Distributions and Sources of Dissolved Iron in the Polar Oceans

De beschikbaarheid van ijzer is van wezenlijk belang voor de groei van algen in de oceanen, en daarmee de gehele voedselketen in de oceaan. In dit onderzoek is gekeken naar de verspreiding en bronnen van ijzer in de Poolzeeen. Opgelost ijzer is gemeten in hoge resolutie in watermonsters verdeeld over de gehele diepte van de Oceaan. In de Arctische Oceaan is gebleken dat water met hoge ijzerconcentraties van de Siberische rivieren wordt vervoerd met de Transpolar Drift tot het midden van de Arctische Oceaan. Verder richting de Canadese kant van de Arctische Oceaan neemt het ijzer weer af, en wordt de concentratie vooral bepaald door smeltend ijs en biologische factoren. In de diepe Arctische Ocean blijken onderzeese vulkanen een belangrijke bron van ijzer. In het Makarov Bassin is een lage concentratie gemeten, dankzij het ontbreken van bronnen en de invloed van organische liganden. In de Zuidelijke Oceaan is een inverse relatie gevonden tussen fluorescentie, indicatief voor algengroei, en opgelost ijzer. De gebruikelijke toename van ijzer richting het continentale plat is afwezig in de Weddell Zee, waarschijnlijk door de ijskap die tot ver in de Oceaan reikt. Lokale ijzebronnen zijn atmosferische depositie aan het oppervlak en onderzeese vulkanen op diepte. Op de nulmeridiaan is de nitraat:fosfaat en nitraat:silicaat opname toe met opgelost ijzer, terwijl er in de Westelijke Wedell Zee geen relatie was. Dit wordt verklaard door de significant grotere algen rond de nulmeridiaan, voor welke er een groter effect van ijzerconcentratie op de nutrienthuishouding en daarmee op de groei is. The availability of iron is very important for algal growth in the ocean, thus for the entire ocean food web. In this research we investigated the distribution and sources of dissolved iron in the Polar Oceans. Iron is measured in high resolution in water samples divided over the entire depth of the ocean. In the Arctic Ocean it appeared that iron from the Siberian rivers is transported with the Transpolar Drift and reaches the middle of the Arctic Ocean. Further towards the Canadian side, iron concentrations decrease the concentration is determined by melting ice and biological factors. In the deep Arctic Ocean, hydrothermal vents are an important source of iron. In the Makarov Basin, a low iron concentration is attributed to the lack of input sources and the influence of organic ligands. In the Southern Ocean an inverse relation between fluorescence, indicative for algal growth, and dissolved iron is found. The common pattern of increasing iron concentrations towards continental shelves is not present in the Weddell Sea, likely as a result of the ice sheet extending far beyond the continent. Local sources of iron are dust deposition at the surface and hydrothermal vents at depth. At the zero meridian the nitrate:phosphate and nitrate:silicate uptake increases with dissolved iron whereas in the Western Weddell Sea there was no relation. This can be explained by the significantly larger algae at the zero meridian, for which there is a much larger effect of iron on the nutrient uptake and thus on the growth.

Modelling and analysing ERTMS hybrid level 3 with the mCRL2 toolset

\u3cp\u3eERTMS Hybrid Level 3 is a recent proposal for a train control system specification that serves to increase the capacity of the railway network by allowing multiple trains with an integrity monitoring system and a GSM-R connection to the trackside on a single section. In this paper we model the principles of ERTMS Hybrid Level 3 in the mCRL2 process algebra and perform an analysis with its associated toolset. Our analysis has resulted in suggestions for improvement of the principles that will be taken into account in the next version of the specification.\u3c/p\u3

Modelling and analysing ERTMS hybrid level 3 with the mCRL2 toolset

ERTMS Hybrid Level 3 is a recent proposal for a train control system specification that serves to increase the capacity of the railway network by allowing multiple trains with an integrity monitoring system and a GSM-R connection to the trackside on a single section. In this paper we model the principles of ERTMS Hybrid Level 3 in the mCRL2 process algebra and perform an analysis with its associated toolset. Our analysis has resulted in suggestions for improvement of the principles that will be taken into account in the next version of the specification

Assessment of architectures for Automatic Train Operation driving functions

Automatic Train Operation (ATO) is well-known in urban railways and gets increasing interest from mainline railways at present to improve capacity and punctuality. A main function of ATO is the train trajectory generation that specifies the speed profile over the given running route considering the timetable and the characteristics of the train and infrastructure. This paper proposes and assesses different possible ATO architecture configurations through allocating the intelligent components on the trackside or onboard. The set of analyzed ATO architecture configurations is based on state-of-the-art architectures proposed in the literature for the related Connected Driver Advisory System (C-DAS). Results of the SWOT analysis highlight that different ATO configurations have diverse advantages or limitations, depending on the type of railway governance and the technological development of the existing railway signaling and communication equipment. In addition, we also use the results to spotlight operational, technological, and business advantages/limitations of the proposed ATO-over-ETCS architecture that is being developed by the European Union Agency for Railways (ERA) and provide a scientific argumentation for it

Assessment of architectures for Automatic Train Operation driving functions

Automatic Train Operation (ATO) is well-known in urban railways and gets increasing interest from mainline railways at present to improve capacity and punctuality. A main function of ATO is the train trajectory generation that specifies the speed profile over the given running route considering the timetable and the characteristics of the train and infrastructure. This paper proposes and assesses different possible ATO architecture configurations through allocating the intelligent components on the trackside or onboard. The set of analyzed ATO architecture configurations is based on state-of-the-art architectures proposed in the literature for the related Connected Driver Advisory System (C-DAS). Results of the SWOT analysis highlight that different ATO configurations have diverse advantages or limitations, depending on the type of railway governance and the technological development of the existing railway signaling and communication equipment. In addition, we also use the results to spotlight operational, technological, and business advantages/limitations of the proposed ATO-over-ETCS architecture that is being developed by the European Union Agency for Railways (ERA) and provide a scientific argumentation for it.Transport and Plannin

The use of formal methods in specification and demonstration of ERTMS Hybrid Level 3

Software has become an essential component in signalling systems. Writing clear, precise and accurate specifications is of course important for these systems.\u3cbr/\u3eCan formal methods help in this process? An interesting case is the recent development of the Hybrid Level 3 for ERTMS/ETCS. This paper addresses the specification and demonstration of ERTMS Hybrid Level 3