| 1. |
- Lindholm, Per, et al.
(författare)
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Contact conditions in a cam and roller contact
- 2001
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Ingår i: Proceedings of World Tribology Congress WT2001. - Wien : Österreichische Tribologishe Gesellshaft. - 390165707X
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Lundgren Mortensen, Anja Charlotte, et al.
(författare)
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Combination therapy of tyrosine kinase inhibitor sorafenib with the HSP90 inhibitor onalespib as a novel treatment regimen for thyroid cancer
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Thyroid cancer is the most common endocrine malignancy, affecting nearly 600,000 new patients worldwide. Treatment with the BRAF inhibitor sorafenib partially prolongs progression-free survival in thyroid cancer patients, but fails to improve overall survival. This study examines enhancing sorafenib efficacy by combination therapy with the novel HSP90 inhibitor onalespib. In vitro efficacy of sorafenib and onalespib monotherapy as well as in combination was assessed in papillary (PTC) and anaplastic (ATC) thyroid cancer cells using cell viability and colony formation assays. Migration potential was studied in wound healing assays. The in vivo efficacy of sorafenib and onalespib therapy was evaluated in mice bearing BHT-101 xenografts. Sorafenib in combination with onalespib significantly inhibited PTC and ATC cell proliferation, decreased metabolic activity and cancer cell migration. In addition, the drug combination approach significantly inhibited tumor growth in the xenograft model and prolonged the median survival. Our results suggest that combination therapy with sorafenib and onalespib could be used as a new therapeutic approach in the treatment of thyroid cancer, significantly improving the results obtained with sorafenib as monotherapy. This approach has the potential to reduce treatment adaptation while at the same time providing therapeutic anti-cancer benefits such as reducing tumor growth and metastatic potential.
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| 3. |
- Mahendar, Senthil Krishnan, 1988-
(författare)
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Mitigating Knock in Heavy Duty Spark Ignition Engines : Experiments and simulations of diluted ethanol and methanol combustion
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To effectively reduce fossil fuel dependence in the transport sector, an unprecedented increase in renewable fuel production is required. Short chain alcohols, such as ethanol and methanol, are well placed as they can be produced in a variety of renewable pathways from most carbon sources. Due to its high autoignition resistance, ethanol and methanol cannot be used as drop-in fuels in compression ignition engines that are prevalent in the heavy duty (HD) transport sector but can be an immense advantage when used in HD spark ignition (SI) engines.One crucial disadvantage experienced by HD SI engines is the end gas autoignition or knock which limits engine load, compression ratio and efficiency. It was not established if ethanol and methanol can in fact achieve the required load range in HD SI engines and if so, how efficient they would be. Diluting the air-fuel mixture with excess air or exhaust gas recirculation can add knock resistance by lowering in-cylinder temperature. Though dilution increases load and efficiency, it also increases instability and ultimately causes misfires. In this thesis, diluted combustion, knock limit and performance of ethanol and methanol was studied using a single cylinder heavy duty research engine. The required load was achieved with relatively good efficiency at lean operation and potential for improving efficiency further was investigated using 1D simulations. The modifications needed to utilize a semi-predictive combustion model in diluted operation were presented. Using simulations, the impact of turbulence on the performance of Miller valve timing and the effect of squish area on piston shapes to improve turbulence was discussed. With Miller timing and fast combustion using high squish pistons, lean burn ethanol and methanol can offer high efficiency, on par with compression ignition engines. If ethanol or methanol production can be scaled up, HD SI engines can provide good performance, low capital and operating cost for future transport.
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| 4. |
- Roos, Fredrik, et al.
(författare)
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Relations between size and gear ratio in spur and planetary gear trains
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report equations for the minimum gear sizes necessary to drive a given load are derived. The equations are based on the Swedish standards for spur gear dimensioning:SS 1863 and SS1871. Minimum size equations for both spur gear pairs and three-wheel planetary gears are presented. Furthermore, expressions for the gear weight and inertiaas function of gear ratio, load torque and gear shape are derived.For a given load torque and gear material, it is possible to retrieve the necessary gearsize, weight and inertia as function of gear ratio. This is useful for gear optimization,but also for optimization of a complete drive system, where the gear size, inertia and weight may affect the requirements on the other parts of the drive system.The results indicate that the Hertzian flank pressure limits the gear size in most cases.The teeth root bending stress is only limiting for very hard steels. Furthermore, then ecessary sizes, weights and inertias are shown to be smaller for planetary gears than for the equivalent pinion and gear configuration. Both these results are consistent with state of practice; planetary gears are commonly known to be compact and to have low inertia.
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| 5. |
- Spiegelberg, Christer, 1975-
(författare)
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Friction and wear in rolling and sliding contacts
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mechanical products are always expected to perform better, last longer, be more environmentally friendly and preferably cost less. Rolling and sliding contacts are found in many mechanical products, and friction and wear in the contacts have a direct impact on the products’ ability to meet these demands. Friction directly influences efficiency; low friction is often wanted to minimize power loss and fuel consumption. Wear generally shortens the lifetime, leading to more frequent service stops and increased costs. Increased demands on the products also means increased demands on the contacts in the products; contacts must work with higher loads and less friction, and they must last longer. The combination of increased demands and the high levels of sophistication of many products puts the spotlight on the contacts, and it becomes perhaps more important than ever to be able to predict and optimize their tribological performance. Simulation of systems with rolling and sliding contacts is a useful tool to understand the contact conditions and to help optimize their performance. This thesis is focused on friction and wear of boundary-lubricated, non-conformal rolling and sliding contacts. It presents a 3D brush model for transient friction in rolling and sliding contacts that can handle rough surfaces, varying surface velocities and varying normal load. Friction is simulated in interference mesh gears, cam mechanisms, a system with a roller between two planes and a system with a contact between two discs. Friction is also studied experimentally in interference mesh gears and in the contact between two discs. A wear model based on a generalized form of Archard’s wear law and the single-point observation method is used to simulate wear in the contact between the rocker arm pad and valve bridge in a cam mechanism of a diesel engine. The results show that the friction model can be used to simulate friction in both motion- controlled and force-controlled systems. The model can be used for both detailed contact studies and studies of the overall behaviour of systems with rolling and sliding contacts. Simulations and experiments show that the efficiency in interference mesh gears decreases significantly depending on the combination of mesh force pressing the gears together and the load on the output shaft. It is also seen that the torque loss varies heavily during a gear mesh depending on the position of the gear teeth and the number of contact points. The results from the simulations are consistent with the experimental results. The simulations of the cam-roller contact show that the creep in the contact is low except at high cam speeds when there is a period with high creep when the contact is close to the tip of the camshaft. The simulations of the rocker arm pad and valve bridge show that the contact radii of the wear pad and the position of the centre of the wear pad radii have a strong influence on the amount of wear. The simulations also show that the change of surface shapes due to wear can worsen contact conditions with high normal pressures. The simulations and experiments of force-controlled systems show that contacts can have a strong influence on a system’s behaviour. The contact acts as a spring damper system and can cause oscillations of the system. Simulations show that the oscillations could, at least in part, be explained by the surface roughness. Simulations also show that the creep in the contact is influenced by the contact stiffness and that the contact stiffness is lower for rough surfaces than for smooth. The experiments also show that the creep is higher for a lubricated contact than a dry contact.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Spiegelberg, Christer, et al.
(författare)
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Simulation of friction and wear in the contact between the valve bridge and rocker arm pad in a cam mechanism
- 2006
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 261:1, s. 58-67
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Tidskriftsartikel (refereegranskat)abstract
- In this paper the surface velocities obtained from a rigid body model are used to simulate friction and wear in the contact between the rocker arm pad and valve bridge in the cam mechanism of a diesel engine. The friction is simulated with two different friction models, a 3D brush model capable of handling transient conditions such as an varying normal load and varying surface velocities and a Coulombian friction model.The wear simulations are based on a generalised form of Archard's wear model. The results presented here show that both the maximum wear depths and the wear distributions are influenced significantly by the combination of wear pad radius and the position of the wear pad radius centre relative to the rocker arm hearing centre. A combination with wear pad radius of 20 mm and centre position of 5 mm is found to give the least wear depths on both the wear pad and the valve bridge. It is also seen that the contact between the wear pad and the valve bridge is mainly a sliding contact and that the transitions from sliding in one direction to the opposite are very rapid. The change of the surface shapes due to wear has a negative effect on the contact situation causing very high contact pressures.
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| 10. |
- Spiegelberg, Christer, et al.
(författare)
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Simulation of transient friction of a cylinder between two planes
- 2003
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Ingår i: Wear. - 0043-1648 .- 1873-2577. ; 254:11, s. 1170-1179
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Tidskriftsartikel (refereegranskat)abstract
- The need for good friction models for transient motions has increased as a consequence of the increased use of mechatronics and control engineering principles in precision mechanics. The machine elements in such equipment often involve rolling and sliding contacts. Most studies of friction in rolling and sliding contacts running under dry or boundary lubricated conditions have examined steady-state conditions. This paper describes simulations of the motion of a cylinder between two planes, first with a step change in velocity and then with an oscillating motion of the upper plane. The motion of the cylinder is determined by the friction in the contacts and the inertia. The friction in the rolling and sliding contacts is simulated with a brush model. The surfaces are assumed to be ideally smooth. For the step change in velocity, there is initially a period of complete sliding in the upper contact. During the sliding period, the friction force is the maximum possible, but it decreases as the complete sliding ends. The simulations show heavily damped oscillations, with frequencies corresponding to the natural translatory and torsional frequencies of the system. For the oscillating motions the sliding increases with the frequency of the motion, as expected.
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| 11. |
- Spiegelberg, Christer, et al.
(författare)
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Torque loss in spur gears with interference
- 2003
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Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : SAGE Publications. - 1350-6501 .- 2041-305X. ; 217, s. 385-395
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Tidskriftsartikel (refereegranskat)abstract
- Gears with interference (zero backlash) are used in robots and other precision equipment. The reason for using interference gearing is to improve positioning and motion control. It is then also desirable to compensate for the friction losses and therefore it is important to model the friction losses accurately. In this paper, results from a model for simulating spur gears with interference are compared with results from a test rig for spur gears with interference. FZG gears are used both in the test rig and in the simulations. Brief descriptions of the test rig and the simulation model are given in the paper; more thorough descriptions can be found in studies by Hedstrom and Karhammar and by Spiegelberg, Andersson and Sellgren respectively. There is also a description of the measurements and the procedure of making them. The aim of this paper is to compare the results from the test rig with the results from the simulation model and to analyse the results from the test rig. The results show that the simulated torque loss corresponds well with the measured torque loss within the range of the test rig. The results from both the test rig and the simulation model show that there are large variations in the frictional torque during one mesh of a gear tooth. The loss increases with the number of contact points and the lowest loss is found when a driving gear flank passes the pitch point. The overall efficiency decreases when the mesh force increases and the lowest efficiency readings are found when a combination of high mesh force and low load is applied.
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| 12. |
- Spiegelberg, Diana, 1982-, et al.
(författare)
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Higher Risk of Recurrence in Patients Treated for Head and Neck Cancer with Low BMI and Elevated Levels of C-Reactive Protein
- 2022
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Ingår i: Cancers. - : MDPI. - 2072-6694. ; 14:20
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Tidskriftsartikel (refereegranskat)abstract
- Simple Summary Head and neck cancer (HNC) treatment poses several challenges in clinical practice, and treatment side effects can be debilitating due to the close proximity of important anatomical structures. Cancer recurrence post-treatment presents some of the most challenging HNC management issues. This prospective study identifies high-risk groups for recurrence of head and neck cancer, based on commonly accessible clinical parameters. In this study with 272 HNC patients, elevated pre- and post-treatment CRP levels, low BMI and advanced stage at admission indicate higher risk for recurrence of disease. Using these parameters, a risk model is proposed which may be useful for estimating the probability of cancer recurrence and allow the identification of high and low-risk patients. This prospective study identifies high-risk groups for recurrence of head and neck cancer by BMI and circulating inflammatory response markers. Head and neck cancer patients from three Swedish hospitals were included (n = 272). Leukocyte and thrombocyte counts, CRP levels, and BMI were measured pre-treatment and post-treatment. Associations between the four factors and treatment failure (residual tumor, loco-regional failure, general failure/distant metastasis) were assessed using a Cox proportional hazards model adjusted for sex, age at the initial visit, smoking status, cancer stage, and hemoglobin count. CRP level was the only significant single variable, with an average increase in risk of recurrence of 74% (p = 0.018) for every doubling. The predictive power of a combined model using all variables was highest during the initial months after treatment, with AUC under the ROC curve 0.75 at the 0-3 month timepoints. Patients with elevated pre- and post-treatment CRP levels are at higher risk for recurrence of disease. Male patients with low post-treatment BMI, advanced stage, and high CRP at any time post treatment are at high risk for recurrence. The combined model may be useful for stratifying post-treatment patients into low and high-risk groups, to enable more detailed follow-up or additional treatment regimens.
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| 13. |
- Söderberg, Anders, 1977-, et al.
(författare)
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Modeling transient behavior of a mechanical system including a rolling and sliding contact
- 2005
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Ingår i: Proceedings of IMECE 1005, 2005 ASME Interantional Mechanical Engineering Congress and Exposition. ; , s. 229-238
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Konferensbidrag (refereegranskat)abstract
- Thefriction and wear of rolling and sliding contacts are criticalfactors for the operation of machine elements such as bearings,gears, and cam mechanisms. In precision machines, for example, themain concern is to compensate for frictional losses, so asto improve control accuracy. In other applications it is oftendesirable to minimize friction losses to improve efficiency, though sometimeshigh friction is desired to prevent sliding and wear. Theaim of this study is to simulate the behavior ofa test equipment and show that simulations can be usedto study and optimize mechanical systems that include rolling andsliding contact. Simulations can be used to study the systemas a whole, as well as the contact conditions. Thetest equipment and the measurement procedure used are described. Inthe simulations, a contact model designed to handle transient contactconditions is integrated into a system model. The results showthat the contact strongly influences the system. The simulations showthat the use of a contact model allows the simulationof systems that contain contacts with different amounts of slip,and that such simulations can be used to study thecontact as well as the system. Surface roughness influences thecontact stiffness and is included in the simulations.
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| 14. |
- Söderberg, Anders, et al.
(författare)
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Simulation models of test equipment for measuring transient friction in a rolling and sliding contact
- 2005
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Ingår i: Proceedings of OST ’05 Symposium On Machine Design.
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Konferensbidrag (refereegranskat)abstract
- This paper investigates how a model for boundary lubricated rolling and sliding contacts can be integrated in a dynamic rigid body model of a mechanical system in order to improve the accuracy of simulations of system behavior. The system modeled is test equipment for the measurement of transient friction in rolling sliding contact between two discs. Two different models of the system were constructed: one neglecting the rolling and sliding contact and the other integrating it in the system model. In the integrated contact model, the pressure distribution was computed using an elastic foundation model. A brush model was used for the friction calculation. Simulations were performed with both models and validated by experiments. The results show that the contact needs to be included in the model in order to capture the behavior of the system. Since the contact model used can handle both microslip and gross slip, it is applicable to a wide range of contact conditions.
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