Novel Bayesian smoothing algorithms for improved track initiation and maintenance in clutter

University of Technology, Sydney. Faculty of Engineering.Target tracking is a well established field with over fifty years of intense research. While in its core, it deals with estimating targets dynamic states, it is also a critical component of all ” Situation Awareness” and threat assessment systems. These higher layer applications take decisions on important questions like number of targets, positions of them, the instant and position of their initiation, the instant and position of their maneuvers and above all, which of them are threatening and/or friendly. The lower level target tracking algorithms feed the necessary information to these decision taking systems. There are a number of target tracking algorithms to cater for the need of such systems. Most of these available algorithms are based on filtering theory. But it is established that smoothing increases the accuracy of the systems at the expense of a slight lag between the instant of estimation and the instant at which the parameter of interest is being estimated. Hence smoothing is not widely used for practical target tracking applications. However, the situation awareness system is expected to perform better if more precise information is obtained about initiation and termination of the targets along with improved discrimination of true/false targets. This thesis addresses the problem of improved track initiation and maintenance with the smoothing framework to provide better information. It first reviews target tracking and filtering literature. It introduces the concept of random set smoother and derives the IPDA smoother under linear Gaussian assumption. IPDA smoother is also derived by extending the PDA smoother. Finally a theoretical link is established between Random Set smoothing and IPDA smoothing framework. To extend the domain into multiple sensor scenario, the problem of out-of-sequence measurements is also addressed in this thesis under target existence uncertainty. Several realistic scenarios are simulated and the results are verified

Tunneling conduction in graphene/(poly)vinyl alcohol composites

Graphene/(Poly)vinyl alcohol (PVA) composite film with thickness $60 \mu m$ were synthesized by solidification of a PVA solution comprising of dispersed graphene nanosheets. The close proximity of the graphene sheets enables the fluctuation induced tunneling of electrons to occur from one sheet to another. The dielectric data show that the present system can be simulated to a parallel resistance-capacitor network. The high frequency exponent of the frequency variation of the ac conductivity indicates that the charge carriers move in a two-dimensional space. The sample preparation technique will be helpful for synthesizing flexible conductors.Comment: 10 pages, 8 figure

Recursive bayesian approaches for auto calibration in drift aware wireless sensor networks

The purpose for wireless sensor networks is to deploy low cost sensors with sufficient computing and communication capabilities to support networked sensing applications. Even when the sensors are properly calibrated at the time of their deployment, they develop drift in their readings leading to biased sensor measurements. Noting that a physical phenomenon in a certain area follows some spatio-temporal correlation, we assume that the sensors readings in that area are correlated. We also assume that the instantiations of drifts are uncorrelated. Based on these assumptions, and inspired by the resemblance of registration problem in radar target tracking with the bias error problem in wireless sensor networks, we follow a Bayesian framework to solve the Drift/Bias problem in wireless sensor networks. We present two methods for solving the drift problem in a densely deployed sensor network, one for smooth drifts and the other for unsmooth drifts. We also show that both methods successfully detect and correct sensor errors and extend the effective life time of the sensor network

Analysis of conducting-system frequency response data for an interfacial amorphous phase of copper-core oxide-shell nanocomposites

Complex electrical-conductivity experimental data sets for the interfacial amorphous phase in copper-core-copper-oxide-shell nanostructured composites have been analyzed using two Kohlrausch-related frequency response models recently developed for analysis of the dispersive electrical response of conductive materials. Such analysis has been carried out for both the precursor (herein referred to as the reference) glass as well as the glass in which the core-shell nanostructure was developed after suitable heat treatment. Complex nonlinear-least-squares data fitting at each temperature employed composite Kohlrausch models that included electrode effects. Because of the lack of sufficient high-frequency data, it was necessary to use fixed, rather than free, values of the shape parameter β1 of the model. On the basis of topological considerations, its values were set at ⅓ and ⅔ for the reference glass and the core-shell structured glass, respectively. The activation energies of resistivity for the reference and the treated glasses were found to have values of about 2 and 0.4 eV, respectively, indicating two different mechanisms of electrical conduction. A blocking-electrode measurement on the reference glass indicated the presence of an electronic as well as an ionic component of the electrical conductivity, with the ionic part dominating at the temperatures for which the present analyses were carried out

High body mass index in children with sickle cell disease- a retrospective single-centre audit

Objective To assess the prevalence of high body mass index (BMI) in children with sickle cell disease and assess correlation between BMI and disease severity. Design Retrospective chart review followed by statistical analysis. Setting A single tertiary paediatric clinic in inner city London. Patients All patients with sickle cell disease, including homozygous haemoglobin (HbSS) and compound heterozygous Hb (HbSC), age 2–18 years receiving clinical care at the centre, were included in the study. Interventions Height and weight measurements, steady-state laboratory blood tests, hospital admission rates, adjunct therapy such as hydroxycarbamide or blood transfusions and obstructive sleep apnoea (OSA) data were obtained from the hospital electronic patient records. Main outcome measures To study the prevalence of high BMI and to identify any correlation between BMI and disease severity. Results 385 patients were included. 64 children (17%) were overweight or obese, of which a significantly higher number of children with HbSC were obese or overweight (23 out of 91, 25%) compared with those with HbSS (36 out of 273, 13%), p≤0.001. No correlation was found between high BMI and presence of OSA, and markers of disease severity such as admission rates, fetal haemoglobin or lactate dehydrogenase levels. Conclusions High BMI did not correlate with disease severity in this cohort of patients with sickle cell disease. Obesity was more prevalent in females and those with HbSC. Further prospective studies are needed to determine long-term effects of BMI in disease severity and outcome