A stateless opportunistic routing protocol for underwater sensor networks

Routing packets in Underwater Sensor Networks (UWSNs) face different challenges, the most notable of which is perhaps how to deal with void communication areas. While this issue is not addressed in some underwater routing protocols, there exist some partially state-full protocols which can guarantee the delivery of packets using excessive communication overhead. However, there is no fully stateless underwater routing protocol, to the best of our knowledge, which can detect and bypass trapped nodes. A trapped node is a node which only leads packets to arrive finally at a void node. In this paper, we propose a Stateless Opportunistic Routing Protocol (SORP), in which the void and trapped nodes are locally detected in the different area of network topology to be excluded during the routing phase using a passive participation approach. SORP also uses a novel scheme to employ an adaptive forwarding area which can be resized and replaced according to the local density and placement of the candidate forwarding nodes to enhance the energy efficiency and reliability. We also make a theoretical analysis on the routing performance in case of considering the shadow zone and variable propagation delays. The results of our extensive simulation study indicate that SORP outperforms other protocols regarding the routing performance metrics

Development of an Ultra-High Efficiency Gas Turbine Engine (UHEGT) with Stator Internal Combustion: Design, Off-Design, and Nonlinear Dynamic Operation

An Ultra-High Efficiency Gas Turbine (UHEGT) technology is developed in this study. In UHEGT, the combustion process is no longer contained in isolation between the compressor and turbine, rather distributed in multiple stages and integrated within the High-Pressure (HP)-turbine stator rows. Fundamental issues of aero-thermodynamic design, combustion, and heat transfer are addressed in this study. The aero-thermodynamic study shows that the UHEGT-concept improves the thermal efficiency of gas turbines by 5-7% above the current most advanced gas turbine engines, such as Alstom GT24. The designed thermodynamic cycle has a 45% thermal efficiency and includes a six-stage turbine with three stages of stator internal combustion. Meanline approach is used to preliminary design the entire flow path in the turbine. Multiple configurations are designed and simulated via Computational Fluid Dynamics (CFD) to achieve the optimum combustion system for UHEGT. Flow patterns, temperature distributions, secondary losses, etc. are among the parameters studied in the results. The final configuration for the combustion system includes two rows of injectors placed before the stator rows in the first three turbine stages. The current injector configuration provides a highly uniform temperature distribution at the rotor inlet, low pressure loss, and low emissions compared to the other cases. Different approaches are numerically studied to lower the stator blade surface temperature distribution in UHEGT from which indexing (clocking) is shown to be very effective. In the final part of this study, a dynamic simulation is performed on the entire engine using the nonlinear generic code GETRAN developed by Schobeiri. The simulations are in 2D (space-time) and include the complete gas turbine engine. The system performance is studied under variable design and off-design conditions. The results show that most of the system parameters fluctuate with similar patterns to the fuel schedule. However, the amplitudes of the fluctuations are different and there is a time lag in the response profiles relative to the fuel schedules. It is shown that thermal efficiency variations are smaller compared to the other parameters which means the system performs in efficiencies close to the design point throughout the entire cycle