900 resultados para Astronautics and state
Resumo:
Breather stability and longevity in thermally relaxing nonlinear arrays is investigated under the scrutiny of the analysis and tools employed for time series and state reconstruction of a dynamical system. We briefly review the methods used in the analysis and characterize a breather in terms of the results obtained with such methods. Our present work focuses on spontaneously appearing breathers in thermal Fermi-Pasta-Ulam arrays but we believe that the conclusions are general enough to describe many other related situations; the particular case described in detail is presented as another example of systems where three incommensurable frequencies dominate their chaotic dynamics (reminiscent of the Ruelle-Takens scenario for the appearance of chaotic behavior in nonlinear systems). This characterization may also be of great help for the discovery of breathers in experimental situations where the temporal evolution of a local variable (like the site energy) is the only available/measured data. © 2005 American Institute of Physics.
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Gymnocypris przewalskii (Kessler 1876) is an endangered and state-protected rare fish species in Qinghai Lake, China. To further understand the life history and distribution of this fish, five surveys were carried out in Qinghai Lake between 2002-2006. Results of these surveys indicate that fishes were predominantly distributed about 2 m under the surface. In July, significant differences in fish density were found between surface and bottom layers (P = 0.001), and/or between middle and bottom layers (P = 0.025). Fish density was the greatest in the surface layer. In August and October, no significant differences were found between the different layers, but the bottom layer had a greater fish density. Furthermore, there were very large differences among different zones in fish distribution density. Differences in horizontal distribution were not significantly correlated to factors such as water depth and inshore distance, possibly because of very low and uniform fish density. Feeding, changes in water temperature, over-wintering and spawning appeared to influence fish distribution. Hydroacoustic estimates of G. przewalskii biomass in Qinghai Lake increased significantly between 2002 and 2006. We attribute this increase to the management measures put in place to protect this species.
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Stannic oxide xerogel was prepared by a forced hydrolysis method using SnCl4 as the precursor. The average grain sizes of the nanosized stannic oxide powders varied with the sintering temperatures. The powders were characterized by several different physico-chemical techniques. TEM was employed for the direct observation on grain sizes, shape and state of aggregation of the particles. XRD technique was used for the determination of the crystalline structure. Microstructural parameters of average crystallite size (
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We describe the automatic synthesis of a global nonlinear controller for stabilizing a magnetic levitation system. The synthesized control system can stabilize the maglev vehicle with large initial displacements from an equilibrium, and possesses a much larger operating region than the classical linear feedback design for the same system. The controller is automatically synthesized by a suite of computational tools. This work demonstrates that the difficult control synthesis task can be automated, using programs that actively exploit knowledge of nonlinear dynamics and state space and combine powerful numerical and symbolic computations with spatial-reasoning techniques.
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We revisit the problem of connection management for reliable transport. At one extreme, a pure soft-state (SS) approach (as in Delta-t [9]) safely removes the state of a connection at the sender and receiver once the state timers expire without the need for explicit removal messages. And new connections are established without an explicit handshaking phase. On the other hand, a hybrid hard-state/soft-state (HS+SS) approach (as in TCP) uses both explicit handshaking as well as timer-based management of the connection’s state. In this paper, we consider the worst-case scenario of reliable single-message communication, and develop a common analytical model that can be instantiated to capture either the SS approach or the HS+SS approach. We compare the two approaches in terms of goodput, message and state overhead. We also use simulations to compare against other approaches, and evaluate them in terms of correctness (with respect to data loss and duplication) and robustness to bad network conditions (high message loss rate and variable channel delays). Our results show that the SS approach is more robust, and has lower message overhead. On the other hand, SS requires more memory to keep connection states, which reduces goodput. Given memories are getting bigger and cheaper, SS presents the best choice over bandwidth-constrained, error-prone networks.
Resumo:
My thesis presents an examination of Ce que c'est que la France toute Catholique (1686) by Pierre Bayle, a prominent figure in the Republic of Letters and the Huguenot Refuge in the seventeenth century. This pamphlet was the first occasional text that Bayle published following the Revocation of the Edict of Nantes in which the religious toleration afforded to the Huguenot minority in France was repealed, a pivotal moment in the history of early modern France. In my thesis, I analyse the specific context within which Bayle wrote this pamphlet as a means of addressing a number of issues, including the legitimacy of forced conversions, the impact of the religious controversy upon exchanges in the Republic of Letters, the nature of religious zeal and finally the alliance of Church and state discourses in the early modern period. An examination of this context provides a basis from which to re-interpret the rhetorical strategies at work within the pamphlet, and also to come to an increased understanding of how, why and to what end he wrote it. In turn this allowed me to examine the relationship between this often overlooked pamphlet and the more extensively studied Commentaire Philosophique, in which Bayle argued in favour of religious toleration. Ultimately, understanding the relationship between these two texts proves essential in order to characterise his response to the Revocation of the Edict of Nantes and to understand the place of the pamphlet within his oeuvre. Furthermore, an analysis of the pamphlet and the Commentaire Philosophique provide a lens through which to elucidate both Bayle's intellectual development at this early stage in his career, and also the wider context of the rise of toleration theory and the evolution of modes of civility within the Republic of Letters on the eve of the Enlightenment.
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This PhD thesis investigates the potential use of science communication models to engage a broader swathe of actors in decision making in relation to scientific and technological innovation in order to address possible democratic deficits in science and technology policy-making. A four-pronged research approach has been employed to examine different representations of the public(s) and different modes of engagement. The first case study investigates whether patient-groups could represent an alternative needs-driven approach to biomedical and health sciences R & D. This is followed by enquiry into the potential for Science Shops to represent a bottom-up approach to promote research and development of local relevance. The barriers and opportunities for the involvement of scientific researchers in science communication are next investigated via a national survey which is comparable to a similar survey conducted in the UK. The final case study investigates to what extent opposition or support regarding nanotechnology (as an emerging technology) is reflected amongst the YouTube user community and the findings are considered in the context of how support or opposition to new or emerging technologies can be addressed using conflict resolution based approaches to manage potential conflict trajectories. The research indicates that the majority of communication exercises of relevance to science policy and planning take the form of a one-way flow of information with little or no facility for public feedback. This thesis proposes that a more bottom-up approach to research and technology would help broaden acceptability and accountability for decisions made relating to new or existing technological trajectories. This approach could be better integrated with and complementary to government, institutional, e.g. university, and research funding agencies activities and help ensure that public needs and issues are better addressed directly by the research community. Such approaches could also facilitate empowerment of societal stakeholders regarding scientific literacy and agenda-setting. One-way information relays could be adapted to facilitate feedback from representative groups e.g. Non-governmental organisations or Civil Society Organisations (such as patient groups) in order to enhance the functioning and socio-economic relevance of knowledge-based societies to the betterment of human livelihoods.
Resumo:
The health of a nation tells much about the nature of a social contract between citizen and state. The way that health care is organised, and the degree to which it is equitably accessible, constitutes a manifestation of the effects of moments and events in that country's history. Using four case studies, this thesis uses a historical genealogical approach to explain the evolution of Ireland's particular version of health care provision. The total social fact of the gift relationship, central to all human relations, will be used to form a theoretical and conceptual framework on which to build an analysis of Ireland's health and welfare conditions. Additionally, social contract theory will enable an examination of the role of solidarity in relation to social expectations around health care provision. Through the analysis of these cases, the complex matrix of the influential forces that have shaped current conditions are exposed and revealed, enabling a critical understanding of the extent of acquiescence to the inequitable system that arguably exists. The vulnerability of citizens in need of care to the external and global effects of market forces and neoliberalism, therefore, becomes central to any argument for state-provided health and welfare. The hegemony of such forces can be seen to influence the manner in which the idea of individual self-reliance, in place of collective solidarity, is conceptualised and subsequently infiltrated into a range of aspects of the social world. For example, the particular discourse of the market and of economic concerns succeeds in shaping understandings of responsibilities around central areas of health and welfare. Similarly the 'possessor principle' can be seen to be misplaced within the context of health and social care, but yet has become normalised within this discourse. Within this matrix of complex influencing factors, the welfare state struggles to impose a balance between market values and social values. Responsibilities of the state to support and compensate its citizens for the ills of the market have become devalued, as the core values of classical liberalism have become distorted beyond recognition, leaving instead bare neoliberal concerns. This thesis traces the genealogical origins of this transition within the recent history of Irish health care and thereby reveals the embedding of individualism in place of solidarity, the on going reneging of the social contract and the corruption of the gift relationship.
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For centuries Cork’s Shawlies, working-class women, survived by trading on public streets. My study explores how the first Irish Free State government, and Cork’s local authority, limited the rights of poor women to earn by subsistence trading with The Street Trading Act, 1926. The government insisted this would regulate street trading. In practice it further marginalised the women economically and socially, containing them outside the privileged, commercial city centre. In Cork the legislation facilitated the gradual disappearance of the Shawlies amid entrenched social processes and relations, contingencies that allowed for the abuse of their rights in the service of amalgamated business interests. This study address the role of discourses in deepening this marginalisation. My theoretical framework is designed to demonstrate how a seemingly innocuous piece of legislation would, in practice, do this. I set out the concepts of ‘Thriving State’, ‘Prosperous State’, and state of ‘Best Intentions’ that uses gentrification to meet these goals. The existing knowledge on women in trade is then examined, highlighting the gaps in what is known about the Shawlies. Chapter 3 details the theory behind my genealogical method. The legislation, debate, and other data produced at the national level is then examined, before moving to the local data. Chapter 6 is devoted to the Shawlies, setting their stories in the larger context of the debates. An examination of studies of contemporary women street traders in poor nations follows, along with a brief history of the decline of street trading in New York city under gentrification. Points of convergence between that process and the one in Cork are identified, along with convergences between contemporary traders and the Shawlies. The conclusion sets out my methodological, theoretical and substantive discoveries, and comments on current nostalgic renderings of the Shawlies in Cork’s newly gentrified Corn Market Street.
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Smoking is an expensive habit. Smoking households spend, on average, more than $US1000 annually on cigarettes. When a family member quits, in addition to the former smoker's improved long-term health, families benefit because savings from reduced cigarette expenditures can be allocated to other goods. For households in which some members continue to smoke, smoking expenditures crowd-out other purchases, which may affect other household members, as well as the smoker. We empirically analyse how expenditures on tobacco crowd-out consumption of other goods, estimating the patterns of substitution and complementarity between tobacco products and other categories of household expenditure. We use the Consumer Expenditure Survey data for the years 1995-2001, which we complement with regional price data and state cigarette prices. We estimate a consumer demand system that includes several main expenditure categories (cigarettes, food, alcohol, housing, apparel, transportation, medical care) and controls for socioeconomic variables and other sources of observable heterogeneity. Descriptive data indicate that, comparing smokers to nonsmokers, smokers spend less on housing. Results from the demand system indicate that as the price of cigarettes rises, households increase the quantity of food purchased, and, in some samples, reduce the quantity of apparel and housing purchased.
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From 2008-2012, a dramatic upsurge in incidents of maritime piracy in the Western Indian Ocean led to renewed global attention to this region: including the deployment of multi national naval patrols, attempts to prosecute suspected pirates, and the development of financial interdiction systems to track and stop the flow of piracy ransoms. Largely seen as the maritime ripple effect of anarchy on land, piracy has been slotted into narratives of state failure and problems of governance and criminality in this region.
This view fails to account for a number of factors that were crucial in making possible the unprecedented rise of Somali piracy and its contemporary transformation. Instead of an emphasis on failed states and crises of governance, my dissertation approaches maritime piracy within a historical and regional configuration of actors and relationships that precede this round of piracy and will outlive it. The story I tell in this work begins before the contemporary upsurge of piracy and closes with a foretaste of the itineraries beyond piracy that are being crafted along the East African coast.
Beginning in the world of port cities in the long nineteenth century, my dissertation locates piracy and the relationship between trade, plunder, and state formation within worlds of exchange, including European incursions into this oceanic space. Scholars of long distance trade have emphasized the sociality engendered through commerce and the centrality of idioms of trust and kinship in structuring mercantile relationships across oceanic divides. To complement this scholarship, my work brings into view the idiom of protection: as a claim to surety, a form of tax, and a moral claim to authority in trans-regional commerce.
To build this theory of protection, my work combines archival sources with a sustained ethnographic engagement in coastal East Africa, including the pirate ports of Northern Somalia, and focuses on the interaction between land-based pastoral economies and maritime trade. This connection between land and sea calls attention to two distinct visions of the ocean: one built around trade and mobility and the other built on the ocean as a space of extraction and sovereignty. Moving between historical encounters over trade and piracy and the development of a national maritime economy during the height of the Somali state, I link the contemporary upsurge of maritime piracy to the confluence of these two conceptualizations of the ocean and the ideas of capture, exchange, and redistribution embedded within them.
The second section of my dissertation reframes piracy as an economy of protection and a form of labor implicated within other legal and illegal economies in the Indian Ocean. Based on extensive field research, including interviews with self-identified pirates, I emphasize the forms of labor, value, and risk that characterize piracy as an economy of protection. The final section of my dissertation focuses on the diverse international, regional, and local responses to maritime piracy. This section locates the response to piracy within a post-Cold War and post-9/11 global order and longer attempts to regulate and assuage the risks of maritime trade. Through an ethnographic focus on maritime insurance markets, navies, and private security contractors, I analyze the centrality of protection as a calculation of risk and profit in the contemporary economy of counter-piracy.
Through this focus on longer histories of trade, empire, and regulation my dissertation reframes maritime piracy as an economy of protection straddling boundaries of land and sea, legality and illegality, law and economy, and history and anthropology.
Resumo:
When farmers need to harvest a large amount of crops in a short period of time, migrant, seasonal, and H-2A Visa workers can often be the best solution to complete the job quickly and affordably. However, there are specific Federal and state legal duties and responsibilities for farmers who employ these types of workers and substantial criminal and civil penalties for failing to adhere to the law.
Resumo:
Bolivia and Peru adopted the same instruments of social policy —conditional cash transfer programs— to solve the same public problems under different political regimes. By means of the qualitative methodology of discourse analysis, this paper studies the representations of poverty and State made by key actors of those social programs. Underlying more differences than similarities, one demonstrates that the same social policy is linked to opposite social representations of poverty and the State role in every country. The main explanation for this is, far from being imposed by international organizations, those programs are adopted and adapted by each political regime.
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This article examines Pierre Bourdieu's sociology of the economy and his more recent politically engaged interventions on 'globalisation'. Many scholars regard these as not being in the same academic league as his classic studies on taste, academia, and state elites, etc., and, instead, dismiss them as a private matter or even, as the spleen of Pierre Bourdieu, the individual. This paper questions this disjunction of the 'academic' and 'politically engaged' sides of Pierre Bourdieu's work. First, it argues that his most recent interventions against a neo-liberal globalisation were the logical result of a particular definition of intellectual practice that had been outlined before in his sociology of the intellectual field. It then demonstrates that Bourdieu's economic sociology and critique of contemporary capitalism not only does not contradict his earlier research, but that it provides valuable and original insights into the current transformation of the political economy of the advanced capitalist countries. The paper concludes with a suggestion of how to strengthen the theoretical foundation of Bourdieu's analysis of contemporary capitalism by relating it to and making it compatible with alternative approaches in the tradition of critical political economy.
Resumo:
Exam timetabling is one of the most important administrative activities that takes place in academic institutions. In this paper we present a critical discussion of the research on exam timetabling in the last decade or so. This last ten years has seen an increased level of attention on this important topic. There has been a range of significant contributions to the scientific literature both in terms of theoretical andpractical aspects. The main aim of this survey is to highlight the new trends and key research achievements that have been carried out in the last decade.We also aim to outline a range of relevant important research issues and challenges that have been generated by this body of work.
We first define the problem and review previous survey papers. Algorithmic approaches are then classified and discussed. These include early techniques (e.g. graph heuristics) and state-of-the-art approaches including meta-heuristics, constraint based methods, multi-criteria techniques, hybridisations, and recent new trends concerning neighbourhood structures, which are motivated by raising the generality of the approaches. Summarising tables are presented to provide an overall view of these techniques. We discuss some issues on decomposition techniques, system tools and languages, models and complexity. We also present and discuss some important issues which have come to light concerning the public benchmark exam timetabling data. Different versions of problem datasetswith the same name have been circulating in the scientific community in the last ten years which has generated a significant amount of confusion. We clarify the situation and present a re-naming of the widely studied datasets to avoid future confusion. We also highlight which research papershave dealt with which dataset. Finally, we draw upon our discussion of the literature to present a (non-exhaustive) range of potential future research directions and open issues in exam timetabling research.