891 resultados para Redes ad hoc veiculares (Redes de computadores)


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In routine industrial design, fatigue life estimation is largely based on S-N curves and ad hoc cycle counting algorithms used with Miner's rule for predicting life under complex loading. However, there are well known deficiencies of the conventional approach. Of the many cumulative damage rules that have been proposed, Manson's Double Linear Damage Rule (DLDR) has been the most successful. Here we follow up, through comparisons with experimental data from many sources, on a new approach to empirical fatigue life estimation (A Constructive Empirical Theory for Metal Fatigue Under Block Cyclic Loading', Proceedings of the Royal Society A, in press). The basic modeling approach is first described: it depends on enforcing mathematical consistency between predictions of simple empirical models that include indeterminate functional forms, and published fatigue data from handbooks. This consistency is enforced through setting up and (with luck) solving a functional equation with three independent variables and six unknown functions. The model, after eliminating or identifying various parameters, retains three fitted parameters; for the experimental data available, one of these may be set to zero. On comparison against data from several different sources, with two fitted parameters, we find that our model works about as well as the DLDR and much better than Miner's rule. We finally discuss some ways in which the model might be used, beyond the scope of the DLDR.

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Social media platforms such as Facebook and Twitter are now widely recognised as playing an increasingly important role in the dissemination of information during crisis events. They are used by emergency management organisations as well as by the public to share information and advice. However, the official use of social media for crisis communication within emergency management organisations is still relatively new and ad hoc, rather than being systematically embedded within or effectively coordinated across agencies. This policy report suggests a more effectively coordinated approach to leverage social media use, involving stronger networking between social media staff within emergency management organisations. This could be realised by establishing a national network of social media practitioners managed by the Australia-New Zealand Emergency Management Committee (ANZEMC), reinforced by a Federal government task force that promotes further policy initiatives in this space.

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Background The School of Clinical Sciences comprises a number of health disciplines including podiatry, paramedic science, pharmacy, medical imaging and radiation therapy. A new inter-professional unit was introduced in 2014, which covered key introductory learnings applicable for future health practitioners. This study examined teaching staff and student perspectives about their experience with the new unit for first year students. Methods Qualitative interviews with teaching staff (n=9) and focus group interviews with students (5 groups which ranged in size from 4-30) were conducted. Extensive notes were taken during the interviews Issues emerging from the interviews were identified and organised according to themes and subthemes. Results Four major themes were identified namely: Something new; To be or not to be that is the question; Advantages of the new unit; and Areas for improvement. Previous staff experience with inter-professional learning (IPL) had been ad-hoc, whereas the new unit brought together several disciplines in a planned and deliberate way. There was strong philosophical agreement about the value of IPL but some debate about the extent to which the unit provided IPL experience. The unit was seen as assisting students’ social and academic adjustment to university and provided opportunity for professional socialisation, exposure to macro and micro aspects of the Australian health care system and various types of communication. For podiatry students it was their first opportunity to formally meet and work with other podiatry students and moved their identity from ‘university student’ to ‘podiatry student’. Other positives included providing the opportunity for staff and students to interact at an early stage with the perceived benefit of reducing attrition. Areas for unit improvement included institutional arrangements, unit administration aspects and assessment. Conclusion The unit was seen as beneficial by staff and students however, students were more polarised in their views than staff. There was a tension between feeling apart of and learning about one's own profession and feeling apart of and learning about the roles of other health professionals in relation to patient care and the health care system.

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Globalisation is set to have a major impact on world horticultural production and distribution of fruit and vegetables throughout the world. In contrast to developing countries such as China, production and consumption of fresh fruit and vegetables in most developed countries is relatively static. For developed countries, we are starting to see consolidation in the number of farms producing fruit and vegetables with falling or static prices and real farm incomes. Global supply chains are now dominated by a few large multi-national retailers supplied by preferred trans-national distribution companies. The major competitive advantages that are emerging are consistency of supply of high quality product over an extended season and the control of genetic resources and their marketing. To capture these new competitive advantages, new strategic analyses and planning processes must be implemented. In the past, strategic analyses and planning has been undertaken on an ad hoc basis without accurate global intelligence. In the future, working ‘on the supply chain’ will become equally, if not more important, than working ‘in the supply chain’. A revised approach to strategic planning, which encompasses and adjusts for the changes caused by globalisation, is urgently needed. A new 6-step strategic analyses process is described.

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The concept of food security is often anchored in popular understandings of the challenge to produce and supply enough food. However, decades of policies for intensive agriculture have not alleviated hunger and malnutrition, with an absence of food security featuring in both economically developing and developed nations. Despite perceptions that the economic growth in advanced, capitalist societies will ensure freedom from hunger, this is not universal across so-called ‘wealthy nations’. To explore the dynamics of food security in economically developed countries, this paper considers institutional approaches to domestic food security primarily through responses to poverty and welfare entitlements, and, secondarily, through food relief. Through the lens of social entitlements to food and their formation under various expressions of welfare capitalism, we highlight how the specific institutional settings of two economically developed nations, Australia and Norway, respond to uncertain or insufficient access to food. Whilst Norway's political agenda on agricultural support, food pricing regulation and universal social security support offers a robust, although indirect, safety net in ensuring entitlements to food, Australia's neoliberal trajectory means that approaches to food security are ad hoc and rely on a combination of self-help, charitable and market responses. Despite its extensive food production Australia appears less capable of ensuring food security for all its inhabitants compared to the highly import-dependent Norway.

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One of the distinctive features of Gold Coast urbanisation is its historically ad hoc approach to development with little or no strategic planning to guide it. Many have commented on the lack of planning on the Gold Coast calling it ‘an experiment in freedom’ or ‘free enterprise city’. Following a major restructuring of the Queensland’s local councils, the 1990s witnessed a shift from ad hoc decision making to more systematic planning on the Gold Coast. Understanding the past is important for shaping the future. This paper reviews the history of regulatory planning on the Gold Coast, encompassing decisions affecting the form and development of its earliest settlements through to its periods of greatest construction and most streamlined decision–making. It focuses mainly on past planning processes, the problems identified in each planning exercise and the interventions introduced, asking whether these were implemented or not and why. The paper positions the Gold Coast as a physical embodiment of this history of decision making, assessing the effects on the city as a whole of specific measures either affording freedoms or insisting on accountability to various levels of regulation. It examines how the absence of some planning measures influenced the form of the city and its internal arrangements and considers how the shift from ad hoc decision making towards more systematic planning efforts affected the city’s urbanisation. The lessons that the Gold Coast example provides will resonate with places elsewhere in Australia and the world, if not always in scale definitely in substance.

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Theories of search and search behavior can be used to glean insights and generate hypotheses about how people interact with retrieval systems. This paper examines three such theories, the long standing Information Foraging Theory, along with the more recently proposed Search Economic Theory and the Interactive Probability Ranking Principle. Our goal is to develop a model for ad-hoc topic retrieval using each approach, all within a common framework, in order to (1) determine what predictions each approach makes about search behavior, and (2) show the relationships, equivalences and differences between the approaches. While each approach takes a different perspective on modeling searcher interactions, we show that under certain assumptions, they lead to similar hypotheses regarding search behavior. Moreover, we show that the models are complementary to each other, but operate at different levels (i.e., sessions, patches and situations). We further show how the differences between the approaches lead to new insights into the theories and new models. This contribution will not only lead to further theoretical developments, but also enables practitioners to employ one of the three equivalent models depending on the data available.

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The notion of being sure that you have completely eradicated an invasive species is fanciful because of imperfect detection and persistent seed banks. Eradication is commonly declared either on an ad hoc basis, on notions of seed bank longevity, or on setting arbitrary thresholds of 1% or 5% confidence that the species is not present. Rather than declaring eradication at some arbitrary level of confidence, we take an economic approach in which we stop looking when the expected costs outweigh the expected benefits. We develop theory that determines the number of years of absent surveys required to minimize the net expected cost. Given detection of a species is imperfect, the optimal stopping time is a trade-off between the cost of continued surveying and the cost of escape and damage if eradication is declared too soon. A simple rule of thumb compares well to the exact optimal solution using stochastic dynamic programming. Application of the approach to the eradication programme of Helenium amarum reveals that the actual stopping time was a precautionary one given the ranges for each parameter.

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The registration of new agricultural chemicals (particularly herbicides) for turf use requires supporting data on their possible phytotoxic effects across a representative range of turfgrass species and cultivars. This process has been streamlined by the establishment of dedicated phytotoxicity testing site. This facility has enabled phytotoxicity screening of new chemicals to be conducted more quickly, thoroughly and economically than the previous piecemeal ad hoc approach. During the three years of this project, 39 products were screened on the site.

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The possibility or the impossibility of separating the particle and the electrode interactions is discussed in a wider context of the effects due to any two interaction potentials on the equation of state. The involved nature of the pressure dependence on two individually definable forces is illustrated through the Percus Yevick results for the adhesive hard spheres. An alternative form of the adsorption isotherm is given to bring home the intimate relationship between the actual equation of state and the free energy of adsorption. Thermodynamic consequences of congruence with respect to E (or q) as reflected through the linear plots of q (or E) vs. θ are well known. Mathematical consequences of simultaneous congruence have been pointed out recently. In this paper, the physical nature of congruence hypothesis is revealed. In passing "the pseudo-congruence" is also discussed. It is emphasised that the problem is no less ambiguous with regard to modelling the particle/particle interaction. The ad hoc nature of our dependence of the available equations of state is emphasised through a discussion on the HFL theory. Finally, a heuristic method for modelling ΔG mathematically-incorporating its behaviour at saturation coverages-is advanced. The more interesting aspects of this approach, which generalises almost all isotherms hitherto known, are sketched.

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Contains the constitution, by-laws, correspondence, papers, and minutes of the Synagogue Council of America (1935-1958), an incomplete set of the minutes of the Plenum, (1949-1965), the minutes of the Executive Committee (1946-1969), Officers' (Summit) Meetings (1955-1967) and the minutes and reports of the Budget Committee (1946-1966), financial reports and statements for 1942-1965 and fundraising activities (1958-1968).

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Sensor networks represent an attractive tool to observe the physical world. Networks of tiny sensors can be used to detect a fire in a forest, to monitor the level of pollution in a river, or to check on the structural integrity of a bridge. Application-specific deployments of static-sensor networks have been widely investigated. Commonly, these networks involve a centralized data-collection point and no sharing of data outside the organization that owns it. Although this approach can accommodate many application scenarios, it significantly deviates from the pervasive computing vision of ubiquitous sensing where user applications seamlessly access anytime, anywhere data produced by sensors embedded in the surroundings. With the ubiquity and ever-increasing capabilities of mobile devices, urban environments can help give substance to the ubiquitous sensing vision through Urbanets, spontaneously created urban networks. Urbanets consist of mobile multi-sensor devices, such as smart phones and vehicular systems, public sensor networks deployed by municipalities, and individual sensors incorporated in buildings, roads, or daily artifacts. My thesis is that "multi-sensor mobile devices can be successfully programmed to become the underpinning elements of an open, infrastructure-less, distributed sensing platform that can bring sensor data out of their traditional close-loop networks into everyday urban applications". Urbanets can support a variety of services ranging from emergency and surveillance to tourist guidance and entertainment. For instance, cars can be used to provide traffic information services to alert drivers to upcoming traffic jams, and phones to provide shopping recommender services to inform users of special offers at the mall. Urbanets cannot be programmed using traditional distributed computing models, which assume underlying networks with functionally homogeneous nodes, stable configurations, and known delays. Conversely, Urbanets have functionally heterogeneous nodes, volatile configurations, and unknown delays. Instead, solutions developed for sensor networks and mobile ad hoc networks can be leveraged to provide novel architectures that address Urbanet-specific requirements, while providing useful abstractions that hide the network complexity from the programmer. This dissertation presents two middleware architectures that can support mobile sensing applications in Urbanets. Contory offers a declarative programming model that views Urbanets as a distributed sensor database and exposes an SQL-like interface to developers. Context-aware Migratory Services provides a client-server paradigm, where services are capable of migrating to different nodes in the network in order to maintain a continuous and semantically correct interaction with clients. Compared to previous approaches to supporting mobile sensing urban applications, our architectures are entirely distributed and do not assume constant availability of Internet connectivity. In addition, they allow on-demand collection of sensor data with the accuracy and at the frequency required by every application. These architectures have been implemented in Java and tested on smart phones. They have proved successful in supporting several prototype applications and experimental results obtained in ad hoc networks of phones have demonstrated their feasibility with reasonable performance in terms of latency, memory, and energy consumption.

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This thesis studies optimisation problems related to modern large-scale distributed systems, such as wireless sensor networks and wireless ad-hoc networks. The concrete tasks that we use as motivating examples are the following: (i) maximising the lifetime of a battery-powered wireless sensor network, (ii) maximising the capacity of a wireless communication network, and (iii) minimising the number of sensors in a surveillance application. A sensor node consumes energy both when it is transmitting or forwarding data, and when it is performing measurements. Hence task (i), lifetime maximisation, can be approached from two different perspectives. First, we can seek for optimal data flows that make the most out of the energy resources available in the network; such optimisation problems are examples of so-called max-min linear programs. Second, we can conserve energy by putting redundant sensors into sleep mode; we arrive at the sleep scheduling problem, in which the objective is to find an optimal schedule that determines when each sensor node is asleep and when it is awake. In a wireless network simultaneous radio transmissions may interfere with each other. Task (ii), capacity maximisation, therefore gives rise to another scheduling problem, the activity scheduling problem, in which the objective is to find a minimum-length conflict-free schedule that satisfies the data transmission requirements of all wireless communication links. Task (iii), minimising the number of sensors, is related to the classical graph problem of finding a minimum dominating set. However, if we are not only interested in detecting an intruder but also locating the intruder, it is not sufficient to solve the dominating set problem; formulations such as minimum-size identifying codes and locating dominating codes are more appropriate. This thesis presents approximation algorithms for each of these optimisation problems, i.e., for max-min linear programs, sleep scheduling, activity scheduling, identifying codes, and locating dominating codes. Two complementary approaches are taken. The main focus is on local algorithms, which are constant-time distributed algorithms. The contributions include local approximation algorithms for max-min linear programs, sleep scheduling, and activity scheduling. In the case of max-min linear programs, tight upper and lower bounds are proved for the best possible approximation ratio that can be achieved by any local algorithm. The second approach is the study of centralised polynomial-time algorithms in local graphs these are geometric graphs whose structure exhibits spatial locality. Among other contributions, it is shown that while identifying codes and locating dominating codes are hard to approximate in general graphs, they admit a polynomial-time approximation scheme in local graphs.

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After the Second World War the public was shocked to learn about the horrors perpetrated. As a response to the Holocaust, the newly established United Nations adopted the Genocide Convention of 1948 to prevent future genocides and to punish the perpetrators. The Convention remained, however, almost dead letter until the present day. In 1994, the long-lasted tension between the major groups of Hutu and Tutsi in Rwanda erupted in mass scale violence towards the Tutsi ethnic group. The purpose was to eradicate the Tutsi population of Rwanda. The international community did not halt the genocide. It stood by idle, failing to follow the swearing-in of the past. The United Nations established the International Criminal Tribunal for Rwanda (the ICTR) to bring to justice persons responsible for the genocide. Ever since its creation the ICTR has delivered a wealth of judgements elucidating the legal ingredients of the crime of genocide. The case law on determining the membership of national, ethnic, racial or religious groups has gradually shifted from the objective to subjective position. The membership of a group is seen as a subjective rather than objective concept. However, a totally subjective approach is not accepted. Therefore, it is necessary to determine some objective existence of a group. The provision on the underlying offences is not so difficult to interpret compared to the corresponding one on the protected groups and the mental element of genocide. The case law examined, e.g., whether there is any difference between the words killing and meurtre, the nature of mental harm caused by the perpetrator and sexual violence in the conflict. The mental element of genocide or dolus specialis of genocide is not thoroughly examined in the case law of the ICTR. In this regard, reference in made, in addition, to the case law of the other ad hoc Tribunal. The ICTR has made a significant contribution to the law of genocide and international criminal justice in general. The corpus of procedural and substantive law constitutes a basis for subsequent trials in international and hybrid tribunals. For national jurisdictions the jurisprudence on substantive law is useful while prosecuting international crimes.

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This work is concerned with presenting a modified theoretical approach to the study of centre-periphery relations in the Russian Federation. In the widely accepted scientific discourse, the Russian federal system under the Yeltsin Administration (1991-2000) was asymmetrical; largely owing to the varying amount of structural autonomy distributed among the federation s 89 constituent units. While providing an improved understanding as to which political and socio-economic structures contributed to federal asymmetry, it is felt that associated large N-studies have underemphasised the role played by actor agency in re-shaping Russian federal institutions. It is the main task of this thesis to reintroduce /re-emphasise the importance of actor agency as a major contributing element of institutional change in the Russian federal system. By focusing on the strategic agency of regional elites simultaneously within regional and federal contexts, the thesis adopts the position that political, ethnic and socio-economic structural factors alone cannot fully determine the extent to which regional leaders were successful in their pursuit of economic and political pay-offs from the institutionally weakened federal centre. Furthermore, this work hypothesises that under conditions of federal institutional uncertainty, it is the ability of regional leaders to simultaneously interpret various mutable structural conditions then translate them into plausible strategies which accounts for the regions ability to extract variable amounts of economic and political pay-offs from the Russian federal system. The thesis finds that while the hypothesis is accurate in its theoretical assumptions, several key conclusions provide paths for further inquiry posed by the initial research question. First, without reliable information or stable institutions to guide their actions, both regional and federal elites were forced into ad-hoc decision-making in order to maintain their core strategic focus: political survival. Second, instead of attributing asymmetry to either actor agency or structural factors exclusively, the empirical data shows that both agency and structures interact symbiotically in the strategic formulation process, thus accounting for the sub-optimal nature of several of the actions taken in the adopted cases. Third, as actor agency and structural factors mutate over time, so, too do the perceived payoffs from elite competition. In the case of the Russian federal system, the stronger the federal centre became, the less likely it was that regional leaders could extract the high degree of economic and political pay-offs that they clamoured for earlier in the Yeltsin period. Finally, traditional approaches to the study of federal systems which focus on institutions as measures of federalism are not fully applicable in the Russian case precisely because the institutions themselves were a secondary point of contention between competing elites. Institutional equilibriums between the regions and Moscow were struck only when highly personalised elite preferences were satisfied. Therefore the Russian federal system is the product of short-term, institutional solutions suited to elite survival strategies developed under conditions of economic, political and social uncertainty.