16,252 research outputs found
A Fleming-Viot process and Bayesian nonparametrics
No full textThis paper provides a construction of a Fleming-Viot measure valued diffusion process, for which the transition function is known, by extending recent ideas of the Gibbs sampler based Markov processes. In particular, we concentrate on the Chapman-Kolmogorov consistency conditions which allows a simple derivation of such a Fleming-Viot process, once a key and apparently new combinatorial result for Polya-urn sequences has been establishe
Bayesian Nonparametric Construction of the Fleming-Viot Process with Fertility Selection
No full textThis paper provides the construction in a Bayesian setting of the Fleming-Viot measurevalued process with diploid fertility selection and highlights new connections between Bayesian nonparametrics and population genetics. Via a generalisation of the Blackwell-MacQueen Polya-urn scheme, a Markov particle process is defined such that the associated process of empirical measures converges to the Fleming-Viot diffusion. The stationary distribution, known from Ethier and Kurtz (1994), is then derived through an application of the Dirichlet process mixture model and shown to be the de Finetti measure of the particle process. The Fleming-Viot process with haploid selection is derived as a special case.Fleming-Viot process; Measure-valued process; Fertility selection; Gibbs sampler; Dirichlet process mixture model; Blackwell-MacQueen urn-scheme
On the Origins of the Fleming-Mundell Model
No full textForty years ago, Marcus Fleming and Robert Mundell developed independent models of macroeconomic policy in open economies. Why do we link the two, and why do we call the result the Mundell-Fleming, rather than Fleming-Mundell model? Copyright 2003, International Monetary Fund
Construction and Stationary Distribution of the Fleming-Viot Process with Viability Selection
No full textThis paper provides an explicit construction of the Fleming-Viot process with viability selection in a Bayesian nonparametric framework, and derives its stationary distribution. The measure-valued diffusion is obtained as the infinite population limit of the empirical measures of a semi-Markov process of exchangeable particles. In the limit the stationary distribution is shown to be the two-parameter Poisson-Dirichlet process, also known as the Pitman-Yor process.Fleming-Viot process; semi-Markov process; viability selection; stationary distribution; two-parameter Poisson-Dirichlet process.
Multiobjective gas turbine engine controller design using genetic algorithms
No full textThis paper describes the use of multiobjective genetic algorithms (MOGAs) in the design of a multivariable control system for a gas turbine engine. The mechanisms employed to facilitate multiobjective search with the genetic algorithm are described with the aid of an example. It is shown that the MOGA confers a number of advantages over conventional multiobjective optimization methods by evolving a family of Pareto-optimal solutions rather than a single solution estimate. This allows the engineer to examine the trade-offs between the different design objectives and configurations during the course of an optimization. In addition, the paper demonstrates how the genetic algorithm can be used to search in both controller structure and parameter space thereby offering a potentially more general approach to optimization in controller design than traditional numerical methods. While the example in the paper deals with control system design, the approach described can be expected to be applicable to more general problems in the fields of computer aided design (CAD) and computer aided engineering (CAE
A Flaming-Viot Process and Bayesian non Parametric
No full textThis paper provides a construction of a Fleming-Viot measure valued diffusion process, for which the transition function is known, by extending recent ideas of Gibbs sampler based Markov processes. In particular, we concentrate on the Chapman-Kolmogorov consistency conditions which allows a simple derivation of such a Fleming-Viot process, once a key, and apparently new combinatorial result for P´olya-urn sequences has been established.Chapman-Kolmogorov; Diffusion process; Dirichlet process; Polyaurn scheme; Population genetics.
Gas turbine engine controller design using multiobjective genetic algorithms
No full textThis paper describes the use of multiobjective genetic algorithms (MOGAs) in the design of a multivariable control system for a gas turbine engine. It is shown how the MOGA confers an immediate advantage over conventional multiobjective optimization methods by evolving a family of Pareto-optimal solutions allowing the control engineer to examine the trade-offs between the different design objectives. In addition, the paper demonstrates how the genetic algorithm can be used to search in both controller structure and parameter space thereby offering a potentially more general approach to optimization in controller design than traditional numerical methods
Fleming, adaptation, and the author biopic
No full textThe mini-series Fleming: The Man Who Would Be Bond, which aired in the U.S. on BBC America and in the U.K. on Sky Atlantic in 2014, offered an entertaining and glamorised account of Ian Fleming, creator of James Bond. Focusing in particular on Fleming’s time during the Second World War, a period in which he served in British Naval Intelligence, successive episodes comprised embroidered accounts of his experiences, with a heavy emphasis on scenes and motifs that chimed with the doings of his most famous character. This approach to the author’s life-story foregrounded the same elements upon which previous small-screen biographies of Ian Fleming had focused, especially his creation of Bond. The TV film Goldeneye: The Secret Life of Ian Fleming (1989) addressed his wartime experiences and subsequent Bond writing, while Spymaker: The Secret Life of Ian Fleming (1990) doubled down on its Bond connections by casting Jason Connery (son of original film 007, Sean Connery) as Fleming in a Second World War adventure with numerous James Bond parallels. Likewise, Ian Fleming: Bondmaker (2005) and Ian Fleming: Where Bond Began (2008) both framed Fleming first and foremost in terms of his literary creation.
With high production values, and a strong cast that included Dominic Cooper, Lara Pulver, and Samuel West, Fleming bore several of the hallmarks of what has come to be called “quality television” (Thompson, 1997) , and was heavily promoted in the weeks running up to its broadcast. However, a contemporary review in Wired by Graeme McMillan saw it as evidence of a problematic tendency in recent biopics. McMillan asserted that while such texts were previously “a mix of entertainment, education and guilt-free voyeurism,” they have become “a contradictory mix of hagiography and revisionism, lionizing their subjects while somehow managing to diminish them in comparison to the products of their imagination” (McMillan, 2014). In this chapter I will look to unpick this contention, and—in particular—to approach Fleming and the author biopic in terms of adaptation
Most recommended medical interventions reach P<0.005 for their primary outcomes in meta-analyses
No full textBackground: It has been proposed that the threshold of statistical significance should shift from P-value < 0.05 to P-value < 0.005, but there is concern that this move may dismiss effective, useful interventions. We aimed to assess how often medical interventions are recommended although their evidence in meta-analyses of randomized trials lies between P-value = 0.05 and P-value = 0.005.
Methods: We included Cochrane systematic reviews (SRs) published from 1 January 2013 to 30 June 2014 that had at least one meta-analysis with GRADE (Grading of Recommendations Assessment, Development and Evaluation) assessment and at least one primary outcome having favourable results for efficacy at P-value < 0.05. Only comparisons of randomized trials between active versus no treatment/placebo were included. We then assessed the respective UpToDate recommendations for clinical practice from 22 May 2018 to 5 October 2018 and recorded how many treatments were recommended and what were the P-values in their meta-analysis evidence. The primary analysis was based on the first-listed outcomes.
Results: Of 608 screened SRs with GRADE assessment, 113 SRs were eligible, including 143 comparisons of which 128 comparisons had first-listed primary outcomes with UpToDate coverage. Altogether, 60% (58/97) of interventions with P-values < 0.005 for their evidence were recommended versus 32% (10/31) of those with P-value 0.005-0.05. Therefore, most (58/68, 85.2%) of the recommended interventions had P-values < 0.005 for the first-listed primary outcome. Of the 10 exceptions, 4 had other primary outcomes with P-values < 0.005 and another 4 had additional extensive evidence for similar indications that would allow extrapolation for practice recommendations.
Conclusions: Few interventions are recommended without their evidence from meta-analyses of randomized trials reaching P-value < 0.005.
Keywords: P-value; Cochrane; UpToDate; meta-analysis; recommendation; statistical threshold
Genetic algorithms in control systems engineering
No full textDevelopments in computational models of evolutionary processes have led to the realization of powerful, robust, and general optimization and adaptive systems collectively called evolutionary algorithms. In this paper, we consider one member of this class of algorithms, the genetic algorithm, and describe the features and characteristics that are particularly appropriate for applications in control systems engineering. The versatility and robust qualities of the algorithm are considered and a number of application areas described. Some prospective future directions are also identifie
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