We investigate a unique wireless sensor network scheduling problem in which all nodes in a cluster send exactly one packet to a designated sink node in an effort to minimize transmission time. However, node transmissions must be sufficiently isolated either in time or in space to avoid collisions. The problem is formulated and solved via graph representation. We prove that an optimal transmission schedule can be obtained efficiently through a pipeline-like schedule when the underlying topology is either line or tree. The minimum time required for a line or tree topology with n nodes is 3ðn À 2Þ. We further prove that our scheduling problem is NP-hard for general graphs. We propose a heuristic algorithm for general graphs. Our heuristic tries to schedule as many independent segments as possible to increase the degree of parallel transmissions. This algorithm is compared to an RTS/CTS based distributed algorithm. Preliminary simulated results indicate that our heuristic algorithm outperforms the RTS/CTS based distributed algorithm (up to 30%) and exhibits stable behavior.

Mathematical models and circuitry necessary for optimal energy conversion have been developed for piezoelectric devices because of their ability to convert mechanical energy to electrical energy. The piezoelectric device that is the focus of this study is a curved, thin unimorph prestressed bender. This device consists of layers of piezoelectric material, polyimide, and metal bonded at high temperatures. Effects of its layer composition and geometry on energy harvesting and actuation are investigated. Through this investigation, a method for developing empirical relationships is established and it is demonstrated that an actuator can be engineered so that the same energy output could be obtained with different materials by adjusting relevant parameters.

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In this paper we describe our experience with implementing a multidisciplinary systems design and engineering course by participation in a national student design competition, while simultaneously satisfying the capstonedesign requirement within the engineering curriculum. A team of faculty from the departments of mechanical, electrical and industrial engineering acted as consultants to a team of twelve electrical and mechanical engineering senior students whose joint task is to design, construct and test a solar-powered boat. The boat will be entered into the 1997 Solar Splash regatta, to be held in June 1997 in Milwaukee, Wisconsin.

The integration of ground wireless adhoc networks and airborne UAVs is a promising solution for realtime data collection in wireless sensor networks. Such networks play a vital role in many mission critical tasks such as forest firefighting and battlefield support. An important problem is to establish/maintain efficient routing structures in the ground sensor network for packet relaying. Our problem is unique in that the base stations are non-static, which necessitates frequent update of the routing structure. The performance of flooding based methods are evaluated. Particularly, in order to deal with non-uniform node density, we propose to introduce an artificial delay factor to control the flooding pattern. We mathematically prove that the delay should be proportional to local node density. Our simulation results show that the proposed method achieves good load balance among multiple base stations.