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The aim of this paper is to investigate the evolution of SO2 and NOx emissions of ten very large combustion plants (LCPs >500 MW) located in the European Union (EU) during 2005–2015. The evolution of NOx and SO2 emissions were analyzed against the EU Directives in force during 2005–2015. The investigation was performed using space-borne observations and estimated emissions collected from the EEA (European Environment Agency) inventory of air pollutant emissions. The power plants were chosen according to their capacity and emissions, located in various parts of Europe, to give an overall picture of atmospheric pollution with NOx and SO2 associated with the activity of very large LCPs in Europe. Satellite observations from OMI (Ozone Monitoring Instrument) are compared with calculated emissions in order to assess whether satellite observations can be used to monitor air quality, as a standard procedure, by governmental or nongovernmental institutions. Our results show that both space observations and estimated emissions of NOx and SO2 atmospheric content have a descending trend until 2010, complying with the EU Directives. The financial and economic crisis during 2007–2009 played an important role in reducing emissions.

Complex workflows arising from practical applications usually combine time, resource, and task priority constraints. The goal of this paper is to formulate a suitable WF net model with all these three types of constraints, and to investigate the soundness property of the resulting model. Thus, the concept of a multilevel resource constrained workflow net (mlRCWF net) as being a place composition of resource constrained workflow (RCWF) nets is introduced, and its soundness property is investigated. This model is then enriched with time and task priority constraints. It is shown that the soundness property of timed priority mlRCWF nets can be reduced in linear time to the soundness property of (untimed) priority RCWF nets. A resource relocation policy is a policy by which resources already allocated to some task are then relocated to urgent tasks, the current task being thus delayed. When the current tasks support an indefinite delay, the soundness of timed priority mlRCWF nets with resource relocation can be reduced in quadratic time to the soundness property of (untimed) priority RCWF nets.