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| 3. |
- Billstein, Mats, et al.
(författare)
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A numerical evaluation of air bubbles as a potential explanation to the higher than expected pore pressures in the core of WAC Bennett Dam
- 2002
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Ingår i: Journal of Hydraulic Research. - : Informa UK Limited. - 0022-1686 .- 1814-2079. ; 40:5, s. 623-630
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to numerically evaluate if the Air Hypothesis is a potential explanation of the unusual pressure behaviour of the core at WAC Bennett Dam. Up to now, the pore pressures have exceeded the expected normal steady state distribution for about 25 years. The Air Hypothesis describes the influence of air bubbles on the pressure distribution in the core. An increased water pressure will compress the air bubbles and increases the amount of air that can go into solution at the upstream side of the core. At the downstream side, the situation is reversed, i.e. the air volume will increase and cause a hydraulic blockage. A one-dimensional numerical model, that is based on relevant conservation laws, physical laws (Darcy's, Boyle's, and Henry's laws) and the relationships between the relative hydraulic conductivity and water saturation level, is able to predict the pressure evolution in both a qualitative and quantitative way. The model is applied to both a hypothetical core and the core of WAC Bennett Dam. Results from a plug flow analysis on the dissolution of the air in the hypothetical core are in fair agreement with the numerical results. Comparisons with pressure measurements from WAC Bennett Dam show that the Air Hypothesis is a potential explanation to the unusual pressure distribution in the core
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| 4. |
- Bilstrup, Urban, et al.
(författare)
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A fault tolerance test enabling QoS in a Bluetooth piconet
- 2004
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Konferensbidrag (populärvet., debatt m.m.)abstract
- An important trend, in personal area networks, is that time critical application becomes more common, e.g., voice over IP, video phone calls, network games. This segment of applications demands for quality of service (QoS) guarantees, to provide the correct functionality. The Bluetooth standard provides an optional interface to support QoS guarantees, but the standard does not suggest any actual implementation. A wireless communication channel is stochastic by nature, providing QoS guarantees with this precondition make traditional deterministic real-time theory obsolete. In this paper a probabilistic fault tolerance test enabling quality of service guarantees in a Bluetooth piconet is given. The basic Bluetooth network architecture is based on a master-slave configuration, i.e., a point to point connection. More advanced network architectures are possible where up to eight Bluetooth equipped units can be active members of one network (piconet). Furthermore, several piconets can interconnect and form a so called scatternet.
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| 5. |
- Bilstrup, Urban, et al.
(författare)
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Capacity limitations in wireless sensor networks
- 2003
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Ingår i: ETFA 2003. - Piscataway, N.J. : IEEE. - 0780379373 ; , s. 529-536
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Konferensbidrag (refereegranskat)abstract
- It is expected that wireless sensor network will be used in home automation and industrial manufacturing in the future. The main driving forces for wireless sensor networks are fault tolerance, energy gain and spatial capacity gain. Unfortunately, an often forgotten issue is the capacity limits that the network topology of a wireless sensor network represents. In this paper we identify gains, losses and limitations in a wireless sensor network, using a simplified theoretical network model. Especially, we want to point out the stringent capacity limitations that this simplified network model provide. Where a comparison between the locality of the performed information exchange and the average capacity available for each node is the main contribution.
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| 6. |
- Bilstrup, Urban, 1971-, et al.
(författare)
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Knowledge Horizon - Dynamic limitations in a wireless ad hoc network
- 2003
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Ingår i: SNCNW 2003 Swedish National Computer Networking Workshop 2003 on-line proceedings. ; , s. 1-3
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate the impact of node mobility in a wireless ad hoc network (WAHN). Especially we investigate the possibility to provide guaranteed services in a WAHN, i.e., the network topology predictability. We combine link expiration time (LET) estimation with information propagation speed (IPS) in a time-space diagram and as result an operation area is revealed. The result gives that a WAHN, where the nodes are mobile, has a knowledge horizon (KH), the distance of which is dependent on the mobility of the nodes. Beyond the KH, knowledge about the network state is impossible to achieve. Thus, we can not predict long distance network topology state when the node mobility is high.
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| 8. |
- Janson, Martin S., et al.
(författare)
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Hydrogen in the wide bandgap semiconductor silicon carbide
- 2004
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T108, s. 99-112
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we give a review of our recent results related to the incorporation of hydrogen (H) in silicon carbide (SiC) and its interaction with acceptor doping atoms and implantation induced defects. Hydrogen is an abundant impurity in the growth of epitaxial SiC since it is present in the precursor gases and since H-2 is used as the carrier gas. High concentrations of hydrogen are indeed incorporated into highly doped p-type epi-layers and it is shown that the main source is the carrier gas. Furthermore, it is revealed that the entire substrate becomes homogeneously filled with hydrogen during growth and that this hydrogen is more thermally stable than that in the epi-layer. Incorporation of hydrogen from an H-2 ambient, at temperatures considerably lower than those used for epitaxy, is also demonstrated in p-type samples coated with a catalytic metal film. This effect is most likely the cause for the increased series resistance observed in p-type SiC Schottky sensor devices using a catalytic metal gate after annealing at 600 degrees C in a H-2 containing ambient. Hydrogen is found to passivate the acceptors Al and B by forming electrically neutral H-acceptor complexes. Unlike in Si and GaAs, the two H-acceptor complexes in SiC exhibit very different dissociation energies, suggesting that the atomic configurations of the complexes are significantly different. The migration of mobile hydrogen in the presence of externally applied, or internal built-in, electric fields further reveals that hydrogen is present as H+ in p-type SiC. Finally, the redistribution and subsequent out-diffusion of low energy implanted H-1 and H-2 is investigated. Two annealing phases for the redistribution are observed, and the activation energies for the processes are extracted.
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| 9. |
- Linnarsson, MK, et al.
(författare)
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Incorporation of hydrogen (1H and 2H) into 4H-SiC during epitaxial growth
- 2002
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Ingår i: Materials Science Forum, Vols. 389-393. ; , s. 565-568
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Konferensbidrag (refereegranskat)abstract
- The hydrogen depth distribution in 4H-SiC after epitaxial growth at 1600 degreesC has been studied in detail with secondary ion mass spectrometry. Both H-1 and H-2 have been employed as carrier gas to trace the origin of the incorporated hydrogen. In particular the substrate as a prospective hydrogen source has been considered. After growth H-2 is detected throughout the whole substrate (similar to400 mum) and a considerable quantity remains after annealing at 1500 degreesC for 15 minutes.
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| 10. |
- Michalecka, Agnieszka, et al.
(författare)
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Arabidopsis genes encoding mitochondrial type II NAD(P)H dehydrogenases have different evolutionary orgin and show distinct responses to light.
- 2003
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; 133:2, s. 642-652
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Tidskriftsartikel (refereegranskat)abstract
- In addition to proton-pumping complex I, plant mitochondria contain several type II NAD(P)H dehydrogenases in the electron transport chain. The extra enzymes allow the nonenergy-conserving electron transfer from cytoplasmic and matrix NAD(P)H to ubiquinone. We have investigated the type II NAD(P)H dehydrogenase gene families in Arabidopsis. This model plant contains two and four genes closely related to potato (Solanum tuberosum) genes nda1 and ndb1, respectively. A novel homolog, termed ndc1, with a lower but significant similarity to potato nda1 and ndb1, is also present. All genes are expressed in several organs of the plant. Among the nda genes, expression of nda1, but not nda2, is dependent on light and circadian regulation, suggesting separate roles in photosynthesis-associated and other respiratory NADH oxidation. Genes from all three gene families encode proteins exclusively targeted to mitochondria, as revealed by expression of green fluorescent fusion proteins and by western blotting of fractionated cells. Phylogenetic analysis indicates that ndc1 affiliates with cyanobacterial type II NADH dehydrogenase genes, suggesting that this gene entered the eukaryotic cell via the chloroplast progenitor. The ndc1 should then have been transferred to the nucleus and acquired a signal for mitochondrial targeting of the protein product. Although they are of different origin, the nda, ndb, and ndc genes carry an identical intron position.
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| 11. |
- Möller, Torgil, et al.
(författare)
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Radiotherapy techniques in current use in Sweden.
- 2003
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 42:5-6, s. 376-386
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Tidskriftsartikel (refereegranskat)abstract
- A systematic assessment of radiotherapy for cancer was conducted by The Swedish Council on Technology Assessment in Health Care (SBU) in 2001. The assessment included a review of radiotherapy techniques in current use in Sweden. The following conclusions were drawn: Radiotherapy demands adequate knowledge of diagnostic methods, anatomy, cancer biology and of the physical and biological properties of ionizing radiation. Well-functioning teamwork on the part of the oncologist, medical physicist and oncology nurse is important.Radiotherapy has a high degree of technical sophistication, including the use of computers, which necessitates expert technical support.Technical development is rapid, and since the previous report, multileaf collimators and electronic portal imaging have been introduced in the clinical routine.The use of brachytherapy for treatment of non-gynaecological malignancies is rapidly increasing.The need for quality assurance in all steps of the radiotherapy procedure is stressed. A critical review of the literature on intraoperative radiotherapy is also included as an Appendix.
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| 12. |
- Svensson, Erik, 1959-, et al.
(författare)
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Bacteriuria in spinal cord injured patients with neurogenic bladder dysfunction
- 2004
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Ingår i: Upsala Journal of Medical Sciences. - 0300-9734 .- 2000-1967. ; 109:1, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence of bacteriuria in spinal cord injured patients with neurogenic bladder dysfunction who used clean intermittent catheterisation to empty their bladders was studied in order to examine cut-off concentration breakpoints for significant bacteriuria in this group of patients using procedures of the European Urinanalysis Guideline. 344 samples were cultured, yielding 285 isolates. Coagulase-negative staphylococci (27 %), Enterococci (25 %), Klebsiella spp (19 %), and Escherichia coli (12 %) were the most common findings. Bacteria grew at concentrations of 105-108 cfu/L, but only a few at 104 cfu/L. It is concluded that low bacterial concentrations in the urine (105 cfu/L) of patients with neurogenic bladder dysfunction who are on intermittent catheterisation might be as significant for bladder contamination with bacteria as a high bacterial concentration and can possibly be responsible for bladder infections.
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