A survey on gas leakage source detection and boundary tracking with wireless sensor networks

Gas leakage source detection and boundary tracking of continuous objects have received a significant research attention in the academic as well as the industries due to the loss and damage caused by toxic gas leakage in large-scale petrochemical plants. With the advance and rapid adoption of wireless sensor networks (WSNs) in the last decades, source localization and boundary estimation have became the priority of research works. In addition, an accurate boundary estimation is a critical issue due to the fast movement, changing shape, and invisibility of the gas leakage compared with the other single object detections. We present various gas diffusion models used in the literature that offer the effective computational approaches to measure the gas concentrations in the large area. In this paper, we compare the continuous object localization and boundary detection schemes with respect to complexity, energy consumption, and estimation accuracy. Moreover, this paper presents the research directions for existing and future gas leakage source localization and boundary estimation schemes with WSNs

Experimental and computational study of molecular communication in turbulent fluid environments

Molecular communication (MC) is a type of communication and networking in the electromagnetic (EM)-denied environments. MC is concerned with information transfer by preserving information in the structure of chemical flow through molecular diffusion, advection or reaction. Hence, the information transmission in MC is closely associated with the physics of fluid dynamics. The mechanism of MC, i.e., using chemical substances for information exchange, is prevalent in nature among organisms at various length scales, from intra-cell signaling and bacterial communication to airborne and waterborne pheromone signals. At nano-scale the physical conditions are such that the main mechanism of transport is mass diffusion. Therefore fluid turbulence, for which other transport mechanisms are relevant, have hitherto hardly been considered at all in the context of MC. Nevertheless, MC is obviously not restricted to nano-scales, as demonstrated by insect and crustacean pheromone signaling. Here turbulence does become a crucial issue affecting the reliability of the message transfer. The goal of this thesis is to draw on turbulence theory to assess implications of relevance to MC at macro scale. The results show that in turbulent channels, viscous shear stresses hinder a reliable transfer of the molecular information between the transmitter and the receiver which results in severe inter-symbol-interference (ISI). In order to mitigate the ISI in turbulent channels, vortex ring are proposed as coherent structures representing a means for modulating information symbols onto them. Each vortex ring can propagate approximately 100× the diameter of the transmission nozzle without losing its compact shape. It is shown that by maintaining a coherent signal structure, the signal-to-inference (SIR) ratio is higher over conventional puffs. Moreover, the results show that the received signals of the same transmitted symbols vary due to the presence of the underlying noise in turbulent channels. To understand the behaviour of the noise in turbulent channels, both of the additive and jitter noises distributions characterised statistically, and a new channel model is proposed. Thereafter, this channel model is used to quantify the mutual information in turbulent channels. Finally, the waterborne chemical plumes are investigated as a paradigm for a means of molecular communication at macro scales. Results from the Richardson’s energy cascade theory are applied and interpreted in the context of MC to characterise an information cascade and the information dissipation rate. The results show that the information dissipation rate decreases with increasing the Reynolds number and distance d from transmitter. This may appear counter intuitive because stronger turbulence levels at higher Reynolds numbers increases energy dissipation rates. However, increased turbulence leads to more efficient scalar mixing and, therewith, the power of the molecular signal quickly reduces to low levels. Accordingly the information dissipation rate necessarily reduces due to the remaining low information content available

Numerical modelling of mesoscale atmospheric dispersion

Fall 1992.Includes bibliographical references

Institute for Computational Mechanics in Propulsion (ICOMP)

The Institute for Computational Mechanics in Propulsion (ICOMP) is a combined activity of Case Western Reserve University, Ohio Aerospace Institute (OAI) and NASA Lewis. The purpose of ICOMP is to develop techniques to improve problem solving capabilities in all aspects of computational mechanics related to propulsion. The activities at ICOMP during 1991 are described

Turbulence: Numerical Analysis, Modelling and Simulation

The problem of accurate and reliable simulation of turbulent flows is a central and intractable challenge that crosses disciplinary boundaries. As the needs for accuracy increase and the applications expand beyond flows where extensive data is available for calibration, the importance of a sound mathematical foundation that addresses the needs of practical computing increases. This Special Issue is directed at this crossroads of rigorous numerical analysis, the physics of turbulence and the practical needs of turbulent flow simulations. It seeks papers providing a broad understanding of the status of the problem considered and open problems that comprise further steps