Showing papers by "Peter Davies published in 2015"

Characterization of sea water ageing effects on mechanical properties of carbon/epoxy composites for tidal turbine blades

Abstract: In recent years, many tidal turbine projects have been developed using composites blades Tidal turbine blades are subject to ocean forces and sea water aggressions, and the reliability of these components is crucial to the profitability of ocean energy recovery systems The majority of tidal turbine developers have preferred carbon/epoxy blades, so there is a need to understand how prolonged immersion in the ocean affects these composites In this study the long term behaviour of different carbon/epoxy composites has been studied using accelerated ageing tests A significant reduction of composite strengths has been observed after saturation of water in the material For longer immersions only small further changes in these properties occur No significant changes have been observed for moduli nor for composite toughness The effect of sea water ageing on damage thresholds and kinetics has been studied and modelled After saturation, the damage threshold is modified while kinetics of damage development remain the same

Does flood rhythm drive ecosystem responses in tropical riverscapes

Abstract: Biotic communities are shaped by adaptations from generations of exposure to selective pressures by recurrent and often infrequent events. In large rivers, floods can act as significant agents of change, causing considerable physical and biotic disturbance while often enhancing productivity and diversity. We show that the relative balance between these seemingly divergent outcomes can be explained by the rhythmicity, or predictability of the timing and magnitude, of flood events. By analyzing biological data for large rivers that span a gradient of rhythmicity in the Neotropics and tropical Australia, we find that systems with rhythmic annual floods have higher fish species richness, more stable avian populations, and elevated rates of riparian forest production compared with those with arrhythmic flood pulses. Intensification of the hydrological cycle driven by climate change, coupled with reductions in runoff due to water extractions for human use and altered discharge from impoundments, is expected to alter the hydrologic rhythmicity of floodplain rivers with significant consequences for both biodiversity and productivity.

Natural Degradation and Biodegradation of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) in Liquid and Solid Marine Environments

Abstract: In this study, natural degradation and biodegradation of poly(3-hydroxybuyrate-co-3-hydroxyvalerate) (PHBV) films were followed in different marine environments. First of all, ageing of PHBV films was investigated in natural seawater for 180 days and degradation was followed by means of weight loss measurements, scanning electron microscopy (SEM), differential scanning calorimetry and steric exclusion chromatography. In a second part, biodegradation tests were performed on PHBV powder, by following carbon dioxide (CO2) release, to highlight the PHBV bioassimilation of marine microorganisms. Three different marine environments were considered for biodegradation tests: a solid inoculum with foreshore sand, a solid–liquid inoculum with sand and seawater and a liquid inoculum with seawater. In the latter, a biofilm was added to study the influence of microorganisms on biodegradation kinetics. The films aged under natural conditions show a large loss of weight after 180 days in immersion, around 36 %, confirmed by SEM pictures which show an increase of the surface erosion and a decrease of the sample thickness. Microorganisms’ attack occurred as suggested by CO2 release during biodegradation tests, whatever the environment studied.

Towards a Framework for Financial Literacy in the Context of Democracy.

Abstract: This paper contrasts the prevailing individualistic approach of financial literacy measurement and financial education with an educational framework that seeks to equip young people to play an active democratic role and to develop a broader understanding of the financial world. In particular, the framework suggests how important dimensions of financial literacy may be addressed in terms of the individual, the financial industry and government.

Microstructure and tensile properties of carbon–epoxy laminates produced by automated fibre placement: Influence of a caul plate on the effects of gap and overlap embedded defects

Abstract: Automated fibre placement (AFP) enables the trajectory of unidirectional composite tape to be optimized, but laying down complex shapes with this technology can result in the introduction of defects. The aim of this experimental study is to investigate the influence of gaps and overlaps on the microstructure and tensile properties of carbon–epoxy laminates. First, a comparison between a hand-layup and AFP layup, draped and cured under the same conditions, shows equivalent microstructures and tensile properties. This provides the reference values for the study. Then, gap and overlap embedded defects (more or less severe) are introduced during manufacturing, on two cross-ply layups [(0°/(90°)5/0°] and [(90°/0°)2/90°]. Autoclave cure without a caul plate results in local thickness variation and microstructural changes which depend on the defect type. This has a strong influence on mechanical performance. Use of a caul plate avoids these variations and in this case embedded defects hardly affect tensile properties.

Linking stream ecology with morphological variability in a native freshwater fish from semi-arid Australia

Abstract: Environmental variation is a potent force affecting phenotypic expression. While freshwater fishes have provided a compelling example of the link between the environment and phenotypic diversity, few studies have been conducted with arid-zone fishes, particularly those that occur in geographically isolated regions where species typically inhabit intermittent and ephemeral creeks. We investigated morphological variation of a freshwater fish (the western rainbowfish, Melanotaenia australis) inhabiting creeks in the Pilbara region of northwest Australia to determine whether body shape variation correlated with local environmental characteristics, including water velocity, habitat complexity, predator presence, and food availability. We expected that the geographic isolation of creeks within this arid region would result in habitat-specific morphological specializations. We used landmark-based geometric morphometrics to quantify the level of morphological variability in fish captured from 14 locations within three distinct subcatchments of a major river system. Western rainbowfish exhibited a range of morphologies, with variation in body depth accounting for a significant proportion (>42%) of the total variance in shape. Sexual dimorphism was also apparent, with males displaying deeper bodies than females. While the measured local habitat characteristics explained little of the observed morphological variation, fish displayed significant morphological differentiation at the level of the subcatchment. Local adaptation may partly explain the geographic patterns of body shape variation, but fine-scale genetic studies are required to disentangle the effects of genetic differentiation from environmentally determined phenotypic plasticity in body shape. Developing a better understanding of environment–phenotype relationships in species from arid regions will provide important insights into ecological and evolutionary processes in these unique and understudied habitats.

Evaluation of Long Term Behaviour of Polymers for Offshore Oil and Gas Applications

Abstract: Polymers and composites are very attractive for underwater applications, but it is essential to evaluate their long term behaviour in sea water if structural integrity of offshore structures is to be guaranteed. Accelerated test procedures are frequently required, and this paper will present three examples showing how the durability of polymers, in the form of fibres, matrix resins in fibre reinforced composites for structural elements, and thermal insulation coatings of flow-lines, have been evaluated for offshore use. The influence of the ageing medium, temperature, and hydrostatic pressure will be discussed first, then an example of the application of ageing test results to predict long term behavior of the thermal insulation coating of a flowline will be presented.

Environmental change: prospects for conservation and agriculture in a southwest Australia biodiversity hotspot

Abstract: Accelerating environmental change is perhaps the greatest challenge for natural resource management; successful strategies need to be effective for decades to come Our objective is to identify opportunities that new environmental conditions may provide for conservation, restoration, and resource use in a globally recognized biodiversity hotspot in southwestern Australia We describe a variety of changes to key taxonomic groups and system-scale characteristics as a consequence of environmental change (climate and land use), and outline strategies for conserving and restoring important ecological and agricultural characteristics Opportunities for conservation and economic adaptation are substantial because of gradients in rainfall, temperature, and land use, extensive areas of remnant native vegetation, the ability to reduce and ameliorate areas affected by secondary salinization, and the existence of large national parks and an extensive network of nature reserves Opportunities presented by the predicted environmental changes encompass agricultural as well as natural ecosystems These may include expansion of aquaculture, transformation of agricultural systems to adapt to drier autumns and winters, and potential increases in spring and summer rain, carbon-offset plantings, and improving the network of conservation reserves A central management dilemma is whether restoration/preservation efforts should have a commercial or biodiversity focus, and how they could be integrated Although the grand challenge is conserving, protecting, restoring, and managing for a future environment, one that balances economic, social, and environmental values, the ultimate goal is to establish a regional culture that values the unique regional environment and balances the utilization of natural resources against protecting remaining natural ecosystems

Porosity in Ocean Racing Yacht Composites: a Review

Abstract: Ocean racing yachts are mainly manufactured from carbon/epoxy composites similar to those used by the aeronautical industry but, with some exceptions such as masts, these structures are not produced in autoclaves. This leads to the presence of higher porosity levels. This paper will first present the different types of porosity found in traditional racing yacht structures. Difficulties in evaluating defect levels will then be discussed and published work characterizing the influence of defects will be reviewed. Current developments to improve racing yacht composite quality such as thin ply technology, out-of-autoclave processing and automated fibre placement will then be described, and their implications for porosity will be discussed.

Temporal variation in benthic primary production in streams of the Australian wet–dry tropics

Abstract: In the Australian wet–dry tropics, seasonal changes in hydrology can influence abiotic conditions and consequently influence standing stocks of benthic biomass and production. While there is some understanding of these processes at riverscape scales, effects of seasonal hydrology on benthic biomass and production in low-order streams remain largely unquantified. We observed changes in water quality, algal and macroinvertebrate biomass, and stream benthic primary productivity over a 15-month period in three low-order streams with contrasting flow regimes in the wet–dry tropics of northern Australia. Water quantity and quality showed a distinct seasonal signature reflected in seasonal peaks in algal (maximum 1.29 µg cm−2) and macroinvertebrate biomass (maximum 0.24 g m−2), and productivity (maximum 0.41 g C m−2 days−1). In particular, transitional periods between dry and wet seasons were key times of elevated production and algal biomass. Overall, variation in biomass and benthic primary production was greater between seasons than among streams indicating that extrapolation between seasons may not be appropriate.

Range and habitat associations of the native macroalga Caulerpa filiformis in New South Wales, Australia

Abstract: Caulerpa filiformis is a green seaweed found in New South Wales (NSW, Australia), South Africa, Mozambique and Peru. It has been suggested that the abundance of the species has increased in NSW over recent decades. Extensive aerial and diver surveys identified a 500-km northerly extension to the range of C. filiformis in NSW (to 28°21′S) compared with previous records. The alga has a disjunct distribution with small isolated populations around rocky headlands in far northern NSW, but then no apparent populations for 350km southwards. The far northern populations could be the result of recent human-mediated transport (a species introduction), or were simply not detected previously. The increased distribution around the previous northerly limit is likely a natural range expansion. The distribution of C. filiformis in NSW and globally seems confined to a temperature range of ~16–23°C. We found no relationship between abundance of C. filiformis and human population or oceanic chlorophyll-a (a surrogate for nutrient availability). We demonstrate that C. filiformis is predominately subtidal, being found along sections of coastline where there is a mixture of rocky reefs and beaches. It is argued that sand movement may have facilitated increases in abundance of C. filiformis.

Analysis of the moisture effect on the mechanical behaviour of an adhesively bonded joint under proportional multi-axial loads

Abstract: The objective of the study is to identify the 3D behaviour of an adhesive in an assembly, and to take into account the effect of ageing in a marine environment To that end, three different tests were employed Gravimetric analyses were used to determine the water diffusion kinetics in the adhesive Bulk tensile tests were performed to highlight the effects of humid ageing on the adhesive behaviour Modified Arcan tests were performed for several ageing times to obtain the experimental database which was necessary to identify constitutive models A Mahnken–Schlimmer type model was determined for the unaged state according to a procedure developed in a previous study This identification used inverse techniques It was based on the unaged modified Arcan results and on a coupling between an optimisation routine and finite-element analysis Then, a global inverse identification procedure was developed Its aim was to relate the unaged parameters to the moisture concentration and overcome the difficulties usu

Defining and assessing enterprise capability in schools

Abstract: This paper describes the development of an instrument for assessing enterprise capability in schools. The approach to assessing enterprise capability builds on previous work by including three dimensions: self-efficacy, aspirations and knowledge and awareness. We find significant but weak associations between these three constructs suggesting that that, whilst they can be considered as providing a coherent description of enterprise capability they can also be regarded as distinct dimensions. The instrument also distinguishes between aspiration towards not-for-profit and for-profit enterprise and also between self-efficacy towards two broad enterprise capabilities: (i) project planning and (ii) working with people and information and two specific, market related capabilities: (iii) market risk and (iv) price and profit. We found only modest associations between students’ sense of enterpriser self-efficacy and their enterprise knowledge and awareness.

Assessing Student Understanding of Price and Opportunity Cost through a Hybrid Test Instrument: An Exploratory Study

Abstract: Students' 'understanding' of opportunity cost and price has been widely regarded as central to economic education (e.g. Sevon & Weckstrom, 1989; Leiser & Halachmi, 2006; Salemi, 2005; Davies & Lundholm, 2012). However, as Davies (2011) points out, evidence from assessments of conceptions of price and opportunity cost leaves a great deal of uncertainty about what it means for a student to 'understand' price or opportunity cost.--This implies a problem for university lecturers evaluating test items on the economic concepts, and for high school teachers using similar test items to gauge students' progress and readiness to proceed to the next level. This is also a problem for researchers trying to judge the effectiveness of different forms of intervention in teaching. In this paper, we aim to shed more light on the nature of these problems faced by economic educators and researchers, and in doing so, pilot a new approach to the design and analysis of assessment of economic 'understanding.' Our method is to examine students' answers to multiple choice questions, which are commonly used on tests to assess economic 'understanding,' alongside their accounts of why they considered a particular option to be correct. We gather evidence of students' conception of price and opportunity cost as expressed in these constructed responses. We also analyze students' multiple choice answers and the quality of their constructed responses as determinants of their overall achievement in the course.1 . Our exploratory methodology reveals variation in students' 'understanding' of opportunity cost and price, which is missed by conventional approaches. 'UNDERSTANDING' PRICE AND OPPORTUNITY COST: CURRENT EVIDENCE While Bloom's taxonomy suggests a distinction between 'understanding' and 'applying' a concept (Bloom, 1956), the research on students' 'understanding' of price does not (e.g. Thompson & Siegler, 2000; Meyer & Shanahan, 2002; Pang & Marton, 2003, 2005; Leiser & Halachmi, 2006). Regardless of whether this research has been undertaken in the social psychology, phenomenographic or another tradition, it has defined 'understanding' as necessarily including 'application' and based on experiences that are familiar to students. Using in-depth interviews with students, researchers have suggested four different conceptions of price which are evident in the way students talk or write about their experiences (Pang & Marton, 2005): 1. Price as a reflection of a good's intrinsic quality 2. Price as a reflection of cost of supply 3. Price as a reflection of consumers' willingness to demand 4. Price as a reflection of demand and supply However, it would be premature to regard this fourfold categorization of conceptions of price as anything more than provisional. For example, Pang & Marton (2005) suggest a fifth category--price as a reflection of relative magnitudes of changes in supply and demand. Further, Davies (2011) proposes that this category be subdivided according to the context used to frame the conception (individual producer, market, or interactions between markets) and whether causation runs only from supply or demand to price or if causation from price to supply and demand is also recognized. There has been less research on students' 'understanding' of opportunity cost. The available evidence is largely based on students' answers to multiple choice questions. Ferraro and Taylor (2005) devised a multiple choice question using the example of buying a concert ticket. By placing the question in the context of an experience which is likely to be familiar, they address the way in which the concept of opportunity cost is 'understood' in everyday experiences. However, this stance is compromised by the actual question which is, 'what is the opportunity cost?' That is, the question turns out to be asking for accuracy in a technical definition rather than seeking to expose the way that respondents understand opportunity cost in their everyday experiences. …

The Role of Accelerated Testing in Reliability Prediction

Abstract: The transition from the early stages of marine renewable energy (MRE) device development towards precommercial status involves rigorous design validation before fullscale testing. The main aim of Technology Readiness Levels (TRLs) 4-6 is to prove that the concept can deliver the required power production performance and also that a level of system reliability is achieved to ensure sufficient availability. Both of these metrics are crucial to obtaining a competitive levelised cost of energy (LCOE). The current state of the MRE sector means that reliability data are sparse or commercially sensitive. Device developers are therefore forced to base reliability predictions on physical testing, detailed numerical analysis or in the absence of these, generic (and potentially unsuitable) failure rate databases. Generic data will only provide a crude estimate of component or subsystem reliability unless modified to suit the application. More accurate estimates of component and subsystem reliability are possible through accelerated testing. As part of the DTOcean (Optimal Design Tools for Ocean Energy Arrays) project, results from physical tests involving synthetic ropes and shackles are used to demonstrate how quantitative accelerated testing can be used to bridge the gap between generic failure rates and those which are applicable to MRE mooring applications.