| 12391. |
- Kuzmin, Leonid, et al.
(författare)
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The contamination, wettability and gliding ability of ski running surfaces
- 2007
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Ingår i: Science and Nordic Skiing. - Oxford : Meyer & Meyer Sport. - 9781841262291 ; , s. 340-
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The UHMWPE (press-sintered) ski base and ski glide waxes are very similar substances. Hence, it should be possible to achieve a same or even better glide on a bare ski base. In this study we examined waxed and unwaxed skis before and after skiing for the purpose of gliding ability, dirt accumulation and wettability. We observed that the skis with unwaxed running surface did retain a same or higher comparative level of all three tested parameters. We can assume that it is a consequence of a soft wax dirt accumulation under warm conditions and of the excessively hot ski base treatment under cold and dry conditions.
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| 12392. |
- Kuznetsov, Evgeny, et al.
(författare)
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Dynamic characteristics of compliant journal bearings considering thermal effects
- 2016
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 94, s. 288-305
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Tidskriftsartikel (refereegranskat)abstract
- A numerical THD model that takes into account mechanical and thermal deformations of a compliant lining is used to investigate the influence of compliance on dynamic characteristics of a two axial groove bearing. A detailed study on the contribution of mechanical and thermal deformation components of the compliant lining to the non-dimensional bearing stiffness and damping is carried out. Thermal deformation is found to increase horizontal stiffness Kyy and cross-coupled stiffness Kxy and slightly reduce journal critical mass. Mechanical deformation of the compliant lining is found to decrease damping, reduce vertical and cross-coupled Kxy stiffness. Radial clearance is found to increase stiffness, except its horizontal component, and decrease horizontal damping. Compliant lining is found to improve bearing stability.
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| 12393. |
- Kvisteroy, Terje, et al.
(författare)
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Far infrared low-cost uncooled bolometer for automotive use
- 2007
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Ingår i: Advanced Microsystems for Automotive Applications 2007. - BERLIN : SPRINGER-VERLAG BERLIN. - 9783540713241 ; , s. 265-278
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Konferensbidrag (refereegranskat)abstract
- A proposed EU regulation requires the automotive industry to develop technologies that will substantially decrease the risk for vulnerable road users such as pedestrians when hit by a vehicle. Automatic brake assist systems, activated by a suitable sensor, will reduce the speed of the vehicle before the impact. Far InfraRed (FIR) detectors are ideal candidates for such sensing systems. In order to enable high volume serial installation, the main development must be focused on cost reduction. Optimizing all aspects of the system, including sensor size, production yield and 3D wafer level vacuum packaging will lower today's "high end" FIR product costs by an order of magnitude. A low-cost FIR infrared bolometer is developed in the Eureka labeled PIMS (Pedestrian Injury Mitigation System) project. In the paper the background and the actual design of the first demonstrator to be finished in 2008 are described in detail.
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| 12394. |
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| 12395. |
- Kyösti, Petter, et al.
(författare)
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Simulation of industrial support systems in the context of functional products
- 2011
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Ingår i: Proceedings of the 19th AR2TS Advances in Risk and Reliability Technology Symposium. - Nottingham : University of Nottingham. ; , s. 275-288
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Konferensbidrag (refereegranskat)abstract
- Functional Products, consisting of hardware and service support systems owned by the supplier, are sold to customers with a guaranteed availability of the function. The availability achieved is dependent on the reliability of both hardware and the service support system. The reliability of the latter can be defined as its ability to provide the required maintenance services in a timely manner. This paper reports simulation of a service support system from an industrial case study in order to predict its reliability. To identify and develop a suitable case together with an industrial partner company, a number of phone meetings were held in order to explain the research question, interview knowledgeable people and plan on-site visits and interviews. A number of interviews face to face were carried out with the industrial partners, where the goal was to obtain enough information to be able to model the support system correctly. The research involved both qualitative information gathering and applied computer aided simulation. An improved model for simulating a service support system is developed that considers the context in which the maintenance procedures are performed within a Functional Product. A software implementation of the model, developed by the authors, is applied to simulate the case study service support system in various scenarios such as different personnel availability and number of systems supported. The results show how the modeling can be used to improve and predict the reliability of the service support system
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| 12396. |
- Kärnell, Samuel, 1993-, et al.
(författare)
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As Simple as Imaginable - An Analysis of Novel Digital Pump Concepts
- 2019
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Konferensbidrag (refereegranskat)abstract
- This paper focuses on how digital displacement can be achieved in a wobble plate pump by connecting thecylinders in the pump to different groups and using by-pass valves to control the flow from each group. The ideais to make a simple and inexpensive electronically controlled pump. The paper deals with two main aspects, thecylinder configuration and the valve configuration. The cylinder configuration refers to how the cylinders in thepump can be grouped and how different groupings will affect the flow pulsations. The valve configuration refersto the by-pass solution. Two principally different solutions are analysed: one that uses 3-way by-pass valvesand one that makes use of check valves in combination with 2-way on/off-valves. A comprehensive simulationmodel has been used as a tool for analysing flow pulsations for the different design configurations. The resultsshow that a cylinder configuration with 3+6 cylinders delivers low flow pulsations for all three displacementsettings. However, if more displacement settings are desired, an interesting finding is that a configuration with3+6+12 cylinders is only slightly better than a configuration with 2+4+8 cylinders, from a pulsation amplitudepoint of view. This is due to the pre-compression in the cylinders. Regarding the valve configuration, it hasbeen shown that both of the analysed configurations might suffer from problems during switching, especially ifthe valves are slow.
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| 12397. |
- Kärnell, Samuel, 1993-, et al.
(författare)
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Classification and Review of Variable Displacement Fluid Power Pumps and Motors
- 2023
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Ingår i: International Journal of Fluid Power. - : River Publishers. - 1439-9776. ; 24:2, s. 207-246
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Tidskriftsartikel (refereegranskat)abstract
- Displacement control of positive displacement machines has been a part of fluid power since the early days. Some of the early hydraulic presses already used two different displacement settings, though this was realised by using two different pumps rather than changing the displacement. Later, radial motors with variable stroke length appeared, followed by other designs of variable machines, such as swashplate machines, bent-axis machines, and variable vane machines. All these solutions control the displacement by varying the volume difference of the displacement element – but there are other ways of achieving this. Most have not passed the research state, but some are commercially available. In this paper, different ways of varying the displacement are presented and classified. The classification divides concepts into either control of displaced fluid or control of usage of displaced fluid. In turn, these concepts can be either on system level or displacement element level. This results in four main classes, which to some extent can describe the characteristics of the control.
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| 12398. |
- Kärnell, Samuel, 1993-, et al.
(författare)
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Digital pumps in speed-controlled systems : an energy study for a loader crane application
- 2020
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Konferensbidrag (refereegranskat)abstract
- Imagine a system with a pump driven by a speed-controlled electric motor. What and how much can be gained by using a pump with discretely variable displacement instead of a conventional fixed pump in such a system? This question is the focus in this paper, in which a simulation study based on a drive cycle for a loader crane is presented. The results indicate that the system efficiency from inverter input to pump output can increase by a few percentages. This might be considered small in relation to the increasing complexity that comes with discrete displacement. However, the results also show that a system with discrete displacement substantially reduces torque and cooling requirements on the electric motor. The required maximum torque can be reduced by 30 to 50 % and the motor can generate up to 40 % less heat since it can work in more efficient conditions. These potential benefits will be obtained with only a few discrete displacement settings available.
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| 12399. |
- Kärnell, Samuel, 1993-, et al.
(författare)
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Hysteresis Control in Pump-Controlled Systems : A Way to Reduce Mode-Switch Oscillations in Closed and Open Circuits
- 2022
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 15:2
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Tidskriftsartikel (refereegranskat)abstract
- There is growing interest in using electric motors as prime movers in mobile hydraulic systems. This increases the interest in so-called pump-controlled systems, where each actuator has its own drive unit. Such architectures are primarily appealing in applications where energy efficiency is important and electric recuperation is relevant. An issue with pump-controlled systems is, however, mode-switch oscillations which can appear when the pressure levels in the system are close to the switching condition. In this paper, the mode-switching behavior of different generalized closed and open circuit configurations is investigated. The results show that the choice of where to sense the pressures has a huge impact on the behavior. They also show that, if the pressure sensing components are properly placed, closed and open circuits can perform very similarly, but that mode-switch oscillations still can occur in all circuits. Active hysteresis control is suggested as a solution and its effectiveness is analyzed. The outcome from the analysis shows that active hysteresis control can reduce the risk for mode-switch oscillations significantly.
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| 12400. |
- Kärnell, Samuel, 1993-, et al.
(författare)
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Pump-Controlled Actuators with Dump Valves
- 2021
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Ingår i: Proceedings of the 17:th Scandinavian International Conference on Fluid Power. - Linköping : Linköping University Electronic Press. - 9789179290139
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Konferensbidrag (refereegranskat)
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