| 1. |
- Böhm, Annette, et al.
(författare)
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Evaluating CALM M5-based vehicle-to-vehicle communication in various road settings through field trials
- 2010
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Ingår i: Proceedings - Conference on Local Computer Networks, LCN, (2010 12 01): 613-620. - Piscataway, N.J. : IEEE Press. - 9781424483877 ; , s. 613-620
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Konferensbidrag (refereegranskat)abstract
- Future cooperative Intelligent Transport Systems (ITS) applications aimed to improve safety, efficiency and comfort on our roads put high demands on the underlying wireless communication system. To gain better understanding of the limitations of the 5.9 GHz frequency band and the set of communication protocols for medium range vehicle to vehicle (V2V) communication, a set of field trials with CALM M5 enabled prototypes has been conducted. This paper describes five different real vehicle traffic scenarios covering both urban and rural settings at varying vehicle speeds and under varying line-of-sight (LOS) conditions and discusses the connectivity (measured as Packet Reception Ratio) that could be achieved between the two test vehicles. Our measurements indicate a quite problematic LOS sensitivity that strongly influences the performance of V2V-based applications. We further discuss how the awareness of these context-based connectivity problems can be used to improve the design of possible future cooperative ITS safety applications.
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| 2. |
- Nilsson, Emil, et al.
(författare)
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Ultra Low Power Wake-Up Radio Using Envelope Detector and Transmission Line Voltage Transformer
- 2013
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Ingår i: IEEE Journal on Emerging and Selected Topics in Circuits and Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3357 .- 2156-3365. ; 3:1, s. 5-12
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Tidskriftsartikel (refereegranskat)abstract
- An ultra-low power wake-up radio receiver using no oscillators is described. The radio utilizes an envelope detector followed by a baseband amplifier and is fabricated in a 130-nm complementary metal-oxide-semiconductor process. The receiver is preceded by a passive radio-frequency voltage transformer, also providing 50 Omega antenna matching, fabricated as transmission lines on the FR4 chip carrier. A sensitivity of -47 dBm with 200 kb/s on-off keying modulation is measured at a current consumption of 2.3 mu A from a 1 V supply. No trimming is used. The receiver accepts a dBm continuous wave blocking signal, or modulated blockers 6 dB below the sensitivity limit, with no loss of sensitivity.
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| 3. |
- Ottermo, Fredric, 1975-, et al.
(författare)
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Resonances and Aerodynamic Damping of a Vertical Axis Wind Turbine
- 2012
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Ingår i: Wind Engineering. - Essex, UK : Multi-Science Publishing. - 0309-524X .- 2048-402X. ; 3:36, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of a straight-bladed vertical axis wind turbine is investigated with respect to oscillations due to the elasticity of struts and shaft connecting to the hub. In particular, for the three-bladed turbine, a concept is proposed for dimensioning the turbine to maximize the size of the resonance free rpm range for operation. The effect of aerodynamic damping on the struts is also considered. The damping of these types of oscillations for a typical turbine is found to be good.
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| 4. |
- Persson, Urban, 1961-
(författare)
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Realise the Potential! : Cost Effective and Energy Efficient District Heating in European Urban Areas
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Member States of EU27 need to accelerate the integration of energy efficient technology solutions to reach the 20% energy efficiency target set for 2020. At current pace, projections indicate that only half of expected primary energy reductions will be reached. To meet the energy demands of growing populations and a vibrant economy, while simultaneously reducing primary energy supplies, the European continent faces a new kind of challenge never previously encountered. The identification and application of feasible, competitive, and comprehensive solutions to this problem are of highest priority if the remaining gap is to be closed in time. How is this multi-dimensional and complex dilemma to be dissolved? In this work, expanded use of district heating technology is conceived as a possible solution to substantially reduce future primary energy demands in Europe. By extended recovery and utilisation of vast volumes of currently disregarded excess heat from energy and industry sector fuel transformation processes, district heating systems and combined generation of heat and power can improve the general efficiency of the European energy balance. To investigate the possible range of this solution, this thesis introduces a set of methodologies, theoretical concepts, and model tools, by which a plausible future excess heat utilisation potential, by means of district heat deliveries to residential and service sectors, is estimated. At current conditions and compared to current levels, this potential correspond to a threefold expansion possibility for directly feasible district heating systems in European urban areas and a fourfold increase of European excess heat utilisation.
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| 5. |
- Sjöberg, Katrin, et al.
(författare)
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Measuring and using the RSSI of IEEE 802.11p
- 2010
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Ingår i: 17th World Congress on Intelligent Transport Systems, ITS 2010, Busan, South Korea, 25-29 October 2010.
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Konferensbidrag (refereegranskat)abstract
- The scalability of intelligent transport systems (ITS) applications is difficult to test in a field operational test (FOT) due to the high number of ITS equipped vehicles required. Therefore, computer simulations for evaluating different wireless communication technologies for ITS different applications can serve as a complement. In this paper we present results from lab measurements conducted on the CVIS hardware platform equipped with the upcoming standard IEEE 802.11p. We have measured the packet error rate versus the signal-to-noise ratio (SNR) for different packet lengths. This lab measurement is the first step towards an outdoor measurement campaign which also considers interference. The outdoor measurements will then be fed into a computer simulator together with a realistic channel model for evaluating the scalability of VANETs in a highway scenario.
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| 6. |
- Berglund, Johan C, 1978, et al.
(författare)
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On finishing of pressing die surfaces using machine hammer peening
- 2011
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Ingår i: The International Journal of Advanced Manufacturing Technology. - Berlin : Springer Berlin/Heidelberg. - 0268-3768 .- 1433-3015. ; 52:1-4, s. 115-121
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Tidskriftsartikel (refereegranskat)abstract
- Machine hammer peening (MHP) is a new method for finishing of surfaces. With this method, the workpiece surface is hammered with a spherical carbide tool. The main objective of the study was to evaluate whether the MHP method could become a plausible substitute for manual polishing in pressing die manufacturing where nodular cast iron is a common workpiece material. To do this, sample nodular cast iron surfaces were hammered and evaluated. Changes to the surfaces were evaluated using surface roughness measurements, hardness measurements and optical images. First of all, the workpiece surface was smoothened. Secondly, the surface hardness was increased significantly. Thirdly, the nodules on the workpiece surface were affected. They appeared to be smaller and not as visible. This effect would likely create a die surface less prone to galling since the cavities would not be filled with sheet metal to the same extent in a forming operation. In addition, with MHP, the amount of polishing needed to manufacture a die surface can be reduced because of the smoothening effect.
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| 7. |
- Böhm, Annette, et al.
(författare)
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Vehicular ad-hoc networks to avoid surprise effects on sparsely trafficked, rural roads
- 2011
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Konferensbidrag (refereegranskat)abstract
- This paper summarizes the main results from a project focusing on the development and evaluation of communication protocols for inter-vehicle communication on sparsely trafficked, rural roads,ensuring the reliable and timely delivery of safety critical data. The project is motivated by traffic safety applications, especially warning systems to avoid surprise effects of unexpected vehicle encounters on sparsely-trafficked, rural roads. The key issue in suchan application is to make sure that the vehicles become aware of each other’s existence by the help of communication as soon as possible. The driver can then be warned in time to avoid a possible accident.The challenge is to gain high probabilities of successful delivery in time, especially when having to cope with bad communication performance caused by e.g. crests.
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| 8. |
- Flys, Olena, 1971-, et al.
(författare)
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Piston ring topography variation and robust characterization
- 2014
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Konferensbidrag (refereegranskat)abstract
- It is a constant challenge for the automotive industry to reduce friction losses and oil consumption in automobile engine. The piston ring friction accounts for approximately 20% of the total mechanical energy losses in a modern engine. Oil control rings limit and control the oil consumption of the engine as well. They scrape off excess lubricating oil from the cylinder walls and return it to the crank case. Piston rings are designed to distribute the thin oil film evenly to ensure piston and ring lubrication. The surface topography of a piston ring is an efficient variable in the control of the oil consumption and friction losses. In places where the interacting surfaces come in contact, the oil film thickness is extremely thin and the surface asperities may deform because of the high pressures. There are different types of oil control rings.The most common one is the twin land oil control ring, which consists of two narrow lands that scrape off the oil on the liner and a spring on the back that exerts the load. In this paper, the surfaces of the two lands were investigated, since they play the key role in its function. The goal is to map the variation in surface roughness of piston rings that appear at different scales from form and waviness to micro and nano roughness. Areal topography measurements were made by white light interferometer designed at the Halmstad University able to measure and scan the total functional area of a piston ring. An significant amount of oil control piston rings of heavy duty truck engines were examined and 24 measurements were made in circumferential direction and on each ring land. The results show both the variation and uncertainty of the ring topography and discuss the instrument and measuring methodology uncertainty. The most stable parameters were found and recommended for an effective quality control. Comparisons between established coherence scanning interferometer and the instrument built in Halmstad were made. To ensure a good quality, the measurements were made both on calibration standards and on piston ring surfaces. Finally the influence on function and energy losses in the final engine assembly is discussed to indicate future design and metrology improvements.
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| 9. |
- Johansson, S., et al.
(författare)
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Frictional evaluation of thermally sprayed coatings applied on the cylinder liner of a heavy duty diesel engine : pilot tribometer analysis and full scale engine test
- 2011
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Ingår i: Wear. - Amsterdam : Elsevier. - 0043-1648 .- 1873-2577. ; 273:1, s. 82-92
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Tidskriftsartikel (refereegranskat)abstract
- The piston system accounts for roughly half of the mechanical friction of an internal combustion engine, thus it is important to optimize. Different thermally sprayed cylinder liners were investigated in order to optimize the frictional impact of the contact between cylinder liner and piston ring/piston. A novel tribometer test setup was used to scan through different materials at different running conditions. Based on these results a full-scale single cylinder test was performed to validate the results from the rig. A comparison of the results between the tribometer and the engine shows the importance of the ratio between viscous and mechanical friction losses.
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| 10. |
- Johnson, Urban, et al.
(författare)
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Sport Psychology Consulting Among Swedish Premier Soccer Coaches
- 2011
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Ingår i: International Journal of Sport and Exercise Psychology. - Fullerton, CA : International Society of Sport Psychology. - 1612-197X .- 1557-251X. ; 9:4, s. 308-322
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to examine knowledge and experience about sport psychology consulting among coaches for Swedish male and female premier soccer teams, and to identify barriers and possibilities that a sport psychology consultant (SPC) encounters in joining a team. All 28 coaches within Swedish male and female premier soccer leagues answered the “Psychology for Football Questionnaire”. In addition, coaches from two male and two female teams were interviewed. The main findings showed that about half the teams had contacted an SPC. Skills favored by coaches were goal setting and team building, and the biggest barriers to using SPCs were lack of knowledge/skepticism about the field, unclear descriptions of services, and problems integrating with the team. Possibilities for entry were feasible time available, and accessing positive role models. Conclusions pertain to the practical implications for applied research and the provision of sport psychology services within premier soccer.
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