| 281. |
- Wiklund, Urban
(författare)
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Abrasion resistance of drill bit steels in flowing saltwater
- 2018
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Ingår i: 18th Nordic Symposium on Tribology - NORDTRIB 2018, Uppsala, Sweden, June 18-21, 2018. - Uppsala.
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Konferensbidrag (refereegranskat)abstract
- A common type of rock drill bits is a steel head studded with cemented carbide buttons. The function of the steel is mainly to hold the buttons in place while the buttons do most of the rock crushing. However, a significant amount of wear also occurs on the steel matrix so also this material must provide adequate wear resistance. Flushing media is provided to the drilling zone. Preferably, the water is fresh water but in certain geographical areas supply of fresh water is scarce. Bringing fresh water in such areas is costly and sea water or mine water can be used instead. This will expose the equipment, and the drill bit in particular, to more or less corrosive media and possibly change the wear mechanisms of the tool. In this four drill bit matrix steels were tested in a lab scale test simulating the rock drilling including supply of cuttings. During the test the contact zone between the button and the rock was flushed with either fresh water or salty water. The wear rate was measured and the wear scar was studied using SEM and EDS to show the influence of salinity on matrix steel wear.
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| 282. |
- Wiklund, Urban, et al.
(författare)
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Adaptive spatio-temporal filtering of disturbed ECGs: a multi-channel approach to heartbeat detection in smart clothing
- 2007
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Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 1741-0444 .- 0140-0118. ; 45:6, s. 515-523
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Tidskriftsartikel (refereegranskat)abstract
- Intermittent disturbances are common in ECG signals recorded with smart clothing: this is mainly because of displacement of the electrodes over the skin. We evaluated a novel adaptive method for spatio-temporal filtering for heartbeat detection in noisy multi-channel ECGs including short signal interruptions in single channels. Using multi-channel database recordings (12-channel ECGs from 10 healthy subjects), the results showed that multi-channel spatio-temporal filtering outperformed regular independent component analysis. We also recorded seven channels of ECG using a T-shirt with textile electrodes. Ten healthy subjects performed different sequences during a 10-min recording: resting, standing, flexing breast muscles, walking and pushups. Using adaptive multi-channel filtering, the sensitivity and precision was above 97% in nine subjects. Adaptive multi-channel spatio-temporal filtering can be used to detect heartbeats in ECGs with high noise levels. One application is heartbeat detection in noisy ECG recordings obtained by integrated textile electrodes in smart clothing.
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| 283. |
- Wiklund, Urban, et al.
(författare)
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AGV navigation by angle measurements
- 1988
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Ingår i: Automated guided vehicle systems. - Kempston, Bedford : IFS. - 1854230247 ; , s. 199-212
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Konferensbidrag (refereegranskat)abstract
- Describes an optical navigation system for the navigation and control of an autonomous guided vehicle (AGV). The navigation system consists of a low-power laser, a rotating mirror and the necessary optics. It is used to measure the angles to several identical reflective beacons. The position and heading of the AGV is recursively updated each time a valid angle is measured. It is easy to define and change the drive path which is a list of coordinates. The AGV follows straight lines between these coordinates. The system has been tested on an AGV prototype
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| 284. |
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| 285. |
- Wiklund, Urban, et al.
(författare)
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Cardiac autonomic function does not improve after liver transplantation for familial amyloidotic polyneuropathy.
- 2010
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Ingår i: Autonomic Neuroscience. - : Elsevier BV. - 1566-0702 .- 1872-7484. ; 156:1-2, s. 124-130
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Liver transplantation is the only potentially curative treatment for familial amyloidotic polyneuropathy (FAP). We investigated cardiac autonomic function in 63 transplanted Swedish FAP patients. METHODS: Heart rate variability (HRV) was recorded between 1-17 (mean 8) months before, and 10-40 (mean 20) months after transplantation. HRV was analysed by power spectrum analysis, but only in patients without arrhythmia (n=38). RESULTS: Patients with moderate cardiac autonomic dysfunction showed a statistically significant reduction in HRV after transplantation, as compared to the pre-transplant recording. Patients with severe cardiac autonomic dysfunction presented unchanged HRV after liver transplantation. Twenty patients were excluded because they presented cardiac arrhythmia, five of these presented increased HRV after transplantation but had developed subtle arrhythmias, thus, they had not improved cardiac autonomic control. Five patients were excluded because they were pacemaker-treated. CONCLUSIONS: The reason why HRV decreased after transplantation remains unclear, but there are several possibilities: 1) liver transplantation did not stop the deterioration in cardiac autonomic function; 2) the deterioration continued until transplantation and was then halted; or 3) a sudden reduction in HRV occurred in connection with the transplantation procedure. Nonetheless, this study failed to disclose any improvement in cardiac autonomic function after liver transplantation for FAP.
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| 286. |
- Wiklund, Urban, et al.
(författare)
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Cardiorespiratory Coherence Analysis of Abnormal Heart Rate Responses during Deep Breathing
- 2013
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Ingår i: 2013 COMPUTING IN CARDIOLOGY CONFERENCE (CINC). - 9781479908844 ; , s. 109-112
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Konferensbidrag (refereegranskat)abstract
- Although the heart rate variability (HRV) normally is highly synchronised with respiration during deep breathing, in patients with transthyretin amyloidosis we occasionally observe abnormal heart rate responses due to subtle arrhythmias, This study evaluates the use of cardiorespiratory coherence analysis for automatic detection of these abnormal patterns.
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| 287. |
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| 288. |
- Wiklund, Urban, et al.
(författare)
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Development of monolayered low friction PVD ceramic coatings for application on tools and mechanical components
- 2006
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Ingår i: Advances in Science and Technology. - : Trans Tech Publications, Switzerland. - 1662-0356. ; 45, s. 122-131
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Ceramic carbon based coatings have become common on tools and machine components, mainly because they offer a greatly reduced friction, as compared to uncoated steel contacts, in combination with a considerable wear protection. Very often they contain alloying elements such as different metals to control properties like hardness, wear resistance and lubricity. Applied to component surfaces, also properties relating to the running-in behaviour become important since an efficient running-in is crucial for their long term steady-state functionality. Also, even though component coatings are meant to provide low friction in dry sliding, they are increasingly used also in lubricated situations. This raises demands for compatibility with common lubricants. All these aspects have to be considered when developing new tribological coatings and some of these are addressed in this work. Results from different sliding tests with coated and uncoated surfaces in both dry and boundary lubricated contacts are presented. The generated tribofilms and their influence on the tribological properties are compared for the different sliding conditions. It is also shown how lubricants and their additives can affect the running-in, the tribofilm formation, and alter the steady state friction.
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| 289. |
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| 290. |
- Wiklund, Urban, et al.
(författare)
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Evaporated vanadium nitride as a friction material in dry sliding against stainless steel
- 2006
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Ingår i: Wear. - Netherlands : Elsevier BV. - 0043-1648 .- 1873-2577. ; 261:1, s. 2-8
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Tidskriftsartikel (refereegranskat)abstract
- High friction coefficients and severe galling have always hampered machining of stainless steel. Lubricants and special procedures in cutting and forming operations are common practice. Coatings deposited on tools in order to alter the adhesive nature of the stainless steel is an appealing idea and it has long been proposed as a solution to the problem. However, to date no coating, which is also capable of enduring the temperatures encountered during machining has successfully fulfilled that prophecy. Despite being one of the first PVD tool coatings commercially produced, titanium nitride (TiN) is still also one of the most widely used. A vast number of coatings have indeed joined TiN for tooling applications but none of these has excelled in contact with stainless steel. Using quantum calculations vanadium nitride (VN), a ceramic compound closely related to TiN, has recently been suggested to be much less prone to adhesive cladding to iron alloys than TiN. Experimental verification of those results is the focus of this work. Reactive electron beam evaporation is regarded as the premier method for producing TiN. Using that very method, VN and TiN coatings were produced for this work and tested in sliding in contact with stainless steel and other selected materials. In these tests VN is shown to be less prone to galling as compared to TiN, especially against stainless steel. [All rights reserved Elsevier]
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