927 resultados para Switched reluctance motors


Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper begins by providing an overview of bike share programs, followed by a critical examination of the growing body of literature on these programs. This synthesis of previous works, both peer-reviewed and grey, includes an identification of the current gaps in knowledge related to the impacts of bike sharing programs. This synthesis represents a critically needed evaluation of the current state of global bike share research, in order to better understand, and maximize the effectiveness of current and future programs. Several consistent themes have emerged within the growing body of research on bike share programs. Firstly, the importance bike share members place on convenience and value for money appears paramount in their motivation to sign up and use these programs. Secondly, and somewhat counter intuitively, scheme members are more likely to own and use private bicycles than non-members. Thirdly, users demonstrate a greater reluctance to wear helmets than private bicycle riders and helmets have acted as a deterrent in jurisdictions in which helmets are mandatory. Finally, and perhaps most importantly from a sustainable transport perspective, the majority of scheme users are substituting from sustainable modes of transport rather than the car.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Understanding the link between tectonic-driven extensional faulting and volcanism is crucial from a hazard perspective in active volcanic environments, while ancient volcanic successions provide records on how volcanic eruption styles, compositions, magnitudes and frequencies can change in response to extension timing, distribution and intensity. Significantly, incorrect tectonic interpretations can be made when the spatial-temporal-compositional trends of, and source contributions to magmatism are not properly considered. This study draws on intimate relationships of volcanism and extension preserved in the Sierra Madre Occidental (SMO) and Gulf of California (GoC) regions of western Mexico. Here, a major Oligocene rhyolitic ignimbrite “flare-up” (>300,000 km3) switched to a dominantly bimodal and mixed effusive-explosive volcanic phase in the Early Miocene (~100,000 km3), associated with distributed extension and opening of numerous grabens. Rhyolitic dome fields were emplaced along graben edges and at intersections of cross-graben and graben-parallel structures during early stages of graben development. Concomitant with this change in rhyolite eruption style was a change in crustal source as revealed by zircon chronochemistry with rapid rates of rhyolite magma generation due to remelting of mid- to upper crustal, highly differentiated igneous rocks emplaced during earlier SMO magmatism. Extension became more focused ~18 Ma resulting in volcanic activity being localised along the site of GoC opening. This localised volcanism (known as the Comondú “arc”) was dominantly effusive and andesite-dacite in composition. This compositional change resulted from increased mixing of basaltic and rhyolitic magmas rather than fluid flux melting of the mantle wedge above the subducting Guadalupe Plate. A poor understanding of space-time relationships of volcanism and extension has thus led to incorrect past tectonic interpretations of Comondú-age volcanism.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The composition of the lithosphere can be fundamentally altered by long-lived subduction processes such that subduction-modified lithosphere can survive for 100's Myrs. Incorrect petrotectonic interpretations result when spatial-temporal-compositional trends of, and source contributions to, magmatism are not properly considered. Western Mexico has had protracted Cenozoic magmatism developed mostly in-board of active oceanic plate subduction beneath western North America. A broad range of igneous compositions from basalt to high-silica rhyolite were erupted with intermediate to silicic compositions in particular, showing calc-alkaline and other typical subduction-related geochemical signatures. A major Oligocene rhyolitic ignimbrite “flare-up” (>300,000 km3) switched to a bimodal volcanic phase in the Early Miocene (~100,000 km3), associated with distributed extension and opening of numerous grabens. Extension became more focussed ~18 Ma resulting in localised volcanic activity along the future site of the Gulf of California. This localised volcanism (known as the Comondú “arc”) was dominantly effusive and andesite-dacite in composition. Past tectonic interpretations of Comondú-age volcanism may have been incorrect as these regional temporal-compositional changes are alternatively interpreted as a result of increased mixing of mantle-derived basaltic and crust-derived rhyolitic magmas in an active rift environment rather than fluid flux melting of the mantle wedge above the subducting Guadalupe Plate.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Understanding the link between tectonic-driven extensional faulting and volcanism is crucial from a hazard perspective in active volcanic environments, while ancient volcanic successions provide records on how volcanic eruption styles, compositions, magnitudes and frequencies can change in response to extension timing, distribution and intensity. This study draws on intimate relationships of volcanism and extension preserved in the Sierra Madre Occidental (SMO) and Gulf of California (GoC) regions of western Mexico. Here, a major Oligocene rhyolitic ignimbrite “flare-up” (>300,000 km3) switched to a dominantly bimodal and mixed effusive-explosive volcanic phase in the Early Miocene (~100,000 km3), associated with distributed extension and opening of numerous grabens. Rhyolitic dome fields were emplaced along graben edges and at intersections of cross-graben and graben-parallel structures during early stages of graben development. Concomitant with this change in rhyolite eruption style was a change in crustal source as revealed by zircon chronochemistry with rapid rates of rhyolite magma generation due to remelting of mid- to upper crustal, highly differentiated igneous rocks emplaced during earlier SMO magmatism. Extension became more focused ~18 Ma resulting in volcanic activity being localised along the site of GoC opening. This localised volcanism (known as the Comondú “arc”) was dominantly effusive and andesite-dacite in composition. This compositional change resulted from increased mixing of basaltic and rhyolitic magmas rather than fluid flux melting of the mantle wedge above the subducting Guadalupe Plate. A poor understanding of space-time relationships of volcanism and extension has thus led to incorrect past tectonic interpretations of Comondú-age volcanism.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In the absence of a benchmarking mechanism specifically designed for local requirements and characteristics, a carbon dioxide footprint assessment and labelling scheme for construction materials is urgently needed to promote carbon dioxide reduction in the construction industry. This paper reports on a recent interview survey of 18 senior industry practitioners in Hong Kong to elicit their knowledge and opinions concerning the potential of such a carbon dioxide labelling scheme. The results of this research indicate the following. A well-designed carbon dioxide label could stimulate demand for low carbon dioxide construction materials. The assessment of carbon dioxide emissions should be extended to different stages of material lifecycles. The benchmarks for low carbon dioxide construction materials should be based on international standards but without sacrificing local integrity. Administration and monitoring of the carbon dioxide labelling scheme could be entrusted to an impartial and independent certification body. The implementation of any carbon dioxide labelling schemes should be on a voluntary basis. Cost, functionality, quality and durability are unlikely to be replaced by environmental considerations in the absence of any compelling incentives or penalties. There are difficulties in developing and operating a suitable scheme, particularly in view of the large data demands involved, reluctance in using low carbon dioxide materials and limited environmental awareness.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Much has been written on Michel Foucault’s reluctance to clearly delineate a research method, particularly with respect to genealogy (Harwood 2000; Meadmore, Hatcher, & McWilliam 2000; Tamboukou 1999). Foucault (1994, p. 288) himself disliked prescription stating, “I take care not to dictate how things should be” and wrote provocatively to disrupt equilibrium and certainty, so that “all those who speak for others or to others” no longer know what to do. It is doubtful, however, that Foucault ever intended for researchers to be stricken by that malaise to the point of being unwilling to make an intellectual commitment to methodological possibilities. Taking criticism of “Foucauldian” discourse analysis as a convenient point of departure to discuss the objectives of poststructural analyses of language, this paper develops what might be called a discursive analytic; a methodological plan to approach the analysis of discourses through the location of statements that function with constitutive effects.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Maritime security has emerged as a critical legal and political issue in the contemporary world. Terrorism in the maritime domain is a major maritime security issue. Ten out of the 44 major terrorist groups of the world, as identified in the US Department of State’s Country Reports on Terrorism, have maritime terrorism capabilities. Prosecution of maritime terrorists is a politically and legally difficult issue, which may create conflicts of jurisdiction. Prosecution of alleged maritime terrorists is carried out by national courts. There is no international judicial institution for the prosecution of maritime terrorists. International law has therefore anticipated a vital role for national courts in this respect. The international legal framework for combating maritime terrorism has been elaborately examined in existing literature therefore this paper will only highlight the issues regarding the prosecution of maritime terrorists. This paper argues that despite having comprehensive intentional legal framework for the prosecution of maritime terrorists there is still some scopes for conflicts of jurisdiction particularly where two or more States are interested to prosecute the same offender. This existing legal problem has been further aggravated in the post September 11 era. Due to the political and security implications, States may show reluctance in ensuring the international law safeguards of alleged perpetrators in the arrest, detention and prosecution process. Nevertheless, international law has established a comprehensive system for the prosecution of maritime terrorists where national courts is the main forum of ensuring the international law safeguards of alleged perpetrators as well as ensuring the effective prosecution of maritime terrorists thereby playing an instrumental role in establishing a rule based system for combating maritime terrorism. Using two case studies, this paper shows that the role of national courts has become more important in the present era because there may be some situations where no State is interested to initiate proceedings in international forums for vindicating rights of an alleged offender even if there is a clear evidence of violation of international human rights law in the arrest, detention and prosecution process. This paper presents that despite some bottlenecks national courts are actively playing this critical role. Overall, this paper highlights the instrumental role of national courts in the international legal order.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This study analyses young gay men's identity management in social networking sites Gaydar and Facebook. It examines the expanded opportunities for identity management made available through the convergence of these spaces, as well as new privacy and safety concerns. Findings from this study are discussed in terms of their significance for gay men's digital culture, the approach to gay men's mental health taken by GLBT organisations and support groups, and within broader concerns around social networking sites and digital inequality.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The Australian Government’s current workforce reforms in early childhood education and care (ECEC) include a major shift in qualification requirements. The new requirement is that university four-year degree-qualified teachers are employed in before-school contexts, including child care. Ironically, recent research studies show that, in Australia, the very preservice teachers who are enrolled in these degree programs have a reluctance to work in childcare. This article reports on part of a larger study which is inquiring into how early childhood teacher professional identities are discursively produced, and provides a partial mapping of the literature. One preservice teacher’s comment provides the starting point, and the paper locates some the discourses that are accessible to preservice teachers as they prepare for the early years workforce. An awareness of the discursive field provides a sound background for preparing early childhood teachers. A challenge for the field is to consider which discourses are dominant, and how they potentially work to privilege work in some ECEC contexts over others.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

School guidance counsellors world-wide seek ways of providing appropriate professional assistance to all students. While young people integrate online technology into their daily lives and go online for information and to communicate with each other, school counsellors in Australia are not offering online support to students. This cross-sectional study reported on the reluctance of school counsellors to offer online counselling and the reasons for this. A survey of 210 school guidance counsellors found that there is conditional support for the introduction of online counselling into the school setting. Counsellors indicated that they would use online counselling if students accepted its use in the school setting though they question how genuine students would be in its use. Most respondents reported a lack of confidence in understanding the ethical and legal implications of online counselling. However, the majority of participants were prepared to undertake further professional development in this mode of counselling. Additionally, they sought confirmation of the effectiveness of counselling students online before committing themselves to it. The implications for school guidance practice are discussed.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

OBJECTIVES: To describe the recruitment strategy and association between facility and staff characteristics and success of resident recruitment for the Promoting Independence in Residential Care (PIRC) trial. DESIGN: Cross-sectional study of staff and facility characteristics and recruitment rates within facilities with calculation of cluster effects of multiple measures. SETTING AND PARTICIPANTS: Staff of low-level dependency residential care facilities and residents able to engage in a physical activity program in 2 cities in New Zealand. MEASURES: A global impression of staff willingness to facilitate research was gauged by research nurses, facility characteristics were measured by staff interview. Relevant outcomes were measured by resident interview and included the following: (1) Function: Late Life FDI scale, timed-up-and-go, FICSIT balance scale and the Elderly Mobility Scale; (2) Quality of Life: EuroQol quality of life scale, Life Satisfaction Index; and (3) falls were assessed by audit of the medical record. Correlation between recruitment rates, facility characteristics and global impression of staff willingness to participate were investigated. Design effects were calculated on outcomes. RESULTS: Forty-one (85%) facilities and 682 (83%) residents participated, median age was 85 years (range 65-101), and 74% were women. Participants had complex health problems. Recruitment rates were associated (but did not increase linearly) with the perceived willingness of staff, and were not associated with facility size. Design effects from the cluster recruitment differed according to outcome. CONCLUSIONS: The recruitment strategy was successful in recruiting a large sample of people with complex comorbidities and high levels of functional disability despite perceptions of staff reluctance. Staff willingness was related to recruitment success.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Purpose This article reports on a research project that explored social media best practice in the public library sector. Design/methodology/approach The primary research approach for the project was case study. Two organisations participated in case studies that involved interviews, document analysis, and social media observation. Findings The two case study organisations use social media effectively to facilitate participatory networks, however, there have been challenges surrounding its implementation in both organisations. Challenges include negotiating requirements of governing bodies and broader organisational environments, and managing staff reluctance around the implementations. As social media use continues to grow and libraries continue to take up new platforms, social media must be considered to be another service point of the virtual branch, and indeed, for the library service as a whole. This acceptance of social media as being core business is critical to the successful implementation of social media based activities. Practical implications The article provides an empirically grounded discussion of best practice and the conditions that support it. The findings are relevant for information organisations across all sectors and could inform the development of policy and practice in other organisations. This paper contributes to the broader dialogue around best practice in participatory service delivery and social media use in library and information organisations.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Permanent magnet (PM) motors utilising ironless stator structures have been incorporated into a wide variety of applications where high efficiency and stringent torque control are required. With recent developments in magnetic materials, improved design strategies, and power outputs of up to 40kW, PM motors have become an attractive candidate for traction drives in electric and hybrid electric vehicles. However, due to their large air gaps and ironless stators these motors can have inductances as low as 2μH, imposing increased requirements on the converter to minimise current ripple. Multilevel converters with n cells can effectively increase the motor inductance by a factor of n2 and are an excellent approach to minimise the motor ripple current. Furthermore by indirectly coupling the outputs of each cell, improvements in converter input and cell ripple current can also be realised. This paper examines the issues in designing a high current indirectly coupled multilevel motor controller for an ironless BLDC traction drive and highlights the limitations of the common ladder core structure.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An ironless motor for use as direct wheel drive is presented. The motor is intended for use in a lightweight (600kg), low drag, series hybrid commuter vehicle under development at The University of Queensland. The vehicle will utilise these ironless motors in each of its rear wheels, with each motor producing a peak torque output of 500Nm and a maximum rotational speed of 1500rpm. The axial flux motor consists of twin Ironless litz wire stators with a central magnetic ring and simplified Halbach magnet arrays on either side. A small amount of iron is used to support the outer Halbach arrays and to improve the peak magnetic flux density. Ducted air cooling is used to remove heat from the motor and will allow for a continuous torque rating of 250Nm. Ironless machines have previously been shown to be effective in high speed, high frequency applications (+1000Hz). They are generally regarded as non-optimal for low speed applications as iron cores allow for better magnet utilisation and do not significantly increase the weight of a machine. However, ironless machines can also be seen to be effective in applications where the average torque requirement is much lower than the peak torque requirement such as in some vehicle drive applications. The low spinning losses in ironless machines are shown to result in very high energy throughput efficiency in a wide range of vehicle driving cycles.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Investigates the braking performance requirements of the UltraCommuter, a lightweight series hybrid electric vehicle currently under development at the University of Queensland. With a predicted vehicle mass of 600 kg and two in-wheel motors each capable of 500 Nm of peak torque, decelerations up to 0.46 g are theoretically possible using purely regenerative braking. With 99% of braking demands less than 0.35 g, essentially all braking can be regenerative. The wheel motors have sufficient peak torque capability to lock the rear wheels in combination with front axle braking, eliminating the need for friction braking at the rear. Emergency braking levels approaching 1 g are achieved by supplementation with front disk brakes. This paper presents equations describing the peak front and rear axle braking forces which occur under straight line braking, including gradients. Conventionally, to guarantee stability, mechanical front/rear proportioning of braking effort ensures that the front axle locks first. In this application, all braking is initially regenerative at the rear, and an adaptive ''by-wire'' proportioning system presented ensures this stability requirement is still satisfied. Front wheel drive and all wheel drive systems are also discussed. Finally, peak and continuous performance measures, not commonly provided for friction brakes, are derived for the UltraCommuter's motor capability and range of operation.