MOBILESAT: Australia's own

Australia will be introducing a dedicated Mobile Satellite Communications System following the launch of the AUSSAT-B satellites late in 1991. The Mobile Satellite System, MOBILESAT, will provide circuit switched voice/data services and packet-switched data services for land, aeronautical and maritime users. Here, an overview is given of the development program being undertaken within Australia to enable a fully commercial service to be introduced in 1992

An exploration of online social support groups for breastfeeding mothers

This thesis provides a portfolio of research that focuses on online social support groups for breastfeeding mothers. The aim of this thesis is to explore how and why online breastfeeding support group are being used, how breastfeeding mothers make sense of and interpret their experiences, and how they perceive the impact on their breastfeeding journey. Acquiring new breastfeeding skills at the same time as being becoming a mother is stressful and experiencing stress may lead some mothers to seek support. Historically people would interact, communicate, and thus seek and receive support from their healthcare provider face-to-face. More recently, this can occur online due to the increasing availability of the internet, home computers, mobile phones, and tablet technologies that provide quick access to others. It is well documented that breastfeeding rates in the UK are some of the lowest in the world, but with professional and peer support a mother is more likely to continue to breastfeed her baby for longer. For these reasons, online support interventions are explored in four original pieces of research, an area of practice only now emerging in the literature. This thesis first examines the use of computer mediated communication in providing patient support. A literature review suggests that online interventions could be both what patients want, and way of delivering support in resource tight environments. This has implications for a range of health support needs and professionals. Secondly, a content analysis documents and describes the posts made to an online breastfeeding support group in the United Kingdom. Mothers are using online groups in their thousands to seek information from people in similar situations and discuss a range of parenting and breastfeeding topics. Thirdly, through Interpretative Phenomenological Analysis, it is highlighted that the online groups have the potential to provide confidence, reassurance, and to normalise breastfeeding. Online groups provide a sense of community that supports an internal vision of what breastfeeding is like for them. The fourth study presents a case study of one mother’s use of online groups to obtain donor milk for her baby. This final piece of research highlights a tangible support type that was not highlighted in the previous studies, and all four studies highlight the complexities around online support, and infant feeding decisions. Throughout this thesis the term support is critically explored, and the theory of social support and becoming a mother is drawn upon to underpin the research. This thesis offers a definition and model of online breastfeeding support to guide practitioners and further research. Infant feeding policies should include a compulsory social support assessment that incorporates online support, and policies should encourage professionals to have conversations around taboo and stigmatised topics. Those supporting breastfeeding mothers need to be aware of the benefits and risks of online support and be encouraged to promote online support to the mothers with whom they work

Automated Markerless Extraction of Walking People Using Deformable Contour Models

We develop a new automated markerless motion capture system for the analysis of walking people. We employ global evidence gathering techniques guided by biomechanical analysis to robustly extract articulated motion. This forms a basis for new deformable contour models, using local image cues to capture shape and motion at a more detailed level. We extend the greedy snake formulation to include temporal constraints and occlusion modelling, increasing the capability of this technique when dealing with cluttered and self-occluding extraction targets. This approach is evaluated on a large database of indoor and outdoor video data, demonstrating fast and autonomous motion capture for walking people

A note on coefficient of restitution models including the effects of impact induced vibration

In this work multi-modal systems subject to impact are considered. Using energy balance techniques for an arbitrary contact interval the effects of modal vibration can be included. The energy balance is used to obtain a relationship between the coefficient of restitution and the modal energy during the contact period. This allows the effects of impact induced vibration to be considered. The subsequent analytical relationships demonstrate that increasing contact duration and excitation of higher modes can reduce the effective value of the coefficient of restitution. It is also shown how this approach can be related to work on energetically consistent impacts

Adaptive control of nonlinear dynamical systems using a model reference approach

In this paper we consider using a model reference adaptive control approach to control nonlinear systems. We consider the controller design and stability analysis associated with these type of adaptive systems. Then we discuss the use of model reference adaptive control algorithms to control systems which exhibit nonlinear dynamical behaviour using the example of a Duffing oscillator being controlled to follow a linear reference model. For this system we show that if the nonlinearity is “small” then standard linear model reference control can be applied. A second example, which is often found in synchronization applications, is when the nonlinearities in the plant and reference model are identical. Again we show that linear model reference adaptive control is sufficient to control the system. Finally we consider controlling more general nonlinear systems using adaptive feedback linearization to control scalar nonlinear systems. As an example we use the Lorenz and Chua systems with parameter values such that they both have chaotic dynamics. The Lorenz system is used as a reference model and a single coordinate from the Chua system is controlled to follow one of the Lorenz system coordinates

Constraints on the presence of water megamaser emission in z~2.5 ultraluminous infrared starburst galaxies

We present Expanded Very Large Array and Arecibo observations of two lensed submm galaxies at z~2.5, in order to search for redshifted 22.235 GHz water megamaser emission. Both SMM J14011+0252 and SMM J16359+6612 have multi-wavelength characteristics consistent with ongoing starburst activity, as well as CO line emission indicating the presence of warm molecular gas. Our observations do not reveal any evidence for H2O megamaser emission in either target, while the lensing allows us to obtain deep limits to the H_2O line luminosities, L(H2O) < 7470 Lsun (3-sigma) in the case of SMM J14011+0252, and L(H2O) < 1893 Lsun for SMM J16359+6612, assuming linewidths of 80 km/s. Our search for, and subsequent non-detection of H2O megamaser emission in two strongly lensed starburst galaxies, rich in gas and dust, suggests that such megamaser emission is not likely to be common within the unlensed population of high-redshift starburst galaxies. We use the recent detection of strong H2O megamaser emission in the lensed quasar, MG J0414+0534 at z = 2.64 to make predictions for future EVLA C-band surveys of H2O megamaser emission in submm galaxies hosting AGN.Comment: AJ accepte

AUSSAT mobile satellite services

An overview of AUSSAT's planned mobile satellite system is given. The development program which is being undertaken to achieve the 1992 service date is described. Both business and technical aspects of the development program are addressed

Periodic sticking motion in a two-degree of freedom impact oscillator

Periodic sticking motions can occur in vibro-impact systems for certain parameter ranges. When the coefficient of restitution is low (or zero), the range of periodic sticking motions can become large. In this work the dynamics of periodic sticking orbits with both zero and non-zero coefficient of restitution are considered. The dynamics of the periodic orbit is simulated as the forcing frequency of the system is varied. In particular, the loci of Poincaré fixed points in the sticking plane are computed as the forcing frequency of the system is varied. For zero coefficient of restitution, the size of the sticking region for a particular choice of parameters appears to be maximized. We consider this idea by computing the sticking region for zero and non-zero coefficient of restitution values. It has been shown that periodic sticking orbits can bifurcate via the rising/multi-sliding bifurcation. In the final part of this paper, we describe three types of post-bifurcation behavior which occur for the zero coefficient of restitution case. This includes two types of rising bifurcation and a border orbit crossing event

A note on using the collocation method for modelling the dynamics of a flexible continuous beam subject to impacts

The use of non-smooth modelling techniques to model the dynamics of a flexible impacting beam has recently been reported in Ref. [1]. The method used was based on taking a Galerkin approximation [2] of the partial differential equation (PDE) governing the dynamics of the beam away from impact, and coupling this to a non-smooth coefficient of restitution rule to model the impact [3]. In this letter, the advantages and limitations of using a collocation method instead of the Galerkin method combined with a non-smooth impact law are discussed

Understanding the dynamics of multi-degree-of-freedom nonlinear systems using backbone curves

In this paper we will describe how backbone curves can be used to explain complex dynamic phenomena that can occur in coupled multi-degree-of-freedom physical systems. Three examples will be used to demonstrate some key points. We will describe cases when backbone curves can be decoupled. In the case of nonlinear resonance (or modal interaction) we explain how to distinguish how many modes are interacting, their unison and relative phase characteristics. Bifurcation of higher order interaction curves from the lower order curves will also be discussed. Finally we will consider an example based on the transverse vibration of a thin plate with pinned boundary conditions. Both finite element simulations and a low order differential equation model are developed for this system. The results show the importance of the nonlinear coupling terms in replicating the frequency shift phenomena which is known to occur in structures of this type. Despite its much smaller size, the low order model is able to show qualitative agreement with the finite element model. Knowledge of the backbone curve behaviour for this system, is used to explain the forced damped behaviour