SUMMARYThe problem of integrated design of controller and communication sequences is addressed for networked control systems with simultaneous consideration of medium access limitations and network-induced delays, packet dropouts and measurement quantization. By exploiting a Lyapunov-Krasovskii functional and by making use of novel techniques for switching delay systems, it is shown that linear time invariant systems can be stabilized with delay-dependent state feedback controllers and communication sequences satisfying appropriate delay-dependent conditions in terms of linear matrix inequalities. Illustrative examples are provided to show the usefulness and advantage of the developed results.

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Emitter clogging, a phenomenon commonly seen in reclaimed wastewater drip irrigation systems, is a severe obstacle to the wide applications and popularization of the irrigation technology. Some experiments showed that the emitter clogging was tightly related to biofilms formation attached to the irrigation system. In this paper, two types of wastewaters reclaimed respectively by fluidizedbed reactor (FBR) process and biological aerated filter (BAF) process were chosen as the experiment objects and then the effects of the average velocity on the growth and topography of biofilms attached to the irrigation laterals were studied. The parameters of biofilms reached their maximal values at a critical velocity of 0.45 m/s. The formation of biofilms was primarily controlled by the transport of the nutrients and suspended particles within the laterals when the average velocity is below the critical velocity, whereas it was primarily controlled by the hydraulic shear force when above the critical velocity. The main mechanism for emitter clogging was that the biofilms detached from laterals accumulated and grew at the inlets and outlets of emitters. A similar variation pattern was observed for both reclaimed wastewaters. However, the growth of biofilms for BAF process was more affected by the shear force than that for FBR process, since the nutrients and suspended particles for BAF were larger than those for FBR.

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