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- Andreasson, Håkan, 1966, et al.
(författare)
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A numerical investigation of the steady states of the spherically symmetric Einstein-Vlasov-Maxwell system
- 2009
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Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 26:14
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Tidskriftsartikel (refereegranskat)abstract
- We construct, by numerical means, static solutions of the spherically symmetric Einstein-Vlasov-Maxwell system and investigate various features of the solutions. This extends a previous investigation (Andreasson and Rein 2007 Class. Quantum Grav. 24 1809) of the chargeless case. We study the possible shapes of the energy density profile as a function of the area radius when the electric charge of an individual particle is varied as a parameter. We find profiles which are multi-peaked, where the peaks are separated either by vacuum or a thin atmosphere, and we find that for a sufficiently large charge parameter the solutions break down at a finite radius. Furthermore, we investigate the inequality root M <= root R/3 + root R/9 + Q(2)/3R, which is derived in Andreasson (2009 Commun. Math. Phys. 288 715) for general matter models, and we find that it is sharp for the Einstein-Vlasov-Maxwell system. Here M is the ADM mass, Q is the charge and R is the area radius of the boundary of the static object. We find two classes of solutions with this property, while there is only one in the chargeless case. In particular we find numerical evidence for the existence of arbitrarily thin shell solutions to the Einstein-Vlasov-Maxwell system. Finally, we consider one-parameter families of steady states, and we find spirals in the mass-radius diagram for all examples of the microscopic equation of state which we consider.
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| 2. |
- Eliasson, Kristina, 1979-
(författare)
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Occupational health services in the prevention of musculoskeletal disorders : Processes, tools and organizational aspects
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Work-related musculoskeletal disorders are associated with high costs and it is essential to prevent them. Occupational Health Services(OHS) provide expert services regarding work environment, health and rehabilitation of work related disorders. Risk assessments of the work environment can be an initial step for preventive measures, and ergonomists can be assigned by clients to assess exposures in the work environment. For such assignments different tools can be used. The aim of this thesis was to explore prerequisites, processes and practices of OHS consultants in Sweden within the domain of primary prevention of work-related musculoskeletal disorders. This was explored through the work of ergonomists in their role of assessing ergonomics risks. The research methodology was both quantitative and qualitative. Data collection includes a web questionnaire, semi-structured interviews and inter- and intra-observer reliability tests. The results shows that ergonomics risk assessments were most commonly initiated reactively and a systematic work methodology for the risk assessment process was often lacking. Swedish ergonomists used only a few standardized tools for risk assessment. The Ergonomics provision from the Swedish Work Environment Authority, AFS-98, was widely used, but other observation-based tools were used far less often. Ergonomics risks were often assessed solely by means of observation, based on ergonomists’ knowledge and experience. The results also pointed to that that the reliability was not acceptable when risk assessment was performed without any standardized tool. Furthermore, the results point to that support from the OHS organizations is an important prerequisite for ergonomists to work with primary prevention. Further, opportunities for specialization within a specific industry sector seem to facilitate ergonomic interventions. It is also important to have close relationships with clients and to make them aware about ergonomists competence. Conclusively, this thesis identifies a numbers of areas in which OHS must develop to improve primary preventive services regarding work environment.
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