Contracting bubbles in Hele-Shaw cells with a power-law fluid

The problem of bubble contraction in a Hele-Shaw cell is studied for the case in which the surrounding fluid is of power-law type. A small perturbation of the radially symmetric problem is first considered, focussing on the behaviour just before the bubble vanishes, it being found that for shear-thinning fluids the radially symmetric solution is stable, while for shear-thickening fluids the aspect ratio of the bubble boundary increases. The borderline (Newtonian) case considered previously is neutrally stable, the bubble boundary becoming elliptic in shape with the eccentricity of the ellipse depending on the initial data. Further light is shed on the bubble contraction problem by considering a long thin Hele-Shaw cell: for early times the leading-order behaviour is one-dimensional in this limit; however, as the bubble contracts its evolution is ultimately determined by the solution of a Wiener-Hopf problem, the transition between the long-thin limit and the extinction limit in which the bubble vanishes being described by what is in effect a similarity solution of the second kind. This same solution describes the generic (slit-like) extinction behaviour for shear-thickening fluids, the interface profiles that generalise the ellipses that characterise the Newtonian case being constructed by the Wiener-Hopf calculation.

Modulation of depth-dependent properties in tissue-engineered cartilage with a semi-permeable membrane and perfusion : a continuum model of matrix metabolism and transport

The functional properties of cartilaginous tissues are determined predominantly by the content, distribution, and organization of proteoglycan and collagen in the extracellular matrix. Extracellular matrix accumulates in tissue-engineered cartilage constructs by metabolism and transport of matrix molecules, processes that are modulated by physical and chemical factors. Constructs incubated under free-swelling conditions with freely permeable or highly permeable membranes exhibit symmetric surface regions of soft tissue. The variation in tissue properties with depth from the surfaces suggests the hypothesis that the transport processes mediated by the boundary conditions govern the distribution of proteoglycan in such constructs. A continuum model (DiMicco and Sah in Transport Porus Med 50:57-73, 2003) was extended to test the effects of membrane permeability and perfusion on proteoglycan accumulation in tissue-engineered cartilage. The concentrations of soluble, bound, and degraded proteoglycan were analyzed as functions of time, space, and non-dimensional parameters for several experimental configurations. The results of the model suggest that the boundary condition at the membrane surface and the rate of perfusion, described by non-dimensional parameters, are important determinants of the pattern of proteoglycan accumulation. With perfusion, the proteoglycan profile is skewed, and decreases or increases in magnitude depending on the level of flow-based stimulation. Utilization of a semi-permeable membrane with or without unidirectional flow may lead to tissues with depth-increasing proteoglycan content, resembling native articular cartilage.

Learning the Kernel Matrix with Semi-Definite Programming

Kernel-based learning algorithms work by embedding the data into a Euclidean space, and then searching for linear relations among the embedded data points. The embedding is performed implicitly, by specifying the inner products between each pair of points in the embedding space. This information is contained in the so-called kernel matrix, a symmetric and positive definite matrix that encodes the relative positions of all points. Specifying this matrix amounts to specifying the geometry of the embedding space and inducing a notion of similarity in the input space -- classical model selection problems in machine learning. In this paper we show how the kernel matrix can be learned from data via semi-definite programming (SDP) techniques. When applied to a kernel matrix associated with both training and test data this gives a powerful transductive algorithm -- using the labelled part of the data one can learn an embedding also for the unlabelled part. The similarity between test points is inferred from training points and their labels. Importantly, these learning problems are convex, so we obtain a method for learning both the model class and the function without local minima. Furthermore, this approach leads directly to a convex method to learn the 2-norm soft margin parameter in support vector machines, solving another important open problem. Finally, the novel approach presented in the paper is supported by positive empirical results.

Reinvigorating the domestic violence sector : systemically addressing conflict, power and practitioner turnover

The purpose of this exploratory Australian study was to consider methods of retaining skilled and experienced staff within the domestic violence sector. The antecedents that might influence turnover of practitioners were investigated and analysed. Antecedents broadly included the work-related factors, organisational factors and professional factors. The changing nature of the domestic violence sector was also examined, in particular, feminist identity and feminist practice frameworks. It became evident, however, that the primary reasons for the turnover of study participants can be described as parallel power processes. The concept of parallel power processes as developed through this research aims to capture how workplace behaviours can strongly mirror, or parallel, behaviours used by domestic violence perpetrators. As such, it appears that some domestic violence practitioners are experiencing their own abusive relationship, not within the confines of their home, but within their workplace. Additionally, parallel power processes are compounded by ineffective conflict management processes within the workplace. These concepts directly contribute to practitioners leaving their workplace and, sometimes, the sector. This qualitative study utilised a feminist research epistemology and focused strongly on practitioners' stories. Interviews were undertaken with fifteen domestic violence practitioners from three services within South-East Queensland, Australia. Two sets of semi-structured interviews provided in-depth information based on practitioners‘ experiences of working within this specialised sector. Analysis was conducted using a thematic analytical frame, drawing attention to the key themes as mentioned above. From these findings, it is suggested that in order to retain practitioners, domestic violence services must identify and address parallel power processes through effective conflict management processes. In an operational sense, it is recommended that education and training be undertaken within all staffing levels, in particular management committees. Lastly, it is recommended that the sector itself places greater attention on the re-invigoration of the feminist principles and philosophy that has traditionally guided the sector.

The impacts of power outages on the residents of contemporary multistorey apartment buildings in subtropical environments

With significant population growth experienced in South East Queensland over the past two decades and a high rate of growth expected to continue in coming decades, the Queensland Government is promoting urban consolidation planning policies to manage growth sustainably. Multi-residential buildings will play an important role in facilitating the increased densities which urban consolidation policies imply. However, a major flood event in January 2011 has brought to light the vulnerability of certain types of multi-residential typologies to power outages. The crisis conditions exposed how contemporary building design and construction practices, coupled with regulatory and planning issues, appear to have compromised the resilience and habitability of multi-storey residential buildings. In the greater urban area of Brisbane, Queensland, the debilitating dependence that certain types of apartment buildings have on mains electricity was highlighted by residents’ experiences of the Brisbane River flood disaster, before, during and after the event. This research examined high density residential buildings in West End, Brisbane, an inner city suburb which was severely affected by the flood and is earmarked for significant urban densification under the Brisbane City Plan. Medium-to-high-density residential buildings in the suburb were mapped in flooded and non-flooded locations and a database containing information about the buildings was created. Parameters included date of construction, number of storeys, systems of access and circulation, and potential for access to natural light and ventilation for habitable areas. A series of semi-structured interviews were conducted with residents involved in the owners’ management committees of several buildings to verify information the mapping could not provide. The interviews identified a number of critical systems failures due to power outage which had a significant impact on residents’ wellbeing, comfort and safety. Building services such as lifts, running water, fire alarms, security systems and air-conditioning ceased to operate when power was disconnected to neighbourhoods and buildings in anticipation of rising flood waters. Lack of access to buildings and dwellings, lack of safety, lack of building security, and lack of thermal comfort affected many residents whether or not their buildings were actually subjected to inundation, with some buildings rendered uninhabitable for a prolonged period. The extent of the impact on residents was dramatically influenced by the scale and type of building inhabited, with those dwelling in buildings under a 25m height limit, with a single lift, found to be most affected. The energy-dependency and strong trend of increasing power demands of high-rise buildings is well-documented. Extended electricity outages such as the one brought about by the 2011 flood in Queensland are likely to happen more frequently than the 50-year average of the flood event itself. Electricity blackouts can result from a number of man-made or natural causes, including shortages caused by demand exceeding supply. This paper highlights the vulnerability of energy-dependent buildings to power outages and investigates options for energy security for occupants of multi-storey buildings and makes recommendations to increase resilience and general liveability in multi-residential buildings in the subtropics through design modifications.

Voltage unbalance improvement in low voltage residential feeders with rooftop PVs using custom power devices

Voltage unbalance is a major power quality problem in low voltage residential feeders due to the random location and rating of single-phase rooftop photovoltaic cells (PV). In this paper, two different improvement methods based on the application of series (DVR) and parallel (DSTATCOM) custom power devices are investigated to improve the voltage unbalance problem in these feeders. First, based on the load flow analysis carried out in MATLAB, the effectiveness of these two custom power devices is studied vis-à-vis the voltage unbalance reduction in urban and semi-urban/rural feeders containing rooftop PVs. Their effectiveness is studied from the installation location and rating points of view. Later, a Monte Carlo based stochastic analysis is carried out to investigate their efficacy for different uncertainties of load and PV rating and location in the network. After the numerical analyses, a converter topology and control algorithm is proposed for the DSTATCOM and DVR for balancing the network voltage at their point of common coupling. A state feedback control, based on pole-shift technique, is developed to regulate the voltage in the output of the DSTATCOM and DVR converters such that the voltage balancing is achieved in the network. The dynamic feasibility of voltage unbalance and profile improvement in LV feeders, by the proposed structure and control algorithm for the DSTATCOM and DVR, is verified through detailed PSCAD/EMTDC simulations.

The Fukushima nuclear power plant disaster and percetions of health risk communication : a case study

This case study was conducted to explore the perceptions of health risk messages sent by the Japanese Government following the Fukushima nuclear power plant disaster. The content of health risk messages from the Japanese Government and the Japanese national broadcaster (NHK) were analysed and semi-structured interviews were conducted with a sample of Tokyo residents. Initially, participants trusted these messages but as the crisis unfolded they became sceptical about the messages. Participants felt the messages did not communicate health risk information effectively because the messages were; not supported by evidence, inconsistent, delayed and changed over time. Despite widespread access to the internet, social media and mobile telephones, most participants relied on television news for information about the health risks. The Japanese Government urgently needs to re-build trust by engaging the community in the planning and development phases of health risk communication strategies.

Assessing capacity in the context of testamentary, enduring power of attorney, and advance care directive documents in Australia

Balancing the competing interests of autonomy and protection of individuals is an escalating challenge confronting an ageing Australian population. Legal and medical professionals are increasingly being asked to determine whether individuals are legally capable to make their own testamentary, financial and/or personal/health care decisions. Diseases such as dementia impact upon cognition which necessitates collaboration between the legal and medical professions to satisfactorily assess the effect of such mentally disabling conditions upon legal competency. Terminological and methodological differences exist between the two professions when assessing capacity in this context which subsequently create miscommunication and misunderstanding. Consequently, it is not necessarily a simple solution for a legal professional to seek the opinion of a medical practitioner. Exacerbating the situation is the fact that no consistent and transparent capacity assessment paradigm currently exists in Australia. Assessments are instead being undertaken on an ad hoc basis dependent upon the skill set of the legal and/or medical professionals involved. A qualitative study seeking the views of legal and medical professionals who practise in this area has been conducted. This incorporated a review of the relevant literature and surveys which informed the semi-structured interviews conducted with 10 legal and 20 medical practitioners. Practitioners were asked whether there is a standard approach to assessment and whether national guidelines would assist. The general consensus was that uniform guidelines would be advantageous. The research also canvassed practitioner views as to the state of the relationship between the professions when assessing capacity. Three promising practices have emerged from this research: first, is the need for the development of national guidelines and supporting principles to satisfactorily assess capacity; second, is the possibility of strengthening the relationship between legal and medical professionals to assist in the satisfactory assessment of legal capacity; and third, the need for increased community education.