Influence and modelling of urban runoff on the peak flows in rivers.
Surface waters and urban drainage systems are usually studied separately. However there are important interactions between both systems. Urban drainage systems can have an important impact on the surface waters, mainly at combined sewer overflows. On the other hand during periods of high water levels in a river, the runoff from the urban drainage system can be significantly influenced by backwater, which increases the probability of flooding in is not obvious, because the modelling tools for both systems are often hard to combine properly. To properly assess the probability of flooding for this kind of integrated water systems, different submodels are needed for both subsystems. In practice often one single model is used to describe the runoff to rivers despite the presence of urban catchments. The main objective of this study is to show the limits of this simplified approach. Furthermore, it is necessary to use continuous long term simulations, because of the differences in runoff behaviour. Detailed hydrodynamic models do not really fit for this purpose because of long simulation times and high demands in memory and disk space. Therefore simplified conceptual models are more useful.
Anthropogenic Influences of Paved Runoff and Sanitary Sewage on the Dissolved Organic Matter Quality of Wet Weather Overflows: An Excitation-Emission Matrix Parallel Factor Analysis Assessment.
The quality of dissolved organic matter (DOM) in a wet weather overflow (WWF) can be broadly influenced by anthropogenic factors, such as nonpoint sources of paved runoff and point sources of sanitary sewage within the drainage networks. This study focused on the anthropogenic influences of the paved runoff and sanitary sewage on the DOM quality of WWF using excitation-emission matrix parallel factor analysis (EEM-PARAFAC). Results show that (1) EEM-PARAFAC fitted terrestrial humic-like, anthropogenic humic-like, tryptophan-like, and tyrosine-like components can be regarded as indicators to identify the types of sewage overflows and the illicit connection status of drainage systems. (2) A short emission wavelength (em: 302-313 nm) peak of the tyrosine-like component occurred in the reserved sanitary sewage, while a type of longer emission wavelength (em: 321-325 nm) peak came from the sump deposit. These tyrosine-like components were gradually evacuated in the initial phase of the overflow process with the fading of their EEM signals. Fluorescence signal transformations of all the components confirmed the potential ability of EEM-PARAFAC to monitor the dynamic changes of the primary pollutant sources. (3) The input of the newly increased sanitary sewage had a dominant influence on the quality and yield of the WWF DOM.
Recent developments in actuators: GTO and related devices
Abstract In addition to the established silicon devices for power switching and motor control, the bipolar transistors and the thyristors, new devices such as power field-effect transistors, gate-turn-off thyristors (GTO) and integrated power devices have been developed in recent years. Power MOS field-effect transistors allow very fast switching with low control power, because they have no stored charge. Their on-state resistance, however, is very high in high voltages devices. Bipolar transistors with high volatge capability have low current gain at high current densities, mainly because of recombination of the stored charge in the emitter layers. GTO thyristors do not suffer from these effects, so they can be designed for very high voltages. Though they need high turn-off current gate pulses, GTO circuits are simpler and, in many applications, more economical than thyristor circuits, because the commutation circuit can be omitted. A short comparative description of these devices is given, and the GTO is described in greater detail. As an important example for power device integration, developments of optothyristors (or optotriacs) are shown which will result in simplified solid-state relay technologies.