912 resultados para piecewise constant argument
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In this paper, a singularly perturbed ordinary differential equation with non-smooth data is considered. The numerical method is generated by means of a Petrov-Galerkin finite element method with the piecewise-exponential test function and the piecewise-linear trial function. At the discontinuous point of the coefficient, a special technique is used. The method is shown to be first-order accurate and singular perturbation parameter uniform convergence. Finally, numerical results are presented, which are in agreement with theoretical results.
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The dynamic interaction between building systems and external climate is extremely complex, involving a large number of difficult-to-predict variables. In order to study the impact of global warming on the built environment, the use of building simulation techniques together with forecast weather data are often necessary. Since all building simulation programs require hourly meteorological input data for their thermal comfort and energy evaluation, the provision of suitable weather data becomes critical. Based on a review of the existing weather data generation models, this paper presents an effective method to generate approximate future hourly weather data suitable for the study of the impact of global warming. Depending on the level of information available for the prediction of future weather condition, it is shown that either the method of retaining to current level, constant offset method or diurnal modelling method may be used to generate the future hourly variation of an individual weather parameter. An example of the application of this method to the different global warming scenarios in Australia is presented. Since there is no reliable projection of possible change in air humidity, solar radiation or wind characters, as a first approximation, these parameters have been assumed to remain at the current level. A sensitivity test of their impact on the building energy performance shows that there is generally a good linear relationship between building cooling load and the changes of weather variables of solar radiation, relative humidity or wind speed.
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The release of ultrafine particles (UFP) from laser printers and office equipment was analyzed using a particle counter (FMPS; Fast Mobility Particle Sizer) with a high time resolution, as well as the appropriate mathematical models. Measurements were carried out in a 1 m³ chamber, a 24 m³ chamber and an office. The time-dependent emission rates were calculated for these environments using a deconvolution model, after which the total amount of emitted particles was calculated. The total amounts of released particles were found to be independent of the environmental parameters and therefore, in principle, they were appropriate for the comparison of different printers. On the basis of the time-dependent emission rates, “initial burst” emitters and constant emitters could also be distinguished. In the case of an “initial burst” emitter, the comparison to other devices is generally affected by strong variations between individual measurements. When conducting exposure assessments for UFP in an office, the spatial distribution of the particles also had to be considered. In this work, the spatial distribution was predicted on a case by case basis, using CFD simulation.
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The use of allograft bone is increasingly common in orthopaedic reconstruction procedures. The optimal method of preparation of allograft bone is subject of great debate. Proponents of fresh-frozen graft cite improved biological and biomechanical characteristics relative to irradiated material, whereas fear of bacterial or viral transmission warrants some to favour irradiated graft. Careful review of the literature is necessary to appreciate the influence of processing techniques on bone quality. Whereas limited clinical trials are available to govern the selection of appropriate bone graft, this review presents the argument favouring the use of fresh-frozen bone allograft as compared to irradiated bone.
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Design as seen from the designer's perspective is a series of amazing imaginative jumps or creative leaps. But design as seen by the design historian is a smooth progression or evolution of ideas that they seem self-evident and inevitable after the event. But the next step is anything but obvious for the artist/creator/inventor/designer stuck at that point just before the creative leap. They know where they have come from and have a general sense of where they are going, but often do not have a precise target or goal. This is why it is misleading to talk of design as a problem-solving activity - it is better defined as a problem-finding activity. This has been very frustrating for those trying to assist the design process with computer-based, problem-solving techniques. By the time the problem has been defined, it has been solved. Indeed the solution is often the very definition of the problem. Design must be creative-or it is mere imitation. But since this crucial creative leap seem inevitable after the event, the question must arise, can we find some way of searching the space ahead? Of course there are serious problems of knowing what we are looking for and the vastness of the search space. It may be better to discard altogether the term "searching" in the context of the design process: Conceptual analogies such as search, search spaces and fitness landscapes aim to elucidate the design process. However, the vastness of the multidimensional spaces involved make these analogies misguided and they thereby actually result in further confounding the issue. The term search becomes a misnomer since it has connotations that imply that it is possible to find what you are looking for. In such vast spaces the term search must be discarded. Thus, any attempt at searching for the highest peak in the fitness landscape as an optimal solution is also meaningless. Futhermore, even the very existence of a fitness landscape is fallacious. Although alternatives in the same region of the vast space can be compared to one another, distant alternatives will stem from radically different roots and will therefore not be comparable in any straightforward manner (Janssen 2000). Nevertheless we still have this tantalizing possibility that if a creative idea seems inevitable after the event, then somehow might the process be rserved? This may be as improbable as attempting to reverse time. A more helpful analogy is from nature, where it is generally assumed that the process of evolution is not long-term goal directed or teleological. Dennett points out a common minsunderstanding of Darwinism: the idea that evolution by natural selection is a procedure for producing human beings. Evolution can have produced humankind by an algorithmic process, without its being true that evolution is an algorithm for producing us. If we were to wind the tape of life back and run this algorithm again, the likelihood of "us" being created again is infinitesimally small (Gould 1989; Dennett 1995). But nevertheless Mother Nature has proved a remarkably successful, resourceful, and imaginative inventor generating a constant flow of incredible new design ideas to fire our imagination. Hence the current interest in the potential of the evolutionary paradigm in design. These evolutionary methods are frequently based on techniques such as the application of evolutionary algorithms that are usually thought of as search algorithms. It is necessary to abandon such connections with searching and see the evolutionary algorithm as a direct analogy with the evolutionary processes of nature. The process of natural selection can generate a wealth of alternative experiements, and the better ones survive. There is no one solution, there is no optimal solution, but there is continuous experiment. Nature is profligate with her prototyping and ruthless in her elimination of less successful experiments. Most importantly, nature has all the time in the world. As designers we cannot afford prototyping and ruthless experiment, nor can we operate on the time scale of the natural design process. Instead we can use the computer to compress space and time and to perform virtual prototyping and evaluation before committing ourselves to actual prototypes. This is the hypothesis underlying the evolutionary paradigm in design (1992, 1995).
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Aim: To review the titles, roles and scope of practice of Advanced Practice Nurses internationally.----- Background: There is a worldwide shortage of nurses but there is also an increased demand for nurses with enhanced skills who can manage a more diverse, complex and acutely ill patient population than ever before. As a result, a variety of nurses in advanced practice positions has evolved around the world. The differences in nomenclature have led to confusion over the roles, scope of practice and professional boundaries of nurses in an international context.----- Method: CINAHL, Medline, and the Cochrane database of Systematic Reviews were searched from 1987 to 2008. Information was also obtained through government health and professional organisation websites. All information in the literature regarding current and past status, and nomenclature of advanced practice nursing was considered relevant.----- Findings: There are many names for Advanced Practice Nurses, and although many of these roles are similar in their function, they can often have different titles.----- Conclusion: Advanced Practice Nurses are critical for the future, provide cost-effective care and are highly regarded by patients/clients. They will be a constant and permanent feature of future health care provision. However, clarification regarding their classification and regulation is necessary in some countries.
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This article provides the background and context to the important issue of assessment and equity in relation to Indigenous students in Australia. Questions about the validity and fairness of assessment are raised and ways forward are suggested by attending to assessment questions in relation to equity and culture-fair assessment. Patterns of under-achievement by Indigenous students are reflected in national benchmark data and international testing programmes like the Trends in International Mathematics and Science Sstudy and the Program for International Student Assessment. The argument developed views equity, in relation to assessment, as more of a sociocultural issue than a technical matter. It highlights how teachers need to distinguish the "funds of knowledge" that Indigenous students draw on and how teachers need to adopt culturally responsive pedagogy to open up the curriculum and assessment practice to allow for different ways of knowing and being.
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Young children engage in a constant process of negotiating and constructing rules, utilizing these rules as cultural resources to manage their social interactions. This paper examines how young children make sense of, and also construct, rules within one early childhood classroom. This paper draws on a recent study conducted in Australia, in which video-recorded episodes of young children’s talk-in-interaction were examined. Analysis revealed four interactional practices that the children used, including manipulating materials and places to claim ownership of resources within the play space; developing or using pre-existing rules and social orders to control the interactions of their peers; strategically using language to regulate the actions of those around them; and creating and using membership categories such as ‘car owner’ or ‘team member’ to include or exclude others and also to control and participate in the unfolding interaction. While the classroom setting was framed within adult conceptions and regulations, analysis of the children’s interaction demonstrated their co-constructions of social order and imposition of their own forms of rules. Young children negotiated both adult constructed social order and also their own peer constructed social order, drawing upon various rules within both social orders as cultural resources by which they managed their interaction.
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The purpose of this paper is to extend marketing knowledge into perceived risk in online transactions beyond the current positivistic, hypotheses-driven research by providing qualitative insights into how individuals construct their accounts of perceived risk online. Additionally, the study reported in this paper aims to explore how communication sources influence both these subjective constructions and individuals' behavioural experiences with transaction activity on the web. Design/methodology/approach - The study was developed within a grounded theory method.Ten in-depth interviews were conducted which were analysed using constant comparison of incidents procedures to provide rich descriptions of the interviewees' subjective perceptions and lived experiences with online transaction activity. Findings - The findings provide insights into how the human clement is present in individuals'perceptions and constructions of their accounts of the risk involved online.The findings also identify the influence of mass communication sources on the construction of these accounts. The study provides insights into whether change agent communication sources, such as marketers or web designers,influence consumers' behaviours towards online transaction activity through mediating their perceptions of the risks involved. The study also reveals how social communication networks influence the interviewees' decisions to use the web (or transaction activities, in particular online purchasing, and how the group in this study might act as a communication source to influence others. Research limitations/Implications - While the findings cannot be generalised to the internet population overall, the sample used was able to provide relevant information regarding the phenomenon of interest. Future research should continue to examine perceived risk and the influence of communications sources, such as e-mail, discussion groups and virtual communities. Originality/value - The value of the paper lies in permitting the participants to account for perceived risk for themselves. The findings ex.plore what this means at increasing levels of personal relevance and the influence of communication sources to create, sustain or mediate perceptions of this phenomenon.
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Using examples from contemporary policy and business discourses, and exemplary historical texts dealing with the notion of value, I put forward an argument as to why a critical scholarship that draws on media history, language analysis, philosophy and political economy is necessary to understand the dynamics of what is being called 'the global knowledge economy'. I argue that the social changes associated with new modes of value determination are closely associated with new media forms.
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In this experimental study the permeability of Australian bagasse chemical pulps obtained from different bagasse fractions were measured in a simple permeability cell and the results compared to one another as well as to eucalypt, Argentinean bagasse and pine pulps. The pulps were characterised in terms of the permeability parameters, the specific surface area, Sv, and the swelling factor, α. It was found that the bagasse fraction used affects these parameters. Fractionation of whole bagasse prior to pulping produced pulps that have permeability properties that compare favourably with eucalypt pulp. The values of Sv and α for bagasse pulp also depend on whether a constant or a variable Kozeny factor is used.
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The end of the Korean War in 1953 marked the beginning of Seoul’s transformation from the shattered capital city of South Korea to one of the most connected, populous, and fast-changing hubs of global economy. Seoul’s technosocial development has been celebrated nationally and internationally. To the outside, young Koreans’ swift and extensive adoption and adaptation to digital technologies has been a subject of exotification; to adults in Korea, it has been a subject of criticism (see Yoon in this volume). With the understanding that ‘the city is connections,’ it is crucial to study not only the macro-level design of the city as a network (through policy, for example), but also its micro-level construction at the intersection of people, place, and technology. Accordingly, this chapter explores this exact intersection to comprehensively portray the constant renewal of the city as imagined and experienced by young Koreans. The chapter is based on fieldwork conducted in Seoul, South Korea, from 2007 to 2008 as part of a research project on the mobile play culture of Seoul transyouth, the transitional demographic situated between youth and adulthood, and the pioneers of the Korean ‘broadband miracle’ (Hazlett, 2004). The study draws upon transdisciplinary research data including interviews, questionnaires, diaries, and Shared Visual Ethnography (SVE) to render the everyday urban social networking of young Seoulites with and through which they interact to constantly (re)create the city and the self.
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China has a reputation as an economy based on utility: the large-scale manufacture of low-priced goods. But useful values like functionality, fitness for purpose and efficiency are only part of the story. More important are what Veblen called ‘honorific’ values, arguably the driving force of development, change and value in any economy. To understand the Chinese economy therefore, it is not sufficient to point to its utilitarian aspect. Honorific status-competition is a more fundamental driver than utilitarian cost-competition. We argue that ‘social network markets’ are the expression of these honorific values, relationships and connections that structure and coordinate individual choices. This paper explores how such markets are developing in China in the area of fashion and fashion media. These, we argue, are an expression of ‘risk culture’ for high-end entrepreneurial consumers and producers alike, providing a stimulus to dynamic innovation in the arena of personal taste and comportment, as part of an international cultural system based on constant change. We examine the launch of Vogue China in 2005, and China’s reception as a fashion player among the international editions of Vogue, as an expression of a ‘decisive moment’ in the integration of China into an international social network market based on honorific values.
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This book analyses and refines the arguments for and against retrospective rule making, concluding that there is one really strong argument against it: the expectation that, if an individual's actions are considered by a future court, the legal consequences of that action will be determined by the law that was discoverable at the time the action was performed. This argument, which goes to the heart of the rule of law, is generally determinative. However, in some cases the argument does not run and this book suggests that, in some areas of law, reliance should be actively discouraged by prospective warnings that the law is subject to change.
Resumo:
For the last two decades heart disease has been the highest single cause of death for the human population. With an alarming number of patients requiring heart transplant, and donations not able to satisfy the demand, treatment looks to mechanical alternatives. Rotary Ventricular Assist Devices, VADs, are miniature pumps which can be implanted alongside the heart to assist its pumping function. These constant flow devices are smaller, more efficient and promise a longer operational life than more traditional pulsatile VADs. The development of rotary VADs has focused on single pumps assisting the left ventricle only to supply blood for the body. In many patients however, failure of both ventricles demands that an additional pulsatile device be used to support the failing right ventricle. This condition renders them hospital bound while they wait for an unlikely heart donation. Reported attempts to use two rotary pumps to support both ventricles concurrently have warned of inherent haemodynamic instability. Poor balancing of the pumps’ flow rates quickly leads to vascular congestion increasing the risk of oedema and ventricular ‘suckdown’ occluding the inlet to the pump. This thesis introduces a novel Bi-Ventricular Assist Device (BiVAD) configuration where the pump outputs are passively balanced by vascular pressure. The BiVAD consists of two rotary pumps straddling the mechanical passive controller. Fluctuations in vascular pressure induce small deflections within both pumps adjusting their outputs allowing them to maintain arterial pressure. To optimise the passive controller’s interaction with the circulation, the controller’s dynamic response is optimised with a spring, mass, damper arrangement. This two part study presents a comprehensive assessment of the prototype’s ‘viability’ as a support device. Its ‘viability’ was considered based on its sensitivity to pathogenic haemodynamics and the ability of the passive response to maintain healthy circulation. The first part of the study is an experimental investigation where a prototype device was designed and built, and then tested in a pulsatile mock circulation loop. The BiVAD was subjected to a range of haemodynamic imbalances as well as a dynamic analysis to assess the functionality of the mechanical damper. The second part introduces the development of a numerical program to simulate human circulation supported by the passively controlled BiVAD. Both investigations showed that the prototype was able to mimic the native baroreceptor response. Simulating hypertension, poor flow balancing and subsequent ventricular failure during BiVAD support allowed the passive controller’s response to be assessed. Triggered by the resulting pressure imbalance, the controller responded by passively adjusting the VAD outputs in order to maintain healthy arterial pressures. This baroreceptor-like response demonstrated the inherent stability of the auto regulating BiVAD prototype. Simulating pulmonary hypertension in the more observable numerical model, however, revealed a serious issue with the passive response. The subsequent decrease in venous return into the left heart went unnoticed by the passive controller. Meanwhile the coupled nature of the passive response not only decreased RVAD output to reduce pulmonary arterial pressure, but it also increased LVAD output. Consequently, the LVAD increased fluid evacuation from the left ventricle, LV, and so actually accelerated the onset of LV collapse. It was concluded that despite the inherently stable baroreceptor-like response of the passive controller, its lack of sensitivity to venous return made it unviable in its present configuration. The study revealed a number of other important findings. Perhaps the most significant was that the reduced pulse experienced during constant flow support unbalanced the ratio of effective resistances of both vascular circuits. Even during steady rotary support therefore, the resulting ventricle volume imbalance increased the likelihood of suckdown. Additionally, mechanical damping of the passive controller’s response successfully filtered out pressure fluctuations from residual ventricular function. Finally, the importance of recognising inertial contributions to blood flow in the atria and ventricles in a numerical simulation were highlighted. This thesis documents the first attempt to create a fully auto regulated rotary cardiac assist device. Initial results encourage development of an inlet configuration sensitive to low flow such as collapsible inlet cannulae. Combining this with the existing baroreceptor-like response of the passive controller will render a highly stable passively controlled BiVAD configuration. The prototype controller’s passive interaction with the vasculature is a significant step towards a highly stable new generation of artificial heart.