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- Johansson, Martin, 1973, et al.
(författare)
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Approximate boundary conditions for a fluid-loaded elastic plate
- 2005
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 118:6, s. 3436-3446
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Tidskriftsartikel (refereegranskat)abstract
- Approximate boundary conditions for an infinite elastic layer immersed in a fluid are derived. By using series expansions in the thickness coordinate of the plate fields, the displacements fields are eliminated, adopting the three-dimensional equations of motion. The sums and differences of the boundary pressure fields and their normal derivatives are related through a set of approximate boundary conditions, one symmetric and one antisymmetric. These equations involve powers in the layer thickness together with partial derivatives with respect to time as well as the spatial variables in the plate plane. The approximate boundary conditions can be truncated to an arbitrary order, and explicit relations are presented including terms of order five. Comparisons are made with effective boundary conditions using classical plate theories. The numerical examples involve reflection and transmission of plane waves incident on the plate at different angles, as well as the pressure fields due to a line force. Three fluid-loading cases are studied: modest, heavy, and light loadings. The results using truncated approximate boundary conditions are compared to exact and classical plate solutions. The examples show that the accuracies of the power series approximations of order three and higher are very good in the frequency interval considered.
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- Johansson, Martin, 1973, et al.
(författare)
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Dispersion free wave splittings for structural elements
- 2006
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Ingår i: Computers and Structures. - : Elsevier BV. - 0045-7949. ; 84:7, s. 514-27
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Tidskriftsartikel (refereegranskat)abstract
- Wave splittings are derived for three types of structural elements: membranes, Timoshenko beams, and Mindlin plates. The Timoshenko beam equation and the Mindlin plate equation are inherently dispersive, as is each Fourier component of the membrane equation in an angular decomposition of the field. The distinctive feature of the wave splittings derived in the present paper is that, in homogeneous regions, they transform the dispersive wave equations into simple one-way wave equations without dispersion. Such splittings have uses both for radial scattering problems in the 2D cases and for scattering problems in dispersive media. As an example of how the splittings may be applied, a direct scattering problem is solved for a membrane with radially varying density. The imbedding method is utilized, and agreement is obtained with an FE simulation.
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- Andersson, Dan, 1967-
(författare)
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Exploring Perceptions of Route Environments in Relation to Walking
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Every walk takes place in a route environment, which can play an important role in deterring or facilitating walking. The focus of this thesis is on the perceptions of environmental variables, and how they relate to appraisals of route environments as hindering – stimulating for walking and unsafe – safe for reasons of traffic, in two metropolitan environments. Another focus is to expand the state of knowledge concerning the criterion-related validity of the Active Commuting Route Environment Scale (ACRES).Methods: Commuting pedestrians in Greater Stockholm, Sweden, were recruited via advertisements. From the inner urban area there were 294 participants (77% women), aged 49.5 years, and from the suburban areas there were 233 participants (82% women), aged 50.0 years. 77 individuals walked in both areas. The participants evaluated their commuting route environments using the ACRES. Correlation, multiple regression, and mediation analyses were used to explore the relationships between the variables. Comparisons of environmental ratings between groups and settings were performed with t-tests. Studies 1 and 2 focused on the inner urban area and studies 3 and 4 on the suburban areas. Studies 1 and 3 focused exclusively on the relations between the four motorized traffic variables (vehicle speed, vehicle flow, noise, and exhaust fumes), and their relations to the outcome variables (hinders – stimulates walking and unsafe – safe traffic). Studies 2 and 4 utilised proxies from studies 1 and 3 and combined them with other environmental variables to further the understanding of route environmental variables in relation to walking.Results: In both areas, aesthetics and greenery were positively related to stimulating walking, whereas noise, a proxy for motorized traffic, was negatively related. Aesthetics was also positively related to unsafe – safe traffic in the inner urban area, whereas greenery had the corresponding role in suburbia. Another important finding was that greenery also influenced aesthetics positively in both areas. Thus, greenery had both a direct and an indirect positive effect. On the other hand, noise influenced aesthetics negatively in the inner urban area, whereas vehicle flow had the corresponding role in suburbia. A number of variables conjointly influenced the outcome unsafe – safe traffic negatively in both areas (speeds of motor vehicles, noise, conflicts, congestion: pedestrians, red lights, and course of the route). The route environment profiles differed distinctly between the two areas.Conclusions: Several route environmental variables appear to be particularly influential in relation to pedestrian commuting, e.g., aesthetics, greenery, and noise. An important finding is that both positive and negative interactions, between certain predictor variables, were disclosed. The contrasting route environment profiles in the different settings strengthen the criterion-related validity of the ACRES. The findings expands the state of knowledge concerning the relations between the environment and walking. If implemented, these findings can influence public health positively.
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- Belfrage, Anna Karin, 1977-, et al.
(författare)
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Pan-NS3 protease inhibitors of hepatitis C virus based on an R3-elongated pyrazinone scaffold
- 2018
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Ingår i: European Journal of Medicinal Chemistry. - : Elsevier. - 0223-5234 .- 1768-3254. ; 148, s. 453-464
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we present the design and synthesis of 2(1H)-pyrazinone based HCV NS3 protease inhibitors and show that elongated R-3 urea substituents were associated with increased inhibitory potencies over several NS3 protein variants. The inhibitors are believed to rely on beta-sheet mimicking hydrogen bonds which are similar over different genotypes and current drug resistant variants and correspond to the beta-sheet interactions of the natural peptide substrate. Inhibitor 36, for example, with a urea substituent including a cyclic imide showed balanced nanomolar inhibitory potencies against genotype la, both wild-type (K-i=30 nM) and R155K (K-i=2 nM), and genotype 3a (K-i=5 nM).
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- Berggren, Peter, 1971-, et al.
(författare)
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Assessing the quality of Shared Priorities in teams using content analysis in a microworld experiment
- 2017
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Ingår i: Theoretical Issues in Ergonomics Science. - : Taylor & Francis. - 1463-922X .- 1464-536X. ; 18:2, s. 128-146
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Tidskriftsartikel (refereegranskat)abstract
- Objective, easy to use, and easy to comprehend assessment methods for measuring shared understanding in teams are hard to find. This paper describes an experiment where a measure called Shared Priorities, which is based on ranking of self-generated strategic items, is assessed. Trained teams were compared to non-trained teams in a dynamic problem-solving task. The maturity of the participating teams was also assessed using a content analysis measure. The Shared Priorities measure was used alongside other well-documented measures of team awareness based on self-rating. Results show that the Shared Priorities measure correlates with task performance and could also distinguish between trained and non-trained teams. However, the Shared Priorities measure did not correlate with the other team measures (cf. CARS – Crew Awareness Rating Scale – and DATMA – Distributed Assessment of Team Mutual Awareness), suggesting that it captures a different quality of teamwork than the self-rating measures. Further, the Shared Priorities measure was found to be easily administered.
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