Fatigue crack growth and fatigue life evaluation for welded steel bridge members with initial crack

Initial crack widely exists in the welded members of steel bridge induced by the welding procedure or by the fatigue damage crack initiation. The behavior of crack growth with a view to fatigue damage accumulation on the tip of cracks is discussed. Fatigue life of welded components with initial crack in bridges under traffic loading is investigated. Based on existing fatigue experiment results of welded members with initial crack and the fatigue experiment results of welded bridge members under constant stress cycles, the crack would keep semi-elliptical shape with variable ratio of a/c during the crack propagation. Based on the concept of continuum damage accumulated on the tip of fatigue cracks,the fatigue damage law suitable for steel bridge members under traffic loading is modified to consider the crack growth.The virtual crack growth method and the semi-elliptical crack shape assumption are proposed in this paper to deduce a new model of fatigue crack growth rate for welded bridge members under traffic loading. And the calculated method of the stress intensity factor necessary for evaluation of the fatigue life of welded bridge members with cracks is discussed.The proposed fatigue crack growth model is then applied to calculate the crack growth and the fatigue life of existing welded members with fatigue experimental results. The fatigue crack propagation computation results show that the ratio of crack depth to the half crack surface length a/c is variable during crack propagation process and the stress cycle increases with the increase of a0/c0 with certain a0/t0 .The calculated and measured fatigue lives are generally in good agreement,at some initial conditions of cracking, for welded members widely used in steel bridges.

Towards designing digital noticeboards with a remote indigenous community

This position paper reflects upon the opportunities and challenges of designing a digital noticeboard system with a remote indigenous community that supports their aspirations for both internal and external communication. The project itself has evolved from a relationship built through ecological work between scientists and the local community on the Groote Eylandt archipelago to study native populations of animal species over the long term. In the course of this work the aspiration has emerged to explore how digital noticeboards might promote and communicate aspects of work and life on the island through both the web and touchscreen noticeboards. This paper introduces the community, the context and the history of the project. We then reflect upon the science project and its outcomes, in order to draw lessons for extending what we see as a pragmatic and relationship based approach towards design.

Strolling through the (post)modern city: Modes of being a flaneur in picture books

The city and the urban condition, popular subjects of art, literature, and film, have been commonly represented as fragmented, isolating, violent, with silent crowds moving through the hustle and bustle of a noisy, polluted cityspace. Included in this diverse artistic field is children’s literature—an area of creative and critical inquiry that continues to play a central role in illuminating and shaping perceptions of the city, of city lifestyles, and of the people who traverse the urban landscape. Fiction’s textual representations of cities, its sites and sights, lifestyles and characters have drawn on traditions of realist, satirical, and fantastic writing to produce the protean urban story—utopian, dystopian, visionary, satirical—with the goal of offering an account or critique of the contemporary city and the urban condition. In writing about cities and urban life, children’s literature variously locates the child in relation to the social (urban) space. This dialogic relation between subject and social space has been at the heart of writings about/of the flâneur: a figure who experiences modes of being in the city as it transforms under the influences of modernism and postmodernism. Within this context of a changing urban ontology brought about by (post)modern styles and practices, this article examines five contemporary picture books: The Cows Are Going to Paris by David Kirby and Allen Woodman; Ooh-la-la (Max in love) by Maira Kalman; Mr Chicken Goes to Paris and Old Tom’s Holiday by Leigh Hobbs; and The Empty City by David Megarrity. I investigate the possibility of these texts reviving the act of flânerie, but in a way that enables different modes of being a flâneur, a neo-flâneur. I suggest that the neo-flâneur retains some of the characteristics of the original flâneur, but incorporates others that take account of the changes wrought by postmodernity and globalization, particularly tourism and consumption. The dual issue at the heart of the discussion is that tourism and consumption as agents of cultural globalization offer a different way of thinking about the phenomenon of flânerie. While the flâneur can be regarded as the precursor to the tourist, the discussion considers how different modes of flânerie, such as the tourist-flâneur, are an inevitable outcome of commodification of the activities that accompany strolling through the (post)modern urban space.

Concept combination and the origins of complex cognition

At the core of our uniquely human cognitive abilities is the capacity to see things from different perspectives, or to place them in a new context. We propose that this was made possible by two cognitive transitions. First, the large brain of Homo erectus facilitated the onset of recursive recall: the ability to string thoughts together into a stream of potentially abstract or imaginative thought. This hypothesis is sup-ported by a set of computational models where an artificial society of agents evolved to generate more diverse and valuable cultural outputs under conditions of recursive recall. We propose that the capacity to see things in context arose much later, following the appearance of anatomically modern humans. This second transition was brought on by the onset of contextual focus: the capacity to shift between a minimally contextual analytic mode of thought, and a highly contextual associative mode of thought, conducive to combining concepts in new ways and ‘breaking out of a rut’. When contextual focus is implemented in an art-generating computer program, the resulting artworks are seen as more creative and appealing. We summarize how both transitions can be modeled using a theory of concepts which high-lights the manner in which different contexts can lead to modern humans attributing very different meanings to the interpretation of one concept.

"Participation" in participatory design research

This thesis is about defining participation in the context of fostering research cohesion in the field of Participatory Design. The systematic and incremental building of new knowledge is the process by which science and research is advanced. This process requires a certain type of cohesion in the way research is undertaken for new knowledge to be built from the knowledge provided by previous projects and research. To support this process and to foster research cohesion three conditions are necessary. These conditions are: common ground between practitioners, problem-space positioning, and adherence to clear research criteria. The challenge of fostering research cohesion in Participatory Design is apparent in at least four themes raised in the literature: the role of politics within Participatory Design epistemology, the role of participation, design with users, and the ability to translate theory into practice. These four thematic challenges frame the context which the research gap is situated. These themes are also further investigated and the research gap – a general lack of research cohesion – along with one avenue for addressing this gap – a clear and operationalizable definition for participation – are identified. The intended contribution of this thesis is to develop a framework and visual tool to address this research gap. In particular, an initial approximation for a clear and operationalizable definition for participation will be proposed such that it can be used within the field of Participatory Design to run projects and foster research cohesion. In pursuit of this contribution, a critical lens is developed and used to analyse some of the principles and practices of Participatory Design that are regarded as foundational. This lens addresses how to define participation in a way that adheres to basic principles of scientific rigour – namely, ensuring that the elements of a theory are operationalizable, falsifiable, generalizable, and useful, and it also treats participation as a construct rather than treating the notion of participation as a variable. A systematic analysis is performed using this lens on the principles and practices that are considered foundational within the field. From this analysis, three components of the participation construct – impact, influence, and agency – are identified. These components are then broken down into two constituent variables each (six in all) and represented visually. Impact is described as the relationship between the quality and use of information. Influence is described as the relationship between the amount and scope of decision making. Agency is described as the relationship between the motivation of the participant and the solidarity of the group. Thus, as a construct, participation is described as the relationship between a participant’s impact, influence, and agency. In the concluding section, the value of this participation construct is explored for its utility in enhancing project work and fostering research cohesion. Three items of potential value that emerge are: the creation of a visual tool through the representation of these six constituent variables in one image; the elaboration of a common language for researchers based on the six constituent variables identified; and the ability to systematically identify and remedy participation gaps throughout the life of the project. While future research exploring the applicability of the participation construct in real world projects is necessary, it is intended that this initial approximation of a participation construct in the form of the visual tool will serve as the basis for a cohesive and rigorous discussion about participation in Participatory Design.

Second Life machinima enhancing the learning of law : Lessons from successful endeavours

A traditional approach centred on weekly lectures, perhaps supported by a tutorial programme, still predominates in modern legal education in Australia. This approach tends to focus on the transmission of knowledge about legal rules and doctrine to students who adopt a largely passive role. Criticisms of the traditional approach have led to law schools expanding their curricula to include the teaching of skills, including the skill of negotiation and an appreciation of legal ethics and professional responsibility. However, in a climate of limited government funding for law schools in Australia, innovation in legal education remains a challenge. This paper considers the successful use of Second Life machinima in two programs, Air Gondwana and Entry into Valhalla and their part in the creation of engaging, effective learning environments. These programs not only engage students in active learning but also facilitate flexibility in their studies and other benefits. The programs yield important lessons concerning the use of machinima innovations in curricula, not only for academics involved in legal education but also those in other disciplines, especially those that rely on traditional passive lectures in their teaching and learning approaches.

Perceiving and pursuing novelty : a grounded theory of adolescent creativity

Creativity plays an increasingly important role in our personal, social, educational, and community lives. For adolescents, creativity can enable self-expression, be a means of pushing boundaries, and assist learning, achievement, and completion of everyday tasks. Moreover, adolescents who demonstrate creativity can potentially enhance their capacity to face unknown future challenges, address mounting social and ecological issues in our global society, and improve their career opportunities and contribution to the economy. For these reasons, creativity is an essential capacity for young people in their present and future, and is highlighted as a priority in current educational policy nationally and internationally. Despite growing recognition of creativity’s importance and attention to creativity in research, the creative experience from the perspectives of the creators themselves and the creativity of adolescents are neglected fields of study. Hence, this research investigated adolescents’ self-reported experiences of creativity to improve understandings of their creative processes and manifestations, and how these can be supported or inhibited. Although some aspects of creativity have been extensively researched, there were no comprehensive, multidisciplinary theoretical frameworks of adolescent creativity to provide a foundation for this study. Therefore, a grounded theory methodology was adopted for the purpose of constructing a new theory to describe and explain adolescents’ creativity in a range of domains. The study’s constructivist-interpretivist perspective viewed the data and findings as interpretations of adolescents’ creative experiences, co-constructed by the participants and the researcher. The research was conducted in two academically selective high schools in Australia: one arts school, and one science, mathematics, and technology school. Twenty adolescent participants (10 from each school) were selected using theoretical sampling. Data were collected via focus groups, individual interviews, an online discussion forum, and email communications. Grounded theory methods informed a process of concurrent data collection and analysis; each iteration of analysis informed subsequent data collection. Findings portray creativity as it was perceived and experienced by participants, presented in a Grounded Theory of Adolescent Creativity. The Grounded Theory of Adolescent Creativity comprises a core category, Perceiving and Pursuing Novelty: Not the Norm, which linked all findings in the study. This core category explains how creativity involved adolescents perceiving stimuli and experiences differently, approaching tasks or life unconventionally, and pursuing novel ideas to create outcomes that are not the norm when compared with outcomes by peers. Elaboration of the core category is provided by the major categories of findings. That is, adolescent creativity entailed utilising a network of Sub-Processes of Creativity, using strategies for Managing Constraints and Challenges, and drawing on different Approaches to Creativity – adaptation, transfer, synthesis, and genesis – to apply the sub-processes and produce creative outcomes. Potentially, there were Effects of Creativity on Creators and Audiences, depending on the adolescent and the task. Three Types of Creativity were identified as the manifestations of the creative process: creative personal expression, creative boundary pushing, and creative task achievement. Interactions among adolescents’ dispositions and environments were influential in their creativity. Patterns and variations of these interactions revealed a framework of four Contexts for Creativity that offered different levels of support for creativity: high creative disposition–supportive environment; high creative disposition–inhibiting environment; low creative disposition–supportive environment; and low creative disposition–inhibiting environment. These contexts represent dimensional ranges of how dispositions and environments supported or inhibited creativity, and reveal that the optimal context for creativity differed depending on the adolescent, task, domain, and environment. This study makes four main contributions, which have methodological and theoretical implications for researchers, as well as practical implications for adolescents, parents, teachers, policy and curriculum developers, and other interested stakeholders who aim to foster the creativity of adolescents. First, this study contributes methodologically through its constructivist-interpretivist grounded theory methodology combining the grounded theory approaches of Corbin and Strauss (2008) and Charmaz (2006). Innovative data collection was also demonstrated through integration of data from online and face-to-face interactions with adolescents, within the grounded theory design. These methodological contributions have broad applicability to researchers examining complex constructs and processes, and with populations who integrate multimedia as a natural form of communication. Second, applicable to creativity in diverse domains, the Grounded Theory of Adolescent Creativity supports a hybrid view of creativity as both domain-general and domain-specific. A third major contribution was identification of a new form of creativity, educational creativity (ed-c), which categorises creativity for learning or achievement within the constraints of formal educational contexts. These theoretical contributions inform further research about creativity in different domains or multidisciplinary areas, and with populations engaged in formal education. However, the key contribution of this research is that it presents an original Theory and Model of Adolescent Creativity to explain the complex, multifaceted phenomenon of adolescents’ creative experiences.

Efficient safety message dissemination for cooperative collision warning via context modelling

A Cooperative Collision Warning System (CCWS) is an active safety techno- logy for road vehicles that can potentially reduce traffic accidents. It provides a driver with situational awareness and early warnings of any possible colli- sions through an on-board unit. CCWS is still under active research, and one of the important technical problems is safety message dissemination. Safety messages are disseminated in a high-speed mobile environment using wireless communication technology such as Dedicated Short Range Communication (DSRC). The wireless communication in CCWS has a limited bandwidth and can become unreliable when used inefficiently, particularly given the dynamic nature of road traffic conditions. Unreliable communication may significantly reduce the performance of CCWS in preventing collisions. There are two types of safety messages: Routine Safety Messages (RSMs) and Event Safety Messages (ESMs). An RSM contains the up-to-date state of a vehicle, and it must be disseminated repeatedly to its neighbouring vehicles. An ESM is a warning message that must be sent to all the endangered vehi- cles. Existing RSM and ESM dissemination schemes are inefficient, unscalable, and unable to give priority to vehicles in the most danger. Thus, this study investigates more efficient and scalable RSM and ESM dissemination schemes that can make use of the context information generated from a particular traffic scenario. Therefore, this study tackles three technical research prob- lems, vehicular traffic scenario modelling and context information generation, context-aware RSM dissemination, and context-aware ESM dissemination. The most relevant context information in CCWS is the information about possible collisions among vehicles given a current vehicular traffic situation. To generate the context information, this study investigates techniques to model interactions among multiple vehicles based on their up-to-date motion state obtained via RSM. To date, there is no existing model that can represent interactions among multiple vehicles in a speciffic region and at a particular time. The major outcome from the first problem is a new interaction graph model that can be used to easily identify the endangered vehicles and their danger severity. By identifying the endangered vehicles, RSM and ESM dis- semination can be optimised while improving safety at the same time. The new model enables the development of context-aware RSM and ESM dissemination schemes. To disseminate RSM efficiently, this study investigates a context-aware dis- semination scheme that can optimise the RSM dissemination rate to improve safety in various vehicle densities. The major outcome from the second problem is a context-aware RSM dissemination protocol. The context-aware protocol can adaptively adjust the dissemination rate based on an estimated channel load and danger severity of vehicle interactions given by the interaction graph model. Unlike existing RSM dissemination schemes, the proposed adaptive scheme can reduce channel congestion and improve safety by prioritising ve- hicles that are most likely to crash with other vehicles. The proposed RSM protocol has been implemented and evaluated by simulation. The simulation results have shown that the proposed RSM protocol outperforms existing pro- tocols in terms of efficiency, scalability and safety. To disseminate ESM efficiently, this study investigates a context-aware ESM dissemination scheme that can reduce unnecessary transmissions and deliver ESMs to endangered vehicles as fast as possible. The major outcome from the third problem is a context-aware ESM dissemination protocol that uses a multicast routing strategy. Existing ESM protocols use broadcast rout- ing, which is not efficient because ESMs may be sent to a large number of ve- hicles in the area. Using multicast routing improves efficiency because ESMs are sent only to the endangered vehicles. The endangered vehicles can be identified using the interaction graph model. The proposed ESM protocol has been implemented and evaluated by simulation. The simulation results have shown that the proposed ESM protocol can prevent potential accidents from occurring better than existing ESM protocols. The context model and the RSM and ESM dissemination protocols can be implemented in any CCWS development to improve the communication and safety performance of CCWS. In effect, the outcomes contribute to the realisation of CCWS that will ultimately improve road safety and save lives.

Introduction : disputes in everyday life – Social and moral orders of children and young people

Volume 15 of Sociological Studies of Children and Youth (SSYC) presents a rich description of children’s and young people’s disputes. Children and young people live and experience their youth in a variety of contexts, settings and situations in contemporary society, and the studies discussed in this volume draw on empirical data to investigate the interactional procedures used by children and young people as disputes arise in varying contexts of their everyday life. The aim of this volume is to extend current understandings of on children’s disputes by examining how, in the varying arenas and social worlds of children and young people, matters of ownership, alignment and social and moral order are always at play. Applying a sociological perspective, the research papers in this special volume show that disputes can offer analytic opportunities to examine, and make visible typically unseen social and moral orders. This consideration provides rich accounts of dispute practices within social and institutional contexts.

Life in the internet economy and the changing face of property use

Increased participation in the internet economy is actively encouraged and supported by all levels of government. Research to date clearly shows the positive impacts that increased internet access can bring, particularly for rural Australia. Meanwhile, for the most part, identification of any negative impacts of increased broadband access on existing and potential property uses is avoided. The aim of this article is to identify issues for property use arising as a consequence of increased engagement in the internet economy. The article commences by clarifying what is meant by the term ‘internet economy’ before highlighting current impacts of the internet. It concludes by suggesting potential impacts for property and property uses in the future.

Sustainable development as a meta-context for engineering education

At the end of the first decade of the twenty-first century, there is unprecedented awareness of the need for a transformation in development, to meet the needs of the present while also preserving the ability of future generations to meet their own needs. However, within engineering, educators still tend to regard such development as an ‘aspect’ of engineering rather than an overarching meta-context, with ad hoc and highly variable references to topics. Furthermore, within a milieu of interpretations there can appear to be conflicting needs for achieving sustainable development, which can be confusing for students and educators alike. Different articulations of sustainable development can create dilemmas around conflicting needs for designers and researchers, at the level of specific designs and (sub-) disciplinary analysis. Hence sustainability issues need to be addressed at a meta-level using a whole of system approach, so that decisions regarding these dilemmas can be made. With this appreciation, and in light of curriculum renewal challenges that also exist in engineering education, this paper considers how educators might take the next step to move from sustainable development being an interesting ‘aspect’ of the curriculum, to sustainable development as a meta-context for curriculum renewal. It is concluded that capacity building for such strategic considerations is critical in engineering education.

Sustainability in road transport : an integrated life cycle analysis for estimating emissions

Despite of a significant contribution of transport sector in the global economy and society, it is one of the largest sources of global energy consumption, green house gas emissions and environmental pollutions. A complete look onto the whole life cycle environmental inventory of this sector will be helpful to generate a holistic understanding of contributory factors causing emissions. Previous studies were mainly based on segmental views which mostly compare environmental impacts of different modes of transport, but very few consider impacts other than the operational phase. Ignoring the impacts of non-operational phases, e.g., manufacture, construction, maintenance, may not accurately reflect total contributions on emissions. Moreover an integrated study for all motorized modes of road transport is also needed to achieve a holistic estimation. The objective of this study is to develop a component based life cycle inventory model which considers impacts of both operational and non-operational phases of the whole life as well as different transport modes. In particular, the whole life cycle of road transport has been segmented into vehicle, infrastructure, fuel and operational components and inventories have been conducted on each component. The inventory model has been demonstrated using the road transport of Singapore. Results show that total life cycle green house gas emissions from the road transport sector of Singapore is 7.8 million tons per year, among which operational phase and non-operational phases contribute about 55% and about 45%, respectively. Total amount of criteria air pollutants are 46, 8.5, 33.6, 13.6 and 2.6 thousand tons per year for CO, SO2, NOx, VOC and PM10, respectively. From the findings, it can be deduced that stringent government policies on emission control measures have a significant impact on reducing environmental pollutions. In combating global warming and environmental pollutions the promotion of public transport over private modes is an effective sustainable policy.

Host location by the fruit fly parasitoid Diachasmimorpha krausii : role of fruit fly species, life stage and host plant

1 Diachasmimorpha krausii is a braconid parasitoid of larval tephritid fruit flies, which feed cryptically within host fruit. At the ovipositor probing stage, the wasp cannot discriminate between hosts that are physiologically suitable or unsuitable for offspring development and must use other cues to locate suitable hosts. 2 To identify the cues used by the parasitoid to find suitable hosts, we offered, to free flying wasps, different combinations of three fruit fly species (Bactrocera tryoni, Bactrocera cacuminata, Bactrocera cucumis), different life stages of those flies (adults and larvae) and different host plants (Solanum lycopersicon, Solanum mauritianum, Cucurbita pepo). In the laboratory, the wasp will readily oviposit into larvae of all three flies but successfully develops only in B. tryoni. Bactrocera tryoni commonly infests S. lycopersicon (tomato), rarely S. mauritianum (wild tobacco) but never C. pepo (zucchini). The latter two plant species are common hosts for B. cacuminata and B. cucumis, respectively. 3 The parasitoid showed little or no response to uninfested plants of any of the test species. The presence of adult B. tryoni, however, increased parasitoid residency time on uninfested tomato. 4 When the three fruit types were all infested with larvae, parasitoid response was strongest to tomato, regardless of whether the larvae were physiologically suitable or unsuitable for offspring development. By contrast, zucchini was rarely visited by the wasp, even when infested with B. tryoni larvae. 5 Wild tobacco was infrequently visited when infested with B. cacuminata larvae but was more frequently visited, with greater parasitoid residency time and probing, when adult flies (either B. cacuminata or B. tryoni) were also present. 6 We conclude that herbivore-induced, nonspecific host fruit wound volatiles were the major cue used by foraging D. krausii. Although positive orientation to infested host plants is well known from previous studies on opiine braconids, the failure of the wasp to orientate to some plants even when infested with physiologically suitable larvae, and the secondary role played by adult fruit flies in wasp host searching, are newly-identified mechanisms that may aid parasitoid host location in environments where both physiologically suitable and unsuitable hosts occur.

Simple rules to contain an invasive species with a complex life cycle and high dispersal capacity

Designing practical rules for controlling invasive species is a challenging task for managers, particularly when species are long-lived, have complex life cycles and high dispersal capacities. Previous findings derived from plant matrix population analyses suggest that effective control of long-lived invaders may be achieved by focusing on killing adult plants. However, the cost-effectiveness of managing different life stages has not been evaluated. We illustrate the benefits of integrating matrix population models with decision theory to undertake this evaluation, using empirical data from the largest infestation of mesquite (Leguminosae: Prosopis spp) within Australia. We include in our model the mesquite life cycle, different dispersal rates and control actions that target individuals at different life stages with varying costs, depending on the intensity of control effort. We then use stochastic dynamic programming to derive cost-effective control strategies that minimize the cost of controlling the core infestation locally below a density threshold and the future cost of control arising from infestation of adjacent areas via seed dispersal. Through sensitivity analysis, we show that four robust management rules guide the allocation of resources between mesquite life stages for this infestation: (i) When there is no seed dispersal, no action is required until density of adults exceeds the control threshold and then only control of adults is needed; (ii) when there is seed dispersal, control strategy is dependent on knowledge of the density of adults and large juveniles (LJ) and broad categories of dispersal rates only; (iii) if density of adults is higher than density of LJ, controlling adults is most cost-effective; (iv) alternatively, if density of LJ is equal or higher than density of adults, management efforts should be spread between adults, large and to a lesser extent small juveniles, but never saplings. Synthesis and applications.In this study, we show that simple rules can be found for managing invasive plants with complex life cycles and high dispersal rates when population models are combined with decision theory. In the case of our mesquite population, focussing effort on controlling adults is not always the most cost-effective way to meet our management objective.