Showing papers by "Peter Davies published in 2005"
01 Jan 2005
TL;DR: In this paper, it has been pointed out that certain students "get stuck" at particular points in the curriculum whilst others grasp concepts with comparative ease, and what might teachers do in relation to the design and teaching of their courses that might help students overcome such barriers to their learning.
Abstract: It has long been a matter of concern to teachers in higher education why certain students ‘get stuck’ at particular points in the curriculum whilst others grasp concepts with comparative ease. What might account for this variation in student performance and, more importantly, what might teachers do in relation to the design and teaching of their courses that might help students overcome such barriers to their learning? As students from a much wider range of educational backgrounds now enter higher education these issues are becoming of increasing importance across all disciplines. A further and related concern is why certain concepts within disciplinary fields appear particularly ‘troublesome’ to students. What makes particular areas of knowledge more troublesome than others, and how might we make such areas less so?
217 citations
TL;DR: Five general principles about food webs and related ecosystem processes that both characterise tropical rivers of northern Australia and have important implications for their management are derived and provide a framework for the formation of testable hypotheses in future research programmes.
Abstract: The tropical rivers of northern Australia have received international and national recognition for their high ecological and cultural values. Unlike many tropical systems elsewhere in the world and their temperate Australian counterparts, they have largely unmodified flow regimes and are comparatively free from the impacts associated with intensive land use. However, there is growing demand for agricultural development and existing pressures, such as invasive plants and feral animals, threaten their ecological integrity. Using the international literature to provide a conceptual framework and drawing on limited published and unpublished data on rivers in northern Australia, we have derived five general principles about food webs and related ecosystem processes that both characterise tropical rivers of northern Australia and have important implications for their management. These are: (1) the seasonal hydrology is a strong driver of ecosystem processes and food-web structure; (2) hydrological connectivity is largely intact and underpins important terrestrial–aquatic food-web subsidies; (3) river and wetland food webs are strongly dependent on algal production; (4) a few common macroconsumer species have a strong influence on benthic food webs; and (5) omnivory is widespread and food chains are short. The implications of these ecosystem attributes for the management and protection of tropical rivers and wetlands of northern Australian are discussed in relation to known threats. These principles provide a framework for the formation of testable hypotheses in future research programmes.
197 citations
TL;DR: Fish appear to feed on potentially lower value resources such as detritus and calanoid copepods during the dry season, when waterholes are isolated and food resources were limited, then capitalize on the "boom" of aquatic production and more diverse food resources associated with episodic flood events.
Abstract: The fish assemblages of an arid zone floodplain river, Cooper Creek, Queensland, Australia, were sampled during two dry periods in isolated waterholes and on the inundated floodplain during the early and late phase of a major flood event Diets were described for nine native species and compared within and between dry and flood periods In the dry season, when fishes were restricted to waterholes, diets were characteristically simple with narrow diet breadths Movement onto the floodplain during flooding clearly increased feeding opportunities, with greater diet breadths evident in all species Despite obvious potential for terrestrial inputs, diets tended to be dominated by aquatic resources in both the waterholes and on the floodplain Stomach fullness, however, varied little between dry season waterhole and floodplain samples Fish appear to feed on potentially lower value resources such as detritus and calanoid copepods during the dry season, when waterholes are isolated and food resources were limited They were then able to capitalize on the "boom" of aquatic production and more diverse food resources associated with episodic flood events
148 citations
TL;DR: In this article, the authors present experimental results obtained from quasi-static and impact indentation tests on thick ±55° filament wound glass/epoxy tubes intended for underwater applications.
Abstract: This paper presents experimental results obtained from quasi-static and impact indentation tests on thick ±55° filament wound glass/epoxy tubes intended for underwater applications. Drop weight impact tests have been performed on 55 mm internal diameter 6 mm thick tubes at energies up to 45 J. Ultrasonic inspection was employed first to determine projected damage areas. A large number of samples were then sectioned and polished and the true damage area was revealed by a dye penetrant technique. This has enabled detailed descriptions of damage development to be made. The true damage area is roughly 10 times the projected area. The influence of impact damage on implosion pressure is described. Above a critical impact energy level a significant drop in implosion resistance is noted, which is related to the appearance of intralaminar cracks.
119 citations
TL;DR: In this paper, an experimental methodology was defined enabling the adhesives of interest to be characterised up to failure, and a metal-metal assembly was considered, in order to concentrate on the analysis of the behavior of thin adhesive films.
105 citations
TL;DR: In this paper, the influence of fiber volume fraction on the mode II interlaminar fracture toughness, G(IIc), using the 4ENF (four point end notched flexure) specimen was investigated.
78 citations
TL;DR: In this paper, the macroscopic analysis proposed by Schapery has been applied to model the non-linear viscoelastic and viscoplastic behaviour of polyester fibres.
Abstract: In this study the macroscopic analysis proposed by Schapery has been applied to model the non-linear viscoelastic and viscoplastic behaviour of polyester fibres. First, a special non-contact extensometry method has been developed in order to measure the fibre response without affecting the behaviour of these extremely anisotropic fibres. An accelerated identification method has then been developed. This enables a unique and independent set of parameters to be determined, which separate the reversible and non-reversible mechanisms responsible for measured strains. The model prediction for an arbitrary loading sequence corresponds closely to the measured strains. The model has been applied here at the yarn level but can equally well be used to predict rope behaviour, either by including the identified parameters in a rope structure analysis or by identifying parameters at the rope level.
48 citations
TL;DR: In this article, the authors present the results from a study in two parts, the first part involves the identification and modeling of damage initiation and development in glass-reinforced epoxy composite cylinders subjected to drop weight impact.
Abstract: This paper presents the results from a study in two parts. The first part involves the identification and modeling of damage initiation and development in glass-reinforced epoxy composite cylinders subjected to drop weight impact. The second is concerned with the evaluation of the influence of this damage on the residual strength under hydrostatic pressure loading. Original results showing the influence of damage on implosion pressure are presented. The improved understanding of these phenomena and the development of predictive tools is part of an ongoing effort to improve the long-term integrity of composite structures for underwater applications.
47 citations
TL;DR: In this article, a study of thermoplastic matrix composites has been performed to investigate their use in underwater applications such as oceanography, submarine, and sub-sea offshore structures.
Abstract: A study of thermoplastic matrix composites has been performed to investigate their use in underwater applications such as oceanography, submarine, and sub-sea offshore structures. This article first presents six candidate materials. Results from simple mechanical and seawater aging screening tests on flat specimens are then described. Glass/epoxy and carbon/epoxy composites are used as reference materials. Two materials emerged from this process, glass/PEI and carbon/PEEK. Cylinders of both were manufactured and subjected to hydrostatic pressure tests, and results are compared to those for glass/epoxy and carbon/epoxy cylinders of similar geometry. The carbon/PEEK material appeared most promising. It resisted pressures in excess of 90 MPa and was retained for damage tolerance assessment studies. Drop weight impact damage zones were smaller in carbon/PEEK than carbon/epoxy for the same impact energies but the loss in residual collapse strength was more rapid in the thermoplastic composite. This was attributed to a change in failure mode, impact damage initiated a local buckling failure.
36 citations
TL;DR: These estuarine processes result in less nitrogen and phosphorus being delivered to the GBR lagoon than is exported from the catchment, which highlights the need for further work to explore modifications in estuaries that drain into the Great Barrier Reef lagoon.
31 citations
TL;DR: In this article, the authors developed a perspective on the role of "boldness" in explaining gender differences in thinking and attitudes and applied this analysis to evidence from Australia, the USA and the UK in relation to economics at school and university levels.
Abstract: In the first half of this paper we develop a perspective on the role of 'boldness' in explaining gender differences in thinking and attitudes. We apply this analysis to evidence from Australia, the USA and the UK in relation to economics at school and university levels. In the second half we present the results of a study of over 1000 15-17-year-olds in UK secondary schools. On the basis of the gender differences revealed in these data and our preceding analysis we offer some implications for learning and teaching.
TL;DR: There is a need for a wider debate about how healthcare systems address individual concerns about genetic concerns and risk, especially given the increasing commercial marketing of genetic tests.
Abstract: To enable primary care medical practitioners to generate a range of possible service delivery models for genetic counselling services and critically assess their suitability.
TL;DR: The authors argue that it is uncertainty about processes internal to the school that are the problem and that an appropriate managerial response to this problem can draw upon business ideas which are not oppositional to professional expertise and values, while questioning professional self-interest.
Abstract: Government policy in England has encouraged schools to adopt a rational planning model on the basis that this will contribute to school effectiveness. This policy has been criticized for neglecting the consequences for the planning process of volatility in schools’ external environment and for replacing well-developed professional knowledge and commitment with inappropriate models from ‘for-profit’ business. We agree that the rational planning model is not an appropriate basis for school management but dispute these diagnoses of the nature of the problem. We suggest that it is uncertainty about processes internal to the school that are the problem and that an appropriate managerial response to this problem can draw upon business ideas which are not oppositional to professional expertise and values, while questioning professional self-interest.
TL;DR: The authors suggest that the target setting process imposed by the government has shifted teachers' focus away from their personal educational priorities, and examine possible explanations for variations in teachers' practice and suggest some implications for policy and school leadership and management.
Abstract: Using the perspective of principal–agent theory, we suggest that the target setting process imposed by the government has shifted teachers’ focus away from their personal educational priorities. Our evidence suggests that schools with a higher proportion of students with high academic achievement differ in their practice of target setting from schools with a below average proportion of students achieving high examination grades. We examine possible explanations for variations in teachers’ practice and suggest some implications for policy and school leadership and management.
01 Jan 2005
TL;DR: In this paper, the authors present results from a project which aims to generate foam core properties under loading rates representative of those encountered during wave impact of racing yachts, where a symmetrical shear test was designed to allow shear stress-strain behaviour to be determined at rates corresponding to those measured at sea.
Abstract: This paper presents first results from a project which aims to generate foam core properties under loading rates representative of those encountered during wave impact of racing yachts. First, special instrumentation enabled shear strain rates to be measured in-situ. Then a symmetrical shear test was designed to allow shear stress-strain behaviour to be determined at rates corresponding to those measured at sea. Image analysis was used to validate the test set-up. First results for high density foams indicate that quasi-static data may suffice for design.
TL;DR: In this paper, a study of the influence of surface preparation on the mechanical performance of overlaminated polyester composites has been conducted, showing that surfaces protected with peel plies show very low GIc propagation energy release rates.
Abstract: This paper presents results from a study of the influence of surface preparation on the mechanical performance of overlaminated polyester composites. Panels of 16 woven glass plies have been prepared in two halves by hand lay-up. After the first 8 plies were laminated the surface was either protected by a peel ply or left in air. The overlamination of the second half of the composite thickness was completed after different periods and interlaminar shear, flexure and mode I fracture specimens were tested. The results enabled the influence of the delay and the surface condition to be related to mechanical performance. Surfaces protected with peel plies show very low GIc propagation energy release rates. Results are compared to those from continuous lamination of the 16 ply composite. Interlaminar fracture tests are shown to be much more sensitive to overlamination conditions than the traditional short beam shear test. Results are interpreted in terms of fracture surface features.
29 Aug 2005
TL;DR: In this article, the stiffness, strength and fracture properties of K-Cor-reinforced sandwich beams are evaluated with a series of three flexure tests applied to each sample.
Abstract: Sandwich beams reinforced with K-Cor™ are characterized in terms of stiffness, strength and fracture by means of static tests, and compared to traditional sandwich materials. Stiffness is evaluated with a series of three flexure tests applied to each sample. Strength tests show different failure mechanisms for the two architectures. Mode I fracture properties are measured and a significant increase in the core toughness of reinforced samples is revealed.
20 Jun 2005
TL;DR: In this paper, a model is developed to predict long term response of synthetic ropes under constant and cyclic loads, where elastic, visco-elastic and, where necessary viscoplastic components of strain are identified.
Abstract: There are many marine applications of synthetic ropes, from small handling lines for oceanography to very large mooring lines for offshore platforms. The fibres used in these ropes are visco-elastic and this behaviour affects their long term performance under constant and cyclic loads. In order to predict long term response a model has been developed which accounts for time-dependent behaviour. This model requires parameters to be identified which characterise elastic, visco-elastic and, where necessary visco-plastic components of strain. A procedure has been defined which allows these parameters to be determined rapidly, either at yarn or rope scale. A specific loading sequence of creep and recovery tests involving strain measurement by accurate non-contact image analysis is presented, which provides the necessary input data to allow strain at a given time to be predicted for any loading history. Examples are discussed for aramid and polyester materials.
23 Aug 2005
TL;DR: In this article, an advanced measurement technique, such as fiber optic Bragg gratings, is used to study the influence of the mesostructure of filament wound cylinders on their mechanical behavior.
Abstract: In order to analyse the influence of the mesostructure of filament wound cylinders on their mechanical behaviour it is essential both to control the fabrication process and to use advanced measurement techniques, such as fiber optic Bragg gratings, to study their behaviour. In this research project advances in unit cell precision positioning are presented. This paper includes a description of the composite pipe, monitoring during fabrication, a pipe reinforcement architecture analysis system and a study of the influence of architecture on mechanical properties. MOTS-CLES : enroulement filamentaire, fibres optiques a reseaux de Bragg, suivi de cuisson
01 Jan 2005
TL;DR: In this article, an analysis of the influence of the mesostructure of filament wound cylinders on their mechanical behavior is presented, which is essential both to control the fabrication process and to use advanced measurement techniques, such as fiber optic Bragg gratings, to study their behaviour.
Abstract: In order to analyse the influence of the mesostructure of filament wound cylinders on their mechanical behaviour it is essential both to control the fabrication process and to use advanced measurement techniques, such as fiber optic Bragg gratings, to study their behaviour. In this research project advances in unit cell precision positioning are presented. This paper includes a description of the composite pipe, monitoring during fabrication, a pipe reinforcement architecture analysis system and a study of the influence of architecture on mechanical properties.
20 Jun 2005
TL;DR: In this paper, the static and cyclic properties of single fibres have been measured and yarn and rope yarn specimens have been tested to evaluate the properties of improved polyester fibres for marine rope applications.
Abstract: This paper describes tests performed to evaluate the properties of improved polyester fibres for marine rope applications. First the static and cyclic properties of single fibres have been measured. Then yarn and rope yarn specimens have been tested. Finally, sub-rope samples of 36 ton break load have been characterized. The data collected are now being used to validate rope performance analyses.