Reliable and Energy Efficient Network Protocols for Wireless Body Area Networks

In a wireless Body Area Network (WBAN) various sensors are attached on clothing, on the body or are even implanted under the skin. The wireless nature of the network and the wide variety of sensors offers numerous new, practical and innovative applications. A motivating example can be found in the world of health monitoring. The sensors of the WBAN measure for example the heartbeat, the body temperature or record a prolonged electrocardiogram. Using a WBAN, the patient experiences a greater physical mobility and is no longer compelled to stay in a hospital. A WBAN imposes the networks some strict and specific requirements. The devices are tiny, leaving only limited space for a battery. It is therefore of uttermost importance to restrict the energy consumption in the network. A possible solution is the development of energy efficient protocols that regulate the communication between the radios. Further, it is also important to consider the reliability of the communication. The data sent contains medical information and one has to make sure that it is correctly received at the personal device. It is not allowed that a critical message gets lost. In addition, a WBAN has to support the heterogeneity of its devices. This thesis focuses on the development of energy efficient and reliable network protocols for WBANs. Considered solutions are the use of multi-hop communication and the improved interaction between the different network layers. Mechanisms to reduce the energy consumption and to grade up the reliability of the communication are presented. In a first step, the physical layer of the communication near the human body is studied and investigated. The probability of a connection between two nodes on the body is modeled and used to investigate which network topologies can be considered as the most energy efficient and reliable. Next, MOFBAN, a lightweight framework for network architecture is presented. Finally, CICADA is presented: a new cross layer protocol for WBANs that both handles channel medium access and routing

Queueing systems with periodic service

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Three-dimensional modeling of diesel engine intake flow, combustion and emissions-2

A three-dimensional computer code, KIVA, is being modified to include state-of-the-art submodels for diesel engine flow and combustion. Improved and/or new submodels which have already been implemented and previously reported are: wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo'vich NO(x), and spray/wall impingement with rebounding and sliding drops. Progress on the implementation of improved spray drop drag and drop breakup models, the formulation and testing of a multistep kinetics ignition model, and preliminary soot modeling results are described. In addition, the use of a block structured version of KIVA to model the intake flow process is described. A grid generation scheme was developed for modeling realistic (complex) engine geometries, and computations were made of intake flow in the ports and combustion chamber of a two-intake-value engine. The research also involves the use of the code to assess the effects of subprocesses on diesel engine performance. The accuracy of the predictions is being tested by comparisons with engine experiments. To date, comparisons were made with measured engine cylinder pressure, temperature and heat flux data, and the model results are in good agreement with the experiments. Work is in progress that will allow validation of in-cylinder flow and soot formation predictions. An engine test facility is described that is being used to provide the needed validation data. Test results were obtained showing the effect of injection rate and split injections on engine performance and emissions

Autonomous dynamic decision making in fuel cycle simulators using a game theoretic approach

A novel methodology for optimizing nuclear fuel cycle transitions that captures interactions between a policy maker and electric utility company is presented. The methodology is demonstrated using a two-person general-sum sequential game with uncertainty that is implemented using a nuclear fuel cycle simulator capable of calculating a material- and technology-constrained material balance, coupled to a multi-objective optimization solver. The solver explicitly treats uncertainties using a stochastic programming approach with chance nodes depicted as a Nature player who moves randomly. The methodology is demonstrated through a Transition Game that features tradeoffs between investments in competing reprocessing and waste disposal technologies, dynamic reactor deployment responses to resolutions in reactor capital cost uncertainty, and the influence of capital subsidies on the future nuclear technology mix. Each player in the game uses a unique set of decision criteria to identify optimal near-term hedging strategies that consider all of Nature’s possible moves as well as the other player’s available decisions. These hedging strategies balance the exchange between the risk of immediate action and delay and maintain flexibility to allow for intelligent recourse decisions once uncertainties are resolved. Results from the Transition Game indicate that early transition to high-temperature gas-cooled reactors is preferred, with the option to abandon the transition following a learning period if capital costs are unfavorable. Under these conditions, transition to used fuel recycling in sodium-cooled fast reactors may be spurred by policy incentives under some certain decision criteria weightings. Otherwise, operating with a baseline set of decision criteria weightings, transition to a closed fuel is never observed when players hedge optimally against Nature’s moves. It is only when players have perfect information regarding Nature’s future moves will transition to a closed fuel be observed.Mechanical Engineerin