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| 2. |
- Johannesson, Niclas, et al.
(författare)
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Selective wave-front based protection algorithm for MTDC systems
- 2016
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Ingår i: IET Conference Publications. - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- Protection algorithms which can differentiate between different faults is a necessity for the reliable operation of multiterminal HVDC systems with multiple DC breakers. For selective detection by single-ended line protection algorithms, current limiting reactors installed in series with the breaker at the opposite side of the line can be used for limiting the reach in the forward direction. In this paper, a further development on the idea of basing the detection on the incident traveling wave is presented. The extraction of the incident wave is achieved by representing the frequency dependent characteristic admittance by a rational approximation. The main advantage over other single-ended protection methods is that the incident wave is independent of the boundary conditions at the terminal of the line. In this paper, this is illustrated by the simulation of both internal and external faults during two different operation scenarios in a four-terminal MTDC system. Finally, the performance of the suggested protection algorithm is compared to other single-ended methods with regard to the protection margin.
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| 5. |
- Larsson, Mikael, et al.
(författare)
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Comprehensive study regarding greenhouse gas emission from iron ore based production at the integrated steel plant SSAB Tunnplåt AB
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:2, s. 171-183
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Tidskriftsartikel (refereegranskat)abstract
- During the years 2001-2002, a comprehensive study regarding CO2 emissions related to the steel production for the integrated steel making production route, was carried out. The study was financed by SSAB and carried out by a research group with members from SSAB, MEFOS and LTV. The aim was to study the emissions from the existing system and how these could be influenced by process changes and by process modifications. The calculations were made using a global spreadsheet model for calculating the CO2 emissions, developed from an existing energy and process integration model of the same system. The calculated cases included the existing BF/BOF route as well as integration of other processes, e.g., an electric arc furnace, DR processes, COREX and a new future smelting reduction process concept (Sidcomet). All new existing alternative ore based process technologies would increase the specific CO2 emission from the system. A technology transfer to scrap based metallurgy would significantly decrease the emission level, but is not feasible for SSAB, due to the future product mix and the structure of scrap availability. In a 5-20 year perspective, the existing steel making process route with the use of magnetite ore for pellet production has the lowest specific CO2 emission. In a long-term perspective, 20-50 years, alternative process routes, e.g., based on H2 and DRI, could be of interest. Studies on such changes are, however, big projects and should be carried out as joint European and/or international efforts
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| 7. |
- McGill, Svena, et al.
(författare)
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Bartonella spp. seroprevalence in healthy Swedish blood donors
- 2005
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 37:10, s. 723-730
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Tidskriftsartikel (refereegranskat)abstract
- Serum samples were collected from healthy blood donors in 5 regions in Sweden in 1999, i.e. from the local Blood Centres (collecting facilities) in Boden, Jönköping, Lund, Skövde, and Uppsala. In total, 498 serum samples (63% males, 37% females) were received and tested by immunofluorescence assay for antibodies against B. elizabethae, B. grahamii, B. henselae (Houston-1), B. henselae (Marseille), B. quintana, and B. vinsonii subsp. vinsonii. An overall Bartonella spp. seroprevalence of 16.1% was found, with a predominance of immunoreactivity to B. elizabethae, at 14.1%; B. grahamii, 2.6%; B. henselae (Houston-1), 1.2%; B. henselae (Marseille), 1.8%; B. quintana, 0.2%; and B. vinsonii subsp. vinsonii, 0.0%. Univariate and multivariate analyses of epidemiological and demographical information revealed an increased rate of B. elizabethae seropositivity in blood donors working outdoors, being out in the wild a minimum of once a week, hunting moose, having cat contact, and travelling to Eastern Europe. Living in the southern region of Sweden (Lund area) was associated with decreased seropositivity to B. elizabethae.
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| 8. |
- Pettersson, Patrik, et al.
(författare)
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A method to measure the permeability of dry fiber mats
- 2006
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 38:3, s. 417-426
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Tidskriftsartikel (refereegranskat)abstract
- Close to the finalization of the medium density fiberboard process, a fairly thick bed of loosely entangled fibers is compressed in a belt-press to often less than a tenth of its original unstressed thickness. This single unit operation is very important to consider when the manufacturing process of the boards is to be optimized. Despite this, there is a lack of knowledge of the interaction between the fiber mat strength and how the fluid flows through it, i.e. de-aeration. Thus, it is of greatest importance to find reliable methods for studying this stage of the manufacturing process. Following this quest, a method is developed with which the gas permeability of fiber mats can be measured. The method offers the potential to measure the permeability at different flow rates and thus at arbitrary pressure gradients through the material. The method is successfully validated with a porous reference material consisting of polymer spheres, and it is shown that the flow follows Darcy's law at the flow rates of interest. Finally, the method is demonstrated by a presentation of permeability measurements on fiber mats consisting of spruce fibers.
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| 9. |
- Pettersson, Patrik, et al.
(författare)
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Development of material models for dewatering of pulp suspension
- 2008
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Ingår i: Proceedings of the 19th International Symposium on Transport Phenomena (ISTP-19). - : University of Iceland, Faculty of Industrial Engineering, Mechanical Engineering and Computer Science.
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Konferensbidrag (refereegranskat)abstract
- During the process of making pulp from wood, free fibers are mixed in a pulp suspension containing a large amount of water (98-50% by mass), wood fibers and often some processing chemicals. The suspension in this process is gradually cleaned from dissolved material. The suspension can be washed in a displacement washing step where the dirty fluid is replaced with a cleaner one. or by a compression step which increases the consistency of the suspension. To reduce costs and to increase the production rate of pulp and paper overall it is important to understand the interaction between fluid and fibers in such processes. During dewatering and washing, fibers are exposed to a drag force from the fluid. As the concentration of fibers increases this drag force and, consequently, the pressure generated from it become proportional to the permeability of the fiber network formed. When contact between fibers increases, an additional pressure emanates caused by bending and compressing of the fibers. By comparing experiments to a numerical model this study shows that for high dewatering velocities the resulting force required to dewater a suspension cannot be found by adding these two pressures. One reason for this may be that intra-fiber flows contribute to the force. Another explanation can be related to reinforcement
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| 10. |
- Pettersson, Patrik, et al.
(författare)
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Method for measuring permeability of pulp suspension at high basis weights
- 2008
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 34:4, s. 191-197
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Tidskriftsartikel (refereegranskat)abstract
- During the formation of pulp to paper, a large amount of water is added to dilute the pulp in order to obtain a homogenous material. This water call be mechanically and/or thermodynamically removed by different process solutions. The pulp suspension flows through various process equipment that influence the pulp suspension by changing its properties before the pulp suspension finally becomes paper. It is important to understand the mechanisms behind the transport path of water in this process in order to reduce cost and to increase the production rate of pulp and paper. The resistance to flow must be known in order to describe the flow path and the corresponding pressure drop in dewatering equipment in a pull.? mill. For networks with a complex geometry, a reliable method is to measure the resistance to flow at discrete points and to fit suitable resistance models to the results obtained. The objective of this study is to investigate how the history of pulp suspensions affects their permeability. A device for measuring the permeability of various pulp suspensions at high basis weights is developed and validated. Then the permeability of a number of virgin pulp species is measured. Some of the suspensions are then circulated in a closed flow loop and permeability is measured as a function of the number of loops. The results from two separate test's show that a basis weight variation and a different process treatment of the pulp suspension do not influence permeability.
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