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- Althoff, Karin, 1974, et al.
(författare)
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Tracking Contrast in Echocardiography by a Combined Snake and Optical Flow Technique
- 2000
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Ingår i: IEEE Conf. on Computers in Cardiology. ; 27
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Konferensbidrag (refereegranskat)abstract
- Contrast-echocardiography in conjunction with real-time video-densiometry can be an effective means of studying right ventricular (RV) structural changes, e.g. in patients diagnosed with Arrhythmogenic Right Ventricular Dysplasia (ARVD). In order to characterize RV flow pattern it may be necessary to track the front of the contrast agent as it enters the RV. Active contour models (ACM) is a standard image analysis method,which can be applied to time-dynamic tracking problem.To improve tracking speed we extended the formulationof ACM by including an additional force, derived fromthe optical flow field, another standard image analysisalgorithm. This reduced the number of iterations needed to find the front of the contrast agent significantly. Also the changes in intensity of the contrast agent over time were studied. Two groups were compared, one with30 patients diagnosed with ARVD and one with 18healthy volunteers. Our study shows that that using our suggested method (calculating wash-in and wash-out time indices) it is possible to discriminate between thetwo groups.
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- Degerman, Johan, et al.
(författare)
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Modeling stem cell migration by Hidden Markov
- 2004
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Ingår i: Proceedings of the Swedish Symposium on Image Analysis, SSBA 2004. ; , s. 122-125
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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- Gustavsson, Per M., 1965-, et al.
(författare)
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Towards Service Oriented Simulations
- 2004
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Ingår i: Fall Simulation Interoperability Workshop 2004. ; , s. 219-229
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the effort to provide simulation support to the future Network Based Defence (NBD)1 that are currently being applied by the Swedish Armed Forces (SwAF), the authors opinion is that simulation should be treated as any other services and use the same architectural requirements addressed in the SwAF Enterprise Architecture (FMA)2 and in subsidiary documents.The choice so far for simulation is the High Level Architecture (HLA). During the author’s participation in ongoing work supporting NBD, questions have gradually been raised if HLA is the simulation path to walk. In the Core Enterprise Services (CES) and FMA Services IT-Kernel, core services are specified and HLA do address a lot of non-simulation specific services giving unwanted redundancy. However, the services already defined may with some enhancements deliver the same services addressed within CES and FMA Services IT-Kernel. Furthermore, HLA also comes with the Federation Development and Execution Process (FEDEP) that introduce process methodology to build HLA federations. Basically FEDEP is a software development process for distributed systems. The Next Generation HLA could be more than just a simulation standard if it utilizes the FMA ideas and avoids the green HLA elephant3.In this paper the authors present the ongoing work, as it stands today, with Service Oriented Simulations, that is an outlook for simulation using the architectural structuring, services, components and infrastructures concepts evolving in FMA and with the Global Information Grid (GIG) Enterprise Services (GES) in mind. The focus is to identify simulation services that encapsulate the core features of simulation. Thereby reducing redundancy in methodology and service as well as enabling interoperable simulation support for the whole system lifecycle – Acquisition, Development, Training, Planning, In-the-Field decision support, System removal – within NBD, entailing that the architecture for simulation is uniform regardless of its application and giving end-users the capability to focus on what to simulate instead of how to simulate.
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- Gustavsson, Tomas G, 1970
(författare)
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Silicone Rubber Insulators: Impacts of Material Formulation in Coastal Environment
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with influences of material formulation on the performance of silicone rubber high voltage insulators in a coastal environment. Samples and insulators with known differences in material compositions have been used in this task. In the first step, a screening test with cylindrical samples was initiated. The electrical performance was quantified by counting the number of peak leakage current values. In addition, the samples were visually inspected for erosion and hydropho-bicity during the test. Afterwards, the materials were analyzed for chemical changes and a dominating aging mechanism was identified. It was found that the thermal energy supplied by short pulsed discharges was the most probable origin for the observed surface changes. These discharges resulted in consumption of the added flame retardant filler and depolymerization of the polydimethylsiloxane matrix of the rubber. Moreover, no significant surface oxidation was found. The electrical performance was improved by increasing the ATH filler content and by adding extra silicone oil. Still, addition of extra silicone oil was judged as unnecessary as the low molar mass siloxane content did not decrease during the aging and that regeneration of such diffusible molecules had taken place. The results from the screening test were utilized for refining the test plan and selecting material formulations for simultaneous tests with cylindrical samples and real insulators having identical material formula-tions. An essential requirement, when the influences of material composition were evaluated in respect to insulator performance, was that the tested insulators had an identical geometry. Such insulators were designed and produced within this work. The highest electric field strength at the insulator surface was reduced to 0.54 kV/mm by means of specially selected terminations, to suppress degradation caused by water droplet corona. The electric field distribution along the insulator was simulated by finite element calculations. In addition, the rotating wheel dip test was used for accelerated aging. This method evaluated the early aging period of hydrophobic materials and both the applicability of this method as well as the performances of the tested materials are evaluated.
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