934 resultados para string breaking


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New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single dc-ac inverter connected to a series string of pv panels, or many small dc-ac inverters which connect one or two panels directly to the ac grid. This paper proposes an alternative topology of nonisolated per-panel dc-dc converters connected in series to create a high voltage string connected to a simplified dc-ac inverter. This offers the advantages of a "converter-per-panel" approach without the cost or efficiency penalties of individual dc-ac grid connected inverters. Buck, boost, buck-boost, and Cu´k converters are considered as possible dc-dc converters that can be cascaded. Matlab simulations are used to compare the efficiency of each topology as well as evaluating the benefits of increasing cost and complexity. The buck and then boost converters are shown to be the most efficient topologies for a given cost, with the buck best suited for long strings and the boost for short strings. While flexible in voltage ranges, buck-boost, and Cu´k converters are always at an efficiency or alternatively cost disadvantage.

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In recent events, notions of political protest, civil disobedience, extremism, and criminal action have become increasingly blurred. The London Riots, the Occupy movement, and the actions of hacking group Anonymous have all sparked heated debate about the limits of legitimate protest, and the distinction between an acceptable action and a criminal offence. Long before these events, environmental activists were challenging convention in protest actions, with several groups engaging in politically motivated law-breaking. The emergence of the term ‘eco-tage’ (the sabotage of equipment in order to protect the environment) signifies the important place environmental activists hold in challenging the traditional boundaries between illegal action and legitimate protest. Many of these groups establish their own boundaries of legitimacy, with some justifying their actions on the basis of civil disobedience or extensional self-defence. This paper examines the statements of environmental activist organisations that have engaged in politically motivated law breaking. It identifies the parameters that these groups set on their illegal actions, as well as the justifications that they provide, with a view to determining where these actions fit in the vast grey area between legal protest and violent extremism.

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Social media adoption in Australia, which provides the geographic focus for this chapter, has been rapid and substantial (ABC News, 2010) – possibly because of the considerable dispersal of the Australian population across the continent, as well as the significant distance of the country from many of its closest partner nations. Social media can play an important role in strengthening and maintaining interpersonal and professional relationships in spite of such physical distance; in particular, social media services are now well-recognised as important tools for the dissemination of news across many developed nations. Hermida (2010) and Burns (2010) both speak of Twitter as a medium for “ambient news”, for example: always-on, operating as a steady stream in the background and at the edge of users’ conscious perception. Much as ambient music is designed to do, it comes to the fore when notable events (such as major breaking news) lead to an increase in volume and demand a greater level of attention from users.

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Among the many meanings of abstraction is the focus on images that are at a distance from their origins. This understanding of abstraction is central to Savanhdary Vongpoothorn’s layered, textured and sensuous canvas Crossing (2003). The references in this painting to Laotian textile design and creation endows it with the sense of a fabric-like nature, gives it the feel of cloth wrapped around bodies and of threads woven into complex symmetrical patterns. Here, the distance from origins is expressed as a separation from the material forms of Lao culture. At the same time the work is a visual reference to the stretching or bending of forms, the breaking up of shapes in the natural or constructed environment, all of which create an expressive effect through the warm rose grid and visual illusions of movement and travel. This visual play suggests the sense that migration or movement is a means through which cultural forms get recoded and translated. The making of Crossing like many of Savanhdary’s works involved manipulation of the canvas through pricking and poking, and then the application of layers and dots of paint. The overall effect is one of a synthesis of different cultural motifs and the addition of new dimensions to familiar forms. This highlights the centrality of the idea of 'reassemblage’ in abstraction, the processes of remaking of self, of the natural world and of cultural artefacts. Savanhdary constructs intricate laced knots of colour and texture in work which expresses the possibilities presented by travel, migration and the subsequent remixture that emerges upon crossing through different cultural worlds.

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Grid connected photovoltaic (PV) inverters fall into three broad categories - central, string and module integrated converters (MICs). MICs offer many advantages in performance and flexibility, but are at a cost disadvantage. Two alternative novel approaches proposed by the author - cascaded dc-dc MICs and bypass dc-dc MICs - integrate a simple non-isolated intelligent dc-dc converter with each PV module to provide the advantages of dc-ac MICs at a lower cost. A suitable universal 150 W 5 A dc-dc converter design is presented based on two interleaved MOSFET half bridges. Testing shows zero voltage switching (ZVS) keeps losses under 1 W for bi-directional power flows up to 15 W between two adjacent 12 V PV modules for the bypass application, and efficiencies over 94% for most of the operational power range for the cascaded converter application. Based on the experimental results, potential optimizations to further reduce losses are discussed.

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New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single DC-AC inverter connected to a series string of PV modules, or many small DC-AC inverters which connect one or two modules directly to the AC grid. This paper shows that a "converter-per-module" approach offers many advantages including individual module maximum power point tracking, which gives great flexibility in module layout, replacement, and insensitivity to shading; better protection of PV sources, and redundancy in the case of source or converter failure; easier and safer installation and maintenance; and better data gathering. Simple nonisolated per-module DC-DC converters can be series connected to create a high voltage string connected to a simplified DC-AC inverter. These advantages are available without the cost or efficiency penalties of individual DC-AC grid connected inverters. Buck, boost, buck-boost and Cuk converters are possible cascadable converters. The boost converter is best if a significant step up is required, such as with a short string of 12 PV modules. A string of buck converters requires many more modules, but can always deliver any combination of module power. The buck converter is the most efficient topology for a given cost. While flexible in voltage ranges, buck-boost and Cuk converters are always at an efficiency or alternatively cost disadvantage

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Every year a number of pedestrians are struck by trains resulting in death and serious injury. While much research has been conducted on train-vehicle collisions, very little is currently known about the aetiology of train-pedestrian collisions. To date, scant research has been undertaken to investigate the demographics of rule breakers, the frequency of deliberate violation versus error making and the influence of the classic deterrence approach on subsequent behaviours. Aim This study aimed to to identify pedestrians’ self-reported reasons for engaging in violations at crossing, the frequency and nature of rule breaking and whether the threat of sanctions influence such events. Method A questionnaire was administered to 511 participants of all ages. Results Analysis revealed that pedestrians (particularly younger groups) were more likely to commit deliberate violations rather than make crossing errors e.g., mistakes. The most frequent reasons given for deliberate violations were participants were running late and did not want to miss their train or participants believed that the gate was taking too long to open so may be malfunctioning. In regards to classical deterrence, an examination of the perceived threat of being apprehended and fined for a crossing violation revealed participants reported the highest mean scores for swiftness of punishment, which suggests they were generally aware that they would receive an “on the spot” fine. However, the overall mean scores for certainty and severity of sanctions (for violating the rules) indicate that the participants did not perceive the certainty and severity of sanctions as very high. This paper will further discuss the research findings in regards to the development of interventions designed to improve pedestrian crossing safety.

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This paper makes a case for thinking about the primary school as a logic machine (apparatus) as a way of thinking about processes of in-school stratification. Firstly we discuss related literature on in-school stratification in primary schools, particularly as it relates to literacy learning. Secondly we explain how school reform can be thought about in terms of the idea of the machine or apparatus. In which case the processes of in-school stratification can be mapped as more than simply concerns about school organisation (such as students grouping) but also involve a politics of truth, played out in each school, that constitutes school culture and what counts as ‘good’ pedagogy. Thirdly, the chapter will focus specifically on research conducted into primary schools in the Northern Suburbs of Adelaide, one of the most educationally disadvantaged regions in Australia, as a case study of the relationship between in-school stratification and the reproduction of inequality. We will draw from more than 20 years of ethnographic work in primary school in the northern suburbs of Adelaide and provide a snapshot of a recent attempt to improve literacy achievement in a few Northern Suburbs public primary schools (SILA project). The SILA project, through diagnostic reviews, has provided a significant analysis of the challenges facing policy and practice in such challenging school contexts that also maps onto existing (inter)national research. These diagnostic reviews said ‘hard things’ that required attention by SILA schools and these included: · an over reliance on whole class, low level, routine tasks and hence a lack of challenge and rigour in the learning tasks offered to students ; · a focus on the 'code breaking' function of language at the expense of richer conceptualisations of literacy that might guide teachers’ understanding of challenging pedagogies ; · the need for substantial shifts in the culture of schools, especially unsettling deficit views of students and their communities ; · a need to provide a more ‘consistent’ approach to teaching literacy across the school; · a need to focus School Improvement Plans in order to implement a clear focus on literacy learning; and, · a need to sustain professional learning to produce new knowledge and practice . The paper will conclude with suggestions for further research and possible reform projects into the primary school as a logic machine.

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Where teachers of English as a foreign language (EFL) once observed a paucity of authentic language input, public displays of written English are now proliferating. Ideas for capitalising on this abundance can be drawn from two strands of pedagogic thought: a psycholinguistic approach to conventional literacy long established in foreign, second and first language education (e.g., Teng, 2009), and a more recent and critical approach informed by diverse theoretical understandings of the ‘linguistic landscape’ (e.g., Rowland, 2013). In this paper I draw from these two approaches to suggest ways of helping EFL learners use environmental print to develop knowledge and skills required of English readers in the twenty-first century: (1) fluency in breaking the codes of English and other languages of publicly displayed text; (2) facility with making meaning as the English of these texts becomes ever more diverse in cultural, historical and contextual implication; (3) use of environmental English in contexts that range from the local to the transnational; and (4) critique of the presence of English and attendant worldviews in the urban environment (Chern & Dooley, forthcoming). The psychological concept of motivation and the complementary sociological concept of investment are at the heart of my deliberations here: realisation of the pedagogic potential of environmental print to develop literate resources requires consideration of sources of motivation in the classroom learning situation (Dörnyei & Ushioda, 2011), as well as learner investment in literate practices in English (Norton, 2010).

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Graphene has been reported with record-breaking properties which have opened up huge potential applications. A considerable research has been devoted to manipulate or modify the properties of graphene to target a more smart nanoscale device. Graphene and carbon nanotube hybrid structure (GNHS) is one of the promising graphene derivates, while their mechanical properties have been rarely discussed in literature. Therefore, such a studied is conducted in this paper basing on the large-scale molecular dynamics simulation. The target GNHS is constructed by considering two separate graphene layers that being connected by single-wall carbon nanotubes (SWCNTs) according to the experimental observations. It is found that the GNHSs exhibit a much lower yield strength, Young’s modulus, and earlier yielding comparing with a bilayer graphene sheet. Fracture of studied GNHSs is found to fracture located at the connecting region between carbon nanotubes (CNTs) and graphene. After failure, monatomic chains are normally observed at the front of the failure region, and the two graphene layers at the failure region without connecting CNTs will adhere to each other, generating a bilayer graphene sheet scheme (with a layer distance about 3.4 Å). This study will enrich the current understanding of the mechanical performance of GNHS, which will guide the design of GNHS and shed lights on its various applications.

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Nanomaterials are prone to influence by chemical adsorption because of their large surface to volume ratios. This enables sensitive detection of adsorbed chemical species which, in turn, can tune the property of the host material. Recent studies discovered that single and multi-layer molybdenum disulfide (MoS2) films are ultra-sensitive to several important environmental molecules. Here we report new findings from ab inito calculations that reveal substantially enhanced adsorption of NO and NH3 on strained monolayer MoS2 with significant impact on the properties of the adsorbates and the MoS2 layer. The magnetic moment of adsorbed NO can be tuned between 0 and 1 μB; strain also induces an electronic phase transition between half-metal and metal. Adsorption of NH3 weakens the MoS2 layer considerably, which explains the large discrepancy between the experimentally measured strength and breaking strain of MoS2 films and previous theoretical predictions. On the other hand, adsorption of NO2, CO, and CO2 is insensitive to the strain condition in the MoS2 layer. This contrasting behavior allows sensitive strain engineering of selective chemical adsorption on MoS2 with effective tuning of mechanical, electronic, and magnetic properties. These results suggest new design strategies for constructing MoS2-based ultrahigh-sensitivity nanoscale sensors and electromechanical devices.

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To this day, realizations in the standard-model of (lossy) trapdoor functions from discrete-log-type assumptions require large public key sizes, e.g., about Θ(λ 2) group elements for a reduction from the decisional Diffie-Hellman assumption (where λ is a security parameter). We propose two realizations of lossy trapdoor functions that achieve public key size of only Θ(λ) group elements in bilinear groups, with a reduction from the decisional Bilinear Diffie-Hellman assumption. Our first construction achieves this result at the expense of a long common reference string of Θ(λ 2) elements, albeit reusable in multiple LTDF instantiations. Our second scheme also achieves public keys of size Θ(λ), entirely in the standard model and in particular without any reference string, at the cost of a slightly more involved construction. The main technical novelty, developed for the second scheme, is a compact encoding technique for generating compressed representations of certain sequences of group elements for the public parameters.

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Thirteen years ago, Kenichi Ohmae proclaimed that the world had become “borderless,” and the nation-state nothing more than a “bit actor” in a globalised economy. Around the same time, “interdisciplinarity” appeared as the prime strategy for breaking down the rigid stratifications of traditional disciplines, promising an equivalently borderless academe. However, despite the rhetoric of globalisation and interdisciplinarity, territorial boundaries—both physical and conceptual—remain in evidence and under contention...

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An encryption scheme is non-malleable if giving an encryption of a message to an adversary does not increase its chances of producing an encryption of a related message (under a given public key). Fischlin introduced a stronger notion, known as complete non-malleability, which requires attackers to have negligible advantage, even if they are allowed to transform the public key under which the related message is encrypted. Ventre and Visconti later proposed a comparison-based definition of this security notion, which is more in line with the well-studied definitions proposed by Bellare et al. The authors also provide additional feasibility results by proposing two constructions of completely non-malleable schemes, one in the common reference string model using non-interactive zero-knowledge proofs, and another using interactive encryption schemes. Therefore, the only previously known completely non-malleable (and non-interactive) scheme in the standard model, is quite inefficient as it relies on generic NIZK approach. They left the existence of efficient schemes in the common reference string model as an open problem. Recently, two efficient public-key encryption schemes have been proposed by Libert and Yung, and Barbosa and Farshim, both of them are based on pairing identity-based encryption. At ACISP 2011, Sepahi et al. proposed a method to achieve completely non-malleable encryption in the public-key setting using lattices but there is no security proof for the proposed scheme. In this paper we review the mentioned scheme and provide its security proof in the standard model. Our study shows that Sepahi’s scheme will remain secure even for post-quantum world since there are currently no known quantum algorithms for solving lattice problems that perform significantly better than the best known classical (i.e., non-quantum) algorithms.

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Health promotion progresses a social justice and empowerment agenda and thus emphasises working with people to increase their control over their health. Certainly, Australia has experienced much success in this endeavour and is internationally recognised as a leader. However, health promotion has failed Indigenous Australians; a fact that is echoed in the health outcomes that ironically provide us with the “moral imperative” to act. Further investigation has also revealed health promotion’s foundation in colonial imaginings. Thus, this paper calls for the culture of health promotion to be examined as a risk factor for poor Indigenous health. To complement this call, this paper presents findings of an ethnographic study of Indigenous health promotion practice, undertaken from a postcolonial and critical whiteness framework. These findings provide a narrative of strength and innovative approaches, highlighting the value of Indigenous knowledge. These findings also contradict the biomedical tendency to construct culture as illness-producing. More broadly, this study’s findings entail important lessons for health promotion to consider, if it is to move beyond the rhetoric, to truly increase people’s control over their health.