431,755 research outputs found

    Evaluation in media texts: a cross-cultural linguistic investigation

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    A quantitative/interpretative approach to the comparative linguistic analysis of media texts is proposed and applied to a contrastive analysis of texts from the English-language China Daily and the UK Times to look for evidence of differences in what Labov calls “evaluation.” These differences are then correlated to differences in the roles played by the media in Britain and China in their respective societies. The aim is to demonstrate that, despite reservations related to the Chinese texts not being written in the journalists' native language, a direct linguistic comparison of British media texts with Chinese media texts written in English can yield valuable insights into the workings of the Chinese media that supplement nonlinguistic studies

    Semiparametric identification of structural dynamic optimal stopping time models

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    This paper presents new identification results for the class of structural dynamic optimal stopping time models that are built upon the framework of the structural discrete Markov decision processes proposed by Rust (1994). We demonstrate how to semiparametrically identify the deep structural parameters of interest in the case where the utility function of an absorbing choice in the model is parametric but the distribution of unobserved heterogeneity is nonparametric. Our identification strategy depends on availability of a continuous observed state variable that satisfies certain exclusion restrictions. If such excluded variable is accessible, we show that the dynamic optimal stopping model is semiparametrically identified using control function approaches

    Painlev\'e V and time dependent Jacobi polynomials

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    In this paper we study the simplest deformation on a sequence of orthogonal polynomials, namely, replacing the original (or reference) weight w0(x)w_0(x) defined on an interval by w0(x)etx.w_0(x)e^{-tx}. It is a well-known fact that under such a deformation the recurrence coefficients denoted as αn\alpha_n and βn\beta_n evolve in tt according to the Toda equations, giving rise to the time dependent orthogonal polynomials, using Sogo's terminology. The resulting "time-dependent" Jacobi polynomials satisfy a linear second order ode. We will show that the coefficients of this ode are intimately related to a particular Painlev\'e V. In addition, we show that the coefficient of zn1z^{n-1} of the monic orthogonal polynomials associated with the "time-dependent" Jacobi weight, satisfies, up to a translation in t,t, the Jimbo-Miwa σ\sigma-form of the same PV;P_{V}; while a recurrence coefficient αn(t),\alpha_n(t), is up to a translation in tt and a linear fractional transformation PV(α2/2,β2/2,2n+1+α+β,1/2).P_{V}(\alpha^2/2,-\beta^2/2, 2n+1+\alpha+\beta,-1/2). These results are found from combining a pair of non-linear difference equations and a pair of Toda equations. This will in turn allow us to show that a certain Fredholm determinant related to a class of Toeplitz plus Hankel operators has a connection to a Painlev\'e equation

    On fast radial propagation of parametrically excited geodesic acoustic mode

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    The spatial and temporal evolution of parametrically excited geodesic acoustic mode (GAM) initial pulse is investigated both analytically and numerically. Our results show that the nonlinearly excited GAM propagates at a group velocity which is, typically, much larger than that due to finite ion Larmor radius as predicted by the linear theory. The nonlinear dispersion relation of GAM driven by a finite amplitude drift wave pump is also derived, showing a nonlinear frequency increment of GAM. Further implications of these findings for interpreting experimental observations are also discussed

    Gibbsian Hypothesis in Turbulence

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    We show that Kolmogorov multipliers in turbulence cannot be statistically independent of others at adjacent scales (or even a finite range apart) by numerical simulation of a shell model and by theory. As the simplest generalization of independent distributions, we suppose that the steady-state statistics of multipliers in the shell model are given by a translation-invariant Gibbs measure with a short-range potential, when expressed in terms of suitable ``spin'' variables: real-valued spins that are logarithms of multipliers and XY-spins defined by local dynamical phases. Numerical evidence is presented in favor of the hypothesis for the shell model, in particular novel scaling laws and derivative relations predicted by the existence of a thermodynamic limit. The Gibbs measure appears to be in a high-temperature, unique-phase regime with ``paramagnetic'' spin order.Comment: 19 pages, 9 figures, greatly expanded content, accepted to appear in J. Stat. Phy

    Cluster synchronization in networks of coupled non-identical dynamical systems

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    In this paper, we study cluster synchronization in networks of coupled non-identical dynamical systems. The vertices in the same cluster have the same dynamics of uncoupled node system but the uncoupled node systems in different clusters are different. We present conditions guaranteeing cluster synchronization and investigate the relation between cluster synchronization and the unweighted graph topology. We indicate that two condition play key roles for cluster synchronization: the common inter-cluster coupling condition and the intra-cluster communication. From the latter one, we interpret the two well-known cluster synchronization schemes: self-organization and driving, by whether the edges of communication paths lie at inter or intra-cluster. By this way, we classify clusters according to whether the set of edges inter- or intra-cluster edges are removable if wanting to keep the communication between pairs of vertices in the same cluster. Also, we propose adaptive feedback algorithms on the weights of the underlying graph, which can synchronize any bi-directed networks satisfying the two conditions above. We also give several numerical examples to illustrate the theoretical results

    Genetic iterative search-centre-shifting K-best sphere detection for rank-deficient SDM-OFDM systems

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    A generic sphere-detection (SD) scheme is proposed, which substantially reduces the detection complexity by decomposing it into two stages, namely the generic iterative search-centre-update phase and the reduced-complexity search around it. This two-stage philosophy circumvents the high complexity of channel-coded soft-decision aided SDs