implant frame-works and bone surrounding osseointegrated implants after securing misfitting superstructures to the implants. Four adult loop-eared rabbits were provided with 3 implants each in the proximal part of 1 tibia each. After a healing period of 8 weeks, a titanium frame-work was connected with a misfit to the central implant. Three-dimensional photographs were taken before and after securing the central screw, which induced a calculated mean preload of 246 N. Measurements and comparisons of the topography of the frame-works and surrounding bone before and after tightening the central screw indicated a complex and inconsistent deformation pattern. Generally, it could be observed that the top edge of the central cylinder showed vertical movement towards the bone of about 150 microns, always in combination with a rotation of the entire super-structure. The head of the central implant seemed to show a corresponding displacement towards the frame-work of about 50 to 200 microns. Bone deformation was found to be basically localized between the implants, where compressions of about half a millimetre were observed. This concentration of bone deformation as a result of misfit may be one contributing factor to initial marginal bone loss, occasionally observed after insertion of implant supported prostheses.
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| 2. |
- Bennerstedt, Ulrika, 1979
(författare)
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Sheeping, sapping and avatars-in-action: An in-screen perspective on online gameplay
- 2008
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Ingår i: In S. Mosberg Iversen (Ed.), Proceedings of The [Player] Conference. IT University of Copenhagen, Denmark, August 2008. ; , s. 28-52
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Konferensbidrag (refereegranskat)abstract
- This paper is about the various practices that players use to coordinate their in-game activities. In the paper, screen-captured video data of one group of players’ gameplay are scrutinized in order to explicate coordination work. Instead of seeing interaction between online players as design issues or focusing off-screen events, the paper reframes in-screen collaboration activities as participants’ concerns. In order to explore empirical examples of players’ accomplishment of tight coordination in massively multiplayer online games, ethnomethodological influenced interaction analysis is used. The paper elaborates a player perspective by bridging the researcher’s knowledge of gameplay with empirical in-screen data. This study shows the work players do as coordinated, referential activities; accomplished by means of avatar movements and actions, as well as highlighted and made observable by visual markers and gaming discourse. The players’ achievement of mundane, jointly activities are termed routine play.
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| 3. |
- Kati, Maliheh Sadeghi, et al.
(författare)
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Robust Static Output Feedback With Dynamic Disturbance Feed-Forward for Lateral Control of Long-Combination Vehicles at High Speeds
- 2023
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Ingår i: Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME. - : ASME International. - 0022-0434 .- 1528-9028. ; 145:3
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Tidskriftsartikel (refereegranskat)abstract
- A control strategy is proposed to improve the high-speed lateral performance of an A double (tractor-semitrailer-dolly-semitrailer) combination vehicle using active steering of the dolly axles. The strategy is realized as an H1-type static output feedback (SOFB) based on a previous work, combined with dynamic disturbance feed-forward (DDFF). In order to synthesize DDFF in a way to facilitate performance improvement in practical problems, the disturbance is accurately characterized with the use of a dynamic weighting filter. As a contribution to the existing literature, novel linear matrix inequality (LMI) conditions are derived for this case, which facilitate the synthesis of a robust DDFF controller when the plant depends on uncertain time-varying parameters. An alternative DDFF synthesis method is also provided based on an adaptation of a previous work. The proposed overall controller has a simple structure and is easy to implement from a practical point of view since it requires only the driver steering angle (for feed-forward) and just one articulation angle measurement (for feedback). Obtained using a high-fidelity vehicle model, the simulation results for an example synthesis confirm a significant reduction in the rearward amplifications of the yaw rate and the lateral acceleration as well as the high-speed transient off-tracking during sudden lane change maneuvers.
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