Rank-based estimation for all-pass time series models

An autoregressive-moving average model in which all roots of the autoregressive polynomial are reciprocals of roots of the moving average polynomial and vice versa is called an all-pass time series model. All-pass models are useful for identifying and modeling noncausal and noninvertible autoregressive-moving average processes. We establish asymptotic normality and consistency for rank-based estimators of all-pass model parameters. The estimators are obtained by minimizing the rank-based residual dispersion function given by Jaeckel [Ann. Math. Statist. 43 (1972) 1449--1458]. These estimators can have the same asymptotic efficiency as maximum likelihood estimators and are robust. The behavior of the estimators for finite samples is studied via simulation and rank estimation is used in the deconvolution of a simulated water gun seismogram.Comment: Published at http://dx.doi.org/10.1214/009053606000001316 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Exploring Communication Patterns in the Discussion of Maternal PKU Syndrome Between Parents and Daughters

Maternal PKU syndrome is the collection of features and birth defects that arise from uncontrolled phenylalanine levels in a pregnant woman with phenylalanine hydroxylase (PAH) deficiency, previously known as phenylketonuria (PKU). Currently, the literature is lacking in exploring what young women are being told about maternal PKU syndrome. In this study, communication patterns between parents and their daughters about maternal PKU syndrome were investigated through an online survey completed by parents. The survey assessed parents’ level of comfort with this topic, the information they discussed with their daughter and the resources they accessed. Followup interviews were conducted with participants to elaborate on survey responses. The majority of participants were very comfortable discussing maternal PKU syndrome (51%); however, 21% reported being very uncomfortable with the discussion. Parents most often discussed health concerns associated with maternal PKU syndrome (94%) and least frequently discussed unplanned pregnancies (58%). The most frequently used resource was a metabolic doctor (73%); however, parents included mothers with PAH deficiency among the most helpful resources. Themes from open-ended responses and interviews emphasized qualities of parents’ discussion with their daughters. Parents commented on the timing and how they presented the information to their daughters. They described challenges such as the emotional impact of the conversation as well as their daughter’s decision-making and consequences of her actions. Lastly, they discussed advice for treatment compliance, resources, and ways to normalize the topic of maternal PKU syndrome. These results can help genetic counselors better understand the parent daughter conversation so that healthcare professionals can better assess and inform families about maternal PKU syndrome

Analysis of Digital Media: Supporting University-Wide Online Learning via Moodle

This report aims to provide an overview of a project which explores teaching and learning within a blended mode of study. Specifically, it looks to analyse the production of digital media and online social networking with a view to enhancing the learning experience. It was the overall aim of the project to contribute to the University’s Learning and Teaching Strategy by developing media content; exploring the production process, analyse digital participation and explore the challenges and opportunities locally within schools. The project has placed emphasis on the production principles which enhance our online courses whilst providing a consistent quality of experience – recognising that our students often access course material produced by staff from across schools and colleges

Analysis of high-speed rotating systems using Timoshenko beam theory in conjunction with the transfer matrix method

Higher operating speeds and increased sensitivity of modern electro-mechanical systems require improved methods for the computation of critical speeds and system response of flexible rotating shafts. Many high-speed systems generally contain disks with masses approaching the mass of the shaft. These observations emphasize the importance of including the effects of rotatory inertia and shear deformation of the shaft in the analysis. Traditional theory, which models a massless shaft, would be inaccurate for these systems. An analysis of flexible rotor systems has been performed using the Transfer Matrix Method. Although the method is well known, the present study utilizes Timoshenko Beam Theory in the construction of field matrices, which relate state vectors at adjacent nodes of the system. This approach takes into consideration the effects of transverse shear and rotatory inertia. Also included in the model are gyroscopic effects of the spinning disks. These effects are generally neglected in classical rotor dynamic theory. A general model was developed for the analysis of typical configurations in which the shaft is simply supported, and can carry an arbitrary number of disks. Numerical simulations were performed for comparision with classical results. These case studies show agreement with what is to be expected by introducing the greater flexibility of Timoshenko Beam Theory and the stiffening effects of gyroscopic couples

Maximum likelihood estimation for α\alpha-stable autoregressive processes

We consider maximum likelihood estimation for both causal and noncausal autoregressive time series processes with non-Gaussian $\alpha$-stable noise. A nondegenerate limiting distribution is given for maximum likelihood estimators of the parameters of the autoregressive model equation and the parameters of the stable noise distribution. The estimators for the autoregressive parameters are $n^{1/\alpha}$-consistent and converge in distribution to the maximizer of a random function. The form of this limiting distribution is intractable, but the shape of the distribution for these estimators can be examined using the bootstrap procedure. The bootstrap is asymptotically valid under general conditions. The estimators for the parameters of the stable noise distribution have the traditional $n^{1/2}$ rate of convergence and are asymptotically normal. The behavior of the estimators for finite samples is studied via simulation, and we use maximum likelihood estimation to fit a noncausal autoregressive model to the natural logarithms of volumes of Wal-Mart stock traded daily on the New York Stock Exchange.Comment: Published in at http://dx.doi.org/10.1214/08-AOS632 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Analysis of Digital Media: Supporting University-Wide Online Learning via Moodle

This report aims to provide an overview of a project which explores teaching and learning within a blended mode of study. Specifically, it looks to analyse the production of digital media and online social networking with a view to enhancing the learning experience. It was the overall aim of the project to contribute to the University’s Learning and Teaching Strategy by developing media content; exploring the production process, analyse digital participation and explore the challenges and opportunities locally within schools. The project has placed emphasis on the production principles which enhance our online courses whilst providing a consistent quality of experience – recognising that our students often access course material produced by staff from across schools and colleges