| 1. |
- Andersson, Nina, et al.
(författare)
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Adaptive method for assessment of cerebrospinal fluid outflow conductance.
- 2007
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Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 45:4, s. 337-343
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Tidskriftsartikel (refereegranskat)abstract
- Outflow conductance (C out) is important for predicting shunt responsiveness in patients with suspected idiopathic adult hydrocephalus syndrome (IAHS). C out is determined by performing an infusion test into the cerebrospinal fluid system, and the reliability of the test is dependent on the measurement time. The objective of this study was to develop an adaptive signal analysis method to reduce the investigation time, by taking the individual intracranial pressure variations of the patient into consideration. The method was evaluated on 28 patients with suspected IAHS. The results from full time investigations (60 min) were compared to the results of the new algorithm. Applying the new adaptive method resulted in a reduction of mean investigation time by 14.3 ± 5.9 min (mean ± SD), p < 0.01. The reduction of reliability in the C out estimation was found clinically negligible. We thus recommend this adaptive method to be used when performing constant pressure infusion tests.
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| 2. |
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| 3. |
- Björ, Bodil, et al.
(författare)
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Acute effects on heart rate variability when exposed to hand transmitted vibration and noise.
- 2007
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Ingår i: International Archives of Occupational and Environmental Health. - : Springer Science and Business Media LLC. - 0340-0131 .- 1432-1246. ; 81:2, s. 193-199
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: This study investigates possible acute effects on heart rate variability (HRV) when people are exposed to hand transmitted vibration and noise individually and simultaneously. METHODS: Ten male and 10 female subjects were recruited by advertisement. Subjects completed a questionnaire concerning their work environment, general health, medication, hearing, and physical activity level. The test started with the subject resting for 15 min while sitting down. After resting, they were exposed to one of four exposure conditions: (1) only vibration; (2) only noise; (3) both noise and vibration; or (4) a control condition of exposure to the static load only. All four exposures lasted 15 min and the resting time between the exposures was 30 min. A continuous electrocardiogram (ECG) signal was recorded and the following HRV parameters were calculated: total spectral power (P(TOT)); the spectral power of the very low frequency component (P(VLF)); the low frequency component (P(LF)); the high frequency component (P(HF)); and the ratio LF/HF. RESULTS: Exposure to only vibration resulted in a lower P(TOT) compared to static load, whereas exposure to only noise resulted in a higher P(TOT). The mean values of P(TOT), P(VLF), P(LF), and P(HF) were lowest during exposure to vibration and simultaneous exposure to vibration and noise. CONCLUSIONS: Exposure to vibration and/or noise acutely affects HRV compared to standing without these exposures. Being exposed to vibration only and being exposed to noise only seem to generate opposite effects. Compared to no exposure, P(TOT) was reduced during vibration exposure and increased during noise exposure.
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| 4. |
- Casas, B., et al.
(författare)
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Adhesion and abrasive wear resistance of TiN deposited on electrical discharge machined WC-Co cements rbides
- 2008
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 265:3-4, s. 490-496
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Tidskriftsartikel (refereegranskat)abstract
- Electrical discharge machining (EDM) is a non-traditional machining method extensively used to manufacture complex geometries of hard and brittle materials such as WC-Co cemented carbides (CC). Although the thermal action of the EDM process is known to yield a relatively poor surface integrity in these materials, it may be minimized through the implementation of multi-step sequential EDM and post-EDM surface treatments. Particularly, hard coating application has been demonstrated to be effective for decreasing the EDM-induced mechanical degradation. However, additional studies are required on such coating-EDMed substrate systems to determine other crucial properties in terms of applications, e.g. adhesion and micro-scale wear behaviour. In this work the adhesion strength and the microabrasive wear resistance of TiN deposited on EDMed substrates have been evaluated by means of scratch and crater grinder testing, respectively. The results indicate that both critical load for decohesion of the coating from the substrate and coating specific wear rate increase with finer-executed EDM, reaching values close to those measured for a TiN coating deposited on a ground and polished substrate.
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| 5. |
- Cegrell, Urban, et al.
(författare)
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A Monge-Ampere norm for Delta-plurisubharmonic functions
- 2005
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Ingår i: Mathematica Scandinavica. - 0025-5521. ; 97:2, s. 201-216
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Tidskriftsartikel (refereegranskat)abstract
- We consider differences of plurisubharmonic functions in the energy classF as a linear space, and equip this space with a norm, depending on the generalized complex Monge-Ampère operator, turning the linear space into a Banach space δF. Fundamental topological questions for this space is studied, and we prove that δF is not separable. Moreover we investigate the dual space. The study is concluded with comparison between δF and the space of delta-plurisubharmonic functions, with norm depending on the total variation of the Laplace mass, studied by the first author in an earlier paper
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| 6. |
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| 7. |
- Coronel, Ernesto, 1973-
(författare)
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Solving Problems in Surface Engineering and Tribology by Means of Analytical Electron Microscopy
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that thin coatings can provide increased lifetime and reduced energy consumption for tools and components. During use, e.g. in sliding contact, mechanical and chemical reactions often lead to the formation of new surface layers, tribofilms, possessing different properties compared to the original surface, hence affecting the overall performance. In this work, analytical electron microscopy was applied to investigate the structure and composition of tribofilms.Concerning coatings, deposition parameter dependencies, stability and tribology were investigated. The carbon content of hydrogen-free TiCx coatings was shown to significantly influence the morphology. Low carbon content resulted in columnar grains with a strong texture while high carbon content led to the formation of randomly ordered TiCx crystals. The application of positive bias to the substrate as opposed to the normally used negative bias gave a fibrous structure of sputtered TiB2 and low residual stress with maintained hardness. Further, oxidation stability was examined on a (Ta,Al)C:C coating where oxidation led to partial oxidation and formation of AlTaO4 with an 8 nm interface.A focused ion beam instrument was used to extract samples from certain areas of worn specimens. Tribological contact was observed to result in phase changes and intermixing of materials present in the contact. Sliding contact involving a Co-alloy led to a phase change from fcc to hcp. A 30 nm Co-rich tribofilm was observed with basal planes parallel to the surface. Fully formulated oil was found to inflict considerable wear to a metal doped carbon film through chemical reaction with the metal dopant. WC/Co cemented carbide used for rock drilling exhibited intermixing of rock and Co binder phase after field tests. Chemical vapour deposited diamond worn in nitrogen and argon showed formation of wear debris with amorphous structure containing nitrogen and graphitic like structure, respectively.
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| 8. |
- Coronel, E, et al.
(författare)
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The effect of carbon content on the microstructure of hydrogen-free physical vapour deposited titanium carbide films
- 2009
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Ingår i: Thin Solid Films. - P.O. Box 211, Amsterdam, 1000 AE, Netherlands : Elsevier BV. - 0040-6090 .- 1879-2731. ; 518:1, s. 71-76
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Tidskriftsartikel (refereegranskat)abstract
- Titanium carbide (TiC) coatings for tribological applications were deposited on high speed steel. Several coatings with different titanium to carbon ratio were deposited by means of physical vapour deposition in which titanium was evaporated and carbon was sputtered. The coatings were characterised using analytical electron microscopy. It was observed that the change in titanium to carbon ratio significantly changed the microstructure of the coatings. The low carbon containing coatings consisted of columnar grains exhibiting a preferred crystallographic orientation whereas the coating with highest carbon content consisted of randomly ordered TiC grains in an amorphous carbon matrix. Energy filtered transmission electron microscopy revealed a change in Ti/C ratio as the distance from the substrate increased. The titanium to carbon ratio was observed to increase with distance from the substrate until a stable level was reached. This is due to a variation in the titanium evaporation during the early stages of film growth. This change of the titanium to carbon ratio affected the columnar growth in the initial stage of coating growth for the coatings with low carbon content. (C) 2009 Elsevier B.V. All rights reserved.
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| 9. |
- Gerth, Julia, 1979-, et al.
(författare)
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On the wear of PVD-coated HSS hobs in dry gear cutting
- 2009
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 266:3-4, s. 444-452
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Tidskriftsartikel (refereegranskat)abstract
- A hob is an advanced gear cutting tool usually made of homogenous high-speed steel (HSS) and coated by physical vapour deposition (PVD). It is designed for regrinding and recoating many times. However, hobs of today suffer from unpredictable wear making it difficult to schedule when they should be taken out for reconditioning. This investigation is aimed to contribute to the fundamental knowledge of the wear mechanisms and wear propagation of hobs used in dry gear cutting. Two AlCrN-coated hobs, used in actual gear cutting, were investigated by scanning electron microscopy (SEM) to study the tool topography, light optical microscopy (LOM) to study metallographic cross-sections and by X-ray photoelectron spectroscopy (XPS) for surface analyses.It is concluded that the high potential of PVD-coated HSS as tool material is not taken full advantage of. The main reason is a combination of a poor surface preparation prior to coating and excessively high compressive residual stresses, making parts of the coating detach along the edge line even on unused cutting teeth. During cutting, the high intrinsic stresses in combination with droplets and defects in the coating facilitated its fragmentation through decohesion and detachment. Simultaneously, the rake face is gradually covered by a thin oxide layer dominated by Fe, Cr and Mn in about equal amounts, and also with a significant content of Si. It is believed but not proved that this layer is beneficial.To improve service life and reliability of gear cutting hobs, precautions should be taken for the grinding–polishing preparation prior to PVD-coating to ensure a smooth substrate free from burning damage and other defects. Also, the edge radius and coating thickness has to be matched with the magnitude of compressive residual stresses in the coating.
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| 10. |
- Gerth, Julia, 1979-, et al.
(författare)
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Reproducing wear mechanisms in gear hobbing : Evaluation of a single insert milling test
- 2009
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 267:12, s. 2257-2268
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Tidskriftsartikel (refereegranskat)abstract
- Gear hobbing is a widely used method in industrial gear manufacturing. The most common type of hob is made of homogenous HSS and protected by a PVD coating. In order to increase the reliability and tool life of these milling tools, further developments of the tool surfaces and cutting edges are necessary. A single tooth milling test, using a HSS insert in a conventional milling machine, has been developed with the aim to reproduce the wear mechanisms seen on real HSS gear hobbing teeth. The benefits of such a test, compared to actual gear hobbing tests, are primarily accessibility and reduced costs for both design and production of test specimens (inserts). The main goal of this study was to verify that the wear mechanisms in the developed test correspond with the wear mechanisms obtained in real gear hobbing. Once this was verified, the influence of surfaces roughness on the performance of TiAlN coated HSS inserts was evaluated by using the tool as delivered or after polishing the tool surfaces. Parameters considered were tool wear, cutting forces and the quality of machined surfaces. The polished inserts, yielded less adhered work material and reduced flank wear but no significant difference in cutting forces as compared to the unpolished inserts.
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