| 1. |
- Elmer, Steven J, et al.
(författare)
-
Fatigue is specific to working muscles : no cross-over during single-leg cycling in trained cyclists
- 2013
-
Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 113:2, s. 479-488
-
Tidskriftsartikel (refereegranskat)abstract
- Fatigue induced via a maximal isometric contraction of a single limb muscle group can evoke a "cross-over" of fatigue that reduces voluntary muscle activation and maximum isometric force in the rested contralateral homologous muscle group. We asked whether a cross-over of fatigue also occurs when fatigue is induced via high-intensity endurance exercise involving a substantial muscle mass. Specifically, we used high-intensity single-leg cycling to induce fatigue and evaluated associated effects on maximum cycling power (P max) in the fatigued ipsilateral leg (FATleg) as well as the rested contralateral leg (RESTleg). On separate days, 12 trained cyclists performed right leg P max trials before and again 30 s, 3, 5, and 10 min after a cycling time trial (TT, 10 min) performed either with their right or left leg. Fatigue was estimated by comparing exercise-induced changes in P max and maximum handgrip isometric force (F max). Mean power produced during the right and left leg TTs did not differ (203 ± 8 vs. 199 ± 8 W). Compared to pre-TT, FATleg P max was reduced by 22 ± 3 % at 30 s post-TT and remained reduced by 9 ± 2 % at 5 min post-TT (both P < 0.05). Despite considerable power loss in the FATleg, post-TT RESTleg P max (596–603 W) did not differ from pre-TT values (596 ± 35 W). There were no alterations in handgrip F max (529–547 N). Our data suggest that any potential cross-over of fatigue, if present at all, was not sufficient to measurably compromise RESTleg P max in trained cyclists. These results along with the lack of changes in handgrip F max indicate that impairments in maximal voluntary neuromuscular function were specific to working muscles.
|
|
| 2. |
- Görtz, Stefan, et al.
(författare)
-
Standard Unstructured Grid Solutions for Cranked Arrow Wing Aerodynamics Project International F-16XL
- 2009
-
Ingår i: Journal of Aircraft. - : American Institute of Aeronautics and Astronautics (AIAA). - 0021-8669 .- 1533-3868. ; 46:2, s. 385-408
-
Tidskriftsartikel (refereegranskat)abstract
- Steady and unsteady viscous flow simulations of a full-scale, semispan, and full-span model of the F-16XL-1 aircraft are performed with three different computational fluid dynamics codes using a common unstructured grid. Six different flight conditions are considered. They represent Reynolds and Mach number combinations at subsonic speeds, with and without sideslip. The steady computations of the flow at these flight conditions are made with several Reynolds-averaged Navier-Stokes turbulence models of different complexity. Detached-eddy simulation, delayed detached-eddy simulation, and an algebraic hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation model are used to quantify unsteady effects at the same flight conditions. The computed results are compared with flight-test data in the form of surface pressures, skin friction, and boundary-layer velocity profiles. The focus of the comparison is on turbulence modeling effects and effects of unsteadiness. The overall agreement with flight data is good, with no clear trend as to which physical modeling approach is superior for this class of flow. The Reynolds-averaged Navier-Stokes turbulence models perform well in predicting the flow in an average sense. However, some of the flow conditions involve locally unsteady flow over the aircraft, which are held responsible for the scatter between the different turbulence modeling approaches. The detached-eddy simulations are able to quantify the unsteady effects, although they are not consistently better than the Reynolds-averaged Navier-Stokes turbulence models in predicting the flow in an average sense in these flow regions. Detached-eddy simulation fails to predict boundary-layer profiles consistently over a range of flow regimes, with delayed detached-eddy simulation and hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation models offering a remedy to recover some of the predictive capabilities of the underlying Reynolds-averaged Navier-Stokes turbulence model. Nonetheless, the confidence in the predictive capabilities of the computational fluid dynamics codes with regard to complex vortical flowfields around high-performance aircraft of this planform increased significantly during this study.
|
|
| 3. |
|
|
| 4. |
- Vierth, Inge, et al.
(författare)
-
Långa och tunga lastbilars effekter på transportsystemet : redovisning av regeringsuppdrag
- 2008
-
Rapport (populärvet., debatt m.m.)abstract
- I Sverige tillåts lastbilar i inrikestrafik som är upp till 25,25 meter långa och 60 ton tunga. Detta skiljer sig från EU-normen, där lastbilar som regel inte är längre än 18,75 meter och väger maximalt 40 ton. Näringsdepartementet har gett VTI i uppdrag att studera vilka samhällsekonomiska konsekvenser avvikelsen har medfört för Sverige samt beskriva konkurrensytan mellan väg- och järnvägstransporter. Effekterna på transportkostnader för näringslivet, avgas- och bulleremissioner, vägslitage, tidsfördröjning för bilister samt trafiksäkerheten har beräknats. En mycket stor andel av godstransporterna på väg utförs med fordon som överskrider EU-normen. Att krympa fordonsstorleken skulle leda till stora samhällsekonomiska förluster. Framför allt är det transportkostnaderna som ökar, men det skulle även uppkomma betydande kostnadsökningar inom områdena trafiksäkerhet, avgasemissioner och bulleremissioner. I utredningen konstateras att det är svårt, åtminstone på kort sikt, att åstadkomma överflyttningar mellan väg och järnväg. Detta beror delvis på att järnvägens kapacitet är högt utnyttjad.
|
|
| 5. |
- Vierth, Inge, et al.
(författare)
-
Modellanalyser som underlag till Kombiterminalutredningen
- 2007
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Government has given Banverket (the Swedish Rail Administration) the task of suggesting a strategic network for combi terminals (using rail and another mode). Banverket has in turn given VTI the task of carrying out model simulations to aid the Combi Terminal Investigation. The investigation has defined strategic networks (Network I, II, III) with four, seven and ten terminals as possible scenarios. In each of the networks the transfer costs in the combi terminals are assumed to decrease by 15 and by 30 percent. We calculate with the help of the Swedish national freight model SAMGODS how modal-split between lorry, wagonload rail and combined transport are affected and how transport volumes differ in the scenarios with adjusted transfer costs. The freight owners, choice of transport solution is assumed to use the minimal generalised costs. We calculate that transport work by combined rail in Sweden increases by 20 to 26 percent with a 30 percent cost decrease is assumed. Redistribution is calculated to mainly shift from wagonload to combined transport. The actual size of the redistribution is however difficult to be sure of due to uncertainties in the input cost data. Road transport is calculated to reduce to a lesser amount. We calculate significant redistribution from road to combined rail when testing a kilometer tax for lorries.
|
|
| 6. |
- Vierth, Inge, et al.
(författare)
-
Representation of the Swedish transport and logistics system : (Logistics Model Version 2.00)
- 2009
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aggregate-disaggregate-aggregate freight models that have been developed in Norway and Sweden take into account the logistic decisions at firm level. The Swedish model is documented in i.e. the Swedish Base Matrices Report and the Method Report Logistics model. This report gives an overview about how the Swedish transport and logistics system is represented in the Logistics Model Version 2, which is a deterministic cost minimization model. Further validation and development is necessary in several aspects. The report describes the setup data (version 2009-01-19) that is needed to run the Version 2 model. In order not to overload the report all input, output, control files, validation material etc. is included on a separate CD.
|
|
| 7. |
- Vierth, Inge, et al.
(författare)
-
The effects of long and heavy trucks on the transport system : report on a government assignment
- 2008
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Trucks up to 25.25 metres in length and weighing up to 60 tonnes are permitted in domestic traffic in Sweden. This deviates from the EU standard, according to which trucks are not to be longer than 18.75 metres or weigh more than 40 tonnes. The Swedish Ministry of Enterprise, Energy and Communications has commissioned VTI to study what economic consequences this deviation has had for Sweden and to describe the competition interface between road and rail transport. The effects on transport costs for business, exhaust and noise emissions, road wear, time delay for motorists and road safety have been estimated. A very large proportion of freight transport by road takes place by vehicles that exceed the EU standard. Reducing vehicle size would lead to large economic losses. Transport costs would increase in particular, but significant cost increases would also occur in the areas of road safety, exhaust emissions and noise emissions. It is noted in the study that it is difficult, at least in the short term, to bring about transfers between road and rail. This is due, in part, to high rate of utilisation of the railway capacity.
|
|
| 8. |
- Vierth, Inge, et al.
(författare)
-
Underlag till Hamnstrategiutredningen
- 2007
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this report is to gather relevant material for the Port Strategy Investigation (Hamnstrategiutredningen). Goods transport volumes and structures today, recent development and a forecast for the year 2020 are highlighted. Use of the transport infrastructure in Sweden is described. The profile as well as land and sea connections are briefly presented for a number of larger ports. Port infrastructure pricing is discussed based on a number of European-wide research projects.
|
|
