927 resultados para Arrow Of Time


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In the absence of an external frame of reference-i.e., in background independent theories such as general relativity-physical degrees of freedom must describe relations between systems. Using a simple model, we investigate how such a relational quantum theory naturally arises by promoting reference systems to the status of dynamical entities. Our goal is twofold. First, we demonstrate using elementary quantum theory how any quantum mechanical experiment admits a purely relational description at a fundamental. Second, we describe how the original non-relational theory approximately emerges from the fully relational theory when reference systems become semi-classical. Our technique is motivated by a Bayesian approach to quantum mechanics, and relies on the noiseless subsystem method of quantum information science used to protect quantum states against undesired noise. The relational theory naturally predicts a fundamental decoherence mechanism, so an arrow of time emerges from a time-symmetric theory. Moreover, our model circumvents the problem of the collapse of the wave packet as the probability interpretation is only ever applied to diagonal density operators. Finally, the physical states of the relational theory can be described in terms of spin networks introduced by Penrose as a combinatorial description of geometry, and widely studied in the loop formulation of quantum gravity. Thus, our simple bottom-up approach (starting from the semiclassical limit to derive the fully relational quantum theory) may offer interesting insights on the low energy limit of quantum gravity.

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This review will critically evaluate two recent texts by white academics working across disciplines of cultural studies, history and anthropology and published by UNSW Press, which share a focus on the relationship between Aboriginality, Philosophy, Place and Time in Australia. I write from the position of a queer white academic committed to engaging politically and intellectually with the challenge of Indigenous sovereignties in this place while also aware that my position as a middle class white woman and intellectual imposes limits on what it is possible for me to know about Indigenous epistemologies (see Moreton-Robinson, 2000). In the course of this review I will demonstrate how anthropology's tendency to fix its objects of study within a circumscribed space of 'difference' limits the capacity of texts produced within this discipline to account for racialized struggles over sovereignty. While these struggles are equally embedded in the ethnographic context and the nation's constitution and political institutions, we will see that Muecke and Bird Rose confront problems in analysing the relationship between the intimate space of the 'field', in which one's research subjects quickly become one's 'friends' and/or 'classificatory kin'—on one hand—and the public space of the nation within which statements about Aboriginality by white academics circulate and are vested with an authority that escapes individual intentions and control—on the other.

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In this thesis work we develop a new generative model of social networks belonging to the family of Time Varying Networks. The importance of correctly modelling the mechanisms shaping the growth of a network and the dynamics of the edges activation and inactivation are of central importance in network science. Indeed, by means of generative models that mimic the real-world dynamics of contacts in social networks it is possible to forecast the outcome of an epidemic process, optimize the immunization campaign or optimally spread an information among individuals. This task can now be tackled taking advantage of the recent availability of large-scale, high-quality and time-resolved datasets. This wealth of digital data has allowed to deepen our understanding of the structure and properties of many real-world networks. Moreover, the empirical evidence of a temporal dimension in networks prompted the switch of paradigm from a static representation of graphs to a time varying one. In this work we exploit the Activity-Driven paradigm (a modeling tool belonging to the family of Time-Varying-Networks) to develop a general dynamical model that encodes fundamental mechanism shaping the social networks' topology and its temporal structure: social capital allocation and burstiness. The former accounts for the fact that individuals does not randomly invest their time and social interactions but they rather allocate it toward already known nodes of the network. The latter accounts for the heavy-tailed distributions of the inter-event time in social networks. We then empirically measure the properties of these two mechanisms from seven real-world datasets and develop a data-driven model, analytically solving it. We then check the results against numerical simulations and test our predictions with real-world datasets, finding a good agreement between the two. Moreover, we find and characterize a non-trivial interplay between burstiness and social capital allocation in the parameters phase space. Finally, we present a novel approach to the development of a complete generative model of Time-Varying-Networks. This model is inspired by the Kaufman's adjacent possible theory and is based on a generalized version of the Polya's urn. Remarkably, most of the complex and heterogeneous feature of real-world social networks are naturally reproduced by this dynamical model, together with many high-order topological properties (clustering coefficient, community structure etc.).

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Aims To date, there is no convincing evidence that non-insulin treated patients who undertake self-blood glucose monitoring (SBGM) have better glycaemic control than those who test their urine. This has led to a recommendation that non-insulin dependent patients undertake urine testing, which is the cheaper option. This recommendation does not take account of patients' experiences and views. This study explores the respective merits of urine testing and SBGM from the perspectives of newly diagnosed patients with Type 2 diabetes. Methods Qualitative study using repeat in-depth interviews with 40 patients. Patients were interviewed three times at 6-monthly intervals over 1 year. Patients were recruited from hospital clinics and general practices in Lothian, Scotland. The study was informed by grounded theory, which involves concurrent data collection and analysis. Results Patients reported strongly negative views of urine testing, particularly when they compared it with SBGM. Patients perceived urine testing as less convenient, less hygienic and less accurate than SBGM. Most patients assumed that blood glucose meters were given to those with a more advanced or serious form of diabetes. This could have implications for how they thought about their own disease. Patients often interpreted negative urine results as indicating that they could not have diabetes. Conclusions Professionals should be aware of the meanings and understandings patients attach to the receipt and use of different types of self-monitoring equipment. Guidelines that promote the use of consistent criteria for equipment allocation are required. The manner in which negative urine results are conveyed needs to be reconsidered.

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At present there is no standard assessment method for rating and comparing the quality of synthesized speech. This study assesses the suitability of Time Frequency Warping (TFW) modulation for use as a reference device for assessing synthesized speech. Time Frequency Warping modulation introduces timing errors into natural speech that produce perceptual errors similar to those found in synthetic speech. It is proposed that TFW modulation used in conjunction with a listening effort test would provide a standard assessment method for rating the quality of synthesized speech. This study identifies the most suitable TFW modulation variable parameter to be used for assessing synthetic speech and assess the results of several assessment tests that rate examples of synthesized speech in terms of the TFW variable parameter and listening effort. The study also attempts to identify the attributes of speech that differentiate synthetic, TFW modulated and natural speech.

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The tendency of managers to focus on short-term results rather than on sustained company success is of particular importance to retail marketing managers, because marketing activities involve expenditures which may only pay off in the longer term. To address the issue of myopic management, our study shows how the complexity of the service profit chain (SPC) can cause managers to make suboptimal decisions. Hence, our paper departs from past research by recognizing that understanding the temporal interplay between operational investments, employee satisfaction, customer satisfaction, and operating profit is essential to achieving sustained success. In particular, we intend to improve understanding of the functioning of the SPC with respect to time lags and feedback loops. Results of our large-scale longitudinal study set in a multi-outlet retail chain reveal time-lag effects between operational investments and employee satisfaction, as well as between customer satisfaction and performance. These findings, along with evidence of a negative interaction effect of employee satisfaction on the relationship between current performance and future investments, show the substantial risk of mismanaging the SPC. We identify specific situations in which the dynamic approach leads to superior marketing investment decisions, when compared to the conventional static view of the SCP. These insights provide valuable managerial guidance for effectively managing the SPC over time. © 2012 New York University.

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An experimental method for characterizing the time-resolved phase noise of a fast switching tunable laser is discussed. The method experimentally determines a complementary cumulative distribution function of the laser's differential phase as a function of time after a switching event. A time resolved bit error rate of differential quadrature phase shift keying formatted data, calculated using the phase noise measurements, was fitted to an experimental time-resolved bit error rate measurement using a field programmable gate array, finding a good agreement between the time-resolved bit error rates.

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This is a report on a study designed to test the applicability of conventional Stated Preference and Revealed Preference models for valuing the time savings of rural travellers in least developed countries and to develop and demonstrate a robust methodology for estimating values of travel time savings which could be used in developing countries.

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DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT

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DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT