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| 2. |
- Bolin, Hans, et al.
(författare)
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Högskolan, museet och fältarkeologin
- 2014
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Ingår i: Tre år i Vång. - Karlskrona : Blekinge Museum. - 9789197980791 ; , s. 32-35
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Bokkapitel (populärvet., debatt m.m.)
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| 3. |
- Cassel, Björn, et al.
(författare)
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Deflections of an implant-supported cantilever beam subjected to vertically directed loads : in vitro measurements in three dimensions using an optoelectronic method. I. Experimental set-up.
- 2011
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Ingår i: Clinical Oral Implants Research. - : Wiley. - 0905-7161 .- 1600-0501. ; 22:3, s. 275-281
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Tidskriftsartikel (refereegranskat)abstract
- Aim: The aim of this in vitro study was to develop and test an experimental set-up consisting of a video camera and computer-based optoelectronic motion analysis system, synchronized with a loading device, for studying load-dependent deflections in three dimensions of single implant-supported cantilever beams.Material and methods: One Brånemark System implant was tightly screwed into a steel plate so that the entire implant became submerged. An abutment was attached to the implant and a cast 22-mm-long cantilever gold alloy beam incorporating a prefabricated gold cylinder was attached to the abutment with a prosthetic gold screw. A force transducer was glued on the upper surface of the beam end with its centre 19.4 mm from the centre of the implant abutment gold cylinder unit to register the applied load. A specially designed loading device was used to apply increasing vertical loads of the beam end via the transducer. The motion analysis system was synchronized with the transducer to enable measurements of three-dimensional positional changes of the beam end related to known loads.Results: Vertical loads from 15.7 to 40.4 N were applied resulting in vertical positional changes of the beam end ranging from 40.8 to 225.2 μm (z-axis). The corresponding horizontal changes perpendicular to the long axis of the beam (y-axis) due to counterclockwise horizontal rotation of the beam around the abutment- and prosthetic cylinder threads varied from 7.4 to 77.4 μm. This rotation changed the position of the beam end from 11.9 to 49.3 μm along the x-axis of the coordinate system toward the supporting implant.Conclusion: It was possible to arrange an experimental set-up for optoelectronic 3-D measurements within such a limited measurement volume that would permit satisfactory registrations of small load-dependent deflections of the prosthetic beam and implant components.
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| 4. |
- Cassel, Björn, et al.
(författare)
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Deflections of an implant-supported cantilever beam subjected to vertically directed loads : In vitro measurements in three dimensions using an optoelectronic method. II Analysis of methodological errors.
- 2010
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Ingår i: Clinical Oral Implants Research. - : Wiley. - 0905-7161 .- 1600-0501. ; 22:6, s. 645-650
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Tidskriftsartikel (refereegranskat)abstract
- Aim: The aim of this study was to evaluate the accuracy, i.e. trueness (validity) and precision (repeatability) for load-dependent deflections in three dimensions of an implant-supported cantilever beam obtained with an optoelectronic motion analysis system compared with a well-known reference method.Materials and methods: A cantilever beam with a length of 22 mm (roughly corresponding to the width of two premolars) was screw-connected to an implant–abutment unit stiffly anchored in a steel plate. The positional changes of beam-end were measured when the beam-end step by step was subjected to four loads, 15.5–40.1 N. This measurement procedure was repeated to comprise six consecutive measurements. The trueness of the method was estimated by comparing the data obtained for vertical deflections with those from a reference method where a hydraulic test system was used to measure the load-deflection ratios of the same beam when subjected to the four mentioned vertical loads.Results: All applied transducer-mediated loads had accuracies (truenesses and repeatabilities below 0.05%). Also, the trueness and precision of the reference method, regarding both movements (deflections) of tested objects and magnitude of applied loads, were tested and found to be high, not exceeding 0.5%.The optoelectronic method however underestimated the smallest vertical deflections for the cantilever beam when compared with the data obtained from the reference method. The underestimation was 26.4%, 15.5% and 8.6% for loads 15.5, 26.6 and 32.6 N, respectively, while there was a slight overestimation of 1.2% for 40.1 N. The precision for the optoelectronic method was found to be for z-axis 1.8 μm, y-axis 3.8 μm and x-axis 1.9 μm.Conclusion: It can be concluded that the trueness (validity) for the optoelectronic method is very high for deflections above 143 μm. The precision (repeatability) of the optoelectronic method was found to be very high.
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| 5. |
- Cassel, Björn, et al.
(författare)
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The influence of stiffness of implant-abutment connection on load-deflection ratios of a screw-retained stiff cantilever beam. 3-D measurements in vitro
- 2013
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Ingår i: Clinical Oral Implants Research. - : Wiley. - 0905-7161 .- 1600-0501. ; 24:11, s. 1251-1256
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Tidskriftsartikel (refereegranskat)abstract
- Aim: The purpose of this in vitro study was to investigate the influence of degree of stiffness of implant-abutment connection of a Brånemark implant system on load- deflection ratios in three dimensions of the beam-end of a screw-retained stiff cantilever beam when subjected to vertically directed loads.Material and methods: Two different implant-abutment connections were tested; welded and screw-retained. One of the abutments (EsthetiCone 2.0; Nobel Biocare AB) was screwed with a torque force of 20 N cm and then laser welded around its entire periphery to one of two Brånemark implants (welded unit). This unit and the other implant were tightly screwed into each of two pre-threaded holes in a steel plate so that the implants became submerged in the plate. The remaining abutment was thereafter screwed to its implant with a torque force of 20 N cm (screw-retained unit). A cantilevered gold beam of 6 mm height and width comprising a gold cylinder (Nobel Biocare AB) was attached to each abutment with a slotted, flat headed, prosthetic gold screw (torque force 10 N cm). A force transducer, synchronized with a 3-D motion analysis system, was glued on the upper surface of each beam-end 19.4 mm from the implant, to register the loads transferred from a specially built loading device. The beam-ends were stepwise subjected to vertically directed loads from 14.9 to 40.3 N and the vertical and horizontal deflections of the beam-ends were registered with the 3-D motion analysis system.Results: For load 14.9–40.3 N the vertical (z-axis) deflections of the beam-end were for the welded implant-abutment connection reduced with 18–46% compared with the screw-retained unit. After maximal loading (40.3 N) the horizontal counter-clockwise rotation of the beam around the screw joints (y-axis rotations) was reduced with 61% for the welded connection. The horizontal movements of the beam-end along the x-axis (x-axis deflections) were reduced with 49% at maximal loading.Conclusion: It was concluded that increased implant-abutment stiffness will substantially reduce both vertical and horizontal deflections of a screw-retained stiff cantilever beam subjected to vertically directed loads.
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| 8. |
- Cassel, Sofia, et al.
(författare)
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Enhanced learning by promoting engineering competencies
- 2014
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Ingår i: Proc. 44th ASEE/IEEE Frontiers in Education Conference. - Piscataway, NJ : IEEE Press. - 9781479939213 ; , s. 2044-2049
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Konferensbidrag (refereegranskat)abstract
- An engineering graduate needs to master a number of important skills: problem solving, critical thinking, communication, collaboration, etc. In this paper we describe how a course in computer security, taught in the Computer and Information Engineering programme at Uppsala University, has been developed over a period of three years. The aim is to better develop the engineering competencies of students, improving their understanding of course contents, training their ability to reflect on it, and to apply their knowledge when facing realistic problems.The course is designed to activate students, based on practical labs and theoretical tasks which are solved in groups. The student reports are assessed at seminars, where the solutions are presented orally, peer-reviewed and discussed. The seminars encourage and reward activities at the higher levels of taxonomies such as Bloom's.The results of the development, based on a CEQ-based course evaluation, indicate that students take a deeper approach to learning. They develop their problem-solving skills to a high degree, appreciate the practical solving of open-ended problems, and take responsibility for collaborative learning. Their overall satisfaction with the course is quite high, despite indications that they find the workload high.
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