| 1101. |
- Persson, Anders, 1982-, et al.
(författare)
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Dynamic Behaviour and Conditioning Time of a Zirconia Flow Sensor for High-Temperature Applications
- 2016
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Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 251, s. 59-65
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Tidskriftsartikel (refereegranskat)abstract
- The temperature dependent ion conductivity of yttria stabilized zirconia (YSZ) can be used to create a miniaturized flow sensor using a calorimetric measurement scheme. Such a sensor is compatible with harsh environments, and can sustain temperatures of up to 1000 degrees C, although thermal crosstalk will limit its performance as the temperature rises. This paper investigates if the integration of thermal isolation in the form of sealed cavities can mitigate the detrimental effect of the thermal crosstalk, particularly by studying the conditioning time of the sensor to temperature changes. To this end, high temperature co-fired ceramic (HTCC) sensors were fabricated from tapes of 8 mol-% YSZ that were screen printed with platinum paste. Definition of channels and structures were made by milling the green tapes, and sacrificial inserts were placed in all cavities to give mechanical support during lamination and sintering. Cavities with widths of 240 mu m, 400 mu m and 560 mu m were investigated, and sensors without cavities were also made to serve as references. Additionally, two different positions of the sensor element with respect to the edge of the cavity (560 or 800 mu m) were investigated. The results showed that it was possible to improve the conditioning time of the sensor by up to five times by the use of isolating cavities, and that this improvement is translated into a reduction in rate-dependent hysteresis for measurements with long elapse times. The latter effect is most pronounced for the sensors with the largest cavities.
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| 1102. |
- Persson, Anders
(författare)
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Dåligt pålästa kunskapsivrare
- 1986
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Ingår i: Helsingborgs Dagblad. - 1103-9388. ; :860318
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Recension (populärvet., debatt m.m.)
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| 1103. |
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| 1104. |
- Persson, Anders, 1978-, et al.
(författare)
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e-Government challenges : Exploring inter-organisational aspects of e-service development
- 2006
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Ingår i: Proceedings of the Fourteenth European Conference on Information Systems, ECIS 2006, Göteborg, Sweden, 2006. - Göteborg : University of Gothenburg. - 9163198940 ; , s. 1419-1430
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Konferensbidrag (refereegranskat)abstract
- In this paper we are applying inter-organizational concepts from the industrial/business network approach on empirical findings from an e-government case, in order to describe and better understand challenges in one-stop government e-service development. We analyze our case by using concepts that characterize an inter-organizational relationship in terms of its level of continuity, complexity, symmetry, informality, and its dimensions (links, bonds, and ties). The purpose of the paper is to explore how these theoretical concepts can help us focus on certain aspects of e-service development challenges. The empirical findings are collected within an on-going action research project for e-service development in the public sector in Sweden. The aim of the project is to develop one-stop government e-services for driver’s license matters as well as a web-based portal where these e-services and information about the driver’s license process will be easily accessible. Our conclusions are that the theoretical concepts helped us reach further understanding of the empirical case. In the spirit of the network approach, we focused on the present situation and been able to give a rather detailed and fine-grained picture of the problems and challenges in this context.
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| 1105. |
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| 1106. |
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| 1107. |
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| 1108. |
- Persson, Anders, 1956-, et al.
(författare)
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Effects of benthivorous fish on biogeochemical processes in lake sediments
- 2006
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Ingår i: Freshwater Biology. - West Sussex, UK : Wiley-Blackwell. - 0046-5070 .- 1365-2427. ; 51:7, s. 1298-1309
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Tidskriftsartikel (refereegranskat)abstract
- 1. Studies of aquatic environments have shown that community organisation may strongly affect ecosystem functioning. One common phenomenon is a change in nutrient level following a shift in the fish community composition. Although several hypotheses have been suggested, there is no consensus on which mechanisms are involved. Our study evaluated indirect effects of benthivorous fish on the biogeochemical processes at the sediment-water interface separately from direct effects caused by nutrient excretion or sediment resuspension.2. We assigned field enclosures to three treatments representing typical pond communities; without fish, addition of approximately 10 small tench or addition of one large bream. After one summer, we monitored the water chemistry, benthic invertebrates and periphyton in the enclosures and sampled sediment cores for laboratory analysis of biochemical process rates (oxygen, phosphorus and nitrogen exchange between sediment and water, and denitrification rate).3. Fish had strong negative effects on benthic invertebrates, but weaker effects on periphyton, organic content and porosity of the sediment. Moreover, there were significant positive fish effects on both phosphorus and nitrogen concentrations in the water. However, there were no general treatment effects on sediment processes that could explain the treatment effects on water chemistry in the enclosures.4. Hence, overall treatment effects attenuated along the chain of interactions. We conclude that the observed effect of benthic fish on water chemistry was probably because of direct effects on nutrient excretion or resuspension of sediment. The similarity between bream and tench treatments suggests large niche complementarity despite their different habitat preferences.
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| 1109. |
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| 1110. |
- Persson, Anders
(författare)
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Effects of Fish Predation and Excretion on the Configuration of Aquatic Food Webs
- 1997
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Ingår i: Oikos. - 1600-0706. ; 79:1, s. 137-146
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Tidskriftsartikel (refereegranskat)abstract
- The relative importance for algae of fish excretion and fish predation on zooplankton was studied in experimental pools. Even- (zoo- and phytoplankton) and odd-link systems (planktivorous fish, zoo- and phytoplankton) were established, in which the standing stock of primary producers was expected to follow the predictions from food chain theory sensu Oksanen. Two intermediate treatments (fish predation and nutrient regeneration by fish alone) were used to determine the relative power of fish in affecting the transition from an even-link system to an odd-link system, i.e. their relative power in the trophic cascade. Algal density and production were found to only be enhanced when both fish predation and fish excretion acted together. A reduction in the grazer biomass alone did not increase the algal biomass. Fish excretion alone increased the algal biomass somewhat, but not significantly so compared with the control. The results suggest that both fish predation on zooplankton and the regeneration of nutrients by fish may be necessary to create the difference in algal biomass between an even- and an odd-link system predicted by food chain models, at least in the absence of an external input of nutrients. In addition, the effects of increased nutrient regeneration due to use of non-zooplankton resources by the fish, nutrient maintenance in living biota, and decreased grazing pressure seem to reinforce the cascading effect of planktivorous fish on algae. Consequently, use of a fixed carrying capacity in simple predatorprey models may lead to loss of important information on the dynamics of aquatic food webs, preventing an adequate understanding of cascading trophic interactions from being achieved.
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