| 1. |
- Di Cairano, S., et al.
(författare)
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Discrete and hybrid stochastic state estimation algorithms for networked control systems
- 2008
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Ingår i: Hybrid Systems. - Berlin, Heidelberg : Springer-Verlag New York. - 9783540789284 ; , s. 144-157
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Bokkapitel (refereegranskat)abstract
- Networked control systems enable for flexible systems operation and reduce cost of installation and maintenance, potentially at the price of increasing the uncertainty due to information exchange over the network. We focus on the problem of information loss in terms of packet drops, which are modelled as stochastic events that depend on the current state of the network. To design reliable control systems the state of the network must be estimated online, together with the state of the controlled process. This paper proposes various approaches to discrete and hybrid stochastic estimation of network and process states, where the network is modelled as a Markov chain and the packet drop probability depends on the states of the Markov chain. The proposed techniques are evaluated on simulations and experimental data.
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| 2. |
- O'Gorman, Eoin J., et al.
(författare)
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Impacts of Warming on the Structure and Functioning of Aquatic Communities : Individual-to Ecosystem-Level Responses
- 2012
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Ingår i: Advances in Ecological Research, Vol 47. - : Elsevier. - 9780123983152 ; , s. 81-176
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Bokkapitel (refereegranskat)abstract
- Environmental warming is predicted to rise dramatically over the next century, yet few studies have investigated its effects in natural, multi-species systems. We present data collated over an 8-year period from a catchment of geothermally heated streams in Iceland, which acts as a natural experiment on the effects of warming across different organisational levels and spatiotemporal scales. Body sizes and population biomasses of individual species responded strongly to temperature, with some providing evidence to support temperature size rules. Macroinvertebrate and meiofaunal community composition also changed dramatically across the thermal gradient. Interactions within the warm streams in particular were characterised by food chains linking algae to snails to the apex predator, brown trout These chains were missing from the colder systems, where snails were replaced by much smaller herbivores and invertebrate omnivores were the top predators. Trout were also subsidised by terrestrial invertebrate prey, which could have an effect analogous to apparent competition within the aquatic prey assemblage. Top-down effects by snails on diatoms were stronger in the warmer streams, which could account for a shallowing of mass-abundance slopes across the community. This may indicate reduced energy transfer efficiency from resources to consumers in the warmer systems and/or a change in predator-prey mass ratios. All the ecosystem process rates investigated increased with temperature, but with differing thermal sensitivities, with important implications for overall ecosystem functioning (e.g. creating potential imbalances in elemental fluxes). Ecosystem respiration rose rapidly with temperature, leading to increased heterotrophy. There were also indications that food web stability may be lower in the warmer streams.
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