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- Wiklund, Ann-Kristin Eriksson, et al.
(författare)
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Effects of warming and shifts of pelagic food web structure on benthic productivity in a coastal marine system
- 2009
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 396, s. 13-25
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Tidskriftsartikel (refereegranskat)abstract
- It has been predicted that climate change will lead to increased temperature and precipitation in northern latitudes, which in turn may lead to brownification of coastal sea areas. This will increase the importance of the heterotrophic microbial food web in areas like the northern Baltic Sea. Such a structural change in the pelagic food web would hamper benthic productivity, since microheterotrophs have lower settling rates than phytoplankton. We tested how variation in temperature and alteration of the pelagic food web structure affected the productivity of a key benthic species, the amphipod Monopoeria affinis, and the pelagic-benthic food web efficiency (FWE). Using water from the northern Baltic Sea, a mesocosm experiment was performed in which the temperature was altered by 5 degrees C. The structure of the pelagic food web changed from one based on algae to one based on bacteria. Amphipod productivity was 3 times higher and FWE was 25 times higher in the algae than in the bacteria-based food web, showing that an altered pelagic food web will have severe effects on benthic productivity. Temperature variation, on the other hand, did not cause any changes in either growth of M. affinis or FWE. Our data indicate that indirect effects of climate change, leading to structural changes in the pelagic food web, will have much more severe effects on benthic productivity than the direct effect of increased temperature.
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| 3. |
- Andersson, Kristin, 1976, et al.
(författare)
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Generation of restart states for manufacturing systems with discarded workpieces
- 2009
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Ingår i: 2009 IEEE Conference on Automation Science and Engineering, CASE 2009, Bangalore, India. - 9781424445783 ; , s. 191-196
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Konferensbidrag (refereegranskat)abstract
- In earlier work we presented a method for restart of manufacturing systems. After correction of an error, the system resumes normal production by returning to a certain restart state in the control function, and from there reexecutes parts of the work schedule. In the present paper the method is extended to handle also systems where some, but not necessarily all, workpieces are discarded during the error correction preceding the restart. The restart process must then replace the discarded workpieces with new ones. The workpieces that remain in the cell may limit the possibilities of executing certain operations needed to process the new workpieces correctly, thus complicating the restart. Properties of the restart states that guarantee a correct restart are defined, typical situations that make the system impossible to restart are presented, and some suggestions are given for modifications that make the system restartable.
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| 5. |
- Andersson, Kristin, 1976
(författare)
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Hierarchical Control and Restart of Flexible Manufacturing Systems
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Product life-cycles are constantly shortening, and the amount of new product types increases, for example in the automotive industry. Growing demands on flexibility and ability to decrease time to market has made it increasingly important to find methods for fast and accurate development of control programs for flexible manufacturing cells. There are several means to achieve this goal. Information present in early steps of the development process, as well as already developed software, should be reused when possible. In addition, formal methods should be used to automatically generate the control functions. To enable information reuse and usage of formal methods, a suitable structure has to be defined for the control program. Also, the methods have to be adapted to industrial work procedures.This thesis presents a methodology for generation of control functions for flexible manufacturing cells. The control program is structured hierarchically and partitioned into two parts. The first part corresponds to hardware and basic cell functions that are essentially the same for different manufacturing cells, and the second part is the actual control function, i.e. the part of the control program that is specific to each cell. By structuring the control information similarly in a hierarchical way, models of the system can be produced and supervisor synthesis can be used to generate the high-level control function. Because of the hierarchical approach, the problem of state space explosion is alleviated. A method for presenting the control function in a simple and easy-to-read way has also been developed. This facilitates the use of the control function by the maintenance personnel handling the manufacturing cell.Furthermore, this thesis contains an approach to solve the restart problem in flexible manufacturing systems. When an error has been detected and solved, it is often a difficult and time-consuming task to resynchronize the controller and the cell, and restart production. Most often the entire restart must be handled manually. The method presented in this thesis analyzes the control function off-line, and synthesizes certain restart states in it, from which a restart is guaranteed to be safe. In contrast to earlier methods, the issues of not increasing the complexity of the cell more than necessary, as well as how to physically move the machines in the cell to the restart states in a safe way, are addressed.
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| 9. |
- Andersson, Kristin, 1976, et al.
(författare)
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Restarting Flexible Manufacturing Systems; Synthesis of Restart States
- 2006
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Ingår i: 2006 8th International Workshop on Discrete Event Systems. - 1424400538 ; , s. 201-206
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Konferensbidrag (refereegranskat)abstract
- A method for restart of flexible manufacturing systems is presented. Based on the execution restrictions on the operations in the control function, a number of restart states are synthesized off-line. We show that a restart from the closest preceding restart state never violates the execution restrictions. The presented method usually produces fewer restart states than an intuitive approach, and the number of paths used solely in the restart is considerably reduced, so less paths have to be updated and maintained. Instead, normal production paths are used in the restart when possible. The on-line part of the restart method can be executed by any PLC, and does not require the use of more powerful computers. The method is able to handle situations in which an error or manual intervention has lead to a machine configuration that is not consistent with any of the states in the control function
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| 10. |
- Andersson, Kristin, et al.
(författare)
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Seroreactivity to Cutaneous Human Papillomaviruses among Patients with Nonmelanoma Skin Cancer or Benign Skin Lesions.
- 2008
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Ingår i: Cancer Epidemiology Biomarkers & Prevention. - 1538-7755. ; 17:1, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- Cutaneous human papillomaviruses (HPV) are common in nonmelanoma skin cancers, benign skin lesions, and healthy skin. Increased seroprevalences for cutaneous HPV among nonmelanoma skin cancer patients have been described. To determine whether antibodies to cutaneous HPV are related to presence of the virus and/or to skin disease, we collected serum and biopsies from both lesions and healthy skin from 434 nonimmunosuppressed patients (72 squamous cell carcinomas, 160 basal cell carcinomas, 81 actinic keratoses, and 121 benign lesions). Biopsies were analyzed for HPV DNA by PCR, cloning, and sequencing. Serum antibodies to the major capsid protein L1 of HPV 1, 5, 6, 8, 9, 10, 15, 16, 20, 24, 32, 36, 38, and 57 as well as to the oncoproteins E6 and E7 of HPV 8 and 38 were detected using a multiplexed fluorescent bead-based assay. Type-specific seroprevalence among patients with the same type of HPV DNA (sensitivity of serology) varied from 0% to at most 28%. Presence of HPV DNA and antibodies to the same HPV type was not significantly correlated. However, seropositivity to any HPV type was significantly more common among patients positive for HPV DNA of any HPV type (odds ratio, 1.90; 95% confidence interval, 1.55-2.34). Seroprevalences were similar among the different patient groups but was, for most HPV types, somewhat higher among squamous cell carcinoma patients than among basal cell carcinoma patients (P < 0.01). In conclusion, additional studies are required to clarify the biological meaning of seropositivity as a marker of cutaneous HPV infection and skin disease. (Cancer Epidemiol Biomarkers Prev 2008;17(1):189-95).
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