| 1. |
- Bourdieu, Pierre, et al.
(författare)
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Leve idrottspedagogiken : En vänbok tillägnad Lars-Magnus Engström
- 2005
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Vem ägnar sig åt idrott? Vilken betydelse har fritiden i barns och ungdomars liv? Vad innebär hälsa i skolämnet idrott och hälsa?Leve idrottspedagogiken! tillägnas Lars-Magnus Engström. Texterna i boken speglar delar av det idrottspedagogiska forskningsområdet i Sverige, vars framväxt Lars-Magnus Engström varit den främste företrädaren för. Läsaren får här ta del av exempelvis idrottskulturen, fritidskulturen och skolans ämne idrott och hälsa. Genomgående handlar texterna om villkoren för barns och ungdomars deltagane och om de olika lärprocesser som sker i anslutning till idrottsutövning.Lars-Magnus Engström har gjort betydande insatser som forskare och lärare samt som professor vid Lärarhögskolan i Stockholm och vid Gymnastik- och idrottshögskolan. I snart fyrtion år har han arbetat med studier kring påverkans- och lärprocesser i idrott. Hans forskning har främst kretsat kring människors idrottsvanor och vilka som utvecklar en fysiskt aktiv livsstil. Idrotts- och motionsutövningar ger både ett så kallat egenvärde och investeringsvärde. Med dessa begrepp bland många andra har Lars-Magnus Engström bidragit till en fördjupad vetenskaplig förståelse av idrottskulturen.De flesta författarna har eller har haft Lars-Magnus Engström som handledare och tillhör forskningsgruppen för pedagogik, idrott och fritidskultur. Redaktörer för boken är Karin Redelius och Håkan Larsson.
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| 2. |
- Lisander, Björn, 1940-, et al.
(författare)
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Enhanced rate of ethanol elimination from blood after intravenous administration of amino acids compared with equicaloric glucose
- 2006
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Ingår i: Alcohol and Alcoholism. - : Oxford University Press (OUP). - 0735-0414 .- 1464-3502. ; 41:1, s. 39-43
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Tidskriftsartikel (refereegranskat)abstract
- Aims: To investigate the effect of an amino acid mixture given intravenously (i.v.) on the rate of ethanol elimination from blood compared with equicaloric glucose and Ringer's acetate as control treatments.Methods: In a randomized cross-over study, six healthy men (mean age 23 years) fasted overnight before receiving either Ringer's acetate, glucose or the amino acid mixture (Vamin 18 g N/l®) by constant rate i.v. infusion over 4.5 h. Ethanol (0.4 g/kg) was given by an i.v. infusion lasting 60 min during the time each of the treatments was administered. At various times post-infusion, blood samples were taken for determination of ethanol by headspace gas chromatography. Blood glucose and heart rate were monitored at regular intervals. Concentration–time profiles of ethanol were plotted for each subject and the rate of ethanol disappearance from blood as well as other pharmacokinetic parameters were compared by repeated measures analysis of variance.Results: The rate of ethanol elimination from blood was increased significantly (P < 0.001) after treatment with amino acids (mean ± SD, 0.174 ± 0.011 g/l/h) compared with equicaloric glucose (0.121 ± 0.016 g/l/h) or Ringer's acetate (0.110 ± 0.013 g/l/h). Heart rate was also slightly higher during infusion of the amino acid mixture (P < 0.05).Conclusions: When the rate of ethanol elimination from blood is relatively slow, such as after an overnight fast, it can be increased by ∼60% after treatment with i.v. amino acids. The efficacy of amino acid treatment was not related to the supply of calories because glucose was no more effective than Ringer's acetate. We suggest that amino acids might increase hepatic oxygen consumption, resulting in a more effective conversion of NADH to NAD+ in mitochondria. An important feature of the experimental design was ensuring hepatic availability of amino acids during much of the time that ethanol was being metabolized.
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| 3. |
- Lundvall, Olle, et al.
(författare)
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A flexible multi-body approach for frictional contact in spur gears
- 2004
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Ingår i: Journal of Sound and Vibration. - : Elsevier. - 0022-460X .- 1095-8568. ; 278:3, s. 479-499
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Tidskriftsartikel (refereegranskat)abstract
- In the present paper, a large rotational approach for dynamic contact problems with friction is proposed. The approach is used for modelling a spur gear pair with shafts and bearings. The model is obtained by superposing small displacement elasticity on rigid-body motions, and postulating tribological laws on the gear flanks. The finite element method is used to model the elastic properties of the gear pair. Shafts and bearings are represented by linear springs. The tribological laws of the contact interface are Signorini's contact law and Coulomb's law of friction. An important feature of the approach is that the difficulties of impacting mass nodes are avoided. The governing equations of the model are numerically treated by use of the augmented Lagrangian approach. In such manner the geometry of the gear flanks are well represented in the numerical simulations. It is possible to study accurately the consequences of different types of profile modifications as well as flank errors. In this work, the dynamic transmission error is studied. For instance, it turns out that the effect from profile modification is less significant for the transmission error when frictional effects are included.
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| 4. |
- Lundvall, Olle, 1967-
(författare)
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Contact mechanics and noise in gears
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, recent findings in the area of computational contact mechanics are applied to gear technology. The focus of this application is gear noise. One of the main goals is to calculate the so called transmission error, which is a measure that relates structural properties of a gear to gear noise.Computational methodologies are developed in order to analyze different types of gear problems. The finite element method forms the basis for the developed models. In addition to the finite element models of the gear wheels, contact laws are used in order to simulate the contact between the gear flanks. These laws are Signorini's contact law and Coulomb's law of friction and by expressing them as B-differential equations the application of Pang's Newton method for B-differential equations is enabled.The transmission error is calculated with good accuracy under both quasi-static and dynamic conditions. By incorporating Archard's wear law into the models, predictions of how wear affects the transmission error are made. It is found that wear can have a significant impact on gear noise.It is shown that friction by no means can be neglected when calculating the transmission error. In the dynamic calculations of this thesis, friction always increases the dynamic transmission error. It is also concluded that the effect from friction becomes more significant if shaft and bearing stiffnesses are small.
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| 5. |
- Lundvall, Olle
(författare)
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Node-to-target formulation in finite element spur gear problems
- 2005
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Ingår i: Mechanics based design of structures and machines. - 1539-7734 .- 1539-7742. ; 33:1, s. 31-49
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a quasistatic finite element model of a spur gear pair is developed. A node-to-target contact formulation is given, where calculations of initial gaps are based upon the actual geometry of the gear flanks rather than upon a contact node and a facet or a line segment. By using a special contact search algorithm, profile modifications and mounting errors are easily incorporated in the analysis. The problem, which also includes friction, is solved by using a nonsmooth Newton method. The static transmission error can be calculated with accuracy with a relatively small number of nodes along the gear flanks. Several examples are given in order to demonstrate the model.
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| 6. |
- Lundvall, Olle, et al.
(författare)
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Prediction of transmission error in spur gears as a consequence of wear
- 2001
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Ingår i: Mechanics of structures and machines (Print). - 0890-5452 .- 1525-612X. ; 29:4, s. 431-449
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this article is to investigate how the so-called transmission error in a gear develops in a wear process. A finite element procedure for calculating wear between two elastic bodies in contact is developed that includes constitutive laws, representing the behavior of the interacting surfaces. When treating a gear problem, large rotations must be included. This is done by analyzing a sequence of finite-element models along with an interpolation procedure. The constitutive laws of interacting surfaces are Signorini's contact law, Coulomb's law of friction, and Archard's law of wear. By formulating both Signorini's contact law and Coulomb's law of friction by means of projection equations, the complete formulation of a time increment of a quasistatic wear-friction evolution problem becomes a system of nonsmooth equations. Then, a modified Newton method is applied to solve this system. The transmission error can be found from the infinitesimal displacement field superposed on the rigid body configuration. Results from the simulations show that wear will increase the peak-to-peak value of the transmission error. This is most significant in a gear when some kind of modification of the gear flank is applied to minimize the transmission error in an initial state.
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| 7. |
- Lundvall, Olle, 1967-
(författare)
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Simulation of contact, friction and wear in gears : a finite element approach
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, resent methods in computational contact mechanics is brought into the process of gear design. The finite element method is used to model two elastic bodies in contact. By defining a contact interface between these two bodies, constitutive laws, regarding normal contact, friction and wear, are included. Then a system of non-smooth equations is obtained which is solved by a modified Newton method. The method developed in this work produces very accurate results, which is important in gear technology where the impact of small geometrical features of the tooth profile affects the overall performance of a loaded gear. Two different gear problems are treated in which gear noise is related to wear.In Paper I, a wear problem in a planetary gear is investigated. In a planetary range gear of a heavy truck, a wear damage develops in a particular operating situation. A whining noise is a consequence of this damage. Two different hypothesis of the cause of this damage were tested by the method developed and then some important conclusions could be drawn.In Paper II, the method is extended so that large rotations can be treated. The method then furnishes an accurate tool for computing the transmission error, which is a measure that is related to gear noise. It is also investigated how the transmission error is affected by wear.
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| 8. |
- Lundvall, Olle, et al.
(författare)
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Simulation of wear by use of a nonsmooth Newton method : a spur gear application
- 2001
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Ingår i: Mechanics of structures and machines (Print). - 0890-5452 .- 1525-612X. ; 29:2, s. 223-238
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a method for calculating wear between two elastic bodies in contact. Discrete representations of the bodies are obtained by the finite element method. Constitutive laws representing the behavior of the interacting surfaces are then added. These are Signorini's contact law, Coulomb's law of friction, and Archard's law of wear. By formulating Signorini's contact law and Coulomb's law of friction by means of projection equations, the complete formulation of a time increment of a quasistatic wear-friction evolution problem becomes a system of nonsmooth equations. A modification of Newton's method is applied to solve this system. The method is applied to a spur gear problem in a heavy truck transmission.
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| 9. |
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