| 1. |
- Borgmästars, Emmy, et al.
(författare)
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Circulating tissue polypeptide-specific antigen in pre-diagnostic pancreatic cancer samples
- 2021
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Ingår i: Cancers. - : MDPI. - 2072-6694. ; 13:21
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Tidskriftsartikel (refereegranskat)abstract
- Early detection of pancreatic ductal adenocarcinoma (PDAC) is challenging, and late diagnosis partly explains the low 5-year survival. Novel and sensitive biomarkers are needed to enable early PDAC detection and improve patient outcomes. Tissue polypeptide specific antigen (TPS) has been studied as a biomarker in PDAC diagnostics, and it has previously been shown to reflect clinical status better than the ‘golden standard’ biomarker carbohydrate antigen 19-9 (CA 19-9) that is most widely used in the clinical setting. In this cross-sectional case-control study using pre-diagnostic plasma samples, we aim to evaluate the potential of TPS as a biomarker for early PDAC detection. Furthermore, in a subset of individuals with multiple samples available at different time points before diagnosis, a longitudinal analysis was used. We assessed plasma TPS levels using enzyme-linked immunosorbent assay (ELISA) in 267 pre-diagnostic PDAC plasma samples taken up to 18.8 years before clinical PDAC diagnosis and in 320 matched healthy controls. TPS levels were also assessed in 25 samples at PDAC diagnosis. Circulating TPS levels were low both in pre-diagnostic samples of future PDAC patients and in healthy controls, whereas TPS levels at PDAC diagnosis were significantly increased (odds ratio 1.03; 95% confidence interval: 1.01–1.05) in a logistic regression model adjusted for age. In conclusion, TPS levels increase late in PDAC progression and hold no potential as a biomarker for early detection.
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| 2. |
- Lundberg, Oskar, 1980-, et al.
(författare)
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A compact internal drum test rig for measurements of rolling contact forces between a single tread block and a substrate
- 2017
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Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 103, s. 370-378
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Tidskriftsartikel (refereegranskat)abstract
- A novel test rig design is presented which enables detailed studies of the three force components generated in the impact and release phase of rolling contact between a tyre tread block and a substrate. The design of the compact internal drum test rig provides realistic impact and release angles for the tread block-substrate contact and enables force measurements at high rolling speeds with a high signal-to-noise ratio. Measurements of the rolling contact forces are presented for different values of rolling velocity, static pre-load and acceleration. It is demonstrated that this test rig provides results which contribute to the understanding of tyre road interaction and can be used as input to modelling-based development of both tyres and roads aiming for improved handling, safety, energy efficiency and comfort.
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| 3. |
- Lundberg, Oskar, 1980-, et al.
(författare)
-
A compact internal drum test rig for measurements of rolling contact forces between a single treadblock and a substrate
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A novel test rig design is presented which enables detailed studies of the three force components generated in the impact and release phase of rolling contact between a tyre tread block and a substrate. The design of the compact internal drum test rig provides realistic impact and release angles for the tread block-substrate contact and enables force measurements at high rolling speeds with a high signal-to-noise ratio. Measurements of the rolling contact forces are presented for different values of rolling velocity, static pre-load and acceleration. It is demonstrated that this test rig provides results which contribute to the understanding of tyre--road interaction and can be used as input to modelling-based development of both tyres and roads aiming for improved handling, safety, energy efficiency and comfort.
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| 4. |
- Lundberg, Oskar, 1980-
(författare)
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An experimental study on the influence of substrate roughness on the friction of a tread block in rolling and sliding contact
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- An experimental study of the friction coefficient is performed for a tyre tread block in rolling and sliding contact with two different asphalt substrates, a smooth aluminium and an anti-slip tape substrate. The sliding friction coefficient is for all substrates seen to increase as the sliding velocity is increasing. However, the slope for the increasing friction as a function of sliding velocity differs significantly between the substrates, presumably due to differences in the respective contribution from adhesive and hysteresis friction mechanisms. Parametric studies of the rolling friction show that the choice of substrate as well as the rolling velocity and the slip ratio has significant influence on the resulting friction coefficient. A linear relation is observed between the longitudinal rolling friction coefficient measured at low values of slip ratio and the sliding friction coefficient measured at low sliding velocities. For the tests of rolling friction at higher values of slip, stick\textendash slip conditions are observed for which the frequency content of the longitudinal force is seen to vary substantially between the different operating conditions and choice of substrate. The outcomes of this study can potentially be used to improve future tyre\textendash road contacts with respect to wear, traction and noise generation.
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| 5. |
- Lundberg, Oskar Erik, 1980-
(författare)
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Vibrations induced by surface roughness in nonlinear rolling contacts
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For efficient transportation in either trains, busses or passenger cars, rolling elements such as wheels, tyres, bearings and transmission elements are fundamental. The energy efficiency and the generation of noise and vibrations in rolling contacts depend on the surface roughness of contacting bodies. In order to optimize the surfaces of rolling elements, prediction of its impact on the dynamic response from rolling excitation is required. A computationally efficient method to include surface roughness in the modelling of rolling contacts is presented. More specifically, nonlinear effects on the contact force due to the threedimensional shape and roughness of the contacting surfaces are introduced in a moving point force formulation. As a consequence of the point force approximation follows the assumption that any dynamic wave motion within the contact area is negligible.The rolling contact force is nonlinear due to a varying relative displacement between contacting bodies and is therefore referred to as state-dependent. A study case for the state-dependent method consisting of a steel ball rolling on a steel beam showed good agreement between numerical predictions and measured beam vibrations. Furthermore, an application to the wheel-rail interaction show that roughness-induced contact nonlinearities have a significant impact on the dynamic response caused by rolling excitation.
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| 6. |
- Lundberg, Oskar, 1980-
(författare)
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Friction of a rubber tread block in rolling and sliding contact with asphalt---An experimental study
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The longitudinal and vertical contact force history of an individual truck tyre tread block in rolling contact with an asphalt surface is experimentally investigated. Different rolling velocities up to approximately 60 km/h and different amount of slip ratios are studied with the use of a novel compact internal drum test rig, leading to results with high signal-to-noise ratio. Interestingly, the longitudinal rolling contact force component and the corresponding friction coefficient exhibit substantial variations not only between the different operating conditions, but also along the contact length of individual impacts. In addition, separate investigatory characterisations for the dynamic elastic deformation of the rubber and for the sliding friction of the rubber\textendash asphalt contact are found to be useful; they provide approximate input values for an initial, promising attempt to separate the contribution from elastic deformation and that from sliding friction. Conclusively, valuable insights are gained which has the potential to further reduce the gap between physically based modelling of friction and empirically based knowledge, which are commonly used in vehicle and tyre industry.
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| 7. |
- Lundberg, Oskar, 1980-, et al.
(författare)
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La generación de ruido en el contacto entre la rueda y el carril – efectos no lineales
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- La fuente más importante de ruido y vibraciones en sistemas ferroviarios proviene del contacto entre la rueda y el carril. Junto con el perfil geométrico de la rueda y del carril, la rugosidad de las superficies definen la magnitud de la rigidez de contacto así como también la magnitud del filtro espacial de contacto que efectivamente reduce la excitación de ruido y vibraciones de altas frecuencias(rugosidades con corta longitud de onda). Normalmente, los modelos de interacción dinámica entre la rueda y el carril son lineales y la solución se deriva en el dominio frecuencial, lo cual conduce a aproximar la magnitud de la rigidez y del filtro espacial a valores constantes. El presente trabajo expone resultados del modelado de dicha interacción dinámica entre la rueda y el carril efectuado en el dominio temporal. El método utilizado incluye los efectos no lineales en la rigidez de contacto y en el filtro espacial generados por el perfil geométrico de la rueda/el carril y la rugosidad de las superficies. Los resultados de una investigación paramétrica revelan la influencia de los efectos no lineales sobre la generación de las fuerzas producidas en el contacto rodante.
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| 8. |
- Lundberg, Oskar, 1980-, et al.
(författare)
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Non-linear contact forces for beam/ball-interaction and its influence on the dynamic response of the beam
- 2013
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Ingår i: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013. - : OAL-Osterreichischer Arbeitsring fur Larmbekampfung. - 9781632662675 ; , s. 238-247
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Konferensbidrag (refereegranskat)abstract
- A well-defined rolling contact problem is studied with the intention to cover interesting aspects of tyre-road contact modeling and rolling contact in general. More specifically, the dynamic response in a steel beam caused by a steel ball rolling over it is studied by theoretical modeling of the beam- And ball dynamics as well as the contact forces. Validation of the dynamic response simulations is achieved by comparison with measurements. The contact model is shown to be greatly dependent on an accurate estimate of the real contact stiffness. A method to estimate the contact stiffness which leads to good accuracy in dynamic response simulations is presented. Although the contact stiffness is significantly lower for rubber- Asphalt interaction than for steel-steel contact, the results give useful insight for tyre-road contact modeling.
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| 9. |
- Lundberg, Oskar, 1980-, et al.
(författare)
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Non-linear contact stiffness and dynamic contact filter for rolling contacts
- 2014
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Ingår i: FISITA 2014 World Automotive Congress - Proceedings. - : FISITA.
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Konferensbidrag (refereegranskat)abstract
- Rolling contacts present in passenger cars such as in bearings and transmission elements are sources of noise and vibration, principally for interior comfort concerns. Moreover, tyre/road noise is the main source of road traffic noise which in turn leads to sleep disturbance and annoyance. In order to simulate friction losses as well as generated noise and vibrations in any rolling contact, it is crucial to have a correct description of the dynamic excitation caused by the roughness of the surfaces in contact. In this paper, a state-dependent modelling approach previously proposed by the authors is applied to a well-defined steel-steel rolling contact. A parametric study investigating the influence of rolling speed on contact conditions is performed, indicating the limits for the use of linear point force expressions for the rolling contact investigated. The state-dependent method is based on pre-calculation of contact stiffness and contact filtering as functions of vertical relative displacement. This leads to a computationally efficient way to include the influence of surface roughness and shape of the contacting bodies in a point force expression. Only vertical contact forces are studied within the scope of this work. Tangential friction forces are likely to affect the resulting vibrations and should therefore be further studied.
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| 10. |
- Lundberg, Oskar, 1980-
(författare)
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On the influence of surface roughness on rolling contact forces
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Road vehicle tyres, railway wheels and ball bearings all generate rolling contact forces which are transferred within a finite area of contact between the rolling element and the substrate. Either it is visible or not for the human eye, a certain degree of roughness is always present on the contacting surfaces and it influences the generation of both vertical and lateral contactforces. The purpose of this investigation is to enhance the understanding and modelling of the influence from small-scale surface roughness on the generation of rolling contact forces. To this end, a computationally efficient method to include roughness-induced contact nonlinearities in the dynamic modelling of rolling contacts is proposed. The method is implemented in a time domain model for vertical wheel–track interaction to model rolling-induced rail vibrations, showing good agreement with measurements. Furthermore, a test rig is developed and used for the investigation of tyre–road rolling contact forces. Detailed studies are performed on the influence of substrate roughness on the resulting contact forces for a tyre tread block which is rolling at different operating conditions. The choice of substrate as well as the rolling velocity and the slip ratio is observed to have significant influence on the resulting friction coefficient. For high slip ratios, stick–slip oscillations appear, exhibiting frequency content which is largely dependent on the choice of substrate. The outcomes of this study can potentially be used to improve future tyre–road contacts with respect to wear, traction and noise generation.
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